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POSTER - 19th International Conference on Magnetism

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Poster M<strong>on</strong>day<br />

PA01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetoelectric polarizati<strong>on</strong> in the field-induced commensurate phase<br />

of Y-hexaferrite Ba 0.7Sr 1.3Zn 2(Fe 1-xAl x) 12O 22<br />

Hak B<strong>on</strong>g Lee, Hun Chang, Young Sang S<strong>on</strong>g, Jae-ho Chung<br />

Department of Physics, Korea Univ., Korea<br />

Hexag<strong>on</strong>al ferrites c<strong>on</strong>taining Fe 3+ (S = 5/2) i<strong>on</strong>s are attracting much attenti<strong>on</strong><br />

because it is expected that soluti<strong>on</strong>s for high-temperature low-field multiferroics<br />

can be found in these materials. Y-type Ba 0.7Sr 1.3Zn 2Fe 12O 22 possesses proper-screw<br />

antiferromagnetic order in zero field, which does not allow spin-current ferroelectric<br />

polarizati<strong>on</strong>. Electric polarizati<strong>on</strong> can, however, be induced when a str<strong>on</strong>g external<br />

field is applied perpendicular to its c axis. The field-resp<strong>on</strong>se can greatly be improved<br />

up<strong>on</strong> Al doping, which is ascribed to the formati<strong>on</strong> of c<strong>on</strong>ical spin structures. In this<br />

work, we investigated the magnetic phase transiti<strong>on</strong>s of single crystal Ba 0.7Sr 1.3Zn 2(Fe 1xAl<br />

x) 12O 22 (x = 0.04 & x = 0.08) in external magnetic field. Both samples exhibited<br />

incommensurate helical antiferromagnetic order in zero-field cooling down to 10 K.<br />

When the external magnetic field was applied so that electric polarizati<strong>on</strong> was induced,<br />

however, the incommensurate order was replaced by a commensurate order in all<br />

samples. Our analysis shows that the commensurate order plays the role of breaking<br />

inversi<strong>on</strong> symmetry, thereby allowing finite electric polarizati<strong>on</strong>. We argue that two<br />

different magnetic anisotropies, easy-axis and easy-plane, play an important role in<br />

establishing stable field-induced electric polarizati<strong>on</strong> in the observed commensurate<br />

magnetic phase.<br />

PA02<br />

Temperature- and field-tuning of magnetic phases in multiferroic<br />

NdFe 3(BO 3) 4<br />

Christie S. Nels<strong>on</strong> 1 *, Le<strong>on</strong>ard N. Bezmaternykh 2 and Irina A. Gudim 2<br />

1 Phot<strong>on</strong> Sciences Directorate, Brookhaven Nati<strong>on</strong>al Laboratory, USA<br />

2 L.V. Kirensky Institute of Physics, Siberian Branch of RAS, Russia<br />

We report the low-temperature coexistence of magnetic phases in NdFe 3(BO 3) 4, which<br />

is a field-induced multiferroic material. The ground state incommensurate magnetic<br />

phase coexists with a strained commensurate magnetic phase that is primarily at the<br />

surface of the crystal. Increasing the temperature or magnetic field decreases the<br />

incommensurability and stabilizes the commensurate magnetic phase above T ic ≈ 14<br />

K or H ic = 0.9 T. A comparis<strong>on</strong> to published studies indicates the <strong>on</strong>set of l<strong>on</strong>gitudinal<br />

magnetostricti<strong>on</strong> and electric polarizati<strong>on</strong> at the field-induced transiti<strong>on</strong>, which may<br />

arise due to a basal plane spin-flop and canting of moments al<strong>on</strong>g the field directi<strong>on</strong>.<br />

Use of the Nati<strong>on</strong>al Synchrotr<strong>on</strong> Light Source, Brookhaven Nati<strong>on</strong>al Laboratory, was<br />

supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy<br />

Sciences, under C<strong>on</strong>tract No. DE-AC02-98CH10886.<br />

PA03<br />

C<strong>on</strong>trol of magnetic anisotropies for stable electric polarizati<strong>on</strong> in<br />

multiferroics hexaferrites<br />

Hun Chang, Hak-b<strong>on</strong>g Lee, Young-sang S<strong>on</strong>g and Jae-ho Chung*<br />

Department of phsics, Korea Univ., Korea<br />

Hexaferrites are widely studied for the hopes of realizing multiferroics working at<br />

room temperature and under low field. It was shown recently that Al-doping can<br />

effectively enhance magnetoelectric susceptibility and low-field behaviors of Y-type<br />

hexaferrite Ba 0.5Sr 1.5Zn 2Fe 12O 22. The key for such enhancement has been suspected<br />

to be the formati<strong>on</strong> of helic<strong>on</strong>ical spin ordering via reducti<strong>on</strong> of planar anisotropy.<br />

Using single crystal neutr<strong>on</strong> diffracti<strong>on</strong>, we investigated in detail the Al-doping<br />

dependence of the magnetic phase transiti<strong>on</strong>s in Ba 0.7Sr 1.3Zn 2(Fe 1-xAl x) 12O 22. We<br />

c<strong>on</strong>firm that the helic<strong>on</strong>ical phases indeed appear up<strong>on</strong> Al doping, and finally collapse<br />

into commensurate phases at excessive doping c<strong>on</strong>centrati<strong>on</strong>s. The observed evoluti<strong>on</strong><br />

of magnetic order coincides with the doping dependence of the magnetoelectricity<br />

previously reported. Analysis of magnetic energy shows, however, that planar<br />

anisotropy al<strong>on</strong>e will not allow the helic<strong>on</strong>ical order to stabilize. We argue that it is<br />

important to have a competiti<strong>on</strong> between easy-axis and easy-plane anisotropies in order<br />

to stabilize the helic<strong>on</strong>ical order, and thereby establish the optimum magnetoelectric<br />

property.<br />

2 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PA04<br />

Chemical c<strong>on</strong>trol of ferroelectric polarizati<strong>on</strong> in Mn1-xCoxWO4 Young-sang S<strong>on</strong>g 1 , Jae-ho Chung 1 *, Sung-beak Kim 2 , Jurg Scheffer 3 , Li Qin Yan 4 ,<br />

Bumsung Lee 4 , Sae-hwan Chun 4 , Kee Ho<strong>on</strong> Kim 4 , A. Nogami 5 and T. Katsufuji 5<br />

1<br />

Department of Physics, Korea University, Seoul, 136-713, Korea<br />

2<br />

Advancement for College Educati<strong>on</strong> Center, K<strong>on</strong>yang University, Chungnam 320-<br />

711, Korea<br />

3<br />

Laboratory for Neutr<strong>on</strong> Scattering, Paul Scherrer Institut, Villigen, Switzerland<br />

4<br />

Department of Physics, Seoul Nati<strong>on</strong>al University, Seoul, 151-742, Korea<br />

5<br />

Department of Physics, Waseda University, Tokyo 169-8555, Japan<br />

MnWO 4 is <strong>on</strong>e of the best known magnetoelectric multiferroics, in which ferroelectric<br />

polarizati<strong>on</strong> appears due to l<strong>on</strong>g-range spin order. Whereas it exhibits three different<br />

antiferromagnetic phases at low temperatures, ferroelectric polarizati<strong>on</strong> al<strong>on</strong>g the b<br />

axis is observed <strong>on</strong>ly in the intermediate phase with an elliptical spiral incommensurate<br />

spin structure. In this work, we present the effect of Co doping <strong>on</strong> the magnetic phase<br />

transiti<strong>on</strong>s and multiferroics properties of Mn 1-xCo xWO 4 using neutr<strong>on</strong> diffracti<strong>on</strong>,<br />

magnetizati<strong>on</strong> and ferroelectric measurements. The main results include the<br />

stabilizati<strong>on</strong> of the incommensurate phase at x ~ 0.03 and the flop of its spiral plane for<br />

x > 0.05. Subsequently, the ferroelectric polarizati<strong>on</strong> appears mainly al<strong>on</strong>g the a axis<br />

in this range. These results indicate that the multiferroics properties of MnWO 4 can be<br />

c<strong>on</strong>trolled via Co doping.<br />

PA05<br />

Multiferroic phase competiti<strong>on</strong> in orthorhombic RMnO 3: M<strong>on</strong>te Carlo<br />

approaches<br />

Jun-ming Liu*<br />

Department of Physics, Nanjing University, China<br />

For type-II multiferroic oxide compounds, the ferroelectricity is believed to be<br />

induced by specific spin orders which can break the spatial inversi<strong>on</strong> symmetry,<br />

allowing an electric polarizati<strong>on</strong> to resp<strong>on</strong>d significantly to external magnetic field.<br />

These phenomena have been receiving attenti<strong>on</strong>s due to the underlying physics and<br />

promising applicati<strong>on</strong> potentials. Nevertheless, c<strong>on</strong>venti<strong>on</strong>al understanding of these<br />

multiferroics remains in an early stage since these materials exhibit typical features<br />

of str<strong>on</strong>gly correlated electr<strong>on</strong> systems in which the spin, charge, orbit, and ph<strong>on</strong><strong>on</strong><br />

degrees of freedom are intrinsically coupled together. So far, rare models other than<br />

the Mochizuki-Furukawa (M-F) model specifically addressing orthorhombic RMnO 3<br />

are available. In this talk, we present our M<strong>on</strong>te Carlo simulati<strong>on</strong>s <strong>on</strong> the multiferroic<br />

behaviors of orthorhombic RMnO 3, based <strong>on</strong> this model. Our simulati<strong>on</strong>s address the<br />

phase competiti<strong>on</strong> between the ab-plane spiral spin order and bc-plane spiral spin order<br />

as well as their coexistence, including the following cases: (1) n<strong>on</strong>magnetic Mn-site<br />

substituti<strong>on</strong>; (2) R-site substituti<strong>on</strong>; (3) interacti<strong>on</strong> between multiferroic RMnO 3 thin<br />

films and magnetic substrates. We will further extend our simulati<strong>on</strong> based <strong>on</strong> the semiquantum<br />

two-orbit double exchange model to the above issues.<br />

PA06<br />

Spin-driven electric polarizati<strong>on</strong> in akermanite Sr 2MSi 2O 7 crystals<br />

Mitsuru Akaki 1 *, Tomoya Tadokoro 1 , Takumi Kihara 2 , Masashi Tokunaga 2 and Hideki<br />

Kuwahara 1<br />

1 Department of Physics, Sophia University, Japan<br />

2 The Institute for Solid State Physics, The University of Tokyo, Japan<br />

Since the magnetoelectric effect was observed in akermanite Ca 2CoSi 2O 7 [1] and Ba 2CoGe 2O 7 [2,3],<br />

the multiferroicity in these materials has been attracting much attenti<strong>on</strong>. The akermanite materials<br />

show the magnetic-field-induced electric polarizati<strong>on</strong> which can be explained by the transiti<strong>on</strong>-metalligand<br />

(p-d) hybridizati<strong>on</strong> depending <strong>on</strong> the spin directi<strong>on</strong> [4]. The multiferroicity of akermanite<br />

materials is, therefore, expected to be influenced by substituti<strong>on</strong> <strong>on</strong> the transiti<strong>on</strong>-metal site. In this<br />

study, we have investigated magnetic and dielectric properties of akermanite Sr 2MSi 2O 7 (M: transiti<strong>on</strong>metal<br />

i<strong>on</strong>) single crystals. In Sr 2CoSi 2O 7, the electric polarizati<strong>on</strong> was not observed in a zero magnetic<br />

field. By applying the magnetic field al<strong>on</strong>g the [110] directi<strong>on</strong>, the electric polarizati<strong>on</strong> emerges al<strong>on</strong>g<br />

the c axis below the magnetic transiti<strong>on</strong> temperature. According to the p-d hybridizati<strong>on</strong> mechanism,<br />

the electric polarizati<strong>on</strong> is proporti<strong>on</strong>al to the spin quantum number S. However, the induced electric<br />

polarizati<strong>on</strong> in Sr 2MnSi 2O 7 (Mn 2+ : S=5/2) is almost two orders of magnitude smaller than that of<br />

Sr 2CoSi 2O 7 (Co 2+ : S=3/2). These results suggest that the electr<strong>on</strong>ic c<strong>on</strong>figurati<strong>on</strong> of the transiti<strong>on</strong>-metal<br />

i<strong>on</strong> is of crucial importance for the appearance of electric polarizati<strong>on</strong>. We will also present and discuss<br />

the results of the comparative study of magnetoelectric properties in other Sr 2MSi 2O 7 crystals.<br />

[1] M. Akaki et al., Appl. Phys. Lett. 94, 212904 (2009). [2] H. T. Yi et al., Appl. Phys. Lett. 92,<br />

212904 (2008). [3] H. Murakawa et al., Phys. Rev. Lett. 105, 137202 (2010). [4] T. Arima, J. Phys.<br />

Soc. Jpn. 76, 073702 (2007).


PA07<br />

Magnetoelectric effects in antiferromagnet Ba 2CoGe 2O 7<br />

Shin Miyahara 1 and Nobuo Furukawa 2<br />

1 JST ERATO-MF, Japan<br />

2 JST ERATO-MF, Aoyama Gakuin University, Japan<br />

We have investigated magnetoelectric effects in Ba 2CoGe 2O 7, which is a quasi two-<br />

dimensi<strong>on</strong>al antiferromagnet[1]. By applying the external magnetic field al<strong>on</strong>g certain<br />

directi<strong>on</strong>s, electric polarizati<strong>on</strong> is induced[2,3]. We c<strong>on</strong>sider a spin-dependent d-p<br />

hybridizati<strong>on</strong> mechanism[4], where the electric polarizati<strong>on</strong> couples to a single spin<br />

structure via the spin-orbit interacti<strong>on</strong>, and we can explain the novel magnetoelectric<br />

behaviors in Ba 2CoGe 2O 7[3]. In this compound, it is recently reported that there<br />

exist magnetic excitati<strong>on</strong>s induced by electric comp<strong>on</strong>ents of electromagnetic wave<br />

at THz frequencies[5]. In additi<strong>on</strong>, the magneto-electric excitati<strong>on</strong> in Ba 2CoGe 2O 7<br />

accompanies a n<strong>on</strong>-reciprocal linear directi<strong>on</strong>al dichroism, where absorpti<strong>on</strong><br />

coefficient depends <strong>on</strong> the directi<strong>on</strong> of the incident electromagnetic wave (+k or<br />

-k). We theoretically clarify the origin of the peculiar features in these dynamical<br />

magnetoelectric phenomena[6]. The n<strong>on</strong>-reciprocal dichroism observed in Ba 2CoGe 2O 7<br />

can be explained by cross-correlated effects, i.e., the interference between the magnetic<br />

and the electric resp<strong>on</strong>ses.<br />

[1] A. Zheludev et al., Phys. Rev. B 68 024428 (2003). [2] H.T. Yi et al., Appl. Phys. Lett 92 212904<br />

(2008). [3] H. Murakawa et al., Phys. Rev. Lett. 105 137202 (2010) [4] T. Arima, J. Phys. Soc. Jpn.<br />

76 073702 (2007). [5] I. Kezsmrki et al., Phys. Rev. Lett. 106 057403 (2011) [6] S. Miyahara and N.<br />

Furukawa, J. Phys. Soc. Jpn 80 073708 (2011)<br />

PA08<br />

X-ray n<strong>on</strong>-reciprocal effects in multiferroic single crystal of GaFeO 3<br />

Andrei Rogalev*, Fabrice Wilhelm and Alexei Bosak<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, France<br />

Ferroelectric and ferrimagnetic ordering coexist in gallium ferrate - GaFeO 3. The<br />

multiferroic properties of this compound have been extensively studied since early<br />

sixties by many different experimental techniques. In order to study these properties<br />

<strong>on</strong> a microscopic level we have measured various X-ray reciprocal and n<strong>on</strong>-reciprocal<br />

dichroisms at the Fe K-edge. The results of these experiments carried out at the ESRF<br />

beamline ID12 <strong>on</strong> a high quality untwined single crystal of GaFeO 3 are presented here.<br />

X-ray magnetochiral dichroism and X-ray n<strong>on</strong>-reciprocal magnetic linear dichroism,<br />

which are a direct measure of the Fe orbital anapole and higher order magnetoelectric<br />

multipole, are disentangled experimentally for the first time. These two dichroic signals<br />

are compared to usual X-ray magnetic circular dichroism which is a measure of orbital<br />

magnetic moment carried by Fe atoms. Moreover, X-ray natural circular dichroism has<br />

been also measured <strong>on</strong> this biaxial n<strong>on</strong>-enantiomorphous crystal. All these dichroisms<br />

are analyzed with the help of a set of the sum rules. This analysis allowed us to deduce<br />

the expectati<strong>on</strong> values of different effective operators related to multiferroic properties<br />

of GaFeO 3.<br />

PA09<br />

NMR study <strong>on</strong> Ba0.5Sr1.5Zn2(Fe0.92Al0.08) 12O22 Sangil Kw<strong>on</strong> 1 , So<strong>on</strong>chil Lee 1 *, D<strong>on</strong>g Young Yo<strong>on</strong> 1 , Sae Hwan Chun 2 , Yi Sheng Chai 2 ,<br />

Kee Ho<strong>on</strong> Kim 2 , Euna Jo 1 , Changsoo Kim 1 and Bye<strong>on</strong>gki Kang 1<br />

1<br />

Department of Physics, Korea Advanced Institute of Science and Technology,<br />

Daeje<strong>on</strong> 305-701, Korea<br />

2<br />

CeNSCMR, Department of Physics and Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Seoul<br />

151-747, Korea<br />

We did zero-field NMR study <strong>on</strong> the annealed single crystal of multiferroic helimagnets<br />

Ba 0.5Sr 1.5Zn 2(Fe 0.92Al 0.08) 12O 22 (Al-BSZFO). This material shows extremely high<br />

magnetoelectric susceptibility so that the critical field for switching electric polarizati<strong>on</strong><br />

is less than 1 mT below 90 K [1]. NMR frequency change by the temperature follows<br />

Bloch’s T3/2 law which presents the low temperature excitati<strong>on</strong> is ferromagnetic spin<br />

wave. The nuclear spin-lattice relaxati<strong>on</strong> rate and the nuclear spin-spin relaxati<strong>on</strong><br />

rate were also measured. Both increased rapidly as the temperature increases above<br />

60 K at which the spin structure changes from normal l<strong>on</strong>gitudinal c<strong>on</strong>es (NLCs) to<br />

alternating l<strong>on</strong>gitudinal c<strong>on</strong>es (ALCs) for the case of as-grown (not annealed) sample<br />

[2]. Due to rapid shortening of spin-spin relaxati<strong>on</strong> time, the NMR signal intensity<br />

abruptly reduced above 60 K. We also studied rf pulse width and power dependence<br />

and revealed that most of the signal came from the domain walls.<br />

[1] S. H. Chun et al., Phys. Rev. Lett. 104, 037204 (2010). [2] H. B. Lee et al., Phys.<br />

Rev. B 83, 144425 (2011).<br />

PA10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic ordering in multiferroic TbFexMn 2-xO 5 with x=0.18<br />

Nadir Aliouane 1 , Andrey Malyuk 2 and Dimitri N. Argyriou 3<br />

1 Laboratory for Neutr<strong>on</strong> scattering, Paul scherrer Institut CH-5232, Villigen-PSI, Switzerland<br />

2 IFW Dresden, Institute for Solid State Research Helmholtzstr. 20 DE-01069 Dresden, Germany<br />

3 Science Directorate, European Spallati<strong>on</strong> Source ESS AB P.O Box 176, SE-221 00 Lund,<br />

Sweden<br />

Manganite compounds present a large range of functi<strong>on</strong>al properties from colossal magnetoresitor to<br />

multiferroicproperties. TbMn 2O 5 is well known multiferroic materials that exhibit complex magnetic phase<br />

transiti<strong>on</strong>s [1] and multifuncti<strong>on</strong>al properties which are tunable by a magnetic field [2,3]. Below 38K, the l<strong>on</strong>g<br />

range incommensurate anti-ferromagnetic ordering induces the ferroelectric behavior through either an exchange<br />

stricti<strong>on</strong> mechanism between neighboring spins wave (Si.Sj≠0) [4] or inverse Dzyaloshinskii-Moriya interacti<strong>on</strong><br />

due to cycloidal spin arrangement [5]. All the magnetic properties in these systems are c<strong>on</strong>trolled by frustrati<strong>on</strong>s.<br />

The frustrati<strong>on</strong> can be tuned in increasing or decreasing the interacti<strong>on</strong>s by substituting Mn 3+ /Mn 4+ with Fe 3+ /Fe 4+<br />

(HS, S=5/2) without structural distorti<strong>on</strong>. Fe doped materials in ceramics sample at similar compositi<strong>on</strong> have<br />

shown enhancement of Ps. Large single crystals of TbMn 2-xFe -xO 5 (x=0.18) have been grown by flux method<br />

and characterized by (ac and dc) susceptibility measurements. Single crystal neutr<strong>on</strong> diffracti<strong>on</strong> <strong>on</strong> E4 and TriCs<br />

diffractometer have been carried out respectively at the Helmoltz Zentrum Berlin and Sing, Paul Scherrer Institut.<br />

Below 38K, Mn/Fe spins order antiferromagnetically (τ(0.5,0,qz) qz~[0.21,0.245]). Below 15K, Tb sublattice<br />

is polarized by Mn/Fe <strong>on</strong>e and orders antiferromagnetically below 5K. Nuclear and magnetic structure has<br />

investigated at 5 and 20K and be presented in this work.<br />

[1] E. F. Berthaut et al. , Solid. Stat. Comm. 5,25 (1925) [2]I. Akinobu and K. Kay, Ferroelectrics 169, 75 (1995) [3] N. Hur et al.<br />

, Nature 429, 392 (2004). [4] L. C. Chap<strong>on</strong>, Phys. Rev. Lett. 96, 976001 (2006). [5] H. Kimura, J Phys Soc Jpn 76, 074706 (2006).<br />

PA11<br />

Strain-induced ferroelectric instabilities in the epitaxial RMn2O5 (R=Dy<br />

and Tb) thin films<br />

J<strong>on</strong>g Hyun S<strong>on</strong>g 1 , Jae Young Kim 2 , Sun Hee Kang 3 , Ill W<strong>on</strong> Kim 3 , Yo<strong>on</strong> Hee Je<strong>on</strong>g 4<br />

and Tae Ye<strong>on</strong>g Koo 2 *<br />

1<br />

Physics Department, Chungnam Nati<strong>on</strong>al University, Korea<br />

2<br />

Pohang Accelerator Laboratory, Korea<br />

3<br />

Physics Department, Ulsan University, Korea<br />

4<br />

Physics Department, Pohang University of Science and Technology, Korea<br />

Epitaxial thin films of DyMn 2O 5 (DMO) and TbMn 2O 5 (TMO) were successfully<br />

grown <strong>on</strong> Nb-doped TiO 2 (110) substrates by the pulsed laser depositi<strong>on</strong> to investigate<br />

the effects of substrate-induced strains <strong>on</strong> multiferroic properties. Synchrotr<strong>on</strong> X-ray<br />

azimuthal angle scans and reciprocal space mappings c<strong>on</strong>firmed the epitaxial qualities<br />

of the films. Magnetic phase transiti<strong>on</strong>s of the films were observed at T n = 43 K,<br />

showing c<strong>on</strong>sistent values with those of the bulk samples. Dielectric c<strong>on</strong>stant showed a<br />

steplike anomaly around 16 K, where a magneto-capacitance effect about 10 % at 8 T<br />

was detected. Magnetizati<strong>on</strong>-induced ferroelectric phases below Tn appear to become<br />

unstable in the epitaxial thin films due to the substrate-induced tensile strains which<br />

make the magnetic exchange interacti<strong>on</strong>s between nearby manganese i<strong>on</strong>s weaker.<br />

PA12<br />

Magnetically driven ferroelectric atomic displacements in perovskitetype<br />

YMnO3 determined by single-crystal structure analysis<br />

Daisuke Okuyama 1 , Shintaro Ishiwata 2 , Youtarou Takahashi 2 , Kunihiko Yamauchi 3 , Silvia Picozzi 4 , Kunihisa<br />

Sugimoto 5 , Hideaki Sakai 6 , Masaki Takata 7 , Ryo Shimano 8 , Yasujiro Taguchi 1 , Taka-hisa Arima 9 and Yoshinori Tokura 2<br />

1<br />

Cross-Correlated Materials Resarch Group (CMRG), and Correlated Electr<strong>on</strong> Research Group (CERG), RIKEN ASI, Japan<br />

2<br />

Department of Applied Physics and Quantum-Phase Electr<strong>on</strong>ics Center (QPEC), University of Tokyo, Japan<br />

3<br />

The Institute of Scientific and Industrial Research (ISIR)-Sanken, Osaka University, Japan<br />

4<br />

C<strong>on</strong>siglio Nazi<strong>on</strong>ale del le Ricerch-Superc<strong>on</strong>ducting and Innovative materials and device (CNR-SPIN), Italy<br />

5<br />

JASRI, SPring-8, Japan<br />

6<br />

School of Physics & Astr<strong>on</strong>omy, University of St Andrews North Haugh, United Kingdom<br />

7<br />

RIKEN, SPring-8 Center, Japan<br />

8<br />

Department of Physics, University of Tokyo, Japan<br />

9<br />

Department of Advanced Materials Science, University of Tokyo, Japan<br />

Multiferroic materials have been intensively studied with a particular focus <strong>on</strong> the driving mechanism of cross-correlated<br />

interacti<strong>on</strong>s between the magnetism and electricity [1]. Many theoretical and experimental works have clarified the<br />

origin of the interplay between magnetism and electricity. However, the lack of informati<strong>on</strong> about the crystal structure in<br />

the multiferroic phase has prevented quantitative discussi<strong>on</strong> of the ferroelectricity driven by magnetic order. In order to<br />

quantitatively discuss the microscopic origin of the ferroelectricity of multiferroic perovskite-YMnO 3, in which the up-updown-down-type<br />

(E-type) antiferromagnetic order causes a ferroelectric polarizati<strong>on</strong> below 30 K [2], we performed the<br />

crystal structural analysis for a twin-free single crystal by using synchrotr<strong>on</strong> x-ray diffractometer at BL02B1 in SPring-8, and<br />

successfully determined the ferroelectric atomic displacements of the order of 0.001 Angstrom. The refined polar structure<br />

shows the characteristic b<strong>on</strong>d alternati<strong>on</strong>, which is c<strong>on</strong>sistent with that expected for the exchange stricti<strong>on</strong> mechanism giving<br />

rise to a ferroelectric polarizati<strong>on</strong> al<strong>on</strong>g the a-axis. From the experimental results of x-ray diffracti<strong>on</strong> and a theoretical firstprinciples<br />

calculati<strong>on</strong>, we quantitatively discuss the origin of the ferroelectricity in multiferroic YMnO 3[3].<br />

[1] Y. Tokura and S. Seki, Adv. Mater. 22, 1554 (2010). [2] S. Ishiwata, Y. Tokunaga, Y. Taguchi, and Y. Tokura, J. Am.<br />

Chem. Soc. 133, 13818 (2011). [3] D. Okuyama, S. Ishiwata, Y. Takahashi, K. Yamauchi, S. Picozzi, K. Sugimoto, H.<br />

Sakai, M. Takata, R. Shimano, Y. Taguchi, T. Arima, and Y. Tokura, Phys. Rev. B 84, 054440 (2011).<br />

July 8 - 13, 2012 Busan, Korea 3<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PA13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic symmetry and electric polarizati<strong>on</strong> <strong>on</strong> Mn 1-xCo xWO 4 multiferroics<br />

Irene Urcelay - Olabarria 1 *, Eric Ressouche 1 , Jose Luis Garcia - Munoz 2 , Vassil<br />

Skumryev 3 , Alexander Mukhin 4 and Juan Manuel Perez - Mato 5<br />

1 Institut Laue Langevin, 38042 Grenoble, Cedex 9, France<br />

2 Instituto de Ciencia de Materiales de Barcel<strong>on</strong>a, ICMAB-CSIC, E-08193 Bellaterra, Spain<br />

3 Institut Catala de Recerca i Estudis Avancats (ICREA), E-08193 Barcel<strong>on</strong>a, Spain<br />

4 Prokhorov General Physics Institute of the Russian Acad. Sci., 119991 Moscow, Russia<br />

5 Dpto. De Fisica de la Materia C<strong>on</strong>densada, Fac. de Ciencia y Tecnologia, Universidad del Pais Vasco, Spain<br />

MnWO 4 exhibits magnetoelectric effects and bel<strong>on</strong>gs to the new class of frustrated multiferroics<br />

in which magnetic and ferroelectric order coexist [1-3]. It undergoes three successive magnetic<br />

phase transiti<strong>on</strong>s [1,2]. Below T n = 13.5 K the spins are collinear and sinusoidally modulated,<br />

(AF3, paraelectric). In the AF2 phase (7.5 K


PA19<br />

C<strong>on</strong>trol of coexisting ferroelectric phases in RMnO 3 crystals with fine<br />

tuning of 4f moment<br />

Tomoya Tadokoro*, Mitsuru Akaki, Haruhiko Kuroe, Tomoyuki Sekine and Hideki<br />

Kuwahara<br />

Department of Physics, Sophia University, Japan<br />

Recently, a new class of multiferroics with a coexistence of magnetic and ferroelectric<br />

ordering has been attracting revived interests. RMnO 3 (R: rare earth) with distorted<br />

orthorhombic structure is <strong>on</strong>e of the most can<strong>on</strong>ical examples for such a multiferroic material.<br />

In TbMnO 3 [1], the electric polarizati<strong>on</strong> lies al<strong>on</strong>g the c axis in the ferroelectric ground state,<br />

and the polarizati<strong>on</strong> does not flop without a magnetic field. Meanwhile, in Eu 0.595Y 0.405MnO 3<br />

without 4f moment [2], the magnetoelectric properties are quite different from those of<br />

TbMnO 3, although they have the same i<strong>on</strong>ic radius of R-site. This result suggests that the<br />

magnetoelectric properties of the RMnO 3 str<strong>on</strong>gly depend <strong>on</strong> the characteristics of the<br />

R-site 4f-moments [3]. In this study, we have systematically investigated magnetic and<br />

dielectric properties of Eu 0.595(Y 1-xHo x) 0.405MnO 3 (0≤x≤1) single crystals with c<strong>on</strong>trol of 4f<br />

moments while keeping the average size of the R-site. In the x = 0.3 crystal, the ferroelectric<br />

polarizati<strong>on</strong> al<strong>on</strong>g the c axis (Pc) emerges at 25K, and then Pc is suppressed and Pa appears<br />

simultaneously with decreasing temperature. On further decreasing temperature, Pa<br />

disappears and Pc appears again. The observed reentrant behavior of the Pc phase indicates<br />

that Pa and Pc phases are str<strong>on</strong>gly competing with each other.<br />

[1] T. Kimura et al., Nature 426, 55 (2003). [2] K. Noda et al., J. Appl. Phys. 99, 08S905 (2003). [3]<br />

M. Hitomi et al., J. Phys. Soc. Jpn. 79, 054704 (2010).<br />

PA20<br />

SmCr 3(BO 3) 4 - A new multiferroic?<br />

Kirill N. Boldyrev 1 *, Marina N. Popova 1 , Viktor V. Mal'tsev 2 and Nicolay I. Le<strong>on</strong>yuk 2<br />

1 Solid State Spectroscopy, Institute of spectroscopy RAS, Russia<br />

2 Faculty of Geology, Moscow State University, Russia<br />

Rare-earth borates with general formula RM 3(BO 3) 4 (R = Y, La-Lu; М = Al, Fe, Cr) are<br />

interesting for science and technology. Ir<strong>on</strong> borates have rich magnetic properties stipulated by<br />

the presence of two interacting magnetic subsystems. It has recently been shown that RFe 3(BO 3) 4<br />

bel<strong>on</strong>g to a new class of multiferroics [1,2]. For this reas<strong>on</strong> it is interesting to study rare-earth<br />

borates with other magnetic i<strong>on</strong> chromium. At present, little is known about these compounds.<br />

Antiferromagnetic phase transiti<strong>on</strong> has been found in NdCr 3(BO 3) 4 at T N=8.0 K [3]. This work<br />

describes an optical study in a wide spectral and temperature range of the SmCr 3(BO 3) 4 crystal,<br />

both pure and doped with erbium or neodymium. We have found that SmCr 3(BO 3) 4 undergoes<br />

a cascade of phase transiti<strong>on</strong>s at temperatures of 8.0 K, 6.7 K and 4.3 K. The first two <strong>on</strong>es are<br />

sec<strong>on</strong>d-order phase transiti<strong>on</strong>s and, supposedly, corresp<strong>on</strong>d to the antiferromagnetic and (anti)<br />

ferroelectric ordering, respectively. First-order phase transiti<strong>on</strong> at 4.3 K is, most probably, the spin<br />

reorientati<strong>on</strong> of the chromium magnetic moments. The presence of the magnetic and ferroelectric<br />

order allows us to talk about samarium chromium borate as a new multiferroic crystal.<br />

[1] A.E. Zvezdin, S.S. Krotov, A.M. Kadomtseva, G.P. Vorob’ev, Yu.F. Popov, A.P. Pyatakov, L.N. Bezmaternykh,<br />

E.A. Popova, JETP Lett. 81, 272 (2005). [2] A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev, A.P. Pyatakov, S.S.<br />

Krotov, K.I. Kamilov, J. Low Temp. Phys., 36(6), 640 (2010). [3] E.A. Popova, N.I. Le<strong>on</strong>yuk, M.N. Popova, E.P.<br />

Chukalina, K.N. Boldyrev, N. Tristan, R. Klingeler, B. Buchner, Phys. Rev. B, 76, 054446 (2007).<br />

PA21<br />

Magnetodielectric effect in the antiferromagnet SrNdFeO 4<br />

Jungmin Hwang 1 , Eun Sang Choi 2 , Haid<strong>on</strong>g Zhou 2 , Yan Xin 2 , Jun Lu 2 and Pedro<br />

Schlottmann 1<br />

1 Florida State University/NHMFL, USA<br />

2 NHMFL (Nati<strong>on</strong>al High Magnetic Field Laboratory), USA<br />

We investigated the magnetic phase diagram of single crystals of the compound<br />

SrNdFeO 4 by measuring the magnetic susceptibility, the magnetizati<strong>on</strong>, the specific<br />

heat and the dielectric c<strong>on</strong>stant. The system has two magnetically active i<strong>on</strong>s, namely<br />

Fe 3+ and Nd 3+ . The Fe 3+ spins are antiferromagnetically ordered below 360 K with<br />

the moments lying in the ab-plane, and undergo a reorientati<strong>on</strong> transiti<strong>on</strong> at about 35-<br />

37 K to an antiferromagnetic order with the moments al<strong>on</strong>g the c-axis. A short-range,<br />

antiferromagnetic ordering of Nd 3+ al<strong>on</strong>g the c-axis was attributed to the reorientati<strong>on</strong><br />

of Fe 3+ followed by a l<strong>on</strong>g-range ordering at lower temperature.[1] At low temperatures<br />

and magnetic fields above 8 T the Nd 3+ moments are completely spin-polarized. The<br />

dielectric c<strong>on</strong>stant also shows anomalies associated with spin c<strong>on</strong>figurati<strong>on</strong> changes.<br />

Remarkably, the sign of the dielectric changes are dependent <strong>on</strong> the directi<strong>on</strong> of the<br />

probing electric field. A possible magnetic structure explaining all the data is presented.<br />

[1] S. Oyama, M. Wakeshima, Y. Hinatsu, and K. Ohoyama, J. Phys.: C<strong>on</strong>dens. Matter. vol. 16, 1823<br />

(2004).<br />

PA22<br />

PA23<br />

PA24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Mössbauer studies of Y-type hexaferrite by Aluminum doping<br />

Jung Tae Lim, Chin Mo Kim, Sung Wook Hyun, Mi Hee W<strong>on</strong>, Taejo<strong>on</strong> Kouh and<br />

Chul Sung Kim*<br />

Department of Physics, Kookmin University, Korea<br />

In recent years, the magnetoelectric effect observed in some of helicalmagnets has<br />

been of great interest. With Al substituti<strong>on</strong>, the improvement of magnetoelectric effect<br />

has been reported due to reducti<strong>on</strong> of the in-plane orbital moment originating from<br />

lowering magnetic anisotropy[1-2]. Therefore, it is important to understand the origin<br />

of magnetic properties in c<strong>on</strong>juncti<strong>on</strong> with the site distributi<strong>on</strong> in hexag<strong>on</strong>al structure.<br />

The crystal structure of polycrystalline Ba 2Co 1.5Mg 0.5(Fe 1-xAl x) 12O 22(x = 0, 0.01, 0.02)<br />

samples were determined to be rhombohedral with the space group of R-3m. From the<br />

temperature-dependent of magnetizati<strong>on</strong> curves under 100 and 300 Oe, all samples<br />

showed ferrimagnet-to-paramagnet and helimagnet-to-ferrimagnet transiti<strong>on</strong>s. Base <strong>on</strong><br />

the applied-field dependent magnetizati<strong>on</strong> measurements up to 10 kOe at 295 K, the<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> (Ms) and coercivity (Hc) of Ba 2Co 1.5Mg 0.5(Fe 1-xAl x) 12O 22(x =<br />

0, 0.01, 0.02) samples were found to be Ms = 28.0, 24.7, 23.4 emu/g and Hc = 255.4,<br />

222.0, 196.2 Oe, respectively. Also, from Mössbauer spectra of 295 K, Isomer shift<br />

values of all samples indicate that the charge states are Fe 3+ . We expect that the decrease<br />

in the Ms with Al i<strong>on</strong> doping is due to the fact that Al i<strong>on</strong>s preferentially occupy the<br />

3bVI, 18hVI and 3aVI octahedral sublattices of up-spin sites[3].<br />

[1] S. Ishiwata, Y. Taguchi, H. Murakawa, Y. Onose, and Y. Tokura, Science 319, 1643 (2008). [2] H. B. Lee,<br />

Y. S. S<strong>on</strong>g, J. H. Chung, S. H. Chun, Y. S. Chai, K. H. Kim, M. Reehuis, K. Prokes, and S. Matas, Phys. Rev.<br />

B 83, 144425 (2011). [3] A. Collomb, M. A. Hadj Farhat and J. C. Joubert, Mat. Res. Bull. 24, 453 (1989).<br />

Optical spectroscopy of the triangular lattice antiferromagnets<br />

CuCrO 2 and alpha-CaCr 2O 4<br />

Michael Schmidt 1 *, Zhe Wang 1 , Franz Mayr 1 , Sandor Toth 2 , Bella Lake 2 , A. T. M.<br />

Nazmul Islam 2 , Vladimir Tsurkan 1 , Alois Loidl 1 and Joachim Deisenhofer 1<br />

1 Experimental Physics V, EKM, Institute of Physics, University of Augsburg, Germany<br />

2 Helmholtz Zentrum Berlin fur Materialien und Energie, Germany<br />

We will compare and discuss our results obtained by optical spectroscopy <strong>on</strong> CuCrO 2<br />

and alpha-CaCr 2O 4. While CuCrO 2 is famous for its multiferroicity [1], in alpha-<br />

CaCr 2O 4 a polarizati<strong>on</strong> can <strong>on</strong>ly be observed under the applicati<strong>on</strong> of electric or<br />

magnetic field, despite having a closely related structure [2]. In alpha-CaCr 2O 4 we<br />

can see a str<strong>on</strong>g, broad absorpti<strong>on</strong> at 57 cm -1 in the magnetically ordered state. The<br />

other compound shows two excitati<strong>on</strong>s at 11 and 48 cm -1 below the magnetic ordering<br />

temperature. At near infrared and visible light frequencies we observe Cr 3+ crystal field<br />

absorpti<strong>on</strong>s and below T N excit<strong>on</strong>s and excit<strong>on</strong>-magn<strong>on</strong>-transiti<strong>on</strong>s appear. The width<br />

of these excit<strong>on</strong>-magn<strong>on</strong> transiti<strong>on</strong>s is analyzed with respect to the existence of Z2<br />

vortices as proposed by Kojima et al. [3].<br />

[1] S. Seki et al., Phys. Rev. Lett. 101, 067240 (2008) [2] K. Singh et al., Phys. Rev. B 84, 064129<br />

(2011) [3] N. Kojima et al., J. Phys. Soc. Jpn. 62, 4137 (1993)<br />

Nuclear forward scattering in high magnetic fields; spin structures in<br />

the magnetic staircase of frustrated multiferroic CuFeO 2<br />

Cornelius Strohm 1 *, Tom T. A. Lummen 2 , Puri I. Handayani 3 , Thomas Roth 1 , Peter J. E.<br />

M. Van Der Linden 1 and Paul H. M. Van Loosdrecht 3<br />

1 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, 6 rue Jules Horowitz 38000 Grenoble, France<br />

2 Department of Materials Science and Engineering, The Pennsylvania State University.<br />

121 Steidle Building, University Park, PA, 16802, USA<br />

3 Zernike Institute for Advanced Materials, University of Gr<strong>on</strong>ingen, Nijenborgh 4, 9747<br />

AG Gr<strong>on</strong>ingen, Netherlands<br />

Geometrically frustrated magnets often show a multitude of nearly degenerate ground states, which may be<br />

stabilized individually by the presence of small internal or external perturbati<strong>on</strong>s. In Copper Ir<strong>on</strong> Oxide, the<br />

combinati<strong>on</strong> of geometrically frustrated interacti<strong>on</strong>s, with uniaxial anisotropy and spin-lattice coupling lead to<br />

a staircase of metamagnetic phases as a functi<strong>on</strong> of applied field [1-3]. We used Nuclear Forward Scattering<br />

of synchrotr<strong>on</strong> radiati<strong>on</strong> in magnetic fields up to 30 T [4, 5] to probe the spin structure of these phases up to<br />

the 1/3-plateau for fields parallel and perpendicular to the c axis [6]. The low field data and all transiti<strong>on</strong> fields<br />

agree with previous work. For the parallel c<strong>on</strong>figurati<strong>on</strong>, we c<strong>on</strong>firm the low field collinear spin structure. The<br />

data for the ferroelectric phase does not support a cycloid structure, while a 3D distributi<strong>on</strong> approximating a<br />

multi-domain transverse proper helix structure gives qualitative agreement. For the 1/3-plateau, the anticipated<br />

collinear 3-sublattice structure best represents the data. In the perpendicular c<strong>on</strong>figurati<strong>on</strong> we directly<br />

evidence the stability of the canted 4-sublattice phase up to the 1/3-plateau, where a collinear three sublattice<br />

c<strong>on</strong>figurati<strong>on</strong> provides the best fit when a small amount of the spins oriented in the H-c plane is allowed for.<br />

[1] R. S. Fishman Phys. Rev. Lett. 106, 037206 (2011). [2] T. T. A. Lummen et al. Phys. Rev. B 80, 012406 (2009). [3] T. T. A. Lummen et<br />

al. Phys. Rev. B 81, 224420 (2010). [4] P. J. E. M. van der Linden et al. Rev. Sci. Instrum. 79, 075104, (2008). [5] C. Strohm, P. van der<br />

Linden and R. Rueffer Phys. Rev Lett. 104, 087601 (2010). [6] C. Strohm, T.T.A. Lummen, P.H.M. van Loosdrecht et al. unpublished.<br />

July 8 - 13, 2012 Busan, Korea 5<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PA25<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic dispersi<strong>on</strong> of the quasi-1D, spin-1/2, multiferroic CuO<br />

Stephen Michael Gaw<br />

Oxford University, United Kingdom<br />

Cupric Oxide (CuO) exhibits a magnetoelectric multiferroic phase over the narrow<br />

but relatively high temperature range of 213-230K [1]. The mechanism for this<br />

magnetoelectric coupling is not fully understood and there have been various<br />

theoretical models proposed [2]. The excitati<strong>on</strong> spectra of CuO in the collinear<br />

antiferromagnetic phase (T


PB06<br />

Hole doping effect for the T’-Ln 2CuO 4 (Ln = La,Nd) cuprate<br />

Wataru Ito, Kenji Kawashima, Suguru Igarashi, Michinori Fukuma and Jun Akimitsu<br />

Physics and Mathematics, Aoyama Gakuin University, Japan<br />

The Ln 2CuO 4 (Ln=La,Nd) cuprate has two different structure types and shows the<br />

superc<strong>on</strong>ductivity for hole doping of La 2CuO 4 and electr<strong>on</strong> doping of Nd 2CuO 4. From<br />

the Madelung energy calculati<strong>on</strong> in hole doping cuprate, T c is enhanced with increasing<br />

the distance between Cu 2+ i<strong>on</strong>s in CuO 2-layer and apical oxygens. Nd 2CuO 4 with T’type<br />

structure has exhibited superc<strong>on</strong>ductivity by electr<strong>on</strong> carrier doping in CuO 2layer.<br />

We focused <strong>on</strong> our attenti<strong>on</strong> to synthesize the hole doping to T’-Ln 2CuO 4,<br />

in which there is no oxygen atom at apical site of CuO 2-layer. We successfully<br />

synthesized the polycrystalline samples of T’-(Ln 3+ ,M 2+ ) 2CuO 4 (Ln=La,Nd, M=Ca,Sr).<br />

In particular, T’-(La 3+ ,Sr 2+ ) 2CuO 4 was synthesized using CaH 2, which is a str<strong>on</strong>g<br />

reducing agent at annealing temperature of 573 K [1]. The powder X-ray diffracti<strong>on</strong><br />

patterns showed that the samples were a single phase, and diffracti<strong>on</strong> peaks indexed<br />

by a tetrag<strong>on</strong>al symmetry of T’-type cuprate of Nd 2CuO 4. The lattice c<strong>on</strong>stants a and<br />

c show the systematic changes by increasing the M 2+ c<strong>on</strong>centrati<strong>on</strong>. We determined<br />

the copper i<strong>on</strong>’s valence state using iodometry method for substituted sample of T’-<br />

(Ln 3+ ,M 2+ ) 2CuO 4 and c<strong>on</strong>firmed that the valence of Cu i<strong>on</strong> is closed to 2+. These facts<br />

indicate that there is oxygen deficiency in Ln 2O 2- or CuO 2-layer of T’-(Ln 3+ ,M 2+ ) 2CuO 4<br />

and canceled hole carriers.<br />

T. Takamaysu, M. Kato, T. Noji, and Y. Koike, Physica C 471 (2011) 679-681<br />

PB07<br />

Thermodynamic properties of copper oxide Cu 6O 8YCl 1-xBr x<br />

Kenji Kawashima, Hiroki Takeda and Jun Akimitsu<br />

Physics and Mathematics, Aoyama Gakuin University, Japan<br />

Copper-oxide family Cu 6O 8MCl (M=cati<strong>on</strong>) has a cubic structure (Fm-3m) with Cu 6O 8-cage<br />

including Cl - i<strong>on</strong> in its crystal structure [1,2]. Cati<strong>on</strong>s of M i<strong>on</strong>s are located in the cuboid space<br />

between Cu 6O 8-cages. The Cu 6O 8-cages share their face to form a three-dimensi<strong>on</strong>al network.<br />

Cu 6O 8YCl shows the metallic and paramagnetic behavior at low temperature. Moreover, Y and<br />

Cl i<strong>on</strong>s have large atomic displacement parameters, suggesting the anharm<strong>on</strong>ic vibrati<strong>on</strong>s like<br />

rattling phenomena of other cage structured compounds. We synthesized the polycrystalline<br />

samples of Cu 6O 8YCl 1-xBr x as a single phase to clarify relati<strong>on</strong>ship between the thermodynamic<br />

properties including its ground state and Cu 6O 8 cage size. In thermo-electr<strong>on</strong>ic measurements<br />

of Cu 6O 8YCl, seebeck coefficient is relatively high value (-14 μV/K at 350K), and thermal<br />

c<strong>on</strong>ductivity exhibits of low value (~0.3W/Km at 350K). The lattice c<strong>on</strong>stant a increases with<br />

increasing Br c<strong>on</strong>centrati<strong>on</strong>, indicating expansi<strong>on</strong> of Cu 6O 8-cage. The temperature dependence<br />

of electrical resistivity of Cu 6O 8YBr exhibits semic<strong>on</strong>ducting behavior, suggesting that the<br />

ground state of Cu 6O 8YCl 1-xBr x changes from metallic to semic<strong>on</strong>ducting by increasing Br<br />

c<strong>on</strong>centrati<strong>on</strong>. Thermal c<strong>on</strong>ductivity undergoes very little change. However, S is enhanced by<br />

substituting Br. These facts indicate that the ground state and physical properties are sensitive <strong>on</strong><br />

the Cu 6O 8-cage size in Cu 6O 8YCl 1-xBr x system.<br />

[1] G.Zouganel, K.Bushida, I.Yazawa N.Terada, M.Jo, H.Hayakawa, and H.Ihara, Sol. St. Comm. 80<br />

(1991) 709. [2] K.Bushida, I.Yazawa, G.Zouganel, T.C<strong>on</strong>nard, N.Terada, K.Kaneko, M.Hirabayashi,<br />

and H.Ihara, Physica C 185-189 (1991) 2727.<br />

PB08<br />

Nodal superc<strong>on</strong>ducting gap in Bi 2201 investigated by low temperature<br />

specific heat measurements<br />

Naoki Mom<strong>on</strong>o 1 *, Nobutaka Saikai 1 , Tohru Kurosawa 2 , Yusuke Amakai 1 , Sigeyuki<br />

Murayama 1 , Hideaki Takano 1 , Migaku Oda 2 and Masayuki Ido 2<br />

1 Applied Sciences, Muroran Institute of Technology, Japan<br />

2 Department of Physics, Hokkaido University, Japan<br />

In order to examine the gap magnitude near nodes in Bi 2201 cuprate superc<strong>on</strong>ductors,<br />

we have measured the magnetic field dependence of low temperature electr<strong>on</strong>ic<br />

specific heat Cel(T, H), which is much more bulk-sensitive than standard ARPES and<br />

STS. In optimally doped Bi 2201, the coefficient of T-linear term in Cel at T


Poster M<strong>on</strong>day<br />

PB12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Enhancement of Ti-Se b<strong>on</strong>ding length in CuxTiSe 2<br />

Sang Wook Han 1 , Han-jin Noh 2 , Daehyun Kim 3 , Jiho<strong>on</strong> Hwang 3 , Je<strong>on</strong>g Soo Kang 3 , W.<br />

F. P<strong>on</strong>g 4 and So<strong>on</strong> Cheol H<strong>on</strong>g 1 *<br />

1 Department of Physics and EHSRC, University of Ulsan, Korea<br />

2 Department of Physics, Ch<strong>on</strong>nam Nati<strong>on</strong> University, Korea<br />

3 Department of Physics, The Catholic University of Korea, Korea<br />

4 Department of Physics, Tamkang University, Taiwan<br />

Titanium diselenide (TiSe 2) undergoes a charge-density-wave (CDW) instability characterized by<br />

a 2x2x2 real-space superstructure [1]. TiSe 2 is not superc<strong>on</strong>ducting at low temperature, but CDW<br />

is suppressed and superc<strong>on</strong>ductivity stabilized either by Cu intercalati<strong>on</strong> (maximum Tc =4.5 K)<br />

[1] or pressure (maximum Tc = 1.8 K) [2]. The resulting phase diagram looks similar to that of<br />

cuprates with the difference that the spin-density wave order has been replaced by a CDW <strong>on</strong>e. The<br />

mechanism at the origin of the CDW and superc<strong>on</strong>ducting phases in TiSe 2 is currently unknown.<br />

The charge-order instability in pure TiSe 2 is known to involve both excit<strong>on</strong> formati<strong>on</strong> and a str<strong>on</strong>g<br />

electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> coupling, it may be expected that the superc<strong>on</strong>ducting phase will likewise involve<br />

a combinati<strong>on</strong> of both excit<strong>on</strong>ic [3] and ph<strong>on</strong>oic [4] c<strong>on</strong>tributi<strong>on</strong>s. In order to elucidate the role of<br />

Cu atoms, we have investigated the Cu-doped TiSe 2 by employing both x-ray absorpti<strong>on</strong> near-edge<br />

structure (XANES) and extended x-ray absorpti<strong>on</strong> fine-structure (EXAFS). The Cu atoms enhance<br />

the b<strong>on</strong>ding length of Ti and Se atoms with lowering temperature. C<strong>on</strong>currently, the Debye-Waller<br />

factors change at the transiti<strong>on</strong> temperatures of CDW and superc<strong>on</strong>ductivity, respectively.<br />

[1] E. Morsan et al., Nature Phys. 2, 544 (2006). [2] A. F. Kusmartseva et al., Phys. Rev. Lett. 103, 236401 (2009). [3] C.<br />

M<strong>on</strong>ney et al., Phys. Rev. Lett. 106, 106404 (2011). [4] M. Calandra and F. Mauri, Phys. Rev. Lett. 106, 196406 (2011).<br />

PB13<br />

Para-c<strong>on</strong>ductivity of (Bi 0.25Cu 0.25Li 0.25Tl 0.25)Ba 2Ca 2Cu 3O 10-δ<br />

superc<strong>on</strong>ductors<br />

Qurat-ul Ain and Nawazish Ali Khan<br />

Physics, Quaid-i-azam university islamabad pakistan, Pakistan<br />

Excess c<strong>on</strong>ductivity analyses of as-prepared and oxygen post-annealed (Bi 0.25Cu 0.25Li 0.25Tl 0.25) Ba 2Ca 2 Cu 3<br />

O 10-δ samples were carried out by following Lorentz-Danish (LD) model bey<strong>on</strong>d the transiti<strong>on</strong> regi<strong>on</strong> and<br />

Ginzburg-Landau (GL) equati<strong>on</strong>s in the critical regime. In these studies the effect of oxygen annealing <strong>on</strong> the<br />

thermodynamic fluctuati<strong>on</strong>s of the Cooper pairs just above the Tc is performed by using Aslamazov-Larkin (AL)<br />

theory. We have observed a major increase in the width of 3D AL and 2D LD regimes after post-annealing in<br />

oxygen atmosphere. Moreover, with the oxygen post-annealing the coherence length al<strong>on</strong>g the c-axis has also<br />

been found to increase al<strong>on</strong>g with inter-plane coupling. The thermodynamic critical magnetic field, the lower<br />

critical magnetic field, the upper critical magnetic field, the critical current density and penetrati<strong>on</strong> depth are also<br />

calculated from the analysis of four regi<strong>on</strong>s namely critical (cr), three dimensi<strong>on</strong>al (3D), two dimensi<strong>on</strong>al (2D)<br />

and zero dimensi<strong>on</strong>al (0D) regi<strong>on</strong> that appeared as the temperature increases. The values of Fermi velocity, phase<br />

relaxati<strong>on</strong> time, penetrati<strong>on</strong> depth, κ values and energy required to break apart the cooper pairs are increased with<br />

the annealing of oxygen. This shows that in (Bi 0.25Cu 0.25Li 0.25Tl 0.25)Ba 2Ca 2Cu 3O 10-δ sample, the optimum density<br />

of carriers in the c<strong>on</strong>ducting CuO2 is essential for enhanced superc<strong>on</strong>ductivity in these compounds.<br />

1) Qiang Lia, M. Suenaga, Junho Gohng, D.K.Finnemore, T. Hikata and K. Sato Phys.Rev. B 46, 3195-3198<br />

(1992). 2) V. V. Schmidt, The physics of superc<strong>on</strong>ductors (Springer, New York, 1997), p. 45. 3)A.L. Solovjov,<br />

V.M. Dmitriev, and H.-U. Habermeier, Phys. Rev. B 55, 8551 (1997). 4)A.L. Solovjov, H.-U. Habermeier, and T.<br />

Haage, Fiz Nizk. Temp. 28, 144 (2002) [Low Temp. Phys. 28, 99 (2002)] 5] C. J. Lobb, Phys. Rev. B 36 (1987)<br />

3930. 6] A. I. Abu Aly, I. H. Ibrahim, R. A. Awad and A. El-Harizy, J. of Superc<strong>on</strong>d. Nov. Magn. 23 (2010) 1325.<br />

PB14<br />

Charge transfer instability governs unc<strong>on</strong>venti<strong>on</strong>al behavior of doped<br />

cuprates<br />

Alexander Moskvin and Alexey Korolev<br />

Department of Theoretical Physics, Ural Federal University, Russia<br />

A large body of experimental data points towards an unique charge transfer (CT)<br />

instability of parent insulating cuprates. True CT gap in these compounds is believed<br />

to be as small as 0.4-0.5 eV as derived from the midinfrared absorpti<strong>on</strong> measurements<br />

[1] rather than 1.5-2.0 eV as usually derived from the fundamental absorpti<strong>on</strong><br />

measurements. Actually we deal with a competiti<strong>on</strong> of the c<strong>on</strong>venti<strong>on</strong>al (3d9) ground<br />

state and a CT state with formati<strong>on</strong> of electr<strong>on</strong>-hole dimers which evolves under doping<br />

to an unc<strong>on</strong>venti<strong>on</strong>al bos<strong>on</strong>ic system [1-3]. Making use of a quantum M<strong>on</strong>te-Carlo<br />

(QMC) technique we study the evoluti<strong>on</strong> of the phase state of CuO 2 planes in a model<br />

CT unstable cuprate La 2-xSr xCuO 4. N<strong>on</strong>isovalent doping gives rise to a suppressi<strong>on</strong> of<br />

parent antiferromagnetic phase with the nucleati<strong>on</strong> of the inhomogeneous supersolid<br />

CO+BS phase characterized by a charge (CO) and off-diag<strong>on</strong>al Bose superfluid<br />

(BS) order parameters which competiti<strong>on</strong> results in a generic T-x phase diagram<br />

with a distinct pseudogap regime due to a charge ordering and emergence of a local<br />

superc<strong>on</strong>ductivity. Our QMC simulati<strong>on</strong> does reproduce all the main features of the<br />

T-x phase diagrams for doped cuprates.<br />

1. A.S. Moskvin, Phys. Rev. B 84, 075116 (2011). 2. A.S. Moskvin, Low Temp. Phys. 33, 234 (2007). 3.<br />

A.S. Moskvin, Phys. Rev. B 69, 214505 (2004).<br />

8 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PB15<br />

The effect of CdO nanoparticles doping and sintering time <strong>on</strong> the<br />

structure and critical temperature of Bi 2223 superc<strong>on</strong>ductor<br />

Morteza Zargar Shoushtari*, S Ebrahim Musavi Ghahfarokhi and Nahid Hossinzadeh<br />

Physics, Shahid Chamran University of Ahvaz, Iran<br />

The effect of CdO nanoparticles doping and sintering time <strong>on</strong> the structure and critical<br />

temperature of Bi 2223 superc<strong>on</strong>ductor M. Zargar shoushtari1, S. E. Musavi Ghahfarokhi,<br />

N. Hossinzadeh 1 Department of physics, Shahid Chamran University of Ahvaz,<br />

Ahvaz, I. R. Iran Presenting author: zargar@scu.ac.ir In this paper, Bi 1.64Pb 0.36Sr 2Ca 2xCd<br />

xCu 3O y (x= 0.0, 0.01, 0.02, 0.03, 0.04, 0.1) superc<strong>on</strong>ductor is prepared by using the<br />

solid state method. The effect of doping CdO nanoparticles for different sintering times<br />

(t= 90, 180 and 270 h) <strong>on</strong> the stracture and critical temperature has been studied. The<br />

structural analysis was carried out using XRD and SEM measurements. The critical<br />

temperature was measured by the standard four-probe method. The results showed that<br />

the more sintering time increases the critical temperature such that the samples prepare<br />

at 270h have maximum critical temperature. Also, our results reveal that, the Bi 1.64Pb<br />

0.36Sr 2Ca 1.97Cd 0.03Cu 3O y sample has the highest Tc (Tc= 137.5k) in between the doped<br />

samples.<br />

PB16<br />

Charging/Discharging and overcurrent characteristics of GdBCO coils<br />

using various partial insulati<strong>on</strong> winding methods<br />

Yo<strong>on</strong> Hyuck Choi, Kwang Lok Kim, Oh Jun Kw<strong>on</strong>, Hyun-jin Shin and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

Eliminating the insulati<strong>on</strong> in high temperature superc<strong>on</strong>ducting (HTS) windings can<br />

allow a system to be compact and well protected by bypassing the excessive current<br />

flow that occurs through the turn-to-turn c<strong>on</strong>tact between uninsulated turns. However,<br />

the time c<strong>on</strong>stant of coils without insulati<strong>on</strong> is much higher than that of completely<br />

insulated coils due to the absence of insulati<strong>on</strong> resistance, resulting in a coil chargedischarge<br />

rate that becomes quite slow. Therefore, this study examined the charging,<br />

operating, and discharging behaviors of Gd-Ba-Cu-O (GdBCO) HTS coils with Kapt<strong>on</strong><br />

insulati<strong>on</strong> every 3, 6, or 9 turns to investigate the effect of changes in insulated turns<br />

<strong>on</strong> the coil’s time c<strong>on</strong>stant. Furthermore, to verify the demagnetizati<strong>on</strong> phenomena of<br />

the coils in the excessive current c<strong>on</strong>diti<strong>on</strong>, the overcurrent characteristics of partially<br />

insulated GdBCO coils were evaluated and discussed in detail.<br />

This work was supported by the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Collaborative R&D Program of<br />

the Korea Institute of Energy Technology Evaluati<strong>on</strong> and Planning (KETEP) grant funded by the<br />

Korean government Ministry of Knowledge Ec<strong>on</strong>omy (20118520020020).<br />

PB17<br />

Effect of filter shape <strong>on</strong> the capture efficiency of a high gradient<br />

magnetic separati<strong>on</strong> (HGMS) system<br />

Young-gyun Kim, Jung-bin S<strong>on</strong>g, D<strong>on</strong>g Gyu Yang, J<strong>on</strong>gseok Lee and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

High gradient magnetic separati<strong>on</strong> (HGMS) using a ferromagnetic filter enables the<br />

capture of fine particles of even weakly magnetic materials by the high gradient of<br />

the magnetic field. In general, such a field gradient, which can determine the capture<br />

capability of the HGMS system, is mainly affected by the filter’s mesh size, wire<br />

diameters, and materials. Therefore, this study examined the capture efficiency of the<br />

HGMS system with respect to mesh size and wire diameter to investigate the effect of<br />

filter shape <strong>on</strong> gradient magnitude. Furthermore, the capture efficiency of various filter<br />

shapes was also examined and compared with the simulati<strong>on</strong>.<br />

This study was supported by the Ministry of Knowledge Ec<strong>on</strong>omy (MKE),<br />

Korea, under the IT R&D Infrastructure Program supervised by the Nati<strong>on</strong>al IT Industry Promoti<strong>on</strong><br />

Agency (NIPA-2011-(B1110-1101-0002)).


PB18<br />

Effects of various epoxy impregnati<strong>on</strong>s <strong>on</strong> the electrical properties of<br />

GdBCO-coated c<strong>on</strong>ductor racetrack pancake coils<br />

Hyun-jin Shin, Kwang Lok Kim, Yo<strong>on</strong> Hyuck Choi, Oh Jun Kw<strong>on</strong>, Ye<strong>on</strong>joo Park and<br />

Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

A high temperature superc<strong>on</strong>ducting (HTS) field coil in a wind turbine generator is<br />

generally impregnated with epoxy resin to provide high mechanical integrity against<br />

the rotati<strong>on</strong>al vibrati<strong>on</strong>s. However, if cooled down, the epoxy-impregnated coil wound<br />

with sec<strong>on</strong>d generati<strong>on</strong> (2G) HTS tape usually encounters superc<strong>on</strong>ducting property<br />

degradati<strong>on</strong> and delaminati<strong>on</strong> due to the thermal c<strong>on</strong>tracti<strong>on</strong> mismatch between the<br />

epoxy and the HTS tape. Therefore, to investigate the effect of various epoxies <strong>on</strong><br />

the coil’s electrical properties, the GdBCO racetrack pancake coils impregnated with<br />

Stycast 2850-FT, Epikote 828R, or Ep<strong>on</strong> 815 were characterized using Ic testing.<br />

Furthermore, degradati<strong>on</strong> of the coils’ superc<strong>on</strong>ducting properties was also examined<br />

using repetitive cooling tests.<br />

This work was supported by the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Collaborative R&D Program of<br />

the Korea Institute of Energy Technology Evaluati<strong>on</strong> and Planning (KETEP) grant funded by the<br />

Korean government Ministry of Knowledge Ec<strong>on</strong>omy (20118520020020).<br />

PB19<br />

Crystal structure of (Ru 0.5Cu 0.5)(Sr 1.47Ba 0.2Nd 0.33)(NdCe)Cu 2O 10-δ<br />

compound<br />

H.k. Lee 1 and Y.i. Kim 2<br />

1 Physics, Kangw<strong>on</strong> Nati<strong>on</strong>al University, Deptartment of Physics, Korea<br />

2 Korea Research Institute of Standards and Science, Korea<br />

PB20<br />

Absence of broken time reversal symmetry below the surface of<br />

(110)-oriented YBCO superc<strong>on</strong>ductors<br />

Hassan Saadaoui 1 *, Zaher Salman 1 , Thomas Prokscha 1 , Hannu Huhtinen 2 and Elvezio<br />

Morenz<strong>on</strong>i 1<br />

1<br />

Laboratory for Mu<strong>on</strong> Spin Spectroscopy, Paul Scherrer Institut, 5232 Villigen PSI,<br />

Switzerland<br />

2<br />

Department of Physics, Wihuri Physical Laboratory, University of Turku, FI-20014<br />

Turku, Finland<br />

WITHDRAWN<br />

Low-energy mu<strong>on</strong> spin rotati<strong>on</strong> (LE-μSR) is a very sensitive local magnetic probe to<br />

study magnetism <strong>on</strong> a nanometer length scale near the surface of materials and thin<br />

films. Here, we report the results of a search for sp<strong>on</strong>taneous magnetizati<strong>on</strong> due to a<br />

time reversal symmetry breaking phase in the superc<strong>on</strong>ducting state of (110)-oriented<br />

YBCO films, expected to develop near the surface in this orientati<strong>on</strong>. Zero field and<br />

weak transverse field measurements performed using LE-μSR few nm inside optimallydoped<br />

YBCO-(110) films showed no appearance of sp<strong>on</strong>taneous magnetizati<strong>on</strong> below<br />

the superc<strong>on</strong>ducting temperature up to 2.9 K, c<strong>on</strong>trary to tunneling measurements. Our<br />

results give an upper limit of 0.01 mT for sp<strong>on</strong>taneous internal fields in these films.<br />

PB21<br />

PB22<br />

PB23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Transport properties of the twin boundary of YBa 2Cu 3O 7 thin films <strong>on</strong><br />

LaAlO 3 substrates<br />

Sung Ho<strong>on</strong> Lee 1 , Sung-hak H<strong>on</strong>g 1 , Jae-hyuk Choi 2 and So<strong>on</strong>-gul Lee 1 *<br />

1 Department of Display and Semic<strong>on</strong>ductor Physics, Korea University, Korea<br />

2 Divisi<strong>on</strong> of C<strong>on</strong>vergence Technology, Korea Research Institute of Standards and<br />

Science, Korea<br />

We have fabricated superc<strong>on</strong>ducting YBa 2Cu 3O 7 (YBCO) twin-boundary juncti<strong>on</strong>s and<br />

studied their critical transport properties. The twin boundary juncti<strong>on</strong>s were fabricated<br />

by using a focusd-i<strong>on</strong>-beam (FIB) etching technique and of the size of nominally 150<br />

nm in width, 100 - 120 nm in length, and 100 nm in thickness. The juncti<strong>on</strong>s showed<br />

Tc = 91 K with 1 K transiti<strong>on</strong> width and a high critical current density of Jc = 15 MA/<br />

cm2 at 77 K. Measured current-voltage (I-V) curves showed the resistively-shuntedjuncti<strong>on</strong><br />

(RSJ) characteristics near the transiti<strong>on</strong> with excess current associated<br />

with flux-flow effect. High-resoluti<strong>on</strong> X-ray diffracti<strong>on</strong> (HR-XRD) spectra str<strong>on</strong>gly<br />

indicated the possibility that the epitaxially-grown YBCO film was also twinned in<br />

commensurate with the twinning of the LAO substrate. Misorientati<strong>on</strong> of the c-axis of<br />

YBCO at the twin boundary is believed to be the major cause of the weak link behavior<br />

of the bridge across the twin boundary.<br />

Displacement waves of oxygen atoms in the Bi, Pb -2223 lattice<br />

of superc<strong>on</strong>ducting composites annealed in an oxygen reduced<br />

atmosphere<br />

Tatiana Krinitsina*, Svetlana Sudareva, Elena Kuznetsova and Julia Blinova<br />

Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, Russia<br />

The Bi, Pb -2223 /Ag composites annealing in oxygen-nitrogen atmosphere is believed to<br />

reduce the number of the accompanying phases, to make c<strong>on</strong>tacts between crystallites<br />

closer and to increase the critical current. The goals of this study were determining<br />

the 2223 lattice changes at annealing in the reduced oxygen atmosphere, revealing<br />

the reas<strong>on</strong>s of these changes and their effect <strong>on</strong> the ceramics superc<strong>on</strong>ductivity. After<br />

such annealing the transversely-polarized waves of oxygen atoms displacement in<br />

[010] directi<strong>on</strong> are observed in the 2223 phase by electr<strong>on</strong> diffracti<strong>on</strong> analysis. These<br />

waves may appear due to the lack of oxygen in the 2223 lattice or to the nitrogen<br />

penetrati<strong>on</strong> in it. As dem<strong>on</strong>strated by the X-ray photo-electr<strong>on</strong> spectroscopy and<br />

nuclear microanalysis, nitrogen does not interact with the 2223 lattice, and the oxygen<br />

index decreases to 9.67, which is lower than the stoichiometric. Thus, the atomic<br />

displacement waves result from the lack of oxygen in Bi-O bilayers.<br />

Irreversibility line in the CNT and carb<strong>on</strong> doped YBCO<br />

superc<strong>on</strong>ductors<br />

Sedigheh Dadras 1 *, Nallayian Manivannan 2 , Vahid Daadmehr 1 and Kee Ho<strong>on</strong> Kim 3<br />

1 physics, Other Academic, Iran<br />

2 physics, Other Academic, India<br />

3 Other Academic, Korea<br />

Irreversibility Line in the CNT and Carb<strong>on</strong> Doped YBCO Superc<strong>on</strong>ductors<br />

S. Dadras 1 *,N. Manivannan 2 , V. Daadmehr 1 , and K. H. Kim 2 1 Magnetic and<br />

Superc<strong>on</strong>ducting Res. Lab., Department of Physics, Alzahra University,<br />

P.C.1993891176, Tehran, Iran. 2eXtreme Multifuncti<strong>on</strong>al Physics Laboratory,<br />

FPRD, School of Physics and Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Seoul 151-747,<br />

Republic of Korea. *dadras@alzahra.ac.ir s_dadras2001@yahoo.com Abstract. We<br />

investigated the irreversibility line (IL) of the carb<strong>on</strong> nano tube (CNT) and carb<strong>on</strong><br />

doped YBa 2Cu 3O 7-δ superc<strong>on</strong>ductor samples using magneto-resistive measurement<br />

results. Irreversibility line moves to higher magnetic fields for CNT doped and to lower<br />

magnetic field for carb<strong>on</strong> doped YBCO samples respect to the undoped sample.<br />

July 8 - 13, 2012 Busan, Korea 9<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PB24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

N<strong>on</strong>local excitati<strong>on</strong>s and 1/8 singularity in cuprates<br />

Yoshiro Kakehashi*, M. Atiqur R. Patoary and Sumal Chandra<br />

Department of Physics, University of the Ryukyus, Japan<br />

Low energy excitati<strong>on</strong>s and unusual behaviors of electr<strong>on</strong>s in the 2D cuprates have<br />

been the questi<strong>on</strong> under debates. Especially the n<strong>on</strong> Fermi liquid behaviors and the<br />

pseudogap remain unresolved theoretically because of the limited range of the intersite<br />

correlati<strong>on</strong>s and the limitati<strong>on</strong> of the momentum and energy resoluti<strong>on</strong>s in the<br />

theory. We present here our results for the momentum-dependent single-particle<br />

excitati<strong>on</strong> spectra of the 2D Hubbard model, which are based <strong>on</strong> the full self-c<strong>on</strong>sistent<br />

projecti<strong>on</strong> operator method. The theory self-c<strong>on</strong>sistently takes into account the l<strong>on</strong>grange<br />

intersite correlati<strong>on</strong>s with use of the off-diag<strong>on</strong>al effective medium, and allows<br />

us to calculate the excitati<strong>on</strong> spectra with high energy and momentum resoluti<strong>on</strong>s. We<br />

obtained the excitati<strong>on</strong> spectra being c<strong>on</strong>sistent with the QMC results and found at T=0<br />

that the n<strong>on</strong>local excitati<strong>on</strong>s enhance the Mott-Hubbard gap and create the shadowband<br />

excitati<strong>on</strong>s due to str<strong>on</strong>g antiferromagnetic correlati<strong>on</strong>s. The present theory yields<br />

the characteristic hole c<strong>on</strong>centrati<strong>on</strong> 1-n* = 0.123 (=1/8) at which the van Hove type<br />

singular peak appears just <strong>on</strong> the Fermi level at T=0, while it is 1-n* = 0.15 at finite<br />

temperatures in the 4x4 DCA. The present result suggests the emergence of the 1/8<br />

stripe phase due to the Fermi surface instability.<br />

PB25<br />

Magnetic memory in a ceramic YBCO superc<strong>on</strong>ductor composed of<br />

sub-micr<strong>on</strong> size grains<br />

Hiroyuki Deguchi 1 *, Takuya Ashida 1 , Mitsuhiro Syudou 1 , Masaki Mito 1 , Makoto<br />

Hagiwara 2 , Kuniyuki Koyama 3 and Seishi Takagi 1<br />

1 Faculty of Engineering, Kyushu Institute of Technology, Japan<br />

2 Faculty of Engineering and Design, Kyoto Institute of Technology, Japan<br />

3 Faculyu of Integrated Arts and Science, The Univercity of Tokushima, Japan<br />

The n<strong>on</strong>equilibrium nature of a ceramic YBCO composed of sub-micr<strong>on</strong> size grains is investigated<br />

by measurements of the dc magnetizati<strong>on</strong>s.The ceramic YBCO is c<strong>on</strong>sidered as random Josephs<strong>on</strong>coupled<br />

networks of 0 and π juncti<strong>on</strong>s and shows successive phase transiti<strong>on</strong>. The first transiti<strong>on</strong><br />

occurs inside each grain at Tc1= 81 K and the sec<strong>on</strong>d transiti<strong>on</strong> occurs am<strong>on</strong>g the grains at Tc2=47 K.<br />

The magnetic glass behavior similar to those of spin-glasses is observed below Tc2.[1] Theoretically,<br />

the frustrati<strong>on</strong> effect due to the random distributi<strong>on</strong> of π juncti<strong>on</strong>s should lead to the chiral-glass state,<br />

as predicted by Kawamura and Li.[2] The memory phenomena are investigated by recording the<br />

zero-field-cooled and thermoremanent magnetizati<strong>on</strong> temperature dependence measured <strong>on</strong> heating<br />

after the cooling process with and without field switches.[3] There are memory effects of the halt<br />

at Ts=44 K imprinted in the system <strong>on</strong> the re-heating the sample. In the case without field switches<br />

at Ts, the influence of the halt is c<strong>on</strong>fined to a narrow temperature regi<strong>on</strong> near the halt temperature,<br />

whereas the memory effects of the halt employing a field switch is extended over a wide temperature<br />

regi<strong>on</strong> below Ts. The results suggest that chiral-glass ordering occurs at Tc2 in the ceramic YBCO.<br />

[1] H.Deguchi et al. , J. Phys. <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series 320 (2011) 012076. [2] H.Kawamura and Li , J.<br />

Phys. Soc. Jpn. 66 (1997) 2110. [3] E.L.Papadopoulou and P.Nordblad , Eur. Phys. J. B 22 (2001) 187.<br />

PB26<br />

Phase diagram of high-tc superc<strong>on</strong>ductivity and antiferromagnetism<br />

revealed by Cu-NMR in multilayered cuprates<br />

Hidekazu Mukuda 1 *, Sunao Shimizu 1 , Akira Iyo 2 and Yoshio Kitaoka 1<br />

1 Osaka University, Japan<br />

2 Nati<strong>on</strong>al institute of Advanced Industrial Science and Technology (AIST), Japan<br />

We present site-selective nuclear magnetic res<strong>on</strong>ance (NMR) studies <strong>on</strong> multilayered<br />

cuprates, which have uncovered the intrinsic phase diagram of antiferromagnetism<br />

(AFM) and high-temperature superc<strong>on</strong>ductivity (HTSC) for a disorder-free CuO 2<br />

plane with hole carriers. We revealed the existence of the AFM metallic state in doped<br />

Mott insulators, the uniformly mixed phase of AFM and HTSC, and the emergence of<br />

d-wave SC with a maximum Tc just outside a critical carrier density, at which the AFM<br />

moment <strong>on</strong> a CuO 2 plane disappears. These results can be accounted for by the Mott<br />

physics based <strong>on</strong> the t-J model, where the superexchange interacti<strong>on</strong> J am<strong>on</strong>g spins<br />

within the plane plays a vital role as a glue for Cooper pairs or mobile spin-singlet<br />

pairs.<br />

10 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PB27<br />

<strong>Magnetism</strong> and superc<strong>on</strong>ductivity in CeCu2Ge2 under high pressures<br />

and magnetic fields<br />

Fuminori H<strong>on</strong>da 1 *, Takashi Maeta 2 , Yusuke Hirose 2 , Atsushi Miyake 3 , Tetsuya Takeuchi 4 ,<br />

Katsuya Shimizu 3 , Tomoko Kagayama 3 , Rikio Settai 2 and Yoshichika Onuki 2<br />

1<br />

Graduate School of Engineering Science, Osaka University, Japan<br />

2<br />

Graduate School of Science, Osaka University, Japan<br />

3<br />

KYOKUGEN, Osaka University, Japan<br />

4<br />

Low Temperature Center, Osaka University, Japan<br />

CeCu 2Ge 2 with the ThCr 2Si 2 type tetrag<strong>on</strong>al structure is an antiferromagnet with TN = 4.2 K<br />

(AF1) and shows two kinds of superc<strong>on</strong>ducting phases named a low-Tsc phase (SC1) and<br />

a high-Tsc phase (SC2) under high pressures [1]. We have grown CeCu 2Ge 2 single crystals<br />

by Sn-flux method and studied an electr<strong>on</strong>ic state under high pressures and magnetic fields<br />

by means of the electrical resistivity measurement. We have found two anomalies at TN =<br />

4.1 K and TN’= 1.3 K at 2.6 GPa for example, implying a Neel temperature and a change of<br />

magnetic structures with the first order. In the temperature-pressure phase diagram, two kinds<br />

of magnetic phases named AF1 and AF2 appear and merge at 5 GPa. At pressures higher than<br />

5 GPa, the AF2 phase becomes dominant. The AF2 phase can be another antiferromagnetic<br />

phase, since the metamagnetic transiti<strong>on</strong> to the AF1 phase is observed around 3 T for the H || [001]<br />

directi<strong>on</strong>. At 8.2 GPa, pressure-induced superc<strong>on</strong>ductivity (SC1) is induced below Tsc(<strong>on</strong>set) =<br />

0.5 K. The upper critical field is 30 kOe for H || [001]. The AF2 phase coexists with SC1 below<br />

10 GPa and the AF2 phase disappears above 11 GPa, revealing <strong>on</strong>ly SC1 phase.<br />

[1] E. Vargoz and D. Jaccard: J. Magn. Magn. Mater. 177-181 (1998) 294.<br />

PB28<br />

Doping and temperature dependence of Fermi arc in cuprate<br />

superc<strong>on</strong>ductors<br />

Shiping Feng*, Huais<strong>on</strong>g Zhao and Lulin Kuang<br />

Department of Physics, Beijing Normal University, China<br />

The pseudogap observed in the excitati<strong>on</strong> spectrum as a suppressi<strong>on</strong> of spectral weight<br />

in the normal-state of cuprate superc<strong>on</strong>ductors is thought to be key to understanding<br />

the mechanism of superc<strong>on</strong>ductivity. Within the framework of the kinetic energy driven<br />

superc<strong>on</strong>ducting mechanism [1], we [2] study the evoluti<strong>on</strong> of the Fermi arc with<br />

doping and temperature by c<strong>on</strong>sidering the interplay between the superc<strong>on</strong>ducting gap<br />

and normal-state pseudogap [3]. It is shown that the system in the underdoped regime<br />

is a nodal liquid, and the length of the Fermi arc increases with increasing temperatures,<br />

in qualitative agreement with the experimental observati<strong>on</strong> <strong>on</strong> cuprate superc<strong>on</strong>ductors<br />

[4]. Our results also show that the unusual behavior of the quasiparticle dispersi<strong>on</strong> and<br />

Fermi arc in cuprate superc<strong>on</strong>ductors is intriguingly related to the effect of the normalstate<br />

pseudogap.<br />

[1] Shiping Feng, Phys. Rev. B 68, 184501 (2003); Shiping Feng et al., Physica C 436, 14 (2006). [2]<br />

Huais<strong>on</strong>g Zhao, Lulin Kuang, and Shiping Feng, unpublished. [3] Shiping Feng, Huais<strong>on</strong>g Zhao,<br />

and Zheyu Huang, arXiv:1109.3973. [4] A. Kanigel et al., Nature Phys. 2, 447 (2006); U. Chatterjee<br />

et al., Nature Phys. 6, 99 (2010).<br />

PB29<br />

Static spin correlati<strong>on</strong> in Pr2-xCaxCuO4 Studied by neutr<strong>on</strong> scattering<br />

Kenji Tsutsumi 1 *, Tomohiro Miura 1 , Masanori Enoki 2 , Kentaro Sato 3 , Masato<br />

Matuura 4 , Kazuyoshi Yamada 5 and Masaki Fujita 6<br />

1<br />

Department of Physics, Tohoku University, Japan<br />

2<br />

Kysyu Institute Technology, Japan<br />

3<br />

Department of Physics, Tohoku university, Japan<br />

4<br />

IMR, Tohoku University, Japan<br />

5<br />

WPI, Tohoku University, Japan<br />

6<br />

IMR, Tohoku Univesity, Japan<br />

It is well known that a small amount of hole-doping into La2CuO4 having K 2NiF 4type<br />

(attributed as T) crystal structure destroys the antiferromagnetic (AF) order and<br />

superc<strong>on</strong>ducting phase appears with further hole doping. On the other hand, recent<br />

experimental study <strong>on</strong> Nd 2CuO 4-type (attributed as T’) structured La 2CuO 4 with no<br />

apical oxygen clarified c<strong>on</strong>trasting properties to that in T-structured La 2CuO 4; that<br />

is Neel temperature is different in two structured systems. [1] Therefore, the crystal<br />

structure is an important factor to determine the physical properties. In order to gain<br />

further insight into the physics of doped Mott insulator, we performed neutr<strong>on</strong>scattering<br />

measurement <strong>on</strong> T’-Pr 2-xCa xCuO 4. The as-grown and annealed x=0.10<br />

samples shows the l<strong>on</strong>g-range AF order below TN~290 K. This result suggests a weak<br />

Ca doping effect <strong>on</strong> the AF order, which is c<strong>on</strong>trast to the results in T-La 2-xSr xCuO 4. In<br />

my poster, the details of doping dependence of magnetic order will be presented.<br />

[1] R. Hord et al., Phys. Rev. B 82, 180508 (2010).


PB30<br />

High-energy neutr<strong>on</strong> scattering study of spin excitati<strong>on</strong> in slightlyoverdoed<br />

La1.82Sr0.18CuO4 Kentaro Sato 1 *, Masato Matsuura 2 , Masaki Fujita 2 , Kenji Tsutsumi 1 , Masanori Enoki 3<br />

and Kazuyoshi Yamada 4<br />

1<br />

Physics, Tohoku University, Japan<br />

2<br />

IMR, Tohoku University, Japan<br />

3<br />

Kyushu Institute of Technology Graduate School of Life Science and Systems Engineering, Japan<br />

4 WPI, Tohoku University, Japan<br />

Antiferromagnetism in the doped cuprate Mott-insulator has been investigated due to its rich physics and close<br />

c<strong>on</strong>necti<strong>on</strong> with the high-Tc superc<strong>on</strong>ductivity. A finding of a generic form of spin excitati<strong>on</strong>s showing the<br />

“hourglass” shape in the different class of superc<strong>on</strong>ductors La 2-x(Sr,Ba) xCuO 4 (La -214 ) [1] and YBa 2Cu 3O 6+d [2]<br />

suggests a comm<strong>on</strong> role of spin fluctuati<strong>on</strong>s in the mechanism of high-Tc superc<strong>on</strong>ductivity. Recently, Vignolle<br />

and co-workers revealed the existence of two energy scales in the spin excitati<strong>on</strong>s of optimally-doped La -214<br />

[3] and pointed out the possibility of different origins for the excitati<strong>on</strong> separated by energy. To study the dual<br />

nature of spin excitati<strong>on</strong>s in more detail, we have performed a high-energy neutr<strong>on</strong> scattering measurement <strong>on</strong><br />

slightly-overdoped La 1.82Sr 0.18CuO 4. The c<strong>on</strong>stant-energy spectrum at low temperature is a broad single-peak in<br />

a wide energy range below ~150meV, although the peak-slitting was observed below ~10meV. This feature is<br />

somehow similar to the dispersi<strong>on</strong> of spin excitati<strong>on</strong> in the overdoped La -214 . On the other hand, the integrated<br />

intensity shows sharp and broad maximums at ~18meV and ~45meV, respectively, as is the case of optimallydoped<br />

system. In the poster, we will present the temperature dependence of the overall excitati<strong>on</strong> spectrum and<br />

discuss the dual nature of the hourglass-shaped excitati<strong>on</strong>.<br />

[1] J. M. Tranquada et al., Nature 429, 534 (2004). [2] S. M. Hayden et al., Nature 429, 531 (2004).<br />

[3] B. Vignolle et al., Nature Physics, 3, 163 (2007).<br />

PB31<br />

Quantized massive gauge fields around the doped holes in high-tc<br />

cuprates and the relati<strong>on</strong> to ir<strong>on</strong> pnictides<br />

Ikuzo Kanazawa*<br />

Physics, Tokyo Gakugei University, Japan<br />

Recently Yazdani[1] has suggested str<strong>on</strong>gly that the high-energy(up to about 400meV)<br />

hole-like excitati<strong>on</strong>s of the normal state are a direct predictor of the strength of<br />

pairing, although he cannot present a model for the excitati<strong>on</strong>s. The present author has<br />

proposed the mechanisms of evoluti<strong>on</strong> of the Fermi arc with increasing temperature[2]<br />

and with increasing of hole-doping[3] in high-Tc cuprates. In this study, we present<br />

<strong>on</strong>e model for the high-energy excitati<strong>on</strong>s, which play an important role <strong>on</strong> strength of<br />

Cooper pairing, and show that quantized massive gauge fields induce short-range spinfluctuati<strong>on</strong>s<br />

and short-range orbital fluctuati<strong>on</strong>s[4,5].<br />

[1] A.Yazdani, J.Phys.C<strong>on</strong>dense Matters 21,164214(2009) [2]I.Kanazawa, J.Phys.Chem.Solids<br />

66,1388(2005) [3]I.Kanazawa, Physica C 470,5183(2010) [4]H.K<strong>on</strong>tani and S.Onari,Phys.Rev.<br />

Lett.104,157001(2010) [5]Y.Yanagi et al. J.Phys.Soc.Jpn. 79,123707(2010)<br />

PB32<br />

Ho-doping effect <strong>on</strong> the static stripe order in La214 superc<strong>on</strong>ductor<br />

Masaki Fujita 1 *, Masanori Enoki 2 , Satoshi Iikubo 2 , Kenji Tsutsumi 3 , Kentaro Sato 3 ,<br />

Masato Matsuura 1 and Kazuyoshi Yamada 4<br />

1<br />

Institute for Materials Research, Tohoku University, Japan<br />

2<br />

Graduate School of Life Science and Systems Engineering, Kyushu Institute of<br />

Technology, Japan<br />

3<br />

Department of Physics, Tohoku University, Japan<br />

4<br />

World Premier <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Research Center, Tohoku University, Japan<br />

We have performed elastic neutr<strong>on</strong> scattering experiments <strong>on</strong> the superc<strong>on</strong>ducting<br />

La 1.84Ho 0.04Sr 0.12CuO 4 to study the substati<strong>on</strong> effect of cati<strong>on</strong> with the large magnetic<br />

moment at La site <strong>on</strong> the static spin correlati<strong>on</strong>. In the Ho-free sample with the hole<br />

c<strong>on</strong>centrati<strong>on</strong> of 0.12, spatially modulated magnetic order is known to be stabilized<br />

below T_spin ~ 30K [1]. In the present Ho-doped sample, we found the appearance of<br />

magnetic peaks at (0.5, 0.5±0.118, 0) positi<strong>on</strong>s below T_spin ~ 35K, which is similar<br />

to the observati<strong>on</strong> in the pristine sample. Furthermore, the volume corrected intensity<br />

in the Ho-free and Ho-doped samples is comparable, suggesting a negligible effect of<br />

Ho-substituti<strong>on</strong> at La site. These results are quite c<strong>on</strong>trast to the huge enhancement<br />

of magnetic intensity and the increase of T_spin by substituting magnetic Fe 3+ i<strong>on</strong>s<br />

<strong>on</strong>to CuO 2 planes [2]. Therefore, the stability of stripe order induced by the cati<strong>on</strong><br />

substituti<strong>on</strong> is sensitive to the substituted site.<br />

[1] H. Kimura et al., Phys. Rev. B 59, 6517 (1999). [2] M. Fujita et al., J. Phys. and Chem. Solids.<br />

69, 3167 (2008).<br />

PB33<br />

PB34<br />

PB35<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

High field paramagnetic meissner effect in Ca doped YBa2Cu3O7-δ single crystals<br />

Valdemar Vieira 1 *, Augusto Falck 1 , Fabio Dias 1 , Douglas Da Silva 1 , Paulo Pureur 2 ,<br />

Jacob Schaf 2 and Frederik Fabris 3<br />

1<br />

Instituto de Fisica e Matematica, UFPEL, Brazil<br />

2<br />

Instituto de Fisica, UFRGS, Brazil<br />

3<br />

Dresden High Magnetic Field Laboratory, HZ Dresden-Rossendorf, Germany<br />

We report <strong>on</strong> dc magnetizati<strong>on</strong> of a series of Y 1-xCa xBa 2Cu 3O 7-δ (x = 0, 0.0025, 0.05, 0.1) single<br />

crystals with the goal to study the role of the hole doping <strong>on</strong> the paramagnetic Meissner effect<br />

(PME). [1] The magnetizati<strong>on</strong> as a functi<strong>on</strong> of the temperature, under c<strong>on</strong>stant magnetic field,<br />

was recorded adopting the field-cooled procedure, Mfc(T) as well as magnetic relaxati<strong>on</strong>, Mfc(t)<br />

for a measurement time up to 50.000s. The Mfc(T) data of our single crystals shows the usual<br />

superc<strong>on</strong>ductor diamagnetic resp<strong>on</strong>se when magnetic fields up to 0.5 kOe are applied. In c<strong>on</strong>trast,<br />

when H > 0.5 kOe are applied, the Mfc(T) data displays a systematic reducti<strong>on</strong> of the superc<strong>on</strong>ductor<br />

diamagnetic resp<strong>on</strong>se until it became predominantly paramagnetic at higher fields not showing<br />

tendency to a temperature saturati<strong>on</strong> behavior in the doped samples. This behavior is a signature of<br />

the high field paramagnetic Meissner effect (HFPME) in HTSC. [2,3] The Mfc(t) data reveals that<br />

the paramagnetic moment of the samples increase c<strong>on</strong>tinuously as a functi<strong>on</strong> of the time. In specific,<br />

the Ca doping promotes an enhancement of the HFPME intensity as compared with no doped<br />

sample. We suggest the flux compressi<strong>on</strong> scenario to explain the HPME in your samples. [4]<br />

[1] V. N. Vieira et al. Phys. Rev. B 76 (2007) 024518-1. [2]F. T. Dias, et al. Physica C 470, S111 (2010).<br />

[3] F.T. Dias et al. Phys. Rev. B 70 (2004) 224519. [4] A.K. Geim et al. Nature 396 (1998) 144.<br />

Growth of a-axis oriented thin films of infinite-layer Sr 1-xLa xCuO 2<br />

Hiroyuki Akatsuka*, Keita Sakuma, Kenji Ueda and Hidehumi Asano<br />

Crystalline Materials Science, Nagoya University, Japan<br />

Electr<strong>on</strong>-doped infinite-layer compound Sr 1-xLa xCuO 2 has the simplest crystal structure,<br />

and is suitable for fundamental studies of high-Tc superc<strong>on</strong>ductivity as well as device<br />

applicati<strong>on</strong>s. The epitaxially grown c-axis oriented Sr 1-xLa xCuO 2 thin films with Tc of around<br />

40 K were fabricated <strong>on</strong> the lattice matched substrates like DyScO 3 and KTaO 3[1]. Since<br />

the in-plane coherence length ξab(4.5nm) of Sr 1-xLa xCuO 2 is larger than the out-of-plane<br />

coherence length ξc(0.3nm)[2], the a-axis oriented film is favorable for juncti<strong>on</strong> fabricati<strong>on</strong>.<br />

In this paper, we will make the first report <strong>on</strong> the preparati<strong>on</strong> and properties of a-axis<br />

oriented thin films. Sr 0.9La 0.1CuO 2(a0=0.3949nm, c0=0.341nm) thin films were prepared<br />

by magnetr<strong>on</strong> sputtering. KTaO3(a0=0.3989nm), SrTiO 3(a0=0.3905nm), (La0.18Sr0.82)<br />

(Al0.59Ta0.41)O 3(LSAT)(a0=0.3868nm) and LaAlO 3(a0=0.3791nm) substrates were used<br />

to investigate the effect of the lattice mismatch. On KTaO 3, LSAT and SrTiO 3 substrates,<br />

c-axis oriented films were obtained. In c<strong>on</strong>trast, <strong>on</strong> LaAlO 3 substrates with a large lattice<br />

mismatch (-4.2%), a-axis oriented films were obtained. One possible reas<strong>on</strong> for the a-axis<br />

growth is due to a higher-order lattice matching, that is, lattice mismatch between ten unit<br />

cell of Sr 0.9La 0.1CuO 2(001)(3.10nm) and nine unit cell of LaAlO 3(100)(3.412nm) is 0.03%.<br />

As-grown thin films showed a semic<strong>on</strong>ducting behavior. Post depositi<strong>on</strong> annealing resulted<br />

in the a-axis oriented films with Tc<strong>on</strong>set of around 30 K.<br />

[1] S. Karimoto and M. Naito, Appl. Phys. Lett. 84, (2004) 12. [2] V. P. Jovanovic, Z. Z. Li, and H.<br />

Raffy, Phys. Rev. B 80, (2009) 024501.<br />

Thermal stability of an epoxy-impregnated HTS racetrack coil without<br />

turn-to-turn insulati<strong>on</strong> for rotating machines<br />

Oh Jun Kw<strong>on</strong>, Kwang Lok Kim, Yo<strong>on</strong> Hyuck Choi, Hyun-jin Shin and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

Since use of the no-insulati<strong>on</strong> (NI) technique creates a compact system with better<br />

thermal and electrical stability, use of a high temperature superc<strong>on</strong>ducting (HTS)<br />

coil without turn-to-turn insulati<strong>on</strong> is now being proposed for the field coil in HTS<br />

rotating machines. Epoxy impregnati<strong>on</strong> of field coils is generally needed to protect<br />

the coil against mechanical disturbances by time-varying magnetic fields and to<br />

provide high mechanical integrity against the rotati<strong>on</strong>al vibrati<strong>on</strong>s. Therefore, to use<br />

the NI technique <strong>on</strong> the practical HTS field coil of a rotating machine, it is essential<br />

to obtain sufficient informati<strong>on</strong> <strong>on</strong> the thermal and electrical behaviors of the epoxyimpregnated<br />

NI coil. In this study, the quench characteristics of epoxy-impregnated<br />

HTS racetrack coils without turn-to-turn insulati<strong>on</strong> were investigated using overcurrent<br />

tests. Furthermore, the thermal stability of the epoxy-impregnated NI coil at various<br />

current charging rates was also investigated and discussed.<br />

This work was supported by a grant from the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Collaborative<br />

R&D Program of the Korea Institute of Energy Technology Evaluati<strong>on</strong> and Planning (KETEP)<br />

funded by the Korean government Ministry of Knowledge Ec<strong>on</strong>omy (20118520020020).<br />

July 8 - 13, 2012 Busan, Korea 11<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PB36<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Design, fabricati<strong>on</strong>, and testing of a cooling system using solid nitrogen<br />

for a 3 T/60-mm RT bore superc<strong>on</strong>ducting HGMS<br />

Jung-bin S<strong>on</strong>g, Kwang Lok Kim, D<strong>on</strong>g Gyu Yang, Yo<strong>on</strong> Hyuck Choi, J<strong>on</strong>gseok Lee<br />

and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

To develop a compact and stable superc<strong>on</strong>ducting high gradient magnetic separator<br />

(HGMS) for the removal of copper and silica from chemical mechanical polishing<br />

wastewater, a 3 T/60-mm room temperature bore HGMS using solid a nitrogen cooling<br />

system was fabricated. The HGMS’s magnet was assembled using 18 GdBCOcoated<br />

c<strong>on</strong>ductor double pancake coils, each of which was wound without turn-toturn<br />

insulati<strong>on</strong>. The cooling capabilities of the solid nitrogen cooling system for the<br />

superc<strong>on</strong>ducting HGMS were examined using cool-down, warm-up, and chargingdischarging<br />

tests in the temperature range of 10-20 K. The capture efficiency of the<br />

superc<strong>on</strong>ducting HGMS using the solid nitrogen cooling system was also evaluated<br />

using a filtrati<strong>on</strong> test.<br />

This work was supported by the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Collaborative R&D Program of<br />

the Korea Institute of Energy Technology Evaluati<strong>on</strong> and Planning (KETEP) grant funded by the<br />

Korean government Ministry of Knowledge Ec<strong>on</strong>omy (20118520020020).<br />

PB37<br />

Purificati<strong>on</strong> of chemical mechanical polishing wastewater using a 2G<br />

HTS high gradient magnetic separati<strong>on</strong> system<br />

D<strong>on</strong>g Gyu Yang, Jung-bin S<strong>on</strong>g, Young-gyun Kim, J<strong>on</strong>gseok Lee, Ye<strong>on</strong>joo Park and<br />

Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

Magnetic separati<strong>on</strong> efficiency is related to the strength of the applied magnetic field<br />

and the field gradient used to trap the magnetic particles. The use of a magnet wound<br />

with high temperature superc<strong>on</strong>ducting (HTS) tape enables the magnetic separati<strong>on</strong><br />

system to more efficiently remove wastewater c<strong>on</strong>taminants than their c<strong>on</strong>venti<strong>on</strong>al<br />

counterparts due to the facile generati<strong>on</strong> of a higher magnetic field due to the absence<br />

of Joule heating losses. In this study, we fabricated and tested the sec<strong>on</strong>d generati<strong>on</strong><br />

(2G) HTS high gradient magnetic separati<strong>on</strong> (HGMS) system for the purificati<strong>on</strong> of<br />

chemical mechanical polishing wastewater. The capturing efficiencies of the 2G HTS<br />

HGMS system were investigated in terms of the wastewater flow velocity and turbidity<br />

using repetitive separati<strong>on</strong> tests. Furthermore, the appropriate purificati<strong>on</strong> process for<br />

enhancing removal efficiency was also discussed.<br />

This study was supported by the Ministry of Knowledge Ec<strong>on</strong>omy (MKE),<br />

Korea, under the IT R&D Infrastructure Program supervised by the Nati<strong>on</strong>al IT Industry Promoti<strong>on</strong><br />

Agency (NIPA-2011-(B1110-1101-0002)).<br />

PB38<br />

Effect of liquid cryogen <strong>on</strong> a 2G HTS magnet using a mixed cryogen<br />

cooling system<br />

Kwang Lok Kim, Jung-bin S<strong>on</strong>g, Yo<strong>on</strong> Hyuck Choi, D<strong>on</strong>g Gyu Yang and Haigun<br />

Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

A cooling system employing a mixture of solid cryogen with small amounts of liquid<br />

cryogen was reported for use in high temperature superc<strong>on</strong>ducting (HTS) applicati<strong>on</strong>s.<br />

Although the liquid cryogen in the mixed cryogen cooling system can improve the<br />

thermal c<strong>on</strong>tact between the solid cryogen and the HTS magnet, it is essential that<br />

further studies be performed because there are insufficient data about the thermal/<br />

electrical behaviors of the HTS magnet that has been subjected to mixed cryogen.<br />

Therefore, in this study, the quench/recovery characteristics of mixed cryogen-cooled<br />

2G HTS magnets with respect to liquid cryogen amount were examined to investigate<br />

the influence of the solid/liquid ratio <strong>on</strong> the thermal/electrical stabilities of the HTS<br />

magnet.<br />

This work was supported by the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Collaborative R&D Program of<br />

the Korea Institute of Energy Technology Evaluati<strong>on</strong> and Planning (KETEP) grant funded by the<br />

Korean government Ministry of Knowledge Ec<strong>on</strong>omy (20118520020020).<br />

12 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PB39<br />

Removal of silica and copper i<strong>on</strong>s from CMP wastewater via magnetic<br />

seeding aggregati<strong>on</strong> using superc<strong>on</strong>ducting HGMS<br />

J<strong>on</strong>gseok Lee, Jung-bin S<strong>on</strong>g, D<strong>on</strong>g Gyu Yang, Ye<strong>on</strong>joo Park and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

With the increased demand for semic<strong>on</strong>ductor devices, the purificati<strong>on</strong> of chemical<br />

mechanical polishing (CMP) wastewater in the semic<strong>on</strong>ductor industry has become<br />

of great importance for worldwide envir<strong>on</strong>mental protecti<strong>on</strong>. Superc<strong>on</strong>ducting high<br />

gradient magnetic separati<strong>on</strong> (HGMS) is <strong>on</strong>e promising technique due to its compact<br />

design and efficient and accurate removal of particles. For the HGMS, various<br />

ferromagnetic materials were required to coagulate n<strong>on</strong>-magnetic heavy metal i<strong>on</strong>s<br />

and various nanoparticles in CMP wastewater. In this study, we suggested the use of a<br />

coagulati<strong>on</strong> process optimized by magnetic seeding aggregati<strong>on</strong> at various pH values<br />

for the separate yet simultaneous removal of copper i<strong>on</strong>s and silica nanoparticles. The<br />

filtrati<strong>on</strong> efficiency of the flocculated substances in an HGMS was evaluated using<br />

turbidity measurements.<br />

This study was supported by the Ministry of Knowledge Ec<strong>on</strong>omy (MKE),<br />

Korea, under the IT R&D Infrastructure Program supervised by the Nati<strong>on</strong>al IT Industry Promoti<strong>on</strong><br />

Agency (NIPA-2011-(B1110-1101-0002)).<br />

PB40<br />

Joint characteristics of ReBCO-coated c<strong>on</strong>ductors using various fusi<strong>on</strong><br />

splicing techniques<br />

Ye<strong>on</strong>joo Park 1 , Hyun-jin Shin 1 , Young-gyun Kim 1 , Young Kun Oh 2 and Haigun Lee 1 *<br />

1 Department of Materials Science and Engineering, Korea University, Korea<br />

2 K-joins Co., Korea<br />

For superc<strong>on</strong>ductor splicing, it is essential that joint resistance be minimized between<br />

superc<strong>on</strong>ducting tapes to operate with the persistent current mode and lengthen them. We have<br />

already proposed the c<strong>on</strong>cept of RE-Ba 2Cu 3O 7-δ (ReBCO) tape fusi<strong>on</strong> splicing technology<br />

that is based <strong>on</strong> the unique ReBCO thermal and structural properties. The melting point of<br />

ReBCO decreases as the surrounding oxygen partial pressure decreases, allowing for low<br />

temperature splicing and recovery of the superc<strong>on</strong>ductivity lost during the joining process by a<br />

subsequent oxygenati<strong>on</strong> annealing process. In this study, the fusi<strong>on</strong> splices with changing joining<br />

parameters, such as PO 2, heating rate, peak temperature and holding time, cooling rate, oxygen<br />

flow rate, temperature and holding time for oxygenati<strong>on</strong> annealing, tape clamping pressure,<br />

and so <strong>on</strong> were performed using the following two splicing methods: 1) the ReBCO-ReBCO<br />

interface was directly c<strong>on</strong>nected by fusi<strong>on</strong>, and 2) the Ag layer was diffused in a face-to-face<br />

manner without solder. The joint characteristics were evaluated in terms of joint resistances,<br />

critical currents, and index numbers. Furthermore, the sample morphologies and structures were<br />

analyzed by scanning electr<strong>on</strong> microscopy (SEM) and X-ray diffracti<strong>on</strong> (XRD), respectively.<br />

This work was supported by the <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Collaborative R&D Program of<br />

the Korea Institute of Energy Technology Evaluati<strong>on</strong> and Planning (KETEP) grant funded by the<br />

Korean government Ministry of Knowledge Ec<strong>on</strong>omy (20118520020020).<br />

PC01<br />

Bulk electr<strong>on</strong>ic structure of LaRu 2P 2 probed by soft X-ray angleresolved<br />

photoemissi<strong>on</strong> spectroscopy (SX-ARPES)<br />

E. Razzoli 1 , M. Kobayashi 1 , V. N. Strocov 1 , B. Delley 1 , Z. Bukowski 2 , J. Karpinski 3 , N.<br />

C. Plumb 1 , M. Radovic 1 , J. Chang 1 , T. Schmitt 1 , L. Patthey 1 , J. Mesot 1 and M. Shi 1 *<br />

1 Paul Scherrer Institute, Switzerland<br />

2 Laboratory for Solid State Physics, ETH Zurich, Switzerland<br />

3 Laboratory for Solid State Physics, ETH Zuurich,, Switzerland<br />

WITHDRAWN


PC02<br />

Superlattice quantum critical point in the cubic metal (Sr/Ca) 3Ir 4Sn 13<br />

Lina Esther Klintberg 1 , Swee Kuan Goh 1 *, Patricia Alireza 1 , Paul Saines 1 , David<br />

Tompsett 1 , Peter Logg 1 , Jinhu Yang 2 , Bin Chen 2 , Kazuyoshi Yoshimura 2 and Malte<br />

Grosche 1<br />

1 University of Cambridge, United Kingdom<br />

2 University of Kyoto, Japan<br />

Structural self-organisati<strong>on</strong> is a central theme in c<strong>on</strong>densed matter physics. Often, the<br />

symmetry of a given parent structure is lowered by subtle structural variati<strong>on</strong>s which<br />

decrease the electr<strong>on</strong>ic degeneracy and thereby the total energy. Examples include<br />

Jahn-Teller and Peierls distorti<strong>on</strong>s and, more generally, modulated lattice distorti<strong>on</strong>s,<br />

or superlattices. The quasi-skutterudite compounds R3T4X13, where R is an earth<br />

alkaline or rare-earth element, T is a transiti<strong>on</strong> metal and X is a group-IV element,<br />

form either in a simple cubic structure, called the I-phase, or in the variant I'-phase,<br />

which can be viewed as a superlattice distorti<strong>on</strong> of the I-phase. Here, we investigate<br />

the borderline system (Sr/Ca) 3Ir 4Sn 13, which we report forms in the I-phase, but<br />

transforms into the I'-phase <strong>on</strong> cooling. Hydrostatic pressure is used to suppress the<br />

sec<strong>on</strong>d order structural transiti<strong>on</strong> enabling the first comprehensive investigati<strong>on</strong> of a<br />

structural quantum critical point in a three-dimensi<strong>on</strong>al charge density wave driven<br />

superc<strong>on</strong>ductor.<br />

PC03<br />

Unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity in PuCoIn 5: An NQR investigati<strong>on</strong>.<br />

Hiroshi Yasuoka 1 , Georgios Koutroulakis 1 *, Hiroyuki Chudo 2 , Eric D. Bauer 1 and Joe<br />

D. Thomps<strong>on</strong> 1<br />

1 Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

2 Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

PC04<br />

Pressure effect <strong>on</strong> the structural and superc<strong>on</strong>ducting transiti<strong>on</strong>s in a<br />

caged compound PrRh2Zn20 Y Sugano 1 , T Ohsuka 1 , K Umeo 2 *, N Nagasawa 1 , T Onimaru 1 and T Takabatake 1<br />

1<br />

AdSM, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8530,<br />

Japan<br />

2<br />

N-BARD, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526,<br />

Japan<br />

WITHDRAWN<br />

PrRh 2Zn 20 crystallizes in a cubic CeCr 2Al 20-type structure, where the Pr 3+ i<strong>on</strong> is<br />

encapsulated in a polyhedr<strong>on</strong> formed by 16 zinc atoms. The crystalline electric field<br />

ground state of 4f2 electr<strong>on</strong>s in the Pr i<strong>on</strong> was found to be a n<strong>on</strong>magnetic Γ3 doublet<br />

[1]. The resistivity of this compound shows a superc<strong>on</strong>ducting transiti<strong>on</strong> at TSC = 0.060<br />

K and a hysteretic behavior in the temperature range from 140 K to 470 K, which<br />

originates from a structural phase transiti<strong>on</strong>. In order to reveal the interplay between the<br />

structural and superc<strong>on</strong>ducting transiti<strong>on</strong>s, we have measured the electrical resistivity<br />

ρ for a single crystalline sample under pressures up to 2 GPa and at temperatures down<br />

to 0.052 K. With increasing pressure up to 2 GPa, the anomaly in ρ(T) at TS = 160<br />

K shifts to higher temperatures by the ratio of 3 K/GPa. This indicates that the lowtemperature<br />

phase (T


Poster M<strong>on</strong>day<br />

PC08<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A novel superc<strong>on</strong>ductivity in Ir oxides with large spin-orbit coupling<br />

Hiroshi Watanabe*, Tom<strong>on</strong>ori Shirakawa and Seiji Yunoki<br />

RIKEN, Japan<br />

Recently, the 5d transiti<strong>on</strong> metal oxides such as Sr 2IrO 4 and Ba 2IrO 4 have attracted<br />

much attenti<strong>on</strong> as a novel Mott insulator. In these materials, three t2g orbitals of<br />

Ir atoms are hybridized with each other by the spin-orbit coupling of 5d electr<strong>on</strong>s.<br />

As a result of the quantum entanglement of spin and orbital degrees of freedom,<br />

an anomalous Jeff=|L-S|=1/2 state is realized, which causes interesting properties<br />

[1]. To clarify the properties of this system, we have studied the ground state of<br />

the three-orbital Hubbard model with a spin-orbit coupling term using variati<strong>on</strong>al<br />

M<strong>on</strong>te Carlo method and variati<strong>on</strong>al cluster approximati<strong>on</strong> [2]. Here, we study the<br />

electr<strong>on</strong>ic states when carriers are doped in this three-orbital system and discuss the<br />

possibility of superc<strong>on</strong>ductivity. The obtained ground state phase diagram reveals<br />

the antiferromagnetic state, stable around the electr<strong>on</strong> density n=5, is destabilized<br />

by carrier doping and the ground state turns to be superc<strong>on</strong>ducting under a certain<br />

c<strong>on</strong>diti<strong>on</strong>. Similar to the high-Tc cuprates, a large asymmetry between electr<strong>on</strong> doping<br />

(n>5) and hole doping (n


PC14<br />

Lateral Josephs<strong>on</strong> juncti<strong>on</strong> induced by inverse proximity effect<br />

Lu-kuei Lin 1 , Ssu-yen Huang 1 , Jin-hua Huang 2 and Shang-fan Lee 1 *<br />

1 Institute of Physics, Academia Sinica, Taiwan<br />

2 Materials Science and Engineering, Nati<strong>on</strong>al Tsing Hua University, Taiwan<br />

A Josephs<strong>on</strong> juncti<strong>on</strong> is characterized by a phase coherent transfer of the Cooper pairs<br />

across a weak link between two superc<strong>on</strong>ducting electrodes. The proximity effect at<br />

the interface between a superc<strong>on</strong>ductor and a ferromagnetic metal occurs, implying<br />

that the Cooper pairs penetrate into the ferromagnet. It results in spatial oscillati<strong>on</strong>s<br />

of the superc<strong>on</strong>ducting order parameter in the ferromagnet. Recently an opposite<br />

effect so-called “inverse proximity effect”, i.e. the inducti<strong>on</strong> of a magnetic moment in<br />

a superc<strong>on</strong>ductor in c<strong>on</strong>tact with a ferromagnet attracted much attenti<strong>on</strong>. We utilize<br />

the inverse proximity effect in superc<strong>on</strong>ductor-ferromagnet bilayer to generate lateral<br />

Josephs<strong>on</strong> juncti<strong>on</strong>s. The weak link is created by a str<strong>on</strong>g ferromagnet Py strip across<br />

a superc<strong>on</strong>ductor Nb bridge due to inverse proximity effect and forms a regi<strong>on</strong> S’.<br />

Samples with different size of weak link regi<strong>on</strong> S’ were fabricated by varying the Py<br />

strip width from 0.5 to 2 μm. The juncti<strong>on</strong>s exhibit a modulati<strong>on</strong> of the critical current<br />

in perpendicular magnetic field similar to a Fraunhofer interference pattern even when<br />

the S’ has such l<strong>on</strong>g distance as 2 μm, which proves the dc Josephs<strong>on</strong> effect and spin<br />

triple comp<strong>on</strong>ent taking place.<br />

PC15<br />

13C NMR study of charge fluctuati<strong>on</strong> induced superc<strong>on</strong>ductivity in<br />

beta''-(BEDT-TTF)4[(H 3O)Ga(C 2O 4) 3]-C 6H 5NO 2<br />

Yoshihiko Ihara*, Harumi Seki and Atsushi Kawamoto<br />

Department of Physics, Graduate School of Science, Hokkaido univerisity, Japan<br />

Superc<strong>on</strong>ductivity emerging near antiferromagnetism has been thoroughly investigated.<br />

The antiferromagnetic fluctuati<strong>on</strong>s in the vicinity of quantum critical point are believed<br />

to induce such superc<strong>on</strong>ductivity. In this paper, we report experimental evidence that<br />

points to the novel possibility of superc<strong>on</strong>ducting state, that is, charge fluctuati<strong>on</strong><br />

induced superc<strong>on</strong>ductivity. The molecular superc<strong>on</strong>ductor beta''-(BEDT-TTF)4[(H 3O)<br />

Ga(C 2O 4) 3]-C 6H 5NO 2 dem<strong>on</strong>strates a charge instability at 100 K, before showing the<br />

superc<strong>on</strong>ducting transiti<strong>on</strong> at 7.5 K [1]. Besides, this salt is intriguing because of its<br />

high upper critical field of 33 T, which is almost three times the Pauli limiting field<br />

[2]. We performed the 13C NMR experiment and revealed <strong>on</strong> the basis of the Knight<br />

shift measurement that the spin-singlet superc<strong>on</strong>ductivity is realized in the charge<br />

disproporti<strong>on</strong>ate state. The nuclear spin-lattice relaxati<strong>on</strong> rate measurement detects<br />

the str<strong>on</strong>g electr<strong>on</strong>-electr<strong>on</strong> correlati<strong>on</strong>s slightly above superc<strong>on</strong>ducting transiti<strong>on</strong><br />

temperature. Since 13C NMR technique can probe <strong>on</strong>ly the magnetic properties, we<br />

measured in-plane resistivity as a complementary probe and found an abrupt increase<br />

below 10 K. These results lead us to address the importance of charge fluctuati<strong>on</strong>s to<br />

induce superc<strong>on</strong>ductivity.<br />

[1] A. I. Coldea et al., PRB 69, 085112 (2004). [2] A. F. Bangura et al., PRB 72, 014543 (2005).<br />

PC16<br />

Ac susceptibility comp<strong>on</strong>ents of a thin type-II superc<strong>on</strong>ducting<br />

annulus carrying a radial current<br />

Aliakbar Babaei Brojeny*, Mostafa Molavi, Asghar Sharbaf Zadeh and Mahdi<br />

Sohrabi<br />

Department of Physics, Isfahan University of Technology, 84156-83111, Iran<br />

By assuming a spatial dependence <strong>on</strong> the sheet-current density, we have investigated<br />

the real (χ') and imaginary parts (χ'') of the susceptibility of a thin type-II<br />

superc<strong>on</strong>ducting annulus in the absence and also in the presence of a transport radial<br />

current, using the Bean critical state model in which the critical current density is<br />

assumed to be independent of the local magnetic field. The results of our calculati<strong>on</strong>s<br />

<strong>on</strong> the comp<strong>on</strong>ents of the magnetic susceptibilities in two cases and for the different<br />

aspect ratios are compared with each other. The comparis<strong>on</strong> shows that by applying a<br />

radial current to the sample, the imaginary part of the susceptibility is increased. We<br />

have also studied the variati<strong>on</strong>s of the χ'' with respect to χ' for a several aspect ratios.<br />

1-Ali A. Babaei-Brojeny and John R. Clem, Phys. Rev. B 68, 174514 (2003). 2-Ali A. Babaei-<br />

Brojeny, Asghar Sharbaf Zadeh and Mostafa Molavi, Journal of Physics:<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series…(2012).<br />

PC17<br />

PC18<br />

PC19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Pressure evoluti<strong>on</strong> of superc<strong>on</strong>ductivity in β-pyrochlore oxides<br />

Takeshi Matsubara 1 , Takayuki Is<strong>on</strong>o 2 , Daisuke Iguchi 1 , Yo Machida 1 , Koichi Izawa 1 *,<br />

Bernard Salce 3 , Jacques Flouquet 3 , Hiroki Ogusu 2 , Jun-ichi Yamaura 2 and Zenji Hiroi 2<br />

1<br />

Department of physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551,<br />

Japan<br />

2<br />

ISSP, University of Tokyo,Kashiwa, Chiba 277-8581, Japan<br />

3<br />

SPSMS, CEA-Grenoble, 38054 Grenoble Cedex 9, France<br />

The β-pyrochlore oxides AOs 2O 6 (A = K, Rb and Cs) have attracted much interest because<br />

of their unusual electr<strong>on</strong>ic properties including the superc<strong>on</strong>ductivity[1]. A unique feature<br />

of this system is the presence of the remarkable anharm<strong>on</strong>ic vibrati<strong>on</strong> of an A i<strong>on</strong>, called<br />

'rattling' moti<strong>on</strong>. Although it has been pointed out by various studies that the rattling moti<strong>on</strong><br />

plays an important role for the occurrence of superc<strong>on</strong>ductivity in this system, its c<strong>on</strong>crete<br />

role for superc<strong>on</strong>ductivity have not been understood yet. In order to clarify the interplay<br />

between the rattling moti<strong>on</strong> and superc<strong>on</strong>ductivity, we study the pressure (P) evoluti<strong>on</strong> of<br />

superc<strong>on</strong>ductivity in magnetic field (H) at low temperatures (T). The rattling moti<strong>on</strong> could be<br />

affected by pressure through the modificati<strong>on</strong> of the crystal lattice. In this paper, we report the<br />

T-H-P phase diagram of AOs 2O 6 and K 0.8Rb 0.2Os 2O 6 obtained by specific heat measurements<br />

and discuss the pressure variati<strong>on</strong> of the electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> coupling and ph<strong>on</strong><strong>on</strong> frequency.<br />

We dem<strong>on</strong>strate that the n<strong>on</strong>-m<strong>on</strong>ot<strong>on</strong>ous pressure dependence of the transiti<strong>on</strong> temperature<br />

can be explained in terms of the competiti<strong>on</strong> between the enhancement of the electr<strong>on</strong>ph<strong>on</strong><strong>on</strong><br />

coupling and the suppressi<strong>on</strong> of the ph<strong>on</strong><strong>on</strong> frequency.<br />

[1]Y.Nagao et al., J.Phys.Soc.Jpn. 78 064702 (2009)<br />

Inverse magnetic proximity effects in superc<strong>on</strong>ducting Sn-Ni<br />

nanoparticle assemblies<br />

Chi-hung Lee, Yen-cheng Chen, Chin-wei Wang and Wen-hsien Li*<br />

Physics, Nati<strong>on</strong>al Central University, Taiwan<br />

Although the superc<strong>on</strong>ductivity of the element Sn, in their bulk form, is believed<br />

to be associated with the spin-singlet s-wave pairing, it is now known that the<br />

superc<strong>on</strong>ducting parameters are str<strong>on</strong>gly dependent <strong>on</strong> the physical size of the system.<br />

Here, we report <strong>on</strong> the results of magnetizati<strong>on</strong>, magnetic susceptibility and resistivity<br />

measurements made <strong>on</strong> Sn, Sn-Ni and Sn-Au nanoparticle assemblies. The thermal<br />

profiles of the magnetic susceptibility of Sn nanoparticle assemblies can be described<br />

by Scalapino’s expressi<strong>on</strong>. Inverse magnetic proximity effect is observed, as the TC of<br />

the superc<strong>on</strong>ducting nanoparticles is found to be noticeably increased, when magnetic<br />

Ni nanoparticles are introduced into the vicinity of the superc<strong>on</strong>ducting nanoparticles.<br />

Closing up the spatial separati<strong>on</strong>s between Sn and Ni nanoparticles leads to a further<br />

increase in TC. There is a critical Ni compositi<strong>on</strong> and a critical spatial separati<strong>on</strong><br />

between the magnetic and superc<strong>on</strong>ducting nanoparticles that must be reached before<br />

their magnetic proximity will suppress the superc<strong>on</strong>ductivity. On the other hand, the<br />

inverse proximity effect of the In-Ni nanoparticle assemblies is not observed in the (Sn-<br />

C)14(Au-A)86 nanoparticle assembly, where TC of Sn remains essentially unaltered<br />

by cold pressing. A qualitative mechanism is proposed to understand the present<br />

observati<strong>on</strong>s.<br />

Pressure study <strong>on</strong> anisotropic electrical resistivity of Hg-doped<br />

CeRhIn 5<br />

So<strong>on</strong>beom Seo 1 , Sol Ju 1 , E.d. Bauer 2 , J.d. Thomps<strong>on</strong> 2 and Tus<strong>on</strong> Park 1 *<br />

1 Physics, Sungkyunkwan University, Korea<br />

2 Physics, Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

The stoichiometric compound CeRhIn 5 is a prototypical antiferromagnet where Ce 4f<br />

moments align below 3.8 K. With increasing pressure, the antiferromagnetic ordering<br />

of CeRhIn 5 disappears and the superc<strong>on</strong>ducting state emerges. When doped with<br />

Hg, the antiferromagnetic transiti<strong>on</strong> TN initially decreases and develops a different<br />

magnetic structure with further increasing Hg c<strong>on</strong>centrati<strong>on</strong>. In this research, we<br />

focused <strong>on</strong> a 0.45 % Hg-doped CeRhIn 5, where TN is suppressed from 3.8 K to 3.4 K<br />

and the magnetic structure is same as that of the undoped compound with Q=(1/2, 1/2,<br />

0.298). By applying hydrostatic pressure, we suppressed TN to zero and measured the<br />

anisotropic electrical transport measurements for the electrical current applied within<br />

and perpendicular to the Ce-In plane. Evoluti<strong>on</strong> of the anisotropic transport property<br />

across the quantum critical point will be discussed.<br />

July 8 - 13, 2012 Busan, Korea 15<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PC20<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

C<strong>on</strong>trol of superc<strong>on</strong>ductivity in parity mixing superc<strong>on</strong>ductors<br />

Li 2T 3B(T:Pt,Pd) by n<strong>on</strong>-magnetic impurity and defect doping<br />

Guizhi Bao 1 , Gaku Eguchi 2 , Akiko Ono 3 , Yoshihiko Inada 4 , Yoshiteru Maeno 2 and Guo-qing Zheng 1<br />

1 Department of Physics, Okayama University, Japan<br />

2 Department of Physics, Graduate School of Science, Kyoto University, Japan<br />

3 Graduate School of Educati<strong>on</strong>, Okayama university, Japan<br />

4 Graduate school of Natural Science and Technology, Graduate School of Educati<strong>on</strong>,<br />

Okayama university, Japan<br />

Recently, superc<strong>on</strong>ductors with n<strong>on</strong>centrosymmetric crystal structures like Li 2T 3B (T:Pd, Pt) have been the focus<br />

of in-depth research with its parity mixing nature. Previous studies of NMR and penetrati<strong>on</strong> depth measurements<br />

suggested that Li 2Pt 3B is a spin triplet dominant and Li 2Pd 3B is a s-wave spin singlet dominant superc<strong>on</strong>ductor,<br />

approximately 2:3 and 4:1 ratio of spin singlet and spin triplet order parameters, respectively [1-3]. It is known<br />

that s-wave superc<strong>on</strong>ductor without the sign inversi<strong>on</strong> of the order parameter <strong>on</strong> the Fermi surface is not affected<br />

by n<strong>on</strong>-magnetic impurity and defects doping as c<strong>on</strong>trasted to that of a n<strong>on</strong> s-wave superc<strong>on</strong>ductor. In this<br />

research, we prepared different quality samples by substituting B with Al. Sample qualities were estimated by<br />

residual resistivity. Li 2Pd 3B exhibits the small Tc suppressi<strong>on</strong> attributed by the n<strong>on</strong>-magnetic impurities and<br />

defects, while Hc 2(0) value increased. This behavior is similar in ordinary s-wave superc<strong>on</strong>ductor. While results<br />

for Li 2Pt 3B show that Tc and Hc 2(0) value were found to be suppressed by disorder. However, the rate of Tcsuppressi<strong>on</strong><br />

by disorder has been found to be not so large to be explained by the pair-breaking effect expected for<br />

the n<strong>on</strong> s-wave superc<strong>on</strong>ductor. Further details will be outlined during the actual presentati<strong>on</strong>.<br />

[1] Nshiyama M, Inada Y, and Zheng Guo-qing, 2007 Phys.Rev. Lett. 98, 047002 [2] Nshiyama M, Inada Y,<br />

and Zheng Guo-qing, 2005 Phys.Rev. B 71, 220505 [3] H. Q. Yuan et al., Phys. Rev. Lett. 97 (2006) 017006<br />

PC21<br />

Pressure-induced metal-insulator transiti<strong>on</strong> of Mott insulator Ba 2IrO 4<br />

Daisuke Orii 1 *, Masafumi Sakata 1 , Atsushi Miyake 1 , Katsuya Shimizu 1 , Hirotaka<br />

Okabe 2 , Masaaki Isobe 2 , Eiji Muromachi 2 and Jun Akimitsu 3<br />

1 KYOKUGEN, Osaka Univ., Japan<br />

2 NIMS, Japan<br />

3 Aoyama Gakuin Univ., Japan<br />

Ba 2IrO 4 is an antiferromagnetic Mott insulator, because the large spin-orbit<br />

interacti<strong>on</strong>s of the 5d electr<strong>on</strong>s in Ir atoms lift the energy levels. The magnetic<br />

moment is suppressed to ~ 0.34 μB/Ir atom because of the spin fluctuati<strong>on</strong>, and the<br />

Neel temperature TN is ~ 240 K. These magnetic properties are similar to <strong>on</strong>es of<br />

La 2CuO 4, which is the parent material of a high-Tc superc<strong>on</strong>ductor [1-3]. The crystal<br />

structures are also similar. Here, in order to inhibit the insulating state and to search the<br />

superc<strong>on</strong>ducting phase, the electrical resistivity of Ba 2IrO 4 has been performed under<br />

high pressure. According to the present results, metal-insulator transiti<strong>on</strong> was observed<br />

at 28 GPa, but not the superc<strong>on</strong>ducting transiti<strong>on</strong> above 50 mK.<br />

[1] H. Okabe et al.: Phys. Rev. B, 83, 155118 (2011). [2] D. Vaknin et al.: Phys. Rev. Lett., 58, 2802<br />

(1987). [3] T. Freltoft et al.: Phys. Rev. B, 36, 826 (1987).<br />

PC22<br />

Charge and spin order of charge stripe ordered La2-xSrxCoO4 Paul G. Freeman 1 , E. Wechke 2 , E. Schierle 2 , A. T. Boothroyd 3 and D. P 3<br />

1<br />

Helmholtz-Zentrum Berlin, Germany; EPFL, Lausanne, Swizerland; ILL, Grenoble,<br />

France<br />

2<br />

Helmholtz-Zentrum Berlin, Germany<br />

3<br />

Department of Physics, Oxford University, United Kingdom<br />

Since the discovery of charge stripe order in the cuprates, the role of stripes in high<br />

temperature superc<strong>on</strong>ductivity, and whether charge stripes are ubiquitous to the cuprates<br />

has been under intensive debate[1]. Recent neutr<strong>on</strong> scattering studies of cobalt and<br />

manganese based charge-stripe ordered materials have dem<strong>on</strong>strated how the striking<br />

hourglass excitati<strong>on</strong> spectrum of the cuprates is c<strong>on</strong>sistent with charge-stripe order[2,3].<br />

One important experimental observati<strong>on</strong> in charge-stripe ordered La 2-xSr xCoO 4 is<br />

however presently missing, direct observati<strong>on</strong> of stripe charge order itself. Although<br />

alternative forms of charge order has been observed in cobaltates in the form of a<br />

checkerboard charge ordered state and a proposed charge river state[4,5]. Here we use<br />

the technique of res<strong>on</strong>ant soft x-ray scattering to study by diffracti<strong>on</strong> the spin and charge<br />

ordering of the charge-stripe phase of La 2-xSr xCoO 4. We report our analysis of the diffuse<br />

order recorded in our study, this study completes the evidence for the charge-stripe<br />

model of this system that is used to explain the hourglass spin excitati<strong>on</strong> spectrum.<br />

[1] M. Tranquada, et. al., Nature 375, 561 (1995). [2] A. T. Boothroyd, et. al., Nature 471, 341-344<br />

(2011). [3] H. Ulbrich, et. al., arXiv:1112.1799. [4] I. A. Zaliznyak, et. al. Phys. Rev. Let. 85, 4353<br />

(2000). [5] N. Sakiyama, et. al. Phys. Rev. B 78, 180406(R) (2008).<br />

16 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PC23<br />

Str<strong>on</strong>g enhancement of superc<strong>on</strong>ductivity in inorganic electride<br />

12CaO•7Al 2O 3:e- under high pressure<br />

Shigeki Tanaka 1 *, Tomoki Kato 1 , Atsushi Miyake 1 , Tomoko Kagayama 1 , Katsuya<br />

Shimizu 1 , Sung Wng Kim 2 , Satoru Matsuishi 3 and Hideo Hos<strong>on</strong>o 4<br />

1 KYOKUGEN, Osaka University, Japan<br />

2 Fr<strong>on</strong>tier Research Center, Tokyo Institute of Technology, Japan<br />

3 Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

4 Fr<strong>on</strong>tier Research Center, Materials and Structures Laboratory, Tokyo Institute of<br />

Technology, Japan<br />

The nanoporous main group oxide 12CaO•7Al 2O 3 (C 12A 7) is a compound in the<br />

system CaO-Al 2O 3 and is used widely as a c<strong>on</strong>stituent of aluminous cements. It can be<br />

transformed from a wide-gap insulator to a metal with substituting electr<strong>on</strong>s for ani<strong>on</strong>s<br />

in cages c<strong>on</strong>stituting a positive frame. A superc<strong>on</strong>ducting transiti<strong>on</strong> was found at Tc<br />

= 0.2-0.4 K for C 12A 7 electride (C 12A 7:e-) doped with ani<strong>on</strong>ic electr<strong>on</strong>s to 2*10^21<br />

per cubic centimeter[1]. We carried out the ac-susceptibility measurement of single<br />

crystalline C 12A 7:e- under high pressure using a pist<strong>on</strong>-cylinder cell and a diam<strong>on</strong>d<br />

anvil cell. With increasing pressure, Tc m<strong>on</strong>ot<strong>on</strong>ically increases up to 1.0 K at 2.4 GPa.<br />

In additi<strong>on</strong>, the upper critical field Hc 2 (T) and -dHc 2/dT becomes larger. The density of<br />

states at the Fermi level is estimated to increase under high pressure, in agreement with<br />

dTc/dP > 0.<br />

[1] M. Miyakawa et al., J. Am. Chem. Soc. Vol. 129 (2007) 7270.<br />

PC24<br />

Superc<strong>on</strong>ductivity in c<strong>on</strong>ical magnets<br />

Gertrud Zwicknagl<br />

Technische Universitaet Braunschweig, Germany<br />

The influence of spatially modulated exchange fields <strong>on</strong> superc<strong>on</strong>ducting properties<br />

is discussed. Of particular interest are c<strong>on</strong>ical magnets where the n<strong>on</strong>-collinear<br />

magnetic structure permits to c<strong>on</strong>trol the symmetry of the pair wave functi<strong>on</strong>. The<br />

limiting cases - homogeneous ferromagnetic and anti-ferromagnetic exchange<br />

field - have been extensively studied. The central focus of the present work is the<br />

variati<strong>on</strong> with modulati<strong>on</strong> length of the superc<strong>on</strong>ducting properties. I discuss the<br />

evoluti<strong>on</strong> of the induced triplet comp<strong>on</strong>ents and analyze their orbital structures. Spinresolved<br />

tunnelling spectra highlight the cross-over from typical pair-breaking to pairweakening<br />

which occurs when the magnetic modulati<strong>on</strong> length is comparable to the<br />

superc<strong>on</strong>ducting coherence length in the absence of exchange fields.<br />

PC25<br />

Observati<strong>on</strong> of Bose-metallic phase in Ta Films<br />

Sungyu Park* and Eunse<strong>on</strong>g Kim<br />

Center for Supersolid & Quantum matter Research, Department of Physics, KAIST,<br />

Daeje<strong>on</strong>, 305-701, Korea<br />

Superc<strong>on</strong>ductor-insulator transiti<strong>on</strong> has been induced by tuning film thickness or<br />

magnetic field [1-3]. Recent electrical transport measurements of Ta thin films<br />

revealed an interesting intermediate metallic phase which intervened superc<strong>on</strong>ducting<br />

and insulating phases in the zero temperature limit [4]. The resistance of Ta films in<br />

this regime exhibited a sharp drop at the transiti<strong>on</strong> temperature but a finite saturated<br />

value at low temperatures. In additi<strong>on</strong>, IV characteristic curves showed n<strong>on</strong>-linear<br />

resp<strong>on</strong>se, indicating possible appearance of a new metallic phase. The intriguing<br />

quantum metallic phase can be interpreted as a c<strong>on</strong>sequence of vortex dynamics or<br />

dislocati<strong>on</strong> resp<strong>on</strong>se in the vortex lattice [5]. Here we present systematic studies <strong>on</strong> the<br />

superc<strong>on</strong>ductor-metal-insulator transiti<strong>on</strong> and n<strong>on</strong>linear transport in two dimensi<strong>on</strong>al<br />

Ta films.<br />

[1] M. P. A. Fisher, PRL 65, 923 (1990) [2] D. B. Haviland, et al. PRL 62. 2180 (1989) [3] V. F.<br />

Gantmakher, et al. JETP Letters 71, 160 (2000) [4] Y. Li, et al. PRB 81, 020505 (2010) [5] D.<br />

Ephr<strong>on</strong>, et al. PRL 76, 1529 (1996)


PC26<br />

N<strong>on</strong>-trivial vortex dynamics in a superc<strong>on</strong>ducting Corbino disk<br />

Masaru Kato and David E. Fujibayashi<br />

Department of Mathematical Sciences, Osaka Prefecture University, Japan<br />

Using the molecular dynamics method for vortex moti<strong>on</strong> and the finite element method<br />

for heat transport, we investigate the vortex moti<strong>on</strong> in a superc<strong>on</strong>ducting corbino disk,<br />

where an external current is injected at the center of the disk and flows toward the<br />

perimeter of the disk. For this geometry, vortices move circularly, but velocity of the<br />

vortices is large around the center and small at the edge of the disk, according to the<br />

magnitude of the external current density. Moving vortices cause resistivity and heat,<br />

and therefore there appear n<strong>on</strong>-uniform temperature distributi<strong>on</strong>. This n<strong>on</strong>-uniform<br />

temperature distributi<strong>on</strong> makes the vortices out of their circular moti<strong>on</strong> through entropy<br />

force. Therefore the moti<strong>on</strong> in the superc<strong>on</strong>ducting corbino disk becomes n<strong>on</strong>-trivial<br />

<strong>on</strong>e. We focused <strong>on</strong> the how heat transport to the outside of superc<strong>on</strong>ductors, such as<br />

a substrate under the superc<strong>on</strong>ductor, affect the vortex moti<strong>on</strong>. And we find that firstly<br />

the vortices move toward the edge of the disk, but finally they form laminar flow for<br />

large heat resistance to the substrate but they show a peculiar ordered state for small<br />

heat resistance. We show details of these vortex moti<strong>on</strong>s.<br />

PC27<br />

Coexistence of ferromagnetism and superc<strong>on</strong>ductivity in single-phase<br />

Bi 3Ni nanostructures<br />

Thomas Herrmannsdoerfer 1 *, Richard Skrotzki 1 , Rico Schoenemann 1 , Yurii Skourski 1 ,<br />

Joachim Wosnitza 1 , Daniel Koehler 2 , Regine Boldt 2 and Michael Ruck 2<br />

1 Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, Germany<br />

2 Department of Chemistry and Food Chemistry, TU Dresden, Germany<br />

We have dem<strong>on</strong>strated the coexistence of superc<strong>on</strong>ductivity and ferromagnetism in Bi 3Ni<br />

nanostructures which have been prepared by making use of novel chemical-reacti<strong>on</strong> paths [1]. We<br />

have characterized their magnetic and superc<strong>on</strong>ducting properties by means of SQUID magnetometry,<br />

ac susceptometry, and electrical-transport measurements in a wide field and temperature range. Here,<br />

we also present recent experiments <strong>on</strong> novel nanostructures, such as m<strong>on</strong>odisperse spherical clusters<br />

with a diameter of 8 nm as well as nanofibers. Pulsed-field susceptibility data up to 60 T allow for<br />

a determinati<strong>on</strong> of the saturati<strong>on</strong> magnetizati<strong>on</strong> of Bi 3Ni nanostructures. Resistivity measurements<br />

performed <strong>on</strong> moderately compacted Bi 3Ni nano fibers down to 40 mK have shown clear evidence<br />

for the existence of an isosbestic point. Superc<strong>on</strong>ductivity in c<strong>on</strong>fined Bi 3Ni emerges in the<br />

ferromagnetically ordered phase and is stable up to remarkably high magnetic fields. This coexistence<br />

would most likely be possible in the case of triplet pairing. The absence of an inversi<strong>on</strong> center of the<br />

lattice of Bi 3Ni nanostructures would allow for the formati<strong>on</strong> of an antisymmetric spatial comp<strong>on</strong>ent<br />

of the electr<strong>on</strong>-wave functi<strong>on</strong> and could lead to a significant admixture of a spin-triplet comp<strong>on</strong>ent of<br />

the order parameter. Part of this work was supported by EuroMagNET, EU-c<strong>on</strong>tract No. 228043.<br />

[1] T. Herrmannsdorfer, R. Skrotzki, J. Wosnitza, D. Kohler, R. Boldt, M. Ruck, Phys. Rev. B 83, 140501(R) (2011)<br />

PC28<br />

Observati<strong>on</strong> of twofold symmetry breaking in the gap functi<strong>on</strong> of<br />

heavy-fermi<strong>on</strong> superc<strong>on</strong>ductor UPt3 Yo Machida 1 , Atsushi Itoh 1 , Yoshitaka So 1 , Koichi Izawa 1 *, Yoshinori Haga 2 , Etsuji<br />

Yamamoto 2 , Noriaki Kimura 3 and Yoshichika Onuki 4<br />

1<br />

Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan<br />

2<br />

Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan<br />

3<br />

Graduate School of Science and Center for Low Temperature Science, Tohoku Universit, Miyagi<br />

980-8577, Japan<br />

4<br />

Graduate School of Science, Osaka University, Toy<strong>on</strong>aka, Osaka 560-0043, Japan<br />

WITHDRAWN<br />

PC29<br />

PC30<br />

PC31<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Investigati<strong>on</strong> of the three-dimensi<strong>on</strong>al electr<strong>on</strong>ic structure of MgB 2 by<br />

soft X-ray angle-resolved photoelectr<strong>on</strong> spectroscopy<br />

Y. Sassa 1 *, M. Manss<strong>on</strong> 1 , B. M. Wojek 2 , M. Kobayashi 3 , V. Strocov 3 , O. Tjernberg 2 , N.<br />

D. Zhigadlo 1 and B. Batlogg 1<br />

1 Laboratory of Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland<br />

2 Materials Physics, Royal Institute of Technology KTH, S-16440 Kista,, Sweden<br />

3 Swiss Light Source, Paul Scherrer Institute, CH- 5234 Villigen PSI, Switzerland<br />

WITHDRAWN<br />

Vortex channeled effect in Nb thin film with artificial pinning array<br />

Tian-chiuan Wu 1 *, Lance Horng 2 , J<strong>on</strong>g-ching Wu 2 and R<strong>on</strong>g Cao 2<br />

1 Department of Electrical Engineering, Nati<strong>on</strong> Formosa University, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al Changhua University of Educati<strong>on</strong>, Taiwan<br />

The vortex pinning effect is a fundamental characteristic in type II superc<strong>on</strong>ductors.<br />

Vortex dynamics in the mixed state in type-II superc<strong>on</strong>ductors is str<strong>on</strong>gly influenced by<br />

the pinning centers. We have studied a channeled-like pinning potential in Nb thin films<br />

which is formed by the pinned vortices. Nb films with periodic pinning arrays show<br />

matching effects in the magnetic field dependence of the resistivity and Hall Effect. It<br />

is suggested that the moti<strong>on</strong> of interstitial vortices has great influence by the channel.<br />

When vortices propagate through these arrays, both the l<strong>on</strong>gitudinal and transversal<br />

voltages show cusp-like anomalies at matching fields. Vortices can be guided by the<br />

channel formed between pinned vortices.<br />

[1] R. Cao, T.C. Wu, P.C. Kang, J.C. Wu, T.J. Yang, Horng Lance, Solid State Comm. 143 (2007)<br />

171. [2] M. Baert, V.V. Metlushko, R. J<strong>on</strong>ckheer, V.V. Moshchalkov, Y. Bruynseraede, Phys. Rev. Lett.<br />

74 (1995) 3269. [3] J.E. Villegas, E.M. G<strong>on</strong>zalez, M.I. M<strong>on</strong>tero, Ivan K. Schuller, J.L. Vicent, Phys.<br />

Rev. B 68 (2003) 224504.<br />

Role of the third dimensi<strong>on</strong> <strong>on</strong> the spectral property and transport<br />

behaviour in layered cuprates<br />

Bhagya Sindhu Tewari<br />

Physics, University of Petroleum and Energy Studies, Dehradun, India<br />

In the present work, we have analyzed the influence of the third dimensi<strong>on</strong> coupling<br />

<strong>on</strong> the normal state electr<strong>on</strong>ic spectra of bilayer cuprates employing Green’s functi<strong>on</strong><br />

equati<strong>on</strong>s of moti<strong>on</strong> approach within tight binding extended Hubbard model and<br />

model, which necessarily includes the three site exchange interacti<strong>on</strong> (J3) and the inter<br />

unit cell res<strong>on</strong>ant tunneling (T12). The influence of inter unit cell res<strong>on</strong>ant tunneling <strong>on</strong><br />

the out of plane (c-axis) c<strong>on</strong>ductivity has also been analyzed for cuprates employing<br />

Kubo formula and Green’s functi<strong>on</strong> technique. On the basis of numerical computati<strong>on</strong>,<br />

it is found that the inter cell res<strong>on</strong>ant tunneling (T12) introduces a broadening in the<br />

spectral functi<strong>on</strong> and increases the c-axis c<strong>on</strong>ductivity. It is also found that the J3 term<br />

suppresses the bilayer splitting in the electr<strong>on</strong>ic spectra. These results are viewed in<br />

terms of recent ARPES measurements.<br />

[1] S. Chakravarty, et. al, Science 61 (1993) 337 [2] E.Dagotto, Rev. Mod. Phys. 68(1994)763<br />

[3] Y.D.Chaung, et.al, Phys. Rev. Lett. ,87 (2001) 117002, [4] B.S. Tewari et. al, Eur.Phys.J. B,<br />

66(2008)67 [5] Q.P.Li, et. al, Phys. Rev. B, 48(1993) 437 [6] R.kubo, J.Phys soc. Japan, 28, (1957)<br />

1402 [7] W.C. Wu, et. Al, J. Superc<strong>on</strong>d. 11, 305 (1998) 305 [8] B.S. Tewari et. al, Physica C 468<br />

(2008) 237 [9] B.E.C. Koltenbah, et. Al, Rev. Mod. Phys. 60 (1997) 23<br />

July 8 - 13, 2012 Busan, Korea 17<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PD01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ground dielectric state of the Mott-doped material<br />

Vladimir Gavrichkov*<br />

Krasnoyarsk, Kirensky Institute of Physics, Russia<br />

Using analytic calculati<strong>on</strong>s, within the framework of the Russell-Saunders scheme<br />

we investigated the dependence of the number of valence states <strong>on</strong> a doping level x<br />

in the full package of the valence bands for the Mott-doped material. According to<br />

our calculati<strong>on</strong>s the total number of valence states Nv(x) coincides with the number<br />

of electr<strong>on</strong>s per unit cell (N-x) if there is a ban (both spin S-, and orbit L-) <strong>on</strong> the first<br />

removal quasiparticle states (frs). Thus is formed an insulating ground state of the<br />

doped material at the T=0K. We believe that such materials with the forbidden frs<br />

states can be attributed the manganites with the L-forbidden states and cobaltites with<br />

the S-forbidden states.<br />

PD02<br />

Temperature-dependent ph<strong>on</strong><strong>on</strong> anomalies in uranium and plut<strong>on</strong>ium<br />

compounds<br />

Peter S Riseborough*<br />

Physics, Temple University, USA<br />

There is evidence that a number of heavy-fermi<strong>on</strong>/mixed-valent materials show<br />

str<strong>on</strong>gly renormalized hybridizati<strong>on</strong> gaps either at the Fermi-energy or close to the<br />

Fermi-energy. In the former case, a heavy-fermi<strong>on</strong> semic<strong>on</strong>ducting state ensues and in<br />

the later case, the system remains metallic at low temperatures. Due to the temperaturedependence<br />

of the electr<strong>on</strong>ic correlati<strong>on</strong>s, the magnitudes of the hybridizati<strong>on</strong> gaps<br />

decrease with increasing temperatures. The existence of a temperature-dependent lowenergy<br />

electr<strong>on</strong>ic energy scale opens up the possibility that the Born-Oppenheimer<br />

approximati<strong>on</strong> may fail and that there may be a res<strong>on</strong>ant coupling between the<br />

ph<strong>on</strong><strong>on</strong>s and the electr<strong>on</strong>ic excitati<strong>on</strong>s. It is argued that such a mechanism may be the<br />

cause of the anomalous temperature-dependence of the ph<strong>on</strong><strong>on</strong> spectrum in Pu and the<br />

anomalous ph<strong>on</strong><strong>on</strong> mode observed in α-uranium.<br />

PD03<br />

N<strong>on</strong>-linear c<strong>on</strong>ductivity of resistive oxides: truths and myths<br />

B. - Fisher*, J. - Genossar, L. - Patlagan and G. M. Reisner<br />

Physics, Techni<strong>on</strong>, Israel<br />

WITHDRAWN<br />

18 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PD04<br />

The modulated spin liquid and hidden order in URu 2Si 2<br />

Sebastien Burdin<br />

Bordeaux University, France<br />

We have shown that near a K<strong>on</strong>do breakdown critical point, a spin liquid with spatial<br />

modulati<strong>on</strong>s is likely to be formed. Unlike its uniform counterpart, we find that this<br />

occurs via a sec<strong>on</strong>d order phase transiti<strong>on</strong>. The amount of entropy quenched when this<br />

ordering is manifest is of the same magnitude as for an antiferromagnet. Moreover,<br />

these two states are in direct competiti<strong>on</strong> with each other, and at low temperatures they<br />

are separated by a first order phase transiti<strong>on</strong>. This suggests that the modulated spin<br />

liquid is indeed a viable candidate for the unique phase of matter which is observed<br />

in the hidden order phase of URu 2Si 2. We investigate the modulated spin liquid<br />

proposal taking full account of the tetrag<strong>on</strong>al-body-centered lattice structure which<br />

characterizes URu 2Si 2. We find that the physical quantities predicted from the model<br />

are in very good qualitative and quantitative agreement with recent experiments,<br />

including thermodynamic properties, inelastic neutr<strong>on</strong> scattering, and Fermi surface<br />

measurements. We also present an overview of other f-electr<strong>on</strong> compounds where<br />

similar phases have been observed.<br />

Refs. : C. Pepin, M.R. Norman, S. Burdin, and A. Ferraz, Phys. Rev. Lett. 106, 106601 (2011) C.<br />

Thomas, S. Burdin, C. Pepin, and A. Ferraz, in preparati<strong>on</strong>.<br />

PD05<br />

Fermi-surface evoluti<strong>on</strong> in Yb-substituted CeCoIn 5<br />

Joachim Wosnitza 1 *, Andrey Polyakov 1 , Andrea D. Bianchi 2 , S. Blackburn 2 , B.<br />

Prevost 2 , G. Seyfarth 2 and Michel Cote 2<br />

1 Hochfeld-Magnetlabor Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany<br />

2 Department de Physique and RQMP, Universite de M<strong>on</strong>treal, M<strong>on</strong>treal H3C 3J7,<br />

Canada<br />

In CeCoIn5, substituti<strong>on</strong> <strong>on</strong> the rare-earth site has been found to influence the K<strong>on</strong>dolattice<br />

coherence and Cooper pairing in a rapid and uniform way. Yb substituti<strong>on</strong>,<br />

however, shows a different behavior in that Tc and the K<strong>on</strong>do-coherence temperature<br />

do not scale, in c<strong>on</strong>trast to other heavy-fermi<strong>on</strong> compounds. We performed a<br />

comprehensive dHvA study <strong>on</strong> Ce1-xYbxCoIn 5. For small Yb c<strong>on</strong>centrati<strong>on</strong>, x =<br />

0.1, the band-structure topology and the ef-fective masses remain nearly unchanged<br />

compared to CeCoIn 5. This c<strong>on</strong>trasts clearly modified Fermi surfaces and light, almost<br />

unrenormalized effective masses for x = 0.2 and above. These observati<strong>on</strong>s cannot<br />

explain the heavy-fermi<strong>on</strong> physics observed in specific-heat and resistivity data even<br />

for high Yb c<strong>on</strong>centrati<strong>on</strong>s. Thus, we suggest the existence of heavy quasiparticles with<br />

short mean free paths, not detectable by dHvA experiments. However, the mechanism<br />

by which superc<strong>on</strong>ductivity can emerge from these charge carriers remains elusive.<br />

Work d<strong>on</strong>e in cooperati<strong>on</strong> with K. Gotze, D. Hurt, Z. Fisk, R. G. Goodrich, I. Sheikin,<br />

M. Richter. Part of this work was supported by EuroMagNET II (EU c<strong>on</strong>tract No.<br />

228043).<br />

PD06<br />

Spin excit<strong>on</strong> formati<strong>on</strong> inside the hidden order phase of CeB 6<br />

Alireza Akbari and Peter Thalmeier<br />

MPI-CPfS, Germany<br />

The heavy fermi<strong>on</strong> metal CeB6 exhibits hidden order of antiferroquadrupolar (AFQ)<br />

type below T Q=3.2K and subsequent antiferromagnetic (AFM) order at T N=2.3K.<br />

It was interpreted as ordering of the quadrupole and dipole moments of a Γ 8 quartet<br />

of localised Ce 4f 1 electr<strong>on</strong>s. This established picture has been profoundly shaken<br />

by recent inelastic neutr<strong>on</strong> scattering[1] that found the evoluti<strong>on</strong> of a feedback spin<br />

excit<strong>on</strong> res<strong>on</strong>ance within the hidden order phase at the AFQ wave vector appears and<br />

is stabilized by the AFM order. We develop an alternative theory based <strong>on</strong> a fourfold<br />

degenerate Anders<strong>on</strong> lattice model, including both order parameters as particle-<br />

hole c<strong>on</strong>densates of itinerant heavy quasiparticles. This explains in a natural way<br />

the appearance of the spin excit<strong>on</strong> res<strong>on</strong>ance and the momentum dependence of its<br />

spectral weight, in particular around the AFQ vector and its rapid disappearance in the<br />

disordered phase. Analogies to the feedback effect in unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors<br />

and K<strong>on</strong>do semic<strong>on</strong>ductors are pointed out.<br />

[1] G. Friemel, et al, Nature Communicati<strong>on</strong>s 3, 830 (2012).<br />

[2] A. Akbari and P. Thalmeier, Phys. Rev. Lett. 108, 146403 (2012).


PD07<br />

Antiferromagnetic fluctuati<strong>on</strong> in hidden order phase of U(Ru,Rh) 2Si 2<br />

Makoto Yokoyama 1 *, Kenichi Tenya 2 and Hiroshi Amitsuka 3<br />

1 Faculty of Science, Ibaraki University, Japan<br />

2 Faculty of Educati<strong>on</strong>, Shinshu University, Japan<br />

3 Graduate School of Science, Hokkaido University, Japan<br />

The origin of so-called hidden-order (HO) transiti<strong>on</strong> observed at To=17.5K in URu 2Si 2<br />

has been <strong>on</strong>e of the l<strong>on</strong>gstanding issues in physics of heavy-fermi<strong>on</strong> systems. In the<br />

mixed compounds U(Ru1-xRhx) 2Si 2, it is found that a large-moment antiferromagnetic<br />

(AF) order replaces HO for 0.02≤x≤0.03 via a first-order phase transiti<strong>on</strong>, and both<br />

orders disappear above x≥0.04. To clarify microscopic features of magnetic fluctuati<strong>on</strong><br />

in both HO and AF phases, we have performed inelastic neutr<strong>on</strong> scattering experiments<br />

for U(Ru1-xRhx) 2Si 2 (x≤0.03). At the AF wave vector Q=(1,0,0), the AF excitati<strong>on</strong><br />

peak is clearly observed in HO phase for 0≤x≤0.02, but it disappears in the AF phase<br />

for 0.02≤x≤0.03. The excitati<strong>on</strong> gap at 1.4K is found to be weakly reduced from 2.4meV<br />

(x=0) to 1.8meV (x=0.015) as x is increased. Temperature variati<strong>on</strong>s of the staggered<br />

susceptibility χ(Q,T) at x=0 estimated from the inelastic-peak intensities show a<br />

weak enhancement in HO phase and a cusp-like anomaly at To. By doping Rh, the<br />

enhancement of χ(Q,T) in HO phase becomes pr<strong>on</strong>ounced, but a cusp-like anomaly at<br />

To is reduced. These features indicate that the AF fluctuati<strong>on</strong> develops <strong>on</strong> the verge of<br />

the first-order phase boundary in HO phase, while it is suppressed in the AF phase.<br />

PD08<br />

Pressure effect <strong>on</strong> the field-induced ordered phase in heavy fermi<strong>on</strong><br />

compound YbCo 2Zn 20<br />

Tetsuya Takeuchi 1 , Yuki Taga 2 , Shingo Yoshiuchi 2 , Masahiro Ohya 2 , Yusuke Hirose 2 ,<br />

Fuminori H<strong>on</strong>da 2 , Rikio Settai 2 and Yoshichika Onuki 2<br />

1 Low Temperature Center, Osaka University, Japan<br />

2 Graduate School of Science, Osaka University, Japan<br />

We succeeded in growing high-quality single crystals of heavy fermi<strong>on</strong> compounds<br />

YbT 2Zn 20 with T = Co, Rh, and Ir, and found a metamagnetic behavior at H m below<br />

the characteristic temperature Tχmax, where the magnetic susceptibility takes a broad<br />

maximum. For YbCo 2Zn 20, H m = 6 kOe and Tχmax = 0.32 K, for example. H m and<br />

Tχmax in these compounds were found to satisfy a universal relati<strong>on</strong> H m (kOe) =<br />

15Tχmax (K). Recently, we found a field-induced ordered phase (FIOP) above H Q<br />

= 60 kOe for H // in YbCo 2Zn 20 below T Q = 0.6 K and suggested an antiferroquadrupole<br />

order for the FIOP. In this work, we performed pressure experiments in<br />

YbCo 2Zn 20 with H // in order to study the pressure effect <strong>on</strong> the FIOP as well<br />

as the pressure-induced antiferromagnetic phase (PIAF) above P c~2 GPa. When the<br />

pressure is applied, the transiti<strong>on</strong> field H Q was found to decrease with increasing<br />

pressure up to around P c. Above P c, there is a pressure regi<strong>on</strong> where the PIAF and<br />

FIOP were observed under the same pressure. In order to investigate how the FIOP<br />

disappears or merges with the PIAF, further pressure experiments are in progress under<br />

higher pressures.<br />

PD09<br />

29Si-NMR Study of antiferromagnet CeRh 2Si 2 using single crystals<br />

Hir<strong>on</strong>ori Sakai, Yo Tokunaga, Shinsaku Kambe, Yuji Matsumoto, Tatsuma D Matsuda<br />

and Yoshinori Haga<br />

Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

29Si-NMR Study of antiferromagnet CeRh 2Si 2 has been performed using single<br />

crystals. Heavy fermi<strong>on</strong> material CeRh 2Si 2 is known to be an antiferromagnet with<br />

str<strong>on</strong>g uniaxial magnetic anisotropy al<strong>on</strong>g the crystallographic c-axis under ambient<br />

pressure. From our measurements of Knight shifts and relaxati<strong>on</strong> rates, the spin<br />

dynamics of this material have been investigated. At ambient pressure, as seen in the<br />

static susceptibility, the Ising-type antiferromagnetic spin fluctuati<strong>on</strong>s al<strong>on</strong>g the c-axis<br />

has been found to be enhanced. In this presentati<strong>on</strong>, we will show our latest data and<br />

discuss about the anisotropy of hyperfine couplings and spin dynamics.<br />

PD10<br />

PD11<br />

PD12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Bulk compressibility of orthorhombic YbFe 2Al 10-type CeRu 2Al 10<br />

Yukihiro Kawamura 1 *, Kazuki Matsui 1 , Keiichi Yamamoto 1 , Yusuke Hori 1 , Junichi<br />

Hayashi 1 , Keiki Takeda 1 , Chihiro Sekine 1 and Takashi Nishioka 2<br />

1 Muroran Institute of Technology, Japan<br />

2 Kochi University, Japan<br />

Orthorhombic YbFe 2Al 10-type CeRu 2Al 10 shows antiferromagnetic transiti<strong>on</strong> at T0~27<br />

K[1]. This antiferromagnetic transiti<strong>on</strong> has various unusual features. One of them is<br />

reduced magnetic moment; The neutr<strong>on</strong> experiment reveals that the magnetic moment<br />

of Ce in the ordered phase <strong>on</strong> CeRu 2Al 10 is 0.34 μB/Ce[2]. C<strong>on</strong>sidering this reduced<br />

magnetic moment, T0 should be much lower. Another unusual feature is abrupt<br />

disappearance of antiferromagnetic transiti<strong>on</strong> by applying pressure[3]. Structural<br />

modulati<strong>on</strong> might be occurred at around the pressure of disappearing T0. Thus, we<br />

performed synchrotr<strong>on</strong> X-ray study at room temperature under pressure by using<br />

diam<strong>on</strong>d anvil pressure cell and investigated bulk compressibility of CeRu 2Al 10. We<br />

revealed that lattice parameters a, b and c m<strong>on</strong>ot<strong>on</strong>ically decreases with increasing<br />

pressure, which indicates that there is no structural modificati<strong>on</strong> up to 9.2 GPa at room<br />

temperature. We also revealed that the decrease ratio of b is smaller than that of a and c.<br />

[1] A. M. Strydom, Physica B 404 (2009) 2981-2984 [2] D. D. Khalyavin et al., Phys. Rev. B 82<br />

(2010) 100405 [3] T. Nishioka et al., J. Phys. Soc. Jpn 78 (2009) 123705<br />

Ultrasound measurements <strong>on</strong> the skutterudite compound SmOs 4P 12<br />

Yoshiki Nakanishi 1 *, Gen Koseki 1 , Dai Tamura 1 , Kohei Kurita 1 , Takeshi Saito 1 ,<br />

Minoru Koseki 1 , Mitsuteru Nakamura 1 , Masahito Yoshizawa 1 , Masahito Yoshizawa 1 ,<br />

Yuya Koyota 2 , Chihiro Sekine 2 and Takehiko Yagi 3<br />

1 Iwate University, Japan<br />

2 Muroran Institute of Technology, Japan<br />

3 ISSP The University of Tokyo, Japan<br />

We present an ultrasound study <strong>on</strong> the Sm-based filled skutterudite compound SmOs 4P 12<br />

for the first time. The measurements were performed <strong>on</strong> a polycrystalline sample using<br />

a phase-sensitive detecti<strong>on</strong> technique. The ternary compound SmOs 4P 12 were prepared<br />

at high temperature and high pressures using a wedge-type cubic-anvil high-pressure<br />

apparatus. SmOs 4P 12 exhibits antiferromagnetic ordering below 4.5 K. A clear decrease<br />

was observed at 4.5 K in the temperature dependence of both l<strong>on</strong>gitudinal and transverse<br />

elastic c<strong>on</strong>stants. However, less or no elastic softening toward the transiti<strong>on</strong> temperature<br />

was observed in the both elastic c<strong>on</strong>stants. Absence of the precursor behavior reminds us<br />

a multipolar ordering, possibly octupolar ordering observed in the isostructural system<br />

SmRu 4P 12, reported previously by our group. The transiti<strong>on</strong> is robust against the external<br />

magnetic field. To be more interesting, the elastic c<strong>on</strong>stants show a minimum around 180<br />

K, possibly related to a rattling moti<strong>on</strong> due to weakly bounded Sm i<strong>on</strong> in an oversized P<br />

cage. We argue a low-lying degenerated levels derived from 4f-multiplets ground state of<br />

Sm i<strong>on</strong> split by crystalline electric field effect in SmOs 4P 12. Furthermore, we discuss the<br />

ph<strong>on</strong><strong>on</strong>ic properties in comparis<strong>on</strong> with other isostructral systems which include an i<strong>on</strong>ic<br />

degrees of freedom of the rattling moti<strong>on</strong>.<br />

YbRh2Si2: Fermi surface and crystal-field splittings of a heavy-<br />

Fermi<strong>on</strong> compound<br />

Steffen Danzenbacher 1 , Denis V. Vyalikh 1 , Kurt Kummer 2 , Yuri Kucherenko 3 ,<br />

Cornelius Krellner 4 , Christoph Geibel 5 , Serguei L. Molodtsov 6 , Ming Shi 7 , Luc<br />

Patthey 7 and Clemens Laubschat 1 *<br />

1<br />

Institut fur Festkorperphysik, Technische Universitat Dresden, D-01062 Dresden,<br />

Germany<br />

2<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, FR-38043 Grenoble Cedex, France<br />

3<br />

Institute of Metal Physics, Nati<strong>on</strong>al Academy of Sciences of Ukraine, UA-03142<br />

Kiev, Ukraine<br />

4<br />

Max-Planck-Institut fur Chemische Physik fester Stoffe, D-01187 Dresden, Germany<br />

5<br />

Max-Planck-Institut fur Chemische Physik fester Stoffe, D-01187 Dresden, Germany<br />

6<br />

European XFEL GmbH, , D-22671 Hamburg, Germany<br />

7<br />

Swiss Light source, Paul Scherrer Institute, CH-5232 Villingen-PSI, Switzerland<br />

YbRh 2Si 2 is a well known heavy Fermi<strong>on</strong> system with a K<strong>on</strong>do temperature of 25 K and a mean valence of 2,9.<br />

Due to the mixing of 4f14 and 4f13 c<strong>on</strong>figurati<strong>on</strong>s in the ground state, the 4f13 state is reproduced as a final<br />

state in a photoemissi<strong>on</strong> experiment allowing for direct observati<strong>on</strong> of near ground state properties. Angleresolved<br />

photoemissi<strong>on</strong> spectra reveal a general dispersi<strong>on</strong> of the 4f13 state with a Fermi-level crossing around<br />

the Γ-point. A clear wave-vector dependence of the crystal-field split states is observed that leads to a variati<strong>on</strong><br />

of the energy splittings across the Brillouin z<strong>on</strong>e and even to an interchange of the sequence of states. The bulk<br />

Fermi surface reveals str<strong>on</strong>g similarities with the <strong>on</strong>e expected for a stable trivalent compound, but is slightly<br />

larger, reveals str<strong>on</strong>g 4f character, and deviates from LDA results by a larger regi<strong>on</strong> without states around the<br />

Γ-point. These properties are well described in the framework of a simple fd-hybridizati<strong>on</strong> model.<br />

July 8 - 13, 2012 Busan, Korea 19<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PD13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Single crystal growth and various electr<strong>on</strong>ic states in Yb-based<br />

compounds<br />

Yusuke Hirose 1 *, Shingo Yoshiuchi 1 , Naoto Nishimura 1 , Jyunya Sakaguchi 1 , Kentaro Enoki 1 , Ken<br />

Iwakawa 1 , Yasunao Miura 1 , Tetsuya Takeuchi 2 , Kiyohiro Sugiyama 1 , Fuminori H<strong>on</strong>da 3 , Etsuji<br />

Yamamoto 4 , Yoshinori Haga 4 , Masayuki Hagiwara 5 , Koichi Kindo 6 , Rikio Settai 1 and Yoshichika Onuki 1<br />

1 Graduate School of Science, Osaka University, Japan<br />

2 Low Temperature Center, Osaka University, Japan<br />

3 Graduate School of Engineering Science, Osaka University, Japan<br />

4 Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

5 KYOKUGEN, Osaka University, Japan<br />

6 ISSP, University of Tokyo, Japan<br />

To clarify the various electr<strong>on</strong>ic states of Yb compounds, we grew single crystals of several Yb compounds such<br />

as YbTIn 5 (T : Co, Rh, Ir), YbCoGa 5, YbT 2Zn 20 (T : Co, Rh, Ir) and Yb 2Pt 2Pb by the flux method, and YbPdGe<br />

and YbPd 5Al 2 by the Bridgman method. YbTIn 5 and YbCoGa 5 are Pauli paramagnets, but the cyclotr<strong>on</strong><br />

effective mass of YbCoGa 5 is by four times larger than that of YbTIn 5. YbT 2Zn 20 (T : Co, Rh, Ir) compounds are<br />

heavy fermi<strong>on</strong> compounds. In fact, the electr<strong>on</strong>ic specific heat coefficient γ is 8000 mJ/K2•mol in YbCo 2Zn 20,<br />

very close to the quantum critical point. YbPdGe is an Ising-type ferromagnet with the Curie temperature TC =<br />

11.4 K and a saturated magnetic moment μs = 1.7 μB/Yb, but possesses a relatively large value of γ = 150 mJ/<br />

K2•mol. Yb 2Pt 2Pb is a Shastry-Sutherland-type antiferromagnet with the Neel temperature TN = 2.1 K. Finally,<br />

YbPd 5Al 2 of which the analogue is a heavy fermi<strong>on</strong> superc<strong>on</strong>ductor NpPd 5Al 2 is a well-known heavy fermi<strong>on</strong><br />

superc<strong>on</strong>ductor[1] is an antiferromagnet with a very small Neel temperature TN = 0.19 K.<br />

[1] D. Aoki et al. : J. Phys. Soc. Jpn. 76 (2007) 063701.<br />

PD14<br />

Physical properties under pressure in a heavy fermi<strong>on</strong> superc<strong>on</strong>ductor<br />

CeIrIn5 Naofumi Aso 1 *, Yuki Tamaki 1 , Yoshinao Takaesu 1 , Masato Hedo 1 , Takao Nakama 1 ,<br />

Kiyoharu Uchima 2 , Kazuyuki Matsubayashi 3 , Yoshiya Uwatoko 3 , Yusuke Ishikawa 4 ,<br />

Kazuhiko Deguchi 4 and Noriaki K. Sato 4<br />

1<br />

Faculty of Science, University of the Ryukyus, Japan<br />

2<br />

General Educati<strong>on</strong>, Okinawa Christian Junior College, Japan<br />

3<br />

ISSP, University of Tokyo, Japan<br />

4<br />

Graduate School of Science, Nagoya University, Japan<br />

CeIrIn 5 is a heavy fermi<strong>on</strong> superc<strong>on</strong>ductor with Tc = 0.4 K and the electr<strong>on</strong>ic specific heat γ = 700 mJ/(K2•mol)<br />

[1]. To investigate the nature and the pressure effect of the K<strong>on</strong>do effect <strong>on</strong> CeIrIn5, electrical resistivity ρ and<br />

magnetizati<strong>on</strong> M under pressure in CeIrIn 5 have been measured using the single-crystalline CeIrIn 5 which<br />

were grown by the In-flux method. The temperature dependence between 2.0 K and 300 K of the a-axis and<br />

c-axis electrical resistivity ρ of CeIrIn 5 under pressure up to 8.0 GPa, which were obtained using a cubic anvil<br />

device, exhibits the typical dense K<strong>on</strong>do behavior: <strong>on</strong> cooling from room temperature at P = 1.0 GPa, the ρ<br />

increases and shows a maximum of the coherence peak, and then goes down into the coherent K<strong>on</strong>do state.<br />

We also find that the coherence peak moves to higher temperatures with pressure, indicating that the K<strong>on</strong>do<br />

temperature of CeIrIn 5 increases by applying the pressure. In the c<strong>on</strong>ference, we will also report the M data<br />

under pressure up to 1.5 GPa and compare the ρ data with our recent thermoelectric power S measurements,<br />

which exhibit a large positive value up to 90 μV/K with a sharp maximum in its temperature dependence. [2]<br />

[1] C. Petrovic et al., Europhys Lett., 53, 354, (2001). [2] Y. Takaesu et al., J. Phys.: C<strong>on</strong>f. Series, 273, 012058, (2011).<br />

PD15<br />

Periodic Anders<strong>on</strong> model with correlated c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s<br />

Imre Hagymasi*, Kazumasa Itai and Jeno Solyom<br />

Theoretical Solid State Physics, Wigner Research Centre for Physics, Hungarian<br />

Academy of Sciences, Hungary<br />

We investigate the so-called periodic Anders<strong>on</strong>-Hubbard model with the aim to<br />

understand the role of interacti<strong>on</strong> between c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s in the formati<strong>on</strong> of the<br />

heavy-fermi<strong>on</strong> and mixed-valence states [1]. We perform variati<strong>on</strong>al calculati<strong>on</strong> using<br />

the Gutzwiller wave functi<strong>on</strong> and exact diag<strong>on</strong>alizati<strong>on</strong> of the Hamilt<strong>on</strong>ian for short<br />

chains. The f-level occupancy and the renormalizati<strong>on</strong> factor of the quasiparticles are<br />

calculated as a functi<strong>on</strong> of the energy of the f-orbital for a wide range of the interacti<strong>on</strong><br />

parameters. The results obtained by the two methods are in reas<strong>on</strong>ably good agreement<br />

for the periodic Anders<strong>on</strong> model. The agreement remains even for the Anders<strong>on</strong>-<br />

Hubbard model, except for the half-filled case. We find that due to this interacti<strong>on</strong> the<br />

energy range of the bare f-level, where heavy-fermi<strong>on</strong> behavior can be observed, shifts<br />

and widens. The Gutzwiller method indicates a robust transiti<strong>on</strong> from K<strong>on</strong>do insulator<br />

to Mott insulator in the half-filled model, while this interacti<strong>on</strong> enhances the quasiparticle<br />

mass when the filling is close to half filling.<br />

[1] I. Hagymasi, K. Itai and J. Solyom Periodic Anders<strong>on</strong> model with correlated c<strong>on</strong>ducti<strong>on</strong><br />

electr<strong>on</strong>s: variati<strong>on</strong>al and exact diag<strong>on</strong>alizati<strong>on</strong> study, arXiv::1106.4999<br />

20 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PD16<br />

Thermoelectric study of the metamagnetic behavior in YbCo 2Z 20<br />

Yo Machida 1 , Tohru Ikeura 1 , Koichi Izawa 1 *, Shingo Yoshiuchi 2 , Fuminori H<strong>on</strong>da 2 ,<br />

Rikio Settai 2 and Yoshichika Onuki 2<br />

1 Department of Physics, Tokyo Institute of Technology, Japan<br />

2 Department of Physics, Osaka University, Japan<br />

Despite the intensive studies <strong>on</strong> the metamagnetic behavior which has been found<br />

in a wide variety of heavy fermi<strong>on</strong> materials such as CeRu 2Si 2, CeCu 6, and UPt 3,<br />

the origin remains under debate. The recent discovered heavy fermi<strong>on</strong> compound<br />

YbCo 2Zn 20 exhibits the metamagnetic behavior under unexpectedly small magnetic<br />

field ~ 0.6 T, providing a new platform for elucidati<strong>on</strong> of the metamagnetism. We<br />

have addressed this issue by means of the thermoelectric transport, which has been<br />

a promising probe to unveil the low-energy itinerant excitati<strong>on</strong>s and the electr<strong>on</strong>ic<br />

transformati<strong>on</strong> across the metamagnetic transiti<strong>on</strong>. We measured the Seebeck and<br />

Nernst coefficients of YbCo 2Zn 20 down to very low temperature. Remarkably, we<br />

found a huge Seebeck coefficient ~ -250 μV/K^2 under zero field, as an indicati<strong>on</strong> of<br />

the “super” heavy fermi<strong>on</strong> state. Moreover, <strong>on</strong> passing through the metamagnetic field<br />

the Seebeck coefficient shows dramatic suppressi<strong>on</strong>, being distinct from that observed<br />

in CeRu 2Si 2 in which the Seebeck coefficient is largely enhanced at the metamganetic<br />

field. In our presentati<strong>on</strong>, we will discuss the thermoelectric resp<strong>on</strong>se of YbCo 2Zn 20<br />

and its implicati<strong>on</strong> to the metamagnetism. The comparis<strong>on</strong> to the other metamagnetic<br />

materials will be also made.<br />

PD17<br />

Raman scattering study of the hidden order state of URu2Si2 J<strong>on</strong>athan Buhot 1 , Marie-aude Meass<strong>on</strong> 1 *, Yann Gallais 1 , Maximilien Cazayous 1 , Alain<br />

Sacuto 1 and Dai Aoki 2<br />

1<br />

Laboratoire Materiaux et Phenomenes Quantiques, UMR 7162 CNRS, Universite<br />

Paris Diderot, France, France<br />

2<br />

SPSMS, UMR-E CEA / UJF-Grenoble 1, INAC, 38054 Grenoble, France, France<br />

For over 25 years, researchers attempt to understand the microscopic origin of the<br />

Hidden Order that appears below T0=17.5 K in the heavy fermi<strong>on</strong>s compound<br />

URu 2Si 2. Mainly, optical measurements <strong>on</strong> URU 2Si 2 are far-infrared reflectance<br />

experiments[1,2]. Only few Raman scattering studies have been performed [3,4] and<br />

<strong>on</strong>ly for c axis. We have studied URu 2Si 2 for both axes, down to low temperature<br />

(2K). We have probed the ph<strong>on</strong><strong>on</strong>ic and electr<strong>on</strong>ic properties and their interacti<strong>on</strong>.<br />

Softening of ph<strong>on</strong><strong>on</strong> modes together with Fano-shape were observed, implying that<br />

a ph<strong>on</strong><strong>on</strong>-electr<strong>on</strong> coupling is at play. At low energy, electr<strong>on</strong>ic Raman signal shows<br />

either fluctuati<strong>on</strong>s or more c<strong>on</strong>venti<strong>on</strong>al Drude shape for different symmetry. We have<br />

studied both signals through the Hidden Order temperature.<br />

D.A. B<strong>on</strong>n et al., PRL 61 1305 (1988), J. Levallois et al., PRB 84, 184420 (2011) S. Cooper et al.,<br />

PRB 36 5743 (1987), D. Lampakis et al., PHYSICA B 378-380, 578 (2006)<br />

PD18<br />

The evoluti<strong>on</strong> of superc<strong>on</strong>ductivity and magnetism in Pd-doped<br />

CeRhIn 5 and Ce 2RhIn 8<br />

Marie Kratochvilova*, Klara Uhlirova, Jiri Prchal, Alexandra Rudajevova, Jeroen<br />

Custers and Vladimir Sechovsky<br />

Department of C<strong>on</strong>densed Matter Physics, Faculty of Mathematics and Physics,<br />

Charles University, Czech Republic<br />

CeRhIn 5 and Ce 2RhIn 8 are heavy fermi<strong>on</strong> antiferromagnets. Unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity can be<br />

induced by hydrostatic pressure or doping [1,2]. By c<strong>on</strong>trast, Ce 2PdIn 8 is a heavy fermi<strong>on</strong> superc<strong>on</strong>ductor<br />

(Tc=0.7K) at ambient pressure. We have examined the influence of Pd doping in single crystals of CeRh 1xPdxIn<br />

5 and Ce 2Rh 1-xPdxIn 8. Since the synthesis of Ce 2PdIn 8 is c<strong>on</strong>nected either to intergrowth of CeIn 3 or<br />

variati<strong>on</strong> of critical temperature, growth c<strong>on</strong>diti<strong>on</strong>s were studied by differential thermal analysis. By this, we<br />

have succeeded in obtaining high-quality single crystals free of CeIn 3 and with a critical temperature Tc~0.7K.<br />

The crystals have been subjected to specific heat, resistivity and AC susceptibility measurements. In additi<strong>on</strong>,<br />

resistivity experiments under hydrostatic pressures up to 3GPa were performed. Surprisingly, at ambient<br />

pressure the Neel temperature of CeRh 1-xPdxIn 5 has <strong>on</strong>ly slightly decreased with increasing Pd c<strong>on</strong>tent. And<br />

moreover, the pressure influence <strong>on</strong> magnetism in CeRh 0.75Pd 0.25In 5 does not significantly differ from CeRhIn 5.<br />

C<strong>on</strong>trary, the superc<strong>on</strong>ducting transiti<strong>on</strong> increases significantly compared to its 115-counterpart. The less twodimensi<strong>on</strong>al<br />

Ce 2Rh 1-xPdxIn 8 behaves different. Here, the antiferromagnetic ordering is immediately lowered<br />

up<strong>on</strong> Pd substituti<strong>on</strong> and vanishes completely at x~0.35 already. The obtained magnetic field-temperature<br />

phase diagrams will be discussed in c<strong>on</strong>text of the physical properties of other CenTIn3n+2 compounds.<br />

[1] H. Hegger et al., Phys. Rev. Lett. 84, 4986 (2000). [2] M. Nicklas et al., Phys. Rev. B 67, 020506 (2003).


PD19<br />

Magnetic phase diagram of the new heavy fermi<strong>on</strong> compound<br />

Ce2PtIn81 Marie Kratochvilova 1 *, Klara Uhlirova 1 , Jiri Prchal 1 , Ivana Cisarova 2 , Jeroen Custers 1<br />

and Vladimir Sechovsky 1<br />

1<br />

Department of C<strong>on</strong>densed Matter Physics, Faculty of Mathematics and Physics, Charles<br />

University, Czech Republic<br />

2<br />

Department of Inorganic Chemistry, Faculty of Science, Charles University, Czech Republic<br />

CenTmIn 3n+2m (n=1,2; m=1; T=transiti<strong>on</strong> metal) type compounds are subject of intense interest in the<br />

c<strong>on</strong>densed-matter community [1]. They are predestinated to investigate the interplay between magnetism<br />

and superc<strong>on</strong>ductivity. Recently, two new compounds from this heavy fermi<strong>on</strong> family have been found.<br />

Ce 2PdIn 8 is an ambient pressure superc<strong>on</strong>ductor while CePt 2In 7 orders antiferromagnetically [2]. We report<br />

<strong>on</strong> the existence of a new compound Ce 2PtIn 8. Similar to Ce 2PdIn 8, the synthesis of Ce 2PtIn 8 is rather<br />

complicated. However, from our studies of soluti<strong>on</strong> growth of Ce 2PdIn 8 and the support by differential<br />

thermal analysis, optimal c<strong>on</strong>diti<strong>on</strong>s for growing Ce 2PtIn 8 were deduced. Single-crystal X-ray diffracti<strong>on</strong><br />

c<strong>on</strong>firmed that Ce 2PtIn 8 crystallizes in Ho 2CoGa 8-type structure with lattice parameters a=4.699A and<br />

c=12.185A. We will present specific heat, resistivity (ambient and under hydrostatic pressure) and<br />

magnetizati<strong>on</strong> measurements. Ce 2PtIn 8 orders magnetically below 2.1K. A sec<strong>on</strong>d transiti<strong>on</strong>, likely into<br />

a magnetic commensurate ordering, is observed just below at 2K. C<strong>on</strong>trary to Ce 2RhIn 8, the magnetic<br />

transiti<strong>on</strong>s shift to lower temperatures in applied magnetic field al<strong>on</strong>g both principal crystallographic<br />

axes suggesting different character of magnetic ordering. Specific heat measurements reveal an enhanced<br />

Sommerfeld coefficient (γ~740 mJ/mol.K2). The magnetic field-temperature phase diagram will be<br />

discussed in the c<strong>on</strong>text of superc<strong>on</strong>ductivity and magnetism evoluti<strong>on</strong> in related compounds.<br />

[1] Ch. Pfleiderer, Rev. Mod. Phys. 81, 2009 [2] E. D. Bauer, et al., Phys. Rev. B 81, 180507 (2010)<br />

PD20<br />

Coexistence and competiti<strong>on</strong> of superc<strong>on</strong>ductivity, magnetism and<br />

charge density waves in rare-earth tri-telluride TbTe 3<br />

Kazuhiko Deguchi, Hiroaki Iwase, Yuya Imai, Koji Yamamoto and Noriaki Sato<br />

Department of Physics, Graduate School of Science, Nagoya University, Japan<br />

Rare-earth tri-telluride RTe 3 (R = Y, La-Sm, Gd-Tm) forms a weakly orthorhombic<br />

crystal lattice, c<strong>on</strong>sisting of alternating double layers of corrugated double RTe layers<br />

and nominally square-planar Te sheets. The RTe layers are resp<strong>on</strong>sible for magnetism<br />

while the square Te sheets c<strong>on</strong>tribute to str<strong>on</strong>gly anisotropic c<strong>on</strong>ducti<strong>on</strong>. Interestingly,<br />

the two-dimensi<strong>on</strong>al c<strong>on</strong>ducti<strong>on</strong> bands originating from Te-5px and 5py orbitals give<br />

rise to Fermi surface nesting, and this hidden <strong>on</strong>e-dimensi<strong>on</strong>ality leads to a charge<br />

density waves (CDW) with a high transiti<strong>on</strong> temperature. Because of this intriguing<br />

feature, RTe 3 attracts great interest in recent years. TbTe 3 has localized 4f electr<strong>on</strong>s,<br />

and exhibits successive phase transiti<strong>on</strong>s of magnetic origin, which all coexist with the<br />

CDW. Surprisingly, superc<strong>on</strong>ductivity emerges under high pressure. The questi<strong>on</strong> is<br />

whether the superc<strong>on</strong>ductivity coexists or competes with the other l<strong>on</strong>g range orders.<br />

Therefore, we investigated the l<strong>on</strong>g-range orders by the electrical resistivity and ac<br />

magnetic susceptibility at high pressures up to 8 GPa and at low temperatures down<br />

to 2 K using a c<strong>on</strong>stant-load cubic-anvil cell with single crystalline samples that were<br />

grown from Te-fluxes. We found that the antiferromagnetism survives even at the<br />

highest pressure of the present experiment. We also c<strong>on</strong>firmed the emergence of the<br />

superc<strong>on</strong>ductivity at high pressures.<br />

PD21<br />

Magnetic properties of Ce 3Rh 4Sn 13 and Ce 3Co 4Sn 13; a comparative<br />

study<br />

Andrzej Slebarski*, Marcin Fijalkowski and Jerzy Goraus<br />

Institute of Physics, University of Silesia, Poland<br />

We report <strong>on</strong> the electr<strong>on</strong>ic structure (XPS) and basic thermodynamic properties<br />

of Ce 3Rh 4Sn 13 and Ce 3Co 4Sn 13 and the reference La-based compounds. The both<br />

compounds were classified as a heavy fermi<strong>on</strong> materials with extremely large low<br />

temperature electr<strong>on</strong>ic specific heat C/T [1] of about 4 J/molK2. The data show that<br />

either Ce 3Rh 4Sn 13 or Ce 3Co 4Sn 13 are very sensitive to applied magnetic fields and<br />

exhibit a cross-over from magnetically correlated state to a single impurity state, when<br />

the applied magnetic field increases. We noted that the low temperature properties are<br />

dependent <strong>on</strong> the stoichiometry of the sample. We also present and discuss the low<br />

temperature properties of Ce 3Co 4Sn 13 doped with La.<br />

1] U. Kohler et al. J. Phys.:C<strong>on</strong>dens. Matter 19 (2007) 386207<br />

PD22<br />

PD23<br />

PD24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Thermoelectric properties of K<strong>on</strong>do semic<strong>on</strong>ductor CeRu 4As 12<br />

prepared under high pressure<br />

Chihiro Sekine 1 *, Tomokazu Kawata 1 , Yukihiro Kawamura 1 and Takehiko Yagi 2<br />

1 Graduate School of Engineering, Muroran Institute of Technology, Japan<br />

2 Institute for Solid State Physics, The University of Tokyo, Japan<br />

The filled skutterudite compound CeRu 4As 12 exhibits a hybridizati<strong>on</strong> gap insulating<br />

state, with a small activati<strong>on</strong> energyΔ/kB of 50K [1]. We report further results for<br />

CeRu 4As 12 prepared under high pressure (4GPa). Thermoelectric power and thermal<br />

c<strong>on</strong>ductivity measurements have been performed <strong>on</strong> this material. The temperature<br />

dependence of thermoelectric power for CeRu 4As 12 shows two peaks (around 80K,<br />

200K). The phenomena could be related to K<strong>on</strong>do behavior at high temperature and<br />

hybridizati<strong>on</strong>-gap-formati<strong>on</strong> process at low temperature.<br />

[1] C. Sekine et al., J. Mag. Mag. Mater., 310 (2007) 260.<br />

Single crystal growth and physical properties of UT 2Al 20 (T=transiti<strong>on</strong><br />

metal)<br />

Yuji Matsumoto 1 , Tatsuma D Matsuda 1 , Naoyuki Tateiwa 2 , Etsuji Yamamoto 1 ,<br />

Yoshinori Haga 1 and Zachary Fisk 3<br />

1 advanced science research center, Japan atomic energy agency, Japan<br />

2 Japan atomic energy agency, Japan<br />

3 University of California, USA<br />

Many anomalous physical properties have been observed in RT 2X 20 (R=Rare metal,<br />

T=transiti<strong>on</strong> metal, X=Al, Zn) system. For example, the quadrupolar order takes place<br />

in PrT 2X 20 system, and the extreme heavy fermi<strong>on</strong> state takes place in YbCo 2Zn 20.<br />

In the uranium analogue, for example, UT 2Al 20 is worth investigating because the<br />

extended 5f wave functi<strong>on</strong> in uranium would lead to peculiar features due to str<strong>on</strong>g<br />

hybridizati<strong>on</strong>. Therefore we have studied single crystal growth and physical properties<br />

of UT 2Al 20. The sample preparati<strong>on</strong> is performed by using Al-self flux method. We<br />

have succeeded to prepare the single crystal of UT 2Al 20 (T=Ti, Nb). We are going to<br />

present about the physical properties of the prepared samples in the <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>.<br />

Anisotropic c-f hybridizati<strong>on</strong> in a K<strong>on</strong>do semic<strong>on</strong>ductor CeFe2Al10 Yuji Muro 1 , Keisuke Yutani 2 , Jumpei Kajino 2 , Takahiro Onimaru 2 and Toshiro Takabatake 3<br />

1<br />

Liberal Arts and Sciences, Toyama Prefectural University, Kurokawa 5180, Imizu 939-<br />

0398, Japan<br />

2<br />

AdSM, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8530, Japan<br />

3<br />

AdSM and IAMR, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-<br />

8530, Japan<br />

We report anisotropic properties of a K<strong>on</strong>do semic<strong>on</strong>ductor CeFe 2Al 10. This compound is the n<strong>on</strong>-magnetic<br />

counterpart of K<strong>on</strong>do semic<strong>on</strong>ductors CeT 2Al 10 (T=Ru and Os) that exhibit an unusual antiferromagnetic<br />

transiti<strong>on</strong> at about 28 K[1-5]. The magnetic susceptibility for B//a, χa(T), shows a broad peak at 70 K due<br />

to the str<strong>on</strong>g c-f hybridizati<strong>on</strong>. The anisotropy in χ, χa>χc>χb, is in comm<strong>on</strong> with those for T = Ru and Os.<br />

Electrical resistivity ρ(T) has a broad maximum at 45, 35 and 110 K for I//a, I//b and I//c, respectively. Below<br />

20 K, ρ’s al<strong>on</strong>g all axes show an upturn due to the opening of a pseudo gap. Thermopower S(T) also shows<br />

a maximum at 190, 150 and 200 K for a-, b- and c-axis, respectively. The temperatures at the maximum in ρ<br />

and S suggest the anisotropy of c-f hybridizati<strong>on</strong> strength Vc>Va>Vb in CeFe 2Al 10 as reported in the study<br />

of optical c<strong>on</strong>ductivity[6]. Furthermore, <strong>on</strong>ly Sc(T) changes the sign from positive to negative at 100 K <strong>on</strong><br />

cooling and shows a minimum at 50 K. The negative minimum was also observed in Sc(T) for T=Ru and<br />

Os[7]. This behavior indicates the development of antiferromagnetic correlati<strong>on</strong> al<strong>on</strong>g the c-axis in CeT2Al10.<br />

[1] Y. Muro et al. J. Phys. Soc. Jpn. 78 (2009) 083707. [2] T. Nishioka et al. J. Phys. Soc. Jpn. 78<br />

(2009) 123705. [3] Y. Muro et al. Phys. Rev. B 81 (2010) 214401. [4] D. D. Khalyavin et al. Phys.<br />

Rev. B 82 (2010) 100405R. [5] D. T. Adroja et al. Phys. Rev. B 82 (2010) 104405. [6] S. Kimura et<br />

al. J. Phys. Soc. Jpn. 80 (2011) 033702. [7] H. Tanida et al. J. Phys. Soc. Jpn. 79 (2010) 063709.<br />

July 8 - 13, 2012 Busan, Korea 21<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PD25<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Cu-NMR studies of heavy-Fermi<strong>on</strong> compound CeCu 6 under high<br />

magnetic fields<br />

Keisuke Kuroda, Kyohei Morita, Hisashi Kotegawa, Hitoshi Sugawara and Hideki<br />

Tou*<br />

Department of Physics, Kobe University, Japan<br />

It is known that the intermetallic compound CeCu 6 is a heavy fermi<strong>on</strong> system showing<br />

a huge specific heat coefficient γ ~ 1600 mJ / K2 mol, without magnetic order or<br />

superc<strong>on</strong>ductivity at low temperatures down to 10 mK[1,2]. The electric resistivity<br />

shows characteristic temperature dependence of ? logT above 10 K, which is ascribed<br />

to the K<strong>on</strong>do effect, and it has a maximum around 10 K. No detailed NMR results have<br />

been reported yet because of a drawback of the complicated Cu NMR spectrum due to<br />

a peculiar orthorhombic crystal structure. We have carried out Cu-NMR measurements<br />

to clarify the heavy fermi<strong>on</strong> state of a single crystal CeCu 6 under several magnetic<br />

fields. We have measured Knight shift and the nuclear spin-lattice relaxati<strong>on</strong> time T1<br />

under magnetic fields up to 15 T al<strong>on</strong>g the a-axis and c-axis in the temperature range of<br />

100-1.5 K. At low temperatures, the Cu-NMR Knight shifts are suppressed as magnetic<br />

field increases. Simultaneously, 1/T1 is suppressed. These features are understood by<br />

the c<strong>on</strong>cept that the heavy fermi<strong>on</strong> state in CeCu 6 is formed through K<strong>on</strong>do effect. We<br />

will report detailed field dependence of the heavy fermi<strong>on</strong> state of CeCu 6 for the first<br />

time.<br />

[1] Y. Onuki, et al.: JPSJ 53 (1984) 1210 [2] Y. Onuki, et al.: JMMM 63-64 (1987) 281<br />

PE01<br />

The underscreened Anders<strong>on</strong> lattice : A model for uranium<br />

compounds.<br />

Peter S Riseborough 1 *, Sergio Magalhaes 2 and Bernard Coqblin 3<br />

1 Physics, Temple University, USA<br />

2 Inst. Fis., Univ. Fed. Fluminense, Rio de Janeiro, Brazil<br />

3 L.P.S., CNRS-Universite Paris-Sud, 91405 Orsay, France<br />

We present a model based <strong>on</strong> the Underscreened Anders<strong>on</strong> Lattice (UAL) with two<br />

5f electr<strong>on</strong>s per site to account for the K<strong>on</strong>do-ferromagnetism co-existence observed<br />

in some actinide compounds. The UAL model allows a descripti<strong>on</strong> of the decrease of<br />

the number of f-electr<strong>on</strong>s and we present a calculati<strong>on</strong> which explains the pressure<br />

dependence observed in some Uranium compounds and particularly in Uranium<br />

m<strong>on</strong>ochalcogenides. On the other hand, we have developed a novel type of phase<br />

transiti<strong>on</strong> within the UAL model and we suggest that this model might describe the<br />

“Hidden Order” transiti<strong>on</strong> in URu 2Si 2. The gaps that appear in the electr<strong>on</strong>ic dispersi<strong>on</strong><br />

relati<strong>on</strong>s of bands of different orbital character are in agreement with experimental<br />

photoemissi<strong>on</strong> results.<br />

PE02<br />

Transport properties of intermetallic compounds RCoGe 2 (R = Ce and<br />

La)<br />

Yung-kang Kuo 1 *, P. C. Chang 2 and C. S. Lue 3<br />

1 Nati<strong>on</strong>al D<strong>on</strong>g Hwa University, Department of Physics, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al D<strong>on</strong>g Hwa University, Taiwan<br />

3 Nati<strong>on</strong>al Cheng Kung University, Nati<strong>on</strong>al D<strong>on</strong>g Hwa University,, Taiwan<br />

The electr<strong>on</strong>ic and magnetic properties of the cerium-based ternary intermetallic<br />

compound compounds with the general formula CeMSi 2 (M = transiti<strong>on</strong> metals)<br />

has been of c<strong>on</strong>siderable interest recently. Am<strong>on</strong>g those compounds, CeCoGe 2 is of<br />

particular interest due to its peculiar physical properties, such as it has a rather high<br />

K<strong>on</strong>do temperature TK ~ 250 K, and it is the first K<strong>on</strong>do system clearly interpreted by<br />

the Coqblin-Schrieffer model with j = 5/2. In this study, measurements of the electrical<br />

resistivity, Seebeck coefficient, and thermal c<strong>on</strong>ductivity <strong>on</strong> CeCoGe 2 have been<br />

performed in the temperature range 10 - 300 K to investigate the electr<strong>on</strong>ic structure.<br />

For comparis<strong>on</strong>, the n<strong>on</strong>magnetic counterpart LaCoGe 2 has also been studied. It is<br />

found that CeCoGe 2 exhibits a broad maximum in Seebeck coefficient at about 75<br />

K, at which the sudden drop in electrical resistivity occurs. This is a typical behavior<br />

comm<strong>on</strong>ly seen in Ce-based K<strong>on</strong>do lattice compounds. A theoretical attempt was made<br />

and found that the electrical ransport and thermoelectric properties of CeCoGe 2 can be<br />

well described by a two-band model with reliable physical parameters. On the other<br />

hand, both electrical resistivity and Seebeck coefficient show a typical metallic-like<br />

behavior for the n<strong>on</strong>magnetic LaCoGe 2.<br />

22 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PE03<br />

The lattice K<strong>on</strong>do effect - A fabric for superc<strong>on</strong>ducting correlati<strong>on</strong>s?<br />

Oliver Bodensiek 1 *, Thomas Pruschke 1 and Rok Zitko 2<br />

1 Department of Physics, University of Goettingen, 37077 Goettingen, Germany<br />

2 Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia<br />

Although the simple K<strong>on</strong>do lattice model c<strong>on</strong>stitutes <strong>on</strong>e of the paradigms for<br />

understanding the physics of heavy-fermi<strong>on</strong> materials, a reliable theoretical<br />

investigati<strong>on</strong> of superc<strong>on</strong>ductivity in this model is still lacking. We present results<br />

based <strong>on</strong> the dynamical mean-field approximati<strong>on</strong> in combinati<strong>on</strong> with the numerical<br />

renormalizati<strong>on</strong> group as impurity solver. While superc<strong>on</strong>ducting order is comm<strong>on</strong>ly<br />

not expected for a correlated lattice model without additi<strong>on</strong>al bos<strong>on</strong>ic degrees of<br />

freedom, we observe str<strong>on</strong>g superc<strong>on</strong>ducting order in the plain K<strong>on</strong>do lattice model<br />

away from half filling. The possible origin of this superc<strong>on</strong>ducting order is discussed<br />

in view of the frequency dependence of the order parameter. In additi<strong>on</strong>, close to half<br />

filling we find this ordered phase to appear most pr<strong>on</strong>ounced in the vicinity of the<br />

antiferromagnetic quantum critical point. Since a characterizati<strong>on</strong> of quantum criticality<br />

within dynamical mean-field theory is not possible, we rather discuss questi<strong>on</strong>s of<br />

principle such as the actual nature of the ordered states, that is, local moment or heavyfermi<strong>on</strong><br />

physics. The latter issue is of c<strong>on</strong>siderable interest addressing the questi<strong>on</strong><br />

whether the ordered states stay in direct competiti<strong>on</strong> or even cooperate with the<br />

coherent K<strong>on</strong>do effect in the lattice.<br />

PE04<br />

Lifshitz transiti<strong>on</strong> with interacti<strong>on</strong>s in high magnetic fields: applicati<strong>on</strong><br />

to CeIn 3<br />

Pedro Schlottmann*<br />

Department of Physics, Florida State University, USA<br />

The Neel ordered state of CeIn 3 is suppressed by a magnetic field of 61 T at<br />

ambient pressure. There is a sec<strong>on</strong>d transiti<strong>on</strong> at ~45 T, which has been associated<br />

with a Lifshitz transiti<strong>on</strong>. Skin depth measurements indicate that the transiti<strong>on</strong> is<br />

disc<strong>on</strong>tinuous as T -> 0 and that the transiti<strong>on</strong> has a weak pressure dependence until<br />

it merges with the Neel transiti<strong>on</strong>. We study the effects of Landau quantizati<strong>on</strong> and<br />

interacti<strong>on</strong> am<strong>on</strong>g carriers <strong>on</strong> a Lifshitz transiti<strong>on</strong>. The Landau quantizati<strong>on</strong> leads<br />

to quasi-<strong>on</strong>e-dimensi<strong>on</strong>al behavior for the directi<strong>on</strong> parallel to the field. Repulsive<br />

Coulomb interacti<strong>on</strong>s give rise to a gas of str<strong>on</strong>gly coupled carriers. The density<br />

correlati<strong>on</strong> functi<strong>on</strong> is calculated for a special l<strong>on</strong>g-ranged potential [1]. For the lowest<br />

Landau level the problem can be mapped <strong>on</strong>to the interacting <strong>on</strong>e-dimensi<strong>on</strong>al electr<strong>on</strong><br />

gas. It is c<strong>on</strong>cluded that in CeIn 3 (a) an electr<strong>on</strong> or hole pocket is being emptied as a<br />

functi<strong>on</strong> of field and (b) in the ground state the pocket is emptied in a disc<strong>on</strong>tinuous<br />

fashi<strong>on</strong>. This disc<strong>on</strong>tinuity is gradually smeared by the temperature in agreement with<br />

the skin depth experiments. Work supported by the Department of Energy under grant<br />

DE-FG02-98ER45707.<br />

[1] P. Schlottmann, Phys. Rev. B 83, 115133 (2011).<br />

PE05<br />

Dynamical mean-field theory of indirect exchange between magnetic<br />

adatoms <strong>on</strong> metallic surfaces<br />

Irakli Titvinidze*, Andrej Schwabe, Niklas Rother and Michael Potthoff<br />

I. Institute of theoretical physics, University of Hamburg, Germany<br />

Two magnetic impurities <strong>on</strong> a metallic substrate surface experience the Ruderman-<br />

Kittel-Kasuya-Yosida (RKKY) exchange interacti<strong>on</strong>. This indirect n<strong>on</strong>-local magnetic<br />

exchange competes with the local K<strong>on</strong>do effect. While the latter is described in<br />

principle exactly within single-site dynamical mean-field theory, the effects of the<br />

RKKY coupling are taken into account approximately <strong>on</strong>ly. Here, this is dem<strong>on</strong>strated<br />

by comparing the DMFT results with numerically exact data obtained by the densitymatrix<br />

renormalizati<strong>on</strong> group for a <strong>on</strong>e-dimensi<strong>on</strong>al model with two Anders<strong>on</strong><br />

impurities. With the two-site DMFT, we also benchmark a simplified DMFT variant.<br />

Varying the inter-impurity distance d and the local exchange coupling J, different<br />

parameter regimes with dominating K<strong>on</strong>do physics or with dominating RKKY<br />

interacti<strong>on</strong> are studied. For the K<strong>on</strong>do regime, our calculati<strong>on</strong>s show that DMFT is<br />

able to reliably describe magnetic nanostructures <strong>on</strong> metallic surfaces. The prospects of<br />

DMFT (and two-site DMFT) as a reliable approach to study nanomagnetism of more<br />

complex RKKY-interacting systems are discussed.


PE06<br />

K<strong>on</strong>do effect near the Van Hove singularity in biased bilayer graphene<br />

Stanislaw Lipinski* and Damian Krychowski<br />

Institute of Molecular Physics, Polish Academy of Sciences, Poland<br />

We study K<strong>on</strong>do impurity in a bilayer graphene with Bernal stacking for adatom<br />

adsorbed <strong>on</strong> the outside of the bilayer or intercalated between the two graphene layers.<br />

The density of states (DOS) close to the gap diverges as the square root of energy -<br />

Van Hove singularity (VHS). The system is modeled by the generalized Anders<strong>on</strong><br />

hamilt<strong>on</strong>ian with bilayer described by Hubbard model. The many-body problem is<br />

studied within the mean field Kotliar-Ruckenstein slave bos<strong>on</strong> approach for SU(2)<br />

and SU(4) symmetries. We examine the impact of tuning the Fermi level (EF) through<br />

the VHS. Increase of the DOS at EF increases hybridizati<strong>on</strong> of the impurity, what<br />

moves the system towards mixed valence regime or even completely suppresses the<br />

many body peak of DOS. Additi<strong>on</strong>ally a competitive influence of magnetic instability<br />

is analyzed. Crossing of the Fermi level with a Van Hove singularity leads to weak<br />

ferromagnetism of the bilayer graphene with str<strong>on</strong>g spin polarizati<strong>on</strong> at EF. The spin<br />

symmetry is broken, what for the case of spin-orbital degeneracy results in a crossover<br />

from SU(4) K<strong>on</strong>do effect to SU(2) and in the case of <strong>on</strong>ly spin degeneracy it leads to a<br />

str<strong>on</strong>g suppressi<strong>on</strong> of SU(2) K<strong>on</strong>do effect.<br />

PE07<br />

Indirect exchange between magnetic atoms <strong>on</strong> surfaces: From two<br />

impurities to diluted chains<br />

Andrej Schwabe*, Irakli Titvinidze, Daniel Gutersloh, Anke Braun and Michael<br />

Potthoff<br />

I. Institute of theoretical physics, University of Hamburg, Germany<br />

Magnetic atoms <strong>on</strong> metallic surfaces are subject to the competiti<strong>on</strong> between K<strong>on</strong>do<br />

screening and indirect magnetic (RKKY) exchange. To study the crossover of the<br />

magnetic properties from the case of a single or two magnetic adatoms to the limit<br />

of a dense chain of indirectly coupled adatoms, we model the metal surface as a <strong>on</strong>edimensi<strong>on</strong>al<br />

tight-binding system and apply the density-matrix renormalizati<strong>on</strong> group<br />

(DMRG) to the resulting K<strong>on</strong>do model. The case of three magnetic atoms turns out<br />

to be particularly interesting as finite-size gaps are found to qualitatively affect the<br />

balance between K<strong>on</strong>do physics and RKKY. With the transiti<strong>on</strong> from the diluted case<br />

with a few magnetic atoms to the dense chain with all atoms RKKY-coupled ferro-<br />

or antiferromagnetically, magnetic l<strong>on</strong>g-range order becomes possible. The resulting<br />

phase diagram is studied in the weak (RKKY) but also in the str<strong>on</strong>g-coupling (K<strong>on</strong>do)<br />

limit. Besides DMRG we employ real-space dynamical mean-field theory (R-DMFT)<br />

in additi<strong>on</strong> and thereby extend the results to higher dimensi<strong>on</strong>s.<br />

PE08<br />

ESR study of hybridizati<strong>on</strong> in some undoped Yb-based alloys<br />

Vladimir Ivanshin*, Tatyana Litvinova and Eduard Gataullin<br />

Institute of Physics, Kazan University, Russia<br />

The hybridizati<strong>on</strong> between a wide c<strong>on</strong>ducti<strong>on</strong> band and correlated f-electr<strong>on</strong>s localized<br />

at lattice sites is investigated using method of electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) in some<br />

dense heavy-fermi<strong>on</strong> compounds. ESR signals arise here both from the local moment<br />

spins and c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s (CE) due to the str<strong>on</strong>g electr<strong>on</strong>ic correlati<strong>on</strong>s because<br />

of the hybridizati<strong>on</strong> between 4f-electr<strong>on</strong>s and CE in the presence of ferromagnetic<br />

(FM) fluctuati<strong>on</strong>s [1]. We review very recent ESR experiments in several undoped Ybbased<br />

intermetallics [2, 3] and discuss the role of chemical compositi<strong>on</strong>, K<strong>on</strong>do effect,<br />

anisotropy, and RKKY interacti<strong>on</strong>s for the ESR linewidth. It is shown that an increase<br />

of the K<strong>on</strong>do interacti<strong>on</strong> and FM correlati<strong>on</strong>s leads to a str<strong>on</strong>ger hybridizati<strong>on</strong> and an<br />

essential ESR line narrowing. Possible hybridizati<strong>on</strong> mechanisms are proposed.<br />

[1] P. Wolfle, E. Abrahams, Ann. Phys. (Berlin) 523 598 (2011) [2] V.A. Ivanshin et al., J. Phys.:<br />

C<strong>on</strong>f. Ser. 324 012019 (2011) [3] T. Gruner et al., Phys. Rev. B 85 035119 (2012)<br />

PE09<br />

PE10<br />

PE11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

ESR study of influence of ani<strong>on</strong>ic and cati<strong>on</strong>ic substituti<strong>on</strong>s in EuB6<br />

<strong>on</strong> the magnetic phase separati<strong>on</strong><br />

Tatiana Semenovna Altshuler 1 *, Yuriy Vladimirovich Goryunov 1 , Anna Vasilievna<br />

Levchenko 2 and Vladimir Borisovich Filippov 2<br />

1 Russian Academy of Sciences, Kazan Physical-Technical Institute, Russia<br />

2 Nati<strong>on</strong>al Academy of Sciences of Ukraine, Institute of Problem of Material Science,<br />

Ukraine<br />

We performed a comparative study of the features of the magnetic phase separati<strong>on</strong> in europium<br />

hexaboride with ani<strong>on</strong>ic and cati<strong>on</strong>ic substituti<strong>on</strong> with d<strong>on</strong>or impurities. The ESR (electr<strong>on</strong> spin<br />

res<strong>on</strong>ance) were measured <strong>on</strong> the single crystal plates EuB_{6-x}C_{x} and Eu_{1-x}Gd_{x}B_{6}<br />

with x < 0.07 in X-band in the temperature range T = 10-300 K. Both types substituti<strong>on</strong> keep integrity<br />

of the magnetic sublattice and they add <strong>on</strong>e electr<strong>on</strong> per the impurity atom in the c<strong>on</strong>ducti<strong>on</strong> band. of<br />

EuB 6. The magnetic field was oriented perpendicular to the sample plane and al<strong>on</strong>g various crystal axis.<br />

In all case we observed the magnetic phase separati<strong>on</strong> and phase transiti<strong>on</strong>s. However, the ratio of the<br />

magnetic phases and their behavior is slightly different for substituti<strong>on</strong> bor<strong>on</strong> in carb<strong>on</strong> and europium<br />

gadolinium. In the latter case, there was the coexistence of ferromagnetic and antiferromagnetic phases.<br />

The obtained ESR data are discussed in frame Falicov-Kimball model the hybridizati<strong>on</strong> of the localized<br />

electr<strong>on</strong>s with two band (valence and c<strong>on</strong>ducti<strong>on</strong> band) itinerant electr<strong>on</strong>s and formati<strong>on</strong> of K<strong>on</strong>do-like<br />

electr<strong>on</strong> states. Work was supported by Grants of RFBR and Presidium of RAS.<br />

[1] Altshuler T S, Goryunov Y V, Shitsevalova N Y, Dukhnenko A, JETP Lett. 88, 779 (2008) [2]<br />

Kunes J, Picket W E, Phys.Rev. B 69, 1651 (2004) [3] Falicov L M, Kimball J C, Phys.Rev.Lett. 22<br />

997 (1969) [4] Kugel K I, Rakhmanov A L, Sboychakov A O, Phys.Rev.Lett. 95, 267210 (2005)<br />

High pressure synthesis of novel bor<strong>on</strong>-cage compounds RB 12 (R=Gd, Sm)<br />

Fumitoshi Iga 1 *, Yusaku Egashira 2 , Tomoaki Noguchi 2 , Toshiro Takabatake 2 , Akinori<br />

K<strong>on</strong>do 3 , Koichi Kindo 3 , Shoji Yamanaka 4 , Kei Inumaru 4 , Norimasa Nishiyama 5 ,<br />

Tetsuo Irifune 5 and Hitoshi Yusa 6<br />

1 Faculty of Science, Ibaraki University, Japan<br />

2 Graduate School of ADSM, Hiroshima University, Japan<br />

3 Institute for Solid State Physics, University of Tokyo, Japan<br />

4 Graduate School of Engineering, Hiroshima University, Japan<br />

5 Geodynamics Reaearch Center, Ehime University, Japan<br />

6 High pressure Science, Nati<strong>on</strong>al Institute Material Sciences, Japan<br />

Rare-earth compounds with cage structures recently attract much attenti<strong>on</strong> because of possibility of new heavy<br />

fermi<strong>on</strong> mechanism using the lattice vibrati<strong>on</strong> [1]. Rare-earth borides such as RB 6 and RB 12 also have such cage<br />

structures composed by bor<strong>on</strong>. However, RB 12 series are known from R = Tb to Lu. Cann<strong>on</strong> has succeeded in<br />

high-pressure synthesis of GdB 12 in pressure of 6.6 GPa and 2,400 C, and reported lattice parameter a = 7.523 A<br />

in the UB 12-type structure [2]. We have also succeeded in high-pressure synthesis of polycrystalline GdB 12 and<br />

SmB 12. Magnetic susceptibility of GdB 12 shows a kink at 38 K indicating of antiferro-magnetic ordering. Highfield<br />

magnetizati<strong>on</strong> of GdB 12 shows the saturati<strong>on</strong> moment is 7 μB. All the reported Neel ordering temperatures<br />

of RB 12 well agree to the values estimated from the trivalent rare-earth dependence of de Gennes factor. From the<br />

x-ray powder diffracti<strong>on</strong> of SmB 12, this compound also has the UB 12-type structure with lattice parameter of a =<br />

7.541 A. Magnetic susceptibility shows two anomalies at 9 K and 19 K different from other RB 12.<br />

[1] T. Hotta and K. Ueda: Phys. Rev. B 67 (2003) 104518. [2] J. F. Cann<strong>on</strong>, et al.: J. Less-Comm<strong>on</strong><br />

Metals 56 (1977) 83.<br />

Magnetic anisotropy of tetrag<strong>on</strong>al rare-earth compounds RRu 2Al 2B (R:<br />

rare-earth metals)<br />

Eiichi Matsuoka 1 *, Yo Tomiyama 1 , Kotaro Iwasawa 1 , Hitoshi Sugawara 1 , Takahiro<br />

Sakurai 2 and Hitoshi Ohta 3<br />

1 Department of Physics, Graduate School of Science, Kobe University, Japan<br />

2 Center for Supports to Research and Educati<strong>on</strong> Activities, Kobe University, Japan<br />

3 Molecular Photoscience Research Center, Kobe University, Japan<br />

Recently, we succeeded to synthesize polycrystalline samples of new tetrag<strong>on</strong>al<br />

rare-earth compounds CeRu 2Al 2B and PrRu 2Al 2B and reported magnetic properties<br />

of these compounds [1]. Both compounds show successive phase transiti<strong>on</strong>s of an<br />

antiferromagnetic and a ferromagnetic ordering. The Neel and Curie temperatures for<br />

CeRu 2Al 2B are 14.3 K and 13 K, respectively, and those for PrRu 2Al 2B are 26 K and<br />

11 K, respectively. The values of magnetizati<strong>on</strong> vary when the angle between sample<br />

directi<strong>on</strong> and applied magnetic field is changed even in the polycrystalline samples.<br />

This fact implies that the grains of polycrystalline samples are oriented partially and the<br />

variati<strong>on</strong> of magnetizati<strong>on</strong> values is due to the magnetic anisotropy. In this study, we<br />

will report <strong>on</strong> the results of magnetizati<strong>on</strong> and magnetic-susceptibility measurements<br />

of grain-oriented powder samples of RRu 2Al 2B (R: rare-earth metals) and will discuss<br />

the magnetic anisotropy.<br />

[1] E. Matsuoka, Y. Tomiyama, H. Sugawara, T. Sakurai, and H. Ohta, J. Phys. Soc. Jpn. 81 (2012)<br />

043704.<br />

July 8 - 13, 2012 Busan, Korea 23<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PE12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Collective magnetic res<strong>on</strong>ance mode in CeB 6.<br />

A. V. Semeno 1 *, V. V. Glushkov 1 , N. E. Sluchanko 1 , N. Yu. Shitsevalova 2 , V. B.<br />

Filipov 2 , A. V. Dukhnenko 2 and S. V. Demishev 1<br />

1 A.M.Prokhorov General Physics Institute RAS, Russia<br />

2 Institute for Problems of Materials Science NAS, Ukraine<br />

The observati<strong>on</strong> of the electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) in low temperature phase<br />

(phase II) of CeB 6 has risen up new questi<strong>on</strong>s about the nature of its ground state [1].<br />

In the present work we study the effects of La doping <strong>on</strong> the ESR parameters in Ce 1xLa<br />

xB 6. Experiments in the doping range 0


PE18<br />

Charge ordering in the K<strong>on</strong>do lattice model at quarter filling<br />

Junki Yoshitake*, Takahiro Misawa and Yukitoshi Motome<br />

Department of Applied Physics, The University of Tokyo, Japan<br />

The K<strong>on</strong>do lattice model is <strong>on</strong>e of the fundamental models for heavy-fermi<strong>on</strong> systems,<br />

where exchange interacti<strong>on</strong>s between itinerant electr<strong>on</strong>s and localized spins play an<br />

important role. Am<strong>on</strong>g many different phases described by this model, emergence of<br />

charge-ordered state [1,2] is interesting possibility, because this model does not include<br />

any bare inter-site repulsi<strong>on</strong>s between electr<strong>on</strong>s. The possibility was first pointed out<br />

by a perturbati<strong>on</strong> expansi<strong>on</strong> in the str<strong>on</strong>g K<strong>on</strong>do coupling limit at quarter filling in 1D<br />

[1], and recently examined by the dynamical mean-field theory in infinite dimensi<strong>on</strong>s<br />

[2]. However, it remains unclear whether the charge-ordered state appears in two and<br />

three dimensi<strong>on</strong>s and what type of magnetic order is accommodated in the chargeordered<br />

state. To clarify these issues, we investigate both the ground state and finitetemperature<br />

properties of the quarter-filled K<strong>on</strong>do lattice model <strong>on</strong> a square lattice by<br />

complementarily using the variati<strong>on</strong>al M<strong>on</strong>te Carlo simulati<strong>on</strong> and cluster dynamical<br />

mean-field theory. We found that charge-ordered state appears in a wider regi<strong>on</strong><br />

than the previous result in infinite dimensi<strong>on</strong>s, and that the antiferromagnetic order<br />

between charge poor sites is accommodated in the charge-ordered state. We discuss the<br />

stabilizati<strong>on</strong> mechanism of charge ordering by carefully analyzing the electr<strong>on</strong>ic and<br />

magnetic properties.<br />

[1] J. E. Hirsch, Phys. Rev. B 30, 5383 (1984). [2] J. Otsuki et al., J. Phys. Soc. Jpn. 78, 034719<br />

(2009).<br />

PE19<br />

Angular-dependent magnetoresistance of the filled skutterudite<br />

CeOs 4As 12<br />

Łukasz Bochenek*, Zygmunt Henkie and Tomasz Cichorek<br />

Divisi<strong>on</strong> of Magnetic Research, Institute of Low Temperature and Structure Research,<br />

Polish Academy of Sciences, Wroclaw, Poland, Poland<br />

The filled skutterudite CeOs 4As 12 compound is a narrow-gap semic<strong>on</strong>ductor whose<br />

low-temperature properties originate from a hybridizati<strong>on</strong> between 4f and c<strong>on</strong>ducti<strong>on</strong><br />

electr<strong>on</strong>s. N<strong>on</strong>magnetic CeOs 4As 12 is the cubic system showing a nodal structure of<br />

hybridizati<strong>on</strong> energy gap(s) as evidenced from low-temperature (T > 0.08 K) and highmagnetic<br />

field (B < 14 T) studies of a directi<strong>on</strong>al dependence of the electrical resistivity<br />

ρ (T): At T < 3 K and for j || B, we found remarkable dissimilarities al<strong>on</strong>g the [001] and<br />

[111] directi<strong>on</strong>s, indicative of an anisotropic suppressi<strong>on</strong> of energy gap(s). Additi<strong>on</strong>ally,<br />

differences observed between the transverse and l<strong>on</strong>gitudinal magnetoresistivity cannot<br />

be ascribed to the Lorentz force and thus, provide a further evidence for magnetic-fieldinduced<br />

anisotropy of hybridizati<strong>on</strong> gap in CeOs 4As 12. High-quality single crystals<br />

of CeOs 4As 12 enable studies of a change of Fermi surface via the angular-dependent<br />

magnetoresistivity both in the field-induced metallic as well as semic<strong>on</strong>ducting state.<br />

Our experiments with the use of the commercial <strong>on</strong>e-axis rotator (PPMS) provide an<br />

additi<strong>on</strong>al evidence for str<strong>on</strong>gly correlated electr<strong>on</strong> phenomena in CeOs 4As 12 that we<br />

tentatively relate to the quartet Γ67 ground state of the Ce 3+ i<strong>on</strong> in the Th symmetry.<br />

PF01<br />

Spin and charge correlati<strong>on</strong> of electr<strong>on</strong>s at variati<strong>on</strong> of interorbital<br />

Coulomb interacti<strong>on</strong><br />

Sergey Stepanovich Aplesnin 1 and Nataly Ivanovna Piskunova 2<br />

1 M.V. Reshetnev Siberian State Aerospace University, Russia<br />

2 Omsk State Agrarian University, Russia<br />

Of great interest for the researches is the i<strong>on</strong>s with orbital degenerati<strong>on</strong> and electr<strong>on</strong><br />

shell with filling more than half. The aim of our work is to evaluate spin and charge<br />

correlati<strong>on</strong> at variati<strong>on</strong> of interorbital Coulomb interacti<strong>on</strong> and competiti<strong>on</strong> of electr<strong>on</strong><br />

hopping parameters between nearest sites <strong>on</strong> the same and different orbitales arising<br />

as a result of variati<strong>on</strong> of orbitales filling. Variati<strong>on</strong> of charge gap may be also cause a<br />

radical change in the electr<strong>on</strong>ic density and spin correlati<strong>on</strong> functi<strong>on</strong>s. We calculated<br />

electr<strong>on</strong> spectrum in the Hubbard model with electr<strong>on</strong> filling n=1.5 and following<br />

parameters: energy level of i<strong>on</strong>s, the matrix element of the hopping between the<br />

nearest sites and orbitales, U and V is the Coulomb repulsi<strong>on</strong> of the electr<strong>on</strong>s <strong>on</strong> site<br />

and between orbitales . We calculated the eigenvalue spectrum and the corresp<strong>on</strong>ding<br />

state vectors by exact diag<strong>on</strong>alizati<strong>on</strong> for small cluster, based <strong>on</strong> which we determined<br />

the spin correlati<strong>on</strong> functi<strong>on</strong>s <strong>on</strong> the l<strong>on</strong>gitudinal and transverse spin comp<strong>on</strong>ents,<br />

correlator of electr<strong>on</strong> density. As a results, critical parameters Vc of the interorbitales<br />

Coulomb interacti<strong>on</strong> and hopping integral are found at which reveal change in the<br />

value and sign of exchange interacti<strong>on</strong> and in the correlator of electr<strong>on</strong> density.<br />

PF02<br />

PF03<br />

PF04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Superfluid state of repulsively interacting three-comp<strong>on</strong>ent fermi<strong>on</strong>ic<br />

atoms in optical lattices<br />

Seiichiro Suga 1 * and Kensuke Inaba 2<br />

1 University of Hyogo, Japan<br />

2 NTT Basic Research Laboratories and JST CREST, Japan<br />

We investigate the superfluid state of repulsively interacting three-comp<strong>on</strong>ent<br />

(color) fermi<strong>on</strong>ic atoms in optical lattices. We first discuss the effective interacti<strong>on</strong>s<br />

using diagrammatic approaches. We then investigate the superfluid properties using<br />

complementary two methods: the dynamical mean-field theory with a perturbative<br />

approach and the self-energy functi<strong>on</strong>al approach. We show that when the anisotropy<br />

of the three repulsive interacti<strong>on</strong>s is str<strong>on</strong>g, atoms of two of the three colors form<br />

Cooper pairs and atoms of the third color remain a Fermi liquid. An effective attractive<br />

interacti<strong>on</strong> is induced by density fluctuati<strong>on</strong>s of the third-color atoms. This superfluid<br />

state is similar to the color superfluid of the attractively interacting three-comp<strong>on</strong>ent<br />

systems. We show from dynamical properties that the Cooper-pairing mechanism<br />

is basically similar to that of the c<strong>on</strong>venti<strong>on</strong>al ph<strong>on</strong><strong>on</strong>-mediated superc<strong>on</strong>ductivity.<br />

The superfluid state is stable against changes in filling close to half filling. We<br />

determine the phase diagrams in terms of temperature, filling, and the anisotropy of the<br />

repulsive interacti<strong>on</strong>s. We also discuss the relati<strong>on</strong> between the theoretical results and<br />

experiments.<br />

<strong>Magnetism</strong> in complex oxides: A challenge for advanced ab-initio<br />

methods.<br />

Alessio Filippetti<br />

Dept. of Physics, CNR-IOM, University of Cagliari, Italy, Italy<br />

The accurate descripti<strong>on</strong> of magnetic properties in complex oxides by first-principles is<br />

tantamount with the possibility of achieving reliable theoretical design of oxide-based<br />

spintr<strong>on</strong>ic devices. Alas, standard first-principles approaches fails to properly describe<br />

str<strong>on</strong>g correlated systems, and more sophisticated approximati<strong>on</strong>s are required.<br />

Recently the novel variati<strong>on</strong>al pseudo-self-interacti<strong>on</strong> corrected density functi<strong>on</strong>al<br />

theory (VPSIC) has been introduced, showing great potential as theoretical tool for<br />

the study of complex oxides and str<strong>on</strong>g-correlated systems in general, and promising<br />

to open the field to reliable designs of magnetic oxide-based devices. Here we apply<br />

the new approach to investigate two prototypical oxide families, i.e. transiti<strong>on</strong> metal<br />

m<strong>on</strong>oxides (MnO, NiO) and perovskite titanates (LaTiO 3, YTiO 3). We give evidence<br />

that the new theory is capable to furnish an unprecedentedly accurate descripti<strong>on</strong> of<br />

both ground-state and finite-temperature magnetic properties, both at equilibrium<br />

and under pressure. As highlights of the results obtained in the work, we menti<strong>on</strong> the<br />

correct determinati<strong>on</strong> of critical temperature and the accurate descripti<strong>on</strong> of orbital<br />

ordering in transiti<strong>on</strong> metal oxides.<br />

Res<strong>on</strong>ating Hartree-Fock Studies for spin fluctuati<strong>on</strong>s in the Hubbard<br />

model <strong>on</strong> triangular lattice<br />

Norikazu Tomita*<br />

Yamagata University, Japan<br />

Electr<strong>on</strong> correlati<strong>on</strong> effects in geometrically frustrated systems have attracted much<br />

attenti<strong>on</strong> in c<strong>on</strong>densed-matter physics. In fact, these systems show a variety of<br />

interesting and n<strong>on</strong>-trivial ground states. On the other hand, theoretical descripti<strong>on</strong> <strong>on</strong><br />

the electr<strong>on</strong> correlati<strong>on</strong>s in these systems is difficult, and origins of such n<strong>on</strong>-trivial<br />

states are not yet clarified. In this research, the electr<strong>on</strong> correlati<strong>on</strong>s are visualized<br />

from the viewpoint of quantum fluctuati<strong>on</strong>s. Such visualizati<strong>on</strong> is important for the<br />

fundamental understanding and applicati<strong>on</strong>s of the frustrated system. A res<strong>on</strong>ating<br />

Hartree-Fock method c<strong>on</strong>structs a many-body wave-functi<strong>on</strong> by superpositi<strong>on</strong> of<br />

n<strong>on</strong>-orthog<strong>on</strong>al Slater determinants, where superpositi<strong>on</strong> coefficients and orbitals in<br />

all the Slater determinants are simultaneously optimized. We can visualize quantum<br />

fluctuati<strong>on</strong>s from the structures of Slater determinants generating the wave-functi<strong>on</strong>.<br />

We have previously dem<strong>on</strong>strated that quantum fluctuati<strong>on</strong>s in the doped Hubbard<br />

model <strong>on</strong> a square lattice are described by vibrati<strong>on</strong>s and translati<strong>on</strong>s of polar<strong>on</strong>s.<br />

[Phys. Rev. Lett. 103(2009)116401.] Now, the half-filled Hubbard model <strong>on</strong> a uniform<br />

triangular lattice are c<strong>on</strong>sidered. The ground state is metallic and n<strong>on</strong>-magnetic when<br />

U is weak. We show that n<strong>on</strong>-magnetic ground state is realized by the large quantum<br />

fluctuati<strong>on</strong>s due to hybridizati<strong>on</strong> of two different co-linear spin-density waves and their<br />

modulati<strong>on</strong>s. [Phys. Rev. B84(2011)245101.]<br />

July 8 - 13, 2012 Busan, Korea 25<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PF05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Theory of momentum-dependent variati<strong>on</strong>al ansatz to str<strong>on</strong>gly<br />

correlated electr<strong>on</strong> system<br />

M. Atiqur R. Patoary* and Yoshiro Kakehashi<br />

Univ. of the Ryukyus, Nishihara, Okinawa, Japan<br />

We have recently developed Momentum dependent Local-Ansatz wavefuncti<strong>on</strong> (MLA)<br />

approach to describe the correlated electr<strong>on</strong> system in the weak and intermediate<br />

Coulomb interacti<strong>on</strong> (U) regime. The theory did not work best in the str<strong>on</strong>g U<br />

regime because we started from the Hartree-Fock (HF) wavefuncti<strong>on</strong>. To overcome<br />

the difficulty, we propose here a new hybrid wavefuncti<strong>on</strong> in which the starting<br />

wavefuncti<strong>on</strong> can vary via a new variati<strong>on</strong>al parameter w from the HF wavefuncti<strong>on</strong><br />

(w=0) suitable for the weak interacti<strong>on</strong> regime to the alloy-analogy (AA) wavefuncti<strong>on</strong><br />

(w=1) suitable in the str<strong>on</strong>g interacti<strong>on</strong> regime. The extended method overcomes<br />

the standard variati<strong>on</strong>al method such as the Gutzwiller wavefuncti<strong>on</strong> approach (GA)<br />

irrespective of U. We have dem<strong>on</strong>strate that the energy for the MLA-AA (w=1) is<br />

lower than those of the MLA-HF (w=0) in the str<strong>on</strong>g U regi<strong>on</strong> for the half-filled band<br />

Hubbard model for the hypercubic lattice in infinite dimensi<strong>on</strong>s. Moreover, the energy<br />

of the MLA (w=0 and 1) is always lower than the GA. We have also verified that the<br />

double occupati<strong>on</strong> number, quasi-particle weight and momentum distributi<strong>on</strong> functi<strong>on</strong><br />

are much improved by the new MLA.<br />

PF06<br />

Metal-insulator transiti<strong>on</strong> in orthorhombic Perovksite PbRuO 3<br />

Young-jo<strong>on</strong> S<strong>on</strong>g 1 and Kwan-woo Lee 2 *<br />

1 Department of Applied Physics, Graduate School, Korea University, Sej<strong>on</strong>g, Korea<br />

2 Department of Display and Semic<strong>on</strong>ductor Physics, Korea University, Sej<strong>on</strong>g, Korea<br />

Transiti<strong>on</strong> metal oxide perovskites show abundant physical phenomena such as<br />

superc<strong>on</strong>ductivity, CMR, ferroelectricity, and unusual magnetic behavior. Recently, the<br />

orthorhombic perovskite PbRuO 3, which was first synthesized 40 years ago, has been<br />

revisited by two experimental groups. Comm<strong>on</strong>ly, the measurements of temperaturedependent<br />

magnetic susceptibility show a kink at 90 K, where a structural transiti<strong>on</strong><br />

occurs, but no magnetic ordering has been observed even at very low T. Remarkably,<br />

the resistivity measurements of Kimber et al. indicate a metal-insulator transiti<strong>on</strong>, but<br />

<strong>on</strong>es of Cheng et al. shows a metal-metal transiti<strong>on</strong> though a kink appears at 90 K.<br />

To understand this discrepancy, we have carried out first principles calculati<strong>on</strong>s using<br />

various approaches: correlated band theory (LDA+U), LDA+U+SOC (spin-orbital<br />

coupling), modified BJ, and fixed spin moment calculati<strong>on</strong>s. In this presentati<strong>on</strong>, we<br />

will address the electr<strong>on</strong>ic and magnetic structures <strong>on</strong> PbRuO 3 in more detail and a<br />

scenario <strong>on</strong> the discrepancy.<br />

PF07<br />

Ferromagnetic semic<strong>on</strong>ductor-metal transiti<strong>on</strong> in heterostructures of<br />

europium m<strong>on</strong>oxide<br />

Tobias Stollenwerk* and Johann Kroha<br />

Physikalisches Institut, University of B<strong>on</strong>n, Germany<br />

WITHDRAWN<br />

26 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PF08<br />

The temperature dependence of the staggered magnetisati<strong>on</strong> in<br />

itinerant weak antiferromagnets<br />

Nobukuni Hatayama 1 , Rikio K<strong>on</strong>no 1 * and Yoshinori Takahashi 2<br />

1 Kinki University Technical College, Japan<br />

2 Graduate School of Material Science, University of Hyogo, Japan<br />

Effect of spin fluctuati<strong>on</strong>s <strong>on</strong> the staggered magnetisati<strong>on</strong> in itinerant weak<br />

antiferromagnets is investigated below the Neel temperature T N. It is known that the<br />

disc<strong>on</strong>tinuous change of the magnetisati<strong>on</strong> occurs at the critical temperature in the<br />

rotati<strong>on</strong>ally invariant treatment in the self-c<strong>on</strong>sistent renormalizati<strong>on</strong> spin fluctuati<strong>on</strong><br />

theory. The difficulty is resolved in itinerant weak ferromagnets by Takahashi [J. Phys.:<br />

C<strong>on</strong>dens. Matter 13 (2001) 6323. ]. In this paper, we extend his theory to the case of<br />

weak antiferromagnets. We have succeeded in deriving the temperature dependence<br />

of the staggered magnetisati<strong>on</strong> below T N, by taking account the effects of spin-waves<br />

excitati<strong>on</strong>s into the transverse comp<strong>on</strong>ent of the dynamical magnetic susceptibility<br />

within the small area of wave-vector space around the staggered wave-vector. We<br />

found T 3/2 -linear behaviour of the staggered magnetisati<strong>on</strong> at low temperatures<br />

compared with T N.<br />

PF09<br />

Theory of excit<strong>on</strong>ic insulator in the two orbital Hubbard model:<br />

Variati<strong>on</strong>al cluster approach<br />

Tatsuya Kaneko 1 *, Kazuhiro Seki 1 , Satoshi Nishimoto 2 and Yukinori Ohta 1<br />

1 Department of Physics, Chiba university, Japan<br />

2 Institut fur Theoretische Festkorperphysik, IFW Dresden, Germany<br />

Motivated by the recent experimental and theoretical studies of excit<strong>on</strong>ic insulators, we<br />

investigate the sp<strong>on</strong>taneous symmetry breaking of the excit<strong>on</strong>ic insulator state in the<br />

two-orbital Hubbard model defined <strong>on</strong> the two-dimensi<strong>on</strong>al square lattice. Using the<br />

variati<strong>on</strong>al cluster approximati<strong>on</strong> (VCA) and Hartree-Fock approximati<strong>on</strong> (HFA), we<br />

evaluate the number of particles <strong>on</strong> each orbital, staggered magnetizati<strong>on</strong> in the Mott<br />

insulator phase, the order parameter indicating the coherence between electr<strong>on</strong>s and<br />

holes in the excit<strong>on</strong>ic insulator phase, and the ground-state phase diagram as functi<strong>on</strong>s<br />

of intra-orbital and inter-orbital Coulomb interacti<strong>on</strong>s. We also calculate the singleparticle<br />

excitati<strong>on</strong> spectra of the band insulator, Mott insulator, and excit<strong>on</strong>ic insulator<br />

phases. We thereby argue that the normal metallic phase is unstable to the formati<strong>on</strong> of<br />

the excit<strong>on</strong>ic insulator phase, which should appear in a wide parameter regi<strong>on</strong> between<br />

the band insulator and Mott insulator phases.<br />

PF10<br />

Layered chalcogenide Ta 2NiSe 5 as a candidate for excit<strong>on</strong>ic insulators -<br />

theoretical aspects<br />

Tatsuya Kaneko 1 *, Tatsuya Toriyama 1 , Takehisa K<strong>on</strong>ishi 2 and Yukinori Ohta 1<br />

1 Department of Physics, Chiba university, Japan<br />

2 Graduate School of Advanced Integrati<strong>on</strong> Science, Chiba university, Japan<br />

The electr<strong>on</strong>ic structure of layered chalcogenide Ta 2NiSe 5, a candidate for excit<strong>on</strong>ic<br />

Insulators, is calculated using the generalized gradient approximati<strong>on</strong> in the density<br />

functi<strong>on</strong>al theory, where the Hubbard-type repulsive interacti<strong>on</strong> is taken into account.<br />

We find for the low-temperature m<strong>on</strong>oclinic phase that the c<strong>on</strong>ducti<strong>on</strong> band has a<br />

cosinelike quasi-<strong>on</strong>e-dimensi<strong>on</strong>al (1D) band dispersi<strong>on</strong> coming mainly from the 5dxy<br />

orbitals of Ta i<strong>on</strong>s arranged al<strong>on</strong>g the a-directi<strong>on</strong> of the lattice, whereas the top of<br />

the valence band has a quasi-1D dispersi<strong>on</strong> coming mainly from the Ni 3dxz+3dyz<br />

and Se 4px+4py orbitals arranged alternately al<strong>on</strong>g the a-directi<strong>on</strong>. The electr<strong>on</strong>ic<br />

state near the Fermi level is thus described by the quasi-1D structural unit c<strong>on</strong>sisting<br />

of these orbitals. The electr<strong>on</strong>ic structure of Ta 2NiS 5, which has the orthorhombic<br />

crystal structure, is also calculated to clarify the role of the lattice distorti<strong>on</strong>. Three<br />

scenarios are suggested to explain the characteristic temperature dependence of the<br />

band structure observed in the angle-resolved photoemissi<strong>on</strong>: a scenario of the band<br />

deformati<strong>on</strong> due to the m<strong>on</strong>oclinic lattice distorti<strong>on</strong>, a scenario of the formati<strong>on</strong> of the<br />

excit<strong>on</strong>ic insulator state, and a scenario made from the combinati<strong>on</strong> of the former two<br />

where the m<strong>on</strong>oclinic lattice distorti<strong>on</strong> and formati<strong>on</strong> of the excit<strong>on</strong>ic insulator state<br />

occur cooperatively.


PF11<br />

Electric dipolar susceptibility of the Anders<strong>on</strong>-Holstein model<br />

Takahiro Fuse* and Takashi Hotta<br />

Department of Physics, Tokyo Metropolitan University, Japan<br />

Recently, cage structure materials have attracted much attenti<strong>on</strong> due to intriguing<br />

magnetic phenomena induced by the coupling effect between electr<strong>on</strong>s and rattling, i.e.,<br />

anharm<strong>on</strong>ic local oscillati<strong>on</strong> of guest i<strong>on</strong> in a cage. When the guest i<strong>on</strong> oscillates in the<br />

cage, there should occur electric dipole moment P, given by P=Zex, where Z denotes<br />

the valence of the guest i<strong>on</strong>, e indicates electr<strong>on</strong> charge, and x is i<strong>on</strong> displacement. In<br />

order to investigate properties of electr<strong>on</strong>-rattling system, we evaluate electric dipolar<br />

susceptibility χp <strong>on</strong> the basis of the Anders<strong>on</strong>-Holstein model, which c<strong>on</strong>sists of<br />

c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong> term, hybridizati<strong>on</strong> between c<strong>on</strong>ducti<strong>on</strong> and localized electr<strong>on</strong>s,<br />

Coulomb interacti<strong>on</strong> between localized electr<strong>on</strong>s, and coupling between i<strong>on</strong> oscillati<strong>on</strong><br />

and local charge density. We analyze the model by using the numerical renormalizati<strong>on</strong><br />

group (NRG) method. Note that χp is directly related to the ph<strong>on</strong><strong>on</strong> Green’s functi<strong>on</strong> D.<br />

For the evaluati<strong>on</strong> of D, we pay due attenti<strong>on</strong> to the ph<strong>on</strong><strong>on</strong> excited states kept in the<br />

renormalizati<strong>on</strong> process. We carefully evaluate D with the use of NRG and compare<br />

it with that obtained from charge susceptibility in the combinati<strong>on</strong> with the Dys<strong>on</strong><br />

equati<strong>on</strong>. Then, we discuss the effects of anharm<strong>on</strong>icity and Coulomb interacti<strong>on</strong> <strong>on</strong><br />

χp.<br />

PF12<br />

Insulator versi<strong>on</strong> of the double-exchange ferromagnetism<br />

Yukinori Ohta 1 *, Satoshi Nishimoto 2 and Kyohei Nakano 1<br />

1 Department of Physics, Chiba University, Japan<br />

2 Institute for Theoretical Solid State Physics, IFW-Dresden, Germany<br />

The double-exchange ferromagnetism is known to appear when the coherent moti<strong>on</strong><br />

of electr<strong>on</strong>s occurs in the c<strong>on</strong>ducti<strong>on</strong> band that is coupled with the localized spins via<br />

the ferromagnetic Heisenberg-type exchange interacti<strong>on</strong>, i.e., the Hund's rule coupling.<br />

A natural and realistic issue that arises is then what happens with the ferromagnetism<br />

when a gap opens in the c<strong>on</strong>ducti<strong>on</strong> band and coherent moti<strong>on</strong> of electr<strong>on</strong>s ceases.<br />

To answer this questi<strong>on</strong> quantitatively, we apply the density-matrix renormalizati<strong>on</strong><br />

group method to the study of the <strong>on</strong>e-dimensi<strong>on</strong>al double-exchange model, where<br />

we introduce the Peierls-type lattice distorti<strong>on</strong> in the c<strong>on</strong>ducti<strong>on</strong> band to make the<br />

system an insulator with the band gap. We find from the analysis that the doubleexchange<br />

ferromagnetism persists str<strong>on</strong>gly unless the strength of the lattice distorti<strong>on</strong><br />

exceeds a certain critical limit; we thus call this an insulator versi<strong>on</strong> of the doubleexchange<br />

ferromagnetism. We note that this type of ferromagnetism actually occurs in<br />

a chromium hollandite K 2Cr 8O 16, where a half-metallic ferromagnet due to the doubleexchange<br />

mechanism undergoes a metal-insulator transiti<strong>on</strong>, resulting in the realizati<strong>on</strong><br />

of a ferromagnetic insulator [1].<br />

[1] Toriyama et al., Phys. Rev. Lett. 107, 266402 (2011).<br />

PF13<br />

Metallic ferromagnetism in the 3D Hubbard model at finite<br />

temperature<br />

Andre Neves Ribeiro and Claudio Andrade Macedo*<br />

Departamento de Fisica, Universidade Federal de Sergipe, Brazil<br />

The dynamical mean-field approximati<strong>on</strong> (DMFA), when used to study str<strong>on</strong>gly<br />

correlated electr<strong>on</strong> systems (SCES), allows the obtainment of thermodynamic<br />

properties in a n<strong>on</strong>perturbative regime. The Hubbard model is the simplest model<br />

capable of describing the essential physics of SCES. Thus, we investigated<br />

the existence of ferromagnetism in the Hubbard model <strong>on</strong> fcc lattices, at finite<br />

temperatures, using the DMFA with effective parameters solved by exact numerical<br />

diag<strong>on</strong>alizati<strong>on</strong>. We calculated the magnetizati<strong>on</strong> for 0.3 n 0.9 (where n is the number<br />

of electr<strong>on</strong>s per site), with temperature of 0.04t/kB (where t is the hopping integral<br />

between nearest-neighbor sites) and the value of the <strong>on</strong>-site Coulombian interacti<strong>on</strong> U<br />

equal to 3W (where W denotes the n<strong>on</strong>interacting energy bandwidth). Our results reveal<br />

a significant magnetizati<strong>on</strong> for n = 0.6, 0.7 and 0.8. The densities of states indicate that<br />

these systems are metallic. In the particular case for n = 0.6, magnetizati<strong>on</strong>, internal<br />

energy and specific-heat curves versus temperature were calculated to that value of U.<br />

This work provides an affirmative answer to the questi<strong>on</strong> whether the Hubbard model<br />

with <strong>on</strong>ly nearest-neighbor hopping, <strong>on</strong> a three-dimensi<strong>on</strong>al lattice, and finite both<br />

temperature and <strong>on</strong>-site Coulombian interacti<strong>on</strong>, exhibits ferromagnetism when solved<br />

using the DMFA.<br />

PF14<br />

PF15<br />

PF16<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

BCS-BEC crossover in the extended Falicov-Kimball model:<br />

Variati<strong>on</strong>al cluster approach<br />

Kazuhiro Seki 1 *, Robert Eder 2 and Yukinori Ohta 1<br />

1 Department of Physics, Chiba University, Japan<br />

2 Institut fuer Festkoerperphysik, Karlsruhe Institute of Technology, Germany<br />

We study the sp<strong>on</strong>taneous symmetry breaking of the excit<strong>on</strong>ic insulator state induced<br />

by the Coulomb interacti<strong>on</strong> U in the two-dimensi<strong>on</strong>al extended Falicov-Kimball model.<br />

Using the variati<strong>on</strong>al cluster approximati<strong>on</strong> (VCA) and Hartree-Fock approximati<strong>on</strong><br />

(HFA), we evaluate the order parameter, single-particle excitati<strong>on</strong> gap, momentum<br />

distributi<strong>on</strong> functi<strong>on</strong>s, coherence length of excit<strong>on</strong>s, and single-particle and anomalous<br />

excitati<strong>on</strong> spectra as functi<strong>on</strong>s of U at zero temperature. We find that in the weak-tointermediate<br />

coupling regime, the Fermi surface plays an essential role and calculated<br />

results can be understood in close corresp<strong>on</strong>dence with the BCS theory, whereas in the<br />

str<strong>on</strong>g-coupling regime, the Fermi surface plays no role and results are c<strong>on</strong>sistent with<br />

the picture of a Bose-Einstein c<strong>on</strong>densate (BEC). Moreover, we find that HFA works<br />

well in both the weak and str<strong>on</strong>g-coupling regimes, and that the difference between<br />

the results of VCA and HFA mostly appears in the intermediate-coupling regime. The<br />

reas<strong>on</strong> for this is discussed from a viewpoint of the self-energy. Details are reported in<br />

Ref. [1].<br />

[1] K. Seki, R. Eder, and Y. Ohta, Phys. Rev. B 84, 245106 (2011).<br />

Theory of the metal-insulator transiti<strong>on</strong> and charge/orbital states in<br />

V 6O 13<br />

Takayoshi Nakayama 1 *, Tatsuya Toriyama 1 , Takehisa K<strong>on</strong>ishi 2 and Yukinori Ohta 1<br />

1 Department of Physics, Chiba University, Japan<br />

2 Graduate School of Advanced Integrati<strong>on</strong> Science, Chiba University, Japan<br />

The Wadsley-phase vanadium oxide V 6O 13 has the crystal structure composed of the<br />

two-dimensi<strong>on</strong>al single and double trellis lattices, where the V i<strong>on</strong>s are in the mixed<br />

valent state with an average valence of V4.33+ (3d0.66); i.e., there are formally<br />

V5+ (3d0) and V4+ (3d1) in a 1 : 2 ratio. This material undergoes a metal-insulator<br />

transiti<strong>on</strong> (MIT) at 150K, which is accompanied by the structural distorti<strong>on</strong>, and<br />

shows an antiferromagnetic order below 55K. To clarify the electr<strong>on</strong>ic structure of this<br />

material, we make the density-functi<strong>on</strong>al-theory-based electr<strong>on</strong>ic structure calculati<strong>on</strong>s<br />

and discuss the mechanism of the MIT, as well as its charge and orbital states above<br />

and below the MIT. We find that the band structure obtained is in reas<strong>on</strong>able agreement<br />

with the observed angle-resolved photoemissi<strong>on</strong> spectra but that the characteristic<br />

distributi<strong>on</strong> of valence electr<strong>on</strong>s is not necessarily compatible with the results of a<br />

recent NMR experiment. We also find that, if we assume the observed low-temperature<br />

crystal structure in the calculati<strong>on</strong>s, we obtain the insulating soluti<strong>on</strong> with an<br />

antiferromagnetic order, which is in agreement with experiment.<br />

Statistical dynamical mean field study of correlated fermi<strong>on</strong>s with<br />

disorder<br />

Masaru Sakaida*, Kazuto Noda and Norio Kawakami<br />

Kyoto university, Japan<br />

Disordered systems with str<strong>on</strong>g correlati<strong>on</strong> effects have been studied in solid state<br />

physics, and even now have attracted much interest. Various experiments have been<br />

performed extensively, and in particular a disordered system of str<strong>on</strong>gly interacting<br />

cold atoms has been experimentally realized recently[1]. Statistical dynamical meanfield<br />

theory[2,3] to treat disorders and str<strong>on</strong>g correlati<strong>on</strong> effects <strong>on</strong> equal footing and<br />

n<strong>on</strong>-perturbatively makes it possible to capture essential features of the Anders<strong>on</strong><br />

transiti<strong>on</strong> bey<strong>on</strong>d the coherent-potential approximati<strong>on</strong>. In this work, we analyze the<br />

tight-binding fermi<strong>on</strong> model <strong>on</strong> the Bethe lattice in which the box disorder manifests<br />

itself by random <strong>on</strong>-site energies. We systematically investigate characteristic behaviors<br />

of the density of states and the c<strong>on</strong>ductivity to estimate competiti<strong>on</strong>s between disorders<br />

and correlati<strong>on</strong> effects in this system.<br />

[1] L. Fallani et al., Phys. Rev. Lett. 98, 130404 (2007) [2] V. Dobrosavljevic et al., Phys. Rev. Lett.<br />

78, 3943 (1997) [3] D. Semmler et al., Phys. Rev. B 84, 115113 (2011)<br />

July 8 - 13, 2012 Busan, Korea 27<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PF17<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Analysis of many-body effects <strong>on</strong> anisotropic magnetic properties of<br />

YbB 12<br />

Yoshihiro Kikuchi*, Yoshiki Imai and Tetsuro Saso<br />

Department of Physics, Saitama University, Japan<br />

YbB 12 is <strong>on</strong>e of the typical K<strong>on</strong>do insulator and many experiments are already reported.<br />

Although it has cubic structure, critical magnetic fields of insulator-to-metal transiti<strong>on</strong><br />

are anisotropic[1]. Moreover anisotropic magnetizati<strong>on</strong> is observed above the critical<br />

field[2]. One of the authors studied the magnetic properties by means of tight binding<br />

model, composed of Yb 5dε and 4f Γ 8 orbitals[3]. The results were qualitatively in<br />

agreement with the experiments but a quantitative disagreement was left, because<br />

many-body effects were not taken into account. Therefore, we introduce coulomb<br />

repulsi<strong>on</strong> between f-electr<strong>on</strong>s in the tight binding model. We apply the dynamical mean<br />

field theory, in which we solve the effective impurity problem by using the c<strong>on</strong>tinuoustime<br />

quantum M<strong>on</strong>te Carlo method. We compare obtained result with the experimental<br />

<strong>on</strong>e’s quantitatively, and discuss the many-body effects in the magnetic properties of<br />

YbB 12.<br />

[1] F. Iga et al. : Jpn. J.Appl. Phys. Series 11(1999)88 [2] S. Hiura, et al.: Physica B<br />

281&282(2000)271 [3] T. Izumi, Y. Imai, T. Saso : J. Phys. Soc. Jpn. 76(2007)084715<br />

PF18<br />

The ground state energies of spinless free fermi<strong>on</strong>s and hard-core<br />

bos<strong>on</strong>s in 2D square lattices<br />

Wenxing Nie 1 and Masaki Oshikawa 2 *<br />

1 The Institute for Solid State Physics, The University of Tokyo, Japan<br />

2 The institute for Solid State Physics, The University of Tokyo, Japan<br />

We compare the ground state energies of hard-core bos<strong>on</strong>s and spinless free fermi<strong>on</strong>s<br />

<strong>on</strong> the same lattice. Ground state energy of bos<strong>on</strong>s is usually expected to be lower<br />

than that of fermi<strong>on</strong>s, because bos<strong>on</strong>s can c<strong>on</strong>dense into the lowest energy state.<br />

However, in the presence of hard-core interacti<strong>on</strong> am<strong>on</strong>g bos<strong>on</strong>s, the c<strong>on</strong>densati<strong>on</strong> is<br />

not perfect and comparis<strong>on</strong> is n<strong>on</strong>trivial. We find that, in the absence of frustrati<strong>on</strong>, the<br />

ground state energy of hard-core bos<strong>on</strong>s is indeed lower than that of free fermi<strong>on</strong>s. In<br />

general, however, the hard-core bos<strong>on</strong>s could have higher ground state energy than the<br />

fermi<strong>on</strong>s <strong>on</strong> the same lattice if there is a frustrati<strong>on</strong>. In fact, there is an exactly solvable<br />

<strong>on</strong>e-dimensi<strong>on</strong>al model, in which the ground state energy of bos<strong>on</strong>s is proved to be<br />

higher. However, the difference vanishes in the thermodynamic limit. We also studied<br />

the two-dimensi<strong>on</strong>al square lattice with uniform magnetic flux perpendicular to the<br />

lattice, by numerical diag<strong>on</strong>alizati<strong>on</strong>. As the magnetic flux introduces frustrati<strong>on</strong>, we<br />

actually find the ground state energy of hard-core bos<strong>on</strong>s is higher for a range of flux<br />

and particle density. In the two dimensi<strong>on</strong>al case, this difference seems to persist in the<br />

thermodynamic limit, in c<strong>on</strong>trast to the <strong>on</strong>e-dimensi<strong>on</strong>al case.<br />

[1]Phys. Rev. B 14, 2239 (1976) [2]Phys. Rev. Lett. 83, 2246(1999) [3]Phys. Rev. Lett. 96, 036406<br />

(2006)<br />

PF19<br />

Correlati<strong>on</strong> effect in ferromagnetic 3d transiti<strong>on</strong> metals<br />

Muneyuki Nishishita 1 , Sudhakar Pandey 2 and Dai Hirashima 1 *<br />

1 Nagoya University, Japan<br />

2 APTPC, Korea<br />

Selfc<strong>on</strong>sistent perturbati<strong>on</strong> theory is applied to ferromagnetic 3d transiti<strong>on</strong> metals, Fe<br />

and Ni. Realistic tight-binding model is used to describe the electr<strong>on</strong>ic states of the<br />

system. It is found that a reas<strong>on</strong>able value of the Curie temperature for Fe is obtained<br />

for realistic strength of the Coulomb interacti<strong>on</strong>. Dynamical transverse susceptibility<br />

is also calculated. Here, vertex correcti<strong>on</strong>s are c<strong>on</strong>sidered so that the spin rotati<strong>on</strong>al<br />

symmetry is preserved. Then, the spin-wave energy correctly vanishes in the l<strong>on</strong>gwavelength<br />

limit. The effect of the electr<strong>on</strong> correlati<strong>on</strong> <strong>on</strong> the spin stiffness is clarified.<br />

We also compare the spin fluctuati<strong>on</strong> spectra below and above the Curie temperature<br />

and discuss the possible short-range order above the Curie temperature.<br />

28 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PG01<br />

Ferrimagnetic compensati<strong>on</strong> in a Fe64Er19B17 glass, - the head of a<br />

dandeli<strong>on</strong>, or the spokes of a wheel?<br />

Andrew R. Wildes 1 *, Neil Cowlam 2 and Nourh A. Al-senany 3<br />

1<br />

Institut Laue-Langevin, BP 156, 6 rue jules Horowitz, 38042 GRENOBLE Cedex 9,<br />

France<br />

2<br />

Department of Physics and Astr<strong>on</strong>omy, University of Sheffield, SHEFFIELD, S3<br />

7RH, United Kingdom<br />

3<br />

Department of Physics and Astr<strong>on</strong>omy, University of Sheffield, SHEFFIELD, S3<br />

7RH, King Abdulaziz University, Jeddah, Saudi Arabia, United Kingdom<br />

Magnetizati<strong>on</strong> and neutr<strong>on</strong> scattering measurements with polarizati<strong>on</strong> analysis were<br />

made <strong>on</strong> a Fe 64Er 19B 17 glass to investigate its ferrimagnetic compensati<strong>on</strong> at T(comp)<br />

= 112 ± 2K. The measurements prove that the glass has a n<strong>on</strong>-collinear magnetic<br />

structure. The two n<strong>on</strong>-spin flip cross-secti<strong>on</strong>s interchange between 100K and 125K,<br />

proving the magnetic structure flips at T(comp). They are identical at 112K where<br />

the forward limit of the spin flip cross-secti<strong>on</strong>s was greatest. The mean collinear<br />

comp<strong>on</strong>ents of the moments therefore go to zero at T(comp). If the moment vectors<br />

were mapped to originate at a point, the data corresp<strong>on</strong>d either to the moments being<br />

randomly oriented like the head of a dandeli<strong>on</strong>, or with a collapse of the moments into<br />

a plane normal to the field, like the spokes of a wheel. The data will be presented and<br />

the possible driving mechanisms for the ferrimagnetic compensati<strong>on</strong> will be discussed.<br />

PG02<br />

Evoluti<strong>on</strong> of reverse magnetized seed in m<strong>on</strong>odomain uniaxial garnet<br />

film elements<br />

Vladimir Skidanov*<br />

Nanoelectr<strong>on</strong>ics and Spintr<strong>on</strong>ics Department, Institute for Design Problems in<br />

Microelectr<strong>on</strong>ics RAS, Russia<br />

Evoluti<strong>on</strong> of cylindrical domain seeded in m<strong>on</strong>odomain film and film circular element<br />

was investigated numerically and experimentally. It is found that in c<strong>on</strong>tinuous film in<br />

zero external magnetic field cylindrical domain may expand unlimitedly or collapse<br />

independently <strong>on</strong> initial diameter of the seed. Single seed expansi<strong>on</strong> followed by<br />

film magnetizati<strong>on</strong> reversal is observed if l/h < 1.38 (where l is garnet characteristic<br />

length, h is film thickness). C<strong>on</strong>stant positive external magnetic field antiparallel<br />

to magnetizati<strong>on</strong> inside seed supports stable domain diameter which is inverse<br />

proporti<strong>on</strong>al to field intensity H. Cylindrical domain inside disk is found stable in<br />

zero and negative external magnetic field due radial gradient of inhomogeneous stray<br />

field of the disk boundary. If l/h > 1.38 reverse magnetized seed collapses in zero<br />

external field. Stable domain doesn’t exist in c<strong>on</strong>stant negative external field parallel<br />

to seed magnetizati<strong>on</strong> this case. Unlimited domain expansi<strong>on</strong> takes place if modulus<br />

of negative H exceeds critical value which is inverse proporti<strong>on</strong>al to initial seed<br />

diameter. Domain is stable if domain wall embraces circular hole in garnet film. This<br />

case garnet boundary stray field prevents from domain c<strong>on</strong>tracti<strong>on</strong> in zero and positive<br />

external field. Two-domain ring-shape elements can be utilized as fast magnetooptical<br />

modulators.<br />

PG03<br />

Re-entrant structure and critical behaviour of Fe-Cr and Fe-V sigmaphase<br />

alloys<br />

Reginaldo Barco 1 , Paulo Pureur 1 , G L F Fraga 1 and Stanislaw M Dubiel 2<br />

1 Physics, UFRGS Porto Alegre, Brazil<br />

2 Physics and Applied Computer Science, AGH University Krakow, Poland<br />

The σ-phase (tetrag<strong>on</strong>al unit cell, space group D144h-P42/mnm) bel<strong>on</strong>gs to a family<br />

of a complex Frank-Kasper phases. It can be formed in transiti<strong>on</strong>-metal alloys. Only<br />

two alloys, am<strong>on</strong>g about 50 examples of σ known to occur in binary systems, viz. Fe-<br />

Cr and Fe-V have well-evidenced magnetic properties. The magnetic ordering of σ<br />

has been regarded as ferromagnetic (FM) with the Curie temperatures, Tc, below ~40<br />

K for σ-FeCr and below ~315 K for σ-FeV. Here we report a clear evidence that the<br />

ground state of the σ-phase Fe 0.53Cr 0.47 and Fe 0.52V 0.48 alloys is a re-entrant spin-glass<br />

(RSG). The evidence was found from a study of magnetizati<strong>on</strong> versus temperature, T,<br />

and magnetic field, H. Based <strong>on</strong> the field-cooled and zero-field-cooled magnetizati<strong>on</strong><br />

curves recorded in different fields, H, phase diagrams in the H-T plane could have been<br />

drawn. They display the locati<strong>on</strong> of the paramagnetic (P), FM and RSG states, and are<br />

in a qualitative accord with predicti<strong>on</strong>s of the mean-field theory. Critical behaviour near<br />

Tc was also studied with both c<strong>on</strong>venti<strong>on</strong>al and extended protocols, and the critical<br />

exp<strong>on</strong>ents β, γ, δ were determined.


PG04<br />

Pressure effects in the ferromagnetic shape memory alloys Ni 2Mn 1xCu<br />

xGa<br />

Tomoya Miura 1 , Yoshiya Adachi 1 *, Keita Endo 2 , Ryosuke Kainuma 2 and Takeshi<br />

Kanomata 3<br />

1 Graduate School of Science and Engineering, Yamagata University, Japan<br />

2 Department of Materials Science, Tohoku University, Japan<br />

3 Faculty of Engineering, Tohoku Gakuin University, Japan<br />

The Heusler alloy Ni 2MnGa attracts attenti<strong>on</strong> as an actuator material because the<br />

magnetic distorti<strong>on</strong> of about 10% is observed just below the martensitic transiti<strong>on</strong><br />

temperature (TM). The pressure dependence coefficient of the Curie temperature of<br />

Ni 2MnGa is +1.0×10-8 K/Pa.[1] In the Ni 2Mn 1-xCu xGa alloy system, TC and TM were<br />

reported by Kataoka et al.[2] that the samples with the range of x < 0.23, 0.23 < x <<br />

0.30 and x > 0.30 are characterized TC > TM, TC = TM and TC < TM, respectively.<br />

We carried out the initial permeability measurements under pressure up to 1 GPa for<br />

Heusler Ni 2Mn 1-xCu xGa system. TM and TC were determined from the change of<br />

the initial permeability under each pressure. It was found that TM was c<strong>on</strong>sidered to<br />

coincide with TC in 0.23 < x < 0.30. Moreover it was obtained dTC/dp is positive<br />

in x < 0.23 and dTC/dp is negative in x > 0.30. As a result, the temperature-pressure<br />

magnetic phase diagram was obtained. We’d like to discuss the mechanism of the<br />

martensitic transformati<strong>on</strong> in Heusler alloy Ni 2Mn 1-xCu xGa system.<br />

[1] T.Kanomata et al.: J. Magn. Magn. Mater 65 (1987) 76. [2] M. Kataoka et al.: Phys. Rev B 82<br />

(2010) 214423.<br />

PG05<br />

Electr<strong>on</strong>ic state of Cr and collapse-like decrease of Fe magnetic<br />

moment in amorphous (Fe-Cr)B alloys<br />

Kazuo Yano 1 *, Tastuo Kamimori 2 , Hiroaki Kanetsuki 2 , Hatsuo Tange 2 , Masayoshi<br />

Itou 3 , Yoshiharu Sakurai 3 , Eiji Kita 4 and Hiromitsu Ino 5<br />

1<br />

College of Science and Technology, Nih<strong>on</strong> University, Japan<br />

2<br />

Faculty of Science, Ehime University, Japan<br />

3<br />

JASRI/SPring8, Japan<br />

4<br />

Applied Physics, University of Tsukuba, Japan<br />

5<br />

Faculty of Engineering, University of Tokyo, Japan<br />

Magnetic properties in amorphous alloys have been extensively investigated in rare earth (RE)-transiti<strong>on</strong><br />

metal (TM) systems and transiti<strong>on</strong> metal (TM)-mettaloids systems. Many interesting and important<br />

problems have been investigated and solved, however, some of the important problems seem to be hard<br />

nuts to crack and remain unsolved. One of the unsolved and interesting problems is an anomaly in Slater-<br />

Pauling curve discovered by Mizoguchi et al. and the Fe magnetic moment decreases abruptly, for example<br />

in (Fe-Cr) 80B 20 amorphous alloys. For instance, the substituti<strong>on</strong> of Fe by <strong>on</strong>ly 10 at% of Cr causes about<br />

50 %decrease of Fe magnetic moment. Mizoguchi et al. suggested that the Cr retained magnetic moment<br />

and coupled anti-parallel to that of Fe, however there have been no decisive experimental results. In order<br />

to detect and examine the Cr magnetic moment, <strong>on</strong>e of the powerful tools for this aim, is the magnetic<br />

Compt<strong>on</strong> scattering profile (MCP) method which can obtain the infornmati<strong>on</strong>s of 3d electr<strong>on</strong>s and the<br />

spin-polarized outer 4s, 4p electr<strong>on</strong>s, separately. The MCP measurement was carried out for (Fe-Cr) 80B 20<br />

(Cr=0.1, 0.2, 0.3) and the result suggest the existence of Cr magnetic moment coupling antiparallel to that<br />

of Fe. Macroscopic magnetic properties were also measured and analyzed.<br />

PG06<br />

Micromagnetic simulati<strong>on</strong> of CNT-MFM probes under magnetic field<br />

Takashi Manago 1 *, Hir<strong>on</strong>ori Asada 2 and Hiromi Kuramochi 3<br />

1 Department of Applied Physics, Fukuoka university, Japan<br />

2 Graduate School of Science and Engineering, Yamaguchi university, Japan<br />

3 <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Center for Materials Nanoarchitect<strong>on</strong>ics, Nati<strong>on</strong>al Institute for<br />

Materials Science(NIMC), Japan<br />

Ferromagnetic-film-coated carb<strong>on</strong> nanotube in a magnetic force microscope (CNT-<br />

MFM) dem<strong>on</strong>strated the high spacial resoluti<strong>on</strong> of about 10 nm and low perturbati<strong>on</strong>.<br />

The magnetic strucutres of CNT-MFM probes were investigated using threedimensi<strong>on</strong>al<br />

micromagnetic simulati<strong>on</strong> and it showed the advantages of the CNT-MFM<br />

probes [1]. In this paper, the stability of the magnetic structure in external magnetic field<br />

was investigated to c<strong>on</strong>firm magnetic robustness using micromagnetic simulati<strong>on</strong>. At a<br />

remanent state, the magnetic moments of the CNT-MFM probe align almost al<strong>on</strong>g the<br />

l<strong>on</strong>gitudinal directi<strong>on</strong> of the CNT lod due to the shape anisotropy. When the opposite<br />

magnetic field applied, the magnetic moments of the probes reversed all at <strong>on</strong>ce at<br />

about 200 mT. In the pyramidal probe, the vortex core was appeared around the tip at<br />

a remanent state. When the opposite magnetic field applied, the magnetizati<strong>on</strong> of the<br />

side wall gradually tilted, and at last the vortex core was reversed. Thus magnetizati<strong>on</strong><br />

reversal process is quite different because of large difference in magnetic structures<br />

between the CNT-MFM and pyramidal probes. We found that the CNT-MFM probes<br />

have better magnetic robustness than the c<strong>on</strong>venti<strong>on</strong>al pyramidal probes.<br />

[1] T. Manago et al., Nanotechnology, 23, 035501 (2012).<br />

PG07<br />

PG08<br />

PG09<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Pressure effect of metamagnetic shape memory alloy Pd 2Mn 1+xSn 1-x<br />

Yohei Yamazaki 1 , Takamitsu Akama 2 , Hir<strong>on</strong>ari Okada 1 *, Takeshi Kanomata 1 and<br />

Ryosuke Kainuma 3<br />

1 Divisi<strong>on</strong> of Engineering Graduate School, Tohoku Gakuin University, Japan<br />

2 Faculty of Engineering, Tohoku Gakuin University, Japan<br />

3 Graduate School of Engineering, Tohoku University, Japan<br />

Recently, it has been reported that NiMnX (X = In, Sn and Sb) Heusler alloys show<br />

metamagnetic shape memory effect. In these alloys, the martensitic transformati<strong>on</strong><br />

temperature decreases with increasing magnetic field, and magnetic field-induced<br />

reverse martensitic transformati<strong>on</strong> associated with metamagnetic transiti<strong>on</strong> occurs<br />

below the martensitic transformati<strong>on</strong> temperature. Since the magnetic fieldinduced<br />

transformati<strong>on</strong> leads an almost perfect shape memory effect, these alloys<br />

attract attenti<strong>on</strong> as new type of ferromagnetic shape memory alloys. Very recently,<br />

similarly to NiMnX Heusler alloys, it has been found that PdMnSn Heusler alloys<br />

show metamagnetic shape memory effects and a drastic change with martensitic<br />

transformati<strong>on</strong> in magnetic and transport properties. In this study, in order to investigate<br />

pressure effect <strong>on</strong> martensitic transformati<strong>on</strong> in PdMnSn Heusler alloys, we performed<br />

electrical resistivity measurements under high pressure. As a result, it was found that<br />

the pressure-temperature phase diagram is similar to the temperature-Mn c<strong>on</strong>tent phase<br />

diagram. These results suggest that the atomic distance plays an important role for<br />

martensitic transformati<strong>on</strong> in PdMnSn Heusler alloys.<br />

Engineering of Co atomic 1-D chains <strong>on</strong> Ag(111) with tailored magnetic<br />

ground state.<br />

David Serrate 1 *, Maria Moro 1 , Marten Piantek 2 , Jose Ignacio Pascual 3 and Manuel<br />

Ricardo Ibarra 1<br />

1 Instituto de Nanociencia de Arag<strong>on</strong>, University of Zaragoza, Spain<br />

2 Instituto de Ciencia de Materiales de Arag<strong>on</strong>, CSIC-University of Zaragoza, Spain<br />

3 Institut fur Experimentalphysik, Freie Universitat Berlin, Germany<br />

Certain magnetic adatoms lying <strong>on</strong> a metal surface give rise to a K<strong>on</strong>do res<strong>on</strong>ance. We used the<br />

model system of Co atoms <strong>on</strong> Ag(111) to investigate their magnetic interacti<strong>on</strong>s through the K<strong>on</strong>do<br />

res<strong>on</strong>ance [1,2] . The Co atoms architecture and the substrate LDOS landscape are artificially<br />

arranged by means of lateral manipulati<strong>on</strong> with a scanning tunneling microscope (STM) tip at 4.8<br />

K. The res<strong>on</strong>ance is subsequently characterized by means of STM spectroscopy. Individual Co<br />

atoms in natural equilibrium positi<strong>on</strong>s at minima of the surface LDOS exhibit K<strong>on</strong>do temperature<br />

TK=90 K in agreement with earlier studies [3]. TK can be gradually varied from 60 to 145 K by<br />

positi<strong>on</strong>ing the same atom in different Ag LDOS values of the interference patterns. The coordinati<strong>on</strong><br />

with neighboring Co atoms increases TK when their distance decreases below four Ag(111) lattice<br />

parameters (2.9 A). In Co chains with N atoms (N=2,3,...,19), both the amplitude and the spatial extent<br />

of the many-body wave functi<strong>on</strong> of the K<strong>on</strong>do res<strong>on</strong>ance are reduced with increasing coordinati<strong>on</strong>. In<br />

the frame of the two impurity K<strong>on</strong>do theory, our data unveil the nature of direct Co-Co and substrate<br />

mediated magnetic interacti<strong>on</strong>s as a functi<strong>on</strong> of the local electr<strong>on</strong>ic and structural envir<strong>on</strong>ment.<br />

[1] A. Otte et al., Nature Phys. 4, 847 (2008) [2] J. Bork et al., Nature Phys. 7, 901 (2011) [3] M.A.<br />

Schneider et al., Phys. Rev. B 65, 121406R (2002)<br />

Pressure-induced suppressi<strong>on</strong> of magnetic ordering in a chiral magnet<br />

Cr1/3NbS2 Takumi Imakyurei 1 , Kousuke Nagai 1 , Masaki Mito 1 , Hiroyuki Deguchi 1 , Jun-ichiro<br />

Kishine 1 , Takayuki Tajiri 2 , Katsuya Inoue 3 , Yuya Nakao 4 , Yusuke Kousaka 4 and Jun<br />

Akimitsu 4<br />

1<br />

Faculty of Engineering, Kyushu Institute of Technology, Japan<br />

2<br />

Faculty of Science, Fukuoka University, Japan<br />

3<br />

Department of Chemistry and Institute for Advanced Materials Research, Hiroshima<br />

University, Japan<br />

4<br />

Department of Physics and Mathematics, Aoyama-Gakuin University, Japan<br />

Cr 1/3NbS 2 is a chiral magnet without structural inversi<strong>on</strong> center. The magnetic property<br />

is attributed to the localized moment of Cr, and metallic c<strong>on</strong>ductivity is attributed<br />

to c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s of Nb. We expect that Cr 1/3NbS 2 would become a n<strong>on</strong>centrosymmetric<br />

superc<strong>on</strong>ductor after disappearance of magnetic ordering at high<br />

pressure. Thus we carried out the AC susceptibility measurements at pressures up to 10<br />

GPa and powder X-ray diffracti<strong>on</strong> experiments at room temperature up to 7 GPa for<br />

the powder sample of Cr 1/3NbS 2. In the pressure regi<strong>on</strong> of below 3 GPa, the anomaly<br />

of magnetic susceptibility due to the magnetic ordering shifted toward low temperature<br />

side and the magnitude was gradually suppressed. At present, the Meissner signal has<br />

not yet been observed in the temperature regi<strong>on</strong> down to 2 K and the pressure regi<strong>on</strong><br />

up to 10 GPa. The lattice parameters exhibited the change of c<strong>on</strong>tracti<strong>on</strong> at around 3<br />

GPa, where it became difficult to evaluate the magnetic ordering temperature.<br />

July 8 - 13, 2012 Busan, Korea 29<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PG10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Multiple ESR spectra in a chiral molecule-based magnet [Cr(CN) 6]<br />

[Mn(R )-pnH(H 2O)](H 2O)<br />

Takuma Nagano 1 , Masaki Mito 1 , Seishi Takagi 1 , Hiroyuki Deguchi 1 , Jun-ichiro<br />

Kishine 1 , Yusuke Yoshida 2 and Katsuya Inoue 2<br />

1 Faculty of Engineering, Kyushu Institute of Technology, Japan<br />

2 Department of Chemistry and Institute for Advanced Materials Research, Hiroshima<br />

University, Japan<br />

A molecule-based magnet [Cr(CN) 6][Mn(R)-pnH(H 2O)](H 2O) (abbreviated as R-GN) is a chiral<br />

magnet without inversi<strong>on</strong> center and mirror reflecti<strong>on</strong>. The magnetic network is c<strong>on</strong>structed with<br />

the help of a chiral ligand diaminopropane. In R-GN, multiple spectra of ESR were observed<br />

below magnetic order temperature by Morgunov et al. [1]. They c<strong>on</strong>cluded that the phenomen<strong>on</strong><br />

was caused by the formati<strong>on</strong> of a chiral solit<strong>on</strong> lattice, which originated from incommensurate<br />

magnetic structure. However, we have a suspici<strong>on</strong> against their interpretati<strong>on</strong>, because R-GN<br />

indeed exhibits no incommensurate magnetic structure. Now, we c<strong>on</strong>ducted the experiment of<br />

X-band ESR measurement in the c<strong>on</strong>diti<strong>on</strong> similar to the experiment by Morgunov et al., and<br />

performed the detailed spectrum analyses: In order to reproduce the main ESR spectra, at least<br />

two Lorentz spectra are required, and the multiplicity was explained by assuming the existence<br />

of two characteristic modes when each periodicity is defined as f or f’ (< f), there is a relati<strong>on</strong> of<br />

f = 2f’. We c<strong>on</strong>sider that the magnetic fine structure originates from the existence of at least two<br />

n<strong>on</strong>equivalent magnetic sites owing to the diaminopropane with electric dipole moment.<br />

[1] R. Morgunov et al., Phys. Rev. B 77 (2008) 184419.<br />

PG11<br />

Valence and spin structures of TFe2O4 spinel oxides (T=Mn, Co, Ni,<br />

Cu) investigated by using synchrotr<strong>on</strong> radiati<strong>on</strong><br />

Jiho<strong>on</strong> Hwang 1 , D. H. Kim 1 , Eunsook Lee 1 , J.-s. Kang 1 , B.-g. Park 2 , J.-y. Kim 2 , S. W.<br />

Han 3 , S. C. H<strong>on</strong>g 3 , S. B. Kim 4 , B<strong>on</strong>gjae Kim 5 and B. I. Min 5<br />

1 Department of Physics, The Catholic University of Korea (CUK), Buche<strong>on</strong> 420-743, Korea, Korea<br />

2 Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Korea, Korea<br />

3 Department of Physics, Ulsan University, Ulsan 680-749, Korea, Korea<br />

4 ACE center, K<strong>on</strong>yang University, N<strong>on</strong>san 320-711, Korea, Korea<br />

5 Department of Physics, POSTECH, Pohang 790-784, Korea, Korea<br />

AB 2O 4-type spinel oxides have attracted much attenti<strong>on</strong> because of the interesting physical phenomena, such as<br />

Jahn-Teller (JT) effects, multiferroic phenomena, and phase separati<strong>on</strong>s [1]. In normal spinels of AB 2O 4, A and<br />

B i<strong>on</strong>s occupy the tetrahedral (Td) and octahedral (Oh) sites, respectively. When both A and B i<strong>on</strong>s are magnetic<br />

i<strong>on</strong>s, a ferrimagnetic (FiM) ordering is often observed because the A-B interacti<strong>on</strong> is mainly antiferromagnetic.<br />

In this work, we have investigated the electr<strong>on</strong>ic structures of FiM spinels of TFe 2O 4 (T=Mn, Co, Ni, Cu) by<br />

employing soft x-ray absorpti<strong>on</strong> spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). It is<br />

found that the valence states of Fe i<strong>on</strong>s are nearly trivalent (-Fe 3+ ) and those of T i<strong>on</strong>s are nearly divalent (-T 2+ ).<br />

The 2p XMCD spectra of MnFe 2O 4 show that the magnetic moments of Mn 2+ and Fe 3+ i<strong>on</strong>s are antiparallel to<br />

each other. On the other hand, the magnetic moments of Co 2+ , Ni 2+ , and Cu 2+ i<strong>on</strong>s are parallel to those of B(Oh)site<br />

Fe 3+ i<strong>on</strong>s, but are antiparallel to those of A(Td)-site Fe 3+ i<strong>on</strong>s, implying that Fe 3+ i<strong>on</strong>s occupy both A and B<br />

sites while Co, Ni, Cu i<strong>on</strong>s occupy mainly B sites. *Corresp<strong>on</strong>ding Author: kangjs@catholic.ac.kr<br />

[1] J.-S. Kang, et al., Phys. Rev. B 77, 035121 (2008).<br />

PG12<br />

Probing the distance dependence of the magnetic exchange interacti<strong>on</strong><br />

with atomic resoluti<strong>on</strong><br />

Alexander Schwarz 1 *, Rene Schmidt 1 , Roland Wiesendanger 1 , Cesar Lazo 2 and Stefan<br />

Heinze 3<br />

1 Institute of Applied Physics, University of Hamburg, Germany<br />

2 Christian-Albrechts Universitat zu Kiel, Germany<br />

3 Christian-Albrechts-Universitat zu Kiel, Germany<br />

Quantifying strength and distance dependence of magnetic interacti<strong>on</strong>s between atoms is crucial<br />

to gain a deeper understanding of magnetic phenomena <strong>on</strong> the nanoscale. Magnetic exchange<br />

force microscopy (MExFM) [1] is a new and very versatile tool to study magnetism with atomic<br />

resoluti<strong>on</strong> in real space. It utilizes an atomically sharp magnetic tip at the free end of a cantilever<br />

to detect the short-ranged electr<strong>on</strong>-mediated magnetic exchange interacti<strong>on</strong> between tip apex and<br />

surface atoms. This force microscopy based technique can be employed to map spin structures<br />

of insulating [1] as well as c<strong>on</strong>ducting [2] magnetic samples with atomic resoluti<strong>on</strong>. Here we<br />

dem<strong>on</strong>strate that its spectroscopic mode, i.e., magnetic exchange force spectroscopy (MExFS),<br />

is able to measure the distance dependence of the magnetic exchange interacti<strong>on</strong> in a very direct<br />

and elegant fashi<strong>on</strong> [3]. Results obtained <strong>on</strong> the antiferromagnetic Fe m<strong>on</strong>olayer <strong>on</strong> W(001) are<br />

compared with theoretical calculati<strong>on</strong>s based <strong>on</strong> density functi<strong>on</strong>al theory. They were performed<br />

for realistic multiatom tips and agree very well with data acquired using n<strong>on</strong>-dissipative stable tips.<br />

[1] U. Kaiser, A. Schwarz, and R. Wiesendanger, Nature 446, 522 (2007). [2] R. Schmidt, C. Lazo, H.<br />

Holscher, U. H. Pi, V. Caciuc, A. Schwarz, R. Wiesendanger, and S. Heinze, Nano. Lett. 9, 200 (2009). [3] R.<br />

Schmidt, C. Lazo, U. Kaiser, A. Schwarz, S. Heinze, and R. Wiesendanger, Phys. Rev. Lett. 106, 257202 (2011).<br />

30 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PG13<br />

Electr<strong>on</strong> correlati<strong>on</strong> in a mixed valence perovskite system of Sr 1xCa<br />

xRu 0.5Mn 0.5O 3<br />

Tomohiro Ohnishi 1 , Soichiro Mizusaki 1 , Makoto Naito 1 , Yoshihiko Noro 2 , Masayoshi<br />

Itou 3 , Yoshiharu Sakurai 3 and Yujiro Nagata 1<br />

1 Electrical Engineering and Electr<strong>on</strong>ics, Aoyama Gakuin Univ., Japan<br />

2 Kawazoe Fr<strong>on</strong>tier Technologies Co. Ltd., Japan<br />

3 Japan Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Institute, Japan<br />

Mixed valence systems are interesting for their fundamental and practical properties. Perovskite-type<br />

oxides Sr 1-xCa xRu 1-yMn yO 3 is a typical mixed valence system.¹ The host itinerant system Sr 1-xCa xRuO 3<br />

shows various interesting properties such as ferromagnetism and paramagnetism.²,³ Mn-substituti<strong>on</strong><br />

induces a mixed valence state of Ru 4+ , Ru 5+ , Mn 4+ and Mn 3+ i<strong>on</strong>s and localized ferromagnetism.¹, 4 However,<br />

understanding of the electr<strong>on</strong> correlati<strong>on</strong> in the mixed valence systems is not yet enough. In this work,<br />

we studied the relati<strong>on</strong>ship between electr<strong>on</strong> correlati<strong>on</strong> and mixed valence state through the experiments<br />

for Sr 1-xCa xRu 0.5Mn 0.5O 3 using the traditi<strong>on</strong>al experimental methods and the synchrotr<strong>on</strong>-based magnetic<br />

Compt<strong>on</strong> scattering. Sr 1-xCa xRu 0.5Mn 0.5O 3 is a good system since the Ca-substituti<strong>on</strong> will modify crystal<br />

symmetry and change the electr<strong>on</strong> correlati<strong>on</strong>. The following results have been obtained; 1. Cell volume<br />

decrease for Ca substituti<strong>on</strong>. 2. insulator-metal transiti<strong>on</strong> occurs for Ca substituti<strong>on</strong>. 3. Ferromagnetism<br />

appears at x ~ 0.3. 4. Antiferromagnetic coupling between Ru and Mn. These facts can be explained as<br />

follows. The decrease in the cell volume enhances the hybridizati<strong>on</strong> between Ru and O orbitals inducing<br />

itinerant electr<strong>on</strong>s. The itinerant electr<strong>on</strong>s enhance the formati<strong>on</strong> of a ferromagnetic order of Ru i<strong>on</strong>s. Mn<br />

i<strong>on</strong>s couples antiferromagnetically with Ru i<strong>on</strong>s by a superexchange interacti<strong>on</strong> via O 2p orbitals.<br />

1. M. Naito et al., J. Appl. Phys. 103 (2008) 07C906-1. 2. A. Kanbayashi, J. Phys. Soc. Jpn. 44 (1978) 108. 3.<br />

T. Kiyama et al. Phys. Rev. B 54 (1996) R756. 4. T. Taniguchi et al. Phys. Rev. B 77 (2008) 014406-1.<br />

PG14<br />

An x-ray scattering study of magnetic order in a pyrochlore iridate<br />

Eu 2Ir 2O 7<br />

Daisuke Uematsu 1 *, Hajime Sagayama 1 , Taka-hisa Arima 1 , Jun J Ishikawa 2 and<br />

Satoru Nakatsuji 2<br />

1 Department of Advanced Materials Science, The University of Tokyo, Japan<br />

2 Institute of Solid State Physics, The University of Tokyo, Japan<br />

The pyrochlore iridate Eu 2Ir 2O 7 undergoes a metal-insulator transiti<strong>on</strong> at T_{MI} = 120<br />

K [1]. Since the magnetic Ir 4+ i<strong>on</strong>s occupy the pyrochlore B-site, str<strong>on</strong>g geometrical<br />

spin frustrati<strong>on</strong> is predicted.Nevertheless, a mu<strong>on</strong> spin rotati<strong>on</strong> study [2] indicated<br />

l<strong>on</strong>g-range orderings spins of Ir 4+ . To determine the spin c<strong>on</strong>figurati<strong>on</strong>, we have<br />

performed the res<strong>on</strong>ant X-ray diffracti<strong>on</strong> measurement at the LIII edge of Ir. A clear<br />

magnetic reflecti<strong>on</strong> was found at (10,0,0) below T_{MI}. The result proposes the allin-all-out-type<br />

magnetic structure.<br />

[1] K. Matsuhira et al., J. Phys. Soc. Jpn. 76, 043706 (2007). [2] S. Zhao et al., Phys. Rev. B. 83,<br />

180402 (2011).<br />

PG15<br />

Magnetic structure analyses by small-angle electr<strong>on</strong> diffracti<strong>on</strong><br />

Yoshihiko Togawa 1 *, Tsukasa Koyama 2 , Shigeo Mori 2 and Ken Harada 2<br />

1<br />

Nanoscience and Nanotechnology Research Center (N2RC), Osaka Prefecture<br />

University, Japan<br />

2<br />

Department of Materials Science, Osaka Prefecture University, Japan<br />

Electr<strong>on</strong>s are deflected at small angles by Lorentz force in magnetic materials. In magnetic<br />

elements in functi<strong>on</strong>al materials and spintr<strong>on</strong>ic devices, observati<strong>on</strong> of Lorentz deflecti<strong>on</strong> of<br />

electr<strong>on</strong>s at the small angle turns to be of significance because Lorentz deflecti<strong>on</strong> angle of<br />

electr<strong>on</strong>s becomes smaller in modern miniaturized magnetic devices composed of thinner<br />

magnetic films. In the present work, electr<strong>on</strong> optical system is c<strong>on</strong>structed in order to obtain<br />

small angle diffracti<strong>on</strong> and Lorentz deflecti<strong>on</strong> of electr<strong>on</strong>s at the order of down to 10-6<br />

radian in the reciprocal space[1]. L<strong>on</strong>g-distance camera length up to 3000 m is achieved<br />

in a c<strong>on</strong>venti<strong>on</strong>al transmissi<strong>on</strong> electr<strong>on</strong> microscope with LaB6 thermal emissi<strong>on</strong> type.<br />

The diffracti<strong>on</strong> pattern at 5 × 10-6 radian is presented in a carb<strong>on</strong> replica grating with 500<br />

nm lattice spacing while the magnetic deflecti<strong>on</strong> pattern at 2 × 10-5 radian is exhibited in<br />

Permalloy elements. A simultaneous recording of electr<strong>on</strong> diffracti<strong>on</strong> and Lorentz deflecti<strong>on</strong><br />

is also dem<strong>on</strong>strated in 180 degree striped magnetic domains of La 0.825Sr 0.175MnO 3[2].<br />

We believe that small-angle Bragg diffracti<strong>on</strong> and Lorentz deflecti<strong>on</strong> analyses provide a<br />

quantitative way to analyze structural and magnetic properties in the reciprocal space. This<br />

study is partly supported by SCOPE project from the MIC in Japan.<br />

[1] T. Koyama, K. Takayanagi, Y. Togawa, S. Mori, and K. Harada, submitted. [2] T. Koyama, Y.<br />

Togawa, K. Takenaka, and S. Mori, to appear in J. Appl. Phys.


PG16<br />

Raman scattering of metal-insulator transiti<strong>on</strong> in Cd2Os2O7 Takumi Hasegawa 1 *, Norio Ogita 1 , Jun-ichi Yamaura 2 , Zenji Hiroi 2 and Masayuki<br />

Udagawa 1<br />

1<br />

Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-<br />

Hiroshima, Hiroshima 739-8521, Japan<br />

2<br />

Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581,<br />

Japan<br />

Cd 2Os 2O 7 is a pyrochlore oxide showing metallic behavior at room temperature,<br />

and it shows metal-insulator transiti<strong>on</strong> at 225 K [1]. It has been suggested that this<br />

metal-insulator transiti<strong>on</strong> is caused by magnetic order [1,2], because any superlattice<br />

reflecti<strong>on</strong> has not been observed by x-ray and neutr<strong>on</strong> [3] diffracti<strong>on</strong> measurements.<br />

However, to c<strong>on</strong>clude no structural distorti<strong>on</strong> precisely below the transiti<strong>on</strong><br />

temperature, it is necessary to perform symmetry sensitive measurements rather<br />

than diffracti<strong>on</strong>s. Raman scattering method is a sensitive tool to observe small lattice<br />

distorti<strong>on</strong> with symmetry breaking. We have measured Raman spectra of Cd 2Os 2O 7<br />

from 4 K to 300 K to investigate possibility of structural distorti<strong>on</strong> in the insulator<br />

phase. Below the transiti<strong>on</strong> temperature, we have not observed any new peak indicating<br />

symmetry breaking from the pyrochlore structure with the space group Fd3m.<br />

[1] A. W. Sleight, J. L. Gills<strong>on</strong>, J. F. Weiher and W. Bindloss, Solid State Commun. 14, 357(1974). [2]<br />

D. Mandrus, et al., Phys. Rev. B 63, 195104(2001). [3] J. Reading and M. T. Weller, J. Mater. Chem.<br />

11, 2373(2001).<br />

PG17<br />

Effects of impurities in the chromic compound CuMoO 4<br />

Takayuki Asano 1 *, Taizo Nishimura 1 , Katsutaka Kubo 1 , Minoru Sanda 1 , Keisuke<br />

Matsuura 1 , Akira Matsuo 2 , Yasuo Narumi 3 and Koichi Kindo 2<br />

1 Department of Physcs, Kyushu University, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

3 Institute for Materials Research, Tohoku University, Japan<br />

Recently interest in “Chromism” phenomena for compounds may be attributed to<br />

the fact that a reversible color change of organic and inorganic materials can occur as<br />

the compound experiences various changes in its envir<strong>on</strong>mental c<strong>on</strong>diti<strong>on</strong>s. Copper<br />

molybdate, CuMoO 4, has dem<strong>on</strong>strated attractive properties of both thermochromism<br />

and piezochromism that are induced by a structural phase transiti<strong>on</strong>. We report a<br />

tunable structural phase transiti<strong>on</strong> and magnetic phenomena using substituti<strong>on</strong>al effects<br />

in Cu 1-xZn xMoO 4(0≤x≤0.1), CuMo 1-yW yO4(0≤y≤0.1), and CuMo 1-zCr zO4(0≤z≤0.1) over<br />

wide ranges of temperatures and magnetic fields. The substituti<strong>on</strong> of magnetic Cu 2+<br />

i<strong>on</strong>s for n<strong>on</strong>magnetic Zn 2+ i<strong>on</strong>s causes the hysteresis in the structural phase transiti<strong>on</strong><br />

to shift to remarkably lower temperatures as x increases by means of magnetic<br />

susceptibility measurement. In c<strong>on</strong>trast, replacing Mo 6+ i<strong>on</strong>s with W 6+ i<strong>on</strong>s results<br />

in a shift of the hysteresis and the structural phase transiti<strong>on</strong> to higher temperatures<br />

as y increases. However, in the case of replacing the Mo 6+ i<strong>on</strong>s with Cr 6+ i<strong>on</strong>s, the<br />

structural phase transiti<strong>on</strong> around 200K is completely disappeared and a ferromagnetic<br />

comp<strong>on</strong>ent is induced below 150K as z increases. We are going to discuss the reas<strong>on</strong><br />

of the shifting structural phase transiti<strong>on</strong>s and also show the magnetic properties under<br />

extreme c<strong>on</strong>diti<strong>on</strong>s.<br />

PG18<br />

Effective exchange interacti<strong>on</strong>s in 5d transiti<strong>on</strong> metal oxides<br />

Tom<strong>on</strong>ori Shirakawa*, Hiroshi Watanabe and Seiji Yunoki<br />

Computati<strong>on</strong>al C<strong>on</strong>densed Matter Physics Laboratory, RIKEN, Japan<br />

5d transiti<strong>on</strong> metal oxides, Sr 2IrO 4 and Ba 2IrO 4, have attracted much attenti<strong>on</strong><br />

because of their unique properties caused by a str<strong>on</strong>g spin-orbit coupling for 5d<br />

transiti<strong>on</strong> element. Both of these compounds behave as Jeff=1/2 Mott insulator at low<br />

temperature [1,2,3]. Recently, these compounds are expected to be a superc<strong>on</strong>ductor<br />

as an analogous system to high-Tc cuprates. According to recent experimental results<br />

<strong>on</strong> magnetic susceptibility and μSR studies, the effective exchange interacti<strong>on</strong>s in<br />

Sr 2IrO 4 and Ba 2IrO 4 are expected to be very large, and comparable to the <strong>on</strong>es of high-<br />

Tc cuprates [3]. Motivated by these experiments, we have studied theoretically the<br />

electr<strong>on</strong>ic and magnetic properties of Sr 2IrO 4 and Ba 2IrO 4 using a three-band Hubbard<br />

model with the spin-orbit coupling [4]. We first obtain the phase diagram of 8-site<br />

cluster in a wide parameter regi<strong>on</strong> using exact diag<strong>on</strong>alizati<strong>on</strong> technique. We find that<br />

there are several phases including the Jeff=1/2 Mott insulating phase which is realized<br />

in Sr 2IrO 4 and Ba 2IrO 4. We then calculate the dynamical spin structure factor composed<br />

by the Jeff=1/2 state in the Jeff=1/2 Mott insulating phase. We then estimate the<br />

values of effective exchange interacti<strong>on</strong>s by comparing the results with the <strong>on</strong>es of an<br />

effective spin model.<br />

[1] B. J. Kim et al., Science 323 (2009) 1329. [2] B. J. Kim et al., Phys. Rev. Lett. 101 (2008)<br />

076402. [3] H. Okabe et al., Phys. Rev. B 83 (2011) 155118. [4] H. Watanabe et al., Phys. Rev. Lett.<br />

105 (2010) 216410.<br />

PG19<br />

PG20<br />

PG21<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic and electrical transport behavior of Ir substituted NiTi<br />

shape memory alloy<br />

Sandhya Dwevedi* and A.k Nigam<br />

Department of C<strong>on</strong>densed Matter Physics and Material Sciences, Tata Institute of<br />

Fundamental Research(TIFR), Mumbai 400 005, India, India<br />

NiTi shape memory alloys (SMAs) show attractive functi<strong>on</strong>al properties for a<br />

number of engineering and medical applicati<strong>on</strong>s [1]. Recently. Somsen et.al [2] have<br />

synthesized the novel Ni-Ti-Ir alloys and have studied its structural properties. This<br />

motivates us to study the other properties of the alloy. In the present work, we have<br />

systematically studied the structural, kinetics, magnetic and transport properties of the<br />

Ni-Ti-Ir alloy. The alloy is formed in the B2- type phase with a small amount of Ti 2NiIr<br />

as an additi<strong>on</strong>al phase. In the DSC curve, two distinct peaks are observed <strong>on</strong> heating<br />

and cooling. These peaks corresp<strong>on</strong>d to the Martensitic transformati<strong>on</strong>s (MT) from<br />

the B2 to R-phase and from R to B19’-phase <strong>on</strong> cooling and, a reverse transformati<strong>on</strong><br />

from B19’-R-B2 phase <strong>on</strong> heating, respectively. From the temperature dependence of<br />

resistivity curve, the Martensitic Start (MS), Martensitic Finish (Mf), Austenite Start (AS)<br />

and Austenite Finish (Af) temperatures are found to be 193 K, 153 K, 267 K and 293 K<br />

respectively. In the Magnetizati<strong>on</strong> versus temperature (M-T) curve, no evidence of the<br />

ferromagnetic ordering temperature is observed. However, the Magnetizati<strong>on</strong> versus<br />

Field (M-H) curve at 5 K and 300 K shows existence of ferromagnetic order in the alloy.<br />

[1]K. Otsuka, C. M. Wayman, Shape Memory Materials(Cambridge University Press) [2]Ch.<br />

Somsen, J. Khalil-AllaFib, E.P. George, Mater. Sci. Eng. A, 378, 170-174 (2004)<br />

X-ray diffuse scattering of pyrochlore niobium oxides R 2Nb 2O 7<br />

Shingo Toyoda 1 , Hajime Sagayama 1 , Kunihisa Sugimoto 2 and Takahisa Arima 1 *<br />

1 Department of Advanced Materials Science, The University of Tokyo, Japan<br />

2 SPring-8, Japan<br />

It was reported that Y 2Nb 2O 7 is a n<strong>on</strong>-magnetic insulator, although the electr<strong>on</strong><br />

c<strong>on</strong>figurati<strong>on</strong> of Nb 4+ is 4d1 with S=1/2. To reveal the origin, we have performed<br />

X-ray scattering measurement of single crystals of R 2Nb 2O 7 (R=Y,Sm,Dy,and Ho). All<br />

the compounds show diffuse scattering, indicating that there exists short-range order.<br />

Analysis of the average structure suggests that Nb i<strong>on</strong>s are displaced al<strong>on</strong>g the (111)<br />

directi<strong>on</strong>. The formati<strong>on</strong> of spin-singlet tetramers cannot explain the observed diffuse<br />

pattern. The short-range correlati<strong>on</strong> implies the formati<strong>on</strong> of spin-singret dimmers,<br />

because the c<strong>on</strong>figurati<strong>on</strong> of dimmers in a pyrochlore latiice can be mapped <strong>on</strong> the icerule<br />

problem. In additi<strong>on</strong>, the diffuse pattern changes with R. The diffuse of Y 2Nb 2O 7 is<br />

the broadest, while that of Dy 2Nb 2O 7 is narrowest and almost spot.<br />

[1] H. Fukazawa , Y. Maeno, Phys. Rev. B 67, 054410 (2003)<br />

Freezing of local lattice strains in the magnetic martensitic/ferroelastic<br />

material system<br />

Yu Wang*, Ch<strong>on</strong>ghui Huang, Xiaoping S<strong>on</strong>g and Xiaobing Ren<br />

Xi'an Jiaot<strong>on</strong>g University, China<br />

Glass state is a frozen disordered state, in which the l<strong>on</strong>g range order is destroyed<br />

but short range order persists. Recently, a new glass phenomen<strong>on</strong> called strain glass<br />

was found in the martensitic/ferroelastic material system [1]. The strain glass state<br />

is a frozen disordered state of local lattice strains (nanosized martensitic/ferroelastic<br />

domains). Experimental measurements show that strain glass possesses obvious glassy<br />

features including dynamic freezing and breaking down of ergodicity in its mechanical<br />

properties [1, 2], being similar to the glassy features of the cluster-spin glass with<br />

froze local spin order. Strain glass can be obtained by doping point defects into normal<br />

martensitic/ferroelastic system [1]. However, whether strain glass can be achieved<br />

in the defect doped magnetic martensitic/ferroelastic system is unknown so far. In<br />

this study, we report that a strain glass transiti<strong>on</strong> with freezing of local lattice strains<br />

can exist in the Co doped magnetic martensitic system Ni-Mn-Ga by using dynamic<br />

mechanical analysis. Moreover, our magnetic measurements show that the strain glass<br />

in the Co doped Ni-Mn-Ga system is ferromagnetic, which is a new form of strain<br />

glass. The finding of the strain glass in magnetic martensitic/ferroelastic system may<br />

lead to novel applicati<strong>on</strong>s.<br />

[1] S. Sarkar, X. Ren and K. Otsuka, Phys. Rev. Lett. 95, 205702(2005) [2] Y. Wang, X. Ren, K.<br />

Otsuka, and A. Saxena, Phys. Rev. B 76, 132201(2007)<br />

July 8 - 13, 2012 Busan, Korea 31<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PG22<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic structure of the new chiral compound [Cr(CN) 6][Mn(S)pnH(DFM)](H<br />

2O)<br />

Cristina Saenz De Pipa<strong>on</strong> 1 , Javier Campo 1 *, Fernando Palacio 1 , Jose Alberto<br />

Rodriguez-velamazan 1 , Katsuya Inoue 2 and Hiroyuki H<strong>on</strong>da 2<br />

1 Materials Science Institute of Arag<strong>on</strong> (CSIC-University of Zaragoza), Spain<br />

2 Hiroshima University, Japan<br />

Research <strong>on</strong> magnetic molecular materials has received str<strong>on</strong>g attenti<strong>on</strong> in the last years for<br />

several reas<strong>on</strong>s, am<strong>on</strong>g them, the possibility of these materials to be multifuncti<strong>on</strong>al, thus<br />

exhibiting more than <strong>on</strong>e functi<strong>on</strong>al property at the same time. A very interesting possibility in<br />

a molecular material is magneto-chirality. Despite this interest, very few molecular candidates<br />

with likely possibilities have been synthesized, because chirality must be c<strong>on</strong>trolled in the<br />

molecular structure and at the same time the crystal must exhibit nuclear chirality. In additi<strong>on</strong>,<br />

the arrangement of the magnetic moments must also be chiral. Nowadays, single crystals of<br />

the cyano-bridged bimetallic complexes have been growth, a 2D chiral ferrimagnet [Cr(CN) 6]<br />

[Mn(R)-pnH(DMF)]•(2H 2O) (1) and a racemic <strong>on</strong>e [Cr(CN) 6][Mn(rac)-pnH(DMF)]•(2H 2O)<br />

(2), where DFM is N,N-dimethylformamide. Compound 1 c<strong>on</strong>sists of two-dimensi<strong>on</strong>al<br />

bimetallic sheets, with the same space group P212121, whereas compound 2 crystallizes under<br />

Pnma [1]. These compounds have been studied employing neutr<strong>on</strong> diffracti<strong>on</strong> techniques at the<br />

Institute Laue Langevin. In this communicati<strong>on</strong>, we present the nuclear and magnetic structures<br />

for (1) and (2). The coexistence of nuclear and magnetic chirality has been dem<strong>on</strong>strated.<br />

[1] H. Imai, K. Inoue, K. Kikuchi, Polyhedr<strong>on</strong> 24, 2808-2812(2005)<br />

PG23<br />

Origin of spin scalar chiral order in frustrated K<strong>on</strong>do lattice model<br />

- higher-order Kohn anomaly and hidden positive biquadratic<br />

interacti<strong>on</strong> -<br />

Yutaka Akagi 1 *, Masafumi Udagawa 2 and Yukitoshi Motome 1<br />

1 University of Tokyo, Japan<br />

2 University of Tokyo, MPI PKS, Japan<br />

Recently, n<strong>on</strong>coplanar spin c<strong>on</strong>figurati<strong>on</strong>s with scalar chirality have drawn c<strong>on</strong>siderable attenti<strong>on</strong> as an<br />

origin of the anomalous Hall effect. In this mechanism, itinerant electr<strong>on</strong>s acquire an internal magnetic<br />

field through the Berry phase according to the solid angle spanned by three spins, which can result in the<br />

anomalous Hall effect. In order to clarify how such n<strong>on</strong>trivial magnetic states appear in spin-charge coupled<br />

systems, we investigate a ferromagnetic K<strong>on</strong>do lattice model <strong>on</strong> a triangular lattice by variati<strong>on</strong>al and<br />

perturbative calculati<strong>on</strong>s. As a result, we find that a n<strong>on</strong>coplanar four-sublattice spin ordering emerges near<br />

1/4-filling [1], in a wider parameter regi<strong>on</strong> compared to the nesting-driven 3/4-filling phase predicted in the<br />

previous study. We unveil that a kinetic-driven positive biqaudratic interacti<strong>on</strong> is critically enhanced and<br />

plays a crucial role <strong>on</strong> stabilizing a chiral ordering near 1/4-filling. The origin of large positive biquadratic<br />

interacti<strong>on</strong> is ascribed to the Fermi surface c<strong>on</strong>necti<strong>on</strong> by the four-sublattice ordering wave vectors, which<br />

we call the higher-order Kohn anomaly [2]. Similar hidden interacti<strong>on</strong>s and resultant n<strong>on</strong>coplanar states<br />

are also found in other frustrated lattices, such as fcc and pyrochlore lattices. Our results suggest a universal<br />

mechanism underlying n<strong>on</strong>trivial spin c<strong>on</strong>figurati<strong>on</strong>s in frustrated spin-charge coupled systems.<br />

[1] Y. Akagi and Y. Motome, J. Phys. Soc. Jpn. 79 (2010) 083711. [2] Y. Akagi, M. Udagawa, and Y.<br />

Motome, preprint (arXiv:1201.3053), accepted for publicati<strong>on</strong> in Phys. Rev. Lett.<br />

PG24<br />

Doping effects <strong>on</strong> the metal-insulator transiti<strong>on</strong> of Li2RuO3 Se<strong>on</strong>gil Choi 1 , Junghwan Park 1 , Sanghyun Lee 1 , Deo-ky<strong>on</strong>g Cho 1 , T. Morioka 2 , H.<br />

Nojiri 2 and J.- G. Park 3 *<br />

1<br />

Center for Str<strong>on</strong>gly Correlated Materials Research, Seoul Nati<strong>on</strong>al University, Seoul<br />

151-742, Korea<br />

2<br />

Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan<br />

3<br />

Department of Physics & Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Seoul 151-742,<br />

Korea<br />

Li 2RuO 3 has a layered rocksalt-type structure and has attracted much attenti<strong>on</strong><br />

because of its interesting physical properties. In particular, it exhibits a metal-insulator<br />

transiti<strong>on</strong> at a very high temperature around 540 K. At the same temperature, the<br />

magnetic susceptibility shows a big drop implying the formati<strong>on</strong> of a spin gap. It is also<br />

interesting to note that all of these physical properties occur <strong>on</strong> the unusual h<strong>on</strong>eycomb<br />

lattice of Ru i<strong>on</strong>s. In order to understand the origin of the metal-insulator transiti<strong>on</strong> and<br />

its related physical properties better, we have carried some extensive studies ranging<br />

from bulk properties to neutr<strong>on</strong> scattering experiments. First, we have investigated the<br />

doping effects <strong>on</strong> the metal-insulator transiti<strong>on</strong> by varying Li c<strong>on</strong>tent. Sec<strong>on</strong>d, we have<br />

examined the field dependence of the physical properties by measuring resistivity and<br />

magnetizati<strong>on</strong> over a wide temperature range. In this report, we are going to summarize<br />

our experimental results and its importance with respect to the reported metal-insulator<br />

transiti<strong>on</strong>.<br />

32 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PG25<br />

Ferromagnetism in hydrothermally treated glassy carb<strong>on</strong><br />

Hyun Jin Cho, Kyu W<strong>on</strong> Lee and Cheol Eui Lee*<br />

Department of physics and institute for Nano Science, Korea University, Korea<br />

We have investigated the magnetic properties of pristine and hydrothermal-treated<br />

glassy carb<strong>on</strong> by means of superc<strong>on</strong>ducting quantum interference device (SQUID)<br />

and electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) measurements. The magnetic properties of the<br />

hydrothermally treated glassy carb<strong>on</strong> showed a sensitive dependence <strong>on</strong> the solvents<br />

and the treatment time. In particular, prominent ferromagnetism was observed in<br />

samples hydrothermally treated in ethanol for a properly chosen time, with the<br />

saturati<strong>on</strong> moment and coercive force being comparable to those of ir<strong>on</strong>. The<br />

ferromagnetism in the hydrothermally treated glassy carb<strong>on</strong> may have to do with the<br />

relative fracti<strong>on</strong>s of the sp3- and sp2-b<strong>on</strong>ds.<br />

[1] X Wang et al 2002 J. Phys.: C<strong>on</strong>dens. Matter 14 10265<br />

PG26<br />

On the structure and symmetry of the spin glass state (SGS)<br />

Jerzy Warczewski*, Pawel Gusin and Daniel Wojcieszyk<br />

Institute of Physics, University of Silesia, Poland<br />

The explanati<strong>on</strong> of uniqueness of SGS has roots in the appearance of a certain<br />

probability functi<strong>on</strong> in the sec<strong>on</strong>d term of the assumed Hamilt<strong>on</strong>ian [1, 2]. This term<br />

describes the random distributi<strong>on</strong> of either dopants or defects in the ferromagnetic<br />

matrix under the percolati<strong>on</strong> threshold. The Gaussian type randomness was derived for<br />

both the global magnetic coupling c<strong>on</strong>stant and the magnetizati<strong>on</strong> vector M, the latter<br />

effect bringing to the statistical features of the magnetic structure and the magnetic<br />

symmetry group of SGS. In both cases the use has been made of the central limit<br />

theorem of the theory of probability (the Lyapunov theorem) [3]. The authors have<br />

earlier proved that a certain sp<strong>on</strong>taneous minimum magnetic field H is necessary for<br />

the stability of SGS [4]. The structure of SGS can then be described in such a way that<br />

M is situated al<strong>on</strong>g a generatrix of a given c<strong>on</strong>e whose axis coincides with the directi<strong>on</strong><br />

of H [4]. Let us call φ the angle between M and H. Any precessi<strong>on</strong> of M around the<br />

directi<strong>on</strong> of H at φ = c<strong>on</strong>st (at c<strong>on</strong>stant energy) makes the symmetry operati<strong>on</strong> of SGS.<br />

Thus the symmetry group of this precessi<strong>on</strong> is SO(2) [3].<br />

[1] J. Warczewski, P. Gusin et al., Journal of N<strong>on</strong>-Linear Optics, Quantum Optics 30 (2003), 301-<br />

320 [2] P. Gusin, J. Warczewski, Mol. Cryst. Liq. Cryst. 521 (2010), 288-292 [3] J. Warczewski, P.<br />

Gusin, D. Wojcieszyk, Mol. Cryst. Liq. Cryst. 554 (2012), 209-220 [4] J. Warczewski, P. Gusin et al.,<br />

J. Phys.: C<strong>on</strong>dens. Matter, 21 (2009), 035402-035407<br />

PG27<br />

Magnetic study of Fe/MgO/Fe and Fe/MgO/Fe/Co multilayer systems<br />

Jitendra Pal Singh 1 , Sanjeev Gautam 2 , K Asokan 1 , D. Kabiraj 1 , D. Kanjilal 1 , M Raju 3 ,<br />

Braj Bhusan Singh 4 , S. Chaudhary 3 , R. Kotnala 4 and Keun Hwa Chae 2 *<br />

1 Inter University Accelerator Centre, Aruna Asaf Ali Marg-110067, New Delhi, India<br />

2 Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea<br />

3 Department of Physics, Indian Institute of Technology, New Delhi - 110 016, India<br />

4 Nati<strong>on</strong>al Physical Laboratory, Dr. K. A. Krishanan Marg, New Delhi -110 012, India<br />

Theoretical calculati<strong>on</strong>s [1-3] show high TMR up to 1000% for Fe/MgO/Fe MTJ’s however TMR ratios of<br />

200% at room temperature could be realized in these systems [4]. The discrepancy between theoretical and<br />

experimental values of TMR is probably due to the interface properties of the heterostructures, as spin dependent<br />

tunneling is sensitive to the interface [3]. In present work, we investigated the magnetic properties of Fe/MgO/<br />

Fe (MFe) and Fe/MgO/Fe/Co (MFeCO) multilayers by vibrating sample magnetometer (VSM) deposited by<br />

electr<strong>on</strong> beam evaporati<strong>on</strong> method [6]. Attributes of perpendicular magnetic anisotropy (PMA) are observed<br />

in MFe multilayer. The PMA arises due to Fe(3d) and O (2p) hybridizati<strong>on</strong> at metal-oxide layer interface and<br />

generally observed in MTJs [6]. The asymmetric coercivity observed in this structure is due to the presence of<br />

exchange bias which arises probably due to oxidati<strong>on</strong> of Fe at surface; resulting in antiferromagnetic Fe 2O 3. The<br />

positive vertical shift al<strong>on</strong>g magnetizati<strong>on</strong> axis may be due to the pinned interfacial uncompensated spins of<br />

unwantedly formed Fe 2O 3 [7]. Apart from this MFeCo multilayer do not exhibit any feature observed in MFe<br />

multilayers. The absence of these is expected almost 3 times increase of Fe layers in MFeCo system [5].<br />

References: 1. A. Lyle, et al. App. Phys. Lett. 97 152504 (2010) 2. J-G. Zhu and C. Park, Materials Today, 9 36 (2006) 3. J.<br />

Math<strong>on</strong> and A. Umerski, Phys. Rev. B 63 220403 (2001). 4. S.S.P. Parkin, , et al., Nat Mater, 3 862 (2004) 5. J. P. Singh et al.,<br />

AIP C<strong>on</strong>f. Proc. (in Press) 6. S. Ikeda et al. Nature Mater. 9 (2010) 721-722 7. H. Ohldag et.al. Phy. Rev. Lett., 91, 017203, 2003


PH01<br />

I<strong>on</strong>ic size effect <strong>on</strong> the spin gap nature of SrCu 2(TeO 3) 2Cl 2<br />

C. N. Kuo, S. C. Chen and C. S. Lue*<br />

Department of physics,, Nati<strong>on</strong>al Cheng Kung University, Tainan 70101, Taiwan,<br />

Taiwan<br />

We report the effects of partial substituti<strong>on</strong> of Br <strong>on</strong>to the Cl sites of SrCu 2(TeO 3) 2Cl 2<br />

by means of magnetic susceptibility measurements. This material has been a subject<br />

of current interest due to indicati<strong>on</strong>s of spin gap behavior. However, the magnetic spin<br />

couplings resp<strong>on</strong>sible for the spin gap nature remains unclear. For each compositi<strong>on</strong> of<br />

SrCu 2(TeO 3) 2(C l1-xBr x) 2, the temperature-dependent susceptibility exhibits a character<br />

of low-dimensi<strong>on</strong>al magnetism with a broad maximum at Tmax. The magnitude<br />

of Tmax gradually shifts to higher temperatures as increasing the Br c<strong>on</strong>centrati<strong>on</strong>.<br />

The experimental data can be well fitted to a coupled spin dimer model, yielding an<br />

increasing trend for the spin gap size from 170 K to 190 K. It thus points out that<br />

the substituti<strong>on</strong> of Br i<strong>on</strong>s has an effect to reduce the distance between Cu(1) and<br />

Cu(2), leading to a str<strong>on</strong>ger antiferromagnetic spin interacti<strong>on</strong>. On the other hand,<br />

the variati<strong>on</strong> of the interdimer coupling is marginal, indicative of weak effects <strong>on</strong> the<br />

distances of Cu(1)-Cu(1) and Cu(2)-Cu(2) in SrCu 2(TeO 3) 2Cl 2.<br />

PH02<br />

<strong>Magnetism</strong> of SrM 3P 4O 14 (M 2+ = 3d i<strong>on</strong>s) investigated using neutr<strong>on</strong>scattering<br />

measurements<br />

Masashi Hase 1 *, Vladimir Yu. Pomjakushin 2 , Lukas Keller 2 , Andreas Doenni 1 ,<br />

Osamu Sakai 1 , Tao Yang 3 , Rih<strong>on</strong>g C<strong>on</strong>g 3 , Jianhua Lin 3 , Kiyoshi Ozawa 1 and Hideaki<br />

Kitazawa 1<br />

1 Nati<strong>on</strong>al Institute for Materials Science (NIMS), Japan<br />

2 Paul Scherrer Institut (PSI), Switzerland<br />

3 Peking University, China<br />

One of intriguing phenomena in magnetism is appearance of qualitatively different magnetism<br />

in isostructural substances. In AM 3P 4O 14 (A = Ca, Sr, Ba or Pb, M 2+ = Ni 2+ : spin-1, Co 2+ : spin-<br />

3/2, Fe 2+ : spin-2 or Mn 2+ : spin-5/2), magnetism in AMn 3P 4O 14 is qualitatively different from<br />

magnetism in the other substances. A 1/3 quantum magnetizati<strong>on</strong> plateau was observed <strong>on</strong>ly<br />

in AMn 3P 4O 14. An antiferromagnetic (AFM) l<strong>on</strong>g-range order (LRO) without a sp<strong>on</strong>taneous<br />

magnetizati<strong>on</strong> appears in AMn 3P 4O 14, while a canted AFM LRO appears in the other<br />

substances. We studied magnetism of SrM 3P 4O 14 using neutr<strong>on</strong>-scattering measurements. In<br />

SrMn 3P 4O 14, we determined the coplanar spiral magnetic structure that had no sp<strong>on</strong>taneous<br />

magnetizati<strong>on</strong>. We c<strong>on</strong>firm that the spin system is a frustrated J1-J1-J2 trimerized spin chain<br />

with dominant AFM J1, small AFM J2, and small next-nearest-neighbor exchange interacti<strong>on</strong>s.<br />

The magnetizati<strong>on</strong> plateau is possible. In SrM 3P 4O 14 (M = Co or Ni), we determined the canted<br />

magnetic structure (the irreducible representati<strong>on</strong> tau1 in the space group P21/c). We c<strong>on</strong>sider<br />

that the spin system c<strong>on</strong>sists of ferromagnetic dimers formed by the dominant J2 interacti<strong>on</strong><br />

and m<strong>on</strong>omers. The magnetizati<strong>on</strong> plateau is impossible.<br />

PH03<br />

Spin-Peierls-like lattice distorti<strong>on</strong> and incommensurate magnetic<br />

structure of geometrically frustrated spinel CdCr 2O 4<br />

J.- H. Chung 1 , J. M. S. Park 2 , K.- P. H<strong>on</strong>g 2 , M. Matsuda 3 , H. Ueda 4 , Y. Ueda 4 and S.- H.<br />

Lee 5 *<br />

1 Department of Physics, Korea University, Korea<br />

2 Korea Atomic Energy Research Institute, Korea<br />

3 Oak Ridge Nati<strong>on</strong>al Laboratory, Korea<br />

4 The University of Tokyo, Japan<br />

5 University of Virginia, USA<br />

ACr 2O 4 spinels (A = Zn, Cd, Hg) with antiferromagnetic Cr 3+ (S = 3/2) <strong>on</strong> B sites are well known for<br />

str<strong>on</strong>g geometrical frustrati<strong>on</strong> preventing l<strong>on</strong>g-range order. The frustrati<strong>on</strong>s in their cubic phases are<br />

finally lifted via spin-Peierls-like lattice distorti<strong>on</strong>s at low temperatures. In spite of their similarities<br />

in the cubic phases, each of them undergo distinctive lattice distorti<strong>on</strong>s and exhibit unique magnetic<br />

order. The nature of their magnetic ground states is thus of great importance in order to understand<br />

these novel transiti<strong>on</strong>s. Nevertheless, the exact spin structure of CdCr 2O 4 has so far never been<br />

reported. We revisited this issue by performing neutr<strong>on</strong> powder diffracti<strong>on</strong> measurement of isotopeenriched<br />

sample for reduced neutr<strong>on</strong> absorpti<strong>on</strong>. We observed the cubic-to-tetrag<strong>on</strong>al distorti<strong>on</strong> and<br />

the subsequent incommensurate magnetic order that are c<strong>on</strong>sistent with previous reports. Using<br />

representati<strong>on</strong> analysis, we found that the spins <strong>on</strong> different sublattices maintain nearly collinear<br />

arrangements within a single tetrahedr<strong>on</strong>. Whereas the obtained spin structure is different from<br />

the <strong>on</strong>e previously c<strong>on</strong>jectured based <strong>on</strong> spin wave frequencies, it is c<strong>on</strong>sistent with the idea that<br />

quantum fluctuati<strong>on</strong> plays an important role in the magnetic ground state of CdCr 2O 4.<br />

PH04<br />

PH05<br />

PH06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Interplay of magnetic order and structural distorti<strong>on</strong>s in multiferroic<br />

GdMnO 3 single crystals<br />

Mathias Doerr 1 *, Sahana Roessler 2 , Martin Rotter 2 , Aditya A. Wagh 3 , P. S. Anil<br />

Kumar 3 , Suja Elizabeth 3 , Steffen Wirth 2 and Michael Loewenhaupt 1<br />

1 Institut fur Festkorperphysik (IFP), Technische Universitat Dresden, Germany<br />

2 Max-Planck-Institut fur Chemische Physik fester Stoffe Dresden, Germany<br />

3 Department of Physics, Indian Institute of Science Bangalore, India<br />

Multiferroics are candidates for magneto-electrical applicati<strong>on</strong>s. Magnetic and dielectric phenomena<br />

in orthorhombic GdMnO 3 are str<strong>on</strong>gly intertwined. In additi<strong>on</strong>, electrically induced magn<strong>on</strong>s exist.<br />

Magnetostricti<strong>on</strong> measurements by high-resoluti<strong>on</strong> capacitive dilatometry, performed in the different<br />

AFM phases below T N = 42 K, show lattice distorti<strong>on</strong>s with stricti<strong>on</strong> of about 10 -4 . All l<strong>on</strong>gitudinal<br />

and transversal comp<strong>on</strong>ents of the magnetostricti<strong>on</strong> tensor were measured for the first time. Although<br />

no changes of the lattice symmetry exist, the measurements reveal magneto-structural phenomena,<br />

especially in the canted-AFM phase. A str<strong>on</strong>g anisotropy of the magnetoelastic properties was found,<br />

in good agreement with the type and propagati<strong>on</strong> of the magnetic structure. As the capacitive method<br />

is sensitive to expansi<strong>on</strong> effects and changes of permittivity, dielectric anomalies could be detected<br />

and compared to the critical values of H and T of the magnetic transiti<strong>on</strong>s. The anomalies especially<br />

exist in the range 10….22 K in which the structure is characterized by magnetic order <strong>on</strong> both the<br />

Gd- and Mn-sites. This dem<strong>on</strong>strates the str<strong>on</strong>g interplay of magnetic, charge and lattice degrees of<br />

freedom. First steps in modelling the magnetizati<strong>on</strong> of GdMnO 3 by the simulati<strong>on</strong> program McPhase<br />

are presented and exchange mechanisms are discussed. These results are examined in c<strong>on</strong>necti<strong>on</strong><br />

with the magnetostricti<strong>on</strong> data.<br />

Uniaxial pressure effect <strong>on</strong> magnetic ordering in a frustrated ising<br />

antiferromagnet CoNb 2O 6<br />

Satoru Kobayashi 1 *, Hiromu Tamatsukuri 2 , Chikafumi Kaneko 2 , Yuki H<strong>on</strong>ma 2 , Taro<br />

Nakajima 2 and Setsuo Mitsuda 2<br />

1 Department of Materials Science and Engineering, Iwate University, Japan<br />

2 Department of Physics, Faculty of Science, Tokyo University of Science, Japan<br />

Uniaxial pressure effect <strong>on</strong> magnetic ordering has been investigated by magnetizati<strong>on</strong><br />

measurements for a frustrated Ising antiferromagnet CoNb 2O 6 where quasi-<strong>on</strong>edimensi<strong>on</strong>al<br />

ferromagnetic chains al<strong>on</strong>g the c axis form a frustrated isosceles triangular<br />

lattice <strong>on</strong> the a-b plane. Under uniaxial pressure and magnetic field al<strong>on</strong>g the a axis, a<br />

critical field of magnetic phase transiti<strong>on</strong>s from antiferromagnetic to incommensurate<br />

magnetic (ICM) phase as well as from ICM to ferromagnetic phase m<strong>on</strong>ot<strong>on</strong>ically<br />

increases, indicating the strengthening of antiferromagnetic interchain exchange<br />

interacti<strong>on</strong>s. Above 700 MPa, a step-like behavior of the magnetizati<strong>on</strong> curve shows<br />

up at around the half of the saturati<strong>on</strong> magnetizati<strong>on</strong>. This behavior implies the<br />

appearance of a pressure-induced magnetically ordered phase characterized by the<br />

propagati<strong>on</strong> wave vector of qM=(0,0.5,0) and/or (0,0.25,0). These observati<strong>on</strong>s were<br />

explained within mean field calculati<strong>on</strong>s with nearest-neighbor and next-nearestneighbor<br />

interchain exchange interacti<strong>on</strong>s.<br />

Thermal and magnetic properties of LiNiPO4 olivine<br />

J. Wieckowski 1 *, M. U. Gutowska 1 , A. Szewczyk 1 , Yu. Kharchenko 2 , M. F.<br />

Kharchenko 2 , M. Kowalczyk 3 , N. Nedelko 1 , S. Lewinska 1 , A. Slawska - Waniewska 1 ,<br />

A. Kulka 4 and J. Molenda 4<br />

1<br />

Institute of Physics, Polish Academy of Sciences, Warsaw, Poland<br />

2<br />

B.Verkin Inst. for Low Temp. Phys. and Engineering, Nati<strong>on</strong>al Academy of Sciences<br />

of Ukraine, Kharkiv, Ukraine<br />

3<br />

Faculty of Materials Engineering, Warsaw University of Technology, Warsaw,<br />

Poland<br />

4<br />

Department of Hydrogen Energy, AGH University of Science and Technology,<br />

Cracow, Poland<br />

On the c<strong>on</strong>trary to LiMPO 4 olivines with M = Mn, Fe, Co, in LiNiPO 4 two step transformati<strong>on</strong> between<br />

the paramagnetic and a uniform in space antiferromagnetic phase occurs. At first, a l<strong>on</strong>g-range magnetic<br />

order develops in the form of an incommensurate antiferromagnetic phase (via a sec<strong>on</strong>d-order transiti<strong>on</strong> at<br />

21.8 K) and then a first-order transiti<strong>on</strong> to the antiferromagnetic phase occurs at 20.9 K. To study thermal<br />

properties of LiNiPO 4, and an influence of magnetic field, B, <strong>on</strong> the magnetic structure, specific heat<br />

measurements of a single crystal were carried out from 3 K to 60 K, in B=0 and in B (up to 9 T) applied<br />

al<strong>on</strong>g three main crystallographic directi<strong>on</strong>s. It was found that B applied al<strong>on</strong>g a and b directi<strong>on</strong>s has no<br />

effect <strong>on</strong> the transiti<strong>on</strong>s, whereas B directed al<strong>on</strong>g c axis shifts both transiti<strong>on</strong>s towards lower temperatures<br />

(with the transiti<strong>on</strong> temperatures depending parabolically <strong>on</strong> B). To elucidate these effects, supplementary<br />

studies of magnetic torque were performed for several B values, for B rotating within a-c and b-c planes,<br />

for a series of fixed temperatures. This work was partly supported by the European Regi<strong>on</strong>al Development<br />

Fund, through the Innovative Ec<strong>on</strong>omy Grants: POIG.01.01.02-00-108/09 and POIG.02.02.00-00-025/09.<br />

July 8 - 13, 2012 Busan, Korea 33<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PH07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Cr- and mo-doping effects <strong>on</strong> structural and orbital order phase<br />

transiti<strong>on</strong> in spinel-type MnV 2O 4<br />

Kazuhiro Hemmi 1*, Ryuichiro Fukuta 1, Ece Uykur 1, Shigeki Miyasaka 1, Setsuko<br />

Tajima 1, Akiko Nakao 2, Hir<strong>on</strong>ori Nakao 2, Reiji Kumai 2 and Youichi Murakami 2<br />

1 Physics, Osaka University, Japan<br />

2 PF/CMRC, KEK, Japan<br />

MnV 2O 4 has orbital degrees of freedom of t2g electr<strong>on</strong>s in V 3+ (3d2), and undergoes magnetic<br />

and orbital order. In this study, we investigated the doping effects of Cr 3+ (3d3) and Mo 3+ (4d3),<br />

which have no orbital degrees of freedom, for the V 3+ site of MnV 2O 4, in order to clarify the Cr-<br />

and Mo-doping effect <strong>on</strong> the electr<strong>on</strong>ic properties in this system. In MnV 2O 4, the paramagnetic<br />

to collinear ferrimagnetic phase transiti<strong>on</strong> and the collinear to n<strong>on</strong>collinear ferrimagnetic phase<br />

transiti<strong>on</strong> occur at TN=59K and TOO=54K, respectively. The structural phase transiti<strong>on</strong> from<br />

cubic to tetrag<strong>on</strong>al lattices takes place at TOO c<strong>on</strong>comitantly with the orbital order. From the<br />

magnetic susceptibility and powder X-ray diffracti<strong>on</strong> measurements, it is clarified that the orbital<br />

order is suppressed by Cr- and Mo-doping and disappears above x=0.12 (x=0.08) in Cr (Mo)doped<br />

samples. The resistivity and optical reflectivity measurements have clarified that the system<br />

becomes almost metallic with increasing Mo c<strong>on</strong>tent, while the Cr-doped samples are still Mott<br />

insulators. These results indicate that the doped Cr and Mo with no orbital degrees of freedom<br />

suppress the orbital order in MnV 2O 4. The introduced 3d electr<strong>on</strong>s remain localized in the Crdoped<br />

system, while 4d electr<strong>on</strong>s become nearly itinerant in the Mo-doped <strong>on</strong>e.<br />

R. Plumier and M. Sougi, Solid State Commun. 64, 53 (1987). S. Suzuki et al., Phys. Rev. Lett. 98, 127203 (2007).<br />

PH08<br />

Dopant-dependence <strong>on</strong> charge/orbital order in impurity doped layered<br />

manganites<br />

Yuki Yamaki 1 , Hir<strong>on</strong>ori Nakao 2 , Yuichi Yamasaki 2 , Youichi Murakami 2 , Yoshio<br />

Kaneko 3 and Yoshinori Tokura 4<br />

1<br />

Tohoku University CMRC/PF, KEK, Japan<br />

2<br />

CMRC/PF, KEK, Japan<br />

3<br />

ERATO-MF, JST CERG, RIKEN, Japan<br />

4<br />

ERATO-MF, JST CERG/CMRG, RIKEN University of Tokyo, Japan<br />

A layered manganite La 0.5Sr 1.5MnO 4 shows charge/orbital order and CE-type<br />

antiferromagnetic structure below 240 K and 110 K, respectively. We have studied how<br />

the ordering state is changed by the substituti<strong>on</strong> of Cr, Fe and Ga i<strong>on</strong>s for Mn i<strong>on</strong>s using a<br />

res<strong>on</strong>ant x-ray scattering (RXS) technique and magnetizati<strong>on</strong> measurement. In trivalent<br />

i<strong>on</strong>s these impurity i<strong>on</strong>s have no orbital degree of freedom and different spin values,<br />

in fact Cr 3+ , Fe 3+ , and Ga 3+ have S = 3/2, S = 5/2, and S = 0, respectively. As a result,<br />

the magnetizati<strong>on</strong> for Ga doped compound shows the same temperature dependence as<br />

pure compound, but in Cr and Fe doped compounds the magnetizati<strong>on</strong>s increase below<br />

90 K and 70 K, respectively. On the other hand, in all doped compounds the RXS<br />

intensities which reflect charge/orbital order are smaller than that in pure compound,<br />

but degrees of decrease are different according to the dopants. Namely, RXS intensity<br />

of Ga-doped compound has the same temperature dependence as pure compound,<br />

while RXS intensities of Cr- and Fe-doped compounds drastically decrease below 90<br />

K and 70 K, respectively.<br />

PH09<br />

Magnetic and n<strong>on</strong>magnetic impurity effect <strong>on</strong> magnetic orderings of<br />

isosceles triangular lattice antiferromagnet CuMnO 2<br />

Noriki Terada 1 , Yoshinori Tsuchiya 1 , Hideaki Kitazawa 1 and Naoto Metoki 2<br />

1 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

2 Japan Atomic Research Agency, Japan<br />

In recent years, chemical substituti<strong>on</strong> effect <strong>on</strong> magnetic and dielectric properties in frustrated magnetic<br />

systems has been a vast field of challenging new physics. Good illustrati<strong>on</strong>s are the drastic and various<br />

effects of a small level of chemical substituti<strong>on</strong> up<strong>on</strong> the magnetic and dielectric properties <strong>on</strong> frustrated<br />

magnetic systems such as CuFeO 2 and MnWO 4. These magnetic ground states stabilized with<br />

str<strong>on</strong>gly competing exchange interacti<strong>on</strong>s should be easily changed by slight chemical disturbance.<br />

In the present study, we have investigated magnetic and n<strong>on</strong>magnetic impurity substituti<strong>on</strong> effects <strong>on</strong><br />

magnetic ordering of a frustrated isosceles triangular lattice antiferromagnet CuMnO 2 by means of<br />

the magnetic neutr<strong>on</strong> diffracti<strong>on</strong> measurements <strong>on</strong> Cu(Mn 1-xCu x)O 2 and Cu(Mn 1-yGa y)O 2. While the<br />

magnetic wave vector of Cu(Mn 1-xCu x)O 2 the magnetic ground state of ``magnetically' substituted with<br />

x=0.04 is Q=(-1/2 1/2 0)[1-3], that in the ``n<strong>on</strong>magnetically' substituted Cu(Mn 1-yGa y)O 2 with y=0.05,<br />

0.15 and 0.20 is Q=(-1/2 1/2 1/2) that is identical to that of pure CuMnO 2. We discuss an influence of<br />

magnetic or n<strong>on</strong>magnetic impurity substituti<strong>on</strong> <strong>on</strong> the magnetic ordering of CuMnO 2, by comparing<br />

the results of Cu(Mn 1-yGa y)O 2 with Cu(Mn 1-xCu x)O 2.<br />

[1]N. Terada, Y. Tsuchiya, H. Kitazawa, T. Osakabe, N. Metoki, N. Igawa and K. Ohoyama, Phys.<br />

Rev. B 84 064432 (2011). [2]M. Poienar, C. Vecchini, G. Andre, A. Daoud-Aladine, I. Margiolaki,<br />

A. Maignan, A. Lappas, L. C. Chap<strong>on</strong>, M. Hervieu, F. Damay, and C. Martin, Chem. Mater. 23, 85<br />

(2011). [3]V. O. Garlea, A. T. Savici, and R. Jin, Phys. Rev. B 83, 172407 (2011).<br />

34 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PH10<br />

Res<strong>on</strong>ant soft X-ray scattering studies <strong>on</strong> half-doped manganite<br />

LaSr 2Mn 2O 7<br />

J.-s. Lee 1 *, C.-c. Kao 1 , C.s. Nels<strong>on</strong> 2 , H. Jang 3 , K.-t. Ko 3 , S.b. Kim 4 , Y.j. Choi 4 , S.w.<br />

Che<strong>on</strong>g 4 , S. Smadici 5 , P. Abbam<strong>on</strong>te 5 and J.-h. Park 3<br />

1 SSRL, SLAC Nati<strong>on</strong>al Accelerator Laboratory, USA<br />

2 BNL, USA<br />

3 POSTECH, Korea<br />

4 Rutgers university, USA<br />

5 UIUC, USA<br />

Recently, a careful doping c<strong>on</strong>trol study, however, reported that the La 2-2xSr 1+2xMn 2O 7<br />

system has an exotic spin phase diagram very near the half doping with extremely<br />

narrow antiferromagnetic (AFM) phase boundaries at x ~ 0.5 +/- 0.005: the CEtype<br />

within the boundaries but the A-type outside. To elucidate complicati<strong>on</strong> of this<br />

spin phase diagram, we investigated the orbital and AFM ordering behaviors of the<br />

half-doped bilayer manganite LaSr 2Mn 2O 7 by using Mn L-edges res<strong>on</strong>ant soft x-ray<br />

scattering. We c<strong>on</strong>firmed the predicted CE-type AFM order for the true half-doped (x =<br />

0.5) case. Furthermore, we found that such a narrow phase boundary is due to the close<br />

competiti<strong>on</strong> of the two AFM phases via 3d Mn eg orbital instability.<br />

PH11<br />

On the n<strong>on</strong>-idle-spin behavior and the field-induced magnetic<br />

transiti<strong>on</strong>s of the trimer chain magnet Cu 3(OH) 4SO 4<br />

Hyun-joo Koo 1 , Reinhard K Kremer 2 and Myung-hwan Whangbo 3<br />

1 Chemistry, Kyung Hee University, Korea<br />

2 Max-Planck-Institut fur Festkorperforschung, Stuttgart, Germany<br />

3 Chemistry, North Carolina State University, USA<br />

The magnetic properties of the Cu(2)-Cu(1)-Cu(2) trimer chain magnet Cu 3(OH) 4SO 4<br />

were examined by evaluating the spin exchange c<strong>on</strong>stants, the Dzyaloshinskii-Moriya<br />

(DM) vectors, and the magnetic anisotropy energies of the Cu(1) and Cu(2) sites <strong>on</strong><br />

the basis of density functi<strong>on</strong>al calculati<strong>on</strong>s. Cu 3(OH) 4SO 4 is not a idle-spin magnet,<br />

the Cu(1) spins have a str<strong>on</strong>g antiferromagnetic coupling in the Cu(1) chain, and the<br />

Cu(2) spin arrangements of a Cu(2)-Cu(1)-Cu(2) trimer chain result from the presence<br />

of two n<strong>on</strong>-equivalent sets of AFM interacti<strong>on</strong>s between the Cu(1) and Cu(2) chains.<br />

We propose the probable spin arrangements of a trimer chain resp<strong>on</strong>sible for the fieldinduced<br />

successive magnetic transiti<strong>on</strong>, and suggest that the nature of the magnetic<br />

transiti<strong>on</strong> depends <strong>on</strong> the field-directi<strong>on</strong> because of the DM interacti<strong>on</strong>s associated<br />

with two str<strong>on</strong>g spin exchange paths.<br />

PH12<br />

Spin state of LaCoO 3 investigated from n<strong>on</strong>-magnetic-i<strong>on</strong> substituti<strong>on</strong><br />

effect of Co sites<br />

Shinichiro Asai*, Ryuji Okazaki, Yukio Yasui and Ichiro Terasaki<br />

Department of Physics, Nagoya University, Japan<br />

The perovskite oxide LaCoO 3 is a fascinating material because of a dramatic change<br />

of its spin state with temperature variati<strong>on</strong>. In low-temperature range, LaCoO 3 is n<strong>on</strong>magnetic<br />

because the d electr<strong>on</strong>s of Co 3+ (3d6) fully occupy the lower t2g orbitals (LS).<br />

On the other hand, the nature of its excited state is c<strong>on</strong>troversial. The spin state of this<br />

system is also sensitive to the chemical substituti<strong>on</strong>s. Most interestingly, n<strong>on</strong>-magnetic<br />

Rh 3+ (4d6: LS) substituti<strong>on</strong> increases the magnetizati<strong>on</strong> at low temperature, which is<br />

different from Ga 3+ (3d10) substituti<strong>on</strong> effect. We have measured the magnetizati<strong>on</strong> and<br />

x-ray diffracti<strong>on</strong> of LaCo 1-xRh xO 3 [1]. We have found a weak ferromagnetic ordering<br />

for 0.1 < x < 0.4, indicating that the Rh substituti<strong>on</strong> stabilizes the magnetic state of<br />

Co 3+ at low temperatures. The effective magnetic moment of LaCo 1-xRh xO 3 evaluated<br />

at room temperature is independent of x for 0 < x < 0.5, and rapidly decreases above<br />

x = 0.5. It indicates that the excited state of Co 3+ is well described as a mixture of the<br />

low- and the high-spin Co 3+ i<strong>on</strong>s, and that a Rh 3+ i<strong>on</strong> favors to substitute for a low-spin<br />

Co 3+ i<strong>on</strong>.<br />

[1]. S. Asai et al.; J. Phys. Soc. Jpn. 80 (2011) 104705.


PH13<br />

First-Principles Calculati<strong>on</strong> of the A-Site Ordered Perovskite<br />

CaCu 3Fe 4O 12<br />

Takuya Ueda 1 , Mitsuru Kodera 1 , Kunihiko Yamauchi 1 and Tamio Oguchi 2 *<br />

1 Osaka University, Japan<br />

2 Osaka University & JST-CREST, Japan<br />

PH14<br />

PH15<br />

UPGRADED<br />

Soft x-ray absorpti<strong>on</strong> spectroscopy study of Prussian blue analogue<br />

MCo[Fe(CN) 6]H 2O Nano-particles (M=Na, K, Rb)<br />

Eunsook Lee 1 , D.h. Kim 1 , Jiho<strong>on</strong> Hwang 1 , Nguyen Van Minh 2 , In-sang Yang 3 , M.<br />

Sawada 4 , T. Ueno 4 and J.-s. Kang 1 *<br />

1 Department of Physics, The Catholic University of Korea, Buche<strong>on</strong> 420-743, Korea<br />

2 Department of Physics, Hanoi Nati<strong>on</strong>al Uninersity of Educati<strong>on</strong>, Hanoi, Viet Nam<br />

3 Department of Physics, Ewha Womans University, Seoul 120-750, Korea<br />

4 Hiroshima Synchrotr<strong>on</strong> Radiati<strong>on</strong> Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan<br />

Molecular-based magnetic materials have been studied for their possible applicati<strong>on</strong>s as nano-magnetic devices<br />

as well as for the understanding of the fundamental physics of their magnetic phenomena. Molecular magnetic<br />

materials of Prussian Blue (PB) analogues, which are represented by the general formula, An[B(CN) 6]m∙xH 2O,<br />

where A and B are transiti<strong>on</strong>-metal i<strong>on</strong>s [1], show various characteristic magnetic properties depending <strong>on</strong> their<br />

transiti<strong>on</strong> metal i<strong>on</strong>s. PB crystallizes in the fcc structure with space group Fm3m [2]. Of special interest is the<br />

photo-induced spin transiti<strong>on</strong>. However, the origin of the photo-induced spin transiti<strong>on</strong> has not been understood<br />

well yet. In this work, we have studied the valence states of PB analogue MCo[Fe(CN) 6]H 2O (M=Na, K,<br />

Rb) nano-size particles by employing synchrotr<strong>on</strong>-radiati<strong>on</strong> soft x-ray absorpti<strong>on</strong> spectroscopy (XAS). The<br />

measured Fe and Co 2p XAS spectra of MCo[Fe(CN) 6]H 2O (M=Na, K, Rb) reveal the systematic changes as<br />

the size of M i<strong>on</strong> changes, from the Fe 2+ -Fe 3+ mixed-valent states and the nearly divalent Co 2+ states to the nearly<br />

trivalent Fe 3+ states and the Co 2+ -Co 3+ mixed-valent states. This finding suggests that the electr<strong>on</strong>ic structures of<br />

PB nano-particles play an important role in determining their magnetic properties.<br />

[1] Amit Kumar and S M Yusuf, Pramana - J. Phys., 63, 239 (2004). [2] Nguyen Van Minh, Phung<br />

Kim Phu, Nguyen Minh Thuan, and In-Sang Yang, J. Magnetics, 13, 149 (2008).<br />

L<strong>on</strong>g-time variati<strong>on</strong> of magnetic structure in multistep metamagnets<br />

Ca 3(Co-M) 2O 6: Effect of disorder<br />

Taketo Moyoshi*, Rui Takahashi, Yuichiro Ito, Ryotaro Irie, Tetsuto Ide, Daiki Syoji<br />

and Kiyoichiro Motoya<br />

Faculty of Science and Technology, Tokyo University of Science, Japan<br />

We have reported that CeIr 3Si 2, Ca 3Co 2O 6 and some other materials show l<strong>on</strong>g-time variati<strong>on</strong><br />

of magnetic structure [1-4]. These materials are uniform compounds including no appreciable<br />

randomness or imperfecti<strong>on</strong>s. All of these compounds show successive magnetic transiti<strong>on</strong>s<br />

and metamagnetic transiti<strong>on</strong>s at low magnetic field, which indicate the presence of competing<br />

magnetic interacti<strong>on</strong>s. Therefore, we think that the l<strong>on</strong>g-time variati<strong>on</strong> of magnetic structure in<br />

these materials is caused by the competing magnetic interacti<strong>on</strong>s. To ensure that randomness<br />

or imperfecti<strong>on</strong>s are not the main factor causing the l<strong>on</strong>g-time variati<strong>on</strong> of magnetic structure,<br />

we have investigated the element substituti<strong>on</strong> effects. In this presentati<strong>on</strong>, we show the time<br />

dependence of the magnetizati<strong>on</strong> in Ca 3(Co 1-xM x) 2O 6 (M=Ga, Mg, Al and Ti). The time<br />

variati<strong>on</strong>s of magnetizati<strong>on</strong> were measured after the sample was cooled to various target<br />

temperatures from T=30 K (T>Tc1) at B=5 mT. Characteristics of the time variati<strong>on</strong> behavior<br />

were not much modified by the disorder produced by the substituti<strong>on</strong> of n<strong>on</strong>-magnetic<br />

elements. These results show that the l<strong>on</strong>g-time variati<strong>on</strong> of the magnetic structure in Ca 3Co 2O 6<br />

is not caused by randomness or imperfecti<strong>on</strong>s.<br />

[1]K. Motoya et al. J. Phys. C<strong>on</strong>f. Series 200 (2010) 032048 [2]T. Moyoshi et al., J. Phys. Soc. Jpn.<br />

81 (2012) 014704 [3]T. Moyoshi and K. Motoya, J. Phys. Soc. Jpn., 80 (2011) 034701 [4]K. Motoya<br />

et al. J. Phys. C<strong>on</strong>f. Series 273 (2011) 012124<br />

PH16<br />

PH17<br />

PH18<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Study of magnetic properties of NdCo1-xNixO3 (x = 0, 0.2, 0.4)<br />

Ravi Kumar 1 , Vinod Kumar 2 , Rajesh Kumar 3 , Dinesh Kumar Shukla 4 , Sunil Kumar<br />

Arora 5 and I V Schvets 6<br />

1<br />

Centre for Materials Science and Engineering, Nati<strong>on</strong>al Institute of Technology, Hamirpur 177005 (H.P.),<br />

India<br />

2<br />

Department of physics, Nati<strong>on</strong>al Institute of Technology, Hamirpur 177005 (H.P.), India<br />

3<br />

Department of physics, Nati<strong>on</strong>al Institute of Technology, Hamirpur 177005 (H.P.), India, India<br />

4<br />

Deutshes Electr<strong>on</strong>en Synchrotr<strong>on</strong> DESY, 22607 Hamburg, Germany, Deutshes Electr<strong>on</strong>en Synchrotr<strong>on</strong><br />

DESY, 22607 Hamburg, Germany, Germany<br />

5<br />

School of Physics, Trinity College Dublin 2, 3School of Physics, Trinity College Dublin 2, Ireland<br />

6<br />

School of Physics, Trinity College Dublin 2, School of Physics, Trinity College Dublin 2, Ireland<br />

We report here the magnetizati<strong>on</strong> studies of the NdCo 1-xNi xO 3 (x = 0, 0.2, 0.4) samples<br />

synthesized using c<strong>on</strong>venti<strong>on</strong>al solid state reacti<strong>on</strong> method. X-ray diffracti<strong>on</strong> followed<br />

by Rietveld refinement, c<strong>on</strong>firms the single phase orthorhombic structure with Pbnm<br />

space group for all the samples. X-ray absorpti<strong>on</strong> spectroscopy studies revealed that both<br />

Co and Ni exist in trivalent state. The zero field cooled and field cooled magnetizati<strong>on</strong><br />

measurements show that below room temperature the magnetizati<strong>on</strong> has str<strong>on</strong>g influence<br />

of paramagnetic rare earth i<strong>on</strong> inhibiting magnetic ordering of cobalt i<strong>on</strong>s. Below a<br />

certain low temperature (T< 50K), samples with x = 0, 0.2, show paramagnetic to anti<br />

ferromagnetic transiti<strong>on</strong> but the sample with x = 0.4 shows paramagnetic to Spin glass<br />

transiti<strong>on</strong>. Isothermal magnetizati<strong>on</strong> hysteresis measurements revealed the similar behavior<br />

at low temperature. The overall magnetic behavior has <strong>on</strong> the basis of various magnetic<br />

interacti<strong>on</strong>s between Nd-sublattice and those of transiti<strong>on</strong> metal networks.<br />

Fluctuati<strong>on</strong>s of charge, orbital, and spin order in single layer<br />

manganite Pr 0.5Ca 1.5MnO 4<br />

Ismudiati Puri Handayani 1 *, Agung Nugroho 2 , Nandang Mufti 3 , Syarif Riyadi 1 , May<br />

On Tjia 2 , T.t.m Palstra 1 and P.h.m Van Loosdrecht 1<br />

1 Zernike Institute for Advanced Material, Netherlands<br />

2 Bandung Institute of Technology, Ind<strong>on</strong>esia<br />

3 State University of Malang, Ind<strong>on</strong>esia<br />

The magnetic and transport properties of doped manganite oxides are intimately related to the<br />

dimensi<strong>on</strong>ality of the MnO 2 network. A three dimensi<strong>on</strong>al system tends to lead to metallicferromagnetic<br />

properties, whereas the two dimensi<strong>on</strong>al (2D) systems is dominated by chargeorbital<br />

order (COO) leading to insulating-antiferromagnetic properties. Pr 0.5Ca 1.5MnO 4 is <strong>on</strong>e of<br />

the more interesting members of the 2D manganite family showing a charge and orbital ordering<br />

transiti<strong>on</strong> above room temperature (TCOO = 320 K) with distinct changes in the magnetic,<br />

transport, and structural properties, evidencing a str<strong>on</strong>g coupling between the orbital, structural,<br />

charge, and spin degrees of freedom. We study the structural, magnetic susceptibility, transport,<br />

specific heat, and Raman spectroscopy of this material. The metal insulator transiti<strong>on</strong> observed<br />

at TCOO is found to be more pr<strong>on</strong>ounced in comparis<strong>on</strong> to the well studied isostructural<br />

La 0.5Sr 1.5MnO 4 compound. The same holds for the changes in the magnetic susceptibility at the<br />

antiferromagnetic transiti<strong>on</strong> (TN=120 K). Even though the COO is accompanied by rather abrupt<br />

changes in the physical properties, our data shows that no full ordering occurs at the transiti<strong>on</strong><br />

temperature. The system exhibits orbital fluctuati<strong>on</strong>s down to a temperature of about 200K, leading<br />

to an unusual temperature dependence of the vibrati<strong>on</strong>al, magnetizati<strong>on</strong>, and transport properties.<br />

Magnetic properties of spinel oxide CuCr 2O 4 investigated by NMR<br />

Euna Jo, So<strong>on</strong>chil Lee*, Changsoo Kim, Bye<strong>on</strong>gki Kang and Sangil Kw<strong>on</strong><br />

Physics, KAIST, Korea<br />

Spinel oxide CuCr 2O 4 is known to have n<strong>on</strong>-collinear spin structure and orbital<br />

ordering in its ground state. NMR spectrum for the magnetic i<strong>on</strong>s Cr 3+ and Cu 2+ was<br />

measured at liquid helium temperature to investigate magnetic properties of CuCr 2O 4.<br />

Temperature dependence of the Cr NMR frequency shows that there exist initial energy<br />

gap in the dispersi<strong>on</strong> relati<strong>on</strong> of the spin wave. This energy gap is larger than that of the<br />

Cu i<strong>on</strong>, implying that spin-orbit coupling of the Cr i<strong>on</strong> is str<strong>on</strong>ger than that of the Cu<br />

i<strong>on</strong>. This is c<strong>on</strong>sistent with theory that predicts orbital order for the Cu i<strong>on</strong> in CuCr 2O 4.<br />

The canting angle of the Cr 3+ spin was estimated to be 80° by external magnetic field<br />

dependence of the Cr NMR frequency. Also the line width of the Cr NMR spectrum<br />

was measured in 7T external magnetic field. The broadening of the spectrum is induced<br />

by the anisotropy field. The broadening of the Cu NMR spectrum is larger than that of<br />

the Cr NMR spectrum, implying that orbital ordering, rather than anisotropy field, is<br />

the main reas<strong>on</strong> of the Cu NMR spectrum broadening.<br />

July 8 - 13, 2012 Busan, Korea 35<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PH19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic frustrati<strong>on</strong> effects in the new colossal magnetoresistance<br />

oxide NaCr 2O 4<br />

Hikaru Takeda 1 *, Yasuhiro Shimizu 1 , Masayuki Itoh 1 , Hiroya Sakurai 2 and Eiji<br />

Takayama- Muromachi 2<br />

1 Department of Physics, Graduate School of Science, Nagoya University, Japan<br />

2 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

In itinerant electr<strong>on</strong> systems <strong>on</strong> a geometrically frustrated lattice, the magnetic frustrati<strong>on</strong> is<br />

c<strong>on</strong>sidered to play a crucial role for their transport properties as seen in LiV 2O 4 which shows the<br />

heavy fermi<strong>on</strong>-like behavior [1]. Recently, a new chromium oxide NaCr 2O 4 with geometrically<br />

frustrated double chains was reported to show the unc<strong>on</strong>venti<strong>on</strong>al colossal magnetoresistance<br />

(CMR) effect [2]. Unlike the c<strong>on</strong>venti<strong>on</strong>al CMR materials represented by the ferromagnetic<br />

manganites, NaCr 2O 4 is an antiferromagnet with the Neel temperature TN = 125 K. The origin<br />

of the CMR effect in NaCr 2O 4 is expected to be closely related to the unc<strong>on</strong>venti<strong>on</strong>al spin<br />

structure generated by the magnetic frustrati<strong>on</strong>. In this study, we have performed 23Na NMR<br />

measurements <strong>on</strong> NaCr 2O 4 to investigate the spin structure in the antiferromagnetic phase and<br />

the magnetic correlati<strong>on</strong>s. We found the presence of a ferromagnetic interacti<strong>on</strong>, which competes<br />

with an antiferromagnetic <strong>on</strong>e, from the temperature dependence of the nuclear spin-lattice<br />

relaxati<strong>on</strong> rate 1/T1. Below TN, 23Na NMR spectra, which change with increasing the external<br />

magnetic field, cannot be explained by a c<strong>on</strong>venti<strong>on</strong>al spin structure. The CMR effect may be<br />

related to the instability of the spin structure in the external field due to the magnetic frustrati<strong>on</strong>.<br />

[1]S. K<strong>on</strong>do, et al., PRL 78, 3729 (1997). [2] H. Sakurai, et al., (unpublished).<br />

PH20<br />

Site-dependent metal-insulator transiti<strong>on</strong> and orbital order in quasi<strong>on</strong>e-dimensi<strong>on</strong>al<br />

V6O13 Satoshi Aoyama 1 , Yasuhiro Shimizu 1 , Masayuki Itoh 2 * and Yutaka Ueda 3<br />

1<br />

Department of Physics, Graduate School of Science, Nagoya University, Furo-cho,<br />

Chikusa-ku, Nagoya, Japan<br />

2<br />

Department of Physics, Graduate School of Science, Nagoya University, Japan<br />

3<br />

Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa,<br />

Japan<br />

Vanadates are prototypes of metal-insulator transiti<strong>on</strong>s with orbital degrees of freedom.<br />

In a quasi-<strong>on</strong>e-dimensi<strong>on</strong>al compound V 6O 13, the mixed valence gives n<strong>on</strong>-uniform<br />

spin-charge distributi<strong>on</strong>s <strong>on</strong> inequivalent V sites even for the metallic state. Our<br />

sophisticated 51V NMR measurements using a single crystal distinguished the sitedependent<br />

orbital order and the local spin susceptibilities <strong>on</strong> two inequivalent chains.<br />

One chain behaves as a metallic <strong>on</strong>e with the moderately depressed susceptibility,<br />

whereas another behaves as an insulating <strong>on</strong>e with the magnetically active local<br />

moment. The result arises from the site dependent electr<strong>on</strong> correlati<strong>on</strong>, giving the<br />

net duality in the c<strong>on</strong>ducting and magnetic properties. A metal-insulator transiti<strong>on</strong><br />

occurring at -150 K accompanies with dramatic changes in the charge and orbital<br />

ordering textures, as we observed in the 51V nuclear quadrupole splitting anisotropy.<br />

Such ordering separates the metallic chain into magnetic and n<strong>on</strong>magnetic sites, giving<br />

a complex antiferromagnetic spin structure below -50 K.<br />

PH21<br />

Synthesis and characterizati<strong>on</strong> of CoMn 2O 4 nanopowders by a reverse<br />

Micelle processing<br />

Hojung Kim and D<strong>on</strong>g Sik Bae*<br />

Department of C<strong>on</strong>vergence Materials Science and Engineering, Changw<strong>on</strong> Nati<strong>on</strong>al<br />

Univ., Korea<br />

CoMn 2O 4 nanoparticles was synthesized by reverse micelle processing the mixed<br />

precursor (c<strong>on</strong>sisting of Co(NO 3) 3 and MnCl 2•4H 2O). The CoMn 2O 4 was prepared<br />

by mixing the aqueous soluti<strong>on</strong> at a molar ratio of Co : Mn = 1 : 2. The synthesized<br />

powders were calcined at 600°C for 2h. The average size and distributi<strong>on</strong> of<br />

synthesized powders were in the range of 10-20nm and narrow, respectively. The<br />

average size of the synthesized powders increased with increasing water to surfactant<br />

molar ratio. The XRD diffracti<strong>on</strong> patterns show that the phase of CoMn 2O 4 was spinel<br />

(JCPDS no.77-0471). The synthesized and calcined powders were characterized by<br />

thermo gravimetry- differential scanning calorimeter (TG-DSC), X-ray diffracti<strong>on</strong><br />

analysis (XRD) and transmissi<strong>on</strong> electr<strong>on</strong> microscopy (TEM). The magnetic property<br />

of the powder was measured by Vibrating Sample Magneto-meter (VSM) at 298K.<br />

The effect of synthesis parameter, such as the molar ratio of water to surfactant, is<br />

discussed.<br />

36 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PH22<br />

The patterning with a circular magnet array, its observati<strong>on</strong> and<br />

domain switching in ferromagnetic ZnCoO:H<br />

W<strong>on</strong>-kyung Kim, Seunghun Lee, Sang-uk Cho, Y<strong>on</strong>g-chan Cho, Hideomi Koinuma and Se-young Je<strong>on</strong>g*<br />

Cogno-Mechatr<strong>on</strong>ics Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

Today’s spintr<strong>on</strong>ic technologies are c<strong>on</strong>sidered to be the most progressive soluti<strong>on</strong> for overcoming the typical<br />

semic<strong>on</strong>ductor electr<strong>on</strong>ics. Many researchers have extensively studied the effect of size, shape, structure<br />

<strong>on</strong> single-domain magnet and its wall moti<strong>on</strong> with permanent magnetic metal for high-density magnetic<br />

memory and logic devices[1,2]. However, the fact that permanent magnetic metals could not reprogram<br />

after the first design for logic devices is still remaining as an important issue. Thus, hydrogen-mediated<br />

Co-doped ZnO(ZnCoO:H) having reversible room-temperature ferromagnetism has been c<strong>on</strong>sidered as<br />

a str<strong>on</strong>g candidate material for spintr<strong>on</strong>ic devices[3]. In this study, we observed domain switching in a<br />

ZnCoO:H in real-space and simulate it using object-oriented micromagnetic framework(OOMMF). ZnCoO<br />

circular patterns are fabricated by rf-sputtering and various lithography processes, and hydrogen is injected<br />

by plasma and hot isostatic pressing(HIP) methods. The reversible magnetic single-domain behavior is<br />

activated and deactivated by hydrogen manipulati<strong>on</strong>, which are investigated with superc<strong>on</strong>ducting quantum<br />

interference device(SQUID) and magnetic force microscopy(MFM) measurements, and the results are<br />

compared with the OOMMF simulati<strong>on</strong>. This reversible room-temperature magnetic switching of the oxide<br />

materials could greatly c<strong>on</strong>tribute to the development of reprogrammable spin logic devices.<br />

[1] S. Y. Chou, Proc. IEEE 85, 652 (1997); G. A. Prinz, Science 282, 1660 (1998) [2] E. R. Lewis et al., Nat. Mater. 9,<br />

980 (2010); J.-C.Lee et al,. Phys. Rev. Lett. 107, 067201 (2011) [3] H. J. Lee et al., Appl. Phys. Lett. 88, 062504 (2006);<br />

S. Lee et al., Appl. Phys. Lett. 94, 212507 (2009); Y. C. Cho et al., Appl. Phys. Lett. 95, 172514 (2009); S. J. Kim et al.,<br />

Phys. Rrev. B 81, 212408 (2010); S. Lee et al., J. Appl. Phys. (accepted); J. M. Shin et al., Phys. Rev. Lett. (submitted)<br />

PH23<br />

Orbitally induced molecule formati<strong>on</strong>s in itinerant triangular<br />

vanadates<br />

Yasuhiro Shimizu 1 *, Ken-ichiro Matsudaira 1 , Masayuki Itoh 1 and Yutaka Ueda 2<br />

1 Nagoya University, Japan<br />

2 University of Tokyo, Japan<br />

An intriguing route that eliminates the geometrical frustrati<strong>on</strong> is the orbitally-induced<br />

symmetry breaking usually described by the Kugel-Khomskii model. In itinerant<br />

systems, however, the model for localized electr<strong>on</strong>s may not be guaranteed, and the<br />

degenerated d orbitals can be partially occupied. We show that the orbital occupati<strong>on</strong><br />

c<strong>on</strong>tinuously changes into a valence-b<strong>on</strong>d-solid ground state in an itinerant vanadate<br />

BaV 10O 15 with a triangular lattice, based <strong>on</strong> the orbital-resolved nuclear magnetic<br />

res<strong>on</strong>ance technique. Owing to the odd number of d electr<strong>on</strong>s, i. e., eleven electr<strong>on</strong>s<br />

for a five-V unit, all the V sites cannot form the valence b<strong>on</strong>ds. Instead, two of the five<br />

V sites, sharing five electr<strong>on</strong>s, remain magnetic with the ferro-orbital ordering [1]. In<br />

clear c<strong>on</strong>trast, no commensurate spin order and orbital order are stabilized in SrV 10O 15.<br />

The result suggests fracti<strong>on</strong>al and incommensurate spin-orbital orders that cannot fully<br />

remove the geometrical frustrati<strong>on</strong>.<br />

[1]Y. Shimizu, K. Matsudaira, M. Itoh, T. Kajita, and T. Katsufuji, Phys. Rev. B. 84, 064421 (2011).<br />

PI01<br />

Investigati<strong>on</strong> of magnetocaloric effect in La 0.45Pr 0.25Ca 0.3MnO 3 by<br />

differential scanning calorimetry and thermal analysis<br />

Aparnadevi M, Sujit Kumar Barik and Ramanathan Mahendiran*<br />

Department of Physics, Nati<strong>on</strong>al university of Singapore, Singapore<br />

We investigated magnetocaloric effect in La 0.45Pr 0.25Ca 0.3MnO 3 by direct (changes in<br />

temperature and latent heat) and indirect methods (magnetizati<strong>on</strong> isotherms). This<br />

compound undergoes a first-order paramagnetic to ferromagnetic transiti<strong>on</strong> with Tc<br />

= 200 K up<strong>on</strong> cooling. The paramagnetic phase becomes unstable and it transforms<br />

into a ferromagnetic phase under the applicati<strong>on</strong> of magnetic field, which results in<br />

field-induced metamagnetic transiti<strong>on</strong> (FIMT). The FIMT is accompanied by release<br />

of latent heat and change in temperature of the sample as evidenced from differential<br />

scanning calorimetry and thermal analysis experiments. A large magnetic entropy<br />

change of ΔSm = -7.3 Jkg-1K-1 at Tc = 212.5 K and refrigerati<strong>on</strong> capacity of 228 J/<br />

kg are observed for a field change of ΔH = 5 T. It is suggested that the nanometer<br />

sized ferromagnetic clusters co-exist with short-range charge-ordered clusters in the<br />

paramagnetic state, resulting in a large value of ΔSm above the Tc.


PI02<br />

Specific heat and magnetic properties of spinel compound FeV 2O 4<br />

Shogo Kawaguchi*, Yoshiki Kubota and Hiroki Ishibashi<br />

Department of Physical Science, Graduate School of Science, Osaka Prefecture<br />

University, Japan<br />

The spinel compound FeV 2O 4 has the orbital degrees of freedom at both eg (Fe 2+ ) and<br />

t2g (V 3+ ) orbitals. This compound shows successive structural phase transiti<strong>on</strong>s at<br />

about 140 K, 110 K accompanied by ferrimagnetic ordering, 70 K and 35 K. However,<br />

the details of the phase transiti<strong>on</strong>s below 110 K are still not understood. In order to<br />

clarify the origin of these phase transiti<strong>on</strong>s, we measured magnetizati<strong>on</strong> and specific<br />

heat capacity for polycrystalline and single crystal of FeV 2O 4. We first observed three<br />

anomalies at 140 K, 109 K and 68 K with decreasing temperature in the specific heat<br />

measurements using the polycrystalline sample. The λ-type anomaly at 109 K indicates<br />

the sec<strong>on</strong>d order phase transiti<strong>on</strong>, which is related to the ferrimagnetic ordering.<br />

Moreover, the anomaly at 68 K has a sharp peak, which c<strong>on</strong>forms to the anomaly<br />

<strong>on</strong> the temperature dependence of magnetic susceptibility. The electr<strong>on</strong>ic specific<br />

coefficient γ =1.8 mJ/molK2 of FeV 2O 4 is smaller than that of of MnV 2O 4 (γ = 12 mJ/<br />

molK2)[2] because the Jahn-Teller effect of Fe 2+ for FeV 2O 4 may weaken the electr<strong>on</strong>electr<strong>on</strong><br />

interacti<strong>on</strong>s. The details of the measurements using single crystal and the<br />

correlati<strong>on</strong> between the crystal and the magnetic structures are also discussed.<br />

[1] T. Katsufuji et al., J. Phys. Soc. Jpn. 77 (2008) 053708 [2] K. M. Whun et al., Phys. Rev. B 83<br />

(2011) 024403<br />

PI03<br />

The crossover to checkerboard charge order: Magnetic excitati<strong>on</strong>s of<br />

charge-stripe ordered of La 2-xSr xNiO 4.<br />

Paul G Freeman 1 , A. T. Boothroyd 2 , D. Prabhakaran 2 , K. Hradil 3 , R. A. Mole 4 and S. R. Giblin 5<br />

1 Helmholtz-Zentrum Berlin, Germany; EPFL, Lausanne, Switzerland; ILL, Grenoble, France<br />

2 Department of Physics, Oxford University, United Kingdom<br />

3 Technische Universitat Wien, Austria; Institut fur Physikalische Chemie, Universitat Gottingen, Germany<br />

4 Bragg Institute, ANSTO, Australia; FRM II, Germany<br />

5 ISIS Facility, Rutherford Applet<strong>on</strong> Laboratory, United Kingdom<br />

Are stripes ubiquitous to the cuprates, and what is the role of stripes in high temperature superc<strong>on</strong>ductivity, are<br />

two questi<strong>on</strong>s that have been intensively debated since the discovery of charge stripe order in the cuprates[1].<br />

From studying the magnetism of charge-stripe ordered La 2-xSr xNiO 4 (LSNO) the magnetic interacti<strong>on</strong>s of a<br />

charge-stripe ordered phase have been quantitatively described[2], although our knowledge is incomplete[3].<br />

For x = 1/2 the ground state order of LSNO is part stripe and part checkerboard like in character, with both<br />

the magnetic excitati<strong>on</strong>s from the ordered moments and charge stripe electr<strong>on</strong>s showing dramatic differences<br />

compared to lower doping levels [2,3]. Variati<strong>on</strong>s of the charge-stripe periodicity, discommensurati<strong>on</strong>s, create<br />

additi<strong>on</strong>al magnetic excitati<strong>on</strong>s from the ordered moments in the x = 1/2 compared to damping the excitati<strong>on</strong>s<br />

at x ~ 1/3. While the magnetic excitati<strong>on</strong>s from the charge stripe electr<strong>on</strong>s have a different wavevector<br />

centring in the x = 1/2 [3,4]. We report a neutr<strong>on</strong> scattering study of the magnetic excitati<strong>on</strong>s in LSNO x = 0.4<br />

and 0.45. Between these two doping levels the magnetic excitati<strong>on</strong>s show a dramatic crossover in character.<br />

We discuss this crossover behaviour with regards to charge-stripe materials with larger charge stripe spacing.<br />

[1] M. Tranquada, et. al., Nature (L<strong>on</strong>d<strong>on</strong>) 375, 561 (1995). [2] H. Woo et. al. Phys. Rev. B 72, 064437 (2005). [3]<br />

P. G. Freeman, et. al. Phys. Rev. B 71, 174412 (2005). [4] A. T. Boothroyd , et. el., Phys. Rev. Lett. 91 257201 (2005).<br />

PI04<br />

Magnetic properties of low-dimensi<strong>on</strong>al α and γ CoV 2O 6<br />

Marc Lenertz*, J<strong>on</strong>athan Alaria, Daniel Stoeffler, Silviu Colis and Aziz Dinia<br />

DCMI, Institut de Physique et Chimie des Materiaux de Strasbourg, CNRS -<br />

Universite de Strasbourg, France<br />

CoV 2O 6 is a low dimensi<strong>on</strong>al oxide existing in two allotropic phases, generally<br />

called α and γ, and showing m<strong>on</strong>oclinic and triclinic structures, respectively. We<br />

synthesized this oxide by solid state reacti<strong>on</strong> and performed neutr<strong>on</strong>s diffracti<strong>on</strong> and<br />

magnetic measurements in order to understand the magnetic behavior in correlati<strong>on</strong><br />

with the low dimensi<strong>on</strong>al structure. The magnetic properties were supported by ab<br />

initio calculati<strong>on</strong>s. Both phases are c<strong>on</strong>stituted of parallel 1D Co chains organized in<br />

planes that are separated by vanadium oxide thin layers and are antiferromagnetic in<br />

the ground state. The magnetizati<strong>on</strong> curves recorded at 5 K show a stepped variati<strong>on</strong><br />

with sharp field-induced magnetic transiti<strong>on</strong>s and a magnetizati<strong>on</strong> plateau at <strong>on</strong>e-third<br />

of the saturati<strong>on</strong> magnetizati<strong>on</strong>. In α-CoV 2O 6, additi<strong>on</strong>al steps are evidenced at 1.8 K.<br />

The magnetic moment per Co i<strong>on</strong> is larger in the α phase (4.5 μB) than in the γ phase<br />

(3 μB), although Co has the same octahedral envir<strong>on</strong>ment in both cases. Ab initio<br />

calculati<strong>on</strong>s show that α-CoV 2O 6 is an antiferromagnetic semic<strong>on</strong>ductor with a gap<br />

of 1.1 eV in which the magnetic moment is essentially carried by Co and can reach a<br />

maximum value of about 4.2 μB for a meta-stable soluti<strong>on</strong>.<br />

M. Lenertz, J. Alaria, D. Stoeffler, S Colis and A. Dinia, J. Phys. Chem. C, 2011, 115, 17190-17196<br />

PI05<br />

PI06<br />

PI07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Structural and magnetic properties of the parent compound T'-<br />

La 2CuO 4 of electr<strong>on</strong>-doped cuprates<br />

Gwendolyne Pascua 1 , Hubertus Luetkens 1 , Marco Guenther 2 , Roland Hord 3 , Lukas<br />

Keller 4 , Vladimir Pomjakushin 4 , Andreas Suter 1 , Hemke Maeter 2 , Alexander Buckow 5 ,<br />

Barbara Albert 3 , Hans-henning Klauss 2 and Lambert Alff 5<br />

1 Laboratory for Mu<strong>on</strong> Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland<br />

2 Institut fuer Festkoerperphysik, TU Dresden, DE-01069 Dresden, Germany<br />

3 Eduard-Zintl-Institute of Inorganic and Physical Chemistry, TU Darmstadt, Petersenstr. 18, DE-<br />

64287, Darmstadt, Germany<br />

4 Laboratory for Neutr<strong>on</strong> Scattering, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland<br />

5 Institute of Materials Science, TU Darmstadt, Petersenstr. 23, DE-64287 Darmstadt, Germany<br />

Recently, we found that the newly synthesized metastable T'-La 2CuO 4 exhibits much lower Neel temperature (TN)<br />

and increased magnetic fluctuati<strong>on</strong>s compared to other mother compounds of electr<strong>on</strong>-doped superc<strong>on</strong>ductors like<br />

Nd 2CuO 4 or Pr 2CuO 4. Mu<strong>on</strong> spin rotati<strong>on</strong> (μSR) reveals a gradual slowing down of dynamic magnetic fluctuati<strong>on</strong>s<br />

below TN1=220K and static magnetic order below TN2=115K in c<strong>on</strong>trast to T-La 2CuO 4 where TN2=300K. In<br />

comparis<strong>on</strong> to our T’-La 2CuO 4, measurements were d<strong>on</strong>e <strong>on</strong> T’-Pr 2CuO 4 to study the effect of a magnetic rare<br />

earth i<strong>on</strong> <strong>on</strong> the magnetism. Zero-Field μSR <strong>on</strong> T’-Pr 2CuO 4 shows oscillati<strong>on</strong>s at high temperatures up to 220K in<br />

sharp c<strong>on</strong>trast to the predominantly dynamic character of the depolarizati<strong>on</strong> in T’-La 2CuO 4 in the same temperature<br />

range. This clearly dem<strong>on</strong>strates that the magnetism of T’-La 2CuO 4 is much more 2-dimensi<strong>on</strong>al than in T’-Pr 2CuO 4.<br />

Interestingly, there is also an abrupt change of the internal field distributi<strong>on</strong> at TN3=40K for both the T’-La 2CuO 4<br />

and the T’-Pr 2CuO 4 compounds c<strong>on</strong>sistent with a reorganizati<strong>on</strong> of the magnetic structure at this temperature. La-<br />

NMR results for the T’-La 2CuO 4 also display anomalies at the abovementi<strong>on</strong>ed characteristic temperatures. In<br />

additi<strong>on</strong>, μSR and neutr<strong>on</strong> scattering results <strong>on</strong> T’-Pr 2CuO 4 indicate a similar behaviour previously observed for<br />

Nd 2CuO 4 pointing to, up-to-now undetected spin reorientati<strong>on</strong> transiti<strong>on</strong>s.<br />

[1] R. Hord, H. Luetkens, et al., Phys. Rev. B 82, 180508(R) (2010). [2] G. M. Luke et al., Phys. Rev. B 42, 7981 (1990).<br />

[3] I.W. Sumarlin, et al., Phys. Rev. B 51, 5824 (1990). [4] V.P. Plakhty et al., Phys. Lett. A 250, 201 (1998). [5] R.<br />

Sachidanandam et. al., Phys. Rev. B 56, 260 (1997). [6] S. Katano, et al., Physica C 215, 92 (1993).<br />

Microscopic magnetic nature of the quasi-<strong>on</strong>e-dimensi<strong>on</strong>al<br />

antiferromagnet BaCo 2V 2O 8<br />

Martin Manss<strong>on</strong> 1 *, Krunoslav Prsa 1 , Jun Sugiyama 2 , Hiroshi Nozaki 2 , Alex Amato 3 ,<br />

Shojiro Kimura 4 , Kumiko Omura 5 , Masayuki Hagiwara 5 and Andrey Zheludev 1<br />

1 Lab. for Solid State Physics, ETH Zurich, Switzerland<br />

2 Toyota Central Research and Development Labs. Inc., Japan<br />

3 LMU, Paul Scherrer Institut, Switzerland<br />

4 Institute for Materials Research, Tohoku University, Japan<br />

5 KYOKUGEN, Osaka University, Japan<br />

BaCo 2V 2O 8, bel<strong>on</strong>gs to a wide group of quasi-1D antiferromagnets (AF). The Q1D compounds display a<br />

variety of fascinating ground states governed by the str<strong>on</strong>g spin-spin coupling al<strong>on</strong>g the 1D directi<strong>on</strong> and a<br />

much weaker coupling al<strong>on</strong>g other directi<strong>on</strong>s. BaCo 2V 2O 8 display a l<strong>on</strong>g-range AF order below TN=5 K<br />

and possibly short-range order all the way up to 30 K. Further, a novel type of field induced magnetic order<br />

has been found for T3.9 T [1,2]. It was determined to be an incommensurate spin structure<br />

caused by quantum fluctuati<strong>on</strong>s, fitting well to theoretical predicti<strong>on</strong>s for a so-called Tom<strong>on</strong>aga-Luttinger<br />

liquid (TLL). To the best of our knowledge, we present here the first μSR investigati<strong>on</strong> of the microscopic<br />

magnetic nature of single crystalline BaCo 2V 2O 8 samples. Our data reveal several clear mu<strong>on</strong> frequencies<br />

below TN indicating the <strong>on</strong>set of a l<strong>on</strong>g-range order. Above 5 K, the μSR spectra are well fitted to a simple<br />

power-exp<strong>on</strong>ential relaxing functi<strong>on</strong>. The temperature dependence of the relaxati<strong>on</strong>-rate as well as the<br />

power display a clear anomaly around T=40 K, indicating the <strong>on</strong>set of short-range 1D correllati<strong>on</strong>s. Finally<br />

we also present initial and intriguing field dependent data.<br />

[1] S. Kimura et al. PRL 100, 057202 (2008) [2] S. Kimura et al. PRL 101, 207201 (2008) Funding<br />

Source: Swiss Nati<strong>on</strong>al Science Foundati<strong>on</strong> (Project 6, NCCR MaNEP) and Toyota CRDL.<br />

Detecti<strong>on</strong> of orbital wave in YVO 3 using inelastic neutr<strong>on</strong> scattering<br />

Daichi Kawana 1 , Youichi Murakami 1 , Tetsuya Yokoo 2 , Shinichi Itoh 2 , Andrei T Savici 3 ,<br />

Garrett E Granroth 3 , Kazuhiko Ikeuchi 4 , Hir<strong>on</strong>ori Nakao 1 , Kazuaki Iwasa 5 , Ryuichiro<br />

Fukuta 6 , Shigeki Miyasaka 6 , Setsuko Tajima 6 , Sumio Ishihara 5 and Yoshinori Tokura 7<br />

1 C<strong>on</strong>densed Matter Research Center, Institute of Materials Structure Science, KEK, Japan<br />

2 Neutr<strong>on</strong> Science Divisi<strong>on</strong>, Institute of Materials Structure Science, KEK, Japan<br />

3 Neutr<strong>on</strong> Scattering Sciences Divisi<strong>on</strong>, Oak Ridge Nati<strong>on</strong>al Laboratory, USA<br />

4 Comprehensive Research Organizati<strong>on</strong> for Science and Society, Japan<br />

5 Department of Physics, Tohoku University, Japan<br />

6 Department of Physics, Osaka University, Japan<br />

7 Department of Applied Physics, University of Tokyo, Japan<br />

We focus <strong>on</strong> an orbital excitati<strong>on</strong> in YVO 3, which shows the complex magnetic and orbital orderings in<br />

the low temperatures [1]. In the phase where the G-type orbital order accompanied with the C-type spin<br />

order (G-OO/C-SO) appears, the existence of the large orbital fluctuati<strong>on</strong> is suggested [2]. Additi<strong>on</strong>ally, a<br />

large dispersive orbital-wave al<strong>on</strong>g the c-axis, due to the str<strong>on</strong>g <strong>on</strong>e-dimensi<strong>on</strong>al spin-orbital correlati<strong>on</strong>,<br />

is calculated [3]. In c<strong>on</strong>siderati<strong>on</strong> of the neutr<strong>on</strong> scattering cross-secti<strong>on</strong> obtained from the correlati<strong>on</strong><br />

functi<strong>on</strong> for the orbital angular moment, we have attempted to detect the orbital excitati<strong>on</strong> using inelastic<br />

neutr<strong>on</strong> scattering spectrometers. We observed a magnetic excitati<strong>on</strong> up to 35 meV. This energy range is<br />

higher than that reported previously [3]. On the other hand, weak excitati<strong>on</strong>s are observed in the range of<br />

40-70 meV. In this Presentati<strong>on</strong>, we discuss whether these are originated from orbital excitati<strong>on</strong> or not.<br />

[1] S. Miyasaka et al., Phys. Rev. B 73, 224436 (2006). [2] C. Ulrich et al., Phys. Rev. Lett. 91,<br />

257202 (2003). [3] S. Ishihara, Phys. Rev. B 69, 075118 (2004).<br />

July 8 - 13, 2012 Busan, Korea 37<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PI08<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Orbital occupati<strong>on</strong> and magnetism of tetrahedrally coordinated Fe in<br />

CaBaFe 4O 7<br />

Nils Hollmann 1 , Martin Valldor 2 , Hua Wu 2 , Zhiwei Hu 1 , Navid Qureshi 2 , Thomas<br />

Willers 2 , Yi-ying Chin 3 , Julio Cezar 4 , Arata Tanaka 5 , Nicholas Brookes 4 and Liu Hao<br />

Tjeng 3<br />

1 Max-Planck-Institute for Chemical Physics of Solids, Dresden, Germany<br />

2 II. Institute of Physics, University of Cologne, Germany<br />

3 Max-Planck-Institute for Chemical Physics of Solids, Germany<br />

4 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, Grenoble, France<br />

5 Department of Quantum Matter, ADSM, Hiroshima University, Japan<br />

CaBaFe 4O 7 is a new mixed-valent transiti<strong>on</strong> metal oxide from the class of<br />

Swedenborgites [1,2] having both Fe 2+ and Fe 3+ i<strong>on</strong>s in tetrahedral coordinati<strong>on</strong> situated<br />

in a Kagome lattice. This class of materials could be an interesting starting point to study<br />

orbital physics in tetrahedral coordinati<strong>on</strong>. Here we characterize its magnetic properties<br />

by magnetizati<strong>on</strong> measurements and investigate its local electr<strong>on</strong>ic structure using<br />

soft x-ray absorpti<strong>on</strong> spectroscopy at the Fe L2,3 edges, in combinati<strong>on</strong> with multiplet<br />

cluster simulati<strong>on</strong>s and band structure calculati<strong>on</strong>s [3]. We found that the Fe 2+ i<strong>on</strong> in the<br />

unusual tetrahedral coordinati<strong>on</strong> is Jahn-Teller active having a minority-spin electr<strong>on</strong><br />

with an x2-y2 character. We deduce that there is an appreciable orbital moment caused<br />

by multiplet interacti<strong>on</strong>s, thereby explaining the observed magnetic anisotropy.<br />

[1] B. Raveau et al., Chem. Mat. 20, 6295 (2008) [2] B. Raveau et al., Z. Anorg. Allg. Chem. 635,<br />

1869 (2009) [3] N. Hollmann et al., Phys. Rev. B 83, 180405 (2011)<br />

PI09<br />

Search for topological spin order in the multiferroic insulator<br />

Cu2OSeO3 M. Wagner 1 , T. Adams 1 , A. Chac<strong>on</strong> 2 , G. Brandl 2 , H. Berger 3 , P. Lemmens 4 and C.<br />

Pfleiderer 1<br />

1<br />

Physik-Department, Technische Universitaet Muenchen, D-85748 Garching,<br />

Germany<br />

2<br />

Physik-Department and Forschungsneutr<strong>on</strong>enquelle Heinz-Maier Leibniz, TU<br />

Muenchen, D-85748 Garching, Germany<br />

3<br />

Ecole Polytechnique Federale Lausanne, CH-1015 Lausanne, Switzerland<br />

4<br />

Institut fuer Physik, Technische Universitaet Braunschweig, Germany<br />

We report a comprehensive study of the magnetic properties of single crystals of the<br />

multiferroic insulator Cu 2OSeO 3. Our study was motivated by the recent discovery of a<br />

skyrmi<strong>on</strong> lattice phase in the B 20 transiti<strong>on</strong> metal Si and Ge transiti<strong>on</strong> metal compounds<br />

[1], which are isostructural siblings of Cu 2OSeO 3. For our study large high-quality single<br />

crystals were grown by vapour transport. The magnetisati<strong>on</strong>, ac susceptibility and specific<br />

heat were measured down to 2K under magnetic fields up to 9T. The magnetic properties<br />

were studied with small angle neutr<strong>on</strong> scattering. We find a paramagnetic to helimagnetic<br />

transiti<strong>on</strong> at T_c - 58K. The magnetic phase diagram of Cu 2OSeO 3 shares remarkable<br />

similarities with the B 20 transiti<strong>on</strong> metal silicides, including the existence of a small phase<br />

pocket below T_c. The putative evidence for topological spin order is compared with the<br />

evidence for a skyrmi<strong>on</strong> lattice in B 20 transiti<strong>on</strong> metal Si and Ge compounds.<br />

[1] S. Muehlbauer et al., Science 323, 915 (2009).<br />

PI10<br />

Studies of neutr<strong>on</strong> scattering and bulk properties of h<strong>on</strong>eycomb lattice<br />

Li2MnO3 Sanghyun Lee 1 , Sungil Choi 1 , Jiye<strong>on</strong> Kim 1 , Cho<strong>on</strong>gjae W<strong>on</strong> 2 , Se<strong>on</strong>gsu Lee 3 , Shin-ae<br />

Kim 3 , Namjung Hur 2 and Je-geun Park 4 *<br />

1<br />

Center for Str<strong>on</strong>gly Correlated Materials Research, Seoul Nati<strong>on</strong>al University, Seoul<br />

151-742, Korea, Korea<br />

2<br />

Department of Physics, Inha University, Inche<strong>on</strong> 402-751, Korea, Korea<br />

3<br />

Neutr<strong>on</strong> Science Divisi<strong>on</strong>, Korea Atomic Energy Research Institute, Daeje<strong>on</strong> 305-<br />

353, Korea, Korea<br />

4<br />

Department of Physics & Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Seoul 151-742,<br />

Korea, Korea<br />

Li 2XO 3 with transiti<strong>on</strong> metal i<strong>on</strong>s occupying the X positi<strong>on</strong> forms an interesting<br />

h<strong>on</strong>eycomb lattice. Am<strong>on</strong>g Li 2XO 3, Li 2RuO 3 was recently found to have an unusual<br />

structural phase transiti<strong>on</strong> involving probably Ru dimerizati<strong>on</strong>. For example, it<br />

was reported that the crystal structure changes from P21/m to C2/m near 540 K,<br />

accompanied by a c<strong>on</strong>comitant metal-insulator transiti<strong>on</strong> and an abrupt change in<br />

the magnetic susceptibility. Li 2MnO 3 is another example having the C2/m crystal<br />

structure with the h<strong>on</strong>eycomb lattice. In order to investigate the magnetic properties of<br />

Li 2MnO 3, we have successfully grown single crystal Li 2MnO 3 by using a flux method.<br />

Using these single crystals, we have carried out both bulk measurements and neutr<strong>on</strong><br />

diffracti<strong>on</strong> studies with high resoluti<strong>on</strong> powder diffractometer (HRPD) and single<br />

crystal diffractometer (FCD) at HANARO, Korea. We also measured the magnetizati<strong>on</strong><br />

and heat capacity of the single crystals.<br />

38 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PI11<br />

Magnetic and calorimetric properties of Mn 2GeO 4 single crystals<br />

Natalia Mihashenok*, Nikita Volkov, Klara Sablina, Alexander Balaev, Maxim<br />

Molokeev, Sergei Popkov and Dmitriy Velikanov<br />

L.V. Kirensky Institute of Physics SB RAS, Russia<br />

Within the framework of our research of manganese oxides the single crystals<br />

Mn 2GeO 4 have been grown by the flux method using the original technique [1]. The<br />

crystal structure, an isomorph of olivine, was determined <strong>on</strong> single crystal by X-ray<br />

diffracti<strong>on</strong> method: cell parameters, a=10.7401 A , b=6.3116 A, c=5.0766 A, and<br />

the space group Pnma. Magnetic measurements were performed in the temperature<br />

range from 2 to 300 K and in magnetic fields up to 50 kOe with the exact orientati<strong>on</strong><br />

of the applied magnetic field relative to the crystallographic directi<strong>on</strong>s of the crystal.<br />

There are three sharp magnetic phase transiti<strong>on</strong> at T1=47 K, T2=17.5 K and T3=5.5<br />

K, with phase transiti<strong>on</strong> at T2 depended <strong>on</strong> applied magnetic field. Also the specific<br />

heat measurements of single crystals were carried out. The heat capacity of Mn 2GeO 4<br />

exhibits three sharp maxima, which exactly correlate with the magnetic phase<br />

transiti<strong>on</strong>.<br />

[1] Sapr<strong>on</strong>ova N.V., Volkov N.V., Sablina K.A., Petrakovskii G.A., Bayukov O.A., Vorotynov A. M.,<br />

Velikanov D.N., Bovina A.F., Vasilyev A.D., B<strong>on</strong>darenko G.V. Phys. Stat. Sol. B., 246 (2009) 206<br />

PI12<br />

Effect of doping <strong>on</strong> the magnetic structure of YMn1-xMxO3 (M = Ga, Ti,<br />

x ≤ 0.1)<br />

Neetika Sharma 1 , Po<strong>on</strong>am Kumari 2 , A. Das 1 * and G. Ravi Kumar 3<br />

1<br />

Solid State Physics Divisi<strong>on</strong>, Bhabha Atomic Research Centre Mumbai, India<br />

2<br />

UM - DAE Centre for Excellence in Basic Sciences University of Mumbai, Mumbai,<br />

India<br />

3<br />

Technical Physics Divisi<strong>on</strong>, Bhabha Atomic Research Centre Mumbai, India<br />

The effect of doping at the Mn site of multiferroic manganites, YMn 1-xM xO 3 (M = Ga, Ti, x<br />

≤ 0.1) have been studied by neutr<strong>on</strong> powder diffracti<strong>on</strong> and magnetic measurements. These<br />

compounds have been prepared by solid state synthesis techniques. All the compounds studied<br />

are isostructural and crystallizes with hexag<strong>on</strong>al structure in P63cm space group. We find that<br />

both Ga 3+ (d10) and Ti 4+ (d0) doping leads to significant reducti<strong>on</strong> in the magnetic transiti<strong>on</strong><br />

temperature (TN) while they influence the magnetic structure of YMnO 3 differently. The<br />

magnetic structure of YMnO 3 is described by the irreducible representati<strong>on</strong> Γ1 (or Γ3 ) with<br />

moment <strong>on</strong> Mn~3μB at 5K, in agreement with previously reported values <strong>on</strong> this compound<br />

[1]. We find that the representati<strong>on</strong> remains the same <strong>on</strong> doping with Ga in YMnO 3 albeit with<br />

a decrease in the value of the moment to 2.5μB at 6K. However, the irreducible representati<strong>on</strong><br />

changes <strong>on</strong> doping with Ti, and this modified structure is given by the basis vectors of the<br />

irreducible representati<strong>on</strong> Γ2 with moment 2.1μB at 6K. The geometrical frustrati<strong>on</strong> parameter,<br />

f = θp/Tn, ~ 7 and reduces with doping. These observati<strong>on</strong>s are different from the earlier<br />

reported doping studies carried out in this compound [2].<br />

[1]. J.A. Al<strong>on</strong>so et al. Phys. Rev. B 62 9498 (2000) [2] J. Park et al., Phys. Rev. B 79 064417 (2009)<br />

PI13<br />

Neutr<strong>on</strong> diffracti<strong>on</strong> and magnetic properties of Ba 2Co 2Fe 12O 22: Co 2Y<br />

Chan Hyuk Rhee 1 , Jung Tae Lim 1 , Sung Wook Yo<strong>on</strong> 1 , Kwang Lae Cho 1 , Sung Baek<br />

Kim 2 and Chul Sung Kim 1 *<br />

1 Department of Physics, Kookmin University, Korea<br />

2 Advancement for College Educati<strong>on</strong> Center, K<strong>on</strong>yang University, Korea<br />

Y-type hexa-ferrites with n<strong>on</strong>-collinear magnetic structure have been studied for<br />

magnetoelectric effect, showing induced electric polarizati<strong>on</strong> under external magnetic<br />

field. The helical magnetic structure of these ferrites depends <strong>on</strong> the temperature and<br />

magnetic field [1]. Here, polycrystalline Y-type barium cobalt ferrite (Ba 2Co 2Fe 12O 22;<br />

Co 2Y) was synthesized by c<strong>on</strong>venti<strong>on</strong>al ceramic method in O 2 gas atmosphere to<br />

reduce the oxygen defect. The temperature and magnetic field dependence of magnetic<br />

structure was investigated by neutr<strong>on</strong> diffracti<strong>on</strong> and vibrati<strong>on</strong> sample magnetometer.<br />

At temperature below TN = 615 K, the crystal structure of Co 2Y was determined to<br />

be rhombohedral with the space group R-3m. It showed soft ferrimagnetic behavior<br />

with Hc of 145 Oe at 297 K. Most of super-lattice peaks from spin structure decreased<br />

with increasing temperature. However, the peak at 21.1o increased with increasing<br />

temperature at temperatures above 205 K. In additi<strong>on</strong>, the slope of zero-field cooled<br />

magnetizati<strong>on</strong> under low field of 0.01 T changed at 205 K. This magnetic structure<br />

transiti<strong>on</strong> temperature of Co 2Y is higher than that of Ba 2Mg 2Fe 12O 22 [1] due to the<br />

presence of cobalt i<strong>on</strong> with str<strong>on</strong>g magnetic anisotropy.<br />

[1] S. Ishiwata, Y. Taguchi, H. Murakawa, Y. Onose, and Y. Tokura, Science 319, 1643 (2008).


PI-14<br />

Mössbauer studies of olivine Fe 1-yMn yPO 4<br />

Woo Jun Kw<strong>on</strong>, In Kyu Lee, Hee Seung Kim, In-bo Shim and Chul Sung Kim*<br />

Department of Physics, Kookmin University, Korea<br />

The olivine structured Fe 1-yMn yPO 4 (y = 0.1, 0.3), a possible cathode material for<br />

lithium i<strong>on</strong> sec<strong>on</strong>dary battery, have been studied by x-ray diffracti<strong>on</strong> and Mössbauer<br />

spectroscopy. These Fe 1-yMn yPO 4 samples were prepared by chemical deintercalati<strong>on</strong><br />

lithium from the LiFe 1-yMn yPO 4. The crystal structures of the Fe 1-yMn yPO 4 samples<br />

were determined to be orthorhombic (space group Pnma) at 295 K by Rietveld<br />

refinement method. The lattice c<strong>on</strong>stants of the Fe 1-yMn yPO 4 samples increased from<br />

a0 = 9.833 Å, b0 = 5.811 Å and c0 = 4.786 Å for y = 0.1 to a0 = 9.979 Å, b0 = 5.895<br />

Å and c0 = 4.799 Å for y = 0.3 with the increasing Mn c<strong>on</strong>centrati<strong>on</strong>. From the<br />

Mössbauer spectra at 295 K, the electric quadrupole splitting (ΔEQ) and isomer shift<br />

(δ) values of the Fe1-yMnyPO4 were determined to be ΔEQ = 1.50 mm/s, δ = 0.31<br />

mm/s for y = 0.1 and ΔEQ = 1.35 mm/s, δ = 0.31 mm/s for y = 0.3. The decrease in<br />

ΔEQ of Fe 1-yMn yPO 4 samples can be explained by the exchange interacti<strong>on</strong> due to the<br />

asymmetry in FeO 6 octahedral sites depending <strong>on</strong> the Mn c<strong>on</strong>centrati<strong>on</strong>s.<br />

[1] B. C. Melot, G. Rousse, J.-N. Chotard, M. Ati, J. Rodriguez-Carvajal, M. C. Kemei, and J.-M.<br />

Tarasc<strong>on</strong>, Chem. Mater. 23, 2922 (2011). [2] W. Kim, C. H. Rhee, H. J. Kim, S. J. Mo<strong>on</strong>, and C. S.<br />

Kim, Appl. Phys. Lett. 96, 242505 (2010).<br />

PI15<br />

Three- dimensi<strong>on</strong>al electr<strong>on</strong>ic structure of Na0.85CoO2 Y. Sassa 1 *, M. Manss<strong>on</strong> 1 , B. M. Wojek 2 , J. Chang 3 , M. Kobayashi 4 , J. Kanter 1 , V.<br />

Strocov 4 , K. Mattenberger 1 and B. Batlogg 1<br />

1<br />

Laboratory of Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland<br />

2<br />

Materials Physics, Royal Institute of Technology KTH, S-16440 Kista, Sweden<br />

3<br />

Laboratory for synchrotr<strong>on</strong> and neutr<strong>on</strong> spectroscopy, Paul Scherrer Institute, CH-<br />

5234 Villigen PSI, Switzerland<br />

4<br />

Swiss Light Source, Paul Scherrer Institute, CH-5234 Villigen PSI, Switzerland<br />

PI16<br />

WITHDRAWN<br />

Formati<strong>on</strong> of stoichiometric of FeO synthesized under high pressure<br />

Yasushi Kanke 1 , Takuro Yoshikawa 2 , Hideto Yanagihara 2 , Eiji Kita 2 , Yorihiko<br />

Tsunoda 3 , Kiiti Siratori 2 and Kay Kohn 3<br />

1 Nati<strong>on</strong>al Institute of Materials Science, Japan<br />

2 Institute of Applied Physics, University of Tsukuba, Japan<br />

3 School of Science and Engineering, Waseda University, Japan<br />

FeO has the simplest NaCl crystalline structure and <strong>on</strong>e electr<strong>on</strong> exists in the<br />

degenerated dε orbitals due to the regular octahedral ligands. Even such simple<br />

structure, the partial quenching of the orbital angular momentum (S = 2 and L = 1)<br />

bring the electr<strong>on</strong>ic structure complex.[1] Difficulty in the sample preparati<strong>on</strong>, <strong>on</strong>ly the<br />

samples Fe XO with X ≤ 0.96 have been obtained, makes the experimental investigati<strong>on</strong><br />

of FeO hard. We have prepared the stoichiometric FeO with the high pressure synthesis<br />

technique.[2] The starting material of the mixture of α-Fe and Fe 2O 3 powder was<br />

sealed in a Pt capsule and was heated up to 1000 °C and 1200 °C under 5.5GPa for 1<br />

hour. The residual ferromagnetic parts were estimated to be less than 0.69 at%. Higher<br />

reacti<strong>on</strong> temperature may bring lower c<strong>on</strong>centrati<strong>on</strong> of ferromagnetic comp<strong>on</strong>ents.<br />

From Mossbauer study, it is found that the Koch-Cohen cluster does exist especially<br />

when the reacti<strong>on</strong> temperature is high. We present the influence of post annealing with<br />

various c<strong>on</strong>diti<strong>on</strong>s for the improvement of degree of stoichiometry.<br />

[1] J. Kanamori: Prog. Theo. Phys. 17, 177 (1957) [2] T. Katsura, B. Iwasaki, S. Kimura, S.<br />

Akimoto : J. Chem. Phys. 47, 4559 (1967)<br />

PI17<br />

PI18<br />

PI19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Charge and spin ordering in Sr 4Fe 4O 11 system<br />

Qiang Liu 1,2,3 , Gwendolyne Pascua 4 , Alexander Komarek 3 , Zhiwei Hu 3 , Nils Hollmann 3 , Olivier<br />

Toulem<strong>on</strong>de 2 , Hubertus Luetkens 4 , Gwilherm Nenert 5 , Alain Wattiaux 2 , Liu Hao Tjeng 3<br />

1 II. Physikalisches Institut, Universität zu Köln, Germany<br />

2 Institut de Chimie de la Matière C<strong>on</strong>densée de Bordeaux, France<br />

3 Max-Planck-Institut für chemische Physik fester Stoffe, Dresden, Germany<br />

4 Laboratory for Mu<strong>on</strong> Spin Spectroscopy, Paul Scherrer Institute,CH-5232 Villigen PSI, Switzerland.<br />

5 Institut Laue-Langevin, 38042 Grenoble Cedex 9, France<br />

Ordering and disordering of charge, spin, lattice and orbital degrees of freedom play an important<br />

role in the physics of str<strong>on</strong>gly correlated electr<strong>on</strong> systems. In the mixed valence (Fe 3+ /Fe 4+ )<br />

compound Sr 4Fe 4O 11, the spin and charge ordering have recently generated a debate arising<br />

from its two crystallographic (pyramidal and octahedral) sites and the distributi<strong>on</strong> of Fe 3+<br />

and Fe 4+ species [1-5]. Due to symmetry reas<strong>on</strong>s, either the Fe 4+ sublattice is frustrated while<br />

Fe 3+ i<strong>on</strong>s order antiferromagnetically or the opposite. We are trying to explore this puzzle by<br />

X-ray Absorpti<strong>on</strong> Spectroscopy, Photoemissi<strong>on</strong> Spectroscopy, muSR, Neutr<strong>on</strong>, Synchr<strong>on</strong>tr<strong>on</strong><br />

X-ray diffracti<strong>on</strong> and MOssbauer measurement <strong>on</strong> precisely adjusted oxygen stoichiometric<br />

polycrystalline samples and single crystals.<br />

1.J. P. Hodges, S. Short, J. D. Jorgensen, X. Xi<strong>on</strong>g, B. Dabrowski, S. M. Mini, and C. W. Kimball. J. Solid. State. Chem.<br />

151,190-209 (2000) 2 M Schmidt, M Hofmann and S J Campbell. J. Phys.: C<strong>on</strong>dens.Matter 15, 8691-8701 (2003) 3<br />

P Adler, A Leb<strong>on</strong>, V Damljanovic, C Ulrich, C Bernhard, AV Boris, A Maljuk, CT Lin, and B Keimer. Phys. Rev. B 73,<br />

094451(2006) 4 R. Vidya, P. Ravindran, H. Fjellvag, and A. Kjekshus. Phys. Rev. B 74, 054422 (2006) 5 P.Adler Comment<br />

Phys. Rev. B 77, 136401 (2008) and R. Vidya Reply Phys. Rev. B 77, 136402 (2008)<br />

Catalyst structure determinati<strong>on</strong> from magnetic properties<br />

Jorge Hernandez-velasco 1 *, Javier Garcia-garcia 2 and Angel Landa-canovas 1<br />

1 Energy, ICMM CSIC, Spain<br />

2 CME UCM, Spain<br />

SbVO 4 series of compounds could be used as oxidati<strong>on</strong> catalysts of industrial<br />

interest yielding 20% cheaper acryl<strong>on</strong>itrile (producti<strong>on</strong> 8 milli<strong>on</strong> t<strong>on</strong>/year) by the<br />

ammoxidati<strong>on</strong> of propane compared to current method based <strong>on</strong> propylene as<br />

starting reactant. SbVO 4 structure was just known to be related to tetrag<strong>on</strong>al rutile.<br />

Nevertheless we have shown that actually there is a n<strong>on</strong>-stoichiometric flexible series<br />

described as Sb 0.9V 0.9+x□ 0.2-xO 4 (0


Poster M<strong>on</strong>day<br />

PI20<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Theoretical modeling of the magnetic properties and magnetocaloric<br />

effect in La 0.1Ca 0.9MnO 3 manganite by M<strong>on</strong>te Carlo study.<br />

Oksana Pavlukhina*, Vacily Buchelnikov and Vladimir Sokolovskiy<br />

Chelyabinsk State University, Russia<br />

Manganites have a special place am<strong>on</strong>g various materials which have a magnetocaloric<br />

effect. This materials, first, allow varying temperature of phase transiti<strong>on</strong>s in wide regi<strong>on</strong><br />

of temperatures, and sec<strong>on</strong>dly, they are cheap and ecological. Experimental studies have<br />

shown that the manganites are also attractive for the applicati<strong>on</strong> in magnetic refrigerati<strong>on</strong> [1].<br />

In this work, using the Heisenberg’s Hamilt<strong>on</strong>ian, we investigated by M<strong>on</strong>te Carlo method<br />

magnetic and magnetocaloric properties of La 0.1Ca 0.9MnO 3. In the simulati<strong>on</strong>, magnetic<br />

Mn 4+ and trivalent Mn 3+ i<strong>on</strong>s are described by classical Heisenberg spins, while oxygen and<br />

calcium i<strong>on</strong>s are c<strong>on</strong>sidered as n<strong>on</strong>-magnetic. Mn magnetic i<strong>on</strong>s are distributed <strong>on</strong> a lattice<br />

according to the perovskite structure of the manganite. For the modelling lattice samples of<br />

size L3 with L=15 were used. Around 5x105 M<strong>on</strong>te Carlo steps per spin were c<strong>on</strong>sidered<br />

in order to compute equilibrium averages. Curie temperature obtained during the theoretical<br />

simulati<strong>on</strong>s (TC ~150 K) agrees well with theoretical result for this compound (TC ~150<br />

K) [2]. The Curie temperature and magnetocaloric effect obtained during the theoretical<br />

simulati<strong>on</strong>s agree well with experimental data. Support by RFBR grants 10-02-96020-r-ural,<br />

11-02-00601 and Federal Target Program № 14.740.11.1442 (03.11.2011) is acknowledged.<br />

1 Phan, Manh-Hu<strong>on</strong>g. 2007, Review of the magnetocaloric effect in manganite materials, J. Magn. Magn.<br />

Mater. 308: 325-340. 2 Restrepo-Parra E. 2011, Magnetic phase diagram simulati<strong>on</strong> of La1-xCaxMnO3 system<br />

by using M<strong>on</strong>te Carlo, Metropolis algorithm and Heisenberg model, J. Magn. Magn. Mater, 323:1477-1483.<br />

PI21<br />

Pressure effects <strong>on</strong> magnetic ordering transiti<strong>on</strong>s of bilayer manganites<br />

Pr(Sr1-xCax) 2Mn2O7 (x=0,1) by neutr<strong>on</strong> diffracti<strong>on</strong> and mu<strong>on</strong> spin<br />

ras<strong>on</strong>ance<br />

Guochu Deng 1 *, Denis Cheptiakov 2 , Ekaterina Pomjakushina 3 and Kazimierz C<strong>on</strong>der 3<br />

1<br />

Bragg Institute, Australian Nuclear Science and Technology Organizati<strong>on</strong>, Australia<br />

2<br />

Laboratory for Neutr<strong>on</strong> Scattering (LNS), Laboratory for Neutr<strong>on</strong> Scattering, Paul<br />

Scherrer Institut, Switzerland<br />

3<br />

Laboratory for Developments and Methods, Paul Scherrer Institute, Switzerland<br />

.<br />

PI22<br />

Magnetizati<strong>on</strong> reversal and chemical pressure effect in the electr<strong>on</strong><br />

doped manganite Ca(Mn 1-xSb x)O 3<br />

Syuya Ohuchi 1 , Michiaki Matsukawa 1 *, Satoru Kobayashi 1 , Shigeki Nimori 2 and<br />

Ramanathan Suryanarayanan 3<br />

1 Dep. of Materials Science and Engineering, Iwate University, Japan<br />

2 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

3 Universite Paris-Sud, France<br />

WITHDRAWN<br />

In ref.1, we have dem<strong>on</strong>strated the effect of hydrostatic pressure of magnetic and<br />

transport properties, and thermal transport properties in the electr<strong>on</strong> doped manganite<br />

Ca(Mn 1-xSb x)O 3. The substituti<strong>on</strong> of Sb 5+ i<strong>on</strong> for Mn4+ site of the parent matrix causes<br />

<strong>on</strong>e-electr<strong>on</strong> doping since the X-ray photoemissi<strong>on</strong> spectroscopy of Sb substituted<br />

CaMnO 3 sample reveals that the valence of Sb i<strong>on</strong> is 5+. Anomalous magnetizati<strong>on</strong><br />

reversals are observed at x=0.05 and 0.08 in the field cooled magnetizati<strong>on</strong> while the<br />

applicati<strong>on</strong> of external pressure induces a suppressi<strong>on</strong> of the negative magnetizati<strong>on</strong>.<br />

The effect of chemical pressure <strong>on</strong> magnetizati<strong>on</strong> of Ca(Mn,Sb)O 3 are examined<br />

through the substituti<strong>on</strong> of Ca i<strong>on</strong> for Sr with larger i<strong>on</strong> radius and are compared<br />

with the effect of external pressure <strong>on</strong> that of the same compound. We believe that<br />

the magnetizati<strong>on</strong> reversal is not caused by ferrimagnet model but is associated with<br />

the presence of the Jahn-Teller type orbital lattice coupling between 3d eg electr<strong>on</strong><br />

and MnO 6 octahedr<strong>on</strong>, giving stabilizati<strong>on</strong> of negative canted spin state through the<br />

Dzyaloshinsky-Moriya interacti<strong>on</strong>.<br />

Ref.1, Y.Murano et al., Phys.Rev.B83,054437 (2011).<br />

40 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PI23<br />

The effect of cu substituti<strong>on</strong> <strong>on</strong> the structural, electrical and magnetic<br />

properties of LaMn 1-xCu xO 3 manganites<br />

Parviz Kameli*, H. Vaezi, B. Aslibeiki and H. Salamati<br />

Isfahan University of Technology, Iran<br />

The hole-doped manganites, La 1-xA xMnO 3 (A = Sr, Ca, Ba or vacancies) with a<br />

Perovskite structure have attracted c<strong>on</strong>siderable attenti<strong>on</strong> due to the discovery of the<br />

phenomen<strong>on</strong> of colossal magnetoresistance (CMR) and its potential applicati<strong>on</strong> [1-<br />

3]. In this study, the effect of Cu substituti<strong>on</strong> <strong>on</strong> structural, electrical and magnetic<br />

properties of LaMn 1-xCu xO 3+δ (0≤ x ≤ 0.075) manganites are investigated by XRD,<br />

electrical resistivity and Ac susceptibility measurements. The XRD refinement<br />

result indicates that the samples are single phase and the lattice parameters and<br />

volumes increase by the increase of the Cu doping level. The resistivity measurement<br />

results show that by increasing Cu doping level, the resistivity decreases and the<br />

heavily doped samples show metal - insulator transiti<strong>on</strong> at low temperatures. The<br />

paramagnetic- ferromagnetic transiti<strong>on</strong> temperature, Tc increases for low level doped<br />

samples and decreases for heavily doped samples. The analysis of the frequency<br />

dependent Ac susceptibility measurements by critical slowing down model, indicates<br />

that the reentrant spin glass (RSG) state exists in x=0.025, 0.05 and 0.075 samples.<br />

The RSG state is mainly ascribed to the coexistence of ferromagnetic (FM) and<br />

antiferromagnetic (AFM) phases and increase of disorder in the FM matrix induced by<br />

the random Cu impurity.<br />

PI24<br />

Investigati<strong>on</strong> of the structural and magnetic peroperties of<br />

La 0.9Sr 0.1MnO 3 nanoparticles<br />

M. Eshraghi 1 *, M. Roshanmehr 1 , F. Khademi 2 , P. Kameli 2 and H. Salamati 2<br />

1 Department of Physics, Payame Noor University, Iran<br />

2 Department of Physics, Isfahan University of Technology, Iran<br />

In recent years, magnetic nanoparticles have been the subject of intense research not<br />

<strong>on</strong>ly for their fundamental scientific interest such as superparamagnetism, but also<br />

for their potential applicati<strong>on</strong>s in magnetic storage media, biosensor devices and<br />

medical applicati<strong>on</strong>s, such as targeted drug delivery and hyperthermia [1-3]. In a large<br />

number of magnetic nanoparticles applicati<strong>on</strong>s, it is important to know the effects of<br />

interacti<strong>on</strong> between nanoparticles <strong>on</strong> physical properties of these systems. In this paper,<br />

we studied the structural and magnetic properties of La 0.9Sr 0.1MnO 3 nanoparticles.<br />

Magnetic nanoparticles of La 0.9Sr 0.1MnO 3 manganite with mean particle sizes of 20<br />

nm were prepared by the Microwave synthesis method. The crystal structure of the<br />

samples were analyzed, using X-ray diffractometer with Cu-kα ( 0.154 nm) radiati<strong>on</strong>.<br />

The morphology of the samples was characterized by a scanning electr<strong>on</strong> microscope<br />

(FESEM). Magnetic dynamics of the samples was studied by the measurement of ac<br />

magnetic susceptibility versus temperature and frequency. The XRD pattern al<strong>on</strong>g<br />

with Rietveld analysis indicates that the samples are nearly single phase. By fitting<br />

the experimental data with Vogel-Fulcher law, the relaxati<strong>on</strong> time, characteristic<br />

temperature, magnetic anisotropy energy and effective magnetic anisotropy c<strong>on</strong>stant<br />

have been estimated.<br />

PJ01<br />

Magnetotransport properties of anisotropic Co(tCo)/Au(tAu)<br />

multilayers<br />

C<strong>on</strong>rad Rizal 1 , Parshu R. Gyawali 2 and Ramesh K. Pokharel 3<br />

1<br />

Electrical and Computer Engineering, University of British Columbia, Canada<br />

2<br />

Laboratory for Nanospintr<strong>on</strong>ics and Nanoelectr<strong>on</strong>ics, Catholic University of<br />

America, USA<br />

3<br />

Electrical and Communicati<strong>on</strong> Engineering, Kyushu University, Japan<br />

Artificially tailored Co/Au multilayers have been the subject of intense research in search of<br />

novel properties for potential applicati<strong>on</strong>s [1] [2]. Earlier, we reported various comp<strong>on</strong>ents<br />

of giant magnetoresistance (GMR) effects and correlated them with microstructure of the<br />

isotropic multilayers [2]. In this work, we have investigated the effects of incident angle of<br />

depositi<strong>on</strong> and magnetic annealing <strong>on</strong> GMR and magnetic properties of anisotropic Co/Au<br />

multilayers as the layer thicknesses of Co and Au are changed. We have investigated physical<br />

mechanisms resp<strong>on</strong>sible for various MR effects and correlated them with the existing<br />

models. The multilayers deposited at an oblique incident angle of 45 degree exhibited str<strong>on</strong>g<br />

magnetic anisotropy. The maximum MR ratio is found to be 2.1 %. The transverse MR<br />

effect is always found to be larger than the l<strong>on</strong>gitudinal MR effect. These multilayers have<br />

been c<strong>on</strong>sidered potential in developing biomagnetic technology.<br />

[1] E. T. Papaioannou et al. 'Magnetic, magneto-optic and magnetotransport properties of<br />

nanocrystalline Co/Au multilayers with ultrathin Au interlayers,' J. Nanosci. Nanotechnl, vol. 8,<br />

pp. 4323-4327, 2008. [2] C. Rizal, 'Study of magnetic anisotropy and magnetoresistance effects in<br />

ferromagnetic Co/Au multilayer films,' J. Magn. Magn. Mater., vol. 310, pp.e646-e648, 2007.


PJ02<br />

The new type of current and spin polarizati<strong>on</strong> oscillati<strong>on</strong>s<br />

Alexander I Kopeliovich and Pavel V Pyshkin<br />

theoretical physics, B.Verkin Institute for Low Temperature Physics and Engineering<br />

of the Nati<strong>on</strong>al Academy of Sciences, Ukraine<br />

In our work we found new type of spin polarizati<strong>on</strong> and current oscillati<strong>on</strong>s in<br />

c<strong>on</strong>ducting rings with inhomogeneous magnetic properties. In case of hydrodynamic<br />

electr<strong>on</strong> transport (when frequency of electr<strong>on</strong>-electr<strong>on</strong> collisi<strong>on</strong>s is more than<br />

frequency of collisi<strong>on</strong>s that does not c<strong>on</strong>serve momentum of electr<strong>on</strong>s) we obtained<br />

spin hydrodynamics equati<strong>on</strong>s for n<strong>on</strong> equilibrium electr<strong>on</strong> spins when the electr<strong>on</strong><br />

spectrum was spatially inhomogeneous. We showed that in case of close c<strong>on</strong>ductor<br />

these equati<strong>on</strong>s had n<strong>on</strong> zero soluti<strong>on</strong> in form of “spin pendulum” oscillati<strong>on</strong>s,<br />

i.e. oscillati<strong>on</strong>s of full current and spin polarizati<strong>on</strong> with frequency determined by<br />

characteristics of magnetic inhomogeneity. We found own oscillati<strong>on</strong>s of electr<strong>on</strong><br />

system in c<strong>on</strong>ducting ring c<strong>on</strong>sisting of two parts with different magnetic properties.<br />

For example it could be realized by c<strong>on</strong>necting DMS and NMS c<strong>on</strong>ductors into a ring<br />

and placing it in magnetic field. We used equati<strong>on</strong>s similar to well-known two-current<br />

model and we showed that c<strong>on</strong>ductance of this system as a functi<strong>on</strong> of external EMF<br />

frequency had <strong>on</strong>e maximum in hydrodynamic regime and this case was c<strong>on</strong>form to<br />

'spin pendulum', and c<strong>on</strong>ductance had many maximums in a case of ballistic regime.<br />

These maximums vanished when magnetic properties of parts of the ring were<br />

identical.<br />

PJ03<br />

Pressure-enhanced giant magnetoresistance in Fe/Cr magnetic<br />

multilayers<br />

Gendo Oomi*<br />

Kurume Institute of Technology, Japan<br />

Pressure-enhanced Giant Magnetoresistance in Fe/Cr Magnetic Multilayers G<br />

Oomi1),S.Higashihara2),K. Suenaga2),K.Saito3),S.Mitani3) and K.Takanashi4)<br />

1)Kurume Institute of Technology,Kurume,Fukuoka,Japan 2)Department of<br />

Physics,Kyushu University,Fukuoka,Japan,3)Institute of Materials Research,Tohoku<br />

University,Sendai,Japan The giant magnetoresistance(GMR) of Fe/Cr magnetic<br />

multilayers has been measured under high pressure at low temperatures. It is found that<br />

the GMR <strong>on</strong> the sec<strong>on</strong>d peak samples is enhanced str<strong>on</strong>gly by applying pressure:the<br />

magnitude of GMR becomes twice at 2 GPa compared with the value at ambient<br />

pressure.The saturati<strong>on</strong> magnetic fields of these samples decreases with increasing<br />

pressure.However the GMR of the first peak samples decreases with increasing<br />

pressure and the saturati<strong>on</strong>fields increases with pressure. These sharp differences in the<br />

behaviour against pressure will be discussed phenomenologically.<br />

PJ04<br />

Spin current-induced by sound wave<br />

Igor Ivanovich Lyapilin<br />

Institut Metal Physics RAS, Russia<br />

In recent years, increased interest in studying the effects that arise in resp<strong>on</strong>se to spin<br />

degrees of freedom of electr<strong>on</strong>s, when the external perturbati<strong>on</strong> acts <strong>on</strong> the kinetic<br />

degrees of freedom. As rule, the external perturbati<strong>on</strong> (electric field) directly affects<br />

<strong>on</strong>ly the kinetic degrees of freedom of electr<strong>on</strong>s and through spin-orbital interacti<strong>on</strong><br />

is transferred to the spin subsystem. There are other ways of influencing the system<br />

of c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s, which are also reflected in the resp<strong>on</strong>se of the spin degrees<br />

of freedom. So, in the ferromagnetic metals temperature gradient leads to the spin<br />

Seebeck effect. It is interesting to c<strong>on</strong>sider the mechanisms of interacti<strong>on</strong> with<br />

external fields, in which the energy of the external field is transmitted simultaneously<br />

in both electr<strong>on</strong>ic subsystems (kinetic and spin). An example of such interacti<strong>on</strong> is<br />

the interacti<strong>on</strong> of c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s with the field of sound waves. We studied the<br />

evoluti<strong>on</strong> of the electr<strong>on</strong>ic system for their interacti<strong>on</strong> with the field of sound wave<br />

analysis of the c<strong>on</strong>diti<strong>on</strong>s of occurrence and the the resp<strong>on</strong>ce of the spin subsystem<br />

in a c<strong>on</strong>stant magnetic field. It is shown that in this case the l<strong>on</strong>gitudinal sound wave<br />

propagati<strong>on</strong> arises transverse spin current, which has a res<strong>on</strong>ant character.<br />

PJ05<br />

PJ06<br />

PJ07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Enhancement of magnetocaloric width in La 2/3Ca 1/3MnO 3 compounds<br />

with remain the compositi<strong>on</strong> ratio between Mn 3+ and Mn 4+<br />

Qing Ji and Xiaoshan Wu*<br />

Physics, Nanjing University, China<br />

Large magnetic entropy in a relative narrow transiti<strong>on</strong> temperature in manganites has<br />

been reported. To explore the enhancement of transiti<strong>on</strong> temperature width with large<br />

magnetocaloric properties, we here designed the samples with the same compositi<strong>on</strong><br />

ratio of Mn 3+ and Mn 4+ , and the same averaged radius at each lattice sites, which we<br />

previously used to find the roles of the local Jahn-Teller distorti<strong>on</strong> <strong>on</strong> the magnetic<br />

properties in manganites. Here, Y and Sr are used together to replace for La and Ca in<br />

La 2/3Ca 1/3MnO 3 (i.e., ABO3) to remain the average radius and the average valance at<br />

A-site. Results show that the averaged unit cell lattice parameters are unchanged. The<br />

ferromagnetic-to-paramagnetic transiti<strong>on</strong> temperature Tc increases abruptly owing to<br />

the increase of the competiti<strong>on</strong> between σ2 and double-exchange interacti<strong>on</strong> resulting<br />

from Mn-O-Mn b<strong>on</strong>d angle. The disordered distributi<strong>on</strong> of cati<strong>on</strong>s at A-site broaden<br />

the phase transiti<strong>on</strong> temperature range (~T~10K or more) with large magnetic entropy<br />

of ΔSM=1.3 J/Kg K, which may be used as a promising candidate for magnetic<br />

refrigerant near room temperature.<br />

Output voltage calculati<strong>on</strong>s in double barrier magnetic tunnel<br />

juncti<strong>on</strong>s with asymmetric voltage behavior<br />

Artur Useinov, Jurgen Kosel and Aurelien Manch<strong>on</strong><br />

King Abdullah University of Science and Technology, Saudi Arabia<br />

We studied the asymmetric voltage behavior of the tunnel magnetoresistance (TMR)<br />

for single and double barrier magnetic tunnel juncti<strong>on</strong>s (S&DMTJ) in range of a<br />

quasi-classical tunneling model. Numerical calculati<strong>on</strong>s of the TMR-V curves, output<br />

voltages and I-V characteristics for the negative and positive applied voltages were<br />

carried out using MTJs with CoFeB/MgO interfaces. Asymmetry is explained by<br />

different values of the minority and majority Fermi wave vectors for the left and right<br />

sides of the tunnel barrier, which can arises due to different annealing regimes. Electr<strong>on</strong><br />

tunneling in DMTJs was simulated in two ways: (I) Coherent tunneling, where the<br />

DMTJ is modeled as <strong>on</strong>e tunnel system and (II) c<strong>on</strong>secutive tunneling, where the<br />

DMTJ is modeled by two SMTJ c<strong>on</strong>nected in series. We found that DMTJs, in range<br />

of model I, the output voltage peaks will be shifted into the regi<strong>on</strong> of low voltages. For<br />

the model II, we found that, in order to provide symmetric output voltage branches in<br />

DMTJ, the c<strong>on</strong>diti<strong>on</strong>s of equal Fermi vectors ratios have to be fulfilled for the left and<br />

right magnetic layers while ratio in the middle layer can be different.<br />

Spin-current manipulati<strong>on</strong> by domain wall moti<strong>on</strong> in the n<strong>on</strong>-local<br />

spin valve<br />

Ryoko Sugano 1 , Masahiko Ichimura 1 , Saburo Takahashi 2 and Sadamichi Maekawa 3<br />

1 Central Reserach Laboratory, Hitachi, Ltd., Japan<br />

2 Institute for Materials Research, Tohoku University and CREST-JST, Japan<br />

3 Advanced Science Research Center, Japan Atomic Energy Agency and CREST-JST,<br />

Japan<br />

A spatially- and time-dependent magnetic spin texture exerts a spin-dependent force <strong>on</strong> c<strong>on</strong>ducti<strong>on</strong><br />

electr<strong>on</strong>s[1]. In particular, spin-motive force generated by a domain wall moti<strong>on</strong> has been theoretically<br />

investigated and experimentally observed by detecti<strong>on</strong> of electric voltage[2,3]. The spin-dependent field<br />

generated by spin-motive force is also expected to directly affect the n<strong>on</strong>-equilibrium magnetizati<strong>on</strong><br />

such as spin accumulati<strong>on</strong>. In order to study the effect of the spin motive force <strong>on</strong> the spin accumulati<strong>on</strong><br />

in a lateral n<strong>on</strong>-local spin-valve (NLSV) structure, we treat the NLSV device attached with a magnetic<br />

wire. The device c<strong>on</strong>sists of spin injector F1 and detector F2 strips bridged by an n<strong>on</strong>-magnetic strip N<br />

and the magnetic wire is attached <strong>on</strong> N through the insulating layer in-between two magnetic stripes.<br />

A domain wall is introduced into F3 and driven by external magnetic fields. The spin-dependent field<br />

drives the pure spin current flowing in the N-channel. This effect can be detected as increase or decrease<br />

in the n<strong>on</strong>local spin-accumulati<strong>on</strong> signals depending <strong>on</strong> the domain wall moti<strong>on</strong>. We evaluated the<br />

spin-dependent field based <strong>on</strong> the LLG approach and calculate the spatial distributi<strong>on</strong> of spin/charge<br />

current of this NLSV by applying a finite element method in three-dimensi<strong>on</strong>s.<br />

[1] S. Barnes and S. Maekawa, Phys. Rev. Lett. 98, 246601 (2007). [2] S. A. Yang et al., Phys. Rev.<br />

Lett. 102, 067201 (2009). [3] P. N. Hai et al., Nature 458, 489 (2009).<br />

July 8 - 13, 2012 Busan, Korea 41<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PJ08<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The study of microwave assisted magnetizati<strong>on</strong> reversal via spin<br />

pumping<br />

Sankha Subhra Mukherjee, Siddharth Rao, Praveen Deorani, Jae Hyun Kw<strong>on</strong>,<br />

Charanjit Singh Bhatia and Hyunsoo Yang*<br />

ECE, Nati<strong>on</strong>al University of Singapore, Singapore<br />

There has been a significant interest to switch high coercivity magnetic bits for the<br />

future magnetic media by lowering the coercivity during the writing process. MAMR<br />

is a popular method of reducing the coercivity. We present a novel method of studying<br />

MAMR via spin pumping and the inverse spin Hall effect (ISHE). In this method, a<br />

Pt layer was placed in c<strong>on</strong>tact with a ferromagnetic (Py) layer, and an rf signal was<br />

applied to the Py via a coplanar waveguide during loop measurements. Due to the<br />

presence of the rf power, magnetizati<strong>on</strong> dynamics in the Py layer pumps spin in the<br />

adjacent n<strong>on</strong>magnetic Py layer, which creates a measurable dc voltage across the Pt due<br />

to the ISHE. The measured signal is of the order of several microvolts and thus does<br />

not affect the magnetizati<strong>on</strong> by any significant amount. It also effectively decouples<br />

the input rf input from the dc output. The coercivity can be easily detected by the field<br />

at which there is a change in the polarity of the measured voltage. The coercivity as a<br />

functi<strong>on</strong> of the applied rf power is studied.<br />

PJ09<br />

C<strong>on</strong>tributi<strong>on</strong>s of domain walls <strong>on</strong> large magnetoresistance effect in<br />

ultrathin TbFeCo wires<br />

Bang Do and Hiroyuki Awano<br />

Toyota Technological Institute, Japan<br />

Perpendicular anisotropy magnetic materials such as TbFeCo are expected to introduce<br />

large effectivity of spin-transfer torque and high domain wall (DW) moti<strong>on</strong> speed as<br />

well as high magnetoresistance (MR) values. We investigated the size dependence<br />

of MR effect in TbFeCo wires. The 80-μm-length and different widths (1 to 80 μm)<br />

of Tb 26Fe 66.8Co 7.2 wire-patterns were designed by using electr<strong>on</strong> beam lithography<br />

technique. The Tb 26Fe 66.8Co 7.2 films with different thicknesses of 6, 18 nm were grown<br />

by RF sputtering. It is found that MR values are str<strong>on</strong>gly depend <strong>on</strong> injecti<strong>on</strong> current<br />

for all applied fields. Large MR values which up to 100% were observed at a low bias<br />

current and depend <strong>on</strong> DW structure inside the TbFeCo wires. On the other hand, the<br />

MR values rapidly reduced at large bias currents which induce magn<strong>on</strong> and ph<strong>on</strong><strong>on</strong><br />

scattering effects. The introducti<strong>on</strong> of DWs in a magnetic wire causes an increase in<br />

spin-dependent scattering inside the DWs and leads to an enhancement of resistivity<br />

expectedly. The well defined and c<strong>on</strong>trollable number of DWs inside magnetic nanowires<br />

will expectedly introduce a new technique to obtain high and multi-level MR<br />

values as well as high potentials <strong>on</strong> future magnetic devices.<br />

PJ10<br />

First-principles study of c<strong>on</strong>ductivity tensor in transiti<strong>on</strong> metals and<br />

alloys<br />

Yohei Kota* and Akimasa Sakuma<br />

Department of Applied Physics, Tohoku University, Japan<br />

Spin-orbit interacti<strong>on</strong> which is a relativistic correcti<strong>on</strong> to electr<strong>on</strong> moti<strong>on</strong> influences the<br />

transport properties, so the resistance anisotropy and Hall effect appear in c<strong>on</strong>ductivity<br />

tensor. In the present work, we calculate the c<strong>on</strong>ductivity tensor of transiti<strong>on</strong> metals<br />

and alloys in first-principles by the Fermi-surface term of Kubo-Streda formula. To<br />

calculate the c<strong>on</strong>ductivity tensor and electr<strong>on</strong>ic structure with spin-orbit interacti<strong>on</strong>,<br />

we employ the tight-binding linear muffin-tin orbital method based <strong>on</strong> the local<br />

spin-density approximati<strong>on</strong> [1]. The substituti<strong>on</strong> disorder of alloys is treated using<br />

the coherent potential approximati<strong>on</strong>. The obtained anomalous Hall c<strong>on</strong>ductivity,<br />

anisotropic magnetoresistance ratio, and also normal resistivity in ferromagnets<br />

such as Fe-Co and Fe-Ni as a functi<strong>on</strong> of the alloys compositi<strong>on</strong> are quantitatively<br />

c<strong>on</strong>sistent with the available experimental measurements in terms of their magnitude<br />

and sign. In particular we find that the Hall resistivities reveal the n<strong>on</strong>trivial behavior<br />

against the magnetizati<strong>on</strong> which can be varied by the modificati<strong>on</strong> of the compositi<strong>on</strong><br />

ratio. Furthermore, the intrinsic and extrinsic c<strong>on</strong>tributi<strong>on</strong> of the Hall c<strong>on</strong>ductivity is<br />

comparable in these alloys systems. Also we show the calculati<strong>on</strong> results about the spin<br />

Hall c<strong>on</strong>ductivity of n<strong>on</strong>magnetic compounds obtained in similar frameworks.<br />

[1] I. Turek, et.at., Philos. Magaz. 88, 2782 (2008); I. Turek, et.al. Phys. Rev. B 65, 125101 (2002).<br />

42 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PJ11<br />

Magnetoresistance of CoFe/Pt nano-c<strong>on</strong>tacts<br />

Muftah Al-mahdawi* and Masashi Sahashi<br />

Department of Electr<strong>on</strong>ic Engineering, Tohoku University, Japan<br />

Using an alumina-based Nano-Oxide Layer (AlO x- NOL) between with many nanoholes<br />

between two ferromagnets [1] has gained more interest in recent years both in<br />

their fundamental physics of spin-scattering off the c<strong>on</strong>fined domain-walls and in<br />

their applicability for next-generati<strong>on</strong> hard-disk-drive reading heads. Also, spin-torque<br />

driven oscillati<strong>on</strong>s of the c<strong>on</strong>fined domain-walls has been reported [2]. Following<br />

the report by [3] that Pt is magnetized at the interface with Co, we examined the<br />

inserti<strong>on</strong> of AlO x- NOL between the Co-rich Co 90Fe 10 and Pt. Film stack was (in nm):<br />

Underlayer/Co 90Fe 10 3/AlO x- NOL/Pt 2/cap. It was deposited using i<strong>on</strong>-beam sputtering<br />

and dc magnetr<strong>on</strong> sputtering depositi<strong>on</strong>. AlO x- NOL was prepared using I<strong>on</strong>-Assisted<br />

Oxidati<strong>on</strong> (IAO) process[1]. IAO process forms direct nano-c<strong>on</strong>tacts (NC) in NOL<br />

between the CoFe and Pt (1~2 nm in diameter, with


PJ14<br />

Domain wall c<strong>on</strong>figurati<strong>on</strong> and magneto-transport properties in dual<br />

spin-valve with nanoc<strong>on</strong>stricti<strong>on</strong><br />

By<strong>on</strong>g Sun Chun 1 , Chan Y<strong>on</strong>g Hwang 1 , Han Chun Wu 2 , Mohamed Abid 3 , Su Jung<br />

Noh 4 and Young Keun Kim 4<br />

1<br />

Korea Research Institute of Standards and Science, Korea<br />

2<br />

Trinity College Dublin, Ireland<br />

3<br />

Ecole Polytechnique Federale de Lausanne/IPMC, Switzerland<br />

4 Korea University, Korea<br />

In this work, we use a synthetic antiferromagnet-based dual spin-valve (SAF-DSV) structure<br />

(i.e. the SV structure is doubled symmetrically with respect to the FM) and present the effect<br />

of the directi<strong>on</strong> of the applied magnetic field with respect to nanoc<strong>on</strong>stricti<strong>on</strong> shapes <strong>on</strong> the<br />

magneto-transport properties including domain wall (DW) c<strong>on</strong>figurati<strong>on</strong> and reversal process.<br />

We can tune the DW c<strong>on</strong>figurati<strong>on</strong> and its reversal process from a vortex to a transverse type<br />

by changing the directi<strong>on</strong> of applied magnetic field respect to the nanoc<strong>on</strong>stricted SAF-DSV.<br />

When the field is applied in the perpendicular directi<strong>on</strong> to the nanoc<strong>on</strong>stricted SAF-DSV, the<br />

perpendicular magnetic moments are developed due to the transverse magnetizati<strong>on</strong> reversal<br />

mode and result in a multistep switching process. This multi step switching process reflects the<br />

pinning and depinning of a DW at the nanoc<strong>on</strong>stricti<strong>on</strong>. Our results also show an asymmetric<br />

depinning field. We dem<strong>on</strong>strate, if nanoc<strong>on</strong>stricti<strong>on</strong> is asymmetric al<strong>on</strong>g its length, i.e.<br />

expansi<strong>on</strong>s from both sides of the neck into the two nanowires are not identical, and then an<br />

asymmetric energy barrier to domain wall propagati<strong>on</strong> is formed. This is due to the difference<br />

in DW width, which leads to an asymmetry in the domain wall depinning forces.<br />

PJ15<br />

Giant magnetocaloric effect of Mn 0.91Ca 0.09As thin film <strong>on</strong> Al 2O 3 (0001)<br />

Du<strong>on</strong>g Anh Tuan 1 , Cho Sunglae 1 *, Dang Duc Dung 2 , Shin Yooleemi 1 and Je<strong>on</strong> Seung<br />

Mok 1<br />

1 Physics, University of Ulsan, Korea<br />

2 Physics, Depart of General Physics, School of Engineering Physics Hanoi<br />

University of Science and Technology., Viet Nam<br />

The MnAs compound is promising to magnetocaloric effect (MCE) applicati<strong>on</strong> [1]. It presents the<br />

first order phase transiti<strong>on</strong> from a ferromagnetic to paramagnetic ~ 318 K, which is accompanied by a<br />

structural transiti<strong>on</strong> from a hexag<strong>on</strong>al NiAs-type (α-MnAs) to orthorhombic MnP-type structure (β-MnAs)<br />

[2]. Recently, the room temperature giant magnetocaloric effect was obtained by substituti<strong>on</strong> of Mn by<br />

Fe, Co, Cu or Cr in MnAs: Co-25 J/kgK at 4T, Cu-175 J/kgK at 5T, Cr and Fe-42 J/kgK at 5T [3-5].<br />

However, there is less informati<strong>on</strong> about group II dopants such as Ca, Ba, and Sr in MnAs. In this work,<br />

we report the magnetism and transport properties of epitaxial Ca 0.09Mn 0.91As thin film <strong>on</strong> Al 2O 3(001)<br />

substrate. The RHEED and XRD results indicated that film were epitaxially grown <strong>on</strong> Al 2O 3(0001). The<br />

temperature dependent resistivity showed metallic and the temperature dependent magnetoresistance<br />

at 7 kOe showed a peak around 325K. The negative anomalous Hall effect was observed in Hall<br />

measurement. The magnetic measurement indicates that the sample is ferromagnetic with TC was around<br />

340K and display the giant magnetocaloric signal. The magnetizati<strong>on</strong> hysteresis loops exhibited the<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> (MS) was around 300 (emu/cm3) at 10K and 180 (emu/cm3) at 300 K.<br />

[1] L. Daweritz, Pep. Prog. Phys. 69, 2581 (2006). [2] J. Mira et al, Phys. Rev. Lett. 90, 097203<br />

(2003). [3] Wang et al, Appl. Phys. Lett. 97, 042502 (2010) [4] D. L. Rocco et al, Appl. Phys. Lett.<br />

90, 242507 (2007). [5]C. S. Mejia et al, Appl. Phys. Lett. 98, 102515 (2011).<br />

PJ16<br />

Anomalous Hall effect of [Amorphous CoSiB/Pt] multilayer films<br />

Hana Lee, Insung Park, Hyungjun Kim, Sungy<strong>on</strong>g Kim, Youngkwang Kim, Hway<strong>on</strong>g<br />

Noh and Taewan Kim*<br />

Sej<strong>on</strong>g university, Korea<br />

We have quantitatively investigated the Anomalous Hall effect (AHE) in [CoSiB/Pt]<br />

multilayer films. The [CoSiB/Pt] multilayers exhibited large Hall effect. In this study,<br />

we compared with the effects of the before and after of patterning. The [amorphous<br />

CoSiB 6A/Pt 14 A]n multilayers were deposited <strong>on</strong> SiOx substrate with a 30 A Pt<br />

and 50 A Ta buffer layer at the room temperature using a DC magnetr<strong>on</strong> sputtering<br />

system. Thereafter the sample was patterned into a hall bar with the line width of 10<br />

μm. Hall effect measurements at room temperature were made up to 3 kOe with the<br />

applied magnetic field perpendicular to the film plane. The samples for the Hall effect<br />

measurement were prepared with a square geometry for the easy applicati<strong>on</strong> of the Van<br />

der Pauw method to measure the Hall voltage of the samples. The applied current was<br />

50μA ~ 1 mA and the measured Hall voltage was in the range of several mV.<br />

PJ17<br />

PJ18<br />

PJ19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Spin transport phenomena through MgO/CuPc hybrid barrier in<br />

magnetic tunnel juncti<strong>on</strong>s<br />

Yu Je<strong>on</strong>g Bae 1 , Nyun J<strong>on</strong>g Lee 1 , Tae Hee Kim 1 *, Hyunduck Cho 2 , Changhee Lee 2 ,<br />

Luke Fleet 3 , Atsufumi Hirohata 3 , Ye<strong>on</strong>g-ah Soh 4 and Gabriel Aeppli 4<br />

1<br />

Physics, EWHA Womans University, Korea<br />

2<br />

School of Electrical Engineering and Computer Science, Seoul Nati<strong>on</strong>al University,<br />

Korea<br />

3<br />

Electr<strong>on</strong>ics, The University of York, United Kingdom<br />

4<br />

L<strong>on</strong>d<strong>on</strong> Centre for Nanotechnology, United Kingdom<br />

For realistic applicati<strong>on</strong>s of organic spintr<strong>on</strong>ic devices, the investigati<strong>on</strong> of the growth<br />

mechanism and electrical properties is of great importance to understand the spin transport<br />

phenomena in metal-organic hybrid systems. As the first step, we focused <strong>on</strong> surface<br />

morphology, growth mode, and thermal stability of thin Cu-phthalocyanine (CuPc) organic<br />

layers grown <strong>on</strong> metal surfaces covered with a few m<strong>on</strong>olayer thick insulating films, such<br />

as MgO(001). Recent reports of achieving spin polarized tunneling across organic-inorganic<br />

hybrid barrier with significant magnetoresistance (MR) values at low temperature (< 10<br />

K) led us to study the organics semic<strong>on</strong>ductor (OSC) thin films for substituting highly<br />

performing inorganic barriers. Therefore, we investigated systematically the spin transport<br />

phenomena through the OSC CuPc barrier with and without MgO(001) layer as a functi<strong>on</strong> of<br />

CuPc thickness. An epitaxial Fe(001)/MgO(001) layer was utilized as a spin injecti<strong>on</strong> layer,<br />

while a polycrystalline Co film as a spin detector. Here, we observed, for the MgO/CuPc<br />

hybrid barrier with a total thickness of ~ 3 nm, the high MR (> 200 %) values at 77 K and ~<br />

10 % MR at 300 K in the Si(001)/MgO/Fe/MgO(001)/CuPc/Co hybrid tunnel juncti<strong>on</strong>s.<br />

Theoretical approach to spin-current absorpti<strong>on</strong> at an interface<br />

Kazuhiro Tsutsui 1 , Kazuhiro Hos<strong>on</strong>o 2 and Takehito Yokoyama 1 *<br />

1 Dept. of Physics, Tokyo Institute of Technology, Japan<br />

2 Dept. of Physics, Tokyo Metropolitan University, Japan<br />

In the development of spintr<strong>on</strong>ic devices, techniques to detect spin currents efficiently<br />

are indispensable as well as the generati<strong>on</strong> of spin currents. In general, the spin-current<br />

detecti<strong>on</strong> is dem<strong>on</strong>strated via the inverse spin Hall effect and the absorpti<strong>on</strong> of the<br />

spin current [1]. In this presentati<strong>on</strong>, we theoretically examine the spin current induced<br />

by an inhomogeneous spin-orbit coupling due to impurities [2]. Using the Keldysh<br />

Green’s functi<strong>on</strong> formalism, we propose analytical expressi<strong>on</strong>s of the diffusive spin<br />

currents under an external electric field and find a spin-current generati<strong>on</strong> in the<br />

presence of both gradient of the spin-orbit strength and that of the external field.<br />

The resulting diffusive spin current indicates the absorpti<strong>on</strong> of the spin current at the<br />

interface between materials with different spin-orbit strengths, which is exemplified<br />

with an experimentally relevant setup.<br />

[1] T. Kimura, Y. Otani, T. Sato, S. Takahashi, and S. Maekawa, Phys. Rev. Lett. 98, 156601 (2007).<br />

[2] K. Hos<strong>on</strong>o, A. Yamaguchi, Y. Nozaki, and G. Tatara, Phys. Rev. B 83, 144428 (2011).<br />

Magneto-transport properties of Al 2O 3-doped Mn-Zn ferrites<br />

Hyo-jin Kim and Sang-im Yoo*<br />

Department of Materials Science and Engineering, Seoul Nati<strong>on</strong>al University, Korea<br />

We report the magneto-transport properties of Al 2O 3-doped Mn-Zn ferrites prepared<br />

by the c<strong>on</strong>venti<strong>on</strong>al solid state reacti<strong>on</strong>. Various amounts of Al 2O 3 were doped to<br />

a pure Mn-Zn ferrite to have the nominal compositi<strong>on</strong> of (Mn 0.8, Zn 0.2) 1-xAl xFe 2O 4<br />

(x = 0.03~0.1). Field dependency of magnetizati<strong>on</strong> was measured with a SQUID<br />

(superc<strong>on</strong>ducting quantum interference device) magnetometer, and low field<br />

magnetoresistance (LFMR) was also measured with the SQUID magnetometer using<br />

an external current source and voltmeter. The X-ray diffracti<strong>on</strong> analyses revealed that<br />

all Al 2O 3-doped Mn-Zn ferrites of the spinel structure were a pure phase without the<br />

sec<strong>on</strong>d phase. From the transport measurements of our samples in the temperature<br />

regi<strong>on</strong> of 100~300 K, it was found that with the additi<strong>on</strong> of the Al 2O 3 dopant the<br />

resistivity level of the pure Mn-Zn ferrite was abruptly dropped over four orders of<br />

magnitude and further the LFMR ratio was greatly improved. High LFMR ratio over<br />

1.7% at 300 K in 0.5 kOe was achievable from 3mol% Al 2O 3-doped Mn-Zn ferrite<br />

without an appreciable increase in its resistivity. Detailed effects of the Al 2O 3 dopant<br />

<strong>on</strong> the microstructures, magnetic and magnetotransport properties of the Mn-Zn ferrite<br />

will be presented for a discussi<strong>on</strong>.<br />

July 8 - 13, 2012 Busan, Korea 43<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PJ20<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Current induced fluctuati<strong>on</strong> of switching fields in Co/Pd nanowires<br />

Mahdi Jamali, Xuepeng Qiu, Kulothungasagaran Narayanapillai and Hyunsoo Yang*<br />

Electrical and Computer Engineering, Nati<strong>on</strong>al University of Singapore, Singapore<br />

Current induced effective magnetic fields in a thin metallic film of a ferromagnetic material<br />

sandwiched by two n<strong>on</strong>magnetic materials have been studied intensively due to its potential<br />

applicati<strong>on</strong>s for the magnetic random access memory [1, 2]. There is a c<strong>on</strong>troversy about<br />

the origin of the effective field such as the Rashba effect [3] or spin torque induced by the<br />

spin Hall effect [4]. We have recently observed current induced effective fields in nanowires<br />

made of Co/Pd multilayer [5]. The further investigati<strong>on</strong> of the switching fields of nanowires<br />

reveals fluctuati<strong>on</strong> in the switching fields up<strong>on</strong> an injecti<strong>on</strong> of different current densities. We<br />

have applied current pulses with a width of 2 ms and repetiti<strong>on</strong> of less than 1 Hz to minimize<br />

the Joule heating effect. At low current densities (J < 10¹¹ A/m²) there is a fluctuati<strong>on</strong> in the<br />

switching field of the nanowire. For a certain value of the input current, the switching field<br />

of the Co/Pd nanowire increases(>6%). Furthermore, the switching fields in the positive and<br />

negative fields are not the same. The relative angle between the sample and magnetic field<br />

has changed and the effect of the angle <strong>on</strong> this fluctuati<strong>on</strong> has been studied.<br />

[1] I. M. Mir<strong>on</strong>, K. Garello, G. Gaudin, P. J. Zermatten, M. V. Costache, S. Auffret, S. Bandiera,<br />

B. Rodmacq, A. Schuhl, and P. Gambardella, Nature 476, 189 (2011). [2] T. Suzuki, S. Fukami, N.<br />

Ishiwata, M. Yamanouchi, S. Ikeda, N. Kasai, and H. Ohno, Appl. Phys. Lett. 98, 142505 (2011). [3]<br />

I. M. Mir<strong>on</strong>, G. Gaudin, S. Auffret, B. Rodmacq, A. Schuhl, S. Pizzini, J. Vogel, and P. Gambardella,<br />

Nat. Mater. 9, 230 (2010). [4] http://arxiv.org/abs/1110.6846. [5] K. Narayanapillai, M. Jamali, and<br />

H. Yang, MMM c<strong>on</strong>ference, Ariz<strong>on</strong>a (2011).<br />

PJ21<br />

Role of structural inversi<strong>on</strong> asymmetry <strong>on</strong> current-induced effective<br />

field in perpendicular magnetized trilayers<br />

Xuepeng Qiu, Kulothungasagaran Narayanapillai and Hyunsoo Yang*<br />

Electrical and Computer Engineering, Nati<strong>on</strong>al University of Singapore, Singapore<br />

The fact that a current pulse can switch the magnetic moment of a perpendicular<br />

magnetized nanodot has attracted much attenti<strong>on</strong> for the next new generati<strong>on</strong> spintr<strong>on</strong>ic<br />

devices [1]. However, the physical origin of this effect is still under debate. Here we<br />

report the pulse delta measurements in perpendicular magnetized substrate/2 MgO 2 Pt 0.8<br />

CoFeB 2 MgO (sample A) and substrate/2 MgO 0.8 CoFeB 2 Pt (in nm) micro-sized hall<br />

bar samples with opposite structural inversi<strong>on</strong> asymmetry (SIA). For both structures,<br />

when the magnetic field applied al<strong>on</strong>g the current directi<strong>on</strong> tilted off-plane by 2°,<br />

positive (negative) current induces a downward (upward) effective field with positive<br />

magnetic fields and the effective field directi<strong>on</strong> switches with negative magnetic fields.<br />

The effective field is around 2,388 Oe per 10¹² A/m² in the sample A. For the other<br />

structure, the effective field shows a n<strong>on</strong>linear correlati<strong>on</strong> with the intensity of current.<br />

With small in-plane external fields, the magnetizati<strong>on</strong> can be switched by pulse current<br />

and the switching hysteresis was the same in the two structures. Our results suggest that<br />

the main c<strong>on</strong>tributi<strong>on</strong> of the current induced effective field arises from the spin Hall<br />

effect rather than the Rashba or other SIA related effects.<br />

[1]. Ioan Mihai Mir<strong>on</strong>, Kevin Garello, Gilles Gaudin, Pierre-Jean Zermatten, Marius V. Costache,<br />

Stephane Auffret, Sebastien Bandiera, Bernard Rodmacq, Alain Schuhl and Pietro Gambardella,<br />

Nature. 476, 189 (2011)<br />

PJ22<br />

Characterizati<strong>on</strong> of mechanically milled Cu-Co powder by 3D-FIB and<br />

atom probe tomography : effect of oxidati<strong>on</strong> <strong>on</strong> the magnetoresistance<br />

Julien Bran, Rodrigue Larde, Malick Jean and Jean-marie Le Bret<strong>on</strong>*<br />

Groupe de Physique des Materiaux - UMR 6634, CNRS - Universite de Rouen,<br />

France<br />

The Giant MagnetoResistance (GMR) effect discovered in 1988 [1] had inspired many researches <strong>on</strong><br />

magnetoresistive materials. The resistance of the device is reduced with the applicati<strong>on</strong> of a magnetic<br />

field and it is due to the spin dependent scattering effect. However, an inverse effect has been observed<br />

after an oxide phase introducti<strong>on</strong> by Khan et al. [2]. This effect appears at low magnetic field and could<br />

be interesting for improving the sensitivity of magnetoresitive devices. In our study, a Cu 80Co 20 powder<br />

was elaborated by mechanical alloying under ambient atmosphere to investigate the oxide formati<strong>on</strong> and<br />

its influence <strong>on</strong> magnetoresistive properties. 3D-Focused I<strong>on</strong> Beam tomography (3D-FIB) and Atom<br />

Probe Tomography (ATP) [3] were used to characterize our samples. It was shown with 3D-FIB that<br />

after 1h30 of milling, the powder exhibits a lamellar structure with micro-sized Co rich regi<strong>on</strong>s. The APT<br />

experiments have revealed that after 20h of milling 1/3 of Co atoms is oxidized leading to the formati<strong>on</strong><br />

of nano-sized CoO clusters embedded in a Cu 85Co 15 matrix. These results bring crucial informati<strong>on</strong>s<br />

to correlate the structural properties with magnetoresistive properties of the Cu-Co-O powder and to<br />

understand the influence of the nano-sized oxide clusters <strong>on</strong> the inverse magnetoresistance.<br />

[1] M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Etienne, G. Creuzet, A. Friederich, and J.<br />

Chazelas, Phys. Rev. Lett., 61(21) (1988) 2472-2475. [2] H. R. Khan, A. Granovsky, M. Prudnikova, V. Prudnikov, F.<br />

Brouers, A. Vedyayev, A. Radkovskaya, J. Magn. Magn. Mater. 183 (1998) 379-386. [3] D. Blavette, B. Dec<strong>on</strong>ihout,<br />

A. Bostel, J. M. Sarrau, M. Bouet, and A. Menand, Review of Scientific Instruments, 64(10) (1993) 2911-2919.<br />

44 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PJ23<br />

Effect of pressure <strong>on</strong> magnetotransport properties in Fe/MgO granular<br />

films<br />

A. Garcia - Garcia 1 , J. A. Pardo 2 , P. A. Algarabel1*, Z. Arnold 3 , J. Kamarad 3 and M. R. Ibarra 2<br />

1 ICMA, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain<br />

2 INA, Universidad de Zaragoza, 50018 Zaragoza, Spain<br />

3 Institute of Physics AS CR, 162 53 Praha 6, Czech Republic<br />

A special example of granular thin films is the disc<strong>on</strong>tinuous metallic and insulator multilayers (DMIMs)<br />

c<strong>on</strong>sisting of metallic layers with different degrees of disc<strong>on</strong>tinuity intercalated between insulating layers.<br />

However, the studies about the effect <strong>on</strong> the magneto-transport properties of the hydrostatic pressure are<br />

scarce[1]. In this work we report the effect of hydrostatic pressure <strong>on</strong> the resistance and magnetoresistance<br />

of a DMIM of nominal compositi<strong>on</strong> [Fe(t=0.7nm)/MgO(t=3 nm)]15 ,deposited <strong>on</strong> a substrate of corning<br />

glass. The DMIM has been characterized previously showing a superparamagnetic behaviour [2]. The<br />

resistivity has been measured at room temperatures with hydrostatic pressure (Ph) up to 7 Kbar. The<br />

resistivity decreases linearly with pressure, indicating an increase in c<strong>on</strong>ducti<strong>on</strong> via tunneling. The value of<br />

the coefficient, (1/ρ0)dρ/dPh =-3.9 10-2 kbar-1 is higher than the value obtained in other granular films. This<br />

result implies that the electr<strong>on</strong>ic state of the DMIM is near the percolati<strong>on</strong> threshold. Magnetoresistance (MR)<br />

isotherms have been measured at room temperatures for Ph=1bar and Ph=7Kbar. At the maximum applied<br />

magnetic field (3KOe) the MR increases from 0.6% at ambient pressure to 1.1% at 7 Kbar. This result will<br />

be explained due to the reducti<strong>on</strong> of the tunnel barrier induced by the hydrostatic pressure.<br />

[1] G. Oomi, Miyawaga H., Sakai T., Saito K., Takanashi K., and Fujimori Hl. Physica B 284 1245<br />

(2000) [2] A. Garcia-Garcia, A. Vovk, J. A. Pardo, P. Strichovanec, C. Magen, E. Snoeck, P. A.<br />

Algarabel, J. M. De Teresa, L. Morell<strong>on</strong>, and M. R. Ibarra J. Appl. Phys. 105, 063909 (2009)<br />

PJ24<br />

Measurement of anomalous nernst effect in [CoSiB/Pt] multilayer<br />

films<br />

Ozgur Kelekci 1 , Ha Na Lee 2 , K. J. Min 2 , H. M. Waseem Khalil 1 , Tae Wan Kim 2 and<br />

Hway<strong>on</strong>g Noh 1 *<br />

1 Physics Department and Graphene Research Institute, Sej<strong>on</strong>g University, Korea<br />

2 Department of Advanced Materials Engineering, Sej<strong>on</strong>g University, Korea<br />

Recently, a new research field taking advantage of both spintr<strong>on</strong>ics and thermoelectr<strong>on</strong>ics, called spin<br />

caloritr<strong>on</strong>ics, has started to attract a great deal of attenti<strong>on</strong> [1]. In c<strong>on</strong>trast to the Anomalous Hall Effect<br />

driven by electrical currents, Anomalous Nernst Effect includes combinati<strong>on</strong> of thermal and spin<br />

transport driven by a temperature gradient in ferromagnets. We have investigated Anomalous Nernst<br />

Effect in [CoSiB/Pt] multilayer films with perpendicular magnetic anisotropy. The layer structure<br />

of samples was SiO 2Ta 50APt 30A(CoSiB 6APt 14A)n. Standard Hall bars were patterned <strong>on</strong> the samples.<br />

Additi<strong>on</strong>ally, heating element was also patterned <strong>on</strong> the samples in order to apply temperature gradient.<br />

Nernst effect measurements were made up to 1.5 kGauss with the applied magnetic field perpendicular<br />

to the film plane. We obtained significant Nernst voltages (VN) by applying temperature gradient ∇T<br />

to the samples. Nernst voltage exhibited similar characteristic as AHE voltage due to the sp<strong>on</strong>taneous<br />

magnetizati<strong>on</strong>. Samples with different number of [CoSiB/Pt] multilayers were measured and compared.<br />

VN increased with increasing number of layers. Dependence of VN <strong>on</strong> the heating power (P) and the<br />

distance from the heating element (d) have been investigated. We have extracted [VN] α [P] and [VN] α<br />

[1/d] dependencies from the measured samples.<br />

[1] G. E. W. Bauer, A. H. MacD<strong>on</strong>ald, S. Maekawa, Solid State Commun., 150, 459, (2010).<br />

PJ25<br />

GMR effect in Co-Cu microwires<br />

Valentina Zhukova 1 *, Rastislav Varga 2 , Carlos Garcia 3 , Juanjo Del Val 1 , Mihail Ipatov 1<br />

and Arcady Zhukov 4<br />

1<br />

Dpto. de Fisica de Materiales, UPV/EHU, Spain<br />

2<br />

Inst. Phys., Fac.Sci., UPJS, Slovak<br />

3<br />

Dept Phys, Bogazici Univ, Turkey<br />

4<br />

Dpto. de Fisica de Materiales, UPV/EHU San Sebastian and IKERBASQUE,<br />

Basque Foundati<strong>on</strong> for Science, Bilbao, Spain<br />

Granular materials exhibiting giant magnetoresistance (GMR) effect attracted c<strong>on</strong>siderable<br />

attenti<strong>on</strong>. For obtaining of the granular structures, melt spinning technique allowing rapid<br />

quenching from the melt is quite suitable. During last years c<strong>on</strong>siderable attenti<strong>on</strong> has been paid<br />

to the studies of glass-coated microwires produced by Taylor- Ulitovski technique allowing to<br />

achieve high quenching rate and producing amorphous, nanocrystalline, microcrystalline or<br />

even granular thin microwires. In this paper, we studied magnetic properties and GMR effect<br />

of Co x- Cu 100-x (10≤x≤30 at%) microwires and observed c<strong>on</strong>siderable magnetoresistance (MR),<br />

ΔR/R. For Co 10Cu90 microwires, ΔR/R increases when the temperature decreases, exhibiting<br />

negative MR, tending to saturate in high magnetic fields, H. On the other hand, for Co 30Cu 70<br />

samples ΔR/R(H) dependences showed n<strong>on</strong>-m<strong>on</strong>ot<strong>on</strong>ic behavior, exhibiting ΔR/R increase<br />

with H at low H-values (up to 5 kOe) and also c<strong>on</strong>siderable GMR effect. X-ray diffracti<strong>on</strong><br />

(XRD) results reveal that the structure of the metallic core is granular with two phases: the main<br />

<strong>on</strong>e, fcc Cu (lattice parameter 3.61 Å) and fcc α-Co (lattice parameter 3.54 Å) which is present<br />

in microwires with higher Co c<strong>on</strong>tent. In the case of low Co c<strong>on</strong>tent, XRD indicates that Co<br />

atoms are distributed within the Cu crystals.


PJ26<br />

Domain wall quantum interferometer<br />

John Eves, N. Grisewood and H. B. Braun<br />

School of Physics, UCD, Ireland<br />

PJ27<br />

Synthesis and magnetic properties of trilayer NiFe/Bi/NiFe films<br />

K<strong>on</strong>stantin Patrin 1 , Viktor Yakovchuk 1 , Gennady Patrin 2 and Stanislav Yarikov 2<br />

1 Institute of Physics of Siberian Branch of Russian Academy of Sciences, Russia<br />

2 Siberian Federal University, Russia<br />

PJ28<br />

A study <strong>on</strong> the pulesd laser deposited metallic spin valve structures<br />

Sayak Ghoshal 1 * and P. S. Anil Kumar 2<br />

1 Physics, Indian Institute of Science, India<br />

2 Indian Institute of Science, India<br />

MOVED<br />

Earlier, it was found [1] that the bismuth spacer formati<strong>on</strong> influences essentially the system<br />

magnetizati<strong>on</strong>. The shape of m(H) curve is changed with bismuth spacer thickness increasing.<br />

In particular, the test film with tBi = 0 has the narrow hysteresis loop and magnetizati<strong>on</strong> curve<br />

of a ferromagnetic type. For the films with tBi ≠ 0 the magnetizati<strong>on</strong> curves are typical for films<br />

possessing either by intra-layer anisotropy or by antiferromagnetic interlayer coupling.<br />

Since anisotropy is not experimentally observed, we attribute such a behavior to the presence of<br />

interlayer antiferromagnetic exchange. The investigati<strong>on</strong>s of electr<strong>on</strong> magnetic res<strong>on</strong>ance were<br />

made in NiFe/Bi/NiFe films. It was established that the magnetic res<strong>on</strong>ance spectrum c<strong>on</strong>sists<br />

of solitary line for films with tBi = 0 nm and tBi = 15 nm, whereas for films with intermediate<br />

value of semi metal spacer the spectrum is superpositi<strong>on</strong> of two lines. Theoretical treatment<br />

of temperature dependences of res<strong>on</strong>ance fields gives c<strong>on</strong>clusi<strong>on</strong> that the interlayer coupling<br />

depends <strong>on</strong> both bismuth interlayer thickness and temperature. Also, the magnetoresistivity of<br />

order of percent units and dependence of its value <strong>on</strong> thickness of bismuth spacer were found in<br />

these films at helium temperatures [2].<br />

[1] G.S. Patrin, V.Yu. Yakovchuk, D.A. Velikanov. Phys. Lett. A, 363, 164 (2007) [2] G. S. Patrin, V.<br />

Yu. Yakovchuk, D.A. Velikanov, K.G. Patrin,and S.A. Yarikov. Bull. Russ. Acad. Sci. Phys., 76, 177<br />

(2012)<br />

It is envisaged that the c<strong>on</strong>venti<strong>on</strong>al Spin Valve (SV) structures will be more<br />

advantageous over Tunneling Magneto-resistance (TMR) for the perpendicular<br />

magnetic recording due to the suitable RA product. Here Pulsed Laser Deposited (PLD)<br />

Spin Valve (SV) and Pseudo Spin Valve (PSV) samples are grown at room temperature<br />

with moderately high MR values using simple NiFe/Au/Co/FeMn structure. Although<br />

PLD is not a popular technique to grow metallic SVs because of its expected large<br />

intermixing of the interfaces, particulate formati<strong>on</strong> etc., still by suitably adjusting the<br />

depositi<strong>on</strong> parameters we could get exchange bias as well as more than 3% MR in<br />

the Current In Plane (CIP) geometry. Different SV and PSV samples are grown to<br />

study anisotropy effects, exchange coupling and exchange bias with anti-ferromagnet.<br />

Angular variati<strong>on</strong> of the MR is also obtained which shows that the hard layer (Co) has<br />

a four-fold anisotropy in the NiFe/Co/Au/Co structures which becomes two-fold in<br />

presence of anti-ferromagnet. In this presentati<strong>on</strong>, properties of these PLD grown SVs<br />

will be discussed in terms of the angular variati<strong>on</strong> of MR, intermixing at the interfaces<br />

as well as details of exchange bias.<br />

(1) S. Yuasa et. al. J. Phys. D: Appl. Phys. 40 R337 (2007) (2) Y. Sakuraba et. al. Appl. Phys. Lett.<br />

94, 012511 (2009)<br />

PJ29<br />

PJ30<br />

PJ31<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Spin torque in a finite two-dimensi<strong>on</strong>al ferromagnet with Rashba<br />

interacti<strong>on</strong><br />

Christian Ortiz, Xuhui Wang and Aurelien Manch<strong>on</strong>*<br />

Physical Science and Engineering Divisi<strong>on</strong>, King Abdullah University of Science and<br />

Technology, Saudi Arabia<br />

The interacti<strong>on</strong> between a ferromagnetic exchange coupling and a Rashba spin-orbit<br />

interacti<strong>on</strong> has shown its potential in magnetizati<strong>on</strong> switching [1, 2]. For such a system,<br />

a coherent theoretical framework has been developed to study the coupled spincharge<br />

diffusive dynamics [3]. Using finite element method, we numerically solve,<br />

in a two-dimensi<strong>on</strong>al (2D) electr<strong>on</strong> system with appropriate boundary c<strong>on</strong>diti<strong>on</strong>s,<br />

the generalized equati<strong>on</strong>s for the diffusive charge and spin dynamics. This numerical<br />

approach allows for an accurate descripti<strong>on</strong> of the spin and charge dynamics (i.e. n<strong>on</strong>equilibrium<br />

accumulati<strong>on</strong> and current) for a wide range of parameters bey<strong>on</strong>d the<br />

limit of weak Rashba interacti<strong>on</strong> [1,3]. The spatial profile of the spin accumulati<strong>on</strong><br />

exhibits a str<strong>on</strong>g presence of a spin precessi<strong>on</strong> arising from both the s-d exchange and<br />

the effective Rashba field. Spin relaxati<strong>on</strong>s due to random magnetic impurities as well<br />

as the D’yak<strong>on</strong>ov-Perel mechanism are embedded in the soluti<strong>on</strong>. We also discuss<br />

the diffusive dynamics and the spin torques in different regimes with respect to the<br />

magnitude of the Rashba spin-orbit interacti<strong>on</strong>.<br />

[1] A. Manch<strong>on</strong> and S. Zhang, Phys. Rev. B. 78, 212405 (2008); 79, 094422 (2009). [2] I. M. Mir<strong>on</strong>,<br />

et al. Nature (L<strong>on</strong>d<strong>on</strong>) 476, 189 (2011). [3] X. Wang and A. Manch<strong>on</strong>, arXiv:1111.1216 (to appear<br />

<strong>on</strong> Phys. Rev. Lett.); arXiv:1111.5466.<br />

Spin transport of Py/Au/Py spin valves with different Au channel<br />

widths<br />

Jang Hae Ku 1 , Jo<strong>on</strong>ye<strong>on</strong> Chang1*, Hyun Cheol Koo 1 , J<strong>on</strong>ghwa Eom 2 , Suk-hee Han 1<br />

and Gyutae Kim 3<br />

1 Spin C<strong>on</strong>vergence Research Center, Korea Institute of Science and Technology (KIST), Korea<br />

2 Department of Physics, Sej<strong>on</strong>g University, Korea<br />

3 Department of Electrical Engineering, Korea University, Korea<br />

Most previous studies <strong>on</strong> spin injecti<strong>on</strong> and transport were dealt with <strong>on</strong>e dimensi<strong>on</strong>al diffusive model and<br />

two-dimensi<strong>on</strong>al c<strong>on</strong>siderati<strong>on</strong> has been neglected for simplicity [1-2]. However, all of the lateral spin valve<br />

devices experimentally dem<strong>on</strong>strated are fabricated based <strong>on</strong> thin film technology so that it is indispensable to<br />

have spatial distributi<strong>on</strong> of spin current in a n<strong>on</strong>-magnetic channel [1-2]. Actually, some of the experimental<br />

data can’t be understood in terms of <strong>on</strong>e-dimensi<strong>on</strong>al c<strong>on</strong>ducti<strong>on</strong> model. Injected spin current usually produce<br />

inhomogeneous spin accumulati<strong>on</strong> which appears to a different magnitude of spin signal (ΔR) depending <strong>on</strong><br />

the positi<strong>on</strong> of voltage probes <strong>on</strong> the detector [3-4]. In the study, n<strong>on</strong>local spin valve (NLSV) measurements<br />

for lateral Permalloy(Py)/Au/Py spin valve devices with different Au channel widths were carried out in two<br />

viable voltage probe c<strong>on</strong>figurati<strong>on</strong>s. The larger channel width is at a fixed center to center channel length, the<br />

lower the magnitude of ΔR is in the NLSV, which is attributed to the increase in juncti<strong>on</strong> area and enhanced<br />

spatial distributi<strong>on</strong> of spin accumulati<strong>on</strong>. The voltage probe c<strong>on</strong>figurati<strong>on</strong> str<strong>on</strong>gly affects the spin valve<br />

signal owing to the n<strong>on</strong>-uniform spin current distributi<strong>on</strong> in lateral Au channel.<br />

[1] M. Johns<strong>on</strong>, Phys. Rev. Lett. 70, 2142 (1993). [2] F.J. Jedema, A.T. Fillip, and B.J. van Wees,<br />

Nature 410, 345 (2001). [3] T. Kimura, Y. Otani, and J. Hamrle, Phys. Rev. B. 73, 132405 (2006). [4]<br />

J. Ku, J. Chang, J. Eom, H. Koo, S. Han, and G. Kim, phys. stat. sol. (b) 244, No. 12, 4530 (2007).<br />

The effect of magnetic impurities in magnetic tunnel juncti<strong>on</strong><br />

Sungjung Joo 1 , K.y. Jung 1 , B.c. Lee 2 , Tae-suk Kim 3 , K.h. Shin 4 , Mung-hwa Jung 5 , Jinki H<strong>on</strong>g 1 and K. Rhie 1 *<br />

1 Department of Display and Semic<strong>on</strong>ductor Physics, Korea University, Korea<br />

2 Department of Physics, Inha University, Korea<br />

3 Department of Physics, Ch<strong>on</strong>nam nati<strong>on</strong>al University, Korea<br />

4 Spintr<strong>on</strong>ics Device Research Center, Korea Institue of Science and Technology, Korea<br />

5 Department of Physics, Sogang University, Korea<br />

Magnetic tunnel juncti<strong>on</strong>s (MTJs) have been extensively investigated for more than a decade, not <strong>on</strong>ly because<br />

of potential applicati<strong>on</strong>s such as next generati<strong>on</strong> memory devices or high frequency spin oscillators, but also<br />

due to scientific interest. The physical properties of MTJs are very sensitive to the c<strong>on</strong>diti<strong>on</strong>s of interface<br />

formati<strong>on</strong> and, therefore, it is essential to understand the various influencing factors to c<strong>on</strong>trol interface quality.<br />

The effect of oxidizing the ferromagnetic layer <strong>on</strong> tunneling magnetoresistance (TMR) is <strong>on</strong>e of the most<br />

interesting problems in MTJs. The ferromagnetic layer in MTJs was oxidized with varying O 2 c<strong>on</strong>centrati<strong>on</strong>s<br />

and the corresp<strong>on</strong>ding effect <strong>on</strong> spin-dependent transport was studied. As expected from our previous results<br />

for MTJs with an over-oxidized AlOx tunnel barrier, a partially oxidized ferromagnetic layer plays an important<br />

role in spin-dependent transport. As the temperature is lowered, the juncti<strong>on</strong> resistance increases dramatically<br />

and the TMR is str<strong>on</strong>gly suppressed. Increasing the O 2 c<strong>on</strong>centrati<strong>on</strong> enhances the increase of resistance and<br />

suppressi<strong>on</strong> of TMR. This work supports our previous c<strong>on</strong>clusi<strong>on</strong> that oxidizing the ferromagnetic layer<br />

generates localized magnetic moments, which act as a scattering center for spin-polarized tunneling electr<strong>on</strong>s.<br />

1. K.J. Rho, J.-S. Lee, K.B. Lee, J.-H. Park, J.Y. Kim, Y. Park, K. Kim, S. Joo, and K. Rhie, Phys. Rev. B 83,<br />

172408 (2011). 2. K. Lee, S. Joo, J. Lee, K. Rhie, T.-S. Kim, W. Lee, K. Shin, B. Lee, P. Leclair, J.-S. Lee, and<br />

J.-H. Park, Phys. Rev. Lett. 98, 107202 (2007). 3. T.-S. Kim and D.L. Cox, Phys. Rev. Lett. 75, 1622 (1995).<br />

July 8 - 13, 2012 Busan, Korea 45<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PJ32<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Effect of cobalt layer thickness <strong>on</strong> the magnetic and magnetoresistance<br />

properties of asymmetrical Co/Cu multilayers<br />

Srikrishna Pandey, Pavel Nikolaev and Sivaram Arepalli*<br />

Department of Energy Science, Sungkyunkwan University, Korea<br />

A series of asymmetrical multilayer thin films of Co/Cu with a systematically<br />

varying cobalt layer thickness tCo= 10, 15, 20, 30, 40 and 50 A was prepared by<br />

DC magnetr<strong>on</strong> sputtering technique to study the effect of tCo <strong>on</strong> its magnetizati<strong>on</strong><br />

and magnetoresistance properties. The XRD pattern of the multilayers showed<br />

the polycrystalline nature with texture (111). The magnetizati<strong>on</strong> measurements at<br />

different temperatures of the series showed that change in tCo leads to the change in<br />

magnetic anisotropy of the multilayers and thus change in coercive field (HC). The<br />

magnetoresistance measurements at different temperature of the series of multilayer<br />

showed a temperature dependent giant magnetoresistance (GMR) due to the inelastic<br />

scattering of electr<strong>on</strong>s by ph<strong>on</strong><strong>on</strong>s and magn<strong>on</strong>s. Moreover, an asymmetry in GMR<br />

curves at low temperature was observed because of the asymmetrical (pseudo spin<br />

valve) structure of the multilayer.<br />

PJ33<br />

Current-induced moti<strong>on</strong> of a transverse magnetic domain wall in the<br />

presence of spin Hall effect<br />

Soo-man Seo 1 , Kyung-whan Kim 2 , Jisu Ryu 2 , Hyun-woo Lee 2 and Kyung-jin Lee 1 *<br />

1 Materials Science and Engineering, Korea university, Korea<br />

2 Physics, Pohang University of Science and Technology, Korea<br />

The electric manipulati<strong>on</strong> of a domain wall (DW) in a magnetic nanowire is subject to the<br />

spin-transfer torque (STT) effect due to the coupling between local magnetic moments of the<br />

DW and spin-polarized currents [1]. Numerous studies <strong>on</strong> this subject have been performed to<br />

understand its fundamental physics [2] and to extend its potential to applicati<strong>on</strong>s such as data<br />

storage and logic devices [3]. In this work, we study theoretically current-induced dynamics<br />

of a transverse magnetic domain wall in bi-layer nanowires c<strong>on</strong>sisting of a ferromagnet <strong>on</strong> top<br />

of a n<strong>on</strong>magnet having str<strong>on</strong>g spin-orbit coupling. Domain wall dynamics is characterized by<br />

two threshold current densities, J(WB) and J(REV), where J(WB) is a threshold for the chirality<br />

switching of the domain wall and J(REV) is another threshold for the reversed domain wall<br />

moti<strong>on</strong> caused by spin Hall effect. The domain wall with a certain chirality may move opposite<br />

to the electr<strong>on</strong>-flow directi<strong>on</strong> with high speed in the current range J(WB) < J < J(REV) for the<br />

system designed to satisfy the c<strong>on</strong>diti<strong>on</strong>s J(WB) > J(REV) and α > β where α is the Gilbert<br />

damping c<strong>on</strong>stant and β is the n<strong>on</strong>adiabaticity of spin torque. Micromagnetic simulati<strong>on</strong>s<br />

c<strong>on</strong>firm the validity of analytical results.<br />

[1] J. C. Sl<strong>on</strong>czewski, J. Magn. Mag. Mater. 159, L1 (1996); L. Berger, Phys. Rev. B 54, 9353 (1996). [2]<br />

A. Yamaguchi et al., Phys. Rev. Lett. 92, 077205 (2004); M. Yamanouchi et al., Nature (L<strong>on</strong>d<strong>on</strong>) 428, 539<br />

(2004); M. Klaui et al., Phys. Rev. Lett. 94, 106601 (2005). [3] S. Parkin et al., Science 320, 190 (2008).<br />

PJ34<br />

Universal spin-hall effect in metallic thin films<br />

Xuhui Wang 1 , Jiang Xiao 2 , Aurelien Manch<strong>on</strong> 1 , and Sadamichi Maekawa 3,4<br />

1<br />

King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering<br />

Divisi<strong>on</strong>, Thuwal 23955-6900, Saudi Arabia.<br />

2<br />

Department of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai<br />

200433, China<br />

3<br />

Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan and<br />

4<br />

CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan<br />

Spin-orbit interacti<strong>on</strong> fills the academic and industrial pursuit for an electrical manipulati<strong>on</strong> of spins.<br />

Fabricated using the state-of-art nanotechnology, semic<strong>on</strong>ductor and metallic thin films embedded between<br />

two asymmetric interfaces in the presence of spin-orbit interacti<strong>on</strong> have attracted intensive theoretical and<br />

experimental interest in recent years. Spin Hall effect [1], voltage-c<strong>on</strong>trolled spin precessi<strong>on</strong> [2] as well<br />

as the recently observed spin-orbit torque [3] all stem from a careful design of spin-orbit coupling in the<br />

bulk or at the interfaces. We predict a large spin-Hall c<strong>on</strong>ductivity due to interfacial spin-orbit interacti<strong>on</strong>s<br />

in an ultrathin normal metal film that is sandwiched by two insulators. While providing a c<strong>on</strong>finement,<br />

the insulator/metal interfaces also serve as a source to the spin-orbit interacti<strong>on</strong> due to inversi<strong>on</strong> symmetry<br />

breaking. More interestingly, the interfacial spin-orbit coupling gives rise to a universal spin-Hall<br />

c<strong>on</strong>ductivity that is independent of microscopic details of the interfacial spin-orbit interacti<strong>on</strong> and is<br />

predicted to be much larger than that induced by bulk impurities.<br />

[1] Y. K. Kato, et al. Science 306, 1910 (2004). [2] H. C. Koo et al., Science 325, 1515 (2009) [3] A.<br />

Manch<strong>on</strong> and S. Zhang, Phys. Rev. B. 78, 212405 (2008); A. Chernyshov, et al. , Nature Physics 5,<br />

656 (2010);I. M. Mir<strong>on</strong>, et al. Nature (L<strong>on</strong>d<strong>on</strong>) 476, 189 (2011).<br />

46 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PK01<br />

C<strong>on</strong>trolling magnetic isolati<strong>on</strong> and moment reversal of FePt (001)<br />

films by Cu capping nanoislands<br />

D. H. Wei 1 *, C. H. Chao1 and Y. D. Yao 2<br />

1 Institute of Manufacturing Technology and Graduate Institute of Mechanical AND<br />

Electrical Engineerin, Nati<strong>on</strong>al Taipei University of Technology, Taiwan<br />

2 Institute of Applied Science and Engineering, Fu Jen University, Taiwan<br />

We aimed to c<strong>on</strong>trol the magnetic interacti<strong>on</strong> of FePt(001) films by introducing Cu<br />

capping nanoislands for applicati<strong>on</strong>s in magnetic recording and permanent magnets.<br />

Fe/Pt multilayers were prepared by e-beam evaporati<strong>on</strong> <strong>on</strong>to MgO substrates, and the<br />

thickness of Cu capping layers was varied from 1 to 6 nm. Out-of-plane coercivity<br />

increases with increasing growth temperature, and the reducti<strong>on</strong> of grain/domain<br />

size and intergrain interacti<strong>on</strong> of FePt can be achieved. Cu could penetrate into FePt<br />

nanostructures al<strong>on</strong>g the grain boundaries and create a strain-energy modulati<strong>on</strong> at the<br />

interface due to its lower surface energy. Studies of angular dependent coercivity show<br />

a tendency of a domain-wall moti<strong>on</strong> shift toward rotati<strong>on</strong> of reverse-domain type with<br />

Cu capping nanoislands. The intergrain interacti<strong>on</strong> was c<strong>on</strong>firmed from the Kelly-<br />

Henkel plot that indicated the str<strong>on</strong>g exchange coupling between neighboring grains in<br />

pure FePt films, and the negative δM value was obtained while FePt films capped with<br />

Cu nanoislands.<br />

PK02<br />

Perpendicular magnetic anisotropy for annealed Co/Ir(111) ultrathin<br />

films<br />

Wen-yuan Chan, Du-cheng Tsai, Cheng-hsun Chang and Jyh-shen Tsay*<br />

Nati<strong>on</strong>al Taiwan Normal University, Taiwan<br />

Compositi<strong>on</strong>s and magnetic properties of Co/Ir(111) ultrathin films thinner than 4<br />

m<strong>on</strong>olayers (ML) have been investigated. As the Co thickness increases to above 2<br />

ML, magnetic hysteresis appears in both the l<strong>on</strong>gitudinal and polar c<strong>on</strong>figurati<strong>on</strong>s<br />

as revealed using surface magneto-optic Kerr effect (SMOKE) technique. After<br />

annealing treatments, the observati<strong>on</strong>s of the attenuati<strong>on</strong> of Co LMM Auger signal<br />

and chemical shifts to lower kinetic energy show that Co atoms diffuse into the Ir(111)<br />

substrate. At higher temperatures, the Kerr intensities in both the l<strong>on</strong>gitudinal and<br />

polar c<strong>on</strong>figurati<strong>on</strong>s decrease due to the reducti<strong>on</strong> of Co overlayer. At a temperature<br />

interval, magnetic hysteresis appears <strong>on</strong>ly in the polar c<strong>on</strong>figurati<strong>on</strong>. This shows that<br />

the magnetic easy axis of Co/Ir(111) could be stabilized in the directi<strong>on</strong> of the surface<br />

normal by thermal annealing treatments. By systematical investigati<strong>on</strong>s for Co/Ir(111)<br />

ultrathin films thinner than 4 ML, a magnetic phase diagram has been established.<br />

Several phases are observed, including a n<strong>on</strong>magnetic phase, canted out-of-plane<br />

anisotropy and perpendicular magnetic anisotropy. On the top of the Co/Ir(111), the<br />

introducti<strong>on</strong> of Ag overlayer shows an oscillatory behavior of the Kerr intensities.<br />

Possible mechanisms of the charge transferring, quantum well effects and completeness<br />

of the Ag layer are discussed.<br />

PK03<br />

Anomalous easy-plane magnetocrystalline anisotropy of compressive<br />

strained (La,Ba)MnO 3 films<br />

H<strong>on</strong>g Zhu*, Jinzeng Tian, Lei Yang, Qingy<strong>on</strong>g Duanmu, Lin Hao and Xiaoping Wang<br />

Department of Physics, University of Science and Technologh of China, China<br />

Magnetic anisotropy of manganite films is sensitive to the epitaxial strain. So far, in Ca-<br />

and Sr-doped manganite films, many authors reported that a lattice expansi<strong>on</strong> induces<br />

easy magnetizati<strong>on</strong> in the corresp<strong>on</strong>ding directi<strong>on</strong>. In this work, magnetocrystalline<br />

anisotropy of La 0.67Ba 0.33MnO 3 epitaxial films suffering large compressive strain<br />

<strong>on</strong> LaAlO 3 substrates (LBMO/LAO) has been investigated by using ferromagnetic<br />

res<strong>on</strong>ance (FMR) technique. By mapping out the dependence of the FMR positi<strong>on</strong> <strong>on</strong><br />

the angle between the applied magnetic field and crystallographic axes of the films,<br />

a large easy-plane anisotropy has been found in such compressive strained LBMO<br />

films, which is in c<strong>on</strong>trast to the comm<strong>on</strong> tendency reported before. The excellent<br />

epitaxial crystallographic orientati<strong>on</strong> gives rise to an observable fourfold symmetry of<br />

the in-plane anisotropy. The results are discussed by taking large tolerance factor and<br />

giant magnetostricti<strong>on</strong> of Ba-doped manganites into account. In the phase diagram<br />

of temperature vs. tolerance factor for doped manganites, we noticed that LBMO<br />

has a larger tolerance factor but a lower Curie temperature than Sr-doped manganite,<br />

meaning that shrinkage of Mn-O-Mn b<strong>on</strong>d length in LBMO is in favor of sp<strong>on</strong>taneous<br />

magnetizati<strong>on</strong>, which in turn results in the anomalous easy-plane anisotropy in the<br />

compressive strained LBMO films.


PK04<br />

Magnetic reversal of Co/Pt multilayer depending <strong>on</strong> Co thickness and<br />

annealing temperature<br />

Seungha Yo<strong>on</strong>, Seungkyo Lee, Jo<strong>on</strong>hyun Kw<strong>on</strong>, Junghy<strong>on</strong> Lee and B. K. Cho*<br />

Materials Science and Engineering, Gwangju Institute of Science and Technology,<br />

Korea<br />

Magnetic reversal behaviors in ferromagnetic thin films are c<strong>on</strong>tinuously studied to<br />

achieve high performance of technological applicati<strong>on</strong>s. Recently, CoPt multilayers<br />

and alloys have been an important issue in perpendicular magnetic anisotropy (PMA)<br />

applicati<strong>on</strong>s. However, fundamental studies of the magnetic properties were not<br />

much presented. In this work, we present a magnetic reversal behavior of Ta(3.0 nm)/<br />

[Co(x nm)/Pt(1.0 nm)]x3 /Ta(1 nm) multilayers, when the Co thickness varied from<br />

0.3 nm to 2.0 nm. The multilayers were deposited using DC magnetr<strong>on</strong> sputter <strong>on</strong> Si/<br />

SiO2 substrate, and annealed with various temperature after depositi<strong>on</strong>. The magnetic<br />

and structural properties of the multilayers were measured using vibrating sample<br />

magnetometer (VSM) and x-ray diffracti<strong>on</strong> (XRD) at room temperature. In additi<strong>on</strong>,<br />

we observed the magnetic reversal behavior with magneto-optic Kerr effect (MOKE)<br />

microscope system, capable time-resolved domain observati<strong>on</strong>.<br />

PK05<br />

Annealing effect <strong>on</strong> the microstructures and magnetic properties of [Fe/<br />

Pt]16 multilayers <strong>on</strong> MgO (001) substrate<br />

Aimei Zhang1 , Weihua Zhu 2 and Xiaoshan Wu 3<br />

1 College of Science, Hohai University, China<br />

2 College of Science, Hohai Unviersity, China<br />

3 Physics, Nanjing University, China<br />

[Fe/Pt]16 multilayers are deposited <strong>on</strong> MgO (001) single crystal substrate by magnetic<br />

sputtering layer by layer with varying the substrate temperature from 150-500oC to<br />

explore the annealing effect <strong>on</strong> the microstructures and magnetic properties of the<br />

films. Results show that FePt alloy with L 10 phase forms at about 300oC, and reaches<br />

a completely ordered state at about 400 oC. FePt film depositing at above 300oC has<br />

(001)-preferred texture which shows that L 10-FePt film has perpendicular magnetic<br />

anisotropy. The out-of-plane coercivity increases with sample transforming from [Fe/<br />

Pt]16 multilayers to L 10-FePt alloy. The out-of-plane coercivity for the morphology,<br />

which is c<strong>on</strong>firmed to have the effects <strong>on</strong> the out-of-phane coercivity, with the<br />

c<strong>on</strong>tinuing surface has an order higher than that for the granular surface.<br />

PK06<br />

Preparati<strong>on</strong> and magnetic studies of room-temperature sputtered [Co/<br />

Pt] multilayer films <strong>on</strong> glass substrates with perpendicular magnetic<br />

anisotropy<br />

Chiuan-fa Huang 1 , Hsian-yuan Wu 1 , An-cheng Sun 1 *, Fu-te Yuan 2 , Jen-hwa Hsu 2 , S. N.<br />

Hsiao 3 and H. Y. Lee 3<br />

1<br />

Department of Chemical Engineering & Materials Science, Yuan Ze University,<br />

Taiwan<br />

2<br />

Department of Physics, Nati<strong>on</strong>al Taiwan University, Taiwan<br />

3<br />

Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Center (NSRRC), Taiwan<br />

Multilayer [Co 10/Pt 7.5]n films were deposited at room temperature (RT) <strong>on</strong> glass substrates with and<br />

without a Pt(111) underlayer. The thicknesses of each Co and Pt layer were set at 1 and 0.75 nm<br />

respectively. The stacking period, n, was varied from 1 to 6, leading to the total thickness of [Co10/<br />

Pt7.5]n films from 1.75 to 10.5 nm. The results of magnetic studies indicate that the perpendicular<br />

magnetic anisotropy (PMA) of [Co 10/Pt 7.5]n films is str<strong>on</strong>gly influenced by inserting a Pt(111)<br />

underlayer and the number of n. Surprisingly, [Co/Pt]n films exhibit PMA behavior with a Pt(111)<br />

underlayer when n exceeds 3 even the films were deposited at room temperature. However without<br />

a Pt(111) underlayer, the films will not exhibit PMA in all cases. The appearance of L11 phase is<br />

found related to the appearance of PMA in [Co 10/Pt 7.5]n/Pt(111) films. The [Co/Pt]n film is grown<br />

al<strong>on</strong>g Pt(111) resulting in the L11(222) orientati<strong>on</strong>, which causes the easy axis al<strong>on</strong>g the<br />

plane normal. In this study, the microstructure at [Co 10/Pt 7.5]n/Pt(111) interface is also studied and<br />

will be presented, which is helpful for understanding the formati<strong>on</strong> mechanism of PMA behavior in<br />

multilayer [Co 10/Pt 7.5]n structure prepared at room temperature.<br />

PK07<br />

Magnetic anisotropy in FeCo thin films<br />

Xiaoxi Liu*, Shinsaku Isomura and Akimitsu Morisako<br />

Department of Informati<strong>on</strong> Engineering, Shinshu University, Japan<br />

PK08<br />

PK09<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Sputtered FeCo films normally show magnetic anisotropy inside the film plane. It is<br />

believed that the magnetic anisotropy are due to the stray field of the magnet of the<br />

target. However, the details of the induced magnetic anisotropy are yet to be fully<br />

understood. In the present work, we have prepared FeCo films by both DC magnetr<strong>on</strong><br />

sputtering system and facing targets sputtering system. The magnetic properties,<br />

crystallographic properties, and microstructure of the films have been investigated.<br />

Films deposited by DC magnetr<strong>on</strong> sputtering show isotropic magnetic properties in the<br />

film plane. However, films deposited by facing targets sputtering show str<strong>on</strong>g magnetic<br />

anisotropy in the film plane. The magnetic anisotropy field increases from 40 Oe to 540<br />

Oe with the increase of the film thickness from 10 nm to 150 nm for films deposited<br />

by facing targets sputtering system. XRD results show that the (110) lattice spacing<br />

of FeCo films increases with the increase of films thickness from 10 nm to 40 nm.<br />

However, lattice spacing almost not changes with further increase of the film thickness.<br />

Of particular interest is thatiInternal stress of the films increased with the decrease of<br />

the film thickness.<br />

Magnetic domain wall energy of Co/Ni superlattice with perpendicular<br />

magnetic anisotropy<br />

Kentaro Toyoki, Yu Shiratsuchi* and Ryoichi Nakatani<br />

Osaka University, Japan<br />

Co/Ni superlattice is a promising material for spintr<strong>on</strong>ics devices, in which the magnetic domain<br />

walls carry informati<strong>on</strong> stored, owing to a perpendicular magnetic anisotropy and a high<br />

saturati<strong>on</strong> magnetizati<strong>on</strong>. Despite the numerous studies <strong>on</strong> the magnetic domain wall moti<strong>on</strong> of<br />

the Co/Ni superlattice, the magnetic domain wall energy density has not been reported. In this<br />

work, we present the experimental determinati<strong>on</strong> of the magnetic domain wall energy density<br />

of the Co/Ni superlattice with perpendicular magnetic anisotropy (PMA). We c<strong>on</strong>firmed that<br />

the epitaxial growth of Co(111)/Ni(111) superlattice <strong>on</strong> the Ag(111)-buffered Si(111) substrate.<br />

Several parameters were determined to obtain the magnetic domain wall energy σW [1], i.e.<br />

the saturati<strong>on</strong> magnetizati<strong>on</strong> MS, the PMA energy, and the magnetic domain period. From the<br />

dependence of the magnetic domain period <strong>on</strong> the ferromagnetic layer thickness, the dipole<br />

length, D0 (≡ σW/2πMS2), is estimated as 22.5±2.5 nm. Using the experimentally obtained<br />

MS (≈660 emu/cc), the magnetic domain wall energy density is estimated as σW = 6.4±1.4<br />

erg/cm2. The estimated σW is about three-times higher than those for L12-CrPt3[2], and about<br />

<strong>on</strong>e-third of that for L10-FePt[3]. From the obtained values, the exchange stiffness c<strong>on</strong>stant is<br />

calculated as about 4.8×10-6 erg/cm, which is comparable to that of bulk-Co.<br />

[1] C. Kooy and U. Enz, Phil. Re. Rept. 15, 7 (1960). [2] Y. Shiratsuchi, M. Yamashita, R. Nakatani<br />

and M. Yamamoto, J. Mag. Soc. Jpn, 33, 447 (2009). [3] S. Okamoto, N. Kikuchi, O. Kitakami, T.<br />

Miyazaki, Y. Shimada and K. Fukamichi, Phys. Rev. B 66, 024413 (2002).<br />

Anisotropic Magnetoresistance of Co/Ni multilayers<br />

Chih_yung Chen 1 , James C Eckert 1 , Natalia Fear 1 , Sheena K. K. Patel 1 , Richard<br />

Sayanagi 1 , Patricia D Sparks 1 , E Shipt<strong>on</strong> 2 and Eric E Fullert<strong>on</strong> 2<br />

1 Harvey Mudd College, USA<br />

2 University of California, San Diego, USA<br />

Co/Ni multilayers exhibit perpendicular magnetic anisotropy, relatively low magnetic<br />

damping and unusual magneto-transport characteristic that make them useful for<br />

spintr<strong>on</strong>ic devices. Anisotropic magnetoresistance was measured for sputtered Ni/<br />

Co films: SiO 2Ta 40ÅPd 40Å(Co 2ÅNi Y) x10Ta 40Å,with Ni thicknesses from Y=2-14Å. Three<br />

AMR c<strong>on</strong>figurati<strong>on</strong>s were studied. Two c<strong>on</strong>figurati<strong>on</strong>s, varying the applied field vs.<br />

current angle, the applied field always in the plane of the sample, AMR1, and varying<br />

the applied field from in plane to out of plane, AMR2, provide similar informati<strong>on</strong>. The<br />

%AMR1 or 2 increases m<strong>on</strong>ot<strong>on</strong>ically as the fracti<strong>on</strong> of Ni increases and shows the<br />

expected cosθ 2 dependence. Rotating the sample with the field always perpendicular<br />

to the current, AMR3, we see anomalous angle-dependence for all samples, at all<br />

temperatures. At the sample orientati<strong>on</strong> where a peak in the AMR is expected, there<br />

is a dip. The relative magnitudes of these c<strong>on</strong>tributi<strong>on</strong>s vary with temperature and Ni<br />

thickness. The magnitude of the AMR3 is approximately half the AMR2. At 5K, the<br />

magnitudes of all AMRs increase with Ni thickness except the AMR3 for the sample<br />

with 3Å of Ni is anomalously low. The temperature variati<strong>on</strong>s for AMR2 and AMR3<br />

are quantitatively different but each varies by approximately a factor of 3 from 5K to<br />

305K.<br />

July 8 - 13, 2012 Busan, Korea 47<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PK10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Interface perpendicular magnetic anisotropy in thick amorphous<br />

CoSiB film by Pt layer<br />

Insung Park, Hana Lee, Hyung Jun Kim, Sung Y<strong>on</strong>g Kim, Young Kwang Kim and<br />

Taewan Kim*<br />

Department of Advanced Materials Engineering, Sej<strong>on</strong>g Univ., Korea<br />

Recently, magnetic tunnel juncti<strong>on</strong>s (MTJs) with perpendicular magnetic anisotropy<br />

(PMA) have attracted a lot of research interest, because they have a potential for<br />

spin transfer torque magnetic random access memories (MRAMs). Devices with<br />

perpendicular magnetic anisotropy have lower switching currents than devices with inplane<br />

magnetic anisotropy. We have investigated the interface perpendicular magnetic<br />

anisotropy (IPMA) of amorphous CoSiB thin film. CoSiB/Pt exhibited perpendicular<br />

magnetic anisotropy. The structure of samples was SiO 2Ta 50ÅPt 30ÅCoSiBx/Pt 30Å and<br />

SiO 2Ta 50ÅPt 30ÅCoSiBx. The thickness of CoSiB were varied in the range of from 2 to<br />

40Å. The sample without Pt capping layer exhibited perpendicular magnetic anisotropy<br />

at tCoSiB=10Å but the sample with Pt capping layer exhibited perpendicular<br />

anisotropy at lower thickness tCoSiB=5Å. Therefore, it was expected that IPMA<br />

properties of amorphous CoSiB <strong>on</strong> Pt layer was suitable for STT-MRAM.<br />

PK11<br />

Perpendicular magnetic anisotropy and superparamagnetism in Ta/<br />

CoFeB/MgO structures<br />

C.c. Tsai 1 , H.m. Chen 2 , Chih-wei Cheng 2 , C.h. Shiue 2 , M.c. Tsai 2 , J. P. Singh 2 , C.w. Su 3 and G. Chern 2 *<br />

1 Department of Engineering and Management of Advanced Technology, Chang Jung<br />

Christian University, Tainan 71101, Taiwan, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al Chung Cheng University, ChiaYi 62102, Taiwan, Taiwan<br />

3 Department of Electrophysics,, Nati<strong>on</strong>al Chiayi University, ChiaYi, 60004, Taiwan, Taiwan<br />

Collapses of tunnel magnetoresistance in perpendicular magnetic tunnel juncti<strong>on</strong>s have been reported<br />

recently[1-2]. These observati<strong>on</strong>s indicate that the coercivity of the reference layer and sensing layer<br />

behaves differently at low temperature. We extend to study the temperature dependence of a series<br />

of films with SiO2 substrate/Ta 5 nmCoFeB x nmMgO 1 nm, 1.5


PK16<br />

Ultrathin Co/Pt films with high thermal stability and large effective<br />

magnetic moment<br />

Prasanta Chowdhury*, Prabhanjan Dilip Kulkarni, Murali Krishnan and Harish C<br />

Barshilia<br />

Surface Engineering Divisi<strong>on</strong>, Nati<strong>on</strong>al Aerospace Laboratories (CSIR), India<br />

PK17<br />

PK18<br />

WITHDRAWN<br />

Magnetic characteristics of amorphous [CoSiB/Pt]n multilayers<br />

Woosuk Yoo 1 , Kyujo<strong>on</strong> Lee 1 , Myung-hwa Jung 1 *, Insung Park 2 , Taewan Kim 2 , E.h.m.<br />

Van Der Heijden 3 and H.j.m. Swagten 3<br />

1 Dept of Physic, Sogang University Seoul. South Korea, Korea<br />

2 Dept of Physic, Sej<strong>on</strong>g University Seoul. South Korea, Korea<br />

3 Department of Applied Physics, Eindhoven University of Technology, Netherlands<br />

The development of electr<strong>on</strong>ics demands an increasing effort in attaining more efficient<br />

electr<strong>on</strong>ic memories. The materials with perpendicular magnetic anisotropy (PMA)<br />

are important in applicati<strong>on</strong>s of electr<strong>on</strong>ic memories. One promising new material is<br />

amorphous PMA multilayers [CoSiB/Pt]n with n the number of repeated bilayers. By<br />

using a VSM-SQUID measurement setup, the magnetic characteristics of the [CoSiB/<br />

Pt]n are gained. The anisotropy c<strong>on</strong>stants k1eff, K1, K2 are obtained by fitting the<br />

hard-axis magnetizati<strong>on</strong> curve with GST equati<strong>on</strong>. The hysteresis loops appear slanted<br />

increasing n. Furthermore magneto- optical Kerr effect (MOKE) imaging c<strong>on</strong>firms<br />

magnetic domain wall moti<strong>on</strong>. The coercive field is first increasing with n and after a<br />

maximum, decreasing with n. This result is caused by the RKKY coupling between the<br />

magnetic layers and the balance between the domain wall energy scaling with n and the<br />

magnetostatic energy scaling with n2. In additi<strong>on</strong> the reversal process is not depending<br />

<strong>on</strong> the strength of the initial magnetizati<strong>on</strong> field.<br />

Effects of phase distributi<strong>on</strong> and grain size <strong>on</strong> the effective anisotropy<br />

and coercivity of nanocomposite PtCo permanent alloy<br />

Tao Liu 1 , Pei Zhao 2 , Zhaohui Guo 1 , Wei Li 1 , Wei Sun 1 and Jingdai Wang 1<br />

1 Divisi<strong>on</strong> of Functi<strong>on</strong>al Materials, Central Ir<strong>on</strong> & Steel Research Institute, China<br />

2 Central Ir<strong>on</strong> & Steel Research Institute, China<br />

Phase distributi<strong>on</strong> and grain size are the key factors c<strong>on</strong>trolling the coercivity of<br />

nanocomposite permanent magnets. Feng et al. have investigated the effective anisotropy<br />

and coercivity of nanocomposite Nd 2Fe 14B/α-Fe magnets. [1] The latest research shows<br />

that the PtCo alloy is composed of nano-structured soft and hard magnetic phases. [2] This<br />

system can be used as an ideal model system for studying exchange coupling between the<br />

magnetically hard and soft phases. There exist three types of grain interfaces with different<br />

exchange-coupling strengths in nanocomposite PtCo permanent magnets. It is necessary to<br />

describe the proporti<strong>on</strong>s of the three kinds of grain interfaces for analyzing the influences<br />

of the exchange-coupling interacti<strong>on</strong>s <strong>on</strong> the magnetic properties. We assume that soft and<br />

hard phases distribute randomly in nanocomposite permanent magnets and that all grains<br />

have cubic shapes.We caculate the dependence of the coercivity Hc of a nanocomposite <strong>on</strong><br />

the hard-grain size Dh. For a given volume fracti<strong>on</strong> vh and soft-grain size Ds, Hc shows a<br />

maximum value as a functi<strong>on</strong> of the hard-grain size Dh, and the maximum positi<strong>on</strong> shifts<br />

to a smaller Dh with the decreasing volume fracti<strong>on</strong> of the hard phase. We shows the<br />

comparis<strong>on</strong>s between the calculated coercivity Hc and experimental results.<br />

[1] W.C. Feng, W. Li, et al., J. Appl. Phys. 98, 044305(2005) [2] Xiao Q F, Bruck E, de Boer F R et<br />

al. , J. Alloys Compd., 364,64(2004)<br />

PK19<br />

PK20<br />

PK21<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Perpendicular magnetic anisotropy and metal layer effect in MgO/<br />

CoFeB/cap (cap = Ta, Ru, and Nb)<br />

Chih-wei Cheng, Tsung-i Cheng and G. Chern*<br />

Department of Physics, Nati<strong>on</strong>al Chung Cheng University, Chiayi 62102, Taiwan,<br />

Taiwan<br />

Perpendicular magnetic anisotropy (PMA) has been observed in MgO/CoFeB/Ta but<br />

not in MgO/CoFeB/Ru, indicating that the metal cap layer is crucial¹-². In this report,<br />

we extend the study to MgO/CoFeB 1.2 nmNb(1 - 5 nm) by sputtering and find again that<br />

PMA can be induced by Nb cap layer. Our experimental results also show that Nb and<br />

Ta have str<strong>on</strong>g interface effect but the PMA occurs in a small window (~ 1 - 3 nm)<br />

while Ru shows much weaker effect and the induced interface anisotropy c<strong>on</strong>stant (Ki)<br />

is basically not high enough to overcome the bulk anisotropy c<strong>on</strong>tributi<strong>on</strong>.<br />

Dependence of perpendicular magnetic anisotropy of CoFeB thin films<br />

<strong>on</strong> thickness of MgO overlayer<br />

Du<strong>on</strong>g Duc Lam 1 , Frederic B<strong>on</strong>ell 1 , Shinji Miwa 1 , Yoichi Shiota 1 , Kay Yakushiji 2 , Hitoshi<br />

Kubota 2 , Takayuki Nozaki 2 , Akio Fukushima 2 , Shinji Yuasa 2 and Yoshishige Suzuki 1 *<br />

1 Graduate School of Engineering Science, Osaka University, Toy<strong>on</strong>aka, Osaka 560-8531, Japan<br />

2 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Spintr<strong>on</strong>ics Research<br />

Center, Japan<br />

The CoFeB/MgO interface is known to favor perpendicular magnetic anisotropy (PMA) which<br />

is already found applicati<strong>on</strong> in the efficient magnetic tunnel juncti<strong>on</strong>s and electric field c<strong>on</strong>trol the<br />

magnetizati<strong>on</strong>. Recently, the PMA of CoFeB/MgO structure has been achieved in both experiment<br />

[1,2] and theory [3], however the origin of PMA is still ambiguous. In this scope, the structure<br />

Ta 5nmCo 10Fe 70B 20(0.9-2.0)nmMgO (0-6.0)nmTa 5nm (unit in nm) was investigated. All samples were fabricated by<br />

sputtering method <strong>on</strong> thermally oxidized Si substrates. We studied the dependence of the total magnetic<br />

moment and the effective magnetic anisotropy energy of the Co 10Fe 70B 20 layer. Magnetic anisotropy is<br />

found to be very sensitive to MgO thickness, favouring to perpendicular directi<strong>on</strong> with thin MgO film<br />

(the maximum interface anisotropy was 1.74 erg/cm2 with the CoFeB/MgO 1nm structrure. Although<br />

thin MgO samples have thick magnetic dead layer, resulting in the reducti<strong>on</strong> of total magnetic moment,<br />

<strong>on</strong>ly the existence of the magnetic dead layer cannot explain the change of the PMA. We found that the<br />

thickness of MgO overlayer plays the very important role for the directi<strong>on</strong> of magnetic anisotropy easy<br />

axis. This work is supported by CREST, Japan Science Technology Agency, Japan.<br />

[1] S. Yakata et al, J. Appl. Phys., 105, 07D131 (2009) [2] S. Ikeda et al, Nature Materials., 9, 721-<br />

724 (2010) [3] H. X. Yang et al, Phys. Rev. B, 84, 054401 (2011)<br />

The study of MgO based surface anisotropy of CoFeB layer<br />

D<strong>on</strong>gseok Kim 1 , Kuyeol Jung 1 , Sungjung Joo 1 , Youngjae Jang 1 , Byungchan Lee 2 ,<br />

Jinki H<strong>on</strong>g 1 and Kungw<strong>on</strong> Rhie 1 *<br />

1 Display and Semic<strong>on</strong>ductor Physics, Korea University, Korea<br />

1 Department of Physics, Inha University, Korea<br />

STT-MRAM (Spin transfer torque-magnetoresistive random access memory)[1] has c<strong>on</strong>sidered<br />

as an outstanding candidate for the next generati<strong>on</strong> memory device. Higher anisotropy c<strong>on</strong>stant<br />

K and low saturati<strong>on</strong> magnetizati<strong>on</strong> Ms are required for the perpendicular magnetic layers<br />

to satisfy the high thermal stability and low current density for current induced magnetic<br />

switching. The PMA(perpendicular magnetic anisotropy) have been reported in Fe-Pt alloy[2]<br />

ordered by L10, Co/Pd multi-layer[3] and CoFeB-MgO[4,5]. We report the PMA of CoFeB<br />

based with MgO using amorphous paramagnetic FeZr buffer layer. Samples are deposited <strong>on</strong><br />

SiO 2 substrate by RF magnetr<strong>on</strong> sputtering machine at room temperature. The structures are<br />

SiO 2FeZr 2nmCoFeB(tCoFeB:0.5-2)/MgO 2.5nmTa 1nm (in nm) and annealing for 1 hour at 400°C<br />

. Figure 1 shows Hall resistance of PMA of CoFeB after annealing. During the annealing<br />

treatment, the lattice of CoFeB became BCC lattice structure al<strong>on</strong>g with crystal structure of<br />

upper MgO. Therefore, the interface anisotropy is formed between CoFeB and MgO layers in<br />

rather thin thickness. In summary, we observed the PMA in CoFe/MgO using the FeZr buffer<br />

layer. We obtain a high anisotropic c<strong>on</strong>stant K with a various c<strong>on</strong>diti<strong>on</strong>s. This method can be an<br />

excellent candiate for PMA- MTJ with low critical current density.<br />

[1] Kishi, T. et al. IEDM Tech. Dig. 309 (2008) [2] Yoshikawa, M. et al. IEEE Trans. Magn. 44,25732576 (2008) [3] Mizunuma,<br />

K. et al. APL. 95, 232516 (2009) [4] S.Yuasa. et al. Nat. Mater. 3, 868 (2004) [5] S.Ikeda. et al. Nat. Mater. 9, 721 (2010)<br />

July 8 - 13, 2012 Busan, Korea 49<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PL01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

BiFeO3 thickness dependence of exchange bias in polycrystalline<br />

BiFeO3/FeNi bilayers<br />

Xiaobo Xue 1 , Xuey<strong>on</strong>g Yuan 2 , Wenbing Rui 1 , Biao You 1 , Qingyu Xu 2 and Jun Du 1 *<br />

1<br />

Nati<strong>on</strong>al Laboratory of Solid State Microstructures and Department of Physics,<br />

Nanjing University, China<br />

2<br />

Department of Physics, Southeast University, China<br />

Due to both ferroelectric and antiferromagnetic transiti<strong>on</strong> temperatures above room<br />

temperature, multiferroic BiFeO 3 has attracted much attenti<strong>on</strong> for uses in the electrical<br />

c<strong>on</strong>trol of magnetic random assess memory. Exchange bias in ferromagnet (FM)/<br />

antiferromagnet (AFM) bilayers has also attracted much attenti<strong>on</strong> because of its<br />

importance in developing magneto-electr<strong>on</strong>ic devices. Although there have been some<br />

reports <strong>on</strong> the exchange bias employing BiFeO 3 as antiferromagnetic layer, most of<br />

them the BiFeO 3 layers were grown epitaxially. In this presented work, single phase<br />

polycrystalline BiFeO 3 films were successfully grown <strong>on</strong> Si substrate with LaNiO 3<br />

buffer layer. Clear exchange bias were observed at room temperature in a series of<br />

BiFeO 3(t)FeNi(3.6nm) bilayers, in which t varies from 8 nm to 240 nm. With increasing t,<br />

both the exchange bias field and the coercivity increase sharply and approach maxima<br />

when t is about 40 nm, which is close to <strong>on</strong>e half of the spin cycloidal modulati<strong>on</strong><br />

period (64 nm) of the bulk BiFeO 3 material. Our results suggest that the cycloidal<br />

spin structure may still exist in the polycrystalline BiFeO 3 film and the interfacial<br />

uncompensated pinned spins may be resp<strong>on</strong>sible for exchange bias in the BiFeO3/FeNi<br />

bilayer films.<br />

PL02<br />

Temperature-dependent magnetic anisotropies in epitaxial Fe/CoO/<br />

MgO(001) system studied by the planar Hall effect<br />

J. Zhu 1 , J. Li 1 , W.n. Cao 2 , J. Zhu 1 and Yizheng Wu 2 *<br />

1 Physics department, Fudan university, China<br />

2 physics department, Fudan university, China<br />

The exchange coupling between ferromagnet (FM) and antiferromagnet (AFM)<br />

has been intensively explored due to fundamental interest and its technological<br />

applicati<strong>on</strong>s. The effect of the magnetic anisotropy of the AFM layer <strong>on</strong> the exchange<br />

coupling has not been well studied, which can <strong>on</strong>ly be performed in single-crystalline<br />

FM/AFM system. In this c<strong>on</strong>tributi<strong>on</strong>, we investigated the exchange-induced inplane<br />

magnetic anisotropies in a single-crystalline Fe/CoO/MgO(001) system in the<br />

temperature range of 10-400K. The temperature-dependent magnetic anisotropies of<br />

the Fe film were quantitatively measured with the torque technique utilizing the planar<br />

Hall effect. We found the field cooling can induce a very str<strong>on</strong>g uniaxial anisotropy<br />

up to 0.196erg/cm2 in Fe film with the easy axis(EA) // CoO, and also a 4-fold<br />

anisotropy with the EA//CoO. Such EA of the exchange-induced anisotropy was<br />

found insensitive to the cooling field orientati<strong>on</strong> and <strong>on</strong>ly related to the CoO crystalline<br />

axis. The CoO thickness dependent exchange-induced anisotropy will be discussed in<br />

this c<strong>on</strong>tributi<strong>on</strong>.<br />

1.W. N. Cao, J. Li, G. Chen, J. Zhu, C. R. Hu, and Y. Z. Wu, Appl. Phys. Lett. 98, 262506 (2011)<br />

PL03<br />

Structural changes and magnetic properties of ultrathin Fe/Pt(111)<br />

films influenced by oxygen exposure<br />

Jyh-shen Tsay 1 *, Hau-chun Jhang 1 , Ying-chen Lee 1 , Wei-hsiang Chen 1 , Yao-jung<br />

Chen 2 and Huei-ying Ho 3<br />

1 Nati<strong>on</strong>al Taiwan Normal University, Taiwan<br />

2 Taipei College of Maritime Technology, Taiwan<br />

3 Nati<strong>on</strong>al Taipei University of Educati<strong>on</strong>, Taiwan<br />

Magnetic properties of Fe/Pt(111) films have received much attenti<strong>on</strong> in the past<br />

decade [1-2]. In this c<strong>on</strong>tributi<strong>on</strong>, we focus <strong>on</strong> the structures and magnetic properties<br />

of ultrathin Fe/Pt(111) films influenced by oxygen exposure. Fe atoms in the<br />

subm<strong>on</strong>olayer regi<strong>on</strong> adapt a smaller layer distance as compared to the BCC structure<br />

of a Fe layer above <strong>on</strong>e m<strong>on</strong>olayer (ML). At saturati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s for absorbed oxygen<br />

<strong>on</strong> Fe/Pt(111), the increase of oxygen in the films coincides with the Fe thickness while<br />

the amount of adsorbed oxygen in the subm<strong>on</strong>olayer range is rather small. In additi<strong>on</strong>,<br />

the amount of oxygen exposure to achieve a saturati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> increases to a<br />

maximum value followed by a reducti<strong>on</strong> for Fe/Pt(111) thicker than 1 ML. This shows<br />

the structure related oxidati<strong>on</strong> efficiency of Fe/Pt(111). The growth of Fermi edge at<br />

620 K shows the segregati<strong>on</strong> of Pt atom to the top layers. Only the Fe/Pt(111) thicker<br />

than 3 ML shows the enhanced coercive force after thermal annealing. This could be<br />

explained by the blocking of the formati<strong>on</strong> of FePt alloy by the ir<strong>on</strong> oxides.<br />

[1] T.U. Nahm, et al, J. Korean Phys. Soc. 46 (2005) S125; [2] Y.J. Chen, et al, APL, 93 (2008)<br />

012503.<br />

50 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PL04<br />

Initial growth of bcc Co films <strong>on</strong> Au(001) studied by STM/BH imaging<br />

T. Kawagoe*, E. Wakabayashi, Y. Murasawa and T. Sakata<br />

Osaka Kyoiku University, Japan<br />

We have studied the surface structure and magnetism of metastable bcc Co films (>1<br />

ML) <strong>on</strong> Au(001) [1]. Here we report the initial growth of subm<strong>on</strong>olayer Co films by<br />

means of barrier height (BH) imaging using STM, which has capability of element<br />

discriminati<strong>on</strong>. The experiments were performed in a UHV-MBE system equipped<br />

with an STM unit. After the clean Au(001) rec<strong>on</strong>structed surface was c<strong>on</strong>firmed by<br />

STM, a subm<strong>on</strong>olayer Co was deposited <strong>on</strong> it at RT. Spatially resolved BH maps,<br />

together with the topographic images were obtained at RT using a tip-sample distance<br />

modulati<strong>on</strong> technique. We have observed numerous islands with different sizes and<br />

heights after 0.15 ML Co coverage and successfully obtained, from the BH imaging,<br />

an element-specific c<strong>on</strong>trast, i.e. recognizing aggregated Au islands and Co islands, and<br />

informati<strong>on</strong> about inhomogenities of BH with proper c<strong>on</strong>siderati<strong>on</strong> of the artifacts near<br />

the step edges. BH of metastable bcc Co film was observed for the first time, and that<br />

showed a large BH value (~6 eV), whereas the observed BH of the Au(001) surface<br />

(~3.5 eV) was c<strong>on</strong>sistent with the previous results.<br />

[1] T. Kawagoe et al., Surf. Sci. 602, L15 (2008).<br />

PL05<br />

Magnetic field induced “switching” of the nanodomain state of<br />

ferromagnet - antiferromagnet frustrated system<br />

Alexander I Morosov and Alexander S Sigov<br />

Electr<strong>on</strong>ics Department, MSTU MIREA, Russia<br />

The presence of atomic steps <strong>on</strong> the interface between the nanolayers of ferromagnet<br />

and antiferromagnet with uncompensated atomic planes parallel to the interface causes<br />

frustrati<strong>on</strong>s of the interlayer exchange interacti<strong>on</strong>. If the exchange integral for the<br />

ferromagnet is less than that <strong>on</strong>e for the antiferromagnet, then, for the layers of equal<br />

thickness, and in the case where the characteristic distance R between the neighboring<br />

edges of the steps <strong>on</strong> the interface exceeds the layer thickness, the ferromagnetic<br />

layer appears to be broken down into 180 o domains. The domain walls separating<br />

such domains generated by frustrati<strong>on</strong>s arise at the atomic step edges and penetrate<br />

the ferromagnetic layer, the domain wall thickness increases with increasing distance<br />

from the interface. An external magnetic field applied parallel to the magnetizati<strong>on</strong>s<br />

of the domains, being in excess of some critical value B*, makes the m<strong>on</strong>odomain<br />

state of the ferromagnetic layer more favorable. If so, the domain walls with more<br />

complicated structure depending <strong>on</strong> the field magnitude arise between 180 o domains in<br />

the antiferromagnet layer. The B* value can be obtained from the equality of the gain<br />

in the Zeeman energy and the difference between the energies of the domain walls in<br />

different layers.<br />

PL06<br />

Stable structural and electr<strong>on</strong>ic properties of adsorpti<strong>on</strong> Tl <strong>on</strong> the<br />

clean Tl/Si(111) surface<br />

Haruki Kato 1 *, Liang Li 1 , Shinya Haraguchi 1 , Junpei Goto 1 , Masahito Tsujikawa 2 and<br />

Tatsuki Oda 3<br />

1 Graduate School of Natural Science and Technology, Kanazawa University, Japan<br />

2 Center for Spintr<strong>on</strong>ics Integrated Systems, Tohoku University, Japan<br />

3 Institute of Science and Engineering, Kanazawa University, Japan<br />

The structural inversi<strong>on</strong> asymmetry shows up surfaces or interfaces. It leads to spin split electr<strong>on</strong>ic<br />

state (Rashba-Bychkov effect) in the material. In particular, heavy metals <strong>on</strong> the light elements like<br />

Si show str<strong>on</strong>g spin-orbit splitting [1] and such property in Tl/Si(111) has also been c<strong>on</strong>firmed both<br />

in simulati<strong>on</strong> and experiment [2]. This surface has been observed as a clean <strong>on</strong>e, indicating the<br />

stability due to the insulating property verified by the experiments and theoretical approaches [3,4].<br />

By d<strong>on</strong>ating (or accepting) electr<strong>on</strong>s, <strong>on</strong>e can introduce carriers with spin polarizati<strong>on</strong> at the part of<br />

states, implying an interesting basis for spintr<strong>on</strong>ics devices. In this work, as a method of d<strong>on</strong>ating<br />

electr<strong>on</strong>s, Tl atom which is the same element as the top surface of Tl/Si(111) is c<strong>on</strong>sidered within<br />

the density functi<strong>on</strong>al first-principles approach of fully relativistic pseudo-potential and planewave<br />

basis. First, the stable adsorpti<strong>on</strong> site has been investigated with using the √3×√3 superlattice of<br />

Tl/Si(111). It was found that <strong>on</strong>e of hollow site models is most stable in the adsorpti<strong>on</strong> models<br />

investigated. In the presentati<strong>on</strong>, we report details of the stable structure and, for typical systems,<br />

we also present electr<strong>on</strong>ic structures and spin splitting in the band dispersi<strong>on</strong> relati<strong>on</strong>s.<br />

[1] C. R. Ast et al., Phys. Rev. Lett. 98, 186807 (2007). [2] K. Sakamoto et al., Phys. Rev. Lett. 102, 096805 (2009). [3]<br />

J. Ibanez-Azpiroz et al., Phys. Rev. B 84, 125435 (2011). [4] S. S. Lee et al., Phys. Rev. B 66, 233312 (2002).


PL07<br />

Exchange bias effect in Ni(Zn)O film<br />

R. Ray 1 *, S. Biswas 1 , S. Das 2 , S. Majumdar 2 and S. Giri 2<br />

1 Department of Physics, Jadavpur University, India<br />

2 Solid State Physics, Indian Associati<strong>on</strong> for the Cultivati<strong>on</strong> of Science, India<br />

Exchange bias (EB) has received significant attenti<strong>on</strong>s for fundamental interest and<br />

potential applicati<strong>on</strong>s in magnetic memory and read heads. Recently, EB is observed in<br />

various alloys and compounds [1]. Magnetic nanoparticles have been found promising<br />

for significant EB effect where surface spins were found to have different magnetic<br />

anisotropy than core spins, causing sizable EB effect. Compared to the studies of EB in<br />

nanoparticles, these studies in film geometry having chemically single phase are rarely<br />

investigated, which is rather promising for technological applicati<strong>on</strong>s. Here, we report<br />

EB in Ni 1-xZn xO films where Zn substituti<strong>on</strong> in NiO significantly modifies magnetic<br />

properties and EB effect. Atomic Force Microcopy exhibits formati<strong>on</strong> of granular films<br />

of average grain size ≈25 nm. We note that EB field (HE) and coercivity (HC) decrease<br />

c<strong>on</strong>siderably with Zn substituti<strong>on</strong> at x = 0.3 and HE vanishes at x = 0.5. Appearance<br />

EB in NiO film is suggested due to significant difference in anisotropy between core<br />

and surface spins, as it has been c<strong>on</strong>jectured for NiO nanoparticles. The Zn substituti<strong>on</strong><br />

appreciably decreases the difference between core and surface anisotropy causing the<br />

reducti<strong>on</strong> of HE as well as HC.<br />

[1] S. Giri et al. J. Phys.: C<strong>on</strong>dens. Mater 23 (2011) 073201.<br />

PL08<br />

Electr<strong>on</strong>ic properties of transiti<strong>on</strong> metal oxides interface between<br />

GdTiO 3SrTiO 3<br />

Sungbin Lee 1 * and Le<strong>on</strong> Balents 2<br />

1 University of California, Santa Barbara, USA<br />

2 Kavli Institute for Theoretical Physics, University of California, Santa Barbara, USA<br />

The creati<strong>on</strong> of a two dimensi<strong>on</strong>al electr<strong>on</strong> gas (2DEG) at the interface between two<br />

insulating oxides has been a subject of great interest, and much experimental activity<br />

has centered <strong>on</strong> the LaAlO 3SrTiO 3 interface. The (001) GdTiO 3SrTiO 3 interface has<br />

the same naive polarizati<strong>on</strong> disc<strong>on</strong>tinuity as the former system, but unlikely it actually<br />

exhibits a 2DEG with the expected e/2 charge per planar unit cell.[1] Motivated by<br />

recent experiments, which show that the 2DEG primarily lives in the SrTiO 3, we<br />

c<strong>on</strong>struct a theoretical tight-binding model and discuss the electr<strong>on</strong>ic properties in<br />

comparis<strong>on</strong> with experiment, and c<strong>on</strong>sider possible magnetism in this system at low<br />

temperature.<br />

[1] P. Moetakef et al., Appl. Phys. Lett. 99, 232116 (2011)<br />

PL09<br />

Parallel ferromagnetic res<strong>on</strong>ance and spin wave excitati<strong>on</strong> in<br />

exchange-biased NiFe/IrMn bilayers<br />

Marcos Sousa 1 *, Fernando Pelegrini 1 , Justiniano Marcatoma 2 , Willian Alayo 2 and<br />

Elisa Baggio-saitovitch 2<br />

1 Universidade Federal de Goias - UFG, Brazil<br />

2 Centro Brasileiro de Pesquisas Fisicas, Brazil<br />

Ferromagnetic Res<strong>on</strong>ance (FMR) investigati<strong>on</strong> of magnetr<strong>on</strong> sputtered exchange-biased<br />

Si 111Ru 7nmNiFe tIrMn 6nmRu 5nm bilayers reveals that spin wave and uniform res<strong>on</strong>ance modes<br />

are excited by the microwave field. The samples studied were produced in the presence of a<br />

400 Oe magnetic field to set the unidirecti<strong>on</strong>al anisotropy and the thickness t of the NiFe layer<br />

varied in the range 55-120 nm. The FMR experiments were d<strong>on</strong>e at room temperature using a<br />

commercial spectrometer with swept static magnetic field and the usual detecti<strong>on</strong> techniques.<br />

In-plane angular variati<strong>on</strong> of res<strong>on</strong>ance fields of spin wave and uniform modes reveal for both<br />

modes the dependence <strong>on</strong> cosθ, where θ is the field angle with respect to the anisotropy axis. The<br />

unidirecti<strong>on</strong>al anisotropy field for the spin wave mode is twice larger than that for the uniform<br />

mode; they are equal to 40 and 20 Oe, respectively, for the Si 111Ru 7nmNiFe 65nmIrMn 6nmRu 5nm<br />

sample. Spin wave res<strong>on</strong>ance theory give for the NiFe layer of this sample the exchange c<strong>on</strong>stant<br />

of 1.2 × 10^(-6) erg/cm. The parallel FMR results at microwave frequencies of 9.45 and 34.1<br />

GHz agree with the values given by the res<strong>on</strong>ance fields of spin wave and uniform modes also<br />

excited in perpendicular FMR at a frequency of 9.45 GHz.<br />

[1] W. Stoeklein, S. S. Parkin and J. C. Scott, Phys. Rev. B 38, 6847 (1988). [2] M. Nisenoff and R. W. Terhune, J. Appl.<br />

Phys. 36, 733 (1964). [3] V. S. Speriosu, S. S. P. Parkin, and C. H. Wilts, IEEE Trans. Magn. 23, 2999 (1987).<br />

PL10<br />

PL11<br />

PL12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Morphological c<strong>on</strong>siderati<strong>on</strong> for post-annealed Cr2O3 surface and<br />

exchange bias in bilayer system<br />

Tomohiro Nozaki*, Naoki Shimomura, Takuya Ashida, Yuji Sato and Masashi<br />

Sahashi<br />

Graduate school of Electr<strong>on</strong>ic Engineering, Tohoku University, Japan<br />

Magnetoelectric Cr 2O 3 has been received renewal of attenti<strong>on</strong>s as a promising material<br />

for the low energy c<strong>on</strong>sumpti<strong>on</strong> electric c<strong>on</strong>trolled spintr<strong>on</strong>ic devices such as MERAM<br />

[1]. High exchange bias field (Hex) between ferromagnetic layer and Cr 2O 3 thin film<br />

layer, and low coercivity (Hc) are essential for the applicati<strong>on</strong>s. Previously we reported<br />

the high Hex (~500 Oe) at the wide temperature range from 10 K to 250 K and the low<br />

Hc (~30 Oe) at 250 K for post-annealed Cr 2O 3 thin film system [2]. In this study we<br />

compared the morphology and magnetic properties of the post-annealed sample with<br />

that of samples fabricated by other manners and examined the origin of the high Hex<br />

and low Hc of the post-annealed sample. The post-annealed sample was identified to be<br />

polycrystalline, which would c<strong>on</strong>tribute to the low Hc. From TEM and AFM images,<br />

flat (1-102) planes (r-planes) were observed diag<strong>on</strong>ally to the film surface which are<br />

formed during the post annealing by grain growth due to the low surface energy [3].<br />

From the fact that Cr 2O 3 has uncompensated spin not <strong>on</strong>ly c-plane but also r-plane, we<br />

c<strong>on</strong>clude that the origin of the high Hex is the uncompensated r-plane.<br />

[1] X. Chen et al., Appl. Phys. Lett., 89 (2006) 202508. [2] T. Ashida et al., The 56th MMM<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, (2011) FE-05. [3] J. Sun et al., Surf. Coat. Tech., 201 (2006) 4205.<br />

Magnetic properties of [NiFe/NiFeCuMo/NiFe]/FeMn¬multilayers<br />

depending <strong>on</strong> a thickness of NiFeCuMo layer<br />

J<strong>on</strong>g-gu Choi 1 , Kwang-jun Park 2 , Jang-rho Rhee 3 and Sangji-suk Lee 2 *<br />

1 Eastern-Western Biomedical Engineering, Sangji University, Korea<br />

2 Oriental Biomedical Engineering, Sangji University, Korea<br />

3 Physics, Sookmyung Women’ University, Korea<br />

Variati<strong>on</strong>s in the exchange bias field (HEX) and coercivity (HC) of the intermediately<br />

super-soft magnetic NiFeCuMo layer were investigated for different thicknesses of the<br />

bottom NiFe layer. HEX of the triple pinned NiFe 4 nmNiFeCuMo (tNiFeCuMo = 1 nm)/<br />

NiFe 4 nmFeMn multilayer has a maximum value that is more less than that of a single<br />

pinned NiFe 8 nmFeMn layer. If a NiFeCuMo layer is inserted between the pinned and<br />

free NiFe layers, this multilayer system can be used as a giant magnetoresistive spinvalve<br />

(GMR-SV) device for biosensors with improved magnetic sensitivity.<br />

[1] J. G. Choi, D. G. Hwang, S. S. Lee, J. H. Choi, K A. Lee, and J. R. Rhee, J. Kor. Magn. Soc. 19,<br />

197 (2009). [2] J. G. Choi, D. G. Hwang, S. S. Lee, and J. R. Rhee, J. Kor. Magn. Soc. 19, 142 (2009).<br />

[3] J. G. Choi, D. G. Hwang, J. R. Rhee, and S. S. Lee, J. Magn. Magn. Mater. 322. 2191 (2010).<br />

[4] W. F. Egelhoff Jr., R. D. McMichael, C. L. Dennis, M. D. Stiles, F. Johns<strong>on</strong>, A. J. Shapiro. B. B.<br />

Maranville, C. J. Popwell, Thin Solid Films 505, 90 (2006).<br />

Structural and magnetic properties of antiferromagnetic Heusler<br />

Ru 2MnGe epitaxial thin films<br />

Naoto Fukatani*, Hirohito Fujita, Tetsuya Miyawaki, Kenji Ueda and Hidefumi<br />

Asano<br />

Nagoya University, Japan<br />

Recently, it is suggested that spin transport phenomena observed in c<strong>on</strong>venti<strong>on</strong>al spintr<strong>on</strong>ics<br />

ought to occur in systems where all FM materials are replaced by antiferromagnetic (AFM)<br />

materials. Although various studies have investigated FM Heusler alloys, very few studies<br />

have been made <strong>on</strong> AFM Heusler alloys in terms of spintr<strong>on</strong>ic applicati<strong>on</strong>s. The AFM<br />

transiti<strong>on</strong> temperatures (TN) of Heusler alloy such as Fe 2VSi can be c<strong>on</strong>trolled by inducing<br />

biaxial strain[1]. Thus we investigate the correlati<strong>on</strong> between structural and magnetic<br />

properties of epitaxial thin films of AFM Ru 2MnGe. Structural characterizati<strong>on</strong> revealed<br />

that Ru 2MnGe films <strong>on</strong> MgO were subjected to compressive strain (c/a = 1.0042). The<br />

strained Ru 2MnGe exhibited markedly enhanced TN of 353 K compared to the bulk value<br />

(316 K)[2]. The in-plane Mn-Mn distance for the strained Ru 2MnGe is slightly smaller than<br />

that of bulk Ru 2MnGe, which may c<strong>on</strong>tribute to reducing the total J2 values, resulting in<br />

the enhancement of TN. We also observed the exchange coupling between Heusler-type<br />

FM half-metal Fe 2CrSi and AFM metal Ru 2MnGe. The present AFM Heusler alloy with<br />

relatively high TN is useful to fabricate high-quality all Heusler-type half-metal FM/AFM<br />

juncti<strong>on</strong>s and is a promising material for the emerging field of AFM spintr<strong>on</strong>ics.<br />

[1] N. Fukatani, C. Shishikura, Y. Takeda, and H. Asano, Appl. Phys. Expr. 2, (2009) 053001. [2] T.<br />

Kanomata, M. Kikuchi, and H. Yamauchi: J. Alloys Compd. 414 (2006) 1-7.<br />

July 8 - 13, 2012 Busan, Korea 51<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PL13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Exchange-spring phenomen<strong>on</strong> of ultrathin Fe/CoPt bilayer<br />

Wei-hsiang Chen 1 , Hsing-hsuane Wu 1 , Huei-ying Ho 2 and Jyh-shen Tsay 1 *<br />

1 Physics, Nati<strong>on</strong>al Taiwan Normal University, Taiwan<br />

2 Physics, Department of Science Educati<strong>on</strong>, Nati<strong>on</strong>al Taipei University of Educati<strong>on</strong>,<br />

Taiwan<br />

A large enhancement in the polar magneto-optic Kerr signal was observed after <strong>on</strong>e<br />

m<strong>on</strong>olayer (ML) of Co adatoms <strong>on</strong> Pt(111) was annealed above 600 K to form a Co-<br />

Pt alloy at the interface [1]. In this c<strong>on</strong>tributi<strong>on</strong>, the compositi<strong>on</strong>, surface structure<br />

and magnetic properties of ultrathin Fe films <strong>on</strong> the top of a Co-Pt(111) surface alloy<br />

has been investigated. As the Fe coverage increases <strong>on</strong> the top of the Co-Pt alloy, the<br />

polar Kerr rotati<strong>on</strong> increases. By way of systematically changing the Fe thickness, the<br />

magnetic properties of Fe/CoPt in both the polar and l<strong>on</strong>gitudinal c<strong>on</strong>figurati<strong>on</strong>s are<br />

investigated for Fe thinner than 7 ML. At an optimal c<strong>on</strong>diti<strong>on</strong> for both the Fe thickness<br />

and the annealing temperature for preparing the Co-Pt alloy, the polar coercive force<br />

remains the same as the Fe coverage increases. The Fe/CoPt system exhibits magnetic<br />

exchange-spring behavior in the polar c<strong>on</strong>figurati<strong>on</strong>. The interfacial c<strong>on</strong>diti<strong>on</strong>s for the<br />

Fe/CoPt system are dem<strong>on</strong>strated to play an important role <strong>on</strong> the exchange-spring<br />

phenomen<strong>on</strong> and will be discussed in this c<strong>on</strong>tributi<strong>on</strong>.<br />

[1] C.S. Shern, J.S. Tsay, H.Y. Her, Y.E. Wu, and R.H. Chen, Surf. Sci. Lett. 429 (1999) L497.<br />

PL14<br />

Neutr<strong>on</strong> magnetic scattering study in manganite thin film system<br />

H. Nakao 1 *, H. Yamada 2 , K. Iwasa 3 , J. Okamoto 1 , Y. Yamasaki 1 , Y. Murakami 1 and A.<br />

Sawa 2<br />

1 C<strong>on</strong>densed Matter Research Center and Phot<strong>on</strong> Factory, IMSS, KEK, Japan<br />

2 Electr<strong>on</strong>ics and Phot<strong>on</strong>ics Research Institute, AIST, Japan<br />

3 Department of Physics, Tohoku University, Japan<br />

Perovskite manganites show various interesting phenomena including colossal magnetoresistance<br />

(MR) due to a close interplay am<strong>on</strong>g charge, orbital, spin, and lattice degrees of freedom. The<br />

superlattice [(LaMnO 3) m(SrMnO 3) m] n was investigated as a stage to c<strong>on</strong>trol the Mn valence<br />

artificially. The physical properties were reported to str<strong>on</strong>gly depend <strong>on</strong> the periodicity m, and<br />

the interface state between LaMnO 3 and SrMnO 3 layer was noted.[1] The stacking structure<br />

of Mn valence state by res<strong>on</strong>ant x-ray scattering technique has been studied.[2] It elucidated<br />

that the physical properties just depend <strong>on</strong> the quality of the film. Recently, however, new large<br />

MR effect was discovered in the high quality superlattice system.[3] To understand the MR<br />

effect microscopically, the Mn valence state and the magnetic field effect were studied. Here the<br />

magnetism is also important, and then neutr<strong>on</strong> magnetic scattering experiment was started using<br />

the neutr<strong>on</strong> spectrometer TOPAN in JRR-3. As a first step, SrMnO 3 film with 80 nm thickness<br />

has been investigated. A signal with about 2 cps at (0.5, 0.5, 0.5) corresp<strong>on</strong>ding G-type AFM<br />

was certainly discovered. The temperature dependence of the signal intensity was also measured.<br />

C<strong>on</strong>sequently we have succeeded in observing magnetic scattering from thin film system.<br />

[1] T. Koida et al., Phys. Rev. B 66 (2002) 14418. [2] H. Nakao et al., J. Phys. Soc. Jpn. 78 (2009)<br />

024602. [3] H. Yamada et al., Phys. Rev. B 81 (2010) 014410.<br />

PL15<br />

Directi<strong>on</strong> and temperature dependences of exchange bias and<br />

coercivity of NiFe/Cr 2(1-x)Fe 2xO 3(x= 0.25, 0.4) bilayers<br />

Sangho<strong>on</strong> Ki, Bye<strong>on</strong>g-ge<strong>on</strong> Kim and Jo<strong>on</strong>ghoe Dho*<br />

Kyungpook Nati<strong>on</strong>al University, Korea<br />

The antiferromagnets α-Fe 2O 3 and α-Cr 2O 3 have the same crystal structure but different<br />

magnetic orderings. The AF spin structure for a-Cr 2O 3(TN~307 K) is represented by<br />

the up-down-up-down spin ordering al<strong>on</strong>g c-axis, while that for a-Fe 2O 3(TN~953 K)<br />

is d<strong>on</strong>e by the up-down-down-up <strong>on</strong>e. As reported in previous neutr<strong>on</strong> diffracti<strong>on</strong><br />

study for the solid soluti<strong>on</strong> Cr 2(1-x)Fe 2xO 3(CFO), such c<strong>on</strong>tradictory spin structures<br />

may result in a new type AF structure such as spiral order or cycloidal order. Here, we<br />

report exchange bias in NiFe/Cr 2(1-x)Fe 2xO 3(x= 0.25, 0.4) bilayers grown <strong>on</strong> c-plane<br />

and r-plane Al 2O 3. The directi<strong>on</strong> and temperature dependences of magnetic property<br />

of NiFe/CFO layer substrates were checked by a surface magneto-optical Kerr effect<br />

(SMOKE) setup. At room temperature, the M(H) loop of the NiFe layer exhibited<br />

enhanced coercivity and exchange bias depending <strong>on</strong> the measurement directi<strong>on</strong> and<br />

the temperature. In order to see the directi<strong>on</strong> dependence of magnetic property of NiFe<br />

layer, the magnetic field was applied to two orthog<strong>on</strong>al directi<strong>on</strong>s within the plane.<br />

Interestingly, the temperature dependence of M(H) loop exhibited some features of<br />

spin reorientati<strong>on</strong> of CFO layer below antiferromagnetic transiti<strong>on</strong> temperature.<br />

52 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PL16<br />

Structure and magnetic properties of epitaxial Fe/MgO/Si (001)<br />

heterostructures<br />

Je<strong>on</strong>g H<strong>on</strong>g Jo 1 , Kyung-ho Kim 2 , Yo<strong>on</strong> Jae Nam 3 , Hyung-jun Kim 2 , Jo<strong>on</strong>ye<strong>on</strong> Chang 2<br />

and Sang Ho Lim 1 *<br />

1<br />

Department of Materials Science and Engineering, Korea University, Seoul 136-713, Korea<br />

2<br />

Spin C<strong>on</strong>vergence Research Center, Korea Institute of Science and Technology, Seoul 136-791,<br />

Korea<br />

3<br />

Department of Nano Semic<strong>on</strong>ductor Engineering, Korea University, Seoul 136-713, Korea<br />

The ferromagnetic metal/semic<strong>on</strong>ductor structures with inserting a thin MgO tunneling barrier are<br />

expected to play a key role in spin-based electr<strong>on</strong>ic applicati<strong>on</strong>s to enhance spin injecti<strong>on</strong> efficiency.<br />

Recently, spin-based devices using silic<strong>on</strong> channel enable seamless integrati<strong>on</strong> with c<strong>on</strong>venti<strong>on</strong>al<br />

MOS-FET technology. However, there are <strong>on</strong>ly a few reports <strong>on</strong> ferromagnetic metal/MgO/Si<br />

system due to large lattice mismatch (3.5%) between Si and MgO. The study <strong>on</strong> strain induced<br />

microstructure of the Fe and MgO layers is essential because the lattice mismatch between Si and<br />

MgO results in distorti<strong>on</strong> in both MgO and Fe layers. In additi<strong>on</strong>, the magnetic property of the<br />

ferromagnetic metal with respect to its microstructure evoluti<strong>on</strong> is also of importance in terms of<br />

spin injecti<strong>on</strong>. In this study, Fe thin films of thinner than 2 nm, were prepared <strong>on</strong> Si (001) substrates<br />

with 4 nm thick MgO buffer layer by a molecular beam epitaxy system at room temperature and<br />

200 °C, respectively. X-ray diffracti<strong>on</strong> and reflecti<strong>on</strong> high-energy electr<strong>on</strong> diffracti<strong>on</strong> results show<br />

epitaxial relati<strong>on</strong>ship of the system. In-plane four-fold magnetic anisotropy was observed by<br />

vibrating sample magnetometer, suggesting that elevated growth temperature of the Fe films leads<br />

to the strain relaxati<strong>on</strong> and the suppressi<strong>on</strong> of two-dimensi<strong>on</strong>al Fe layer formati<strong>on</strong>.<br />

PL17<br />

Uncompensated magnetic moment around Mn 3Ir / Fe-Co-Ni bilayer<br />

interface<br />

Yohei Kota*, Hirokazu Takahashi, Masakiyo Tsunoda and Akimasa Sakuma<br />

Graduate School of Engineering, Tohoku University, Japan<br />

We study the microscopic origin of the uncompensated moment in Mn 3Ir / Fe-Co-Ni bilayer,<br />

which is practically utilized system due to the excellent property of exchange anisotropy, by the<br />

theoretical and experimental approach. In order to induce exchange anisotropy, the magnetic<br />

structure in the ferromagnetic / antiferromagnetic bilayer needs to have some asymmetry<br />

against the field reversal, and the uncompensated moments around the interface is a candidate<br />

for the spin asymmetry. We previously reported that there is a linear correlati<strong>on</strong> between the<br />

exchange anisotropy and uncompensated moments measured by the x-ray magnetic circular<br />

dichroism (XMCD) experiment in Mn-Ir / Co-Fe bilayer [1]. Therefore, in the present work, we<br />

investigate the compositi<strong>on</strong> dependence of the uncompensated moment in Mn 3Ir / Fe-Co-Ni by<br />

performing the first-principles calculati<strong>on</strong> and the XMCD measurement to clarify the origin of<br />

the uncompensated moment. In the comparis<strong>on</strong> of the calculati<strong>on</strong> and experimental results, the<br />

obtained uncompensated moments are in good agreement for their sign and relative magnitude<br />

[2]. Furthermore, the calculated result reveals that the uncompensated moment originates<br />

from the local magnetic correlati<strong>on</strong> near the interface. So we find that the reorientati<strong>on</strong> of the<br />

magnetic moments of Mn occur at the very interface with the ferromagnetic layer.<br />

[1] M. Tsunoda, H. Takahashi, T. Nakamura, C. Mitsumata, S. Isogami, and M. Takahashi, Appl.<br />

Phys. Lett. 97, 072501 (2010). [2] H. Takahashi, Y. Kota, M. Tsunoda, T. Nakamura, K. Kodama, A.<br />

Sakuma, and M. Takahashi, J. Appl. Phys. 110, 123920 (2011).<br />

PL18<br />

Unusual exchange bias effects in NiFe/Mn thin films induced via i<strong>on</strong>beam<br />

bombardment<br />

Chi-hsin Liu 1 , Chin Shueh 1 , Yi-wen Ting 1 , Wen-chen Chen 2 , Te-ho Wu 2 , Johan Van Lierop 3 and Ko-wei Lin 1 *<br />

1 Dept of Materials Science and Engineering, Nati<strong>on</strong>al Chung Hsing University, Taiwan<br />

2 Graduate School of Material Science, Nati<strong>on</strong>al Yunlin University of Science and Technology, Taiwan<br />

3 Department of Physics and Astr<strong>on</strong>omy, University of Manitoba, Canada<br />

When spins at the interface between a ferromagnet (FM) and an antiferromagnet (AF) couple, a<br />

unidirecti<strong>on</strong>al anisotropy occurs, resulting in exchange bias [1,2]. In this study, we wish to identify the<br />

dependence of the exchange bias <strong>on</strong> the interface microstructure in NiFe/Mn thin films. A series of [NiFe/<br />

Mn] multilayer thin films were fabricated using a dual i<strong>on</strong>-beam depositi<strong>on</strong> technique [3]. Different Ar-i<strong>on</strong><br />

depositi<strong>on</strong> voltages created striking differences in magnetic properties. The [NiFe/Mn] (VEH= 0 V, i.e. unbombarded)<br />

thin film (~ 200 nm) at 5 K when 20 kOe field-cooled (FC), exhibited an enhanced coercivity<br />

(Hc~ 935 Oe) and positive exchange bias field, Hex~ +130 Oe. By c<strong>on</strong>trast, the [NiFe/Mn] (VEH= 150<br />

V) Ar-i<strong>on</strong> bombarded thin film (~ 20 nm) at 5 K when 20 kOe field cooled showed a larger positive Hex<br />

(~ +160 Oe) with smaller Hc (~ 610 Oe) accompanied by an asymmetric hysteresis loop. The observed<br />

enhanced positive Hex indicated that the transiti<strong>on</strong> from FM to AF coupling was made possible by<br />

changing the i<strong>on</strong>-beam bombardment voltages. Further, the role of Ar i<strong>on</strong>-bombardment seems to change<br />

both the spin orientati<strong>on</strong>s in FM NiFe and AF Mn and thus gives rise to the positive enhanced Hex.<br />

[1] T. Saerbeck, F. Klose, D. Lott, G.J. Mankey, Z. Lu, P.R. LeClair, W. Schmidt, A. Stampfl, S. Danilkin, M.<br />

Yethiraj, A. Schreyer, Phys. Rev. B 82, 134409 (2010). [2] H. Ouyang, Y.-H. Han, S.-C. Lo, C.-H. Su, Y.-R.<br />

Shiu, K.-W. Lin, R. D. Desautels, and J. van Lierop, Phys. Rev. B 81, 224412 (2010). [3] K.-W. Lin, V. V.<br />

Volobuev, J.-Y. Guo, S.-H. Chung, H. Ouyang, and J. van Lierop, J. Appl. Phys. 107, 09D712 (2010).


PL19<br />

Exchange bias effect in BiFeO 3 thin films<br />

Kil-d<strong>on</strong>g Sung and J<strong>on</strong>gho<strong>on</strong> Jung*<br />

Physics, Inha University, Korea<br />

We fabricated BiFeO3 thin films with Bi 2O 3 or γ-Fe 2O 3 impurities by changing oxygen<br />

partial pressures and characterized their magnetic properties. Since Bi 2O 3 impurity is a<br />

n<strong>on</strong>-magnetic material, <strong>on</strong>ly antiferromagnetic spins of BiFeO 3 will c<strong>on</strong>tribute to whole<br />

magnetic properties. But γ-Fe 2O 3 impurity is a well known ferrimagnetic material,<br />

so there is a possibility to show exchange bias effect with antiferromagnetic spins of<br />

BiFeO 3. We measured M(H) loop at various temperatures after zero- and ±5 T-field<br />

cooling. Almost no but very small amount of M(H) hysteresis loop was appeared<br />

in BiFeO 3 with Bi 2O 3 impurity. Which indicate that there is uncompensated spins<br />

in BiFeO 3 which generate exchange bias effect with γ-Fe 2O 3. Significant hysteresis<br />

loop was appeared in BiFeO 3 with γ-Fe 2O 3 impurity. Depending <strong>on</strong> the field cooling<br />

directi<strong>on</strong>, the M(H) loops also shifted to the opposite directi<strong>on</strong>s. But unlike other<br />

c<strong>on</strong>venti<strong>on</strong>al exchange bias systems, the interacti<strong>on</strong> between ferrimagnetic spins of<br />

γ-Fe 2O 3 and antiferromagnetic spins of BiFeO 3 is not so str<strong>on</strong>g as shown in the training<br />

effect result.<br />

PL20<br />

Experiment evidence to the existence of interacti<strong>on</strong> between<br />

antiferromagnetic domains in IrMn/Pt/Co/Pt multilayers<br />

X. J. Bai 1 , Z. Shi 2 , S. M. Zhou 2 *, X. R. Zhao 1 and C. D. Cao 1<br />

1<br />

Key Laboratory of Space Applied Physics and Chemistry, Northwestern<br />

Polytechnical University, Xi’an, China<br />

2<br />

Department of Physics, T<strong>on</strong>gji University, Shanghai 200092, China<br />

Exchange bias phenomen<strong>on</strong> has become an integral part of the modern magnetism, with implicati<strong>on</strong>s<br />

in basic research and applicati<strong>on</strong>s in magnetoelectr<strong>on</strong>ic devices. In the numerous experimental and<br />

theoretical studies, the surface layer of antiferromagnetic (AFM) material is often regarded as an<br />

assembly of uniaxial domains, which are independence from each other. This basic assumpti<strong>on</strong> is<br />

really suspect. In our presented work, experiment evidence of interacti<strong>on</strong> between AFM domains has<br />

been found. The IrMn/Pt/Co/Pt perpendicular exchange bias systems were fabricated and treated by<br />

AC demagnetizati<strong>on</strong> (ACDM) parallel to the film plane at high temperature. The purpose of ACDM<br />

is to get the pinned demagnetizati<strong>on</strong> state in ferromagnetic layer. In the corresp<strong>on</strong>ding hysteresis<br />

loop, two minor-loops shift oppositely al<strong>on</strong>g the magnetic field axis and locate totally <strong>on</strong> <strong>on</strong>e side<br />

of the vertical axis. Compare the training effects of the minor-loop and full-loop, we found that <strong>on</strong>e<br />

minor-loop measurement gives influence to the other. It is reas<strong>on</strong>able that the influence is attributed<br />

to the interacti<strong>on</strong> between the IrMn surface domains. Our experiment facts can not be explained by<br />

the past theory models, new energy item of interacti<strong>on</strong> between AFM domains should be c<strong>on</strong>sidered.<br />

[1] C. H. Lai, W. E. Bailey, R. L. White, T. C. Anth<strong>on</strong>y, J. Appl. Phys. 81 4990 (1997) [2] T. Hauet, S. Mangin, J. McCord, F.<br />

M<strong>on</strong>taigne, and E. E. Fullert<strong>on</strong>, Phys. Rev. B 76, 144423 (2007) [3] X. P. Qiu, D. Z. Yang, S. M. Zhou, R. Chantrell, K. O’Grady, U.<br />

Nowak, J. Du, X. J. Bai, and L. Sun, Phys. Rev. Lett. 101, 147207 (2008) [4] E. Fulcomer, S. H. Charap, J. Appl. Phys. 43, 4190 (1972)<br />

PL21<br />

Nanoscale investigati<strong>on</strong> of the Cr/Fe(001) interface grown by oxygen<br />

assisted epitaxy<br />

Alberto Brambilla 1 *, Andrea Pic<strong>on</strong>e 1 , Guido Fratesi 2 , Alberto Call<strong>on</strong>i 1 , Michele Riva 1 , Gianlorenzo<br />

Bussetti 1 , Alberto Ferrari 1 , Lamberto Duo' 1 , Marco Finazzi 1 , Mario Italo Tri<strong>on</strong>i 3 and Franco Ciccacci 1<br />

1 Dipartimento di Fisica, Politecnico di Milano, Piazza Le<strong>on</strong>ardo Da Vinci 32, 20133 Milano, Italy<br />

2 Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy<br />

3 CNR, Nati<strong>on</strong>al Research Council of Italy, ISTM, Via Golgi 19, 20133 Milano, Italy<br />

Cr depositi<strong>on</strong> <strong>on</strong> Fe(100) has been the subject of intense investigati<strong>on</strong>s in the past, being an excellent<br />

model system for thin film magnetism, and also because Fe/Cr multilayers played a fundamental role in the<br />

development of giant magneto resistive devices [1]. The magnetic properties of such systems can be affected<br />

by parameters like interfacial mixing, strain and defects. For instance, previous investigati<strong>on</strong>s have shown<br />

that, within the atom distributi<strong>on</strong> resulting from Cr incorporati<strong>on</strong> into the Fe substrate, nearest neighbour Cr-<br />

Cr coupling is energetically less favorable than next nearest neighbor coupling, due to magnetic frustrati<strong>on</strong>s<br />

[2]. Here we employ experimental and theoretical methods to highlight and characterize deviati<strong>on</strong>s in the<br />

micromagnetic structure of the Cr/Fe interface due to the presence of adsorbed O, which induces a layerby-layer<br />

Cr growth at room temperature, as we recently dem<strong>on</strong>strated [3]. Scanning tunnelling microscopy<br />

(STM) is used to investigate the depositi<strong>on</strong> of Cr <strong>on</strong> the Fe-p(1x1)O surface since the first stages of interface<br />

formati<strong>on</strong>. Atomic resoluti<strong>on</strong> STM images reveal the occurrence of different magnetic c<strong>on</strong>figurati<strong>on</strong>s,<br />

including first-neighboring Cr atoms in the Fe matrix. The observati<strong>on</strong>s are discussed in the light of densityfuncti<strong>on</strong>al<br />

simulati<strong>on</strong>s with the generalized gradient approximati<strong>on</strong> and plane waves basis set [4].<br />

[1] B. Heinrich, J.A.C. Bland (Eds.), Ultrathin Magnetic Structures, Springer Verlag, Berlin, (1994). [2] A. Davies, Joseph A.<br />

Stroscio, D. T. Pierce, and R. J. Celotta, Phys. Rev. Lett. 76, 4175 (1996). [3] A. Call<strong>on</strong>i, A. Pic<strong>on</strong>e, A. Brambilla, M. Finazzi, L. Duo, F.<br />

Ciccacci Surf. Sci. 605, 2095 (2011). [4] P. Giannozzi, N. Bar<strong>on</strong>i, M. B<strong>on</strong>ini et al., J. Phys.: C<strong>on</strong>dens. Matter 21, 395502 (2009).<br />

PM01<br />

PM02<br />

PM03<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Correlati<strong>on</strong> of soft magnetic properties with free volume and medium<br />

range ordering in metallic glasses<br />

Amit P Srivastava 1 *, D Srivastava 1 , P K Pujari 1 , K G Suresh 2 and G K Dey 1<br />

1 Bhabha Atomic Research Centre, Mumbai, India<br />

2 Indian Institute of Technology Bombay, Mumbai, India<br />

The effect of cooling rate <strong>on</strong> thickness and soft magnetic properties of the metallic<br />

glass of alloy compositi<strong>on</strong> Co 64.5Fe 3.5Si 16B 14Ni 2 have been studied. The amorphous<br />

structure has been characterized by positr<strong>on</strong> annihilati<strong>on</strong> spectroscopy (PAS) and<br />

fluctuati<strong>on</strong> electr<strong>on</strong> microscopy (FEM) techniques. These studies suggest that the<br />

first lifetime comp<strong>on</strong>ent is associated with MRO present in the amorphous structure.<br />

Theoretical calculati<strong>on</strong>s showed that sec<strong>on</strong>d comp<strong>on</strong>ent is associated with nanovoids<br />

having free volume equivalent to that of a vacancy defect c<strong>on</strong>sisting of 4 and more<br />

atom vacancy cluster. Coercivity of the samples showed small variati<strong>on</strong>s with wheel<br />

speed and it was found to decrease with the decrease in effective size of the defects<br />

present in the samples. This study reveals that, in case of amorphous metallic glass, the<br />

variati<strong>on</strong> in coercivity is mainly c<strong>on</strong>trolled by the defects formed during processing<br />

rather than the small variati<strong>on</strong>s in MRO introduced due to different cooling rates.<br />

Microscopic magnetic hysteresis measurement of amorphous Tb-TM<br />

(TM=Fe and Co) thin films by magnetic Compt<strong>on</strong> scattering<br />

Akane Agui 1 *, Tetsuya Unno 2 , Sayaka Matsumoto 2 , Kousuke Suzuki 2 and Hiroshi Sakurai 2<br />

1 Japan Atomic Energy Agency, Japan<br />

2 Dept. Producti<strong>on</strong> Sci & Technol., Gunma Univ., Japan<br />

Rare earth transiti<strong>on</strong> metal (RE-TM) alloys have attracted c<strong>on</strong>siderable attenti<strong>on</strong> from the viewpoint<br />

of fundamental research and technology. For instance, they have been studied as candidate heatassisted<br />

magnetic recording media for high-density magnetic storage. It is known that magnetic<br />

moment of RE and TM form ferrimagnetisms and have anisotropy dispersi<strong>on</strong> al<strong>on</strong>g magnetic<br />

easy axes, so-called sperri-magnetism [1]. The magnetic switching process of sperri magnetism<br />

is c<strong>on</strong>sidered not to be simple. In this report, we have study spin, orbital and also element specific<br />

magnetic switching process of amorphous Tb-TM (TM=Fe and Co) films by means of combinati<strong>on</strong><br />

of magnetic Compt<strong>on</strong> scattering [2, 3] and c<strong>on</strong>venti<strong>on</strong>al macroscopic magnetizati<strong>on</strong> measurements.<br />

As specimen, amorphous Tb 43Co 57 and Tb 32Fe 55 (O 13) thin films were fabricated by an RF sputtering<br />

<strong>on</strong>to a thin Al foil substrates. The macroscopic magnetizati<strong>on</strong> curves were measured by SQUID<br />

and VSM magnetometers. Magnetic Compt<strong>on</strong> scattering measurements were carried out at AR-<br />

NE1A of KEK [2] and at BL08W of SPring-8 [3], Japan. The present results suggest that magnetic<br />

switching can be different am<strong>on</strong>g the spin moment, the orbital moment, and even the states of<br />

electr<strong>on</strong>s, e.g., the Tb 4f electr<strong>on</strong>, TM 3d electr<strong>on</strong>, and itinerant electr<strong>on</strong>.<br />

References: [1] J. M. D. Coey, J. Chappert, J. P. Rebouillat, and T. S. Wang, Phys. Rev. Lett. 36 (1976) 1061. [2] A.<br />

Agui, H. Sakurai, T. Tamura, T. Kurachi, M. Tanaka, H. Adachi, and H. Kawata, J. Synchrotr<strong>on</strong> Rad., 17 (2010) 321. [3]<br />

A. Agui, S. Matsumoto, H. Sakurai, N. Tsuji, S. H<strong>on</strong>ma, Y. Sakurai, and M. Itou, APEX 4 (2011) 083002.<br />

A significant reducti<strong>on</strong> of hysteresis in MnFe(P,Si) compounds<br />

O. Tegus 1 *, Y. X. Geng 1 and J. H. Huang 2<br />

1<br />

Physics and Electr<strong>on</strong>ic Informati<strong>on</strong> College, Inner M<strong>on</strong>golia Normal University,<br />

Hohhot 010022, China<br />

2<br />

Baotou Research Institute of Rare Earths, Baotou 014030, China<br />

The magnetocaloric effects in Mn 1.3Fe 0.7-xCo xP 0.46Si 0.54 compounds with x = 0, 0.025,<br />

0.05 and 0.1 are studied systematically. X-ray diffracti<strong>on</strong> shows that the compounds<br />

in the range from x = 0 to 0.1 crystallize in the Fe 2P-type hexag<strong>on</strong>al structure with<br />

space group P-62m symmetry. Magnetic measurements show that the paramagneticferromagnetic<br />

transiti<strong>on</strong> temperatures range from 247 to 298 K. The maximum of<br />

magnetic entropy changes in Mn 1.3Fe 0.7P 0.46Si 0.54 compound reaches 8.3 J/kgK in a<br />

field change of 0 to 1.5 T, and the thermal hysteresis of these compounds is less than<br />

3 K. The maximum adiabatic temperature change is 2.2 K in Mn 1.3Fe 0.7P 0.46Si 0.54 and<br />

Mn 1.3Fe 0.65Co 0.05P 0.46Si 0.54 compounds for a field change from 0 to 1.48 T.<br />

July 8 - 13, 2012 Busan, Korea 53<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

PM04<br />

Temperature dependence of creep-induced anisotropy in<br />

nanocrystalline FeCuNbSiB alloys<br />

Giselher Herzer*, Mie Marsilius and Christian Polak<br />

R&D Rapid Solidificati<strong>on</strong> Technology, Vacuumschmelze GmbH & Co. KG, Germany<br />

We have investigated the creep induced anisotropy in nanocrystalline<br />

Fe 75Cu 1Nb 3Si xB 21-x alloys as a functi<strong>on</strong> of the measuring temperature. The samples<br />

were produced by annealing originally amorphous ribb<strong>on</strong>s for about 4 s between 500°C<br />

and 700°C with a tensile stress applied al<strong>on</strong>g the ribb<strong>on</strong> axis. For Si-c<strong>on</strong>tents equal<br />

or larger than 9 at% the annealed ribb<strong>on</strong>s reveal a linear hysteresis loop indicative of<br />

an easy magnetic plane perpendicular to the stress axis. For lower Si-c<strong>on</strong>tents, stress<br />

annealing results in a square loop indicative of an easy magnetic axis parallel to the<br />

stress axis. This transiti<strong>on</strong> from an easy plane to an easy axis as a functi<strong>on</strong> of the Sic<strong>on</strong>tent<br />

is well-known from previous investigati<strong>on</strong>s and is related to the dependence<br />

of local magnetostricti<strong>on</strong> of the nanocrystals <strong>on</strong> the Si-c<strong>on</strong>tent. However, the<br />

investigati<strong>on</strong>s so far have been <strong>on</strong>ly carried out at room temperature. The present work,<br />

for the first time, reveals that the Si-c<strong>on</strong>tents where the easy axis changes its directi<strong>on</strong><br />

shifts to higher c<strong>on</strong>centrati<strong>on</strong>s as the temperature increases. This is also nicely reflected<br />

in a reversible change from a linear hysteresis loop with low remanence to a square<br />

loop as a functi<strong>on</strong> of the measuring temperature.<br />

PM05<br />

Magnetocaloric properties of Ni-Co-Mn-In ribb<strong>on</strong><br />

M. U. Gutowska 1 *, J. Wieckowski 1 , A. Szewczyk 1 , W. Maziarz 2 , N. Nedelko 1 , S.<br />

Lewinska 1 , A. Slawska - Waniewska 1 , M. Kowalczyk 3 and A. Kolano - Burian 4<br />

1<br />

Institute of Physics, Polish Academy of Sciences, Warsaw, Poland<br />

2<br />

Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Cracow,<br />

Poland<br />

3<br />

Faculty of Materials Engineering, Warsaw University of Technology, Warsaw,<br />

Poland<br />

4<br />

Institute of N<strong>on</strong>-Ferrous Metals, Gliwice, Poland<br />

Temperature dependences of two parameters characterizing magnetocaloric effect (isothermal change<br />

in entropy and adiabatic change in temperature) were determined for a Ni 47Co 3Mn 35.5In 14.5 ribb<strong>on</strong>. Two<br />

experimental methods were used, i.e., measuring temperature dependences of a specific heat (from 3 to<br />

380 K) in zero magnetic field and in the field B=1 T, and measuring dependences of magnetizati<strong>on</strong> <strong>on</strong><br />

temperature and <strong>on</strong> B. In the former method, both parameters were determined by analyzing the system<br />

entropy (determined by integrating the measured specific heat). In the latter method, the Maxwell relati<strong>on</strong><br />

was applied to get the isothermal change in entropy. The magnetocaloric effect shows two extrema of<br />

opposite sign, <strong>on</strong>e near the transiti<strong>on</strong> between martensitic and austenitic phases, and the other <strong>on</strong>e at<br />

the Curie temperature. The parameters characterizing the magnetocaloric effect near room temperature<br />

in relatively low B (1 T) make this material promising for applicati<strong>on</strong> in magnetic refrigerators. The<br />

magnetocaloric effect was found to be highly anisotropic, being much larger for B applied in the ribb<strong>on</strong><br />

plane. This property is particularly useful for designs, in which the active medium rotates in the field.<br />

This work was supported by the European Regi<strong>on</strong>al Development Fund, Innovative Ec<strong>on</strong>omy Grants<br />

POIG.01.01.02-00-108/09, POIG.01.03.01-00-058/08 and POIG.02.02.00-00-025/09.<br />

PM06<br />

Influence of bismuth substituti<strong>on</strong> <strong>on</strong> the magnetocaloric properties of<br />

Gd5Si2Ge2 compound<br />

Corneliu Bazil Cizmas 1 *, Rim Guetari 2 , Lotfi Bessais 3 , Najeh Thabet Mliki 2 and Sorin Adam 1<br />

1<br />

Department of Electrical Engineering and Applied Physics, Transilvania University<br />

of Brasov, Bd. Eroilor 29, 500036 Brasov, Romania<br />

2<br />

LMOP, Department of Physics, Faculty of Sciences of Tunis, Tunis El Manar<br />

University, 2092 El Manar, Tunisia<br />

3<br />

ICMPE, UMR7182 CNRS, Universite Paris-Est Creteil, 2/8 rue Henri Dunant, B.P.<br />

28 F-94320 Thiais, France, France<br />

In order to study the influence of relative small Bi additi<strong>on</strong> <strong>on</strong> the magnetocaloric effect of Gd 5Si 2Ge 2, a<br />

series of Gd 5Si 2-xGe 2-xBi 2x (2x=0; 0.02; 0.04; 0.06 and 0.08) alloys was prepared by arc melting method.<br />

Investigati<strong>on</strong>s of Gd 5Si 2-xGe 2-xBi 2x properties where carried out using X-ray diffracti<strong>on</strong>, thermomagnetic<br />

analysis, magnetizati<strong>on</strong> isotherms measurements and differential scanning calorimetry (DSC). After a heat<br />

treatment at 1250°C for 200 min., all the alloys have, at room temperature, a m<strong>on</strong>oclinic structural phase<br />

of Gd 5Si 2Ge 2 type (S.G.: P112_1/a) with a small amount of hexag<strong>on</strong>al structural phase of Gd 5Si 3 type (S.G.:<br />

P63/mcm). The Curie temperature is around ~ 285K (±2K). The results of the DSC measurements show<br />

a difference of ~10K in the peak of the heating and cooling curves associated with a first order structural<br />

phase transiti<strong>on</strong>. The peak slightly decreases with Bi c<strong>on</strong>tent. This is expected to be related to the<br />

increasing of the Si/Ge b<strong>on</strong>d distance in the m<strong>on</strong>oclinic phase with Bi additi<strong>on</strong>. The maximum isothermal<br />

magnetic entropy change decreases with Bi additi<strong>on</strong>, however a giant magnetocaloric effect was obtained<br />

for all alloys. As an example, the maximum magnetic entropy change for the Gd 5Si 1.98Ge 1.98Bi 0.04 was<br />

found to be 12.6 J/kg•K under an applied field of 5T.<br />

54 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PM07<br />

I<strong>on</strong> incient energy effects <strong>on</strong> the giant magnetoimpedance<br />

enhancement<br />

Ho<strong>on</strong> S<strong>on</strong>g and D.g. Park*<br />

korea atomic energy research institute, Korea<br />

The present experiment investigates the physical effects of i<strong>on</strong> irradiati<strong>on</strong> <strong>on</strong> the<br />

magnetic properties of the amorphous ribb<strong>on</strong>. Samples were commercial amorphous<br />

ribb<strong>on</strong> with sizes of 2 mm x 40 mm x 20 μm. The Ar i<strong>on</strong>s were provided by an i<strong>on</strong><br />

implanter at various dosages from 100 keV to 200 keV at the 1.0 x1018 i<strong>on</strong>/cm2.<br />

The GMI ratio was measured as a functi<strong>on</strong> of the DC magnetic field (Hmax=35 Oe)<br />

at different driving frequencies up to 10 MHz with a 5 mA amplitude applied to the<br />

sample irradiated with different energy. The irradiated samples show a clear change<br />

in the impedance resp<strong>on</strong>se with applied field. When energetic i<strong>on</strong>s with energies of<br />

several tens of keV penetrate into a thin film, the collisi<strong>on</strong> cascade cause displacements<br />

of the target atoms that induce a uniaxial anisotropy in the sample. I<strong>on</strong> irradiati<strong>on</strong><br />

induces uniaxial anisotropy al<strong>on</strong>g the transverse directi<strong>on</strong>, which is accompanied by an<br />

effective transverse susceptibility. Therefore, the increase in the GMI ratio in an i<strong>on</strong>irradiated<br />

sample is attributed to the increase in associated uniaxial anisotropy created<br />

by i<strong>on</strong> bombardment.We found that c<strong>on</strong>trolling the i<strong>on</strong> energy can be <strong>on</strong>e of the<br />

effective ways of c<strong>on</strong>trolling the GMI property for i<strong>on</strong><br />

[1] E. Lee, S. Lee, W. Lee and C. E. Lee, J. Korean Phys. Soc. 56, 2108 (2010). [2] D. Pathak and R.<br />

K. Bedi, J. Korean Phys. Soc. 57, 474 (2010).<br />

PM08<br />

Investigati<strong>on</strong> of electrodeposited FeNi film prepared from tartaric acid<br />

based bath<br />

Takaya Shimokawa*, Takeshi Yanai, Ken-ichiro Takahashi, Masaki Nakano and<br />

Hirotoshi Fukunaga<br />

Nagasaki University, Japan<br />

FeNi films have been plated by using boric acid as pH buffer agent. However, the<br />

boric acid is needed to be replaced by another <strong>on</strong>e which does not include bor<strong>on</strong>,<br />

because bor<strong>on</strong> is an envir<strong>on</strong>mentally hazardous substance. In order to achieve bor<strong>on</strong>free<br />

electroplating of FeNi, we applied the method proposed by Luisa et al for the<br />

CuNi electroplating [1] to that of FeNi, in which they successfully plated CuNi with<br />

good surface morphology by using tartaric acid. We electroplated FeNi films with<br />

Fe c<strong>on</strong>tent of 17-45 at.% from the bath including NiSO 4•6H 2O, FeSO 4•7H 2O, NaCl,<br />

C 7H 4NNaO 3S•2H 2O and C 4H 6O 6 (tartaric acid). The c<strong>on</strong>tent of Fe was c<strong>on</strong>trolled by<br />

varying the amounts of tartaric acid between 0-200 g/L. The coercive force of the asdeposited<br />

films varied with the c<strong>on</strong>tent of Fe, and showed a sharp bottom of 20 A/m at<br />

around 22 at.% of Fe. This result is c<strong>on</strong>sistent with the fact that FeNi alloys have nearly<br />

zero values of magnetocrystalline anisotropy and saturati<strong>on</strong> magnetostricti<strong>on</strong> at around<br />

22 at.% of Fe. From the above result, we c<strong>on</strong>cluded that tartaric acid based bath film is<br />

<strong>on</strong>e of hopeful plating bath for electroplating of FeNi films.<br />

[1] Luisa et al, J. Appl. Electrochem, 41 (2011) 415.<br />

PM09<br />

Electrodeposited Fe-Co film prepared from citric acid-based plating<br />

bath<br />

Takeshi Yanai*, Haruka Uto, Takaya Shimokawa, Ken-ichiro Takahashi, Masaki<br />

Nakano and Hirotoshi Fukunaga<br />

Nagasaki University, Japan<br />

Although a lot of the electrodeposited Fe-Co films with good soft magnetic properties<br />

were reported [1-3], bor<strong>on</strong>, which is harmful and restricted by the regulati<strong>on</strong> of<br />

envir<strong>on</strong>mental protecti<strong>on</strong> in Japan, was included in the plating bath as boric acid for<br />

c<strong>on</strong>trolling pH. Therefore, in order to remove bor<strong>on</strong>, we focused <strong>on</strong> the citric acidbased<br />

plating bath and investigated effect of citric acid for the electrodeposited Fe-Co<br />

films. The plating bath was c<strong>on</strong>sisted of FeSO 4•7H 2O(100 g/L), CoSO 4•7H 2O(100 g/<br />

L), NaCl(50 g/L), C 6H 8O 7•H 2O(0 - 270 g/L).An Fe plate as anode and a Cu plate as<br />

cathode were used, and Fe-Co film was deposited <strong>on</strong> the Cu plate. Current density<br />

was kept at 2 mA/mm2 and bath temperature was set at 50 °C during the depositi<strong>on</strong>.<br />

The coercivity of the deposited film was drastically reduced from 1700 to 200 A/m<br />

with increasing c<strong>on</strong>tent of citric acid from 0 to 100 g/L, and then slightly increased.<br />

The Fe-Co film prepared from the bath with citric acid of 100 g/L has high saturati<strong>on</strong><br />

magnetizati<strong>on</strong> of over 2.2 T and we can c<strong>on</strong>clude that citric acid-based plating bath<br />

is <strong>on</strong>e of hopeful plating <strong>on</strong>es to obtain good soft magnetic film with high saturati<strong>on</strong><br />

magnetizati<strong>on</strong>.<br />

[1] Qiang et al., Appl. Surf. Sci., 257 (2010) 1371. [2] Kockar et al., J. MMM, 322 (2010) 1095. [3]<br />

Teh et al., IEEE Trans. Magn., 47 (2011) 4398.


PM10<br />

Magnetic and magnetocaloric properties of polycrystalline Fe2P under<br />

hydrostatic pressure<br />

Luana Car<strong>on</strong> 1 *, Viktor Hoglin 2 , Yv<strong>on</strong>ne Anderss<strong>on</strong> 2 , Per Nordblad 3 and Ekkes Bruck 4<br />

1<br />

Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, TU Delft, Mekelweg 15,<br />

2629 JB Delft, The Netherlands, Netherlands<br />

2<br />

Department of Materials Chemistry, Uppsala University, Box 538, 751 21 Uppsala, Sweden, Sweden<br />

3<br />

Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala, Sweden, Sweden<br />

4<br />

Fundamental Aspects of Materials and Energy, TU Delft, Mekelweg 15, 2629 JB Delft, The<br />

Netherlands, Netherlands<br />

Magnetocaloric-based refrigerati<strong>on</strong> presents itself as an envir<strong>on</strong>mentally-friendly energy-efficient technology<br />

capable of beneficially replacing the current gas compressi<strong>on</strong>-based technology. Some of the most promising<br />

magnetocaloric working materials found to date, such as (Fe,Mn)2(P,Si), are based <strong>on</strong> the Fe 2P binary<br />

compound. Fe 2P itself presents a first order magnetoelastic transiti<strong>on</strong> between FM and PM states at around<br />

219 K and a low magnetic entropy change spanning a large temperature range. What makes Fe 2P so<br />

unique is the coupling presented by its magnetic and crystal lattices which gives rise to the so-called mixed<br />

magnetism[1]. We believe that the mixed magnetism is resp<strong>on</strong>sible for the giant magnetic entropy change<br />

present in Fe 2P-based compounds. To further advance our understanding of this coupling we performed<br />

magnetizati<strong>on</strong> experiments under hydrostatic pressures up to 8 kbar <strong>on</strong> pure Fe 2P in its polycrystalline form.<br />

Pressure is found to decrease Tc at a rate of 6 K/kbar, about twice the rate reported in literature[2]. The Tc<br />

dependence <strong>on</strong> field is found to be n<strong>on</strong>-linear and is <strong>on</strong>ly weakly affected by pressure. The magnetic entropy<br />

change peak is slightly decreased by increasing pressure whereas the total entropy increases by ~ 6%.<br />

[1] Dung, N.H. et al. Advanced Energy Materials 1, 1215 (2011). [2] Fujii, H., Hokabe, T.,<br />

Kamigaichi, T. & Okamoto, T., J. Phys. Soc. Jpn. 43, 41-46 (1977).<br />

PM11<br />

Influence of Er doping <strong>on</strong> magnetic and magnetocaloric properties of<br />

(NiCo) 2MnGa<br />

Jiří Kaštil 1 *, Jiří Kamarád 2 and Zdenĕk Arnold 2<br />

1 Faculty of Mathematics and Physics, Charles University,Prague, Czech Republic<br />

2 Institute of Physics ASCR, Prague 8, Czech Republic., Czech Republic<br />

Recently, an attenti<strong>on</strong> has been paid to magnetocaloric properties of the Co-doped Heusler Ni 2MnGa<br />

alloys with a paramagnetic gap in martensitic phase that can be tuned by their compositi<strong>on</strong> [1]. The<br />

str<strong>on</strong>g influence of a rare-earth doping has been calculated and observed <strong>on</strong> the valence orbitals<br />

of Mn that makes the main c<strong>on</strong>tributi<strong>on</strong> to the magnetic properties of these alloys [2]. We have<br />

prepared Co-doped Ni 2MnGa alloys with a very small amount of Er. The polycrystalline sample of<br />

Ni 42.9Co 7Mn 31Ga 19Er 0.1 was checked by the EDX analysis and a segregati<strong>on</strong> of Er was discovered <strong>on</strong><br />

grain boundaries as it was expected in [2]. Saturated magnetizati<strong>on</strong> M(5K,0)=2.38μB/f.u. and the<br />

Curie temperatures TCM=318 K and TCA=440 K of martensite and austenite, respectively, were<br />

observed in Er free sample by a SQUID magnetometer. The inverse magnetocaloric effect at vicinity<br />

of martensitic transiti<strong>on</strong>, TM-A=379 K, was measured by direct method with ΔT=1.2K. In the Erdoped<br />

alloy, M(5K,0)=2.83μB/f.u. and paramagnetic gap was diminished in martensitic phase.<br />

TCA=450 K has been detected <strong>on</strong>ly and magnetic susceptibility obey nicely the Currie-Weis law with<br />

paramagnetic moment of mP=5.09 μB/f.u. above TCA. The effect of the Er-segregati<strong>on</strong> <strong>on</strong> crystal<br />

texture and magnetic behaviour of the Co-doped Ni 2MnGa alloys will be discussed.<br />

[1] S. Fabbrici, J. Kamarad, Z. Arnold, F. Casoli, A. Paoluzi, F. Bolz<strong>on</strong>i, R. Cabassi, M. Solzi, G.<br />

Porcari, C. Pernechele, F. Albertini, Acta Materialia 59 (2011) 412-419 [2] J. Wan, Y. Fei, J. Wang,<br />

Journal of Rare Earths 24 (2006) 373-375<br />

PM12<br />

Structural and magnetic properties of FeMnAl nanocrystalline alloys<br />

K<strong>on</strong>tan Tarigan, Young-yeal S<strong>on</strong>g and Se<strong>on</strong>g-cho Yu*<br />

BK21 Physics Program and Department of Physics, Chungbuk Nati<strong>on</strong>al University,<br />

Che<strong>on</strong>gju 361-763, Korea<br />

Nanocrystalline magnetic alloys have been promising materials for magnetic device applicati<strong>on</strong>s<br />

requiring high saturati<strong>on</strong> magnetic flux density, high permeability, and low core loss. Am<strong>on</strong>g<br />

the magnetic alloys, Fe-Mn-Al system has been <strong>on</strong>e of the most interesting tenary alloys with<br />

several magnetic phases. The magnetic properties were studied in <strong>on</strong>e particular compound in<br />

previous works [1,2]. More systematic research of Fe-Mn-Al alloys would c<strong>on</strong>tribute to better<br />

understanding with Al c<strong>on</strong>tens. Nanocrystalline Fe 90-xMn 10Al x prepared via mechanical alloying<br />

using Fe, Mn, and Al powder with 48 hrs milling time. The structural and magnetic properties<br />

were studied. All peaks of XRD data are broader and shifted to smaller angle with increasing Al<br />

c<strong>on</strong>tents depending <strong>on</strong> the crystalline size and the lattice paramenter, respectively. All the samples<br />

exhibit alloys behavior with an average crystallite size around 10 nm. The magnetic saturati<strong>on</strong>, the<br />

coercivity, and the permeability, obtained from measurements by vibrating sample magnetometer<br />

showed str<strong>on</strong>g dependence <strong>on</strong> the Al c<strong>on</strong>tents, and these dependences were related to the changes<br />

in structure and crystallite size. In additi<strong>on</strong> Mossbauer experiments c<strong>on</strong>firm tha Al diffuses into<br />

Fe bcc grains. Furthermore, these results suggest that, by adjusting the Al c<strong>on</strong>tent, appropriate<br />

structural transformati<strong>on</strong> and appropriate magnetizati<strong>on</strong> values can be obtained.<br />

[1] K<strong>on</strong>tan Tarigan, Y<strong>on</strong>g-Goo Yoo, D<strong>on</strong>g-Seok Yang, J. M. Greneche, and Se<strong>on</strong>g-Cho Yu, IEEE<br />

Trans. Mag. 45, No. 6 (2009) 2492-2495. [2] E.A. Vela´squez, L.F. Duque, J. Mazo-Zuluaga, J.<br />

Restrepo, Physica B 398 (2007) 364-368.<br />

PM13<br />

Magnetocaloric effect in Fe doped La 0.67Ba 0.33MnO 3 system.<br />

Hirofumi Kawanaka 1 *, Hiroshi Bando 1 and Yoshikazu Nishihara 2<br />

1 Advanced Industrial Science and Technology, Japan<br />

2 Ibaraki Univ., Japan<br />

PM14<br />

PM15<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The perovskite-type oxides of La 0.67Ba 0.33Mn 1-xFe xO 3 were synthesized by the<br />

c<strong>on</strong>venti<strong>on</strong>al solid-state reacti<strong>on</strong> method. The Curie temperature Tc and magnetic<br />

entropy change (MCE) in these samples are determined and compared to those of Gddoped<br />

systems. [1,2] The Curie temperature Tc decreases from 350 K to 290 K with<br />

increasing Fe c<strong>on</strong>centrati<strong>on</strong> x from 0 to 0.05. The relatively large MCE with a broad<br />

peak around Curie temperature compared with other oxides is observed in this system.<br />

These results suggest this system is a suitable candidate as magnetic refrigerator<br />

material working at room temperature.<br />

[1] Z. Juan, W. Gui, J. Magn. Magn. Mater. 321 (2009) 43-46 [2] M. H. Phan, S. C. Yu, J. Magn.<br />

Magn. Mater. 308 (2007) 325-340<br />

Study of magnetic transiti<strong>on</strong> and magnetic entropy changes of<br />

La 0.7Sr 0.3MnO 3 and La 0.7Ca 0.1Sr 0.2MnO 3<br />

Anwar Mohammad Shafique, Shalendra Kumar, Faheem Ahmed, G. W. Kim and B<strong>on</strong><br />

Heun Koo*<br />

School of Nano & Advanced Materials Engineering, Changw<strong>on</strong> nati<strong>on</strong>al university,<br />

Korea<br />

Magnetocaloric effect (MCE) and its most straightforward applicati<strong>on</strong>, magnetic<br />

refrigerati<strong>on</strong>, are becoming fields of increasing research interest. On the <strong>on</strong>e hand,<br />

there are reas<strong>on</strong>able expectati<strong>on</strong>s that these subjects will give rise to energy-efficient,<br />

envir<strong>on</strong>mentally friendly technological applicati<strong>on</strong>s. On the other hand, the study<br />

of some model materials gives some more insight into the physics underlying these<br />

phenomena. In this paper, complex magnetic materials La 0.7Sr 0.3MnO 3, La 0.7Ca 0.3MnO 3<br />

and La 0.7Ca 0.1Sr 0.2MnO 3, suitable for the magnetic refrigerati<strong>on</strong>, has been investigated.<br />

We have found that the substituti<strong>on</strong> of the Sr with Ca leads to an important decrease<br />

of the Curie temperature (TC) from 374 K to 345 K. The magnetocaloric study<br />

exposes a quite large value of the magnetic entropy changes for La 0.7Ca 0.3MnO 3<br />

and La 0.7Ca 0.1Sr 0.2MnO 3. In cooling applicati<strong>on</strong>s, another important parameter is<br />

relative cooling power (RCP), a good indicator of cooling efficiency of a magnetic<br />

refrigerant. For an applied magnetic field of 2 T, the RCP value is found to be 203 J/<br />

kg for La 0.7Ca 0.1Sr 0.2MnO 3. As a result, the studied compounds could be c<strong>on</strong>sidered as<br />

potential material for magnetic refrigerati<strong>on</strong> near and above room temperature.<br />

Perpendicular magnetic anisotropy of amorphous ferromagnetic<br />

CoSiB multilayer<br />

Sol Jung 1 , H. I. Yim 1 *, Ahri Kim 2 and Sumin Kim 2<br />

1 Physics, Sookmyung Women's University, Korea<br />

2 Nano-Physics, Sookmyung Women's University, Korea<br />

Perpendicular magnetic anisotropy (PMA) is worthy of notice in both fields of science<br />

and industry due to its high integrate. In the previous study, we used CoSiB (75:15:10,<br />

atm%) and CoSiB/Pt multilayer showed the str<strong>on</strong>g dependence <strong>on</strong> both the thicknesses<br />

of CoSiB and Pt. For the [CoSiB 3A/ Pt 14A]x5 multilayer, the maximum coercivity<br />

was ~ 224 Oe and the maximum PMA c<strong>on</strong>stant was obtained as ~ 2 × 10 6 erg/cm 31 .<br />

In additi<strong>on</strong>, this film has the coercivity (Hc) and the saturati<strong>on</strong> magnetizati<strong>on</strong> (Ms)<br />

with respect to 1.6 Oe and 407 emu/cm 3 . C<strong>on</strong>sidering this result, we suggest the new<br />

idea of CoSiB/Au/CoSiB sandwich structure and CoSiB/Pd multilayer. 1 m<strong>on</strong>o-layerthick<br />

of Au and Pt are 144pm, 139pm and they are diamagnetic and ferromagnetic<br />

materials, respectively. CoSiB/Au/CoSiB sandwich structure and CoSiB/Pd multilayer<br />

is expected to show PMA and it can be developed to the magnetic random access<br />

memory (MRAM).<br />

[1] J. Y. Hwang, S. S. Kim, and J. R. Rhee, J. Magn. Magn. 310, 1943 (2007). [2] J. S. Park, H. I.<br />

Yim, J. Y. Hwang, S.B. Lee, T. W. Kim, J. Phys. Soc. 57, 1672 (2010). [3] S. Je<strong>on</strong>g, H. I. Yim, J. Phys.<br />

soc. 60, 450 (2012).<br />

July 8 - 13, 2012 Busan, Korea 55<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

PM16<br />

Thickness dependence of magnetic inducti<strong>on</strong> in inhibitor-free 3%<br />

silic<strong>on</strong> steels<br />

Sang-beom Kim 1 *, Jo<strong>on</strong>-young Soh 1 , Sang-yun Lee 1 , Heej<strong>on</strong>g Jung 2 and J<strong>on</strong>gryoul<br />

Kim 2<br />

1 Korea Electric Power Corporati<strong>on</strong> Research Institute, Korea<br />

2 Department of Metallurgy and Materials Science, Hanyang University, Korea<br />

Cold-rolled sheets of differing thicknesses were prepared through the c<strong>on</strong>venti<strong>on</strong>al<br />

hot and cold rolling process. After annealing at 1200°C, final texture greatly varied<br />

with heating rate and sheet thickness. The 0.2 mm thick samples c<strong>on</strong>tained no or<br />

few {110} grains within the tested range of heating rates, yielding a poor magnetic<br />

inducti<strong>on</strong>. On the c<strong>on</strong>trary, the 0.15 mm thick samples c<strong>on</strong>sisted entirely of {110}<br />

grains, and c<strong>on</strong>sequently resulted in a very high magnetic inducti<strong>on</strong> of over 1.95 Tesla.<br />

The 0.1 mm samples were also composed of {110} grains either at a very slow or at a<br />

very fast heating rate, but they unexpectedly exhibited a poor magnetic inducti<strong>on</strong> due<br />

to the deviated directi<strong>on</strong> of {110} grains from rolling directi<strong>on</strong>. Orientati<strong>on</strong><br />

distributi<strong>on</strong> functi<strong>on</strong>s of the samples taken from each cold rolling pass revealed that<br />

initial {111} texture comp<strong>on</strong>ents started to move toward {111} at a<br />

thickness of 0.13 mm. According to the nucleati<strong>on</strong> and selective growth mechanism [1],<br />

primarily recrystallized texture takes after cold rolling texture, and hence the deviated<br />

final texture was obtained. This study indicates that there exists an optimum thickness<br />

for obtaining high magnetic inducti<strong>on</strong> and low ir<strong>on</strong> loss.<br />

[1] N. H. Heo et al., Acta Mater. 51 (2003), 4953-4964.<br />

PM17<br />

Effect of M (= Ge, Y, Hf) additi<strong>on</strong> <strong>on</strong> soft magnetic properties of Fe-B-<br />

Si-M metallic glass alloys<br />

Juho Lee 1 , Hwijun Kim 1 , Jungchan Bae 1 and Dohyang Kim 2 *<br />

1 Korea Institute of Industrial Technology, Korea<br />

2 Center for n<strong>on</strong>crystalline Materials, Y<strong>on</strong>sei University, Korea<br />

Fe-based metallic glass (MG) alloys exhibit good soft magnetic properties such as<br />

low coercivity and core loss but have the limits for industrial applicati<strong>on</strong> because of<br />

low saturati<strong>on</strong> flux density below 1.5T. Therefore, Fe-based MG alloys with high<br />

saturati<strong>on</strong> flux density above 1.7T are very attractive soft magnetic alloy systems. In<br />

order to investigate the effect of M(= Ge, Y, Hf) additi<strong>on</strong> <strong>on</strong> soft magnetic properties<br />

of Fe-B-Si-M metallic glass alloys, structural variati<strong>on</strong>s and magnetic properties<br />

of Fe 83-XB 10Si 7M X (X=1~5 at atomic percent) MG alloys were examined by X-ray<br />

diffracti<strong>on</strong>(XRD) and vibrati<strong>on</strong> sample magnetometer(VSM) after fabricating<br />

Fe 83-XB 10Si 7M X MG ribb<strong>on</strong>s by a single-roller melt-spinning technique under<br />

arg<strong>on</strong> atmosphere. The thermal stability was measured by Differential Scanning<br />

Calorimetry(DSC) at a heating rate of 20K/min. Fe 83-XB 10Si 7M X MG alloys added Ge,<br />

Y or Hf exhibited a fully amorphous structure. Saturati<strong>on</strong> flux density and coercive<br />

force of these alloys were Bs = 1.6~1.8T and Hc = 20~40 A/m, respectively. After<br />

annealing for 1 hr at 773K, Fe80B10Si7Ge3 MG alloy displayed excellent soft<br />

magnetic properties such as saturati<strong>on</strong> flux density of 1.8T and corecivity of 20A/m.<br />

PM18<br />

Effects of film compositi<strong>on</strong> and substrate temperature <strong>on</strong> the structure<br />

and magnetic properties of FeCoB alloy films formed <strong>on</strong> MgO singlecrystal<br />

substrates<br />

Yugo Asai*, Mitsuru Ohtake, Tetsuroh Kawai and Masaaki Futamoto<br />

Chuo University, Japan<br />

Tri-layer films c<strong>on</strong>sisting of FeCoB and MgO layers have been investigated for MTJ applicati<strong>on</strong>s.<br />

Theoretical studies show that the TMR ratio of MTJ prepared using epitaxial layers is <strong>on</strong>e order of<br />

magnitude greater than that obtainable with amorphous layers [1,2]. The structure of bulk FeCoB<br />

alloy changes from crystalline to amorphous as the B c<strong>on</strong>tent exceeds around 10 at. %. However<br />

in a form of thin film, there is a possibility of crystallizati<strong>on</strong> for B rich compositi<strong>on</strong>s. In the present<br />

study, (Fe 0.7Co 0.3) 100-xB x (x = 0-15 at. %) films were sputter deposited <strong>on</strong> MgO substrates of (100),<br />

(110), and (111) orientati<strong>on</strong>s at different substrate temperatures to investigate the effects of film<br />

compositi<strong>on</strong>, temperature, and substrate orientati<strong>on</strong> <strong>on</strong> the structure and magnetic properties.<br />

Epitaxial films were obtained for all compositi<strong>on</strong>s by adjusting substrate temperature. For example,<br />

(FeCo) 95B 5 and (FeCo) 85B 15 epitaxial films were respectively obtained at temperatures higher than<br />

200 and 600 °C, while amorphous films were formed below these temperatures. The epitaxial<br />

films formed <strong>on</strong> MgO (100), (110), and (111) orientati<strong>on</strong>s c<strong>on</strong>sisted of bcc(100), bcc(211), and<br />

bcc(110) crystals, respectively. The magnetocrystalline anisotropy decreased with increasing the B<br />

c<strong>on</strong>tent. Improved soft magnetic properties were realized in films with high B c<strong>on</strong>tents.<br />

[1] W. H. Butler, X.-G. Zhang, T. C. Schulthess, and J. M. MacLaren: Phys. Rev. B., 63, 054416<br />

(2001). [2] J Math<strong>on</strong> and A Umerski: Phys. Rev. B., 63, 220403 (2001).<br />

56 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PM19<br />

Arrangement of different magnetic alloy sheets for effective magnetic<br />

shielding<br />

Sang-yun Lee, Yun-seog Lim, Ho-se<strong>on</strong>g Ahn, D<strong>on</strong>g-il Lee and Sang-beom Kim*<br />

Korea Electric Power Corporati<strong>on</strong> Research Institute, Korea<br />

The purpose of this study is to provide an effective shielding method for power<br />

frequency magnetic field emanating from a neutral ground reactor (NGR). The<br />

0.35 mm thick commercial grade grain-oriented electrical steel (GO), n<strong>on</strong>-oriented<br />

electrical steel (NGO), and permalloy (PC) were used as shielding materials. The area<br />

of 1200x1200 mm2 was blocked with the alloy sheets at a place 600 mm away from<br />

the NGR. In a weak magnetic field, PC is the best in shielding performance, whereas<br />

GO is the best in a str<strong>on</strong>g magnetic field. NGO is worse than GO, but is better than PC<br />

in a very str<strong>on</strong>g magentic field. For multi-layered shields, it was observed that GO/PC<br />

pair (GO is close to source) was most effective, yielding a shielding factor less than<br />

0.06 in the wide range of magentic fields. These results are explained by variati<strong>on</strong> of<br />

shielding effectiveness of a magnetic material with magnitude of magnetic field. The<br />

inner GO sheet effectively shields a str<strong>on</strong>g magnetic field first, and then the outer PC<br />

sheet effectively shields the weakened field. Furthermore, this study dem<strong>on</strong>strates<br />

some spacing between laminati<strong>on</strong>s is essential to achieve best shielding performance in<br />

the ‘shunt’ mechanism of magnetic shielding.<br />

PM20<br />

Fabricati<strong>on</strong> of pariculated Fe-Mg thin films by selective oxidati<strong>on</strong> and<br />

their magnetic properties<br />

Pyungwoo Jang*<br />

College of Science and Engineering, Che<strong>on</strong>gju university, Korea<br />

It is impossible to manufacture Fe-Mg bulk alloys even in vacuum melting system<br />

because of very low melting temperature, high affinity with oxygen, and very high<br />

vapor pressure of Magnesium. However, it is very easy to fabricate Fe-Mg thin films<br />

by sputtering. Becasue of big difference of enthalpy of Fe-O and MgO, Mg can be<br />

selectively oxidized in a mixture atmosphere of hydrogen and water vapor. 10 - 200<br />

nm thick sputtered Fe-Mg films were selectively oxidized in a damp atmosphere and<br />

annealed at 800-900oC for 10 - 200 min. With increasing oxidati<strong>on</strong> time, saturatio<br />

magnetizatin of Fe-Mg films increased due to selective oxidati<strong>on</strong> of Mg. Furthermore,<br />

Initial permeability as well as the slope of magnetizatio loops of the films decreased,<br />

which was attributed from the facts that morphology of the films were changed from<br />

c<strong>on</strong>tinuous type to pariculated type. when the films were annealed in pure hyderogen<br />

atmosphere the rate of change is very slow. The reas<strong>on</strong> for the expedited change is<br />

probably due to energy transfer to Fe atoms during migrati<strong>on</strong> of Mg atoms to film<br />

surface .<br />

PM21<br />

Optimum spacing of magnetic alloy strips in open-type magnetic<br />

shielding<br />

Yun-seog Lim, Sang-yun Lee, Ho-se<strong>on</strong>g Ahn, D<strong>on</strong>g-il Lee and Sang-beom Kim*<br />

Korea Electric Power Corporati<strong>on</strong> Research Institute, Korea<br />

This study suggests an effective shielding method for power frequency magnetic<br />

field in open-type magnetic shielding, which secures the clear view of field sources<br />

by aligning magnetic alloy strips sparsely. A neutral ground reactor (NGR) was used<br />

as a field source. The 0.35 mm thick commercial grade grain-oriented electrical steel<br />

(GO) and permalloy (PC) were cut into a size of 50x1200 mm2 and then placed<br />

vertically 600 mm away from the center of the NGR. In a weak magnetic field, PC<br />

was the best in shieldng performance, whereas GO was the best in a str<strong>on</strong>g magnetic<br />

field due to change in hierachy of material permeability with increasing magnetic field<br />

strength. In case of multi-layered shields, it was observed that combinati<strong>on</strong> of GO/PC/<br />

GO was more effective than the triple-layered shield of the same material. However,<br />

closely c<strong>on</strong>joined GO/PC/GO shield showed worse shielding performance than the<br />

same layered shield seperated from each other, which dem<strong>on</strong>strates it acts as <strong>on</strong>e<br />

body regardless of presence of thin surface insulati<strong>on</strong> layers. This study reports that<br />

introducing air gap between laminati<strong>on</strong>s of each layered shield is important to obtain<br />

desired shieding performances and optimum spacing between alloy strips exits in opentype<br />

magnetic shielding.


PM22<br />

Magnetocaloric effect in Ni 2.27Mn 0.73Ga Heusler alloy<br />

Mikhail Drobosyuk, Vasiliy Buchelnikov, Sergey Taskaev and Rafael Fayzullin<br />

Chelyabinsk state university, Russia<br />

Drobosyuk Mikhail, Buchelnikov Vasiliy, Taskaev Sergey, Fayzullin Rafael<br />

Chelyabinsk State University, Chelyabinsk, Russia m.syuk@mail.ru type of<br />

presentati<strong>on</strong>: poster There are many theoretical and experimental works devoted<br />

a possibility any magnetic materials to change its temperature after applying an<br />

external magnetic field. This effect is called the magnetocaloric effect (MCE).<br />

Recent experimental studies have shown that Ni-Mn-Ga Heusler alloys have<br />

unique properties such as the shape memory effect, the large magnetostricti<strong>on</strong>, the<br />

large magnetoresistance and other magnetic properties. In this work we present the<br />

experimental studies of the MCE for Ni 2.27Mn 0.73Ga Heusler alloy. Polycrystalline<br />

ingot was prepared by a c<strong>on</strong>venti<strong>on</strong>al arc-melting method. Samples for measurements<br />

were cut from the middle part of the ingot. The magnetocaloric measurements were<br />

performed by the Magnetocaloric Measuring Setup produced by AMT&C. The results<br />

of measurements will be shown <strong>on</strong> the poster.<br />

PM23<br />

Soft magnetic properties of Fe-6.5wt.%Si alloy sheets fabricated by<br />

powder hot-rolling<br />

Hunju Lee 1 , Hwijun Kim 2 and Mooyoung Huh 1 *<br />

1 Department of Materials Science and Engineering, Korea University, Korea<br />

2 Korea Institute of Industrial Technology, Korea<br />

It is widely known that Fe-6.5 wt.% Si alloys have excellent soft magnetic properties.<br />

In this work, Fe-6.5 wt.% Si sheets were rolled by powder hot-rolling process without<br />

cracking and soft magnetic properties were investigated with microstructural defects.<br />

The cylindrical preforms were prepared by inert gas atomizati<strong>on</strong> and subsequent spark<br />

plasma sintering of Fe-6.5 wt.% Si powders at 1223K. The Fe-6.5 wt.% Si sheets were<br />

fabricated by hot rolling of copper canned preforms at 1173K with total reducti<strong>on</strong> of<br />

70%, 80% and 90%, respectively. The hot rolled sheets were annealed at 1073K in an<br />

arg<strong>on</strong> atmosphere. Microstructures and magnetic properties (magnetic flux density,<br />

coercivity and core loss) of the hot rolled and annealed Fe-6.5 wt.% Si sheets were<br />

examined by scanning electr<strong>on</strong> microscopy (SEM), vibrati<strong>on</strong> sample magnetometer<br />

(VSM) and B-H analyzer. The hot rolled Fe-6.5wt.% Si sheet with reducti<strong>on</strong> of 90%<br />

and subsequent annealing exhibited soft magnetic properties such as magnetic flux<br />

density of 1.8 T and coercivity of 20 A/m. This result is due to the eliminati<strong>on</strong> of<br />

microstructural defects and the increase of the average grain size and density.<br />

PM24<br />

Structure and magnetic properties of nano/micro-sized Mn-Al alloy<br />

powders produced by plasma arc-discharge and gas atomizati<strong>on</strong><br />

Junggoo Lee 1 *, Younkyoung Baek 1 , Hwijun Kim 2 and Chuljin Choi 1<br />

1 Powder & Ceramics Divisi<strong>on</strong>, Korea Institute of Materials Science, Korea<br />

2 Eco-Materials and Processing Divisi<strong>on</strong>, Korea Institute of Industrial Technology,<br />

Korea<br />

The τ-phase in the Mn-Al system has attracted great attenti<strong>on</strong> due to the remarkable magnetic properties<br />

superior to the Alnicos and hard ferrites, low cost, as well as good machinability and corrosi<strong>on</strong> resistance.<br />

Due to these reas<strong>on</strong>, several methods have been employed to produce τ-phase Mn-Al alloy powder until<br />

now. On the other hand, plasma arc-discharge and gas-atomizati<strong>on</strong> method has been widely used for the<br />

producti<strong>on</strong> of nano-sized and micro-sized powders, respectively. To our best knowledge, however, there is<br />

no comparis<strong>on</strong> study of Mn-Al alloy powder produced by these two methods. In the present study, Mn-Al<br />

alloy powders were prepared by the methods of plasma arc-discharge and gas-atomizati<strong>on</strong> and influence of<br />

process parameters <strong>on</strong> compositi<strong>on</strong>, particle size, and magnetic properties of the powders was systematically<br />

investigated. Mn-Al powder produced by plasma arc-discharge was smaller than its single magnetic domain<br />

and exhibited the coercivity of 5.6 kOe, which is the highest am<strong>on</strong>g the values reported until now. It was<br />

also c<strong>on</strong>firmed that the magnetic properties of micro-sized powder produced by gas-atomizati<strong>on</strong> have been<br />

improved by subsequent treatments such as annealing and mechanical milling Based up<strong>on</strong> these results, the<br />

magnetic properties of these two types of Mn-Al alloy powders will be discussed.<br />

This research was supported by a grant from the Fundamental R&D Program for Core Technology of<br />

Materials funded by the Ministry of Knowledge Ec<strong>on</strong>omy, Republic of Korea.<br />

PM25<br />

PM26<br />

PM27<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ultra high speed pm type synchr<strong>on</strong>ous motor-generator with<br />

amorphous core for micro turbine<br />

Do-kwan H<strong>on</strong>g*, Ye<strong>on</strong>-ho Je<strong>on</strong>g, Dae-suk Joo, Byung-chul Woo and Dae-hyun Koo<br />

Electric Motor Research Center, Korea Electrotechnology Research Institute, Korea<br />

Temperature dependence of magnetic domains in grain-oriented<br />

silic<strong>on</strong> steel<br />

H. L. Park 1 , R. Schaefer 2 , O. Y. Kw<strong>on</strong> 3 and Y. H. Je<strong>on</strong>g 1 *<br />

1 Physics, POSTECH, Korea<br />

2 IFW Dresden, Institute for Metallic Materials,, Germany<br />

3 Pohang Ir<strong>on</strong> and Steel Company, Korea<br />

WITHDRAWN<br />

Abstract: Silic<strong>on</strong> steels are essential for transformers and the reducti<strong>on</strong> of loss in them<br />

is of utmost importance in this green age. Since the loss in steels are closely related<br />

to their magnetic domain structures, the magnetic domain structures in turn are of<br />

exceeding interest. We studied magnetic domains of 3% silic<strong>on</strong> steel single crystals<br />

with (110) [001] texture as a functi<strong>on</strong> of temperature via magnetooptical Kerr effect<br />

(MOKE) microscopy. Generally, the silic<strong>on</strong> steels (110) [001] have 180° main domains<br />

oriented al<strong>on</strong>g the [001] axis, and they also have complimentary Lancet domains in<br />

case of misorientati<strong>on</strong>. [1, 2, 3] The MOKE images shown in Figure 1 clearly reveal<br />

that the domain patterns change as temperature is changed. The width of the 180°<br />

main domains, for instance, decreases with increasing temperature. In order to go<br />

<strong>on</strong>e step further from mere qualitative observati<strong>on</strong>s, we analyzed the MOKE images<br />

quantitatively, and, in particular, investigated temperature dependence of the 180°<br />

domain width and the Lancet domain density. These temperature characteristics will be<br />

interpreted from the standpoint of total energy minimizati<strong>on</strong>.<br />

[1] A. Hubert, R.Schaefer, Magnetic domains(1998),Springer [2] Y. Ushigami, J. Magn. Magn.<br />

Mater. 254-255(2003), 307-314 [3] M. Imamura, Physica Scripta. T 24 (1988)<br />

A tri-layer stress impedance sensor using amorphous magnetostrictive<br />

thin film<br />

Bod<strong>on</strong>g Li*, Ahmed Alfadhel and Jurgen Kosel<br />

KAUST, Saudi Arabia<br />

Mechanical stress sensors have a wide area of applicati<strong>on</strong>s in strain and torque<br />

measurements. Thin film stress impedance (SI) sensors have several advantages over<br />

other stress sensors such as high sensitivity in small stress range, miniaturizati<strong>on</strong><br />

possibility as well as the integrati<strong>on</strong> capability with other devices. Stress sensors<br />

that utilize amorphous magnetostrictive thin films have been proposed previously.<br />

The permeability change of the magnetostrictive material up<strong>on</strong> the applied external<br />

stress was evaluated throughout an impedance measurement. In this work, a tri-layer<br />

thin film stress sensor is fabricated and analyzed. The sensor has a Fe 40Ni 38Mo 4B 18/<br />

Ti/ Fe 40Ni 38Mo 4B 18 tri-layer structure with 900 nm thickness each and dimensi<strong>on</strong>s of<br />

10×0.1 mm2. After the depositi<strong>on</strong>, the sensor is annealed at 300 °C with a magnetic<br />

field of 500 Oe applied in the transverse directi<strong>on</strong> to induce an in-plane transverse<br />

anisotropy. The magnetic behavior is studied with a vibrating sample magnetometer<br />

and the crystallographic structure is studied with using X-ray diffracti<strong>on</strong>. The sensor<br />

is tested by applying compressive and tensile stresses and the sensor resp<strong>on</strong>se was<br />

obtained from an impedance analyzer. The results show high sensitivity at strains<br />

between 0-80 ppm with a maximum impedance change of 16% at 50 MHz.<br />

Frommberger, M.; Glasmachers, S.; Schmutz, C.; McCord, J.; Quandt, E., IEEE Trans. Magn., vol.<br />

41, pp.3691 - 3693, 2005<br />

July 8 - 13, 2012 Busan, Korea 57<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

PM28<br />

Magnetoimpedance(GMI) effect in the NiFe shell/Cu core wires<br />

fabricated by electrodepositi<strong>on</strong><br />

D<strong>on</strong>g Young Kim, Sung Jae Je<strong>on</strong>, Jung D<strong>on</strong>g Kim and Seok Soo Yo<strong>on</strong>*<br />

Physics, And<strong>on</strong>g Nati<strong>on</strong>al University, Korea<br />

Microwires with NiFe shell <strong>on</strong> Cu core of 90 μm diameter were fabricated by<br />

electrodepositi<strong>on</strong> method. The thickness of NiFe shell was well c<strong>on</strong>trolled by<br />

depositi<strong>on</strong> time in the range of 4 μm ~18 μm. Giant magnetoimpedance(GMI) effect<br />

in the NiFe/Cu core shell wire was measured in frequency range of 10 kHz ~ 10 MHz<br />

and in the magnetic field range of -300 Oe ~ 300 Oe. The variati<strong>on</strong>s GMI ratio with<br />

frequency and NiFe shell thickness were analyzed in terms of magnetic relaxati<strong>on</strong> and<br />

skin depth at ac field. We obtained maximum GMI ratio of 250 % at 300 kHz in the<br />

wire with NiFe shell of 11.5 μm thickness.<br />

PN01<br />

SQUID, XRD and Raman studies of Mn implanted gallium nitride at<br />

elevated temperature<br />

N. S. Pradhan 1 , Sheshmani K. Dubey 2 , A. D. Yadav 1 , B. K. Panigrahi 3 , K. G. M. Nair 4<br />

and M. Roy 5<br />

1<br />

Department of Physics, University of Mumbai, Mumbai, India<br />

2<br />

Deparment of Physics, University of Mumbai, India<br />

3<br />

Materials Science Divisi<strong>on</strong>, Indira Gandhi Centre for Atomic Research,<br />

Kalpakkam-603 102, India<br />

4<br />

Materials Science Divisi<strong>on</strong>,, Indira Gandhi Centre for Atomic Research,<br />

Kalpakkam-603 102, India<br />

5<br />

Chemistry Devisi<strong>on</strong>, Bhabha Atomic Research Center, Mumbai - 400 005, India<br />

The magnetic and structural properties of GaN samples implanted with 325 keV Mn 2+<br />

i<strong>on</strong>s at 350 0C substrate temperature for various fluences varying from 1.75 x 1015<br />

to 2.0 x 1016 i<strong>on</strong>s cm-2 were studied using SQUID, XRD and Raman scattering<br />

techniques. Magnetic properties were found to vary with the i<strong>on</strong> fluence.The 5 MeV<br />

Si + i<strong>on</strong> irradiati<strong>on</strong> with fluence of 1 x 1016 i<strong>on</strong>s cm-2 was performed <strong>on</strong> the sample<br />

implanted for i<strong>on</strong> fluence 2 x 1016 cm-2.The Curie temperature estimated for asimplanted<br />

and after irradiated with 5 MeV Si++ i<strong>on</strong> samples was found to 301 and<br />

326 K respectively. XRD spectra showed GaN peak at (002) reflecti<strong>on</strong>, this peak<br />

shifted toward lower angle indicated the incorporati<strong>on</strong> of Mn i<strong>on</strong> in GaN film.Raman<br />

spectra of the samples showed bands at ~300 and 670 cm-1 were attributed to the local<br />

vibrati<strong>on</strong> modes of gallium and nitrogen vacancies related defects respectively.<br />

PN02<br />

Oxidati<strong>on</strong> of m<strong>on</strong>ovacancies in graphene by oxygen<br />

Thaneshwor Prashad Kal<strong>on</strong>i and U. Schwingenschlögl<br />

King Abdullah University of Science and Technology, Saudi Arabia<br />

We study the oxidati<strong>on</strong> of m<strong>on</strong>ovacancies in graphene by oxygen molecules using<br />

first principles calculati<strong>on</strong>s. In particular, we address the local magnetic moments<br />

which develop at m<strong>on</strong>ovacancies and show that they remain intact when a molecule<br />

is adsorbed such that the dangling carb<strong>on</strong> b<strong>on</strong>ds are not fully saturated. The observed<br />

value of magnetic moment is 1.35 Bohr Magnet<strong>on</strong> for m<strong>on</strong>ovacancy and it becomes<br />

1.86 Bohr Magnet<strong>on</strong> by oxygen adsorpti<strong>on</strong> <strong>on</strong> m<strong>on</strong>ovacancy in graphene. However,<br />

the lowest energy c<strong>on</strong>figurati<strong>on</strong> does not maintain dangling b<strong>on</strong>ds and is found to<br />

be semic<strong>on</strong>ducting. Our data can explain the experimentally observed behavior of<br />

graphene under exposure to an oxygen plasma.<br />

58 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PN03<br />

Structural , compositi<strong>on</strong>al and magnetic study of bulk Fe doped ZnO<br />

system and impurity phase formati<strong>on</strong><br />

Shumaila Karamat 1 *, Rajdeep Singh Rawat 2 , Paul Lee 3 , Tan Tuck Lee Augustine 4 and<br />

Muhammad Ghaffari 5<br />

1<br />

Physics, 1. NIE, Nanyang technological University, Singapore 2. COMSATS<br />

Islamabad, Pakistan, Pakistan<br />

2<br />

NSSE-NIE, Nanyang Terchnological University, Singapore, Singapore<br />

3<br />

NSSE-NIE, Nanyang Technological Unievrsity Singapore, Singapore<br />

4<br />

Physics, Nanyang Technological University, Singapore, Singapore<br />

5<br />

EEE, Nanyang Technological University, Singapore, Singapore<br />

Structural, compositi<strong>on</strong>al, optical, vibrati<strong>on</strong>al and magnetic properties have been studied for (ZnO) 1x(Fe<br />

2O 3) x≤0.10 series of bulk samples. The ZnO based ceramic samples with different doping percentage<br />

of Fe 2O 3 were prepared by ball milling process. The phase compositi<strong>on</strong> of the pellets was determined via<br />

X-ray diffracti<strong>on</strong> analysis. Raman spectroscopy give informati<strong>on</strong> about the additi<strong>on</strong>al modes appear in the<br />

ZnO spectrum having Fe doping which assures the presence of Fe in the ZnO matrix. The de-c<strong>on</strong>voluti<strong>on</strong><br />

of XPS spectra of core peaks of different elements indicated the presence of different b<strong>on</strong>d breakage due<br />

to Fe substituti<strong>on</strong> in ZnO lattice. The appearance of shaking satellites in XPS spectra also c<strong>on</strong>firmed the<br />

presence of different valance states of Fe i<strong>on</strong>s. The red shift in energy band gap estimated from reflectance<br />

UV-VIS spectroscopy was observed for all bulk samples. The magnetic behavior of the samples was<br />

examined by using Vibrating Sample Magnetometer (VSM) indicating ferromagnetic behavior at room<br />

temperature. The effective magnetic moment per Fe atom decreases with the increase in doping percentage<br />

which indicates that ferromagnetic behavior is due to substituti<strong>on</strong> of Fe i<strong>on</strong>s in the ZnO lattice.<br />

PN04<br />

Enhanced magnetizati<strong>on</strong> and spin injecti<strong>on</strong> in Co/ZnO films by Al<br />

doping<br />

Zhiy<strong>on</strong>g Quan, Wei Liu and Xiaoh<strong>on</strong>g Xu*<br />

School of Chemistry and Materials Science, shanxi normal university, China<br />

An important hurdle in the development of semic<strong>on</strong>ductor spintr<strong>on</strong>ic devices is<br />

the inefficient injecti<strong>on</strong> of spin polarized currents from metallic ferromagnets<br />

into semic<strong>on</strong>ductors due to the large c<strong>on</strong>ductivity mismatch. Inserting a magnetic<br />

semic<strong>on</strong>ductor at the interface was regarded as an effectively route for spin injecti<strong>on</strong><br />

into semic<strong>on</strong>ductors. In this work, we investigate the magnetism and electrical spin<br />

injecti<strong>on</strong> into ZnO and Al-doped ZnO (Al 2at.%) matrix from Co particles in Co/<br />

ZnO and Co/ZnAlO films, which were prepared by depositing ultrathin Co layers<br />

and semic<strong>on</strong>ductor layers at room temperature. The films c<strong>on</strong>sist of Co particles<br />

dispersed in the semic<strong>on</strong>ductor matrix. The graded magnetic semic<strong>on</strong>ductors were<br />

formed at the transiti<strong>on</strong> regi<strong>on</strong> between metallic Co particles and semic<strong>on</strong>ductor matrix<br />

with the substituti<strong>on</strong> of Zn 2+ with Co 2+ i<strong>on</strong>s. The increasing of magnetizati<strong>on</strong> of Co/<br />

ZnAlO films compared to the corresp<strong>on</strong>ding Co/ZnO films is probably due to the<br />

enhanced magnetizati<strong>on</strong> of graded magnetic semic<strong>on</strong>ductors with Al enhancing carrier<br />

c<strong>on</strong>centrati<strong>on</strong>. The room temperature magnetoresistance of Co/ZnAlO film with 1.0<br />

nm of ZnAlO layer reaches -12.3% which is higher than -8.4% of the corresp<strong>on</strong>ding<br />

film without Al, probably due to the large spin filter effect occurring in the graded<br />

magnetic semic<strong>on</strong>ductors having a relative lager polarizati<strong>on</strong>.<br />

PN05<br />

Structure, magnetic, and transport properties in Cu 1-xMn xO<br />

compounds<br />

Jinzhu Cai, Li Li, Bin Lv, Shen Wang, Wenqin Zou, Fengming Zhang* and Xiaoshan<br />

Wu<br />

Physics, Nanjing University, China<br />

By annealing at air, O 2, N 2 atmosphere, the polycrystalline Cu 1-xMn xO powders,<br />

which are prepared by sol-gel method with the c<strong>on</strong>centrati<strong>on</strong> range of 0≤x≤0.2, are<br />

synthesized. The phase comp<strong>on</strong>ent and atomic structure of the main phase are obtained<br />

by X-ray diffracti<strong>on</strong> (XRD) with Rietveld refinements. The b<strong>on</strong>d length of Cu(Mn)-O<br />

decreases, and the b<strong>on</strong>d-angle of Cu(Mn)-O-Cu(O) increases, with increasing the<br />

dopant. <strong>Magnetism</strong> measurements (SQUID) show that the ferromagnetic transiti<strong>on</strong><br />

temperature, Tc, and the saturati<strong>on</strong> moment, Ms, increase with the doped c<strong>on</strong>centrati<strong>on</strong><br />

of Mn, although all the samples show that the Tc is less than 100 K. All samples show<br />

the well defined thermal active mechanism with the thermal active energy varying with<br />

the annealing atmosphere. Results reveal that annealed in O 2 may increase the carrier<br />

c<strong>on</strong>centrati<strong>on</strong> of the prepared samples while annealed in N 2 the reverse.


PN06<br />

A probe into the structural, magnetic and dielectric properties of<br />

barium and lithium substituted pseudobrookites<br />

Pushpinder Gupta Bhatia 1 * and Radha Srinivasan 2<br />

1 Physics, Department of Physics, Guru Nanak college, Mumbai-37, India<br />

2 Physics, Department of Physics, University of Mumbai, Mumbai-98, India<br />

The versatile nature of the Fe-Ti oxides makes them attractive candidates in<br />

applicati<strong>on</strong>s in which their coupled semic<strong>on</strong>ductor, magnetic and dielectric properties<br />

can be exploited and they appear to be good candidates for emerging technologies<br />

such as spintr<strong>on</strong>ics, magneto-electr<strong>on</strong>ics, and radar electr<strong>on</strong>ics. In the present work,<br />

pure pseudobrookite Fe 2TiO 5 and its lithium and barium substituted varieties namely<br />

Ba 2y Fe 2-x Li 3xTi 1-yO 5 and Ba 3x/2 Fe 2-x Li 4yTi 1-yO 5 (x = y = 0.05) are synthesized by the<br />

solid-state reacti<strong>on</strong> method. Powder x-ray diffracti<strong>on</strong> studies show the single phase<br />

orthorhombic structure. Substituti<strong>on</strong> has reduced the crystallite size but enhanced the<br />

grain size. A new intense plane (122) is observed in the barium-substituted sample.<br />

Lithium intercalati<strong>on</strong> is also observed. Room temperature dielectric studies have<br />

c<strong>on</strong>firmed the Maxwell- Wagner interfacial polarizati<strong>on</strong> and space charge is seen to<br />

have almost doubled with doping. The magnetic hysteresis loops show an asymmetric<br />

shift and c<strong>on</strong>stricti<strong>on</strong> of loops. Variati<strong>on</strong> of normalised susceptibility with absolute<br />

temperature is plotted. Presence of barium and lithium have also brought about a l<strong>on</strong>g<br />

range magnetic ordering in the pseudobrookite. Susceptibility measurements also<br />

show that the Curie temperature in the barium-rich pseudobrookite approaches room<br />

temperature making it a potential switch material.<br />

PN07<br />

Oxygen vacancy and magnetism of a room temperature ferromagnet<br />

Co-doped TiO2 Ikuo Nakai 1 *, Masashi Sasano 1 , Yingjie Li 2 , Ken Inui 1 , Tomoya Korekawa 1 , Hiroyuki<br />

Ishijima 1 , Hisashi Katoh 1 and Makio Kurisu 3<br />

1<br />

Department of Electrical and Electr<strong>on</strong>ic Engineering, Graduate School of<br />

Engineering, Tottori University, Japan<br />

2<br />

Inner M<strong>on</strong>golia Key Laboratory for Physics and Chemistry of Functi<strong>on</strong>al Materials,<br />

Inner M<strong>on</strong>golia Normal University, China<br />

3<br />

Department of Physics, Graduate School of Science and Engineering, Ehime<br />

University, Japan<br />

We report the magnetic and local structural study of a room temperature ferromagnetic<br />

Co-doped TiO 2 prepared by the solid state reacti<strong>on</strong>. The ferromagnet with 5% Co<br />

shows a rutile-type structure and has a saturati<strong>on</strong> magnetizati<strong>on</strong> of 0.005 JT-1kg-1<br />

and a coercive force of 0.02 T. We have found that it has some oxygen vacancy sites<br />

around a Co atom <strong>on</strong>ly from the extended x-ray absorpti<strong>on</strong> fine structure (EXAFS)<br />

measurement. The charge compensati<strong>on</strong> makes the oxygen vacancy around Co 2+ and/<br />

or Co 3+ substituted with Ti 4+ .<br />

PN08<br />

Effect of annealing <strong>on</strong> the magnetic anisotropy of GaMnAs film with<br />

low Mn c<strong>on</strong>centrati<strong>on</strong><br />

Hyehye<strong>on</strong> Bye<strong>on</strong> 1 , Yo<strong>on</strong>jung Gw<strong>on</strong> 1 , Jaehyuk W<strong>on</strong> 1 , Taehee Yoo 1 , Sangho<strong>on</strong> Lee 1 *, X.<br />

Liu 2 and J. K. Furdyna 2<br />

1 Physics Department, Korea University, Korea<br />

2 Physics Department, University of Notre Dame, USA<br />

We have investigated the effect of annealing <strong>on</strong> the magnetic anisotropy of a GaMnAs<br />

film with a low Mn compositi<strong>on</strong> of 2 %. Three pieces of samples were cleaved from<br />

the sample and two of them we are annealed at 200 and 300 °C, respectively, for<br />

3 hours in air. In case of as-grown sample, abrupt transiti<strong>on</strong>s in the Hall resistance<br />

appeared with a negative coercive field, when field strength was swept at a fixed<br />

directi<strong>on</strong> in the film plan. The phenomen<strong>on</strong> turned out to be related to the presence of<br />

magnetic domains with a vertical easy axis in the film, which was identified via the<br />

Hall measurement that was performed with a field directi<strong>on</strong> that was normal to the<br />

plane. The porti<strong>on</strong> of domain with dominant out-of-plane magnetic anisotropy in the<br />

GaMnAs film was systematically decreased with an increasing annealing temperature.<br />

Especially, the negative coercive field disappeared in the sample annealed at 300 °C<br />

and two abrupt positive switching fields we are observed in the field scan of the planar<br />

Hall resistance. This indicates that the annealing significantly affects the magnetic<br />

anisotropy of GaMnAs film by changing from out-of-plane dominant to in-plane<br />

dominant anisotropy.<br />

PN09<br />

PN10<br />

PN11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Low field magnetizati<strong>on</strong> reversal behavior of ferromagnetic GaMnAs<br />

film<br />

Yo<strong>on</strong>jung Gw<strong>on</strong> 1 , Hyehye<strong>on</strong> Bye<strong>on</strong> 1 , Jaehyuk W<strong>on</strong> 1 , Hakjo<strong>on</strong> Lee 1 , Sangho<strong>on</strong> Lee 1 *,<br />

X. Liu 2 and J. K. Furdyna 2<br />

1 Physics Department, Korea University, Korea<br />

2 Physics Department, University of Notre Dame, USA<br />

We have investigated magnetizati<strong>on</strong> reversal process of a GaMnAs film by using<br />

planar Hall effect. The angle-dependent measurements of the planar Hall resistance<br />

(PHR) showed sinusoidal behavior without hysteresis between clockwise and counter<br />

clockwise rotati<strong>on</strong> with str<strong>on</strong>g field. However, the magnetizati<strong>on</strong> reversal behavior<br />

changes significantly by showing abrupt transiti<strong>on</strong> at the directi<strong>on</strong>s as the field<br />

strength reduced to 200 Oe. Furthermore, when a smaller field is used, the PHR displays<br />

four stable values arising from the formati<strong>on</strong> of four different multidomain states during<br />

the rotati<strong>on</strong> of the external field directi<strong>on</strong> over 360°. Two of these states, showing<br />

maximum and minimum values of the PHR, corresp<strong>on</strong>d to the sample fully magnetized<br />

al<strong>on</strong>g <strong>on</strong>e of the easy axes. Other two intermediate states are multi-domain states in<br />

which a fracti<strong>on</strong> of the domains populates <strong>on</strong>e easy [100] directi<strong>on</strong>, and the remaining<br />

fracti<strong>on</strong> populates an orthog<strong>on</strong>al easy [010] directi<strong>on</strong>. We showed that the relative<br />

populati<strong>on</strong>s of the magnetic domains corresp<strong>on</strong>ding to the two orthog<strong>on</strong>al easy axes<br />

can be c<strong>on</strong>trolled by the value of the applied field during the process of magnetizati<strong>on</strong><br />

reversal. This phenomen<strong>on</strong> was understood by c<strong>on</strong>sidering the differences in domainpinning<br />

fields and their distributi<strong>on</strong>s required for crossing the two hard axes.<br />

Half-metallic antiferromagnetism in the ordered Cr 1-xCa xSb alloy from<br />

first-principles calculati<strong>on</strong>s<br />

Guoying Gao* and Kailun Yao<br />

School of Physics, Huazh<strong>on</strong>g University of Science and Technology, China<br />

Compared to half-metallic ferromagnets, half-metallic antiferromagnets (precisely<br />

called half-metallic fully compensated ferrimagnets) are more promising candidates<br />

for spintr<strong>on</strong>ic applicati<strong>on</strong>s since their zero magnetizati<strong>on</strong> leads to lower stray fields and<br />

thus tiny energy losses. Using the first-principles calculati<strong>on</strong>s, we have systematically<br />

investigated the electr<strong>on</strong>ic and magnetic properties of the ordered Cr 1-xCa xSb alloy.<br />

It is found that Cr 1-xCa xSb with x = 0.125, 0.25, 0.5 and 0.75 all are half-metals like<br />

zinc-blende CrSb and CaSb which have been fabricated experimentally or predicted<br />

theoretically. Interestingly, Cr 0.25Ca 0.75Sb is a half-metallic antiferromagnet with<br />

complete spin polarizati<strong>on</strong>, and the half-metallic antiferromagnetism is robust against<br />

the lattice compressi<strong>on</strong> and expansi<strong>on</strong> and the choice of electr<strong>on</strong>ic exchange and<br />

correlati<strong>on</strong> functi<strong>on</strong>al.<br />

[1] H. Akai, M. Ogura, Phys. Rev. Lett. 97, 026401 (2006). [2] B.-G. Liu, Phys. Rev. B 67, 172411<br />

(2003). [3] M. Sieberer, et al., Phys. Rev. B 73, 024404 (2006). [4] G.Y. Gao, et al., Phys. Rev. B 75,<br />

174442 (2007); [5] J.H. Zhao, et al., Appl. Phys. Lett. 79, 2776 (2001). [6] G. Y. Gao, J. Chen, and<br />

K.L. Yao, Phys. Lett. A 375, 4053 (2011).<br />

Translati<strong>on</strong> & rotati<strong>on</strong> of diamagnetic material induced by a low field<br />

of a permanent magnet and terminal identificati<strong>on</strong> of a micr<strong>on</strong>-sized<br />

particle<br />

Keiji Hisayoshi and Chiaki Uyeda<br />

Osaka university, Japan<br />

It has been generally believed that field-induced moti<strong>on</strong> of an ordinary diamagnetic<br />

material can be induced <strong>on</strong>ly at high field above several Tesla. However, translati<strong>on</strong>s<br />

were recently observed <strong>on</strong> various diamagnetic crystals in a directi<strong>on</strong> of m<strong>on</strong>ot<strong>on</strong>ously<br />

decreasing field produced by a permanent magnet [1]; the crystals were released in<br />

diffused micro-gravity area. In a given field distributi<strong>on</strong>, terminal velocity of translati<strong>on</strong><br />

is uniquely determined by intrinsic susceptibility of material; the velocity is independent<br />

to mass of particle. Rotati<strong>on</strong>al oscillati<strong>on</strong>, caused by diamagnetic anisotropy energy, was<br />

also reported for the crystals [1]. When the above moti<strong>on</strong>s are observable, diamagnetic<br />

susceptibility & anisotropy of a small particle can be detected, irrespective of its size,<br />

since the measurements are both free from interference of a sample holder and from<br />

mass measurement of sample. Material identificati<strong>on</strong> of particle is easily performed<br />

by comparing the obtained susceptibility (& anisotropy) with published values. A<br />

simple and n<strong>on</strong>destructive method to identify the material of a small particle is desired<br />

in various fields of nano-science. By introducing a compact NdFeB magnet, the<br />

measurement was realized in an ordinary laboratory using a chamber-type drop shaft.<br />

[1] C. Uyeda et al: Jpn. Phys. Soc. Jpn. 79, 064709 (2010). 246<br />

July 8 - 13, 2012 Busan, Korea 59<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PN12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetoresistance effect in electr<strong>on</strong>-injected p-type silic<strong>on</strong><br />

Michael P. Delmo*, Eiji Shikoh, Teruya Shinjo and Masashi Shiraishi<br />

Graduate School of Engineering Science, Osaka University, Japan<br />

Magnetoresistance (MR) effect in silic<strong>on</strong> has gained a renewed interest in recent<br />

years because it is large and n<strong>on</strong>-saturating [1-3]. It is known that the presence of<br />

“static” inhomogeneity, like phosphorus in low-doped silic<strong>on</strong>, generates large and<br />

n<strong>on</strong>-saturating MR effect [2,4]. Inhomogeneity can also be introduced “dynamically”<br />

by injecting electr<strong>on</strong>s or holes into a low-doped silic<strong>on</strong> [1,3]. In n-type silic<strong>on</strong> (n-Si),<br />

electr<strong>on</strong> injecti<strong>on</strong> generates space-charge effect [1], whereas, the hole injecti<strong>on</strong> induces<br />

the formati<strong>on</strong> of a hole-electr<strong>on</strong> (p-n) boundary [3]. These dynamic inhomogeneities<br />

induce large MR effect even up to room temperature. Most of the silic<strong>on</strong> devices used<br />

in inhomogeneity-induced MR effect studies are n-type, and no study has ever been<br />

reported for p-type, so far. In this study, we investigated the MR effect in indium (In)/<br />

p-type silic<strong>on</strong> (p-Si)/In devices. Current (I)-voltage (V) characteristic of the device<br />

shows an Ohmic and n<strong>on</strong>-Ohmic I-V regime (I is proporti<strong>on</strong>al to the square root of<br />

V), which indicates electr<strong>on</strong> space-charge injecti<strong>on</strong> into p-type silic<strong>on</strong> [5]. MR of the<br />

In/p-Si/In device is small (10%) compared to that of In/n-Si/In device (1,000%) for<br />

the same c<strong>on</strong>diti<strong>on</strong> (3 T, 300 K). This suggests that the electr<strong>on</strong>-hole compensati<strong>on</strong> or<br />

recombinati<strong>on</strong> suppress inhomogeneity formati<strong>on</strong> in the silic<strong>on</strong> device.<br />

[1] Delmo, M.P. et al. Nature 457, 1112 (2009). [2] Porter, N.A. & Marrows, C.H., arXiv:1105.2174<br />

[c<strong>on</strong>d-mat.mtrl-sci]. [3] Wan, Caihua et al. Nature 477, 304 (2011). [4] Herring, C. J. Appl. Phys.<br />

31, 1939 (1960). [5] Roberts, G.G. Phys. Stat. Sol. 27, 209 (1968).<br />

PN13<br />

First-principles investigati<strong>on</strong> of the influence of adsorbed atom <strong>on</strong> the<br />

defect and impurity substitute graphene<br />

Kengo Nakada 1 and Akira Ishii 2<br />

1 JST-CREST, Japan<br />

2 Department of Applied Mathematics and Physics, Tottori University, Japan<br />

Graphene is well-known to be two-dimensi<strong>on</strong>al material made of carb<strong>on</strong> atoms.<br />

Graphene is a substance that attracts attenti<strong>on</strong> not <strong>on</strong>ly as parts of the nanocarb<strong>on</strong>s<br />

but also for its own interesting electr<strong>on</strong>ic and mechanic properties. It is important<br />

for the applicati<strong>on</strong> that charge and magnetic are c<strong>on</strong>trolled by defect and impurity<br />

in the graphene. Furthermore, influence of defect and the impurity are important in<br />

the growth of the compound <strong>on</strong> the graphene. The technological uses of c<strong>on</strong>trollable<br />

charge and magnetic carb<strong>on</strong> systems are extensive, and it is important that the<br />

mechanism is known. In previous study, we investigated the adsorpti<strong>on</strong> energies and<br />

magnetism in adsorpti<strong>on</strong> sites <strong>on</strong> graphene from atomic number 1 to 83, using the<br />

DFT. We discussed the charge transfer and the magnetism. When several adatoms is<br />

adsorbed, the defect graphene develops magnetic. In this study, we performed atom<br />

substitute in the graphene and atomic adsorpti<strong>on</strong> <strong>on</strong> the graphene with the defect. The<br />

aim of the research is discussi<strong>on</strong> about the magnetic and stability when several adatoms<br />

adsorbed <strong>on</strong> defects and impurities substitue in graphene. In additi<strong>on</strong>, we discuss the<br />

growth mechanism of the nitrided compounds. We used a band calculati<strong>on</strong> technique<br />

based <strong>on</strong> the DFT calculati<strong>on</strong>.<br />

PN14<br />

Room-temperature fabricati<strong>on</strong> of highly transparent magnetic<br />

nanocomposite systems by aerosol depositi<strong>on</strong><br />

Jae-hyuk Park* and Akedo Jun<br />

Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Japan<br />

Nanocomposite systems, materials c<strong>on</strong>taining particles of nanometer dimensi<strong>on</strong>s have shown<br />

interesting properties related to its extremely small size. Some of their optical, magnetic, electr<strong>on</strong>ic,<br />

mechanical, and chemical properties are different from those exhibited by the same compositi<strong>on</strong> in<br />

bulk material[1]. We have proposed novel c<strong>on</strong>cept for materializing nanoocmposite systems using<br />

aerosol depositi<strong>on</strong> (AD) process[2-3]. Our c<strong>on</strong>cept can apply various sizes of nanoparticles, and<br />

achieves desirable distributi<strong>on</strong> of nanoparticles in host matrix because the structure of deposited<br />

layer is similar to that of composite powder. In this report, we developed highly transparent<br />

magnetic nanocomposite thick films c<strong>on</strong>sisting of cobalt nanoparticles embedded in a host matrix<br />

of ferroelectric lead zirc<strong>on</strong>ate titanate (PZT) by AD process at room temperature. Transparent<br />

thick nanocomposite cobalt/PZT films display very dense without any pores as well as any cracks.<br />

As the wt% of nanocobalt increased, magneto-optic effect measured in the transmissi<strong>on</strong> mode,<br />

especially Faraday rotati<strong>on</strong> effect of nanocomposite layers gradually increases with good linearity.<br />

The 0.1 wt% nanocobalt -c<strong>on</strong>taining nanocomposite film acquired the Faraday rotati<strong>on</strong> angle of<br />

approximately 0.2 degree. These results would str<strong>on</strong>gly show potential of optical multiferroics <strong>on</strong><br />

transparent nanocomposite systems.<br />

[1] M. Abe, M Gomi, and F. Yokoyama, J. Appl. Phys., Vol. 57, pp. 3909-3911, 1985. [2]J. Akedo,<br />

J. Am. Ceram. Soc., Vol. 89, pp. 1834-1839, 2006. [3] Jae-Hyuk Park, Jun Akedo and Masafumi<br />

Nakada, Jpn. J. Appl. Phys., Vol.45, pp. 7512-7515, 2006<br />

60 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PN15<br />

Effect of transiti<strong>on</strong> metal (Co, Ni and Cu) doping <strong>on</strong> lattice volume,<br />

band gap, morphology and saturati<strong>on</strong> magnetizati<strong>on</strong> of ZnO<br />

nanostructures<br />

Faheem Ahmed, Shalendra Kumar, Nishat Arshi, M S Anwar and B<strong>on</strong> Heun Koo*<br />

Changw<strong>on</strong> Nati<strong>on</strong>al University, Korea<br />

The interest in transiti<strong>on</strong>-metal (TM)-doped ZnO has increased because of promising<br />

applicati<strong>on</strong>s in the field of semic<strong>on</strong>ductor spintr<strong>on</strong>ics, which seeks to extend the<br />

properties and applicati<strong>on</strong>s of established electr<strong>on</strong>ic devices by using the spin of<br />

electr<strong>on</strong>s in additi<strong>on</strong> to their charge. In this work, the effect of different TM (Co, Ni<br />

and Cu) doping <strong>on</strong> structural, optical and magnetic properties of ZnO nanostructures<br />

have been studied. Zn 1-xTM xO (TM=Co, Ni and Cu) nanostructures were prepared by a<br />

microwave assisted chemical route and characterized by X-ray diffracti<strong>on</strong> (XRD), field<br />

emissi<strong>on</strong> scanning electr<strong>on</strong> microscopy (FESEM), transmissi<strong>on</strong> electr<strong>on</strong> microscopy<br />

(TEM), Raman spectroscopy, UV-Vis and magnetizati<strong>on</strong> measurements. The X-ray<br />

diffracti<strong>on</strong> (XRD) and TEM analysis showed that the TM-doped nanostructures had<br />

single phase nature with the wurtzite structure. There is a str<strong>on</strong>g correlati<strong>on</strong> between<br />

changes in the lattice parameters, bandgap energy, morphology and the saturati<strong>on</strong><br />

magnetizati<strong>on</strong> of Zn 1-xTM xO nanostrutures. Lattice volume and bandgap determined<br />

from XRD and UV-Vis, respectively, were found to decrease as the atomic number<br />

of the dopant moved away from Co. Magnetic studies showed that all the TM-doped<br />

ZnO exhibit room temperature ferromagnetism and the decreasing trend of saturati<strong>on</strong><br />

magnetizati<strong>on</strong> was observed with the increase of 3d electr<strong>on</strong>s number from Co to Cu.<br />

PN16<br />

Functi<strong>on</strong>alized graphene as a room-temperature ferromagnetic<br />

semic<strong>on</strong>ductor<br />

Je<strong>on</strong>gmin H<strong>on</strong>g 1 *, Sandip Niyogi 2 , Elena Bekyarova 2 , Mikhail E. Itkis 2 , Palanisamy Ramesh 2 ,<br />

Claire Berger 3 , Walt A. Deheer 4 , Robert C. Hadd<strong>on</strong> 2 and Sakhrat Khizroev 5<br />

1 Electrical and Computer Engineering, Florida <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> University, USA<br />

2 Department of Chemistry, Department of Chemical Engineering, Center for Nano Scale Science<br />

and Eng, University of California-Riverside, USA<br />

3 CNRS, Institut Neel, France<br />

4 School of Physics, Georgia Institute of Technology, USA<br />

5 Department of Electrical and Computer Engineering, Florida <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> University, USA<br />

Low-temperature magneto-transport and vibrating sample magnetometry (VSM) combined with superc<strong>on</strong>ducting<br />

quantum interference device (SQUID) measurements indicated that graphene, when functi<strong>on</strong>alized with aryl<br />

radicals, behaved as a room-temperature ferromagnet and therefore might form the basis for a new approach to<br />

semic<strong>on</strong>ducting ferromagnetism. After radical functi<strong>on</strong>alizati<strong>on</strong>, epitaxially grown graphene samples became<br />

semic<strong>on</strong>ductors and at the same time displayed high-density magnetism, with a room temperature saturati<strong>on</strong><br />

magnetizati<strong>on</strong> of approximately 0.1 Bohr magnet<strong>on</strong>s per carb<strong>on</strong> atom. The bulk measurements with VSM and<br />

SQUID were corroborated with local studies using atomic force microscopy (AFM), electrostatic force microscopy<br />

(EFM), magnetic force microscopy (MFM), scanning tunneling microscoy (STM), and Raman Spectra<br />

measurements. Both local and bulk measurements indicated a str<strong>on</strong>g dependence <strong>on</strong> the degree of coverage of the<br />

graphene surface with functi<strong>on</strong>alized sites. The measurements showed the presence of a superparamagnetic order<br />

in the graphene regi<strong>on</strong>s with a relatively low-density of functi<strong>on</strong>alized sites in the entire temperature range from 2 to<br />

300 K. In c<strong>on</strong>trast, the regi<strong>on</strong>s with a relatively high-density of functi<strong>on</strong>alized sites displayed a ferromagnetic order<br />

even at room temperature. In summary, the measurements indicated that aryl radical functi<strong>on</strong>alied multi-layered<br />

graphene <strong>on</strong> Silic<strong>on</strong> Carbide could simultaneously be a semic<strong>on</strong>ductor and a ferromagnet at room temperature.<br />

PN17<br />

Tuning of the curie temperature by varying reducti<strong>on</strong> potential in<br />

electrochemically prepared thin films of Prussian blue analogue based<br />

molecular magnets<br />

Pramod Bhatt*, M. D. Mukadam and S. M. Yusuf<br />

Solid State Physics Divisi<strong>on</strong>, Bhabha Atomic Research Centre, Mumbai-400085, India<br />

The quest for molecular magnets with ordering temperature at or above room<br />

temperature is highly desirable for their practical applicati<strong>on</strong>s at ambient c<strong>on</strong>diti<strong>on</strong>s.<br />

In order to increase the ordering temperatures, many efforts have been devoted<br />

to synthesizing compounds with appropriate choice of organic/inorganic ligands,<br />

their valence modulati<strong>on</strong> and spin centers, and alkali metal i<strong>on</strong> doping, etc., using<br />

organometallic and/or coordinati<strong>on</strong> chemical methods. However, we have shown<br />

that, the magnetic ordering temperature in PBAs (Prussian blue analogues) can be<br />

enhanced by varying reducti<strong>on</strong> potential in electrodepositi<strong>on</strong> method. In this regard,<br />

the electrochemically prepared films of PBAs, XjFeIIk[CrIII(CN)6]l.mH2O with<br />

varying reducti<strong>on</strong> potential are investigated using dc magnetizati<strong>on</strong> measurements. The<br />

magnetizati<strong>on</strong> data for film deposited at lower reducti<strong>on</strong> voltage shows ferromagnetic<br />

ordering with TC (Curie temperature) of ~ 21 K, similar to previously reported<br />

ordering temperature for this compound. However, an increase in TC up to ~50 K has<br />

been observed for film deposited at higher reducti<strong>on</strong> potential. The observed variati<strong>on</strong><br />

in TC is mainly attributed to the inclusi<strong>on</strong> of potassium i<strong>on</strong> (K+) at higher reducti<strong>on</strong><br />

potential, which changes stoichiometry of the film. The ability of tuning TC just by<br />

changing reducti<strong>on</strong> potential could be useful for designing future device applicati<strong>on</strong>s.


PN18<br />

Evoluti<strong>on</strong> of multifuncti<strong>on</strong>al behavior in site specific cati<strong>on</strong> substituted<br />

Na 0.5Bi 0.45Gd 0.05Ti 0.95Mn 0.05O 3 ceramics<br />

T Karthik 1,2 and Saket Asthana 1 *<br />

1 Advanced Functi<strong>on</strong>al Materials Laboratory, Department of Physics,<br />

Indian Institute of Technology Hyderabad, Andhra Pradesh - 502205, India<br />

2 Department of Materials Science and Engineering,<br />

Indian Institute of Technology Hyderabad, Andhra Pradesh - 502205, India<br />

A novel multifuncti<strong>on</strong>al behavior was observed by site specific cati<strong>on</strong> substituti<strong>on</strong> in<br />

NBT ceramics prepared by c<strong>on</strong>venti<strong>on</strong>al solid state reacti<strong>on</strong> technique. X-ray diffracti<strong>on</strong><br />

studies revealed the co-existence of orthorhombic reflecti<strong>on</strong>s in co-substituted NBT<br />

system al<strong>on</strong>g with the primary R3c phase. Raman spectroscopy of NBT-GM ceramics<br />

reveals a substantial change in all ph<strong>on</strong><strong>on</strong> modes in terms of suppressi<strong>on</strong> and shift<br />

indicates that the substituti<strong>on</strong> affects nature of the cati<strong>on</strong> displacement, octahedral tilt<br />

and hybridizati<strong>on</strong>. Reduced polarizati<strong>on</strong> value in NBT-GM ceramics with n<strong>on</strong>-saturated<br />

hysteresis loops gives evidence for the suppressi<strong>on</strong> of ferroelectricity. Temperature<br />

dependent magnetizati<strong>on</strong> measurements from R.T to 2.5K in NBT-GM ceramics show<br />

the occurrence of spin-paramagnetic behavior. Susceptibility plots show some evidence<br />

for weak interacti<strong>on</strong> between Mn 4+ i<strong>on</strong>s at low temperatures below 30K. UV-Vis<br />

spectroscopy measurements reveal the indirect transiti<strong>on</strong> allowed band gap nature for<br />

both NBT and NBT-GM ceramics with a slight increase in band gap (E g) value for NBT-<br />

GM ceramics. Photoluminescence measurements show a str<strong>on</strong>g blue emissi<strong>on</strong> at ~390nm<br />

(3.18 eV) in Gd-Mn substituted NBT system, which corresp<strong>on</strong>ds to radiative transiti<strong>on</strong><br />

from 4 T 1g → 4 A 2g energy levels of Mn 4+ -i<strong>on</strong>s.<br />

PN19<br />

Magnetic doping effect <strong>on</strong> physical properties of PbPdO 2<br />

Kyujo<strong>on</strong> Lee, Se<strong>on</strong>gmin Choo and Myung-hwa Jung*<br />

Sogang University, Korea<br />

The exotic features of gapless semic<strong>on</strong>ductors have attracted many researchers in solid<br />

state physics. Materials such as HgCdTe have been studied as a gapless semic<strong>on</strong>ductor.<br />

Recently PbPdO 2 has been theoretically proposed to be a gapless semic<strong>on</strong>ductor.<br />

In additi<strong>on</strong>, by substituting Co for Pd i<strong>on</strong>s the material becomes a spin gapless<br />

semic<strong>on</strong>ductor which has full spin polarizati<strong>on</strong>. In this study we have experimentally<br />

shown the changes in the physical properties of PbPdO 2 by doping different magnetic<br />

i<strong>on</strong>s such as Co, Mn, and Zn. PbPdO 2 shows a metal-insulator-like transiti<strong>on</strong> at<br />

TMI=100 K in the resistivity vs. temperature measurements. The magnetic properties<br />

show a diamagnetic behavior at high temperatures and a ferromagnetic behavior at<br />

low temperatures. The TMI increases to 150 K by Co doping and the diamagnetic<br />

behavior changes to paramagnetic behavior. By Mn doping, the TMI decreases<br />

to 73 K and the magnetic behavior changes drastically to show antiferromagnetic<br />

ordering at low temperatures. However no difference has been found by Zn doping.<br />

The comm<strong>on</strong> feature for all materials is that the charge carrier density increases with<br />

doping. The easily tuned properties of PbPdO 2 show evidence that PbPdO 2 is a gapless<br />

semic<strong>on</strong>ductor and could be tuned to be a spin gapless semic<strong>on</strong>ductor.<br />

PN20<br />

An experimental approach using EPR and XMCD to explore hydrogen<br />

mediated ferromagnetism<br />

Seunghun Lee 1 , Bun-su Kim 1 , Y<strong>on</strong>g Nam Choi 2 , Naoki Ishimatsu 3 , Masahiro Sawada 3 ,<br />

W<strong>on</strong>-kyung Kim 1 , Ji Hun Park 1 , Y<strong>on</strong>g Chan Cho 1 and Se-young Je<strong>on</strong>g 1 *<br />

1 Cogno-Mechatr<strong>on</strong>ics Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

2 Korea Atomic Energy Research Institute, Korea<br />

3 Hiroshima University, Japan<br />

Since the ferromagnetism of III-VI based DMS materials such as GaMnAs was turned out to be based<br />

<strong>on</strong> carrier induced model, much progress has been made in developing its applicability but low operati<strong>on</strong><br />

temperature has limited the approach to functi<strong>on</strong>al devices[1]. Am<strong>on</strong>g other materials, Co doped ZnO has<br />

been regarded as str<strong>on</strong>g candidate for room temperature DMS but the origin of ferromagnetism has been <strong>on</strong><br />

c<strong>on</strong>troversy[2]. Previously, we reported experimental results <strong>on</strong> Co-H-Co resp<strong>on</strong>sible for ferromagnetism<br />

depending <strong>on</strong> hydrogen c<strong>on</strong>tents and positi<strong>on</strong>[3-5]. Here, in order to apply these phenomena for new<br />

functi<strong>on</strong>al devices, more c<strong>on</strong>vincing experimental evidence for Co-H-Co is necessary. In this study, we<br />

show the experimental approaches to hydrogen mediated ferromagnetic spin ordering in ZnCoO through<br />

electr<strong>on</strong> paramagnetic res<strong>on</strong>ance(EPR) and x-ray magnetic circular dichroism(XMCD). The signal intensity<br />

of ferromagnetic res<strong>on</strong>ance is attributed to hydrogen c<strong>on</strong>tents and spin/angular magnetic moments compared<br />

with theoretical model of Co-H-Co are calculated from XMCD spectrum. In additi<strong>on</strong>, the results of<br />

photoluminescence and spectrum of magnetic circular dichroism within UV-Vis range suggests the possibility<br />

for creating and manipulating spin-polarized carrier using hydrogenated ZnCoO. Through advanced theoretical<br />

calculati<strong>on</strong> for Co-H-Co model, we are expecting to obtain the direct evidence for Co-H-Co unit.<br />

[1] D. A. Allwood et al., Science, 309, 1688 (2005) [2] S. Lee et al., Appl. Phys. Lett. 94, 212507 (2009) [3] Y. C. Cho et al., Appl.<br />

Phys. Lett. 95, 172504 (2009) [4] S. J. Kim et al., Phys. Rev. B 81, 212408 (2009) [5] S. Lee et al., J. Appl. Phys. (in press, 2012)<br />

PN21<br />

PN22<br />

PN23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A role of mobility in hydrogen mediated ferromagnetism of ZnCoO<br />

Ji Hun Park 1 , Seunghun Lee 1 , W<strong>on</strong>-kyung Kim 1 , J<strong>on</strong>g Mo<strong>on</strong> Shin 2 , Y<strong>on</strong>g Chan Cho 1 ,<br />

Chae Ry<strong>on</strong>g Cho 2 , Hideomi Koinuma 1 and Se-young Je<strong>on</strong>g 1 *<br />

1 Dept. of Cogno-Mecatr<strong>on</strong>ics Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

2 Dept. of Nano Fusi<strong>on</strong> Technology, Pusan Nati<strong>on</strong>al University, Korea<br />

Diluted magnetic semic<strong>on</strong>ductors (DMSs) have recently been attracting much attenti<strong>on</strong> for<br />

their potential as spin manipulati<strong>on</strong> layers [1]. Although there have been reported several<br />

authorized DMSs, such as Mn doped GaAs, their limited operating temperature requires new<br />

DMS materials with high Curie temperature. Up to now, many theoretical and experimental<br />

studies about hydrogen mediated ferromagnetism in ZnCoO have been introduced [2-<br />

3]; however, the interacti<strong>on</strong> between such magnetic units as Co-H-Co complexes has not<br />

yet been c<strong>on</strong>firmed. Delocalized electr<strong>on</strong> in ZnCoO lattice is possibly c<strong>on</strong>sidered to play<br />

a crucial role in the correlati<strong>on</strong> [4]. In this work, we investigated the correlati<strong>on</strong> between<br />

carrier mobility and ferromagnetic spin ordering in ZnCoO. Electr<strong>on</strong> mobility was artificially<br />

c<strong>on</strong>trolled with the manipulati<strong>on</strong> of crystallinity and hydrogen c<strong>on</strong>tents. Hydrogen treatment<br />

is carried out using hot isostatic pressing (HIP) system. The correlati<strong>on</strong> between carrier<br />

mobility and ferromagnetic spin ordering was analyzed in terms of Co-H-Co magnetic units.<br />

Mobility-dependent ferromagnetic spin ordering is discussed in our experiment.<br />

[1] H. Ohno, Science, 281, 951 (1998). [2] C. H. Park and D. J. Chadi, Phys. Rev. Lett. 94, 127204<br />

(2005). [3] S. Lee et al., Appl. Phys. Lett. 94, 212507 (2009); Y. C. Cho et al., Appl. Phys. Lett. 95,<br />

172514 (2009); S. J. Kim et al., Phys. Rev. B 81, 212408 (2010). [4] Z. Lu et al., Appl. Phys. Lett.<br />

94, 152507 (2009).<br />

Magnetic and magneto-optical properties of TiO2:V semic<strong>on</strong>ductor<br />

oxide films with various resistivity<br />

Andrey F Orlov 1 , Le<strong>on</strong>id A Balagurov 1 , Ivan V Kulemanov 1 , Elena A Petrova 1 , Nikolai Perov 2 *, Elena<br />

A Gan'shina 2 , Le<strong>on</strong>id Yu Fetisov 2 , Anna S Semisalova 2 , Anastasia D Rubacheva 2 , Andrey Rogalev 3 ,<br />

Alevtina G Smekhova 4 and Lada V Yashina 2<br />

1<br />

Institute for Rare Metals, Moscow, 119017, Russian Federati<strong>on</strong>, Russia<br />

2<br />

Lom<strong>on</strong>osov Moscow State University, Russia<br />

3<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, Grenoble Cedex, France<br />

4<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, Grenoble Cedex, France; Lom<strong>on</strong>osov Moscow State University, Russia<br />

We present the investigati<strong>on</strong> results of semic<strong>on</strong>ducting films TiO2:V with 3-18%at. of vanadium, which<br />

develop our previous research of doped titanium oxide [1,2]. The films have been grown by RF magnetr<strong>on</strong><br />

sputtering <strong>on</strong> either LaAlO3 or rutile TiO2 substrates and revealed the room temperature ferromagnetic<br />

ordering in the wide range of resistivity (10-3-106 Ω•cm). For degenerate semic<strong>on</strong>ductors the values of<br />

magnetizati<strong>on</strong> were found to be lower. Magnetizati<strong>on</strong> of TiO2 doped with vanadium is maximum for all<br />

semic<strong>on</strong>ductor oxides doped with transiti<strong>on</strong> metal impurities. Maximum values of magnetizati<strong>on</strong> were<br />

observed in the films with a small c<strong>on</strong>tent of V impurity and corresp<strong>on</strong>ded to 4.8 Bohr magnet<strong>on</strong> per V atom.<br />

The V impurity was found to be utterly in the oxidized state <strong>on</strong>ly in the films with a small V c<strong>on</strong>centrati<strong>on</strong>.<br />

The magneto-optical resp<strong>on</strong>se in the 1.5-3.0 eV energy range was observed in samples with a high magnetic<br />

moment <strong>on</strong>ly. The results are discussed within the model of charge-transfer ferromagnetism suggested by<br />

Coey et al. [3,4]. Supported by RFBR and Ministry of Science and Educati<strong>on</strong> No.16.513.11.3088.<br />

[1] A.F. Orlov et al., JMMM, 320, 895 (2008); [2] E.A. Gan’shina et al., JMMM, 321, 723 (2009); [3] J.M.D. Coey et al., J. Phys. D: Appl. Phys.,<br />

41, 134012 (2008); [4] J.M.D. Coey et al., New J. Phys., 12, 053025 (2010).<br />

Magnetic properties and electrical c<strong>on</strong>ductivity <strong>on</strong> oxygen-deficient<br />

europium m<strong>on</strong>oxide<br />

Jun-young Kim 1 *, Pedro M.d.s. M<strong>on</strong>teiro 1 , Kiyoung Lee 1 , Adrian I<strong>on</strong>escu 1 , Stuart N Holmes 2 , Crispin H.w.<br />

Barnes 1 , Peter J Baker 3 , Sean Langridge 3 , Zaher Salman 4 , Andreas Suter 4 and Thomas Prokscha 4<br />

1<br />

Department of Physics, Cavendish Laboratory, University of Cambridge, J J Thoms<strong>on</strong> Avenue, Cambridge,<br />

CB3 0HE, United Kingdom<br />

2<br />

Toshiba Cambridge Research Laboratory, 208 Cambridge Science Park, Milt<strong>on</strong> Road, Cambridge, CB4<br />

OGZ, United Kingdom<br />

3<br />

ISIS, Harwell Science and Innovati<strong>on</strong> Campus, STFC, Ox<strong>on</strong> OX11 0QX, United Kingdom<br />

4<br />

Laboratory for Mu<strong>on</strong>-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland<br />

Pristine europium m<strong>on</strong>oxide (EuO) is a ferromagnetic semic<strong>on</strong>ductor with a Curie temperature (Tc) of 70<br />

K. Below Tc, the c<strong>on</strong>ducti<strong>on</strong> band is 100% spin-polarised [1] while at Tc it undergoes a metal-to-insulator<br />

transiti<strong>on</strong> [2]. These properties render it a promising material for future spintr<strong>on</strong>ic devices such as spin injecti<strong>on</strong><br />

electrodes or filters [3]. Tunable c<strong>on</strong>trol of magnetic properties is obtained by doping with oxygen vacancies.<br />

We present results <strong>on</strong> co-sputtered EuO 1-x films with Tc as high as 140 K. The films were characterized by<br />

SQUID magnetometry, x-ray and polarized neutr<strong>on</strong> reflectometry. The magnetic moment was found to increase<br />

m<strong>on</strong>ot<strong>on</strong>ically with oxygen vacancy c<strong>on</strong>centrati<strong>on</strong>. Density-functi<strong>on</strong>al theory calculati<strong>on</strong>s of EuO 1-x show<br />

that oxygen vacancies act as n-type dopants and that the excess electr<strong>on</strong>s preferentially populate the majority<br />

spin branch of the c<strong>on</strong>ducti<strong>on</strong> band [4]. We also present thickness-dependent magnetic properties of EuO 1-x<br />

thin films, where surface-induced changes were observed in films with below 5 nm thickness [5]. Mu<strong>on</strong><br />

spin rotati<strong>on</strong> measurements investigated microscopic magnetic behaviour and magnetic volume fracti<strong>on</strong> as a<br />

functi<strong>on</strong> of temperature. Electrical transport measurements in the Hall geometry will also be presented.<br />

[1] R. P. Panguluri, T. S. Santos, E. Negusse, J. Dvorak, Y. Idzerda, J. S. Moodera, and B. Nadgorny, Phys. Rev. B 78, 125307 (2008)<br />

[2] G. Petrich, S. v<strong>on</strong> Molnar, and T. Penney, Phys. Rev. Lett. 26, 885 - 888 (1971) [3] A. Schmehl et al., Nature Materials 6, 882 -<br />

887 (2007) [4] M. Barbagallo et al., Phys. Rev. B 81, 235216 (2010) [5] M. Barbagallo et al., Phys. Rev. B 84, 075219 (2011)<br />

July 8 - 13, 2012 Busan, Korea 61<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PN24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

<strong>Magnetism</strong> and optical properties of diluted magnetic semic<strong>on</strong>ductor<br />

superlattice GaGdAs/GaAs with GaGdAs nanograins<br />

Miyagawa Hayato*, Yuuki Uda, Shoutaro Matsumoto, Nakaba Funaki and Shyun<br />

Koshiba<br />

Faculty of Engineering, Kagawa University, Japan<br />

We found ferromagnetic coupling in the rare earth elements Gd doped GaAs DMS,<br />

abbreviated as GaGdAs, which was grown by molecular beam epitaxy (MBE).<br />

However, GaGdAs is easy to have distorti<strong>on</strong>s or dislocati<strong>on</strong>s, because the atomic size<br />

of Gd is large compared to GaAs matrix, and also there is lattice mismatch between<br />

GaGdAs layer and substrate. Superlattice (SL) structure of GaGdAs/GaAs, in which<br />

GaGdAs layers are interleaved with a few ML thick GaAs layer, is c<strong>on</strong>sidered to<br />

have a good crystallinity. We fabricate magnetic semic<strong>on</strong>ductor superlattice GaGdAs/<br />

GaAs and m<strong>on</strong>o layer GaGdAs by MBE and analyze the crystal structure by means of<br />

Transmissi<strong>on</strong> Electr<strong>on</strong> Microscopy (TEM) and measured the macroscopic magnetic<br />

properties by Alternating Gradient Magnetometer (AGM). In high resoluti<strong>on</strong> TEM<br />

images, there are GaGdAs grains of 2-3 nm, which has high Gd c<strong>on</strong>centrati<strong>on</strong> and<br />

lattice-matching in GaAs Matrix. The result of magnetic measurements shows that<br />

superlattice structures have larger saturated magnetizati<strong>on</strong> and smaller coercive field<br />

than that of m<strong>on</strong>olayers. We think that the GaGdAs grains, which are observed <strong>on</strong>ly<br />

in SL structures, possibly has main c<strong>on</strong>tributi<strong>on</strong> to generate ferromagnetism in room<br />

temperature. We also measured Photoluminescence of GaGdAs samples and found the<br />

energy band gap is larger than GaAs.<br />

PN25<br />

Ferromagnetism in hydrogenated fullerene<br />

Kyu W<strong>on</strong> Lee, Gi-wan Je<strong>on</strong> and Cheol Eui Lee*<br />

Physics, Korea University, Korea<br />

We identify St<strong>on</strong>er ferromagnetism in fcc C 60Hn (n=odd) by using a local density<br />

approximati<strong>on</strong> in the framework of the density functi<strong>on</strong>al theory. Hydrogen<br />

chemisorpti<strong>on</strong> <strong>on</strong> fullerenes creates quasilocalized π-electr<strong>on</strong>s <strong>on</strong> the fullerene surface,<br />

overlapping of their wave functi<strong>on</strong>s giving rise to a narrow half filled impurity band in<br />

the fcc C 60Hn. The St<strong>on</strong>er-type ferromagnetic exchange between the itinerant electr<strong>on</strong>s<br />

leads to spin-split impurity bands. The magnetic moment per C 60Hn molecule is 1 μB<br />

(for n=odd) or 0 (for n=even, including zero), <strong>on</strong>ly <strong>on</strong>e of the hydrogens c<strong>on</strong>tributing<br />

to the spin-split states. Direct overlapping of the quasilocalized π-electr<strong>on</strong> orbitals is<br />

essential for the ferromagnetism.<br />

1. T. L. Makarova, B. Sundqvist, R. Ho¨hne, P. Esquinazi, Y. Kopelevich, P. Scharff, V. A. Davydov,<br />

L. S. Kashevarova, and A.V. Rakhmanina, Nature (L<strong>on</strong>d<strong>on</strong>) 413, 716 (2001). 2. T. L. Makarova, B.<br />

Sundqvist, R. Ho¨hne, P. Esquinazi, Y. Kopelevich, P. Scharff, V. Davydov, L. S. Kashevarova, and<br />

A.V. Rakhmanina, Nature (L<strong>on</strong>d<strong>on</strong>) 440, 707 (2006). 3. S. Okada and A. Oshiyama, Phys. Rev. B 68,<br />

235402 (2003).<br />

PN26<br />

Enhancement of the magneto-optical effect by an additi<strong>on</strong> of Co in<br />

pseudo-quaternary II-VI magnetic semic<strong>on</strong>ductor CdMnCoTe films<br />

Masaaki Imamura* and Keisuke Ninomiya<br />

Electrical Engineering, Fukuoka Institute of Technology, Japan<br />

Magneto-optical properties with pseudo-quaternary magnetic semic<strong>on</strong>ductor<br />

CdMnCoTe films deposited <strong>on</strong> quartz glass substrates by using MBE equipment [1]<br />

have been studied at a visible wavelength regi<strong>on</strong> at room temperature. Depositi<strong>on</strong><br />

was made at an average rate of ~1 Å/sec for 8h using a 4N Co target sputtered by an<br />

electr<strong>on</strong> gun having an emissi<strong>on</strong>-current of 20 mA, a 5N CdTe effusi<strong>on</strong> cell heated at<br />

490˚C and a 4N MnTe cell at 1020˚C. Using this system, ~2-μm-thick CdMnTe and<br />

CdMnCoTe films were prepared <strong>on</strong> 0.5-mm-thick QG substrates. These films exhibited<br />

the preferred (111) growth and paramagnetic characteristics. The magnetizati<strong>on</strong><br />

intensity at 15 kOe at room temperature was approximately 2.5x10-4 emu for the<br />

Cd 0.65Mn 0.35Te film and 2.8x10-4 emu for the Cd 0.56Mn 0.39Co 0.05Te film, showing the<br />

values that were almost the same for two films. Faraday rotati<strong>on</strong> measured at 620 nm<br />

in the CdMnCoTe film was -0.32 deg/cm-G and that in the CdMnTe film was -0.10<br />

deg/cm-G. Thus the Faraday rotati<strong>on</strong> in the CdMnCoTe films was largely enhanced<br />

compared to that in the CdMnTe films. A direct ac Faraday rotati<strong>on</strong> observati<strong>on</strong> under<br />

1.27 kHz ac fields generated by a ring magnet [2] has successfully been carried out for<br />

the CdMnCoTe films.<br />

[1] A. Okada et al., IEEE Trans. Magn. 39, 3175 (2003). [2] A. Okada et al., J.Magn. Soc. Jpn., 31,<br />

328 (2007).<br />

62 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PN27<br />

Origin of ferromagnetism in Co-doped (La,Sr)TiO 3 diluted magnetic<br />

semic<strong>on</strong>ductors<br />

Xuefeng Wang 1 , Fengqi S<strong>on</strong>g 2 , Yi Shi 1 , R<strong>on</strong>g Zhang 1 and Jianbin Xu 3<br />

1 School of Electr<strong>on</strong>ic Science and Engineering, Nanjing University, China<br />

2 Department of Physics, Nanjing University, China<br />

3 Department of Electr<strong>on</strong>ic Engineering, The Chinese University of H<strong>on</strong>g K<strong>on</strong>g,<br />

China<br />

Diluted magnetic semic<strong>on</strong>ductors (DMSs) are <strong>on</strong>e of the important supporting materials<br />

for the new-generati<strong>on</strong> of spintr<strong>on</strong>ic devices. We prepared (La,Sr)TiO 3 (LSTO) and Codoped<br />

LSTO DMS nanocrystals through solvothemal technique combined with postannealing<br />

process. After that, the effects of c<strong>on</strong>centrati<strong>on</strong> of Co dopant, the annealing<br />

atmosphere, temperature, durati<strong>on</strong> and other c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the microstructures and<br />

magnetic properties were investigated. When the doping c<strong>on</strong>centrati<strong>on</strong> is lower than<br />

5 at.%, the observed room-temperature ferromagnetism (RTFM) of our samples is<br />

of intrinsic property. Meantime, it is found that the magnetism has the close relati<strong>on</strong><br />

with the c<strong>on</strong>centrati<strong>on</strong> of Co dopant and the amorphous carb<strong>on</strong> which is remained<br />

after annealing. Through c<strong>on</strong>trolling the annealing atmosphere and durati<strong>on</strong>, we can<br />

synthesize single-phase Co-doped LSTO nanocrystals. It is dem<strong>on</strong>strated that the RTFM<br />

is correlated with the structural defects induced in the Ar annealing process. It is also<br />

shown that Co-doped LSTO nanocrystals will have the CoO sec<strong>on</strong>dary phase when the<br />

Co doping c<strong>on</strong>centrati<strong>on</strong> is higher than 5 at.%. According to the interesting exchange<br />

biasing phenomen<strong>on</strong>, the RTFM of our samples is ascribed to the collecti<strong>on</strong> of the CoO<br />

nanophase or amorphous Co metallic impurities.<br />

PN28<br />

Two dimensi<strong>on</strong>al growth of Nb doped SrTiO 3 thin films and its<br />

superlattices<br />

Abhijit Biswas, Y<strong>on</strong>g Woo Lee, Min Hwa Jung and Yo<strong>on</strong> Hee Je<strong>on</strong>g*<br />

Department of Physics, Pohang University of Science and Technology, Korea<br />

Two dimensi<strong>on</strong>al growth modes were obtained for Nb doped SrTiO 3 thin films grown<br />

<strong>on</strong> TiO 2 terminated SrTiO 3 (001) substrates; as m<strong>on</strong>itored by in-situ reflecti<strong>on</strong> highenergy<br />

electr<strong>on</strong> diffracti<strong>on</strong> (RHEED). At low substrate temperature ordinary RHEED<br />

oscillati<strong>on</strong> was observed, indicating layer by layer growth. At high temperature,<br />

recovery of RHEED intensity after switching off laser pulses indicated the step flow<br />

growth mode. In both cases, films show metallic behavior with resistivity (ρ)~10-3<br />

Ω-cm. Nb:SrTiO 3/SrTiO 3 (NSTOm/STOn) superlattices were also being fabricated<br />

at low temperature c<strong>on</strong>taining five unit cell thick NSTO layers with various stacking<br />

sequences. Film surfaces were characterized by atomic force microscopy (AFM),<br />

showing high crystalline quality having steps of 3.9 A. At room temperature, resistivity<br />

was found to be 1~2 Ω-cm. The oxide superlattice growth approach might provide a<br />

useful way to c<strong>on</strong>trol the charge carrier and resistivity for novel device applicati<strong>on</strong>s.<br />

PN29<br />

Anomalous hall effect in ferromagnetic nanocomposite FeGa/Fe 3Ga<br />

thin films<br />

Dang Duc Dung 1 , Du<strong>on</strong>g Anh Tuan 2 , Yooleemi Shin 2 and Sunglae Cho 2 *<br />

1 Department of General Physics, School of Engineering Physic,Ha Noi University of<br />

Science and Technology, 1 Dai Co Viet road, Ha Noi, Viet Nam<br />

2 Department of Physics, University of Ulsan, Ulsan 680-749,, Korea<br />

The anomalous Hall effect (AHE) is a central topic in the study of the ferromagnetic materials because<br />

it exhibit <strong>on</strong>e of the str<strong>on</strong>g evidence for spin polarizati<strong>on</strong> [1]. There are three main mechanisms for AHE<br />

including intrinsic deflecti<strong>on</strong>, side jump and skew scattering. The AHE in intrinsic homogeneous magnetic<br />

material is related to spin polarize due to difference state of spin up and spin down at the Fermi energy<br />

level and matched to the Berry phase theory [2]. In inhomogeneous magnetic material, AHE implies the<br />

presence of spin dependent scattering mechanism. The skew scattering dominates at low temperature,<br />

while the side jump becomes important at high temperature [3]. Recently, we reported the observati<strong>on</strong> of<br />

weak AHE in FeGa epitaxial thin film <strong>on</strong> GaAs(001) substrate where FeGa displayed the A2 structure [4].<br />

The FeGa were recently rapidly studied because of its giant magnetostrictive characteristics [5, 6]. In this<br />

work, we report the observati<strong>on</strong> of AHE in nanocomposite FeGa/Fe cGa epitaxial thin film <strong>on</strong> GaAs(001).<br />

Unlike FeGa (A2-structure), the str<strong>on</strong>g AHE were shown up to 400 K. Interestingly, the nanocomposite<br />

FeGa/Fe 3Ga film exhibited str<strong>on</strong>g out-of-plane magnetizati<strong>on</strong>. We suggest that the origin of str<strong>on</strong>g AHE<br />

are magnetizati<strong>on</strong> orientati<strong>on</strong> of epitaxial Fe 3Ga (DO3-structure).<br />

[1] N. Nagaosa et al., Rev. Mod. Phys. 82, 1539 (2010). [2] M. V. Berry, Proc. Roy. Soc. of L<strong>on</strong>d<strong>on</strong> 392, 45 (1984). [3] P.<br />

Xi<strong>on</strong>g et al.,Phys. Rev. Lett. 69, 3220 (1992). [4] D. A. Tuan et al., to be printed in JAP. [5] J. Atulasimha et al., Smart Mater.<br />

Struct. 20, 043001 (2011). [6] O. M. J. van’t Erve et al., Appl. Phys. Lett. 91, 122515 (2007), and reference therein.


PN30<br />

MnAs nanoclusters embedded in GaAs: <strong>Magnetism</strong> and transport<br />

properties<br />

Du<strong>on</strong>g Van Thiet 1 , Dang Duc Dung 2 , Yooleemi Shin 3 and Sunglae Cho 3 *<br />

1<br />

Department of Physics, University of Ulsan, Ulsan 680-749, Republic of Korea,<br />

Korea<br />

2<br />

Department of General Physics, School of Engineering Physics,Ha Noi University of<br />

Science and Technology,1 Dai Co Viet road, Ha Noi, Viet Nam<br />

3<br />

Department of Physics, University of Ulsan, Ulsan 680-749,, Korea<br />

The fabricati<strong>on</strong> of magnetic nanocluster embedded in c<strong>on</strong>venti<strong>on</strong>al semic<strong>on</strong>ductor is a research trend<br />

because of their unique physical properties in electr<strong>on</strong>ics, optics and magnetism. The understanding of<br />

magnetic clusters effect <strong>on</strong> the transport and magnetic properties in semic<strong>on</strong>ductor is timely demanded for<br />

the spintr<strong>on</strong>ic device applicati<strong>on</strong>. In this work we embedded MnAs nanoclusters in GaAs(001) by growing<br />

MnAs/GaAs multilayer structure using molecular beam epitaxy. After growing 2000 A GaAs buffer layer<br />

<strong>on</strong> GaAs (100) substrate, the [MnAs (20 A)/GaAs (tGaAs)]4 multi-layer c<strong>on</strong>figurati<strong>on</strong>s were grown at<br />

400 oC, finally followed by the growth of 200 A-thickGaAs capping layer to avoid the oxidati<strong>on</strong> of inner<br />

layer. The tGaAs was selected as 100, 200 and 300 A. The reflecti<strong>on</strong> high energy diffracti<strong>on</strong> (RHEED)<br />

exhibited spotty patterns, indicating the island-growth of MnAs nanocluster. The result of cross-secti<strong>on</strong>al<br />

TEM measurement also showed that MnAs nanocluster are embedded in GaAs matrix successfully. The<br />

resistance was increased rapidly with decreasing temperature, indicating that the samples dem<strong>on</strong>strate<br />

semic<strong>on</strong>ductor behavior. The magnetic properties were carried out by the superc<strong>on</strong>ductor quantum interface<br />

devices (SQUID) measurement, which showed the TC above room temperature. The detail sample growth,<br />

and magnetic and transport properties of MnAs nanocluster embedded <strong>on</strong> GaAs will be discussed.<br />

PN31<br />

Half-metallic and ferromagnetic properties of carrier doping in Zn1 xCuxO Byung-sub Kang 1 , Kie-mo<strong>on</strong> S<strong>on</strong>g 1 , Y<strong>on</strong>g-sik Lim 1 , Kye<strong>on</strong>g-sup Kim 2 , Young-yeal<br />

S<strong>on</strong>g 2 and Se<strong>on</strong>g-cho Yu 2<br />

1<br />

Dept. of Nano science and Mechanical engineering, K<strong>on</strong>kuk University, Korea,<br />

Democratic Peoples’ Republic<br />

2<br />

Dept. of Physics and BK21 Physics Program, Chungbuk Nati<strong>on</strong>al University, Korea,<br />

Democratic Peoples’ Republic<br />

Diluted magnetic semic<strong>on</strong>ductors (DMSs) have attracted a great deal of attenti<strong>on</strong> because of the<br />

possibility of incorporating magnetic degrees of freedom in traditi<strong>on</strong>al semic<strong>on</strong>ductors. However,<br />

it is <strong>on</strong>e of the primary challenges to create the ferromagnetic semic<strong>on</strong>ductors due to the difficulty<br />

in the spin-injecti<strong>on</strong> into the semic<strong>on</strong>ductors to form DMSs at room temperature or above room<br />

temperature. Since ZnO is a direct wide-band gap semic<strong>on</strong>ductor which is piezoelectric, ZnO-based<br />

DMS would be useful for transparent thin film transistors, blue and UV light-emitting diodes and<br />

laser diodes. The precipitates of n<strong>on</strong>magnetic Cu dopants do not c<strong>on</strong>tribute to the magnetism. In<br />

our work, the stability of ferromagnetic state in ZnO-based DMSs with a c<strong>on</strong>centrati<strong>on</strong> of 2.77%,<br />

5.55%, and 8.33% has been investigated by first-principles calculati<strong>on</strong>s. The magnetic moments<br />

are not affected by changing the doping c<strong>on</strong>centrati<strong>on</strong>s, while the band gap is decreased as for<br />

increasing of Cu c<strong>on</strong>centrati<strong>on</strong>. The band gaps in Cu-doped ZnO are 0.65, 0.22, and 0.08 eV for the<br />

Cu c<strong>on</strong>centrati<strong>on</strong> of 2.77%, 5.55%, and 8.33%, respectively. The half-metallic character shows at<br />

low Cu c<strong>on</strong>centrati<strong>on</strong>, while it is disappeared as for increasing of Cu c<strong>on</strong>centrati<strong>on</strong>. The effects <strong>on</strong><br />

the electr<strong>on</strong>ic state by the hole (Nitrogen) doping have been investigated.<br />

PO01<br />

Synthesis and characterizati<strong>on</strong> of surface functi<strong>on</strong>alized magnetic<br />

polymer microspheres with multi-shell structure<br />

Zuli Liu*, Qing Li and Kailun Yao<br />

physics, Huazh<strong>on</strong>g university of science and technology, China<br />

We synthesize magnetic polymer microspheres with amino/ carboxyl groups<br />

<strong>on</strong> the surface. We also fabricate the microspheres by incorporating magnetite<br />

nanoparticles(MPs) into a silica shell around preformed polystyrene(PSt)/SiO 2<br />

core/shell microspheres. Due to the silanizati<strong>on</strong> reacti<strong>on</strong> with 3-aminopropyl<br />

triethoxysilane(APTES), the outermost silica shell is formed and linked with amino<br />

group at the same time. And we use PEG diacid to obtain carboxyl functi<strong>on</strong>alized<br />

microspheres via the reacti<strong>on</strong> between -NH2 and -COOH. Optical microscope and<br />

scanning electr<strong>on</strong> microscopy(SEM) show that the microspheres are m<strong>on</strong>odisperse<br />

with the average diameter about 2um; vibrating sample magnetometer(VSM)<br />

indicates that the synthesized sample with amino-group <strong>on</strong> the surface exhibits<br />

superparamagnetism with the saturati<strong>on</strong> magnetizati<strong>on</strong> 7emu/g; thermogravimetry(TG)<br />

reveals that the microspheres are thermally stable when temperature is below 300°C<br />

and the Fe 3O 4 c<strong>on</strong>tent is 20.68%. Last, the fluorescence microscope shows that the<br />

microspheres obtained can be successfully c<strong>on</strong>jugated with biomolecular, including<br />

streptavidin and antibody.<br />

PO02<br />

PO03<br />

PO04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Producti<strong>on</strong> of Fe 3-xZn xO 4 nanoparticles for agents in hyperthermia<br />

treatment<br />

Hiromasa Takeuchi*, Akinobu Kurokawa, Takuya Yanoh, Shinya Yano and Yuko<br />

Ichiyanagi<br />

Yokohama Nati<strong>on</strong>al University, Japan<br />

Fe 3-xZn xO 4(x=0.2, 0.4, 0.6, 0.8, 1) nanoparticle with average diameters 12nm were<br />

produced by our novel wet chemical method. The crystal structure and magnetic<br />

property of the obtained particle were investigated by X-ray diffracti<strong>on</strong> and SQUID<br />

magnetometer. DC magnetizati<strong>on</strong> measurement showed that the coercive force Hc and<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> Ms decreased as the composite parameter x increased. This<br />

phenomen<strong>on</strong> suggests that Zn 2+ i<strong>on</strong>s located <strong>on</strong> A-sites weaken the superexchange<br />

interacti<strong>on</strong> between A and B sites. From the AC magnetic susceptibility, a sample with<br />

compositi<strong>on</strong> of x=0.4 is expected for heating by external field. Temperature increase<br />

depending <strong>on</strong> the magnetic field strength and frequency supported that samples<br />

with compositi<strong>on</strong> of x=0.2, 0.4 were appropriate for use as an agent in hyperthermia<br />

treatment.<br />

Gene delivery using polyethylenimine-coated magnetic nanoparticles<br />

by static and oscillating magnetic field<br />

Yoshiyuki Takahashi 1 , Satoshi Ota 1 , Asahi Tomitaka 1 , Tsutomu Yamada 1 , Daisuke<br />

Kami 2 , Shogo Takeda 3 , Masatoshi Watanabe 3 and Yasushi Takemura 1<br />

1 Electrical and Computer Engineering, Yokohama Nati<strong>on</strong>al University, Japan<br />

2 Kyoto Prefectural University of Medicine, Japan<br />

3 Materials and Chemical Engineering, Yokohama Nati<strong>on</strong>al University, Japan<br />

Recently gene delivery without viral vectors attracts rising attenti<strong>on</strong>. Low transfecti<strong>on</strong><br />

efficiencies of n<strong>on</strong>viral gene vectors such as transfecti<strong>on</strong> reagent limit their utility in gene<br />

therapy. To overcome this disadvantage, we report a transfecti<strong>on</strong> method using cati<strong>on</strong>ic<br />

polymer polyethylenimine(PEI)-coated magnetic nanoparticles and an external magnetic field.<br />

It shows high transfecti<strong>on</strong> efficiency as well as low cytotoxicity. In this study, transfecti<strong>on</strong><br />

efficiency of plasmid DNA in complex with PEI-coated magnetic nanoparticles was studied.<br />

HeLa cells were seeded the day before transfecti<strong>on</strong>. Immediately before transfecti<strong>on</strong>, the PEIcoated<br />

magnetic nanoparticles (γ-Fe 2O 3) were mixed with plasmid DNA. The complexes were<br />

incubated and added to HeLa cells <strong>on</strong> a NdFeB magnet and a coil. After 48 hours, transfecti<strong>on</strong><br />

efficiency of plasmid DNA to HeLa cells was evaluated by the average percentage of the<br />

fluorescent cells imaged by a fluorescent microscope in triplicate. The optimal amount of<br />

magnetic nanoparticles was 3.0 μg/sample <strong>on</strong> a magnet for 4 h. The transfecti<strong>on</strong> efficiency was<br />

increased five-times compared without magnetic nanoparticles (<strong>on</strong>ly PEI). Higher transfecti<strong>on</strong><br />

efficiency was obtained by applying an ac magnetic field. Further analysis <strong>on</strong> other parameters<br />

of an applied magnetic field and endocytosis are reported.<br />

Fabricati<strong>on</strong> of QD-anchored magnetic nanocomposites for biomedical<br />

applicati<strong>on</strong>s<br />

Hangdeok Oh and Sang-wha Lee*<br />

Department of Chemical and Bio Engineering, Kyungw<strong>on</strong> University, Korea<br />

WITHDRAWN<br />

July 8 - 13, 2012 Busan, Korea 63<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PO05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Determinati<strong>on</strong> of biomolecule interacti<strong>on</strong> in magnetic particle by<br />

voltammetry and ac impedance<br />

Ho<strong>on</strong> S<strong>on</strong>g and D. G. Park*<br />

korea atomic energy research institute, Korea<br />

Magnetic biochip based immunoassay have potential in many fields, such as<br />

envir<strong>on</strong>mental immunoassay, diagnostic immunoassay, and biochemical studies<br />

and immunosensors [1]. In the field of immunoassays, cyclic voltammetry (CV)<br />

technique have become known independently as methods suitable for the detecti<strong>on</strong><br />

of immunological reacti<strong>on</strong>s. CV measurements are the current signals based <strong>on</strong> the<br />

electrochemical species c<strong>on</strong>sumed and/or generated during a biological and chemical<br />

interacti<strong>on</strong> process of a biologically active substance and substrate. To apply to the real<br />

biomarker and verify the sensitivity of CV-based sensor, we used the biomarker scheme<br />

using the applied the real protein <strong>on</strong> the gold surface. The capture antibodies (P21<br />

m<strong>on</strong>o antibody) are first immobilized <strong>on</strong> the positive gold sensor surface. The samples<br />

with biomarkers (P21 recombinati<strong>on</strong> protein) to give antibody and antigen reacti<strong>on</strong><br />

are applied <strong>on</strong> gold surface. After the n<strong>on</strong> specific binding labels were successfully<br />

removed through the washing progress, <strong>on</strong>ly the chemically bounded bio molecules<br />

were remained <strong>on</strong> the Au surface. This enables to increase the sensitivity of the sensor<br />

for the binding of biomolecules <strong>on</strong> the gold surface. The difference in the CV represents<br />

the quantity of the antigen of interest and could be applied to the biosensor.<br />

[1] Choi JW, Chun BS, Oh BK, Lee W, Lee WH (2005) Fabricati<strong>on</strong> of DNA-protein c<strong>on</strong>jugate layer<br />

<strong>on</strong> gold-substrate and its applicati<strong>on</strong> to immunosensor. Coll Surf B 40:173-177<br />

PO06<br />

The effects of pulsed magnetic field stimulus <strong>on</strong> electromyographic<br />

activity<br />

Juye<strong>on</strong> Seo 1 , Y<strong>on</strong>gjin Kim 1 , Jaehyun Kim 1 , Sunghyun Kim 1 , Do Gwen Hwang 1 , Yunyeop<br />

Cha 2 and Hyun Sook Lee 1 *<br />

1 Department of Oriental Biomedical Engineering, Sangji University, Korea<br />

2 Department of Oriental rehabilitati<strong>on</strong> medicine, Sangji University, Korea<br />

Pulsed magnetic fields (PMF) c<strong>on</strong>ducting impulses toward the deep tissues as well as transcutaneous<br />

tissues are well known to be alternative n<strong>on</strong>-invasive medical treatment for influencing human<br />

physiology as compared with acupuncture. In traditi<strong>on</strong>al Chinese medicine, acupuncture is used<br />

clinically to relieve myalgia and many studies have attempted to elucidate its mechanism of<br />

acti<strong>on</strong> [1]. The aim of the present study was to examine the immediate effects of PMF stimulus<br />

<strong>on</strong> the electromyographic (EMG) activity at acupoint HT2, Quingling, which is a trigger point as<br />

hyperirritable spots in biceps brachii muscle <strong>on</strong> the arm [2]. Six healthy volunteers were asked to<br />

perform four repetiti<strong>on</strong>s of withstanding maximal isometric c<strong>on</strong>tracti<strong>on</strong> with 5-kg load and an elbow<br />

angle of 90o to cause fatigue in biceps brachii muscle <strong>on</strong> the arm. Analyzing power density spectrum<br />

from fast Fourier transformati<strong>on</strong> of EMG signal, we observed that median power frequency (MDF)<br />

decreased and median power increased due to muscle fatigue during isometric c<strong>on</strong>tracti<strong>on</strong>s. It was<br />

proved that PMF stimulus <strong>on</strong> acupoint was effective in relieving muscle pain by means of increased<br />

MDF and amplitude probability distributi<strong>on</strong> of RMS EMG shifted to high amplitude. Therefore, it<br />

may be c<strong>on</strong>cluded that appropriate PMF stimulus affects neuromuscular functi<strong>on</strong>.<br />

[1] K. Toma, R. C<strong>on</strong>atser, R. Gilders, and F. Hagerman, J. Strength & C<strong>on</strong>dit. Res. 12(4), 253-<br />

257(1998). [2] J. Majlesi & H. Unalan, Curr Pain Headache Rep 14,353-360(2010)<br />

PO07<br />

Magnetic anisotropy of Co dFe 3-dO 4 nanoparticles for applicati<strong>on</strong>s in<br />

magnetic hyperthermia<br />

Costica Caizer*<br />

Electricity and <strong>Magnetism</strong>, West University of Timisoara, Romania<br />

The magnetic behaviour of the Co dFe 3-dO 4 (d = 0 ~ 1.5) nanoparticles str<strong>on</strong>gly depends <strong>on</strong> the<br />

c<strong>on</strong>centrati<strong>on</strong> (d) of the cobalt i<strong>on</strong>s within the spinelic ferrite structure; this is a superparamagnetic<br />

behaviour for low d, a soft magnetic behaviour for moderate d, and a hard magnetic behaviour for high<br />

d. The d parameter determines a certain value of the magnetocrystalline anisotropy [1]. The effective<br />

magnetic anisotropy in the case of nanoparticles is a very important intrinsic parameter (besides their<br />

diameter) to obtain the magnetic hyperthermia (MHT), with a great influence <strong>on</strong> the specific absorpti<strong>on</strong><br />

rate (SAR), in the case of their usage in medicine to obtain tumour magnetic hyperthermia (to destroy<br />

tumour cells) [2,3]. The purpose of this research is to determine the magnetic anisotropy of the Co dFe 3dO<br />

4 nanoparticles, having the diameters of 2 ~ 17 nm, to identify its origin (magnetocystalline or/<br />

and other nature (surface anisotropy or/and shape anisotropy)), and also to establish, based <strong>on</strong> the<br />

experimental results, the most suited nanoparticles (as anisotropy and diameter) in order to use them in<br />

intracellular MHT [4]. The obtained results are presented and discussed in detail in the paper.<br />

Acknowledgement: This work was supported by PCCA-2012 project from the UEFISCDI-ANCS<br />

Romania. References [1] R. Valenzuela, Magnetic Ceramics (Cambridge Univ. Press, Cambridge)<br />

(1994). [2] C.L. Ondeck, A.H. Habib, P. Ohodnicki, K. Miller, C.A. Sawyer, P. Chaudhary, M.E.<br />

McHenry, J. Appl. Phys. 105 (2008) 07B324. [3]. C. Caizer, N. Hadaruga, D. Hadaruga, G.<br />

Tanasie, P. Vlazan, 7th Int. C<strong>on</strong>f. <strong>on</strong> Inorganic Materials, 12 - 14 Sept. 2010, Biarritz, France. [4] J.P.<br />

Fortin, F. Gazeau, Eur. Biophys. J. 37 (2008) 223.<br />

64 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PO08<br />

Magnetic nanoemulsi<strong>on</strong> as advanced drug delivery system applied to<br />

synergic procedures in the photodynamic therapy and hyperthermia<br />

trials using human mesenchymal stem cells as biological model<br />

Fernando Lucas Primo 1 , Daniela Regina Jardim 1 , Paulo Cesar Morais 2 and Ant<strong>on</strong>io Claudio Tedesco 1 *<br />

1 Chemistry, Nanotechnology and Tissue Engineering Center, FFCLRP, Sao Paulo University, Ribeirao Preto, SP, Brazil<br />

2 Physical, Brasilia University - UnB, Physical Institute, Brasilia-DF, 70910-900., Brazil<br />

Tissue engineering and nanotechnology are important research fields in the future development of biological models<br />

useful for the understanding of wound healing processes, extracellular matrix activity and other biological skin<br />

activities[1]. This study reports <strong>on</strong> the synthesis and characterizati<strong>on</strong> of advanced drug delivery system with magnetic<br />

properties useful to Photodynamic Therapy (PDT) and Hyperthermia (HPT). Magnetic-Nanoemulsi<strong>on</strong> (MNE) was<br />

obtained from sp<strong>on</strong>taneous nanoemulsificati<strong>on</strong> to entrapment/c<strong>on</strong>trolled-release of lipophilic drugs as described by<br />

Siqueira-Moura[2]. The results dem<strong>on</strong>strated appropriated physical-chemistry stability to MNE biomaterial with size<br />

< 200 nm, exhibited a narrow size distributi<strong>on</strong> (polydispersity index < 0.1) and zeta potential with modular value<br />

> Ι40Ι mV. Biological studies were carried out <strong>on</strong> human b<strong>on</strong>e mesenchymal stem cells determinati<strong>on</strong> of in vitro<br />

biocompatibility after incubati<strong>on</strong> with MNE which shown a safe c<strong>on</strong>centrati<strong>on</strong> drug specific for each cellular type.<br />

Besides, the in vitro synergic effect of PDT and HPT were evaluated after simultaneous inducti<strong>on</strong> of photodynamic<br />

effects and magnetic field (40 Oe) applicati<strong>on</strong>. These results c<strong>on</strong>firmed that the use of nanotechnology associated<br />

with PDT and HPT procedures led to in vitro tumor inactivati<strong>on</strong> by advanced protocols that can be useful to future<br />

<strong>on</strong>cological treatment. Financial grant CNPq (D.R.J.) and FAPESP projects 2009/15363-9 and 2008/53719-4 (F.L.P.).<br />

[1] Primo, F L.; Reis, M. B. C.; Porci<strong>on</strong>atto, M. A.; Tedesco, A. C. In vitro Evaluati<strong>on</strong> of Chloroaluminum Phthalocyanine<br />

Nanoemulsi<strong>on</strong> and Low-Level Laser Therapy <strong>on</strong> Human Skin Dermal Equivalents and B<strong>on</strong>e Marrow Mesenchymal<br />

Stem Cells. Current Medicinal Chemistry, 18, 3376-3381, 2011. [2] Siqueira-Moura, M.P.; Primo, F.L.; Peti, A.P.F.;<br />

Tedesco, A.C. Validated spectrophotometric and spectrofluorimetric methods for determinati<strong>on</strong> of chloroaluminum<br />

phthalocyanine in nanocarriers. Pharmazie, 65, 1-6. 2010.<br />

PO09<br />

The morphological change of red blood cells in the hand exposed to the<br />

stimulus of str<strong>on</strong>g pulse magnetic field<br />

Jiny<strong>on</strong>g Lee 1 , Hyun Sook Lee 1 , Jun Sang Yu 2 and Do Guwn Hwang 1 *<br />

1 Oriental Medical Engineering, Sangji University, Korea<br />

2 Oriental Medical, Sangji University, Korea<br />

The influence of magnetic field <strong>on</strong> human body has been studied to use as applicati<strong>on</strong> of<br />

therapeutic equipment for a l<strong>on</strong>g time. Some studies have carefully suggested that vascular<br />

blood flow volume can be increased by an electromagnetic field stimulus [1-3]. In this<br />

study, live blood analysis (LBA) of blood collected in the hand stimulated by str<strong>on</strong>g pulsed<br />

magnetic field was used in vitro to get the morphological change of red blood cells before<br />

and after magnetic stimulus. The LBA is a test methodology to approach the risk factors of<br />

illness, states of immunity, nutriti<strong>on</strong>al states of cells, degrees of hidden lesi<strong>on</strong>s, or treatments<br />

over time. The analysis can accomplish these goals functi<strong>on</strong>ally and preventively by<br />

observing morphological changes of ingredients c<strong>on</strong>stituting blood, which is alive without<br />

being chromated and collect through peripheral blood vessel. Our system was designed to<br />

generate a pulsed magnetic field that had a maximum intensity variati<strong>on</strong> of 0.48 T and a<br />

transiti<strong>on</strong> time of 0.102 msec. LBA were d<strong>on</strong>e in the blood collected before and after the<br />

stimulati<strong>on</strong> of 10 minutes in the hand. As a result, the hemadsorpti<strong>on</strong> (adhesi<strong>on</strong> of red blood<br />

cells) observed before stimulus were normally distributed after stimulus of blood.<br />

[1] D. Roland, M. Ferder, R. Kothura, T. Faierman, and B. Strauch, Plast. Rec<strong>on</strong>str. Surg. 105, 1371<br />

(2000). [2] H. N. Mayrovitz and P. B. Larsen, Wounds 4, 197 (1992). [3] H. N. Mayrovitz and P. B.<br />

Larsen, Wounds 7, 90 (1995).<br />

PO10<br />

An analytical comparis<strong>on</strong> in electoencephalography and<br />

electrocardiography during stimulus of pulsed magnetic field and<br />

acupuncture <strong>on</strong> acupoint PC9<br />

Jinyoung Lee 1 , Do Guwn Hwang 1 , Yun-Yeop Cha 2 and Hyun Sook Lee 1 *<br />

1 Department of Oriental Biomedical Engineering, Sangji University, Korea<br />

2 Department of Oriental rehabilitati<strong>on</strong> medicine, Sangji University, Korea<br />

With recent increasing attenti<strong>on</strong> <strong>on</strong> the pulsed magnetic field stimulus as n<strong>on</strong>-invasive medical<br />

treatment, diverse studies are being c<strong>on</strong>ducted to elucidate its effects <strong>on</strong> human physiology<br />

[1]. Am<strong>on</strong>g several bio-signals obtained from human body, electroencephalography and<br />

electrocardiography are known to have no side effect and provide real-time informati<strong>on</strong> <strong>on</strong><br />

aut<strong>on</strong>omic nervous activity with spectral analysis. The aim of the present study was to compare the<br />

changes of EEG and ECG during the PMF and acupuncture stimulus <strong>on</strong> acupoint, which is known to<br />

sedati<strong>on</strong> and t<strong>on</strong>ificati<strong>on</strong> point. In order to compare qualitatively the effect of PMF and acupuncture<br />

stimulus, the difference of alpha activities are calculated from EEG spectra compared with before,<br />

during and after stimulus, and the spectrum curves of ECG were analyzed in the frequency domain<br />

of heart rate variability. The increase of alpha activities after both stimuli could be explained that the<br />

impulse of stimulus <strong>on</strong> PC9 might pass through sensory nerve following meridian and approach the<br />

cerebral cortex, causing the CNS to be activated for pacifying emoti<strong>on</strong> and calming the mind [2].<br />

The decrease in index of sympathovagal activity after both stimuli indicates that parasympathetic<br />

nerves were activated and the sympathetic nerves were in c<strong>on</strong>strained c<strong>on</strong>diti<strong>on</strong>.<br />

[1] N.M. Shupak, F.S. Prato, and A.W. Thomas, Neurosci. Lett. 363, 157 (2004). [2] H.S. Lee, S.W.<br />

Kim, D.G. Hwang, IEEE transacti<strong>on</strong> <strong>on</strong> Magn. 47(10), 3060 (2011).


PO11<br />

Reliability of a head movement compensati<strong>on</strong> method based <strong>on</strong><br />

minimum norm estimati<strong>on</strong> for magnetoencephalographic recordings<br />

Sanghyun Lim and Kiwo<strong>on</strong>g Kim*<br />

brain and cogniti<strong>on</strong> measurement lab, KRISS, Korea<br />

N<strong>on</strong>-invasive multi-channel recordings of neur<strong>on</strong>al activity of brain play an important<br />

role in brain research fields. Magnetoencephalography (MEG) which measures<br />

magnetic field generated by synchr<strong>on</strong>ous firing of group of neur<strong>on</strong>s, has superior<br />

spatial and temporal resoluti<strong>on</strong>s with quick and easy recording procedures. However,<br />

a movement of subject’s head during recordings makes significant data distorti<strong>on</strong>s,<br />

since the array of multi-channel sensors is not physically fixed to subject’s head.<br />

One approach compensating these distorti<strong>on</strong>s is to utilize a singular-value-truncated<br />

minimum norm estimati<strong>on</strong> (MNE) method to generate virtual MEG signals at a<br />

comm<strong>on</strong> reference head positi<strong>on</strong>. Since MNE is biased to minimize the total output<br />

power, this approach can be applied to signals which have a number of distinct sources<br />

generating event related fields (ERF), but not to sp<strong>on</strong>taneous neur<strong>on</strong>al recordings.<br />

In this study, we calculated compensati<strong>on</strong> errors of ERF recordings and sp<strong>on</strong>taneous<br />

neur<strong>on</strong>al recordings, by comparing real sensor signals to virtually-generated signals, to<br />

see the reliability of the method for sp<strong>on</strong>taneous recordings. MEG data were recorded<br />

using a 152-channel whole head helmet MEG system (KRISS MEG system) within a<br />

magnetically shielded room, and each channel was simulated and compared with each<br />

time trials.<br />

PO12<br />

The effect of small quantities of irradiati<strong>on</strong> damage <strong>on</strong> the magnetic<br />

properties of Steel 316.<br />

Robert Aldus 1 , Jack Muir 1 , Greg Lumpkin 2 and Paolo Imperia 1 *<br />

1 bragg institute, ANSTO, Australia<br />

2 IME, ANSTO, Australia<br />

The Steel 300 series is often used in applicati<strong>on</strong>s where a n<strong>on</strong>-magnetic steel is<br />

required. The materials take the austentite FCC crystal structure as opposed to the<br />

ferrite structure comm<strong>on</strong> in magnetic steels. It has previously been suggested that<br />

large doses of radiati<strong>on</strong> (approximately 1022 i<strong>on</strong>s/cm2) can cause a change in the<br />

local crystal structure of steel-316 to the ferrite structure and thus creating a magnetic<br />

signal [1]. We have performed x-ray absorpti<strong>on</strong>, x-ray dichroism and neutr<strong>on</strong> scattering<br />

using WOMBAT at ANTSO where we also commissi<strong>on</strong>ed the new ANSTO Oxford<br />

Instruments cryomagnet. The samples of steel-316 were irradiated to <strong>on</strong>ly about 10 15<br />

i<strong>on</strong>s/cm2 using He + i<strong>on</strong>s. This level of irradiati<strong>on</strong> should not be enough to change the<br />

bulk crystal structure and yet we observe some magnetic signal. We present our results<br />

and explanati<strong>on</strong> for our findings.<br />

PO13<br />

Study of a hybrid magnet array for an electrodynamic maglev c<strong>on</strong>trol<br />

Chan Ham 1 , Kurt Lin 2 , Youngho<strong>on</strong> Joo 3 and W<strong>on</strong>suk Ko 4 *<br />

1 Mechatr<strong>on</strong>ics Engineering, Southern Polytechnic State University, USA<br />

2 Mechanical, Materials, and Aerospace, University of Central Florida, USA<br />

3 Kunsan Nat’l University, Korea<br />

4 Kyungw<strong>on</strong>.Univ, Korea<br />

This paper introduces an innovative hybrid array c<strong>on</strong>sisted of both permanent and electro magnets<br />

that would enable us to develop an active c<strong>on</strong>trol mechanism for underdamped EDS Maglev<br />

systems. The proposed scheme is based <strong>on</strong> the Halbach array c<strong>on</strong>figurati<strong>on</strong> in order to take the<br />

major technical advantage from the original Halbach characteristics: a str<strong>on</strong>gly c<strong>on</strong>centrated<br />

magnetic field <strong>on</strong> a side of the array and a cancelled field <strong>on</strong> the opposite side. The magnetic force<br />

produced by the proposed hybrid array can also be actively c<strong>on</strong>trolled. This force c<strong>on</strong>trollability<br />

resulted from a variable magnetic field is instrumental to provide a dynamic damping force to<br />

compensate the instability of EDS Maglev system caused by external perturbati<strong>on</strong>s and guideway<br />

irregularities. In this study, the magnetic characteristics and capability of the proposed array<br />

compared to the basic Halbach c<strong>on</strong>cept are focused. The results show that the proposed array is<br />

capable to produce an equivalent suspensi<strong>on</strong> force of the basic Halbach permanent magnet array but<br />

in a c<strong>on</strong>trolled mode. The effectiveness of the proposed array c<strong>on</strong>firms that this study can be used as<br />

a technical framework to develop an active c<strong>on</strong>trol mechanism for an EDS Maglev system.<br />

[1] D<strong>on</strong>ald M. Rote and Yigang Cai, “Review of Dynamic Stability of Repulsive-Force Maglev Suspensi<strong>on</strong> Systems,” IEEE<br />

Transacti<strong>on</strong>s On Magnetics, Vol. 38, No. 2, 1383-1390, March 2002 [2] R. F. Post and D. D. Ryutov, “The Inductrack: A<br />

Simpler Approach to Magnetic Levitati<strong>on</strong>,” IEEE Transacti<strong>on</strong>s <strong>on</strong> Applied Superc<strong>on</strong>ductivity, Vol. 10, 901-904, 2000<br />

PO14<br />

PO15<br />

PO16<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

FEM simulati<strong>on</strong> of magnetic treatment of surface vessel<br />

Y<strong>on</strong>gmin Kim 1 , Hwiseok Kim 2 , Kwan-seob Yo<strong>on</strong> 3 , Se<strong>on</strong>-ho Lim 3 , Jaew<strong>on</strong> Doh 2 ,<br />

Young-hak Kim 4 and Kwang-ho Shin 1 *<br />

1<br />

Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Kyungsung University,<br />

Korea<br />

2<br />

S/W R&D Center, Project 5 team, LIGNex1, Korea<br />

3<br />

S/W R&D Center, Project 4 team, LIGNex1, Korea<br />

4<br />

Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Puky<strong>on</strong>g Nati<strong>on</strong>al<br />

University, Korea<br />

Since most of surface vessels and submarines are c<strong>on</strong>structed with ferromagnetic materials, mainly<br />

Fe-C, Magnetic treatment (Deperm) of surface vessels and submarines is required to camouflage<br />

them against magnetic detecti<strong>on</strong> from enemy marine force. We investigated whether we could<br />

analyze practically magnetic treatment process of a surface vessel with FEM simulati<strong>on</strong>. Because<br />

a surface vessel has n<strong>on</strong>-linear ferromagnetic property as well as complicated structure with very<br />

large dimensi<strong>on</strong>, it is impossible to analyze the magnetic treatment process through c<strong>on</strong>venti<strong>on</strong>al<br />

FEM using scalar material c<strong>on</strong>stants. We tried to do the FEM analysis a hysteresis model. The<br />

magnetic property including hysteresis of the c<strong>on</strong>structing material of the submarine was calculated<br />

with the hysteresis model, and compared with the material property measured with the ferrite yoke<br />

method. The alternating magnetic field applied to the submarine in FEM analysis had several tens<br />

steps, and the maximum field was 1000 A/m. The analysis results showed that overall magnetic<br />

remanence was almost the same with that of hysteresis model. However, it was found that the<br />

magnetizati<strong>on</strong> in the endpiece of the vessel was changed n<strong>on</strong>-linearly. The simulated results could<br />

be analyzed with the ferromagnetic exchanging coupling of magnetic nodes in FEM model.<br />

Magnetically exchange-coupled nanoparticles as efficient heat inductor<br />

Seung Ho Mo<strong>on</strong>, Jung-tak Jang, Seung-hyun Noh, Jae-hyun Lee and Jinwoo Che<strong>on</strong>*<br />

Chemistry, Y<strong>on</strong>sei University, Korea<br />

The c<strong>on</strong>versi<strong>on</strong> of electromagnetic energy into heat by nanoparticles has the potential<br />

to be a powerful, n<strong>on</strong>-invasive technique for biotechnology, but poor c<strong>on</strong>versi<strong>on</strong><br />

efficiencies have hindered practical applicati<strong>on</strong>s so far. We dem<strong>on</strong>strate a significant<br />

increase in the efficiency of magnetic thermal inducti<strong>on</strong> by nanoparticles. We<br />

take advantage of the exchange coupling between a magnetically hard core and<br />

magnetically soft shell to tune the magnetic properties of the nanoparticle and<br />

maximize the specific loss power (SLP), which is a gauge of the c<strong>on</strong>versi<strong>on</strong> efficiency.<br />

We simulated SLP as a functi<strong>on</strong> of magnetocrystalline anisotropy K, diameter of the<br />

nanoparticle D, and magnetizati<strong>on</strong> M. The dependency <strong>on</strong> K chiefly results from the<br />

internal magnetic spin fluctuati<strong>on</strong> (Neel relaxati<strong>on</strong>), and the dependency <strong>on</strong> D is due<br />

to both Neel and Brownian relaxati<strong>on</strong>. Our simulati<strong>on</strong> indicates the optimal range of<br />

K and D for nanoparticles with high SLP values. High magnetizati<strong>on</strong> M is beneficial,<br />

too. The optimized core-shell magnetic nanoparticles have SLP values that are an order<br />

of magnitude larger than c<strong>on</strong>venti<strong>on</strong>al ir<strong>on</strong>-oxide nanoparticles. We also perform an<br />

antitumour study in mice, and find that the therapeutic efficacy of these nanoparticles is<br />

superior to that of a comm<strong>on</strong> anticancer drug.<br />

Nature Nanotech. 2011, 6(7), 418-422<br />

Theranostic magnetic nanoparticles<br />

Seung-hyun Noh, D<strong>on</strong>gw<strong>on</strong> Yoo, Jae-hyun Lee, Jung-tak Jang, Seung Ho Mo<strong>on</strong> and<br />

Jinwoo Che<strong>on</strong>*<br />

center for evoluti<strong>on</strong>ary nanoparticles, Korea<br />

The property of magnetic materials can be defined using some parameters such as<br />

saturati<strong>on</strong> magnetizati<strong>on</strong>(Ms), coercivity(Hc), and magnetocrystalline anisotropy(K).<br />

Understanding the interplay of these parameters is critical for optimizing magnetic<br />

characteristics we need for their effective use. We can c<strong>on</strong>trol these parameters by<br />

changing the shape, size and compositi<strong>on</strong> of nanoparticles. Because there are various<br />

species of applicati<strong>on</strong> of nanoparticles and magnetic properties needed to be optimized<br />

in each field of applicati<strong>on</strong> are all different flexible tuning of magnetic parameters<br />

is very important. Important capabilities of magnetic nanoparticles are the external<br />

c<strong>on</strong>trollability of magnetic heat generati<strong>on</strong> and magnetic attractive forces for the<br />

transportati<strong>on</strong> and movement of biological objects. We show that these functi<strong>on</strong>s can<br />

be utilized not <strong>on</strong>ly for therapeutic hyperthermia of cancer but also for c<strong>on</strong>trolled<br />

release of drugs through the applicati<strong>on</strong> of an external magnetic field. Additi<strong>on</strong>ally, the<br />

use of magnetic nanoparticles to drive mechanical forces is dem<strong>on</strong>strated to be useful<br />

for molecular-level cell signaling and for c<strong>on</strong>trolling the ultimate fate of the cell. The<br />

wide range of accessible features of magnetic nanoparticles underscores their potential<br />

as the most promising platform material available for theranostics.<br />

July 8 - 13, 2012 Busan, Korea 65<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PO17<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

I<strong>on</strong>-texturing & Dynamics in Layered Compounds: From Electric Automobiles to Frustrated <strong>Magnetism</strong><br />

Martin Manss<strong>on</strong> 1 *, Jun Sugiyama 2 , Kazuhiko Mukai 2 , Yutaka Ikedo 3 , Hiroshi Nozaki 2 , Kazuya Kamazawa 2 ,<br />

Masashi Harada 2 , Marisa Medarde 4 , Fanni Juranyi 5 , Jorge Gavilano 5 , James S. Lord 6 , Isao Watanabe 7 , Ekaterina<br />

Pomjakushina 4 , Kazimierz C<strong>on</strong>der 4 , Vladimir Pomjakushin 5 , Tsutomu Ohzuku 8 and Tsunehiro Takeuchi 9<br />

1 Lab. for Solid State Physics, ETH Zurich, Switzerland<br />

2 Toyota Central Research and Development Labs. Inc., Japan<br />

3 Mu<strong>on</strong> Science Laboratory, KEK, Japan<br />

4 LDM, Paul Scherrer Institut, Switzerland<br />

5 Lab. for Neutr<strong>on</strong> Scattering, Paul Scherrer Institut, Switzerland<br />

6 ISIS, Rutherford Applet<strong>on</strong> Laboratory, United Kingdom<br />

7 Mu<strong>on</strong> Science Laboratory, RIKEN, Japan<br />

8 Department of Applied Chemistry, Osaka City University, Japan<br />

9 Department of Applied Physics, Nagoya University, Japan<br />

The drastic change from an antiferromagnetic to a superc<strong>on</strong>ducting state in cuprates exemplifies how a slight change in<br />

carrier-density str<strong>on</strong>gly governs magnetic and electr<strong>on</strong>ic properties. In cuprates the intermediate i<strong>on</strong>-layers are thought<br />

to <strong>on</strong>ly serve as 'passive' charge-reservoirs. However, it has become increasingly clear that also i<strong>on</strong>-order within these<br />

layers is of great importance [1]. Further, it was recently dem<strong>on</strong>strated that also i<strong>on</strong>-dynamics needs to be c<strong>on</strong>sidered. In<br />

the Na 0.8CoO 2 compound it was shown that the low-T magnetic properties could be c<strong>on</strong>nected to Na dynamics a much<br />

higher temperatures [3,4]. From the c<strong>on</strong>text of rechargeable Li-i<strong>on</strong> batteries for electrical cars, our group has recently<br />

presented a novel experimental method [5] to investigate microscopic i<strong>on</strong>-dynamics in lithium-transiti<strong>on</strong>-metal-oxides<br />

(Li-TMO). By using the μSR technique we have obtained results regarding i<strong>on</strong>-dynamics in a wide range of Li-TMO's<br />

[6-7]. We will here give an overview of the method/results as well as discuss their importance for the development of<br />

thin-film batteries for the future. Finally, we will also present our latest results regarding Na-dynamics in magnetically<br />

frustrated compound Na xCoO 2. With the use of μSR, neutr<strong>on</strong> quasi-elastic neutr<strong>on</strong> scattering and diffracti<strong>on</strong>, we show<br />

how solid state dynamics is imperative for tuning this compound's magnetic/electr<strong>on</strong>ic/thermoelectric properties.<br />

[1] Y. Sassa et al., PRB 83, 140511(R) (2011) [2] W. Bao et al., arXiv:1102.3674v1 (2011) [3] T. F. Schulze et al., PRL 100, 026407 (2008) [4]<br />

M. Weller et al., PRL 102, 056401 (2009) [5] J. Sugiyama et al., PRL 103, 147601 (2009) [6] J. Sugiyama et al., PRB 82, 224412 (2010) [7] J.<br />

Sugiyama et al., PRB 84, 054430 (2011) Funding Source: Swiss Nati<strong>on</strong>al Science Foundati<strong>on</strong> (Project 6, NCCR MaNEP) and Toyota CRDL.<br />

PO18<br />

Large resistive switching phenomen<strong>on</strong> induced by magnetic field in<br />

nano c<strong>on</strong>ducti<strong>on</strong> path formed in SiO 2<br />

Shintaro Otsuka, Tomohiro Shimizu*, Takashi Kato, Takuya Kyomi and Shoso<br />

Shingubara<br />

Kansai University, Japan<br />

A large magnetoresistance (MR) exceeded 800% was observed in a nano c<strong>on</strong>ducti<strong>on</strong><br />

path (NCP) formed in SiO 2 layer sandwiched between Co film and Si substrate.<br />

Applied a high voltage of 20 MV / cm between the Co film and the backside of<br />

Si substrate, the NCP was formed by dielectric breakdown of SiO 2 layer. The<br />

Magnetoresistance of the NCP in in-plane magnetic field for NCP was measured.<br />

Using Ni layer instead of Co, the large MR also appeared, but could not be observed<br />

in the case of using n<strong>on</strong>-magnetic materials. The structure of the device was similar to<br />

the resistive switching memory device, regarding Co layer and Si substrate as top and<br />

bottom electrode. Therefore we also measured I-V characteristic of the NCP device,<br />

and the resistive switching effect was observed. We haven’t fully understood the<br />

mechanism of this large MR switching phenomen<strong>on</strong> yet. However, it is speculated that<br />

the atomic scale NCP c<strong>on</strong>sisted of Co atoms was formed due to dielectric breakdown<br />

of SiO 2, and the nano gap in NCP was formed by magnetic field.<br />

Jpn. J. Appl. Phys., 50 (2011) 06GG15.<br />

PO19<br />

Size dependence simulati<strong>on</strong> of saturated field in circular permalloy<br />

Xinghao Hu, Byunghwa Lim, Ilgyo Je<strong>on</strong>g and Cheolgi Kim*<br />

Department of Materials Science and Engineering, Chungnam Nati<strong>on</strong>al University,<br />

Korea<br />

Manipulati<strong>on</strong> of magnetic beads for biomoleculars and cells separati<strong>on</strong>, purificati<strong>on</strong> and<br />

sensing applicati<strong>on</strong> is of great fundamental and practical interest [1]. On-chip magnets<br />

of soft magnetic structure of permalloy is a classic manipulati<strong>on</strong> systems for magnetic<br />

beads, which utilizes external magnetic fields for c<strong>on</strong>trol of the magnetic beads [2].<br />

The maximum of magntic force generated by <strong>on</strong>-chip magnet in an applied field should<br />

be obtained for transportati<strong>on</strong> of magnetic beads. We present a simulati<strong>on</strong> method that<br />

is available to enable a maximum value of magnetic force under an advisable field. As<br />

shown in simulati<strong>on</strong>s, when the applied field is gradually increased to 130 Oe <strong>on</strong> the<br />

<strong>on</strong>-chip magnet of 5 um radius, the magnetizati<strong>on</strong> of the <strong>on</strong>-chip magnet is saturated<br />

that means a maximum value of magnetic force is obtained. Therefore, this simulati<strong>on</strong><br />

method can assist researchers to obtain the advisable field for maximum of magntic<br />

force in designing variform <strong>on</strong>-chip magnets.<br />

[1] J. Dobs<strong>on</strong>, Nat. Nanotech., 2008, 3, 139. [2] K. Gunnarss<strong>on</strong>, P. E. Roy, S. Felt<strong>on</strong>, J. Pihl, P.<br />

Svedlindh, S. Berner, H. Lidbaum, and S. Oscarss<strong>on</strong>, Adv.Mater., 2005, 17, 1730.<br />

66 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PO20<br />

A new definiti<strong>on</strong> of magneto-mechatr<strong>on</strong>ics and applicati<strong>on</strong>s<br />

Sung Ho<strong>on</strong> Kim*, Jaew<strong>on</strong> Shin, Shuichiro Hashi and Kazushi Ishiyama<br />

Research Institute of Electrical communicati<strong>on</strong>, Tohoku University, Japan<br />

Recently, magnetic wireless sensors and actuators have been developed for use in biomedical fields. In<br />

particular, their mechanisms depend <strong>on</strong> magnetics, such as magnetic material and physical phenomena.<br />

However, their research boundary has not been clear. Researchers talk of magnetic micro-robots, magnetic<br />

actuators and sensors, and so <strong>on</strong> [1-3]. Therefore, a new and correct definiti<strong>on</strong> is required. Magneticmechatr<strong>on</strong>ics<br />

is synergistic integrati<strong>on</strong> of magnetic engineering, mechanical engineering, and electr<strong>on</strong>ics/<br />

computer engineering in the design, manufacturing, and c<strong>on</strong>trol process. In particular, magneticmechanical<br />

mechanisms are directly c<strong>on</strong>trolled by external magnetic fields. Magneto-mechatr<strong>on</strong>ics is<br />

offered as a new definiti<strong>on</strong> of magnetic sensors and actuators. In this study, we introduce and investigate<br />

methods of magnetic field c<strong>on</strong>trol and their suitable magnetic mechanisms. In general, the c<strong>on</strong>trol methods<br />

and mechanisms are determined according to the types of magnetic field: gradient, alternating, and<br />

rotating magnetic fields. Because the magnetic field c<strong>on</strong>trols are suitable for use in the restricted spaces,<br />

magnetic devices based <strong>on</strong> magneto-mechatr<strong>on</strong>ics can be widely used medical applicati<strong>on</strong>s. In magnetomechatr<strong>on</strong>ics,<br />

the combinati<strong>on</strong> of magnetic, mechanical, and computer engineering provides physical<br />

hardware, system modeling, and analysis, whereas the combinati<strong>on</strong> of magnetic, electrical, and computer<br />

engineering provides c<strong>on</strong>trol methods and its algorithm, and an interface, and so <strong>on</strong>.<br />

[1] K. Ishiyama, M. Sendoh, A. Yamazaki, and K. I. Arai, “Swimming Micro-machine driven by Magnetic Torque,” Sens.<br />

Actuators A, Phys. 91, 141-4, 2001. [2]L. Zhang, J. J Abbott, L. D<strong>on</strong>g , K. E. Peyer, B. E. Kratochvil, H. Zhang, C. Bergeles.<br />

and B. J. Nels<strong>on</strong>, “Characterizing the Swimming Properties of Artificial Bacterial Flagella,” Nano Letters 9, 3663-3667,<br />

2009. [3]S. Hashi, M. Toyoda, M. Ohya, Y. Okazaki, S. Yabukami, K. Ishiyama, and K. I. Arai, “Magnetic moti<strong>on</strong> capture<br />

system using LC res<strong>on</strong>ant magnetic marker composed of Ni-Zn ferrite core,” J. Appl. Phys. 99, 08B312, 2006.<br />

PO21<br />

AC magnetic field frequency dependence of drug release characteristics<br />

for magnetic hyperthermia based polymer-drug encapsulate system<br />

for cancer treatment applicati<strong>on</strong>s<br />

Tejabhiram Yadavalli 1 , Shivaraman Ramasamy 1 , Gopalakrishnan Chandrasekaran 1<br />

and Ramasamy R 2<br />

1 Nanotechnology Research Centre, SRM University, India<br />

2 School of Pharmacy, SRM University, India<br />

Ferromagnetic nickel, cobalt and gadolinium ferrite nanomaterials with Curie<br />

temperature values in the range of 40-50°C have been synthesized by wet chemical<br />

routes. These nanoparticles were then coated with Poly n-isopropyl Acrylamide<br />

thermo-sensitive polymer and doxorubicin drug forming a drug-polymer-nanoparticle<br />

c<strong>on</strong>jugate. The c<strong>on</strong>jugate was then tested for the drug release characteristics invitro<br />

by the applicati<strong>on</strong> of alternating magnetic field to it. The study was c<strong>on</strong>ducted<br />

to understand the heating rate of the nanoparticles in the c<strong>on</strong>jugate system and the<br />

quantitative drug release due to the heating of the nanoparticle. The quantitative study<br />

was c<strong>on</strong>ducted using a homemade magnetic hyperthermia setup and High Precisi<strong>on</strong><br />

Liquid Chromatography (HPLC) with doxorubicin standards. The study was c<strong>on</strong>ducted<br />

in the range of 100 to 1000 kHz with 20 W power rating. The maximum heating<br />

rate and the drug release rate per minute was seen at around 900 kHz which was in<br />

c<strong>on</strong>currence with the theoretical calculati<strong>on</strong>s d<strong>on</strong>e using the hysteresis loop area of the<br />

material. These results will later be useful for testing <strong>on</strong> animal models to analyze invivo<br />

drug release characteristics of the c<strong>on</strong>jugate.<br />

PO22<br />

Account of the image forces in the Bi 1-xSb x-insulator film structures.<br />

K<strong>on</strong>stantin Nicolaevich Kashirin<br />

The Russian State Agrarian University-Moscow Timiryasev Agricultural Academy,<br />

Kaluga Branch, Russia<br />

Semic<strong>on</strong>ducting alloy Bi 1-xSb x (x=0,11) films of the different fixed thickness with a thin layer<br />

of insulating coating (SiO 2) of variable thickness are investigated. The measuring of kinetic<br />

parameters was c<strong>on</strong>ducted in a superc<strong>on</strong>ducting solenoid gap (with magnetic inducti<strong>on</strong> to 9 T) and<br />

<strong>on</strong> the different temperatures (4,2÷200 K). The calculati<strong>on</strong>s of magnetic resistance, of the carries<br />

mobility and the Hall coefficient was d<strong>on</strong>e. The resistance oscillati<strong>on</strong>s is observed depending <strong>on</strong><br />

the thickness of insulating coating for all films. The kinetic parameters oscillati<strong>on</strong>s was observed<br />

as functi<strong>on</strong> of coating thickness at different temperature and <strong>on</strong> magnetic field. So, the following<br />

should be noted by the results of experimental investigati<strong>on</strong>s: - the resistance oscillati<strong>on</strong>s of all<br />

investigated bismuth-antim<strong>on</strong>y alloy films is observed depending <strong>on</strong> the thickness of dielectric<br />

coating and the period of oscillati<strong>on</strong>s is amounts 80-100 A average; - the magnetic resistance and<br />

the Hall coefficient oscillate with the variati<strong>on</strong> of the dielectric coating thickness in antiphase<br />

with the analogous oscillati<strong>on</strong> resistance; - the sphere of negative magnetic resistance is observed.<br />

One of the possible mechanisms accounting for the oscillati<strong>on</strong>s of the kinetic parameters of<br />

semic<strong>on</strong>ducting films with insulator coating is taking into accounts the image forces.<br />

Semic<strong>on</strong>ducting alloy Bi 1-xSb x (x=0,11) films of the different fixed thickness with a thin layer of insulating coating<br />

(SiO 2) of variable thickness are investigated. The measuring of kinetic parameters was c<strong>on</strong>ducted in a superc<strong>on</strong>ducting<br />

solenoid gap and <strong>on</strong> the different temperatures. The calculati<strong>on</strong>s of magnetic resistance, of the carries mobility and the<br />

Hall coefficient was d<strong>on</strong>e. The assumpti<strong>on</strong>s that the <strong>on</strong>e of the possible mechanisms accounting for the oscillati<strong>on</strong>s of the<br />

kinetic parameters of semic<strong>on</strong>ducting films with dielectric coating is taking into accounts the reflecti<strong>on</strong> forces were d<strong>on</strong>e.


PO23<br />

Time-resolved pump-probe measurement of polarizati<strong>on</strong> rotati<strong>on</strong> in<br />

nano-structured chiral metamaterial<br />

J. H. Woo 1 , H. -y. Shin 1 , M. J. Gw<strong>on</strong> 1 , M. Vomir 2 , M. Barthelemy 2 , D. -w. Kim 1 , S.<br />

Yo<strong>on</strong> 1 , J.-y. Bigot 2 and J. W. Wu 1 *<br />

1 Department of Physics & CNRS- Ewha <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g>, Ewha Womans University, Korea<br />

2 CNRS-IPCMS, University of Strasbourg, France<br />

In this study, we performed time resolved pump-probe measurement in two nano-structured<br />

metamaterials with opposite chirality which were fabricated by e-beam lithography <strong>on</strong> 30nm thick<br />

gold film. Transient absorpti<strong>on</strong> was measured to investigate the temporal behavior of the polarizati<strong>on</strong><br />

rotati<strong>on</strong> in metamaterial. It is well known that surface plasm<strong>on</strong>ic res<strong>on</strong>ances in metamaterial<br />

are originated from its structure rather than compositi<strong>on</strong> [1,2]. Surface plasm<strong>on</strong>ic res<strong>on</strong>ances in<br />

metamaterials which were used in this study were located in the visible spectral range with res<strong>on</strong>ance<br />

peaks at 625nm and 670nm and an optical rotatory dispersi<strong>on</strong> was observed. Time resolved pumpprobe<br />

measurements were carried out with 35fs Ti:sapphire laser operating at 800nm. BBO crystal was<br />

used to generate a 400nm pump pulses. For the probe, a sapphire crystal plate was used to generate a<br />

white light c<strong>on</strong>tinuum. With linearly polarized pump beam, the electr<strong>on</strong> dynamics in the metamaterial<br />

structure was studied. Also with right and left circularly polarized pump, we investigated the time<br />

dependent rotati<strong>on</strong> of polarizati<strong>on</strong> of the probe beam in a polarizati<strong>on</strong> bridge c<strong>on</strong>figurati<strong>on</strong>.<br />

[1] V. A. Fedotov, M. Rose, S. L. Prosvirnin, N. Papasimakis, and N. I. Zheludev, “Sharp trapped-mode res<strong>on</strong>ances in<br />

planar metamaterials with a broken structural symmetry”, Phys. Rev. Lett. 99, 147401 (2007). [2] Boyoung Kang, E.<br />

Choi, Hyun-Hee Lee, E.S. Kim, J. H. Woo, J. Kim, Tae Y. H<strong>on</strong>g, Jae H. Kim, and J.W. Wu, “Polarizati<strong>on</strong> angle c<strong>on</strong>trol<br />

of coherent coupling in metamaterial superlattice for closed mode excitati<strong>on</strong>”, Opt. Express 18, 11552 (2010).<br />

PO24<br />

Structural and magnetic properties of glassy like carb<strong>on</strong> synthesized<br />

by pyrolysis of sucrose<br />

Shivaraman Ramaswamy* and C Gopalakrishnan<br />

Nanotechnology Research Center, SRM University, India<br />

The structure and properties of glassy carb<strong>on</strong> (GC), a technologically important and<br />

widely used material, is still not well established. The glassy carb<strong>on</strong> samples were<br />

produced by a low-temperature pyrolysis of sucrose. The thermal destructi<strong>on</strong> occurred<br />

in five stages to minimize carb<strong>on</strong> losses. At the first stage (175 °C, 3 h) a viscous melt<br />

was obtained due to detachment of volatile comp<strong>on</strong>ents and water. After the sec<strong>on</strong>d<br />

and the third stages (300 °C, 1 h and 400 °C, 0.5 h, respectively) the material becomes<br />

solid. The next stage (525 °C, 1h) and the last stage (700 °C, 1 h) are performed to<br />

complete removal of all volatile impurities. The samples were then characterized using<br />

AFM and SEM to determine its structure and morphology. The magnetic properties<br />

were studied using vibrating sample magnetometer. It was found that the glassy carb<strong>on</strong><br />

sample has an inherent fullerene like morphology whose c<strong>on</strong>centrati<strong>on</strong> increases<br />

with increased heat treatment. Further, the samples also exhibited a distinct change in<br />

magnetic properties based <strong>on</strong> the pyrolysis. Paramagnetic and diamagnetic properties<br />

were found in the samples. The same has been explained based <strong>on</strong> the compositi<strong>on</strong> of<br />

the samples and structural properties.<br />

[1] A.A. Ovchinnikov and V.N. Spector, “Organic ferromagnets. New results,” Synth. Met., vol. 27,<br />

pp. 615-624, Dec. 1988. [2] H. Ohldag, et al., “Electr<strong>on</strong> Ferromagnetism in Metal-Free Carb<strong>on</strong><br />

Probed by Soft X-Ray Dichroism”, Phys. Rev. Lett., vol. 98, May 2007.<br />

PO25<br />

Simulati<strong>on</strong> of energy dispersive mode for RITA-type cold neutr<strong>on</strong><br />

triple axis spectrometer SIKA<br />

Guochu Deng 1 *, Peter Vorderwisch 2 , Chun-ming Wu 2 , Garry Mcintyre 1 and Wenhsien<br />

Li 2<br />

1 Bragg Institute, Australian Nuclear Science and Technology Organizati<strong>on</strong>, Australia<br />

2 Department of Physics, Nati<strong>on</strong>al Central University, Jh<strong>on</strong>gli 32054, Taiwan,<br />

Australia<br />

SIKA is a high flux cold-neutr<strong>on</strong> triple axis spectrometer in Bragg Institute. Equipped with a multiblade<br />

analyser system (13 PG(002) blade) and positi<strong>on</strong> sensitive detector, SIKA possesses high<br />

flexibility to efficiently run in a traditi<strong>on</strong>al step-by-step mode or various mapping (or dispersive)<br />

modes by changing the c<strong>on</strong>figurati<strong>on</strong> of analysers and detectors. In this study, the energy dispersive<br />

modes, namely the so-called E1 mode [1] at two different energy transfers is simulated using M<strong>on</strong>te<br />

Carlo ray-trace package SIMRES. [2] The simulated results show that SIKA could effectively work<br />

<strong>on</strong> E1 mode at low and intermediate energy transfer with reas<strong>on</strong>able energy and Q resoluti<strong>on</strong>s. The<br />

energy resoluti<strong>on</strong> is around 0.23meV at Ei=5meV while it increases to1.8meV at Ei=15meV. This<br />

simulati<strong>on</strong> shows SIKA has the potential in operati<strong>on</strong> flexibility and data-acquisiti<strong>on</strong> efficiency, and<br />

provides valuable references to the future inelastic neutr<strong>on</strong> scattering experiments <strong>on</strong> SIKA.<br />

[1] Lefmann K, McMorrow D F, R<strong>on</strong>now H M et al. 2000 Physica B 283 343 [2] ©aroun J and<br />

Kulda J 1997 Physica B, 234-236 1102 [3] Shirane G, Shapiro Stephen M, and Tranquada John<br />

M, 2002, Neutr<strong>on</strong> scattering with a triple-axis spectrometer, (Cambridge University Press) p 123<br />

[4] Clausen K N et al. 1998 Physica B 241-243 50 [5] Demmel F, Grach N and R<strong>on</strong>now H M 2004<br />

Nuclear Instruments & Methods in Physics Research Secti<strong>on</strong> A 530 404<br />

PO26<br />

PO27<br />

PO28<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Efficiency of Energy base deperm protocol<br />

Y<strong>on</strong>gmin Kim 1 , Young-hak Kim 2 and Kwang-ho Shin 1 *<br />

1 Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Kyungsung University,<br />

Korea<br />

2 Puky<strong>on</strong>g Nati<strong>on</strong>al University, Korea<br />

Magnetic treatment of surface vessels and submarines (Deperm) is a required to<br />

camouflage them against magnetic detecti<strong>on</strong> from enemy marine force. So far, deperm<br />

has been accomplished by applying an alternating magnetic field of which amplitude<br />

decreases linearly. However, the reducti<strong>on</strong> of the residual flux density in the directi<strong>on</strong><br />

of magnetic field is not linear in the case of the linear protocol, since the ferromagnetic<br />

material used to c<strong>on</strong>struct a surface vessel, mainly Fe-C, shows a n<strong>on</strong>linear behavior in<br />

an alternating magnetic field. This is <strong>on</strong>e of main reas<strong>on</strong>s to make an ordinary deperm<br />

protocol inefficient. In this paper, we propose an energy base deperm protocol which<br />

calculated by an algebraic hysteresis model, and present how to optimize the deperm<br />

protocol with the minor loops of magnetic hysteresis. We found out that step number<br />

could be reduced in the energy base deperm protocol compare with in the linear<br />

protocol, because the larger numbers of deperm steps are dedicated in the irreversible<br />

domain process regi<strong>on</strong> <strong>on</strong> the magnetic hysteresis.<br />

Effect of a magnetic field <strong>on</strong> mixed c<strong>on</strong>vecti<strong>on</strong> of a nanofluid in a<br />

square cavity<br />

G. A. Sheikhzadeh 1 *, S. Mazrouei Sebdani 1 , M. Mahmoodi 2 , Elham Safaeizadeh 3 and<br />

Sayed Ebrahim Hashemi 1<br />

1 Mechanical Engineering Department, University of Kashan, Iran<br />

2 Mechanical Engineering Department, Amirkabir University of Technology, Iran<br />

3 Department of Mathematics, Payame Noor University, Najafabad, Isfahan, Iran<br />

The problem of mixed c<strong>on</strong>vecti<strong>on</strong> in a differentially heated lid-driven square cavity<br />

filled with Cu-water nanofluid under effect of a magnetic field is investigated<br />

numerically. The left and right walls of the cavity are kept at temperatures of Th and<br />

Tc respectively while the horiz<strong>on</strong>tal walls are adiabatic. The top wall of the cavity<br />

moves in own plane from left to right. The effects of some pertinent parameters such as<br />

Richards<strong>on</strong> number (ranging from 0.1 to 10), the volume fracti<strong>on</strong> of the nanoparticles<br />

(ranging 0 to 0.1) and the Hartmann number (ranging from 0 to 100) <strong>on</strong> the fluid flow<br />

and temperature fields and the rate of heat transfer in the cavity are investigated. It<br />

must be noted that in all calculati<strong>on</strong>s the Prandtl number of water as the pure fluid is<br />

kept at 6.8, while the Grashof number is c<strong>on</strong>sidered fixed at 10 4 . The obtained results<br />

show that the rate of heat transfer increases with an increase of the Rayleigh number,<br />

while but it decreases with increase in the Hartmann number. Moreover it is found<br />

that by increase in volume fracti<strong>on</strong> of the nanoparticles the rate of heat transfer can be<br />

enhanced or deteriorated compared to the based fluid.<br />

Magnetohydrodynamic free c<strong>on</strong>vecti<strong>on</strong> in a square cavity heated from<br />

below and cooled from other walls<br />

Ali Akbar Abbasian Arani*, Mostafa Mahmoodi and Saeed Mazrouei Sebdani<br />

Mechanical Engineering, University of Kashan, Iran<br />

Magnetohydrodynamic free c<strong>on</strong>vecti<strong>on</strong> fluid flow and heat transfer in a square cavity<br />

filled with an electric c<strong>on</strong>ductive fluid with Prandtl number of 0.7 has been investigated<br />

numerically. The horiz<strong>on</strong>tal bottom wall of the cavity was kept at Th while the side<br />

and top walls of the cavity were maintained at a c<strong>on</strong>stant temperature Tc with Th>Tc.<br />

The governing equati<strong>on</strong>s were solved numerically while the SIMPLER algorithm was<br />

used. A parametric study was performed, and the effects of the Rayleigh number and<br />

the Hartman number <strong>on</strong> the fluid flow and heat transfer were investigated. The results<br />

showed that temperature distributi<strong>on</strong> and flow pattern depended <strong>on</strong> both strength of the<br />

magnetic field and Rayleigh number. For all cases two rotating eddies were formed.<br />

Using the l<strong>on</strong>gitudinal magnetic field results in a force (Lorentz force) opposite to the<br />

flow directi<strong>on</strong> that tends to decrease the flow velocity. The magnetic field decreased the<br />

free c<strong>on</strong>vecti<strong>on</strong> and flow velocity. Also it was found that for higher Rayleigh numbers<br />

a relatively str<strong>on</strong>ger magnetic field was needed to decrease the heat transfer. Moreover<br />

for low Rayleigh numbers, by increase in the Hartman number, free c<strong>on</strong>vecti<strong>on</strong> is<br />

suppressed and heat transfer occurs through c<strong>on</strong>ducti<strong>on</strong> mainly.<br />

July 8 - 13, 2012 Busan, Korea 67<br />

Poster M<strong>on</strong>day


Poster M<strong>on</strong>day<br />

PO29<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Interacti<strong>on</strong> of a magnetic field and buoyancy force in a square cavity<br />

filled with a fluid with low Prandtl number<br />

G. A. Sheikhzadeh 1 *, S. E. Hashemi 1 , S. Mazrouei Sebdani 1 , M. Mahmoodi 2 and<br />

Elham Safaeizadeh 3<br />

1<br />

Mechanical Engineering Department, University of Kashan, Iran<br />

2<br />

Mechanical Engineering Department, Amirkabir University of Technology, Tehran,<br />

Iran<br />

3<br />

Department of Mathematics, Payame Noor University, Najafabad, Isfahan, Iran<br />

In this paper, influences of Lorentz force due to a magnetic field <strong>on</strong> buoyancy<br />

driven heat transfer in a square cavity c<strong>on</strong>taining a fluid with low Prandtl number is<br />

investigated numerically. The left and right walls of the cavity are kept at temperatures<br />

of Tc and Th respectively, while the horiz<strong>on</strong>tal walls are kept adiabatic. Effect of<br />

existence of an adiabatic body in the middle of the cavity is c<strong>on</strong>sidered too.The<br />

dimensi<strong>on</strong>less governing equati<strong>on</strong>s associated with the boundary c<strong>on</strong>diti<strong>on</strong>s are solved<br />

numerically using the finite volume method. Streamlines and isotherms are shown<br />

for Grashof number (ranging from 10 5 to 10 7 ), Hartman number (ranging from 0 to<br />

100) and Prandtl number (ranging from 0.005 to 0.1). The results show that variati<strong>on</strong>s<br />

of magnetic field d<strong>on</strong>ot have noticeable effect <strong>on</strong> buoyancy force, while increase<br />

in magnetic field increases Lorentz force. Moreover buoyancy and Lorentz forces<br />

increase by increase in Grashof number in a c<strong>on</strong>stant Hartman and Prandtl numbers.<br />

PO30<br />

Numerical study of magnetic field effects <strong>on</strong> flow field and heat<br />

transfer in a cavity filled with porous materials<br />

G. A. Sheikhzadeh*, M. Aliakbari Miyan Mahaleh, A. A. Abbasian Arani and S.<br />

Mazrouei Sebdani<br />

Mechanical Engineering Department, University of Kashan, Iran<br />

Natural c<strong>on</strong>vecti<strong>on</strong> flows in a square cavity filled with a fluid-saturated porous medium<br />

under the effect of magnetic field has been studied numerically. A square hot body<br />

with length W is placed in the center of the cavity (with length L). The ratio of W/L is<br />

assumed to be 0.5. C<strong>on</strong>tinuity, momentum and energy equati<strong>on</strong>s are solved using the<br />

finite volume technique under the boundary c<strong>on</strong>diti<strong>on</strong>s. The two vertical sides of the<br />

cavity are cooled and two horiz<strong>on</strong>tal bottom and top walls are adiabatic. The Prandtl<br />

number is 0.71, the Rayleigh number changes from 10 4 to 10 6 , the Darcy number<br />

varies from 10 -5 to 10 -3 and the Hartmann number alters from 0 to 100. Numerical<br />

results are presented in terms of stream functi<strong>on</strong>s, temperature profiles. The results<br />

say increasing the braking effect of magnetic field as increasing the Hartman number;<br />

lead to decreases the heat transfer. Also at low Darcy number, fluid circulati<strong>on</strong> is weak<br />

due to high hydraulic resistance offered by porous medium for Darcy number down<br />

to 10 -5 . Average Nusselt number increases with enhancement of Rayleigh number and<br />

decreasing the Hartmann number.<br />

PO31<br />

Numerical simulati<strong>on</strong> of magnetohydrodynamic Benard c<strong>on</strong>vecti<strong>on</strong> in<br />

a shallow enclosure<br />

G. A. Sheikhzadeh*, M. Mahmoodi and S. Mazrouei Sebdani<br />

Mechanical Engineering Department, University of Kashan, Iran<br />

In this paper the problem of magnetohydrodynamic Benard c<strong>on</strong>vecti<strong>on</strong> in a shallow<br />

rectangular enclosure with aspect ratio of 10 (width to height ratio) has been<br />

investigated numerically. The enclosure is filled with an electric c<strong>on</strong>ductive fluid with<br />

Prandtl number of 1. The bottom and the top walls of the cavity are maintained at a<br />

c<strong>on</strong>stant temperature Th and Tc respectively, with Th > Tc, while; the side walls of the<br />

cavity are kept insulated. The governing equati<strong>on</strong>s written in terms of the primitive<br />

variables are solved numerically using the finite volume method and the SIMPLER<br />

algorithm is employed to couple velocity and pressure fields. Using the developed<br />

code, a parametric study is performed, and the effects of the Rayleigh number and<br />

the Hartman number <strong>on</strong> the fluid flow and heat transfer inside the enclosure are<br />

investigated. The results show that temperature distributi<strong>on</strong> and flow pattern inside<br />

the enclosure depend <strong>on</strong> both the strength of the magnetic field and Rayleigh number.<br />

Moreover it was found that at low Rayleigh number with increase in Hartman number<br />

the flow intensity decreases and fluid becomes stagnant. At high Rayleigh numbers<br />

number of the Benard cell decreases by increase in Hartman number.<br />

68 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

PO32<br />

Near-electrode effcets of magnetic fields in electrochemistry<br />

Michael Coey and Peter Dunne<br />

Physics, Trinity College dublin, Ireland<br />

Remarkable influences of magnetic fields have been discovered <strong>on</strong> the diffusi<strong>on</strong> layer<br />

and <strong>on</strong> the electrochemical double layer. The former are mainly due to magnetic<br />

pressure, which allows the patterning of deposits from both paramagnetic and<br />

diamagentic i<strong>on</strong>s (using a n<strong>on</strong>electroactive paramagnetic species such as Dy 3+ ).<br />

The effects of small cylindrical [1] and linear magnet arrays are dem<strong>on</strong>strated. The<br />

magnetic patterning is estimated to be effective down to about the 100 micr<strong>on</strong> scale.<br />

The essential requirement for patterning of this type are orthog<strong>on</strong>al c<strong>on</strong>centrati<strong>on</strong><br />

gradients and magnetic field gradients. More surprising is the evidence we have found<br />

for an influence of a static magnetic field <strong>on</strong> the electrochemical double layer, a poorly<br />

understood regi<strong>on</strong> about 1 nm thick at the cathode. Using a nitrobenzene model redox<br />

system, we show that the double layer capacitance can be modified by a factor of two<br />

at an appropriate potential. The influence of Maxwell stress <strong>on</strong> the free radicals in<br />

soluti<strong>on</strong> is discussed as a possible explanati<strong>on</strong>. More remarkable are<br />

[1] P. Dunne, L. Mazza and J. M. D. Coey, Phys Rev Letters 107 042501 (2011)<br />

QA01<br />

Res<strong>on</strong>ant magnetic x-ray scattering: Beamline P09 at PETRA III at<br />

DESY<br />

Joerg Strempfer, S<strong>on</strong>ia Francoual, Dinesh K. Shukla and Arvid Skaugen<br />

DESY, Germany<br />

Res<strong>on</strong>ant and n<strong>on</strong>-res<strong>on</strong>ant magnetic scattering are complementary tools to magnetic<br />

neutr<strong>on</strong> diffracti<strong>on</strong> for the investigati<strong>on</strong> of magnetic properties in solids. Res<strong>on</strong>ant<br />

magnetic x-ray scattering opens the possibility to investigate magnetic order in single<br />

crystals and layered systems element selectively. Also the interference of magnetic<br />

order with orbital or charge order can be determined through the polarizati<strong>on</strong> properties<br />

of the x-ray and the special form of the scattering cross secti<strong>on</strong>s, describing the<br />

variati<strong>on</strong> of the polarizati<strong>on</strong> states through the scattering process. The new beamline<br />

for Res<strong>on</strong>ant Scattering and Diffracti<strong>on</strong> (RSD), P09 at PETRA III, is designed<br />

especially to address the above menti<strong>on</strong>ed issues. Low temperature cryostats and high<br />

magnetic fields of up to 14T allow the investigati<strong>on</strong> of magnetic properties of materials<br />

as functi<strong>on</strong> of polarizati<strong>on</strong>, temperature and field. Two diffractometers are available to<br />

c<strong>on</strong>duct experiments using the highly brilliant synchrotr<strong>on</strong> beam available at PETRA<br />

III. The polarizati<strong>on</strong> of the incident x-ray beam can be varied arbitrarily through x-ray<br />

phase-plates and the polarizati<strong>on</strong> of the scattered beam is analyzed by a polarizati<strong>on</strong><br />

analyzer. Examples for the performance of the beamline and experimental results <strong>on</strong><br />

magnetic scattering from multiferroic systems will be presented.<br />

QA02<br />

Magnetic and dielectric properties of FeTiO 3<br />

Takayasu Kiyokawa 1 *, Shigeki Yamada 1 and Takatsugu Masuda 2<br />

1 Nanosystem Science, Yokohama City University, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

The magnetic and dielectric properties of single crystal ir<strong>on</strong> ilmenite FeTiO 3 have been<br />

investigated. The temperature dependence of the magnetizati<strong>on</strong> for H parallel to the c<br />

axis (M//c) has a sharp peak at 58 K (T N) and abruptly decreases below T N, while the<br />

magnetizati<strong>on</strong> for H perpendicular to the c axis (M┴c) is almost independent of the<br />

temperature. These features indicate that the ground state is Neel state with the easy<br />

axis in the c directi<strong>on</strong>. Above T N the value of M//c is larger than that of M┴c due to the<br />

magnetic anisotropy. These results are c<strong>on</strong>sistent with previous report by Kato et al..<br />

The temperature dependence of the dielectric c<strong>on</strong>stant for E parallel to the c axis also<br />

shows a kink at T N. Furthremore the dielectric polarizati<strong>on</strong> for E parallel to the c axis<br />

abruptly increases at T N. Hence this kink is ascribed to ferroelectric phase transiti<strong>on</strong>.<br />

These results indicate that FeTiO 3 is a str<strong>on</strong>g candidate for a new type of multiferroic<br />

materials.


QA03<br />

Theoretical study of tuning polarizati<strong>on</strong> and magnetism of BiCoO 3<br />

Yu-jun Zhao and Xing-yuan Chen<br />

Department of Physics, South China University of Technology, China<br />

QA04<br />

QA05<br />

WITHDRAWN<br />

Soft x-ray synchrotr<strong>on</strong> radiati<strong>on</strong> spectroscopy study of<br />

Co 0.6Fe 0.9Mn 1.5O 4 spinel with nano-checkerboard patterns<br />

D.h. Kim 1 , Jiho<strong>on</strong> Hwang 1 , Eunsook Lee 1 , S.-w. Che<strong>on</strong>g 2 , B.-g. Park 3 , J.-y. Kim 3 and<br />

J.-s. Kang 1 *<br />

1 Department of Physics, The Catholic University of Korea, Korea<br />

2 Department of Physics and Astr<strong>on</strong>omy, Rutgers University, USA<br />

3 Pohang Accelerator Laboratory, POSTECH, Korea<br />

In the AB 2O 4-type spinels, transiti<strong>on</strong>-metal i<strong>on</strong>s occupy either the tetrahedral (Td) A<br />

site or the octahedral (Oh) B site. Recently, nano-checkerboard (CB) patterns have<br />

been observed in ZnMnGaO 4, MgMn 1.5Fe 0.5O 4, and Co 0.6Fe 0.9Mn 1.5O 4 [1]. When<br />

properly annealed, these spinels show two different structures with different chemical<br />

phases, where <strong>on</strong>e is cubic and the other is tetrag<strong>on</strong>al or orthorhombic. This structural<br />

and chemical phase separati<strong>on</strong> has been explained by the Jahn-Teller (JT) distorti<strong>on</strong>. To<br />

c<strong>on</strong>firm this idea, it is important to determine the valence states of the transiti<strong>on</strong>-metal<br />

i<strong>on</strong>s that c<strong>on</strong>stitute these spinel oxides. In this work, we have studied the electr<strong>on</strong>ic<br />

structure of checkerboard Co 0.6Fe 0.9Mn 1.5O 4 single crystal by employing soft x-ray<br />

absorpti<strong>on</strong> spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD).<br />

The measured T 2p XAS spectra (T=Co, Fe, Mn) of Co 0.6Fe 0.9Mn 1.5O 4 reveal that the<br />

valence states of Co, Fe, and Mn i<strong>on</strong>s are nearly divalent (Co 2+ ), trivalent (Fe 3+ ), and<br />

mixed-valent (Mn 2+ -Mn 3+ ), respectively. Very weak XMCD signals are observed in<br />

checkerboard Co 0.6 Fe 0.9 Mn 1.5 O 4. *Corresp<strong>on</strong>ding Author : kangjs@catholic.ac.kr<br />

[1] C.L. Zhang, et al., Appl. Phys. Lett. 91, 233110 (2007).<br />

Zn-substituti<strong>on</strong> effects in multiferroic Cu 3Mo 2O 9<br />

Haruhiko Kuroe 1 *, Kento Aoki 1 , Ryusuke Itoh 1 , Tomohiro Hosaka 1 , Takuya<br />

Hasegawa 1 , Suguru Hachiuma 1 , Mitsuru Akaki 1 , Hideki Kuwahara 1 , Tomoyuki<br />

Sekine 1 , Masashi Hase 2 , Kunihiko Oka 3 , Toshimitsu Ito 3 and Hiroshi Eisaki 3<br />

1 Department of Physics, Sophia University, Japan<br />

2 Nati<strong>on</strong>al Institute for Material Science (NIMS), Japan<br />

3 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Japan<br />

We present the Zn substituti<strong>on</strong> effects <strong>on</strong> the quasi-<strong>on</strong>e dimensi<strong>on</strong>al frustrating spin<br />

system Cu 3Mo 2O 9. This material has S = 1/2 distorted tetrahedral spin chains and<br />

undergoes the multiferroic phase below 7.9 K without magnetic field [T. Hamasaki<br />

et al., Phys. Rev. B 77 (2008) 134419, H. Kuroe et al., J. Phys. Soc. Jpn. 80 (2011)<br />

083705]. The S = 0 Zn 2+ i<strong>on</strong>s substitute for the S = 1/2 Cu 2+ i<strong>on</strong>s at the three<br />

crystallographically different sites, namely Cu 1, Cu 2, and Cu 3. The spins at the Cu 2 and<br />

Cu 3 sites form nearly spin-singlet spin dimers at the bisectors of the nearest neighbor<br />

C u1 sites in the quasi-<strong>on</strong>e dimensi<strong>on</strong>al spin chain [H. Kuroe et al., J. Phys.: C<strong>on</strong>f. Ser.<br />

200 (2010) 022028, H. Kuroe et al., Phys. Rev. B 83 (2011) 184423]. In this study,<br />

we focus <strong>on</strong> the magnetic, electric, and thermodynamical properties of the single<br />

crystal of (Cu,Zn) 3Mo 2O 9. Comparing our previous results in polycrystalline samples<br />

[M. Hase et al., J. Phys. Soc. Jpn. 77 (2008) 034706], we discuss the reducti<strong>on</strong> of the<br />

antiferromagnetic correlati<strong>on</strong> and the singlet-pair breaking effect <strong>on</strong> the Cu 2-Cu 3 spin<br />

dimers. The dielectric c<strong>on</strong>stant and the specific heat in (Cu,Zn) 3Mo 2O 9 will also be<br />

discussed in this study.<br />

QA06<br />

QA07<br />

QA08<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Effects of bismuth substituti<strong>on</strong> <strong>on</strong> the magnetic properties of BixCo2 xMnO4 Maria Elenice Dos Santos 1 , Paulo Nor<strong>on</strong>ha Lisboa-filho 2 and Octavio Pena 1<br />

1<br />

Institut des Sciences Chimiques de Rennes, Universite de Rennes 1, France<br />

2<br />

Laboratorio de Materiais Eletr<strong>on</strong>icos, Universidade Estadual Paulista, Brazil<br />

Coexistence of magnetism and ferroelectricity, al<strong>on</strong>g with coupling between them, ensures many<br />

technological applicati<strong>on</strong>s of materials named multiferroics. Transiti<strong>on</strong> metal and/or rare earth<br />

oxides with ABO 3 perovskite and AB 2O 4 spinel structures are good candidates due to the substituti<strong>on</strong><br />

of magnetic and n<strong>on</strong>-magnetic i<strong>on</strong>s at the A and/or B sites [1]. Bi-substituted Bi xCo 2-xMnO 4<br />

multiferroic samples, well-characterized structurally by XRD and Rietveld refinement together with<br />

SEM-EDX techniques, were synthesized by a polymeric precursors method. A gradual expansi<strong>on</strong><br />

of the lattice parameter due to the substituti<strong>on</strong> of Co 3+ by Bi 3+ is observed for x = 0.1, 0.2 and 0.3.<br />

Magnetic characterizati<strong>on</strong> was carried out by SQUID measurements. The inverse susceptibility<br />

exhibited ferrimagnetic behaviour, as also proved by the str<strong>on</strong>g antiferromagnetic and ferromagnetic<br />

interacti<strong>on</strong>s shown by the ZFC and FC curves. The M(H) loops performed at various temperatures<br />

below T C showed larger loop areas when decreasing the temperature, indicating an increasing<br />

ferromagnetism. The inclusi<strong>on</strong> of Bi in Co 2MnO 4 creates fluctuating valence states of both Co<br />

and Mn i<strong>on</strong>s (Co 2+ /Co 3+ , Mn 2+ /Mn 3+ /Mn 4+ ) which occupy the tetrahedral and octahedral sites [2].<br />

Magnetizati<strong>on</strong> measurements showed that T C and M S increase with increasing Bi 3+ c<strong>on</strong>centrati<strong>on</strong><br />

due to the redistributi<strong>on</strong> of the magnetic cati<strong>on</strong>s, in particular the Mn 3+ and Mn 4+ <strong>on</strong>es.<br />

[1] P. Barah<strong>on</strong>a, et. al. J. Chil. Chem. Soc. 50. N 2 (2005) 495. [2] N. E. Rajeevan, et. al. Mater. Sci.<br />

Eng. B 163(2009) 48.<br />

Cross-correlati<strong>on</strong> effects in multiferroic Cu 3Mo 2O 9<br />

Ryusuke Itoh 1 *, Tomohiro Hosaka 1 , Takuya Hasegawa 1 , Haruhiko Kuroe 1 , Tomoyuki<br />

Sekine 1 , Masashi Hase 2 , Kunihiko Oka 3 , Toshimitsu Ito 3 and Hiroshi Eisaki 3<br />

1 Sophia University, Japan<br />

2 Nati<strong>on</strong>al Institute for Materials Science (NIMS), Japan<br />

3 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Japan<br />

We present the cross correlati<strong>on</strong> effects in a multiferroic material Cu 3Mo 2O 9. This<br />

material c<strong>on</strong>tains spin tetrahedra made from the Cu 2+ i<strong>on</strong>s which form a edge<br />

sharing spin chain. The quasi-<strong>on</strong>e dimensi<strong>on</strong>al magn<strong>on</strong> dispersi<strong>on</strong> curve, the<br />

ferroelectric properties caused by the geometrical magnetic frustrati<strong>on</strong>, and a str<strong>on</strong>g<br />

magnetocapacitance effect have been reported [H. Kuroe et al., Phys. Rev. B 83<br />

(2011) 184423, H. Kuroe et al., J. Phys. Soc. Jpn. 80 (2011) 083705]. In this study, we<br />

focus <strong>on</strong> the change of the l<strong>on</strong>gitudinal magnetizati<strong>on</strong> under the electric field. Using<br />

a SQUID magnetometor which has two electric leads, we measured the l<strong>on</strong>gitudical<br />

magnetizati<strong>on</strong> Ma al<strong>on</strong>g the a axis and the electric polarizati<strong>on</strong> Pc al<strong>on</strong>g the c axis of<br />

a plate-like single crystal of Cu 3Mo 2O 9 simultaneously. We measured the l<strong>on</strong>gitudinal<br />

magnetizati<strong>on</strong> al<strong>on</strong>g the a axis (Ma-Ha loop) under the static electric field Ec al<strong>on</strong>g the<br />

c axis, and the Ma-Ec loop under the static Ha. The details of our results including the<br />

change of the Ma-Ha loop under the static electric field and butterfly-loop in the Ma-Ec<br />

loop will be presented in this study.<br />

N<strong>on</strong>linear current-voltage characteristics of (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3<br />

Single crystals: Possible manifestati<strong>on</strong> of the internal heating of charge<br />

carriers<br />

Kirill Shaykhutdinov*<br />

Kirensky Institute of Physics, Russia<br />

Current--voltage characteristics of the polycrystalline substituted lanthanum manganite<br />

La 0.7Ca 0.3MnO 3 were experimentally studied at Т = 77.4 K in magnetic fields up to 13<br />

kOe. In these characteristics, a porti<strong>on</strong> of negative differential resistivity was observed<br />

above a certain threshold value of critical current density j caused, in our opini<strong>on</strong>,<br />

by n<strong>on</strong>equilibrium heating of the electr<strong>on</strong> gas due to low thermal c<strong>on</strong>ductivity of the<br />

manganite material. Because of the n<strong>on</strong>linearity of the current--voltage characteristics,<br />

the field dependences of resistivity ρ(H) appear extremely sensitive to the value of a<br />

transport current. In this case, the ρ(H) dependences reveal both ordinary negative and<br />

positive magnetoresistance.<br />

July 8 - 13, 2012 Busan, Korea 69<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QA09<br />

High field phase diagram in multiferroic Cu 3Mo 2O 9<br />

Haruhiko Kuroe 1 *, Ryo Kino 1 , Ryusuke Itoh 1 , Tomohiro Hosaka 1 , Takuya Hasegawa1,<br />

Tomoyuki Sekine 1 , Takumi Kihara 2 , Masashi Tokunaga 2 , Masashi Hase 3 , Kanji<br />

Takehana 3 , Hideaki Kitazawa 3 , Kunihiko Oka 4 , Toshimitsu Ito 4 and Hiroshi Eisaki 4<br />

1 Department of Physics, Sophia University, Japan<br />

2 The Institute for Solid State Physics, The University of Tokyo, Japan<br />

3 Nati<strong>on</strong>al Institute for Materials Science (NIMS), Japan<br />

4 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Japan<br />

We present the multiferroic behavior in the quasi-<strong>on</strong>e dimensi<strong>on</strong>al antiferromagnet Cu 3Mo 2O 9.<br />

This material has spin chains of the distorted spin tetrahedra made from S = 1/2 Cu 2+ i<strong>on</strong>s.<br />

In ICM2009, we have presented that the magn<strong>on</strong> dispersi<strong>on</strong> relati<strong>on</strong> in Cu 3Mo 2O 9, which is<br />

well explained by the hybridizati<strong>on</strong> effects between a magn<strong>on</strong> excitati<strong>on</strong> from the quasi-<strong>on</strong>e<br />

dimensi<strong>on</strong>al spin system and that from the isolated spin dimers [H. Kuroe et al., J. Phys.: C<strong>on</strong>f.<br />

Ser. 200 (2010) 022028, H. Kuroe et al., Phys. Rev. B 83 (2011) 184423]. Recently, we found<br />

that this material shows a multiferroic behavior [H. Kuroe et al., J. Phys. Soc. Jpn. 80 (2011)<br />

083705]. We proposed that the origin of the multiferroic behaviors in Cu 3Mo 2O 9 is the charge<br />

redistributi<strong>on</strong> effect in a frustrated Mott insulator studied by Bulaevskii et al.[L. N. Bulaevskii<br />

et al., PRB 78 (2008) 024402.], which is presented by Khomskii as an invited talk in ICM2009<br />

[D. I. Khomskii, J. Phys.: C<strong>on</strong>dens. Matter 22 (2010) 164209]. In this study, we present<br />

the magnetic-field-temperature phase diagram up to 55 T obtained from the temperature<br />

and magnetic-field dependences of the magnetizati<strong>on</strong>, the dielectric c<strong>on</strong>stants, the electric<br />

polarizati<strong>on</strong>, the pyroelectric current, and the specific heat.<br />

QA10<br />

Magnetoelectric effect in Ca 2FeAlO 5<br />

Nobuyuki Abe 1 *, Khanh Duy Nguyen 2 , Yoichi Nii 2 , Yutaro Kitagawa 3 and Taka-hisa<br />

Arima 1<br />

1 Department of Advanced Materials Science, The University of Tokyo, Japan<br />

2 Department of Physics, Tohoku University, Japan<br />

3 Department of Applied Physics, The University of Tokyo, Japan<br />

Ca 2FeAlO 5 has the same crystal structure as mineral Brownmillerite. The oxygen deficient<br />

perovskite type structure is c<strong>on</strong>structed by the alternate stacking of (Fe,Al)O 6 octahedra and<br />

(Fe,Al)O 4 tetrahedra. An early structure analysis showed that Ca 2FeAlO 5 bel<strong>on</strong>gs to a n<strong>on</strong>centrosymmetric<br />

space group Ibm2 [1], which originats from the in-phase stacking of (Fe,Al)<br />

O 4 tetrahedra. This compound shows antiferromagnetic order below 350 K. Mossbauer<br />

spectroscopy measurements c<strong>on</strong>clude that the magnetic moments of Fe 3+ align al<strong>on</strong>g the<br />

a-axis[2]. Because the crystal structure lacks the inversi<strong>on</strong> symmetry, Ca 2FeAlO 5 is a<br />

candidate material which has a magnetoelectric coupling. Here we show the measurements<br />

of magnetoelectric effect in single crystalline Ca 2FeAlO 5. The field dependence of the<br />

magnetizati<strong>on</strong> al<strong>on</strong>g the a-axis shows a metamagnetic transiti<strong>on</strong> caused by the spin flop of<br />

Fe 3+ moments. Moreover, the dielectric c<strong>on</strong>stant and electric polarizati<strong>on</strong> show an anomaly<br />

at around the phase transiti<strong>on</strong>. These results indicate that Ca 2FeAlO 5 shows magnetoelectric<br />

effect in a magnetic field induced spin flop phase, which is <strong>on</strong>e example of a new route to<br />

realize a magnetoelectric coupling above the room temperature.<br />

[1] A. A. Colville and S. Geller, Acta Cryst, B27, 2311(1971) [2] R. W. Grant et.al. , J. Appl. Phys.<br />

39, 1122 (1968)<br />

QA11<br />

Electr<strong>on</strong>ic and magnetic phase separati<strong>on</strong> in the semimetallic<br />

ferromagnet EuB 6<br />

Pintu Das 1 , Adham Amyan 1 , Jens Brandenburg 1 , Jens Mueller 1 *, Peng Xi<strong>on</strong>g 2 ,<br />

Stephan V<strong>on</strong> Molnar 2 and Zachary Fisk 3<br />

1 Institute of Physics, Goethe University Frankfurt, Germany<br />

2 Dept. of Physics, Florida State University, Tallahassee, USA<br />

3 Dept. of Physics, University of California, Irvine, USA<br />

EuB 6 is a low-carrier semimetal, which undergoes a unique paramagnetic to ferromagnetic<br />

transiti<strong>on</strong> displaying two c<strong>on</strong>secutive features at T c1= 15.5 K and T c2 = 12.6 K in electrical<br />

transport, magnetizati<strong>on</strong> and specific heat. Its structural and electr<strong>on</strong>ic simplicity makes EuB 6<br />

an ideal model system for studying the effect the magnetic state of a system has <strong>on</strong> its electr<strong>on</strong>ic<br />

transport properties. In particular, the fundamentals of intrinsic electr<strong>on</strong>ic and magnetic phase<br />

separati<strong>on</strong> can be studied, which play a critical role for the colossal magnetoresistance (CMR)<br />

in magnetic semic<strong>on</strong>ductors and manganites. In explaining CMR in EuB 6, being largest at<br />

T c1, the c<strong>on</strong>cept of magnetic polar<strong>on</strong> (MP) percolati<strong>on</strong> has been invoked. We report resistance<br />

noise and weakly n<strong>on</strong>linear transport measurements, being sensitive to the microgeometry of<br />

the electr<strong>on</strong>ic system. We find direct evidence for electr<strong>on</strong>ic phase separati<strong>on</strong> when cooling<br />

through T c1 and a diverging noise level at T c2, which we interpret as magnetically-driven<br />

percolati<strong>on</strong> resulting from the overlap of spatial inhomogeneities in c<strong>on</strong>ductivity produced<br />

by MP. Interestingly, MP percolati<strong>on</strong> can be induced also by applying magnetic fields in the<br />

paramagnetic regi<strong>on</strong>. We find that the density of MP can be described by a universal scaling<br />

functi<strong>on</strong>, being related to a single critical magnetizati<strong>on</strong>.<br />

70 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QA12<br />

Study of magnetic and magnetodielectric properties of perovskite<br />

YbCrO 3<br />

J<strong>on</strong>g-suck Jung, Ayato Iyama*, Hiroyuki Nakamura, Yusuke Wakabayashi and<br />

Tsuyoshi Kimura<br />

Divisi<strong>on</strong> of Materials Physics, Osaka University, Japan<br />

Perovskite YbCrO 3 shows the G-type antiferromagnetic ground state for Cr 3+ moments<br />

(T N ~ 118 K). Because of the Dzyaloshinskii-Moriya interacti<strong>on</strong>, the G-type structure<br />

becomes canted, and then YbCrO 3 exhibits weak ferromagnetism. When weak<br />

magnetic fields are applied (B ≤ 0.3 T), temperature-induced magnetizati<strong>on</strong> reversal is<br />

observed. The magnetizati<strong>on</strong> reversal is probably associated with a keen competiti<strong>on</strong><br />

between antiferromagnetically coupled Cr 3+ - Yb 3+ moments. Recently, a distinct<br />

magnetodielectric effect was observed in another perovskite SmMnO 3 which also<br />

shows temperature-induced magnetizati<strong>on</strong> reversal due to the competiti<strong>on</strong> between<br />

antiferromagnetically coupled Mn 3+ - Sm 3+ moments [1]. Thus, it is intriguing to study<br />

magnetodielectric properties of YbCrO 3. In this study, we investigated magnetic and<br />

magnetodielectric properties for single crystals of YbCrO 3 grown by the flux method.<br />

The comparis<strong>on</strong> of magnetodielectric properties between YbCrO 3 and SmMnO 3<br />

provides useful informati<strong>on</strong> to understand the distinct magnetodielectric effect<br />

observed in SmMnO 3.<br />

[1] J.-S. Jung et al. Phys. Rev. B 82, 212403 (2010)<br />

QA13<br />

Interplay am<strong>on</strong>g spin, orbital, and lattice degrees of freedom in a<br />

frustrated spinel Mn 3O 4<br />

Yoichi Nii 1 *, Hiroshi Umetsu 1 , Hajime Sagayama 2 , Nobuyuki Abe 2 , Kouji Taniguchi 2<br />

and Taka-hisa Arima 2<br />

1 Dept. of Phys., Tohoku University, Japan<br />

2 Dept. of Advanced Mater. Sci., The University of Tokyo, Japan<br />

Spinel oxides, AB 2O 4, are <strong>on</strong>e of the typical systems for studying the effects of geometrical<br />

frustrati<strong>on</strong> and the possible coupling am<strong>on</strong>g spin, orbital and lattice degrees of freedom. Mn 3O 4<br />

exhibits the cooperative Jahn-Teller (JT) transiti<strong>on</strong> from cubic to tetrag<strong>on</strong>al structure at 1443 K with<br />

the 3z2-r2 ferro-orbital order at B-site Mn 3+ . The gigantic JT distorti<strong>on</strong> (~16 %) would encourage<br />

the formati<strong>on</strong> of <strong>on</strong>e-dimensi<strong>on</strong>al (1D) antiferromagnetic spin chains at B-site Mn 3+ normal to the<br />

c-axis. A macroscopic degeneracy of the arrangements of 1D-spin-chains still remains, even if <strong>on</strong>e<br />

c<strong>on</strong>siders the magnetic interacti<strong>on</strong> between the nearest neighbor 1D-chains. It was reported that<br />

Mn 3O 4 exhibits successive magnetic phase transiti<strong>on</strong>s from paramagnetic to Yafet-Kittel (43 K),<br />

incommensurate (IC) (40 K) and commensurate (C) phase (34 K)[1], which is an indicative of the<br />

surviving magnetic frustrati<strong>on</strong>. Another phase transiti<strong>on</strong> is induced by applying magnetic field in the<br />

low-temperature C phase [2]. In order to elucidate the magnetic-field induced phase transiti<strong>on</strong>, we<br />

have measured synchrotr<strong>on</strong> x-ray diffracti<strong>on</strong> and neutr<strong>on</strong> scattering in a magnetic field al<strong>on</strong>g [100]<br />

c. We propose a scenario of the magnetic-field induced phase transiti<strong>on</strong>, where the rearrangement of<br />

1D-spin-chains is triggered by orbital hybridizati<strong>on</strong> at B-site Mn 3+ through the spin-orbit coupling.<br />

[1] R. Tackett et al., Phys. Rev. B 76, 024409 (2007). [2] T. Suzuki et al., Phys. Rev. B 77, 220402(R) (2008)<br />

QA14<br />

Structural and dielectric study of hexag<strong>on</strong>al Y 0.8Sr 0.2MnO 3 Compound<br />

Rajesh K. Thakur 1 *, Rasna Thakur 2 , A. Bharathi 3 and N.k. Gaur 2<br />

1 Department of Physics, Barkatullah University,Bhopal, India<br />

2 Department of Physics, Barkatullah University, Bhopal, India<br />

3 C<strong>on</strong>densed Matter Physics Divisi<strong>on</strong>, Materials Science Group, Indira Gandhi Centre<br />

for Atomic Research, Kalpakkam, India, India<br />

Str<strong>on</strong>tium doped YMnO 3 compound have been prepared in single-phase form by<br />

using high temperature solid sate reacti<strong>on</strong> method. The structural and dielectric<br />

properties of the prepared sample have been carried out in the wide range of<br />

temperature and frequency. Temperature and frequency variati<strong>on</strong>s of dielectric<br />

permittivity measurements show that the present hole doped YMnO 3 compound<br />

exhibits a competing interacti<strong>on</strong> in between the ferromagnetic double - exchange<br />

and antiferromagnetic super-exchange interacti<strong>on</strong>s, further a weak signature of<br />

ferromagnetic ordering at lower temperature has been witnessed. Our resistivity<br />

measurement reveals that the material is highly insulating at lower temperature just<br />

below the reported AFM transiti<strong>on</strong> in this class of materials.


QA15<br />

C<strong>on</strong>trolling the superparamagnetic limit using the magnetoelectric<br />

effect<br />

Hyungsuk K. D. Kim 1 , Laura Schelhas 2 , Sarah Tolbert 2 and Gregory P. Carman 3 *<br />

1 Department of Materials Science and Engineering, UCLA, USA<br />

2 Department of Chemistry and Biochemistry, UCLA, USA<br />

3 Department of Mechanical and Aerospace Engineering, UCLA, USA<br />

MRAM (Magnetic Random Access Memory) is attracting c<strong>on</strong>siderable attenti<strong>on</strong> as a possible candidate<br />

for next generati<strong>on</strong> of n<strong>on</strong>-volatile memory devices. Major challenges facing scientists today are<br />

overcoming thermal instability and reducing the writing energy. As bit density increases, this requires<br />

smaller magnetic regi<strong>on</strong>s to be written magnetically at small scales and external energies become<br />

a dominant feature. For example in the small scale, thermal energy becomes larger than magnetic<br />

anisotropy, resulting in superparamagnetic behavior. For a given small scale size, the temperature<br />

above which superparamagnetism begins is referred to as the blocking temperature. Superparamagnetic<br />

behavior is undesirable due to limits it places <strong>on</strong> the size of a bit of informati<strong>on</strong>. Recently, researchers<br />

have begun to study magnetoelectric (ME) memory related to some issues with memory. Their focus<br />

has been <strong>on</strong> writing processes using electric field-induced strain rather than addressing the more<br />

challenging topic of c<strong>on</strong>trolling superparamagnetism. Here we report experimental results showing the<br />

introducti<strong>on</strong> of a magnetoelectric anisotropy energy to alter the blocking temperature and thus c<strong>on</strong>trol the<br />

superparamagnetic behavior. This is achieved via an electric field-induced strain in a ME composite. Our<br />

results show 50 K increase of the blocking temperature with the applicati<strong>on</strong> of an electric field.<br />

1. Y. Jun, J. Seo, J. Che<strong>on</strong>, Accounts of chemical research 41, 179 (2008). 2. F. Zavaliche et al., Nano letters 7, 1586 (2007).<br />

3. T. Wu et al., Applied Physics Letters 98, 012504 (2011). 4. M. Bibes, A. Barthelemy, Nature Materials 7, 425 (2008).<br />

QA16<br />

Magneto-Capacitance Effect and Electric Polarizati<strong>on</strong> in Spinel<br />

Co 2MnO 4<br />

Sun Hee Kang 1 , San Youn Park 2 , Ill W<strong>on</strong> Kim 1 , Yo<strong>on</strong> Hee Je<strong>on</strong>g 3 and Tae Ye<strong>on</strong>g<br />

Koo 4 *<br />

1 Physics Department, Ulsan University, Korea<br />

2 Physics Department, Pohang Univsersity of Science and Technology, Korea<br />

3 Physics Department, Pohang University of Science and Technology, Korea<br />

4 Pohang Accelerator Laboratory, Korea<br />

Structural phase diagram of spinel Co 3-xMn xO 4 (1.0 ≤ x≤ 2.0) was reexamined at the<br />

room temperature with a focus <strong>on</strong> the cubic-tetrag<strong>on</strong>al phase boundary. A specific<br />

compositi<strong>on</strong> of Co 2MnO 4 (x=1.0) was selected from the phase diagram study under<br />

the requirement of both high ferrimagnetic transiti<strong>on</strong> temperature (Tc) and n<strong>on</strong>-mixed<br />

structural phase c<strong>on</strong>diti<strong>on</strong>. Experimental result of magnetizati<strong>on</strong> measurements and<br />

local distorti<strong>on</strong>s due to the Jahn-Teller Mn 3+ i<strong>on</strong>s support the stabilizati<strong>on</strong> of Yafet-<br />

Kittel type magnetic c<strong>on</strong>figurati<strong>on</strong> in the cubic inverse spinel Co 2MnO 4. Correlati<strong>on</strong><br />

between the observed forced magnetizati<strong>on</strong> - a c<strong>on</strong>tinual increment of magnetizati<strong>on</strong><br />

above the saturati<strong>on</strong> field - and magneto-capacitance effect (MCE) was clarified. MCE<br />

of up to 7 % at 8 T around Tc was observed without an appreciable hysteresis and<br />

n<strong>on</strong>linearity in the field variati<strong>on</strong>. Diffracti<strong>on</strong>-spectroscopy techniques were also used<br />

to identify the local chemical and structural envir<strong>on</strong>ments of both Co and Mn i<strong>on</strong>s at<br />

two crystallographic sites of the spinel structure.<br />

QA17<br />

Magnetically induced polarizati<strong>on</strong> in copper metaborate CuB 2O 4<br />

Khanh Duy Nguyen 1 , Nobuyuki Abe 2 , Masashi Tokunaga 3 , Mitsuru Saito 1 and Takahisa<br />

Arima 2 *<br />

1 Deparment of Physics, Tohoku University, Japan<br />

2 Department of Advanced Materials Science, The University of Tokyo, Japan<br />

3 Institute for Solid State Physics, The University of Tokyo, Japan<br />

Intriguing electro-magneto optic effect of n<strong>on</strong>-centrosymmetric magnet copper metaborate has<br />

attracted huge c<strong>on</strong>siderati<strong>on</strong> during last time [1]. In here we report the magneto-electric behavior of<br />

CuB 2O 4 under external magnetic field. It is well known that CuB 2O 4 undergoes a phase transiti<strong>on</strong><br />

from paramagnetic state to canted-antiferromagnet at 21 K, then followed by a sec<strong>on</strong>d transiti<strong>on</strong><br />

to spiral order around 10 K. Although the magnetic structure at low temperature below 10 K has<br />

not completely been made clear yet, some evidences of incommensurate helical order in this<br />

range of temperature have been observed [2]. Result of magnetizati<strong>on</strong> measurement points out<br />

the existence of an anomaly around 1, 3 T at 2 K, then disappeared when increasing temperature<br />

above 10 K, which may be attributed to the transiti<strong>on</strong> from commensurate to incommensurate<br />

phase. Furthermore, electric polarizati<strong>on</strong> was also observed by applying a magnetic field al<strong>on</strong>g the<br />

[110] and [1-10] axes without poling electric field in low temperature regime. The magnitude of<br />

polarizati<strong>on</strong> in static field was found to be compatible with the measurement in pulse magnetic field.<br />

Besides novel optical characteristic, these results show the ability of generati<strong>on</strong> and c<strong>on</strong>trol electric<br />

polarizati<strong>on</strong> by magnetic field in CuB 2O 4 as well as applicati<strong>on</strong> to opto-electr<strong>on</strong>ic devices.<br />

[1] M. Saito, K. Ishikawa, S. K<strong>on</strong>no, K. Taniguchi and T. Arima, Nature Mater. 8, 634 (2009) [2] M.Boehm, B. Roessli, J.<br />

Schefer, A. S. Wills, B. Ouladdiaf, E. Lelievre-Berna, U. Staub and G. A. Petrakovskii, Phys. Rev. B 68, 024405 (2003)<br />

QA18<br />

QA19<br />

QA20<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Impedance spectroscopy of ferromagnetic oxide: Pr 0.6Sr 0.4MnO 3<br />

D V Maheswar Repaka 1 and Mahendiran Ramanathan 2<br />

1 PHYSICS, Nati<strong>on</strong>al University of Singapore, Singapore<br />

2 Physics, Nati<strong>on</strong>al University of Singapore, Singapore<br />

In recent years, coupling between electrical and magnetic polarizati<strong>on</strong>s in multiferroicmagnetoelectrics<br />

have become a topic of c<strong>on</strong>siderable interest due to novel applicati<strong>on</strong>s and<br />

fundamental physics involved [1]. Impedance spectroscopy has been extensively used to<br />

investigate cross coupling between magnetic and electrical dipole ordering. Anomalies in lowfrequency<br />

(f = 1-10 kHz) dielectric c<strong>on</strong>stant at magnetic transiti<strong>on</strong> have been reported in YMnO 3<br />

[2], BiMnO 3 [3] etc. However, measurement in MHz range has been hardly reported. In this work,<br />

we report temperature, frequency and magnetic field dependence of impedance in Pr 0.6Sr 0.4MnO 3<br />

which shows ferromagnetic transiti<strong>on</strong> near room temperature (T C= 303 K). It is found that with<br />

increasing frequency of the ac current, an anomaly in the form of a sharp peak appears at the<br />

Curie temperature. A sec<strong>on</strong>d anomaly in the form of an abrupt decrease occurs at T= 100 K much<br />

below the Curie temperature. These anomalies are suppressed under external magnetic field. It is<br />

suggested that the observed anomalies are not necessarily caused by ordering of electrical dipoles.<br />

The observed features in impedance closely correlate with the magnetizati<strong>on</strong>. We suggest that<br />

impedance spectroscopy in these materials can probe magnetizati<strong>on</strong> dynamics, which is often<br />

neglected in studies of magnetocapacitance effect in multiferroic materials.<br />

[1] S.W. Che<strong>on</strong>g and M. Mostovoy, Nat.Mater. 6 (2007) 13. [2] S. Lee, A. Pirogov, M. Kang, K.H.<br />

Jang, M. Y<strong>on</strong>emura, T. Kamiyama, S.W. Che<strong>on</strong>g, F. Gozzo, N. Shin, H. Kimura, Y. Noda, and J.G. Park,<br />

Nature (L<strong>on</strong>d<strong>on</strong>) 451, (2008) 451. [3] R. Seshadri and N. A. Hill, Chem.Mater. 13, (2001) 2892.<br />

Structures and magnetic properties of Tm 1-yY yMn 1-xCo xO 3<br />

Toshiyuki Tanaka, Yusuke Amakai, Naoki Mom<strong>on</strong>o, Shigeyuki Murayama and<br />

Hideaki Takano*<br />

Department of Applied Sciences, Muroran Institute of Technology, Japan<br />

The structure and magnetic properties of Tm 1-yY yMn 1-xCo xO 3 with 0≤x≤0.5 and<br />

0≤y≤0.3 were investigated by X-ray diffracti<strong>on</strong>, specific heat and magnetizati<strong>on</strong><br />

measurements. A thulium manganite TmMnO 3 prepared by the solid state synthesis<br />

method in ambient pressure is hexag<strong>on</strong>al and antiferromagnetic with Neel temperature<br />

T N=86 K. The substituti<strong>on</strong> of Y for Tm in TmMnO 3 does not largely affect the<br />

fundamental hexag<strong>on</strong>al structure. We can roughly understand the results of the<br />

magnetizati<strong>on</strong> and the specific heat of Tm 1-yY yMnO 3 in terms of a diluti<strong>on</strong> effect of<br />

Tm by Y. On the other hand, the structure of TmMn 1-xCo xO 3 gradually changes from<br />

hexag<strong>on</strong>al to orthorhombic with the substituti<strong>on</strong> of Co for Mn and hexag<strong>on</strong>al and<br />

orthorhombic phases coexist in samples for x≤0.3, and TmMn 0.6Co 0.4O 3 become almost<br />

orthorhombic single phase. The magnetizati<strong>on</strong> of TmMn 0.6Co 0.4O 3 in a field of 250<br />

Oe increases rapidly below about 60 K with decreasing temperature. The discrepancy<br />

of the zero-field-cooled (ZFC) and the field-cooled (FC) magnetizati<strong>on</strong> remarkablely<br />

expands below about 60 K. Moreover, temperature dependence of ZFC and FC<br />

magnetizati<strong>on</strong> show peaks at 40 K and 27 K, respectively. TmMn 1-xCo xO 3 we obtained<br />

shows complicated magnetic properties.<br />

Complex magnetic and electric orders in multiferroic Co 3TeO 6<br />

Chin-wei Wang1, Chih-jen Wang1, Wen-hsien Li1*, Chih-chieh Chou2, Hung-duen Yang2, Yang<br />

Zhao3, Sung Chang3, Jeffrey W. Lynn3 and Helmuth Berger4<br />

1 Department of Physics and Center for Neutr<strong>on</strong> Beam Applicati<strong>on</strong>s, Nati<strong>on</strong>al Central University, Taiwan<br />

2 Department of Physics and Center for Nanoscience and Nanotechnology, Nati<strong>on</strong>al Sun Yat-Sen<br />

University, Taiwan<br />

3 NIST Center for Neutr<strong>on</strong> Research, Nati<strong>on</strong>al Institute of Standards and Technology, Gaithersburg, USA<br />

4 Institute of Physics of Complex Matter, EPFL, Lausanne, Switzerland<br />

Multiferroics, where both ferroelectric and magnetic order coexist, are quite uncomm<strong>on</strong>, but<br />

are of particular interest both to understand the fundamental interacti<strong>on</strong>s between the two<br />

types of order as well as for the potential for practical applicati<strong>on</strong>s. The novel metal tellurates<br />

M3TeO6, where M is a first-row transiti<strong>on</strong> metal, have been shown to be rich in crystalline<br />

chemistry. Ferroelectricity and magnetic-field-driven polarizati<strong>on</strong> have been observed. Here, we<br />

report <strong>on</strong> the results of neutr<strong>on</strong> diffracti<strong>on</strong>, magnetic susceptibility, specific heat, and dielectric<br />

c<strong>on</strong>stant measurements made <strong>on</strong> a single crystal Co3TeO6 to study the interplay between<br />

the ferroelectricity and magnetic order. A str<strong>on</strong>g interplay between the order parameters of<br />

ferroelectricity and both commensurate and incommensurate magnetic order are observed. L<strong>on</strong>g<br />

range incommensurate magnetic order develops below TM1=26 K, which is followed by three<br />

additi<strong>on</strong>al zero-field phase transiti<strong>on</strong>s at TM2=19.5 K, TM3=18 K, and TM4=16 K where the<br />

incommensurate order changes and commensurate order develops. In magnetic fields up to 14 T<br />

we find that the magnetic intensities and incommensurate wave vector are dramatically altered<br />

as ferroelectricity develops, with a fifth abrupt transiti<strong>on</strong> around 10 T. The overall behavior<br />

characterizes Co3TeO6 as a type-II multiferroic.<br />

July 8 - 13, 2012 Busan, Korea 71<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QA21<br />

Annealing induced colossal magnetocapacitance and colossal<br />

magnetoresistance in in-doped CdCr 2S 4<br />

Zhaor<strong>on</strong>g Yang*<br />

Institute of Solid State Physics, Chinese Academy of Sciences, China<br />

Colossal magnetocapacitance (CMC) and colossal magnetoresistance (CMR) induced<br />

by annealing polycrystalline Cd 0.97In 0.03Cr 2S 4 are reported. In agreement with the<br />

appearance of CMR near the Curie temperature Tc, a insulator-metal transiti<strong>on</strong> is<br />

observed with decreasing temperature at zero magnetic field. On the c<strong>on</strong>trary, after<br />

the same annealing treatment, CdCr 2S 4 displays typical semic<strong>on</strong>ductor behavior and<br />

does not show magnetic field dependent dielectric and electric transport properties.<br />

Accordingly, the simultaneous occurrence of CMC and CMR effects implies that the<br />

CMC in the annealed Cd .97In 0.03Cr 2S 4 could be explained qualitatively by a combinati<strong>on</strong><br />

of CMR and Maxwell-Wagner effect.<br />

QA22<br />

Critical dynamics in LiCuVO 4<br />

Christoph Grams 1 *, Maximilian Schalenbach 1 , Daniel Niermann 1 , Petra Becker 2 and<br />

Joachim Hemberger 1<br />

1 II. Physikalisches Institut, University of Cologne, Germany<br />

2 Institut fur Kristallographie, University of Cologne, Germany<br />

QA23<br />

WITHDRAWN<br />

High quality crystal growth and Low temperature diffuse scattering<br />

studies<br />

Shilpa Adiga*, Yixi Su, Jrg Perss<strong>on</strong> and Manuel Angst<br />

PGI-4, Forschungszentrum Juelich, Germany<br />

The 120 K Verwey-transiti<strong>on</strong> [1] in magnetite Fe 3O 4 is the classical example for charge<br />

or- dering, but the complex low-temperature structure was unresolved during decades.<br />

Early experimental studies and recent calculati<strong>on</strong>s suggest ferroelectricity (FE) due<br />

to charge ordering, which would be significant if c<strong>on</strong>firmed. Very recent structural<br />

refinement [2] supports the necessary polar structure. Recently, signatures of relaxor<br />

FE were observed below 40 K [3] . Specific diffuse scattering would be expected in<br />

such a case [4], best re- solved <strong>on</strong> high quality single crystals. The Verwey transiti<strong>on</strong><br />

depends sensitively oxygen stoichiometry [5] and the high quality crystals are obtained<br />

by the direct synthesis in an appropriate CO/CO 2 flow [6].We have grown high quality<br />

single crystals of magnetite under the tailored growth c<strong>on</strong>diti<strong>on</strong>s by optical floating<br />

z<strong>on</strong>e method and characterized them primarily by specific heat measurement. We<br />

present the results of high energy x-rays and neutr<strong>on</strong>s diffuse scattering experiments,<br />

performed to test the proposed relaxor FE. The presence of weak diffuse scattering at<br />

very low temperature is observed <strong>on</strong>ly by neutr<strong>on</strong> scattering, and thus likely magnetic,<br />

not supporting relaxor FE. Proof of the latter would require time resolved scattering.<br />

1.E.J.W.Verwey, Nature 144, 327 (1939). 2.Mark S.Senn et al, Nature Letter (2011). 3.F.Schrettle et<br />

al, Phys. Rev. B. 83 195109 (2011). 4.Grace Y<strong>on</strong>g et al , Phys. Rev. B. 62, 14763 (2000). 5.P.Shepherd<br />

et al., Phys. Rev. B 43, 8461 (1991). 6.R.Arag<strong>on</strong> et al., J. crystal growth, 61, 221 (1983)<br />

72 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QA24<br />

Anomalous magnetodielectric and magnetostrictive effect via spin<br />

reorientati<strong>on</strong> in terbium ir<strong>on</strong> garnet<br />

Ki-myung S<strong>on</strong>g 1 , Se<strong>on</strong>gsu Lee 2 and Namjung Hur 1 *<br />

1 Dept. of physics, Inha univ., Korea<br />

2 Neutr<strong>on</strong> Science Divisi<strong>on</strong>, Korea Atomic Energy Research Institute, Korea<br />

We have investigated the relati<strong>on</strong>ship am<strong>on</strong>g the magnetic, dielectric and<br />

magnetostrictive properties of terbium ir<strong>on</strong> garnet (TbIG). In this presentati<strong>on</strong>, we<br />

report experimental observati<strong>on</strong>s which are extraordinary magnetostricti<strong>on</strong> and<br />

magnetodielectric effects in TbIG with a n<strong>on</strong>-collinear spin structure in a single<br />

unit cell. The distinct effects of magnetism <strong>on</strong> the lattice are also dem<strong>on</strong>strated by<br />

the unprecedented magnetostricti<strong>on</strong> with a negative poiss<strong>on</strong> ratio. We attribute the<br />

observed magnetodielectric effects and the huge magnetostricti<strong>on</strong> to the magnetic field<br />

induced spin reorientati<strong>on</strong> from n<strong>on</strong>-collinear to collinear. In this study, we analyzed<br />

crystallographic and spin structure of TbIG in various temperatures by the Fullprof<br />

program. We investigated the effect of the n<strong>on</strong>-collinear spin structure <strong>on</strong> the crystal<br />

structure of TbIG to elucidate the relati<strong>on</strong> between them through analyzing neutr<strong>on</strong><br />

diffracti<strong>on</strong> data.<br />

QA25<br />

Template based synthesis of multiferroic BiMnO 3 nanotubes and shape<br />

dependent study of its magnetic properties<br />

Geo George Phillip, Anuraj Sundar, Mahdiyar Bagheri, Helen Annal Therese* and<br />

Gopalakrishnan Chandrasekaran<br />

Nanotechnology Research Centre, SRM University, India<br />

The synthesis of Bismuth manganite nanotubes was d<strong>on</strong>e by templating precursors of<br />

bismuth and manganese <strong>on</strong> titanium dioxide nanotubes. The yield was post treated to<br />

remove the template material and sintered at 400 C. The resulting powders were studied using<br />

X-ray Diffractometer and Scanning Electr<strong>on</strong> Microscope, which revealed the formati<strong>on</strong> of<br />

perovskite nanotubes . The BiMnO 3 nanotubes were characterized for its magnetic properties<br />

by Vibrating sample magnetometer that revealed the intrinsic ferromagnetic nature with<br />

increase in its magnetic saturati<strong>on</strong> that could have been due to the shape anisotropy of the<br />

nanotubes. The magnetizati<strong>on</strong> under field cooled and zero-field cooled was also found to<br />

differ significantly with applied magnetic field. These results indicate the co-existence of<br />

antiferromagnetic behavior at higher temperatures al<strong>on</strong>g with its intrinsic ferromagnetic nature<br />

which deviate from its bulk counterpart that <strong>on</strong>ly exhibits ferromagnetic nature.<br />

1. Srikala, D., Singh, V.N., Banerjee, A., Mehta, B.R.Effect of induced shape anisotropy <strong>on</strong> magnetic properties of<br />

ferromagnetic cobalt nanocubes (2010) Journal of Nanoscience and Nanotechnology, 10 (12), pp. 8088-8094. 2.<br />

Tajiri, T., Haraz<strong>on</strong>o, M., Deguchi, H., Mito, M., Kohno, A., Kohiki, S. Synthesis and magnetic property of multiferroic<br />

BiMnO3 nanoparticles in the pores of mesoporous silica (2010) Japanese Journal of Applied Physics, 49 (6 PART 2),<br />

pp. 06GH041-06GH044. 3. Xu, E., Qian, T., Zhang, G., Zhang, T., Li, G., Wang, W., Li, X. Fabricati<strong>on</strong> and magnetic<br />

properties of multiferroic BiFeO3 nanotube arrays (2007) Chemistry Letters, 36 (1), pp. 112-113.<br />

QA26<br />

Solitary reentrant superc<strong>on</strong>ductivity predicti<strong>on</strong> in asymmetrical<br />

ferromagnet-superc<strong>on</strong>ductor-ferromagnet trilayer<br />

Yurii N. Proshin*, Marat M. Khusainov, Arthur Minnullin and Mansur G. Khusainov<br />

Theoretical Physics Department, Kazan Federal University, Russia<br />

The theory of proximity effect for thin bilayer FS, trilayer FSF and fourlayered system<br />

FSFS, where F is a ferromagnetic metal, and S is superc<strong>on</strong>ductor, is proposed <strong>on</strong> the<br />

base of new boundary-value problem for the Eilenberger functi<strong>on</strong>. For all systems the<br />

dependencies of critical temperature <strong>on</strong> an exchange field of the F metal, electr<strong>on</strong>ic<br />

correlati<strong>on</strong>s in the S and F metals, and thicknesses of layers F and S are derived. It<br />

is shown that the possibility of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state<br />

observati<strong>on</strong> is especially increased in the asymmetrical systems (FSF' and FSF'S') for<br />

which solitary reentrant superc<strong>on</strong>ductivity is predicted. On the basis of a proximity<br />

effect we propose new method of probe of electr<strong>on</strong>ic parameters of c<strong>on</strong>tacting<br />

materials. If well known BCS superc<strong>on</strong>ductor S is used as a probe, <strong>on</strong>e can determine<br />

the exchange field, the electr<strong>on</strong>-electr<strong>on</strong> c<strong>on</strong>stant in various magnetics F for the FS<br />

structures. It allows us to predict the sign and value of the c<strong>on</strong>stant of electr<strong>on</strong>-electr<strong>on</strong><br />

interacti<strong>on</strong> in gadolinium and to explain a surprisingly high critical temperature Tc ~<br />

5K in the short-periodic Gd/La superlattice [1].<br />

P.P. Deen, et al. J. Phys.: C<strong>on</strong>d. Matt. 17, 3305 (2005).


QA27<br />

Tuning magnetic order, electromagn<strong>on</strong>s and exchange bias by epitaxial<br />

strain in BiFeO3 thin films<br />

Manuel Bibes 1 *, Daniel Sando 1 , Arsene Agbelele 2 , Maximilien Cazayous 3 , Ingrid Infante 4 , Wei<br />

Ren 5 , Sergey Lisenkov 6 , Cecile Carretero 1 , Agnes Barthelemy 1 , Laurent Bellaiche 5 , Jean Juraszek 2<br />

and Brahim Dkhil 4<br />

1 Unite Mixte de Physique CNRS/Thales, France<br />

2 Universite de Rouen, France<br />

3 Universite Paris Diderot, France<br />

4 Ecole Centrale Paris, France<br />

5 University of Arkansas, USA<br />

6 Universiy of South Florida, USA<br />

With a ferroelectric Curie temperature of 1100 K and a Neel temperature of 640K, BiFeO3 is <strong>on</strong>e<br />

the very few room-temperature multiferroics [1]. Its ferroelectric polarizati<strong>on</strong> is as high as 100 μC/<br />

cm² and in the bulk it is a G-type antiferromagnet, with a superimposed cycloidal modulati<strong>on</strong>. In<br />

additi<strong>on</strong> to showing magnetoelectric coupling between its ferroic orders, BiFeO3 also exhibits coupling<br />

between dynamic lattice and spin excitati<strong>on</strong>s (electromagn<strong>on</strong>s), enabling an electrical c<strong>on</strong>trol of spin<br />

waves [2]. We have explored the influence of epitaxial strain [3] <strong>on</strong> the antiferromagnetic properties<br />

of BiFeO3 thin films. Combining Mossbauer spectroscopy and Raman scattering, we have found that<br />

the harm<strong>on</strong>ic cycloidal order is stable at low strain but is replaced at higher strain by c<strong>on</strong>venti<strong>on</strong>al<br />

antiferromagnetism. This is accompanied by str<strong>on</strong>g changes in the electromagn<strong>on</strong> spectra and <strong>on</strong> their<br />

dependence <strong>on</strong> external stimuli. In additi<strong>on</strong>, the mean antiferromagnetic vector progressively rotates as<br />

strain varies, offering novel strategies to c<strong>on</strong>trol exchange bias with ferromagnetic overlayers.<br />

[1] G. Catalan et al, Adv. Mater. 21, 2463 (2009) ; [2] P. Rovillain et al, Nature Mater. 9 975 (2010) ;[3] I.C. Infante et<br />

al, Phys. Rev. Lett. 105, 057601 (2010)<br />

QB01<br />

Magnetic-enhanced electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> coupling and vacancy effect in<br />

'111' type ir<strong>on</strong> pnictides from first-principles calculati<strong>on</strong>s<br />

Mei Liu 1 and Bin Li 2<br />

1 Dept. of Physics, Southeast University, China<br />

2 Department of Physics, Southeast University, China<br />

We investigate the lattice dynamics in both n<strong>on</strong>magnetic and striped antiferromagnetic<br />

states of '111' type ir<strong>on</strong> pnictides using the density-functi<strong>on</strong>al perturbati<strong>on</strong> theory.<br />

The anisotropic spin-ph<strong>on</strong><strong>on</strong> effects lead to the softening of ph<strong>on</strong><strong>on</strong> frequencies<br />

and the renormalizati<strong>on</strong> of electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> matrix elements, so as to increase the<br />

electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> couplings by 68%, 65%, and 0.9% for LiFeAs, NaFeAs, and LiFeP,<br />

respectively. Taking into account the vacancy effects in the three ir<strong>on</strong> pnictides, we<br />

find that the electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> couplings are further enhanced by hole doping, yielding<br />

superc<strong>on</strong>ducting transiti<strong>on</strong> temperatures close to their experimental values.<br />

QB02<br />

Penetrati<strong>on</strong> depth and knight shift in ir<strong>on</strong>-based superc<strong>on</strong>ductor Ba1 xKxFe2As2 Kazuki Ohishi 1 *, Yasuyuki Ishii 2 , Isao Watanabe 3 , Taku Saito 4 , Hideto Fukazawa 4 ,<br />

Yoh Kohori 4 , Kunihiro Kihou 5 , Chul-ho Lee 5 , Hijiri Kito 5 , Akira Iyo 5 and Hiroshi<br />

Eisaki 5<br />

1<br />

Research Center for Neutr<strong>on</strong> Science and Technology, CROSS, Japan<br />

2<br />

Department of Physics, Tokyo Medical University, Japan<br />

3<br />

Advanced Mes<strong>on</strong> Science Laboratory, RIKEN, Japan<br />

4<br />

Department of Physics, Chiba University, Japan<br />

5 AIST, Japan<br />

We have observed temperature and magnetic field dependence of penetrati<strong>on</strong> depth λ<br />

in single crystalline samples of Ba 1-xK xFe 2As 2 (x = 0.27, 0.64, 0.7, 0.8, 0.94 and 1.0) in<br />

order to clarify the superc<strong>on</strong>ducting gap mechanism. We have found that T dependence<br />

of 1/λ^2 in KFe 2As 2 with H//c and H┴c are completely different. While the T<br />

dependence of 1/λ^2 observed with H//c is well fitted by a two-full-gap model, T-linear<br />

behavior is clearly observed below ~T_c/2 with H┴c, suggesting the existence of line<br />

node. These results are well interpreted when we take into account the horiz<strong>on</strong>tal line<br />

node (line node in ab-plane) in KFe 2As 2. At the presentati<strong>on</strong>, we will also report the T<br />

and H dependence of λ and Knight shift over a wide x regi<strong>on</strong> of Ba 1-xK xFe 2As 2.<br />

QB03<br />

QB04<br />

QB05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Raman scattering study of the lattice dynamics in LiFeAs and Fe1+yTe1 xSex Youngje Um<br />

Max-Planck institute, Stuttgart, Germany<br />

Following the recent discovery of superc<strong>on</strong>ductivity in F doped LaFeAsO with Tc of<br />

26 K, numerous families of the Fe-based superc<strong>on</strong>ductors such as REFeAs(O 1-xF x)<br />

(RE = rare earth), MFe 2As 2 (M = Ba, Ca, Sr, K, ...), LiFeAs/NaFeAs and Fe 1+yTe 1xSe<br />

x have been found and investigated. Most of these compounds have closely related<br />

phase diagrams and present an antiferromagnetic parent compound at low temperature,<br />

which turns superc<strong>on</strong>ductor up<strong>on</strong> doping. A noticeable excepti<strong>on</strong> is LiFeAs, in which<br />

superc<strong>on</strong>ductivity is observed already in the parent compound. Recent ARPES results<br />

suggest str<strong>on</strong>g electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> coupling in LiFeAs, but so far no experimental study<br />

of its lattice dynamics is available. Here, we present first Raman light scattering<br />

investigati<strong>on</strong>s of lattice dynamics <strong>on</strong> superc<strong>on</strong>ducting LiFeAs. Five of the six expected<br />

ph<strong>on</strong><strong>on</strong> modes are observed, and show a c<strong>on</strong>venti<strong>on</strong>al anharm<strong>on</strong>ic behavior. No clear<br />

evidence for coupling of electr<strong>on</strong> with z<strong>on</strong>e center ph<strong>on</strong><strong>on</strong> is observed. Then, we<br />

present a systematic study of the lattice dynamics in Fe 1+yTe 1-xSe x as a functi<strong>on</strong> of Se<br />

and excess Fe c<strong>on</strong>tents, with special emphasis <strong>on</strong> the Fe ph<strong>on</strong><strong>on</strong>. A peculiar doping<br />

dependence of the mode is observed, which suggests an original coupling of this<br />

ph<strong>on</strong><strong>on</strong> to the low energy spin excitati<strong>on</strong>s induced by excess ir<strong>on</strong>.<br />

<strong>Magnetism</strong> and Superc<strong>on</strong>ductivity in Rb xFe 2-ySe 2<br />

Kazuki Ohishi 1 *, Shouhei Kototani 2 , Shunsuke Saiki 2 , Yoshiaki Kobayashi 2 , Masayuki<br />

Itoh 2 and Masatoshi Sato 1<br />

1 Research Center for Neutr<strong>on</strong> Science and Technology, CROSS, Japan<br />

2 Department of Physics, Nagoya University, Japan<br />

The recent discovery of superc<strong>on</strong>ductivity in A xFe 2-ySe 2 (A = alkali metal), with<br />

transiti<strong>on</strong> temperatures up to Tc ~ 32 K, has led to a renewed interest for ir<strong>on</strong> based<br />

chalcogenide systems. A remarkable observati<strong>on</strong> is that, beside the superc<strong>on</strong>ducting<br />

state, a str<strong>on</strong>g antiferromagnetic (AFM) state with magnetic moments up to 3.3μB<br />

per Fe i<strong>on</strong> is observed below TN~550 K. The key issue in A xFe 2-ySe 2 is whether AFM<br />

order and superc<strong>on</strong>ductivity cohabit due to phase separati<strong>on</strong> or share a microscopic<br />

coexistence. We have performed mu<strong>on</strong> spin relaxati<strong>on</strong>/rotati<strong>on</strong> measurements in<br />

single crystalline samples of superc<strong>on</strong>ducting (SC) Rb 0.8Fe 1.6Se 2 (Tc = 29 K) and n<strong>on</strong>-<br />

SC Rb 0.8Fe 1.6Se 2, which doesn’t show superc<strong>on</strong>ductivity, in order to elucidate whether<br />

there is difference of magnetic state between SC and n<strong>on</strong>-SC samples. In SC sample,<br />

we found that SC volume fracti<strong>on</strong> is <strong>on</strong>ly ~6% and the rest of amount is AFM ordered<br />

phase, suggesting SC and AFM ordered phases are separated. We found that mu<strong>on</strong><br />

spin depolarizati<strong>on</strong> increases with decreasing temperature in n<strong>on</strong>-SC sample, while no<br />

change was observed in SC sample. It suggests the appearance of new magnetic state<br />

below 40 K in n<strong>on</strong>-SC sample.<br />

Magnetic Res<strong>on</strong>ant mode in the Spin-Excitati<strong>on</strong> Spectrum of<br />

Superc<strong>on</strong>ducting Rb2Fe4Se5 Single Crystals<br />

Jitae Park<br />

Max-Planck-Institute for Solid State Research, Germany<br />

WITHDRAWN<br />

July 8 - 13, 2012 Busan, Korea 73<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QB06<br />

Magnetic field-induced superc<strong>on</strong>ductivity in the canted<br />

antiferromagnet Eu(Fe0.81Co0.19) 2As2 Vinh Hung Tran 1 *, T A Zaleski 2 , Z Bukowski 1 , L M Tran 1 and A J Zaleski 1<br />

1<br />

Institute of Low Temperature and Structure Research, Polish Academy of Sciences,<br />

50-950 Wroclaw, Poland<br />

2<br />

Institute of Low Temperature and Structure Research, Polish Academy of Sciences,<br />

50-950, Poland<br />

We present results of ac-magnetic susceptibility, dc-magnetizati<strong>on</strong>, specific heat and<br />

magnetotransport measurements <strong>on</strong> a single crystal of magnetic Eu(Fe 0.81Co 0.19) 2As 2<br />

superc<strong>on</strong>ductor. The compound undergoes multiple phase transiti<strong>on</strong>s; from<br />

paramagnetic to a spin-density-wave (SDW) at TSDW = 80 K, to canted<br />

antiferromagnetic (C-AF) state at TN = 16.5 K and superc<strong>on</strong>ducting (SC) state at Tc<br />

= 5.15 K at zero field. Up<strong>on</strong> applying fields both the C-AF and SC states evolve in an<br />

unc<strong>on</strong>venti<strong>on</strong>al manner. Magnetic field distinctly affects the spin canting, resulting in<br />

separati<strong>on</strong> of the C-AF into two a new C-AF and ferromagnetic phases. The unusual<br />

behavior of the SC state deserves the observati<strong>on</strong> that Tc can be increased up to 6.5 K<br />

with magnetic fields applied parallel to the ab-plane of crystals. The observed fieldinduced<br />

superc<strong>on</strong>ductivity is interpreted as a result of a weakening of the orbital pairbreaking<br />

effect. From the experimental data we propose the field-temperature phase<br />

diagrams for Eu(Fe 0.81Co 0.19) 2As 2.<br />

QB07<br />

Superc<strong>on</strong>ductivity and spin fluctuati<strong>on</strong>s in Ca 1-xPr xFe 2As 2<br />

superc<strong>on</strong>ductors studied by 75As NMR<br />

L<strong>on</strong>g Ma 1 *, Gaofeng Ji 1 , Jia Dai 1 , S. R. Saha 2 , J. Pagli<strong>on</strong>e 2 and Weiqiang Yu 1<br />

1 Department of Physics, Renmin University of China, China<br />

2 Center for Nanophysics and Advanced Materials, Department of Physics, University<br />

of Maryland, USA<br />

The observati<strong>on</strong> of superc<strong>on</strong>ductivity in the rare earth doped CaFe 2As 2 with Tc as<br />

high as 47 K is still not understood. Here we report the first NMR study <strong>on</strong> the newly<br />

discovered Ca 1-xPr xFe 2As 2 (x=0.075, 0.15) single crystals. The magnetizati<strong>on</strong> shows<br />

superc<strong>on</strong>ductivity at ~25 K with a small volume ratio for both samples. A first order<br />

structural transiti<strong>on</strong> from the tetrag<strong>on</strong>al to the collapsed tetrag<strong>on</strong>al phase in both<br />

crystals is shown by 75As spectra. Residual tetrag<strong>on</strong>al phase is seen in the x = 0.075<br />

sample with a finite volume, but not seen in the x = 0.15 sample. We also observed<br />

a sharp drop of Knight shift below Ts in both samples, suggesting a suppressi<strong>on</strong> of<br />

local moments in the collapsed phase. However, the 1/75T1 is enhanced below 50<br />

K and shows a prominent peak at about 25 K. Such behaviors indicate str<strong>on</strong>g lowenergy<br />

antiferromagnetic spin fluctuati<strong>on</strong>s, with static or quasi-static magnetic ordering<br />

at low temperatures, which is probably caused by Pr 3+ doping. The absence of the<br />

residual tetrag<strong>on</strong>al phase and the observati<strong>on</strong> of antiferromagnetic spin fluctuati<strong>on</strong>s in<br />

the x=0.15 sample suggest that superc<strong>on</strong>ductivity in Ca 1-xPr xFe 2As 2 is not tied to the<br />

tetrag<strong>on</strong>al phase and may have a magnetic origin.<br />

QB08<br />

Importance and details of the spin excitati<strong>on</strong> spectra in high-Tc<br />

pnictide superc<strong>on</strong>ductors<br />

Tanmoy Das and A. V. Balatsky<br />

Theoretical Divisi<strong>on</strong>, Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

One comm<strong>on</strong> feature that underlies all high-Tc superc<strong>on</strong>ductor families is the development<br />

of a magnetic res<strong>on</strong>ance peak at or around the antiferromagnetic ‘hot-spot’ vector. This<br />

feature has proven to give valuable informati<strong>on</strong> about the pairing symmetry, and bulk<br />

Fermi surface properties. We provide a random-phase approximati<strong>on</strong> (RPA) based BCS<br />

susceptibility calculati<strong>on</strong> using material specific band structure for 122 family of ir<strong>on</strong>pnictide<br />

and layered ir<strong>on</strong> selenide superc<strong>on</strong>ductors. (i) In ir<strong>on</strong>-pnictide, we show that<br />

when two hole-pockets at Gamma point and the electr<strong>on</strong> pockets at M point are present<br />

<strong>on</strong> the Fermi surface, the spin-excitati<strong>on</strong> spectra split into two distinct res<strong>on</strong>ance branches.<br />

[1] The energy separati<strong>on</strong> between the two res<strong>on</strong>ances is related to the differences in the<br />

superc<strong>on</strong>ducting gaps <strong>on</strong> two hole-pockets. Again, the momentum resoluti<strong>on</strong> between the<br />

two modes comes from the differences in Fermi surface areas of the two hole-pockets. (ii)<br />

We also show that when <strong>on</strong>e hole-pocket disappears, <strong>on</strong>e of the res<strong>on</strong>ances disappears.<br />

Furthermore, when both hole pockets vanish, the magnetic scattering between the<br />

remaining electr<strong>on</strong>-pockets lead to a change in the gap symmetry from s± to d-wave. The<br />

latter is observed in the newly discovered ir<strong>on</strong>-selenide superc<strong>on</strong>ductors. [2] Finally, we<br />

will present the resulting spin-excitati<strong>on</strong> spectra for both materials.<br />

[1] T. Das, and A. V. Balatsky, Phys. Rev. Lett. 106, 157004 (2011). [2] T. Das, and A. V. Balatsky,<br />

Phys. Rev. B 84, 014521 (2011).<br />

74 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QB09<br />

Angular dependence of the resistive upper critical field of an ir<strong>on</strong>based<br />

superc<strong>on</strong>ductor Fe(Te,Se) in high magnetic fields<br />

Takanori Kida 1 , Yoshikazu Mizuguchi 2 , Yoshihiko Takano 3 and Masayuki Hagiwara 1<br />

1 KYOKUGEN, Osaka university, 1-3 Machikaneyama, Toy<strong>on</strong>aka, Osaka 560-8531, Japan<br />

2 Grad. Sch. Sci. Eng., Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Japan<br />

3 Nati<strong>on</strong>al Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan<br />

The 11-system FeCh (Ch=S, Se, Te) superc<strong>on</strong>ductors are of great importance in<br />

understanding the mechanism of superc<strong>on</strong>ductivity in ir<strong>on</strong>-based superc<strong>on</strong>ductors owing<br />

to their simple structures. Previously, we have reported the temperature dependence of the<br />

resistive upper critical field (Hc2) <strong>on</strong> Fe 1.05Te 0.85Se 0.15, which exhibits superc<strong>on</strong>ductivity<br />

at T = 14 K [1,2]. The Hc2 of this compound at low temperature is c<strong>on</strong>siderably smaller<br />

than that expected from the Werthamer-Helfand-Hohenberg model, manifesting the Pauli<br />

limiting behavior. It suggests that this compound shows the spin-singlet pairing in the<br />

superc<strong>on</strong>ducting state. The anisotropy coefficient of Hc2 decreases from 2.4 near Tc to<br />

~1 (nearly isotropic) at low temperatures. In this study, we have investigated an angular<br />

dependence of Hc2 of a single crystal of Fe 1.05Te 0.85Se 0.15 in pulsed high magnetic fields up<br />

to 52 T. At T = 10 K, the Hc2 increases with increasing Θ, which is the angle between the<br />

c-axis and applied magnetic fields directi<strong>on</strong>. We have found that the angular dependence of<br />

Hc2 is well agreement with the Gintzbrug-Landau effective-mass predicti<strong>on</strong>.<br />

[1] T. Kida et al., J. Phys. Soc. Jpn. Vol.78 (2009) 113701. [2] T. Kida et al., J. Phys. Soc. Jpn.<br />

Vol.79 (2010) 074706.<br />

QB10<br />

Ab initio evidence of str<strong>on</strong>g correlati<strong>on</strong> and large Mott proximity in<br />

ir<strong>on</strong>-based superc<strong>on</strong>ductors<br />

Takahiro Misawa, Kazuma Nakamura and Masatoshi Imada<br />

Dept. Appied Physics, Univ. of Tokyo, Japan<br />

Recently discovered ir<strong>on</strong>-based superc<strong>on</strong>ductors have attracted much interest in their<br />

high superc<strong>on</strong>ducting critical temperatures (Tc). Although it is believed that electr<strong>on</strong><br />

correlati<strong>on</strong>s mediate the unc<strong>on</strong>venti<strong>on</strong>al high-Tc superc<strong>on</strong>ductivity, their roles are<br />

not fully understood yet. To clarify electr<strong>on</strong> correlati<strong>on</strong> effects from a microscopic<br />

point of view, we study the ab initio low-energy effective model for ir<strong>on</strong>-based<br />

superc<strong>on</strong>ductors by using multi-variable variati<strong>on</strong>al M<strong>on</strong>te Carlo method. From<br />

this ab initio calculati<strong>on</strong>s, we show that ir<strong>on</strong>-based superc<strong>on</strong>ductors discovered near<br />

d6 c<strong>on</strong>figurati<strong>on</strong> (5 Fe 3d orbitals filled by 6 electr<strong>on</strong>s) is located <strong>on</strong> the foot of an<br />

unexpectedly large dome of correlated electr<strong>on</strong> matter centered at the Mott insulator<br />

at d5 (namely, half filling). The d5 Mott proximity extends to subsequent emergence<br />

of incoherent metals, orbital differentiati<strong>on</strong>s due to the Mott physics and Hund’s-rule<br />

coupling, followed by antiferromagnetic quantum criticality, in quantitative accordance<br />

with available experiments.<br />

QB11<br />

As-NQR study of LaFeAsO 1-xF x<br />

Toshihide Oka 1 *, Z Li 2 , S Kawasaki 1 , G F Chen 2 , N L Wang 2 and G -q Zheng 1<br />

1 Department of Physics, Okayama uiversity, Japan<br />

2 Beijing Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics, Institute of Physics,<br />

Chinese Academy of Science, China<br />

The discovery of superc<strong>on</strong>ductivity in LaFeAsO 1-xF x at superc<strong>on</strong>ducting transiti<strong>on</strong><br />

temperature Tc=26K, followed by that in ReFeAsO 1-xF x(Re:Ce,Pr,Nd,Sm) with<br />

Tc as high as 55K, has gained much attenti<strong>on</strong>. We have performed systematic Asnuclear<br />

quadrupole res<strong>on</strong>ance(NQR) measurements <strong>on</strong> LaFeAsO 1-xF x to elucidate<br />

its superc<strong>on</strong>ducting gap structure and mechanism of the Cooper pair formati<strong>on</strong>.<br />

For x=0.03, we find the spin-lattice relaxati<strong>on</strong> rate(1/T1) exhibits a small upturn at<br />

TN=58K, below which the spectra become broadened due to the internal magnetic<br />

field attributed to an antiferromagnetic ordering. Above TN, 1/T1T increases with<br />

decreasing T due to the antiferromagnetic spin fluctuati<strong>on</strong>(AFSF), which persists in<br />

the x=0.04,0.06, and 0.08 compounds. A dome-shaped x dependence of Tc is found,<br />

with the highest Tc=27 K at x=0.06, which is realized under significant AFSF. With<br />

increasing x further, AFSF decreases, and so does Tc. These features resemble the<br />

cuprates La 2-xSr xCuO 4, which suggests that AFSF is also important in producing high<br />

Tc superc<strong>on</strong>ductivity in LaFeAsO 1-xF x . In the superc<strong>on</strong>ducting state, we find that 1/T1<br />

decreases exp<strong>on</strong>entially below Tc down to 0.13Tc for x=0.06, which suggests that the<br />

energy gaps are fully opened. Meanwhile, 1/T1 below Tc decreases n<strong>on</strong>exp<strong>on</strong>entially<br />

for x either smaller or larger than 0.06, which is accounted for by impurity scattering.


QB12<br />

Interplay between 3d- and 4f-electr<strong>on</strong>s in ReFe 1-xCo xAsO (Re = Ce,Gd)<br />

T. Shang 1 , L. Yang 1 , Y. Chen 1 , L. Jiao 1 , J. L. Zhang 1 , J. Chen 1 , H. Q. Yuan 1 *, N.<br />

Cornell 2 , A. Howard 2 , A. Zakhidov 2 , M. B. Salamom 2 , F. R<strong>on</strong>ning 3 , E. D. Bauer 3 and J.<br />

D. Thomps<strong>on</strong> 3<br />

1 Department of Physics and Center for Correlated Matter, Zhejiang University, China<br />

2 UTD-NanoTech Institute, The University of Texas at Dallas, USA<br />

3 Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

In order to study the evoluti<strong>on</strong> from a high Tc superc<strong>on</strong>ductor to a str<strong>on</strong>gly correlated system<br />

with largely enhanced effective mass in ir<strong>on</strong> pnictides, we have synthesized a series of ReFe 1xCo<br />

xAsO (x=0-1) polycrystalline samples and characterized their physical properties by<br />

means of electrical resistivity, magnetizati<strong>on</strong> and specific heat. It is shown that, for CeFe 1xCo<br />

xAsO, the SDW transiti<strong>on</strong> of the 3d-electr<strong>on</strong>s is quickly suppressed up<strong>on</strong> substituting Fe<br />

with Co and superc<strong>on</strong>ductivity appears in a narrow doping range of 0.05


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QB18<br />

Spectroscopy and anisotropies in the magnetic state of ir<strong>on</strong> pnictides<br />

Belen Valenzuela, Maria Jose Calder<strong>on</strong>, Gladys Le<strong>on</strong>, Noel A. Garcia and Elena<br />

Basc<strong>on</strong>es*<br />

Theory and Simulati<strong>on</strong>s of Materials, Instituto de Ciencia de Materiales de Madrid,<br />

Spain<br />

QB19<br />

QB20<br />

WITHDRAWN<br />

Magnetic interacti<strong>on</strong>s in ir<strong>on</strong> pnictides<br />

Maria Jose Calder<strong>on</strong>, Gladys Le<strong>on</strong>, Belen Valenzuela and Elena . Basc<strong>on</strong>es*<br />

Theory and Simulati<strong>on</strong>s of Materials, Instituto de Ciencia de Materiales de Madrid,<br />

Spain<br />

WITHDRAWN<br />

Te-doped K 0.80Fe 1.81Se 2-xTe x single crystals<br />

C T Lin*<br />

Crystal Growth, Max Planck Institute for Solid State Research, Germany<br />

We report the growth a serious of Te-substituted K 0.80Fe 1.81Se 2-xTe x (x~0, 0.09, 0.16, 0.34<br />

and 0.55) single crystals using optical floating-z<strong>on</strong>e technique under applicati<strong>on</strong> of 8<br />

bar of arg<strong>on</strong> pressure. Study of XRD indicated that the undoped single crystals c<strong>on</strong>tain<br />

a significant intergrowth of two sets of the c-axis characterized by slightly different<br />

lattice c<strong>on</strong>stants, i.e., the phase separati<strong>on</strong> phenomen<strong>on</strong>. Our results dem<strong>on</strong>strate that<br />

the partial substituti<strong>on</strong> of Se by Te atoms can lead to the expansi<strong>on</strong> of the c-lattice<br />

c<strong>on</strong>stant, whereas the phase separati<strong>on</strong> phenomen<strong>on</strong> is suppressed c<strong>on</strong>tinuously with<br />

the increase of substituti<strong>on</strong> level and vanished at x~0.55. The magnetizati<strong>on</strong> data show<br />

the superc<strong>on</strong>ducting transiti<strong>on</strong> temperature is gradually depressed for Tc ~32, 27, 25,<br />

15, and 0 K with the substituti<strong>on</strong> level x~0, 0.09, 0.16, 0.34 and 0.55, respectively.<br />

76 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QB21<br />

High-pressure res<strong>on</strong>ant x-ray emissi<strong>on</strong> study of Fe 1.01Se<br />

superc<strong>on</strong>ductors<br />

Jin-ming Chen, S. C. Haw, J. M. Lee, S. A. Chen, K. T. Lu, N. Hiraoka, H. Ishii and K.<br />

D. Tsuei<br />

Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Center, Taiwan<br />

The Fe 3d valence states, electr<strong>on</strong> structures and spin states of ir<strong>on</strong>-chalcogenide<br />

Fe 1.01Se superc<strong>on</strong>ductors under pressure up to 45 GPa were probed by res<strong>on</strong>ant<br />

x-ray emissi<strong>on</strong> spectroscopy (RXES) and and x-ray absorpti<strong>on</strong> spectra. The Fe 1s3p-<br />

RXES spectra of Fe 1.01Se at ambient pressure, 6 GPa and 45 GPa were measured to<br />

deduce the variati<strong>on</strong> of Fe 3d valence states. The 1s3p-RXES data obtained at the Fe<br />

K edge clearly reveal that unoccupied Fe 3d states exhibit a relatively delocalized<br />

character, stemming from hybridizati<strong>on</strong> of the Fe 3d states with the Fe 4p orbitals.<br />

The pr<strong>on</strong>ounced pre-edge peak at ~7112.7 eV in Fe K-edge x-ray absorpti<strong>on</strong> spectra<br />

of Fe 1.01Se predominantly originates from the dipole transiti<strong>on</strong> of a Fe 1s electr<strong>on</strong> to<br />

unoccupied Fe 3d-Se 4p hybrid bands. The larger compressi<strong>on</strong> accompanied with a<br />

significant distorti<strong>on</strong> around the Fe atoms al<strong>on</strong>g the c axis in Fe1.01Se up<strong>on</strong> applying<br />

pressure suppresses the Fe 3d-Se 4p and Fe 4p-Se 4d hybridizati<strong>on</strong>. The applied<br />

pressure suppresses the nearest-neighbor ferromagnetic superexchange interacti<strong>on</strong><br />

and enhances spin fluctuati<strong>on</strong>s <strong>on</strong> the Fe sites in Fe 1.01Se. Fe1.01Se shows a small net<br />

magnetic moment of Fe 2+ at ambient pressure.<br />

QB22<br />

Microscopic coexistence and competiti<strong>on</strong> of magnetism and<br />

superc<strong>on</strong>ductivity in Ba 1-xK xFe 2As 2 : A structural, magnetic, and<br />

superc<strong>on</strong>ducting phase diagram<br />

Gwendolyne Pascua 1 , Hubertus Luetkens 1 , Erwin Wiesenmayer 2 , Zurab Shermadini 1 ,<br />

Rustem Khasanov 1 , Alex Amato 1 , Hans-henning Klauss 3 and Dirk Johrendt 2<br />

1 Laboratory for Mu<strong>on</strong> Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland<br />

2 Department Chemie,, Ludwig-Maximilians-Universitaet Muenchen, D-81377 Muenchen,, Germany<br />

3 Institut fuer Festkoerperphysik,, TU Dresden, DE-01069 Dresden, Germany<br />

It is widely believed that in c<strong>on</strong>trast to its electr<strong>on</strong>-doped counterparts, the hole-doped<br />

compound Ba 1-xK xFe 2As 2 exhibits a mesoscopic phase separati<strong>on</strong> of magnetism and<br />

superc<strong>on</strong>ductivity in the underdoped regi<strong>on</strong> of the phase diagram. Here, we report a combined<br />

high-resoluti<strong>on</strong> X-ray powder diffracti<strong>on</strong> and volume-sensitive mu<strong>on</strong> spin rotati<strong>on</strong> (μSR)<br />

study of Ba 1-xK xFe 2As 2 showing that this paradigm does not hold true in the underdoped<br />

regi<strong>on</strong> of the phase diagram (0 ≤ x ≤ 0.25). Instead, we find a microscopic coexistence<br />

of the two forms of order. A competiti<strong>on</strong> of magnetism and superc<strong>on</strong>ductivity is evident<br />

from a significant reducti<strong>on</strong> of the magnetic moment and a c<strong>on</strong>comitant decrease of the<br />

magnetoelastically coupled orthorhombic lattice distorti<strong>on</strong> below the superc<strong>on</strong>ducting phase<br />

transiti<strong>on</strong>. The doping dependence of structural, magnetic, and superc<strong>on</strong>ducting properties is<br />

completed in a phase diagram (0≤ x ≤ 1) herein presented and discussed.<br />

[1] E. Wiesenmayer, H. Luetkens et al., Phys. Rev. Lett. 107, 237001 (2011). [2] M. Rotter et al., Nature Physics 5, 141<br />

(2009). [3] A. A. Aczel et al., Phys. Rev. B 78, 214503 (2008). [4] T. Goko et al., Phys. Rev. B 80, 024508 (2009).<br />

QB23<br />

Anomalous superc<strong>on</strong>ducting phase in LaFeAsO 1-xH x studied via 75As<br />

NMR<br />

N. Fujiwara 1 *, S. Tsutsumi 1 , S. Iimura 2 , S. Matsuishi 2 and H. Hos<strong>on</strong>o 2<br />

1 Gradutate School of Human & Envir<strong>on</strong>mental Studies, Kyoto University, Japan<br />

2 Fr<strong>on</strong>tier Research Center (FRC), Tokyo Institute of Technology, Japan<br />

LaFeAsO 1-xF x ( La1111 series ) is a prototype of high-Tc pnictides and has been<br />

investigated extensively by means of various experimental techniques. The<br />

electr<strong>on</strong>ic phase diagram is unique compared to other high-Tc pinctides in that the<br />

antiferromagnetic ( AF ) phase hardly overlaps the superc<strong>on</strong>ducting ( SC ) phase,<br />

and the optimal doping level is located away from the AF phase boundary. The latter<br />

feature is comm<strong>on</strong> to the R1111 series ( R = Ce, Nd, etc. ). Recently, an exotic phase<br />

diagram has been obtained in LaFeAsO 1-xH x in which a high Tc is maintained even<br />

in an overdoping regime, and the sec<strong>on</strong>d SC dome emerges up<strong>on</strong> excess H doping.<br />

To investigate the exotic electr<strong>on</strong>ic state <strong>on</strong> a microscopic level, we performed 75As<br />

NMR measurements for 20% and 40% doped samples. The former doping level<br />

corresp<strong>on</strong>ds to the boundary between two SC domes, and the latter corresp<strong>on</strong>ds to the<br />

optimal doping level of the sec<strong>on</strong>d dome. The relaxati<strong>on</strong> rates for 20% doped samples<br />

are comparable with those of LaFeAsO 1-xF x (x = 14%) , however rates for 40% doped<br />

samples enhanced at a fixed temperature implying that some spin fluctuati<strong>on</strong>s return<br />

and some magnetic ordering would occur up<strong>on</strong> excess H doping.


QB24<br />

Multi-frequency ESR in EuFe2As2 Masami Ikeda 1 , Tatsuya Kobayashi 2 , Wataru Hirata 2 , Shigeki Miyasaka 2 , Setsuko<br />

Tajima 2 and Masayuki Hagiwara 1<br />

1<br />

KYOKUGEN, Osaka University, 1-3 Machikaneyama, Toy<strong>on</strong>aka, Osaka 560-8531,<br />

Japan<br />

2<br />

Dep. of Phys., Faculty of Science, Osaka University, 1-1 Machikaneyama, Toy<strong>on</strong>aka,<br />

Osaka 560-0043, Japan<br />

One kind of the ir<strong>on</strong> based superc<strong>on</strong>ductors is called ‘122’ system. Most parent<br />

materials of the ‘122’ system exhibit a spin-density wave (SDW) transiti<strong>on</strong> that<br />

is accompanied by a structural phase transiti<strong>on</strong> [1]. EuFe 2As 2 shows the SDW<br />

transiti<strong>on</strong> at TSDW=190 K, and the large local moment Eu 2+ (S =7/2, L =0) orders<br />

antiferomagnetically below TN=19 K. Above TSDW, it is believed that Eu 2+ localized<br />

magnetic moments interact with itinerant electr<strong>on</strong>s. Below TSDW, the interlayer<br />

interacti<strong>on</strong> turns to be weak and the system becomes anisotropic [2]. To study the<br />

above natures of EuFe 2As 2 in more details, we have performed multi-frequency (20-<br />

35 GHz) electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) measurements. Above TN, the res<strong>on</strong>ance<br />

signal can be fitted with the Dys<strong>on</strong>ian functi<strong>on</strong>, and the temperature dependence of the<br />

linewidth obtained by this fitting obeys the Korringa relati<strong>on</strong> above TSDW as observed<br />

at X-band ESR [2]. From this relati<strong>on</strong>, we will discuss the exchange interacti<strong>on</strong><br />

between Eu 2+ moments and c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong> spins.<br />

[1]Y. Xiao et al., Phys. Rev. B 80 (2009) 174424. [2]E. Dengler et al., Phys. Rev. B 81 (2010)<br />

024406.<br />

QB25<br />

Analysis of the critical current density and flux pinning properties in<br />

ir<strong>on</strong>-based Ba 0.55K 0.45Fe 2As 2 high T c superc<strong>on</strong>ductor<br />

Dawood Ahmad 1 , I S Park 1 , G C Kim 1 , Rock Kil Ko 1,2 , J H Lee 1 , and Y C Kim 1<br />

1 Department of Physics, Pusan Nati<strong>on</strong>al University, Korea<br />

2 Korea Electrotechnology Research Institute, Changw<strong>on</strong> 641-120, Korea<br />

The critical current density and flux pinning properties of the Ba 0.55K 0.45Fe 2As 2 high<br />

Tc superc<strong>on</strong>ductor with T c = 37K are studied using field and time dependence of<br />

the magnetizati<strong>on</strong>. The temperature dependence of the critical current density J c(T)<br />

have been found to follow the form J c ∝ (1-T/T c ) n and is c<strong>on</strong>sistent with δ T c type<br />

pinning due to the randomly distributed defects larger than the coherence length ξ.<br />

The temperature dependence of the magnetic relaxati<strong>on</strong> rate S exhibits a peak at<br />

much lower temperature which corresp<strong>on</strong>ds to the smaller pinning energy in the<br />

Ba 0.55K 0.45Fe 2As 2 superc<strong>on</strong>ductor. Moreover, the effective pinning potential U o increases<br />

with the increase in temperature this behavior is in agreement with those of high T c<br />

cuprate superc<strong>on</strong>ductors.<br />

QB26<br />

In-plane anisotropy of magnetic and electric properties of the Fe<br />

pnictide Ba(Fe 1-xCo x) 2As 2<br />

Yoshiaki Kobayashi 1 *, Akihiro Ichikawa 1 , Masayuki Itoh 1 and Masatoshi Sato 2<br />

1 Department of Physics, Graduate School of Science, Nagoya University, Japan<br />

2 Research Center For Neutr<strong>on</strong> Science And Technology, CROSS, Japan<br />

The anisotropy of electr<strong>on</strong>ic and magnetic properties within FeAs-planes of Co(2%)doped<br />

BaFe 2As 2 was investigated by 75As-NMR measurements of the As sites As0<br />

with all four nearest neighbor sites occupied by Fe. Interestingly, even in the tetrag<strong>on</strong>al<br />

phase (T >100 K), two sets of NMR spectra with two fold symmetry of in-plane<br />

Knight shifts and electr<strong>on</strong>ic nuclear quadrupole frequencies were observed. They<br />

originate from the existence of two domains with their symmetry axes lying at rightangles<br />

to each other. The anisotropy of the electr<strong>on</strong>ic and magnetic properties become<br />

pr<strong>on</strong>ounced <strong>on</strong> cooling at ~140 K, below which the in-plane anisotropy was reported to<br />

appear for the electrical resistivity under the pressure al<strong>on</strong>g <strong>on</strong>e of Fe-Fe directi<strong>on</strong>s [1].<br />

75As-NMR was also carried out at the As site As1 surrounded by <strong>on</strong>e Co and three Fe.<br />

From the data, we can see that the spin susceptibility at As1 is ~1/3 of the value at As0<br />

and that the antiferromagnetic spin fluctuati<strong>on</strong> at As1 is fairly suppressed as compared<br />

with the value at As0. We discuss these behaviors of the FeAs layer in c<strong>on</strong>necti<strong>on</strong> with<br />

the impurity-induced local orbital ordering suggested by the theoretical studies.<br />

[1] J.-H. Chu, J. G. Analytis, K. D. Greve, P. L. McMah<strong>on</strong>, Z. Islam, Y. Yamamoto and I. R. Fisher<br />

:Science 329 (2010) 824.<br />

QB27<br />

Vortex tunneling spectra of ir<strong>on</strong>-pnictide superc<strong>on</strong>ductors<br />

Yuhei Kikuchi* and Hiroki Tsuchiura<br />

Applied Physics, Tohoku University, Japan<br />

QB28<br />

QB29<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Symmetry and structure of the superc<strong>on</strong>ducting gap functi<strong>on</strong>s in ir<strong>on</strong>-pnictides have<br />

been still under spirited debate. Quasi-particle states around surfaces/interfaces or<br />

impurities have played a crucial role for identifying the gap functi<strong>on</strong>s in several<br />

unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors such as cuprates or Sr 2RuO 4. However, the gap<br />

symmetry of ir<strong>on</strong>-pnictide is believed to be s-wave, and the point at issue is to identify<br />

whether the gap structure has inter-band sign reversal (s+-) or not (s++). Thus, it<br />

will be difficult to distinguish these gap structures based <strong>on</strong> surfaces/interfaces<br />

informati<strong>on</strong>. There exist several studies <strong>on</strong> impurity-induced states in ir<strong>on</strong>-pnictides.<br />

However, because of the complex band-structures of such systems, theoreticalmodeling<br />

of impurities in ir<strong>on</strong>-pnictide is not free of ambiguity. Vortex core states can<br />

be another “probe” to identify the gap symmetries and structures in unc<strong>on</strong>venti<strong>on</strong>al<br />

superc<strong>on</strong>ductors. Since a vortex core is not a chemical substance, there are no<br />

ambiguities in theoretical modeling. Thus, in this work, we theoretically study the<br />

quasi-particle states induced around a vortex core in ir<strong>on</strong>-pnictides using two- or five-<br />

band effective two-dimensi<strong>on</strong>al lattice models [1][2] within the Bogoliubov-de Gennes<br />

theory. We will also examine the impurity-induced quasi-particle states, and discuss the<br />

relati<strong>on</strong> between present results and recent STM/S experimental results.<br />

[1]T. Kariyado and M. Ogata, J. Phys. Soc. Jpn. 79, 083704 (2010). [2]S. Raghu et al., Phys. Rev. B<br />

77, 220503 (2010).<br />

Direct observati<strong>on</strong> of superc<strong>on</strong>ducting gaps and their anisotropies in<br />

Ba 1-xK xFe 2As 2<br />

Y. Ota 1 *, K. Okazaki 2 , Y. Kotani 2 , T. Shimojima 3 , T. Kiss 4 , C. - T. Chen 5 , S. Watanabe 6 , K. Kihou 7 , C. H. Lee 7 , A.<br />

Iyo 7 , H. Eisaki 7 , T. Saito 8 , H. Fukazawa 9 , Y Kohori9 and S. Shin 10<br />

1 ISSP, Japan<br />

2 ISSP, JST-CREST, Japan<br />

3 Univ. of Tokyo, Japan<br />

4 Osaka Univ., Japan<br />

5 CAS, China<br />

6 Tokyo Univ. of Sci., Japan<br />

7 AIST, JST-TRIP, Japan<br />

8 Chiba Univ., Japan<br />

9 JST-TRIP, Chiba Univ., Japan<br />

10 ISSP, JST-CREST, JST-TRIP, RIKEN, Japan<br />

Am<strong>on</strong>g the ir<strong>on</strong>-pnictides, (Ba,K)Fe 2As 2 (BaK122) system is the most interesting: while the<br />

optimally-doped BaK122 has a full gap (no node in the superc<strong>on</strong>ducting(SC) gap), the extremely<br />

hole-doped KFe 2As 2 (K122), which has no electr<strong>on</strong> pocket, has been suggested to have SCgap<br />

nodes from several experiments. From the previous studies of laser-excited angle-resolved<br />

photoemissi<strong>on</strong> spectroscopy (laser ARPES), the optimally doped BaK122 has no anisotropy and<br />

Fermi surface (FS) sheet dependence in SC-gap sizes <strong>on</strong> the three hole FS around the Brillouin<br />

z<strong>on</strong>e center. On the other hand, we found that K122 has clear anisotropies and sheet dependence.<br />

In additi<strong>on</strong>, we found that the middle hole FS has eight nodes and identified their Fermi momenta.<br />

It should be important to investigate doping dependence of anisotropies and FS-sheet dependence<br />

of SC-gap sizes, and node existence to clarify the paring mechanism at each doping level. We have<br />

directly observed superc<strong>on</strong>ducting gaps and their anisotropies in the overdoped BaK122 utilizing<br />

laser ARPES. We will discuss these results and c<strong>on</strong>trast them with other experimental and theoretical<br />

results available in literature.<br />

C<strong>on</strong>trasting superc<strong>on</strong>ducting property in Fe-based superc<strong>on</strong>ductors<br />

(Ca4Al2O6-y)(Fe2Pn2)[Pn=As and P]<br />

Hiroaki Kinouchi 1 , Hidekazu Mukuda 1 , Mitsuharu Yashima 1 , Yoshio Kitaoka 1 , Chulho<br />

Lee 2 , Parasharam M. Shirage 2 , Hiroshi Eisaki 2 and Akira Iyo 2<br />

1<br />

Department of Materials Engineering Science, Graduate School of Engineering<br />

Science, Osaka University, Japan<br />

2<br />

Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Japan<br />

We report As-nuclear quadrupole res<strong>on</strong>ance (NQR) study <strong>on</strong> (Ca 4Al 2O 6-y)(Fe 2As 2) with<br />

Tc=27K, and P-nuclear magnetic res<strong>on</strong>ance (NMR) study <strong>on</strong> (Ca 4Al 2O 6-y)(Fe 2As 2) with<br />

Tc=17K. (Ca 4Al 2O 6-y)(Fe 2As 2) possesses the characteristic structural parameters such as short<br />

a-axis length, high pnictgen height, narrow As-Fe-As angle, and thick perovskite-type blocking<br />

layer. A measurement of the nuclear spin relaxati<strong>on</strong> rate 1/T1 revealed a significant evoluti<strong>on</strong> of<br />

antiferromagnetic (AFM) spin fluctuati<strong>on</strong>s in normal state, which originates from the possible<br />

well nested hole and electr<strong>on</strong> Fermi surfaces. Below Tc, the 1/T1 decreases steeply up<strong>on</strong> cooling<br />

without any trace of Hebel-Slichter peak, which is c<strong>on</strong>sistently accounted for within the framework<br />

of nodeless s(+-)-wave multiple gap model. On the other hands, (Ca 4Al 2O 6-y)(Fe 2As 2) is<br />

characterized by lower pnictgen height and wider As-Fe-As angle than that of (Ca 4Al 2O 6-y)(Fe 2As 2),<br />

where FeP_4 forms nearly regular tetrahedr<strong>on</strong>. The P-NMR- 1/T1 measurement revealed the<br />

presence of AFM spin fluctuati<strong>on</strong>s in normal state and gapless SC state. These facts indicate the<br />

close relati<strong>on</strong>ship between the local structural characters of FePn_4 and the SC properties.<br />

H. Kinouchi, H. Mukuda, M. Yashima, Y. Kitaoka, P. M. Shirage, C-H. Lee, H. Eisaki, and A. Iyo<br />

July 8 - 13, 2012 Busan, Korea 77<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QB30<br />

Superc<strong>on</strong>ducting properties of FeTe 1-xSe x single crystals: impact of<br />

disorder and hydrostatic pressure<br />

Roman Puzniak*, Dariusz J. Gawryluk, Marek Berkowski, Piotr Dluzewski, Jaroslaw<br />

Pietosa, Aleksander Wittlin and Andrzej Wisniewski<br />

Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668<br />

Warsaw, Poland<br />

It was found that chemical and structural disorder in superc<strong>on</strong>ducting single crystals<br />

of Fe(Te,Se), originating from kinetics of crystal growth process, str<strong>on</strong>gly influences<br />

superc<strong>on</strong>ducting properties. The sharpness of a transiti<strong>on</strong> to the superc<strong>on</strong>ducting state is<br />

evidently inversely correlated with crystallographic quality. I<strong>on</strong>s inhomogeneous spatial<br />

distributi<strong>on</strong> seems to enhance the superc<strong>on</strong>ductivity and inhomogeneous distributi<strong>on</strong> of<br />

host atoms might be an intrinsic feature of superc<strong>on</strong>ducting chalcogenides. Small disorder<br />

introduced into magnetic sublattice, by partial replacement of Fe i<strong>on</strong>s by slight amount<br />

of n<strong>on</strong>magnetic i<strong>on</strong>s of Cu or by magnetic i<strong>on</strong>s of Ni and Co with spin value different<br />

than that of Fe i<strong>on</strong>, completely suppresses superc<strong>on</strong>ductivity. Even if superc<strong>on</strong>ductivity is<br />

observed in the system c<strong>on</strong>taining magnetic i<strong>on</strong>s it can not survive when the disorder in<br />

magnetic i<strong>on</strong>s sublattice is introduced. We have found pressure-induced enhancement of<br />

all of the superc<strong>on</strong>ducting state properties of FeTe 0.5Se 0.5 single crystals, which entails a<br />

growth of the density of superc<strong>on</strong>ducting carriers. We noticed more pr<strong>on</strong>ounced increase<br />

in superc<strong>on</strong>ducting carrier density under pressure than that in the critical temperature what<br />

may indicate an appearance of a mechanism limiting the increase of Tc with pressure. The<br />

critical current density increases under pressure by at least <strong>on</strong>e order of magnitude.<br />

QB31<br />

The influence of superc<strong>on</strong>ductivity with magnetism in superc<strong>on</strong>ductor/<br />

magnetic heterostructures<br />

Jeeho<strong>on</strong> Kim*, R. Baumbach, N. Haberkorn, J. Lee, L. Civale, Q. Jia, A. J. Taylor, E.<br />

Bauer, J. D. Thomps<strong>on</strong> and R. Movshovich<br />

Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

Interplay between superc<strong>on</strong>ductivity and magnetism c<strong>on</strong>tinues to be <strong>on</strong>e of the<br />

central themes in C<strong>on</strong>densed Matter Physics. We have investigated a variety of<br />

superc<strong>on</strong>ductor/ferromagnetic heterostructures, such as YBCO/LSMO, Nb/GCMO,<br />

and Nb/CeRu 2Al 2B using low temperature magnetic force microscopy, addressing<br />

mainly magnetic pinning and domain wall superc<strong>on</strong>ductivity. In YBCO/LSMO, we<br />

focused <strong>on</strong> the critical state and observed effects of magnetism <strong>on</strong> superc<strong>on</strong>ductivity.<br />

In Nb/GCMO, we found that magnetic domains provide weak pinning centers, and<br />

act as magnetic templates. A recently discovered CeRu 2Al 2B system shows a variety<br />

of magnetic phases such as antiferromagnetic, ferromagnetic, and ferrimagnetic<br />

domains in the field/ temperature plane. We will discuss how we can manipulate<br />

superc<strong>on</strong>ducting domains in superc<strong>on</strong>ducting film (Nb) via these magnetic phases in<br />

close proximity.<br />

QC01<br />

The influence of the magnetic moment <strong>on</strong> the atomic distance in<br />

amorphous CexRu 100-x<br />

Yingjie Li 1 , Nakai Ikuo 2 *, Amakai Yusuke 3 and Shigeyuki Murayama 3<br />

1 1Inner M<strong>on</strong>golia Key Laboratory for Physics and Chemistry of Functi<strong>on</strong>al<br />

Materials, Physics and Electr<strong>on</strong>ic Informati<strong>on</strong> College, Inner M<strong>on</strong>golia Normal<br />

University, Hohhot 010022, China<br />

2 Department of Electrical and Electr<strong>on</strong>ic Engineering, Graduate School of<br />

Engineering, Tottori University,Tottori 680-8552, Japan<br />

3 Department of Materials Science and Engineering, Muroran Institute of Technology,<br />

Hokkaido 050-8585, Japan<br />

The extended x-ray absorpti<strong>on</strong> fine structure (EXAFS) measurement was performed<br />

in amorphous alloys CexRu 100-x (x=9, 43 and 80). We found that the Ce-Ce interatomic<br />

distance increases with increasing the Ce c<strong>on</strong>tent while those of Ce-Ru and Ru-Ru<br />

pairs are unchanged and that the Ce-Ce interatomic distance is exactly proporti<strong>on</strong>al<br />

to the Ce effective magnetic moment. We discuss the relati<strong>on</strong> between the Ce-Ce<br />

atomic distance and the effective magnetic moment 1) from the point of view of the<br />

magnetovolume effect.<br />

1) Y. Amakai et al., J. Phys. : C<strong>on</strong>f. Ser. 150 (2009) 042004.<br />

78 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QC02<br />

Theoretical studies of the superc<strong>on</strong>ductivity and antiferromagnetism<br />

coexistence and the divergence of effective electr<strong>on</strong> mass near quantum<br />

critical point in CeRhIn 5<br />

Valery V. Val'kov and Ant<strong>on</strong> O. Zlotnikov<br />

Laboratory of Theoretical Physics, L.V. Kirensky Institute of Physics, Russia<br />

Competiti<strong>on</strong> and coexistence of superc<strong>on</strong>ductivity and antiferromagnetism have been studied in the framework<br />

of the periodic Anders<strong>on</strong> model taking into account the superexchange interacti<strong>on</strong> between localized 4f<br />

electr<strong>on</strong>s. It has been shown that pressure-induced energy change of the localized states leads to modifying<br />

antiferromagnetic and superc<strong>on</strong>ducting order parameters. This modificati<strong>on</strong> of the order parameters develops<br />

in such way that a str<strong>on</strong>g competiti<strong>on</strong> is suggested between antiferromagnetism and superc<strong>on</strong>ductivity. It has<br />

been proposed that the energy increase is caused by pressure growth. In spite of the competiti<strong>on</strong> menti<strong>on</strong>ed<br />

above, c<strong>on</strong>diti<strong>on</strong>s have been found for the coexistence of superc<strong>on</strong>ductivity and antiferromagnetism in the<br />

model. Theoretical results of the pressure effects <strong>on</strong> the ground state character of the heavy-fermi<strong>on</strong> systems<br />

are in good agreement with specific heat data for CeRhIn 5 [1, 2]. In the coexistence phase there occur two<br />

types of Cooper pairing due to the antiferromagnetic exchange field. The divergence of the effective electr<strong>on</strong><br />

mass produced by suppressing antiferromagnetic order has also been analyzed in the same framework. Further<br />

it has been shown that at quantum critical point there occurs the transiti<strong>on</strong> from small to large Fermi surface.<br />

Such features have been found in the de Haas-van Alphen experiments for CeRhIn 5 [3].<br />

1. H. Hegger, C. Petrovich, E.G. Moshopoulou, M.F. Hundley, J.L. Sarrao, Z. Fisk, J.D. Thomps<strong>on</strong>,<br />

Phys. Rev. Lett. 84, 4986 (2000). 2. T. Park, J.D. Thomps<strong>on</strong>, New Journal of Physics 11, 055062<br />

(2009). 3. H. Shishido, R. Settai, H. Harima, Y. Onuki, J. Phys. Soc. Jap. 74, 1103 (2005).<br />

QC03<br />

Josephs<strong>on</strong> effect between UPt 3 and Nb under pressure<br />

Akihiko Sumiyama 1 *, Jun Gouchi 1 , Gaku Motoyama 1 , Akira Yamaguchi 1 , Noriaki<br />

Kimura 2 , Etsuji Yamamoto 3 , Yoshinori Haga 3 and Yoshichika Onuki 4<br />

1 Univ. of Hyogo, Japan<br />

2 Tohoku Univ., Japan<br />

3 JAEA, Japan<br />

4 Osaka Univ., Japan<br />

The heavy-fermi<strong>on</strong> compound UPt 3 is an odd-parity superc<strong>on</strong>ductor and possesses a complex<br />

field-temperature (H-T) phase diagram with three phases: A (low H and high T), B (low H and<br />

low T) and C (high H and high T) phases. We have investigated the Josephs<strong>on</strong> effect between UPt 3<br />

and Nb and observed an anisotropic temperature dependence of Josephs<strong>on</strong> critical current Ic at<br />

the transiti<strong>on</strong> from A to B phases[1]. However, the Josephs<strong>on</strong> effect, which is easily destroyed by<br />

a small magnetic field, has not been measured in C phase. C<strong>on</strong>sidering that C phase appears even<br />

in zero field by applying pressure[2], we have investigated the pressure dependence of Josephs<strong>on</strong><br />

effect together with resistance and Meissner effect of UPt 3. The superc<strong>on</strong>ducting transiti<strong>on</strong> occurs<br />

at lower temperature and becomes broader by applying pressure. As the pressure is increased, the<br />

Josephs<strong>on</strong> effect appears at lower temperature than the zero-resistivity temperature of UPt 3, while<br />

Ic increases more rapidly; the increasing rate -dIc/dT is a linear functi<strong>on</strong> of pressure. Although<br />

the Josephs<strong>on</strong> effect in C phase has been observed for the first time, an abrupt change in the<br />

temperature dependence of Ic caused by the transiti<strong>on</strong> to C phase has not been found yet.<br />

[1] A. Sumiyama et al.: Phys. Rev. Lett. 81 (1998) 5213; A. Sumiyama et al.: Jpn. J. Appl. Phys.<br />

Series 11 (1999) 47. [2] M. Boukhny et al. : Phys. Rev. Lett. 73 (1994) 1707.<br />

QC04<br />

Hidden order in URu 2Si 2 --- Analysis based <strong>on</strong> the first-principles<br />

approach<br />

Hiroaki Ikeda 1 *, Michi-to Suzuki 2 , Ryotaro Arita 3 , Tetsuya Takimoto 4 , Takasada<br />

Shibauchi1 and Yuji Matsuda 1<br />

1 Department of Physics, Kyoto university, Japan<br />

2 CCSE, Japan Atomic Energy Agency, Japan<br />

3 Department of Appliced Physics, University of Tokyo, Japan<br />

4 Asia Pacific Center for Theoretical Physics, POSTECH, Korea<br />

The so-called 'hidden-order' phase transiti<strong>on</strong> at $T_{HO}=17.5$K in the heavy-electr<strong>on</strong> metal<br />

URu 2Si 2, specified by a clear jump in the specific heat measurement, is a l<strong>on</strong>g-standing mystery<br />

in the c<strong>on</strong>densed-matter physics since the discovery in 1985. In spite of every effort, it remains<br />

still dark what kind of symmetry is broken below $T_{HO}$. So far, there are no evidence<br />

for magnetic/structural and any low-rank multipole orders. Recent advanced angle-resolved<br />

photo-emissi<strong>on</strong> spectroscopy indicates that $5f$ electr<strong>on</strong>s appears to be itinerant rather than<br />

localized. Thus, the detailed analysis of the complicated band structures including the spinorbit<br />

coupling has been str<strong>on</strong>gly desired. We show here the first report of the complete set of<br />

itinerant multipole correlati<strong>on</strong>s up to the fifth rank within the random-phase approximati<strong>on</strong> and<br />

bey<strong>on</strong>d. The itinerant Hamilt<strong>on</strong>ian is obtained by the advanced Wannier method from the firstprinciples<br />

calculati<strong>on</strong>s. From the most divergent correlati<strong>on</strong>s, we obtain nearly degenerate two<br />

staggered-ordered states of rank-1 dipole with $A_2^-$ and rank-5 dotriac<strong>on</strong>tapole with $E^-<br />

$; the former corresp<strong>on</strong>ds to the antiferromagnetic state realized under high pressures, and the<br />

latter the hidden-order state. This novel high-rank electr<strong>on</strong>ic state provides natural explanati<strong>on</strong>s<br />

of the key features for the hidden order including sp<strong>on</strong>taneous fourfold symmetry breaking.


QC05<br />

Sb NQR study of filled skutterudite CeFe 4Sb 12 synthesized under high<br />

pressure<br />

Ko-ichi Magishi 1 *, Hitoshi Sugawara 2 , Masahiro Takahashi 1 , Takahito Saito 1 ,<br />

Kuniyuki Koyama 1 , Takashi Saito 3 , Sho Tatsuoka 3 , Kenya Tanaka 3 and Hideyuki Sato 3<br />

1 Institute for Socio-Arts and Sciences, The University of Tokushima, Japan<br />

2 Graduate School of Science, Kobe University, Japan<br />

3 Graduate School of Science, Tokyo Metropolitan University, Japan<br />

Am<strong>on</strong>g filled skutterudites, the influence of the filling fracti<strong>on</strong> of R i<strong>on</strong> <strong>on</strong> the<br />

physical properties has been argued, especially in Sb-based filled skutterudites with<br />

a large pnictogen cage. On RFe 4Sb 12 system, the drastic effect of the R-site vacancy<br />

<strong>on</strong> the basic properties has been pointed out. Recently, it has been reported that<br />

CeFe 4Sb 12synthesized under high pressure (HP) in order to increase the Ce-site filling<br />

fracti<strong>on</strong> shows the semic<strong>on</strong>ducting transport property at low temperatures, in c<strong>on</strong>trast<br />

that the sample synthesized under ambient pressure (AP) shows the metallic behavior.<br />

At the presentati<strong>on</strong>, we report <strong>on</strong> the result of the Sb NQR measurements for the HP<br />

sample of CeFe 4Sb 12, and compare with that for the AP sample in order to understand<br />

the influence of the Ce-site filling fracti<strong>on</strong>. In the high temperature range, the nuclear<br />

spin-lattice relaxati<strong>on</strong> rate for the HP sample decreases <strong>on</strong> cooling, and follows the<br />

exp<strong>on</strong>ential decrease above 100 K with the energy gap of 270 K. The value of the<br />

gap for the HP sample is larger than that for the AP sample, which suggests that the<br />

hybridizati<strong>on</strong> is enhanced by increasing the Ce-site filling fracti<strong>on</strong>. More detailed<br />

results and analyses will be presented at the c<strong>on</strong>ference.<br />

QC06<br />

High-mobility magnetotransport of the narrow-gap semic<strong>on</strong>ductor<br />

FeSb 2<br />

Hidefumi Takahashi*, Ryuji Okazaki, Yukio Yasui and Ichiro Terasaki<br />

Department of Physics, Nagoya University, Japan<br />

Recently, a huge Seebeck coefficient S (-45 mV/K at 10 K) was reported for singlecrystalline<br />

FeSb 2 samples. Such a huge value seems bey<strong>on</strong>d c<strong>on</strong>venti<strong>on</strong>al semic<strong>on</strong>ductor<br />

physics, indicating a novel mechanism to enhance the Seebeck coefficient such as a str<strong>on</strong>g<br />

electr<strong>on</strong> correlati<strong>on</strong> expected in so-called 'K<strong>on</strong>do insulators'. We study the magnetotransport<br />

properties of FeSb 2 single crystals to investigate its electr<strong>on</strong>ic state at low temperatures[1].<br />

The c<strong>on</strong>ductivity tensor is well analyzed using a two-carrier model, leading to proper<br />

evaluati<strong>on</strong> of the mobility and carrier c<strong>on</strong>centrati<strong>on</strong>. The mobility significantly increases<br />

with decreasing temperature and reaches 28000 cm2/Vs at 4 K. The carrier c<strong>on</strong>centrati<strong>on</strong><br />

decreases from 1 down to 10-4 ppm/unit cell with decreasing temperature from 30 down<br />

to 4 K, which is well described by thermal activati<strong>on</strong> with a small gap of 6 meV. We also<br />

find that the magnetoresistive behavior dramatically changes from positive to negative<br />

at lower temperatures. The negative magnetoresistance is generally observed in doped<br />

semic<strong>on</strong>ductors and derives from a weak localizati<strong>on</strong> of carriers, indicating a c<strong>on</strong>siderable<br />

impurity level in the electr<strong>on</strong>ic structure. Our magnetotransport measurements, as well as<br />

the impurity-effect study[2], str<strong>on</strong>gly suggest that the low-temperature transport is well<br />

understood within an extrinsic semic<strong>on</strong>ductor picture with ppm-level impurity.<br />

[1] H. Takahashi et al. Phys. Rev. B 84, 205215 (2011). [2] H. Takahashi et al. J. Phys. Soc. Jpn. 80,<br />

054708 (2011).<br />

QC07<br />

A possible ferromagnetic quantum critical point in CeFe 1-x Ru xPO<br />

Tetsuro Nakmura 1 , Takashi Yamamoto 2 , Masanori Matoba 1 , Yasuaki Einaga 2 and<br />

Yoichi Kamihara 1<br />

1 Department of Applied Physics and Physico-Informatics, Keio University., Japan<br />

2 Department of Chemistry, Keio University., Japan<br />

Many materials have their own magnetic transiti<strong>on</strong> temperature, and it is c<strong>on</strong>trollable by the applicati<strong>on</strong><br />

of a pressure, field or through chemical substituti<strong>on</strong>. In particular, phase transiti<strong>on</strong>s which take place at<br />

absolute zero are called quantum phase transiti<strong>on</strong>s, and the transiti<strong>on</strong> point is called a quantum critical<br />

point. Quantum critical points have attracted much attenti<strong>on</strong> since some materials exhibit superc<strong>on</strong>ductivity<br />

in proximity to a magnetic quantum critical point. [1] Both CeFePO and CeRuPO are heavy-fermi<strong>on</strong><br />

materials c<strong>on</strong>taining Ce 4f-electr<strong>on</strong>’s sublattice inducing K<strong>on</strong>do effects. Although CeFePO exhibits no<br />

magnetic transiti<strong>on</strong> down to 0.4 K, CeRuPO is <strong>on</strong>e of rare examples of a ferromagnetic K<strong>on</strong>do lattice,<br />

whose transiti<strong>on</strong> temperature is 15 K [2]-[5]. In this study, we synthesized CeFe 1-xRu xPO by a solid<br />

reacti<strong>on</strong> to quantify a chemical compositi<strong>on</strong> which is a boundary between ferromagnetic phase and<br />

paramagnetic phase indicating the quantum critical point. Electrical resistivity and magnetic susceptibility<br />

are measured at temperatures from 4 K to 300 K. Furthermore, 57Fe Mossbauer spectroscopy was applied<br />

to CeFe 1-xRu xPO to c<strong>on</strong>firm the ordering of the magnetic sublattice. Our results tentatively indicate that<br />

CeFe 1-xRu xPO is heavy-fermi<strong>on</strong> metal, and the magnetic quantum critical point exists at x~0.15.<br />

1) A. J. Millis: Phys. Rev. B 48 7183 (1993). 2) E. M. Bruning, C. Krellner, M. Baenitz, A. Jesche, F. Steglich,<br />

and C. Geibel: Phys. Rev. Lett. 101 117206 (2008). 3) S. Kitagawa, H. Ikeda, Y. Nakai, T. Hattori, K. Ishida, Y.<br />

Kamihara, M. Hirano, and H. Hos<strong>on</strong>o: Phys. Rev. Lett. 107 277002 (2011). 4) Y. Kamihara, H. Hiramatsu, M.<br />

Hirano, H. Yanagi, T. Kamiya and H. Hos<strong>on</strong>o: J. Phys. Chem. Solids. 69 2916 (2008). 5) C. Krellner, N. S. Kini, E.<br />

M. Bruning, K. Koch, H, Rosner, M. Nicklas, M.Baenitz, and C.Geibel: Phys. Rev. B 76 104418 (2007).<br />

QC08<br />

QC09<br />

QC10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ru doping evoluti<strong>on</strong> of magnetic properties in Ce(Fe 1-xRu x)PO studied<br />

by 31P-NMR<br />

Shunsaku Kitagawa 1 *, Yusuke Nakai 2 , Kenji Ishida 1 , Hiroaki Ikeda 3 , Kensuke Iritani 4 ,<br />

Masanori Matoba 4 , Youichi Kamihara 4 , Masahiro Hirano 5 and Hideo Hos<strong>on</strong>o 6<br />

1 Department of Physics, Kyoto University JST-TRIP, Japan<br />

2 Department of Physics, Kyoto University JST-TRIP *present address Graduate School of Science,<br />

Tokyo Metropolitan Univers, Japan<br />

3 Department of Physics, Kyoto University, Japan<br />

4 Departments of Applied Physics and Physico-Informatics, Keio University, Japan<br />

5 Fr<strong>on</strong>tier Research Center, Tokyo Institute of Technology, Japan<br />

6 Fr<strong>on</strong>tier Research Center, Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

CeFePO and CeRuPO have the same layered crystal structure as ir<strong>on</strong> pnictide superc<strong>on</strong>ductors RFeAs(O 1-xF x) (R:<br />

rare earth). CeFePO is a paramagnetic down to 80 mK and possesses a large Sommerfeld coefficient gamma ~<br />

700 mJ/mol K2 at low temperatures, indicating that CeFePO is a heavy fermi<strong>on</strong> compounds originated from Ce<br />

4f electr<strong>on</strong>s[1]. On the other hand, CeRuPO is a ferromagnetic K<strong>on</strong>do lattice system with TCurie = 15 K and<br />

coherent temperature TK ~ 10 K[2]. We have performed 31P-NMR <strong>on</strong> Ce(Fe 1-xRu x)PO system to investigate<br />

the evoluti<strong>on</strong> of magnetic properties at low temperatures. Knight shift and spin-lattice relaxati<strong>on</strong> rate 1/T1<br />

shows extremely large anisotropy. In CeFePO, we found a metamagnetic transiti<strong>on</strong> at around mu0H = 4 T and<br />

below 5 K characterized by the sudden increase in Knight shift when fields are applied perpendicular to the c<br />

axis[3]. As far as we know, this is the first example of the metamagnetic behavior in a heavy fermi<strong>on</strong> observed<br />

with XY spin anisotropy. Moreover, Ce(Fe 0.75Ru 0.25)PO shows ferromagnetic ordering at ~ 3 K with str<strong>on</strong>g two<br />

dimensi<strong>on</strong>al ferromagnetic fluctuati<strong>on</strong>s. We will show the phase diagram in Ce(Fe 1-xRu x)PO and discuss how<br />

two dimensi<strong>on</strong>al ferromagnetic fluctuati<strong>on</strong>s are changed with the Ru doping.<br />

[1] E. M. Bruning et al., Phys. Rev. Lett. 101, 117206 (2008). [2] C. Krellner et al. J. Cryst. Growth<br />

310, 1875 (2008). [3]S.Kitagawa et al., Phys. Rev. Lett. 107, 277002 (2011).<br />

Determining the orientati<strong>on</strong> of the 4f ground state orbital in CeCu2Si2 with vector q dependent n<strong>on</strong>-res<strong>on</strong>ant inelastic X-ray scattering (NRIXS).<br />

Thomas Willers 1 *, Fabio Strigari 1 , Y<strong>on</strong>g Cai 2 , Nozomu Hiraoka 3 , Ku-ding Tsuei 3 , Yen-fa Liao 3 , Maurits Wim<br />

Haverkort 4 , Silvia Seiro 5 , Christoph Geibel 5 , Frank Steglich 5 , Liu Hao Tjeng 5 and Andrea Severing 1<br />

1<br />

Institute of Physics II, University of Cologne, Germany<br />

2<br />

Brookhaven Nati<strong>on</strong>al Laboratory, USA<br />

3<br />

Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Center, Hsinchu, Taiwan<br />

4<br />

Max Planck Institute for Solid State Research, Stuttgart, Germany<br />

5<br />

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany<br />

WITHDRAWN<br />

Possible superc<strong>on</strong>ducting fluctuati<strong>on</strong> in pressure-induced heavyfermi<strong>on</strong><br />

superc<strong>on</strong>ductor CeRhSi 3<br />

Noriaki Kimura*, Tetsuya Sugawara, Hiroki Iida and Haruyoshi Aoki<br />

Department of Physics, Tohoku University, Japan<br />

CeRhSi 3 is a heavy fermi<strong>on</strong> antiferromagnet whose transiti<strong>on</strong> temperature is 1.6K.<br />

The itinerant f electr<strong>on</strong> is thought to be resp<strong>on</strong>sible for the magnetism in this material.<br />

Applicati<strong>on</strong> of pressure suppresses the magnetism and simultaneously induces<br />

the superc<strong>on</strong>ductivity. At pressures from 0.2GPa to 2.4GPa, the superc<strong>on</strong>ductivity<br />

coexists with the antiferromagnetism. In this pressure regi<strong>on</strong>, a broad drop of the<br />

electrical resistivity and weak shielding in the ac-susceptibility are observed at the<br />

superc<strong>on</strong>ducting transiti<strong>on</strong> temperature. We argue a possibility of the superc<strong>on</strong>ducting<br />

fluctuati<strong>on</strong> realized in the coexisting regi<strong>on</strong> of the superc<strong>on</strong>ductivity and<br />

antiferromagnetism.<br />

July 8 - 13, 2012 Busan, Korea 79<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QC11<br />

Thermoelectric power in a single-crystalline CeRhSi 3<br />

Hidekazu Tanaka 1 *, Naofumi Aso 2 , Yoshinao Takaesu 1 , Masato Hedo 2 , Takao<br />

Nakama 2 , Hiroki Iida 3 , Noriaki Kimura 3 and Haruyoshi Aoki 3<br />

1 Graduate School of Engineering and Science, University of the Ryukyus, Japan<br />

2 Faculty of Science, University of the Ryukyus, Japan<br />

3 Graduate School of Science, Tohoku University, Japan<br />

CeRhSi 3 is a n<strong>on</strong>-centrosymmetric heavy fermi<strong>on</strong> superc<strong>on</strong>ductor.[1] The a- and c-axis<br />

thermoelectric power S_a and S_c of a single-crystalline CeRhSi 3 were measured under<br />

pressure up to around 2.7 GPa in the temperature range from 1.5 K to 300 K. Both S_a<br />

and S_c exhibit a large positive value up to around 60 μV/K, which is characteristic of<br />

heavy-fermi<strong>on</strong> systems. S_a and S_c show a maximum in its temperature dependence<br />

due to the K<strong>on</strong>do effect and its maximum temperature T_Smax gradually moves to<br />

higher temperatures from about 90 K (at ambient pressure) to about 130 K (at 2.7<br />

GPa) by applying the pressure. In both directi<strong>on</strong>s, such behaviors of thermoelectric<br />

power are very similar to those in the CeIrSi 3.[2] In the c<strong>on</strong>ference, we will discuss<br />

the anisotropy of the thermoelectric power in c<strong>on</strong>necti<strong>on</strong> with the superc<strong>on</strong>ductivity in<br />

CeRhSi 3.<br />

[1] N.Kimura et al., Phys. Rev. Lett. 95 (2005) 247004. [2] Y.Takaesu et al., J. Phys. Soc. Jpn. 80<br />

(2011) SA068.<br />

QC12<br />

Valence of CeM2Al10 (M=Ru, Os, and Fe) determined with hard X-ray<br />

photo emissi<strong>on</strong> spectroscopy (HAXPES).<br />

Fabio Strigari 1 , Thomas Willers 1 , Ku Ding Tsuei 2 , Yen Fa Liao 2 , Arata Tanaka 3 , K.<br />

Yutani 3 , Y. Muro 3 , Toshiro Takabatake 3 , Liu Hao Tjeng 4 and Andrea Severing 1 *<br />

1<br />

University of Cologne, Germany<br />

2<br />

Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Center, Taiwan<br />

3<br />

ADSM, Hiroshima University, Japan<br />

4<br />

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany<br />

QC13<br />

WITHDRAWN<br />

Studies <strong>on</strong> novel tetrag<strong>on</strong>al Ce 2RhGa 12 heavy fermi<strong>on</strong> compound.<br />

Ramamoorthi Nagalakshmi 1 *, Sengodan Nallamuthu 1 , Varadharajan Krishnakumar 2 ,<br />

Celine Besnard 3 , Hans Hagemann 4 and Marian Reiffers 5<br />

1 Physics, Nati<strong>on</strong>al Institute of Technology, Tiruchirappalli, India<br />

2 Physics, Periyar University, Salem, India<br />

3 Laboratory of Crystallography, Laboratory of Crystallography, University of Geneva, 24 Quai<br />

Ernest-Ansermet, CH-1211 Geneva 4, Swit, Switzerland<br />

4 Physical Chemistry, University of Geneva, Geneva, Switzerland, Switzerland<br />

5 Physics, Institute of Experimental Physics, Slovak Academy of Sciences, Kosice, Slovakia, Slovak<br />

Single crystals of Ce 2RhGa 12 have been synthesized using Ga flux and their structure was determined by<br />

single-crystal X-ray diffracti<strong>on</strong>. The Ce 2RhGa 12 crystallizes in the tetrag<strong>on</strong>al P4/nbm space group (No.<br />

125), which is isostructural to Ce 2PdGa 12, with Z = 2 and lattice parameters a 6.0405 A and c= 15.706 A.<br />

Data were collected at the Swiss Norwegian Beam Line at the European Synchrotr<strong>on</strong> Facility, Grenoble<br />

France. Also the Laue diffracti<strong>on</strong> was carried out to c<strong>on</strong>firm the single crystal quality possessing<br />

tetrag<strong>on</strong>al symmetry. The tetrag<strong>on</strong>al structure of Ce 2RhGa 12 is composed of Ce-Ga and PdGa8/2 layers<br />

similar to CePdGa 6 [1] . The structure is isomorphous to Ce 2MGa 12 M=(Ni, Cu[2], Pd). Al<strong>on</strong>g the c axis<br />

slabs of edge-sharing rectangular prism of RhGa8 alternates with Ga rich areas in which Ce atoms occupy<br />

cavities made of Ga atoms. The bulk anti ferromagnetic transiti<strong>on</strong> of Ce 2RhGa 12 at 3.5 K is exhibited<br />

by a big jump up to12 J/mol K. The value of γ above magnetic transiti<strong>on</strong> in specific heat measurements<br />

suggests that it is a heavy-fermi<strong>on</strong> system with γ = 420 mJ mol-1 K-2. The magnetic measurements are in<br />

progress to c<strong>on</strong>firm the c<strong>on</strong>sistency of the ordering temperature and the further studies are in progress.<br />

1. Robin T. Macaluso, S. Nakatsuji, H. Lee, Z. Fisk, M. Moldovan, D.P. Young, and Julia Y. Chana<br />

Journal of Solid State Chemistry 174, 296-301(2003) 2. J.Y. Cho, J.N. Millican, C. Capan, D.A. Solokov, M.<br />

Moldovan, A.B. Karki, D.P.Young, M.C. Ar<strong>on</strong>s<strong>on</strong>, J.Y. Chan, Chem. Mater. 20, 6116-6123(2008)<br />

80 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QC14<br />

Electr<strong>on</strong>ic structures of plut<strong>on</strong>ium compounds with the NaCl-type<br />

m<strong>on</strong>ochalcogenides structure<br />

Takahiro Maehira 1 *, Yasutomi Tatetsu 2 and Eijiro Sakai 1<br />

1<br />

Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan,<br />

Japan<br />

2<br />

Graduate school of Engineering and Science, University of the Ryukyus , Nishihara,<br />

Okinawa 903-0213, Japan, Japan<br />

Some of the uranium and the transuranium compounds are characterized as str<strong>on</strong>gly<br />

correlated f electr<strong>on</strong> systems and have attracted particular interest because of rich<br />

variety of anomalous physical phenomena such as the valence fluctuati<strong>on</strong>, the K<strong>on</strong>do<br />

lattice, exotic magnetism, unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity, etc. Am<strong>on</strong>g such<br />

compounds, the plut<strong>on</strong>ium m<strong>on</strong>ochalcogenides display a variety of anomalous physical<br />

properties. For PuX (X=S, Se, Te) have been studied intensively both theoretically<br />

and experimentally[1,2]. To understand the electr<strong>on</strong>ic properties of these materials,<br />

the features of the ground state should be first clarified. The calculati<strong>on</strong>s for the energy<br />

band structure have been d<strong>on</strong>e by using the relativistic linear augmented-plane-wave<br />

(RLAPW) method. Note here that relativity should be taken into account, because of<br />

large atomic numbers of the c<strong>on</strong>stituent atoms. In the presentati<strong>on</strong>, we try to understand<br />

what the key issues are to c<strong>on</strong>struct the energy band structures around the Fermi energy<br />

for PuS, PuSe and PuTe.<br />

[1] A. Hasegawa, and H. Yamagami, J. Magn. Magn. Mater. 104-107, 65 (1992). [2] P. M.<br />

Oppeneer, T. Kraft, and M. S. S. Brooks, Phys. Rev. B61, 12825 (2000).<br />

QC15<br />

Electr<strong>on</strong>ic property of ThSn 3 in comparis<strong>on</strong> with uranium and<br />

transuranium compounds<br />

Yasutomi Tatetsu 1 *, Takahiro Maehira 2 and Eijiro Sakai 2<br />

1 Graduate school of Engineering and Science, University of the Ryukyus, Japan<br />

2 Faculty of Science, University of the Ryukyus, Japan<br />

Recent rapid expansi<strong>on</strong> of the research fr<strong>on</strong>tier of c<strong>on</strong>densed matter physics from<br />

uranium to transuranium compounds has stimulated renewed attenti<strong>on</strong> and much<br />

interest <strong>on</strong> exotic properties of actinides and related compounds. It is a challenge to<br />

modern electr<strong>on</strong>ic-structure theory to understand the appearance of a large number<br />

of excepti<strong>on</strong>ally complicated crystal structures of actinide metal. It is important to<br />

clarify electr<strong>on</strong>ic structure of actinide compounds which exhibit exotic magnetism<br />

and unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity. By using a relativistic linear augmentedplane-wave<br />

(RLAPW) method with the <strong>on</strong>e-electr<strong>on</strong> potential in the local-density<br />

approximati<strong>on</strong>, we investigate energy band structures and the Fermi surfaces of<br />

transuranium compounds ThSn 3, USn 3, NpSn 3 and PuSn 3. It is found in comm<strong>on</strong><br />

that the energy bands in the vicinity of the Fermi level are mainly due to the large<br />

hybridizati<strong>on</strong> between 5f and Sn 5p electr<strong>on</strong>s. Thorium c<strong>on</strong>tains no occupied 5f states,<br />

thorium compounds provide good comparative systems for investigating the role of 5f<br />

electr<strong>on</strong>s. In the presentati<strong>on</strong>, we try to understand what the key issues are to c<strong>on</strong>struct<br />

the energy band structures around the Fermi energy for ThSn 3, USn 3, NpSn 3 and PuSn 3,<br />

we attempt to unveil 5f electr<strong>on</strong> properties purely originating from actinide atoms.<br />

QC16<br />

Multipolar phase transiti<strong>on</strong> of the 4f2 n<strong>on</strong>magnetic doublet in a caged<br />

compound PrRh 2Zn 20<br />

Nagasawa Naohiro 1 , Matsumoto T Keisuke 1 , Wakiya Kazuhei 1 , Onimaru Takahiro 1 ,<br />

Umeo Kazunori 1 , Kittaka Shunichiro 2 , Sakakibara Toshiro 2 and Takabatake Toshiro 1<br />

1 Hiroshima University, Japan<br />

2 The University of Tokyo, Japan<br />

The caged compound PrIr 2Zn 20 with the Pr 3+ i<strong>on</strong> in the Γ3 doublet ground state exhibits a<br />

superc<strong>on</strong>ducting transiti<strong>on</strong> at TSC=0.05K in the presence of an antiferroquadrupolar (AFQ)<br />

order below TQ=0.11K [1, 2]. The entropy release up to TQ is <strong>on</strong>ly 20% of Rln 2 which<br />

is expected for the Γ3 doublet with the quadrupolar degrees of freedom. It suggests that<br />

quadrupolar degrees of freedom remain active even below TQ and quadrupole fluctuati<strong>on</strong>s<br />

play an important role in forming the Cooper pair in the superc<strong>on</strong>ducting state. In the<br />

present work, we have focused an isostructural and isoelectr<strong>on</strong>ic compound PrRh 2Zn 20. The<br />

electrical resistivity shows a hysteretic behavior between 140K and 470K, suggesting a firstorder<br />

structural transiti<strong>on</strong>. In spite of the possible structural transiti<strong>on</strong>, a Schottky-like peak<br />

at around 10K in the specific heat and anisotropic behavior of the isothermal magnetizati<strong>on</strong><br />

at 1.8K indicate the crystalline electric field ground state to be the Γ3 doublet. The specific<br />

heat exhibits a peak at TQ=0.06K, where the entropy release is evaluated to be <strong>on</strong>ly 6% of<br />

Rln 2. Because of the increment of TQ in the magnetic fields and the anisotropic B-T phase<br />

diagram, the phase transiti<strong>on</strong> at TQ should be an AFQ order.<br />

[1] T. Onimaru et al., J. Phys. Soc. Jpn. 79 033704 (2010). [2] T. Onimaru et al., Phys. Rev. Lett.<br />

106 177001 (2011).


QC17<br />

Crystal growth and low temperature properties of n<strong>on</strong>-centrosymetric<br />

heavy-fermi<strong>on</strong> comound CeTAl 3 (T = Cu, Ag, Au)<br />

Christian Franz, Alexander Regnat, Andreas Bauer and Christian Pleiderer<br />

Department fur Physik, Technische Universitat Munchen, Germany<br />

For a l<strong>on</strong>g time full inversi<strong>on</strong> symmetry was thought to be a prec<strong>on</strong>diti<strong>on</strong> for heavyfermi<strong>on</strong><br />

superc<strong>on</strong>ductivity. The discovery of heavy-fermi<strong>on</strong> superc<strong>on</strong>ductivity in<br />

the antiferromagnetic state of CePt 3Si at ambient pressure and CeRhSi 3, CeIrSi 3 and<br />

CeCoGe 3 at high pressure c<strong>on</strong>tradicted these paradigms. All compounds in this class<br />

crystallize in a P4mm or subclass crystal structure. Here we report <strong>on</strong> the single crystal<br />

growth of CeTAl 3 (T = Cu, Ag, Au) with crystal structure I4mm, being isostructural<br />

to CeRhSi 3 and CeIrSi 3. High purity elements (>5N) have been used as starting<br />

materials. A special build image furnace was used for crystal growth. Crystal quality<br />

was determined by Laue x-ray scattering, x-ray powder diffracti<strong>on</strong> and edx. Low<br />

temperature properties have been investigated by measurements of bulk properties<br />

including magnetisati<strong>on</strong>, heat capacity and electrical resistivity.<br />

QC18<br />

Enhancement of the hall coefficient under pressure in CeCu 2Si 2<br />

Shingo Araki 1 *, Naoto Nishiumi 1 , Minami Hayashida 1 , Takafumi Shinohara 1 , Yoichi<br />

Ikeda 1 , Tatsuo C. Kobayashi 1 , Silvia Seiro 2 , Christoph Geibel 2 and Frank Steglich 2<br />

1 Department of Physics, Okayama University, Japan<br />

2 Max Planck Institute for Chemical Physics of Solids, Germany<br />

CeCu 2Si 2 is the heavy fermi<strong>on</strong> superc<strong>on</strong>ductor discovered in 1979. The unc<strong>on</strong>venti<strong>on</strong>al<br />

superc<strong>on</strong>ductivity with Tc ~ 0.6 K at ambient pressure is believed to be mediated<br />

by antiferromagnetic spin fluctuati<strong>on</strong> around the AFM quantum critical point.<br />

With increasing pressure, Tc increases to reach the maximum at 4.2 GPa, although<br />

antiferromagnetic spin fluctuati<strong>on</strong> decreases. The existence of the critical valence<br />

fluctuati<strong>on</strong> around the critical valence transiti<strong>on</strong> is proposed to explain the enhancement<br />

of Tc under pressure [1]. However, there is no direct evidence to reveal the existence of<br />

the valence fluctuati<strong>on</strong>. In this study, we investigated the Hall effect <strong>on</strong> single crystal<br />

of CeCu 2Si 2 under high pressure. The temperature dependence of the Hall coefficient at<br />

ambient pressure shows a peak at TmL = 4 K for H // [001] and [100]. In additi<strong>on</strong>, the<br />

Hall coefficient shows the other peak at T1max for H // [100]. The magnitude of the<br />

Hall coefficient at TmL increases with increasing pressure and reaches the maximum<br />

at around 4 GPa, coincident with the enhancement of Tc. We will discuss the relati<strong>on</strong><br />

between the enhancement of the Hall coefficient and Tc.<br />

[1] K. Miyake et al.: J. Phys.: C<strong>on</strong>dens. Matter 19 (2007) 125201.<br />

QC19<br />

Saturati<strong>on</strong> moment in the ferromagnetic state of EuB6 Vladimir V. Glushkov 1 *, Alexey V. Bogach 1 , Alexey V. Semeno 1 , Sergey V. Demishev 1 , Vsevolod Yu.<br />

Ivanov 1 , Nickolay E. Sluchanko 1 , Alexey V. Kuznetsov 2 , Sergey Yu. Gavrilkin 3 , Kirill V. Mitsen 3 , Natalja Yu.<br />

Shitsevalova 4 , Vladimir B. Filipov 4 , Johan Vanacken 5 and Victor Moshchalkov 5<br />

1<br />

Low Temperatures and Cryogenic Engineering Dept., A.M.Prokhorov General Physics Institute of<br />

RAS, Russia<br />

2<br />

Nati<strong>on</strong>al Research Nuclear University MEPhI, Russia<br />

3<br />

P.N.Lebedev Physical Institute of RAS, Russia<br />

4<br />

I. Frantsevich Institute for Problems of Materials Science NASU, Ukraine<br />

5<br />

Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Belgium<br />

Two c<strong>on</strong>sequtive phase transiti<strong>on</strong>s featuring the <strong>on</strong>set of ferromagnetism in europium hexaboride [1-4] are<br />

comm<strong>on</strong>ly associated with percolati<strong>on</strong> in the system of linked magnetic polar<strong>on</strong>s at T_M~15.6 K and with<br />

l<strong>on</strong>g range magnetic ordering below T_C=12.6-13.9 K [1]. However, the recent study of high frequency<br />

electr<strong>on</strong> spin res<strong>on</strong>ance [5] showed neither magnetic phase separati<strong>on</strong> nor MP formati<strong>on</strong> features in the<br />

system of localized magnetic moments of Eu 2+ . To shed more light <strong>on</strong> the nature of ferromagnetism we<br />

studied the magnetic and thermal properties of the EuB 6 single crystals in pulsed (up to 40 T) and steady<br />

(up to 9 T) magnetic fields at temperatures 2-40 К. The estimated saturati<strong>on</strong> moment M_{sat}~7.4μ_B is<br />

found to exceed noticeably the magnetic moment of Eu 2+ i<strong>on</strong>. The difference is shown to be induced by<br />

an additi<strong>on</strong>al c<strong>on</strong>tributi<strong>on</strong> to magnetizati<strong>on</strong> due to the formati<strong>on</strong> of intermediate magnetic phase below T_<br />

M. The observed renormalizati<strong>on</strong> of M_{sat} is discussed in terms of the effects of the spin polarizati<strong>on</strong><br />

in 5d-band and the short range magnetic ordering in the system of Eu 2+ i<strong>on</strong>s. Support from RFBR 11-02-<br />

00623 project, Federal Programme “Scientific and Educati<strong>on</strong>al Human Resources of Innovative Russia”<br />

and the Methusalem Funding by the Flemish Government is acknowledged.<br />

[1] U.Yu, B.I.Min, Phys. Rev. B, v.74, p.094413 (2006). [2] S.Sullow et al., Phys. Rev. B, v.57, p.5860<br />

(1998). [3] V.V.Glushkov et al., JETP v.105, p.32 (2007). [4] J.Kim et al., Phys Rev B, v.78, p.165120<br />

(2008). [5] A.V.Semeno et al., Phys Rev B, v.79, p.014423 (2009).<br />

QC20<br />

QC21<br />

QC22<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetizati<strong>on</strong> of Tm1-xYbxB12 in str<strong>on</strong>g pulsed and steady magnetic<br />

fields.<br />

Alexey Bogach 1 *, Nickolay Sluchanko 1 , Vladimir Glushkov 1 , Sergey Demishev 1 ,<br />

Andrey Azarevich 1 , Vladimir Filipov 2 , Natalia Shitsevalova 2 , Slavomir Gabani 3 , Karol<br />

Flachbart 3 , Johan Vanacken 4 and Victor Moshchalkov 4<br />

1<br />

Low temperature and cryogenic engineering, A.M.Prokhorov General Physics<br />

Institute RAS, Russia<br />

2<br />

Institute for Problems of Materials Science NASU, Ukraine<br />

3<br />

Institute of Experimental Physics, Slovak Academy of Sciences, Slovak<br />

4<br />

Institute for Nanoscale Physics and Chemistry of KUL, Belgium<br />

The magnetizati<strong>on</strong> of solid soluti<strong>on</strong>s Tm 1-xYb xB 12 (00.7. Comparis<strong>on</strong> between the steady and pulsed field magnetizati<strong>on</strong> behavior provides<br />

additi<strong>on</strong>al arguments in favor of magnetic nanoclusters formati<strong>on</strong>, short range ordering and<br />

electr<strong>on</strong> phase separati<strong>on</strong> effects in Tm 1-xYb xB 12.<br />

Stabilizati<strong>on</strong> of ferromagnetism and existence of ferromagnetic<br />

quantum criticality in UCo 1-xRu xGe system<br />

Michal Valiska*, Jiri Pospisil, Martin Divis, Jan Prokleska and Vladimir Sechovsky<br />

DCMP, Charles University, Ke Karlovu 5, 121 16, Prague, Czech Republic<br />

We have prepared polycrystalline samples of UCoGe doped by Ru <strong>on</strong> the Co-site about<br />

nominal stoichiometry UCo 1-xRu xGe where x = 0.01-0.35 with step 0.01 to studied<br />

the magnetic state and ferromagnetic instability in UCoGe. The whole series of doped<br />

materials keeps the orthorhombic TiNiSi-type structure. The evoluti<strong>on</strong> of the lattice<br />

parameters well follows Vegard’s law respecting the pure parent UCoGe and URuGe.<br />

While the UCoGe is well known ferromagnetic superc<strong>on</strong>ductor (TC = 2.5 K, TSC =<br />

0.6 K) the URuGe is paramagnetic down the lowest temperatures. Nevertheless the<br />

ruthenium doping of UCoGe leads to surprising stabilizati<strong>on</strong> of the ferromagnetic<br />

state when the maximum TC = 8.5 K has been found in 12 % Ru doped sample. The<br />

further increase of the Ru c<strong>on</strong>tent destabilizes previous ferromagnetic state and it is<br />

terminated by ferromagnetic quantum critical point at c<strong>on</strong>centrati<strong>on</strong> of 30 % of Ru. We<br />

have prepared single crystal of the UCo 0.88Ru 0.12Ge and UCo 0.70Ru 0.30Ge for detail study<br />

of the ferromagnetic state, individual c<strong>on</strong>tributi<strong>on</strong>s of the U, Co and Ru comp<strong>on</strong>ents to<br />

total magnetic moment, magnetic anisotropy and destabilizati<strong>on</strong> of the ferromagnetism<br />

in UCoGe in relati<strong>on</strong> to superc<strong>on</strong>ductivity. The results are discussed <strong>on</strong> the basis of the<br />

change of electr<strong>on</strong>ic structure.<br />

Thermal properties of RB 6 (R-La, Ce, Pr, Nd)<br />

M. A. Anisimov 1 *, A. V. Bogach 1 , V. V. Glushkov 1 , S. V. Demishev 1 , N. A. Samarin 1 , S. Gavrilkin2, N.<br />

Yu. Shitsevalova3, A. V. Levchenko3, V. B. Filipov3, S. Gabani4, K. Flachbart4 and N. E. Sluchanko1<br />

1 Low Temperatures and Cryogenic Engineering Dept., A.M.Prokhorov General Physics Institute of RAS, Russia<br />

2 P.N.Lebedev Physical Institute of RAS, Russia<br />

3 Institute for Problems of Materials Science NAS, Ukraine<br />

4 Institute of Experimental Physics of SAS, Slovak<br />

Rare earth (RE) hexaborides RB_6 represent a class of compounds with variety of magnetic properties including<br />

antiferromagnetic (R-Ce, Pr, Nd, Gd, Dy, Tb, Ho), ferromagnetic (EuB_6), intermediate valence (SmB_6)<br />

and heavy fermi<strong>on</strong> behavior (CeB_6). Here we investigate the heat capacity C_P(T) <strong>on</strong> the high quality single<br />

crystals of light hexaborides (R-La, Ce, Pr, Nd) in the wide range of temperatures 2-300K. The data obtained<br />

allow to estimate correctly (i) the electr<strong>on</strong>ic comp<strong>on</strong>ent with γ(LaB_6)~2.4mJ/(mol•K), (ii) c<strong>on</strong>tributi<strong>on</strong> from<br />

quasilocal vibrati<strong>on</strong>al mode of R^{3+} i<strong>on</strong> with Θ_E~119 - 152K, (iii) the Debye-type term from rigid bor<strong>on</strong><br />

cage with Θ_D~1160K. Our data also suggest the additi<strong>on</strong>al (iv) defect mode comp<strong>on</strong>ent which is provided by<br />

the c<strong>on</strong>tributi<strong>on</strong> of the bor<strong>on</strong> vacancies. The estimated values of residual c<strong>on</strong>centrati<strong>on</strong> N_{vac}~1-4% agrees<br />

with the results of X-ray studies of RB_6 [1], [2]. The analysis of magnetic c<strong>on</strong>tributi<strong>on</strong> shows that magnetic<br />

entropy S=∫ΔC_{mag}/TdT reaches the value corresp<strong>on</strong>ding to the ground state of 4f-multiplet in the range<br />

2-4T_N. Taking into account the results of previous thermal investigati<strong>on</strong>s [3] we c<strong>on</strong>clude in favour of the spinpolar<strong>on</strong><br />

formati<strong>on</strong> (see [4], [5] for details) in the paramagnetic vicinity of Neel temperature.<br />

[1] V.A.Trunov, A.L.Malyshev et al., J. Phys.: C<strong>on</strong>d. Mat. v. 5, p. 2479 (1993). [2] M.M.Korsukova, V.N.Gurin et al., J. Less-<br />

Comm<strong>on</strong>. Met. v. 117, p. 73 (1986). [3] M.Sera, S.Kobayashi et al., Phys. Rev. B v. 54, p. R5207 (1996). [4] N.E.Sluchanko,<br />

A.V.Bogach et al., JETP v. 104, p. 120 (2007). [5] M.A.Anisimov, A.V.Bogach, V.V.Glushkov et al., JETP v. 109, p. 815 (2009).<br />

July 8 - 13, 2012 Busan, Korea 81<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QC23<br />

Magnetic penetrati<strong>on</strong> depth and skin depth study of superc<strong>on</strong>ductivity<br />

and quantum criticality in Ce 1-xR xCoIn 5 (R=La and Nd)<br />

H. Kim 1 , M. A. Tanatar 1 , K. Cho 1 , J. Murphy 1 , R. Hu 2 , C. Petrovic 2 and R. Prozorov 1 *<br />

1 The Ames Laboratory, USA<br />

2 Brookhaven Nati<strong>on</strong>al Laboratory, USA<br />

A heavy fermi<strong>on</strong> superc<strong>on</strong>ductor CeCoIn 5 shows different resp<strong>on</strong>ses to Nd- or La-<br />

substituti<strong>on</strong>s for Ce, with the former inducing l<strong>on</strong>g range magnetic order coexisting<br />

with superc<strong>on</strong>ductivity. To understand the origin of the differences, we studied the<br />

temperature and field dependent in-plane magnetic penetrati<strong>on</strong> depth, $\lambda(T)$,<br />

in single crystals of (Ce,R)CoIn 5 (R=La, Nd). Measurements were performed with a<br />

tunnel diode res<strong>on</strong>ator down to 50~mK in a diluti<strong>on</strong> refrigerator, in magnetic field up<br />

to 14 T parallel to the $c$-axis. These low-temperature and high field measurements<br />

allowed for the explorati<strong>on</strong> for the full domain of superc<strong>on</strong>ductivity and quantum<br />

criticality in the T H phase diagram. Some previously unreported features were observed<br />

and will be discussed from the point of view of measured differential magnetic<br />

susceptibility. These measurements bring new insight into the interplay between<br />

superc<strong>on</strong>ductivity and magnetism as well as field-tuned quantum critical behavior of<br />

doped 115 systems.<br />

QC24<br />

Low energy spin excitati<strong>on</strong>s in single-crystalline CeCu 2Ge 2 in magnetic<br />

fields up to 10T<br />

Astrid Schneidewind 1 *, Michael Loewenhaupt 2 , Oliver Stockert 3 and Enrico<br />

Faulhaber 1<br />

1 Helmholtz-Zentrum Berlin fur Materialien und Energie, Germany<br />

2 IFP, TU Dresden, Germany<br />

3 MPI-CPfS Dresden, Germany<br />

CeCu 2Ge 2 is K<strong>on</strong>do lattice with a moderately enhanced Sommerfeld coefficient of the<br />

specific heat γ =140 mJ/molK2. It exhibits antiferromagnetic order below TN = 4.1 K.<br />

The incommensurate magnetic structure can be explained by the nesting properties of<br />

the calculated Fermi surface when taking into account an itinerant comp<strong>on</strong>ent of the<br />

Ce 4f-moments in additi<strong>on</strong> to their local character. We performed low-energy inelastic<br />

neutr<strong>on</strong> scattering experiments <strong>on</strong> a 2g single crystal of CeCu 2Ge 2 using the cold threeaxes<br />

spectrometer PANDA at FRM II. Data were taken at 1.5 K and in magnetic fields<br />

up to 10T applied perpendicular to the (110/001) scattering plane. At zero field the<br />

spin excitati<strong>on</strong>s show an energy gap of 0.5 meV at the magnetic z<strong>on</strong>e center. Away<br />

the magnetic excitati<strong>on</strong>s become dispersive merging into a band of excitati<strong>on</strong>s around<br />

1 meV. For increasing magnetic fields, the gap energy is lowered indicating opposite<br />

acti<strong>on</strong> of external and internal fields. The results will be discussed in the framework of<br />

local, crystal-field related, and n<strong>on</strong>-local, spin-wave-like, magnetic excitati<strong>on</strong>s.<br />

QC25<br />

Magnetizati<strong>on</strong> measurements under high pressure <strong>on</strong> incommensuratecommensurate<br />

phase transiti<strong>on</strong>s <strong>on</strong> UPd 2Si 2<br />

Hiroyuki Hidaka, Hideki Igarashi, Yusei Shimizu, Chihiro Tabata, Tatsuya<br />

Yanagisawa and Hiroshi Amitsuka<br />

Graduate School of Science, Hokkaido University, Japan<br />

UPd 2Si 2 has the ThCr 2Si 2-type body-centered tetrag<strong>on</strong>al structure. This compound<br />

shows an incommensurate-antiferromagnetic (IC-AFM) ordering with a propagati<strong>on</strong><br />

vector Q = 0.73c* at 135 K (= TNh), and successively undergoes a simple<br />

commensurate (C) type-I AFM ordering at 108 K (=TNl). It is known that the phase<br />

transiti<strong>on</strong>s are of sec<strong>on</strong>d order at TNh and of first order at TNl. In additi<strong>on</strong>, an antiphase<br />

ordering state (Q = 2/3c*) becomes stable in high magnetic field applied al<strong>on</strong>g<br />

the c-axis. The magnetism of UPd 2Si 2 is phenomenologically well explained in terms<br />

of the <strong>on</strong>e-dimensi<strong>on</strong>al Ising model assuming localized 5f spins, whereas Fermi liquid<br />

behavior with a moderately large electric-specific-heat coefficient ~ 30 mJ/molK2 is<br />

also seen at low temperature [1]. In the present study, we have measured magnetizati<strong>on</strong><br />

of UPd 2Si 2 under high pressure up to 5.5 GPa and high magnetic field up to 7 T in<br />

order to investigate the duality between the localized and the itinerant features of<br />

the 5f-electr<strong>on</strong>ic states in U compounds. From the results of the magnetizati<strong>on</strong> and<br />

previous resistivity measurements under high pressure [2], we will discuss about the<br />

5f-electr<strong>on</strong>ic states of the compound.<br />

[1] H. H<strong>on</strong>ma et al., J. Phys. Soc. Jpn. 67 (1998) 1017. [2] H. Hidaka et al, J. Phys.: C<strong>on</strong>f. Ser. 273<br />

(2011) 012032.<br />

82 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QD01<br />

Fe doping and magnetic field effect in the valence fluctuating heavy<br />

fermi<strong>on</strong> system α-YbAlB 4<br />

Kentaro Kuga, Keita S<strong>on</strong>e, Yosuke Matsumoto, Eoin C<strong>on</strong>or O'farrell and Satoru<br />

Nakatsuji<br />

Institute for Solid State Physics, Japan<br />

The Yb-based heavy fermi<strong>on</strong> system, α-YbAlB 4, has a n<strong>on</strong>centrosymmetric<br />

crystal structure, while the structure of the isostoichiometric system, β-YbAlB 4 is<br />

centrosymmetric [1]. β-YbAlB4 is a unique example of the Yb based heavy fermi<strong>on</strong><br />

systems that shows pr<strong>on</strong>ounced n<strong>on</strong> Fermi liquid behaviors and a superc<strong>on</strong>ducting<br />

transiti<strong>on</strong> at 80 mK under ambient pressure and field [2,3,4]. On the other hand,<br />

α-YbAlB 4 at low temperatures is well fit to a Fermi liquid type descripti<strong>on</strong>. Both α and<br />

β-YbAlB 4 are valence fluctuating systems with the Yb valence of 2.73 for α-YbAlB 4<br />

and 2.75 for β-YbAlB 4 [5]. We succeeded in substituting Fe for Al in α-YbAlB 4,<br />

and found an antiferromagnetic order at 10 K. By a small substituti<strong>on</strong> to α-YbAlB 4,<br />

we also succeeded in inducing n<strong>on</strong>-Fermi liquid behaviors. The antiferromagnetic<br />

ordering temperature is suppressed by magnetic field and n<strong>on</strong>-Fermi liquid behaviors<br />

are induced where the Neel temperature vanishes. In this presentati<strong>on</strong>, we will discuss<br />

the difference of the two n<strong>on</strong>-Fermi liquid behaviors in Fe doped α-YbAlB 4 showing<br />

thermodynamic and transport properties.<br />

[1] R. T. Macaluso et al, Chemistry of Materials 19, 1918 (2007). [2] S. Nakatsuji et al, Nature Physics 4,<br />

603 (2008). [3] K. Kuga et al, Physical Review Letters 101, 137004 (2008). [4] Y. Matsumoto et al,<br />

Science 21, 316 (2011). [5] M. Okawa et al, Physical Review Letters 104, 247201 (2010).<br />

QD02<br />

Magnetic and electric properties of single crystal SmBaMn 2O 6<br />

Youichi Maeda 1 *, Shigeki Yamada 1 and Takahisa Arima 2<br />

1 Yokohama city univercity, Japan<br />

2 Univercity of Tokyo, Japan<br />

We have succeeded in growth of single crystals of an A-site ordered perovskite<br />

manganese oxide, SmBaMn 2O 6, and investigated the magnetic and electric properties.<br />

Since Sm and Ba i<strong>on</strong>s alternately occupy the perovskite A-site, it is expected that<br />

the magnetic and electric properties should be anisotropic. Moreover, the anisotropy<br />

may be modified with the charge orbital ordering. We also found that a peak in<br />

magnetic susceptibility of polycrystals at about 250 K. The magnetic susceptibility<br />

of a single crystal shows an anomaly which is accompanied by a hysteresis between<br />

170 K and 210 K. This anomaly is caused by a rearrangement of charge orbital<br />

ordering. A clear magnetic anisotropy is observed below this temperature indicating<br />

that this rearrangement of charge orbital ordering accompanies the simultaneous<br />

antiferromagnetic spin ordering. Temperature dependence of the dielectric c<strong>on</strong>stant<br />

al<strong>on</strong>g the c axis also shows an anomaly at the rearrangement temperature, while no<br />

clear anomaly is observed for E perpendicular to the c axis. This result is c<strong>on</strong>sistent<br />

with the rearrangement of the stacking of the charge- and orbital-ordered sheets al<strong>on</strong>g<br />

the c axis.<br />

QD03<br />

Phase diagram and Eu valence state in EuPtP 1-xAs x<br />

Masaki Sugishima 1 , Akihiro Mitsuda 1 , Hirofumi Wada 1 *, Masahiko Isobe 2 and Yutaka<br />

Ueda 2<br />

1 Department of Physics, Kyushu University, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

EuPtP is known to exhibit two valence order transiti<strong>on</strong>s at T 1 = 235 K and T 2 = 190 K<br />

[1]. At T > T 1, the Eu i<strong>on</strong>s have a single valence state with the mean valence of 2.16. At<br />

T 2 < T < T 1, the Eu valence state is ordered with the sequence of -Eu 2+ -Eu 2+ -Eu 3+ -Eu 2+ -<br />

Eu 2+ -Eu 3+ - al<strong>on</strong>g the c-axis. Moreover, the stacking is replaced by another sequence<br />

with -Eu 2+ -Eu 3+ -Eu 2+ -Eu 3+ - below T 2 [2]. C<strong>on</strong>sequently, the successive valence order<br />

transiti<strong>on</strong>s are accompanied by increase in the Eu mean valence up<strong>on</strong> cooling. The<br />

substituti<strong>on</strong> of As for P expands the lattice and decreases both T 1 and T 2 [3]. In this<br />

study, we report a phase diagram and the Eu valence state in EuPtP 1-xAs x. For 0


QD04<br />

Investigati<strong>on</strong> of crystal structure, magnetism and transport properties<br />

of SrFe 1-xTi xO 3-δ systems<br />

Sendilkumar A 1 , Babu P. D. 2 , Manivelraja M 3 , R.reddy V. 4 and Srinath S 1 *<br />

1 School of Physics, University of Hyderabad, India<br />

2 UGC-DAE C<strong>on</strong>sortium for Scientific Research, R-5 Shed, B.A.R.C,Mumbai, 400 085,India, India<br />

3 School of Physics, Advanced Magnetics Group ,DMRL,Hyderabad, 500 046 ,A.P ,India, India<br />

4 4UGC-DAEF ,Khandwa Road, Indore, 425017, M.P, India, India<br />

SrFeO 3 has attracted lot of attenti<strong>on</strong> in the recent past due to the exciting electric and magnetic properties<br />

that can be achieved by varying oxygen stoichiometry. In this investigati<strong>on</strong>, partial replacement of Fe 4+<br />

with a n<strong>on</strong>-magnetic i<strong>on</strong> of Ti 4+ in SrFeO 3-δ is carried out to reduce the magnetic complexity of the helical<br />

structure and determine the resulting chemical and magnetic structure using neutr<strong>on</strong> powder diffracti<strong>on</strong><br />

and Mossbauer spectroscopy. Rietveld refinement of the neutr<strong>on</strong> data indicated the presence of<br />

tetrag<strong>on</strong>al symmetry with I4/mmm space group in δ~0.125. Our neutr<strong>on</strong> and Mossabauer measurements<br />

c<strong>on</strong>firm that Fe exists in three different sites both crystallographically as well as magnetically in all four<br />

compositi<strong>on</strong>s. oxygen deficient SrFe 1-xTi xO 3-δ (x = 0 to 0.3) show an insulating behavior with a canted<br />

antiferromagnetic spin ordering, in comparis<strong>on</strong> to a metallic, helical spin arrangement of x=0. Resistivity<br />

of x = 0 to 0.3 follows the Mott’s 2-dimensi<strong>on</strong>al variable range hopping (VRH), ρ= ρ0 exp(T0/T)-<br />

1/3. The compositi<strong>on</strong> dependence of ac c<strong>on</strong>ductivity is carried out in the frequency range 40 Hz to 1<br />

MHz and the cole-cole plots show a single semicircular arc representing the grain c<strong>on</strong>tributi<strong>on</strong>. The<br />

temperature coefficient of resistance (TCR) changes from negative to positive (PTCR) for x = 0.2.<br />

[1] J.P.Hodges , S.Short, J.D.Jorgensen, X.Xi<strong>on</strong>g,B.Dabrowski, S.M.Mini and C.W.Kimball Journal of Solid State Chemistry 151,(2000)<br />

190-209. [2] P.K.Gallagher ,J.B.Mac Chesney and D.N.E.Buchanan, The Journal of Chemical Physics 41, 8(1964) 2429. [3] Y.Takeda,<br />

K.Kanno ,T.Takada, O.Yamamoto, M.Takano, N.Nakayama and Y.Bandol J.Solid State Chemistry 63,(1986) 237-249. [4] M.Takano, T.Okita,<br />

N.Nakayama, Y.Bando, Y.Takeda, O.Yamamoto and J.B.Goodenough J.Solid State Chemistry 73,(1988) 140-150. [5]A.Leb<strong>on</strong>, P.Alder,<br />

C.Bernhard, A.V.Boris, A.V.Pimenov, A.Maljuk, C.T.Lin, C.Ulrich and B.Keimer Phy.Rev.Lett. 92,3(2004) 037202 [6]Peter Alder and Sten<br />

Erikss<strong>on</strong> , Z.Anorg. Allg. Chem. 626 (2000) 118-214. [7] S. Srinath, M. Mahesh Kumar, M. L. Post, and H. Srikanth, Phys. Rev. B 72 (2005)<br />

QD05<br />

Evoluti<strong>on</strong> from a localized to an intermediate valence regime in<br />

Ce 2Cu 2-xNi xIn<br />

Adam Pikul* and Dariusz Kaczorowski<br />

Institute of Low Temperature and Structure Research, Polish Academy of Sciences,<br />

Poland<br />

Ce 2Cu 2In and Ce 2Ni 2In crystallize in a primitive tetrag<strong>on</strong>al structure of the Mo 2FeB 2<br />

type. The former compound orders antiferromagnetically at the Neel temperature of<br />

5.5 K, while the latter <strong>on</strong>e is a system with fluctuating valence [1]. Here we report<br />

<strong>on</strong> low temperature physical properties of the solid soluti<strong>on</strong> Ce 2Cu 2-xNi xIn studied by<br />

means of x-ray powder diffracti<strong>on</strong>, magnetic susceptibility and electrical resistivity<br />

measurements, using polycrystalline specimens. We show that partial substituti<strong>on</strong><br />

of Cu by Ni results in a quasi-linear decrease of the lattice parameters and unit cell<br />

volume of the system. The lattice compressi<strong>on</strong> leads to an increase in the exchange<br />

integral and yields a reversal in the order of the magnetic 4f1 and n<strong>on</strong>magnetic 4f0<br />

states, being in line with the D<strong>on</strong>iach phase diagram. In the localized regime, where an<br />

interplay of the K<strong>on</strong>do scattering and the crystalline electric field effect occurs, the rise<br />

in the hybridizati<strong>on</strong> strength is accompanied by a relative reducti<strong>on</strong> in the scattering<br />

c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s <strong>on</strong> excited crystal field levels.<br />

[1] D. Kaczorowski, P. Rogl and K. Hiebl, Phys. Rev. B 54 (1996) 9891.<br />

QD06<br />

Substituti<strong>on</strong> effect in CeFe 2Al 10<br />

Takashi Nishioka 1 , Yuta Oogane 1 , Daishi Hirai 1 , Harukazu Kato 1 , Masahiro<br />

Matsumura 1 , Yukihiro Kawamura 2 and Chihiro Sekine 2<br />

1 Physics, Kochi University, Japan<br />

2 Physics, Muroran Institute of Technology, Japan<br />

CeFe 2 Al 10 is an important reference material as CeRu 2 Al 10 which indicates a<br />

mysterious phase transiti<strong>on</strong>. We have performed the electrical resistivity and magnetic<br />

susceptibility of substiututed systems, i.e., (Ce,La)Fe 2 Al 10 and Ce(Fe,Co)Ru 2 Al 10 .<br />

The former system reveals the effect of periodicity and the latter <strong>on</strong>e reveals that of<br />

electr<strong>on</strong> number. A broad peak, which is attributed to K<strong>on</strong>do effect, m<strong>on</strong>ot<strong>on</strong>ically<br />

shifts to higher and lower temperatures with La- and Co-substituti<strong>on</strong>, respectively.<br />

The electrical resistivity of CeFe 2 Al 10 shows a broad peak at 60 K and sharp increase<br />

below 15 K. A slight substituti<strong>on</strong> of Ce by La and Fe by Co site remove the broad peak<br />

and the increase at low temperatures. These results indicate the broad peak is due to<br />

coherence effect and the increase is due to a semic<strong>on</strong>ducting gap.<br />

QD07<br />

QD08<br />

QD09<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Fermi surface and electr<strong>on</strong>ic correlati<strong>on</strong>s in a valence fluctuating Eusystem:<br />

an experimental and theoretical study of EuIr 2Si 2<br />

Silvia Seiro 1 , Oleg Ignatchik 2 , Violeta Guritanu 1 , Vivien Petzold 1 , Takuya Iizuka 3 ,<br />

Kathrin Gotze 2 , Jorg Sichelschmidt 1 , Shin-ichi Kimura 3 , Horst Borrmann 1 , Jochen<br />

Wosnitza 2 , Helge Rosner 1 and Christoph Geibel 1 *<br />

1 Max Planck Institute for Chemical Physics of Solids, Germany<br />

2 High Magnetic Field Laboratory Dresden, Helmholtz Center Dresden-Rossendorf, Germany<br />

3 Institute for Molecular Science, UVSOR Facility, Okazaki 444-8585, Japan<br />

Electr<strong>on</strong>ic correlati<strong>on</strong>s can induce str<strong>on</strong>g changes in electr<strong>on</strong>ic states, especially those at the Fermi level. These<br />

effects are presently the subject of intense theoretical and experimental investigati<strong>on</strong>s, especially <strong>on</strong> Ce- and<br />

U-based heavy fermi<strong>on</strong> systems as well as <strong>on</strong> High Tc cuprates. In c<strong>on</strong>trast valence fluctuating Eu-systems<br />

have yet not been investigated in this respect, although the valence fluctuati<strong>on</strong>s of Eu should have a str<strong>on</strong>g<br />

impact. We have recently grown high quality single crystals of the valence fluctuating compound EuIr 2Si 2 and<br />

started a thorough investigati<strong>on</strong> of its electr<strong>on</strong>ic properties. From previous Moessbauer studies the valence<br />

v of Eu in EuIr 2Si 2 was reported to decrease c<strong>on</strong>tinuously with temperature, from v = 2.3 at 300 K to v =<br />

2.8 below 20 K [1, 2]. Our T-dependent XRD, susceptibility, resistivity, and specific heat measurements <strong>on</strong><br />

these single crystals c<strong>on</strong>firm such a str<strong>on</strong>g evoluti<strong>on</strong> of the valence and give insight into global effects of the<br />

str<strong>on</strong>g correlati<strong>on</strong>s. These single crystals allowed the first observati<strong>on</strong> of de Haas-van Alphen oscillati<strong>on</strong>s in a<br />

valence fluctuating Eu-system, as well as the first determinati<strong>on</strong> of the optical c<strong>on</strong>ductivity in such a system.<br />

Comparing these results with DFT-based calculati<strong>on</strong>s give a deeper insight into the correlati<strong>on</strong> effects.<br />

[1] B. Chevalier, J.M.D Coey, B. Lloret, and J. Etourneau; J. Phys. C: Solid State Phys. 19 (1986) 4521. [2] S.<br />

Patil, R. Nagarajan, L.C. Gupta, R. Vijayaraghavan, and B.D. Padalia; Solid State Comm. 63 (1987) 955<br />

Heat capacity and electrical resistivity of CeNi5-xGex Mariana Zapotokova 1 , Ivan Curlik 2 , Marian Reiffers 3 and Mauro Giovannini 4<br />

1<br />

Institute of Experimental physics, Wats<strong>on</strong>ova 47, SK 043 53 Kosice, Slovakia, Slovak<br />

2<br />

Centre od Low Temperature Physics, Institute of Experimental Physics, Wats<strong>on</strong>ova<br />

47, SK 043 53 Kosice, Slovakia, Slovak<br />

3<br />

Centre od Low Temperature Physics, Institute of Experimental Physics, Slovak<br />

Academy of Sciences, Kosice, Slovakia, Slovak<br />

4<br />

CNR-SPIN and Department of Chemistry, CNR-SPIN and Department of Chemistry,<br />

University of Genova I-16146 Genova, Italy, Italy<br />

Metallic Ce compounds are of great interest for the intriguing physical properties<br />

associated with the 4f electr<strong>on</strong>s. One notable example of compound intensively studied<br />

for many years is CeNi 5 crystallizing in the hexag<strong>on</strong>al CaCu 5 type, which results to<br />

be a St<strong>on</strong>er enhanced paramagnet characterized by a spin fluctuati<strong>on</strong> c<strong>on</strong>tributi<strong>on</strong> <strong>on</strong><br />

its transport properties. Here the effect of the Ni/Ge substituti<strong>on</strong> <strong>on</strong> the ground state<br />

of CeNi 5 is presented. Several ternary germanides CeNi 5-x Gex (x=0.1, 0.2, 0.5, 0.8)<br />

were prepared by arc melting method. All the alloys crystallize in the CaCu 5 structure.<br />

Single phase of the polycrystalline samples was c<strong>on</strong>firmed by X ray diffracti<strong>on</strong>. The<br />

measurements of resistivity between 2-300 K and heat capacity between 0.4-300 K<br />

were provided and the results are presented. The resistivity measurements show typical<br />

metallic behaviour. No phase transiti<strong>on</strong> was observed in resistivity and heat capacity<br />

measurements.<br />

Antiferromagnetic order in Yb5Rh4Ge10 Kazunori Umeo 1 *, Kenichi Katoh 2 and Toshiro Takabatake 3<br />

1<br />

N-BARD, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526,<br />

Japan<br />

2<br />

Department of Applied Physics, Nati<strong>on</strong>al Defense Academy, Yokosuka 239-8686,<br />

Japan<br />

3<br />

AdSM and IAMR, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima<br />

739-8530, Japan<br />

The titled compound has three Yb sites in the tetrag<strong>on</strong>al Sc 5Co 4Si 10-type structure.<br />

The magnetizati<strong>on</strong> process shows str<strong>on</strong>g anisotropy [1]. At 2 K, M (B//a) is saturated<br />

to 4.5 μB/f.u. in 5 T, whereas M (B//c) increases linearly up to 0.9 μB/f.u. at 5 T. The<br />

effective magnetic moment for B//a is 4.25 μB/Yb, which is close to the value of 4.53<br />

μB/Yb expected for the Yb 3+ free-i<strong>on</strong> [1]. The c<strong>on</strong>tinuous increase in the specific heat<br />

down to the lowest measured temperature 2 K suggests a magnetic order below 2 K<br />

[1]. Therefore, we have measured the temperature dependence of the magnetizati<strong>on</strong><br />

M, specific heat C and resistivity down to 0.3 K. A cusp in M (B//a) and sharp peak<br />

in C(T) were observed at 0.5 K, both of which were suppressed by applying magnetic<br />

fields up to 0.8 T. These findings indicate an antiferromagnetic order at TN = 0.5 K.<br />

However, the magnetic entropy Sm at TN is <strong>on</strong>ly 60 % of Rln 2. This observati<strong>on</strong><br />

suggests a heterogeneous mixed valence state where three of five Yb i<strong>on</strong>s in formula<br />

unit are in trivalent state and the rest two are in divalent state.<br />

[1] K. Katoh et al., Physica B 373 (2006) 111.<br />

July 8 - 13, 2012 Busan, Korea 83<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QD10<br />

Magnetic field dependence of the resistivity minimum of nanosized YbAl 3<br />

C. Echevarria-B<strong>on</strong>et 1 *, D. P. Rojas 2 , L. Fernandez Barquin 1 , J. C. Gomez Sal 1 , S. N.<br />

Kaul 3 , B. Coqblin 4 , S. G. Magalhaes 5 and E. Bauer 6<br />

1 CITIMAC, Universidad de Cantabria, Spain<br />

2 Departamento de Fisica, Universidad Carlos III de Madrid, Spain<br />

3 School of Physics and Centre for Nanotechnology, University of Hyderabad, India<br />

4 Laboratoire de Physique des Solides, CNRS-Universite Paris-Sud, France<br />

5 Instituto de Fisica, Universidade Federal Fluminense, Brazil<br />

6 Institute of Solid State Physics, TU Wien, Austria<br />

Yb-based alloys follow the D<strong>on</strong>iach phase diagram where the competiti<strong>on</strong> between RKKY and K<strong>on</strong>do<br />

interacti<strong>on</strong> plays a predominant role. Am<strong>on</strong>g them, a simple cubic compound (Pm-3m) YbAl 3 is a fine example<br />

of str<strong>on</strong>g electr<strong>on</strong> correlati<strong>on</strong>s leading to intermediate valence behavior [1]. Recently, we have investigated<br />

the effect of crystallite size <strong>on</strong> the electr<strong>on</strong>ic and magnetic properties of the nanometric samples of this<br />

alloy, prepared by high-energy milling of arc-melted ingots. Milling yields massive quantities of 4f-alloys in<br />

nanocrystalline (nc-) form with a relatively narrow size distributi<strong>on</strong> [2]. In nc-YbAl 3, the variati<strong>on</strong> of valence is<br />

due to a modificati<strong>on</strong> of the fracti<strong>on</strong> of surface atoms compared to the total number of particles. This affects both<br />

specific heat and susceptibility data [3]. Here, we present a magnetic field (H)-dependent study of the electrical<br />

resistivity, ρ, of annealed and pressed pellets of nc-YbAl 3. The XRD Rietveld refinements yield particle sizes<br />

of maximum ~10 nm whereas slightly smaller values are detected by HRTEM. The results are striking in that<br />

the physical properties change drastically compared to the bulk [4] and an unexpected minimum in ρ(T) occurs<br />

around 15 K. With increasing H, the minimum becomes more pr<strong>on</strong>ounced and shifts to higher temperatures.<br />

[1] E. Bauer et al., Phys. Rev. B 52, 4327 (1995). [2] D. P. Rojas et al., J. Phys: C<strong>on</strong>d. Matter 19, 186214 (2007). [3]<br />

D. P. Rojas et al., Phys. Rev B 78, 094412 (2008). [4] D. M. Rowe et al., J. Phys. D: Appl. Phys. 35, 2183 (2002).<br />

QD11<br />

Electr<strong>on</strong>ic states of Eu 4As 3 under high pressure<br />

Hisao Kobayashi 1 *, Yoshitaka Yoda 2 and Akira Ochai 3<br />

1 Graduate School of Material Science, University of Hyogo, Japan<br />

2 Japan Synchrotr<strong>on</strong> Radiati<strong>on</strong> Institute, Japan<br />

3 Department of Physics, Tohoku University, Japan<br />

The mixed valence Eu 4As 3 compound with an anti-Th 3P 4 structure shows the charge ordering<br />

at 345 K and ambient pressure accompanied by trig<strong>on</strong>al distorti<strong>on</strong>, which is similar to those in<br />

Yb 4As 3 and Sm 4Bi 3 [1-3]. The hybridizati<strong>on</strong> of a narrow 4f band with broad c<strong>on</strong>ducti<strong>on</strong> bands<br />

is <strong>on</strong>e of the important parameters in these charge-ordering compounds, which is possible to be<br />

c<strong>on</strong>trolled by hydrostatic pressure. We observed the melting of the static charge order at about<br />

10 GPa and room temperature without structural change using high-pressure X-ray diffracti<strong>on</strong><br />

[4]. We have carried out 151Eu nuclear forward scattering (NFS) measurements using<br />

synchrotr<strong>on</strong> radiati<strong>on</strong> under high pressures at low temperatures to investigate the magnetic<br />

properties of Eu 4As 3. Clear quantum beats due to magnetic hyperfine field were observed<br />

in 151Eu NFS spectra at 6 K under pressure up to 14.5 GPa. The results of temperature<br />

dependences of 151Eu NFS spectra reveal that a magnetic ordering temperature increases<br />

linearly with pressure up to 10 GPa. Above 10 GPa, the magnetic ordering temperature<br />

decreases gradually with pressure. C<strong>on</strong>sequently, the pressure dependence of the magnetic<br />

ordering temperature is related to the melting of the static charge order.<br />

[1] A. Ochiai, et al., J. Phys. Soc. Jpn. 72, 3174 (2003). [2] A. Ochiai, et al., J. Phys. Soc. Jpn. 59,<br />

4129 (1990). [3] A. Ochiai, et al., J. Magn. Magn. Mater. 52, 13 (1985). [4] H. Kobayashi, et al., J.<br />

Phys.: C<strong>on</strong>dens. Matter 20 415217 (2008).<br />

QD12<br />

Pressure effect <strong>on</strong> intermediate valence semic<strong>on</strong>ductor SmB6 :<br />

11B-NMR<br />

Kouhei Nishiyama 1 , Gabriel Pristas 2 , Takeshi Mito 1 , Takao Kohara 1 , Slavomir<br />

Gabani 2 , Marian Reiffers 2 , Yasuhiro Komaki 3 , Mitutane Kokubu 3 , Hideto Fukazawa 3 ,<br />

Yoh Kohori 3 , Nao Takeshita 4 and Natalia Shitsevalova 5<br />

1<br />

Graduate school of Material Science, University of Hyogo, Japan<br />

2<br />

Institute of Experimental Physics, Slovak Academy of science, Slovak<br />

3<br />

Graduate School of Science, Chiba University, Japan<br />

4<br />

Nanoelectr<strong>on</strong>ics Research Institute, Nati<strong>on</strong>al Institute of Advanced Industrial<br />

Science and Technology, Japan<br />

5<br />

Institute for Problems of Material Science, Nati<strong>on</strong>al Academy of science of Ukraine,<br />

Ukraine<br />

The intermetallic compound SmB 6 is <strong>on</strong>e of the most famous compounds in terms of the physics of<br />

intermediated valence state, heavy Fermi<strong>on</strong> systems and K<strong>on</strong>do insulators. Recent high pressure measurements<br />

of 149Sm nuclear forward scattering and resistivity revealed that a pressure-induced insulator-metal transiti<strong>on</strong><br />

of SmB 6 is intimately c<strong>on</strong>nected with a l<strong>on</strong>g-range magnetic order, which has renewed interest in this<br />

compound. In order to investigate variati<strong>on</strong>s of the ground state and magnetic properties in SmB 6, we have<br />

carried out 11B-NMR measurement under pressure. While our group had reported the results of 11B-NMR<br />

measurements up to 2.6 GPa with a pist<strong>on</strong>-cylinder type pressure cell, the use of a Bridgman Anvil Cell has<br />

recently enabled us to perform NMR measurements at higher pressures than 4.5 GPa. Spin-lattice relaxati<strong>on</strong><br />

rate 1/T1 above 20 K roughly follows an exp<strong>on</strong>ential functi<strong>on</strong> of temperature, Exp(-Eg/2kBT), c<strong>on</strong>sistent with<br />

previous reports. 1/T1 between 20 and 100 K increases with increasing pressure, indicating a reducti<strong>on</strong> of the<br />

insulating gap. We will discuss detailed pressure dependences of the energy gap and the Sm valence.<br />

84 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QD13<br />

Magnetic properties of ytterbium fluoride sulfide Yb3F4S2 Masashi Kosaka 1 , Takuya Kobiyama 1 , Hiroko Aruga Katori 2 and Naoki Shirakawa 3<br />

1<br />

Graduate School of Science and Engineering, Saitama University, Japan<br />

2<br />

Divisi<strong>on</strong> of Advanced Fr<strong>on</strong>tier Applied Physics, Tokyo University of Agriculture and<br />

Technology, Japan<br />

3<br />

Nanosystem Research Institute, Nati<strong>on</strong>al Institute of Advanced Industrial Science<br />

and Technology, Japan<br />

The ternary ytterbium fluoride sulfide Yb 3F 4S 2 crystallizes in the tetrag<strong>on</strong>al structure<br />

with space group I4/mmm. This structure can be described as an alternative stack of<br />

<strong>on</strong>e layer of YbF 2 and two layers of YbFS al<strong>on</strong>g the c-axis. In a previous paper, it was<br />

suggested that there are two different ytterbium cati<strong>on</strong>s (Yb2 +) (Yb 3+ )2(F - )4(S 2- )2 present<br />

[1]. An anomaly with the l<strong>on</strong>g-range magnetic order has not been observed down to 0.4<br />

K by magnetizati<strong>on</strong> measurements, and the magnetic susceptibility exhibits a Curie-<br />

Weiss behavior above 50 K. However, it has become clear that the estimated value of<br />

the effective magnetic moment cannot be explained by a model which assumes that<br />

Yb 2+ and Yb 3+ occupy the two different crystallographic sites. A Schottky anomaly is<br />

found in the temperature dependence of the specific heat around 1.0 K at zero magnetic<br />

field. This anomaly is shifted towards higher temperatures with increasing applied<br />

magnetic field, and a release of the residual entropy is observed simultaneously.<br />

[1] T. Schleid et al., Z. Anorg. Allg. Chem. 626 (2000) 2429.<br />

QD14<br />

Physical properties of the layered oxypnictides (CeO)MnPn; Pn=As,<br />

Sb<br />

Morosawa Yasuhiro 1 , Takase Koichi 1 *, Onizawa Manami 1 , Moriyoshi Chikako 2 ,<br />

Kuroiwa Yoshihiro 1 , Watanabe Tadataka 1 and Takano Yoshiki 1<br />

1 Nih<strong>on</strong> University, Japan<br />

2 Hiroshima University, Japan<br />

Recently, the layered ir<strong>on</strong> oxypnictides (LaO)FePn ; Pn = P, As, Sb, which bel<strong>on</strong>g to the tetrag<strong>on</strong>al system,<br />

have attracted much attenti<strong>on</strong> due to the discovery of the superc<strong>on</strong>ductors (LaO)FeP [1] and (LaO)FeAs [2].<br />

Many efforts have been dedicated to explore the superc<strong>on</strong>ductor with the highest transiti<strong>on</strong> temperature.<br />

In this tidal stream, many new materials with different physical properties have been found. In case of<br />

selecti<strong>on</strong> of the cerium atom as a rare earth element, these materials of (CeO)FeP [3], (CeO)FeAs [4],<br />

(CeO)CoP [5], (CeO)CoAs [6] show the typical metallic properties and the Fermi liquid behaviors at<br />

low temperature. In these systems, the 3d electr<strong>on</strong>s of the ir<strong>on</strong> and cobalt have finite density of state at<br />

the Fermi energy, and the cerium atom provides the f electr<strong>on</strong>s as carriers at the same time. Namely, it is<br />

difficult to know which effects are dominant. In our group, the semic<strong>on</strong>ductor based materials (LaO)MnPn<br />

have been focused and the substituti<strong>on</strong> effects of the rare earth elements <strong>on</strong> the physical properties have<br />

been investigated. (CeO)MnAs and (CeO)MnSb indicate metallic character and the Fermi liquid behaviors<br />

below 30K and 8 K, respectively due to the valence fluctuati<strong>on</strong> of the Ce f electr<strong>on</strong>s.<br />

[1] Y.Kamihara et al., PHYSICAL REVIEW B 77, 214515 (2008). [2] Y.kamihara et al., J. AM. CHEM. SOC.<br />

130, NO. 11, 3296-3297 (2008). [3] Y.Kamihara et al., Journal of Physics and Chemistry of Solids 69 2916-<br />

2918 (2008). [4] G. F. Chen et al., PHYSICAL REVIEW LETTERS 100, 247002 (2008). [5] C. Krellner et al.,<br />

PHYSICAL REVIEW B 404, 3206-3209 (2009). [6] Rajib Sarkar et al., Phys. Rev. B 82, 054423 (2010).<br />

QD15<br />

31P-NMR study of valence fluctuating compound EuPtP<br />

Takeshi Mito 1 , Koji Nishitani 1 , Takehide Koyama 1 , Koichi Ueda 1 , Takao Kohara 1 ,<br />

Akihiro Mitsuda 2 , Masaki Sugishima 2 and Hirofumi Wada 2<br />

1 University of Hyogo, Japan<br />

2 Kyushu University, Japan<br />

We report the results of the first 31P-NMR measurements <strong>on</strong> the hexag<strong>on</strong>al layered<br />

compound EuPtP. This compound exhibits two valence transiti<strong>on</strong>s at T1= 235 K<br />

and T2= 190 K. Various experiments, including magnetizati<strong>on</strong>, Eu Mossbauer, and<br />

x-ray diffracti<strong>on</strong> measurements [1-5], have been carried out in order to investigate the<br />

valence transiti<strong>on</strong>s so far, however the ordered structures below T1 and T2 have not<br />

been fully clarified. We observed 31P-NMR signals in all three phases. They show<br />

anomalies at T1 and T2, and the Knight shift of the 31P-NMR lines reach ~ 20 % at<br />

low temperatures due to large effective moments of magnetic Eu 2+ i<strong>on</strong>s. Below T2,<br />

three res<strong>on</strong>ance lines of 31P-NMR were observed, which should reflect local symmetry<br />

at the P-site. Based <strong>on</strong> these informati<strong>on</strong> obtained from the NMR measurements<br />

(spectrum and spin lattice relaxati<strong>on</strong> time T1, and so <strong>on</strong>), we discuss possible ordered<br />

structures at low temperatures of EuPtP.<br />

[1] N. Lossau et al., Z. Phys. B 74, 227 (1989). [2] N. Lossau et al., Z. Phys. B 77, 393 (1989). [3] G.<br />

Michels et al., Z. Phys. B 98, 75(1989). [4] A. Mitsuda et al., J. Phys: C<strong>on</strong>dens. Matter 22, 226003<br />

(2010). [5] T. Inami et al., Phys. Rev. B 82, 195133 (2010).


QD16<br />

Magnetic behavior of polycrystalline Eu 5Si 3 compound<br />

Sujata M. Patil 1 *, P. L. Paulose 2 and E. V. Sampathkumaran 2<br />

1 Wils<strong>on</strong> College, Mumbai 400007, India<br />

2 Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India<br />

The series R 5X 3 (R= light rare earth and X = Ga,Si,Ge,Sn,Sb), form in Cr 5B 3-type<br />

tetrag<strong>on</strong>al structure. There are two inequivalent ‘R’ sites in this structure, <strong>on</strong>e of them<br />

showing a very short distance between rare-earth atoms. Single crystal studies of Ce 5Si 3<br />

show that metamagnetic transiti<strong>on</strong> temperature is different al<strong>on</strong>g ‘a’ axis and ‘c’ axis,<br />

which was attributed to the two inequivalent sites of Ce atoms. Studies of R 5X 3 have<br />

been extensively reported for different rare earths with excepti<strong>on</strong> of Eu 5Si 3. Rietveld<br />

analysis of x-ray diffracti<strong>on</strong> shows the formati<strong>on</strong> Eu 5Si 3 in the Cr 5Br 3-type tetrag<strong>on</strong>al<br />

structure (space group I4/mcm). Magnetizati<strong>on</strong> display a prominent cusp around<br />

32K corresp<strong>on</strong>ding to antiferromagnetic ordering. Zero field cooled and field cooled<br />

magnetizati<strong>on</strong> is different below 30K, thereby showing a complex magnetic structure.<br />

Magnetizati<strong>on</strong> for applied magnetic fields up to 12 T shows that this sample does not<br />

undergo metamagnetic transiti<strong>on</strong> like that in Ce 5Si 3. Heat capacity shows a peak below<br />

32K which shifts to lower temperatures up<strong>on</strong> applicati<strong>on</strong> of magnetic fields, like in a<br />

typical antiferromagnet. Specific heat also shows a str<strong>on</strong>g magnetic field dependence<br />

below 20K, revealing the complex nature of magnetic ordering.<br />

1. R. Pottgen et. al.Z. Anorganische und allgemeine Chemie, 624, 1998, 945. 2. Y. Ushida, M.<br />

K<strong>on</strong>tani, Physica B, 281-282, (2000), 86-87. 3. Y. Ushida et. al. J. Phys. Soc. Japan, 70, (2001) 513.<br />

4. F. Canepa et al J. Alloys and Comp. 203, (1994) L11.<br />

QD17<br />

Valence fluctuati<strong>on</strong> study by using X-ray absorpti<strong>on</strong> and emissi<strong>on</strong><br />

spectroscopies at Yb L3-edge in YbNi 3X 9 (X=Al and Ga)<br />

Naomi Kawamura 1 , Masaichiro Mizumaki 1 , Hisashi Hayashi 2 , Noriko Kanai 2 ,<br />

Kazuyuki Matsubayashi 3 , Yoshiya Uwatoko 3 , Tetsuro Yamashita 4 and Shigeo Ohara 4<br />

1 Japan Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Institute (JASRI/SPring-8), Japan<br />

2 Department of Chemical and Biological Science, Japan Women's University, Japan<br />

3 Institute for Solid State Physics, University of Tokyo, Japan<br />

4 Department of Engineering Physics, Nagoya Institute of Technology, Japan<br />

Quantum criticality of Ce- and Yb-based heavy fermi<strong>on</strong> system has been recently<br />

discussed from a viewpoint of valence fluctuati<strong>on</strong> [1], thus the estimati<strong>on</strong> of valence<br />

guides in the soluti<strong>on</strong> for several anomalies observed near the quantum critical point<br />

(QCP). Recently, high-quality YbNi 3X 9 (X = Al and Ga) is newly synthesized [2,3] and is<br />

desired to investigate the electr<strong>on</strong>ic states including the valence state as a heavy fermi<strong>on</strong><br />

system. In order to clarify the Yb valence state in YbNi 3X 9, X-ray absorpti<strong>on</strong> and emissi<strong>on</strong><br />

spectroscopies at the Yb L3-edge have been performed at BL39XU of SPring-8. For<br />

YbNi 3Ga 9, the Yb valence of 2.71 at room temperature almost linearly decreases to 2.60 at<br />

55 K with decreasing temperature, and then the valence maintains a c<strong>on</strong>stant value at 2-55<br />

K, while the valence of YbNi 3Al 9 is almost trivalent in a temperature range of 2-300 K.<br />

Moreover, the XES spectra for YbNi 3X 9 give us detail informati<strong>on</strong> of Yb electr<strong>on</strong>ic states<br />

by comparis<strong>on</strong> with the result in several Yb-based compounds.<br />

[1] S. Watanabe, et al., Phys. Rev. Lett. 105, 186403 (2010). [2] S. Ohara, et al., J. Phys.: C<strong>on</strong>f. Ser.<br />

273, 012048 (2011). [3] T, Yamashita, et al., J. Phys. Soc. Jpn. 81, 034705 (2012).<br />

QD18<br />

Angle-resolved photoemissi<strong>on</strong> spectroscopy of mixed-valence Sm1-xYxS Keiichiro Imura 1 *, Tetsuya Hajiri 2 , Masaki Kaneko 2 , Yusuke Nishi 2 , Hiroyuki S.<br />

Suzuki 3 , Noriaki K. Sato 2 , Takahiro Ito 2 , Masaharu Matsunami 1 and Shin-ichi Kimura 1<br />

1<br />

UVSOR Facility, Institute for Molecular Science, Japan<br />

2<br />

Nagoya University, Japan<br />

3<br />

Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

It is known that samarium m<strong>on</strong>o-sulfide (SmS) exhibits an insulator-to-metal transiti<strong>on</strong>,<br />

so called Black-to-Golden phase transiti<strong>on</strong>, by the applicati<strong>on</strong> of pressure or by the<br />

substituti<strong>on</strong> of Sm i<strong>on</strong>s [1,2]. Although extensive studies to investigate the mechanism<br />

of this transiti<strong>on</strong> as well as the ground state of golden phase have been made, the phase<br />

transiti<strong>on</strong> has net been perfectly clarified yet. In this study, we focus <strong>on</strong> Sm 1-xY xS<br />

system in order to investigate the electr<strong>on</strong>ic structure of these two phases by an angleresolved<br />

photoemissi<strong>on</strong> spectroscopy (ARPES). Single crystals of Sm 1-xY xS (x = 0, 0.17,<br />

0.33) were grown by the Bridgman technique using a high-frequency inducti<strong>on</strong> furnace<br />

installed in NIMS. Photoemissi<strong>on</strong> spectroscopy measurement <strong>on</strong> these crystals was<br />

performed at UVSOR-II BL5U end stati<strong>on</strong>. The obtained ARPES spectrum of pure<br />

SmS (x = 0) has an energy gap of about 0.4 eV which is c<strong>on</strong>sistent with a previous<br />

report [3]. This energy gap decreases with increasing x, and the top of the Sm 2+ 4f band<br />

touches the Fermi level in x = 0.33. This result suggests that the Golden phase induced<br />

by the yttrium substituti<strong>on</strong> is a mixed-valence state.<br />

[1] A. Jayaraman, et al., Phys. Rev. Lett. 25 (1970) 1430. [2] L. J. Tao and F. Holtzberg Phys. Rev.<br />

B 15 (1975) 3842. [3] T. Ito, et al., Phys. Rev. B 65 (2002) 155202.<br />

QE01<br />

QE02<br />

QE03<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Critical behavior of a spin-1 triangular lattice Ising antiferromagnet<br />

Milan Zukovic* and Andrej Bobak<br />

Department of Theoretical Physics and Astrophysics, Faculty of Science, P. J. Safarik<br />

University, Slovakia<br />

We employ M<strong>on</strong>te Carlo simulati<strong>on</strong>s in order to investigate critical behavior of a<br />

frustrated spin-1 Ising antiferromagnet <strong>on</strong> a triangular lattice in the presence of a<br />

single-i<strong>on</strong> anisotropy. It has been previously found that no l<strong>on</strong>g-range order can exist<br />

in the system with spin 1/2 [1] but it can occur if the spin is larger than some critical<br />

value estimated as 11/2 [2]. We dem<strong>on</strong>strate that even small amount of the singlei<strong>on</strong><br />

anisotropy can change this scenario. More specifically, we show that l<strong>on</strong>g-range<br />

order can exist in the low-temperature regi<strong>on</strong> even below this critical value, namely<br />

for spin 1, within a certain range of the single-i<strong>on</strong> anisotropy strength. At higher<br />

temperatures we identify another phase of the Berezinsky-Kosterlitz-Thouless type<br />

characterized by a power-law decay of the spin correlati<strong>on</strong> functi<strong>on</strong>. We perform finitesize<br />

scaling analyses to calculate the correlati<strong>on</strong> decay exp<strong>on</strong>ent. Subsequently, we<br />

estimate the critical boundaries of both phases and plot the phase diagram as a functi<strong>on</strong><br />

of the single-i<strong>on</strong> anisotropy strength. This work was supported by the Scientific Grant<br />

Agency of Ministry of Educati<strong>on</strong> of Slovak Republic (Grant No. 1/0234/12).<br />

[1] G.H. Wannier, Phys. Rev. 79 (1950) 357. [2] Y. Yamada et.al., J. Magn. Magn. Mater. 140-144<br />

(1995) 1749.<br />

Selectively diluted triangular lattice Ising antiferromagnet in an<br />

external magnetic field<br />

Andrej Bobak*, Michal Borovsky and Milan Zukovic<br />

Department of Theoretical Physics and Astrophysics, Faculty of Science, P.J. Safarik<br />

University, Slovakia<br />

It is well known that the pure Ising model with nearest-neighbor antiferromagnetic<br />

interacti<strong>on</strong>s <strong>on</strong> a triangular lattice shows no l<strong>on</strong>g-range ordering due to a high degree<br />

of frustrati<strong>on</strong>. Diluti<strong>on</strong> of <strong>on</strong>e out of three sublattices with n<strong>on</strong>magnetic impurities<br />

can relieve the geometrical frustrati<strong>on</strong> globally and, above a certain diluti<strong>on</strong> threshold,<br />

the system starts showing l<strong>on</strong>g-range magnetic ordering characterized by the sec<strong>on</strong>dorder<br />

phase transiti<strong>on</strong>s [1]. Within the effective-field theory with correlati<strong>on</strong>s we<br />

dem<strong>on</strong>strate that the presence of a finite external field in the selectively diluted system<br />

can dramatically change its critical behavior. In particular, above a certain field value<br />

the system starts displaying tricritical behavior, i.e., as the diluti<strong>on</strong> increases the phase<br />

transiti<strong>on</strong> becomes initially of first order and <strong>on</strong>ly up<strong>on</strong> further diluti<strong>on</strong> changes to<br />

the sec<strong>on</strong>d order. We c<strong>on</strong>firm the existence of the first-order transiti<strong>on</strong> in the regi<strong>on</strong><br />

of moderate diluti<strong>on</strong> and relatively high fields by M<strong>on</strong>te Carlo simulati<strong>on</strong>s. An Ising<br />

antiferromagnet <strong>on</strong> a h<strong>on</strong>eycomb lattice is treated as a special case when <strong>on</strong>e sublattice<br />

is completely removed by diluti<strong>on</strong>. This work was supported by the Grant VEGA No.<br />

1/0234/12.<br />

[1] H. Kaya, A.N. Berker, Phys. Rev. E 62 (2000) R1469.<br />

Possible magnetic transiti<strong>on</strong> observed in S=1/2 kagome<br />

antiferromagnet volborthite by high field ESR<br />

Hitoshi Ohta 1 *, Wei-min Zhang 1 , Susumu Okubo 1 , Takahiro Sakurai 2 , Yoshihiko<br />

Okamoto 3 , Hiroyuki Yoshida 4 and Zenji Hiroi 3<br />

1 Molecular Photoscience Research Center, Kobe University, Japan<br />

2 Center for Supports to Research and Educati<strong>on</strong> Activities, Kobe University, Japan<br />

3 Institute for Solid State Physics, University of Tokyo, Japan<br />

4 Nati<strong>on</strong>al Institute for Materials Science (NIMS), Japan<br />

Due to the recent discovery of model substances, such as ZnCu 3(OH) 6C l2<br />

(herbertsmithite), Cu 3V 2O 7(OH) 2∙ 2H 2O(volborthite) and BaCu 3V 2O 8(OH) 2(vesignieite),<br />

S=1/2 kagome antiferromanet has attracted much interest experimentally, and we<br />

suggested a gapless spin liquid state in vesignieite [W. Zhang et al, J, Phys. Soc. Jpn.<br />

79 (2010) 023708.]. In this paper we will report <strong>on</strong> high field ESR results of volborthite<br />

powder sample. For the spin dynamics volborthite shows the g-shift below around 20 K<br />

similar to vesignieite [H. Ohta et al., Phys. Status Solidi B 247(2010) 679.]. However,<br />

it shows two modes at 1.8 K, mode A with a very small gap of about 40 GHz (1.9 K)<br />

and mode B with no gap. Existence of mode B may suggest the spin liquid state with<br />

no spin gap at 1.8 K. Moreover, two modes cross at around 4.5 T, which corresp<strong>on</strong>ds<br />

to magnetizati<strong>on</strong> anomaly at 4.3 T. Detailed frequency dependence measurement up to<br />

30 T at 1.8 K shows also new anomaly at 14 T. Possible magnetic transiti<strong>on</strong>s at 4.3 and<br />

14 T will be discussed in c<strong>on</strong>necti<strong>on</strong> with recent NMR result <strong>on</strong> volborthite powder.<br />

Finally very recent high-filed ESR result using single crystal of volborthite will be also<br />

presented.<br />

July 8 - 13, 2012 Busan, Korea 85<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QE04<br />

Field-induced staggered moment stabilizati<strong>on</strong> in frustrated quantum<br />

magnets<br />

Burkhard Schmidt*, Mohammad Siahatgar and Peter Thalmeier<br />

Max-Planck-Institut fur Chemische Physik fester Stoffe, Germany<br />

For low-dimensi<strong>on</strong>al frustrated magnets, the dependence of the staggered moment<br />

<strong>on</strong> a magnetic field is n<strong>on</strong>m<strong>on</strong>ot<strong>on</strong>ic: For small and intermediate fields, quantum<br />

fluctuati<strong>on</strong>s are gradually suppressed, leading to an increase of the staggered moment<br />

as functi<strong>on</strong> of the field strength. For large applied magnetic fields, the classically<br />

expected field dependence is recovered, namely a m<strong>on</strong>ot<strong>on</strong>ous decrease with increasing<br />

field strength. The staggered moment is eventually suppressed when reaching the<br />

fully polarized state at saturati<strong>on</strong>. The quantitative analysis of this behavior is an<br />

excellent tool to determine the frustrati<strong>on</strong> parameter of magnetic compounds. We have<br />

developed a general finite-size scaling scheme for numerical exact-diag<strong>on</strong>alizati<strong>on</strong><br />

data of low-dimensi<strong>on</strong>al frustrated magnets, which we apply to the recently measured<br />

field dependence of the magnetic neutr<strong>on</strong> scattering intensity of Cu(pz) 2(ClO 4) 2 in<br />

the framework of the S=1/2 two-dimensi<strong>on</strong>al J _1-J 2 Heisenberg model. We also apply<br />

linear spin-wave theory to complement our numerical findings. Our results show<br />

that Cu(pz) 2(ClO 4) 2 is a quasi-2D antiferromagnet with intermediate frustrati<strong>on</strong> J_2/<br />

J_1=0.2. A self-c<strong>on</strong>sistent RPA theory for the magnetic ordering temperature shows<br />

that with this ratio the observed reentrant behavior of the latter as functi<strong>on</strong> of the<br />

applied magnetic field can be understood as a c<strong>on</strong>sequence of the reduced quantum<br />

fluctuati<strong>on</strong>s as well.<br />

QE05<br />

Structural and magnetic properties of single crystals of volborthite<br />

comprising a distorted spin-1/2 kagome lattice<br />

Hajime Ishikawa 1 *, Yoshihiko Okamoto 1 , Junichi Yamaura 1 , Hiroyuki Yoshida 2 ,<br />

Gøran J. Nilsen 1 and Zenji Hiroi 1<br />

1 ISSP, the University of Tokyo, Japan<br />

2 NIMS, Japan<br />

In geometrically frustrated magnets, exotic ground states such as a spin liquid<br />

are expected to realize as a result of competing magnetic interacti<strong>on</strong>. Volborthite<br />

Cu 3V 2O 7(OH) 2∙2H 2O has drawn attenti<strong>on</strong> as a model compound for the distorted spin-<br />

1/2 kagome antiferromagnet. Previous studies using powder samples showed a peculiar<br />

magnetic transiti<strong>on</strong> at 1 K. Recently, H. Yoshida et al. synthesized a small single<br />

crystal, and found a structural phase transiti<strong>on</strong> at 310 K and two magnetic transiti<strong>on</strong>s at<br />

around 1 K, which have not been observed in powder samples. To clarify the physical<br />

properties of volborthite at low temperatures, we tried to synthesize a large and highquality<br />

single crystal and obtained large single crystals of 2.5×1.5×0.1 mm in size as a<br />

result of improving synthesis c<strong>on</strong>diti<strong>on</strong>s. By means of single crystal XRD, we found<br />

a new crystal polymorph at room temperature which crystallizes in space group C2/<br />

c, not in C2/m as reported before. There is a phase transiti<strong>on</strong> up<strong>on</strong> cooling at around<br />

290 K to an I2/a phase, similar as in the C2/m phase. In this presentati<strong>on</strong>, we show the<br />

differences of structure and magnetic properties between various polymorphs.<br />

QE06<br />

High-field study of multiferroic Ni 3V 2O 8<br />

Junfeng Wang 1 , Masashi Tokunaga 2 , Zhangzhen He 3 and Koichi Kindo 2<br />

1 Wuhan Nati<strong>on</strong>al High Magnetic Field Center, China<br />

2 The Institute for Solid State Physics (ISSP), The University of Tokyo, Japan<br />

3 Fujian Institute of Research <strong>on</strong> the Structure of Matter, Chinese Academy of<br />

Sciences, China<br />

WITHDRAWN<br />

86 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QE07<br />

Gapless spin excitati<strong>on</strong> of the triangular-lattice antiferromagnet<br />

Hiroki Nakano 1 * and Toru Sakai 2<br />

1 University of Hyogo, Japan<br />

2 JAEA, SPring8, Japan<br />

Two-dimensi<strong>on</strong>al frustrated magets including the triangular-lattice antiferromagnet<br />

(TLA) have attracted much attenti<strong>on</strong>. However, a useful method am<strong>on</strong>g unbaised<br />

computati<strong>on</strong>al methods is limited to being the numerical-diag<strong>on</strong>alizati<strong>on</strong> method that<br />

can treat <strong>on</strong>ly small systems. In spite of such situati<strong>on</strong>, great efforts have been d<strong>on</strong>e for<br />

studies of the TLA; it is widely believed that the ground state of TLA has a l<strong>on</strong>g-range<br />

order of 120-degree structure. The existence of this order indicates that spin excitati<strong>on</strong><br />

is gapless; however, the system size (N) dependence of the singlet-triplet energy<br />

difference of finite-size clusters shows a peculiarity that a n<strong>on</strong>zero spin gap seems to<br />

survive in the extrapolati<strong>on</strong> with respect to N[1]. Under circumstances, we calculate the<br />

singlet-triplet energy difference of possible all the finite-size clusters up to 39 sites by<br />

our MPI-parallelized code of the numerical-diag<strong>on</strong>alizati<strong>on</strong> method. The analysis used<br />

in the study of the spin-gap issue of the kagome-lattice antiferromagnet[2] is applied<br />

to the TLA. The present examinati<strong>on</strong> successfully c<strong>on</strong>firms a gapless spin excitati<strong>on</strong>,<br />

which is c<strong>on</strong>sistent with the existence of the l<strong>on</strong>g-range order.<br />

[1] J. Richter et al.: Phys. Rev. B 70 (2004) 174454. [2] H. Nakano and T. Sakai: J. Phys. Soc. Jpn.<br />

80 (2011) 053704.<br />

QE08<br />

Magnetic properties of the spin-1/2 kagome antiferromagnets:<br />

vesignieite BaCu 3V 2O 8(OH) 2 and CdCu 3(OH) 6Br 2<br />

Yoshihiko Okamoto 1 *, Makoto Yoshida 1 , Hajime Ishikawa 1 , Gøran J. Nilsen 1 ,<br />

Hiroyuki Yoshida 2 , Masashi Takigawa 1 and Zenji Hiroi 1<br />

1 Institute for Solid State Physics, Univ. of Tokyo, Japan<br />

2 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

An ideal model system for the spin-1/2 kagome antiferromagnet has not yet been<br />

obtained and the search for that is still going <strong>on</strong>. Here we report the magnetic<br />

properties of two Cu minerals, vesignieite BaCu 3V 2O 8(OH) 2 and CdCu 3(OH) 6Br 2, both<br />

of which comprise spin-1/2 kagome lattices. Vesignieite has a nearly isotropic kagome<br />

lattice and was found to show neither Neel order nor a spin-glass transiti<strong>on</strong> above 2<br />

K [1]. However, the intrinsic ground state has remained unsolved, because previous<br />

samples c<strong>on</strong>tained many impurity spins caused by the low crystallinity. Recently, we<br />

succeeded in improving the sample quality by optimizing preparati<strong>on</strong> parameters under<br />

hydrothermal c<strong>on</strong>diti<strong>on</strong>s. The magnetic susceptibility of the new sample increases<br />

steeply below 15 K, followed by a sharp peak at 9 K that is indicative of l<strong>on</strong>g-range<br />

antiferromagnetic order. CdCu 3(OH) 6Br 2 has an isotropic kagome lattice made of Cu 2+<br />

i<strong>on</strong>s. The compound is an antiferromagnet with a Weiss temperature of -48 K and<br />

shows l<strong>on</strong>g-range antiferromagnetic order at 7 K. Thus, both the compounds show<br />

l<strong>on</strong>g-range order at rather high temperatures, which may be due to significantly large<br />

interlayer magnetic interacti<strong>on</strong>s.<br />

[1] Y. Okamoto et al., J. Phys. Soc. Jpn. 78, 033701 (2009).<br />

QE09<br />

Spin dynamics of triangular spin tubes<br />

Hirotaka Manaka 1 * and Yoko Miura 2<br />

1 Graduate School of Science and Engineering, Kagoshima University, Japan<br />

2 Suzuka Nati<strong>on</strong>al College of Technology, Japan<br />

Triangular spin tubes bel<strong>on</strong>g to a new category of <strong>on</strong>e-dimensi<strong>on</strong>al Heisenberg<br />

antiferromagnets al<strong>on</strong>g the tubes coexisting with geometrically frustrated spin systems<br />

in the triangular plane. Recently, we discovered that chromium fluoride CsCrF 4 forms<br />

ideal equilateral triangular spin tubes with S=3/2[1]. All Cr i<strong>on</strong>s are at equivalent sites,<br />

and each angle of Cr-Cr-Cr in the triangular plane is 60 deg.[2] Because superexchange<br />

interacti<strong>on</strong>s through the three Cr-F-Cr paths in each equilateral triangle may be kept<br />

in equilibrium at 0 K, we propose res<strong>on</strong>ating spin-singlet pairs in each equilateral<br />

triangle. From DC magnetic susceptibility and adiabatic heat capacity data above 1.5 K,<br />

we c<strong>on</strong>cluded that there is no magnetic phase transiti<strong>on</strong>. Therefore, CsCrF 4 c<strong>on</strong>sists of<br />

a gapless spin-liquid ground state encompassing res<strong>on</strong>ating spin-singlet pairs not <strong>on</strong>ly<br />

in each equilateral triangle but also al<strong>on</strong>g the tubes[2]. To clarify spin dynamics of the<br />

spin-liquid ground state, we performed linear and n<strong>on</strong>linear AC magnetic susceptibility<br />

measurements <strong>on</strong> CsCrF 4. As a result, temperature dependence of a linear susceptibility<br />

exhibits a positive peak at around 4 K, while a n<strong>on</strong>linear susceptibility exhibits a broad<br />

and negative peak at around 3.5 K. We found that a spin-glass like state was realized<br />

below 4 K.<br />

[1] H. Manaka et al., J. Phys. Soc. Jpn. 78, 093701 (2009). [2] H. Manaka et al., J. Phys. Soc. Jpn.<br />

80, 084714 (2011).


QE10<br />

Origin of field induced magnetic ordering in frustrated h<strong>on</strong>eycomb<br />

lattice antiferromagnet<br />

Susumu Okubo 1 *, Tom<strong>on</strong>ari Ueda 2 , Wei-min Zhang 3 , Takahiro Sakurai 4 , Masashi Fujisawa 1 , Hitoshi<br />

Ohta 1 , Nozomi Ohnishi 5 , Masaki Azuma 6 , Yuichi Shimakawa 5 and Nobuhiro Kumada 7<br />

1 Molecular Photoscience Research Center, Kobe University, Japan<br />

2 Graduate School of Science, Kobe University, Japan<br />

3 Center for Collaborative Research and Technology Development, Kobe University, Japan<br />

4 Center for Supports to Research and Educati<strong>on</strong> Activities, Kobe University, Japan<br />

5 Institute for Chemical Research, Kyoto University, Japan<br />

6 Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

7 Graduate School of Medicine and Engineering, University of Yamanashi, Japan<br />

The ground state of h<strong>on</strong>eycomb lattice antiferromagnet (HLAF) have been c<strong>on</strong>sidered theoretically<br />

to be the Neel state similar to the square lattice antiferromagnet because both antiferromagnets<br />

are bipartite lattices. However, the h<strong>on</strong>eycomb lattice has smaller coordinati<strong>on</strong> number 3 than<br />

the square lattice of 4 and it is close to the <strong>on</strong>e dimensi<strong>on</strong>al chain. Therefore, the str<strong>on</strong>ger spin<br />

fluctuati<strong>on</strong> is expected in the HLAF. Actually, anomalous spin dynamics are reported in S=1/2<br />

HLAF InCu 3/2V 1/3O 3 [1]. On the other hand, the spin liquid state is expected in S=3/2 HLAF<br />

Bi 3Mn 4O 12(NO 3) due to no l<strong>on</strong>g range order down to 0.4K despite of the large Weiss temperature.<br />

Although no spin gap has been observed in the magnetic susceptibility of Bi 3Mn 4O 12(NO 3),<br />

it shows the field-induced magnetic ordering (FIMO) above around 6 T. Neutr<strong>on</strong> diffracti<strong>on</strong><br />

measurements c<strong>on</strong>firmed FIMO state and suggested that Dzyaloshinski-Moriya (DM) interacti<strong>on</strong><br />

plays an important role in the FIMO state. In order to estimate the DM interacti<strong>on</strong>, high-field ESR<br />

measurements have been performed. The D-term of DM interacti<strong>on</strong> is estimated to be 1.3K from<br />

the analysis of observed antiferromagnetic res<strong>on</strong>ance mode. Origin of FIMO will be discussed in<br />

c<strong>on</strong>necti<strong>on</strong> with the DM interacti<strong>on</strong> and the other magnetic anisotropy.<br />

[1] S. Okubo et al, J. Phys. Soc. Jpn. 80 (2011) 023705<br />

QE11<br />

Semi-classical spin-liquid state as a low-energy excited state in<br />

frustrated quantum spin systems <strong>on</strong> triangle-based lattice system<br />

Makoto Isoda 1 , Hiroki Nakano 2 and T^oru Sakai 3<br />

1 Kagawa University, Japan<br />

2 University of Hyogo, Japan<br />

3 JAEA SPring-8, Japan<br />

The magnetic and the thermal properties of the spin-1/2 Heisenberg antiferromagnets <strong>on</strong> the trianglebased<br />

lattice are summarized , focusing <strong>on</strong> the realizati<strong>on</strong> of the semi-classical spin-liquid state of<br />

the res<strong>on</strong>ating doublet trimers formed <strong>on</strong> triangles, through the calculati<strong>on</strong>s for various systems<br />

such as the triangular , the kagome, the triangulated-kagome1), the Sierpinski-gasket like2) and the<br />

spatially anisotropic triangular lattices, which interpolates the triangular and the kagome lattices.<br />

The calculati<strong>on</strong>s have been performed by the numerical diag<strong>on</strong>alizati<strong>on</strong> method. On these systems,<br />

the peculiar behaviors have been found in the Heisenberg3,4) and the Ising5) models for spin-<br />

1/2 <strong>on</strong> those triangle-based lattices with nearest neighbor (nn) antiferromagnetic interacti<strong>on</strong>. The<br />

peculiarities are the bending of the magnetic susceptibility as a functi<strong>on</strong> of temperature, the more than<br />

two peaks structure <strong>on</strong> the specific heat and the 1/3 magnetizati<strong>on</strong> plateau under magnetic field. Each<br />

of these peculiarities appears at the characteristic temperature or magnetic field corresp<strong>on</strong>ding to the<br />

magnitude of nn interacti<strong>on</strong>, suggesting the predominance of the doublet trimer low energy excited<br />

state. The peculiarities reveal as an intrinsic character of the systems with the nn antiferromagnetic<br />

interacti<strong>on</strong> depending <strong>on</strong> whether the lattice is formed by the equilateral triangle as a unit cell or not.<br />

1) M.G<strong>on</strong>zalez et al., Mol. Cry. Liq. Cry. 233 (1993) 317. 2) T. Stosic et al., Phys. Rev. E 49 (1994) 1009. 3) M.Isoda,<br />

H.Nakano and T.Sakai, Mod. Phys. Lett. B 25 (2011) 909. 4) M.Isoda, H.Nakano and T.Sakai, J. Phys. Soc. Jpn. 80 (2011)<br />

084704. 5) M.Isoda, J. Phys.: C<strong>on</strong>dens. Matter 20 (2008) 315202.<br />

QE12<br />

High pressure and low-temperature 31P NMR study of the twodimensi<strong>on</strong>al<br />

frustrated square lattice compound BaCdVO(PO4) 2<br />

Yuji Furukawa 1 , Beas Roy 1 , Ramesh Nath 2 , David C Johnst<strong>on</strong> 1 , Yasuhiro Komaki 3 ,<br />

Hideto Fukazawa 3 and Yoh Kohori 3<br />

1<br />

Department of Physics and Astr<strong>on</strong>omy, Iowa State University / Ames Laboratory,<br />

USA<br />

2<br />

Indian Institute of Science Educati<strong>on</strong> and Research, India<br />

3<br />

Department of Physics, Chiba University, Japan<br />

We report first NMR study under pressures <strong>on</strong> BaCdVO(PO 4) 2, a S = 1/2 frustrated<br />

square-lattice (FSL) compound with a nearest neighbor exchange coupling J1 ~ - 3.36<br />

K and a next-nearest neighbor exchange coupling J2 ~ 3.53 K bearing J2/ J1 ~ 1.05.<br />

Based <strong>on</strong> the J2/J1 ratio, the system is known to be located close to the disordered<br />

ground state (known as 'nematic state') regime of the phase diagram. We have<br />

carried out 31P-NMR measurements under high pressure (up to ~ 2 GPa) and at low<br />

temperatures (down to ~0.1 K) using a diluti<strong>on</strong> refrigerator to investigate the pressure<br />

effects <strong>on</strong> the magnetic properties of the system from microscopic point of view. Under<br />

ambient pressure, we observed a sharp peak in 31P spin lattice relaxati<strong>on</strong> rate (1/T1)<br />

at TN ~ 1.05 K at H = 2.67 T, which corresp<strong>on</strong>ds to the antiferromagnetic ordering<br />

temperature. With increasing pressure, the peak positi<strong>on</strong> of 1/T1 shifts to lower<br />

temperature. This indicates that TN decreases with the applicati<strong>on</strong> of pressure. We will<br />

discuss pressure effects <strong>on</strong> magnetic state based <strong>on</strong> the temperature dependence of the<br />

NMR spectra and of the 1/T1 under different magnetic fields and pressures.<br />

QE13<br />

QE14<br />

QE15<br />

Str<strong>on</strong>g geometrical frustrati<strong>on</strong> in Fe oxychalcogenide<br />

Sungdae Ji 1 , K. Horigane 2 and K. Yamada 3<br />

1 CROSS, Japan<br />

2 University of Virginia, USA<br />

3 Tohoku University, Japan<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Kasteleyn transiti<strong>on</strong>s in the spin ice Dy2Ti2O7 Hiroaki Kadowaki 1 *, Naohiro Doi 1 , Hiroshi Takatsu 1 , Ryuji Higasginaka 1 , Yuji Muro 2 , Kiyoichiro<br />

Motoya 3 , Rei Morinaga 4 , Taku J Sato 4 , Takashi Tayama 5 , Toshiro Sakakibara 4 , Kazuyuki Matsuhira 6<br />

and Zenji Hiroi 4<br />

1<br />

Department of Physics, Tokyo Metropolitan University, Japan<br />

2<br />

Toyama Prefectural University, Japan<br />

3<br />

Department of Physics, Tokyo University of Science, Japan<br />

4<br />

Institute for Solid State Physics, University of Tokyo, Japan<br />

5<br />

Department of Physics, University of Toyama, Japan<br />

6<br />

Department of Electr<strong>on</strong>ics, Kyushu Institute of Technology, Japan<br />

The spin ice model in the pyrochlore lattice, e.g. Dy 2Ti 2O 7, c<strong>on</strong>sisting of corner sharing tetrahedra<br />

has attracted much attenti<strong>on</strong> because of its intriguing frustrati<strong>on</strong> mechanism. The ground states of this<br />

system are macroscopically degenerate with the finite zero-temperature entropy, and the spins freeze<br />

in this manifold at low temperatures. The macroscopic degeneracy of the ground states is partly lifted<br />

under magnetic fields, where degrees of the degeneracy depend <strong>on</strong> directi<strong>on</strong> and strength of the field.<br />

Interesting theoretical predicti<strong>on</strong>s, which have not been seriously investigated to date by experiments,<br />

are Kasteleyn transiti<strong>on</strong>s [1] in three and two space dimensi<strong>on</strong>s, which may occur under magnetic<br />

fields al<strong>on</strong>g a [100] directi<strong>on</strong> [2] and fields tilted slightly from a [111] directi<strong>on</strong> [3]. These transiti<strong>on</strong>s<br />

are classified into topological phase transiti<strong>on</strong>s which are characterized by line (string) defects. We<br />

have investigated these possibilities in the spin ice compound Dy 2Ti 2O 7 using magnetizati<strong>on</strong> and<br />

specific heat measurements.<br />

[1] P. W. Kasteleyn, J. Math. Phys. 4, 287 (1963). [2] L. D. C. Jaubert et al. Phys. Rev. Lett. 100,<br />

067207 (2008). [3] R. Moessner, S. L. S<strong>on</strong>dhi, Phys. Rev. B 68, 064411 (2003).<br />

Novel frustrated quantum antiferromagnets in the solid-soluti<strong>on</strong><br />

Cs 2CuCl 4-xBr x through site-selective halide substituti<strong>on</strong><br />

Bernd Wolf*, Pham Thanh C<strong>on</strong>g, Natalia Kruger, Franz Ritter, Wolf Assmus and<br />

Michael Lang<br />

Physics Institute, Goethe-University Frankfurt (M), SFB/TR 49, D-60438 Frankfurt<br />

(M), Germany, Germany<br />

We report <strong>on</strong> the magnetic properties of tetrag<strong>on</strong>al and orthorhombic single crystals of the solid<br />

soluti<strong>on</strong> Cs 2CuCl 4-xBr x (0 ≤ x ≤ 4). Two phase regi<strong>on</strong>s, namely an A-type orthorhombic and a<br />

B-type tetrag<strong>on</strong>al structure, were detected in this system depending <strong>on</strong> the growing c<strong>on</strong>diti<strong>on</strong>s.<br />

The two known orthorhombic end-member compounds Cs 2CuCl 4 and Cs 2CuBr 4 are classified<br />

as quasi-two-dimensi<strong>on</strong>al quantum antiferromagnets with different degrees of magnetic<br />

frustrati<strong>on</strong>. By measurements of the magnetic susceptibility χ(T) <strong>on</strong> orthorhombic single<br />

crystals with different Br c<strong>on</strong>centrati<strong>on</strong>s, we found that the in-plane and out-of-plane magnetic<br />

correlati<strong>on</strong>s, probed by the positi<strong>on</strong> and height of a maximum in χ(T), respectively, do not show<br />

a smooth variati<strong>on</strong> with x. Instead three distinct c<strong>on</strong>centrati<strong>on</strong> regimes can be identified, which<br />

are separated by critical c<strong>on</strong>centrati<strong>on</strong>s xc1 = 1 and xc2 = 2. This unusual magnetic behaviour<br />

can be explained by c<strong>on</strong>sidering the structural peculiarities of the materials, which support a<br />

site-selective replacement of Cl- by Br- i<strong>on</strong>s [1]. C<strong>on</strong>sequently, the critical c<strong>on</strong>centrati<strong>on</strong>s xc1<br />

(xc2) mark particularly interesting systems, where <strong>on</strong>e (two) halide-sublattice positi<strong>on</strong>s are fully<br />

occupied. The magnetic properties of the tetrag<strong>on</strong>al phase of Cs 2CuCl 4-xBr x differ str<strong>on</strong>gly from<br />

those of the orthorhombic variants, reflecting changes in the Cu-coordinati<strong>on</strong>.<br />

[1] P. T. C<strong>on</strong>g et al., PRB 83, 064425, (2011)<br />

After Fe-based superc<strong>on</strong>ductors have emerged, it has generated a lot of c<strong>on</strong>troversies<br />

regarding to low ordered moments in parent compounds which have been explained<br />

by itinerant magnetism with Fermi surface nesting vs. magnetic frustrati<strong>on</strong> and/<br />

or fluctuati<strong>on</strong> effects in a large-local-moment system [1]. Very recently, Feoxychalcogenide<br />

has drawn attenti<strong>on</strong>, because it has been identified as a layered<br />

insulating antiferromagnet with the geometrically frustrated, so-called, “double<br />

diag<strong>on</strong>al stripe” spin structure which is realized <strong>on</strong>ly in Ir<strong>on</strong> telluride am<strong>on</strong>g the<br />

family of Fe-based superc<strong>on</strong>ductors [2,3]. Here, we report elastic and inelastic neutr<strong>on</strong><br />

scattering study <strong>on</strong> La 2O 2Fe 2OSe 2. Our elastic neutr<strong>on</strong> measurement at 5 K shows that<br />

magnetic Bragg peaks are diffusive and a obtained magnetic moment is 2.2 μ_B, which<br />

is smaller than a localized spin, S=5/2. Inelastic neutr<strong>on</strong> scattering measurement shows<br />

that a str<strong>on</strong>g magnetic fluctuati<strong>on</strong> survives even at 300 K far above magnetic transiti<strong>on</strong><br />

temperature, T_N = 90 K. Moreover, observed dispersive excitati<strong>on</strong> reveals that the<br />

3rd nearest neighbor interacti<strong>on</strong> is the key to explain a magnetic ground state <strong>on</strong> the<br />

geometrically frustrated lattice.<br />

[1]. David C. Johnst<strong>on</strong>, Adv. in Phys. 59, 803 (2010). [2]. Jian-Xin Zhu et al., Phys. Rev. Lett. 104,<br />

216405 (2010). [3]. David G. Free and John S. O. Evans, Phys. Rev. B 81, 214433 (2010).<br />

July 8 - 13, 2012 Busan, Korea 87<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QE16<br />

Magnetic properties of the frustrated magnet Cu5(PO4) 3(OH) 4 <strong>on</strong> a<br />

peculiar spin network composed of pentag<strong>on</strong>s and triangles<br />

Hikomitsu Kikuchi 1 , Nguyen Thi Tinh Y 1 , Yutaka Fujii 2 , Masashi Fujisawa 3 , Akira<br />

Matsuo 4 and Koichi Kindo 4<br />

1<br />

Department of Applied Physics, University of Fukui, Japan<br />

2<br />

Research Center for Development of Far-Infrared Regi<strong>on</strong>, University of Fukui,<br />

Japan<br />

3<br />

Research Center for Low Temperature Physics, Tokyo Tech, Japan<br />

4<br />

ISSP, The University of Tokyo, Japan<br />

Orthorombic Cu 5(PO 4) 2(OH) 4 (pseudomalachite) is a layered compound. Each Cu-O<br />

layer in this compound is well separated by PO 4 tetrahedr<strong>on</strong>s. Spin network in bcplane<br />

of pseudomlachite is composed of triangles and pentag<strong>on</strong>s, which will induce the<br />

spin frustrati<strong>on</strong> effect. This network can be a new type of geometrically frustrated spin<br />

lattice. Magnetic susceptibility, specific heat, high field magnetizati<strong>on</strong> are measured to<br />

study magnetic properties of Cu 5(PO 4) 2(OH) 4 using natural mineral samples. Magnetic<br />

ordering is observed at around 4.2 K. Spin entropy change at the transiti<strong>on</strong> temperature<br />

is about <strong>on</strong>e fifth times smaller than that expected for a usual l<strong>on</strong>g range order. 1/5<br />

magnetizati<strong>on</strong> plateau is observed in the high field magnetizati<strong>on</strong> curve. The plateau<br />

can be explained based <strong>on</strong> the simple model in which the spin network is assumed to<br />

be composed of chain, dimer and m<strong>on</strong>omer units.<br />

QE17<br />

Single crystal growth and magnetic properties of novel kagome<br />

compound KMn3Ge2O9<br />

Shigeo Hara* and Hirohiko Sato<br />

Department of Physics, Chuo-univ, Japan<br />

We have succeeded in synthesizing single crystals of a novel manganese oxide<br />

KMn 3Ge 2O 9 by a hydrothermal method. This compound has a hexag<strong>on</strong>al unit cell<br />

with lattice c<strong>on</strong>stants a = 11.77 Å and c = 13.77 Å. In this structure, edge-shared<br />

MnO 6 octahedra form layers separated by GeO 4 tetrahedra. In each layer, Mn i<strong>on</strong>s<br />

with S = 2 spin form a rippled kagome lattice. Therefore, we can expect a frustrated<br />

magnetism. We measured temperature dependence of the magnetic susceptibility <strong>on</strong> a<br />

single crystal. The result suggests the existence of a str<strong>on</strong>g magnetic frustrati<strong>on</strong>. The<br />

Curie c<strong>on</strong>stant and Weiss temperature are estimated at 3.4 emu K/mol Mn and - 84<br />

K, respectively. The negative Weiss temperature indicates that the nearest-neighbor<br />

exchange interacti<strong>on</strong> am<strong>on</strong>g Mn i<strong>on</strong>s is antiferromagnetic. At low temperatures, the<br />

susceptibility suggests the existence of multiple magnetic phases. For example, the<br />

susceptibility shows an antiferromagnetic like transiti<strong>on</strong> at 40 K and a spin-glass like<br />

transiti<strong>on</strong> at 20 K under 0.5 T of magnetic field perpendicular to the kagome lattice.<br />

The successive transiti<strong>on</strong>s are also observed in other c<strong>on</strong>diti<strong>on</strong>s of magnetic field. We<br />

c<strong>on</strong>sider that these behaviors are driven from the str<strong>on</strong>g magnetic frustrati<strong>on</strong> of the<br />

kagome lattice.<br />

QE18<br />

Specific heat study of geometrically frustrated magnet botallackite<br />

Cu 2(OH) 3Cl<br />

Hiroki Morodomi 1 , Yuji Inagaki 1 , Tatsuya Kawae 1 , Masato Hagihala 2 and X.g. Zhen 3<br />

1 Department of Applied Quantum Physics, Kyushu University, Japan<br />

2 Department of Physics, Saga University, Japan<br />

3 Department of Physics, Saga University, Japan<br />

Specific heat measurements have been performed in the geometrically frustrated<br />

magnets botallackite, Cu 2(OH) 3Cl with the triangular structure of the Cu 2+ i<strong>on</strong>s. This<br />

is a different polymorphic form of clinoatacamite with the corner-sharing tetrahedral<br />

structure, which exhibits the coexistence of spin fluctuati<strong>on</strong> and l<strong>on</strong>g range ordering<br />

below 6.2 K[1]. The specific heat of botallackite shows a sharp peak at TN=7.0K and<br />

approximately exhibits T3-dependence with lowering temperature in zero magnetic<br />

field. When a magnetic field is applied, TN shifts to lower temperatures and the peaks<br />

disappears at H=8 T. Moreover, no residual entropy is observed at lower temperatures.<br />

[1] X.G. Zheng, et. al., Phys. Rev. Lett. 95 057201 (2005).<br />

88 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QE19<br />

Order and excitati<strong>on</strong>s in the frustrated quantum spin ladder BiCu 2PO 6<br />

P. Merchant 1 , S. Wang 2 , O. Zaharko 3 , Ch. Niedermayer 3 , L. P. Regnault 4 , M. Boehm 4 ,<br />

M. Kenzelmann 2 and Ch. Ruegg 3<br />

1 L<strong>on</strong>d<strong>on</strong> Centre for Nanotechnology, University College L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

2 Laboratory for Developments and Methods, Paul Scherrer Institute, Switzerland<br />

3 Laboratory for Neutr<strong>on</strong> Scattering, Paul Scherrer Institute, Switzerland<br />

4 Institut Laue-Langevin, France<br />

Quantum spin ladders are excepti<strong>on</strong>al model systems showing n<strong>on</strong>-trivial phenomena<br />

ranging from complex spin correlati<strong>on</strong>s in the ground state to rich phase diagrams with<br />

several quantum critical points. A fully quantitative understanding of their magnetic<br />

and thermodynamic properties may be achieved e.g. by powerful computati<strong>on</strong>al<br />

methods (DMRG, ED, b<strong>on</strong>d operators) [1, 2] and comparis<strong>on</strong> with high-precisi<strong>on</strong><br />

experimental data, which may <strong>on</strong>ly be possible in such model systems [3]. BiCu 2PO 6<br />

is a new prototypical model material in which the spin ladders are frustrated by nextnearest<br />

neighbour exchange al<strong>on</strong>g the ladder legs, furthermore it can be doped with<br />

n<strong>on</strong>-magnetic Zn 2+ impurities. The results of comprehensive neutr<strong>on</strong> scattering studies<br />

<strong>on</strong> single crystals are presented of the elementary excitati<strong>on</strong>s and spin Hamilt<strong>on</strong>ian of<br />

this frustrated ladder compound, as well as of the Zn-induced magnetic order and phase<br />

diagrams. The physics in this system is dominated by incommensurate correlati<strong>on</strong>s <strong>on</strong><br />

all energy scales.<br />

[1] P. Bouillot et al., Phys. Rev. B 83, 054407 (2011). [2] B. Normand and Ch. Ruegg, Phys. Rev. B<br />

83, 054415 (2011). [3] e.g. see B. Thielemann et al., Phys. Rev. Lett. 102, 107204 (2009).<br />

QE20<br />

Melting of the spin ice state in Dy 2(Ti 1-xZr x) 2O 7 without diluti<strong>on</strong> of rareearth<br />

i<strong>on</strong><br />

Yuta Kodama, Kousuke Tsuruta, Daisuke Akahoshi and Toshiaki Saito*<br />

Department of Physics, Faculty of Science, Toho University, Funabashi City, Chiba<br />

274-8510, Japan<br />

The pyrochlore Dy 2Ti 2O 7 is a spin ice material, in which the spins reside <strong>on</strong> the lattice of<br />

corner-sharing tetrahedra with single-i<strong>on</strong> anisotropy al<strong>on</strong>g each local axis. The effective<br />

ferromagnetic interacti<strong>on</strong> between spins leads to a highly degenerate ground state. Earlier<br />

researches [1][2] reported that the magnetic relaxati<strong>on</strong> shows three successive processes;<br />

thermally activated Arrhenius process above 13 K, quantum tunneling process between 4 K<br />

~ 13 K, and process with str<strong>on</strong>g spin correlati<strong>on</strong> below 4 K. The relaxati<strong>on</strong> in the medium<br />

temperature regime is the Davids<strong>on</strong>-Cole type [3] characterized by a wide distributi<strong>on</strong><br />

of relaxati<strong>on</strong> time τ with a cut-off τ. The diluti<strong>on</strong> of Dy causes disappearance of the ac<br />

susceptibility 15 K peak [1] due to a speeding up of relaxati<strong>on</strong> [2]. In this talk, we examined the<br />

magnetic relaxati<strong>on</strong> of Dy 2(Ti 1-xZr x) 2O 7 through ac magnetic susceptibility measurements in<br />

order to study B-site disorder effect. We found, for x above about 0.01, disappearance of the 15<br />

K peak, small frequency dependence, and substantial change of the magnetic relaxati<strong>on</strong> from<br />

the Davids<strong>on</strong>-Cole type into the Cole-Cole <strong>on</strong>e having no cut-off τ, indicating a major effect of<br />

B-site disorder <strong>on</strong> the spin ice state toward melting without diluti<strong>on</strong> of Dy i<strong>on</strong>.<br />

[1] J. Snyder et al., Phys. Rev. B 70 (2004) 184431. [2] G. Ehlers et al., J. Phys. C<strong>on</strong>dens. Matter 15<br />

(2003) L9. [3] K. Matsuhira et al., J. Phys. C<strong>on</strong>dens. Matter 13 (2001) L737. [4] L.D.Jaubert and<br />

P.C.Holdsworth, J. Phys. C<strong>on</strong>dens. Matter 23 (2011) 164222.<br />

QE21<br />

Unusual magnetic ordering of kagome lattice magnet<br />

[Cu3(CO3) 2(bpe) 3]•2ClO4 Hikomitsu Kikuchi 1 , Hayato Nakata 1 , Yutaka Fujii 2 and Toshifumi Taniguchi 3<br />

1<br />

Department of Applied Physics, University of Fukui, Japan<br />

2<br />

Research Center for Development of Far-Infrared Regi<strong>on</strong>, University of Fukui,<br />

Japan<br />

3<br />

Graduate School of Science, Osaka University, Japan<br />

Cu 2+ i<strong>on</strong>s in a hexag<strong>on</strong>al compound [Cu 3(CO 3) 2(bpe) 3]• 2ClO 4 (space group; P-6)<br />

form slightly distorted kagome lattice in its c-plane. Former study1) reported that the<br />

magnetic susceptibility increased rapidly below about 7 K indicating an occurrence<br />

of the ferromagnetic transiti<strong>on</strong>. Surprisingly, however, no anomaly in the specific heat<br />

was observed at the transiti<strong>on</strong> temperature in this compound. In order to scrutinize<br />

the magnetic properties, we measure the specific heat of this compound using single<br />

crystals under an applied magnetic field up to 7 T. 1H-NMR measurement is also<br />

carried out. NMR spectra-broadening and a divergent behavior of the spin-lattice<br />

relaxati<strong>on</strong> rate are observed at around 7 K. Slight anomaly in the specific heat is<br />

observed and the anomaly temperature is found to depend <strong>on</strong> the magnetic field. These<br />

results suggest that entropy change associated with the magnetic ordering of this<br />

compound is vanishingly small.<br />

1) P. Kanoo et al. Dalt<strong>on</strong> Trans. 2009, 5062.


QE22<br />

Field-induced staggered moments in the spin-gapped antiferromagnet<br />

<strong>on</strong> a deformed kagome lattice, Rb 2Cu 3SnF 12<br />

Hiroshi Tashiro 1 *, Masahide Nishiyama 1 , Akira Oyamada 1 , Tetsuaki Itou 1 , Satoru<br />

Maegawa 1 , Midori Yano 2 , Toshio Ono 3 and Hidekazu Tanaka 2<br />

1 Graduate School of Human and Envir<strong>on</strong>mental Studies, Kyoto University, Japan<br />

2 Department of Physics, Tokyo Institute of Technology, Japan<br />

3 Department of Physical Science, Osaka Prefecture University, Japan<br />

Rb 2Cu 3SnF 12 is a kagome lattice antiferromagnet in which Cu 2+ i<strong>on</strong>s with spin 1/2 interact with four<br />

exchange interacti<strong>on</strong>s, J1~200K>J2>J3>J4~100K. The ground state of this compound is a valence b<strong>on</strong>d<br />

solid owing to the quantum and frustrati<strong>on</strong> effects, so that no magnetic ordering occurs [1,2]. We have<br />

performed 19F-NMR experiments <strong>on</strong> a single crystal of Rb 2Cu 3SnF 12 in order to clarify the microscopic<br />

property of the ground state. One sharp 19F-NMR spectrum at high temperature splits to several peaks at<br />

low temperatures due to different magnetic sites of 19F. The shifts of these peaks increase steeply below<br />

around 70K, whereas the static susceptibility decreases exp<strong>on</strong>entially below this temperature owing to<br />

the singlet ground state with the spin-gap. The shifts are proporti<strong>on</strong>al to the applied field. These results<br />

str<strong>on</strong>gly suggest that the local fields are produced by the staggered moments induced by the external field<br />

through Dzyaloshinsky-Moriya interacti<strong>on</strong>. The staggered moments become dominant below 70K, while<br />

the parallel moments are remarkably small because of the large exchange interacti<strong>on</strong>. This characteristic<br />

temperature differs from the spin-gap of 20K obtained from the susceptibility, because the large density of<br />

state in the dispersi<strong>on</strong> curve around 70K c<strong>on</strong>tributes to the generati<strong>on</strong> of the staggered moments [3].<br />

[1] K. Morita, M. Yano, T. Ono, H. Tanaka, K. Fujii, H. Uekusa, Y. Narumi, and K. Kindo, J. Phys. Soc. Jpn. 77, 043707 (2008). [2]<br />

K. Matan, T. Ono, Y. Fukumoto, T. J. Sato, J. Yamaura, M. Yano, K. Morita, and H. Tanaka, Nature Phys. 6, 865-869 (2010). [3] H.<br />

Tashiro, M. Nishiyama, A. Oyamada, T. Itou, S. Maegawa, M. Yano, T. Ono, and H. Tanaka, J. Phys.: C<strong>on</strong>f. Ser. 320, 012052 (2011).<br />

QE23<br />

Magnetic order in finite size domains of the h<strong>on</strong>eycomb lattice<br />

compound InCu2/3V1/3O3 E. Vavilova 1 *, M. Yakovleva 1 , M. Yehia 2 , R. Klingeler 3 , V. Kataev 2 , T. Taetz 4 , U. Loew 5 , A. Moeller 6<br />

and B. Buechner 2<br />

1<br />

Zavoisky Physical Technical Institute, RAS, Kazan, Russia<br />

2<br />

IFW Dresden, Dresden, Germany<br />

3<br />

Heidelberg University, Heidelberg,, Germany<br />

4<br />

Institut fur Anorganische Chemie, Universitaat zu Koln, Germany<br />

5<br />

Technische Universitaat Dortmund, Germany<br />

6<br />

University of Houst<strong>on</strong>, Department of Chemistry and Texas Center for Superc<strong>on</strong>ductivity, USA<br />

The results of high field electr<strong>on</strong> spin res<strong>on</strong>ance, nuclear magnetic res<strong>on</strong>ance, nuclear<br />

quadrupole res<strong>on</strong>ance and magnetizati<strong>on</strong> studies addressing the ground state of the<br />

quasi two-dimensi<strong>on</strong>al spin-1/2 h<strong>on</strong>eycomb lattice compound InCu 2/3V 1/3O 3 are<br />

reported. Uncorrelated finite size structural domains occurring in the h<strong>on</strong>eycomb planes<br />

are expected to inhibit l<strong>on</strong>g range magnetic order. Surprisingly, magnetic res<strong>on</strong>ance<br />

data show the development of two collinear antiferromagnetic (AFM) sublattices below<br />

35K and the presence of the staggered internal field. Magnetizati<strong>on</strong> data evidence a<br />

spin reorientati<strong>on</strong> transiti<strong>on</strong> at 5.7T. Quantum M<strong>on</strong>te-Carlo calculati<strong>on</strong>s show that<br />

switching <strong>on</strong> the coupling between the h<strong>on</strong>eycomb spin planes in a finite size cluster<br />

yields a Neel-like AFM spin structure with a substantial staggered magnetizati<strong>on</strong> at<br />

finite temperatures. ESR, NMR and NQR data allow to retrace the development of<br />

staggered magnetizati<strong>on</strong> during the crossover to ordered ground state.<br />

A. Yehia, et al., Phys. Rev. B 81, 060414 (2010)<br />

QE24<br />

Z_2 vortices in frustrated background of cuprates<br />

Maciej Fidrysiak and Paweł Rusek*<br />

Wroclaw University of Technology, Poland<br />

La 2-xSr xCuO 4 (LSCO) in the underdoped regime (x=0.02 - 0.05) is a n<strong>on</strong>-collinear<br />

quantum antiferromagnet. The relevant order parameter is a triad of orth<strong>on</strong>ormal<br />

vectors. The topology of the order parameter space allows the existence of Z_2<br />

vortices. Randomly distributed Sr dopants introduce holes into the Cu-O planes which<br />

are the source of fluctuating dipolar fields resulting in frustrated spin background. We<br />

study Z_2 vortices in the system in the framework of n<strong>on</strong>-linear sigma-model coupled<br />

to SO(3) gauge fields which represent fluctuating frustrated background. In this model<br />

we describe explicitly not <strong>on</strong>ly spin degrees of freedom, but also the distributi<strong>on</strong> of<br />

frustrati<strong>on</strong>s as opposed to pure spin systems. We have found explicitly a finite energy<br />

Z_2 vortex soluti<strong>on</strong>. Frustrati<strong>on</strong>s are c<strong>on</strong>centrated in the soft core of Z_2 vortices and<br />

exp<strong>on</strong>entially decrease at large distances. The chirality of spin system changes its sign<br />

in the vortex core as expected. Our vortex seems to be more relevant to the study of<br />

frustrated Heisenberg spin systems and the charge transport by vortices in cuprates than<br />

Z_2 vortices in pure spin degrees of freedom.<br />

QE25<br />

First-principles study of S=1/2 Kagome antiferromagnet<br />

Chung-yuan Ren*<br />

Nati<strong>on</strong>al Kaohsiung Normal University, Taiwan<br />

QE26<br />

Exotic phases in the frustrated hexag<strong>on</strong>al lattice<br />

Daniel C. Cabra*<br />

Physics Department, Nati<strong>on</strong>al University of La Plata, Argentina<br />

QE27<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

3-D systems with interacting spins usually develop static l<strong>on</strong>g-range order when they<br />

are cooled. However, quantum fluctuati<strong>on</strong>s are enhanced in low dimensi<strong>on</strong>ality system<br />

with low spin value and lead to suppress the l<strong>on</strong>g-range ordering, and can show some<br />

extremely subtle, complex, and sometimes even useful magnetic behavior in solids.<br />

Here, using first-principles calculati<strong>on</strong>s, we investigated the atomic structural and<br />

magnetic properties of S=1/2 Kagome antiferromagnet A xCu 4-x(OH) 6Cl 2 (A=Zn, alkali<br />

metal i<strong>on</strong>). Cu i<strong>on</strong>s are indeed found to locate at the tetrag<strong>on</strong>ally el<strong>on</strong>gated intralayer<br />

site and Zn i<strong>on</strong>s favorably rest <strong>on</strong> the higher symmetry interlayer site, in support of<br />

experimental c<strong>on</strong>tenti<strong>on</strong>. The intra- and inter-layer exchange interacti<strong>on</strong>s are studied<br />

in details. The effect of Dzyaloshinskii-Moriya interacti<strong>on</strong> <strong>on</strong> the magnetic structure is<br />

also discussed.<br />

[1] M. P. Shores, E. A. Nytko, B. M. Bartlett, and D. G. Nocera, J. Am. Chem. Soc 127, 13462, (2005)<br />

[2] S. Chu, T.M McQueen, R. Chisnell, D.E. Freedman, P. Muller, Y.S. Lee, and D.G. Nocera, J. Am.<br />

Chem. Soc. (2010).<br />

We study the phase diagram of the Heisenberg model <strong>on</strong> the H<strong>on</strong>eycomb lattice with<br />

antiferromagnetic interacti<strong>on</strong>s up to third neighbors al<strong>on</strong>g the line J2=J3, close to the<br />

point where it has macroscopic degeneracy at the classical level. Using the Schwinger<br />

bos<strong>on</strong> technique followed by a mean field decoupling and exact diag<strong>on</strong>alizati<strong>on</strong><br />

for small systems we find an intermediate phase with a spin gap and short range<br />

Neel correlati<strong>on</strong>s even in the str<strong>on</strong>g quantum limit 1/2. We have also studied the<br />

magnetizati<strong>on</strong> curve for J3=0, close to J2/J1 = 1/2 where the classical ground state is<br />

also highly degenerate. The properties of the magnetizati<strong>on</strong> curve and phase transiti<strong>on</strong>s<br />

are studied by means of M<strong>on</strong>tecarlo, which shows many interesting transiti<strong>on</strong>s.<br />

Light scattering in spin liquid systems<br />

Dirk Wulferding 1 *, Peter Lemmens 1 , Vladimir Gnezdilov 2 , Tianheng Han 3 , Young S.<br />

Lee 3 , Hiroyuki Yoshida 4 , Yoshihiko Okamoto 5 and Olga Volkova 6<br />

1 IPKM, TU-BS, Braunschweig, Germany<br />

2 ILTPE NAS, Ukraine<br />

3 MIT, Massachusetts, USA<br />

4 NIMS, Tsukuba, Japan<br />

5 ISSP, Tokyo, Japan<br />

6 MSU, Moscow, Russia<br />

When quantum spin systems are restricted in dimensi<strong>on</strong>ality and coordinati<strong>on</strong> they<br />

realize spin liquid states with enhanced quantum fluctuati<strong>on</strong>s and exotic correlati<strong>on</strong><br />

functi<strong>on</strong>s. We compare the experimentally determined excitati<strong>on</strong> spectra of different<br />

spin liquid candidates such as the s=1/2 Heisenberg antiferromagnet <strong>on</strong> a kagome<br />

lattice and weakly coupled spin chain system in Herbertsmithite and (NO)Cu(NO 3) 3<br />

using Raman scattering. This technique is sensitive to fracti<strong>on</strong>al spin<strong>on</strong> excitati<strong>on</strong>s. The<br />

effect of the crystal’s lattice structure and defects <strong>on</strong> the spin dynamics is investigated.<br />

The data is also compared with recent theoretical modelling. Work supported by DFG,<br />

B-IGSM and NTH School for C<strong>on</strong>tacts in Nanosystems.<br />

D. Wulferding, et al., Phys. Rev. B 82, 144412 (2010) V. Gnezdilov, et al., arXiv:1203.2818 (2012) D.<br />

Wulferding, et al., arXiv :1111.2167 (2012)<br />

July 8 - 13, 2012 Busan, Korea 89<br />

Poster Tuesday


Poster Tuesday<br />

QF01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Molecular nanomagnets as quantum simulators<br />

Paolo Santini<br />

University of Parma. Italy<br />

Quantum simulators (QSs) are c<strong>on</strong>trollable quantum systems that can be used to<br />

simulate other quantum systems. QSs can tackle problems intractable <strong>on</strong> classical<br />

computers. Here we focus <strong>on</strong> the dynamics of qubits encoded in chains of molecular<br />

nanomagnets. For istance, we have shown that Cr 7Ni rings are good candidates qubits<br />

and can be linked to each other either directly or through magnetic complexes [1,2].<br />

We theoretically show that the dynamics of such chains can be c<strong>on</strong>trolled by means of<br />

uniform magnetic pulsed fields and used to mimic the coherent time evoluti<strong>on</strong> of other<br />

quantum systems (e.g., spin-<strong>on</strong>e chains) [3]. We propose two significant proof-ofprinciple<br />

experiments [3].<br />

[1] G.A. Timco et al., Nature Nanotechnology 4, 173 (2009) [2] A. Candini et al., Phys. Rev. Lett.<br />

104, 037203 (2010) [3] P. Santini, S. Carretta, F. Troiani, G. Amoretti, Phys. Rev. Lett. 107, 230502<br />

(2011)<br />

QF02<br />

ESR signature of the next-nearest-neighbor interacti<strong>on</strong>s in the S = 1/2<br />

chain compound (6MAP)CuCl3. M. Ozerov 1 , A. A. Zvyagin 2 , E. Cizmar 3 , F. Xiao 4 , C. P. Landee 4 , J. Wosnitza 1 and S. A.<br />

Zvyagin 1<br />

1<br />

Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf,<br />

Dresden, Germany<br />

2<br />

Institut fur Festkorperphysik, Technische Universitat Dresden, Dresden, Germany<br />

3<br />

Centre of Low Temperature Physics, P.J. Safarik University, Kosice, Slovak<br />

4<br />

Department of Physics and Carls<strong>on</strong> School of Chemistry, Clark University,<br />

Worcester, Massachusetts, USA<br />

Electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) studies of the S = 1/2 chain material (6MAP)CuCl 3<br />

[6MAP = C 6H 9N 2] are presented. Two modes with asymmetric with respect to a<br />

simple gapless Zeeman splitting res<strong>on</strong>ance positi<strong>on</strong>s have been observed in the<br />

low-temperature ESR spectrum. This shows that the simple S = 1/2 Heisenberg<br />

antiferromagnet chain model, employed so far, is not sufficient for a complete<br />

descripti<strong>on</strong>. The frequency-field diagram of magnetic excitati<strong>on</strong>s is interpreted in<br />

the frame of the recently developed theory for S = 1/2 chains with nearest- and nextnearest-neighbor<br />

interacti<strong>on</strong>s [A.A. Zvyagin, Phys. Rev. B 79, 064422 (2009)]. A good<br />

qualitative agreement with experiment has been achieved. The work was supported in<br />

part by DFG and EuroMagNET II (EU C<strong>on</strong>tract No. 228043).<br />

QF03<br />

Electr<strong>on</strong> spin res<strong>on</strong>ance in the spin-ladder compound BPCB<br />

S. Zvyagin 1 , E. Cizmar 2 , M. Ozerov 1 and J. Wosnitza 1<br />

1<br />

Dresden High Magnetic Field Laboratory (HLD) Helmholtz-Zentrum Dresden-<br />

Rossendorf, Dresden, Germany<br />

2<br />

Centre of Low Temperature Physics, P.J. Safarik University, Kosice, Slovak<br />

Magnetic excitati<strong>on</strong>s in the spin-ladder material (C5 2H 12N 2)CuBr 4 (known as BPCB)<br />

are probed by means of electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) spectroscopy in magnetic<br />

fields up to 16 T. The gap between the ground state and the first excited state, 16.5<br />

K (or 1.42 meV), is detected directly. In additi<strong>on</strong>, our experiments provide clear<br />

evidence for a pr<strong>on</strong>ounced anisotropy (~ 5% of the dominant exchange interacti<strong>on</strong>),<br />

resp<strong>on</strong>sible for a shift of the observed ESR line and a specific angular dependence of<br />

res<strong>on</strong>ance absorpti<strong>on</strong>s. The results are explained in frame of the recently developed<br />

theory for ESR in spin-ladders (Furuya et al., arXiv: 1107.5965). The work was d<strong>on</strong>e<br />

in collaborati<strong>on</strong> with B. Thielemann, K. W. Kramer, Ch. Ruegg, O. Piovesana, M.<br />

Klanjsek, M. Horvatic, and C. Berthier. The work was supported in part by DFG and<br />

EuroMagNET II (EU C<strong>on</strong>tract No. 228043).<br />

90 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QF04<br />

N<strong>on</strong>-magnetic impurity effect of S=1/2 spin ladder system (pipdH) 2Cu1 xZnxBr4 Chiori Yokoyama 1 , Weimin Zhang 2 , Takahiro Sakurai 3 , Susumu Okubo 4 *, Hitoshi Ohta 5 , Eiichi<br />

Matsuoka 6 , Hitoshi Sugawara 7 and Hikomitsu Kikuchi 8<br />

1<br />

Kobe University, Japan<br />

2<br />

Center for Collaborative Research and Technology Development, Kobe University, Japan<br />

3<br />

Center for Supports to Research and Educati<strong>on</strong> Activities, Kobe University, Japan<br />

4<br />

Molecular Photoscience Research Center, Kobe University, Japan<br />

5<br />

Molecular Photoscience Research, Kobe University, Japan<br />

6<br />

1Graduate School of Science, Kobe University, Japan<br />

7<br />

Graduate School of Science, Kobe University, Japan<br />

8<br />

Department of Applied Physics, University of Fukui, Japan<br />

Low dimensi<strong>on</strong>al spin system shows fruitful magnetic properties such as the Bose-Einstein c<strong>on</strong>densati<strong>on</strong><br />

of magn<strong>on</strong> or the spin liquid state. N<strong>on</strong>-magnetic impurity effect in a quantum spin chain, which arises<br />

as an appearance of magnetic moment with spin correlati<strong>on</strong> at around the impurity, is <strong>on</strong>e of typical<br />

quantum effects of correlated spins. (pipdH) 2CuBr 4 is known as a model substance of weakly coupled<br />

spin 1/2 Heisenberg antiferromagnetic ladder system. Recently, we succeeded in synthesizing Zn-doped<br />

(pipdH) 2Cu 1-xZn 1-xBr 4 single crystal. Samples were c<strong>on</strong>firmed to be in a single phase and have the same<br />

crystal structure as the pure system (pipdH) 2CuBr 4 by X-ray diffracti<strong>on</strong> measurements. To check magnetic<br />

properties, the magnetic susceptibility and the magnetizati<strong>on</strong> measurements are performed by the SQUID<br />

magnetometer. The magnetic susceptibility shows a maximum related to the spin ladder and the Curie<br />

increase at low temperature related to the doping of Zn. The Curie term increases as the Zn c<strong>on</strong>centrati<strong>on</strong><br />

increase. Observed n<strong>on</strong>-magnetic impurity effect of S=1/2 spin ladder system will be discussed in<br />

c<strong>on</strong>necti<strong>on</strong> with AKLT model.<br />

QF05<br />

High-field multi-frequency ESR in the S=2 Heisenberg<br />

antiferromagnetic chain compound MnCl3(bpy) Masayuki Hagiwara 1 *, Shojiro Kimura 2 , Yuichi Idutsu 1 and Zentaro H<strong>on</strong>da 3<br />

1<br />

KYOKUGEN, Osaka University, Japan<br />

2<br />

IMR, Tohoku University, Japan<br />

3<br />

Graduate School of Science and Engineering, Saitama University, Japan<br />

QF06<br />

MOVED<br />

High field magnetizati<strong>on</strong> of bimetallic chain with alternating ising and<br />

Heisenberg spins<br />

Yibo Han 1 , Jozef Strecka 2 , Takanori Kida 1 , Zentaro H<strong>on</strong>da 3 , Masami Ikeda 1 and Masayuki<br />

Hagiwara 1 *<br />

1<br />

KYOKUGEN, Osaka University, 1-3 Machikaneyama, Toy<strong>on</strong>aka, Osaka 560-8531, Japan<br />

2<br />

Department of Physics, Faculty of Science, P. J. Safarik University, Park Angelinum 9,040 01<br />

Kosice, Slovakia, Slovak<br />

3<br />

Department of Functi<strong>on</strong>al Materials Science, Graduate School of Science and Engineering,<br />

Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan<br />

3d-4f bimetallic chain [Dy(NO3)(DMSO)2Cu(opba)(DMSO)2] built from alternating<br />

dysprosium(3+) and copper(2+) i<strong>on</strong>s has been synthesized and magnetically studied.<br />

Magnetic susceptibility as well as high-field magnetizati<strong>on</strong> of the polycrystalline sample<br />

was measured under the temperature down to 1.3 K and the magnetic field up to 52 T. After<br />

performing correcti<strong>on</strong> for the temperature independent paramagnetism, the magnetizati<strong>on</strong><br />

curve recorded at 1.3 K shows a rapid increase with the magnetic field in the low-field<br />

range 0-3 T, followed up with a less steep increase in the field range 5-34 T before tending<br />

towards its saturati<strong>on</strong> value at 34 T. The observed magnetizati<strong>on</strong> process can be interpreted<br />

in terms of the spin-1/2 chain model with alternating Ising and Heisenberg spins, which<br />

accounts for both parallel and perpendicular Zeeman's energy of Dy and Cu i<strong>on</strong>s. The good<br />

fitting of the experimental data by using the above theoretical model suggest the effective<br />

antiferromagnetic exchange c<strong>on</strong>stant J/kB= -26 K, the highly anisotropic g-factor of Dy<br />

i<strong>on</strong>s and almost isotropic g-factor of Cu i<strong>on</strong>s. It was c<strong>on</strong>cluded that a new type of <strong>on</strong>edimensi<strong>on</strong>al<br />

Ising-Heisenberg spin chain was found.


QF07<br />

Thermal c<strong>on</strong>ductivity and magnetic susceptibility of the 4-leg spinladder<br />

system (La 1-xY x) 2Cu 2O 5 and the 5-leg spin-ladder system (La 1-<br />

XEu x) 8Cu 7O 19<br />

Takayuki Kawamata*, Takashi Noji and Yoji Koike<br />

Department of Applied Physics, Tohoku University, Japan<br />

We have measured the thermal c<strong>on</strong>ductivity and magnetic susceptibility of the 4-leg spin-ladder<br />

system (La 1-xY x) 2Cu 2O 5 (x = 0.01) and the 5-leg spin-ladder system (La 1-xEu x) 8Cu 7O 19 (x = 0,<br />

0.01). It has been found that the temperature dependence of the thermal c<strong>on</strong>ductivity al<strong>on</strong>g<br />

the spin-ladders of (La 0.99Y 0.01) 2Cu 2O 5, La 8Cu 7O 19 and (La 0.99Eu 0.01) 8Cu 7O 19 shows <strong>on</strong>ly <strong>on</strong>e<br />

peak originating from the thermal c<strong>on</strong>ductivity due to ph<strong>on</strong><strong>on</strong>s at ~15K. That is, the thermal<br />

c<strong>on</strong>ductivity due to spins, κspin, has not been observed in these compounds, though κspin<br />

was expected to be large owing to the exchange interacti<strong>on</strong> al<strong>on</strong>g the spin-ladders as large as<br />

~1000K. Since the antiferromagnetic transiti<strong>on</strong> temperature, TN, is as large as 137K and 103K<br />

in La 2Cu 2O 5 [1] and La 8Cu 7O 19 [2], respectively, it has been c<strong>on</strong>cluded that the comparatively<br />

large exchange interacti<strong>on</strong> between spin-ladders disturbs the thermal c<strong>on</strong>ducti<strong>on</strong> due to<br />

spins al<strong>on</strong>g the spin-ladders. Moreover, it has been found that the temperature dependence<br />

of the magnetic susceptibility below TN is clearly different between (La 0.99Y 0.01) 2Cu 2O 5 and<br />

(La 0.99Eu 0.01) 8Cu 7O 19, which may be related to the difference of the ground state between the<br />

odd- and even-leg spin-ladder systems.<br />

[1] K. Kudo et al., J. Phys. Soc. Jpn. 72 (2003) 2551. [2] I. A. Zobkalo et al., Physica B 234-236<br />

(1997) 734.<br />

QF08<br />

Magnetic susceptibility of the quasi <strong>on</strong>e-dimensi<strong>on</strong>al spin system<br />

Sr 2V 3O 9<br />

Takayuki Kawamata*, Masanori Uesaka, Mitsuhide Sato and Yoji Koike<br />

Department of Applied Physics, Tohoku University, Japan<br />

According to the magnetic susceptibility of polycrystalline samples of the quasi <strong>on</strong>edimensi<strong>on</strong>al<br />

spin system Sr 2V 3O 9, this compound undergoes a weak ferromagnetic<br />

transiti<strong>on</strong> due to the Dzyaloshinsky-Moriya (DM) interacti<strong>on</strong> at TN ~ 5K [1]. We have<br />

grown single crystals of Sr 2V 3O 9 [2] and measured the magnetic susceptibility al<strong>on</strong>g<br />

the [101] directi<strong>on</strong>, χ[101], al<strong>on</strong>g the [10-1] directi<strong>on</strong>, χ[10-1], and al<strong>on</strong>g the b-axis,<br />

χb. It has been found that temperature dependences of χ[101], χ[10-1] and χb show<br />

B<strong>on</strong>ner-Fisher-type behavior and that the anisotropy is very small at high temperatures<br />

above TN, indicating that Sr 2V 3O 9 is regarded as an isotropic <strong>on</strong>e-dimensi<strong>on</strong>al<br />

Heisenberg spin system. At low temperatures below TN, however, both χ[10-1] and<br />

χb increase with decreasing temperature, while χ[101] decreases. This anisotropic<br />

behavior is c<strong>on</strong>sistent with the canted spin state proposed from the ESR measurements<br />

[3].<br />

[1] E. E. Kaul et al., Phys. Rev. B 67 (2003) 174417. [2] M. Uesaka et al., J. Phys.: C<strong>on</strong>f. Ser. 200<br />

(2010) 022068. [3] V. A. Ivanshin et al., Phys. Rev. B 68 (2003) 064404.<br />

QF09<br />

Magnetic property of a single crystal of spin-1/2 triple-chain magnet<br />

Cu3(OH) 4SO4 Yutaka Fujii 1 *, Yuya Ishikawa 2 , Hikomitsu Kikuchi 2 , Yasuo Narumi 3 , Hiroyuki<br />

Nojiri 3 , Shigeo Hara 4 and Hirohiko Sato 4<br />

1<br />

Research Center for Development of Far-Infrared Regi<strong>on</strong>, University of Fukui,<br />

Japan<br />

2<br />

Department of Applied Physics, University of Fukui, Japan<br />

3<br />

Institute for Materials Research, Tohoku University, Japan<br />

4<br />

Department of Physics, Chuo University, Japan<br />

A spin-1/2 triple-chain magnet Cu 3(OH) 4SO 4 (antlerite) is a candidate 'idle-spin' system in<br />

which magnetic moments <strong>on</strong> central spin chain seem to disappear, while the rest exhibit<br />

a l<strong>on</strong>g-range order below TN=5.5 K [1]. Our previous prot<strong>on</strong> NMR study with a powder<br />

sample almost supported this scenario, although it was difficult to determine the spin<br />

structure [2]. Recently, successive phase transiti<strong>on</strong>s and anisotropy of phase diagram were<br />

found from the results of magnetizati<strong>on</strong> measurements with high-quality single crystals<br />

of Cu 3(OH) 4SO 4 [3]. In order to study phase transiti<strong>on</strong>s in the present compound in detail,<br />

we have performed specific heat measurements under magnetic fields up to 7 T and in the<br />

temperature range down to 2 K and prot<strong>on</strong> NMR experiments at several frequencies with<br />

single crystals. We found at least three successive phase transiti<strong>on</strong>s at zero field around<br />

TN. Complicated phase diagrams involving changes of spin structures were suggested.<br />

[1] S. Vilminot et al., J. Solid State Chem., 170, (2003) 255. [2] Y. Fujii et al., J. Phys.: C<strong>on</strong>f. Ser.,<br />

145, (2009) 012061. [3] S. Hara et al., J. Phys. Soc. Jpn., 80, (2011) 043701.<br />

QF10<br />

QF11<br />

QF12<br />

Thermal c<strong>on</strong>ductivity of anisotropic spin ladder<br />

Hamed Rezania*<br />

razi university, Iran<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Thermal c<strong>on</strong>ductivity due to magn<strong>on</strong>s in high-quality single crystals of<br />

the two-leg spin ladder system (Ca,Sr,La) 14Cu 24O 41<br />

Koki Naruse 1 *, Takayuki Kawamata 1 , Mitsuhide Sato 1 , Masumi Ohno 1 , Kazutaka Kudo 2 , Norio<br />

Kobayashi 3 and Yoji Koike 1<br />

1 Department of Applied Physics, Tohoku University, Japan<br />

2 Department of Physics, Okayama University, Japan<br />

3 Institute for Materials Research, Tohoku University, Japan<br />

In order to enhance the thermal c<strong>on</strong>ductivity due to magn<strong>on</strong>s, κmagn<strong>on</strong>, in the two-leg spin<br />

ladder system (Ca,Sr,La) 14Cu 24O 41, we have grown single crystals using high-purity raw materials,<br />

improved the quality of the single crystals by annealing in O2 and measured the thermal<br />

c<strong>on</strong>ductivity al<strong>on</strong>g the spin ladders. In both Ca 9La 5Cu 24O 41 and Sr 9La 5Cu 24O 41, the thermal<br />

c<strong>on</strong>ductivity shows a very large peak around 150K owing to the c<strong>on</strong>tributi<strong>on</strong> of κmagn<strong>on</strong> al<strong>on</strong>g<br />

the spin ladders[1,2]. However, no enhancement of κmagn<strong>on</strong> has been observed in spite of the<br />

increase of the purity of the raw materials and the O2-annealing. In Sr 14Cu 24O 41, <strong>on</strong> the other hand,<br />

a large enhancement of κmagn<strong>on</strong> has been observed through the O2-annealing. These results<br />

indicate that the mean free path of magn<strong>on</strong>s, lmagn<strong>on</strong>, has already limited by the disorder of the<br />

atomic arrangement due to the substituti<strong>on</strong> of Ca and La for Sr in Ca 9La 5Cu 24O 41 and Sr 9La 5Cu 24O 41,<br />

while lmagn<strong>on</strong> is enhanced owing to the decrease of spin defects through the O2-annealing in n<strong>on</strong>substituted<br />

Sr 14Cu 24O 41. Accoringly, it is necessary for the enhancement of κmagn<strong>on</strong> to remove the<br />

disorder of the atomic arrangement in the spin ladders in (Ca,Sr,La) 14Cu 24O 41.<br />

[1] K. Kudo, S. Ishikawa, T. Noji, T. adachi, Y. Koike, K. Maki, S. Tsuji, and K. Kumagai: J. Phys.<br />

Soc. Jpn. 70, 437 (2001). [2] C. Hess C. Baumann, U. Ammerahl, B. Buchner, F. Heidrich-Meisner, W.<br />

Brenig, and A. Revcolevschi: Phys. Rev. B 64, 184305 (2001).<br />

Magnetic property of Ni 2+ antiferromagnetic perfect triangle cluster<br />

Emika Takata 1,2 *, Minoru Sanda 1 , Katsutaka Kubo 2 , Takayuki Asano 2 , Akira Matsuo 1 ,<br />

Koichi Kindo 1 and Masaki Oshikawa 1<br />

1 Institute for Solid State Physics, University of Tokyo, Japan<br />

2 Department of Physics, Kyushu University, Japan<br />

The magnetic properties of spin systems with frustrati<strong>on</strong> have attracted much attenti<strong>on</strong><br />

for a l<strong>on</strong>g time. The fundamental structure causing the frustrati<strong>on</strong> is “triangle”. The<br />

magnetic properties of the antiferromagnetic perfect triangular cluster (APTC) with<br />

half-integer spins have been already studied well. [1] By c<strong>on</strong>trast, there are little<br />

experimental data <strong>on</strong> the APTC with integer spins. Such an APTC is expected to<br />

possess a n<strong>on</strong>-magnetic, singlet ground state. Recently, Liu et al. have investigated<br />

magnetic properties of S=1 APTC, [Ni 3(μ 1,3-N 3) 3(2,2'-bpy) 3](ClO 4) 3•3H 2O. It is<br />

believed as <strong>on</strong>e of model materials for the S=1 APTC. [2] We synthesized it and<br />

measured the magnetizati<strong>on</strong> process (M(H)) and the temperature dependence of the<br />

magnetic susceptibility (χ(T)) of the material. We calculated M(H) and χ(T) in the<br />

simple ISOTROPIC S=1 APTC. However, the experimental results clearly cannot<br />

be accounted for by the calculated results. When the spin is greater than or equal to<br />

1, generally a single i<strong>on</strong> anisotropy D can present. Thus we c<strong>on</strong>sider an anisotropic<br />

model Hamilt<strong>on</strong>ian by including D. We will discuss the experimental data based <strong>on</strong><br />

calculati<strong>on</strong>s using the new Hamilt<strong>on</strong>ian with D.<br />

[1] for example T. Yosida et al., J. Phys. Soc. Jpn. 57 (1988) 1428. [2]J.L. Liu et al., Aust. J. Chem.<br />

63 (2010) 1111.<br />

We have studied the thermal c<strong>on</strong>ductivity of anisotropic spin ladder model with<br />

antiferromagnetic coupling c<strong>on</strong>stants between spins <strong>on</strong> the both rung and ladder<br />

directi<strong>on</strong>s. Kubo formalism has been applied to study temperature dependency of<br />

thermal c<strong>on</strong>ductivity of this model hamillt<strong>on</strong>ian. The b<strong>on</strong>d operator formalism is<br />

used to transform the spin model to a hard core bos<strong>on</strong>ic gas. We have used the green's<br />

functi<strong>on</strong> approach to obtain the temperature dependence of spin excitati<strong>on</strong> spectrum.<br />

We have found the temperature dependence of the thermal c<strong>on</strong>ductivity for various<br />

exchange coupling c<strong>on</strong>stants and anisotropies in both coupling strengths. We have<br />

obtained the increase of coupling c<strong>on</strong>stant al<strong>on</strong>g ladder directi<strong>on</strong> leads to decrease<br />

of thermal c<strong>on</strong>ductivity. Furthermore the effect of local anisotropy anisotropy <strong>on</strong> the<br />

thermal c<strong>on</strong>ductivity has more significant in comparis<strong>on</strong> with other <strong>on</strong>e.<br />

1)E. Dagootto and T. M. Rice, Science 271, 618 (1996) 2)A. Klumper and D. C. Johnst<strong>on</strong>, Phys.<br />

Rev. Lett, 84, 4701 (2000) 3)A. V. Sologubenko and K. Gianno, H. R. Ott, U. Ammerahl and A.<br />

Revolevschi, Phys. Rev. Lett, 84, 2714(2000) 4)X. Zotos, F. Naef, P. Prelovse, Phys. Rev. B, 55,<br />

11029 (1997) 5)K. Louis, P. Prelovse and X. Zotos, Phys . Rev. B 74, 235118(2006)<br />

July 8 - 13, 2012 Busan, Korea 91<br />

Poster Tuesday


Poster Tuesday<br />

QF13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The magnetic properties of the newly synthesized trinuclear copper<br />

complex<br />

A. N. P<strong>on</strong>omaryov 1 *, K. Y. Choi 1 , N. Kim 2 , S. Yo<strong>on</strong> 2 , B. J. Suh 3 and Z. H. Jang 4<br />

1 Department of Physics, Chung-Ang University, Seoul, Korea<br />

2 Department of Chemistry, Kookmin University, Seoul, Korea<br />

3 Department of Physics, The Catholic University of Korea, Buche<strong>on</strong>, Korea<br />

4 Department of Physics, Kookmin University, Seoul, Korea<br />

We present magnetic properties of a newly synthesized single molecule magnet (SMM)<br />

Cu 3(μ 3-OMe)(μ-OMe)(μ-O 2CAr 4F-Ph ) 2(O 2CAr 4F-Ph) 2(HOMe) 3. In this compound, three<br />

copper i<strong>on</strong>s with s=1/2, c<strong>on</strong>nected by <strong>on</strong>e μ 3-bridged methoxide, form a spin triangle,<br />

whereby two Cu 2+ i<strong>on</strong>s are 5 coordinated and the other Cu 2+ i<strong>on</strong> is 4 coordinated. By<br />

means of SQUID magnetometer, temperature dependence of magnetic susceptibility<br />

χ(T) was measured in the range from 2 K to 300 K at the external field of 100 Oe<br />

and field dependence of magnetizati<strong>on</strong> M(H) was measured at 2 K and 300 K in the<br />

range from 0 to 7 T. From an analysis of the magnetizati<strong>on</strong> data of the polycrystalline<br />

powder sample using ITO (Irreducible Tensor Operator) method, we obtain the<br />

antiferromagnetic exchange coupling c<strong>on</strong>stants of J 1 = -143.65 K, J 2 = -143.78 K, J 3 =<br />

-143.61 K and the g-factor of g = 2.66. A further analysis with a model Hamilt<strong>on</strong>ian<br />

including anisotropic exchange interacti<strong>on</strong>s is <strong>on</strong>-going.<br />

QF14<br />

Magnetizati<strong>on</strong> process of S=1/2 diam<strong>on</strong>d chain compound<br />

Na 2Cu 3Ge 4O 12<br />

Minoru Sanda 1 *, Keisuke Matsuura 1 , Takayuki Asano 1 , Junfeng Wang 2 , Akira Matsuo 2 , Koichi<br />

Kindo 2 , Hiroki Morodomi 3 , Yuji Inagaki 3 and Tatsuya Kawae 3<br />

1 Department of Physics, Kyushu University, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

3 Department of Applied Physics, Kyushu University, Japan<br />

Frustrated magnetism is <strong>on</strong>e of the most fascinating systems because these systems have a great variety of<br />

quantum phenomena, and a lot of research activities are going <strong>on</strong>. Diam<strong>on</strong>d chain in which spins exist <strong>on</strong><br />

the Diam<strong>on</strong>d-shaped lattice is <strong>on</strong>e of examples of 1D-frustrated magnet. In this system, it is theoretically<br />

expected that not <strong>on</strong>ly the frustrati<strong>on</strong> but also low-dimensi<strong>on</strong>ality induces the quantum phenomena.<br />

Experimentally, Cu 3(CO 3)(OH) 2 was reported as an S=1/2 Diam<strong>on</strong>d chain compound, and its magnetic<br />

properties are studied actively [1]. Recently, Mo et al. reported the crystal structure of Na 2Cu 3Ge 4O 12,<br />

which has magnetic i<strong>on</strong>s Cu 2+ (3d9:S=1/2) arranging in Diam<strong>on</strong>d chain [2]. This compound has a shortrange<br />

order at T(SLO)~10K and a l<strong>on</strong>g-range order at T(N)=2K by means of magnetic susceptibility and<br />

heat capacity measurements [2][3]. We performed high field magnetizati<strong>on</strong> measurement using pulse<br />

magnetic field up to 55T at T(N)


QF19<br />

Spectral signatures of magnetic Bloch oscillati<strong>on</strong>s in 1D ferromagnets<br />

Sergey Shinkevich and Olav F. Syljuasen<br />

Department of Physics, University of Oslo, Norway<br />

Domain walls in a <strong>on</strong>e-dimensi<strong>on</strong>al gapped easy-axis ferromagnet can exhibit Bloch<br />

oscillati<strong>on</strong>s in an applied magnetic field. We investigate how exchange couplings<br />

modify this behavior within an approximati<strong>on</strong> based <strong>on</strong> n<strong>on</strong>-interacting domainwall<br />

bound states. In particular we obtain analytical results for the spectrum and the<br />

dynamic structure factor, and show where in momentum space to expect equidistant<br />

energy levels, the Wannier-Zeeman ladder, which is the spectral signature of magnetic<br />

Bloch oscillati<strong>on</strong>s. We compare our results to previous calculati<strong>on</strong>s employing a single<br />

domain-wall-approximati<strong>on</strong>, and make predicti<strong>on</strong>s relevant for the material cobalt<br />

chloride dihydrate (CoCl 2•2H 2O).<br />

1) Jordan Kyriakidis and Daniel Loss, Phys. Rev. B 58, 5568 (1998). 2) W. M<strong>on</strong>tfrooij, G. E.<br />

Granroth, D. G. Mandrus, and S. E. Nagler, Phys. Rev. B 64, 134426 (2001). 3) N.B. Christensen, K.<br />

Lefmann, I. Johannsen, and O. Jørgensen, Physica B 276, 784 (2000).<br />

QF20<br />

Quasi-<strong>on</strong>e-dimensi<strong>on</strong>al magnetic phase as a competing ground state in<br />

a frustrated magnet<br />

Krunoslav Prsa 1 , Mark Laver 2 , Martin Manss<strong>on</strong> 1 , Ivica Zivkovic 3 , Peter Derlet 4 , Sebastian Guerrero 4 ,<br />

Christopher Mudry 4 , Oksana Zaharko 2 , Sang-wook Che<strong>on</strong>g 5 , Hee-taek Yi 5 , Jorge Gavilano 2 , Joachim<br />

Kohlbrecher 2 , Michel Kenzelmann 6 and Joel Mesot 2<br />

1<br />

Laboratory for Solid State Physics, ETH Zurich, Switzerland<br />

2<br />

Laboratory for Neutr<strong>on</strong> Scattering, Paul Scherrer Institute, Switzerland<br />

3<br />

Institute of Physics, Croatia<br />

4<br />

C<strong>on</strong>densed Matter Theory, Paul Scherrer Institute, Switzerland<br />

5<br />

Department of Physics and Astr<strong>on</strong>omy, Rutgers University, USA<br />

6<br />

Laboratory for Developments and Methods, Paul Scherrer Institute, Switzerland<br />

Low-dimensi<strong>on</strong>al physics is interesting because it is driven by fluctuati<strong>on</strong>s and it may result in exotic<br />

phenomena, like the fracti<strong>on</strong>alizati<strong>on</strong> of quantum numbers and spin<strong>on</strong>s in magnetic chains. In magnetic<br />

systems, the reducti<strong>on</strong> of dimensi<strong>on</strong>ality occurs due to anisotropic short-ranged interacti<strong>on</strong>s. Generally,<br />

transiti<strong>on</strong> metal oxides order at low temperatures. Here, in geometrically frustrated Ca 3Co 2O 6, we<br />

show that by geometric frustrati<strong>on</strong> a stable quasi--<strong>on</strong>e--dimensi<strong>on</strong>al (Q1D) magnetic phase emerges<br />

from a competiti<strong>on</strong> of degenerate ground states. This phase coexists and competes with the 3D<br />

antiferromagnetism in a large range below the 3D ordering temperature. We show that (i) c<strong>on</strong>stituent<br />

entities of this Q1D phase are shaped as rods in real space with alternating up and down magnetized<br />

secti<strong>on</strong>s (d=15A, l=320A at 15 K) al<strong>on</strong>g the chain axis where (ii) the secti<strong>on</strong>s bel<strong>on</strong>g to a degenerate<br />

ferrimagnetic class of ground states, (iii) these magnetic rods are arranged randomly in the frustrated<br />

triangular plane, (iv) they occupy a significant volume fracti<strong>on</strong> (estimated 25% of moments at 15K) and<br />

(v) they are correlated with the magnetic resp<strong>on</strong>se of this material. These results provide a new general<br />

possibility of a frustrati<strong>on</strong>--stabilized <strong>on</strong>e--dimensi<strong>on</strong>al phase in physics.<br />

QF21<br />

Crossover of magnetic relaxati<strong>on</strong> from 2D-spin ice like state to ordered<br />

state in layered single molecular magnet networks<br />

Yuta Kodama 1 , Rikako Ishii 2 , Chihiro Kachi-terajima 2 , Hitoshi Miyasaka 3 , Daisuke<br />

Akahoshi 1 and Toshiaki Saito 1 *<br />

1 Dept. of Phys., Fac. of Sci., Toho Univ., Funabashi , Chiba 274-8510, Japan<br />

2 Dept. of Chem., Fac. of Sci., Toho Univ., Funabashi , Chiba 274-8510, Japan<br />

3 Dept.of Chem., Div. of Mat. Sci., Grad. Sch. of Nat. Sci. and Tech., Kanazawa Univ.,<br />

Ishikawa 920-1192, Japan<br />

Layered 2D single molecular magnet (SMM) network [Mn(saltmen)]4[M(CN) 6]ClO 4•nH 2O (M=Mn,<br />

Fe[1]) is a str<strong>on</strong>gly frustrated system. The each SMM unit [Mn(saltmen) ] (ST =4) is ferromagnetically<br />

c<strong>on</strong>nected through the [M(CN)6] unit (S=1 for Mn, and S=1/2 for Fe) within a layer. The origin of<br />

the frustrati<strong>on</strong> [2] is a competiti<strong>on</strong> between the orthog<strong>on</strong>ally oriented two uniaxial axes of the SMM<br />

unit and the ferromagnetic interacti<strong>on</strong>, leading to a macroscopically degenerated ground state as the<br />

pyroclore 3D-spin ice. Our previous work [2] for M=Mn showed no transiti<strong>on</strong> down to 2 K through<br />

the Weiss temperature Θ= 8.3 K and Davids<strong>on</strong>-Cole (DC) type magnetic relaxati<strong>on</strong> as 3D-spin ice<br />

[3]. However, for M=Fe, a distinct anomaly of relaxati<strong>on</strong> time is observed at 2.6 K (Θ = 7.5 K), and<br />

the relaxati<strong>on</strong> is the Cole-Cole (CC) type, suggesting a magnetic order. In this work, we measured<br />

ac susceptibility of M = Mn1-xFex (x = 0 ~ 1.0). We found that the relaxati<strong>on</strong> is not the DC type for<br />

x=0.1, and changes into CC type for x > 0.3 accompanying the distinct anomaly of relaxati<strong>on</strong> time. The<br />

results suggest that 2D-spin ice-like state is ordered into a randomly frozen state above x ~ 0.1.<br />

[1] H. Miyasaka et al., J. Am. Chem. Soc. 118 (1996) 981. [2] T. Saito et al. (2012), in preparati<strong>on</strong><br />

(partly presented in ICM 2009). [3] K. Matsuhira et al., J. Phys. C<strong>on</strong>dens. Matter 13 (2001) L737.<br />

QF22<br />

QF23<br />

QF24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of the novel low-dimensi<strong>on</strong>al spin-1/2 magnet α-Cu 2As 2O 7<br />

V. Kataev 1 *, Y. C. Arango 1 , E. Vavilova 2 , M. Abdel - Hafiez 1 , O. Jans<strong>on</strong> 3 , A. Tsirlin 3 , H. Rosner 3 , S.-l.<br />

Drechsler 1 , M. Weil 4 , G. Nenert 5 , R. Klingeler 6 , O. Volkova 7 , A. Vasiliev 7 and B. Buechner 1<br />

1 Leibniz Institute for Solid State and Materials Research IFW Dresden, Germany<br />

2 Zavoisky Physical Technical Institute of the Russian Academy of Sciences, 420029, Kazan, Russia<br />

3 Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany<br />

4 Institute for Chemical Technologies and Analytics, Vienna University of Technology, A-1060 Vienna, Austria<br />

5 Institut Laue-Langevin, Boıte Postale 156, 38042 Grenoble Cedex 9, France<br />

6 Kirchhoff Institute for Physics, University of Heidelberg, D-69120 Heidelberg, Germany<br />

7 Low Temperature Physics Department, Moscow State University, Moscow 119991, Russia<br />

In copper pyroarsenate α-Cu 2As 2O 7, the quantum spins S = 1/2 localised at the Cu sites in the<br />

structurally well defined dimer chains interact predominantly in <strong>on</strong>e spatial dimensi<strong>on</strong> (<strong>on</strong>edimensi<strong>on</strong>al<br />

spin systems). Magnetic properties of this new material have been thoroughly<br />

investigated by means of magnetizati<strong>on</strong>, heat capacity, electr<strong>on</strong> spin res<strong>on</strong>ance, and nuclear magnetic<br />

res<strong>on</strong>ance techniques, as well as by density functi<strong>on</strong>al theory (DFT) calculati<strong>on</strong>s and quantum M<strong>on</strong>te<br />

Carlo (QMC) simulati<strong>on</strong>s. The data reveal that the magnetic Cu-O chains in the crystal structure<br />

represent a realizati<strong>on</strong> of a quasi-<strong>on</strong>e-dimensi<strong>on</strong>al (1-D) coupled alternating spin-1/2 Heisenberg<br />

chain model with relevant pathways through n<strong>on</strong>magnetic AsO4 tetrahedra. Owing to residual 3-D<br />

interacti<strong>on</strong>s, antiferromagnetic l<strong>on</strong>g range ordering at TN ~10 K takes place. The experimental data<br />

suggest that substantial quantum spin fluctuati<strong>on</strong>s take place at low magnetic fields in the ordered<br />

state. DFT calculati<strong>on</strong>s and QMC fits enable quantitative evaluati<strong>on</strong> of the exchange couplings. We<br />

c<strong>on</strong>clude that the electr<strong>on</strong>ic state of the central i<strong>on</strong> in the n<strong>on</strong>magnetic AsO 4 side groups plays a<br />

crucial role for determining the relevant interchain pathways which makes α-Cu 2As 2O 7 distinct in its<br />

magnetic properties from other representatives of this class of compounds [1].<br />

[1] Y.C. Arango, E. Vavilova, M. Abdel-Hafiez et al., Phys. Rev. B 84, 134430 (2011)<br />

Low temperature magnetic properties of the dilutable frustrated spinladder<br />

Bi(Cu1-xZnx) 2PO6 Shuang Wang 1 , Krunoslav Prsa 2 , Neda Nikseresht 2 , Christian Ruegg 3 , E. Pomjakushina 4 , Kazimierz<br />

C<strong>on</strong>der 4 and Henrik M R<strong>on</strong>now 2<br />

1<br />

Laboratory for Quantum <strong>Magnetism</strong>/Laboratory for Developments and Methods, Ecole Polytechnique<br />

Federale de Lausanne, 1015 Lausanne Paul Scherrer Institut, 5232 Villigen, Switzerland<br />

2<br />

Laboratory for Quantum <strong>Magnetism</strong>, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne,<br />

Switzerland<br />

3<br />

Laboratory for Neutr<strong>on</strong> Scattering, Paul Scherrer Institut,5232 Villigen, Switzerland<br />

4<br />

Laboratory for Developments and Methods, Paul Scherrer Institut,5232 Villigen, Switzerland<br />

Quantum antiferromagnets with a spin-ladder magnetic network show an energy gap in the spin excitati<strong>on</strong><br />

spectrum and may possess an intrinsically disordered (spin liquid) ground state. BiCu 2PO 6 (BCPO)<br />

shows a structure where Cu 2+ magnetic i<strong>on</strong>s (S=1/2) form two-leg zigzag ladders al<strong>on</strong>g the b-axis, which<br />

closely corresp<strong>on</strong>ds to theoretical quasi-1D AF spin ladder model. We can reveal quantum nature of low<br />

temperature behavior by studying the effect of n<strong>on</strong>-magnetic impurities (e.g. Zn 2+ , Ni + ) introduced at<br />

magnetic Cu-sites. Recently, single crystals of Bi(Cu 1-xZn x) 2PO 6 (0≤x≤0.05) were successfully synthesized<br />

and studied by NMR for the first time [1,2]. We present here the specific heat Cp (H,T), ac susceptibility<br />

(f,T) and dc magnetizati<strong>on</strong> M(H,T) <strong>on</strong> single crystal sample of the undoped BCPO and 5% Zn-doped<br />

BCPO (Zn005BCPO) with field applied al<strong>on</strong>g main crystallographic axes focusing <strong>on</strong> low temperatures<br />

T < 10 K. We argue that the ground state of the Zn doped compound (Zn005BCPO) has features of both<br />

spin-glass and l<strong>on</strong>g range magnetic order, and that glassiness is lost under applicati<strong>on</strong> of higher magnetic<br />

fields. We show the H-T magnetic phase diagram.<br />

[1] S.Wang., E. Pomjakushina, T. Shiroka, G. Deng, N. Nikseresht, Ch. Ruegg, H.M. Rønnow, and K. C<strong>on</strong>der. J.Crystal.Growth.313,<br />

51-55 (2010) [2 ]F. Casola, T. Shiroka, S. Wang, K. C<strong>on</strong>der, E. Pomjakushina, J. Mesot and H.-R. Ott, Phys. Rev. Lett. 105, 067203<br />

(2010)<br />

51V-NMR study of the quasi-<strong>on</strong>e-dimensi<strong>on</strong>al antiferromagnet<br />

BaCo2V2O8 Yukiichi Ideta 1 , Yu Kawasaki 1 , Yutaka Kishimoto 1 , Takashi Ohno 1 , Yoshitaka<br />

Michihiro 1 , Zhangzhen He 2 , Yutaka Ueda 3 and Mitsuru Itoh 4<br />

1<br />

Institute of Technology and Science, The University of Tokushima, Japan<br />

2<br />

Fujian Institute of Research <strong>on</strong> the Structure of Matter, Chinese Academy of<br />

Sciences, China<br />

3<br />

Institute for Solid State Physics, University of Tokyo, Japan<br />

4<br />

Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

The double rectangle-like powder pattern has been observed in the 51V-NMR<br />

spectrum for the quasi-<strong>on</strong>e dimensi<strong>on</strong>al antiferromagnet BaCo 2V 2O 8 below TN = 5.4<br />

K. The powder pattern indicates the existence of two V sites with different internal<br />

field, 2.1 and 3.8 kOe, although V atoms occupy <strong>on</strong>ly <strong>on</strong>e magnetically symmetric site<br />

where the scalar type transferred field from the surrounding Co 2+ magnetic moments is<br />

zero. The internal field at V site is explained by taking into account of the classical and<br />

the pseudo-dipolar fields from Co 2+ magnetic moments. In the paramagnetic state, the<br />

nuclear spin-lattice relaxati<strong>on</strong> is dominated by the antiferromagnetic spin fluctuati<strong>on</strong><br />

via the dipolar field, which is proved by the linear relati<strong>on</strong> between the nuclear spinlattice<br />

relaxati<strong>on</strong> rate divided by temperature 1/T1T and the magnetic susceptibility.<br />

The change in the slope of 1/T1T against the magnetic susceptibility around 150 K<br />

suggests the change in the antiferromagnetic spin fluctuati<strong>on</strong> spectrum. Below 60 K, 1/<br />

T1 shows the thermal activati<strong>on</strong>-type temperature dependence signaling the formati<strong>on</strong><br />

of spin gap.<br />

July 8 - 13, 2012 Busan, Korea 93<br />

Poster Tuesday


Poster Tuesday<br />

QF25<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of <strong>on</strong>e-dimensi<strong>on</strong>al chain of O2 c<strong>on</strong>fined in<br />

nanospaces of MFI-zeolite<br />

Akihiro Hori 1 , Kanako Kuwana 2 , Tatsuo C Kobayashi 2 , Yasushi Wanikawa 3 , Yoshiki Kubota 3 ,<br />

Kenichi Kato 1 , Masaki Takata 1 , Ryotaro Matsuda 4 and Susumu Kitagawa 1<br />

1<br />

RIKEN SPring-8 Center, Japan<br />

2<br />

Okayama University, Japan<br />

3<br />

Osaka Prefecture University, Japan<br />

4<br />

Exploratory Research for Advanced Technology (ERATO), Japan<br />

We have studied the molecular arrangement and the magnetic properties in O 2 adsorbed in nanoporous<br />

compounds [1-3]. We found that the O 2 adsorbed in MFI zeolite form a <strong>on</strong>e-dimensi<strong>on</strong>al chain. The O 2<br />

adsorpti<strong>on</strong> isotherm shows a plateau and the step, indicating a phase transiti<strong>on</strong>. It is found by means of the<br />

x-ray diffracti<strong>on</strong> measurements that the zeolite deforms from m<strong>on</strong>oclinic to orthorhombic corresp<strong>on</strong>ding<br />

to the step of adsorpti<strong>on</strong> isotherm.In the low-adsorpti<strong>on</strong> case, the adsorbed O 2 aligns linearly in the straight<br />

and sinusoidal channels in MFI zeolite. In the high-field magnetizati<strong>on</strong> measurements, the magnetizati<strong>on</strong><br />

process does not show the linear field dependence characteristic to <strong>on</strong>e-dimensi<strong>on</strong>al Heisenberg<br />

antiferromagnet and presents the metamagnetic transiti<strong>on</strong> similar to the case of O 2-O 2 dimer reported<br />

previously [1, 2]. This result may suggest that the singlet ground state is realized at low fields and the fieldinduced<br />

orientati<strong>on</strong>al change of molecular axis occurs. In the high-adsorpti<strong>on</strong> case, the adsorbed O 2 seems<br />

to align in rows of two. The temperature dependence of susceptibility shows the first-order transiti<strong>on</strong> with<br />

large hysteresis. By XRD measurement, the structural phase transiti<strong>on</strong> from orthorhombic to m<strong>on</strong>oclinic<br />

with decreasing temperature was found, which is not observed in N 2 adsorbed compound.<br />

[1] T. C. Kobayashi et al., Prog. Theor. Phys. Suppl. 159 (2005) 271. [2] A. Hori et al., J. Phys. 200 (2010) 0022018. [3]<br />

A. Hori et al., J. Low. Temp. Phys. 159 (2010) 122.<br />

QF26<br />

Quantum spin transport in a Heisenberg spin chain<br />

Nan-h<strong>on</strong>g Kuo 1 , Sujit Sarkar 2 and Ch<strong>on</strong>g Der Hu 1 *<br />

1 Physics, Nati<strong>on</strong>alTaiwan University, Taiwan<br />

2 PoornaPrajna Institute of Scientific Research, India<br />

QG01<br />

WITHDRAWN<br />

Magnetic transiti<strong>on</strong> of plastic deformed Si-doped Ni 3Mn alloy<br />

Kowan-young Ko 1 *, Sung-w<strong>on</strong> Ko 2 and John Graham Booth 3<br />

1 Faculty of mechanical engineering, Ulsan College University, Korea<br />

2 Department of biological science, Sungkyunkwan University, Korea<br />

3 School of computing, science and engineering, Salford University, United Kingdom<br />

Structural and magnetic properties of plastic deformed Si-doped Ni 3Mn alloy were<br />

studied and compared with those of undeformed specimen investigated by powder<br />

neutr<strong>on</strong> diffracti<strong>on</strong> and diffuse purely magnetic scattering measurements in which<br />

coexistences of ferromagnetic and antiferromagnetic interacti<strong>on</strong>s were still existing<br />

even far above Neel temperature. Two specimens showed spin glass properties and<br />

disordered face-centered cubic structure but lattice parameters were a little different<br />

value of 3.5961 Å and 3.5890 Å. Magnetic properties showed very different Neel<br />

temperatures of 87.5 K and 62.5 K respectively. The paramagnetic Curie temperature<br />

appeared by -325 K and 125 K and therefore effective magnetic moments were<br />

calculated by 3.51 μB and 0.41 μB respectively. The reas<strong>on</strong>s for different magnetic<br />

transiti<strong>on</strong> could be introduced by the el<strong>on</strong>gati<strong>on</strong> of ferromagnetic clusters and change<br />

of atomic envir<strong>on</strong>ments effect after plastic deformati<strong>on</strong>. This report shows two kinds of<br />

magnetic properties by plastic deformati<strong>on</strong>.<br />

94 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QG02<br />

Incommensurate-commensurate phase transiti<strong>on</strong> in TbNi 5 induced by<br />

external magnetic field.<br />

Elena Sherstobitova 1 *, Alexander Pirogov 1 , Vadim Sikolenko 2 , Savva Bogdanov 1 and<br />

Roland Schedler 3<br />

1 Institute of Metal Physics of UD of RAS, Russia<br />

2 Joint Institute for Nuclear Research, Dubna, Russia<br />

3 Hahn-Meitner Institute, Berlin, Germany<br />

The rare earth intermetallic RNi 5 compounds are attractive subjects for the study of<br />

the exchange and crystal field interacti<strong>on</strong>s due to their simple crystal and magnetic<br />

structures. The magnetic ordering in TbNi 5 compound has been interpreted in terms<br />

of FAN-like incommensurate structure at temperatures between 23 K and 10 K. On<br />

cooling sample down to T = 10 K order-order type magnetic phase transiti<strong>on</strong> from the<br />

incommensurate phase to a “lock-in' phase takes place. In the present work we report<br />

the results of neutr<strong>on</strong> diffracti<strong>on</strong> experiment <strong>on</strong> TbNi 5 single crystal sample in external<br />

magnetic field up to μ0H = 1T. Abrupt change of the intensity of (001) Bragg peak and<br />

satellites (001)± occurs within temperature interval 7 K -10 K due to magnetic phase<br />

transiti<strong>on</strong> from the incommensurate phase to a “lock-in' phase. It has been found that<br />

the applicati<strong>on</strong> of external magnetic field up to μ0H = 0.1T at the temperature T = 11K<br />

al<strong>on</strong>g [100]-axis of TbNi 5 single crystal recovers zero-field low temperature 'lockin'<br />

magnetic structure. The external magnetic field increase up to μ0H = 0.4T leads to<br />

transformati<strong>on</strong> of the modulated magnetic structure to a ferromagnetic structure.<br />

QG03<br />

First-principles dynamical CPA study of ferro- and antiferromagnetism<br />

of transiti<strong>on</strong> metals<br />

Yoshiro Kakehashi* and Sumal Chandra<br />

Department of Physics, University of the Ryukyus, Japan<br />

Quantitative explanati<strong>on</strong> of the finite-temperature properties of 3d transiti<strong>on</strong> metals and<br />

alloys has been a l<strong>on</strong>g standing problem in metallic magnetism because their Coulomb<br />

interacti<strong>on</strong>s are comparable to the band widths and simple perturbati<strong>on</strong> approach is<br />

not applicable to such systems. We present here the first-principles dynamical CPA<br />

combined with the LDA+U Hamilt<strong>on</strong>ian toward quantitative calculati<strong>on</strong>s of magnetic<br />

properties at finite temperatures and explain quantitatively or semi-quantitatively the<br />

finite-temperature magnetism of 3d transiti<strong>on</strong> metals from V to Ni. We obtained the<br />

Curie-Weiss spin susceptibility with meff=1.8 muB (Expt. 2.1 muB) in V, the Pauli<br />

paramagnetic susceptibility in Cr being in agreement with the experimental data, as<br />

well as the Curie-Weiss susceptibilities in Fe, Co, and Ni whose meff quantitatively<br />

agree with the experimental data (3.2, 3.2, and 1.6 muB). Calculated ground-state<br />

magnetizati<strong>on</strong>s are 2.58, 1.72, and 0.64 muB for Fe, Co, and Ni, being in good<br />

agreement with the experimental data (2.2, 1.74, and 0.62 muB). On the other hand we<br />

obtained the Curie temperatures 1900K, 2100K, and 620K for Fe, Co, and Ni which<br />

are somewhat overestimated because of the single-site approximati<strong>on</strong>. We also clarify<br />

the systematic change of the single-particle DOS in these systems.<br />

QG04<br />

High-coercive metastable ferromagnetic state induced in the Ising<br />

antiferromagnet Fe 0.5TiS 2<br />

Nikolay Baranov 1 *, Elizaveta Sherokalova 2 , Alexey Volegov 2 , Alexey Proshkin 3 ,<br />

Nadezshda Selezneva 2 , Andrey Gubkin 4 and Ekaterina Proskurina 2<br />

1 Micromagnetic laboratory, Institute of Metal Physics, Russia<br />

2 Institute of Natural Sciences, Ural Federal University, Russia<br />

3 Laboratory of ferromagnetic alloys, Institute of Metal Physics, Russia<br />

4 Laboratoty of neutr<strong>on</strong> studies of matter, Institute of Metal Physics, Russia<br />

The transiti<strong>on</strong> metal (T) dichalcogenides TX2 (X = S, Se, Te) with a layer crystal structure being<br />

intercalated with 3d-transiti<strong>on</strong> (M) metals dem<strong>on</strong>strate different magnetic states depending <strong>on</strong> the<br />

type and c<strong>on</strong>centrati<strong>on</strong> of M-atoms as well as <strong>on</strong> the parent TX2 matrix [1]. In the present work, the<br />

magnetic susceptibility, magnetizati<strong>on</strong>, electrical resistivity, magnetoresistance and powder neutr<strong>on</strong><br />

diffracti<strong>on</strong> measurements have been performed for the Fe intercalated compound Fe 0.5TiS 2. It has been<br />

shown that this compound exhibits an antiferromagnetic (AF) ground state below the Neel temperature<br />

TN = 140 K. Applicati<strong>on</strong> of the magnetic field at T < TN induces a metamagnetic phase transiti<strong>on</strong> to<br />

the ferromagnetic (F) state, which is accompanied by the large magnetoresistance effect (~ -27 %).<br />

The field-induced AF-F transiti<strong>on</strong> is found to be irreversible below 100 K. At low temperatures, the<br />

magnetizati<strong>on</strong> reversal in the metastable F state is accompanied by substantial hysteresis (up to 100<br />

kOe) which is associated with the Ising character of Fe i<strong>on</strong>s. This work was supported by the RFBR<br />

(project 12-02-00778) and by the program of the Ural Branch of RAS (project № 12-T-1012).<br />

[1] Baranov N. V. et al. J. Phys. C<strong>on</strong>dens. Matter. 17 (2005) 5255


QG05<br />

Magnetic and thermoelectric properties of the solid soluti<strong>on</strong>s Mn 1-<br />

XNi XS<br />

Sergey Aplesnin 1 , Oksana Romanova 1 , Ludmila Ryabinkina 1 , Olga Demidenko 2 ,<br />

Anatoly Galyas 2 and Kazimir Yanushkevich 2<br />

1 L.V. Kirensky Institute of Physics, Russia<br />

2 Scientific-Practical Materials Research Centre NAS of Belarus, Belarus<br />

In c<strong>on</strong>necti<strong>on</strong> with intensive development of a microelectr<strong>on</strong>ics and spintr<strong>on</strong>ics, interest<br />

of researchers to the magnetic semic<strong>on</strong>ductor materials showing magnetoresistivity<br />

effect and metal-insulator transiti<strong>on</strong> has increased. New sulphide solid soluti<strong>on</strong>s<br />

Mn 1-XNi XS (0 TN. The effective magnetic moment are found to be μef.<br />

f=5,04 μВ for Х=0,05 and μeff.=5,16 μВ for Х=0,1. Change in the c<strong>on</strong>ductivity type<br />

from the hole to the electr<strong>on</strong>ic at Х=0,05 is revealed <strong>on</strong> the basis of measurements of<br />

thermoelectric power.<br />

QG06<br />

Field induced anisotropy in NiMn and NiMnPt alloys<br />

Yildirhan Oner<br />

Department of Physics, Istanbul Technical University, Dept. of Physics, 34469,<br />

Istanbul, Turkey<br />

We report the detailed characterizati<strong>on</strong> of the magnetic properties of polycrystalline<br />

disks of Ni 72Mn 28 and Ni 72-xMn 28Pt x (x=1.0, 4.0, and 10.0) at 4.2 K induced by field<br />

cooling (FC). It is found that the FC-induced anisotropy field ,HK and coercivity , HC<br />

are str<strong>on</strong>gly enhanced by the additi<strong>on</strong> of n<strong>on</strong>magnetic Pt impurities. The remanent<br />

magnetizati<strong>on</strong> in the directi<strong>on</strong> of the initial applied field (in the disk plane) for each<br />

samples can be rotated from 0° to 1800 and back to 0° in various stati<strong>on</strong>ary fields above<br />

and below HK and the parallel comp<strong>on</strong>ent of the rotated remanents are measured.<br />

From the analysis of the angular dependence of ML, we show that these results can be<br />

accounted for by the coexistence of Mn(Ni)-rich and /or Mn(Ni)-deficient nano scale<br />

regi<strong>on</strong>s coupled antiferromagnetically. It is found that the unidirecti<strong>on</strong>al anisotropy<br />

originates from interfacial exchange interacti<strong>on</strong>s between these regi<strong>on</strong>s. Up to some<br />

critical angle rotati<strong>on</strong> (θC) relative to H, the unidirecti<strong>on</strong>al anisotropy field turns<br />

rigidly with the sample, while above θC, the coupled regi<strong>on</strong>s become unstable and<br />

magnetically rearrange such that a unidirecti<strong>on</strong>al anisotropy is induced al<strong>on</strong>g H .<br />

QG07<br />

X-ray-absorpti<strong>on</strong> near-edge structure and X-ray magnetic circular<br />

dichroism studies of a Lu 2Fe 16.5Ru 0.5 single crystal<br />

E. A. Tereshina 1 , A. Smekhova 2 , O. Isnard 3 , A. V. Andreev 4 and A. Rogalev 5<br />

1 Institute of Physics, Academy of Sciences, 18221 Prague, Czech Republic<br />

2 Faculty of Physics, Moscow State University, 119991 Moscow, Russia<br />

3 Universite Joseph Fourier/Institut Neel (CNRS), 38042 Grenoble Cedex, France<br />

4 Institute of Physics, Academy of Sciences, Czech Republic<br />

5 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility (ESRF), 38043 Grenoble Cedex, France<br />

The magnetism of R 2Fe 17 with the smallest rare-earth R=Lu (hexag<strong>on</strong>al Th 2Ni 17 structure type) is essentially<br />

associated with its Fe sublattice behavior. Str<strong>on</strong>g c<strong>on</strong>tributi<strong>on</strong> of the local antiferromagnetic (AF) Fe-Fe<br />

interacti<strong>on</strong>s in the overall ferromagnetic (F) exchange c<strong>on</strong>siderably lowers the ordering temperature (TN=274<br />

K) and balances the n<strong>on</strong>-collinear antiferromagnetic phase above the Curie temperature TC=130 K. Generally,<br />

various doping elements (M) in Lu 2Fe 17- xM x suppress fully the AF states by strengthening the ferromagnetic <strong>on</strong>es<br />

accompanied by a dramatic TC increase. However, recently a unique case of antiferromagnetism stabilizati<strong>on</strong> in<br />

the whole range of magnetic ordering in Lu 2Fe 17- xRu 1x was reported [1], and this work is dealing with the local<br />

studies of intrinsic magnetic properties of Lu 2Fe 16.5Ru 0.5. A single-crystalline sample of Lu 2Fe 16.5Ru 0.5 has been<br />

investigated by X-ray-absorpti<strong>on</strong> (XANES) and X-ray magnetic circular dichroism (XMCD) techniques in the<br />

applied magnetic field up to ±3 T at 7 K. By probing the lutetium L2,3-, ir<strong>on</strong> K- and ruthenium L2 absorpti<strong>on</strong><br />

edges, informati<strong>on</strong> <strong>on</strong> magnetic states of the c<strong>on</strong>stituents of Lu 2Fe 16.5Ru 0.5 is obtained. Small but noticeable<br />

induced magnetic moments with an antiparallel orientati<strong>on</strong> to Fe moments have been registered <strong>on</strong> Lu and Ru<br />

sites.<br />

[1] E.A. Tereshina et al., J. Appl. Phys. 105 (2009) Art. No. 07A747.<br />

QG08<br />

QG09<br />

QG10<br />

The magnetovolume effect of Y 2Fe 17-xGa x<br />

Daiki Haruna and Tatsuo Kamimori<br />

Ehime University, Japan<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Study of the metamagnetic behavior of Ni-Co-Mn-Sb alloy in high<br />

magnetic fields<br />

Rie Y Umetsu 1 *, Xiao Xu 2 , Wataru Ito 3 , Takumi Kihara 4 , Masashi Tokunaga 4 , Kohki<br />

Takahashi 1 and Ryosuke Kainuma 2<br />

1 Institute for Materials Research, Tohoku University, Japan<br />

2 Department of Materials Science, Graduate School of Engineering, Tohoku University, Japan<br />

3 Department of Materials and Envir<strong>on</strong>mental Engineering, Sendai Nati<strong>on</strong>al College of Technology, Japan<br />

4 <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> MegaGauss Science Laboratory, Institute for Solid State Physics, The University of Tokyo,<br />

Japan<br />

In order to investigate metamagnetic behavior and temperature dependence of equilibrium magnetic field<br />

of the martensitic transformati<strong>on</strong> for Ni-Co-Mn-Sb, magnetizati<strong>on</strong> experiments up to 18 T static magnetic<br />

field and up to 40 T pulsed magnetic field were performed. Polycrystalline specimen of Ni 41Co 9Mn 39Sb 11<br />

was prepared by inducti<strong>on</strong> melting, and annealed at 1173 K for 1 day. Transformati<strong>on</strong> temperatures, TM, and<br />

entropy change, ΔS, between the martensite phase and parent phase were examined with DSC. Magnetic<br />

measurements were performed with using a SQUID magentometer up to 5 T, by extracting method up<br />

to 18 T static magnetic fields, and also by inducti<strong>on</strong> method up to 40 T pulsed magnetic fields. In the<br />

thermomagnetizati<strong>on</strong> curves, it was observed that TM decreased with increasing the applying magnetic field,<br />

H, with a rate of dTM/dH = 3.8 K/T. An estimated value of ΔS from the Clausius-Clapeyr<strong>on</strong> relati<strong>on</strong>, is about<br />

15.8 J/K-kg, being in good agreement with the value obtained by the DSC. For the isothermal magnetizati<strong>on</strong><br />

curves, metamagnetic behavior associated with the magnetic field induced martensitic reverse transformati<strong>on</strong><br />

was observed. Arresting behavior of the martensitic transformati<strong>on</strong> was c<strong>on</strong>firmed in lower temperature, as<br />

similar to the Ni(Co)-Mn-Z (Z = In, Sn, Ga) alloys.<br />

Magnetic Transiti<strong>on</strong> and Thermal Expansi<strong>on</strong> in LaFe13-x-yCoySix Jianli Wang 1 , Stewart James Campbell 2 *, Shane J Kennedy 3 , Precious Shamba 4 , R<strong>on</strong>g<br />

Zeng 4 , Shixue Dou 4 and Guang Heng Wu 5<br />

1<br />

Institute for Superc<strong>on</strong>ducting & Electr<strong>on</strong>ic Materials, The university of Woll<strong>on</strong>g<strong>on</strong>g, Australia<br />

2<br />

School of PEMS, The University of New South Wales, Canberra, Australia<br />

3<br />

Bragg Institute, ANSTO, Australia<br />

4<br />

Institute for Superc<strong>on</strong>ductivity and Electr<strong>on</strong>ic Materials, The University of Woll<strong>on</strong>g<strong>on</strong>g, Australia<br />

5<br />

Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics, Institute of Physics,, Chinese Academy of<br />

Sciences, China<br />

Materials with a large magnetocaloric effect (MCE) c<strong>on</strong>tinue to attract significant attenti<strong>on</strong> for cooling<br />

applicati<strong>on</strong>s with particular interest in the isothermal entropy changes at first-order magnetic transiti<strong>on</strong>s [1].<br />

The large entropy change in LaFe 13-xSi x is associated with negative lattice expansi<strong>on</strong> and metamagnetic<br />

transiti<strong>on</strong> behaviour [2]. We have investigated LaFe 13-x-yCo ySi x to clarify the influence of magneto-structural<br />

coupling <strong>on</strong> the MCE. The Curie temperatures of LaFe 13-xSi x increase with Si c<strong>on</strong>tent from TC=219 K for<br />

x=1.6 to TC=250 K for x=2.6 with further enhancement to TC=281 K <strong>on</strong> substituti<strong>on</strong> of Co to LaFe 9.4CoSi 2.6.<br />

A pr<strong>on</strong>ounced positive sp<strong>on</strong>taneous volume magnetostricti<strong>on</strong> has been observed below TC and the anomalous<br />

thermal expansi<strong>on</strong> attributed to the volume dependence of the magnetic energy. Our results show that the<br />

magnetic transiti<strong>on</strong> changes from first order for LaFe 11.4Si 1.6 to sec<strong>on</strong>d order for LaFe 10.4Si 2.6 and LaFe 9.4CoSi 2.6.<br />

The different natures of the magnetic transiti<strong>on</strong>s in LaFe 13-x-yCo ySi x have been discussed in terms of the<br />

classical model for itinerant ferromagnets and the volume dependence of the magnetic energy.<br />

[1] KA Gschneidner, Jr., VK Pecharsky and AO Tsoko, Rep. Prog. Phys. 68, 1479 (2005) [2] FX Hu,<br />

BG Shen, JR Sun, ZH Cheng, GH Rao, X Zhang, Appl. Phys. Lett. 78, 3675 (2001)<br />

The unit cell volume and the Curie temperature of Y 2Fe 17 increases by substituti<strong>on</strong> of<br />

Ga for Fe. This phenomen<strong>on</strong> is understood as a property of Invar materials, dTc/dV ><br />

0, because the compounds R 2Fe 17 have Invar properties. However, in the substituti<strong>on</strong><br />

of Si for Fe, dTc/dV is negative. Kamimori et. al. proposed damping of the Invar<br />

properties by these substituti<strong>on</strong>s. In this work, the magnetovolume effect of Y 2Fe 17xGax<br />

was investigated by measuring temperature dependence of unit cell volume<br />

and forced volume magnetostricti<strong>on</strong>. X-ray diffracti<strong>on</strong> was used to measure unit cell<br />

volume at under R.T. and thermal expansi<strong>on</strong> meter at above R.T.. The forced volume<br />

magnetostricti<strong>on</strong> was measured by three terminals capacitacne method under magnetic<br />

field up to 1.5T. The forced volume magnetostricti<strong>on</strong> at R.T. is positive. This shows<br />

Y 2Fe 17-xGa x compounds have Invar property. However, the magnitude of the forced<br />

volume magnetostricti<strong>on</strong> decreases violently by the substituti<strong>on</strong> of Ga for Fe. This<br />

tells us the substituti<strong>on</strong> of Ga for Fe in R 2Fe 17 decreases magnetovolume effect and<br />

attenuates Invar characters of the compounds.<br />

July 8 - 13, 2012 Busan, Korea 95<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QG11<br />

Pressure effect <strong>on</strong> the electrical resistivity of La1.09(Fe0.845Si0.155) 13<br />

compound<br />

Makio Kurisu 1 *, D. T. K. Anh 2 and Go Nakamoto 3<br />

1<br />

Department of Physics, Ehime University, Japan<br />

2<br />

School of Materials Science, Japan Advanced Institute of Science and Technology,<br />

Japan<br />

3<br />

School of Materials Science, Japan Advansed Institute of Science and Technology,<br />

Japan<br />

QG12<br />

QG13<br />

WITHDRAWN<br />

One- and two-magn<strong>on</strong> and excit<strong>on</strong> raman scattering in<br />

antiferromagnetic CoF2: Experiment and theory<br />

Eric Meloche 1 , Michael Cottam 1 and David Lockwood 2<br />

1 Department of Physics and Astr<strong>on</strong>omy, University of Western Ontario, Canada<br />

2 Institute for Microstructural Sciences, Nati<strong>on</strong>al Research Council, Canada<br />

Experimental data are reported for the temperature and polarizati<strong>on</strong> dependence of the<br />

<strong>on</strong>e- and two-magn<strong>on</strong> Raman light scattering in the rutile-structure antiferromagnet<br />

CoF 2 (Neel temperature = 38 K). A detailed analysis of the <strong>on</strong>e-magn<strong>on</strong> Stokes and<br />

anti-Stokes Raman spectra is presented resulting in comprehensive experimental data<br />

for the temperature variati<strong>on</strong> of the <strong>on</strong>e-magn<strong>on</strong> frequency, line width, and integrated<br />

intensity. A similar analysis was carried out for the two-magn<strong>on</strong> scattering. The lowlying<br />

excit<strong>on</strong>s were also investigated at low temperatures and comparis<strong>on</strong>s are made<br />

with results from earlier Raman, infrared, and neutr<strong>on</strong> scattering work. The Green’s<br />

functi<strong>on</strong> equati<strong>on</strong> of moti<strong>on</strong> method was employed to derive the excitati<strong>on</strong> energies<br />

and spectral intensities over a broad range of temperatures for the magnetic excitati<strong>on</strong>s<br />

in a spin S = 3/2 anisotropic antiferromagnet with str<strong>on</strong>g spin-orbit coupling. Results<br />

were obtained using RPA for the product of operators at different sites while the singlei<strong>on</strong><br />

anisotropy terms were treated exactly by generating a closed set of coupled Green’s<br />

functi<strong>on</strong> equati<strong>on</strong>s. The numerical results are in good agreement with <strong>on</strong>e-magn<strong>on</strong><br />

Raman light scattering data. Results were deduced for some exchange and anisotropy<br />

parameters and the relative magnitudes of the magneto-optical coefficients in the<br />

interacti<strong>on</strong> Hamilt<strong>on</strong>ian.<br />

Thermodynamic and transport properties of Ru 2-xFe xCrSi (1.3 ≤ x ≤<br />

1.8)<br />

Masakazu Ito*, Toru Hisamatsu, Tsugumi Rokkaku, Iduru Shigeta and Masahiko<br />

Hiroi<br />

Department of Physics and Astr<strong>on</strong>omy, Graduate School of Science and Engineering,<br />

Kagoshima University, Japan<br />

Full-Heusler compounds with the generic chemical formula X 2YZ (X and Y are<br />

transiti<strong>on</strong> elements, Z is sp element) attract much interests because this system shows a<br />

number of physical properties and some of them have a potential for the technological<br />

applicati<strong>on</strong>s. The ferromagnetic Heusler compound Ru2-xFexCrSi is <strong>on</strong>e of candidate<br />

materials expected a half metallicity1] and this system has relatively high Curie<br />

temperature TC~500 K for x > 1.4 2]. We have carried out electric resistivity ρ(T) and<br />

specific heat Cp(T) measurement of Fe-rich Ru 2-xFe xCrSi ( x = 1.3, 1.6, and 1.8 ). For<br />

all samples, ρ(T) shows metallic behavior ( ∂ρ/∂T ) in 20 < T < 300 K, and upturn<br />

at around 20 K. In low-temperature range, Cp(T) can be described by Debye’s law.<br />

Although a coefficient of lattice specific heat β is insensitive for Fe c<strong>on</strong>centrati<strong>on</strong> x, a<br />

electr<strong>on</strong>ic specific heat part γ decreases slightly with increasing x. For each x sample,<br />

we estimated total density of states (DOS) at the Fermi level D(EF) from γ.<br />

1]S. Mizutani et al., Mater. Trans. 47, 25 (2006). 2]M. Hiroi et al., Phys. Rev. B 79, 224423 (2009)<br />

96 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QG14<br />

Magnetic structure and excitati<strong>on</strong>s of the <strong>on</strong>e-dimensi<strong>on</strong>al quantum<br />

antiferromagnet RbCoCl3 Mattia Mena 1 *, Eva Hirtenlechner 2 , Nora Haenni 3 , Sim<strong>on</strong> Ward 4 , Karl Kraemer 3 ,<br />

Christian Ruegg 4 and Des Mcmorrow 1<br />

1<br />

L<strong>on</strong>d<strong>on</strong> Center for Nanotechnology, UCL, United Kingdom<br />

2<br />

Institut Laue-Langevin, France<br />

3<br />

University of Bern, Switzerland<br />

4<br />

Paul Scherrer Institut PSI, Switzerland<br />

RbCoCl 3 is a hexag<strong>on</strong>al perovskite in which the Co 2+ i<strong>on</strong>s have an effective spin S = 1/2 and form <strong>on</strong>edimensi<strong>on</strong>al<br />

(1D) chains perpendicular to the basal plane. Measurements of the magnetic susceptibility<br />

c<strong>on</strong>firm its antiferromagnetic behaviour; the difference between the maximum of the susceptibility and the<br />

Neel temperature indicates 1D magnetic correlati<strong>on</strong>. Isostructural materials, such as CsCoCl 3 and TlCoCl 3, are<br />

quasi-1D Ising-like spin systems[1][2]. The lowest-lying magnetic modes in their spectrum c<strong>on</strong>sist of pairs<br />

of domain-wall excitati<strong>on</strong>s and are described by a str<strong>on</strong>gly anisotropic Heisenberg Hamilt<strong>on</strong>ian[3]. Here we<br />

report the first results of a comprehensive neutr<strong>on</strong> scattering study of the magnetic structure and excitati<strong>on</strong>s in<br />

RbCoCl 3. A neutr<strong>on</strong> diffracti<strong>on</strong> experiment <strong>on</strong> HRPT (SINQ,PSI,Switzerland) revealed the existence of two<br />

phase transiti<strong>on</strong>s at TN1=28K and TN2=14K. At TN1 there is a paramagnetic-to-antiferromagnetic transiti<strong>on</strong>,<br />

while at TN2 a low-temperature phase with a new propagati<strong>on</strong> vector develops. Inelastic neutr<strong>on</strong> scattering<br />

experiments were performed <strong>on</strong> LET (ISIS,RAL,UK) and IN22 (ILL,Grenoble,FR). Between TN1 and TN2,<br />

as well as above TN1, excitati<strong>on</strong>s characteristic for an Ising magnet are observed. Below TN2 an additi<strong>on</strong>al<br />

splitting of the modes is discovered. Results and analysis of the data from LET will be presented and discussed.<br />

[1] J. P. Goff, D. A. Tennant and S. E. Nagler, Phys.Rev. B 52, 15992 (1995). [2] A. Oosawa, Y. Nishiwaki, T. Kato<br />

and K. Kakurai, J. Phys. Soc. Jpn. 75, 15002 (2006). [3] N. Ishimura and H. Shiba, Progr. Theor. Phys. 63, 743 (1980).<br />

QG15<br />

Antiferromagnetic transiti<strong>on</strong> in Ru 2CrSi in magnetic fields<br />

Masahiko Hiroi 1 *, Kaori Uchida 1 , Iduru Shigeta 1 , Masakazu Ito 1 , Keiichi Koyama 1 ,<br />

Shojiro Kimura 2 and Kazuo Watanabe 2<br />

1 Department of Physics and Astr<strong>on</strong>omy, Kagoshima University, Japan<br />

2 Institute for Materials Research, Tohoku University, Japan<br />

Heusler compounds Ru 2-xFe xCrSi for Fe-rich regi<strong>on</strong> were recently found to be<br />

ferromagnetic and to be candidates for a half-metal, where c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s are<br />

fully spin-polarized.[1] In the Heusler compound Ru 2CrSi, <strong>on</strong> the other hand, an<br />

antiferromagnetic (AF) transiti<strong>on</strong> at TN =14 K was revealed by specific heat and<br />

magnetizati<strong>on</strong> measurements.[2] In this study electrical resistivity is measured in<br />

magnetic fields up to 14.5 T and the AF transiti<strong>on</strong> in magnetic fields is investigated. In<br />

the temperature dependence of the resistivity at zero field a clear kink is observed at<br />

TN =14 K. With decreasing temperature the resistivity turns upward from the kink at<br />

TN. This kink can be regarded as an indicati<strong>on</strong> of the AF transiti<strong>on</strong>. With increasing<br />

magnetic field the resistivity <strong>on</strong>ly slightly changes and even at 14.5 T the clear kink is<br />

observed. From the kink TN is found to decrease just a little in high magnetic fields.<br />

TN at 14.5 T is lower than TN at zero field by 0.5 K. These results dem<strong>on</strong>strate that the<br />

AF state in Ru2CrSi is unusually unaffected by str<strong>on</strong>g magnetic field.<br />

[1] M. Hiroi et al., Phys. Rev. B 76, 132401 (2007). [2] M. Hiroi et al., to be published in J. Phys.:<br />

C<strong>on</strong>f. Series.<br />

QG16<br />

Assessment of Curie temperature by magnetizati<strong>on</strong> vs. temperature<br />

(M-T) scans in a granular magnetic Cu-Fe-Ni alloy<br />

Sung Kang 1 , Atsuki Takano 2 , D<strong>on</strong>g-hae Lee 2 , Mahoto Takeda 2 *, Zenji Hiroi 3 and<br />

Masaki Takeguchi 4<br />

1<br />

Research Institute of Industrial Science & Technology (RIST), Korea<br />

2<br />

Yokohama Nati<strong>on</strong>al University, Japan<br />

3<br />

University of Tokyo, Japan<br />

4<br />

Nati<strong>on</strong>al Institute for Materials Science (NIMS), Japan<br />

The present study has investigated the Curie temperature of Cu-Fe-Ni ternary alloy which is known as a<br />

granular giant magneto-resistance (GMR) material with a high magneto-resistance (MR) ratio. At first, we<br />

surveyed the relati<strong>on</strong>ship between the microstructure and the aging temperature of precipitates formed in Cu-<br />

Fe-Ni alloys isothermally annealed at 873K and 1073K for various aging times, using a transmissi<strong>on</strong> electr<strong>on</strong><br />

microscopy (TEM). According to TEM observati<strong>on</strong>s, we have revealed that two or more nano-scale particles<br />

with a cubic shape and rod shape precipitates were formed at 873K and 1073K, respectively. The critical<br />

temperature of the drastic change of the microstructure coincides with the Curie temperature of magnetism<br />

of the alloy. And, the Curie temperature has been determined by the magnetizati<strong>on</strong> (M) vs. temperature (T)<br />

scans, using the SQUID magnetometer. The experimentally determined temperature of 1028K was as high as<br />

a bulk Fe-Ni alloy, even though nano-scale ferromagnetic particles are finely distributed in copper matrices.<br />

The high Curie temperature has, however, well explained the temporal evoluti<strong>on</strong>s in both microstructure and<br />

magnetic properties occurring during isothermal annealing.<br />

[1] S. Kang, M. Takeda, Z. Hiroi, G. W. Kim, C. G. Lee, and B. H. Koo, J. Phys. D: Appl. Phys. 43,<br />

415001 (2010) [2] S. Kang, M. Takeda, M. Takeguchi, and D. S. Bae, J. Alloy. Compds. 496, 196 (2010)


QG17<br />

Design strategy for str<strong>on</strong>gly coupled diradicals: Systematic Approaches<br />

of intramolecular magnetic interacti<strong>on</strong>s<br />

Kyoung Chul Ko, Daeheum Cho and Jin Y<strong>on</strong>g Lee*<br />

Department of Chemistry, SungKyunKwan University, Korea<br />

A new series of neutral radicals (DP1-DP6) based <strong>on</strong> diazaphenalenyl were designed<br />

via heteroatomic modificati<strong>on</strong>s. As spin sources, the designed radicals were<br />

implemented in four different diradical model systems (Model I, II, III, and IV)<br />

by changing the reference radical and the linkage, and their magnetic interacti<strong>on</strong>s<br />

between the designed radicals and the reference radical were investigated by using<br />

density functi<strong>on</strong>al theory calculati<strong>on</strong>s. The trend in strength of magnetic interacti<strong>on</strong>s<br />

of radicals was found to be identical in different model systems. In particular, as a new<br />

family of spin source radical, DP3 could be a potential candidate in designing new<br />

organic magnetic materials due to its str<strong>on</strong>g magnetic coupling and high stability in<br />

diradical systems.(1) We divided 8 m<strong>on</strong>oradicals into α-group and β-group according<br />

to Mulliken spin density values of the c<strong>on</strong>nected atoms. The overall trends in the<br />

strength of magnetic interacti<strong>on</strong>s of diradicals were found to be identical in three<br />

different model systems (Model I, II and V). NN-ethylene-PO was calculated to have<br />

the str<strong>on</strong>gest magnetic coupling c<strong>on</strong>stant with ferromagnetism, and even str<strong>on</strong>ger (more<br />

than twice) than NN-ethylene-NN which was reported to have str<strong>on</strong>g antiferromagnetic<br />

interacti<strong>on</strong>s in a previous experiment.<br />

(1) Ko, K. C.; S<strong>on</strong>, S. U.; Lee, S.; Lee, J. Y. J. Phys. Chem. B 2011, 115, 8401.<br />

QG18<br />

Single crystal growth and physical properties of metalic<br />

antiferromagnet (Mn,Fe) 3Si<br />

So Nara 1 , Sun Chang Che 1 , Haruhiro Hiraka 2 , Kenji Ohoyama 2 , Yasuo Yamaguchi 2 ,<br />

Hiroyuki Miki 3 and Kazuyoshi Yamada 4<br />

1 Dept. of Physics, Tohoku University, Japan<br />

2 IMR,Tohoku University, Japan<br />

3 IFS,Tohoku University, Japan<br />

4 WPI,Tohoku University, Japan<br />

Heusler alloys Mn 3-x Fe x Si(x=0~3) have a face centered cubic (DO3 type) structure in the whole<br />

x-regi<strong>on</strong> from the antiferromagnet Mn 3 Si(TN~23K) to the ferromagnet Fe 3 Si(TC~850K). As a<br />

characteristic point, Mn3Si shows anomalous magnetic excitati<strong>on</strong>s so-called “chimney-type” <strong>on</strong>es,<br />

which is difficult to understood by normal spin waves, while Fe3Si shows typical ferromagnetic<br />

spin wave excitati<strong>on</strong>s. Our final goal is to clarify how the spin dynamics qualitatively changes from<br />

antiferromagnet to ferromagnet in this (Mn,Fe)3Si system, so that a deep insight into the origin<br />

of magnetism would be gained. The purpose of current work is to grow high quality large single<br />

crystals of Mn 3-x Fe x Si for inelastic neur<strong>on</strong> scattering experiments, which can reveal generalized<br />

magnetic susceptibility directly. Besides, for accurate measurement of bulk properties, such as<br />

electric resistivity ρ(T) and magnetic susceptibility χ(T) , minimizing amount of impurities is<br />

important. So far, we have succeeded in growing large single crystals of x=0, 0.2, 0.6, 1.0, and<br />

1.5 by the Bridgman method. At present, an impurity phase (several-% order) is still observable<br />

in X-ray powder diffracti<strong>on</strong> patterns. In this work, we report the details of single crystal growth of<br />

Mn 3-x Fe x Si, assignment of impurity phase,and resultant χ(T), and ρ(T).<br />

QG19<br />

AC magnetic measurement of LiFeAs at pressures up to 5.2 GPa:<br />

Verificati<strong>on</strong> of the relati<strong>on</strong> between Tc and structural parameters<br />

Shuhei Yamaguchi 1 , Nobuhiro Yamaguchi 1 , Masaki Mito 1 , Hiroyuki Deguchi 1 ,<br />

Michael. J. Pitcher 2 , Peter. J. Baker 3 , Stephen. J. Blundell 3 , Dinah. R. Parker 2 and<br />

Sim<strong>on</strong>. J. Clarke 2<br />

1 Fac. of Eng, Kyushu Inst. of Tech, Japan<br />

2 Dep. of Chem, Univ. of Oxford, United Kingdom<br />

3 Dep. of Phys, Univ. of Oxford, United Kingdom<br />

We have already c<strong>on</strong>ducted AC susceptibility measurements at pressures up to 1.5<br />

GPa and X-ray diffracti<strong>on</strong> experiment up to 20 GPa for a 111 type of ir<strong>on</strong>-based<br />

superc<strong>on</strong>ductor, LiFeAs[1]. Now, we have enlarged the pressure range of the AC<br />

susceptibility measurement for the same sample up to 5.2 GPa. The superc<strong>on</strong>ducting<br />

transiti<strong>on</strong> temperature Tc decreased from 17 K at 0 GPa to 10 K at 5.2 GPa. Tc has<br />

been related to two structural parameters, an As-Fe-As b<strong>on</strong>d angle α and the height of<br />

As from the Fe layers (hAs): Lee et al. have suggested that Tc has the highest value<br />

at the optimal α of 109.47°[2]. Kuroki et al. have suggested that Tc increases with<br />

increasing hAs[3]. According to our previous study, α changes from 101.5° at 0 GPa to<br />

97.8° at 17 GPa, and hAs changes from 0.154 nm at 0 GPa to 0.156 nm at 17 GPa. The<br />

present pressure-induced decrease in Tc is not explained by the change in hAs, but is<br />

qualitatively c<strong>on</strong>sistent with the change in α.<br />

[1] M. Mito et al., J. Am. Chem. Soc., 131 (2009) 2986. [2] C.H. Lee et al., J. Phys. Soc. Jpn. 77<br />

(2008) 083704. [3] K. Kuroki et al., Phys.Rev.B 79 (2009) 224511.<br />

QG20<br />

QG21<br />

QG22<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Fundamental <strong>Magnetism</strong> of Fe-P Alloys and Fe3P Compounds: A<br />

density functi<strong>on</strong>al study<br />

W<strong>on</strong> Seok Yun, Jee Y<strong>on</strong>g Lee and In Gee Kim*<br />

Graduate Institute of Ferrous Technology, POSTECH, Korea<br />

Phosphorus (P) is quite harmful <strong>on</strong> the mechanical properties of steel. For instance,<br />

the decrease of the strength and plastic properties of G13L steel is nearly half when it<br />

c<strong>on</strong>tains 0.065 wt.% P compared to the case of 0.028 wt.% P steel. On the c<strong>on</strong>trary, P<br />

is an important comp<strong>on</strong>ent in the making phosphor br<strong>on</strong>ze which enhances wear and<br />

water corrosi<strong>on</strong> resistant. On the purpose of solid soluti<strong>on</strong> strengthening, P c<strong>on</strong>taining<br />

interstitial free steel is very important in the automotive industry due to their excellent<br />

deep drawability. However, there is no systematic first-principles study d<strong>on</strong>e for<br />

understanding the Fe-P alloys and Fe3P compounds. Thus, we investigated fundamental<br />

magnetic and thermodynamic properties of ferrites with the various P c<strong>on</strong>centrati<strong>on</strong>s<br />

(Fe 1-xP x alloys, x = 0.037, 0.0625, and 0.125) and (L12, D03, and I-4 structured) Fe 3P<br />

compounds using the highly precise all-electr<strong>on</strong> full-potential linealized augmented<br />

plane wave method. As a result, the ferromagnetic state for I-4 structured Fe 3P<br />

compound is more stable than the n<strong>on</strong>mangetic <strong>on</strong>e by energy difference of about<br />

809 meV. The calculated magnetic moments are rather overestimated compared to the<br />

neutr<strong>on</strong> diffracti<strong>on</strong> study. Detailed discussi<strong>on</strong> <strong>on</strong> the magnetic and thermodynamic<br />

properties of Fe 1-xP x alloys and Fe 3P compounds will be given.<br />

Analysis of spin-polar<strong>on</strong> formati<strong>on</strong> in Hund lattices<br />

Yesenia Arred<strong>on</strong>do 1 *, Emmanuel Vallejo 2 , Oracio Navarro 1 and Michel Avign<strong>on</strong> 3<br />

1 Instituto de Investigaci<strong>on</strong>es en Materiales, Universidad Naci<strong>on</strong>al Aut<strong>on</strong>oma de Mexico, Mexico<br />

2 Facultad de Ingenieria Mecanica y Electrica, Universidad Aut<strong>on</strong>oma de Coahuila, Mexico<br />

3 Institut Neel, CNRS and Universite Joseph Fourier, France<br />

The ferromagnetic K<strong>on</strong>do lattice model, also known as Hund lattice model, is a well-established model to<br />

study the interplay between charge and spin degrees of freedom in str<strong>on</strong>gly correlated fermi<strong>on</strong>ic systems<br />

such as transiti<strong>on</strong>-metal oxides. Their electr<strong>on</strong>ic, magnetic and transport properties have displayed interesting<br />

physics such as the phenomen<strong>on</strong> of magnetoresistance [1]. Their properties depend as well str<strong>on</strong>gly <strong>on</strong> the<br />

doping of the materials, which leads to formati<strong>on</strong> of magnetically ordered regimes [2]. In our work, we study<br />

numerically the formati<strong>on</strong> of spin-polar<strong>on</strong>s in <strong>on</strong>e-dimensi<strong>on</strong>al systems. We c<strong>on</strong>sider a Hund lattice model<br />

where a c<strong>on</strong>ducting band is coupled to a background of localized spins interacting antiferromagnetically with<br />

coupling c<strong>on</strong>stant J. Even though the zero-temperature of such lattice model has been intensively studied [3<br />

,4], the physics of its phase diagram is still not exhausted. We investigated the ground state phase diagram<br />

as a functi<strong>on</strong> of the exchange coupling J and as a functi<strong>on</strong> of the band filling and found different evolving<br />

magnetic orderings. We report measurements of static properties such as spin structure factor. We study the<br />

quasi-particle formati<strong>on</strong> and phase separati<strong>on</strong> using the density-matrix renormalizati<strong>on</strong> group method, which<br />

is a highly efficient method to investigate quasi-<strong>on</strong>e-dimensi<strong>on</strong>al str<strong>on</strong>gly correlated systems[5].<br />

1. D. D. Sarma, P. Mahadevan, T. Saha-Dasgupta, S. Ray, A. Kumar, Phys. Rev. Lett. 85, 2549(2000). 2. T.<br />

Kumar, M. Greenblatt. In Functi<strong>on</strong>al Oxides, John Wiley & S<strong>on</strong>s, 2010. 3. E. Vallejo, F. Lopez-Urias, O.<br />

Navarro, M. Avign<strong>on</strong>, Solid State Commun. 149, 126(2009). 4. D. J. Garcia, K. Hallberg, B. Alascio, M.<br />

Avign<strong>on</strong>, Phys. Rev. Lett. 93, 177204(2004). 5. U. Schollwock, Rev. Mod. Phys. 77, 259(2005).<br />

Chiral magnetic orders in chiral helimagnet Cr1/3NbS2 Yoshihiko Togawa 1 *, Tsukasa Koyama 2 , Shigeo Mori 2 , Yusuke Kousaka 3 , Jun<br />

Akimitsu 3 , Sadafumi Nishihara 4 , Katsuya Inoue 4 , Alexander Sasha Ovchinnikov 5 and<br />

Jun-ichiro Kishine 6<br />

1<br />

Nanoscience and Nanotechnology Research Center (N2RC), Osaka Prefecture<br />

University, Japan<br />

2<br />

Department of Materials Science, Osaka Prefecture University, Japan<br />

3<br />

Department of Physics, Aoyama Gakuin University, Japan<br />

4<br />

Department of Chemistry, Hiroshima University, Japan<br />

5<br />

Department of Physics, Ural Federal University, Russia<br />

6<br />

Graduate School of Arts and Sciences, The Open University of Japan, Japan<br />

We directly present that chiral magnetic orders emerge in chiral helimagnet Cr 1/3NbS 2 in small magnetic fields<br />

by means of low-temperature Lorenz transmissi<strong>on</strong> electr<strong>on</strong> microscopy and small-angle electr<strong>on</strong> diffracti<strong>on</strong><br />

technique. Based <strong>on</strong> precise analyses in both real and reciprocal space, we undoubtedly dem<strong>on</strong>strate that chiral<br />

magnetic solit<strong>on</strong> lattice (CSL) develops from chiral helimagnetic structure (CHM) with increasing the spatial<br />

period from 48 nm toward infinity in rising magnetic fields perpendicular to the helical axis. CSL and CHM do<br />

not exhibit any structural dislocati<strong>on</strong>, indicating their high stability and robustness. This is because chiral magnetic<br />

orders are macroscopically induced by the uniaxial Dzyaloshinkii-Moriya (DM) exchange interacti<strong>on</strong>s that is<br />

allowed in Cr 1/3NbS 2 hexag<strong>on</strong>al crystals bel<strong>on</strong>ging to n<strong>on</strong>centrosymmetric chiral space group. Theoretical sides<br />

of this talk will be given in this topic category by Prof. Jun-ichiro Kishine from the Open University of Japan.<br />

[1] Y. Togawa, T. Koyama, K. Takayanagi, S. Mori, Y. Kousaka, J. Akimitsu, S. Nishihara, K. Inoue, A.<br />

S. Ovchinnikov, and J. Kishine, to appear in Phys. Rev. Lett.<br />

July 8 - 13, 2012 Busan, Korea 97<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QG23<br />

ESR study of AFM - Ordering in the orthorhombic CuMnAs<br />

Yuriy Vladimirovich Goryunov 1 * and Alexandr Nikolaevich Nateprov 2<br />

1<br />

Russian Academy of Sciences, Kazan Physical-Technical Institute of the Russian<br />

Academy of Sciences, Russia<br />

2<br />

Academy of Sciences of Moldova, Institute of Applied Physics, Moldova<br />

At the present time the Mn based compounds with elements of I or V group were<br />

studied intensively as advances materials for spintr<strong>on</strong>ic. One from such compounds<br />

is CuMnAs. CuMnAs is ordered antiferromagneticaly above room temperature. We<br />

have studied electr<strong>on</strong>ic spin res<strong>on</strong>ance (X-band) in this compound at temperature<br />

range 10 - 400 K At all temperature we observed symmetric Lorentz’s shape res<strong>on</strong>ance<br />

lines from Mn 2+ i<strong>on</strong>s with g - factor 2.00. The lineswidth increase in 2 times at<br />

temperature decreasing to 10 K. The sec<strong>on</strong>d line with a g-factor of 2.55 has appeared<br />

in the spectrum at temperatures below 60 K N<strong>on</strong> res<strong>on</strong>ant absorpti<strong>on</strong> was observed<br />

for powder samples. We interpreted our results in terms Mn-Cu-Mn and Mn-As-<br />

Mn indirect superexchange interacti<strong>on</strong>. Work was supported by Grants of RFBR and<br />

Presidium of the RAS.<br />

[1] F. Maca, J. Masek,O. Stelmakhovych, et al., ArXiv: 1102.5373v1 [c<strong>on</strong>d-mat. matrl-sci] 25<br />

Feb 2011 [2] T. Je<strong>on</strong>g, Ruben Weht,W. E. Pickett, Phys.Rev. B 71, 184103 (2005) [3] J. Boeuf, C.<br />

Pfleiderer, A. Faißt, Phys.Rev. B 74, 024428 (2006) [4] T. Jungwirth, V. Novak, X. Martı, M. Cukr, et<br />

al., Phys.Rev. B 83, 035321 (2011)<br />

QG24<br />

Elastic properties and stability of Heusler compounds<br />

S.-c. Wu*, S. S. Naghavi, G. H. Fecher and C. Felser<br />

Max Planck Inst. for Chem. Phys. of Solids; Inst. for Inorg. and Analy. Chem., Uni.<br />

Mainz, Germany<br />

The physical properties of Heusler compounds which are promising materials for<br />

spintr<strong>on</strong>ics are important. Various Heusler compounds are investigated with respect<br />

to their malleability and stability. The elastic c<strong>on</strong>stants are calculated by applying<br />

isotropic strain in different ways to the cubic crystal. We used FP-LAPW implemented<br />

in Wien2K to calculate the elastic c<strong>on</strong>stants as well as further physical properties<br />

(b<strong>on</strong>ding, hardness, velocity of sound, Debye temperature, etc.) that can be derived<br />

from the elastic c<strong>on</strong>stants. The result of the cubic elastic anisotropy can be used to<br />

decide the structural stability. Zener's ratios of the most stable compounds are in the<br />

range of 1.0 < Ae < 2.5. Ae < 0 is not stable and Ae = 0 is isotropic. We observed phase<br />

transiti<strong>on</strong>s in some of Heusler compounds with Ae < 0. It is shown that calculating<br />

elastic c<strong>on</strong>stants provides an estimate for studying phase transiti<strong>on</strong>s.<br />

QG25<br />

Electr<strong>on</strong>ic and magnetic properties of ferromagnet/dilute-magnetic<br />

semic<strong>on</strong>ductor interfaces<br />

Alessandra C<strong>on</strong>tinenza* and Gianni Profeta<br />

Physics, Universita' degli studi dell'Aquila, Italy<br />

A. C<strong>on</strong>tinenza and G. Profeta Experimental findings [1-4] report exchange-bias effects<br />

at the Fe/GaMnAs together with interesting possible magnetic prossimity effects at the<br />

interface between the ferromagnetic (FM) material and the dilute semic<strong>on</strong>ductor (DMS).<br />

In this work we perform ab-initio calculati<strong>on</strong>s of different FM/DMS geometries<br />

(superlattice systems and periodic slab) for Fe/Ge:Mn and Fe/GaAs:Mn interfaces. We<br />

examine different interfaces to assess the most stable structures, the magnetic coupling<br />

between the magnetic overlayer and the Mn dopant atoms and how the ferromagnetic<br />

overlayer affects the interacti<strong>on</strong> between two Mn atoms dispersed in the semic<strong>on</strong>ductor<br />

matrix. An antiferromagnetic coupling between the overlayer Fe and the Mn is found<br />

for Mn close to the interface layers, fading away with the distance of the Mn atom<br />

from the interface. A study of how the magnetic coupling between overlayer and dilute<br />

Mn and between dilute Mn's at different locati<strong>on</strong>s is performed and discussed. We find<br />

a rather large magnetic coupling enhancement in the case of Ge while the situati<strong>on</strong> for<br />

GaAs looks to be much more complex due to chemical effects at the GaA/Fe interface.<br />

Results are discussed in terms of local densities of states, magnetic moments and total<br />

energies.<br />

[1] Phys. Rev. Lett. 101, 267201 (2008) [2] Phys. Rev. B 81, 104402 (2010) [3] Phys. Rev. B<br />

81.035211 (2011) [4] J. Appl. Phys. 109, 07C505 (2011)<br />

98 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QG26<br />

Mn-Sublattice of YbMn2Si2 Stewart J Campbell 1 *, Michael Hofmann 2 , Richard A Mole 3 , Karel Prokes 4 , Jianli Wang 5 and Dirk Wallacher 6<br />

1<br />

School of Physical, Envir<strong>on</strong>mental and Mathematical Sciences,ADFA, The University of New South<br />

Wales, Australia<br />

2<br />

Forschungsneutr<strong>on</strong>enquelle Heinz Maier-Leibnitz (FRM II), Technische Universitat Munchen, Germany<br />

3<br />

Bragg Institute,, ANSTO, Australia<br />

4<br />

Helmholz Zentrum Berlin, Lise Meitner Campus, Germany<br />

5<br />

Institute for Superc<strong>on</strong>ducting & Electr<strong>on</strong>ic Materia, University of Woll<strong>on</strong>g<strong>on</strong>g, Australia<br />

6<br />

Helmholz Zentrum Berlin,, Lise Meitner Campus, Germany<br />

The instability of the f shell in Yb and the small energy difference between the Yb 2+ divalent and<br />

Yb 3+ trivalent states, has led to the wide range of physical and magnetic properties exhibited by ytterbiumbased<br />

intermetallic compounds. The ranges of effects are linked with many physical states such as: mixed<br />

valence, K<strong>on</strong>do effect, heavy fermi<strong>on</strong>s, spin wave excitati<strong>on</strong>s, superc<strong>on</strong>ductivity and magnetic quantum<br />

critical point [e.g. 1]. Trivalent YbMn 2Si 2 exhibits a collinear antiferromagnetic AFil structure below TN1 =<br />

526(4) K with a doubling of the magnetic c-lattice below TN2 = 30(5) K; this structure of the Mn-sublattice<br />

would therefore be expected to result in different envir<strong>on</strong>ments for Yb atoms in the doubled unit cell [2].<br />

However 170Yb Mossbauer studies led to the c<strong>on</strong>clusi<strong>on</strong> that the observed spectra are inc<strong>on</strong>sistent with the<br />

cell-doubling [3]. To clarify this discrepancy, we have re-investigated the magnetic behaviour of YbMn2Si2<br />

over the temperature range ~0.4-50 K using the E6 neutr<strong>on</strong> diffractometer, HZB. The high density of<br />

diffracti<strong>on</strong> patterns c<strong>on</strong>firm the cell doubled magnetic behaviour of the Mn-sublattice below 27.3(2) K with<br />

the <strong>on</strong>set of the satellite reflecti<strong>on</strong>s (propagati<strong>on</strong> vector k = 00½) described well by a power law.<br />

[1] C. Klingner, C. Krellner, M. Brando, C. Geibel, F. Steglich, D. V. Vyalikh, K. Kummer, S. Danzenbacher, S. L. Molodtsov, and C.<br />

Laubschat, T. Kinoshita, Y. Kato, and T. Muro, Phys. Rev. B 83, 144405 (2011). [2] M. Hofmann, S.J. Campbell, A.V.J. Edge and A.J. Studer, J.<br />

Phys.: C<strong>on</strong>dens. Matter 13, 9773 (2001). [3] D. H. Ryan, J. M. Cadogan, and A.V.J. Edge, J. Phys.: C<strong>on</strong>dens. Matter 16, 6129 (2004)<br />

QG27<br />

Electr<strong>on</strong>ic structures and magnetic properties of full and half Fe-Mn-<br />

Ga Heusler alloys<br />

Y. V. Kudryavtsev 1 , N.v. Uvarov 1 , J. Dubowik 2 , I.n. Glavatskyy 3 , Y. J. Yoo 4 and Y. P. Lee 4 *<br />

1 G.V.Kurdumov Institute of Metal Physics NAS of Ukraine, Ukraine<br />

2 Institute of Molecular Physics, PAS, Poland<br />

3 Helmholtz Centre Berlin for Materials and Energy, Germany<br />

4 Dept. of Physics, Hanyang University, Korea<br />

Electr<strong>on</strong>ic and magnetic structures of bulk and film Fe 2MnGa and FeMnGa alloys near 2:1:1 and 1:1:1<br />

stoichiometric compositi<strong>on</strong>s have been investigated theoretically and experimentally. It was experimentally<br />

found that unlike most of full stoichiometric Heusler compounds, bulk Fe 50,4Mn 24,2Ga 25,4 alloy with<br />

the Curie temperature of 800 K and saturati<strong>on</strong> magnetizati<strong>on</strong> of 4.86 μB/f.u. crystallizes in the facecentered-cubic<br />

(FCC) ordered lattice of L12 (Cu 3Au)-type with small admixture of B2-phase. According<br />

to results of our first-principle calculati<strong>on</strong>s of full electr<strong>on</strong> energy ferromagnetic metallic FCC phase<br />

(μFCC=6.11 μB/f.u.) is energetically more preferable than ferrimagnetic half-metallic phase with L21 type<br />

of structure (μL21=2.04 μB/f.u.) or ferrimagnetic metallic FCC phase (μFCC=0.48 μB/f.u.). Metamagnetic<br />

transiti<strong>on</strong> in Fe 50,4Mn 24,2Ga 25,4 alloy from antiferromagnetic to ferromagnetic phase was observed at low<br />

temperatures. Bulk Fe 33.5Mn 32.0Ga 34.5 alloy has hexag<strong>on</strong>al structure and saturati<strong>on</strong> magnetizati<strong>on</strong> at T=15<br />

K of μ=3.00 μB/f.u. and the Curie temperature of 453 K. Magnetic properties of Fe 33.6Mn 32.9Ga 32.8 alloy<br />

films str<strong>on</strong>gly depend <strong>on</strong> their structure. Atomic disorder in amorphous state significantly reduces the film<br />

magnetizati<strong>on</strong> nearly to zero at room temperature. Depending <strong>on</strong> depositi<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s, unlike the bulk<br />

alloy, crystalline Fe 33.6Mn 32.9Ga 32.8 alloy films exhibit BCC- or FCC-ordering that result in anomalous<br />

temperature dependencies of magnetizati<strong>on</strong> in low-temperature regi<strong>on</strong>.<br />

QG28<br />

Microscopic analysis of magnetic orders in MnP single crystals<br />

Tsukasa Koyama 1 , Shin-ichiro Yano 2 , Yoshihiko Togawa 3 , Yusuke Kousaka 2 , Shigeo<br />

Mori 1 , Jun-ichiro Kishine 4 and Jun Akimitsu 2<br />

1<br />

Department of Materials Science, Osaka Prefecture University, Japan<br />

2<br />

Department of Physics, Aoyama Gakuin University, Japan<br />

3<br />

Nanoscience and Nanotechnology Research Center, Osaka Prefecture University,<br />

Japan<br />

4<br />

Graduate School of Arts and Sciences, The Open University of Japan, Japan<br />

Manganese phosphide (MnP) has been extensively studied because of its richness of magnetically<br />

ordered phases in the magnetic phase diagram. In this study, as a first step to understand the mechanism<br />

of the magnetic phase transiti<strong>on</strong> from the ferromagnetic (FM) phase to the proper screw spiral phase<br />

or FAN phase, we have studied FM structures in the FM phase of MnP single crystals by means of<br />

low-temperature Lorentz transmissi<strong>on</strong> electr<strong>on</strong> microscopy and small-angle electr<strong>on</strong> diffracti<strong>on</strong>[1].<br />

In Lorentz Fresnel micrographs, striped FM domain structures were observed in external magnetic<br />

field less than 10 Oe in the specimens with the ab-plane in the plane of the specimen. From real- and<br />

reciprocal-space analyses, it was undoubtedly identified that striped FM domains oriented to the c-axis<br />

appear with Bloch-type domain walls in the b directi<strong>on</strong> and arrange regularly al<strong>on</strong>g the a-axis with 64<br />

nm separati<strong>on</strong>. Moreover, the magnetic chirality reverses in alternate FM domain walls. These specific<br />

spin c<strong>on</strong>figurati<strong>on</strong> of striped FM domains will affect the magnetic phase transiti<strong>on</strong> from the FM phase<br />

to the proper screw spiral phase at the low temperature or the FAN phase in the magnetic field in MnP.<br />

[1] T. Koyama, S. Yano, Y. Togawa, Y. Kousaka, S. Mori, K. Inoue, J. Kishine, and J. Akimitsu,<br />

submitted.


QH01<br />

Structural and magnetic properties of Fe2Mn0.5Cu0.5Al Nanocrystalline<br />

Alloys<br />

Dwi Nanto 1 , D<strong>on</strong>g-seok Yang 2 , Suhk-kun Oh 1 and Se<strong>on</strong>g-cho Yu 1 *<br />

1<br />

Dept. of Physics, BK 21 Physics Program and Dept. of Physics, Chungbuk Nati<strong>on</strong>al<br />

University, Che<strong>on</strong>gju, 361-763, Korea<br />

2<br />

Dept. of Physics Educati<strong>on</strong>, Physics Divisi<strong>on</strong>, Chungbuk Nati<strong>on</strong>al University,<br />

Che<strong>on</strong>gju, 361-763, Korea<br />

We synthesized Fe 2Mn 0.5Cu 0.5Al nanocrystalline alloys by mechanical alloying<br />

technique and studied as a functi<strong>on</strong> of milling time. The milling times were 1, 3, 6, 9,<br />

and 24 hrs. The effect of milling time <strong>on</strong> structure formati<strong>on</strong> was investigated by X-ray<br />

Diffracti<strong>on</strong> (XRD), and magnetic properties was investigated using vibrati<strong>on</strong> sample<br />

magnetometer (VSM). Alloy nature of Fe 2Mn 0.5Cu 0.5Al was c<strong>on</strong>firmed after 24 hrs. The<br />

crystallite size after 24 hrs of milling time was estimated using Scherer formula, and<br />

the value was 24 nm. Magnetic saturati<strong>on</strong> was decreased with increased milling time,<br />

which seemed be due to co-existence of Mn and Cu atoms. The magnetic saturati<strong>on</strong><br />

was 86.19 (emu/gr) and the coercivity was 376.59 Oe after 24 hrs of milling time. The<br />

coercivity (Hc) was increased with milling time presumably due to magnetic domain<br />

growth towards stable structure. Keywords: Heusler compound, nanocrytalline<br />

References: [1] Tanja Graf, Claudia Felser, Stuart S.P. Parkin, Progress in Solid State Chemistry<br />

39 (2011) 1-50 [2] Shane Stadler1, Mahmud Khan1, Joseph Mitchell1, Naushad Ali1, Angelo M.<br />

Gomes2, Igor Dubenko3, Armando Y. Takeuchi3, and Alberto P. Guimaraes3 Appl. Phys. Lett. 88,<br />

192511 (2006)<br />

QH02<br />

Antiferromagnetic res<strong>on</strong>ance in the <strong>on</strong>e-dimensi<strong>on</strong>al magnet<br />

IPACu(Cl 1-xBr x) 3 (x=0.83)<br />

Takahito Fujita 1 , Masayuki Hagiwara 1 and Hirotaka Manaka 2<br />

1 KYOKUGEN, Osaka university, KYOKUGEN, Osaka university, 1-3<br />

Machikaneyama, Toy<strong>on</strong>aka, Osaka 560-8531, Japan<br />

2 Graduate School of Science and Engineering, Kagoshima University, Graduate<br />

School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto,<br />

Kagoshima 890-00, Japan<br />

Low-dimensi<strong>on</strong>al antiferromagnets with a small spin value exhibit various fascinating<br />

properties. IPACuCl 3 and IPACuBr 3 (IPA: isopropyl-amine) having magnetic Cu 2+ (spin<br />

S=1/2) i<strong>on</strong>s form the ladder chain in the b plane. The ground states of IPACuCl 3 and<br />

IPACuBr 3 are c<strong>on</strong>sidered to be the Haldane state [1] and the singlet dimer state [2]. It<br />

was reported that IPACu(Cl xBr 1-x) 3 (0.44 < x


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QH07<br />

Effect of doped Mn i<strong>on</strong>s in thermoelectric material of Mg 3Sb 2<br />

Soo Hyun Kim 1 , Chung Man Kim 1 , Junpei Kajino 2 , Toshiro Takabatake 2 and Myunghwa<br />

Jung 1 *<br />

1 Physics, Sogang university, Korea<br />

2 Physics, Hiroshima University, Japan<br />

Spin caloritr<strong>on</strong>ics is about the physics that c<strong>on</strong>trol of heat, charge and spin currents in<br />

structures, devices, and materials. Here we focus <strong>on</strong> the spin-related thermoelectric<br />

properties and study the effect of magnetic i<strong>on</strong> doping <strong>on</strong> the thermoelectric material<br />

of Mg 3Sb 2. We have synthesized single crystals of Mg 3Sb 2 and Mn-doped Mg 3Sb 2 by<br />

using Bridgeman method. The X-ray diffracti<strong>on</strong> data show that the crystals are singlephased<br />

and c-axis oriented. In order to illustrate the thermoelectric performance, we<br />

have measured the seebeck coefficient (S), electrical c<strong>on</strong>ductivity (σ), and thermal<br />

c<strong>on</strong>ductivity (κ) as a functi<strong>on</strong> of temperature. The efficiency of thermoelectric<br />

performance is dominated by the figure of merit, ZT=S 2 ∙σ∙T/κ. The obtained S, σ,<br />

and κ values at 300K are 600 μV/K, 16 S/m, and 3.5 W/mK, respectively for Mg 3Sb 2.<br />

Because of the lower σ, the ZT value is estimated to be small. However, by doping<br />

Mn i<strong>on</strong>s into Mg 3Sb 2, we find the electrical properties to be improved. We will<br />

discuss more about the optimal c<strong>on</strong>diti<strong>on</strong> of Mn doping rate in Mg 3Sb 2 to promote the<br />

thermoelectric performance.<br />

QH08<br />

X-ray diffracti<strong>on</strong> study <strong>on</strong> crystal structure of Mn 1.8Co 0.2Sb under high<br />

magnetic fields<br />

Hiroki Orihashi 1 *, Daisuke Mitsunaga 1 , Masahiko Hiroi 1 , Yoshifuru Mitsui 2 , Kohki<br />

Takahashi 2 , Kazuo Watanabe 2 and Keiichi Koyama 1<br />

1 Graduate School of Science Engineering, Kagoshima University, Japan<br />

2 HFLSM, IMR, Tohoku University, Japan<br />

Measurements of magnetizati<strong>on</strong>, electrical resistivity and high field X-ray powder<br />

diffracti<strong>on</strong> (XRD) were carried out for polycrystalline Mn 1.8Co 0.2Sb in magnetic<br />

fields up to 5 T in 4.2-300 K temperature range, in order to investigate the structural<br />

properties affected by magnetic fields. In a zero field, the compound shows the firstorder<br />

magnetic transiti<strong>on</strong> from the ferrimagntetic (FRI) to antiferromagnetic (AFM)<br />

states at Tt = 145 K with decreasing temperature. By applying magnetic fields of 5 T,<br />

Tt decreased to 60 K with thermal hysteresis of 35 K. From the XRD measurements,<br />

not <strong>on</strong>ly the AFM phase but also the residual FRI phase was c<strong>on</strong>firmed even at 10 K<br />

in cooling process under 5 T. Results obtained indicate that the residual FRI phase is<br />

kinetically arrested [1].<br />

[1] H. Orihashi et al. Mater. Trans. [Selected Papers from JIM Fall Meeting(2011)] 76 (2011) in<br />

press<br />

QH09<br />

Emergence of Ferromagnetism under pressure in (Mn 1-xFe x) 3GaN<br />

S. Iikubo 1,6 , T. Inagaki 2 , K. Takenaka 2 , K. Matsubayashi 3 , Y. Uwatoko 3 , H. Takagi 4 ,<br />

and H. Ohtani 5,6<br />

1 Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology<br />

2 Department of Crystalline Materials Science, Nagoya University<br />

3 Institute for Solid State Physics University of Tokyo<br />

4 RIKEN (The Institute of Physical and Chemical Research)<br />

5 Department of Materials Science and Engineering, Kyushu Institute of Technology<br />

6 JST, CREST<br />

The recent development of “metallic” antiperovskite nitrides Mn 3AN, where A is a metal or a<br />

semic<strong>on</strong>ducting element, has promoted research toward practical use. We found an intimate<br />

relati<strong>on</strong>ship between the large magneto-volume effect (MVE) in cubic Mn 3AN and the Γ 5g -type<br />

antiferromagnetic (AF) ordering. As a tunable thermodynamic parameter, the external pressure<br />

may play an important role in this system, because it can affect not <strong>on</strong>ly the crystal structure but<br />

also the magnetic structure. We report the pressure effect <strong>on</strong> the stability of magnetic structure of<br />

(Mn 1-xFe x) 3GaN.<br />

In this system, it was reported that a few percent of Fe dopants at the Mn sites alters the AF spin<br />

structure of Mn 3GaN and induces a first-order antiferromag-netic-ferromagnetic phase transiti<strong>on</strong>.<br />

We have measured the magnetizati<strong>on</strong> of (Mn 1-xFe x) 3GaN with x=0, 0.05 and 0.07 and Mn 3Ga(N 1yC<br />

y) with y=0, 0.05 and 0.1 under pressure up to 1.3 GPa. A magnetic transiti<strong>on</strong> from an AF to an<br />

ferromagnetic (FM) state with sp<strong>on</strong>taneous magnetizati<strong>on</strong> is observed under pressure. Especially,<br />

a sp<strong>on</strong>taneous magnetizati<strong>on</strong> in Mn3GaN is 0.24 μB per Mn under pressure. The applicati<strong>on</strong> of<br />

pressure increases the magnetizati<strong>on</strong> in the FM phase for all these compounds.<br />

100 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QH10<br />

First-principles-calculati<strong>on</strong>s of the magnetic anisotropy energy of<br />

FeCo and FeNi alloys<br />

Masanori Enoki 1 , Satoshi Iikubo 2 and Hiroshi Ohtani 3<br />

1<br />

Graduate School of Engineering, Kyushu Institute of Technology, Japan Science and<br />

Technology CREST, Japan<br />

2<br />

Graduate School of Life Science and Systems Engineering, Kyushu Institute of<br />

Technology, Japan Science and Technology CREST, Japan<br />

3<br />

Department of Materials Science, Kyushu Institute of Technology, Japan Science<br />

and Technology CREST, Japan<br />

The calculati<strong>on</strong>s of T.Burkert et at. predict an unusually large magnetic anisotropy energy (MAE)<br />

of ~700 μeV/atom for the Fe 0.4Co 0.6 random alloy at a ratio of 'c/a'[1]. This result suggests that other<br />

transiti<strong>on</strong> metal alloys are also candidate for emerging a high MAE with altering the 'c/a'. In order<br />

to seek new design of materials, we research MAE and electr<strong>on</strong>ic structures for Fe-Co and Fe-Ni<br />

alloys with using the first-principles-calculati<strong>on</strong>s. The calculati<strong>on</strong>s were carried out using the VASP<br />

code. At first, we optimized the length of lattice c<strong>on</strong>stant 'a' against the fixed 'c/a' at range of 1.10-<br />

1.35. The MAE were evaluated by subtracting the energy with polarized spin directi<strong>on</strong> parallel to<br />

[100] from that to [001]. For the Fe-Co alloy, the estimated MAE has maximum at c/a~1.25 and<br />

Fe 0.5Co 0.5, which is roughly c<strong>on</strong>sistent with the previous result of Burkert et al. On the other hand,<br />

Fe-Ni system has the high MAE (~300 μeV/atom) is found at the Fe 0.75Ni 0.25. We will present the<br />

origin of the large MAE from the electr<strong>on</strong>ic structures in these systems.<br />

[1]T. Burkert et al. Phys. Rev. Lett. 93 027203 (2004)<br />

QH11<br />

Tuning the magnetic properties of amorphous FeZr thin by hydrogen<br />

implantati<strong>on</strong><br />

Atieh Zamani 1 *, Anders Hall 2 , Per Nordblad 3 , Bjorgvin Hjorvarss<strong>on</strong>1 and Petra<br />

J<strong>on</strong>ss<strong>on</strong>1<br />

1 Physics and Astr<strong>on</strong>omy,Material Physics, Uppsala University, Sweden<br />

2 School of Informati<strong>on</strong> and Communicati<strong>on</strong> Technology (ICT), KTH, Sweden<br />

3 Department of Engineering Sciences,, Uppsala University, Sweden<br />

Amorphous FeZr alloys order ferromagnetically, with a maximum in the ferromagnetic<br />

transiti<strong>on</strong> temperature near 240K for Zr c<strong>on</strong>tents between 10-20 at.% . Interestingly,<br />

hydrogen can be introduced into the alloy, enhancing its Curie temperature, magnetic<br />

moment and soft magnetic properties. In order to understand the magnetism of the<br />

Fe(Zr) binary system, and the e ect of hydrogen <strong>on</strong> the magnetic interacti<strong>on</strong>, we have<br />

investigated in details the magnetic properties of amorphous thin lms of Fe(Zr). Fe1<br />

xZrx lms with compositi<strong>on</strong>s x=7.5, 9.5, 11.5, 12.5 and 13.5 at.% were grown by cosputtering<br />

<strong>on</strong> Si substrate in ultra high vacuum (UHV) c<strong>on</strong>diti<strong>on</strong>s. The compositi<strong>on</strong>s,<br />

structural and magnetic properties of the lms were investigated by Rutherford<br />

Backscattering spectrometry (RBS), X-ray di racti<strong>on</strong>, and SQUID magnetometery<br />

respectively before and after hydrogenati<strong>on</strong>. The hydrogen implanted samples show<br />

an increased value of the Curie temperature with increasing hydrogen c<strong>on</strong>tent. The<br />

magnetizati<strong>on</strong> curves at low temperature show a c<strong>on</strong>tinuous increase with increasing<br />

eld also at quite high temperature c<strong>on</strong> rming the presence of random anisotropy. This<br />

anisotropy is heavily suppressed by hydrogen implantati<strong>on</strong>. Keywords: Amorphous<br />

Fe(Zr), Magnetizati<strong>on</strong>, H-implantati<strong>on</strong><br />

QH12<br />

Normal and intrinsic anomalous Hall effect in NbFe 2<br />

Sven Friedemann 1 *, William J Duncan 2 , Andreas Neubauer 3 , Manuel Brando 4 ,<br />

Christian Pfleiderer 3 and F Malte Grosche 1<br />

1 Cavendish Laboratory, University of Cambridge, United Kingdom<br />

2 Department of Physics, Royal Holloway University of L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

3 Physik Department E21, Technical University Munich, Germany<br />

4 Max Planck Institute for Chemical Physics of Solids, Dresden, Germany<br />

Hall effect studies are a powerful probe of the Fermi surface of metals via the normal<br />

c<strong>on</strong>tributi<strong>on</strong> whilst the anomalous c<strong>on</strong>tributi<strong>on</strong> may give substantial insight into spinorbit<br />

interacti<strong>on</strong>s. Here, we present Hall effect measurements <strong>on</strong> selected samples of<br />

the band magnet system NbFe 2. In the diluti<strong>on</strong> series Nb 1-yFe 2+y compositi<strong>on</strong> tuning<br />

allows to access various magnetic ground states including a complete suppressi<strong>on</strong> at<br />

a quantum critical point. We observe normal and anomalous c<strong>on</strong>tributi<strong>on</strong>s in the Hall<br />

effect. C<strong>on</strong>sistent analysis of the anomalous c<strong>on</strong>tributi<strong>on</strong>, however, is <strong>on</strong>ly possible<br />

for Fe-rich Nb 0.985Fe 2.015 featuring a ferromagnetic ground state. Here, a positive<br />

normal Hall coefficient is found at all temperatures with a moderate maximum at the<br />

spin-density-wave transiti<strong>on</strong>. The anomalous Hall effect is covered by an intrinsic<br />

(Berry-phase) c<strong>on</strong>tributi<strong>on</strong> which is c<strong>on</strong>stant below the ordering temperature TC and<br />

c<strong>on</strong>tinuously vanishes above TC. For samples with antiferromagnetic ground state, i.e.,<br />

stoichiometric NbFe 2 and Nb-rich Nb 1.01Fe 1.99, an additi<strong>on</strong>al c<strong>on</strong>tributi<strong>on</strong> to the Hall<br />

resistivity impedes a complete analysis and indicates the need for more sophisticated<br />

models of the anomalous Hall effect in itinerant antiferromagnets.


QH13<br />

Magnetovolume effect in the itinerant-electr<strong>on</strong> frustrated magnet<br />

Fe 3Mo 3N<br />

Yoshikazu Tabata 1 *, Masaki Yamamoto1 1 Shinsuke Terazawa 1 , Takeshi Waki 1 , Kenji<br />

Ishida 2 and Hiroyuki Nakamura 1<br />

1 Department of Materials Science and Engineering, Kyoto University, Japan<br />

2 Department of Physics, Kyoto University, Japan<br />

The η-carbide-type compound Fe 3Mo 3N, including the frustrated stella-quadrangula<br />

Fe-sublattice, is a novel itinerant-electr<strong>on</strong> frustrated magnet and exhibits intriguing<br />

features such as n<strong>on</strong>-Fermi-liquid behavior without parameter-tuning and sharp<br />

metamagnetic transiti<strong>on</strong> [1]. We performed thermal expansi<strong>on</strong> and magnetostricti<strong>on</strong><br />

measurements of Fe 3Mo 3N up to 15 T. A large volume expansi<strong>on</strong> is found at the<br />

metamagnetic transiti<strong>on</strong> field and the magnetovolume coupling c<strong>on</strong>stant is estimated<br />

as about 4 × 10 -3 μB -2 , being the same of magnitude of those of Co Laves phase<br />

compounds [2]. It indicates that the metamagnetic transiti<strong>on</strong> of Fe 3Mo 3N is a typical<br />

moment-induced-type in n<strong>on</strong>magnetic itinerant electr<strong>on</strong> systems. The n<strong>on</strong>magnetic<br />

ground state of Fe 3Mo 3N at zero field is emergent due to the frustrati<strong>on</strong> effect built into<br />

the stella quadrangula lattice.<br />

[1] T. Waki et al., J. Phys. Soc. Jpn. 79, 043701 (2010).; T. Waki et al., Europhys. Lett. 94, 37004<br />

(2011). [2] Y. Muraoka et al., J. Phys. Soc. Jpn. 53, 331 (1984).<br />

QH14<br />

NMR studies of magnetic properties in the spinel-type Cu(Cr 1-xHf x) 2S 4<br />

Haruo Niki 1 *, Morihito Oshiro 1 , Saori Nakamura 1 , Ayaka Uechi 1 , Mamoru Yogi 1 ,<br />

Shuji Ebisu 2 and Shoichi Nagata 2<br />

1 Department of Physics, Faculty of Science, University of the Ryukyus, Japan<br />

2 Muroran Institute of Materials Research, Japan<br />

A chalcogenide tiospinel CuCr 2S 4 is a metallic ferromagnet with Tc = 380 K. The<br />

increase of x for the mixed spinel Cu(Cr 1-xHf x) 2S 4 shows a successive change from<br />

a ferromagnetic, a re-entrant spin-glass, a spin-glass, and finally to a paramagnetic<br />

state. A step-like anomaly in magnetizati<strong>on</strong> is also found around 160 K in the range<br />

of 0.50 ≤ x ≤ 0.70 due to a spin crossover phenomen<strong>on</strong> [1]. In order to investigate<br />

the magnetic properties of Hf rich side in Cu(Cr 1-xHf x) 2S 4 from a microscopic point<br />

of view, 63Cu NMR have been carried out between 4.2 and 300 K. Temperature<br />

dependences of res<strong>on</strong>ance line-width, Knight shift and spin-lattice relaxati<strong>on</strong> time (T1)<br />

have been measured. Knight shift in the range of 0.50 ≤ x ≤ 0.70 gradually shifts to<br />

negative side down to 130 K, but rapidly shifts to negative side below 130 K due to<br />

the core polarizati<strong>on</strong> of d c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s. Temperature dependence of 1/T1T in<br />

the range of 0.50 ≤ x ≤ 0.70 obeys the Korringa relati<strong>on</strong> (T1T = c<strong>on</strong>stant) down to 130<br />

K, as expected in a Pauli-paramagnetic metallic state. However, the values of 1/T1T<br />

=c<strong>on</strong>stant abruptly change between 130 and 90 K, and keep c<strong>on</strong>stant below 90 K.<br />

[1] F. Kariya, K. Ebina, K. Hasegawa, K. Koshimizu, B. Wuritunasitu, K. H<strong>on</strong>dou, S. Ebisu and S.<br />

Nagata, J. Solid State Chem. 182 (2009) 2018.<br />

QH15<br />

Relati<strong>on</strong>ship between microstructure and magnetic properties of nanoscale<br />

magnetic particles formed in a Cu-Ni-Co alloy<br />

D<strong>on</strong>ghae Lee 1 , Mahoto Takeda 1 *, Sung Kang 2 and Takahiro Moriki 1<br />

1 Department of materials engineering,Yokohama nati<strong>on</strong>al university, Japan<br />

2 Research Institute of Industrial Science & Technology(RIST), Korea<br />

The discovery of Giant Magnetic Resistance (GMR) has invoked str<strong>on</strong>g interest to relati<strong>on</strong>ship<br />

between microstructure and magnetic properties of nano-scale particles. The magnetic<br />

properties of nano-scale particles are str<strong>on</strong>gly dependent <strong>on</strong> their structures, particle sizes,<br />

shapes, and interparticle distances particularly in granular magnets. The present study aimed<br />

to investigate the relati<strong>on</strong>ship between the microstructure and the magnetic properties of<br />

granular Cu-Ni-Co alloys, using transmissi<strong>on</strong> electr<strong>on</strong> microscope (TEM), a superc<strong>on</strong>ducting<br />

quantum interference device (SQUID) magnetometer and thermo gravimetric-differential<br />

thermal analysis (TG-DTA). The present TEM observati<strong>on</strong>s revealed a specific feature that<br />

spherical ferromagnetic precipitates are transformed into cubic <strong>on</strong>es, and subsequently two<br />

or more cubic precipitates are aligned al<strong>on</strong>g the orientati<strong>on</strong> of a Cu matrix, which<br />

feature was significantly different from previous recogniti<strong>on</strong> to c<strong>on</strong>venti<strong>on</strong>al precipitati<strong>on</strong>.<br />

SQUID measurements shows that the magnetic property of the specimen changes from superparamagnetism<br />

to ferromagnetic in character with increasing isothermal annealing period<br />

from M-T curves. The present TG/DTA curves showed that a ferromagnetic to paramagnetic<br />

transiti<strong>on</strong> occurred at low temperatures (~950K) but paramagnetic to ferromagnetic transiti<strong>on</strong><br />

at high temperatures(600~700K). This suggests that the coalescence of magnetic atoms and<br />

accordingly the Curie point are sensitive to annealing temperature.<br />

QH16<br />

QH17<br />

QH18<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic study of mechanically deformed FeAlSi alloys<br />

Estibaliz Legarra 1 , Estibaliz Apinaniz 2 , Damian Martin-rodriguez 3 , Jose Javier<br />

Garita<strong>on</strong>andia 4 and Fernando Plazaola 1<br />

1 Department of Electricity and Electr<strong>on</strong>ics, Basque Country University, UPV/EHU, p. c. 644, 48080,<br />

Bilbao, Spain<br />

2 Department of Applied Physics I, Basque Country University, UPV/EHU, Alameda Urquijo s/n, 48013,<br />

Bilbao, Spain<br />

3 Julich Centre for Neutr<strong>on</strong> Science and Institute for Complex Systems, Forschungszentrum Julich GmbH,<br />

52425 Julich, Germany<br />

4 Department of Applied Plysics II, Basque Country University, UPV/EHU, p. c. 644, 48080, Bilbao, Spain<br />

The mechanical deformati<strong>on</strong> of Fe-Al alloys produces order-disorder transiti<strong>on</strong> that induces an enlargement<br />

of the magnetism of the alloys. It has been dem<strong>on</strong>strated that this enlargement is related to atomic disorder and<br />

cell volume increase [1]. The behaviour of the saturati<strong>on</strong> magnetizati<strong>on</strong> with milling and Si c<strong>on</strong>tent in Fe 75Al 25xSi<br />

x anf Fe 70Al 30-xSi x alloys is similar to the behaviour shown by the mean magnetic hyperfine field. Their<br />

values increase with disordering in alloys with low Si c<strong>on</strong>tent, but decrease in alloys with higher Si c<strong>on</strong>tent.<br />

The behaviour observed indicates clearly that the introducti<strong>on</strong> of Si in the binary Fe 75Al 25 and Fe 70Al 30 alloys<br />

opposes the magnetic behaviour induced by Al in the magnetism of Fe. These opposite behaviours are related to<br />

the lower increase of the lattice parameter with disorder for FeSi alloys. Besides, when plotting the normalized<br />

variati<strong>on</strong> of lattice parameter produced by the disorder versus the normalized variati<strong>on</strong> of magnetizati<strong>on</strong> we<br />

observe a linear relati<strong>on</strong>ship, showing that lattice parameter and magnetic properties are related. The study of<br />

the hyperfine fields also indicates that there is a redistributi<strong>on</strong> of n<strong>on</strong>-ferrous atoms around Fe atoms with the<br />

disordering, indeed, there is an inversi<strong>on</strong> of the behaviour of the hyperfine fields.<br />

[1] A. Hernando, X. Amils, J. Nogues, S. Surinach, M. D. Baro, and M. R. Ibarra, Phys. Rev. B 58 11864 (1998).<br />

The propagati<strong>on</strong> of electromagnetic waves in magnetic with<br />

ferromagnetic spiral<br />

Igor Valer'evich Bychkov 1 , Vasily Dmitrievich Buchelnikov 1 , Dmitry Aleksandrovich<br />

Kuzmin 1 and Vladimir Grigor'evich Shavrov 2<br />

1 Cheliabinsk State University, Russia<br />

2 The Institute of Radioengineering and Electr<strong>on</strong>ics of RAS, Russia<br />

Recently, spiral magnetic materials have attracted researchers' attenti<strong>on</strong> for their<br />

unusual physical properties. However, the spectrum and dynamic properties of magnets<br />

in a phase are not studied enough. In the present work the<br />

spectrum of the coupled spin and electromagnetic waves in spiral magnetic structure of<br />

type is investigated. Also the reflecti<strong>on</strong> of electromagnetic<br />

waves from a layer of magnetic having the ferromagnetic spiral and the Faradey effect<br />

are c<strong>on</strong>sidered. We use approach L >> a, where L - the spiral period, a - the lattice<br />

c<strong>on</strong>stant. Studies showed that the spectrum of the coupled waves has band structure.<br />

The band gap depends <strong>on</strong> the angle of the ferromagnetic spiral, and hence <strong>on</strong> the<br />

external magnetic field. The frequency dependence of the reflecti<strong>on</strong> coefficient of<br />

electromagnetic waves from the plate of the magnetic with a ferromagnetic spiral at<br />

different angles of the helix has been calculated. As the angle increases the opacity<br />

regi<strong>on</strong> broadens and shifts to higher frequencies. Thickening of the plate also leads to<br />

broadening of the opacity regi<strong>on</strong>. The Faraday effect has been observed for different<br />

frequencies. The angle of plate-of-polarizati<strong>on</strong> rotati<strong>on</strong> increases near the band gap.<br />

The Verdet c<strong>on</strong>stant has been calculated.<br />

<strong>Magnetism</strong> of sigma-phase Fe-Mo and Fe-Re systems<br />

Jakub Cieslak 1 *, Stanislaw M Dubiel 1 , Michael Reissner 2 and Janusz Tobola 1<br />

1<br />

Academy of Mining and Metallurgy, AGH al. Mickiewicza 30, 30-059 Krakow,<br />

Poland<br />

2<br />

Institute of Solid State Physics, Vienna University of Technology, A-1040 Wien,<br />

Austria<br />

Sigma phase exists in five binary systems of the Fe-X type viz. for X = Cr, V, Mo,<br />

Re and Tc. It is characterized by a lack of chemical order <strong>on</strong> all five sublattices of the<br />

tetrahedral unit cell. Until now, the magnetic properties have been known <strong>on</strong>ly for<br />

sigma-FeCr and sigma-FeV systems. The newly discovered low temperature magnetic<br />

properties of sigma-FeMo and sigma-FeRe phases will be presented and analyzed in<br />

detail in the whole c<strong>on</strong>centrati<strong>on</strong> range in which this phase occurs. In particular, in both<br />

cases, the observed increase in an average magnetic moment and magnetic ordering<br />

temperature with increasing of Fe c<strong>on</strong>tent is evident. Differences in Zero-Field Cooling<br />

and Field Cooling magnetizati<strong>on</strong> measurements suggest the magnetic ordering of<br />

spin-glass type or a large magnetic anisotropy in the measured samples. Electr<strong>on</strong>ic<br />

structure calculati<strong>on</strong>s using the KKR method were carried out for more than a dozen<br />

semi-ordered unit cells. The results of these calculati<strong>on</strong>s show a linear dependence of<br />

magnetic moments and hyperfine fields of Fe atoms at different sites versus the number<br />

of Fe atoms being their nearest neighbors. They also suggest a n<strong>on</strong>collinear magnetic<br />

structure in some sublattices.<br />

July 8 - 13, 2012 Busan, Korea 101<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QH19<br />

Sec<strong>on</strong>d order magnetizati<strong>on</strong> effects in bcc Fe<br />

Dominik Legut*, Jaroslav Hamrle and Jaromir Pistora<br />

Nanotechnology Centre, VSB-Technical University of Ostrava, Czech Republic, Czech<br />

Republic<br />

Sec<strong>on</strong>d order effect in magnetizati<strong>on</strong> are becoming an important way of<br />

characterizati<strong>on</strong> of the magnetic samples. One of the examples of sec<strong>on</strong>d order effect<br />

in magnetizati<strong>on</strong> are anisotropic magnetoresistance (AMR), Voigt effect, quadratic<br />

magneto-optical Kerr effect (QMOKE) or X-ray magnetic linear dichroism (XMLD).<br />

All those effects are originating from c<strong>on</strong>ductivity (or permittivity) tensor, which<br />

elements are varying with directi<strong>on</strong> of the sample magnetizati<strong>on</strong>. This dependence<br />

is determined by symmetry arguments describing break of the symmetry by<br />

magnetizati<strong>on</strong> in the crystal. From first principles we have calculated the complete<br />

angular dependence of all elements of the permittivity tensor with respect to the change<br />

of magnetizati<strong>on</strong> axis in a wide spectral range (from dc to ultraviolet) for a bodycentered<br />

cubic Fe. The correctness of calculati<strong>on</strong>s are verified by careful comparis<strong>on</strong><br />

with expected dependences provided by symmetry arguments. The calculati<strong>on</strong>s are<br />

based <strong>on</strong> density functi<strong>on</strong>al theorem utilizing <strong>on</strong>e of the most accurate full potnetial<br />

augmented plane-wave code. The effect of the spin-orbit interacti<strong>on</strong> for valence and<br />

semicore states is included as well.<br />

QH20<br />

Magnetic structure of nearly equiatomic MnRh alloy<br />

Yuki Matsuoka 1 and Aya Takasaki 2<br />

1 Nara Women's University, Japan<br />

2 Graduate School of Humanities and Sciences, Nara Women's University, Japan<br />

MnRh shows various kind of magnetic state. The magnetic structure and the transiti<strong>on</strong><br />

temperature of MnRh are expected to be very sensitive to the atomic compositi<strong>on</strong>.<br />

At the equiatomic compositi<strong>on</strong>, this alloy shows antiferromagnetic - paramagnetic<br />

transiti<strong>on</strong>. By increasing Mn ratio, this alloy shows complicated magnetic property,<br />

ferromagnetic - weak ferromagnetic transiti<strong>on</strong>.[1] Yamada et.al. reported that<br />

antiferromagnetic structure is most stable in this alloy.[2] To determine the magnetic<br />

structure, we performed neutr<strong>on</strong> diffracti<strong>on</strong> measurements and observed some magnetic<br />

scattering peaks. The intensities of magnetic scattering peaks were almost same even<br />

just below the phase transiti<strong>on</strong> temperature. On the other hand, magnetizati<strong>on</strong> curve of<br />

same comp<strong>on</strong>ent alloy suggests magnetic phase transiti<strong>on</strong>. We attempt to determine the<br />

magnetic structure and to make magnetic phase diagram of nearly equiatomic MnRh.<br />

[1] Matsuoka Y, 1995 MA Thesis [2] Yamada H, Shimizu H, Yamamoto K, Uebayashi K, 2006 J.Alloys<br />

Comp. 415 31<br />

QH21<br />

Magnetic and transport properties of Pd 2Mn 1+xIn 1-x Heusler alloys<br />

Hir<strong>on</strong>ari Okada 1 *, Yohei Yamazaki 2 , Takashi Yasuda 1 and Takeshi Kanomata 1<br />

1 Faculty of Engineering, Tohoku Gakuin University, Japan<br />

2 Divisi<strong>on</strong> of Engineering, Graduate School of Tohoku Gakuin University, Japan<br />

Recently, it was reported that Ni-Mn-In and Ni-Mn-Sn Heusler alloys having a<br />

ferromangetically ordered L21 type structure show a magnetic-field-induced reverse<br />

martensitic transformati<strong>on</strong> associated with a metamagnetic transiti<strong>on</strong> [1]. The interplay<br />

between the martensitic transformati<strong>on</strong> and the magnetic transiti<strong>on</strong> gives rise to a<br />

magnetic-field-induced shape recovery effect and a magnetoresistance effect. Pd 2MnIn<br />

has an antiferromagnetically ordered L21 type Heusler structure [2], which is different<br />

from the magnetic ordered state of Ni 2MnIn. In this work, in order to investigate<br />

the magnetic and transport properties of the antiferromagnetic Heusler alloys, we<br />

performed magnetizati<strong>on</strong> and electrical resistivity measurements for Pd 2Mn 1+xIn 1-x.<br />

In Pd 2Mn 1+xIn 1-x with x > 0.2, a sudden increase of the resistivity was observed.<br />

The temperature at which the anomaly of the resistivity appears shifts to the higher<br />

temperature with increasing Mn c<strong>on</strong>tent, and no anomaly was detected for the Mn<br />

c<strong>on</strong>tent with x = 0.55. The results of powder X-ray diffracti<strong>on</strong> experiment indicate<br />

that a martensitic phase appears for the Mn c<strong>on</strong>tent with x = 0.55 at room temperature.<br />

Therefore, it is c<strong>on</strong>sidered that the anomalous behavior of the resistivity results from<br />

the martensitic transformati<strong>on</strong>.<br />

[1] R. Kaimuma et al, Nature 439 (2006) 957. [2] P. J. Webster and R. S. Tebble, Phil. Mag. 16 (1967)<br />

347.<br />

102 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QH22<br />

Structural and magnetic properties of (Co, Fe, Ni), (Fe, Mg, Zn) and<br />

(Fe, Mn, Zn) alloys deposited <strong>on</strong>to Al 2O 3 and SiO 2<br />

L<strong>on</strong>zeche Jean Augustin Lodya 1 *, Adli Beck 2 , Rudelle White 3 , B<strong>on</strong>gani Xaba 1 ,<br />

Siyanda Lubhelwane 1 , Khuselwa Vundisa 1 and Jeanette Ngubane 1<br />

1 Research & Development, Sasol Technology, South Africa<br />

2 Chemistry Department, University of Stellenbosch, South Africa<br />

3 Chemistry Department, North-West University, South Africa<br />

Structural and magnetic properties of (Co, Fe, Ni), (Fe, Mg, Zn) and (Fe, Mn, Zn) alloys<br />

deposited <strong>on</strong>to Al 2O 3 and SiO 2 supports are reported. The samples were synthesised by ball<br />

milling and characterised using magnetic measurements (MM), Mossbauer spectroscopy (MS),<br />

XRD, SEM, TPR and (BET). Granular and irregular shaped particles were formed. MM, MS<br />

measurements and XRD data revealed the formati<strong>on</strong> of peculiar solid soluti<strong>on</strong>s some of them<br />

having spinel structures. In all the samples small crystallites in a superparamagnetic (SPM)<br />

state at room temperature were found to coexist with larger <strong>on</strong>es, their fracti<strong>on</strong>s depending <strong>on</strong><br />

the energy imparted during the ball milling process. That is, crystallites were predominantly in<br />

a SPM state at a relatively high ball-to-powder ratio while larger crystallites were prevalent at<br />

a relatively low ball-to-powder ratio. The ball milling process resulted also in low surface areas<br />

and collapse of pores. Further, the existence of str<strong>on</strong>g metal support interacti<strong>on</strong>s (SMSI) was<br />

inferred in all the samples; this rendered reducti<strong>on</strong> difficult and/or led to incomplete reducti<strong>on</strong>.<br />

Fittings of the Curie-Weiss model to the experimental temperature dependences of AC<br />

magnetic susceptibility were used to determine the effective magnetic moments associated with<br />

magnetic cati<strong>on</strong>s and the nature of their interacti<strong>on</strong>s.<br />

QH23<br />

Structure disorder effect of L1 0 FePt within supercell method<br />

Kazuhiko Uebayashi<br />

Secti<strong>on</strong> of Natural Science, Akita Nati<strong>on</strong>al College of Technology, Japan<br />

L1 0 FePt alloy is famous for a good candidate of high density magnetic recording<br />

media. In my previous work[1], I have performed energy-band calculati<strong>on</strong>s for the<br />

L1 0 bulk alloy FePt by using the linear muffin-tin orbital method with atomic sphere<br />

approximati<strong>on</strong>s. This previous calculated study shows that the calculated lattice<br />

c<strong>on</strong>stants and magnetic moments are good agreement with observed <strong>on</strong>es. The<br />

experimental stable-magnetic state is ferro magnetic, but in the calculati<strong>on</strong> <strong>on</strong>e of<br />

the anti-ferro magnetic state is most stable, and the sec<strong>on</strong>d is ferro magnetic above 1<br />

mRy/ f.u. The difference between the experimental and calculated result for L1 0FePt<br />

is known by another work[2]. To improve the difference, I carry out structure-disorder<br />

band calculati<strong>on</strong> for FePt with supercell method. I assumed that the supercell is as 8<br />

times large as a formula unit. In the supercell with <strong>on</strong>ly <strong>on</strong>e substituti<strong>on</strong> Fe and Pt,<br />

the most stable state becomes ferro and the difference between ferro and anti-ferro<br />

magnetic state is about 10 2 mRy. The result indicate that the structure disorder of L1 0<br />

FePt in the supercell makes ferro magnetic stable with observed lattice c<strong>on</strong>stants.<br />

[1] K. Uebayashi, JOURNAL OF APPLIED PHYSICS 107, 09A733 (2010) [2] G. Brown,<br />

PHYSICAL REVIEW B 68, 052405 (2003)<br />

QH24<br />

Itinerant antiferromagnetism in high-quality single crystal CrB2<br />

Andreas Bauer 1 *, Alexander Regnat 1 , Christian Blum 2 , Saskia Gottlieb-schoenmeyer 1 ,<br />

Bjoern Pedersen 3 , Sabine Wurmehl 2 , Bernd Buechner 2 and Christian Pfleiderer 1<br />

1<br />

Physik-Department E21, Technische Universitaet Muenchen, D-85748 Garching,<br />

Germany<br />

2<br />

Leibniz Institute for Solid State and Materials Research IFW, D-01171 Dresden,<br />

Germany<br />

3<br />

Forschungsneutr<strong>on</strong>enquelle Heinz-Maier Leibniz, Technische Universitaet<br />

Muenchen, D-85748 Garching, Germany<br />

Transiti<strong>on</strong> metal and rare earth diborides with the hexag<strong>on</strong>al AlB 2 structure form a series<br />

of compounds with a remarkably wide range of different electr<strong>on</strong>ic ground states. We<br />

report the properties of isotopically enriched high-purity single crystals of CrB 2 grown by<br />

optical float-z<strong>on</strong>ing. The temperature dependence of the electric resistivity and specific<br />

heat provide unambiguous evidence of spin density wave type order with a slightly<br />

anisotropic charge gap Δ(001) = 230 K and Δ(100) = 212 K, respectively. We also find<br />

that the Neel temperature of 88.5 K remains unchanged under magnetic fields up to 14<br />

T, the highest field studied. A detailed neutr<strong>on</strong> scattering study, made possible through<br />

the use of 99% isotopically enriched 11B, provides for the first time unambiguous<br />

evidence of antiferromagnetic order, and identifies CrB 2 as a textbook example of itinerant<br />

antiferromagnetism. In comparis<strong>on</strong> to the properties of other high-quality single crystal<br />

transiti<strong>on</strong> metal and rare earth diborides we have prepared, our studies of CrB 2 shed an<br />

unexpected new light <strong>on</strong> the properties of this exciting series of compounds.


QH25<br />

Magnetic orderings in Fe-intercalated TiX 2 (X=S, Se)<br />

Seung Ill Hyun and J.h. Shim*<br />

Chemistry, POSTECH, Korea<br />

Titanium dichalcogenides shares the same layered structure, except TiO 2. Their<br />

physical properties, however, are different from each other. TiSe 2, for example, is the<br />

<strong>on</strong>ly compound that bears an unc<strong>on</strong>venti<strong>on</strong>al charge-density wave (CDW) transiti<strong>on</strong><br />

under 200K, whereas the others show no distinct structural distorti<strong>on</strong>.[1] Furthermore,<br />

Ir<strong>on</strong>-intercalated TiS 2 and TiSe 2 exhibit different types of magnetism. Fe 0.5TiS 2 displays<br />

a ferromagnetic ordering under 80K, Fe 0.5TiSe 2 shows an antiferromagnetic ordering<br />

under 135K.[2,3] In order to describe the magnetic interacti<strong>on</strong>s between Fe atoms, we<br />

apply the first principle calculati<strong>on</strong> <strong>on</strong> Fe 0.5TiX 2 (X=S, Se) and explain the experimental<br />

observati<strong>on</strong>s correctly. We also discuss the origin of different magnetic behaviors based<br />

<strong>on</strong> the structural & elemental effect.<br />

[1] K. C. Woo, F. C. Brown, W. L. McMillan, R. J. Miller, M. J. Schaffman, and M. P. Sears, Phys.<br />

Rev. B 14, 3242 (1976) [2] N. V. Selezneva, N. V. Baranov, V. G. Pleshchev, N. V. Mushinikov, and<br />

V. I. Maksimov, Phys. Solid State 53 (2), 329 (2011) [3] N. V. Baranov, V. G. Pleshchev, E. M.<br />

Sherokalova, N. V. Selezneva and A. S. Volegov, Phys. Solid State 53 (4), 701 (2011)<br />

QH26<br />

N<strong>on</strong>-St<strong>on</strong>er Itinerant Ferromagnetism of a Transiti<strong>on</strong> Metal M<strong>on</strong>omer<br />

Hanhim Kang, Geunsik Lee, P. Dua, Ji-ho<strong>on</strong> Shim and Kwang S Kim*<br />

Department of Chemistry, POSTECH, Korea<br />

We investigated the <strong>on</strong>e-dimensi<strong>on</strong>al m<strong>on</strong>omer chain of 3d transiti<strong>on</strong> metals ( Fe, Co,<br />

and Ni ) by ab-initio band structure calculati<strong>on</strong> with quasiparticle GW method [1].<br />

We also studied the role of pair hopping interacti<strong>on</strong> <strong>on</strong> the magnetic properties using<br />

the extended Hubbard model [2][3]. GW calculati<strong>on</strong> of transiti<strong>on</strong> metal m<strong>on</strong>omer<br />

shows the spin-dependent band width changes as well as spin-dependent transport<br />

properties in ferromagnetic phase. Such behavior is well described by the extended<br />

Hubbard model, where the pair hopping enhances the metallic ferromagnetism in <strong>on</strong>edimensi<strong>on</strong>.<br />

We suggest that the electr<strong>on</strong> correlati<strong>on</strong> effect such as pair hopping usually<br />

has important role in the metallic ferromagnetism of low dimensi<strong>on</strong>al system.<br />

[1] T. Kotani, M. van Schilfgaarde, and S. Faleev, Phys. Rev. B, 76 (2007). [2] J. Hirsch, Phys. Rev. B.<br />

59, 6256 (1999) [3] J. Hirsch, Phys. Rev. B. 43, 701 (1991)<br />

QH27<br />

Magnetic structure variati<strong>on</strong> with structural phase transiti<strong>on</strong> in<br />

SrMnSb 2<br />

M. Arshad Farhan, Geunsik Lee and Ji Ho<strong>on</strong> Shim*<br />

Chemistry, POSTECH, Korea<br />

RMnSb 2 system (R = Alkali Earth Metal) is analyzed by first principle DFT calculati<strong>on</strong><br />

using full potential linearized augmented plane wave method while PBE-GGA is used<br />

to account for the Exchange-Correlati<strong>on</strong> potential. SrMnSb 2 has zig-zag chains of Sb<br />

i<strong>on</strong>s while BaMnSb 2 has square planes of it. The applicati<strong>on</strong> of pressure <strong>on</strong> SrMnSb 2<br />

leads to a phase transformati<strong>on</strong> from chain like semi-metal phase to BaMnSb 2 like<br />

Square planner structure showing metallic properties. The density of states for AFM<br />

SrMnSb 2 changes with the structural phase change indicating a magnetic transiti<strong>on</strong>.<br />

While for a similar chain to square transiti<strong>on</strong> in BaMnSb2 accompanying an Insulator<br />

to Metal transiti<strong>on</strong>, no such variati<strong>on</strong> in magnetic structure is observed.<br />

QH28<br />

QH29<br />

QI01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetoresistance effect of Heusler-type Fe 2VAl single crystal<br />

Rika Hamada 1 , Hidetoshi Miyazaki 2 * and Yoichi Nishino 1<br />

1 Department of Fr<strong>on</strong>tier Materials, Nagoya Institute of Technology, Japan<br />

2 Center for Fostering Young and Innovative Researchers, Nagoya Institute of<br />

Technology, Japan<br />

The Heusler-type intermetallic compound Fe 2VAl has attracted str<strong>on</strong>g attenti<strong>on</strong> because<br />

of a semic<strong>on</strong>ducting behavior of ρ and a large electr<strong>on</strong>ic specific heat coefficient γ,<br />

14 mJ/(K2mol). The band calculati<strong>on</strong> revealed that the Fe 2VAl was a semimetal and<br />

n<strong>on</strong>magnetic with a pseudogap around the Fermi level [2]. Endo et al. discovered<br />

the giant magnetoresistance (GMR) effect in the Heusler type alloys Fe 2+xV 1-xAl poly<br />

crystal of about 30 % for Fe 2.1V 0.9Al at 4.2 K in the field of 55 kOe [3]. Recently we<br />

have succeeded in fabricating single crystals of Fe 2.1V 0.9Al using Czochralski method<br />

and investigated their electric and magnetic properties. The temperature dependence of<br />

GMR is negative below the Curie temperature (TC). The maximum value of GMR is<br />

about 35 % around the TC. The value of GMR in Fe 2.1V 0.9Al single crystal is similar in<br />

that of poly crystal.<br />

[1] Y. Nishino et al., Phys. Rev. Lett. 79, 1909 (1997). [2] G. Y. Guo, G. A. Bottom and Y. Nishino,<br />

J. Phys.: C<strong>on</strong>dens. Matter 10 L119 (1998). [3] K. Endo et al., J. Magn. Magn. Mater. 177-181 1437<br />

(1998).<br />

Electr<strong>on</strong>ic structures and magnetic properties of antiferromagnetic<br />

BaFe 2As 2<br />

Jae Kyung Chang, Ju Young Kim, Chang Hyun Yi and Joo Yull Rhee*<br />

Department of physics, Sungkyunkwan university, Korea<br />

In low dimensi<strong>on</strong>al metals the electr<strong>on</strong>s can be organized into regular patterns,<br />

which is known to be the charge-density wave(CDW) or spin-density wave(SDW).<br />

The parent compound of ir<strong>on</strong>-based superc<strong>on</strong>ductors, BaFe 2As 2, undergoes both<br />

structural and magnetic phase transiti<strong>on</strong>s. The crystal structure changes from tetrag<strong>on</strong>al<br />

to orthorhombic, and the magnetic ground state changes from paramagnetic to<br />

antiferromagnetic at ~140 K and neutr<strong>on</strong> scattering measurements show the magnetic<br />

moment of 0.87μB per Fe in antiferromagnetic state. SDW anomaly at 140 K, which<br />

is believed to be an important prerequisite for high-Tc superc<strong>on</strong>ductivity in ir<strong>on</strong>based<br />

superc<strong>on</strong>ductors, was also observed. We performed the electr<strong>on</strong>ic-structure<br />

calculati<strong>on</strong> for the BaFe 2As 2 compound in various antiferromagnetic states, and the<br />

electr<strong>on</strong>ic structures and Fermi surfaces are carefully investigated. While there have<br />

been c<strong>on</strong>siderable debates as to whether the antiferromagnetism is due to the Fermisurface<br />

nesting or the sec<strong>on</strong>d-neighbor superexchange, via comparing our results with<br />

experimental and hypothetical cases, we can deduce the correlati<strong>on</strong> between the SDW<br />

and the Fermi-surface nesting.<br />

Development of magnetic order in the TbNi(Al,In) series and<br />

magnetocrystalline anisotropy in TbTX compounds<br />

Milan Klicpera 1 *, Pavel Javorsky 1 , Ines Puente Orench 2 , Eva Santava 3 and Stanislav<br />

Danis 1<br />

1<br />

Department of C<strong>on</strong>densed Matter Physics, Charles University in Prague, Faculty of<br />

Mathematics and Physics, Czech Republic<br />

2<br />

Institut Laue-Langevin, Grenoble, France<br />

3<br />

The Academy of Sciences of the Czech Republic, Czech Republic<br />

We present recent study of magnetocrystalline anisotropy in TbNi(Al,In) series, crystallizing in hexag<strong>on</strong>al<br />

ZrNiAl structure. The properties of this series were investigated by magnetic measurements, lowtemperature<br />

x-ray diffracti<strong>on</strong> in magnetic field and mainly by powder neutr<strong>on</strong> diffracti<strong>on</strong>. Parent compounds<br />

of our series were previously studied. TbNiAl orders antiferromagnetically with propagati<strong>on</strong> (1/2,0,1/2) and<br />

at lower temperatures undegoes another magnetic phase transiti<strong>on</strong> when <strong>on</strong>e third of magnetic moments is<br />

reduced to almost zero. TbNiIn shows complex magnetic ordering with propagati<strong>on</strong> vector (0,0,0) and other<br />

propagati<strong>on</strong> (1/2,0,1/2) occurs at lower temperatures. Our data reveal suppressi<strong>on</strong> of the antiferromagnetic<br />

structure of TbNiAl with substituti<strong>on</strong> of 10% Al by In. Instead, dominant ferromagnetic order appears,<br />

while the directi<strong>on</strong> of Tb magnetic moments al<strong>on</strong>g the c-axis is retained. Additi<strong>on</strong>al weak antiferromagnetic<br />

comp<strong>on</strong>ents arranged within the basal plane and described by k=(1/2,0,1/2) appear at low temperatures.<br />

This antiferromagnetic comp<strong>on</strong>ent is presented in the whole rest of series. Dominant comp<strong>on</strong>ent described<br />

by (0,0,0) propagati<strong>on</strong> then undergoes change from c-axis ferromagnetic order to a more complex basalplane<br />

structure around 40% of In. Anisotropy change in this series is related to str<strong>on</strong>g change of the c/a ratio<br />

of lattice parameters. This behaviour can be generalized for other hexag<strong>on</strong>al Tb-based compounds.<br />

July 8 - 13, 2012 Busan, Korea 103<br />

Poster Tuesday


Poster Tuesday<br />

QI02<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of Ho 1-xLu xB 12 solid soluti<strong>on</strong>s<br />

Slavomir Gabani 1 , Emil Gazo 1 , Gabriel Pristas 1 , Marian Reiffers 1 , Iveta Takacova 1 ,<br />

Natasha Shitsevalova 2 , K<strong>on</strong>rad Siemensmeyer 3 , Nickolay Sluchanko 4 and Karo l<br />

Flachbart l *<br />

1 Institute of Experimental Physics of Slovak Academy of Sciences, Kosice, Slovak<br />

2 Institute for Problems of Materials Sciences, NASU, Kiev, Ukraine<br />

3 Helmholtz Zentrum Berlin, Berlin, Germany<br />

4 General Physics Institute, RAS, Moscow, Russia<br />

Rare earth dodecaborides (REB 12) have attracted c<strong>on</strong>siderable attenti<strong>on</strong> in recent<br />

years, above all due to the wide variety of their physical properties. In our c<strong>on</strong>tributi<strong>on</strong><br />

we present the magnetic properties of the geometrically frustrated antiferromagnet<br />

HoB 12 (with ordering temperature T_N = 7.4 K) modified by substituti<strong>on</strong> of magnetic<br />

Ho atoms through n<strong>on</strong>magnetic Lu <strong>on</strong>es. In this case, in the so-called solid soluti<strong>on</strong><br />

Ho 1-xLu xB 12, both chemical pressure (as Lu 3+ i<strong>on</strong>s and Ho 3+ i<strong>on</strong>s have different radii)<br />

and magnetic diluti<strong>on</strong> take place with the increasing c<strong>on</strong>tent of Lu that change the<br />

properties of the system. The received results show str<strong>on</strong>g indicati<strong>on</strong> for the existence<br />

of a quantum critical point close to x = 0.9. This critical point separates the regi<strong>on</strong> of<br />

magnetic order (starting with HoB 12 for x = 0) and the n<strong>on</strong>magnetic regi<strong>on</strong> (ending<br />

with superc<strong>on</strong>ducting LuB 12 for x = 1). The work was supported by the Slovak<br />

Scientific Agency VEGA (0148-10), the Slovak Research and Development Agency<br />

APVV, and by the Center of Excellence of the Slovak Academy of Sciences.<br />

QI03<br />

High-field magnetizati<strong>on</strong> of Tm2Fe17 and its deuteride<br />

A. V. Andreev 1 *, O. Isnard 2 , M. D. Kuz'min 3 , Y. Skourski 4 , D. I. Gorbunov 1 , J.<br />

Wosnitza 4 , N. V. Kudrevatykh 5 , A. Iwasa 6 , A. K<strong>on</strong>do 6 , A. Matsuo 6 and K. Kindo 6<br />

1<br />

Institute of Physics ASCR, 18221 Prague, Czech Republic<br />

2<br />

Institut Neel CNRS and Universite Joseph Fourier, BP166X, Grenoble, France<br />

3<br />

IFW, 01171 Dresden, Germany<br />

4<br />

High Magnetic Field Laboratory, 01314 Dresden, Germany<br />

5<br />

Ural Federal University, 620083 Ekaterinburg, Russia<br />

6<br />

ISSP, Tokyo University, 277-8581 Kashiwa, Japan<br />

A magnetizati<strong>on</strong> study of a Tm 2Fe 17 single crystal and aligned powder of the deuteride<br />

Tm 2Fe 17D 3 has been carried out in steady (14 T) and pulsed (60 T) magnetic fields at 1.5-<br />

300 K. Tm 2Fe 17 is a ferrimagnet with T C=295 K and a sp<strong>on</strong>taneous moment of 21 μ B/f.u.<br />

Due to competing magnetic anisotropy of the Tm and Fe sublattices, a spin-reorientati<strong>on</strong><br />

occurs at 70-100 K, from the easy-axis to the easy-plane type via a c<strong>on</strong>e of easy axes.<br />

Two metamagnetic transiti<strong>on</strong>s, at 41 and 53.5 T, are observed at 2 K in fields applied<br />

al<strong>on</strong>g the c axis. At 60 T the magnetizati<strong>on</strong> reaches 43 μ B/f.u., i.e. the sublattices are not<br />

yet parallel (M Fe+M Tm= 49 μ B). In the basal plane a wide S-shape magnetizati<strong>on</strong> curve is<br />

observed. The high-field behavior of Tm 2Fe 17 is compared with that of two other easyaxis<br />

R 2T 17 compounds, Tm 2Co 17 and Er 2Co 17. Hydrogenati<strong>on</strong> (deuterati<strong>on</strong>) stabilizes easyplane<br />

anisotropy in Tm 2Fe 17D 3 over whole ferrimagnetic range (up to T C=465 K). Despite<br />

different types of magnetic anisotropy, the high-field behavior of the deuteride and the<br />

parent compound is qualitatively similar. The transiti<strong>on</strong>s al<strong>on</strong>g the c axis occur in the same<br />

fields, being less pr<strong>on</strong>ounced in the deuteride.<br />

QI04<br />

RKKY interacti<strong>on</strong> and magnetic properties in (Y-Gd)Ni compounds<br />

Kazuo Yano 1 *, Katsuhiko Nishimura 2 , Eiji Kita 3 , Tsuyoshi Ohta 4 and Kiyoo Sato 5<br />

1<br />

College of Science and Technology, Nih<strong>on</strong> University, Japan<br />

2<br />

Graduate Scool of Science and Engineering for Research, University of Toyama,<br />

Japan<br />

3<br />

Applied Physics, University of Tsukuba, Japan<br />

4<br />

Quatum Desighn Japan, Japan<br />

5<br />

Faculty of Engineering, Yokohama Nati<strong>on</strong>al University, Japan<br />

CeNi is well known as <strong>on</strong>e of the most famous heavy fermi<strong>on</strong> compounds and shows<br />

a peculiar behavior as an enhanced Pauli-paramagnet. That is, both Ce and Ni seem to<br />

be n<strong>on</strong>-magntetic in CeNi. On the other hand, GdNi, which has the same structure as<br />

that of CeNi, is a ferri-magnet and not <strong>on</strong>ly Gd but also Ni are magnetic. It follows that<br />

the result that Ni is n<strong>on</strong>-magnetic in CeNi becomes not self-evident and the mechanism<br />

of disappearance of Ni magnetic moment is important and interesting problem. Based<br />

<strong>on</strong> such scenario, we have been investigating a (Ce-Gd)Ni compound system. One of<br />

the results obtained is a linear relati<strong>on</strong>ship in M(T) in Gd-poor c<strong>on</strong>tent (Gd


QI08<br />

Giant magnetoresistance and field-induced phase transiti<strong>on</strong>s in Tb 7Rh 3<br />

single crystal<br />

Takanori Tsutaoka 1 *, Koji Shimomura 1 , Nikolay V. Baranov 2 , Alexey V. Proshkin 2 ,<br />

Evgeny G. Gerasimov 3 and Pavel B. Terentev 3<br />

1 Graduate School of Educati<strong>on</strong>, Hiroshima University, Japan<br />

2 Institute of Natural Sciences, Ural Federal University, Russia<br />

3 Institute of Metal Physics, Ural Branch of RAS, Russia<br />

The rare earth intermetallic compound Tb 7Rh 3 crystallizes in the Th 7Fe3 type hexag<strong>on</strong>al<br />

structure with the space group P63mc in which Tb occupies three n<strong>on</strong>-equivalent sites.<br />

Tb 7Rh 3 enters an antiferromagnetic (AF) state below TN = 91 K and shows further magnetic<br />

transformati<strong>on</strong>s with decreasing temperature below ~ 73 K [1]. Unusual negative temperature<br />

coefficient of the resistivity in a wide temperature range above TN [1] and the large<br />

magnetoresistance even in paramagnetic state [2] were observed for this compound. In this<br />

study, we have performed high field magnetizati<strong>on</strong> (up to 350 kOe) and magnetoresistance<br />

(up to 120 kOe) measurements <strong>on</strong> a Tb 7Rh 3 single crystal. The metamagnetic transiti<strong>on</strong> al<strong>on</strong>g<br />

the b-axis is observed to be accompanied by the giant magnetoresistance effect (~ 65 %) in the<br />

field interval (70 -110) kOe. The magnetizati<strong>on</strong> measurements al<strong>on</strong>g the c-axis have revealed<br />

multiple phase transiti<strong>on</strong>s at fields above 200 kOe. The magnetizati<strong>on</strong> curves measured in<br />

the paramagnetic state al<strong>on</strong>g the c-axis show an inflecti<strong>on</strong> point up to 140 K, which may be<br />

indicative of the persistence of antiferromagnetic short-range magnetic order in the c-plane.<br />

[1] Y. Nakamori et al. Physica B, 304 (2001) 1. [2] K. Sengupta et al. Solid State Comm., 39 (2006)<br />

351<br />

QI09<br />

Magnetic properties of a GdFe 5Al 7 single crystal<br />

D. I. Gorbunov 1 *, A. V. Andreev 1 and M. D. Kuz'min 2<br />

1 Institute of Physics ASCR, 18221 Prague, Czech Republic<br />

2 IFW, 01171 Dresden, Germany<br />

A magnetizati<strong>on</strong> study of a GdFe 5Al 7 single crystal has been carried out in static<br />

magnetic fields up to 14 T at temperatures between 2 and 300 K. The compound is<br />

found to order ferrimagnetically at T C = 266 K. The sp<strong>on</strong>taneous magnetic moment<br />

is 0.56 μ B at 2 K. There is no compensati<strong>on</strong> point in GdFe 5Al 7, as distinct from<br />

isomorphic compounds DyFe 5Al 7 and HoFe 5Al 7. GdFe 5Al 7 is endowed with an<br />

appreciable magnetic anisotropy, the 4-fold axis being a hard magnetizati<strong>on</strong> directi<strong>on</strong>.<br />

The easy directi<strong>on</strong> is [110] and the anisotropy within the basal plane is also rather<br />

str<strong>on</strong>g. The latter is quite remarkable for a system devoid of significant orbital<br />

moments. The possible cause of the in-plane anisotropy in GdFe 5Al 7 could be the<br />

unusually large crystal field parameter B 44, as observed in other compounds with the<br />

ThMn 12-type structure, e.g., in DyFe 11Ti. The crystal field effect could be mediated<br />

by a small admixture of the 4f 8 c<strong>on</strong>figurati<strong>on</strong> to the ground state 4f 7 . The exchange<br />

field <strong>on</strong> the Gd sublattice is determined from the high-field slope of the basal-plane<br />

magnetizati<strong>on</strong> curves to equal 62 T.<br />

QI10<br />

Study of multipole ordering in CePd3S4 by res<strong>on</strong>ant X-ray diffracti<strong>on</strong><br />

with full polarizati<strong>on</strong> analysis<br />

Sinji Michimura 1 *, Toshiya Inami 1 , Toru Otsubo 2 , Takeshi Matsumura 2 , Hiroshi<br />

Tanida 2 , Masafumi Sera 2 , Eiichi Matsuoka 3 , Masanori Watahiki 4 , Katsumi Tanigaki 4<br />

and Hideya Onodera4<br />

1<br />

C<strong>on</strong>densed Matter Science Divisi<strong>on</strong>, Japan Atomic Energy Agency, Japan<br />

2<br />

AdSM, Hiroshima University, Japan<br />

3<br />

Department of Physics, Kobe University, Japan<br />

4<br />

Department of Physics, Tohoku University, Japan<br />

In rare-earth palladium br<strong>on</strong>zes RPd 3S 4 (R = La-Yb) compounds with a cubic structure, it is expected that<br />

the multipole interacti<strong>on</strong>s dominate the low temperature properties because the degeneracy of the orbital<br />

degree of freedom remains in the crystalline electric field ground states of R 3+ in RPd 3S 4 except for R =<br />

Tm.[1] CePd 3S 4 orders ferromagnetically below the transiti<strong>on</strong> temperature TC = 6.3 K.[2] Recently we<br />

revealed that the O20-type quadrupole moments order below TC, and infered that the magnetic structure<br />

is a ferrimagnetic structure by res<strong>on</strong>ant x-ray diffracti<strong>on</strong> (RXD) experiments.[3] Since the symmetry of the<br />

magnetic and O20-type quadrupole moments differs from each other, simultaneous order of them below<br />

TC suggests the involvement of the octupole interacti<strong>on</strong>. We performed full polarizati<strong>on</strong> analysis of RXD<br />

experiments in magnetic fields to study the c<strong>on</strong>tributi<strong>on</strong> of an octupole interacti<strong>on</strong>. The experiments were<br />

performed at the Ce-L 3 absorpti<strong>on</strong> edge using a single crystal at BL22XU in SPring-8. In our presentati<strong>on</strong>,<br />

we will discuss the c<strong>on</strong>tributi<strong>on</strong> of multipole interacti<strong>on</strong>s for the low temperature properties in detail.<br />

[1] K. abe et al.: Phys. Rev. Lett. 76 (1999) 5366. [2] E. Matsuoka et al.: J. Phys. Soc. Jpn. 77 (2008)<br />

114706. [3] S. Michimura et al., submitted to J. Phys. Soc. Jpn.<br />

QI11<br />

QI12<br />

QI13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Effect of temperature and magnetic field history <strong>on</strong> magnetizati<strong>on</strong><br />

behavior of NdVO 3 polycrystalline<br />

Zhengcai Xia*<br />

wuhan nati<strong>on</strong>al high magnetic field center, huazh<strong>on</strong>g university of science and<br />

technology, China<br />

The magnetic properties of NdVO 3 polycrystalline have been studied in the<br />

temperature range from 300 to 1.8K and in magnetic fields up to 16 T. It is found<br />

that in an applied field less than 1 T remarkable magnetizati<strong>on</strong> reversals occurred<br />

in field cooling mode: a diamagnetic behavior was observed below a compensati<strong>on</strong><br />

temperature Tcomp. Most interestingly, the diamagnetic behavior was dependent to<br />

both the temperature and applied magnetic field, where the temperature window is 50-<br />

100K, and magnetic field below 1T. Bey<strong>on</strong>d the temperature window and above the<br />

magnetic field, the diamagnetic behavior disappeared. That is the magnetizati<strong>on</strong> always<br />

switches to the opposite directi<strong>on</strong> if the sample is cooled through the temperature<br />

window in a field less than 1 T. However, the temperature dependence of the resistance<br />

has an almost independent to the applied magnetic field in the range from 0 to 16T. A<br />

possible mechanismbased <strong>on</strong> the competiti<strong>on</strong> of the single-i<strong>on</strong> magnetic anisotropy<br />

and the antisymmetric Dzyaloshinsky-Moriya interacti<strong>on</strong> accompanied by a change of<br />

orbital ordering is discussed.<br />

Phase diagram and transport properties of Y1-xNdxCo2 pseudo-binary<br />

alloys<br />

Alexander T Burkov 1 , Masataka Takeda 2 , Ai Nakamura 2 , Yoshinao Takaesu 2 ,<br />

Kiyoharu Uchima 3 , Masato Hedo 2 , Takao Nakama 2 *, Katsuma Yagasaki 2 and Yoshiya<br />

Uwatoko 4<br />

1<br />

A. F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, Russia<br />

2<br />

Department of Physics and Earth Sciences, Faculty of Science, University of the<br />

Ryukyus, Japan<br />

3<br />

General Educati<strong>on</strong>, Okinawa Christian Junior College, Japan<br />

4<br />

Institute for Solid State Physics, University of Tokyo, Japan<br />

Electrical resistivity ρ and thermopower S of pseudo-binary Y 1-xNd xCo 2 alloys have been measured at<br />

temperatures from 2 K to 300 K, under pressures up to 3.5 GPa. NdCo 2 is a ferromagnet with Curie<br />

temperature TC of 99 K. In ferromagnetic phase it undergoes 4f spin-reorientati<strong>on</strong> transiti<strong>on</strong> at TR = 40 K.<br />

At this transiti<strong>on</strong> the easy directi<strong>on</strong> of 4f magnetizati<strong>on</strong> is changed from [100] above TR to [110] below<br />

TR. The system phase diagram TC(x,P) and TR(x,P) is inferred from the temperature dependencies of the<br />

electrical resistivity and thermopower. The Curie temperature of the alloys, TC decreases with decreasing<br />

Nd c<strong>on</strong>centrati<strong>on</strong> x and vanishes around xc=0.3. Above xc the Curie temperature decreases with pressure.<br />

The spin-reorientati<strong>on</strong> temperature is weakly dependent <strong>on</strong> compositi<strong>on</strong> and <strong>on</strong> pressure until it merges<br />

with TC. There is a large regi<strong>on</strong> of the phase diagram, partly overlapping with the ferromagnetic phase,<br />

where cobalt 3d electr<strong>on</strong> system is n<strong>on</strong>-uniformly magnetized due to spatial fluctuati<strong>on</strong>s of the 4f-3d<br />

exchange field, related to random distributi<strong>on</strong> of Nd 4f magnetic moments over R-sublattice. In this regi<strong>on</strong>,<br />

spanning the range 0 < x < xm, large static 3d magnetic fluctuati<strong>on</strong>s govern the electr<strong>on</strong>ic transport.<br />

Effect of partial magnetic order <strong>on</strong> resistivity and thermopower of<br />

Ho(Co1-xAlx) 2 alloys<br />

Takao Nakama 1 *, Chojun Zukeran 1 , Ai Nakamura 1 , Atsushi Teruya 1 , Sentaro<br />

Hirakawa 1 , Shintaro Watanabe 1 , Masataka Takeda 1 , Yoshinao Takaesu 1 , Kiyoharu<br />

Uchima 2 , Masato Hedo 1 , Katsuma Yagasaki 1 and Alexander T Burkov 3<br />

1<br />

Department of Physics and Earth Sciences, Faculty of Science, University of the<br />

Ryukyus, Japan<br />

2<br />

General Educati<strong>on</strong>, Okinawa Christian Junior College, Japan<br />

3<br />

A. F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, Russia<br />

The electrical resistivity ρ and thermopower S of Ho(Co 1-xAl x) 2 alloys (x = 0, 0.15 and<br />

0.2) were measured from 2 K to 300 K in magnetic fields up to 10 T and under pressures<br />

up to 3 GPa. While ρ(T) and S(T) of the pure HoCo 2 reveal abrupt changes at the<br />

magnetic ordering temperature TC, indicating the first order transiti<strong>on</strong>, the temperature<br />

variati<strong>on</strong> of both properties across the ordering temperature in Ho(Co 1-xAl x) 2 alloys<br />

clearly show that the type of the magnetic transiti<strong>on</strong> changes under substituti<strong>on</strong> of Al for<br />

Co from the first order to the sec<strong>on</strong>d order. ρ(T ) of the Al substituted samples (x = 0.15<br />

and 0.2) has a very unusual variati<strong>on</strong> below TC. Usually, the resistivity of an itinerant<br />

ferromagnet decreases below TC with decreasing temperature at higher rate than above<br />

TC, its temperature derivative having positive “lambda” anomaly at the ordering point.<br />

In c<strong>on</strong>trast, ρ(T ) of Ho(Co 1-xAl x) 2 alloys (x=0.15 and x=0.2) increases below TC.<br />

Moreover, the magnetoresistance of these alloys is positive around TC, this is also in a<br />

sharp c<strong>on</strong>trast to usually observed negative magnetoresistance.<br />

July 8 - 13, 2012 Busan, Korea 105<br />

Poster Tuesday


Poster Tuesday<br />

QI14<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Breakdown of Hund’s third rule for intrinsic magnetic moments<br />

Julia Herrero-albillos 1 *, Fernando Bartolome 2 , Luis Miguel Garcia 2 and A. T. Young 3<br />

1<br />

CUD, Centro Universitario de la Defensa, Ctra. de Huesca s/n, E-50090 Zaragoza,<br />

Spain, Spain<br />

2<br />

ICMA, ICMA and Dpto. de Fisica de la Mat. C<strong>on</strong>d. CSIC - Universidad de<br />

Zaragoza, Pedro Cerbuna 12, Spain, Spain<br />

3<br />

Advanced Light Source, Lawrence Berkeley Nati<strong>on</strong>al Laboratory, University of<br />

California Berkeley, CA, USA<br />

Hund’s rules were originally developed in an atomistic picture, and it is therefore<br />

surprising that they also hold, almost universally, for molecules and solids. Here we<br />

report the first experimental example of a breakdown of Hund’s third rule in an intrinsic<br />

magnetic moment: the Co 3d moment of the unorthodox ferrimagnet ErCo 2. The<br />

applicati<strong>on</strong> of magneto-optical sum rules to X-ray magnetic circular dichroic spectra<br />

allows for the determinati<strong>on</strong> of the Co orbital and spin magnetic moments both in the<br />

ferrimagnetic and paramagnetic phases of ErCo 2. In agreement with the predicti<strong>on</strong>s<br />

of Hund’s third rule, Co orbital and spin moments are parallel throughout the overall<br />

temperature range, except in a narrow temperature window within the paramagnetic<br />

phase, in which they are overall coupled antiparallel. A qualitative c<strong>on</strong>siderati<strong>on</strong> of<br />

the balance between the interatomic and intra-atomic interacti<strong>on</strong>s acting <strong>on</strong> the cobalt<br />

atoms explains the phenomen<strong>on</strong>. This situati<strong>on</strong> also leads to the observati<strong>on</strong> of other<br />

exotic forms of magnetism in solids, such as a “pure” spin or a “pure” orbital moment<br />

<strong>on</strong> the same compound at selected temperature and fields.<br />

QI15<br />

Magnetic properties of Y substituted TbB4 Boyoun Kang 1 , Sungsu Lee 1 , Juyoung Kim 2 and B. K. Cho 1 *<br />

1<br />

School of Materials Science & Engineering, Gwangju Institute of Science and<br />

Technology, Korea<br />

2<br />

Advanced matallic materials research department, Research Institute of Industrial<br />

Science & Technology, Korea<br />

We synthesized the single crystals of Tb 1-xY xB 4 (x=0.0, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5,<br />

and 0.6)using metallic flux method. The lattice parameters of these crystals are<br />

c<strong>on</strong>firmed by powder x-ray diffracti<strong>on</strong> using Fullprof program. The lattice parameters<br />

are decreased with increasing substituted Y ratio, according to Vegard’s law. The<br />

measurements of temperature-dependent magnetizati<strong>on</strong> M(T) is carried out for the<br />

single crystals of Tb 1-xY xB 4 (x=0.0, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5, and 0.6) in 1 Tesla.<br />

The compounds reveal antiferromagnetic ordering and its Neel temperatures are<br />

decreased with increasing Y ratio. We c<strong>on</strong>firm the spin directi<strong>on</strong> of antiferromagnetic<br />

c<strong>on</strong>tributi<strong>on</strong> in Tb 0.65Y 0.35B 4 using single crystal neutr<strong>on</strong> scattering. The directi<strong>on</strong> of Tb<br />

spin magnetic moment is tilted from a axis.<br />

QI16<br />

High pressure effects <strong>on</strong> antiferroquadrupolar orders in RB 2C 2 (R =<br />

Dy and Ho)<br />

Hiroki Yamauchi 1 *, Toyotaka Osakabe 1 , Masashi Kosaka 2 , Eiichi Matsuoka 3 and<br />

Hideya Onodera 4<br />

1 Quantum Beam Science Directorate, Japan Atomic Energy Agency, Japan<br />

2 Graduate School of Science and Engineering, Saitama University, Japan<br />

3 Department of Physics, Graduate School of Science, Kobe University, Japan<br />

4 Department of Physics, Graduate School of Science, Tohoku University, Japan<br />

Single-crystal neutr<strong>on</strong> diffracti<strong>on</strong> experiments under 10 GPa class pressure were performed<br />

<strong>on</strong> tetrag<strong>on</strong>al DyB 2C 2 and HoB 2C 2 compounds showing antiferroquadrupolar (AFQ) and<br />

antiferromagnetic (AFM) orders. Both magnetic structures in the ground state phases are<br />

basically same and described mainly by the propagati<strong>on</strong> vectors k1 = (1, 0, 0) and k2 = (0, 1,<br />

1/2) for an AFM alignment in the c-plane and an orthog<strong>on</strong>al arrangement al<strong>on</strong>g the c-axis. This<br />

characteristic zigzag structure is attributed to the competitive coexistence of the underlying<br />

AFQ order with the AFM order. Our purpose is to investigate pressure effects <strong>on</strong> the AFQ and<br />

AFM orders through the alterati<strong>on</strong> of the magnetic structures with k1 and k2. The high pressure<br />

experiments revealed that applying pressure enhanced the AFM interacti<strong>on</strong>s and simultaneously<br />

suppressed the AFQ orders in the both compounds. In additi<strong>on</strong>, we found that applying pressure<br />

shranks the crystal volumes more greatly in the directi<strong>on</strong> of the c-axis even under hydrostatic<br />

pressure. Therefore, we presume that the volume shrinkage by applying pressure c<strong>on</strong>strains the<br />

buckling accompanied by the AFQ orders, which means a local atomic displacement of (B-C)<br />

layers al<strong>on</strong>g the c-axis, and leads to the suppressi<strong>on</strong> of the AFQ orders in the both compounds.<br />

106 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QI17<br />

Antiferromagnetism of TbPd 2Ge 2 Single Crystals<br />

Takahiro Hasegawa 1 *, Fujiwara Tetsuya 1 , Matsubayashi Kazuyuki 2 , Uwatoko<br />

Yoshiya 2 and Shigeoka Toru 1<br />

1 Grad. Sch. Sci. and Eng. Yamagnchi Univ., Japan<br />

2 ISSP. Univ. Tokyo., Japan<br />

The compound TbPd 2Ge 2, having the tetrag<strong>on</strong>al ThCr 2Si 2-type crystal structure,<br />

exhibits an antiferromagnetic order below TN=4 K [1]. The details are not clear. In<br />

order to clarify magnetic behavior, we have grown TbPd 2Ge 2 single crystals, and<br />

carried out magnetic and specific heat measurements using the single crystals. The<br />

magnetic susceptibility shows an anomaly at 13 K in susceptibility vs. T curves,<br />

indicating an antiferromagnetic order. The appearance of anomaly at 13K is c<strong>on</strong>firmed<br />

in specific heat. This transiti<strong>on</strong> temperature is fairly higher than <strong>on</strong>e reported previously<br />

[1]. The easy magnetizati<strong>on</strong> directi<strong>on</strong> is the [100] directi<strong>on</strong> in the basal plane within<br />

this experimental magnetic field up to 7 T. Three metamagnetic transiti<strong>on</strong>s appear in<br />

the process at low temperatures. In the [110] magnetizati<strong>on</strong> process, two metamagnetic<br />

transiti<strong>on</strong>s are observed. In magnetizati<strong>on</strong> curves al<strong>on</strong>g the all directi<strong>on</strong>s, downward<br />

curvatures can be seen, suggesting a precursor of further transiti<strong>on</strong>. From these results,<br />

the magnetic behavior of this compound is discussed in detail.<br />

[1] A.Szytula et al., Solid State Commun.66 (1988) 309.<br />

QI18<br />

Multi-step metamagnetic processes in PrPd 2Si 2 single crystal<br />

Toru Shigeoka 1 *, Tetsuya Fujiwara 1 , Kazuyuki Matsubayashi 2 , Yoshiya Uwatoko 2 ,<br />

Shoji Kimura 3 and Kazuo Watanabe 3<br />

1 Yamaguchi University, Japan<br />

2 ISSP., University of Tokyo, Japan<br />

3 IMR., Tohoku University, Japan<br />

Magnetic studies have been performed in detail <strong>on</strong> a PrPr 2Si 2 single crystal which is<br />

crystallized in the tetrag<strong>on</strong>al ThCr 2Si 2-type structure. The temperature dependence<br />

of magnetic susceptibility indicate the compound orders antiferromagnetically<br />

below TN=3.0 K. The transiti<strong>on</strong> has been c<strong>on</strong>firmed by specific heat. Magnetizati<strong>on</strong><br />

measurements up to 18 T have been performed and obtained following results. The easy<br />

magnetizati<strong>on</strong> directi<strong>on</strong> is the [100] directi<strong>on</strong> in the basal plane. In the magnetizati<strong>on</strong><br />

process, four metamagnetic transiti<strong>on</strong>s appear; it is a four-step metamagnetic <strong>on</strong>e. The<br />

[110] magnetizati<strong>on</strong> process is a three-step <strong>on</strong>e. A str<strong>on</strong>g magnetic anisotropy between<br />

the [100] and [110] directi<strong>on</strong>s is observed within the basal plane in high magnetic<br />

fields. Al<strong>on</strong>g the hard magnetizati<strong>on</strong> directi<strong>on</strong> of the c-axis, a metamagnetic transiti<strong>on</strong><br />

appears. A magnetic anisotropy between the [100] and [001] directi<strong>on</strong>s is also str<strong>on</strong>g.<br />

These behaviors are discussed from an analysis of crystal field effects.<br />

QI19<br />

Anisotropic properties of Tb 2Pd 2In single crystal<br />

Silvie Maskova 1 , Ladislav Havela 1 , Olexander Kolomiets 2 , Alexander V. Andreev 3 and<br />

Pavel Svoboda 1 *<br />

1 Department of C<strong>on</strong>densed Matter Physics, Charles University, Czech Republic<br />

2 Department of Physics, Lviv Polytechnic Nati<strong>on</strong>al University, Ukraine<br />

3 Institute of Physics, ASCR, Czech Republic<br />

Tb 2Pd 2In (tetrag<strong>on</strong>al Mo 2FeB 2 structure type) was reported to be an antiferromagnet<br />

with the Neel temperature TN = 32 K and metamagnetic transiti<strong>on</strong> at μ0Hc = 4 T [1].<br />

On the c<strong>on</strong>trary, our magnetizati<strong>on</strong> measurements <strong>on</strong> polycrystalline sample indicate<br />

that the magnetizati<strong>on</strong> curve of Tb 2Pd 2In has 4 metamagnetic features in the field range<br />

to 14 T. We have succeeded to prepare singe-crystalline sample of Tb 2Pd 2In using<br />

Czochralski method. The magnetic susceptibility measured <strong>on</strong> single-crystal in various<br />

crystallographic directi<strong>on</strong>s shows that magnetic properties of Tb 2Pd 2In are highly<br />

anisotropic. c-axis was found to be an easy magnetizati<strong>on</strong> directi<strong>on</strong>. The magnetizati<strong>on</strong><br />

curve al<strong>on</strong>g the c-directi<strong>on</strong> at T = 2 K shows two metamagnetic transiti<strong>on</strong>s (μ0Hc<br />

= 5 and 8 T). The magnetizati<strong>on</strong> is completely saturated at 14 T (Ms = 19.1 μB/<br />

f.u.). We have also observed another metamagnetic transiti<strong>on</strong> al<strong>on</strong>g the a-directi<strong>on</strong>.<br />

The magnetizati<strong>on</strong> in the a-directi<strong>on</strong> does not show any tendency to saturati<strong>on</strong> in the<br />

highest available fields.<br />

[1] M. Giovannini et al., J. Alloys Compd. 280, 26 (1998).


QJ01<br />

Successive magnetic transiti<strong>on</strong>s of PrRh 2Ge 2 single crystal<br />

Okawara Yuu 1 *, Cui Jingwei 1 , Fujiwara Tetsuya 1 , Matsubayashi Kazuyuki 2 , Uwatoko<br />

Yoshiya 2 , Kimura Shoji 3 , Watanabe Kazuo 3 and Shigeoka Toru 1<br />

1 Grad. Sch. Sci. and Eng. Yamagnchi Univ., Japan<br />

2 ISSP. Univ. Tokyo., Japan<br />

3 IMR. Tohoku Univ., Japan<br />

The ternary compound PrRh 2Ge 2, having the tetrag<strong>on</strong>al ThCr 2Si 2-type crystal structure,<br />

shows an interesting magnetic behavior; it orders antiferromagnetically below TN=45<br />

K and exhibits an additi<strong>on</strong>al magnetic transiti<strong>on</strong> at Tt=30 K [1]. The details have been,<br />

however, unknown yet. In order to elucidate its magnetic behavior, measurements of<br />

magnetizati<strong>on</strong> and specific heat have been performed <strong>on</strong> a PrRh 2Ge 2 single crystal. A much<br />

large magnetic anisotropy with the easy magnetizati<strong>on</strong> directi<strong>on</strong> of c-axis is observed.<br />

Four anomalies appear in the temperature dependence of magnetic susceptibility al<strong>on</strong>g the<br />

c-axis; a cusp at TN=52 K, a high peak at T3=38 K, a shoulder at T2=33 K and a small<br />

peak at T1=4 K are observed. Specific heat also shows four anomalies at corresp<strong>on</strong>ding<br />

temperatures where magnetic anomalies appear, c<strong>on</strong>firming an occurrence of successive<br />

magnetic transiti<strong>on</strong>s. A clear two-step metamagnetic process appears al<strong>on</strong>g the easy<br />

magnetizati<strong>on</strong> directi<strong>on</strong> of the c-axis at low temperatures. The magnetizati<strong>on</strong> in the first<br />

step is almost flat and is corresp<strong>on</strong>ding to (1/5) Ms, indicating this field-induce phase has a<br />

l<strong>on</strong>g period magnetic structure. This behavior is discussed as <strong>on</strong>e of characteristic features<br />

for Ising-like system with competing exchange interacti<strong>on</strong>s.<br />

[1] A. Szytula et al., Intermetallics 18 (2010) 1766.<br />

QJ02<br />

Phase diagram of the magnetically frustrated system SmPd2Al3 studied<br />

by neutr<strong>on</strong> diffracti<strong>on</strong><br />

Jiri Pospisil 1 *, Gwilherm Nenert 2 , Hideaki Kitazawa 3 , Martin Divis 1 , Jan Prokleska 1<br />

and Vladimir Sechovsky 1<br />

1<br />

DCMP, Charles University, Ke Karlovu 5, 121 16, Prague, Czech Republic<br />

2<br />

Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, F-38042 Grenoble Cedex 9,<br />

France<br />

3<br />

Nati<strong>on</strong>al Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan<br />

SmPd 2Al 3 represents a distinctive example of Sm magnetism exhibiting a complex magnetic behavior [1].<br />

The complexity of magnetism is caused by specific features of the Sm 3+ i<strong>on</strong>, namely by nearness of the<br />

ground-state multiplet J = 5/2 and the first excited multiplet J = 7/2 in c<strong>on</strong>juncti<strong>on</strong> with str<strong>on</strong>g crystal field. We<br />

have established a magnetic phase diagram based <strong>on</strong> magnetizati<strong>on</strong> data. Detailed informati<strong>on</strong> regarding the<br />

magnetic structure of each magnetic phase was lacking and neutr<strong>on</strong> diffracti<strong>on</strong> was highly desirable. To reduce<br />

the neutr<strong>on</strong> absorpti<strong>on</strong> by the Sm we have performed an experiment at the ILL Grenoble D9 diffractometer with<br />

the short wavelength neutr<strong>on</strong>s which are much less absorbed by the natural Sm. The four successive magnetic<br />

phases have been detected within the neutr<strong>on</strong> diffracti<strong>on</strong> experiment providing the values of the critical<br />

temperatures 3.5, 4, 4.5 and 12.4. Despite the still str<strong>on</strong>g Sm neutr<strong>on</strong> absorpti<strong>on</strong> and the low effective magnetic<br />

moment we have determined the magnetic k-vector (1/3 1/3 0) of the phase existing in the temperature interval<br />

12.4-4.5 K which classifies the SmPd 2Al 3 to the unique group of magnetically frustrated systems. Discussi<strong>on</strong><br />

will be drawn in the c<strong>on</strong>text of recent theoretical approaches to geometrically frustrated magnetic systems.<br />

[1] J. Pospisil, M. Kratochvilova, J. Prokleska, M. Divis, V. Sechovsky; Phys. Rev. B 81, 024413<br />

(2010)<br />

QJ03<br />

Interplay of rare-earth and ir<strong>on</strong> sublattices in NdFeAsO<br />

Gwendolyne Pascua 1 , Hubertus Luetkens 1 , Yurii G. Pashkevich 2 , Hemke Maeter 3 and<br />

Hans-henning Klauss 3<br />

1<br />

Laboratory for Mu<strong>on</strong> Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen<br />

PSI, Switzerland<br />

2<br />

A.A. Galkin D<strong>on</strong>etsk Phystek,, NASU, 83114 D<strong>on</strong>etsk,, Ukraine<br />

3<br />

Institut fur Festkorperphysik,, TU Dresden, DE-01069 Dresden,, Germany<br />

We report zero-field (ZF) mu<strong>on</strong> spin relaxati<strong>on</strong> (μSR) measurements <strong>on</strong> NdFeAsO<br />

polycrystalline samples. We investigate the interacti<strong>on</strong> of the Fe magnetic sublattice with<br />

the RE (rare-earth) paramagnetic moment in the n<strong>on</strong>superc<strong>on</strong>ducting magnetically ordered<br />

Nd oxypnictide by a detailed analysis of the hyperfine fields at the mu<strong>on</strong> site. At high<br />

temperatures, the fluctuati<strong>on</strong>s of the Nd moments are evident from the observed exp<strong>on</strong>ential<br />

depolarizati<strong>on</strong> of the μSR signal. Microscopic evidence of static commensurate magnetic<br />

order of Fe moments is revealed by μSR at temperatures below TΝ(Fe) = 136K. Drastic<br />

slowing down of RE moment fluctuati<strong>on</strong>s is observed <strong>on</strong>ly below TΝ(RE) = 2K. In the<br />

intermediate temperature range, a Schottky-like polarizati<strong>on</strong> of the Nd magnetic sublattice by<br />

the ordered Fe system is observed. In the Fe system, a transiti<strong>on</strong> between a high- and a low-<br />

temperature magnetic structures is proposed <strong>on</strong> the basis of a detailed symmetry analysis and<br />

magnetic dipole-field calculati<strong>on</strong>s at the mu<strong>on</strong> site. The observed behavior resembles the <strong>on</strong>e<br />

of the spin reorientati<strong>on</strong> in the structurally-related Nd 2CuO 4.<br />

[1] H. Maeter, H. Luetkens, Y. Pashkevich, et.al. Phys. Rev. B. 80 094524 (2009). [2] W. Tian, et.al.<br />

Phys. Rev. B. 82, 060514 (2010). [3] Y. Qiu, et.al. Phys. Rev. Lett. 101, 257002 (2008).<br />

QJ04<br />

QJ05<br />

QJ06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of C15 laves phase compound SmRu 2<br />

Yusuke Amakai*, Mototsugu Sato, Naoki Mom<strong>on</strong>o, Hideaki Takano and Shigeyuki<br />

Murayama<br />

Graduate School of Engineering, Muroran Institute of Technology, Japan<br />

We report the magnetic properties of polycrystalline C15 laves phase rare-earth<br />

compound SmRu 2. The sample of SmRu 2 was made by an arc-melt method and was<br />

annealed at 500 °C in vacuumed quartz tube for 50 hours. The susceptibility χ of<br />

SmRu 2 follows a typical Curie-Weiss law above 80 K. The effective magnetic moment<br />

peff is 1.39 μB/Sm-atom, and the Weiss temperature θ is a positive value of 42 K. The<br />

low-temperature χ for T < 70 K increases rapidly with decreasing temperature. In the<br />

resistivity ρ and the specific heat Cp, we found a small anomaly and a jump at about<br />

55 K. Furthermore, we observed a hysteresis in the magnetic field dependence of<br />

magnetizati<strong>on</strong> at 2 K. These experimental results suggest that C15 laves phase SmRu 2<br />

is ferromagnetic material <strong>on</strong> Tc ~ 55 K. Detailed discussi<strong>on</strong> will be presented at the<br />

c<strong>on</strong>ference.<br />

Pressure effect <strong>on</strong> the electrical resistivity of a ferromagnetic clathrate<br />

Eu8Ga16Ge30 T Iizuka 1 , K Umeo 2 *, M A Avila 3 and T Takabatake 1<br />

1<br />

AdSM, Hiroshima Univ., Kagamiyama 1-3-1, Higashi-Hiroshima 739-8530, Japan<br />

2<br />

N-BARD, Hiroshima Univ., Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526,<br />

Japan<br />

+ Federal University of ABC, Santo Andre, SP, 09210-170, Brazil<br />

Eu 8Ga 16Ge 30 is a unique intermetallic clathrate in which the guest sites are fully<br />

occupied by a rare-earth element. The Eu 2+ i<strong>on</strong>s in the tetrakaidecahedral cages in the<br />

type-I structure are rattling am<strong>on</strong>g off-center positi<strong>on</strong>s [1]. This compound exhibits a<br />

ferromagnetic transiti<strong>on</strong> at Tc=36K. Both the electrical resistivity ρ and the temperature<br />

deviative of magnetizati<strong>on</strong> exhibit peaks at Tc and T*. Up<strong>on</strong> applying pressure of<br />

6GPa at 290K, the off-center rattling state of Eu i<strong>on</strong>s changes to the <strong>on</strong>-centered state.<br />

Furthermore, at Ps=14GPa, a structural transiti<strong>on</strong> occurs with the volume reducti<strong>on</strong><br />

of about 4% [2]. In order to examine the pressure dependence of Tc and T*, we have<br />

measured the temperature dependence of ρ under various pressures up to 15GPa, by<br />

using a Bridgman anvil cell made of sintered diam<strong>on</strong>d. With increasing pressure, Tc<br />

shifts to higher temperatures. Broading of the peak at T* for P≥4GPa is attributed to<br />

the change from the off-center to <strong>on</strong>-center state. At 290K, ρ(P) jumps at 13GPa, which<br />

must be the manifestati<strong>on</strong> of the structural transiti<strong>on</strong>.<br />

[1] B. C. Sales, et al., Phys. Rev. B 63, 245113 (2001). [2] T. Kume et al., unpublished.<br />

Magnetic transiti<strong>on</strong>s under pressure in GdCo 2B 2<br />

Guanghui Hu 1 *, Izuru Umehara 1 , Lingwei Li 2 and Katsuhiko Nishimura 3<br />

1 Department of Physics, Yokohama Nati<strong>on</strong>al University, Japan<br />

2 Institute of Materials Physics, Hangzhou Dianzi University, China<br />

3 Graduate School of Science and Engineering, University of Toyama, Japan<br />

The pressure effect <strong>on</strong> magnetic transiti<strong>on</strong>s of GdCo 2B 2 compound was studied by dc susceptibility and ac<br />

heat capacity in the temperature range 2 K ~ 300 K. The temperature dependence of dc susceptibility for<br />

GdCo 2B 2 under various pressure in 0.1 T magnetic field show two informati<strong>on</strong>. First, the Antiferromagnetic<br />

transiti<strong>on</strong> temperature TN decrease with pressure increasing from 12.5 K in 0GPa decrease to 6.3 K in 1.07<br />

GPa and disappeared near to 1.30 GPa with a slope of dTN/dP about -5.8 K/Gpa. Sec<strong>on</strong>d, ferromagnetic<br />

transiti<strong>on</strong> TC increases alightly with pressure increasing from 20.4 K in 0 GPa to 22.1 in 1.27 GPa with<br />

a slope of dTC/dP about 1.5 K/Gpa. They were also found in ac heat capacity measurements. It can be<br />

understand that there is a str<strong>on</strong>g interacti<strong>on</strong> in the ferromagnetic state and a very weak interacti<strong>on</strong> in<br />

antiferromagnetic state which can easily be destroyed by pressure and magnetic field. The transiti<strong>on</strong>s<br />

are proved to be the sec<strong>on</strong>d-order transiti<strong>on</strong>. In additi<strong>on</strong>, a transiti<strong>on</strong> temperature TM which comes from<br />

domains of ferromagnetism in heat capacity measurements was found increase from 17.5 K under 0 GPa<br />

to 22.0 K under 2.36 GPa with a ratio dTM/dP about 2.2 K/GPa.<br />

[1] L. Li, K. Nishimura, and H. Yamane, Appl. Phys. Lett. 94 (2009) 102509 [2] L. Li, D. Huo, Z.<br />

Qian, and K. Nishimura, J. Phys.: C<strong>on</strong>f. Ser. 263 (2011) 012017 [3] I. Felner, Sol. Sta. Comm. 52<br />

(1984) 191-195 [4] V. K. Pecharsky, and K. A. Gschneidner, Jr., Int. J. Refrig, 29 (2006) 1239 [5]<br />

I. Umehara, F. Tomioka, A. Tsuboi, T. Ono, M. Hedo, Y. Uwatoko, J. Magn. Magn. Mater. 272-276<br />

(2004) 2301-2302.<br />

July 8 - 13, 2012 Busan, Korea 107<br />

Poster Tuesday


Poster Tuesday<br />

QJ07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

New ferromagnetic compounds with n<strong>on</strong>centrosymmetric crystal<br />

structures<br />

Yoshihiko Inada 1 *, Guizhi Bao 2 and Akiko Ono 1<br />

1 Graduate School of Educati<strong>on</strong>, Okayama University, Japan<br />

2 Department of Physics, Okayama University, Japan<br />

Recently, physical properties in n<strong>on</strong>centrosymmetric crystal structures have attracted<br />

c<strong>on</strong>siderable attenti<strong>on</strong>s. The broken inversi<strong>on</strong> symmetry in the crystal causes finite<br />

antisymmetric spin orbit coupling (ASOC). A spin-polarized electr<strong>on</strong>s that originates<br />

from the ASOC effect is formed even for n<strong>on</strong>magnetic materials. Generally, the<br />

electr<strong>on</strong>ic states of opposite spin orientati<strong>on</strong> are c<strong>on</strong>sidered to be degenerate in<br />

n<strong>on</strong>magnetic materials due to the presence of both time-reversal and space-inversi<strong>on</strong><br />

symmetries. However, this degeneracy will be solved by the ASOC in broken spaceinversi<strong>on</strong><br />

symmetries with n<strong>on</strong>centrosymmetric crystal structures. A pair of split bands<br />

is produced in the k-space. Ferromagnetic compounds with n<strong>on</strong>centrosymmetric<br />

crystal structures are interesting materials, because the time-reversal symmetries<br />

also broken. We discovered new ferromagnetic compouds, Pr 4Bi 3 and Nd 4Bi 3, with<br />

n<strong>on</strong>centrosymmetric crystal structures. They are crystalized in anti-Th 3P 4 structure<br />

(space group I-43d), which has no inversi<strong>on</strong> center. Curie temperature T_C are 48K<br />

and 94K, respectively. Large ASOC is expected caused by heavy material of Bi. We<br />

will report further results in detail.<br />

QJ08<br />

Singlet-triplet crossover in the two-dimensi<strong>on</strong>al dimer spin system<br />

YbAl 3C 3<br />

Shunichiro Kittaka 1 *, Tomoyoshi Sugiyama 1 , Yasuyuki Shimura 1 , Toshiro<br />

Sakakibara 1 , Saori Matsuda 2 and Akira Ochiai 2<br />

1 Institute for Solid State Physics, University of Tokyo, Japan<br />

2 Department of Physics, Tohoku University, Japan<br />

YbAl 3C 3 has the hexag<strong>on</strong>al ScAl 3C 3 type structure in which magnetic Yb 3+ i<strong>on</strong>s form a<br />

two-dimensi<strong>on</strong>al triangular lattice. At 80 K, it exhibits a structural phase transiti<strong>on</strong> to an<br />

orthorhombic structure with a slight displacement of the Yb atoms [1]. Interestingly, a<br />

dimer ground state with the singlet-triplet energy gap of about 15 K has been suggested<br />

from the magnetic susceptibility and the specific heat at low temperatures [2]. Indeed, a<br />

direct observati<strong>on</strong> of the singlet-triplet excitati<strong>on</strong>s has been reported from the inelastic<br />

neutr<strong>on</strong> experiments [3]. To investigate the variati<strong>on</strong> of the ground states in magnetic<br />

fields, we measured magnetizati<strong>on</strong> of a single crystal of YbAl 3C 3 down to 0.07 K and<br />

in fields up to 14.5 T. At low temperatures below 0.8 K, several magnetizati<strong>on</strong> steps<br />

were clearly observed for H||c in 6 T < μ0H < 9 T, whereas <strong>on</strong>ly two transiti<strong>on</strong>s were<br />

observed at 4.7 and 6.6 T for H||ab. At fields above 9 T, the magnetizati<strong>on</strong> becomes<br />

almost saturated for both H||c and H||ab. Our results indicate that the singlet-triplet<br />

crossover occurs in a relatively narrow field range, suggesting a rather weak interdimer<br />

interacti<strong>on</strong> in spite of the nearly triangular lattice of Yb i<strong>on</strong>s.<br />

[1] T. Matsumura et al., J. Phys. Soc. Jpn. 77, 103601 (2008). [2] A. Ochiai et al., J. Phys. Soc. Jpn.<br />

76, 123703 (2007). [3] Y. Kato et al., J. Phys. Soc. Jpn. 77, 053701 (2008).<br />

QJ09<br />

Magnetic structure transiti<strong>on</strong> in PrPd 3<br />

Hiroyuki S. Suzuki 1 *, Noriki Terada 1 , Akiko Kikkawa 1 , Koji Kaneko 2 and Naoto<br />

Metoki 2<br />

1 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

2 Japan Atomic Energy Agency, Japan<br />

A complex magnetic phase diagram of PrPd 3 with AuCu 3-type structure was reported<br />

[1]. The specific heat shows double peaks at TN = 0. 88 K and 0.77 K, which are<br />

relatively low compared with the Curie-Weiss temperature Θp ~ 17 K. The temperature<br />

of the peak at higher temperature is increased but another decreased with the magnetic<br />

field. A large tail above TN in the specific heat is also observed. C<strong>on</strong>sidering no<br />

geometric frustrati<strong>on</strong>s in the simple cubic structure of the Pr site, these behavior suggest<br />

a competiti<strong>on</strong> of inter-site interacti<strong>on</strong>s. The magnetic field dependence of the peak at<br />

higher temperature, which is typical in the quadrupole ordering system, also suggests<br />

an importance of the multipole effect arising from the crystalline electric field ground<br />

state. We have investigated the multipole effect using the single crystal by specific heat,<br />

magnetic susceptibility, ultra-s<strong>on</strong>ic and also neutr<strong>on</strong> scattering measurements. In this<br />

report, we focus <strong>on</strong> the magnetic structure and its transiti<strong>on</strong>. We have found first the<br />

1st transiti<strong>on</strong> of the magnetic phase at 0.5 K. The propagati<strong>on</strong> vector observed in the<br />

neutr<strong>on</strong> scattering is changed from the incommensurate to commensurate <strong>on</strong>e. We will<br />

discuss the complex magnetic phase based of the multipole effect.<br />

[1] S. Zhang, et al., Journal of Physics : <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series, 15 (2009) 042074<br />

108 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QJ10<br />

Competiti<strong>on</strong> between magnetic ordering and random spin freezing in<br />

Dy 2PtSi 3<br />

D. X. Li 1 *, T. Yamamura 1 , S. Nimori 2 and T. Shikama 1<br />

1 Institute for Materials Research, Tohoku University, Japan<br />

2 Tsukuba Magnet Laboratory, Nati<strong>on</strong>al Research Institute for Metals, Japan<br />

We have been paying special attenti<strong>on</strong> to a new family of the ternary intermetallic compounds<br />

R 2PtSi 3. The spin-glass or cluster-glass-like effect can be observed in some R 2PtSi 3 compounds<br />

with heavy rare earth element, which have been c<strong>on</strong>firmed to crystallize in the ordered hexag<strong>on</strong>al<br />

structure [1]. The mechanisms of the anomalous magnetic behaviors are very interesting in<br />

physics. Recently, we prepared a polycrystalline Dy 2PtSi 3 sample and systematically measured<br />

its magnetic properties including ac susceptibility (Χac), FC and ZFC magnetizati<strong>on</strong>, magnetic<br />

relaxati<strong>on</strong>, electrical resistivity and specific heat. The most important observati<strong>on</strong> is the evident<br />

peak in Χac(T) curve near Tc~6 K, which shifts to high temperature with increasing frequency<br />

suggesting the presence of random spin freezing effect. The observed l<strong>on</strong>g-time magnetic<br />

relaxati<strong>on</strong> and the low temperature irreversible magnetism give further evidence for this<br />

c<strong>on</strong>clusi<strong>on</strong>. However, specific heat measurement shows an evident peak at Tc and the electrical<br />

resistivity drops rapidly as decreasing the temperature just below Tc. In this sense, the l<strong>on</strong>g-range<br />

magnetic exchange interacti<strong>on</strong>s have also important influence <strong>on</strong> the magnetic behavior. Thus it<br />

seems to be appropriate to classify the Dy 2PtSi 3 sample as a large magnetic cluster system with<br />

competiti<strong>on</strong> between magnetic ordering and random spin freezing.<br />

[1] D. X. Li , S. Nimori, Y. Homma and Y. Shiokawa, J. Phys. Soc. Jpn., 71 (2002) Suppl. 211.<br />

QJ11<br />

Dilatometric investigati<strong>on</strong>s <strong>on</strong> the semimetallic ferromagnet EuB6 Rudra Sekhar Manna 1 , Frank Schnelle 1 , Mariano De Souza 1 , Michael Lang 1 , Pintu<br />

Das 1 , Adham Amyan 1 , Jens Mueller 1 , Stephan V<strong>on</strong> Molnar 2 , Peng Xi<strong>on</strong>g 2 and Zachary<br />

Fisk 3<br />

1<br />

Physics Institute, Goethe-University Frankfurt (M), SFB/TR 49, D-60438 Frankfurt<br />

(M), Germany<br />

2<br />

Department of Physics, Florida State University, Tallahassee, Florida 32306, USA<br />

3<br />

Department of Physics, University of California, Irvine, California 92697, USA<br />

EuB 6 is a semimetallic correlated electr<strong>on</strong> system, which exhibits a complex<br />

sequence of electr<strong>on</strong>ic and magnetic phase transiti<strong>on</strong>s at ~ 15.5 K (Tc1) and 12.5 K<br />

(Tc2). The material also shows a colossal magnetoresistance effect which is largest<br />

at Tc1. A percolative transiti<strong>on</strong> of magnetic polar<strong>on</strong>s, i.e., clusters of ordered Eu 2+<br />

moments polarized by the spins of localized charge carriers (holes), is involved in the<br />

paramagnetic to ferromagnetic transiti<strong>on</strong>. Thermal expansi<strong>on</strong> and magnetostricti<strong>on</strong><br />

measurements have been performed <strong>on</strong> this material to explore to which extent lattice<br />

degrees of freedom are involved in these phase transiti<strong>on</strong>s. We find two corresp<strong>on</strong>ding<br />

anomalies in the thermal expansi<strong>on</strong>, the <strong>on</strong>e occurring at Tc2 being much larger than<br />

that at Tc1. By applying a small magnetic field of less than 50 mT, the anomaly at<br />

Tc1 is fully suppressed, while the lower-temperature anomaly at Tc2 shifts to higher<br />

temperature as the field is increased and finally fades out at a field B > 5 T. These<br />

measurements are complemented by magnetostricti<strong>on</strong> measurements for a set of<br />

temperatures from below Tc2 to above Tc1, highlighting the extraordinarily large<br />

magnetoelastic effects in this material.<br />

QJ12<br />

The magnetic anisotropy and magnetostricti<strong>on</strong> of RAl 2 (R= rare earth)<br />

compounds<br />

Masashi Ohashi, Yusuke Araki and Kazuma Sawami<br />

Kanazawa University, Japan<br />

The RAl 2 (R : rare earth element) intermetallic compounds crystallize in the MgCu 2<br />

cubic Laves phase structure. In most of these compounds the R i<strong>on</strong>s are trivalent<br />

3+ and ferromagnetic ordering has been observed with Curie temperature TC up<br />

to 170 K. It is expected that some of structural transiti<strong>on</strong> occurs due to magnetic<br />

symmetry braking below TC. In the present work, sp<strong>on</strong>taneous magnetostricti<strong>on</strong> of<br />

ferromagnetic RAl 2 compounds are studied from the X-ray diffracti<strong>on</strong> measurement at<br />

low temperature and the thermal expansi<strong>on</strong> of the single crystal. The X-ray diffracti<strong>on</strong><br />

pattern shows the d-spilliting at several peaks of TbAl 2 and DyAl 2 due to the large<br />

magnetic anisotropy below TC. From these results, the crystal structures are estimated<br />

at ferromagnetic phase of TbAl 2 and DyAl 2. The anisotropic magnetoelastic c<strong>on</strong>stants<br />

have been calculated by using the results of the magnetizati<strong>on</strong> and the magnetostricti<strong>on</strong><br />

at the ferromagnetic phase and at the magnetic field up to 2 T.


QJ13<br />

Influence of weak-magnetic, n<strong>on</strong>-magnetic and disoriented grains <strong>on</strong><br />

remagnetizati<strong>on</strong> processes of Nd-Fe-B alloys<br />

Anna Starikova*, Alexey Lileev and Olga Arinicheva<br />

Nati<strong>on</strong>al University of Science and Technology 'MISIS' (MISIS), Russia<br />

The uniaxial high-anisotropic materials, in which magnetostatic interacti<strong>on</strong> between<br />

volumes have a significant influence were investigated. The analysis of domain<br />

structure formati<strong>on</strong> during magnetizati<strong>on</strong> reversal these materials in the presence of<br />

weak-magnetic, n<strong>on</strong>-magnetic and disoriented grains was carried out. The modeling<br />

ensemble simulating magnetic properties of sintered alloy neodymium- ir<strong>on</strong> - bor<strong>on</strong><br />

(Nd 15Fe 77B 8) was selected. Research of influence of inclusi<strong>on</strong>s was c<strong>on</strong>ducted <strong>on</strong> the<br />

basis of model experiments with the received ensemble. The program, devised for<br />

uniaxial high-anisotropic ferromagnetics, in which the sample is presented by ensemble<br />

from 1000 particles having transitive domain structure and following individual<br />

characteristics was used. After selecti<strong>on</strong> of all parameters of the ensemble simulating<br />

this material, for researching the influence of inclusi<strong>on</strong>s <strong>on</strong> magnetic reversal processes,<br />

key parameters of some microvolumes (Мs, Номах, Нs, Angle) were changed. It was<br />

c<strong>on</strong>cluded that magnetic reversal is realized by the channels formed at the expense<br />

of directed magnetostatic interacti<strong>on</strong>. Weak-magnetic, n<strong>on</strong>-magnetic and disoriented<br />

grains are the magnetic reversal centers, i.e. they are the beginning of formati<strong>on</strong> of the<br />

channel of magnetic reversal.<br />

QJ14<br />

Cobalt magnetism in HoCo 2 under pressure<br />

Jaroslav Valenta, Jiri Prchal*, Marie Kratochvilova, Martin Misek and Vladimir<br />

Sechovsky<br />

Department of C<strong>on</strong>densed Matter Physics, Charles University in Prague, Czech<br />

Republic<br />

HoCo 2 bel<strong>on</strong>gs to a group of RCo 2 (R = rare earth metal) compounds forming in the<br />

cubic Laves phase structure. The Ho localized 4f-electr<strong>on</strong> magnetic moments coexist<br />

together with the itinerant Co 3d moments, which appear <strong>on</strong> the verge of magnetism,<br />

similar to the ErCo 2 system [1]. Below TC, the large exchange field due to the<br />

ferromagnetically ordered Ho moments polarizes the Co 3d-electr<strong>on</strong> states and the<br />

emerged moments in the Co sublattice orient antiparallel to the Ho sublattice. Weak<br />

Co moments survive rather far above TC (= 79,5 K) in Co magnetic clusters remaining<br />

coupled antiparallel to paramagnetic Ho moments forming a parimagnetic phase. This<br />

causes a susceptibility anomaly at the parimagnetic transiti<strong>on</strong> temperature Tf (= 125 K).<br />

At low temperatures the easy magnetizati<strong>on</strong> directi<strong>on</strong> changes at the spin-reorientati<strong>on</strong><br />

temperature TR = (16,4 ± 0,5) K. We will present variati<strong>on</strong>s of the three transiti<strong>on</strong><br />

temperatures with applying hydrostatic pressure up to 3 GPa. TC and TR coincidently<br />

decrease with increasing pressure whereas TR increases. The results will be discussed<br />

in term of suppressing the Co magnetic moments and varying the exchange and crystalfield<br />

interacti<strong>on</strong>s with applying the hydrostatic pressure.<br />

[1] J. Herrero-Albillos et al., Phys.Rev.B 76 (2007) 094409.<br />

QJ15<br />

High-field magnetizati<strong>on</strong> study of ErCo2 Maurice Guillot 1 and Yildirhan Oner 2 *<br />

1<br />

1. Grenoble High Magnetic Field Laboratory, CNRS, BP166, 38042 Grenoble<br />

Cedex 9, France,, France<br />

2<br />

Department of Physics, Istanbul Technical University, Turkey<br />

In this work are presented new results <strong>on</strong> the magnetic properties of the ErCo 2<br />

compound in which three magnetic phases (ferrimagnetic, parimagnetic and<br />

paramagnetic) were proposed very recently. This study is based <strong>on</strong> the investigati<strong>on</strong><br />

of the magnetizati<strong>on</strong> under c<strong>on</strong>tinuous high magnetic fields (up to 330 kOe at 4.2K<br />

and up to 230 kOe in the 4.2-300K respectively). At low temperatures the stability of<br />

the ferrimagnetic structure is shown although the saturati<strong>on</strong> was never found. Special<br />

attenti<strong>on</strong> was paid to the 35-100K temperature range where the transiti<strong>on</strong>s between<br />

the different magnetic phases occur c<strong>on</strong>firming of the parimagnetic” orderings.<br />

The transiti<strong>on</strong> temperature Tc from the ferrimagnetic to the parimagnetic phase<br />

increases from ? 34 to 62 K with the applied field. For the values of H smaller than<br />

100 kOe. At H values greater than this Tc remains c<strong>on</strong>stant at (62 ±5) K. The atomic<br />

magnetic moment of Co is independent of the magnetic structure is and in the order of<br />

1μBatom-1.<br />

QJ16<br />

QJ17<br />

QJ18<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Res<strong>on</strong>ance, magnetic and neutr<strong>on</strong> investigati<strong>on</strong>s of magnetic structures<br />

in Pr 1-xY xFe 3(BO 3) 4 system<br />

A Pankrats 1 , V Tugarinov 1 *, C Ritter 2 , D Velikanov 1 , I Gudim 1 and V Temerov 1<br />

1 Kirensky Institute of Physics SB RAS, Krasnoyarsk, Russia<br />

2 Institute Laue-Langevin, Grenoble, France<br />

The rare earth borates RFe 3(BO 3) 4 with the structure of the huntite mineral are interesting as materials with<br />

two magnetic subsystems with competing anisotropy. In this work we present data <strong>on</strong> antiferromagnetic<br />

res<strong>on</strong>ance (AFMR), magnetic properties and neutr<strong>on</strong> investigati<strong>on</strong> of Pr 1-xY xFe 3(BO 3) 4 system. Our AFMR<br />

and neutr<strong>on</strong> investigati<strong>on</strong>s [1-3] show that the last points of the system, YFe 3(BO 3) 4 and PrFe 3(BO 3) 4,<br />

are easy-plane (EP) and easy-axis (EA) antiferromagnets, respectively, c<strong>on</strong>firming the magnetic data<br />

for R=Pr [4]. A diluti<strong>on</strong> of the Pr 3+ subsystem by diamagnetic yttrium reduces the magnetic anisotropy<br />

of the Pr subsystem and can lead to a transiti<strong>on</strong> from EA to EP state at some yttrium c<strong>on</strong>tent. The single<br />

crystals Pr 1-xY xFe 3(BO 3) 4 with x=0.25, 0.325, 0.5 and x=0.75 were grown. Magnetic and res<strong>on</strong>ance<br />

investigati<strong>on</strong>s show that the crystals with x = 0.25 and 0.325 are EA antiferromagnets with the energy gap<br />

at T=4.2 K close to 75 and 60 GHz, respectively, but the crystals with x=0.5 and 0.75 are EP <strong>on</strong>es. Neutr<strong>on</strong><br />

investigati<strong>on</strong>s showed that the c<strong>on</strong>centrati<strong>on</strong> transiti<strong>on</strong> from EP to EA state occurs via an inclined magnetic<br />

structure which was found for x=0.325.The c<strong>on</strong>centrati<strong>on</strong> dependency of AFMR energy gap is studied at<br />

T=4.2 K. This work was supported by RFBR grant #10-02-00765.<br />

[1] A.I. Pankrats, G.A. Petrakovskii, L.N. Bezmaternykh, V.L. Temerov, Physics of Solid State, 2008,<br />

Vol. 50, p. 79. [2] Ritter C., Vorotynov A., Pankrats A., et al., J. Phys.: C<strong>on</strong>d. Matter., 2008, V. 20,<br />

p. 365209. [3] Ritter C., Vorotynov A., Pankrats A., et al., J. Phys.: C<strong>on</strong>d. Matter, 2010, V. 22, p.<br />

206002. [4] A. M. Kadomtseva, Yu. F. Popov, G. P. Vorob’ev et al, JETP Lett., 2008, V. 87, p. 45.<br />

Anisotropic transport and magnetic properties of PrGe single crystal<br />

Pranab Kumar Das, Neeraj Goyal, Ruta Kulkarni, Arumugam Thamizhavel and<br />

Sudesh Kumar Dhar<br />

Department of C<strong>on</strong>densed Matter Physics and Materials Science, Tata Institute of<br />

Fundamental Research, Mumbai, India<br />

The compounds RGe (R = La, Ce, Pr and Nd) crystallize in the two closely related CrB and<br />

FeB-type orthorhombic crystal structures, depending up<strong>on</strong> R and heat treatment. We have<br />

recently reported the anisotropic magnetic properties of CeGe in detail which crystallizes<br />

in the FeB-type crystal structure [1]. In c<strong>on</strong>tinuati<strong>on</strong> of our studies <strong>on</strong> RGe compounds,<br />

we report here the anisotropic properties of a single crystal of PrGe grown by Czochralski<br />

method. PrGe exhibits dimorphism in which the high temperature FeB-type structure<br />

transforms into CrB-type structure at lower temperatures [2]. From the powder X-ray<br />

diffracti<strong>on</strong> we have c<strong>on</strong>firmed that the grown single crystal of PrGe possesses CrB-type<br />

crystal structure with the space group Cmcm(#63). The anisotropic magnetic properties<br />

have been studied al<strong>on</strong>g the three principal crystallographic directi<strong>on</strong>s. From the magnetic<br />

and transport properties we find that PrGe exhibits two magnetic transiti<strong>on</strong>s at 44 K and<br />

41.6 K al<strong>on</strong>g [100] and [010] directi<strong>on</strong>s, whereas al<strong>on</strong>g [001] directi<strong>on</strong> <strong>on</strong>ly a ferromagnetic<br />

ordering at 44 K is observed. The susceptibility data clearly indicate that the high temperature<br />

ordering is antiferromagnetic and the low temperature <strong>on</strong>e is ferromagnetic. The specific heat<br />

capacity data also c<strong>on</strong>firm the two magnetic transiti<strong>on</strong>s in PrGe.<br />

[1] Pranab Kumar Das, Neeraj Kumar, Ruta Kulkarni, S.K. Dhar and A. Thamizhavel, arXiv:<br />

1108.1291 [2] D. Hohnke and E. Parthe, Acta Crys. 20 (1966) 572.<br />

Theoretical investigati<strong>on</strong> of the phase transiti<strong>on</strong> and the spin-gap<br />

behavior of the triangular antiferromagnet YbAl 3C 3<br />

Changho<strong>on</strong> Lee 1 *, Myung-hwan Whangbo 2 , Juergen Koehler 3 and Ji-ho<strong>on</strong> Shim 1<br />

1 Chemistry, Postech, Korea<br />

2 Chemistry, North Carolina State University, USA<br />

3 MPI for Solid State Research, Stuttgart, Germany<br />

Ytterbium aluminum carbide YbAl 3C 3, first reported in 1992,[1] has recently attracted much attenti<strong>on</strong><br />

c<strong>on</strong>cerning the nature of its phase transiti<strong>on</strong> at T* = 77 K.[2-4] YbAl 3C 3 c<strong>on</strong>taining triangular sheets of<br />

magnetic i<strong>on</strong>s Yb 3+ (f13) undergoes a phase transiti<strong>on</strong> at T* = 77 K and exhibits a spin-gap behavior.<br />

The two model structures of YbAl 3C 3, proposed to explain these observati<strong>on</strong>s, give unreas<strong>on</strong>ably<br />

short C-Al distances. These model structures were optimized by density functi<strong>on</strong>al calculati<strong>on</strong>s to<br />

find that the Model 2 structure is more stable than the Model 1 structure, with chemically reas<strong>on</strong>able<br />

C-Al distances, and that the phase transiti<strong>on</strong> at T* is a cooperative sec<strong>on</strong>d-order Jahn-Teller distorti<strong>on</strong><br />

involving the layers of corner-sharing CAl5 trig<strong>on</strong>al bipyramids. The spin exchanges between nearestneighbor<br />

Yb 3+ i<strong>on</strong>s, evaluated by density functi<strong>on</strong>al calculati<strong>on</strong>s for the optimized Model 2 structure,<br />

show that YbAl 3C 3 has a two-dimensi<strong>on</strong>al spin lattice described by three antiferromagnetic exchanges,<br />

but exhibits a spin-gap behavior because <strong>on</strong>e exchange is substantially str<strong>on</strong>ger than the other two.<br />

(1) Gesing, T. M.; Pottgen, R.; Jeitschko W.; Wortmann, U. J. Alloys Compd. 1992, 186, 321. (2) Kosaka,<br />

M.; Kato, Y.; Araki, C.; Mori, N.; Nakanishi, Y.; Yoshizawa, M.; Ohoyama, K.; Martin C.; Tozer, S. W. J.<br />

Phys. Soc. Jpn. 2005, 74, 2413. (3) Ochiai, A.; Inukai, T.; Matsumura, T.; Oyamada A.; Katoh, K. J. Phys.<br />

Soc. Jpn. 2007, 76, 123703. (4) Kato, Y.; Kosaka, M.; Nowatari, H.; Saiga, Y.; Yamada, A.; Kobiyama, T.;<br />

Katano, S.; Ohoyama, K.; Suzuki, H. S.; Aso N.; Iwasa, K. J. Phys. Soc. Jpn. 2008, 77, 053701.<br />

July 8 - 13, 2012 Busan, Korea 109<br />

Poster Tuesday


Poster Tuesday<br />

QJ19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

First Principle Analysis for Pressure Effect <strong>on</strong> Charge Density Wave<br />

Phases of SmNiC 2<br />

Jae Nye<strong>on</strong>g Kim and Ji-ho<strong>on</strong> Shim*<br />

chemistry, POSTECH, Korea<br />

Using a first principles calculati<strong>on</strong>, we have investigated pressure effect <strong>on</strong> the electr<strong>on</strong>ic<br />

structure anisotropies, Fermi surface properties, and transport properties of SmNiC 2 to<br />

check their effects <strong>on</strong> the charge density wave instabilities. Both band structure and electric<br />

c<strong>on</strong>ductivity results show that SmNiC 2 has quasi 1D electr<strong>on</strong>ic structure by Ni 1D chain<br />

al<strong>on</strong>g a axis. However hybridizati<strong>on</strong> between nearest Sm 1D chain makes its charge density<br />

wave (CDW) properties 2D like with CDW vector q 1=(0.5, 0.5, 0) and another weak CDW<br />

vector q R=(0.5, 0.5, 0.5) at -6 GPa. With increasing pressure, highly anisotropic change<br />

of lattice induces these CDW vector to become incommensurate with flattening Fermi<br />

surface (FS) in the [110] plane and suppressing FS in [111] plane. The FS nesting vector<br />

q 1 is gradually shifted from q 1=(0.5, 0.50, 0) at -6 GPa to q 1=(0.5, 0.56, 0) at 14 GPa, while<br />

q1=(0.5, 0.52, 0) at 0 GPa, coincide with experimental results. Also, q R=(0.5, 0.5, 0.5), which<br />

is significant local maximum at -6GPa, becomes almost saddle point like with its nesting<br />

vector shifting another points. We c<strong>on</strong>clude that CDW strength al<strong>on</strong>g q 1 vector become<br />

str<strong>on</strong>ger with flattening (more 1D like) FS, but CDW strength al<strong>on</strong>g q R vector become weak<br />

with highly anisotropic change of lattice.<br />

[1] S. Shimomura, C. Hayashi, G. Asaka, N. Wakabayashi, M. Mizumaki, and H. Onodera, Phys. Rev. Lett. 102, 076404<br />

(2009). [2] Alexander Wolfel, Liang Li, Susumu Shimomura, Hideya Onodera, and Sander van Smaalen, Phys. Rev. B 82,<br />

054120 (2010). [3] J. Laverock, T. D. Haynes, C. Utfeld, and S. B. Dugdale, Phys. Rev. B 80, 125111 (2009).<br />

QK01<br />

The magnetoresistance of sandwich-structure organic spin-valve<br />

Feng Li*, Fapei Zhang and Yu Xiao<br />

High Magnetic Field Laboratory, Chinese Academy of Science, China<br />

We studied the magnetoresistance (MR) effect in an organic spin-valve structure<br />

of ferromagnetic/organic semic<strong>on</strong>ductor/ferromagnetic system theoretically using<br />

the spin-diffusi<strong>on</strong> theory and Ohm’s law. Spin polar<strong>on</strong>s and spinless bipolar<strong>on</strong>s are<br />

assumed to be the main carriers in organic semic<strong>on</strong>ductors. From the calculati<strong>on</strong>, it<br />

is obtained that MR value increases with the increase of the polar<strong>on</strong> proporti<strong>on</strong> and<br />

rapidly decreases with the increase of the thickness of organic layer. MR ratio can<br />

be enhanced remarkably when the interfacial resistances are spin related. We also<br />

investigated MR value dependence of the effects of the matching c<strong>on</strong>ductivity and the<br />

spin-polarizati<strong>on</strong> of ferromagnetic layer.<br />

QK02<br />

First-principles calculati<strong>on</strong>s investigati<strong>on</strong> of interfacial roles in spindependent<br />

transport properties in OMTJs<br />

Shiheng Liang 1 , D<strong>on</strong>gping Liu 1 , Lingling Tao 1 , H<strong>on</strong>g Guo 2 and Xiufeng Han 1 *<br />

1<br />

Beijing Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics, Institute of Physics,<br />

Chinese Academy of Sciences, China<br />

2<br />

Department of Physics and Center for the Physics of Materials, McGill University,<br />

M<strong>on</strong>treal, Quebec, Canada<br />

Organic spin valves and organic magnetic tunnel juncti<strong>on</strong>s (OMTJs) are new and promising<br />

research fields and show advantages for spin-dependent transport due to relatively weak<br />

spin-orbital coupling and hyperfine interacti<strong>on</strong>. L<strong>on</strong>g-chain alkanoic acids usually form<br />

close-packed m<strong>on</strong>olayer films with alkyl chains highly oriented <strong>on</strong> substrates. The<br />

characterizati<strong>on</strong> of stearic acid adsorbed <strong>on</strong> Ni(111) surface has been studied. Our results<br />

suggest that the stearic acid is chemically adsorbed <strong>on</strong> the Ni surface via a bidentate<br />

interacti<strong>on</strong> with a distance of about 1.8 A. We also investigated spin-dependent transport<br />

characterizati<strong>on</strong> through two kinds of organic magnetic tunneling juncti<strong>on</strong>s (OMTJs), as<br />

Ni/1-stearic acid radical (1-SAR)/Ni and Ni/1,18-stearic diacid radical (1,18-SDR)/Ni. We<br />

found magnetoresistance (MR) of Ni/1-SAR/Ni is -19.6%, and it is 13.7% for Ni/1,18-<br />

SDR/Ni OMTJ. There is a magnetic proximity effect in the interface, and the magnetic<br />

decay rate is dissimilar in different interfaces. Due to interacti<strong>on</strong> at hybrid organic/magnetic<br />

interface, the electr<strong>on</strong>ic properties of interfacial atoms are modified. These effects influence<br />

the spin-dependent transport properties, and there appears positive or negative tunneling<br />

magnetoresistance (TMR) due to different interface. Our results suggest, the interface<br />

between organic barrier and FM electrode play an important role in the transport behavior.<br />

110 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QK03<br />

GMR properties <strong>on</strong> flexible polymer film with bending stress<br />

Jo<strong>on</strong>hyun Kw<strong>on</strong>, Seungha Yo<strong>on</strong>, Seungkyo Lee, Je<strong>on</strong>ghye<strong>on</strong> Lee and B. K. Cho*<br />

School of Materials Science and Engineering, Gwangju Institute of Science and<br />

Technology (GIST), Korea<br />

Recently, demands and researches about variable flexible devices have been<br />

c<strong>on</strong>stant. In other to satisfy such demands, researches about magnetic properties in<br />

flexible envir<strong>on</strong>ment also have been c<strong>on</strong>tinued. In these researches, the simple giant<br />

magnetoresistance (GMR) spin valve structure was deposited <strong>on</strong> flexible polymer films,<br />

then was induced by external tensile stress from repetitive bending fatigue. As bending<br />

samples, bending directi<strong>on</strong>s were decided whether parallel or transverse directi<strong>on</strong>s to<br />

easy axis directi<strong>on</strong>s of GMR structure. As a result, when increasing parallel bending<br />

times, switching field interval range of free layer also increased, inversely as increasing<br />

transverse bending times, coercivity of free layer also increased. Such tendency had<br />

opposite properties to inverse magnetostricti<strong>on</strong> effect theory from the view of bending<br />

directi<strong>on</strong>, because flexible films had larger elastic recovery forces than tensile forces<br />

after bending. Therefore we anticipate that such elastic recovery forces was the reas<strong>on</strong><br />

of opposite tendency from the aspect of directi<strong>on</strong>. Based <strong>on</strong> these results, we clarified<br />

possibilities that the coercivity could be c<strong>on</strong>trolled without curvature, moreover axis<br />

behavior, e.g., easy axis or hard axis, also could be c<strong>on</strong>trolled without curvature and<br />

extra annealing processes.<br />

QK04<br />

Giant magnetoresistance in graphene nanoribb<strong>on</strong>s: Geometry,<br />

interface and dephasing effects<br />

Stefan Krompiewski*<br />

Institute of Molecular Physics, Polish Academy of Sciences, Poznan, Poland<br />

Motivated by the <strong>on</strong>going debate <strong>on</strong> the role of external c<strong>on</strong>tacts <strong>on</strong> electr<strong>on</strong>ic transport<br />

through carb<strong>on</strong> nanostructures [1-3], we theoretically estimate the combined effects<br />

- due to (i) geometry, (ii) the way the external c<strong>on</strong>tacts are attached and (iii) possible<br />

dephasing processes - in graphene nanoribb<strong>on</strong> (GNR). The method is based <strong>on</strong> the<br />

tight binding model, the Green functi<strong>on</strong> technique and the Landauer-type formalism.<br />

It is shown that giant magnetoresistance in GNRs depends str<strong>on</strong>gly not <strong>on</strong>ly <strong>on</strong> the<br />

aspect ratio of the sample and the current directi<strong>on</strong>, but also <strong>on</strong> whether ferromagnetic<br />

electrodes are attached in the end- or side-c<strong>on</strong>tacted manner. Typically the former<br />

attachment is favorable for c<strong>on</strong>ductivity. However the observed tendency is that the<br />

higher c<strong>on</strong>ductive systems reveal the lower giant magnetoresistive effect, and vice<br />

versa. Accordingly, the dephasing usually decreases c<strong>on</strong>ductivity, thereby increasing<br />

the GMR.<br />

[1] X. S<strong>on</strong>g et al, Nanotechnology 20 195202 (2009). [2] Y. Matsuda et al, J. Phys. Chem. C, 114,<br />

17845 (2010). [3] S. Krompiewski, Nanotechnology, 22, 445201 (2011). Acknowledgment This work<br />

was supported by the Polish Ministry of Science and Higher Educati<strong>on</strong> as a research project No. N<br />

N202 199239 for 2010-2013.<br />

QK05<br />

Negative magnetoresistance in ferromagnet/semic<strong>on</strong>ductor/<br />

ferromagnet structures with cubic dresselhaus spin-orbit-interacti<strong>on</strong><br />

Kenji K<strong>on</strong>do*<br />

Laboratory of Quantum Electr<strong>on</strong>ics, Research Institute for Electr<strong>on</strong>ic Science, Japan<br />

We have investigated the spin transport in Ferromagnet (FM)/Semic<strong>on</strong>ductor (SC)/<br />

Ferromagnet (FM) structures with a central SC barrier exhibiting cubic Dresselhaus<br />

spin-orbit-interacti<strong>on</strong> (SOI). The energy profile of the barrier is assumed to be a square<br />

with height V and thickness d al<strong>on</strong>g z-directi<strong>on</strong>. The magnetoresistance (MR) ratio has<br />

been calculated for three different barriers, GaAs, GaSb, and GaAs without SOI as a<br />

functi<strong>on</strong> of barrier thickness. Both ferromagnets are assumed to be Fe. Intriguingly,<br />

MR ratios exhibit negative values for two different barriers in some range of thickness.<br />

For GaAs, the MR ratio is negative when the thickness is larger than 0.03 nm. For<br />

GaSb, the MR ratio is negative in the range of 0.02 to 0.9 nm, changing the sign<br />

gradually from negative to positive at a thickness of about 0.9 nm. Afterwards, its value<br />

increases m<strong>on</strong>ot<strong>on</strong>ically and reaches a c<strong>on</strong>stant value at a thickness of 2.5 nm. We can<br />

attribute these phenomena to spin filtering effects caused by both the spin precessi<strong>on</strong><br />

and the energy-splitting in the central SC regi<strong>on</strong>. Without SOI, the MR ratio shows<br />

positive value in all the range since the spin does not rotate in the barrier.


QK06<br />

Spin valve effect of NiFe/graphene/NiFe juncti<strong>on</strong>s<br />

Muhammad Zahir Iqbal, Muhammad Waqas Iqbal and J<strong>on</strong>ghwa Eom*<br />

Department of Physics & Graphene Research Institute, Sej<strong>on</strong>g University, Korea<br />

Novel linear dispersi<strong>on</strong> in graphene makes unique electr<strong>on</strong>ic properties such as<br />

ambipolar transport and Dirac particle quantum Hall effect. Although graphene was<br />

previously c<strong>on</strong>sidered to be a physically unstable form until it was shown to exist<br />

<strong>on</strong> the Si substrate, various methods to synthesize graphene have been developed.<br />

Exploiting such superior electr<strong>on</strong>ic properties combined with recently developed large<br />

scale growth of graphene by chemical vapor depositi<strong>on</strong> (CVD), has led to field effect<br />

devices integrated <strong>on</strong> a wafer scale showing promise for future electr<strong>on</strong>ic applicati<strong>on</strong>s.<br />

In this paper, CVD-grown graphene is used as intervened spacer between two<br />

ferromagnetic electrodes. The device is composed of 55 nm thick NiFe film, graphene<br />

and 75 nm thick NiFe film. The current-to-perpendicular-to-plane magnetoresistance<br />

(MR) shows the spin valve effect. The increased resistance in the antiparallel<br />

c<strong>on</strong>figurati<strong>on</strong>s of magnetizati<strong>on</strong>s is due to the spin dependent scattering inside the<br />

magnetic films or at interfaces. A positive MR ratio of the order of 0.045% has been<br />

observed at 300 K and this signal grows up to 0.14 % at 10 K. The juncti<strong>on</strong> resistance<br />

is found to be m<strong>on</strong>ot<strong>on</strong>ically increasing with temperature. Graphene functi<strong>on</strong>s as not a<br />

tunnel barrier but a resistive thin film between two NiFe electrodes.<br />

QK07<br />

Giant magnetoimpedance and photoinduced magnetoresistance effects<br />

in ferromagnet/SiO2/p-Si hybrid structures<br />

N. V. Volkov*, A. S. Tarasov, E. V. Eremin, A. V. Eremin, S. N. Varnakov and S. G.<br />

Ovchinnikov<br />

L.V. Kirensky Institute of Physics SB RAS, Russia<br />

We report the electr<strong>on</strong> transport properties in the Fe/SiO 2/p-Si hybrid structure. The<br />

results of dc studies show that the features of the transport properties of the structure<br />

are caused by a metal/insulator/semic<strong>on</strong>ductor transiti<strong>on</strong> with a Schottky barrier<br />

formed at the SiO 2/p-Si in-terface [1]. The magnetoresistance effect is determined by<br />

c<strong>on</strong>tributi<strong>on</strong>s of the processes occurring in the volume of a semic<strong>on</strong>ductor and in a<br />

inversi<strong>on</strong> layer near the SiO 2/p-Si inter-face. Study of the impedance Z = R + iX and<br />

magnetoimpedance allows separating the dynamic c<strong>on</strong>tributi<strong>on</strong>s determined by charge<br />

and spin transport in different regi<strong>on</strong>s of the hybrid structure. The str<strong>on</strong>gest effect of a<br />

magnetic field <strong>on</strong> R and X is caused by the presence of magnetic impurity centers in<br />

the semic<strong>on</strong>ductor near the SiO 2/p-Si interface. Magnetoimpedance originates from<br />

spin-dependent tunneling between a ferromagnetic electrode and magnetic impurity<br />

centers via a potential barrier (SiO 2). The magnetic impurity centers determine also<br />

the change in photoc<strong>on</strong>ductivity in a magnetic field. The structure, as a matter of fact,<br />

exhibits giant magnetoresistance induced by optical radiati<strong>on</strong>. As a mechanism of<br />

this effect, we c<strong>on</strong>sider the spin-dependent tunnel photocurrent, i. e., the current of<br />

photoexcited electr<strong>on</strong>s, from p-Si to Fe via the SiO 2 barrier.<br />

1. N.V. Volkov, A.S. Tarasov, E.V. Eremin, et al., J. Appl. Phys. 109, 123924 (2011).<br />

QK08<br />

Charge imbalance with the same decaying length as spin accumulati<strong>on</strong><br />

Yao-hui Zhu*<br />

Physics Department, Beijing Technology and Business University, China<br />

Starting from the Valet-Fert theory of the current-perpendicular-to-plane giant<br />

magnetoresistance, we study the charge imbalance in ferromagnetic metals by<br />

solving Poiss<strong>on</strong>'s equati<strong>on</strong>. Our results show that, in ferromagnetic layers, the charge<br />

imbalance has two exp<strong>on</strong>ential terms with different decaying lengths: the Thomas-<br />

Fermi screening length (<strong>on</strong> the order of angstrom) and the spin diffusi<strong>on</strong> length (tens<br />

of nm in 3d ferromagnetic metals). The charge imbalance <strong>on</strong> the scale of the screening<br />

length has been well studied and it is also present in spin-unpolarized transport in<br />

n<strong>on</strong>magnetic multilayers. However, the charge imbalance <strong>on</strong> the scale of the spin<br />

diffusi<strong>on</strong> length has never been studied before and it shows up <strong>on</strong>ly in ferromagnetic<br />

layers with spin accumulati<strong>on</strong>, which also decays <strong>on</strong> the scale of the spin diffusi<strong>on</strong><br />

length. This charge imbalance is essential to the giant magnetoresistance effect and<br />

thus <strong>on</strong>e should be cautious when using quasi-neutrality c<strong>on</strong>diti<strong>on</strong>, which neglects the<br />

charge imbalance.<br />

[1] T. Valet and A. Fert, Phys. Rev. B 48, 7099 (1993). [2] Y.-H. Zhu, B. Hillebrands, and H. C.<br />

Schneider, Phys. Rev. B 78, 054429 (2008). [3] S. Zhang, Phys. Rev. Lett. 83, 640 (1999).<br />

QK09<br />

QK10<br />

QK11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Simulati<strong>on</strong> of spin-dependent transport in GaAs: Effect of electr<strong>on</strong>electr<strong>on</strong><br />

interacti<strong>on</strong>s<br />

Matthew Hodgs<strong>on</strong>, Gi<strong>on</strong>ni Marchetti, Roy W. Chantrell and Irene D'amico<br />

Physics, University of York, United Kingdom<br />

We investigate the effect of electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong> <strong>on</strong> electr<strong>on</strong>ic spin transport in<br />

bulk GaAs. We use Ensemble M<strong>on</strong>te Carlo (EMC) techniques to simulate the electr<strong>on</strong><br />

and spin dynamics. EMC has been successfully used in the study of charge transport<br />

and more recently in spin transport. However electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong>s are often<br />

neglected, also due to computati<strong>on</strong>al costs. Here, in additi<strong>on</strong> to electr<strong>on</strong>-electr<strong>on</strong><br />

scattering we include scattering from optical and acoustic ph<strong>on</strong><strong>on</strong>, and charged defect<br />

scattering. Spin decoherence occurs due to the spin-orbit interacti<strong>on</strong> (Dresselhaus<br />

term), which arises from the lack of inversi<strong>on</strong> symmetry in GaAs. The electr<strong>on</strong>-electr<strong>on</strong><br />

interacti<strong>on</strong> is described by the screened Coulomb potential. At variance with previous<br />

simulati<strong>on</strong>s, we implement both spin dependent (Mott) and spinless (Rutherford)<br />

scattering. We also propose a new, more realistic, method for choosing partners<br />

undergoing electr<strong>on</strong>-electr<strong>on</strong> collisi<strong>on</strong>s which properly accounts for the dependence <strong>on</strong><br />

the distance between electr<strong>on</strong>s. We show that, in EMC simulati<strong>on</strong>s, electr<strong>on</strong>-electr<strong>on</strong><br />

interacti<strong>on</strong>s should not be discarded, as doing so may result in an anomalous drop in<br />

the spin relaxati<strong>on</strong> time at temperatures as high as 100K.<br />

Electrical detecti<strong>on</strong> of spin-polarized current in InAs quantum point<br />

c<strong>on</strong>tacts<br />

Taeyueb Kim 1, 2 , Sungjung Joo1, Jinki H<strong>on</strong>g 1 *, Kungw<strong>on</strong> Rhie 1 , Hyuncheol Koo 2 *,<br />

Jind<strong>on</strong>g S<strong>on</strong>g 3 , Jo<strong>on</strong>ye<strong>on</strong> Chang 2 , Sukhee Han 2 , Kyungho Shin 2<br />

1 Department of Applied Physics, Korea University, Chochiw<strong>on</strong>, Korea<br />

2 Spin device research center, Korea Institute of Science and Technology, Seoul 136-791, Korea<br />

3 Nano Phot<strong>on</strong>ics research center, Korea Institute of Science and Technology, Seoul 136-791, Korea<br />

The c<strong>on</strong>trolled generati<strong>on</strong>, manipulati<strong>on</strong> and detecti<strong>on</strong> of spin-polarized currents in semic<strong>on</strong>ductor<br />

is an important issue in spintr<strong>on</strong>ic devices [1]. The Rashba spin-orbit interacti<strong>on</strong> has been focused to<br />

manipulate spin currents. Furthermore, the quantum point c<strong>on</strong>tact (QPC) having the Rashba interacti<strong>on</strong><br />

was recently proposed as a spin-current generator. [2], [3] In this work QPCs were fabricated from InAs<br />

quantum well. Gates were installed <strong>on</strong> the sides of the quantum well, and narrow c<strong>on</strong>ducting channels, i.e.<br />

QPC, were formed by applicati<strong>on</strong> of voltages <strong>on</strong> theses gates. Two QPCs were c<strong>on</strong>nected in series and the<br />

distance between them was less than 1.6 micro-meter. An external magnetic field was applied in parallel<br />

with the line c<strong>on</strong>necting the two QPCs. Oscillati<strong>on</strong>s of resistance according to the magnetic field have<br />

been observed in this device at 1.8K. We believe that these data can be an evidence for our QPCs to work<br />

as a spin polarizer with a following scenario; the first QPC works as a spin-polarizer, and the sec<strong>on</strong>d does<br />

as a detector. The spin-current produced by the first QPC precesses by the external magnetic field, which<br />

makes the oscillatory resistance as the magnetic field changes.<br />

[1] Mikio Eto, Tetsuya Hayashi and Yuji Kurotani, J. Phys. Soc. Jpn. 74, 7, 193(2005) [2] P. Debray, S. M. S.<br />

Rahman, J. Wan, R. S. Newrock, M. Cahay, A. T. Ngo, S. E. Ulloa, S. T. Herbert, M. Muhammad and M. Johns<strong>on</strong>,<br />

Nature Nanotech. 4, 759 (2009) [3] A. Reynoso, G<strong>on</strong>zalo Usaj, and C. A. Balseiro , Phys. Rev. B. 75, 085321 (2007)<br />

Gate dependence of spin-orbit interacti<strong>on</strong> in a two-dimensi<strong>on</strong>al hole<br />

gas structure<br />

Youn Ho Park 1 , Hyun Cheol Koo 1 *, Sang-ho<strong>on</strong> Shin 1 , Jin D<strong>on</strong>g S<strong>on</strong>g 1 , Hyung-jun<br />

Kim 1 , Jo<strong>on</strong>ye<strong>on</strong> Chang 1 , Suk Hee Han 1 and He<strong>on</strong>-jin Choi 2<br />

1 Spin Device Research Center, Korea Institute of Science and Technology, Korea<br />

2 Department of Materials Science and Engineering, Y<strong>on</strong>sei University, Korea<br />

In order to implement spin-Field Effect Transistor (spin-FET), gate c<strong>on</strong>trol of spinorbit<br />

interacti<strong>on</strong> parameter (α) is a key factor in a quantum well structure because spin<br />

precessi<strong>on</strong> is influenced by strength of the α [1]. Many papers utilized n-type channel<br />

for the spin transport, however, for the complementary logic device p-type channel<br />

should be also necessary. We have investigated the spin-orbit interacti<strong>on</strong> parameter<br />

and the effective mass using the Shubnikov-de Haas (SdH) oscillati<strong>on</strong> measurement<br />

in a GaSb two-dimensi<strong>on</strong>al hole gas (2DHG) structure. The α of 1.71 × 10^11eVm<br />

and effective mass of 0.98m0 are obtained at T = 1.8 K, respectively. We also found<br />

the gate dependence of the α and the hole c<strong>on</strong>centrati<strong>on</strong> at 1.8 K. As increasing the<br />

gate voltage both the α and the hole c<strong>on</strong>centrati<strong>on</strong> are reduced, which indicates the α<br />

increases with the carrier c<strong>on</strong>centrati<strong>on</strong> in p-type channel. On the order hand, n-type<br />

channel shows opposite gate dependence [1, 2]. Therefore, the combined device of p<br />

and n-type channel spin transistor would be a good candidate for the complimentary<br />

logic device.<br />

[1] H. C. Koo, J. H. Kw<strong>on</strong>, J. Eom, J. Chang, S. H. Han, and M. Johns<strong>on</strong>, Science, 325, 1515 (2009).<br />

[2] J. Nitta, T. Akazaki, and H. Takayanagi, Phys. Rev. Lett. 78, 1335 (1997).<br />

July 8 - 13, 2012 Busan, Korea 111<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QK12<br />

Perpendicular spin transport in ferromagnet/MgO/GaAs structures<br />

Joohyung Bae 1 , Kyung-ho Kim 1 , Hyun Cheol Koo 1 *, Hyung-jun Kim 1 , Jo<strong>on</strong>ye<strong>on</strong><br />

Chang 1 , Suk Hee Han 1 and Sang Ho Lim 2<br />

1 Spin Device Research Center, Korea Institute of Science and Technology, Korea<br />

2 Department of Materials Science and Engineering, Korea University, Korea<br />

The electrical spin transport from TbFeCo/CoFeB into GaAs using MgO tunnel barrier<br />

is investigated. The 20 nm thick TbFeCo layer produces perpendicular magnetizati<strong>on</strong><br />

and the 0.8 nm thick CoFeB layer, which c<strong>on</strong>tacts the MgO/GaAs layer, enhances the<br />

spin polarizati<strong>on</strong> of the injector. The MgO layer has a role of spin filter for efficient<br />

spin injecti<strong>on</strong>. In order to reduce the c<strong>on</strong>tact resistance, the heavily doped GaAs<br />

layer is inserted between TbFeCo/CoFeB/MgO and GaAs substrate. We measured<br />

spin accumulati<strong>on</strong> and spin lifetime using three-terminal Hanle measurements with<br />

temperature range from 1.8 K to 300 K. In this geometry, the bias current is applied<br />

from the top TbFeCo layer to the GaAs channel and the voltage is measured at the<br />

interface. The perpendicular spin is injected so the in-plane magnetic field is swept to<br />

observe the spin relaxati<strong>on</strong> at the interface. For a bias current of 1.5 mA, the spin signal<br />

of 0.12 mV and 0.03 mV are obtained at T = 1.8 K and 300 K, respectively. From the<br />

analysis of the Hanle curve, a spin life time of 0.4 ns is extracted at 300 K.<br />

QK13<br />

Spin hall effect in 2DEG in the presence of Rashba spin-orbit<br />

interati<strong>on</strong><br />

W<strong>on</strong> Young Choi, Hyung-jun Kim, Jo<strong>on</strong>ye<strong>on</strong> Chang, Suk Hee Han and Hyun Cheol<br />

Koo*<br />

Korea Institute of science and technology, Korea<br />

Spin Hall effect using an InAs-based 2DEG system with a str<strong>on</strong>g Rasba effect is<br />

researched. To make all electric devices, permalloy is used as spin injector <strong>on</strong> Hall<br />

bar geometry. Two kinds of equivalent measurement, inverse and direct spin Hall, are<br />

performed. Inverse and direct spin Hall are the c<strong>on</strong>versi<strong>on</strong> of spin to charge and charge<br />

to spin, respectively. Also to c<strong>on</strong>firm the effect of precessi<strong>on</strong>, dependences of channel<br />

length and magnetizati<strong>on</strong> directi<strong>on</strong> are systematically investigated. The bias current<br />

between ferromagnet and neutral regi<strong>on</strong> of channel induces the injecti<strong>on</strong> of in-plane<br />

spin. Inside the channel, spin precessi<strong>on</strong> occurs and then spin orientati<strong>on</strong> is changed to<br />

the perpendicular directi<strong>on</strong> at the Hall cross. The spin signal as a functi<strong>on</strong> of channel<br />

length shows oscillati<strong>on</strong> behavior which is also evidence of spin precessi<strong>on</strong>. At 1.8K, a<br />

spin Hall voltage of 4 μV is detected for a bias current 0.1 mA and a channel length of<br />

0.64 μm. From this experiment, we c<strong>on</strong>firm the spin Hall effect and spin precessi<strong>on</strong> at<br />

the same time.<br />

[1] J. Wunderlich, B. G. Park, and A. C. Irvine et al, Science 330, 1801 (2010) [2] L. Sheng, D. N.<br />

Sheng, and C. S. Ting, PRL 94, 016602 (2005) [3] H. C. Koo, J. H. Kw<strong>on</strong>, J. Eom, J. Chang, S. H.<br />

Han, and M. Johns<strong>on</strong>, Science 325, 1515 (2009).<br />

QK14<br />

Spin transport and spin injecti<strong>on</strong> into turbostratic graphene<br />

June Seo Kim 1 , Sebastian Schweitzer 2 , Ajit K Patra 2 , Yenny Hernandez 3 , Klaus<br />

Muellen 3 , Xinliang Feng 3 and Mathias Klaeui 1 *<br />

1 Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, Germany<br />

2 Fachbereich Physik, Universitaet K<strong>on</strong>stanz, Germany<br />

3 Max Planck Institute for Polymer Research, Germany<br />

The remarkable physical properties of graphene, a m<strong>on</strong>olayer of carb<strong>on</strong> atoms packed into a twodimensi<strong>on</strong>al<br />

hexag<strong>on</strong>al lattice, make it a promising material for applicati<strong>on</strong>s, In particular, the high<br />

electr<strong>on</strong> mobility [1] and the relatively l<strong>on</strong>g spin lifetime (weak interacti<strong>on</strong> of the electr<strong>on</strong>s spin<br />

and orbital degree of freedom [2]) resulting in l<strong>on</strong>g spin diffusi<strong>on</strong> lengths λ up to 2 μm [3], make<br />

it an interesting candidate for spintr<strong>on</strong>ics. However, λ is currently limited by the str<strong>on</strong>g interacti<strong>on</strong><br />

between graphene and the underlying substrate and by the intrinsic corrugati<strong>on</strong> of mechanically<br />

exfoliated graphene sheets. This can be overcome by using turbostratic graphene (TG), a multilayer<br />

graphene stack c<strong>on</strong>sisting of tens of electr<strong>on</strong>ically decoupled layers. TG combines the exciting<br />

properties of graphene with the higher robustness to envir<strong>on</strong>mental influences and the absence of<br />

inner corrugati<strong>on</strong>s of a microstructured material [4]. In this study, we have successfully performed<br />

spin injecti<strong>on</strong> from ferromagnetic electrodes into TG discs and detected the spin transport using a<br />

n<strong>on</strong>-local spin valve c<strong>on</strong>figurati<strong>on</strong> [3]. Moreover we can also investigate the correlati<strong>on</strong> between<br />

the charge carrier transport properties and the spin injecti<strong>on</strong> efficiency.<br />

[1] A. K. Geim et al., Nature Materials 6, 183 (2007), Science 324, 1530 (2009). [2] Hernando et<br />

al., Phys. Rev. B 74, 155426 (2006). [3] N. Tombros et al., Nature 448, 571 (2007). [4] M. Orlita et<br />

al., Phys. Rev. Lett. 101, 267601 (2008).<br />

112 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QK15<br />

Spin signal in metallic lateral spin valves made by a shadow<br />

evaporati<strong>on</strong> technique<br />

Piotr Laczkowski, Laurent Vila, Williams Savero-torres, Van Dai Nguyen, Juan Carlos<br />

Rojas-sanchez, Murat Cubukcu, Alain Marty, Lucien Notin, Cyrille Beigne and Jeanphilippe<br />

Attane<br />

Universite Joseph Fourier, BP 53, 38041, Grenoble and INAC/ CEA Grenoble,<br />

France<br />

Amidst the large variety of proposed spin structures, Lateral Spin Valves (LSV) devices attracted<br />

recently an increasing attenti<strong>on</strong>. These lateral devices c<strong>on</strong>sist in two ferromagnetic electrodes<br />

c<strong>on</strong>nected by a n<strong>on</strong>-magnetic metallic wire allowing to tune the transport properties according to the<br />

respective magnetic states of the two ferromagnetic electrodes. They allow realizing n<strong>on</strong>-local transport<br />

measurements, by separating the spin current from the charge current using a four probe c<strong>on</strong>necti<strong>on</strong>s<br />

to an interface. We are developing n<strong>on</strong>-local spin injecti<strong>on</strong> and detecti<strong>on</strong> technique in lateral spin valve<br />

structure made by electr<strong>on</strong> beam lithography and angle evaporati<strong>on</strong> techniques with a special emphasis<br />

<strong>on</strong> the study of the spin Hall effect. The spin signal depends mainly <strong>on</strong> the geometry of the LSV, <strong>on</strong> the<br />

quality of the interfaces, and <strong>on</strong> the choice of the used materials. We present a method used to optimize<br />

the spin signal of lateral spin valves using a technique to form and c<strong>on</strong>nect nanowires in a single step<br />

in vacuum, avoiding interface c<strong>on</strong>taminati<strong>on</strong> and oxidati<strong>on</strong>. By using different evaporati<strong>on</strong> angles of<br />

materials through a resist mask and by reducing the devices geometry, we succeeded in obtaining spin<br />

signals close to 25 mΩ at 77K in devices with transparent interfaces.<br />

P. Łaczkowski et al., Applied Physics Express, Volume 4, Issue 6, pp. 063007-063007-3 (2011)<br />

QK16<br />

Hanle effect with in-plane magnetic fields in metallic lateral spin valves<br />

Juan-carlos Rojas Sanchez, Laurent Vila, Matthieu Jamet, Piotr Laczkowski, Murat<br />

Cubukcu, Williams Savero-torres, Van Dai Nguyen, Alain Marty, Cyrille Beigne and<br />

Jean-philippe Attane<br />

Universite Joseph Fourier, BP 53, 38041, Grenoble and INAC/ CEA Grenoble,<br />

France<br />

When a charge current crosses the interface between a ferromagnetic (FM) and a n<strong>on</strong>magnetic<br />

(NM) material, a spin current appears that occurs <strong>on</strong> the length scale of the<br />

spin diffusi<strong>on</strong>. It is possible to detect this spin accumulati<strong>on</strong> by measuring the voltage<br />

between the NM wire and the other FM wire. We show that the spin signal amplitude<br />

can be enhanced by inserting a natural Al oxide between the interface of Py and Al,<br />

achieving spin signals above 150 mOhms at 77 K (instead of 24mOhms with transparent<br />

c<strong>on</strong>tacts) and 38 mOhms at RT. When the magnetic field is applied perpendicularly to<br />

the LSV plane, the injected spins in the normal channel precess around an axe parallel<br />

to H. The decoherence and/or the precessi<strong>on</strong> induced by the magnetic field can lead to<br />

oscillati<strong>on</strong>s and disappearance of the spin signal (Hanle effect). Hanle measurements<br />

are usually performed by applying H perpendicular to the sample plane [1], the spin<br />

precessing in plane. Here we show that it is possible to carry out Hanle measurements<br />

by applying H in the sample plane, generating out-of-plane spin precessi<strong>on</strong>, and thus<br />

gaining a degree of freedom for the c<strong>on</strong>trol of the spin current.<br />

[1] “Electrical detecti<strong>on</strong> of spin precessi<strong>on</strong> in a metallic mesoscopic spin valve” F.J. Jedema, H.B.<br />

Heersche, A.T. Filip, J.J.A. Baselmans and J. van Wees, Nature 416, 713 (2002).<br />

QK17<br />

Detecting the magnetizati<strong>on</strong> switching of a ferromagnetic dot using<br />

n<strong>on</strong> local spin injecti<strong>on</strong> by means of lateral spin valve structures<br />

Williams Savero-torres, Laurent Vila, Alain Marty, Piotr Laczkowski, Van Dai<br />

Nguyen, Murat Cubukcu, Juan-carlos Rojas Sanchez, Lucien Notin and Jean-philippe<br />

Attane<br />

Universite Joseph Fourier, BP 53, 38041, Grenoble and INAC/ CEA Grenoble,<br />

France<br />

In most researches <strong>on</strong> Spin Torque, the charge and spin currents cannot be separated. To solve<br />

this problem, spin injecti<strong>on</strong> using lateral spin-valves, made of magnetic and n<strong>on</strong> magnetic<br />

materials, have been proposed [1]. In this c<strong>on</strong>text, we study the spin torque generated by pure<br />

spin current <strong>on</strong> a ferromagnetic dot, using lateral spin-valve structures. The nanostructure<br />

is composed of two parallel ferromagnetic electrodes, <strong>on</strong>e transversal metallic channel, and<br />

<strong>on</strong>e ferromagnetic dot at the middle of the structure. The width of wires and dots is 50 nm.<br />

To detect the dot magnetizati<strong>on</strong> switching, n<strong>on</strong>-local measurements are performed. The spin<br />

polarised current is injected <strong>on</strong> <strong>on</strong>e side using a ferromagnetic electrode. The spin accumulati<strong>on</strong><br />

produces the splitting of the electrochemical potential, enabling the diffusi<strong>on</strong> of the pure spin<br />

current al<strong>on</strong>g the channel. The pure-spin current is found to be adsorbed by the ferromagnetic<br />

dot, decreasing the spin signal amplitude, which is detected using the sec<strong>on</strong>d ferromagnetic<br />

electrode. The n<strong>on</strong> local geometry enables the spin current and the charge current separati<strong>on</strong>,<br />

giving the possibility to test the magnetizati<strong>on</strong> switching induced by a pure spin current.<br />

[1] T. Yang, T. Kimura, and Y. Otani, Giant spin-accumulati<strong>on</strong> signal and pure spin-current-induced<br />

reversible magnetizati<strong>on</strong> switching, Nat. Phys. 4, 851 (2008).


QK18<br />

Perfect spin filter and highly spin-polarized current induced by fano<br />

antires<strong>on</strong>ance effect in the multiple-quantum-dot nanodevices<br />

Hua-hua Fu 1 , Kai-lun Yao 2 * and Zu-li Liu 2<br />

1<br />

Department of Physics, Huazh<strong>on</strong>g University of Science and Technology, Wuhan<br />

430074,, China<br />

2<br />

Physics Department, Huazh<strong>on</strong>g University of Science and Technology, Wuhan<br />

430074,, China<br />

To realize perfect spin filter or to generate highly spin-polarized current is <strong>on</strong>e of the fundamental<br />

requirements of any applicati<strong>on</strong>s <strong>on</strong> spintr<strong>on</strong>ics, and in what material or model structure to achieve this<br />

goal effectively is still <strong>on</strong>e of the central issues in spintr<strong>on</strong>ics. To realize these aims, multiple-quantumdot<br />

system which can be man-made in a c<strong>on</strong>trollable way have been attracted much attenti<strong>on</strong>. In this<br />

report, we propose a practical design to realize perfect spin filter in a periodic diam<strong>on</strong>dlike network<br />

composed of multiple quantum dots (QDs). In our design, by producing an energy difference between<br />

the site energy between the upper and down QDs in the network, the c<strong>on</strong>ductance spectra show<br />

a valley structure with a zero point due to the Fano antires<strong>on</strong>ance effect. As the energy difference<br />

increases or the network size increases to a not very large value, the antires<strong>on</strong>ance valley changes to a<br />

well-defined insulating band. Moreover, the c<strong>on</strong>diti<strong>on</strong>s for the occurrence of the Fano antires<strong>on</strong>ance<br />

and its relati<strong>on</strong> with the formati<strong>on</strong> of the well-defined insulating band are determined. By a Zeeman<br />

effect, the spin-splitting c<strong>on</strong>ductance spectra show several highly to 100% spin-polarized windows,<br />

str<strong>on</strong>gly proposing that this network can be applied as a perfect spin filter.<br />

1. H. H. Fu, K. L. Yao, Appl. Phys. Lett. 110, 013502, 2012. 2. H. H. Fu, K. L. Yao, J. Chem. Phys.<br />

134, 054903 (2011). 3. H. H. Fu, K. L. Yao, J. Appl. Phys. 108, 084510 (2010); 110, 094502 (2011).<br />

QK19<br />

Transmissi<strong>on</strong> of spin polarized photoelectr<strong>on</strong>s across ferromagnet/<br />

semic<strong>on</strong>ductor interfaces using oblique Hanle effect<br />

Yasuhiro Shirahata 1 , Toshiyuki Isozaki 1 , Ippei Suzuki 1 , Eiji Wada 1 , Mitsuru Itoh 1 ,<br />

Masahito Yamaguchi 2 and Tomoyasu Taniyama 1<br />

1 Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

2 Department of Electrical Engineering and Computer Science, Nagoya University,<br />

Japan<br />

We dem<strong>on</strong>strate spin-dependent transmissi<strong>on</strong> of photoelectr<strong>on</strong>s from a GaAs quantum<br />

well (QW) into a ferromagnetic FeGa layer under optical spin orientati<strong>on</strong> in a small<br />

oblique magnetic field. The applicati<strong>on</strong> of the oblique magnetic field enables us to<br />

measure the spin-dependent electr<strong>on</strong> transmissi<strong>on</strong> across the interface due to the inplane<br />

spin comp<strong>on</strong>ent of photoelectr<strong>on</strong>s caused by the Larmor precessi<strong>on</strong> of electr<strong>on</strong><br />

spins about the magnetic field. A clear field dependence of the spin-dependent<br />

photocurrent is observed for a 20-nm-thick FeGa/GaAs QW sample, showing that<br />

the filtering of in-plane polarized electr<strong>on</strong> spins which are generated by the Larmor<br />

precessi<strong>on</strong> occurs at the interface. To get c<strong>on</strong>crete evidence for the spin filtering effect,<br />

we measure the magnetic field dependence of the phase shift between the circular<br />

polarizati<strong>on</strong> of light irradiated and the spin-dependent photocurrent. The phase shift<br />

exhibits a hysteresis behavior as a functi<strong>on</strong> of magnetic field, in compatible with the inplane<br />

magnetizati<strong>on</strong> process of the FeGa layer. These results clearly dem<strong>on</strong>strate that<br />

a very efficient spin filtering effect occurs at the FeGa/GaAs interface even at a low<br />

magnetic field, providing a promising basis for designing spin detecti<strong>on</strong> technology<br />

based <strong>on</strong> spin filtering effect.<br />

QK20<br />

Electric field tunning and spin coulomb drag in spin field effect<br />

transistors (spin-FETs)<br />

George Alexandru Nemnes, Lucian I<strong>on</strong> and Stefan Antohe<br />

University of Bucharest, Faculty of Physics, Romania<br />

The quasi-bound states which appear as a c<strong>on</strong>sequence of the Rashba spin-orbit (SO) coupling,<br />

introduce a str<strong>on</strong>gly irregular behavior of the spin-FET c<strong>on</strong>ductance at large Rashba parameter<br />

[1]. However, by introducing stray electric fields in additi<strong>on</strong> to the SO couplings, the effect<br />

of the SO induced quasi-bound states can be tuned. The oscillati<strong>on</strong>s of the spin-resolved<br />

c<strong>on</strong>ductance become smoother, resulting the possibility to c<strong>on</strong>trol the spin-FET characteristics<br />

[2]. Besides these effects, the Coulomb interacti<strong>on</strong> gives rise to new and interesting manybody<br />

phenomena. D'Amico et al. discussed recently the physical origin of spin Coulomb drag<br />

effect (SCD) in rather general three-, two- and <strong>on</strong>e dimensi<strong>on</strong>al systems. Here, a step closer to<br />

a realistic device is made: the SCD effect will be investigated in a nanowire spin-FET structure<br />

within the framework of self-c<strong>on</strong>sistent calculati<strong>on</strong>s for the open quantum system [3]. The spin<br />

drag trans-resistivity as a measure for SCD effect will be obtained, in the c<strong>on</strong>text of adjusting<br />

the spin injecti<strong>on</strong> efficiency from the c<strong>on</strong>tacts. In additi<strong>on</strong>, the SCD effect in the presence of<br />

Rashba spin-orbit coupling will be analyzed. The Coulomb interacti<strong>on</strong> will also be introduced<br />

in an exact manner for a few electr<strong>on</strong> system, using the exact diag<strong>on</strong>alizati<strong>on</strong> method [4].<br />

[1] M. M. Gelabert et al., Phys. Rev. B 81, 165317 (2010). [2] G. A. Nemnes, A. Manolescu, V.<br />

Gudmundss<strong>on</strong>, IOP - JPCS (to be published, 2012). [3] G. A. Nemnes, L. I<strong>on</strong>, and S. Antohe, J.<br />

Appl. Phys. 106, 113714 (2009). [4] C. Yannouleas and U. Landman, Rep. Prog. Phys. 70, 2067<br />

(2007).<br />

QK21<br />

QK22<br />

Geometry effect <strong>on</strong> quasi-twodimensi<strong>on</strong>al electr<strong>on</strong> system<br />

Kuo-chin Chen, Hsin-han Lee and Ching-ray Chang*<br />

Nati<strong>on</strong>al Taiwan University, Taiwan<br />

QK23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The Rashba-type Spin splitting in Pb m<strong>on</strong>olayer <strong>on</strong> Si and Ge<br />

surfaces: a First-principles study<br />

Hyungjun Lee 1 and Hyoung Jo<strong>on</strong> Choi 2 *<br />

1 Department of Physics, Y<strong>on</strong>sei University, Korea<br />

2 Department of physics, Y<strong>on</strong>sei University, Korea<br />

Rashba spin-orbit splitting of the surface states due to structural inversi<strong>on</strong> asymmetry<br />

is a rapidly growing field of research. Specifically, owing to a technological importance<br />

in spin-dependent electr<strong>on</strong>ics, spin-polarized metallic surface states <strong>on</strong> semic<strong>on</strong>ductor<br />

surfaces would be highly interesting. Al<strong>on</strong>g this line, we have performed first-principles<br />

calculati<strong>on</strong>s of electr<strong>on</strong>ic structures of m<strong>on</strong>olayer of heavy element deposited <strong>on</strong><br />

semic<strong>on</strong>ductor surfaces, Pb/Si(111) and Ge(111)-√3×√3 surfaces, by including the<br />

spin-orbit coupling in the form of additi<strong>on</strong>al n<strong>on</strong>local pseudopotential projectors.<br />

We investigate and compare energy band dispersi<strong>on</strong>s and spin polarizati<strong>on</strong>s of these<br />

systems and simulate angle-resolved photoemissi<strong>on</strong> spectra for direct comparis<strong>on</strong><br />

with experimental results. We also discuss our results focusing <strong>on</strong> the difference from<br />

the Rashba splitting in the Shockley surface states <strong>on</strong> Au(111) surface. This work<br />

was supported by the NRF of Korea (Grant No. 2011-0018306), and computati<strong>on</strong>al<br />

resources have been provided by KISTI Supercomputing Center (Project No. KSC-<br />

2011-C3-06).<br />

We calculate the local charge density and local spin density in a deformed square lattice<br />

system with Rashba spin orbital interacti<strong>on</strong>. Use n<strong>on</strong>equilibrium Keldysh Green’s<br />

functi<strong>on</strong> formalism, within the tight-binding framework. The system c<strong>on</strong>sists of normal<br />

metal lead and deformed central part. We treat the deformed system as adding effective<br />

magnetic field that introduces Zeeman effect. We also present the charge and spin<br />

current. The deformati<strong>on</strong> we adopt is hemispherical shape and Gaussian shape. We will<br />

compare the result with the case that deformati<strong>on</strong> vanished.<br />

Electrical measurement of spin accumulati<strong>on</strong> and transport in Fe/<br />

AlGaAs heterostructures<br />

Jo<strong>on</strong>-il Kim 1 *, Jennifer Misuraca 1 , Kangkang Meng 2 , Jun Lu 2 , Lin Chen 2 , Jianhua<br />

Zhao 2 , Stephan V<strong>on</strong> Molnar 1 and Peng Xi<strong>on</strong>g 1<br />

1<br />

Physics, Department of Physics, Florida State University, Tallahassee, Florida,<br />

USA, USA<br />

2<br />

Physics, Institute of Semic<strong>on</strong>ductors, Chinese Academy of Sciences, Beijing, China,<br />

China<br />

Utilizing the persistent photoc<strong>on</strong>ductivity effect, we report <strong>on</strong> spin accumulati<strong>on</strong> and transport<br />

in AlGaAs at different carrier densities under the same experimental c<strong>on</strong>diti<strong>on</strong>s without the<br />

necessity for making replicas to access different doping levels. We c<strong>on</strong>ducted n<strong>on</strong>-local 3<br />

and 4 terminal Hanle effect measurements in AlGaAs to measure spin accumulati<strong>on</strong> and<br />

spin transport respectively at different carrier densities. We will present our recent results,<br />

especially the carrier density dependence of the spin lifetime derived from our n<strong>on</strong>-local spin<br />

measurements. We also report the bias current dependence of the spin lifetime. From optical<br />

studies, the spin life-time at zero bias and at low temperature was reported to be larger than 100<br />

ns in n-GaAs <strong>on</strong> the insulating side and ~80 ns <strong>on</strong> the metallic side [1]. Based <strong>on</strong> our n<strong>on</strong>-local<br />

3 terminal measurement in Si:Al 0.3Ga 0.3As, the extrapolated spin life-time at zero bias and at 5<br />

K was found to be as large as ~2 ns <strong>on</strong> the insulating side and decreased with increasing bias<br />

current. This work was supported by NSF DMR-0908625 and NSFC 10920101071.<br />

[1] M. Furis, D.L. Smith, and S.A. Crooker and J.L. Reno, Appl. Phys. Lett. 89, 102102 (2006).<br />

July 8 - 13, 2012 Busan, Korea 113<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QK24<br />

Pure spin current injecti<strong>on</strong> into a Gd wire<br />

Seiji N<strong>on</strong>oguchi, Tatsuya Nomura and Takashi Kimura*<br />

Kyushu University, Japan<br />

In magnetocaloric effects, the spin entropy is transformed to the thermal entropy<br />

because of an interacti<strong>on</strong> between spin and heat. Since the spin entropy can be<br />

c<strong>on</strong>trolled by the external magnetic field, the envir<strong>on</strong>ment temperature also can<br />

be tuned by the external magnetic field. Although such methods can be operated<br />

efficiently, it is difficult to reduce the size of the entire system. An effective magnetic<br />

field can be produced also by injecting spin currents via the interacti<strong>on</strong> between the<br />

c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s and localized magnetic moments. Therefore, when a pure spin<br />

current is injected into the magnetocaloric material, we may c<strong>on</strong>trol the spin entropy<br />

because of the spin transfer torque and/or spin accumulati<strong>on</strong>. Such a cooling effect has<br />

a possibility for a highly efficient nanosized refrigerati<strong>on</strong> device. To dem<strong>on</strong>strate this<br />

effect, we prepared a lateral spin valve with the Gd middle wire, which is a magnetocaloric<br />

material. We observed the reducti<strong>on</strong> of n<strong>on</strong>local spin signal by inserting the<br />

middle Gd wire, meaning the pure spin current was injected into the Gd wire. We<br />

also found that the background resistance decreases with increasing DC current. This<br />

implies that the device was cooled by the pure spin current injecti<strong>on</strong> into the Gd wire.<br />

QL01<br />

Synthesis and characterizati<strong>on</strong> of Ba 3Co 2Fe 24O 41 by the proteic sol-gel<br />

process<br />

Bruna Andrade, Petrucio Silva and Marcelo Macedo*<br />

Physics, Federal University of Sergipe, Brazil<br />

In this work, we show the producti<strong>on</strong> of hexag<strong>on</strong>al Z-type barium ferrite (<br />

Ba 3Co 2Fe 24O 41) prepared via the proteic sol-gel process as well as their structural<br />

characterizati<strong>on</strong> and magnetic properties. The precursor materials were ir<strong>on</strong> nitrate,<br />

cobalt nitrate and barium carb<strong>on</strong>ate which formed a sol after being stoichiometrically<br />

dissolved in coc<strong>on</strong>ut water. We carried out a heat treatment at 100°C/24 h for the<br />

formati<strong>on</strong> of an amorphous xerogel and a calcinati<strong>on</strong> at 1000°C/1 h for phase formati<strong>on</strong><br />

of Z-type barium ferrite. The material exhibited a magnetizati<strong>on</strong> curve as a functi<strong>on</strong> of<br />

temperature characteristic of ferrimagnetic material with Tc > 300 K and a hysteresis<br />

at room temperature with low coercive field (142 Oe) and saturati<strong>on</strong> magnetizati<strong>on</strong><br />

around 48 emu/g for a field of 7 T. Our results indicate that the proteic sol-gel process<br />

may be a route of great potential for obtaining Z-type ferrites.<br />

QL02<br />

Ferromagnetism in vanadium doped ZnO thin films grown by pulsed<br />

laser depositi<strong>on</strong><br />

Shumaila Karamat 1 *, Rajdeep Singh Rawat 2 , Paul Lee 3 , Tan Lee Augustine 4 , Raju V<br />

Ramanujan 5 and H.d Sun 6<br />

1<br />

Physics, 1. NIE, Nanyang Technological University, Singapore 2. COMSATS,Islamabad, Pakistan,<br />

Pakistan<br />

2<br />

Physics, Nati<strong>on</strong>al Institute of Educati<strong>on</strong>, Nanyang Technological University, Singapore, Singapore<br />

3<br />

Physics, NIE-NTU, Singapore, Singapore<br />

4<br />

Physics, NIE-NTU Singapore, Singapore<br />

5<br />

Material Science, MSE-NTU Singapore, Singapore<br />

6<br />

SPMS, SPMS-NTU, Singapore<br />

This paper investigates the structural, compositi<strong>on</strong>al and magnetic properties of vanadium doped ZnO films<br />

((ZnO) 1-x(V 2O 5) x where x = 0.02, 0.03 and 0.05) deposited by pulsed laser technique (PLD). Thin films were<br />

deposited for a c<strong>on</strong>stant durati<strong>on</strong> of 1 hr at 2×10-2 mbar O2 ambient gas pressure by using frequency doubled<br />

Nd:YAG laser at 750 °C substrate temperature. The preferred orientati<strong>on</strong> in thin films is al<strong>on</strong>g the (002) plane of<br />

ZnO. The lattice parameter c derived from the (002) diffracti<strong>on</strong> peak increases as vanadium c<strong>on</strong>tent increases,<br />

suggesting that vanadium substitutes for Zn in ZnO lattice. The PL measurement at low temperature shows<br />

the emissi<strong>on</strong> peak at 3.30 eV which is usually caused by acceptor-related transiti<strong>on</strong>s such as free electr<strong>on</strong> to<br />

neutral acceptor (FA) and d<strong>on</strong>or-acceptor-pair (DAP). The XPS results show that vanadium exist in V 2+ and<br />

V4+ valence state which is in agreement with the XRD and PL results and points to the fact that the ZnVO<br />

phase, desirable in DMS, is formed in thin film samples. Furthermore, the hysteresis curves exhibiting the<br />

ferromagnetism for all thin films samples further support the formati<strong>on</strong> of ZnVO phase in thin films samples.<br />

114 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QL03<br />

The magnetic and dielectric properties of multiferroic Bi 1-xGd xFeO 3<br />

Takuya Yanoh*, Naoki Sakai, Liming Zhu, Akinobu Kurokawa, Hiromasa Takeuchi,<br />

Shinya Yano, Kazuki Onuma, Takaya K<strong>on</strong>do, Kazunari Miike, Toshiki Miyasaka and<br />

Yuko Ichiyanagi<br />

Physics, Yokohama Nati<strong>on</strong>al University, Japan<br />

BiFeO 3 is known as multiferroic material with antiferromagnetic and ferroelectric<br />

properties. Especially, ferroelectricity at room temperature is remarkable and BiFeO 3 is<br />

expected for new device materials. However, BiFeO 3 has antiferromagnetic ordering,<br />

as the result, magnetic values such as remanent magnetizati<strong>on</strong> Mr and coercive force<br />

HC are rather small for further applicati<strong>on</strong>. In this study, in order to improve magnetic<br />

property and to evaluate dielectric property, we tried to synthesize Bi 1-xGd xFeO 3<br />

particles where x = 0 to 1.0 by our original wet chemical method. The structural,<br />

magnetic and dielectric properties of prepared samples were investigated. Crystal<br />

structure change from rhombohedral to orthorhombic was found around x = 0.2 from<br />

the X-ray diffracti<strong>on</strong> (XRD) measurement. Lattice c<strong>on</strong>stants a and c estimated by XRD<br />

decreased as Gd i<strong>on</strong> increased, supporting that Gd i<strong>on</strong>s were doped exactly in BiFeO 3.<br />

The magnetic properties of Bi 0.9Gd 0.1FeO 3 which has rhombohedral (BiFeO 3 type)<br />

structure exhibited canted antiferromagnetism at 5 K. Both remanent magnetizati<strong>on</strong><br />

Mr and coercive force HC significantly increased as Gd i<strong>on</strong> increased compared with<br />

BiFeO 3. The dielectric properties of Bi 0.9Gd 0.1FeO 3 showed that dielectric loss (tanδ)<br />

has been drastically improved compared with that of BiFeO 3 for about 90%, while real<br />

dielectric c<strong>on</strong>stant ε’ decreased about 15%.<br />

QL04<br />

Double-exchange interacti<strong>on</strong> in heavily Mn-doped CuO thin films<br />

Li Li, Bin Lv, Shen Wang, Jinzhu Cai, Wenqin Zou, Fengming Zhang* and Xiaoshan<br />

Wu<br />

Physics, Nanjing University, China<br />

RKKY exchange, double-exchange interacti<strong>on</strong>s are two main mechanisms which are<br />

proposed to explain the origin of ferromagnetism of Mn-doped CuO films. C<strong>on</strong>sider<br />

that double-exchange interacti<strong>on</strong>s cannot produce l<strong>on</strong>g-range magnetic order at<br />

c<strong>on</strong>centrati<strong>on</strong>s of magnetic cati<strong>on</strong>s of low percent, Heavily Mn-doped CuO films have<br />

been prepared by PEVCD in air and in O 2. The M-T and M-H curves show that the<br />

average magnetic moment of the films prepared in O 2 is larger than those prepared<br />

in air, which may attribute to the variati<strong>on</strong> of Mn chemical valence state. Doubleexchange<br />

between Mn 2+ and Mn 3+ can be used to understand the ferromagnetism of<br />

CuO under heavily Mn-doping.. The Curie temperature varies slightly with the growth<br />

atmosphere. The structure and magnetic properties vary with the annealing parameters<br />

obviously, which may indicate that the strain and carriers may play roles <strong>on</strong> the double<br />

exchange.<br />

QL05<br />

Magnetic properties of Cu-doped GaN films grown by MBE<br />

Philipp R. Ganz 1 , Christoph Suergers 2 *, Gerda Fischer 3 and Daniel M. Schaadt 4<br />

1<br />

Institut fur Angewandte Physik and DFG-Center for Functi<strong>on</strong>al Nanostructures,<br />

Karlsruhe Institute of Technology (KIT), Germany<br />

2<br />

Physikalisches Institut and DFG Center for Functi<strong>on</strong>al Nanostructures, Karlsruhe<br />

Institute of Technology (KIT), Germany<br />

3<br />

Physikalisches Institut, Karlsruhe Institute of Technology (KIT), Germany<br />

4<br />

Institute for Energy Research and Physical Technologies, Clausthal University of<br />

Technology, Germany<br />

The magnetic properties of Cu-doped GaN films have been investigated in dependence<br />

of Cu doping level and film thickness. The films were epitaxially grown at different Cuto-Ga<br />

beam-equivalent-pressure ratios (BEPR) by molecular beam epitaxy <strong>on</strong> sapphire<br />

substrates with an AlN buffer and were characterized by scanning electr<strong>on</strong> microscopy,<br />

energy dispersive x-ray spectroscopy, and x-ray diffracti<strong>on</strong>. Within a narrow range of<br />

BEPR around 1 %, a ferromagnetic behavior with a Curie temperature higher than 400<br />

K is observed. For BEPR > 1 %, n<strong>on</strong>ferromagnetic Cu-Ga islands are predominantly<br />

formed at the surface. The saturati<strong>on</strong> magnetizati<strong>on</strong> of ferromagnetic films with BEPR<br />

= 1 % decreases with increasing film thickness. This suggests that the ferromagnetic<br />

behavior is due to defects created during the growth process and by the incorporati<strong>on</strong><br />

of Cu into GaN for BEPR ≤ 1 % leading to a l<strong>on</strong>g-range magnetic polarizati<strong>on</strong>.


QL06<br />

<strong>Magnetism</strong> and electr<strong>on</strong>ic transport of MnAs single nanostructures<br />

Federico Fernandez Baldis 1 , Marina Tortarolo 2 , Martin Sirena+, Laura Steren 3 , Victor<br />

Etgens 2 and Mahmoud Eddrief 2<br />

1 Centro Atomico Bariloche, Argentina<br />

2 Institut des NanoSciences de Paris, France<br />

3 Centro Atomico C<strong>on</strong>stituyentes, Argentina<br />

The magneto-structural properties of MnAs thin films grown <strong>on</strong>to GaAs have recently<br />

drawn much attenti<strong>on</strong> due to its potential applicati<strong>on</strong> in spintr<strong>on</strong>ics devices. The MnAs<br />

thin films exhibit a coexistence of a low-temperature ferromagnetic hexag<strong>on</strong>al phase (α)<br />

and a paramagnetic orthorhombic (β) <strong>on</strong>e in a finite temperature range below the Curie<br />

temperature. When MnAs is grown <strong>on</strong>to GaAs[100], both phases are self-organized in a<br />

regular stripes array. This pattern is affected when the MnAs films are c<strong>on</strong>fined laterally<br />

to micrometric sizes and depends <strong>on</strong> the directi<strong>on</strong> of the c<strong>on</strong>finement. In this work,<br />

we present an investigati<strong>on</strong> of the temperature dependence of the magnetic domain<br />

structure and magneto-transport properties of MnAs nanoribb<strong>on</strong>s in order to determine<br />

the anisotropic resp<strong>on</strong>se of the system, regarding both the magnetism and electr<strong>on</strong>ic<br />

transport. The c<strong>on</strong>finement effects were examined at the low-temperature pure<br />

ferromagnetic phase and at the α-β phase-coexistence regime. Nanoribb<strong>on</strong>s c<strong>on</strong>fined<br />

al<strong>on</strong>g the (I) α-MnAs[1120] and (II) α-MnAs[0001] directi<strong>on</strong>s were fabricated by<br />

e-beam lithography combined with optical lithography. The magnetic domain imaging<br />

was performed with a MFM, home-adapted for variable temperature measurements<br />

between 284K and 320K. The magneto-resistance and Hall effect measurements were<br />

made between 50K and 320K using a 9 Tesla superc<strong>on</strong>ducting magnet.<br />

QL07<br />

The generated antiferromagnetic and ferromagnetic states in<br />

nanocrystalline Cu-Cu 2O system and the c<strong>on</strong>sequences for spin<br />

chemistry<br />

Anatoly Yermakov 1 *, Michael Uimin 1 , Alexandre Korolyov 1 , Ilya Byzov 1 , Alexey<br />

Mysik 1 , Vladislav Maikov 1 and Mamoru Senna 2<br />

1 Institute of Metal Physics, Ural Branch of RAS, Russia<br />

2 Faculty of Science and Technology, Keio University, Japan<br />

Under investigati<strong>on</strong>s of nanocrystalline Cu-Cu 2O oxides it has been established that they<br />

actually possess heterogeneous magnetic states in nanoscale range. In nano-structured Cu-Cu 2O<br />

oxides, ferromagnetic (FE) and anti-ferromagnetic (AF) states are coexisting at above room<br />

temperature. The new idea based <strong>on</strong> the magnetic phase transformati<strong>on</strong> from AF to FE state<br />

at an external field was suggested as a hypothesis to understand the variati<strong>on</strong> of chemical rate<br />

transformati<strong>on</strong>s. The point is that a metamagnetic phase transiti<strong>on</strong> is accompanied by a variati<strong>on</strong><br />

of an electr<strong>on</strong>ic state of carrier from localized to delocalized <strong>on</strong>e which can result in a variati<strong>on</strong><br />

of nanoreagents reactivity. In fact, the influence of magnetic field <strong>on</strong> the rate of chemical<br />

transformati<strong>on</strong>s, e.g. Cu amm<strong>on</strong>ium complex formati<strong>on</strong> using Cu-Cu 2O nanomaterials, as<br />

magneto-c<strong>on</strong>trolled reagents, has been reliably observed. Thus, the nanocrystalline copper<br />

oxides having a liquid-like potential are a remarkable example of energy-wise degenerated<br />

different magnetic states that can be operated by fairly weak external magnetic fields to c<strong>on</strong>trol<br />

a rate of chemical transformati<strong>on</strong>s and other properties. We think the principle we here propose<br />

could be extended to other transiti<strong>on</strong> metal oxide nanoparticles with a similar electr<strong>on</strong>ic states.<br />

Thanks to RFBR Grants # 10-02-00323 and # 10-02-546 for support.<br />

QL08<br />

Unidirecti<strong>on</strong>al anisotropy observed in Fe film grown <strong>on</strong> GaAs at low<br />

temperature<br />

Se<strong>on</strong>gho<strong>on</strong> Choi 1 , Taehee Yoo 1 , S. Khym 1 , Sangho<strong>on</strong> Lee 1 *, X. Liu 2 and J. K.<br />

Furdyna 2<br />

1 Physics Department, Korea University, Korea<br />

2 Physics Department, University of Notre Dame, USA<br />

The magnetic anisotropy properties of Fe films have been investigated by planar<br />

Hall effect (PHE) measurements. A 4 nm thick Fe film was grown <strong>on</strong> a (001) GaAs<br />

substrate by MBE technique at room temperature. The field scans of the planar Hall<br />

resistance (PHR) at room temperature show an abrupt transiti<strong>on</strong> with hysteresis<br />

centered at zero field during the magnetizati<strong>on</strong> reversal, indicating the presence of<br />

symmetric magnetic easy axes in the film plane. However, the hysteresis in the PHR<br />

appeared to be shifted toward <strong>on</strong>e field directi<strong>on</strong> when the temperature decreased to 3<br />

K. This asymmetry in the magnetizati<strong>on</strong> reversal process at 3 K can be understood by<br />

introducing an unidirecti<strong>on</strong>al anisotropy field H ud. Interestingly, the directi<strong>on</strong> of the H ud<br />

directly follows the directi<strong>on</strong> of the cooling field. This indicates that the directi<strong>on</strong> of the<br />

H ud is not fixed but can be changed by the cooling field. For the case of the cooling field<br />

al<strong>on</strong>g the [-1-10] directi<strong>on</strong>, we obtained the values of cubic, uniaxial and unidirecti<strong>on</strong>al<br />

anisotropy fields by analyzing angular dependence of PHR. The magnitude of H ud<br />

was <strong>on</strong>e order of magnitude smaller than other anisotropy fields although it caused a<br />

significant asymmetry in the PHR hysteresis.<br />

QL09<br />

QL10<br />

QL11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of hydrothermally synthesized ZnO<br />

nanostructures<br />

H Hadiyawarman, Kadek J. Parwanta, Bowha Lee and Chunli Liu*<br />

Department of Physics, Hankuk University of Foreign Studies, Korea<br />

We report the study <strong>on</strong> the ferromagnetism in ZnO nanostructures fabricated by<br />

hydrothermal method at low temperature and with three different pH values. No posttreatment<br />

was applied to all samples. X-ray diffracti<strong>on</strong> shows that the samples possess<br />

typical wurtzite structure and have no other impurity phases. Magnetizati<strong>on</strong> properties<br />

of ZnO samples were measured. With the defect analysis based <strong>on</strong> low temperature<br />

photoluminescence spectroscopy, the effective defects c<strong>on</strong>tributed to the magnetic<br />

properties were investigated. The result suggests that oxygen defects and synthesis<br />

c<strong>on</strong>diti<strong>on</strong>s play an important role in mediating the magnetic property in the undopped<br />

ZnO nanostructures.<br />

Electrical, magnetic and magnetoimpedance studies of LSMO thin<br />

film prepared by sol gel method<br />

Pawan Kumar and Ramanathan Mahendiran<br />

Physics, NUS, Singapore<br />

In this work, we have prepared La 0.7Sr 0.3MnO 3 by sol-gel method using Si (100)<br />

substrate and characterized the sample by XRD,dc magnetizati<strong>on</strong>, dc magnetoresistance,<br />

and atomic force microscopy. The sample is found to be ferromagnetic below 367 K<br />

from the magnetic measurement. Impedance spectroscopy study has been reported<br />

<strong>on</strong> the thin film for the first time. We have studied the ac electrical impedance (Z) in<br />

LSMO thin film as functi<strong>on</strong> of Temperature (T) and magnetic field in resp<strong>on</strong>se to radio<br />

frequency (f=0.1-5MHz) ac current flowing directly through the sample. DC resistivity<br />

and Z (T) shows transiti<strong>on</strong> around 365K which is corresp<strong>on</strong>d to Tc of LSMO thin film.<br />

In Z (T) peaks around Tc decreases in magnitude with applied field (1KOe), which<br />

is not affected much in DC resistivity. Magnetoimpedance ΔZ/Z= -30% is observed<br />

in MHz frequency range. It is suggested that observed magnetoimpedance results<br />

from suppressi<strong>on</strong> of the high frequency transverse permeability by an external field.<br />

Our study suggests that magnetoimpedance in manganite thin films might find new<br />

applicati<strong>on</strong> in radio frequency regime.<br />

References: (1). Gang Zou , Xian You, Pingsheng He, Materials Letters 62 (2008) 1785-1788.<br />

Differential c<strong>on</strong>ductance measurements in Ni nanoscale c<strong>on</strong>tact<br />

fabricated by electromigrati<strong>on</strong><br />

Junya Sakai 1 *, Koichiro Ienaga 1 , Yuji Inagaki 1 , Hiroyuki Tsujii 2 , Ryuya Nomura 3 ,<br />

Seiji N<strong>on</strong>oguchi 3 , Takashi Kimura 4 and Tatsuya Kawae 5<br />

1 Department of Applied Quantum Physics, kyushu university, Japan<br />

2 Faculty of Educati<strong>on</strong>, Kanazawa university, Japan<br />

3 INAMORI Fr<strong>on</strong>tier Research Center, Kyushu University, Japan<br />

4 INAMORI Fr<strong>on</strong>tier Research Center, Kyushu University, Japan<br />

5 Department of Applied Quantum Physics, Kyushu University, Japan<br />

A zero-bias anomaly in differential c<strong>on</strong>ductance has been reported in atomic-size<br />

c<strong>on</strong>tacts fabricated from the ferromagnets, Fe, Co and Ni, which is c<strong>on</strong>sidered to come<br />

from the K<strong>on</strong>do effect [1]. This is interesting because the K<strong>on</strong>do effect usually requires<br />

two species of atom and is thought to be incompatible with ferromagnetic interacti<strong>on</strong>.<br />

In order to clarify the origin of K<strong>on</strong>do effect in atomic ferromagnetic c<strong>on</strong>tact, we have<br />

studied the size dependence of the zero-bais anomaly in Ni nanoscale c<strong>on</strong>tacts by<br />

mechanical c<strong>on</strong>trollable break juncti<strong>on</strong> technique and observe the anomaly in a large<br />

size where the ferromagnetism appears[2]. In this presentati<strong>on</strong>, we study differential<br />

c<strong>on</strong>ductance in Ni nanoscale c<strong>on</strong>tacts with decreasing the size by electromigrati<strong>on</strong>.<br />

In large size c<strong>on</strong>tacts, zero-bias anomaly is not observed. When the c<strong>on</strong>ductance is<br />

smaller than 200G0 (G0=2e2/h), the anomaly is clearly observed.<br />

[1]M. Reyes-Calvo et al., Nature 458, 1150 (2009) [2]K. Ienaga et al., to be published.<br />

July 8 - 13, 2012 Busan, Korea 115<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QL12<br />

Magnetoresistance measurements in Pd atomic-scale c<strong>on</strong>tact at 4.2K<br />

Koichiro Ienaga 1 *, Naoya Nakashima 1 , Yuji Inagaki 1 , Hiroyuki Tsujii 2 and Tatsuya<br />

Kawae 1<br />

1 Department of Applied Quantum Physics, Kyushu University, Japan<br />

2 Faculty of Educati<strong>on</strong>, Kanazawa University, Japan<br />

QL13<br />

QL14<br />

WITHDRAWN<br />

Differential c<strong>on</strong>ductance measurements in Cu-Mn atomic-scale<br />

c<strong>on</strong>tacts<br />

Koichiro Ienaga 1 , Naoya Nakashima 1 , Yuji Inagaki 1 , Hiroyuki Tsujii 2 and Tatsuya<br />

Kawae 1 *<br />

1 Dapartment of Applied Quantum Physics, Kyushu University, Japan<br />

2 Faculty of Educati<strong>on</strong>, Kanazawa University, Japan<br />

WITHDRAWN<br />

Tuning the magnetic interacti<strong>on</strong> in carb<strong>on</strong> nanotube/NiO<br />

nanocomposite system<br />

S Chattopadhyay, S Giri and S Majumdar*<br />

Department of Solid State Physics, Indian Associati<strong>on</strong> for the Cultivati<strong>on</strong> of Science,<br />

India<br />

We have prepared a series of nanocomposite materials with multi-walled CNTs and<br />

NiO nanoparticles by varying the c<strong>on</strong>centrati<strong>on</strong> of nickel nitrate soluti<strong>on</strong>. Transmissi<strong>on</strong><br />

electr<strong>on</strong> microscopy shows that the average size of the nanoparticles is about 10 nm<br />

and they are predominantly embedded either <strong>on</strong> the inner or the outer wall of the<br />

multi-walled CNTs forming a quasi <strong>on</strong>e dimensi<strong>on</strong>al arrangement. It is also observed<br />

that the particles are well separated and density of the product NiO nanoparticles<br />

increases systematically with increasing c<strong>on</strong>centrati<strong>on</strong> of the nickel nitrate<br />

soluti<strong>on</strong>. DC magnetizati<strong>on</strong> measurement shows the presence of thermomagnetic<br />

irreversibility in the temperature variati<strong>on</strong> of the magnetizati<strong>on</strong> data. In c<strong>on</strong>trary to the<br />

antiferromagnetic bulk NiO, field dependence of magnetizati<strong>on</strong> reveals the presence<br />

of str<strong>on</strong>g ferromagnetic interacti<strong>on</strong> al<strong>on</strong>g with prominent exchange bias effect. These<br />

materials also show magnetizati<strong>on</strong> relaxati<strong>on</strong> which is an indicati<strong>on</strong> of n<strong>on</strong>-ergodicity<br />

in the magnetic ground state. This system provides a rare opportunity to externally<br />

fabricate the degree of isolati<strong>on</strong> am<strong>on</strong>g the particles and to tune the interparticle<br />

magnetic interacti<strong>on</strong>s as well for performing a systematic investigati<strong>on</strong> <strong>on</strong> the evoluti<strong>on</strong><br />

of the magnetic ground state with the variati<strong>on</strong> of the interacti<strong>on</strong> strength.<br />

116 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QL15<br />

Bias-voltage dependence of magnetotransport properties in codeposited<br />

Co-C granular thin films<br />

Jun-goo Kang 1 *, Masaki Mizuguchi 1 , Shiro Entani 2 , Seiji Sakai 2 and Koki Takanashi 1<br />

1 Institute for Materials Research, Tohoku University, Japan<br />

2 Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

Granular systems c<strong>on</strong>sisting of ferromagnetic nanoparticles dispersed in a n<strong>on</strong>magnetic<br />

matrix exhibit giant magnetoresistance (MR) due to spin dependent transport. Carb<strong>on</strong>-based<br />

nanocomposite thin films have large applicati<strong>on</strong> potential as spin transport materials because<br />

l<strong>on</strong>g spin relaxati<strong>on</strong> time is expected due to its weak spin-orbit interacti<strong>on</strong> [1]. We have found<br />

that co-deposited Co-C films exhibit a large negative magnetoresistance (MR: 27.6% at 2 K)<br />

[2]. It is expected that the bias voltage dependence of MR includes significant informati<strong>on</strong> <strong>on</strong><br />

the mechanism of the MR. In this study, the bias-voltage dependence of magneto-transport<br />

properties for Co-C granular thin films has been investigated. Co-C granular thin films were<br />

fabricated by a co-sputtering technique. The current (I)- bias-voltage (V) characteristics and the<br />

MR behavior of the Co-C films were measured at temperatures of 2-30 K in a two-terminal<br />

geometry with the electrical current and magnetic fields (up to 70 kOe) in the in-plane directi<strong>on</strong>.<br />

It was found that the magnitude of the MR ratio changed remarkably with bias voltage. A clear<br />

increase in the MR ratio with bias voltage was observed, and it reached 66.6 % for V= 25 V.<br />

[1] S. Sakai, K. Yakushiji, S. Mitani, K. Takanashi, H. Naramoto, P. V. Avramov, K. Narumi, V.<br />

Lavrentiev, and Y. Maeda, Appl. Phys. Lett. 89, 113118 (2006). [2] R. Tang, M. Mizuguchi, H. Wang,<br />

R. Yu, and K. Takanashi, IEEE Trans. Magn. 46, 2144 (2010).<br />

QL16<br />

Switchable voltage c<strong>on</strong>trol of the magnetic anisotropy in<br />

heterostructured nanocomposites of CoFe/NiFe/PZT<br />

Thang D. Pham 1 *, H<strong>on</strong>g T. M. Nguyen 2 , D<strong>on</strong>g H. Kim 3 , Tiep H. Nguyen 2 and Cu<strong>on</strong>g V.<br />

Le 2<br />

1 Faculty of Engineering Physics and Nanotechnology, University of Engineering and<br />

Technology, Vietnam Nati<strong>on</strong>al University, Hanoi, Viet Nam<br />

2 Laboratory for Micro and Nanotechnology, University of Engineering and<br />

Technology, Vietnam Nati<strong>on</strong>al University, Hanoi, Viet Nam<br />

3 Department of Physics, Chungbuk Nati<strong>on</strong>al University, South Korea, Korea<br />

Heterostructures of nanostructured ferromagnetic (FM) and ferroelectric (FE) layers are<br />

of increasing interest due to the coupling between the magnetic moment and electric<br />

polarizati<strong>on</strong>s. In particular electric voltage, rather than the c<strong>on</strong>venti<strong>on</strong>al magnetic field, can<br />

be directly used to c<strong>on</strong>trol the magnetic properties of the magnetic layers. This magneticelectric<br />

coupling may open promising applicati<strong>on</strong>s towards novel spin electr<strong>on</strong>ic devices<br />

with low power c<strong>on</strong>sumpti<strong>on</strong> and high-speed data access. In this article, we study <strong>on</strong> the<br />

crystallographic structure and magnetic properties of CoFe/NiFe/PZT heterostructures. In<br />

these nanocomposites, the magnetic behaviors, such as magnetizati<strong>on</strong> significantly changes<br />

in the presence of an applied voltage. The change also depends <strong>on</strong> the FM layer thickness,<br />

the magnetic field directi<strong>on</strong> and it can reaches up to more than 100%. Furthermore we<br />

observed the switching in magnetizati<strong>on</strong> at suitable applied voltage. Besides, we present<br />

a phenomenological approach to investigate stress-induced magnetic anisotropy, which<br />

originated from magnetoelectric coupling between two FM and FE phases.<br />

QL17<br />

Origin of the ferromagnetism in scandium-doped ZnO thin films<br />

Mohammed Benali Kanoun*, Souraya Goumri-said, Udo Schwingenschlogl and<br />

Aurelien Manch<strong>on</strong><br />

1 King Abdullah University of Science and Technology(KAUST), Saudi Arabia<br />

In recent years, there have been more startling discoveries in diluted magnetic semic<strong>on</strong>ductors [1]<br />

achieving possible room-temperature ferromagnetism in undoped (ZnO [2]) and n<strong>on</strong>-transiti<strong>on</strong> metaldoped<br />

(ZnO:C [3]) systems. ZnO--based materials serve as model systems for the dilute magnetic<br />

oxides and are am<strong>on</strong>g the most intensely studied systems so far [4]. Interestingly, Venkatesan et al [5]<br />

have shown that room temperature ferromagnetism is observed in Sc-doped ZnO films. We note that<br />

in the bulk phase Sc has different crystal structures and n<strong>on</strong>magnetic properties. How different are their<br />

magnetic properties when doped in ZnO thin films? Why do experimental results differ so much? To<br />

answer these questi<strong>on</strong>s, we have carried out comprehensive first-principles theoretical investigati<strong>on</strong>s<br />

of energetics, electr<strong>on</strong>ic structure, and magnetic properties of Sc-doped ZnO (11-20) thin films. In this<br />

work, the ZnO thin film was modeled by a (1×2) seven-layer slab supercell having a wurtzite structure<br />

al<strong>on</strong>g the [11-20] surface orientati<strong>on</strong>. Each slab was separated from the other by a vacuum regi<strong>on</strong> of 10<br />

A al<strong>on</strong>g the [11-20] directi<strong>on</strong>. Even though Sc is not magnetic in its natural phase, we found that it is<br />

likely to order ferromagnetically in ZnO thin film, in agreement with experiment [5].<br />

[1] T. Dietl et al., Science 287, 1019 (2000). [2] Q. Xu et al., Appl. Phys. Lett. 92, 082508 (2008).<br />

[3] C. Liu et al., J. Mater. Sci. 16, 555 (2005). [4] Q. Ma, D. B. Buchholz, and R. P. H. Chang, Phys.<br />

Rev. B 78, 214429 (2008). [5] M. Venkatesan, C. B. Fitzgerald, J. G. Lunney, and J. M. D. Coey,<br />

Phys. Rev. Lett. 93, 177206 (2004).


QL18<br />

Magnetic c<strong>on</strong>trol of the hydrogen storage of hydrogen-injected ZnCoO<br />

Bum-su Kim 1 , Seunghun Lee1 1 J<strong>on</strong>g Mo<strong>on</strong> Shin 2 , Y<strong>on</strong>g-chan Cho 1 , Y<strong>on</strong>g Nam Choi 3 ,<br />

Hee-ju Lee 3 , Chae Ry<strong>on</strong>g Cho 2 , Hideomi Koinuma 1 and Se-young Je<strong>on</strong>g 1 *<br />

1 Cogno-Mechatr<strong>on</strong>ics Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

2 Nano fusi<strong>on</strong> technology, Pusan Nati<strong>on</strong>al University, Korea<br />

3 Korea Atomic Energy Research Institute, Korea<br />

Many researchers have tried to apply ZnO for hydrogen storage through additi<strong>on</strong>al doping and nanostructure<br />

which increase hydrogen capability[1]. It has been regarded for Zn-O b<strong>on</strong>d center and oxygen vacancy<br />

as practicable positi<strong>on</strong> for hydrogen storage. Co-Co dimer in ZnCoO has been suggested as appropriate<br />

positi<strong>on</strong> for its reversibility, and hydrogen placed in Co-Co dimer mediates ferromagnetic spin ordering by<br />

Co-H-Co complex[2,3]. In our recent research, we have reported the correlati<strong>on</strong> between hydrogen c<strong>on</strong>tent<br />

and ferromagnetism in Co doped ZnO (ZnCoO) and suggested that ZnCoO can be exploited for hydrogen<br />

storage and the tools for the measurement of hydrogen[4]. In this study, ZnCoO powder was fabricated by<br />

sol-gel method and annealing process was performed at 300 °C and subsequently 800 °C for removing<br />

organic compound. Pt was coated <strong>on</strong> ZnCoO powder as hydrogen catalyst. The hydrogen absorpti<strong>on</strong> and<br />

change in structure are characterized by the press compositi<strong>on</strong> and temperature (PCT) system and neutr<strong>on</strong><br />

diffracti<strong>on</strong>, in-situ. We investigate the correlati<strong>on</strong> between hydrogen c<strong>on</strong>tents and magnetism in ZnCoO and<br />

discuss its applicability for hydrogen storage. We also show the hydrogen c<strong>on</strong>tents in ZnCoO depending <strong>on</strong><br />

the Pt layer and the spillover effect between Pt layer and ZnCoO nanocrystal.<br />

[1] Q. Wan et al., Appl. Phys. Lett. 84, 124 (2004). [2] S. Lee et al., Appl. Phys. Lett. 94, 212507<br />

(2009). [3] Y. C. Cho et al., Appl. Phys. Lett. 95, 172514 (2009). [4] S. Lee et al., J. Appl. Phys. (in<br />

press, 2012).<br />

QL19<br />

Ferromagnetism in Co-doped TiO2 films probed by low-energy mu<strong>on</strong><br />

spin rotati<strong>on</strong><br />

Hassan Saadaoui 1 *, Jiabao Yi 2 , Zaher Salman 1 , Thomas Prokscha 1 and Elvezio<br />

Morenz<strong>on</strong>i 1<br />

1<br />

Laboratory for Mu<strong>on</strong> Spin Spectroscopy, Paul Scherrer Institut, 5232 Villigen PSI,<br />

Switzerland<br />

2<br />

School of Materials Science and Engineering, University of New South Wales,<br />

Kensingt<strong>on</strong>, NSW, 2052, Australia<br />

Ferromagnetic semic<strong>on</strong>ductors have been widely studied recently for potential<br />

applicati<strong>on</strong>s in spintr<strong>on</strong>ics. In this experiment, we probe the magnetism in Co-doped<br />

TiO 2 ferromagnetic semic<strong>on</strong>ducting films using Low-energy mu<strong>on</strong> spin rotati<strong>on</strong> (LEμSR).<br />

This technique is very powerful to probe the magnetic properties of thin films<br />

and interfaces <strong>on</strong> a nanometer length scale. We investigated Co-doped (5%) TiO 2-δ<br />

films grown in different oxygen pressures. We find the internal magnetism in these<br />

films to be str<strong>on</strong>gly dependent <strong>on</strong> the oxygen pressure during growth. The oxygen<br />

vacancies, modified by pressure, act as electr<strong>on</strong> d<strong>on</strong>ors and alter the electr<strong>on</strong> density.<br />

As the pressure increases, the magnetic volume fracti<strong>on</strong> is str<strong>on</strong>gly reduced. In this<br />

work, we present the temperature, magnetic field and depth dependence of the internal<br />

magnetism, and discuss its origin.<br />

QL20<br />

Structural and magnetic changes induced by high energy ball milling<br />

of CdFe 2O 4 oxide<br />

Justice Msomi and Ta Nhlapo<br />

School of Chemistry and Physics, University of KwaZulu-Natal, South Africa<br />

Bulk CdFe 2O 4 ferrite nanoparticles have been synthesized by solid state reacti<strong>on</strong>.<br />

The fine powders of CdFe 2O 4 oxide were produced by high energy ball milling. The<br />

structural and magnetic changes induced by high energy ball milling are investigated.<br />

The oxides have been characterised by XRD, Mossbauer spectroscopy and VSM<br />

measurements. A general decrease in lattice c<strong>on</strong>stant with increasing milling time is<br />

observed. The Mossbauer spectra indicate paramagnetic spin state in all the samples.<br />

Magnetizati<strong>on</strong> increases with reducti<strong>on</strong> in particle size. This can be explained by the<br />

redistributi<strong>on</strong> of Cd i<strong>on</strong>s in both tetrahedral (A) and octahedral (B) sites. The coercive<br />

field of the milled CdFe 2O 4 oxide are highly sensitive to temperature compared to that<br />

of the bulk compound. An increase in coercive field for 50 hours milled oxide from<br />

about 9 Oe at 300 K to 520 Oe at 10 K has been observed. A smaller increase from<br />

9 Oe at 300 K to 200 Oe at 10 K occurs in the coercive field of the bulk oxide. The<br />

variati<strong>on</strong> of magnetizati<strong>on</strong> as a functi<strong>on</strong> of measuring temperature is also presented.<br />

An anomalous variati<strong>on</strong> of field cooled magnetizati<strong>on</strong> as a functi<strong>on</strong> of temperature has<br />

been observed.<br />

QL21<br />

QM01<br />

QM02<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Room temperature ferromagnetism in Zn 1-xNi xS diluted magnetic<br />

semic<strong>on</strong>ducting nanocrystalline thin films<br />

M A El-hagary 1 *, Soltan Soltan 2 , M Emam-ismail 1 and S Althoyaib 1<br />

1 Physics Department, Qassim University, Saudi Arabia<br />

2 Physics Department, Helwan University, Helwan, Cairo, Egypt, Egypt<br />

We have investigated the magnetic properties of Ni doped Zn 1-xNi xS diluted magnetic<br />

semic<strong>on</strong>ducting nanocrystalline thin films for different doping c<strong>on</strong>centrati<strong>on</strong>s (0.005<br />

≤ x ≤ 0.2) synthesized by electr<strong>on</strong> beam evaporati<strong>on</strong> technique. X-ray diffracti<strong>on</strong><br />

patterns c<strong>on</strong>firm the existence of single phase nature in all the Ni doped Zn 1-xNi xS<br />

samples with cubic zinc blend type structure. Evidence of nanocrystalline nature of<br />

the films was observed from the investigati<strong>on</strong> of surface morphology using scanning<br />

electr<strong>on</strong> microscopy and atomic force microscopy. Magnetic domains were observed<br />

by using magnetic force microscopy at room temperature indicating the existence<br />

of ferromagnetism over the film surface. The temperature and field dependent<br />

magnetizati<strong>on</strong> measurements by using superc<strong>on</strong>ducting quantum interface device<br />

showed ferromagnetic behavior between room and low temperatures (5 K) with a Tc<br />

at or above room temperature for the nanostructure samples with 0.1 ≤ x ≤ 0.2. The<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> for Zn 1-xNi xS system is found to increase with the dopant<br />

c<strong>on</strong>centrati<strong>on</strong> (x). The exchange interacti<strong>on</strong> between local spin polarized electr<strong>on</strong>s (Ni<br />

i<strong>on</strong>s) and c<strong>on</strong>ductive electr<strong>on</strong>s according to RKKY mechanism, rather than from the<br />

Ni oxide impurities, is proposed to be the possible mechanism for ferromagnetism.<br />

Extraordinary hall measurements of Co/Ni multilayers<br />

Chih-yung Chen 1 , James C Eckert 1 , Natalia Fear 1 , Sheena K. K. Patel 1 , Richard<br />

Sayanagi 1 , Patricia D Sparks 1 , E Shipt<strong>on</strong> 2 and Eric E Fullert<strong>on</strong> 2<br />

1 Physics, Harvey Mudd College, USA<br />

2 University of California, San Diego, USA<br />

Interest in Co/Ni multilayers is driven by their unusual magnetic properties. They<br />

exhibit perpendicular magnetic anisotropy, relatively low magnetic damping and<br />

unusual magneto-transport characteristics making them well suited for spintr<strong>on</strong>ic<br />

devices. To understand their magnetic and magneto-transport properties we measured<br />

the temperature dependence of the Hall effect for a series of sputtered Ni/Co films:<br />

SiO2/Ta(40A)/Pd(40A)/[Co(2A)/Ni(Y)]x10/Ta(40A)), with Ni thicknesses from Y=2-<br />

14 A. Because the signs, and the temperature dependence, of the extraordinary Hall<br />

effects (EHE) differ for Co and Ni, the behavior for the multilayers is complex. At<br />

room temperature the sign of the EHE changes as the Ni thickness increases from 4 to<br />

5A. For Y=4A, the sign of the EHE is temperature dependent, going to zero near 220K<br />

and changing sign for lower temperatures. The magnitude of the EHE increases with<br />

increasing temperature for Y6A. We used the EHE to measure the magnetizati<strong>on</strong> properties finding a decrease<br />

in the coercive field for increasing Y. For Y


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QM03<br />

Cross over from anisotropic magnetoresistance to magn<strong>on</strong><br />

magnetoresistance in PLD grown permalloy nanowires<br />

Vineeth Mohanan Parakkat and Anil P. S Kumar<br />

Physics, Indian Institute of Science, India<br />

We are able to observe and distinguish Anisotropic-Magnetoresistance(AMR) and<br />

Magn<strong>on</strong> Magnetoresistance(MMR) [1] c<strong>on</strong>tributi<strong>on</strong>s clearly in Permalloy nanowires by<br />

varying their width thereby tuning their shape anisotropy. Nanowires of thickness 20nm<br />

and varying widths down to 160nm were prepared by e-beam lithography and Pulsed<br />

Laser Depositi<strong>on</strong>. A linear n<strong>on</strong>-saturating l<strong>on</strong>gitudinal MR observed in high field regime<br />

for NiFe nanowires could never be explained using AMR but <strong>on</strong>ly MMR can account<br />

for it. MMR follows as ρ=α(M/Ms)B, where M is magnetizati<strong>on</strong> al<strong>on</strong>g the easy axis,<br />

Ms saturati<strong>on</strong> magnetizati<strong>on</strong>, B magnetic field applied al<strong>on</strong>g the easy axis, α=(dρ/dB) is<br />

the slope of ρ(B) at magnetic saturati<strong>on</strong>. A cross over in magnetoresistance at low field<br />

from AMR-dominant to MMR-dominant <strong>on</strong>e was observed as wire width reduces since<br />

the AMR value is getting reduced from 1.2% for 650nm wide wire to 0.26% for 160nm,<br />

however the c<strong>on</strong>tributi<strong>on</strong>s from the electr<strong>on</strong>-magn<strong>on</strong> interacti<strong>on</strong>s still persist. At 280nm<br />

itself the AMR c<strong>on</strong>tributi<strong>on</strong> to the l<strong>on</strong>gitudinal MR has substantially reduced so that<br />

<strong>on</strong>ly magn<strong>on</strong> effect is visible. The MMR proves to be an excellent way of determining<br />

M/Ms, understanding the magnetizati<strong>on</strong> reversal mechanisms in nanostructures, domain<br />

wall dynamics and also fundamental problems like electr<strong>on</strong> magn<strong>on</strong> interacti<strong>on</strong>s.<br />

1. A. P. Mihai et al Phy. Rev. B 77, 060401 (2008).<br />

QM04<br />

Investigati<strong>on</strong> of magnetic anisotropy of ferromagnetic GaMnAs film<br />

by planar Hall effect<br />

Jaehyuk W<strong>on</strong> 1 , Jinsik Shin 1 , Yo<strong>on</strong>jung Gw<strong>on</strong> 1 , Hyehye<strong>on</strong> Bye<strong>on</strong> 1 , Sangyeop Lee 1 ,<br />

Sangho<strong>on</strong> Lee 1 *, X. Liu 2 and J. K. Furdyna 2<br />

1 Physics Department, Korea University, Korea<br />

2 Physics Department, University of Notre Dame, USA<br />

Magnetic anisotropy properties of the GaMnAs ferromagnetic film have been<br />

investigated by using planar Hall effect measurements. The field scan of the planar<br />

Hall resistance (PHR) showed a two-step switching behavior indicating a str<strong>on</strong>g cubic<br />

anisotropy al<strong>on</strong>g the directi<strong>on</strong>s. The difference in the behavior of the PHR for the<br />

two applied field directi<strong>on</strong>s between the [11 0] and the [110] was understood via wellknown<br />

uniaxial anisotropy al<strong>on</strong>g the [110] directi<strong>on</strong>. In additi<strong>on</strong> to such known effects,<br />

we also found the presence of asymmetry for the field directi<strong>on</strong>s between the [010] and<br />

the [100] directi<strong>on</strong>s. This new asymmetry phenomen<strong>on</strong> was explained by introducing an<br />

additi<strong>on</strong>al uniaxial anisotropy field H U2 al<strong>on</strong>g the [100] and the [100] directi<strong>on</strong>s, which<br />

coincides with the two directi<strong>on</strong>s of cubic anisotropy. The values of the anisotropy fields,<br />

cubic (H c), first uniaxial (H U1), and sec<strong>on</strong>d uniaxial (H U2), were obtained by analyzing<br />

the angle dependence of the PHR. Although the value of is small, its effect is clearly<br />

observed at high temperature above 25 K, where the transiti<strong>on</strong> of magnetizati<strong>on</strong> occurred<br />

before the field directi<strong>on</strong> is reversed during the magnetizati<strong>on</strong> reversal process.<br />

PACS number: 73.50.-h; 75.50.Pp; 75.30.Gw<br />

Keywords: Ferromagnetic semic<strong>on</strong>ductor, Magnetic anisotropy, Planar Hall effect<br />

QM05<br />

A crossover between magnetic vortex state and strip domains in<br />

electrodeposited nanogranular nickel films<br />

Alexander Sergeevich Samardak 1 *, Ekaterina Sukovatitsina 1 , Alexey Ognev 1 , Ludmila<br />

Chebotkevich 1 , S. M. Janjan 2 and Farzad Nasirpouri 2<br />

1<br />

School of Natural Sciences, Far Eastern Federal University, Institute of Automati<strong>on</strong><br />

and C<strong>on</strong>trol Processes FEBRAS, Russia<br />

2<br />

Department of Materials Engineering, Sahand University of Technology, Iran<br />

We have investigated the change of magnetizati<strong>on</strong> mode of nanogranular nickel films<br />

electrodeposited <strong>on</strong> silic<strong>on</strong>. The electrodepositi<strong>on</strong> of nickel at a distinct potential starts with the<br />

formati<strong>on</strong> of isolated nanogranules with size of 130÷190 nm which subsequently tend to coalesce<br />

forming a c<strong>on</strong>tinuous nanogranular film. Assuming nickel nanogranules as oblate spheroids<br />

and calculating the critical size for single domain state, we find that the nickel nanogranules are<br />

magnetized under vortex ground state. Micromagnetic simulati<strong>on</strong>s calculated for this isolated<br />

nanogranules and MFM images c<strong>on</strong>firm the magnetic vortex states for electrodeposited nickel<br />

nanogranules. Up<strong>on</strong> the nanogranules joining each other, coercivity increases due to the reducti<strong>on</strong><br />

of intergranular space and strengthening of magnetostatic interacti<strong>on</strong>. Further growth leads to the<br />

formati<strong>on</strong> of c<strong>on</strong>tinuous nanogranular film which is associated with decrease in coercivity and<br />

rotati<strong>on</strong> of the easy axis of magnetizati<strong>on</strong> to in- plane mode which is characterized by the domain<br />

wall displacement and strip-like multidomain pattern. The crossover between vortex ground state<br />

and multidomain magnetic pattern leads to the significant decrease in coercive force. C<strong>on</strong>tinuous<br />

nickel films electrodeposited <strong>on</strong> silic<strong>on</strong> have anisotropic magnetoresistance the value of which<br />

increases as the thickness and, appropriately, uniformity of film is increased.<br />

118 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QM06<br />

N<strong>on</strong>-linear susceptibility of nanogranular FeAg films at the verge of<br />

superferromagnetism<br />

D. Alba Venero 1 , L. Fernandez Barquin 1 *, S. N. Kaul 2 , J Al<strong>on</strong>so 3 and M. L. Fdezgubieda<br />

3<br />

1<br />

CITIMAC, Universidad de Cantabria, Santander 39005, Spain., Spain<br />

2<br />

School of Physics and Centre for Nanotechnology, University of Hyderabad,<br />

Hyderabad - 500046, India, India<br />

3<br />

Electricidad y Electr<strong>on</strong>ica, Universidad del Pais Vasco, Bilbao 48080, Spain, Spain<br />

A detailed magnetizati<strong>on</strong> study of Fe xAg 100-x films, comprising nanoparticles (3 nm) of Fe embedded in a Ag<br />

matrix, has recently revealed [1] a crossover from superspin glass state to superferromagnetic state at x?30. This<br />

changeover is presumably caused by an interplay between the direct exchange, dipolar and RKKY interacti<strong>on</strong>s<br />

operating between the particle magnetic moments. In order to gain further insight into the nature of inter-particle<br />

interacti<strong>on</strong>s and their role, first five harm<strong>on</strong>ics χ1- χ5 of the ac magnetic resp<strong>on</strong>se were measured at several<br />

frequencies and magnetic fields over the temperature range 5-300 K <strong>on</strong> DC-sputtered Fe xAg 100-x (x = 25, 35,<br />

below and above the percolati<strong>on</strong> threshold, respectively) 100 nm thick films. Susceptibilities χ1- χ5 measured<br />

in the absence of the superposed dc magnetic field, Hdc, exhibit features that are characteristic of a spin glass<br />

and a ferromagnet in x = 25, 35. The ferromagnetic fingerprints in the temperature variati<strong>on</strong>s of the linear and<br />

n<strong>on</strong>linear susceptibilities become all the more apparent when Hdc is applied. The data are analyzed <strong>on</strong> the same<br />

lines as those in the previous works <strong>on</strong> magnetically disordered CMR manganites [2, 3] and LiNiO insulators [4].<br />

[1] J. Al<strong>on</strong>so et al., Phys. Rev. B 82, 54406 (2010). [2] Y. Bitla and S. N. Kaul, EuroPhys. Lett. 96,<br />

37012 (2011). [3] L. Fernandez Barquin and R. Garcia Calder<strong>on</strong>, J. Phys.: C<strong>on</strong>f. Ser. 17, 87 (2005).<br />

[4] A. Bajpai and A. Banerjee, Phys. Rev. B 62, 8996 (2000).<br />

QM07<br />

Dynamics of Ni-Fe elliptical dot arrays based <strong>on</strong> CPW-FMR<br />

measurements<br />

Yasushi Endo, Naomi Skashita*, Yutaka Shimada and Masahiro Yamaguchi<br />

Graduate School of Engineering, Tohoku University, Japan<br />

The dynamics of nanomagnets have been studied intensively for high-frequency<br />

applicati<strong>on</strong>s in spintr<strong>on</strong>ic devices. The dynamics closely correlate with the damping<br />

c<strong>on</strong>stant α which determines the strength of damping torque in nanomagnets. α has<br />

been evaluated by exciting ferromagnetic res<strong>on</strong>ance (FMR) in nanomagnets using<br />

microwave cavities and coplanar waveguides (CPWs). Advantages of CPW-FMR<br />

measurements are a wide range of radio frequencies and external field intensity and<br />

micr<strong>on</strong>-scale samples. Herein to clarify the dynamics of nanomagnets, we employed<br />

FMR measurements with CPW to evaluate α in 50-nm-thick Ni-Fe elliptical dot<br />

arrays. Effective in-plane anisotropy field Hk,eff increases markedly as the dot size<br />

decreases, which may be attributed to enhanced magnetostatic energy. Eeffective<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> 4πMs,eff decreases slightly as the dot size decreases because<br />

the demagnetizati<strong>on</strong> field coefficient changes as the dot size decreases. Additi<strong>on</strong>ally, α<br />

increases m<strong>on</strong>ot<strong>on</strong>ically from 0.01 to 0.02 as the dot size decreases in a 500 Oe external<br />

magnetic field applied in the l<strong>on</strong>gitudinal axial directi<strong>on</strong> of the dots. Their values are<br />

higher than that of the Ni-Fe film (α= 0.009) likely because the inhomogeneity of the<br />

demagnetizati<strong>on</strong> field distributi<strong>on</strong> near dot edges. Therefore, these results propose that<br />

CPW-FMR measurements can evaluate the dynamics of nanomagnets in detail.<br />

QM08<br />

Structure and magnetic properties of SiO 2(Co) granular film <strong>on</strong> GaAs substrate.<br />

Victor Ukleev 1 *, Natalya Grigoryeva 2 , Ekaterina Dyadkina 1 , Alexei Vorobiev 3 , Dieter Lott 4 ,<br />

Le<strong>on</strong>id Lutsev 5 , Alexandr Stognij 6 , Dirk Menzel 7 , Nicolay Novitskiy 6 and Sergei Grigoriev 1<br />

1 Petersburg Nuclear Physics Institute, Russia<br />

2 Saint-Petersburg State University, Russia<br />

3 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, France<br />

4 Helmholtz-Zentrum Geesthacht, Germany<br />

5 Ioffe Physical-Technical Institute, Russia<br />

6 Scientific and Practical Materials Research Centre of NAS of Belarus, Belarus<br />

7 Institut fur Physik der K<strong>on</strong>densierten Materie, TU Braunschweig, Germany<br />

The effect of giant injecti<strong>on</strong> magnetoresistance (GIMR) was recently observed in a granular SiO 2/<br />

(54 - 75 at.% Co) film <strong>on</strong> a semic<strong>on</strong>ductor GaAs substrate in a temperature range near T = 300 K. The<br />

magnetoresistance reaches the value of 10000% in the magnetic field of 1.9 T and at the voltage of 90<br />

V [1]. The grazing-incidence small-angle X-ray scattering (GISAXS) data indicated the layer of lower<br />

c<strong>on</strong>centrati<strong>on</strong> of cobalt particles at the granular film/semic<strong>on</strong>ducter interface if compared to the SiO 2(Co)<br />

granular film itself. The thickness of this interface layer is about 70 A [2]. The polarized neutr<strong>on</strong> reflectometry<br />

c<strong>on</strong>firms the existence of the additi<strong>on</strong>al layer <strong>on</strong> the granular film/substrate interface. The temperature<br />

dependence of the magnetizati<strong>on</strong> M(T) shows the presence of two types of magnetic nanoparticles with<br />

different blocking temperatures and magnetizati<strong>on</strong> dynamics. The hysteresis curve of the magnetizati<strong>on</strong><br />

dem<strong>on</strong>strates two-loop structure in regi<strong>on</strong> of the fields 0 - 80 mT and 80 - 200 mT. Data obtained by<br />

polarized neutr<strong>on</strong> reflectometry, GISAXS and SQUID measurements are well correlated with each other<br />

and give the possibility to develop the GIMR effect theory paying attenti<strong>on</strong> to the interface features.<br />

[1] L.V. Lutsev, A.I. Stognij, and N.N. Novitskii, Phys. Rev. B, 184423 (2009). [2] N. Grigor'eva, A. Vorob'ev, V.<br />

Ukleev, E. Dyad'kina, L. Lutsev, A. Stognij, N. Novitskii, and S. Grigor'ev, JETP Letters, 92:767 - 773, 2010.


QM09<br />

Magnetic properties and structure of electrodeposited nickel <strong>on</strong> thin<br />

niobium film<br />

Huei-ying Ho 1 *, Wei-yan Lin 1 , Shih-jia Chen 1 , H<strong>on</strong>g-wen Cheng 1 and Yung Liou 2<br />

1 Department of Science Educati<strong>on</strong>, Nati<strong>on</strong>al Taipei University of Educati<strong>on</strong>, Taiwan<br />

2 Institute of Physics, Academia Sinica, Taiwan<br />

Cyclic voltammetry, chr<strong>on</strong>opotentiometry, atomic force microscope, magneto-optical<br />

Kerr effect, and X-ray diffracti<strong>on</strong> were used to investigate the magnetic property and<br />

structure of thin Ni films electrodepositing <strong>on</strong>to a 100 nm Nb. C<strong>on</strong>stant-current method<br />

was used to grow the Ni films in this study. During the reducti<strong>on</strong> process of Ni, a small<br />

amount of β-Ni(OH) 2 is formed; it becomes intense when the applied potential is more<br />

cathodic. The average size of the Ni grains grows and the coercivity of the Ni film<br />

decreases during the steady-state depositing process. The preferred orientati<strong>on</strong>s of the<br />

electrodeposited Ni film are fcc-(111) and fcc-(200), the easy axis of the magnetizati<strong>on</strong><br />

of it is in the in-plane directi<strong>on</strong>, however. This may due to the formati<strong>on</strong> of the<br />

β-Ni(OH) 2. The effects of current density <strong>on</strong> the magnetism and structure were also<br />

studied. The high current density does not make any significant change in the magnetic<br />

property if the current density is higher than 5.2 mA/cm 2 . This may due to the intense<br />

hydrogen evoluti<strong>on</strong> reacti<strong>on</strong> during the high current density depositi<strong>on</strong>. These results<br />

could be the foundati<strong>on</strong> of further research in the hydrogen energy area.<br />

QM10<br />

Characterizati<strong>on</strong> of epitaxial EuS(111) thin films <strong>on</strong> BaF2(111) and<br />

SrF2(111) substrates grown by molecular beam epitaxy<br />

Shinya Senba 1 *, Naoki Matsumoto 2 , Mitsuhiro Jomura 2 , Hir<strong>on</strong>ori Asada 2 , Yasuhiro<br />

Fukuma 3 , Tsuyoshi Koyanagi 2 and Kengo Kishimoto 2<br />

1 Ube Nati<strong>on</strong>al College of Technology, Japan<br />

2 Graduate School of Science and Engineering, Yamaguchi University, Japan<br />

3 Faculty of Computer Science and Systems Engineering, Kyushu Institute of<br />

Technology, Japan<br />

A ferromagnetic insulating EuS thin film has received c<strong>on</strong>siderable attenti<strong>on</strong>s in fundamental studies of spin<br />

injecti<strong>on</strong> devices because of its very high spin filter efficiency[1]. It has been reported that EuS thin films<br />

<strong>on</strong> Si(100) and GaAs(100) substrates become insulating at a growth temperature(Ts) of 300°C and above,<br />

and the resistivity of that decreases with decreasing Ts due to the sulfur deficiency[2]. In this study, we have<br />

successfully grown EuS(111) epitaxial films <strong>on</strong> BaF2(111) and SrF2(111) substrates using molecular beam<br />

epitaxy at Ts=100~500°C. Pole figures of x-ray diffracti<strong>on</strong> indicate a high degree of in-plane orientati<strong>on</strong>, and<br />

all of the samples show very high resistivity. The arithmetic mean deviati<strong>on</strong> of the surface for 10 nm-thick<br />

EuS films <strong>on</strong> BaF2(111) and SrF2(111) substrates measured by AFM are 0.122 and 0.092 nm, respectively.<br />

The Curie temperature of EuS films increases up to ~16 K with increasing Ts. In order to achieve an antiparallel<br />

state between two ferromagnetic layers in spin injecti<strong>on</strong> devices, we try to manipulate the coercive<br />

force by Te doping. The obtained coercive force of Te-doped film (110 Oe) is large compared with that of<br />

undoped <strong>on</strong>e (20 Oe).Optical properties such as a magnetic circular dichroism are also presented.<br />

[1] P. LeClair et al., Appl. Phys. Lett. 80, 625 (2002). [2] I. J. Guilaran et al., Phys. Rev. B 68,<br />

144424 (2003).<br />

QM11<br />

The cati<strong>on</strong> distributi<strong>on</strong> and electrical hopping in Fe 3-xCo xO 4 (0


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QM15<br />

Parallel spin wave res<strong>on</strong>ance in exchange-biased NiFe/FeMn/NiFe<br />

trilayers<br />

Fernando Pelegrini 1 *, Valberto Pedruzi Nascimento 2 , Armando Bi<strong>on</strong>do 2 , Eds<strong>on</strong><br />

Caetano Passamani 2 and Elisa Baggio-saitovitch 3<br />

1 Instituto de Fisica, Universidade Federal de Goias, Brazil<br />

2 Departamento de Fisica, Universidade Federal do Espirito Santo, Brazil<br />

3 Centro Brasileiro de Pesquisas Fisicas, Brazil<br />

The Ferromagnetic Res<strong>on</strong>ance (FMR) technique was used to study the magnetic properties of asymmetrical<br />

NiFe 30nmFeMn 15nmNiFe 10nm trilayers magnetr<strong>on</strong> sputtered under working pressures of 2, 5 and 10 mTorr, in the<br />

presence of a 460 Oe magnetic field to set the unidirecti<strong>on</strong>al anisotropy. The FMR experiments were d<strong>on</strong>e at<br />

room temperature using a commercial spectrometer operating with microwave frequencies of 9.79 and 34.0<br />

GHz, swept static magnetic field and the usual detecti<strong>on</strong> techniques. At a microwave frequency of 34.0 GHz,<br />

the parallel FMR spectra reveal that spin wave and uniform res<strong>on</strong>ance modes are excited by the microwave<br />

field. The study of the in-plane angular dependences of the res<strong>on</strong>ance fields reveals for both modes the effect<br />

of the unidirecti<strong>on</strong>al anisotropy. The dependences of the absorpti<strong>on</strong> fields <strong>on</strong> cosθ, where θ is the field angle<br />

with respect to the anisotropy axis, give for the spin wave and uniform modes of the sample produced under<br />

the pressure of 2 mTorr the anisotropy fields of 66 and 37 Oe, respectively. The parallel FMR results and spin<br />

wave res<strong>on</strong>ance theory imply for this sample the exchange c<strong>on</strong>stant of 0.92 x 10-6 erg/cm. This result agrees<br />

with perpendicular FMR measurements at a microwave frequency of 9.79 GHz.<br />

[1] V. P. Nascimento, E. Baggio-Saitovitch, F. Pelegrini, L. C. Figueiredo, A. Bi<strong>on</strong>do and E. C.<br />

Passamani, J. Appl. Phys. 99 (2006) 08C108. [2] W. Stoeklein, S. S. Parkin and J. C. Scott, Phys.<br />

Rev. B 38 (1988) 6847. [3] M. Nisenoff and R. W. Terhune, J. Appl. Phys. 36 (1964) 733.<br />

QM16<br />

Studies <strong>on</strong> local structures and magnetism at buried Fe/ Fe3O4 interfaces using synchrotr<strong>on</strong>-radiati<strong>on</strong> Mössbauer spectroscopy<br />

Ko Mibu 1 *, Hideto Yanagihara 2 , Takaya Mitsui 3 , Ryo Masuda 3 , Shiori Hori 1 , Atsushi<br />

Murata 1 , Masaaki Tanaka 1 , Kazuya Suzuki 2 , Eiji Kita 2 and Makoto Seto 4<br />

1<br />

Graduate School of Engineering, Nagoya Institute of Technology, Japan<br />

2<br />

Institute of Applied Physics, University of Tsukuba, Japan<br />

3<br />

Japan Atomic Energy Agency, Japan<br />

4<br />

Research Reactor Institute, Kyoto University, Japan<br />

Str<strong>on</strong>g antiparallel magnetic coupling was found recently in Fe/ Fe 3O 4 bilayers [1],<br />

and attenti<strong>on</strong> has been paid as a new and noble-metal-free “synthetic antiferromagnet”<br />

for magnetic recording devices. In order to clarify the mechanism of this interfacial<br />

magnetic coupling, it is important to elucidate the local crystallographic structure<br />

and magnetism at the buried interface experimentally. Mössbauer spectroscopy is a<br />

useful method to obtain such informati<strong>on</strong> through absorpti<strong>on</strong> spectra of gamma-rays<br />

(or X-rays) by the c<strong>on</strong>stituent Fe nuclei. In this presentati<strong>on</strong>, we report the results<br />

we have obtained using recently developed synchrotr<strong>on</strong>-radiati<strong>on</strong>-based Mössbauer<br />

spectroscopy with a nuclear Bragg m<strong>on</strong>ochromator at BL11XU, SPring-8 [2]. The<br />

structures and magnetism at the buried Fe/ Fe 3O 4 interface are discussed <strong>on</strong> the basis of<br />

the obtained spectra.<br />

[1] H. Yanagihara et al., Appl. Phys. Express 1 (2008) 111303. [2] T. Mitsui et al., J. Synchrotr<strong>on</strong><br />

Radiati<strong>on</strong> 19 (2012), in press.<br />

QM17<br />

Dependence of in-plane magnetic anisotropy of Au/Co/Au<br />

heterostructures <strong>on</strong> thickness of Co-comp<strong>on</strong>ent layer: An FMR study<br />

Leszek Gladczuk, Pavlo Aleshkevych and Piotr Przysłupski<br />

Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL02-668<br />

Warsaw, Poland., Poland<br />

Recently, there was a lot of interest in magnetic tunnel juncti<strong>on</strong>s built from electrodes<br />

characterized by in-plane magnetic anisotropy. In the present study; ultrathin Mo/Au/<br />

Co/Au heterostructures where the cobalt layer is of the wedge shape (i.e. with thickness<br />

gradually changing al<strong>on</strong>g the sample) were grown <strong>on</strong> a sapphire substrate by molecular<br />

beam epitaxy. Room temperature ferromagnetic res<strong>on</strong>ance (FMR) measurements<br />

were used to evaluate the res<strong>on</strong>ance field as a functi<strong>on</strong> of (i) the in-plane and the outof-plane<br />

orientati<strong>on</strong> of external magnetic field and of (ii) the cobalt layer thickness.<br />

The experiments dem<strong>on</strong>strates an interesting effect of enhancement of the in-plane<br />

anisotropy for heterostructures with wedge-shaped Co layer. This finding provides a<br />

method to modify the magnetic anisotropy, which can be of a great importance for the<br />

applicati<strong>on</strong> in magnetic tunneling juncti<strong>on</strong>s. A comparis<strong>on</strong> of the obtained results with<br />

earlier data <strong>on</strong> Co anisotropy will be presented.<br />

120 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QM18<br />

Depth dependent chemical and magnetic informati<strong>on</strong> of CoFeB/<br />

MgO multilayered thin films studied by x-ray and polarized neutr<strong>on</strong><br />

reflectometry<br />

Ki Ye<strong>on</strong> Kim 1 *, Il Jae Shin 2 , Byoung Chul Min 2 , Hyeok Cheol Choi 3 , Chun Yeol<br />

You 3 , Je<strong>on</strong>g Soo Lee 1 , Surendra Singh 4 , M. R. Fitzsimm<strong>on</strong>s 4 and Sungkyun Park 5<br />

1<br />

Neutr<strong>on</strong> Science Divisi<strong>on</strong>, Korea Atomic Energy Research Institute, Korea<br />

2<br />

Center for Spintr<strong>on</strong>ics Research, Korea Institute of Science and Technology, Korea<br />

3<br />

Department of Physics, Inha University, Korea<br />

4<br />

Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

5<br />

Department of Physics, Pusan Nati<strong>on</strong>al Laboratory, Korea<br />

Magnetic Tunnel Juncti<strong>on</strong>s (MTJs), c<strong>on</strong>sisting of a crystalline MgO barrier sandwiched by amorphous CoFeB<br />

layers, have received much attenti<strong>on</strong> owing to novel magnetic and transport properties such as perpendicular<br />

magnetic anisotropy and large tunneling magneto-resistance at room temperature [1-2]. With a combined study<br />

of x-ray (XRR) and polarized neutr<strong>on</strong> reflectometry (PNR), depth-dependent chemical and magnetic profiles<br />

in Co 40Fe 40B 20/MgO multilayered thin films were investigated. The annealing was d<strong>on</strong>e at 400°C for half an<br />

hour in an applied field of 4 kOe after sample growth. In additi<strong>on</strong> to XRR and PNR, structure characterizati<strong>on</strong><br />

was also c<strong>on</strong>ducted using high-angle theta/2theta x-ray diffracti<strong>on</strong>, and high resoluti<strong>on</strong> tunneling electr<strong>on</strong><br />

microscopy (HR-XTEM); the magnetic property was studied using vibrating sample magnetometer. The<br />

bor<strong>on</strong> diffusi<strong>on</strong> and magnetic moment around both CoFeB/MgO interfaces will be discussed in detail.<br />

[1] S. Ikeda, K. Miura, H. Yamamoto, K. Mizunuma, H. D. Gan, M. Endo, S. Kanai, H. Hasegawa, J. Hayakawa,<br />

F. Matsukura, and H. Ohno, Nature Mater. 9, 721 (2010). [2] D. D. Djayaprawira, K. Tsunekawa, M. Nagai, H.<br />

Maehara, S. Yamagata, N. Watanabe, S. Yuasa, Y. Suzuki, and K. Ando, Appl. Phys. Lett. 86, 092502 (2005).<br />

QM19<br />

Depth-resolved rotati<strong>on</strong>al hysteresis of exchange-coupled Fe/Cr<br />

multilayers<br />

Tatyana Guryeva, Kai Schlage, Hans-christian Wille and Ralf Roehlsberger<br />

HASYLAB, Deutsches Elektr<strong>on</strong>en-Synchrotr<strong>on</strong> (DESY), Germany<br />

QM20<br />

WITHDRAWN<br />

Magnetizati<strong>on</strong> reversal behavior in exchange-coupled NiFe/FeMn/<br />

CoFe trilayers: vectorial MOKE & PNR study<br />

Ki Ye<strong>on</strong> Kim 1 *, Ji Wan Kim 2 , Hyeok Cheol Choi 3 , Anke Teichert 4 , Chun Yeol You 3 ,<br />

Sungkyun Park 5 , Sung Chul Shin 2 and Je<strong>on</strong>g Soo Lee 1<br />

1 Neutr<strong>on</strong> Science Divisi<strong>on</strong>, Korea Atomic Energy Research Institute, Korea<br />

2 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, Korea<br />

Advanced Institute of Science and Technology, Korea<br />

3 Department of Physics, Inha University, Korea<br />

4 Helmholtz Zentrum Berlin fur Materialien und Energie, Germany<br />

5 Department of Physics, Pusan Nati<strong>on</strong>al Laboratory, Korea<br />

With a combinati<strong>on</strong> of vector magneto-optic Kerr effect (MOKE) magnetometry and polarized neutr<strong>on</strong><br />

reflectometry(PNR), the detailed magnetizati<strong>on</strong> reversal mechanism of the exchange-biased Py(30-nm)/<br />

FeMn[t_AF=0-30nm]/CoFe(30-nm) trilayers was studied.[1] We found that Py/FeMn(15-nm) and FeMn/<br />

CoFe bilayers show completely different magnetizati<strong>on</strong> reversal modes, whereas they become very similar<br />

to each other in the corresp<strong>on</strong>ding Py/FeMn/CoFe trilayers. This is c<strong>on</strong>vincing evidence that the 15nm<br />

FeMn layer mediates the magnetizati<strong>on</strong> reversal behaviors of Py and CoFe layers through interlayer<br />

exchange bias coupling. Furthermore, magnetizati<strong>on</strong> reversal of Py and CoFe layers are decoupled for t_<br />

AF=30 nm, indicating that both Py and CoFe layers separated by an intermediate FeMn layer are exchangecoupled<br />

within 30 nm distance. This is in reas<strong>on</strong>able agreement with the theoretically predicted domain-wall<br />

width such as 28 nm for the polycrystalline FeMn/Co bilayers and 50 nm for the perfect Fe 50Mn 50 crystal.<br />

[1]Ki-Ye<strong>on</strong> Kim, Ji-Wan Kim, Hyeok-Cheol Choi, A. Teichert, Chun-Yeol You, Sungkyun Park, Sung-<br />

Chul Shin, and Je<strong>on</strong>g-Soo Lee, Phys. Rev. B. 84,144410 (2011).


QM21<br />

Uniaxial magnetic anisotropy of La 0.7Sr 0.3MnO 3 film grown <strong>on</strong> stepterrace<br />

surface SrTiO 3 (100) substrate<br />

Bye<strong>on</strong>g-ge<strong>on</strong> Kim, Sangho<strong>on</strong> Ki and Jo<strong>on</strong>ghoe Dho*<br />

Kyungpook Nati<strong>on</strong>al University, Korea<br />

In this work, we used the step-terrace surface STO (100) substrates to c<strong>on</strong>trol the spin<br />

directi<strong>on</strong> of the La 0.7Sr 0.3MnO 3 (LSMO) film in the atomic level. The shape magnetic<br />

anisotropy in the nano scale was induced by using step-terrace surface STO (100)<br />

substrates with small vicinal angle of 0.1 degree. Atomically flat STO substrate was<br />

prepared by annealing after etching by HCL (hydrochloric acid), and the surface<br />

morphology of the STO substrate with molecular step-and-terrace was observed by<br />

atomic force microscopy. Here, we simultaneously deposited two La 0.7Sr 0.3MnO 3 films<br />

<strong>on</strong> the processed and unprocessed STO substrates by using pulsed laser depositi<strong>on</strong>.<br />

The directi<strong>on</strong> dependence of magnetic hysteresis within the film plane was investigated<br />

by using SMOKE (Surface Magneto-Optical Kerr Effect) system. The magnetic<br />

hysteresis loops of the LSMO film <strong>on</strong> the unprocessed STO substrate showed weak<br />

directi<strong>on</strong> dependence within the plane, while those <strong>on</strong> the step-terrace surface STO did<br />

a significant uniaxial magnetic anisotropy al<strong>on</strong>g the l<strong>on</strong>gitudinal directi<strong>on</strong> of the stepterrace<br />

of the STO substrate.<br />

QM22<br />

The effect of compositi<strong>on</strong>al ratio <strong>on</strong> the magnetocaloric effect<br />

Ho-sup Kim 1 , Sang-soo Oh 1 , Kiran Shinde 1 , Seung-kyu Baik 1 , Kook-chae Chung 2 and<br />

Bhavesh Bharat Sinha 2<br />

1 Korea Electrotechnology Research Institute, Korea<br />

2 Korea Institute of Materials Science, Korea<br />

Film type Ni-Mn-Ga alloys were prepared using co-evaporati<strong>on</strong> method in order to<br />

investigate the effect of compositi<strong>on</strong>al ratio <strong>on</strong> magnetocaloric effect (MCE). In the<br />

depositi<strong>on</strong> process <strong>on</strong> the metal substrate, Ni was evaporated by an inducti<strong>on</strong> heating,<br />

and Mn and Ga were evaporated by a resistive heating. The depositi<strong>on</strong> rate of each<br />

element was measured by Quartz Crystal Microbalance and the rate was c<strong>on</strong>trolled<br />

up to 0.1 mm / hour to get a thick Ni-Mn-Ga film. Three crucibles of Ni, Mn, and Ga<br />

were arranged triangularly to form the compositi<strong>on</strong> gradient of Ni-Mn-Ga film <strong>on</strong> the<br />

surface of whole substrate. L<strong>on</strong>g tape samples with different compositi<strong>on</strong> of Ni, Mn,<br />

and Ga al<strong>on</strong>g the length were prepared. The magnetic property of prepared sample at<br />

around transiti<strong>on</strong> temperature was c<strong>on</strong>tinuously evaluated by a reel to reel Hall probe<br />

measurement system with a temperature c<strong>on</strong>troller. The Hall probe signal is related to<br />

the relative value of MCE so that the optimal compositi<strong>on</strong> ratio could be obtained by<br />

analyzing it. The secti<strong>on</strong> which exhibited the highest value in Hall probe measurement<br />

was cut and analyzed by XRD and followed by MCE measurement using PPMS<br />

equipment. Detailed experimental results will be reported in the presentati<strong>on</strong>.<br />

1. V. Recarte et al.,Appl. Phys. Lett., 95, 141908, 2009. 2. Yuepeng Zhang et al.,Smart Mater. Struct.,<br />

18 , 025019, 2009. 3. V A Chernenko et al.,J. Phys.: C<strong>on</strong>dens. Matter ,17,5215-5224, 2005.<br />

QM23<br />

Magnetocaloric effect in Ni doped Zn ferrite nanoparticles grown by<br />

the combusti<strong>on</strong> method<br />

Kyungd<strong>on</strong>g Lee, Rahul Chandrakant Kambale and Namjung Hur*<br />

Department of Physics, Inha university, Korea<br />

We studied the magnetocaloric effect (MCE) in two different compositi<strong>on</strong>s of Ni-<br />

Zn ferrite nanoparticles (Ni xZn 1-xFe 2O 4, x=0.2 and 0.3) which were prepared by<br />

the combusti<strong>on</strong> method. From the temperature and the magnetic field dependent<br />

magnetizati<strong>on</strong> curves, the magnetic entropy changes (ΔS) and the adiabatic temperature<br />

changes (ΔT) were evaluated. Magnetocaloric effect in these nanoparticles is compared<br />

to that in bulk system with the same compositi<strong>on</strong>s to study the effects of grain size.<br />

Although the values of ΔS and ΔT at 2 T magnetic fields in these nanoparticles are<br />

lower than the values in the bulk <strong>on</strong>e, wider effect transiti<strong>on</strong> windows were observed<br />

in nanoparticle systems. As the domain size of Ni-Zn ferrite nanoparticles affects the<br />

temperature and magnetic field dependence of magnetizati<strong>on</strong>, the maximum ΔS and ΔT<br />

are also influenced by the grain size around the magnetic transiti<strong>on</strong> temperature (TC).<br />

Therefore, the field dependence of ΔT at TC, which can be analyzed by the mean field<br />

approximati<strong>on</strong> denoted by the exp<strong>on</strong>ential p, was found to be different from the typical<br />

<strong>on</strong>e.<br />

QM24<br />

QM25<br />

QM26<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Interlayer interacti<strong>on</strong> In ReCoPO (La, Nd and Sm): 31P NMR Study<br />

M Majumder 1 , K Ghoshray 1 *, A Ghoshray 1 , A Pal 2 and V. P. S Awana 2<br />

1 ECMP Divisi<strong>on</strong>, Saha Institute of Nuclear Physics, Kolkata, India<br />

2 QPA Divisi<strong>on</strong>, Nati<strong>on</strong>al Physical Laboratory (CSIR) Dr. K.S. Krishnan Marg, New<br />

Delhi-110012, India<br />

31P NMR result is presented in Co based n<strong>on</strong>-superc<strong>on</strong>ducting members of pnictides<br />

family revealing the importance of the interlayer interacti<strong>on</strong>, a key factor that<br />

determines the ground state. In ReCoPO (Re = rare earth) series, La and Ce show<br />

<strong>on</strong>ly PM → FM transiti<strong>on</strong>, whereas Nd and Sm show successive PM → FM → AFM<br />

transiti<strong>on</strong> with varying degree of TC and TN. 31P NMR spectrum in polycrystalline<br />

La, Nd and SmCoPO respectively corresp<strong>on</strong>ds to a powder pattern for a spin 1/2<br />

nucleus with axially symmetric local magnetic field showing varying degree of shift<br />

parameters. In particular, Nd and Sm compound show large temperature dependent<br />

shift anisotropy with similar magnitude of Kiso and Kax. However, relaxati<strong>on</strong> rate (1/<br />

T1T) in Sm is atleast two orders of magnitude higher than that observed in other two<br />

compounds. Our earlier 31P and 139La NMR [1] measurements in LaCoPO (quasi 2D<br />

Fermi surface) reveal dominant 2D spin fluctuati<strong>on</strong> of 3d electr<strong>on</strong>s in PM state with<br />

n<strong>on</strong> negligible 3D part and in the FM state spin fluctuati<strong>on</strong> is 3D in nature. Whereas,<br />

in SmCoPO the present result is able to distinguish the FM in plane spin-correlati<strong>on</strong>s<br />

from the AFM type out of plane spin-correlati<strong>on</strong>s.<br />

1. M. Majumder, K. Ghoshray, A. Ghoshray, B. Bandyopadhyay, M. Ghosh , Phys. Rev. B 82, 054422<br />

(2010).<br />

Jahn-teller distorti<strong>on</strong> and enhancement of curie temperature of Mn 3xNi<br />

xO 4 films <strong>on</strong> MgO (001) by molecular beam epitaxy<br />

Der-sheng Lee 1 , K. M. Kuo 2 and Gung Chern 2 *<br />

1 Electrical Engineering Department, DA-YEH University , Chunghua, Taiwan<br />

2 Physics Department and SPIN Research Center, Nati<strong>on</strong>al Chung Cheng<br />

University,Chia-Yi, Taiwan<br />

We report <strong>on</strong> x-ray diffracti<strong>on</strong>, scanning electr<strong>on</strong> micrograph, and magnetizati<strong>on</strong><br />

measurements vs. external field and temperature of Mn 3-xNi xO 4 (x=0, 0.25, 0.5,<br />

0.75, 1) films grown <strong>on</strong> MgO (001) and (011) substrates by molecular beam<br />

epitaxy. Magnetizati<strong>on</strong> vs. temperature measurements reveal that Curie temperature<br />

increases from 43 K to 103 K as the Ni compositi<strong>on</strong> increasing. This increase of Tc<br />

is qualitatively understood as a result of the decrease of the exchange coupling of the<br />

cati<strong>on</strong>s between B site and B site (JBB). The Jahn-Teller distorti<strong>on</strong> also reduces as the<br />

Ni compositi<strong>on</strong> increasing and the cubic structure is estimated to be recovered as x<br />

approaches ~ 1.2. The cati<strong>on</strong> distributi<strong>on</strong> in the present films is different from the bulk<br />

and can be described as [Mn²+1-xMn³+2x/3Ni²+x/3]A[Ni²+2x/3Mn³+2-2x/3]BO 4.<br />

Anomalous switching of in-plane magnetic anisotropy of Fe and Co<br />

thin films grown <strong>on</strong> curved Pt(001) surface<br />

W<strong>on</strong>d<strong>on</strong>g Kim 1 *, Chany<strong>on</strong>g Hwang 1 and Z.-q. Qiu 2<br />

1 Korea Research Institute of Standards and Science, Korea<br />

2 Physics Department, University of California at Berkeley, USA<br />

We investigated the step-induced magnetic anisotropy of Fe and Co thin films grown<br />

<strong>on</strong> the curved Pt(001) surface using Surface Magneto-Optical Kerr Effect(SMOKE)<br />

and Scanning Tunneling Microscopy(STM). The c<strong>on</strong>tinuous variati<strong>on</strong> of step density<br />

of the curved Pt(001 surface are c<strong>on</strong>firmed by STM experiment. From SMOKE<br />

measurements <strong>on</strong> both of Fe and Co thin films, we observed the switching of the<br />

magnetic easy axis from the parallel-to-step directi<strong>on</strong> to the step-normal directi<strong>on</strong> with<br />

increase of the step-density. We attributed The origin of this anomalous transiti<strong>on</strong> to the<br />

abrupt change in the step structure at high-step density positi<strong>on</strong>, which was revealed by<br />

STM measurements.<br />

July 8 - 13, 2012 Busan, Korea 121<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QM27<br />

Magnetic-field and temperature-dependent relaxati<strong>on</strong> in ferrofluids<br />

characterized with a high-Tc SQUID-based nuclear magnetic<br />

res<strong>on</strong>ance spectrometer<br />

H<strong>on</strong>g-chang Yang 1 *, Chieh-wen Liu 2 , Shu-hsien Liao 3 , M.j. Chen 1 , K.l. Chen 1 , Hsinhsien<br />

Chen 3 , Herng-er Horng 3 , L.m. Wang 1 and S.y. Yang 3<br />

1 Department of physics, Nati<strong>on</strong>al Taiwan University, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al Taiwan University, Taiwan<br />

3 Institute of Electro-Optical Science and Technology, Nati<strong>on</strong>al Taiwan Normal<br />

University, Taiwan<br />

In this work the magnetic-field and temperature dependent spin-lattice relaxati<strong>on</strong><br />

rate, 1/T1, and spin-spin relaxati<strong>on</strong> rate, 1/T2, of ferrofluids are characterized using a<br />

high-Tc SQUID-based magnetometer as the detector. The ferrofluids are c<strong>on</strong>sisted of<br />

detrain-coated Fe 3O 4 dispersed in phosphate buffer saline soluti<strong>on</strong>. It was found that 1/<br />

T1 measured in a magnetic field of 56.8 mT is significantly higher than 1/T2 measured<br />

in a magnetic field of 102 μT. We attribute this to the magnetic-field gradients from<br />

magnetic nanoparticles that accelerate the T1-relaxati<strong>on</strong> more in a high strength of<br />

magnetic fields than they are in a low strength of magnetic fields. Furthermore, 1/T1<br />

and 1/T2 decrease when temperature increases. We attribute this to the improved fieldhomogeneity<br />

seen by prot<strong>on</strong>s’ spins under the influence of enhanced Brownian moti<strong>on</strong><br />

of magnetic nanoparticles at high temperatures than they are at low temperatures.<br />

Characterizing the relaxati<strong>on</strong> rates of ferrofluids in low c<strong>on</strong>centrati<strong>on</strong> regimes will be<br />

helpful for their future applicati<strong>on</strong>s such as the low field MR imaging.<br />

QM28<br />

Influence of metal precursor <strong>on</strong> synthesis and magnetic properties of<br />

nanocrystalline str<strong>on</strong>tium hexaferrite thin films<br />

S. M. Masoudpanah, S. A. Seyyed Ebrahimi* and M. Khodaei<br />

Center of Excellence for Magnetic Materials, University of Tehran, Iran<br />

The effects of starting metal salts <strong>on</strong> the structure and magnetic properties of str<strong>on</strong>tium<br />

hexaferrite thin films synthesized by sol gel process have been investigated. Fourier<br />

transform infrared and thermal analyses were c<strong>on</strong>ducted to determine the chelated<br />

species and thermal decompositi<strong>on</strong> of the gels, respectively. X-ray diffracti<strong>on</strong>,<br />

scanning electr<strong>on</strong> microscopy and vibrating sample magnetometery techniques were<br />

also applied to evaluate the microstructure, compositi<strong>on</strong>, crystallite size and magnetic<br />

properties of the thin films. The results showed the film prepared from nitrate precursor<br />

offered a single phase str<strong>on</strong>tium hexaferrite with nanocrystalline structure and higher<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> after calcinati<strong>on</strong>. However, the films obtained from hydroxide<br />

and chloride precursors had higher coercivity due to smaller crystallite size.<br />

QM29<br />

Planar Hall effects measurements of sensitive magnetizati<strong>on</strong> resp<strong>on</strong>se<br />

in epitaxial Fe thin films<br />

Anis Faridah Md Nor 1 *, Tatsuya Matsumoto 2 , Teppei Takashima 2 , Terumitsu Tanaka 2<br />

and Kimihide Matsuyama 2<br />

1 Physics Department, University of Malaya, Malaysia<br />

2 Department of Electr<strong>on</strong>ics, ISEE, University of Kyushu, Japan<br />

The Fe thin film is a promising candidate for future magnetic microwave devices, owing to<br />

the high ferromagnetic res<strong>on</strong>ance frequency with an order of 10 GHz [1-2]. A high sensitive<br />

magnetizati<strong>on</strong> resp<strong>on</strong>se is crucial for the low power device operati<strong>on</strong>. In the present study, we<br />

prepared Fe(100) thin films deposited <strong>on</strong> MgO(100) substrates using magnetr<strong>on</strong> sputtering<br />

system and investigate the magnetizati<strong>on</strong> process using the planar Hall effect (PHE).The<br />

PHE measurements were carried out with several Fe thicknesses and temperatures. In the<br />

PHE measurements, alternating external magnetic fields al<strong>on</strong>g vertical easy axis were applied<br />

with various amplitudes and the sense current was applied al<strong>on</strong>g the horiz<strong>on</strong>tal easy axis.<br />

With increase of alternating magnetic field, the PHE voltage increased due to the dispositi<strong>on</strong><br />

of Fe magnetizati<strong>on</strong> from easy axis. When the alternating magnetic field exceed a threshold<br />

value, the PHE voltage decreased rapidly. The threshold value depend <strong>on</strong> the thickness of Fe<br />

film and the PHE voltage decreased with decreasing temperature. These results suggest that<br />

the magnetizati<strong>on</strong> rotates exceeding the hard axis directi<strong>on</strong> and reversible susceptibility can<br />

be realized. The stochastic aspect of the magnetizati<strong>on</strong> process also appears at 10 K.<br />

[1] E. Schloeman et al., J. Appl. Phys., 63, 3140 (1988). [2] N. Cramer et al., J. Appl. Phys., 87,<br />

6911 (2000).<br />

122 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QN01<br />

Antiferromagnetic order and domains in Sr 3Ir 2O 7<br />

S. Boseggia 1 , R. Springell 1 , H. C. Walker 2 , A. T. Boothroyd 3 , D. Prabhakaran 3 , D.<br />

Wermeille 4 , L. Bouchenoire 4 , S. P. Collins 5 and D. F. Mcmorrow 1<br />

1 Physics and Astr<strong>on</strong>omy, L<strong>on</strong>d<strong>on</strong> Centre for Nanotechnology, UCL, United Kingdom<br />

2 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, France<br />

3 Clarend<strong>on</strong> Laboratory, University of Oxford, United Kingdom<br />

4 5XMaS, UK-CRG, European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, France<br />

5 Diam<strong>on</strong>d Light Source, Didcot, Oxfordshire, United Kingdom<br />

Res<strong>on</strong>ant scattering at the Ir L2, 3 edge has been used to determine that Sr 3Ir 2O 7 is a<br />

l<strong>on</strong>g-range ordered antiferromagnet below TN~230 K with an ordering wavevector,<br />

q = (½, ½, 0). The energy res<strong>on</strong>ance at the L3 edge was found to be a factor of ~30<br />

times larger than that at the L2. This remarkable effect has been seen in the single<br />

layer compound Sr 2IrO 4 and has been linked to the observati<strong>on</strong> of a Jeff= 1/2 spin-orbit<br />

insulator. Our result shows that despite the modified electr<strong>on</strong>ic structure of the bilayer<br />

compound, caused by the larger bandwidth, the effect of str<strong>on</strong>g spin-orbit coupling<br />

<strong>on</strong> the res<strong>on</strong>ant magnetic scattering persists. Using the programme SARAh, we have<br />

determined that the magnetic order c<strong>on</strong>sists of two domains with propagati<strong>on</strong> vectors<br />

k1 = (½, ½, 0) and k2 = (½,-½, 0), respectively. A raster measurement of a focussed<br />

x-ray beam across the surface of the sample yielded images of domains of the order<br />

of 100 μm size, with odd and even l comp<strong>on</strong>ents, respectively. Fully relativistic,<br />

m<strong>on</strong>oelectr<strong>on</strong>ic calculati<strong>on</strong>s (FDMNES) have been employed to calculate the relative<br />

intensities of the L2, 3 edge res<strong>on</strong>ances, comparing the effects of including spin-orbit<br />

coupling and the Hubbard, U, term.<br />

QN02<br />

High frequency permeability of Fe-Co and Co granular composite<br />

materials<br />

Teruhiro Kasagi 1 *, Aiko Tsurunaga 2 , Takanori Tsutaoka 2 and Kenichi Hatakeyama 3<br />

1 Tokuyama College of Technology, Japan<br />

2 Graduate School of Educati<strong>on</strong>, Hiroshima University, Japan<br />

3 Graduate School of Engineering, University of Hyogo, Japan<br />

Relative complex permeability and permittivity spectra of Fe 50Co 50 (Permendur)<br />

and Co granular composite materials have been studied in the microwave frequency<br />

range up to 18 GHz. Particles were heat-treated in air using an electric furnace<br />

in order to suppress the eddy current effect in the composite structure c<strong>on</strong>taining<br />

percolated particles. Composite materials were prepared by mixing these particles<br />

with Polyphenylene sulfide resin. The 78 vol.% Fe 50Co 50 granular composite has<br />

the larger relative permeability value than that of the 79 vol.% Co composite at 100<br />

MHz. The negative frequency dispersi<strong>on</strong> of permeability was observed above 7 and<br />

8 GHz for Fe 50Co 50 and Co composites, respectively. The dc magnetic field effect <strong>on</strong><br />

the permeability spectra revealed that the permeability dispersi<strong>on</strong> of Co composites in<br />

the microwave range is mainly attributed to the gyromagnetic res<strong>on</strong>ance. The relative<br />

permittivity spectra of 78 vol.% Fe 50Co 50 and 79 vol.% Co composites show the<br />

insulating property up to several GHz; the permittivity value increases with increasing<br />

particle c<strong>on</strong>tent in both composites.<br />

QN03<br />

Magnetic carb<strong>on</strong>yl ir<strong>on</strong> suspensi<strong>on</strong> with nanoclay additive and its<br />

magnetorheological properties<br />

Cheng Hai H<strong>on</strong>g, Ying Dan Liu and Hyoung Jin Choi*<br />

Department of Polymer Science and Engineering, Inha University, Korea<br />

Soft magnetic carb<strong>on</strong>yl ir<strong>on</strong> (CI) based magnetorheological (MR) fluids with different<br />

loadings of nanoclay were prepared, in which the MR fluid is a complex colloidal<br />

suspensi<strong>on</strong> c<strong>on</strong>sisting of magnetic particles dispersed in a liquid, showing its rapid,<br />

reversible and tunable change between a liquid-like and solid-like state with an applied<br />

external magnetic field. The MR characteristics were measured via rotati<strong>on</strong>al tests, in<br />

which the flow curves exhibited a n<strong>on</strong>-Newt<strong>on</strong>ian behavior for all investigated samples<br />

under applied magnetic fields. Flow curves showed not <strong>on</strong>ly the dynamic yield stress<br />

change measured as a functi<strong>on</strong> of magnetic field strength using a power law fit but also<br />

the existence of a solid-like character. Sedimentati<strong>on</strong> of the MR fluid with and without<br />

an additive was also examined.


QN04<br />

Hysteresis analysis: A study <strong>on</strong> the demanetizati<strong>on</strong> by using M-B<br />

preisach model for improved stability of numerical analysis<br />

Hyuk W<strong>on</strong> and Gwan Soo Park*<br />

School of Electrical Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

It is necessary to describe the hysteresis characteristic of magnetic material precisely<br />

for the analysis of design of system with ferromagnetic materials. Although<br />

Preisach model is regarded as the most accurate method to describe the hysteresis<br />

characteristics, it is not applied widely to the real systems because of some difficulties.<br />

The c<strong>on</strong>venti<strong>on</strong>al Preisach model shows the numerical instabilities during the iterative<br />

computati<strong>on</strong>s because the density distributi<strong>on</strong> obtained from the sets of M-H curves<br />

are str<strong>on</strong>gly localized. To remove such numerical instabilities, if we use a M-B variable<br />

instead of M-H variable would be better the results. In this paper, we suggest method<br />

for a M-H variable to change a M-B variable, and also, from the computed results of<br />

used normal Preisach, M-H cure method and M-B curve method, we shows better than<br />

numerical stabilities by using two dimensi<strong>on</strong>al finite element method.<br />

QN05<br />

A study <strong>on</strong> the design of transmitting coils and receiving coils <strong>on</strong> active<br />

magnetic snesor using finite element method<br />

Hye Sun Ju and Gwan Soo Park*<br />

Pusan Nati<strong>on</strong>al University, Korea<br />

Proximity magnetic sensor is able to detect the object target accurately in close range<br />

and it has been widely used in the underwater guided weap<strong>on</strong> system because there<br />

is no countermeasures from the target. In order to increase the damage of target by<br />

shock wave due to explosi<strong>on</strong> of the underwater guided weap<strong>on</strong> system, the maximum<br />

detecti<strong>on</strong> range of the proximity magnetic sensor needs to be increased. In this paper,<br />

we describe the techniques of the optimum transmitting and receiving coils design<br />

using the Finite Element Method for the output power enhancement of the transmitter<br />

and the sensitivity improvement of the receiver. Finally, the proposed design techniques<br />

of the transmitter and the receiver were verified using a experimental setup and a<br />

prototype.<br />

QN06<br />

What can we learn from isothermal remanent magnetizati<strong>on</strong> curves <strong>on</strong><br />

diluted nanoparticle assemblies?<br />

Florent Tournus*, Arnaud Hilli<strong>on</strong>, Alexandre Tami<strong>on</strong> and Ver<strong>on</strong>ique Dupuis<br />

LPMCN, CNRS & Univ. Ly<strong>on</strong> 1, France<br />

Isothermal remanent magnetizati<strong>on</strong> (IRM) and direct-current demagnetizati<strong>on</strong> (DcD)<br />

curves are mainly used to characterize interacti<strong>on</strong>s in a granular magnetic media and to<br />

determine the switching field distributi<strong>on</strong>. These curves are <strong>on</strong>ly sensitive to irreversible<br />

changes, i.e. to the particle magnetizati<strong>on</strong> switching for samples made of clusters<br />

embedded in a matrix. Moreover, at remanence there is no unsuitable c<strong>on</strong>tributi<strong>on</strong><br />

(superparamagnetic, diamagnetic or paramagnetic) to the signal. This makes IRM/DcD<br />

curves of great interest in the investigati<strong>on</strong> of the intrinsic properties of nanoparticles. The<br />

underlying process, i.e. macrospin switching by applying a field, is complementary to the<br />

thermal switching observed with ZFC/FC curves where the particle size distributi<strong>on</strong> has a<br />

critical influence. Interestingly, IRM curves have a high sensitivity to other characteristics<br />

such as an anisotropy c<strong>on</strong>stant distributi<strong>on</strong>, n<strong>on</strong>-uniaxial terms of the anisotropy, and of<br />

course inter-particle interacti<strong>on</strong>s. We show how IRM/DcD curves can be modelled for an<br />

assembly of randomly oriented and n<strong>on</strong>-interacting macrospins, thus allowing efficient<br />

and realistic simulati<strong>on</strong>s of experimental curves (taking into account the size distributi<strong>on</strong>,<br />

temperature, etc). This modelling is then c<strong>on</strong>fr<strong>on</strong>ted to a series of measurements <strong>on</strong> diluted<br />

Co nanoparticle samples prepared by low-energy cluster-beam depositi<strong>on</strong>. Experiment/<br />

theory comparis<strong>on</strong> can provide new insights <strong>on</strong> their magnetic properties.<br />

QN07<br />

QN08<br />

QN09<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

On real-time hysteresis compensati<strong>on</strong> for magentostirictive sound<br />

transducers<br />

Hae Jung Park and Young-woo Park*<br />

Department of Mechatr<strong>on</strong>ics Engineering, Chungnam Nati<strong>on</strong>al Univers, Korea<br />

Magnetostrictive actuators show inherent hysteresis, and it hinders wide applicati<strong>on</strong>s.<br />

To solve this problem, in the literature, ‘Jiles-Athert<strong>on</strong> model’ and ‘Preisach model’<br />

have been used mostly. But the methods require huge CPU time, or need complex<br />

mathematics. Thus, for real-time, ability of hysteresis compensati<strong>on</strong> using capacitor<br />

is proposed by park et al [1]. In this paper, class-D amplifier c<strong>on</strong>taining capacitor as<br />

hysteresis compensator is proposed. The Class-D amplifier c<strong>on</strong>sists of comparator,<br />

current supplier and R-C circuit. Hysteresis compensator is implemented by a<br />

R-C circuit, because the output voltage of capacitor has similarity to a hysteresis<br />

compensated input, and the process of development is as follows: 1. Generati<strong>on</strong> of<br />

Hysteresis compensated input by Preisach model; 2. Comparis<strong>on</strong> between hysteresis<br />

compensated input and R-C circuit model by n<strong>on</strong>-linear regressi<strong>on</strong>; 3. Applicati<strong>on</strong><br />

found capacitance to the class-D amplifier. Experimental setup is c<strong>on</strong>sisted of a<br />

capacitance displacement sensor, a digital oscilloscope and a functi<strong>on</strong> generator.<br />

Hysteresis loss observed about 19 percent before applicati<strong>on</strong> of hysteresis compensator,<br />

and hysteresis loss observed less than 13 percent after applicati<strong>on</strong> of hysteresis<br />

compensator at 10 Hz by using the 3 uF of capacitor.<br />

[1] Ki-Hyun Ji, Hae-Jung Park, and Young-Woo Park, “Semiempirical Approach to Compensate<br />

Hysteresis in Magnetostrictive Actuator”, IEEE <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Magnetics <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> 2011, 2011<br />

The investigati<strong>on</strong> <strong>on</strong> structural and magnetic properties of Ni-Cu-Zn-<br />

Mn-Mg-Li ferrites<br />

Chih-wen Chen*, Mean-June Tung and Shi-Yuan T<strong>on</strong>g<br />

Industrial Technology Research Institute, Taiwan<br />

In this work, additi<strong>on</strong> of seven raw materials inclusive of nickel oxide, copper oxide,<br />

zinc oxide, manganese oxide, magnesium oxide, lithium oxide, and ir<strong>on</strong> oxide to form<br />

a new multi-comp<strong>on</strong>ent ferrite system. The Ni-Cu-Zn-Mn-Mg-Li substituted ferrites<br />

were prepared by c<strong>on</strong>venti<strong>on</strong>al solid-state-reacti<strong>on</strong> process and sintered at 1100°C<br />

for 2 h in air atmosphere. The influences of Ni-Cu-Zn-Mn-Mg-Li substituti<strong>on</strong> <strong>on</strong><br />

structural and magnetic properties were investigated by scanning electr<strong>on</strong> microscopy,<br />

RF impedance/material analyzer, B-H curve loop tracer, and vibrating sample<br />

magnetometer. The experimental results show that the additives with low melting point<br />

form precipitates at the grain boundaries.[1] The average grain size of sintered ferrites<br />

decreases with a decrease of Ni/Mn ratio. The sintered ferrites, Ni/Mn=0.79, showed<br />

largest initial permeability (μi=85), largest saturati<strong>on</strong> magnetism (Bs=3930 gauss), and<br />

better saturati<strong>on</strong> magnetizati<strong>on</strong> (Ms=74.91 emug-1).<br />

[1]Guiqing Wang, Xiufang Bian, Weimin Wang, Junyan Zhang,Mater. Lett., 57 (2003) 4083-4087.<br />

Magnetorheology of xanthan gum coated soft magnetic carb<strong>on</strong>yl ir<strong>on</strong><br />

microspheres and their polishing characteristics<br />

Seung Hyuk Kw<strong>on</strong> 1 , Hyoung Jin Choi 1 *, Jung W<strong>on</strong> Lee 2 , Kwang Pyo H<strong>on</strong>g 2 and<br />

Mye<strong>on</strong>g Woo Cho 2<br />

1 Department of Polymer Science and Engineering, Inha University, Korea<br />

2 Department of Mechanical Engineering, Inha University, Korea<br />

Magnetorheological fluids, complex colloidal suspensi<strong>on</strong>s c<strong>on</strong>sisting of magnetic particles<br />

dispersed in a liquid, showing their rapid, reversible change between a liquid-like and solidlike<br />

state with an applied magnetic field. Am<strong>on</strong>g these applicati<strong>on</strong>s, MR polishing arrests<br />

a lot of attenti<strong>on</strong> due to its smart c<strong>on</strong>trolling polishing characteristics for dedicated MEMS<br />

applicati<strong>on</strong>s. In order to improve polishing characteristics of MR fluids, in this study,<br />

carb<strong>on</strong>yl ir<strong>on</strong> (CI) microspheres coated with xanthan gum (XG) were fabricated via solvent<br />

casting method. The morphologies and densities of both pure CI and CI/XG particles were<br />

characterized via SEM and pycnometer, respectively. In additi<strong>on</strong>, rheological characteristics<br />

of the MR fluids under applied magnetic field strengths were examined via a rotati<strong>on</strong>al<br />

rheometer, in which shear viscosity, storage modulus, normal force the variati<strong>on</strong> in MR<br />

performance under applied magnetic fields. Especially, the normal force was measured<br />

for different gap distances to simulate the work c<strong>on</strong>diti<strong>on</strong> of MR polishing. MR polishing<br />

characteristics were c<strong>on</strong>ducted using an MR polishing machine to investigate the surface<br />

roughness from the MR polishing with nano ceria slurry abrasives. A series of experiments<br />

were performed for fused silica glass using prepared slurry by changing the processing<br />

parameters such as a rotating wheel speed and polishing time.<br />

July 8 - 13, 2012 Busan, Korea 123<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QN10<br />

Cluster-glass-like magnetic state in rare-earth intermetallic compound<br />

Tb 5Pd 2<br />

Andrey F. Gubkin 1 *, Pavel E. Terent'ev 2 , Elena A. Sherstobitova 1 and Nikolai V.<br />

Baranov 3<br />

1 Laboratory of neutr<strong>on</strong> scattering, Institute of Metal Physics, Russia<br />

2 Laboratory of ferromagnetic alloys, Institute of Metal Physics, Russia<br />

3 Laboratory of micromagnetic materials, Institute of Metal Physics, Ural Federal University, Russia<br />

The rare-earth intermetallic Tb 5Pd 2 compound crystallizes in a cubic crystal structure with site disorder<br />

and magnetic frustrati<strong>on</strong>s due to triangle-like arrangement of Tb atoms [1]. In this work the DC and AC<br />

magnetic susceptibility measurements together with powder neutr<strong>on</strong> diffracti<strong>on</strong> have been performed<br />

in order to study the Tb 5Pd 2 magnetic state. The susceptibility measurements <strong>on</strong> a polycrystalline<br />

Tb 5Pd 2sample have revealed a complex highly irreversible behaviour below 58 K, which can be associated<br />

with the existence of a spin-glass-like magnetic state. According to our neutr<strong>on</strong> diffracti<strong>on</strong> data the Tb 5Pd 2<br />

compound doesn’t exhibit a l<strong>on</strong>g-range magnetic down to 5 K. However below and above the freezing<br />

temperature TG ? 58 K, the appearance of the broad diffuse maxima of magnetic origin has been detected<br />

in the low angle regi<strong>on</strong>. The sec<strong>on</strong>d anomaly of the susceptibility was observed at TB ? 25 K, which can<br />

be ascribed to the blocking process of uncompensated magnetic moments of antiferromagnetically shortrange<br />

correlated regi<strong>on</strong>s. The results obtained allow us to suggest that the Tb 5Pd 2 compound exhibits a<br />

complex n<strong>on</strong>-ergodic magnetic state of a cluster-glass type associated with frustrati<strong>on</strong>s of the RKKY-type<br />

exchange interacti<strong>on</strong>. This work was supported by the program of RAS (Projects RAS UB 11-2-НП-265).<br />

1. M. L. Fornasini, A. Palenz<strong>on</strong>, J. Less-Comm<strong>on</strong> Metals, 38, (1974) 77-82.<br />

QN11<br />

Microwave absorpti<strong>on</strong> properties of polymer composites with<br />

amorphous Fe-B and Ni-Zn-Co ferrite nanoparticles<br />

Kazuaki Shimba*, Shozo Yuki, Nobuki Tezuka and Satoshi Sugimoto<br />

Materials Science, Tohoku University, Japan<br />

Recently, many communicati<strong>on</strong> devices use GHz-range microwave. It causes serious<br />

issue, such as electromagnetic interference and multipath interference. To prevent these<br />

problem, microwave absorbers (MA) c<strong>on</strong>sisting of polymer composites of magnetic<br />

powders are paid attenti<strong>on</strong>. With the current trend being to miniaturize devices, thinner<br />

MA are now required. We reported that polymer composites with amorphous Fe-B<br />

particles (AFBP) and Ni-Zn ferrite nanoparticles showed high permeability of μ'r =<br />

9.5 at 1.0 GHz and good microwave absorpti<strong>on</strong> properties at 0.6-1.1 GHz and resulted<br />

in thinner MA than reported MA [1]. However, they cannot used as MA over 1.1<br />

GHz, because of their low res<strong>on</strong>ant frequency (fr = 1.2 GHz). In this study, Ni-Zn-Co<br />

ferrite nanoparticles (NZCFN) were mixed with AFBP for increasing fr in polymer<br />

composites. XRD analyses show that NZCFN exhibit typical spinel structure. The fr<br />

of NZCFN increases from 0.7 to 3.6 GHz with increasing Co c<strong>on</strong>tents. It indicates<br />

that the magnetocrystalline anisotropy of NZCFN is increased by Co additi<strong>on</strong>. The fr<br />

of polymer composites with AFBP and NZCFN can be increased to 2.6 GHz. They<br />

exhibites good microwave absorpti<strong>on</strong> properties at 0.8-1.4 GHz with thicknesses of<br />

2.4-3.9 mm and resulted in thin MA at 1-1.4 GHz.<br />

[1] K. Shimba, N. Tezuka, S. Sugimoto; Materials Science and Engineering B 177 (2012) 251-256<br />

QN12<br />

Magnetostrictive properties of Mn substituted sintered cobalt ferrite<br />

derived from nanocrystalline materials<br />

Khaja Mohaideen Kamal and P A Joy*<br />

Materials chemistry divisi<strong>on</strong>, Nati<strong>on</strong>al Chemical Laboratory, India<br />

Magnetostrictive smart materials are of great importance for sensor applicati<strong>on</strong>s. Cobalt<br />

ferrite is well known for its highest magnetostrictive strain at room temperature am<strong>on</strong>g<br />

the oxide based magnetostrictive materials. The substituti<strong>on</strong> of manganese for ir<strong>on</strong> in<br />

cobalt ferrite, CoFe 2O 4, increases the strain derivative even though the magnetostricti<strong>on</strong><br />

value is decreased for the material synthesized through the c<strong>on</strong>venti<strong>on</strong>al ceramic route<br />

[1,2]. In the present study we have investigated the influence of the initial particle<br />

size of the powders of manganese substituted cobalt ferrite <strong>on</strong> the magnetostrictive<br />

coefficient of the sintered ferrite samples with compositi<strong>on</strong>s 0≤x≤0.3 in CoFe 2xMn<br />

xO 4. Nanoparticles of CoFe 2-xMn xO 4 of size less than 10 nm were synthesized by<br />

an autocombusti<strong>on</strong> method and the resulting powders were sintered in air at 1300° C.<br />

Magnetic characteristics of the nanocrystalline powders and sintered products have<br />

been studied. Magnetostricti<strong>on</strong> measurements were performed <strong>on</strong> the sintered samples<br />

to determine the influence of initial particle size of the starting powders. Higher<br />

magnetostricti<strong>on</strong> at low fields is obtained al<strong>on</strong>g with enhanced strain derivative for the<br />

sintered Mn substituted cobalt ferrite derived from nanocrystalline materials compared<br />

to the bulk counterparts.<br />

1. J.A. Pauls<strong>on</strong> et al. J. Appl. Phys., 97, 44502 (2005). 2. S.D. Bhame and P.A. Joy, J. Appl. Phys.,<br />

100, 113911 (2006).<br />

124 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QN13<br />

Magnetic Properties of Co 2Z Ferrite Densified through High BET<br />

Powders<br />

Ji Ye<strong>on</strong> S<strong>on</strong>g and Young Ho Han*<br />

Materials Engineering, Sungkyunkwan University, Korea<br />

Co 2Z is a planar hexag<strong>on</strong>al ferrite that exhibits high permeability (μi) and high<br />

res<strong>on</strong>ance frequency (fr) up to the GHz regi<strong>on</strong>. Z-type Ba 3Co 2Fe 24O 41 hexag<strong>on</strong>al<br />

ferrite was prepared by two-step calcinati<strong>on</strong>s [1]. Single phase Co 2Z ferrite powders<br />

were possible after post-calcinati<strong>on</strong> at 1300°C. Various sintering aids improved<br />

densificati<strong>on</strong> of ceramic bodies, but lowered magnetic permeability due to n<strong>on</strong>magnetic<br />

characteristics of sintering additives. In order to increase permeability, Co 2Z<br />

specimen was sintered without sintering aids. The densities of sintered bodies increased<br />

with increasing specific surface area (BET) of calcined powders, and Co 2Z with BET<br />

7.80m2/g led to significantly high densificati<strong>on</strong>(5.23g/cm3, 97% theoretical density).<br />

Permeability of Co 2Z gradually increased with increasing density, whereas their<br />

res<strong>on</strong>ance frequencies decreased with increasing permeability, where the product of μi<br />

x fr was estimated to be ~10.3GHz. It was thus c<strong>on</strong>firmed that the calcined powders<br />

with high BET could enhance sintering kinetics of Co 2Z hexag<strong>on</strong>al ferrites without<br />

sintering additives and significantly increase magnetic permeability.<br />

[1] J. Je<strong>on</strong>g, K.W. Cho, D.W. Hahn, B.C. Mo<strong>on</strong>, Y.H. Han, Mater. Lett. 59 (2005) 3959-62<br />

QN14<br />

Magnetic properties of Cr 3+ substituted Mg-Cd ferrites<br />

S A Masti 1 *, A. K Sharma 2 and P. N. Vasambekar 3<br />

1 Physics, Dr. Ghali College, Gadhinglaj, India<br />

2 Physics, Shivaji University, Kolhapur, India<br />

3 Electr<strong>on</strong>ics, Shivaji University, Kolhapur, India<br />

Magnetizati<strong>on</strong> and susceptibility of polycrystalline ferrites with general formula Cd x<br />

Mg 1-x Fe 2-y Cr y O 4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0; y = 0, 0.05 and 0.10) were studied.<br />

Study of saturati<strong>on</strong> magnetizati<strong>on</strong> reveals that the Neels two sublattice model exists<br />

up to x = 0.4, for y = 0, 0.05 and 0.1 and a three sublattice model (YK-model) is<br />

predominant for x > 0.4, y = 0, 0.05 and 0.10. The saturati<strong>on</strong> magnetizati<strong>on</strong> and<br />

magnetic moment were found to decrease with the increase of Cr 3+ c<strong>on</strong>tents, which is<br />

attributed to the diluti<strong>on</strong> of B-B site interacti<strong>on</strong>. Temperature dependence normalized<br />

AC susceptibility study reveals that MgFe 2O 4 exibits single domain(SD) structure. On<br />

substituti<strong>on</strong> of Cd 2+ , single to multi domain transiti<strong>on</strong> takes place. Curie temperature<br />

decreases with Cd 2+ ,was attributed to decrease in A-B intracti<strong>on</strong>. On substituti<strong>on</strong> of<br />

Cr 3+ , peak obtained in MgFe 2O 4 was supressed which is attributed to decrease in grain<br />

size and further decrease<br />

QN15<br />

Docking Speaker Based <strong>on</strong> Magnetostrictive Sound Transducer<br />

Han Sam Kang, Jin H<strong>on</strong>g Min and Young Woo Park*<br />

Department of Mechatr<strong>on</strong>ics Engineering, Chungnam Nati<strong>on</strong>al University, Korea<br />

All docking speakers available in the market are equipped with iDevice cradle and<br />

with c<strong>on</strong>e-type sound unit. This paper presents a novel docking speaker without them.<br />

It is based <strong>on</strong> the magnetostrictive sound transducer (MST), which transforms any flat<br />

surface into speaker. The docking speaker c<strong>on</strong>sists of <strong>on</strong>e MST, two circuit boards, and<br />

aluminum housing. One circuit board c<strong>on</strong>tains a Bluetooth module, a power amplifier<br />

module, Aux, and a recharge adapter. The other board is called a c<strong>on</strong>trol board, which<br />

ATmega128 is used to c<strong>on</strong>trol a digital clock, a LCD module, four c<strong>on</strong>trol switches,<br />

and a power amplifier module. The reluctance c<strong>on</strong>cept is utilized to the magnetic circuit<br />

for the MST. Allowable current and number of coil turns are determined through this<br />

procedure. The result is compared with the simulati<strong>on</strong> result. Then, circuit board and<br />

housing are designed. The assembled docking speaker is subjected to the experiments.<br />

For the experiments, the MST is placed and bolted between the wood and glass panels.<br />

An accelerometer sensor, ADXL001, is firstly located beneath the center of the MST.<br />

Then, the locati<strong>on</strong> is placed away by 50 mm from the center of the MST. It is proved<br />

that the developed docking speaker works well.


QN16<br />

Characteristics of composite materials Ba 0.5Sr 0.5Fe 11.7Mn 0.15Ti 0.15O 19/<br />

La 0.7Ba 0.3MnO 3 as a microwave absorber<br />

V. Vekky R. Repi* and Azwar Manaf<br />

Graduate Program of Materials Science Study, Universitas Ind<strong>on</strong>esia, Ind<strong>on</strong>esia<br />

QN17<br />

The effect of shape anisotropy to acoustical performance of<br />

magnetostrictive sound transducer<br />

Hae Jung Park, Young Woo Park* and Ok Kyun Oh<br />

Department of Mechatr<strong>on</strong>ics Engineering, Chungnam Nati<strong>on</strong>al Univers, Korea<br />

This paper presents the experimental approach to investigate the effect of the<br />

shape anisotropy of magnetostrictive material (MM) to acoustical performance of<br />

magnetostrictive sound transducer. The assumpti<strong>on</strong> is that the volume of MM is kept<br />

c<strong>on</strong>stant. In the experiments, four MM samples are used with a volume of 295 mm^3<br />

and input currents are swept from 20 Hz to 20 kHz. The diameters of MM samples<br />

are 4, 5, 6 and 10 mm and the lengths are 23.5, 15, 10.5 and 3.5 mm, respectively. The<br />

displacements are measured from 2.1 to 0.8 um at 20 Hz. Forces are measured from<br />

81 to 120 N at 20 Hz. Am<strong>on</strong>g the samples, the MM sample of 23.5mm length shows<br />

the largest displacement and force. SPL is obtained from forces of MM and a area<br />

of vibrati<strong>on</strong> panel. The largest SPL is observed at 20 Hz and the SPL is measured to<br />

115dB. Also, the SPL of the samples show the level from 103 dB at 1 kHz to 81 dB at<br />

20 kHz. The displacement and force are measured from 0.36 um and 29N at 1 kHz to<br />

15.3 nm and 2.5 N at 20 kHz.<br />

QN18<br />

WITHDRAWN<br />

Size effects <strong>on</strong> magnetic properties of nanocrystalline Sr 2CuCo 2Fe 24O 41<br />

prepared by Co-precipitati<strong>on</strong> method<br />

K Praveena and K Sadhana<br />

Materials Research Centre, Indian Institute of Science, India<br />

The nanocrystalline z-type hexaferrite powders were synthesized by Co-precipitati<strong>on</strong><br />

method using aqueous soluti<strong>on</strong>s of str<strong>on</strong>tium, copper, cobalt ir<strong>on</strong> and nitrates. The<br />

as synthesized powders were characterized using XRD, TEM and TG/DTA. The<br />

average particle size of the powders was found to be 48nm.The effect of calcinati<strong>on</strong>s<br />

temperature <strong>on</strong> crystallinity, morphology and magnetic properties have been<br />

investigated. The sintered samples were characterized using XRD, FE-SEM and EDS.<br />

The hexag<strong>on</strong>al ferrite formati<strong>on</strong> was observed around 900°C which is c<strong>on</strong>firmed with<br />

the TG/DTA curves. The plate shape grains were observed in FE-SEM at 950°C. The<br />

grain sizes of sintered hexaferrites are in the range of 220nm to 850nm. The value of<br />

Ms= 70 emu/g and Hc=540 Oe was obtained at 900°C/5h.<br />

QN19<br />

QN21<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Structural and magnetic properties of Mn 2Rh 1-xCo xSn Heusler alloys<br />

Olga Meshcheriakova 1 , Jurgen Winterlik 1 , Gerhard H. Fecher 2 , Benjamin Balke 1 and Claudia Felser 3<br />

1 Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Germany<br />

2 Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Max<br />

Planck Institute for Chemical Physics of Solids, Dresden, Germany<br />

3 Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Max<br />

Planck Institute for Chemical Physics of Solids, Dresden,, Germany<br />

Mn 2-based Heusler compounds are promising candidates for spintr<strong>on</strong>ic applicati<strong>on</strong>s as they are<br />

known to crystallize with cubic and tetrag<strong>on</strong>al structures or exhibit cubic-tetrag<strong>on</strong>al phase transiti<strong>on</strong>s.<br />

Sn-c<strong>on</strong>taining compounds have <strong>on</strong>ly a small lattice mismatch with MgO thus providing higher<br />

symmetry correlati<strong>on</strong> between magnetic film and tunneling barrier. Quaternary Mn 2Rh 1-xCo xSn<br />

and Mn 2+xRh 1-xSn Heusler alloys have been synthesized with a step of x = 0,1 and their magnetic<br />

properties were experimentally investigated. In the present work the structural and magnetic properties<br />

are discussed depending <strong>on</strong> the Rh and Co c<strong>on</strong>tent. The frst series undergoes a cubic-tetrag<strong>on</strong>al<br />

transiti<strong>on</strong> at x = 0,5, while the latter <strong>on</strong>e experiences a hexag<strong>on</strong>al-tetrag<strong>on</strong>al change of structure. The<br />

presence of Co increases the Curie temperature keeping the magnetic moment unchanged. This work<br />

is supported by the Graduate School of Excellence Materials Science in Mainz (MAINZ).<br />

[1] Simple Rules for the Understanding of Heusler Compounds, Tanja Graf, Stuart S. P. Parkin, and Claudia Felser,<br />

Progress in Solid State Chemistry 39 (2011) 1-50, invited review. doi:10.1016/j.progsolidstchem.2011.02.001. [2]<br />

Electr<strong>on</strong>ic, magnetic, and structural properties of the ferrimagnet Mn2CoSn, Jurgen Winterlik, Gerhard H. Fecher,<br />

Benjamin Balke, Tanja Graf, Vajiheh Alijani, Vadim Ksenof<strong>on</strong>tov, Catherine A. Jenkins, Olga Meshcheriakova, and<br />

Claudia Felser 83 (2011) 174448. [3] Quaternary half-metallic Heusler ferromagnets for spintr<strong>on</strong>ics applicati<strong>on</strong>s,<br />

V Alijani, J. Winterlik, G. H. Fecher, S. S. Naghavi, C. Felser, Phys. Rev. B 83 (2011) 184428<br />

QN20<br />

Magnetic properties of Mn 2Sb 1-xGe x (0.05 ≤ x ≤ 0.2) in high magnetic<br />

fields<br />

Daisuke Shimada 1 *, Hiroki Orihashi 1 , Daisuke Mitsunaga 1 , Kohki Takahashi 2 ,<br />

Masahiko Hiroi 1 , Masakazu Ito 1 , Kazuyuki Matsubayashi 3 , Yoshiya Uwatoko 3 and<br />

Keiichi Koyama 1<br />

1 Kagoshima University, Japan<br />

2 Tohoku University, Japan<br />

3 Tokyo University, Japan<br />

The Mn 2Sb compound with a Cu 2Sb-type tetrag<strong>on</strong>al structure is ferromagnetic (FRI) below TC ~<br />

550 K. The substituti<strong>on</strong> of various elements (V, Cr, Co, Cu and Zn) for Mn as well as (As, Ge and<br />

Sn) for Sb results in a first-order magnetic (FOM) transiti<strong>on</strong> from the ferromagnetic (FRI) to an<br />

antiferromagnetic (AFM) states with decreasing temperature [1]. Mn 2-xCoSb, it has been reported<br />

that the FOM transiti<strong>on</strong> occurs accompanied with large change in unit cell volume, resistivity and<br />

magnetizati<strong>on</strong> etc. However, detailed results <strong>on</strong> Mn2Sb 1-xGe x have not been reported yet. In this<br />

study, magnetizati<strong>on</strong> and electrical resistivity measurements were carried out for polycrystalline<br />

Mn 2Sb 1-xGe x (0.05 ≤ x ≤ 0.2) in magnetic fields up to 16 T in 4.2-600 K temperature range, in order<br />

to investigate the magnetic and electrical properties affected by magnetic fields. Mn 2Sb 0.92Ge 0.08<br />

showed the Curie temperature Tc of 532 K and the FOM transiti<strong>on</strong> at Tt = 230 K in a zero magnetic<br />

field. With increasing x, Tc decreased and Tt increased. For Mn 2Sb 0.92Ge 0.08, we observed a<br />

matamagnetic transiti<strong>on</strong> from the AFM to FRI with a hysteresis of 0.5 T at 200 K.<br />

[1] O. Beckman and L. Lundgren: Handbook of Magnetic Materials vol 6, ed K H J Buschow<br />

(Amsterdam: Elsevier) chapter 3, (1991) p 181-287<br />

Microwave magnetic properties of FeNi films prepared by<br />

electrodepositi<strong>on</strong><br />

D<strong>on</strong>g Zhou1, Wei Li 1 , Minggang Zhu 1 *, Yanfeng Li 1 , Wei Sun1 and Fashen Li 2<br />

1 Central Ir<strong>on</strong> & Steel Research Institute, China<br />

2 Lanzhou University, China<br />

With the development of computers and communicati<strong>on</strong> devices using the<br />

electromagnetic wave of GHz range, the serious electromagnetic interference (EMI)<br />

have been emerged. The electromagneic wave absorbers have been widely investigated<br />

to eliminate the EMI problems. Electrodepositi<strong>on</strong> is <strong>on</strong>e of the simplest, most<br />

flexible, and cheapest processes available for the fabricati<strong>on</strong> of single comp<strong>on</strong>ent and<br />

multilayered thin films. In this study, FeNi alloys thin films have been successfully<br />

electrodeposited <strong>on</strong> Ag films. The morphology, structure, compositi<strong>on</strong>, and magnetic<br />

property of the FeCo films were characterized by scanning electr<strong>on</strong> microscopy,<br />

x-ray diffracti<strong>on</strong>, energy dispersive spectrometer, vibrating sample magnetometer and<br />

network analyzer. With the increase of deposti<strong>on</strong> time, the coercivity of deposited<br />

FeNi films reduce until getting a minimum value and the the real part of permeability<br />

increase. At the same time, the increase of the thickness leads to the decrease of<br />

res<strong>on</strong>ance frequency. We also study the effect of the composti<strong>on</strong> <strong>on</strong> the coercivity and<br />

microwave magnetic properties. By changing the composit<strong>on</strong> of FeNi alloy films, the<br />

effective permeability and the res<strong>on</strong>ance frequency can be adjusted.<br />

July 8 - 13, 2012 Busan, Korea 125<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QN22<br />

Preparati<strong>on</strong> and characterizati<strong>on</strong> of ferromagnetic fluid and magnetorheological<br />

fluid<br />

Tae Min H<strong>on</strong>g 1 , J<strong>on</strong>g Hee Kim 2 , Cheolgi Kim 3 and Seung Goo Lee 1 *<br />

1<br />

Advanced Organic Materials & Textile System Engineering, Chungnam Nati<strong>on</strong>al<br />

University, Korea<br />

2<br />

Research Center for Advanced Magnetic Material, Chungnam Nati<strong>on</strong>al University,<br />

Korea<br />

3<br />

Materials Science & Engineering, Chungnam Nati<strong>on</strong>al University, Korea<br />

Ferromagnetic fluid and magneto-rheological fluid are liquids that nanometer-sized<br />

particles of ir<strong>on</strong> dispersed in the medium. PEG(polyethylene glycol) and silic<strong>on</strong><br />

oil were used as the fluidic media. Fluids are flexible dispersi<strong>on</strong> state under a n<strong>on</strong>magnetic<br />

field. But, under a magnetic field, particles are oriented in the directi<strong>on</strong> of the<br />

magnetic field and the fluid shows the solid-like behavior. In this study, we studied to<br />

know how the magnetic field impacts the yield stress of ferromagnetic and magnetorheological<br />

fluids. Yield stress of the fluid is evaluated by the viscosity measurement.<br />

Viscosity behaviors of ferromagnetic and magneto-rheological fluids are measured<br />

with a magneto-rheological viscometer (MCR 301, Ant<strong>on</strong> paar, Austria) with applying<br />

magnetic field from the plate. Two types of experiment were c<strong>on</strong>ducted. One is a static<br />

test in which the viscosity of fluids is measured with increasing shear rate while the<br />

applied magnetic field is fixed. The other <strong>on</strong>e is a dynamic test in which the viscosity<br />

of fluids is measured with increasing magnetic field while shear rate is fixed. As the<br />

results, viscosity of ferromagnetic fluid and magneto-rheological fluid increased largely<br />

by applying magnetic field in all c<strong>on</strong>diti<strong>on</strong>s.<br />

QN23<br />

Microwave magnetic and absorbing properties of the planaranisotropy<br />

Ce 2Fe 17N 3-δ powder composite<br />

Jianqiang Wei, Wenliang Zuo, Tao Wang and Fashen Li*<br />

Key Laboratory of <strong>Magnetism</strong> and Magnetic Materials of Ministry of Educati<strong>on</strong>,<br />

Lanzhou University, China<br />

Ce 2Fe 17N 3-δ powders were prepared by arc-melting, milling and nitrogenati<strong>on</strong>. The microstructure<br />

and static magnetic properties of the powders were analyzed by x-ray diffracti<strong>on</strong> (XRD) and<br />

vibrating sample magnetometer (VSM), respectively. The c-plane alignment of Ce 2Fe 17N 3-δ was<br />

evaluated with the XRD data of an aligned composite sample. The effective complex permeability<br />

of Ce 2Fe 17N 3-δ powders/epoxy resin composite was measured in the frequency range of 0.1-15 GHz.<br />

The intrinsic static permeability of Ce 2Fe 17N 3-δ powder was calculated by Bruggerman (BG) effective<br />

medium theory. The natural res<strong>on</strong>ance frequency of Ce 2Fe 17N 3-δ was obtained using Landua-Lifshitz-<br />

Gilbert (LLG) equati<strong>on</strong>. The Snoek's product of the effective static susceptibility and the res<strong>on</strong>ance<br />

frequency is much larger than the Snoek's limit of the composite. The reflecti<strong>on</strong> loss of the composite<br />

sample was determined by simulati<strong>on</strong> and by measuring the S11 parameters after rear face of<br />

sample was terminated by metal. The minimum reflecti<strong>on</strong> loss was found moving towards the lower<br />

frequency regi<strong>on</strong> with increasing the sample thickness. Quantitatively analysis reveals that the peak<br />

frequencies (fp) of the dips (minimum reflecti<strong>on</strong> loss), the μ(fp), the ε(fp) and the sample thickness<br />

obey the quarter-wavelength (λ/4) formula. Accordingly, the quarter-wavelength formula have been<br />

successfully applied to explain and predict the microwave absorbing properties.<br />

This work is supported by the Nati<strong>on</strong>al Basic Research Program of China (Grant No.<br />

2012CB933101) and the Nati<strong>on</strong>al Natural Science Foundati<strong>on</strong> of China (Grant No. 11144008).<br />

QN24<br />

Co 2Y-NiCuZn ferrite composites for high frequency applicati<strong>on</strong>s<br />

Ruei-lin Lin and Hsing-i Hsiang*<br />

Resources Engineering, Nati<strong>on</strong>al Cheng Kung University, Taiwan<br />

The most comm<strong>on</strong>ly used materials in inductors for high-frequency applicati<strong>on</strong>s are<br />

NiCuZn ferrites, or n<strong>on</strong>-magnetic materials such as low-temperature cofired ceramics.<br />

The n<strong>on</strong>-magnetic materials are used for high-frequency applicati<strong>on</strong>s because NiCuZn<br />

ferrites (ferroxcube) typically exhibit severe property changes above 200MHz due to<br />

the Snoek limit. The maximum quality factor frequency in chip inductors made of n<strong>on</strong>magnetic<br />

material is over 500 MHz. However, the quality factors at frequencies around<br />

200-300MHz are much lower than those at higher frequencies. Because chip inductors<br />

are prepared by winding a wire around a n<strong>on</strong>-magnetic material core it is necessary<br />

to have a larger number of coil winding turns to obtain the desired inductance; thus<br />

limiting miniaturizati<strong>on</strong>. Therefore, it is desirable to develop a magnetic material that<br />

has a higher initial permeability and quality factor than n<strong>on</strong>-magnetic materials at 200-<br />

300 MHz, for use in making high frequency inductors. In this study, a Co 2Y-NiCuZn<br />

ferrite composite with high permeability was prepared by coating NiCuZn ferrites <strong>on</strong>to<br />

the surface of Co 2Y ferrites using heterogeneous nucleati<strong>on</strong> process. The effects of<br />

NiCuZn ferrites additi<strong>on</strong> <strong>on</strong> the densificati<strong>on</strong> behavior, micro-structure and magnetic<br />

property of Co 2Y-NiCuZn ferrite composites were investigated.<br />

126 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QN25<br />

A novel low-temperature-fired multifuncti<strong>on</strong>al varistor-magnetic<br />

NiCuZn ferrites<br />

Wei-hung Hsu, Hsing-i Hsiang* and Li-then Mei<br />

Resources Engineering, Nati<strong>on</strong>al Cheng Kung University, Taiwan<br />

A novel low temperature-fired(950°C) multifuncti<strong>on</strong>al varistor-magnetic ferrite<br />

materials can be obtained by adding Bi 2O 3 into Zn 0.5Ni 0.3Cu 0.19Nb 0.01Fe 2.02O 4 ferrites.<br />

The relati<strong>on</strong>ship between the microstructure and varistor properties were investigated<br />

using scanning electr<strong>on</strong> microscopy (SEM), X-ray Diffracti<strong>on</strong> (XRD), and impedance<br />

analysis. For Zn 0.5Ni 0.3Cu 0.19Nb 0.01Fe 2.02O 4 ferrites with 2.5wt% Bi 2O 3 c<strong>on</strong>tent<br />

sintered at 950°C for 2h, the n<strong>on</strong>linearity exp<strong>on</strong>ent (α) can reach 5.1 and the initial<br />

permeability(μ) is about 200 to 250. Moreover, the αvalue can be promoted to 67.8 for<br />

the Zn 0.5Ni 0.3Cu 0.19Nb 0.01Fe 2.02O 4 ferrites added with 9Bi 2O 3-CuO sintered at 950°C for<br />

2h.<br />

QN26<br />

Synthesis and magnetic properties of transiti<strong>on</strong> metal ferrite<br />

nanoparticles<br />

Tejabhiram Yadavalli 1 , Shivaraman Ramaswamy 1 , Gopalakrishnan Chandrasekaran 1<br />

and Ramasamy R 2<br />

1 Nanotechnology Research Centre, SRM University, India<br />

2 School of Pharmacy, SRM University, India<br />

The use of ferromagnetic metal ferrite particles for magnetic hyperthermia applicati<strong>on</strong><br />

has been extensively studied by many scientists. The use of ferromagnetic particles with<br />

low curie temperatures result in the formati<strong>on</strong> of self regulated magnetic hyperthermia.<br />

In this c<strong>on</strong>text, multiple experiments <strong>on</strong> synthesizing ferrite nanoparticles with varying<br />

cobalt and nickel oxide c<strong>on</strong>centrati<strong>on</strong>s have been d<strong>on</strong>e. The products were analyzed<br />

using scanning electr<strong>on</strong> microscopy, energy dispersive spectroscopy, X-ray diffracti<strong>on</strong><br />

and vibrating sample magnetometer. The microscope images indicated the formati<strong>on</strong><br />

of nanoparticles while the spectroscopy and diffracti<strong>on</strong> patterns indicated the formati<strong>on</strong><br />

of nickel and cobalt ferrite nanoparticles al<strong>on</strong>g with additi<strong>on</strong>al nickel oxide and cobalt<br />

oxide. Magnetometer analysis c<strong>on</strong>ducted <strong>on</strong> the samples indicated a reduced magnetic<br />

saturati<strong>on</strong> and hysteresis. Hysteresis loss energy was determined by calculating the area<br />

under the hysteresis loop, frequency of the magnetic field and the curie temperature of<br />

the material. The results indicated a two-fold decrease in the hysteresis energy giving a<br />

hint for their use in c<strong>on</strong>trolled magnetic hyperthermia treatment.<br />

QO01<br />

High room temperature power factor (Z) in K xRhO 2<br />

Nirpendra Singh, Yasir Saeed and Udo Schwingenschlog l *<br />

King Abdullah University Science and Technology Thuwal, Saudi Arabia<br />

We discuss the thermoelectric and optical properties of layered K xRhO 2 by means of<br />

the electr<strong>on</strong>ic structure determined by first principles calculati<strong>on</strong>s as well as Boltzmann<br />

transport theory. The main c<strong>on</strong>tributi<strong>on</strong> to the optical spectra are due to intra and interband<br />

transiti<strong>on</strong>s between the Rh 4d and O 2p states. Our results of transport perproties<br />

of K xRhO 2 at room temperature show highest value am<strong>on</strong>g hole-type materials.<br />

Specially at 100 K, the Z value of K xRhO 2 is 3x10 -3 K -1 . Our results show that the<br />

electr<strong>on</strong>ic and optical properties of K xRhO 2 are similar to Na xCoO 2 with an enhanced<br />

transport properties.


QO02<br />

Optimized Halbach array based magnet systems for Lorentz force<br />

velocimetry purposes<br />

Michael Werner 1 * and Bernd Halbedel 2<br />

1 University of Technology Ilmenau, Germany<br />

2 Department of Inorganic-N<strong>on</strong>metallic Materials, University of Technology Ilmenau,<br />

Germany<br />

Lorentz Force Velocimetry (LFV) is in research since 2003. The Lorentz force acting<br />

<strong>on</strong> a source magnet system is providing a velocity dependent signal. The efficiency of<br />

the magnet system (ratio of generated Lorentz forces to the mass of the system) is an<br />

essential parameter for sufficient resoluti<strong>on</strong>s of the whole LFV sensor device. The full<br />

article will propose a very efficient combinati<strong>on</strong> of permanent magnet arrays, where<br />

the particular permanent magnets have different magnetizati<strong>on</strong> directi<strong>on</strong>s. Here an<br />

ir<strong>on</strong> yoke is not necessary, respectively ineffective, and so the arrays can be assembled<br />

with a very light carb<strong>on</strong> fiber composite fixture in order to reduce the overall mass<br />

further. The underlying principle of this array combinati<strong>on</strong> will be presented and the<br />

geometric optimizati<strong>on</strong> with commercial software, as well as the assembling method,<br />

will be explained. On an experimental test channel for LFV <strong>on</strong> electrolyte flows the<br />

magnet system is tested and compared to another simple standard magnet system with<br />

single permanent magnet blocks instead of the arrays. From previous finite element<br />

simulati<strong>on</strong>s an increase of a factor of three in efficiency is estimated and will be proven<br />

in the experiment. Further improvement using cladding technique will be introduced<br />

too.<br />

QO03<br />

Growth and characterizati<strong>on</strong> of SmFe 6Ge 6 single crystals<br />

Rodrigo S. M<strong>on</strong>teiro, Lucas K. Piquini, E. Thizay Magnavita, Raquel A. Ribeiro and<br />

Marcos A. Avila*<br />

Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Brazil<br />

Hexag<strong>on</strong>al single crystal plates of SmFe 6Ge 6 have been grown by the flux method<br />

using a 4th flux element (Sn), extending the range of members in the RFe 6Ge 6 family<br />

of magnetic compounds, whose physical properties have so far been described<br />

<strong>on</strong>ly for rare earths R = Gd-Lu [1]. This family exhibits antiferromagnetic (AF II)<br />

ordering at 450 K of the layered Fe h<strong>on</strong>eycomb sublattice, and independent ordering<br />

(or no ordering) of the R sublattice moments below 30 K. Here we present a basic<br />

characterizati<strong>on</strong> of the structural, magnetic and transport properties of the SmFe 6Ge 6<br />

crystals and compare the general anisotropic behavior with other members of the<br />

family. We thank the support of Brazilian agencies FAPESP and CNPq.<br />

[1] G. Venturini, R. Welter and B. Malaman, J. Alloys Comp. 185 (1992) 99-107.<br />

QO04<br />

Anomalous magnetic and related properties of Nd 5Ge 3<br />

Bibekananda Maji 1 *, K G Suresh 1 and A K Nigam 2<br />

1 Physics, Indian Institute of Technology Bombay, Mumbai- 400076, India<br />

2 Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai- 400005,<br />

India<br />

We have observed that the stoichiometric intermetallic compound Nd 5Ge 3 shows many<br />

anomalies in the magnetizati<strong>on</strong>, resistivity and heat capacity data. This compound<br />

undergoes an antiferromagnetic (AFM) transiti<strong>on</strong> at 46 K and another <strong>on</strong>e at 30 K <strong>on</strong><br />

cooling. It is found that the strengths of these two antiferromagnetic states are different.<br />

Ultra-sharp jumps are seen in the low temperature isotherms of magnetizati<strong>on</strong>, heat<br />

capacity and electrical resistivity. Another important anomaly is the field-induced<br />

irreversibility in all these three properties, which suggests that the spin, electr<strong>on</strong>ic and<br />

lattices states are str<strong>on</strong>gly coupled in this compound. The memory effect seen here is<br />

quite remarkable and is c<strong>on</strong>sistently seen in various measurements. Another striking<br />

observati<strong>on</strong> is the sp<strong>on</strong>taneous evoluti<strong>on</strong> of the ferromagnetic (FM) phase as a functi<strong>on</strong><br />

of time, at a fixed temperature and at the critical field. Sweep rate and cooling field<br />

dependencies point towards the role of martensitic strains in the anomalous behavior.<br />

The compound appears to show the coexistence of FM and AFM comp<strong>on</strong>ents at low<br />

temperatures. The features seen in this compound indicate the presence of disorder in<br />

influencing the magnetic and related properties c<strong>on</strong>siderably. The correlati<strong>on</strong> of various<br />

properties as seen from the martensitic scenario will be presented.<br />

QO05<br />

QO06<br />

QO07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magn<strong>on</strong>ic meta- and meta-meta-materials<br />

Rostislav V. Mikhaylovskiy 1 *, Michal Mruczkiewicz 2 , Maciej Krawczyk 2 and<br />

Volodymyr V. Kruglyak 1<br />

1 School of Physics, University of Exeter, United Kingdom<br />

2 Faculty of Physics, Adam Mickiewicz University, Poznan, Poland<br />

We report <strong>on</strong> magn<strong>on</strong>ic metamaterials represented by a system of magnetic layers<br />

separated by those of a dielectric n<strong>on</strong>-magnetic material. In such a metamaterial, the<br />

c<strong>on</strong>stituent elements are made from a magnetic material that provides an easy way<br />

to c<strong>on</strong>trol its electromagnetic resp<strong>on</strong>se by tuning the bias magnetic field. Firstly, we<br />

report a theory of the effective permeability of planar multilayered metamaterials<br />

c<strong>on</strong>taining thin ferromagnetic layers with magnetizati<strong>on</strong> pinned <strong>on</strong> either <strong>on</strong>e or both<br />

surfaces. The pinning of the magn<strong>on</strong>ic modes at film surfaces facilitates their coupling<br />

to the uniform magnetic field of the incident electromagnetic wave. We dem<strong>on</strong>strate<br />

that such structures, for magnetic parameters characteristic for c<strong>on</strong>venti<strong>on</strong>al transiti<strong>on</strong><br />

metal alloys, exhibit a negative refractive index at sub-THz frequencies. Furthermore,<br />

we show how the c<strong>on</strong>stituent magnetic layers of such systems could themselves be<br />

nanostructured into planar magn<strong>on</strong>ic crystals, with the whole structure therefore<br />

representing a meta-metamaterial. Due to the additi<strong>on</strong>al nanostructuring, the negative<br />

permeability at sub-THz frequencies can be achieved as a result of a small lattice<br />

c<strong>on</strong>stant and lateral quantizati<strong>on</strong> of spin waves. Finally, we discuss the prospects for<br />

fabricati<strong>on</strong> of such metamaterials and their experimental studies.<br />

Understanding the nature of magnetic phase transiti<strong>on</strong> in relevance to<br />

magnetic refrigerati<strong>on</strong><br />

S M Yusuf*<br />

SOLID STATE PHYSICS DIVISION, BHABHA ATOMIC RESEARCH CENTRE,<br />

MUMBAI 400085, India<br />

It is important to understand the nature of magnetic phase transiti<strong>on</strong> for a material suitable for magnetic<br />

refrigerati<strong>on</strong>. With this aim, we have studied a wide class of intermetallic compounds with diversity in their nature<br />

of magnetic ordering and phase transiti<strong>on</strong>, such as ferromagnetic ordering, ferrimagnetic ordering, coexistence<br />

of ferromagnetic and antiferromagnetic ordering, metamagnetic transiti<strong>on</strong>, and magnetostructural transiti<strong>on</strong>. The<br />

dependences of the nature of magnetic phase transiti<strong>on</strong> <strong>on</strong> temperature, magnetic field and chemical substituti<strong>on</strong>s<br />

have been investigated. The role of the nature of exchange interacti<strong>on</strong> and universality class in determining<br />

magnetocatoric effect (MCE) has been brought out by investigating the intermetallic compounds TbCo 2-xFe x and<br />

Mn 4FeGe 3-xSi x. A phase coexistence of ferromagnetic and antiferromagnetic phases has been observed in Cu 1xNi<br />

xMnSb semi-Heusler alloys around x = 0.15 where a large MCE is found as a low applied magnetic field<br />

causes an AFM to FM phase transformati<strong>on</strong>. A broad operating temperature range due to coexistence of AFM<br />

and FM phases, and quenched disorder has also been obtained. The role of other interesting phenomena, such as<br />

metamagnetic transiti<strong>on</strong>s and domain wall pinning in obtaining a large MCE and an inverse MCE, respectively,<br />

has been brought out through the investigati<strong>on</strong> of the intermetallic compounds NdMn 2-xCo xSi 2.<br />

[1] M. Halder, S. M. Yusuf, M. D. Mukadam, and K. Shashikala, Phys. Rev. B 81, 174402 (2010). [2] M.<br />

Halder, S. M. Yusuf, A. Kumar, A. K. Nigam and L. Keller, Phys. Rev. B 84, 094435 (2011). [3] M. Halder, S.<br />

M. Yusuf and A. K. Nigam, J. Appl. Phys. 110, 113915 (2011). [4] M.D. Mukadam, and S.M. Yusuf, Physica B:<br />

C<strong>on</strong>d. Matter 405, 686 (2010). [5] M. D. Mukadam and S. M. Yusuf, J. Appl. Phys. 105, 063910 (2009).<br />

Specific heat study <strong>on</strong> successive magnetic transiti<strong>on</strong>s in α-Dy 2S 3 single<br />

crystal under magnetic fields<br />

Shuji Ebisu*, Yuji Ushiki and Shin Takahashi<br />

Divisi<strong>on</strong> of Applied Sciences, Muroran Institute of Technology, Japan<br />

Specific heat measurements in magnetic fields have been performed <strong>on</strong> α-Dy 2S 3 single<br />

crystal which shows successive magnetic transiti<strong>on</strong>s at TN1 = 11.5 K and TN2 = 6.4<br />

K¹. The specific heat in no magnetic field exhibits sharp peaks at both temperatures<br />

of TN1 and TN2. The change of magnetic entropy at each transiti<strong>on</strong> is estimated as<br />

N0kBln 2 per mole of Dy 2S 3, which suggests Dy moments <strong>on</strong> <strong>on</strong>ly <strong>on</strong>e site between two<br />

crystallographically inequivalent Dy sites order at each transiti<strong>on</strong> temperature. When<br />

the magnetic field is applied al<strong>on</strong>g the b-axis of the orthorhombic system, two peaks of<br />

the specific heat shift toward lower temperatures. On the other hand, the magnetic field<br />

perpendicular to the b-axis shifts the peaks toward higher temperatures. The transiti<strong>on</strong><br />

temperature TN1 shifts to 9.6 K (H//b) and 12.5 K (H┴b) with keeping sharpness of<br />

the peak under the magnetic field of μ0H=2 T. The peak of TN2 broadens gradually<br />

with increasing the magnetic field for each directi<strong>on</strong>, and the peak is c<strong>on</strong>sequently<br />

obscure under the field of 2 T.<br />

¹ S. Ebisu, M. Narumi, M. Gorai and S. Nagata, J. Magn. Magn. Mater. 310, 1741 (2007).<br />

July 8 - 13, 2012 Busan, Korea 127<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QO08<br />

Magneto-inductive wave in periodic chains of ferrite cores and chip<br />

capacitors<br />

Y<strong>on</strong>gmin Kim and Kwang-ho Shin*<br />

Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Kyungsung University, Korea<br />

In this paper, we present a new magneto-inductive wave generated in a chain of<br />

res<strong>on</strong>ators fabricated with ferrite cores and chip capacitors. RF signal propagates to<br />

neighbor res<strong>on</strong>ator <strong>on</strong>e by <strong>on</strong>e as a c<strong>on</strong>sequence of the magnetical coupling between<br />

two res<strong>on</strong>ators in our device. The magnetical coupling is due to the mutual inductances<br />

al<strong>on</strong>g chains of res<strong>on</strong>ators. So, the signal amplitude (? coupling intensity) is inversely<br />

proporti<strong>on</strong>al to the distance between two elements. In order to design the device, some<br />

electromagnetic simulati<strong>on</strong>s and experiments have been carried out systemically.<br />

The transmissi<strong>on</strong> characteristics of a magneto-inductive wave could be c<strong>on</strong>trolled by<br />

applied external magnetic field. For, the device composed of 5 res<strong>on</strong>ance elements,<br />

the center frequencies were estimated to be 41.1 MHz and 34.8 MHz with the external<br />

magnetic flux density of 750.72 G and 2680 G, respectability. The reported result<br />

opens a promising way to a high variety of applicati<strong>on</strong>s in <strong>on</strong>e- and two-dimensi<strong>on</strong>al<br />

functi<strong>on</strong>al devices, such as transducers, delay lines, power dividers and couplers.<br />

QO09<br />

Large refrigerant capacity in Ni2.9Co0.1MnIn type-Heusler alloy<br />

Catalina Salazar Mejia 1 , Angelo M Gomes 1 , Ana Lima Sharma 2 and Fivos R<br />

Drymiotis 3<br />

1<br />

Instituto de Fisica, Universidade Federal do Rio de Janeiro, Brazil<br />

2<br />

Materials Physics Department, Sandia Nati<strong>on</strong>al Laboratory, Livermore, CA, United<br />

States, USA<br />

3<br />

Department of Physics and Astr<strong>on</strong>omy, Clems<strong>on</strong> University, Clems<strong>on</strong>, SC, United<br />

States., USA<br />

Magnetic refrigerati<strong>on</strong> (MR) is a cooling method that is based <strong>on</strong> the magnetocaloric effect (MCE). Our<br />

research effort focuses <strong>on</strong> identifying magnetic structures that may have improved efficiency with suitable<br />

characteristics for MR i.e. good magnetocaloric properties with small or zero thermal and magnetic<br />

hysteresis. Some Heusler alloys may meet these criteria. The Ni 2MnIn full-Heusler alloy exhibits a sec<strong>on</strong>dorder<br />

paramagnetic to ferromagnetic transiti<strong>on</strong> at 300 K, but its MCE is small [1,2]. However, we observe<br />

a large improvement in the refrigerant capacity (RC) value when the Ni 2MnIn is Co and Ni-doped. In this<br />

paper, we present the study of the magnetic, structural and magnetocaloric properties of the Ni 2.9Co 0.1MnIn<br />

Heusler-type alloy. The samples crystallizes in a cubic structure. Magnetizati<strong>on</strong> measurements show a<br />

ferromagnetic transiti<strong>on</strong> at 207 K. The transiti<strong>on</strong> is almost 40 K wide, and thermal hysteresis is negligible.<br />

The magnetic entropy change, ΔSM, for ΔH=5T, was calculated from heat capacity data and the maximum<br />

value found is -2.75 J/kg K, with broad temperature range which leads to RC=261.3 J/kg. The large RC<br />

value found and the absence of thermal hysteresis makes this material a good candidate for magnetic<br />

refrigerati<strong>on</strong> applicati<strong>on</strong>s. C.S.M. and A.M.G. would like to thank CNPq and FAPERJ.<br />

[1] T. Krenke, et al., Phys. Rev. B 73, 174413 (2006). [2] C. Salazar Mejia, et al., unpublished.<br />

QO10<br />

Reducti<strong>on</strong> of weak localizati<strong>on</strong> strength <strong>on</strong> c<strong>on</strong>trolling oxygen defects<br />

by ex-situ annealing<br />

Se<strong>on</strong>g-min Choo 1 , Kyujo<strong>on</strong> Lee 1 , Sungmin Park 1 , Gwang-seo Park 1 , Jungw<strong>on</strong> Jang 2 ,<br />

Jinhee Kim 2 and Myung-hwa Jung 1 *<br />

1 Department of Physics, Sogang university, Korea<br />

2 Korea Research Institute Standard Science, Korea<br />

We have studied Pb-based gapless semic<strong>on</strong>ductors, which are very sensitive to external<br />

parameters such as temperature, pressure, magnetic field, electric field, etc [1]. Based<br />

<strong>on</strong> the theoretical paper, this material has a str<strong>on</strong>g spin-orbit interacti<strong>on</strong>. So, we have<br />

fabricated pure PbPdO 2, Co- and Mn-doped PbPdO 2 thin films. Because a Pb is an<br />

easily vaporized element when we grow the films, the films have a lot of oxygen<br />

vacancies. It may induce other problems. For example, Pd is unstable state as Pd+1<br />

and the oxygen vacancies act as additi<strong>on</strong>al hole carriers. To study intrinsic properties<br />

of doped PbPdO 2 thin films, we tried to various methods to enhance the films quality.<br />

Because Pb is hard to handle in growth process, we have annealed thin films with<br />

different annealing time, temperature, and envir<strong>on</strong>ments after depositi<strong>on</strong>. The carrier<br />

densities for all the samples are deceased with annealing time while the electric<br />

resistivities are changed in different way. More importantly, weak localizati<strong>on</strong> strength<br />

is most likely to be reduced by ex-situ annealing. Furthermore, magnetoresistance ratio<br />

is also reduced by increasing ex-situ annealing time.<br />

128 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QO11<br />

Rec<strong>on</strong>structi<strong>on</strong> of cubic rs-ZnO <strong>on</strong> MgO (200) substrate through 100<br />

plane of w-Zn for transparent electr<strong>on</strong>ic applicati<strong>on</strong><br />

Chungman Kim 1 , Santosh M Bobade 1 , Se<strong>on</strong>g-min Choo 1 , Suhyun Kim 1 , Kyung Ho<br />

Shin 2 and Myung-haw Jung 1 *<br />

1 Sogang University, Korea<br />

2 Korea Institute of Science and Technology, Seoul, Korea<br />

ZnO crystallizes in various crystallographic forms. However, wurtzite (w) ZnO is<br />

generally observed structure while the rock salt (rs) structure of ZnO appear at high<br />

pressure. We present rs-ZnO structure grown <strong>on</strong> MgO (200) substrate at certain<br />

growth envir<strong>on</strong>ments, not high pressure. The lattice c<strong>on</strong>stant of MgO. The possible<br />

c<strong>on</strong>figurati<strong>on</strong>al path for transformati<strong>on</strong> is proposed, so that the compressi<strong>on</strong> of w-ZnO<br />

al<strong>on</strong>g c-axis and movement of Zn or O sublattice al<strong>on</strong>g (110) directi<strong>on</strong> and (110)plane.<br />

These results are c<strong>on</strong>firmed by X-ray diffracti<strong>on</strong> and X-ray photoemissi<strong>on</strong> spectrum<br />

experiments. It has also been observed that rs-ZnO <strong>on</strong> MgO substrate is stable for<br />

certain minimum thickness (in this case, it is 150nm) and possible be stabilize at lower<br />

temperature for few nm thickness<br />

QO12<br />

Magnetic cooling machine prototype based <strong>on</strong> cold rolled Gd foil<br />

Sergey V. Taskaev*, Vasiliy D. Buchelnikov, Victor V. Nikolenko, Ivan A. Chernets<br />

and Andrey N. Denisovsky<br />

Physics department, Chelyabinsk State University, Russia<br />

With the discovery of the “giant magnetocaloric effect“ (Pecharsky and Gschneidner, 1997)<br />

the development of magnetic refrigerati<strong>on</strong> gained increased momentum [1]. One of the<br />

ways of engineering MCE materials is tightly c<strong>on</strong>nected with preparing very thin (a few<br />

micr<strong>on</strong>s) ribb<strong>on</strong>s of high value MCE alloys with good mechanical properties. At present rapid<br />

solidificati<strong>on</strong> is the main technique for producing this kind of materials [2]. In our work we<br />

present magnetic cooling device which is used Gd cold rolled samples of different thickness as<br />

a working body. Magnetocaloric, mechanical and other properties of this material are discussed<br />

Morphology of the surface was investigated by AFM methods. Magnetocaloric effect was<br />

measured by direct method <strong>on</strong> AMT&C setup. Mechanical properties was investigated <strong>on</strong><br />

Netzsch DMA 242C. Magnetic properties was measured <strong>on</strong> SQUID magnetometer. X-ray<br />

analysis was performed <strong>on</strong> Brucker D8 Advance difractometer. Several axial magnetic systems<br />

are proposed as the source of high gradient magnetic field. Depending <strong>on</strong> the air gap of<br />

magnetic system the residual magnetic inducti<strong>on</strong> is in 600 mT..1900 mT range. It is shown, that<br />

cold rolling technique is the alternative way for producing thin ribb<strong>on</strong>s of MCE materials with<br />

good mechanical properties for magnetocaloric applicati<strong>on</strong>.<br />

1.Gschneidner K.A. Jr. et al. Thirty years of near room temperature magnetic cooling: Where we are<br />

today and future prospects, Int. J. Refrig, 31, 945 (2008). 2.P. M. Shan et al. Magnetic behavior of<br />

melt-spun gadolinium, Phys. Rev. B. 77, 184415 (2008).<br />

QO13<br />

Research <strong>on</strong> the orbital state of IrO2 with res<strong>on</strong>ant x-ray scattering<br />

method<br />

Yasuyuki Hirata 1 , Kenya Ohgushi 1 , Junich Yamaura 1 , Hiroyuki Ohsumi 2 , Soshi<br />

Takeshita 2 and Takahisa Arima 3<br />

1<br />

Institute for Solid State Physics, University of Tokyo, Japan<br />

2<br />

RIKEN SPring-8, Japan<br />

3<br />

Department of Advanced Materials Science, University of Tokyo, Japan<br />

In the 5d electr<strong>on</strong> systems of iridium oxides, the crystal fields, the Coulomb repulsi<strong>on</strong>, and<br />

the spin-orbit interacti<strong>on</strong> compete with each other, which results in various exotic physical<br />

properties. For example, magnetic iridium oxides Sr 2IrO 4 and CaIrO 3 are known to be<br />

spin-orbit-induced Mott insulators: the reported res<strong>on</strong>ant x-ray scattering experiments<br />

showed that 5d t2g orbitals of Ir are rec<strong>on</strong>structed by the spin-orbit interacti<strong>on</strong> and realize<br />

the complex Jeff=1/2 orbital states, which form a narrow band and enhance the electr<strong>on</strong><br />

correlati<strong>on</strong>.[1] On the other hand, the orbital states of metallic iridium oxides like IrO 2,<br />

which is attracting attenti<strong>on</strong> for a gigantic spin-Hall effect, are yet to be investigated. We<br />

performed a res<strong>on</strong>ant X-ray scattering measurement for metallic iridium oxide IrO 2 which<br />

has a rutile-type structure, and observed the 0 0 3 reflecti<strong>on</strong> coming from the anisotropic<br />

tensor of susceptibility (ATS). In the energy spectrum the peak corresp<strong>on</strong>ding to the<br />

excitati<strong>on</strong> to 5d t2g orbitals appeared around the L3 absorpti<strong>on</strong> edge, but did not appear<br />

around the L2 absorpti<strong>on</strong> edge. These results indicate that the complex Jeff=1/2 states of<br />

5d t2g orbitals are realized even in metallic iridium oxides IrO 2.<br />

[1] B. J. Kim et al., Science 323, 1329 (2009).


QO14<br />

Investigati<strong>on</strong> of magnetic-field tunable properties of<br />

magnetorheological elastomers<br />

Nikolai Perov 1 *, Anna Semisalova 1 , Elena Yu Kramarenko 1 , Alexey R Khokhlov 1 and<br />

Gennady V Stepanov 2<br />

1 Lom<strong>on</strong>osov Moscow State University, Russia<br />

2 State Research Institute for Chemistry and Technology of Organoelement<br />

Compounds, Moscow, Russia<br />

In this work we present the results of investigati<strong>on</strong> of magnetic field influence <strong>on</strong> the<br />

value of dielectric permittivity and magnetic susceptibility in magnetorheological<br />

elastomers (MRE) based <strong>on</strong> the powders with various magnetic properties - Fe, FeNdB<br />

and Fe 3O 4. Both magnetic susceptibility and dielectric permittivity have been found to<br />

be c<strong>on</strong>siderably changed under magnetic field, the changing of permittivity value up to<br />

150% has been observed. The field dependence of the dynamic dielectric permittivity<br />

was significantly n<strong>on</strong>-linear. The anisotropy of field influence <strong>on</strong> the permittivity and<br />

susceptibility was observed as well. The saturati<strong>on</strong> magnetizati<strong>on</strong> and coercivity of the<br />

magnetic fillers have been shown to be the most important factors affecting the field<br />

dependence of permittivity. In additi<strong>on</strong>, the size and c<strong>on</strong>centrati<strong>on</strong> of particles as well as<br />

c<strong>on</strong>ductivity of magnetic material have significant influence <strong>on</strong> the type of field effect.<br />

The influence of named parameters <strong>on</strong> the permittivity and susceptibility changing is<br />

discussing; we c<strong>on</strong>sider the mechanisms determining the features of magnetic field<br />

influence <strong>on</strong> studied physical properties in detail. It is shown that MRE based <strong>on</strong> various<br />

magnetic particles can be c<strong>on</strong>sidered as promising materials with magnetic-field tunable<br />

properties. Supported by Russian Foundati<strong>on</strong> for Basic Research.<br />

QO15<br />

Disagreement between modificati<strong>on</strong> methods for magnetism-absorbing<br />

agent<br />

Wu Chao, Lv Xuliang*, Zeng Zhaoyang, Wen Xiaodi and Wen Liuqiang<br />

PLA University of Science and Technology, China<br />

Two methods are widely used to improve absorbing properties of the microwave<br />

magnetism-absorbing agent: mixing with the other material such as resistance<br />

carb<strong>on</strong> fiber absorbent, or wrapping the microwave magnetism-absorbing agent<br />

in that material. However, do these two methods coincide with each other? If not,<br />

which method should be used as better way to represent the absorbing properties of<br />

magnetism-absorbing agents? To answer these questi<strong>on</strong>s, both methods are carried out<br />

<strong>on</strong> the same magnetism-absorbing agents, of which the results are compared. Distinct<br />

difference between these measured results is found, and the possible reas<strong>on</strong>s for the<br />

difference are also discussed.<br />

QO16<br />

Ordered magnetic arrays of cobalt SMM: properties and the<br />

relati<strong>on</strong>ship with crystal symmetry and SMM envir<strong>on</strong>ment<br />

Milagros Tomas 1 , Cristina Saenz De Pipa<strong>on</strong> 2 , Elena Forcen-vazquez 2 , Isabel Mayoral 2 ,<br />

Larry Falvello 3 , Javier Campo 2 and Fernando Palacio 4 *<br />

1 Instituto de Sintesis Quimica y Catalisis Homogenea (ISQCH), C<strong>on</strong>sejo Superior de<br />

Investigaci<strong>on</strong>es Cientificas and University of Zaragoza, Spain<br />

2 Instituto de Ciencia de Materiales de Arag<strong>on</strong>, C<strong>on</strong>sejo Superior de Investigaci<strong>on</strong>es<br />

Cientificas and University of Zaragoza, Spain<br />

3 Departamento de Quimica Inorganica and Instituto de Ciencia de Materiales de Arag<strong>on</strong>,<br />

C<strong>on</strong>sejo Superior de Investigaci<strong>on</strong>es Cientificas and University of Zaragoza, Spain<br />

4 Instituto de Ciencia de Materiales de Arag<strong>on</strong> (ICMA), C<strong>on</strong>sejo Superior de<br />

Investigaci<strong>on</strong>es Cientificas and University of Zaragoza, Spain<br />

The modulati<strong>on</strong> of the magnetic properties of SMMs and their organizati<strong>on</strong> in extended magnetic arrays<br />

are, at the present, some of the top areas in the field of molecular magnetism for the implicati<strong>on</strong> in the<br />

improvement of the physical properties of the SMM and the potential use in devices such as for data<br />

storage. Few polymers of SMM have been structurally characterized in spite of the number of known<br />

SMM. [Co4citrate4]8- cubanes can behave as SMM.(1) We have reported recently(2) the uni<strong>on</strong> of<br />

these cubanes through “Co(H 2O) 2ETG” (ETG=ethylene glycol) bridges and the formati<strong>on</strong> of ani<strong>on</strong>ic<br />

2D layers. These layers crystallize in the tetrag<strong>on</strong>al system, P-421c space group, with counteri<strong>on</strong>s (Cs +<br />

or Rb + ), water and ETG molecules c<strong>on</strong>necting the layers though electrostatic interacti<strong>on</strong>s and hydrogen<br />

bridges. The magnetic studies show the co-existence of two magnetic nets: the SMM net and the <strong>on</strong>e<br />

formed by the bridged cobalt atoms and also shows the influence of the counteri<strong>on</strong>s in the layer magnetic<br />

properties. Two intriguing relaxati<strong>on</strong> processes with different characteristics timescales are observed.<br />

Moreover, [Co4citrate4]8- cubanes can also organize in 3D, diam<strong>on</strong>d-like structural arrays showing<br />

SMM magnetic behaviour below 6K with an energy barrier of 54K and magnetic ordering below 2.7K.<br />

1- M. Murrie, Chem. Soc. Rev. 2010, 39, 1986 -1995. 2- E. Burzuri, J. Campo, L. Falvello, E. Forcen-Vazquez, F.<br />

Luis, I. Mayoral, F. Palacio, Cristina Saenz de Pipa<strong>on</strong>, M. Tomas. Chem. Eur. J. 2011, 17, 2818-2822.<br />

QO17<br />

QO18<br />

QO19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Enhancement of the refrigerant capacity in Gd 65Fe 20Al 10B 5 alloys by<br />

partial crystallizati<strong>on</strong> of melt-spun amorphous ribb<strong>on</strong>s<br />

Jozef Marcin 1 , Zbigniew Sniadecki 2 , Jozef Kovac 1 , Peter Svec 3 , Bogdan Idzikowski 2<br />

and Ivan Skorvanek 1 *<br />

1 Institute of Experimental Physics SAS, Kosice, Slovak<br />

2 Institute of Molecular Physics PAS, Poznan, Poland<br />

3 Institute of Physics SAS, Bratislava, Slovak<br />

The magnetocaloric effect (MCE) is attracting a great deal of scientific interest because it is a basis of the<br />

envir<strong>on</strong>mentally friendly magnetic refrigerati<strong>on</strong> technology. Am<strong>on</strong>g the recently developed magnetic<br />

refrigerant materials, the Gd(Fe,Mn)Al-based glassy alloys combine good magnetic entropy characteristics<br />

with sufficiently high effective magnetic moment per volume, which makes them promising candidates<br />

for magnetic refrigerati<strong>on</strong> in the operating temperatures around 150 K [1,2]. In this work, we report <strong>on</strong> the<br />

beneficial effect of partial crystallizati<strong>on</strong> <strong>on</strong> magnetocaloric properties of melt-spun Gd 65Fe 20Al 10B 5 alloys. The<br />

magnetic entropy changes, ΔSm, were calculated from the magnetizati<strong>on</strong> versus applied field dependences<br />

measured in the temperature range from 5 to 390 K. The value of the maximum magnetic entropy change<br />

under 50 kOe for the Gd 65Fe 20Al 10B 5 ribb<strong>on</strong> reached 5.01 J/kg K at 185 K. The corresp<strong>on</strong>ding value of the<br />

refrigerati<strong>on</strong> capacity, RC, determined as the area below the ΔSm peak with the integrati<strong>on</strong> limits at its half<br />

maximum is 647 J/kg. We have found that this value can be further enhanced by suitable heat treatment<br />

of melt-spun ribb<strong>on</strong>s leading to a formati<strong>on</strong> of hexag<strong>on</strong>al Gd particles with higher Curie temperature. The<br />

observed improvement is discussed in relati<strong>on</strong> with two-phase character of partially crystallized samples.<br />

[1] S. Gorsse, B. Chevalier, G. Orveill<strong>on</strong>, Appl. Phys. Lett. 92 (2008) 122501 [2] Y.K. Fang, C.H.<br />

Lai, C.C. Hsieh, X.G. Zhao, H. W. Chang, W.C. Chang W.Li, J. Appl. Phys. 107 (2010) 09A901<br />

Chemical pressure effects <strong>on</strong> half-metallic properties in single crystals<br />

of A 2FeMoO 6 (A = Ca, Sr, and Ba)<br />

Akira Isayama* and Takao Sasagawa<br />

Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

An ordered double perovskite oxide Sr 2FeMoO 6 has been predicted and widely studied<br />

as a half-metal, in which electr<strong>on</strong>s with <strong>on</strong>ly <strong>on</strong>e spin directi<strong>on</strong> present at the Fermi<br />

level (100% spin polarizati<strong>on</strong>), above room temperature. In this study, in order to<br />

improve the half-metallic properties, the chemical pressure effects, through A-site<br />

substituti<strong>on</strong>, <strong>on</strong> the magnetic and electr<strong>on</strong>ic properties have been examined using single<br />

crystalline samples of A2FeMoO 6 (A = Ca, Sr, and Ba) grown by the floating z<strong>on</strong>e<br />

method. In the A = Ca crystal, every property related to the half-metallic performance<br />

was found to be degraded as compared with the A = Sr and Ba crystals: the saturati<strong>on</strong><br />

magnetizati<strong>on</strong> and the Curie temperature were significantly decreased, metallic<br />

c<strong>on</strong>ductivity became more than twice larger, and the spin polarizati<strong>on</strong> (evaluated by<br />

Andreev reflecti<strong>on</strong> spectroscopy) was reduced below 50%. From the results in the<br />

A = Sr and Ba crystals, it is suggested that the optimized half-metallic performance<br />

will be obtained in between these two compositi<strong>on</strong>s. Optical measurements were also<br />

performed to gain insight into the change of electr<strong>on</strong>ic structures with respect to the<br />

A-site substituti<strong>on</strong>.<br />

Magnetic label field collector of biochip sensor<br />

Sunj<strong>on</strong>g Oh, Brajalal Sinha, Jaein Lim and Chelgi Kim*<br />

Department of Materials Science and Engineering, Center for NanoBioengineering<br />

and Spintr<strong>on</strong>ics, Chungnam Nati<strong>on</strong>al University, Korea<br />

We have proposed a new method called stray field collector (SFC) of magnetic labels<br />

for signal enhancement in the magnetoresistive biosensors. The proposed design related<br />

to qualitative as well as quantitative detecti<strong>on</strong> of magnetic beads. The integrati<strong>on</strong> of<br />

SFC in magnetic sensor will increase the amount of stray field via the increase of active<br />

surface area. Therefore, this SFC may have great potential to improve the performance<br />

of magnetic biosensor.<br />

[1] Adarsh Sandhu, et al, “High efficiency Hall effect micro-biosensor platform for detecti<strong>on</strong><br />

of magnetically labeled biomolecules,” Biosensors and Bioelectr<strong>on</strong>ics, 22, 2115-2120, 2007.<br />

[2] Guanxi<strong>on</strong>g Li, et al, “Spin valve sensors for ultrasensitive detecti<strong>on</strong> of superparamagnetic<br />

nanoparticles for biological applicati<strong>on</strong>s,” Sens Actuators A Phys., 126(1), 98-106, 2006. [3] W.<br />

Clark Griffith, et al, “Miniature atomic magnetometer integrated with flux c<strong>on</strong>centrators,” Applied<br />

Physics Letters, 94, 023502, 2009.<br />

July 8 - 13, 2012 Busan, Korea 129<br />

Poster Tuesday


Poster Tuesday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

QO20<br />

Cogging torque cancellati<strong>on</strong> technique for dual rotor type motor using<br />

adjustment between outer and inner rotor magnet angle.<br />

Tae W<strong>on</strong> Je<strong>on</strong>g 1 , Hyun Rok Cha 1 *, Dae Ye<strong>on</strong>g Im 1 , Kwang He<strong>on</strong> Kim 2 and Hyoung<br />

Uk Nam 1<br />

1 Automotive comp<strong>on</strong>ents R&D group, korea institute of industrial technology, Korea<br />

2 Department of Electrical Engineering University of the Ch<strong>on</strong>nam, Korea<br />

In this paper, we design the IPM motor and discuss the design method of double rotor permanent<br />

magnet motor for cancelling the cogging torque. According to downsizing the electric motor, high torque<br />

and power density are the most serious requirements for electric machines. Double rotor permanent<br />

magnet motor is proposed to solve the problem. But it has a large cogging torque that generates the<br />

large acoustic noise. A variety of techniques exist for reducing the cogging torque of c<strong>on</strong>venti<strong>on</strong>al radial<br />

flux IPM machines. This paper introduces a new cogging torque minimizati<strong>on</strong> technique for radial flux<br />

multiple IPM motors. Optimizati<strong>on</strong> of the adjustment magnet angle between outer rotor and inner rotor<br />

which results in offset cogging torque and assessment of the effect <strong>on</strong> the maximum available torque<br />

using Finite Element Analysis (FEA) is investigated. In our experiments, Prototype dual rotor type<br />

motor has achieved the outer rotor and inner rotor cancellati<strong>on</strong> of cogging torque by 70 percent.<br />

[1] R. Qu and T. A. Lipo, 'Dual-rotor, radial-flux, toroidally wound, permanent-magnet machines',<br />

IEEE Transacti<strong>on</strong>s <strong>on</strong> Industry Applicati<strong>on</strong>s, Vol. 39, No.6, Nov/Dec 2003, pp.1655-1673. [2] R.<br />

Qu, and T. A. Lipo, 'Design and parameter effect analysis of dualrotor, radial-flux, toroidally wound,<br />

permanent-magnet machines', IEEE Transacti<strong>on</strong>s <strong>on</strong> Industry Applicati<strong>on</strong>s, Vol. 40, No.3, May/<br />

June 2004, pp.771-779 [3] R. Qu and T. A. Lipo, 'Sizing Equati<strong>on</strong>s and Power Density Evaluati<strong>on</strong><br />

of Dual-Rotor, Radial-Flux, Toroidally Wound, Permanent-Magnet Machines,' XVI <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Electrical Machines, ICEM 200r, Cracow, Poland, Sept 2004.<br />

QO21<br />

A broadband circuit analog absorber based <strong>on</strong> printed dipole antenna<br />

Li Xiaopeng 1 , Cui Chuan'an 1 , Lv Xuliang 1 * and Lin Shaofeng 2<br />

1 Engineering Institute of Corps of Engineers,PLA University of Science and<br />

Technology, China<br />

2 Xi'an Communicati<strong>on</strong> Institute, China<br />

Based <strong>on</strong> the equivalent transmissi<strong>on</strong> line theory, a composite absorber with broadband<br />

planar array antenna is designed. The first layer is an array antenna, which uses<br />

printed dipole with balun feed as basic unit. The sec<strong>on</strong>d layer a PIN diode array,<br />

which corresp<strong>on</strong>ded with antenna feeding units. The impedance match characteristic<br />

of the absorber can be adjusted by setting the microstrip balun. And the reflecti<strong>on</strong><br />

characteristic of the absorber can be adjusted by adjusting the bias voltage of the PIN<br />

diode array. Simulated by electromagnetic simulati<strong>on</strong> software HFSS, the results show<br />

that the absorber reflecti<strong>on</strong> coefficient is below -10dB at 3.5-15GHz.The experimental<br />

result, which replace PIN diodes with surface mount device resistors, is in good<br />

agreement with simulati<strong>on</strong> data.<br />

QO22<br />

Effect of oxygen pressure to magnetism and transport properties of<br />

epitaxial Fe 3O 4 grown by molecular beam epitaxy<br />

Dang Duc Dung 1 , Wuwei Feng 2 , Du<strong>on</strong>g Van Thiet 3 , Du<strong>on</strong>g Anh Tuan 3 and Sunglae<br />

Cho 3 *<br />

1 Department of General Physics, School of Engineering Physics,Ha Noi University of<br />

Science and Technology,1 Dai Co Viet road, Ha Noi, Viet Nam<br />

2 Department of Physics, University of Ulsan, Ulsan 680-749,, Korea<br />

3 Department of Physics, University of Ulsan, Ulsan 680-749, Korea<br />

Fe 3O 4 is predicted to possess as half-metallic nature, ~ 100% spin polarizati<strong>on</strong>, and has a high Curie temperature<br />

and an ultrahigh room temperature magnetoresistance (MR) for tunneling magnetoresistance (TMR) juncti<strong>on</strong>s<br />

with Fe 3O 4 electrodes [1]. However, for the TMR juncti<strong>on</strong>, a highly c<strong>on</strong>ductive under layer and the sharp between<br />

interfaces are required because the poor c<strong>on</strong>ductivity and roughness of films may lead to a n<strong>on</strong>-uniform current<br />

distributi<strong>on</strong> [2]. In additi<strong>on</strong>, the Verwey transiti<strong>on</strong> (TV, a first order metal-insulator transiti<strong>on</strong>) of 120 K in bulk<br />

Fe 3O 4 is still under c<strong>on</strong>troversy because many parameters such as orientati<strong>on</strong> of substrate, buffer layer, thickness,<br />

pressure, and thermo-chemical treatment affect the TV [3, 4]. Epitaxial Fe 3O 4 films were grown <strong>on</strong> MgO(001)<br />

substrates via molecular beam epitaxy. The growth modes, magnetism, and transport properties of the thin films<br />

were str<strong>on</strong>gly dependent <strong>on</strong> the oxygen pressure during film growth. The average roughness decreased from 1.021<br />

to 0.263 nm when the oxygen pressure was increased from 2.3x10-7 to 8.2x10-6 Torr, respectively. In additi<strong>on</strong>,<br />

the saturati<strong>on</strong> magnetic moment reduced as increasing the oxygen pressure during grown. Moreover, the Verwey<br />

transiti<strong>on</strong> in the Fe 3O 4 disappeared for a sample grown at a high oxygen pressure.<br />

[1] Z. Zhang et al., Phys. Rev. B 44, 13319 (1991). [2] P. H. Huang et al., J. Appl. Phys. 97, 10C311 (2005). [3] E. J. W.<br />

Verwey et al., Physica 8, 979 (1941). [4] A. R. Muxworthy et al., Geophys. J. Int. 140, 101 (2000), and reference therein.<br />

130 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QO23<br />

<strong>Magnetism</strong> and transport properties of epitaxial Mn 5Ge 3 thin films <strong>on</strong><br />

GaAs(001) and GaSb(001)<br />

Dang Duc Dung 1 , Doji Odkhuu 2 and Sunglae Cho 2 *<br />

1 Department of General Physics, School of Engineering Physics, Ha Noi University<br />

of Science and Technology,1 Dai Co Viet road,Ha Noi, Viet Nam<br />

2 Department of Physics, University of Ulsan, Ulsan 680-749, Korea<br />

The epitaxially ferromagnetic Mn 5Ge 3 thin films were grown <strong>on</strong> GaSb(001) and<br />

GaAs(001) substrates using molecular beam epitaxy. Our result revealed that the<br />

substrate facilitates to modify magnetic and electrical properties due to tensile strain<br />

effect. The Curie temperature was remained above 350 K for samples grown <strong>on</strong><br />

GaAs(001), while was about 320 K for samples grown <strong>on</strong> GaSb(001). The anomalous<br />

Hall effect were observed up to 370 K and 320 K for films grown <strong>on</strong> GaAs(001)<br />

and GaSb(001), respectively, which are str<strong>on</strong>g evidence for spin polarizati<strong>on</strong>. Our<br />

electr<strong>on</strong>ic calculati<strong>on</strong> indicated that the difference in Mn-Mn b<strong>on</strong>d length in Mn 5Ge 3<br />

modified the magnetizati<strong>on</strong> and spin polarizati<strong>on</strong>. The strains are promised to c<strong>on</strong>trol<br />

both magnetic properties and spin polarizati<strong>on</strong>.<br />

QO24<br />

Current-driven domain wall moti<strong>on</strong> in artificial magnetic domain structures<br />

Ke Wang 1 , Murali Krishnan Hari 1 *, Sim<strong>on</strong> Bending 1 , Erhan Arac 2 , Del Atkins<strong>on</strong> 2 ,<br />

Serban Lepadatu 3 , J S Clayd<strong>on</strong> 3 and Chris Marrows 3<br />

1 Department of Physics, University of Bath, United Kingdom<br />

2 Department of Physics, University of Durham, United Kingdom<br />

3 School of Physics and Astr<strong>on</strong>omy, University of Leeds, United Kingdom<br />

We report progress towards optimisati<strong>on</strong> of artificial magnetic domain structures for efficient spin transfer torque<br />

domain wall (DW) moti<strong>on</strong> [1]. Co/Pt multilayer samples have been sputtered <strong>on</strong> (100) Si/SiO 2 substrates and<br />

perpendicular magnetic anisotropy c<strong>on</strong>firmed using polar magneto-optical Kerr effect (MOKE) measurements.<br />

The influence of the thickness of Co and Pt layers <strong>on</strong> the coercivity and switching behaviour was systematically<br />

investigated and the c<strong>on</strong>diti<strong>on</strong>s established for realising well-suited structures with medium coercivity (~100<br />

Oe) and sharp switching fields [2]. Optimised Co/Pt multilayer films were lithographically patterned into<br />

nanowire devices for time-resolved extraordinary Hall effect (EHE) measurements. Our devices are based <strong>on</strong><br />

50 W coplanar waveguides incorporating single and double Hall cross structures. The coercivity of the regi<strong>on</strong><br />

surrounding the Co/Pt Hall crosses was reduced by local focussed i<strong>on</strong> beam (FIB) irradiati<strong>on</strong> [3] allowing<br />

the c<strong>on</strong>trolled nucleati<strong>on</strong> of domain walls at the edges of these regi<strong>on</strong>s by applicati<strong>on</strong> of an appropriate field<br />

sequence. We describe polar MOKE experiments that show how DC currents lead to asymmetric switching of<br />

these artificial domains due to current-assisted DW moti<strong>on</strong> across them. We will also present preliminary results<br />

of time-resolved EHE and MOKE measurements of current-driven DW moti<strong>on</strong> in these structures.<br />

[1] O. Boulle et.al, Phys. Rev. Lett. 101, 216601 (2008); I.M. Mir<strong>on</strong>, P.-J. Zermatten, G. Gaudin, S. Auffret, B.<br />

Rodmacq, and A. Schuhl, Phys. Rev. Lett. 102, 137202 (2009); L. San Emeterio Alvarez, K.Y. Wang, S. Lepadatu, S.<br />

Landi, S. J. Bending, and C. H. Marrows, Phys. Rev. Lett. 104, 137205 (2010) [2] K. Wang, M-C. Wu, S. Lepadatu, J. S.<br />

Clayd<strong>on</strong>, C.H. Marrows, and S. J. Bending, J. Appl. Phys. 110, 083913 (2011). [3] A. Aziz et.al, J. Appl. Phys. 98,<br />

QO25<br />

The cellular uptake mechanism of SPIONs: an in-vitro study<br />

Yasmin Khan 1 and Radha Srinivasan 2 *<br />

1 Department of Life Sciences, Sophia College, Mumbai, India<br />

2 Department of Physics, University of Mumbai, India<br />

The Superparamagnetic Ir<strong>on</strong> Oxide Nanoparticles of sizes ranging from 10-50 nm<br />

are being used in a large number of biological studies because of their peculiar<br />

characteristics of inducing local hyperthermia, MR imaging, specific targeting and<br />

drug delivery. An in-vitro study of the cytotoxicity and an understanding of the specific<br />

pathway of cellular uptake will enable manipulati<strong>on</strong> of c<strong>on</strong>diti<strong>on</strong>s for optimal cellular<br />

uptake of SPIONs for targeted therapy. The objective of the present study was to<br />

identify the endocytotic pathway through which the SPIONs are taken up by C6 glioma<br />

cells. The cells were pre-incubated with different c<strong>on</strong>centrati<strong>on</strong>s of pharmacological<br />

inhibitors and then exposed to SPIONs for a few hours. The endocytosed particles were<br />

localized and quantitatively estimated using Perl's or Prussian Blue reacti<strong>on</strong>. There<br />

was significant reducti<strong>on</strong> in the uptake of SPIONs when incubated with the inhibitor<br />

indicating the uptake of nanoparticles is being inhibited.This reducti<strong>on</strong> in SPION<br />

uptake was found to be dependent <strong>on</strong> the c<strong>on</strong>centrati<strong>on</strong> of the inhibitors and also the<br />

nature of the inhibitors. By a systematic study of choosing various inhibitors, the data<br />

can be narrowed down to the final pathway that may be involved in the SPION uptake.


QO26<br />

Theoretical and experimental studies of valence states in Fe-Mo<br />

compounds<br />

Francisco Estrada 1 *, Reginaldo M<strong>on</strong>drag<strong>on</strong> 1 , Humberto Noverola 2 , Jaime Raul<br />

Suarez 3 , Martha Teresita Ochoa 1 , Francisco Espinosa 1 , Lorena Alvarez 1 , Ricardo<br />

Morales 4 , Jose Lemus 4 , Oracio Navarro 2 and Michel Avign<strong>on</strong> 3<br />

1<br />

Centro de Investigaci<strong>on</strong> en Materiales Avanzados, S. C, Mexico<br />

2<br />

Instituto de Investigaci<strong>on</strong>es en Materiales, Universidad Naci<strong>on</strong>al Aut<strong>on</strong>oma de<br />

Mexico, Mexico<br />

3<br />

Institut Neel, CNRS and Universite Joseph Fourier, France<br />

4<br />

Instituto de Investigaci<strong>on</strong>es Metalurgicas, UMSNH, Mexico<br />

The half-metallic ferromagnetic double perovskite compound Sr 2FeMoO 6 is c<strong>on</strong>sidered as an<br />

important material in view of its potential spintr<strong>on</strong>ic applicati<strong>on</strong>s. It appears to be fundamental to<br />

understand the role of electr<strong>on</strong>ic parameters c<strong>on</strong>trolling the half-metallic ground state. In particular,<br />

half-metallic ferromagnetic compounds have been searched as a source of spin polarized currents. In<br />

this work, we study the valence states of cati<strong>on</strong>s in Fe-Mo based double perovskites from theoretical<br />

and experimental point of view. In the experimental case, we apply the electr<strong>on</strong> energy-loss<br />

spectroscopy (EELS) technique. For transiti<strong>on</strong> metals, L2,3 edges of EELS are characterized by two<br />

sharp peaks, known as white lines. EELS experiments have shown that the change in valence states<br />

of cati<strong>on</strong>s introduces significant modificati<strong>on</strong> in the energy and shape of the white lines, leading to the<br />

possibility of identifying cati<strong>on</strong> valence states. These results are compared with those coming from<br />

theoretical calculati<strong>on</strong> using the Green functi<strong>on</strong>s and the renormalizati<strong>on</strong> perturbati<strong>on</strong> expansi<strong>on</strong><br />

method. The theoretical model is based <strong>on</strong> a correlated electr<strong>on</strong> picture with localized Fe-spins and<br />

c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s interacting with the local spins via a double-exchange-type mechanism.<br />

QO27<br />

Structural modificati<strong>on</strong>s in magnetic MWCNT by 100 MeV SHI<br />

irradiati<strong>on</strong>s<br />

Sanjeev Gautam 1 , Keun Hwa Chae 1 , J<strong>on</strong>g Han S<strong>on</strong>g 1 , Saji Augstine 2 , J.k. Kang 2 and K.<br />

Asokan 3<br />

1<br />

Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Korea<br />

2<br />

Material Science and Engineering, Korea Advanced Institute of Science and<br />

Technology (KAIST), Korea<br />

3<br />

Material Science Center, Inter-University Accelerator Center, New Delhi, India<br />

Carb<strong>on</strong> nanotubes (CNTs) possess unique mechanical and electr<strong>on</strong>ic properties suitable for<br />

fabricating the nano-scale building blocks of nanodevices [1]. One of the requirements for<br />

applicati<strong>on</strong>s is to cut the CNT in small dimensi<strong>on</strong>s in the order of few nanometers. To this<br />

respect, we investigate the effect of heavy i<strong>on</strong> beams, namely, 100 MeV of O and Ni i<strong>on</strong> beam<br />

<strong>on</strong> CNT synthesized by chemical vapor depositi<strong>on</strong> (CVD) technique[2]. The i<strong>on</strong> fluence<br />

selected for this study was 1e13 i<strong>on</strong>s per cm 2 . High energy heavy i<strong>on</strong> irradiati<strong>on</strong> was carried out<br />

at Inter-University Accelerator Centre, New Delhi, India. This paper reports the experimental<br />

results obtained from X-ray diffracti<strong>on</strong> pattern and images of scanning electr<strong>on</strong> microscopy<br />

(SEM) and transmissi<strong>on</strong> electr<strong>on</strong> microscope (TEM) measured at Nano Materials Analysis<br />

Center, KIST, Korea. These results show that heavy i<strong>on</strong>s can induce damage or cut in an<br />

ordered periodicity of few nanometers. Apart from above studies, we also carried out near-edge<br />

x-ray absorpti<strong>on</strong> spectroscopy investigati<strong>on</strong>s for electr<strong>on</strong>ic structure modificati<strong>on</strong>s.<br />

[1] E. Wohlfarth, in: G. Rado, H. Suhl (Eds.), <strong>Magnetism</strong>,Vol. 3 (Acad Press, New York, 1963). [2]<br />

Gautam S, Thakur P, Augustine S, Kang JK, Kim JY, et al. arXiv: 1111.5416v1 (Nov. 23 2011).<br />

QO28<br />

Magnetic and magneto-transport properties of (Mn 0.8, Zn 0.2) 1-xGa xFe 2O 4<br />

ferrites<br />

Hyo-jin Kim and Sang-im Yoo*<br />

Department of Materials Science and Engineering, Seoul Nati<strong>on</strong>al University, Korea<br />

A significant enhancement of low-field magnetoresistance (LFMR) could be achieved<br />

from polycrystalline samples of Ga 2O 3-doped Mn-Zn ferrites. For this study, the<br />

magnetic and magnetotransport properties of samples with two different nominal<br />

compositi<strong>on</strong>s of (Mn 0.8, Zn 0.2) 1-xGa xFe 2O 4 (x = 0.05, 0.1) were carefully investigated.<br />

The X-ray diffracti<strong>on</strong> analyses revealed that all Ga 2O 3-doped Mn-Zn ferrites of the<br />

spinel structure were a pure phase without the sec<strong>on</strong>d phase. By doping Ga 2O 3 to the<br />

pure Mn-Zn ferrite, the resistivity level was abruptly decreased over four orders of<br />

magnitude. The 5 mol% Ga 2O 3-doped Mn-Zn ferrite sample exhibited the LFMR ratio<br />

over 1.7 % at 300 K in 0.5 k Oe without appreciable increase in its resistivity. Detailed<br />

doping effects of Ga 2O 3 <strong>on</strong> the magnetic and maneto-transport properties of the Mn-Zn<br />

ferrite will be presented and discussed in this paper.<br />

QP01<br />

QP02<br />

QP03<br />

Effect of the external fields <strong>on</strong> SpinRAM switching time<br />

Mitsuhiro Shiomi* and Yoshinobu Nakatani<br />

Univ. of Electro- Communicati<strong>on</strong>s, Japan<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic coupling at the CoO/Ni interface<br />

Sergiy Grytsyuk*, Fabrizio Cossu and Udo Schwingenschlogl<br />

Physical Sciences and Engineering, King Abdullah University of Science &<br />

Technology, Saudi Arabia<br />

We study the CoO/Ni interface. Since the lattice mismatch between Ni and CoO is<br />

21%, we use a large supercell for our first principles calculati<strong>on</strong>s which reduces the<br />

lattice mismatch to 0.8%. We investigate the structural, electr<strong>on</strong>ic, and magnetic<br />

properties of two interface c<strong>on</strong>figurati<strong>on</strong>s: (1) An O layer mediates the coupling<br />

between Ni and Co and (2) a direct Ni-Co c<strong>on</strong>tact. Our results indicate that the<br />

magnetizati<strong>on</strong> is reduced by 19% in the first case, while in the sec<strong>on</strong>d case it increases<br />

by 100% as compared to bulk Ni. The magnetic moments obtained at the interfaces<br />

can be explained by the local envir<strong>on</strong>ment of the interface atoms. In additi<strong>on</strong>, we find<br />

effects of charge transfer between the interface atoms.<br />

Electr<strong>on</strong>ic, structural, and magnetic properties of O and Py deficient<br />

CoO/Py interfaces.<br />

Sergiy Grytsyuk* and Udo Schwingenschlogl<br />

Physical Sciences and Engineering, King Abdullah University of Science &<br />

Technology, Saudi Arabia<br />

The development of magnetic devices, which are based <strong>on</strong> coupling between<br />

ferromagnet and antiferromagnet (such as spin-valves), depends str<strong>on</strong>gly <strong>on</strong> the<br />

interfacial magnetic structure. Since vacancies at the interface are expected to be<br />

important in determining the macroscopic properties of such systems, a quantitative<br />

determinati<strong>on</strong> of their influence <strong>on</strong> the interfacial magnetizati<strong>on</strong> is essential. We<br />

therefore investigate the CoO/Py interface (Py = Ni 80Fe 20, Permalloy). Py has a high<br />

permeability, low magnetostricti<strong>on</strong>, and high anisotropic magnetoresistance. It is a<br />

good c<strong>on</strong>ductor for spin-majority electr<strong>on</strong>s and poor c<strong>on</strong>ductor for spin-minority<br />

electr<strong>on</strong>s. At the same time the Neel temperature of CoO is approximately room<br />

temperature and its magnetocrystalline anisotropy is high. Since the lattice mismatch<br />

between Py and CoO is about 20%, we use a large supercell for our first principles<br />

calculati<strong>on</strong>s which reduces the lattice mismatch to less than 0.1%. We describe the<br />

dependence of the interface magnetizati<strong>on</strong> <strong>on</strong> the amount of O and Py vacancies and<br />

address the exchange bias.<br />

Spin current driven magneto resistive random access memory (SpinRAM) is <strong>on</strong>e of the<br />

candidates for the next generati<strong>on</strong> n<strong>on</strong> volatile memory. There are still many problems<br />

to realize it. One of the problems is the switching speed. The method for fast switching<br />

with lower current is required. Field assist switching is <strong>on</strong>e way. In this paper, the<br />

effect of the DC and AC external field <strong>on</strong> the switching time of the SpinRAM with<br />

perpendicular anisotropy is investigated by simulati<strong>on</strong>. The effect of the thermal noise<br />

is also investigated. From the results without thermal noise, the switching time was<br />

decreased by both of the DC and AC field. However, AC field is effective for fast<br />

switching compared with DC field. From the results with thermal noise, the switching<br />

time was not decreased by weak DC field and more str<strong>on</strong>g DC field was required to<br />

reduce the switching time. On the other hand, the switching time was decreased by<br />

weak AC field. From these results, it was found that AC field is more effective than<br />

DC field to reduce the switching time. This study was supported by New Energy and<br />

Industrial Technology Development organizati<strong>on</strong> (NEDO) partly.<br />

July 8 - 13, 2012 Busan, Korea 131<br />

Poster Tuesday


Poster Tuesday<br />

QP04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A study <strong>on</strong> the perpendicular toggle-MRAM system by using new<br />

combined hysteresis method for high Gb/Chip<br />

Hyuk W<strong>on</strong> and Gwan Soo Park*<br />

School of Electrical Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

C<strong>on</strong>venti<strong>on</strong>al (toggle) MRAM has unlimited read/write endurance but has a low<br />

capacity than flash technology. A lot of work has been d<strong>on</strong>e for the commercializati<strong>on</strong><br />

of submicrometer MRAM in recent years. A low-power 1Mb MRAM with copper<br />

interc<strong>on</strong>nects and cladding layer, and about 35 ns access and cycle times tested in the<br />

previous work show the potential of this technology. A new multibit MRAM cell of<br />

toggle switching type has been reported and also, a heat interacti<strong>on</strong> investigati<strong>on</strong> in<br />

thermally assisted MRAM has been reported. In this paper we presents a new design<br />

that has advantages c<strong>on</strong>venti<strong>on</strong>al MRAM <strong>on</strong> injected current and cell size. It is pole<br />

type perpendicular MRAM (PTP MRAM). PTP MRAM uses perpendicular magnetic<br />

field in order to change the state of the free layer in a perpendicular magnetic tunnel<br />

juncti<strong>on</strong> (pMTJ). In this paper, new efficient algorithm to combine two models are<br />

presented and tested. This approach reduces computing time and gives more precise<br />

results because the result of 2 dimensi<strong>on</strong>al Preisach model becomes an initial values of<br />

3 dimensi<strong>on</strong>al micromagnetics.<br />

QP05<br />

Room temperature exchange bias in the multiferroic BiFe 0.8Mn 0.2O 3<br />

nanoparticles with a core-shell structure<br />

S M Yusuf* and P K Manna<br />

SOLID STATE PHYSICS DIVISION, BHABHA ATOMIC RESEARCH CENTRE,<br />

MUMBAI 400085, India<br />

The compound BiFeO 3 shows a multiferroic character. We have shown that the<br />

BiFeO 3-based compound viz. BiFe 0.8Mn 0.2O 3 nanoparticle system exhibits other<br />

important multifuncti<strong>on</strong>al behaviour as well. We have observed the exchange<br />

bias effect, in the form of a shift in the field-cooled hysteresis loop, and a training<br />

effect in a dc magnetizati<strong>on</strong> study. From transmissi<strong>on</strong> electr<strong>on</strong> microscopy, neutr<strong>on</strong><br />

diffracti<strong>on</strong>, thermoremanent magnetizati<strong>on</strong>, and isothermoremanent magnetizati<strong>on</strong><br />

measurements, the nanoparticles are found to be core-shell in nature, c<strong>on</strong>sisting of<br />

an antiferromagnetic (AFM) core, and a two-dimensi<strong>on</strong>al diluted AFM (DAFF) shell<br />

with a net magnetizati<strong>on</strong> under a field. Our calculati<strong>on</strong> using the Binek’s model <strong>on</strong> the<br />

training effect yields a theoretical understanding of the observed loop shift which arises<br />

entirely due to an interface exchange coupling between core and shell. The intrinsic<br />

c<strong>on</strong>tributi<strong>on</strong> of the DAFF shell to the total loop shift is zero. The present study is useful<br />

to understand the origin of exchange bias in other DAFF-based systems as well. The<br />

significantly high value of the exchange bias field (~ 0.16 kOe), observed at room<br />

temperature, in the present nanoparticle system has made it a blue-eyed candidate for<br />

the next generati<strong>on</strong> advanced nano-technological applicati<strong>on</strong>s in the area of magnetic<br />

storage devices.<br />

QP06<br />

Magnetic and Transport Properties of Mn 3-xGa/MgO/Mn 3-xGa<br />

Magnetic Tunnel Juncti<strong>on</strong>s: A First-Principles Study<br />

Zhaoqiang Bai, Y<strong>on</strong>gqing Cai, Lei Shen, Guchang Han and Yuanping Feng*<br />

Physics, Nati<strong>on</strong>al University of Singapore, Singapore<br />

Magnetic and transport properties of Mn 3-xGa/MgO/Mn 3-xGa (0≤x≤1) magnetic tunnel<br />

juncti<strong>on</strong>s are studied using first-principles approach based <strong>on</strong> density functi<strong>on</strong>al theory<br />

and n<strong>on</strong>-equilibrium Green's functi<strong>on</strong>. Perpendicular magnetizati<strong>on</strong>, of which the<br />

magnetic anisotropy energy reaches more than 1 meV/unit-cell, is c<strong>on</strong>firmed to be<br />

energetically favoured by both Mn 2Ga and Mn 3Ga thin films. Furthermore, despite<br />

high spin-polarizati<strong>on</strong> at Fermi energy for both these compounds as reported, our<br />

transport calculati<strong>on</strong> shows c<strong>on</strong>siderable disparity in the transmissi<strong>on</strong> behaviour<br />

between Mn 2Ga/MgO/Mn 2Ga(001) and Mn 3Ga/MgO/Mn 3Ga(001) magnetic tunnel<br />

jucti<strong>on</strong>s: huge optimistic tunneling magnetoresistance ratio ~ 1000% for the former,<br />

and nevertheless, no tunneling magnetoresistance effect absolutely for the latter. This<br />

phenomen<strong>on</strong> is attributed to the spin symmetry filtering effect of the MgO spacer.<br />

On this premise, Mn 3-xGa compounds with low Mn c<strong>on</strong>centrati<strong>on</strong> are predicted to be<br />

promising candidate materials to serve as the electrodes of spin-transfer toque devices<br />

in<br />

132 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QP07<br />

C<strong>on</strong>comitant memory effect in CrO 2/Cr 2O 3 core-shell nanorods<br />

Ashish Chhaganlal Gandhi and Sheng Yun Wu*<br />

Department of Physics, Nati<strong>on</strong>al D<strong>on</strong>g Hwa University, Taiwan<br />

The c<strong>on</strong>comitant memory effects are intensively studied in last few decades and are mostly observed in<br />

spin-glass and superparamagnetic systems [1-3]. The memory effects were observed in the interacting<br />

permalloy nanoparticles [4] and isolated nanoparticles [5], providing us interesting informati<strong>on</strong><br />

about the investigati<strong>on</strong> of nature of the low temperature phase. In the present work, we succeeded<br />

in preparing CrO 2/Cr 2O 3 core-shell nanorods using the chemical vapor depositi<strong>on</strong> method. The<br />

magnetic properties of CrO 2/Cr 2O 3 core-shell nanoparticles can be treated as a ferromagnetic-CrO 2core<br />

and antiferromagnetic-Cr 2O 3O-shell compound coupled by an exchange interface coupling and<br />

raised magnetic anisotropy energy between them. The evoluti<strong>on</strong> of core shell magnetizati<strong>on</strong> triggered<br />

by an applied magnetic field at 1.8 K was observed, and a core-shell anisotropic energy model was<br />

applied to simulate the competiti<strong>on</strong> between the surface magnetic anisotropy and exchange interface<br />

coupling. Memory and aging effects were observed and overcame the superparamagnetic limit [3] up<br />

to sufficiently high temperature which makes it an important candidate in magnetic data storage, as<br />

an applicati<strong>on</strong>. Acknowledgments: This research was supported by a grant from the Nati<strong>on</strong>al Science<br />

Council of Taiwan, the Republic of China, under Grant Number NSC-100-2112-M-259-003-MY3.<br />

[1] M. Sasaki, P. E. J<strong>on</strong>ss<strong>on</strong>, H. Takayama, and H. Mamiya; Phys. Rev. B 71, 104405 (2005). [2]<br />

Malay Bandyopadhyay and Sushanta Dattagupta; Phys. Rev. B 74, 214410 (2006). [3] V. Skumryev,<br />

S. Stoyanov, Y. Zhang, G. Hadjipanayis, D. Givord and J. Nogues Nature 423, 850 (2003). [4]<br />

Young Sun, M. B. Salam<strong>on</strong>, K. Garnier and R. S. Averback; Phys. Rev. Lett. 91, 167206 (2003). [5]M.<br />

Sasaki, P. E. J<strong>on</strong>ss<strong>on</strong>, H. Takayama, and P. Norblad, Phys. Rev. Lett. 24, 139701 (2004).<br />

QP08<br />

High resoluti<strong>on</strong> probes for magnetic force microscope<br />

Xiaoxi Liu*, Shinsaku Isomura and Akimitsu Morisako<br />

Department of Informati<strong>on</strong> Engineering, Shinshu University, Japan<br />

Magnetic force microscopy is a c<strong>on</strong>venient and efficient method to detect magnetic<br />

domain structures in magnetic recording media or nano-magnet. In this work, we<br />

present a simple process to fabricate probes for magnetic force microscopy with<br />

sub-ten nanometer resoluti<strong>on</strong>. A thin layer of FeCo is deposited <strong>on</strong>to commercially<br />

available silic<strong>on</strong> probes by a facing targets sputtering system. We choose facing targets<br />

sputtering because this kind of system can minimize the damage of the films from high<br />

energy particle bombardment. The radius of the curvature of the probes is depended <strong>on</strong><br />

the FeCo film thickness. High resoluti<strong>on</strong> scanning microscope image show the radius<br />

of the curvature is less than 20 nm for a 20 nm thick FeCo coating. Magnetic force<br />

microscopy images show our probes have resoluti<strong>on</strong> better than 10 nm. Due to the high<br />

magnetic moment of FeCo, we can get magnetic c<strong>on</strong>trast for FeCo coating as thin as<br />

10 nm. Micromagnetic simulati<strong>on</strong>s indicate than the formati<strong>on</strong> of a magnetic vortex at<br />

the apex of the probe is crucial for the high resoluti<strong>on</strong>.<br />

QP09<br />

Selective magnetizati<strong>on</strong> switching by microwave assistance for layered<br />

magnetic pillar<br />

Terumitsu Tanaka 1 *, Yuto Otsuka 1 , Yoshitoki Furomoto 1 , Kimihide Matsuyama 1 and<br />

Yukio Nozaki 2<br />

1 ISEE, Kyushu University, Japan<br />

2 Department of Physics, Keio University, Japan<br />

Microwave assisted magnetizati<strong>on</strong> reversal (MAMR)[1] is a promising candidate for<br />

future magnetic recording technology. In MAMR, magnetizati<strong>on</strong> switches <strong>on</strong>ly when DC<br />

and microwave fields are applied to magnetic material at particular microwave frequency.<br />

Utilizing such a feature, possibility of selective switching of magnetizati<strong>on</strong>s was estimated by<br />

micromagnetic calculati<strong>on</strong> for realizing 3-dimensi<strong>on</strong>al magnetic recording. In the calculati<strong>on</strong>, a<br />

magnetic pillar composed of 3 layered materials was c<strong>on</strong>sidered. Pillar diameter is 11 nm, and<br />

thickness of the 1st, 2nd, and 3rd layers are 5, 13, and 14 nm, respectively. Hk 1 (= 24kOe), Ms 1<br />

(= 600 emu/cc), Hk 2 (= 13kOe), Ms 2 (= 400 emu/cc), and Hk 3 (= 6 kOe), Ms 3 (= 800 emu/cc)<br />

represent anisotropy fields and saturati<strong>on</strong> magnetizati<strong>on</strong>s of 1st, 2nd, and 3rd layers. These values<br />

give sufficient thermal stability indices (greater than 60 at 300 K) for every layer. Magnetizati<strong>on</strong><br />

switching probabilities equal to 1 were obtained at particular microwave frequencies for every<br />

layer; selective switching occurs at 1st, 2nd, and 3rd layer when microwave frequency is 8,<br />

18, and 28 GHz, respectively. In this calculati<strong>on</strong>, the single pillar has shown to store 3 bits<br />

informati<strong>on</strong>. These results imply MAMR has a potential in 3-dimensi<strong>on</strong>al magnetic recording.<br />

[1] J. -G. Zhu, X. Zhu and Y. Tang, IEEE Trans. Magn. 44, 125 (2008)


QP10<br />

Thermal effect in microwave assisted magnetizati<strong>on</strong> reversal<br />

Yoshitoki Furomoto, Yuto Otsuka, Terumitsu Tanaka* and Kimihide Matsuyama<br />

ISEE, Kyushu University, Japan<br />

Microwave assisted magnetizati<strong>on</strong> reversal (MAMR)[1] has potential applicati<strong>on</strong><br />

in future magnetic recording. The critical curves for MAMR in a single-domain<br />

particle is theoretically estimated by Bertotti et al.[2, 3], which well explains steady<br />

state magnetizati<strong>on</strong> switching at 0 K and the equati<strong>on</strong>s allow three soluti<strong>on</strong>s “stable”,<br />

“unstable” and “saddle”. In this study, MAMR properties in a single-domain particle<br />

were simulated solving the Landau-Lifshitz-Gilbert equati<strong>on</strong> taking account of<br />

temperature elevati<strong>on</strong> due to ferro-magnetic res<strong>on</strong>ance. Magnetizati<strong>on</strong> switching<br />

probability at 400 K widely distributes in HMW in unstable regi<strong>on</strong>. The critical values<br />

of HMW are greater than that at 0 K nevertheless thermal activati<strong>on</strong> decreases energy<br />

barrier height. This implies stochastic thermal fields reduce efficiency in MAMR in<br />

the regi<strong>on</strong>. On the other hand, thermal activati<strong>on</strong> gives 25-35 % of reducti<strong>on</strong> in critical<br />

value of HMW in stable regi<strong>on</strong>, which is achievable for recording head of recent hard<br />

disk drive.<br />

[1] J. O. Artman, S. H. Charap, and D. J. Seagle, IEEE Trans. Magn. MAG-19, 1814 (1983). [2] G.<br />

Bertotti, C. Serpico, and I. Mayergoyz, Phys. Rev. Lett. 86, 724 (2001). [3] S. Batra and W. Scholz,<br />

IEEE Trans. Magn. 44, 3392 (2008).<br />

QP11<br />

Stable magnetizati<strong>on</strong> switching with microwave assistance for<br />

exchange coupled composite grain<br />

Terumitsu Tanaka*, Yoshitoki Furomoto, Yuto Otsuka and Kimihide Matsuyama<br />

ISEE, Kyushu University, Japan<br />

Microwave assisted magnetizati<strong>on</strong> reversal (MAMR)[1] is a promising candidate for<br />

future magnetic recording. Li et al. proposed ECC medium for solving the potential<br />

problems in microwave power and frequency for MAMR[2]. Bertotti et al. theoretically<br />

analyzed MAMR process taking a single spin for example[3], which showed the LLG<br />

equati<strong>on</strong> can be written in the other forms[4]. The equati<strong>on</strong> allows three soluti<strong>on</strong>s<br />

“stable”, “unstable” and “saddle”. However, the theory cannot be applied to exchange<br />

coupled composite (ECC) structured grain. In this study, distributi<strong>on</strong>s of the regi<strong>on</strong>s<br />

defined by the three soluti<strong>on</strong>s were estimated for an ECC grain. In the ECC grain,<br />

stable switching regi<strong>on</strong>, in which magnetizati<strong>on</strong> reversal modes are hardly affected by<br />

disturbance such as thermal fluctuati<strong>on</strong>, distributes at lower fields regi<strong>on</strong> comparing<br />

to that for the single spin particle. This result means that stable magnetizati<strong>on</strong> reversal<br />

occurs with relatively weak magnetic fields even for ultra high Hk materials assigned<br />

to future high density recording.<br />

[1] J. -G. Zhu, X. Zhu and Y. Tang, IEEE Trans. Magn. 44, 125 (2008). [2] S. Li, B. Livshitz, H. N.<br />

Bertam, M. Schabes, T. Schrefl, E. E. Fullert<strong>on</strong> and V. Lomakin, Appl. Phys. Lett. 94, 202509 (2009).<br />

[3]Giorgio Bertotti , Claudio Serpico , and Isaak D. Mayergoyz , Phys. Rev. Lett. 86, 724 (2001) [4]<br />

Werner Scholz and Sharat Batra , J. Appl. Phys.103, 07F539 (2008)<br />

QP12<br />

Low-temperature epitaxial growth of FePt <strong>on</strong> glass substrates for<br />

ultrahigh magnetic recording densities<br />

Thanassis Speliotis 1 *, George Giannopoulos 1 and Dimitris G Niarchos 2<br />

1 Institute of Materials Science, NCSR DEMOKRITOS, Greece<br />

2 Institute of Materials Science, NCSR Demokritos, Greece<br />

Magnetic FePt alloy thin film with ordered L10 structure is a promising material<br />

for perpendicular magnetic recording (PMR) applicati<strong>on</strong>, duo to its huge uniaxial<br />

magnetocrystalline anisotropy (Ku), high saturati<strong>on</strong> magnetizati<strong>on</strong> (Ms), high coercivity (Hc)<br />

and outstanding corrosive resistance. Ku value of L10 FePt is about 7 MJ/m3 which sets the<br />

superparamagnetic limit of L10 FePt as small as 2.8 nm. In PMR applicati<strong>on</strong> the preferred<br />

orientati<strong>on</strong> has to be transformed into (001) that makes the [001]-axis perpendicular to the<br />

film. Accordingly, developing an effective way to prepare L10 FePt (001) thin film with<br />

perpendicular magnetic anisotropy at low order-disorder transformati<strong>on</strong> temperature is the<br />

c<strong>on</strong>cern of first priority.Although excellent properties can be obtained in sputtered FePt <strong>on</strong><br />

single crystal MgO (001) much effort is needed to obtain PMR properties of sputtered FePt<br />

films <strong>on</strong> glass substrates. A number of underlayers have been used to induce texture such<br />

as CrRu, MgO and very recently TiN. Here we report a systematic study of the system {<br />

Hoya glass/CrRu/MgO/FePt/Ta} and through optimizati<strong>on</strong> of layer thickness, depositi<strong>on</strong><br />

temperature and sputtering power , we achieved perpendicular anisotropy, coercivity in<br />

excess of 1 T and depositi<strong>on</strong> temperatures around 400 0C.<br />

Supported by the project TERAMAGSTOR of the EU<br />

QP13<br />

QP14<br />

QP15<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

C<strong>on</strong>trolling nanostructure in FePt films: Co-sputtering of FePt and C<br />

or SiO 2<br />

George Giannopoulos*, Thanassis Speliotis and Dimitris G Niarchos<br />

Institute of Materials Science, NCSR DEMOKRITOS, Greece<br />

Achieving magnetic recording densities in excess of 1Tbit/in2 requires not <strong>on</strong>ly<br />

perpendicular media with anisotropy larger than 7 MJ/m3, which makes the FePt alloy<br />

as the best choice , but also narrow distributi<strong>on</strong> and small sizes below 10 nm for a<br />

reduced S/N ratio al<strong>on</strong>g with high thermal stability. Previous work has shown that the<br />

L10 FePt grain size can be c<strong>on</strong>trolled by alloying FePt with materials such as C, Ag,<br />

and insulator like AlOx, MgO act to segregate and magnetically decouple the FePt<br />

grains. Better results were obtained with C with respect to the uniformity of grains and<br />

SiO 2 with respect to the shape, but far from optimizati<strong>on</strong>. We present our results by cosputtering<br />

FePt with C or SiO 2 (up to 30 vol % ) <strong>on</strong> MgO (001) single crystal substrates<br />

at 350 and 500 0C. With C or SiO 2 additi<strong>on</strong> we achieved the grain size reducti<strong>on</strong>, the<br />

shape c<strong>on</strong>trol and isolated structure formati<strong>on</strong>, by producing c<strong>on</strong>tinuous films with<br />

high uniformity and narrow main size distributi<strong>on</strong> down to 10 nm. This also reflected<br />

in the variati<strong>on</strong> of coercivity as a functi<strong>on</strong> of the additi<strong>on</strong>al phase, thus giving us a<br />

possibility to simultaneously c<strong>on</strong>trol the coercivity and the S/N ratio.<br />

Retenti<strong>on</strong> time under currents and magnetic fields in a CoFeB/MgO<br />

perpendicular magnetic tunnel juncti<strong>on</strong><br />

Michihiko Yamanouchi*, Hideo Sato, Katsuya Miura, Shoji Ikeda, Fumihiro<br />

Matsukura and Hideo Ohno<br />

Center for Spintr<strong>on</strong>ics Integrated Systems, Tohoku University, Japan<br />

CoFeB/MgO based magnetic tunnel juncti<strong>on</strong>s with perpendicular anisotropy (p-MTJs)<br />

[1,2] have been investigated extensively because of their potential for realizati<strong>on</strong><br />

of n<strong>on</strong>volatile logic circuits and random access memories [3-6]. For ensuring their<br />

n<strong>on</strong>volatility, effects of current (I) and magnetic field (H) <strong>on</strong> cumulative distributi<strong>on</strong> of<br />

retenti<strong>on</strong> time (tr) of magnetizati<strong>on</strong> directi<strong>on</strong> in the recording layer should be clarified.<br />

Theoretical expressi<strong>on</strong> for the distributi<strong>on</strong> under I and H has been proposed [7]. However<br />

it has not been compared with experimental results in CoFeB/MgO p-MTJs. In this work,<br />

we investigated tr under I and perpendicular H in the same CoFeB/MgO p-MTJ with 40<br />

nm in diameter and compared it with the theoretical expressi<strong>on</strong> [7]. It was found that the<br />

cumulative distributi<strong>on</strong> of tr under I (H) can be fitted well with the theoretical expressi<strong>on</strong><br />

in the range of tr = 30 μs - 100 s (5 - 960 s). From tr under I (H), thermal stability factor<br />

is evaluated to be 44 (39), which agrees well with previous results in similar MTJs [1,4].<br />

This work was supported by the FIRST program from JSPS.<br />

[1] M. Endo et al., Appl. Phys. Lett. 96, 212503 (2010). [2] S. Ikeda et al., Nature Mater. 9, 721<br />

(2010). [3] D. C. Worledge et al., Appl. Phys. Lett. 98, 022501 (2011). [4] H. Sato et al., Appl. Phys.<br />

Lett. 99, 042501 (2011). [5] H. D. Gan et al., Appl. Phys. Lett. 99, 252507 (2011). [6] J. J. Nowak et<br />

al., IEEE Magn. Lett. 2, 3000204 (2011). [7] Z. Li et al., Phys. Rev. B 69, 134416 (2004).<br />

Thermal diffusi<strong>on</strong> in magneto-optic collinear volumetric hologram<br />

memory<br />

Seungmin Baek, Hiroyuki Sakurai, Pang Boey Lim and Mitsuteru Inoue<br />

Toyohashi University of Technology, Japan<br />

Collinear holography memory is a good candidate of the next generati<strong>on</strong> of optical<br />

memory. Recently we have investigated the magneto-optical recording with thick<br />

polycrystalline magnetic garnet films by collinear holography. Rewritable properties<br />

and shift multiplexing of the magnetic holograms were c<strong>on</strong>firmed experimentally.<br />

However, it has still high noise level in the retrieved image. We investigated the<br />

suppressi<strong>on</strong> method of thermal diffusi<strong>on</strong> in magnetic hologram recording numerically<br />

and experimentally. The recording principles of the magnetic holography are<br />

basically similar with thermomagnetic recording. The interference patterns with<br />

signal informati<strong>on</strong> are recorded as magnetizati<strong>on</strong> patterns. Due to thermal diffusi<strong>on</strong><br />

in recording process, the interference patterns were in disorder. It could be shown in<br />

results of the low diffracti<strong>on</strong> efficiency and high noise level. Numerical simulati<strong>on</strong><br />

result shows the influence of thermal diffusi<strong>on</strong> was suppressed with below 10-9 sec<strong>on</strong>d<br />

of laser pulse width. Experimental result with two-beam interferometer also shows<br />

over 200 % higher diffracti<strong>on</strong> efficiency recorded by 50 ps pulse width laser than 25 ns<br />

<strong>on</strong>e in high spatial frequency range.<br />

July 8 - 13, 2012 Busan, Korea 133<br />

Poster Tuesday


Poster Tuesday<br />

QP16<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Resoluti<strong>on</strong> of magnetic garnet films for magneto-optic collinear<br />

volumetric hologram memory<br />

Seungmin Baek, Hiroyuki Sakurai, Naoto Sagara, Pang Boey Lim and Mitsuteru<br />

Inoue<br />

Toyohashi University of Technology, Japan<br />

Collinear holography memory is promising optical memory of the next generati<strong>on</strong>.<br />

The photopolymer materials have received much attenti<strong>on</strong> because of high sensitivity,<br />

high dynamic range and low costs as recording materials. On the other hands,<br />

magnetic garnet films have the advantage of rewritable, no necessity of shading, and<br />

no shrinkage, as compared to photopolymer which has write-<strong>on</strong>ce property. In this<br />

study, we fabricated the different grain sizes of magnetic garnet films by annealing<br />

time. The fundamental properties of samples and the SNR of the retrieved images with<br />

single hologram were investigated. Bi-substituted ir<strong>on</strong> garnet films (3.3 μm thick) were<br />

fabricated by RF magnetr<strong>on</strong> sputtering <strong>on</strong> SGGG substrates. Samples were annealed<br />

at 750 °C in air for several annealing time. The retrieved images were evaluated by<br />

collinear holographic system. The resoluti<strong>on</strong> of magnetic recording media was related<br />

with the grain size of magnetic recording media. The results show SNR of the retrieved<br />

image was improved by reducti<strong>on</strong> of the grain size.<br />

QP17<br />

Room temperature ordering perpendicular magnetic anisotropy L11<br />

CoPtCu thin film <strong>on</strong> glass substrate<br />

Chiuan-fa Huang 1 , L<strong>on</strong>g-jie Li 1 , An-cheng Sun 1 *, Fu-te Yuan 2 , Jen-hwa Hsu 2 , S. N.<br />

Hsiao 3 and H. Y. Lee 3<br />

1 Department of Chemical Engineering & Materials Science, Yuan-Ze University, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al Taiwan University, Taiwan<br />

3 Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Center (NSRRC), Taiwan<br />

Rhombohedral unit cell of L11 CoPt films have attracted a lot of attenti<strong>on</strong> due to their large magnetocrystalline<br />

anisotropy (Ku ~ 107 erg/cm3) as well as relatively low ordering temperature (~ 200 oC) [1,2]. The additi<strong>on</strong> of<br />

Cu significantly improves the alignment of c-axis, chemical ordering and enhances perpendicular coercivity (Hc┴)<br />

of L11 CoPtCu phase deposited at 350 oC [3-5]. In this study, Co 27Pt 50Cu 23 films with a Pt underlayer were<br />

deposited <strong>on</strong> glass substrates at room temperature (RT) to 500 oC by sputtering. The thickness of the film was 5<br />

nm. Interestingly, the high perpendicular magnetic anisotropy (PMA) was observed when the film was deposited<br />

at RT. Furthermore, PMA was maintained until the substrate temperature (Ts) exceeded 450 oC. Hc was largely<br />

enhanced from 0.25 to 2.6 kOe when Ts was increased from RT to 350 oC. Bey<strong>on</strong>d 350 oC Hc started to decline.<br />

The appearance of high PMA suggests that the ordered L11 structure is formed in CoPtCu film even prepared at<br />

room temperature. This finding promotes the applicati<strong>on</strong>s of L11 CoPtCu films in future perpendicular magnetic<br />

recording and spintr<strong>on</strong>ic device. The variati<strong>on</strong> of phase structure and microstructure with Ts will be presented.<br />

[1] S. Iwata, S. Yamashita, S. Tsunashima, IEEE Trans. Magn. 33 (1997) 3670. [2] F.T. Yuan, A.C. Sun, J.H. Hsu, Scripta Materialia<br />

62 (2010) 762. [3] F-T. Yuan, A-C. Sun, J-H. Hsu, C.S. Tan, P.C. Kuo, W.M. Liao, H.Y. Lee J. Appl. Phys. 108 (2010) 113909. [4]<br />

F-T. Yuan, A-C. Sun, J-H. Hsu, C.S. Tan, P.C. Kuo, W.M. Liao, H.Y. Lee J. Appl. Phys. 109 (2011) 07B714. [5] Fu-Te Yuan, L. J. Li,<br />

Jen-Hwa Hsu, S. N. Hsiao, H. Y. Lee, Hsi-Chuan Lu, Sea-Fue Wang, C. Y. Shen, and An-Cheng Sun, J. Appl. Phys. (accepted)<br />

QP18<br />

Magnetic anisotropy and chemical ordering in Fe-Pt films prepared by<br />

low-temperature growth technique<br />

Nyun J<strong>on</strong>g Lee 1 , Jae Young Ahn 1 , Yu Je<strong>on</strong>g Bae 1 , Dominique Eyidi 2 *, Anny Michel 2 *<br />

and Tae Hee Kim 1 *<br />

1 Department of Physics, Ewha Womans University, Korea<br />

2 Departement de Physique et Mecanique des Materiaux, Institut Pprime, UPR 3346,<br />

CNRS-Universite de Poitiers-ENSMA, F86962 Futuroscope-Chasseneuil cedex,<br />

France<br />

We investigated the chemical ordering and perpendicular magnetic anisotropy (PMA)<br />

in L1 0 FePt and L1 2 FePt 3 films. FePt films with different thickness of 35 and 70 A were<br />

grown, at the substrate temperature T s = 300 °C by MBE co-evaporati<strong>on</strong> and layer-by-layer<br />

growth, <strong>on</strong>to a MgO layer deposited <strong>on</strong> Si wafer. In order to optimize the growth of highly<br />

ordered FePt(001) films in c<strong>on</strong>diti<strong>on</strong>s of low-temperature fabricati<strong>on</strong>, the influence of a<br />

thin (001)-oriented fcc Pt buffer layer <strong>on</strong> the c-axis oriented texture was explored by high<br />

resoluti<strong>on</strong> TEM and X-ray diffracti<strong>on</strong> (XRD). Our results showed a str<strong>on</strong>g enhancement<br />

of PMA without high-temperature annealing, for 35 A thick FePt films, while a decrease in<br />

PMA was observed for L1 2 FePt 3. By introducing a small percentage of Bor<strong>on</strong> into the L1 2<br />

ordered FePt 3, enhanced structural ordering was seen in XRD. However, no significant<br />

change of magnetic properties was observed, in c<strong>on</strong>tradicti<strong>on</strong> with the expectati<strong>on</strong> to<br />

induce PMA by altering the chemical ordering in FePt 3 L1 2 phase. In this work, we discuss<br />

the origin of spin reorientati<strong>on</strong> transiti<strong>on</strong> phenomena related to our results. *corresp<strong>on</strong>ding<br />

authors : taehee@ewha,ac,kr; Anny.S.Michel@univ-poitiers.fr<br />

134 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

QP19<br />

Nanoscale i<strong>on</strong> beam etching process for reducing damage and leakage<br />

path of magnetic tunnel juncti<strong>on</strong><br />

Daeh<strong>on</strong>g Kim 1 , B<strong>on</strong>gho Kim 1 , Sungwoo Chun 1 , Hyungyu Kim 1 , Se<strong>on</strong>jun Choi 1 and<br />

Seung-beck Lee 2 *<br />

1 Department of Electr<strong>on</strong>ic Engineering, Hanyang University, Seoul, Korea<br />

2 Institute of Nano Science and Technology, Hanyang University, Seoul, Korea<br />

To integrate ultrahigh density spin-transfer torque magnetic random access memory (STT-MRAM),<br />

a stable process to pattern metallic magnetic tunnel juncti<strong>on</strong>s (MTJs) is required. [1] We investigated<br />

the i<strong>on</strong> milling process to fabricate the MTJ cells for perpendicular STT-MRAM applicati<strong>on</strong> with<br />

minimized redepositi<strong>on</strong> layer by a gradati<strong>on</strong>al stage tilting process and low damage of MTJ by<br />

reduced beam supply voltage. The hard mask used a 30nm diameter negative electr<strong>on</strong>-beam resist<br />

patterned by electr<strong>on</strong> beam lithography. Thereafter, i<strong>on</strong> milling process was c<strong>on</strong>ducted through<br />

regulati<strong>on</strong> of beam/accelerate supply voltage and stage tilting angle. We found that the highest<br />

MTJ slope angle was attained at the stage tilt angle of 80° which was the angle of the incident i<strong>on</strong><br />

flux to the stage surface. However, high angle etching resulted in a thick redepositi<strong>on</strong> layer. For<br />

reducing redeposited layers, we have utilized variable-angle multi-step i<strong>on</strong> milling process. Also<br />

for reduced MTJ sidewall damage by high beam supply voltage, reduced the beam supply voltage.<br />

C<strong>on</strong>sequently, sidewall damage of MTJ layer was minimized. The TMR ratio and the resistance of<br />

the fabricated MTJ cells were 13% and 1kΩ respectively. Our results showed the potential of using<br />

optimized i<strong>on</strong> milling for fabricating nanoscale MTJs for ultrahigh density STT-MRAMs.<br />

[1] M. Hosomi, H. Yamagishi, T. Yamamoto, K. Bessho, Y. Higo, K. Yamane, H. Yamada, M. Shoji, H.<br />

Hachino, C. Fukumoto, H. Nagao,and H. Kano: IEDM Tech. Dig., 2005, p. 459.<br />

QP20<br />

A new planer patterned media with anti-ferro / ferro transformati<strong>on</strong><br />

Hiroaki Ono and Hiroyuki Awano<br />

Toyota Technological Institute Informati<strong>on</strong> Storage Material Lab., Japan<br />

For next-generati<strong>on</strong> HDD, the planer patterned media which need neither pattern<br />

etching nor smoothing processing is attractive.1),2) As a proposal of the new media,<br />

ferro-magnetized patterned area in the flat anti-ferro-magnetized layer has been<br />

prepared by using near field laser irradiati<strong>on</strong> or masked i<strong>on</strong> implantati<strong>on</strong>. On the ferromagnetized<br />

area, required data can be recorded. We prepared several kinds of TbFeCo/<br />

Rh/TbFeCo tri-layers. When the Rh thickness is some period, str<strong>on</strong>g anti-ferromagnetic<br />

coupling (AFC) is realized. In the combinati<strong>on</strong>, Rh thickness of the 1st peak<br />

of the anti-ferro-coupling was 0.45nm. Since the thickness of the TbFeCo was thick<br />

and Rh thickness was very thin, the transformati<strong>on</strong> from AFC to FC can be c<strong>on</strong>trol<br />

easily. The coercive force was 1.5kOe. Also the Hc can be designed by c<strong>on</strong>trolling Tb<br />

c<strong>on</strong>centrati<strong>on</strong>. For example, in this case, the transformati<strong>on</strong> temperature was 100 °C.It<br />

is also easy to c<strong>on</strong>trol by changing TbFeCo thickness. Moreover, the patterned media<br />

can be applied as a write <strong>on</strong>ce HDD, since it is impossible to change recorded area for<br />

the ferro-magnetized area.<br />

1) I. Nakatani,T. Takahashi,M. Hijikata, T. kobayashi, K. Ozawa, and H. Hanaoka: Japanese Patent<br />

No.888363, filed in June 1989. 2) T.Kato et al., J. Appl. Phys., 105, 07C117 (2009)<br />

QP21<br />

Topology optimizati<strong>on</strong> of perpendicular magnetic recording head<br />

c<strong>on</strong>sidering magnetic saturati<strong>on</strong> effect<br />

Park So<strong>on</strong> Ok*<br />

Y<strong>on</strong>sei University Graduate school, Korea<br />

The topology optimizati<strong>on</strong> method is an attractive scheme for magnetic device design<br />

because an initial c<strong>on</strong>ceptual design can be obtained without any prototype model. However,<br />

studies c<strong>on</strong>cerning the three-dimensi<strong>on</strong>al magnetic device design by topology optimizati<strong>on</strong><br />

are rare. Even more, topology optimizati<strong>on</strong> of magnetic systems has been generally<br />

accomplished by using the two-dimensi<strong>on</strong>al finite element method while the n<strong>on</strong>linear<br />

saturati<strong>on</strong> effect of the material property between magnetic field strength and magnetic flux<br />

density has not been fully c<strong>on</strong>sidered. This study proposes a topology optimizati<strong>on</strong> technique<br />

of the three-dimensi<strong>on</strong>al design as well as the two-dimensi<strong>on</strong>al design based <strong>on</strong> the density<br />

method c<strong>on</strong>sidering the n<strong>on</strong>linear saturati<strong>on</strong> effects. The proposed method makes it possible<br />

to provide useful and practical process for magnetic system design and may lead to improved<br />

design with light system weight. The proposed method is applied to the optimizati<strong>on</strong><br />

problem of a magnetic recording system. During the design process, the reluctivity of<br />

magnetic material is changed according to the n<strong>on</strong>linear B-H relati<strong>on</strong>ship during magneto<br />

static analysis. The sensitivity analysis and the update of design variables are accomplished<br />

by the adjoint variable method and the sequential linear programming, respectively.<br />

Topology optimizati<strong>on</strong>; finite element analysis; magnetic saturati<strong>on</strong> effect; three dimensi<strong>on</strong>al<br />

design; density method; adjoint variable method.


QP22<br />

The effect of capped layer thickness <strong>on</strong> switching behavior in coupled<br />

granular/c<strong>on</strong>tinuous media<br />

Weimin Li 1 , Jun Ding 1 * and Jianzh<strong>on</strong>g Shi 2<br />

1<br />

Department of materials science and engineering, Nati<strong>on</strong>al University of Singapore,<br />

Singapore<br />

2<br />

Data Storage Institute, Agency for Science, Technology and Research (A*STAR),<br />

Singapore<br />

Coupled granular/c<strong>on</strong>tinuous (CGC) media (a CoPtCrB c<strong>on</strong>tinuous layer exchange coupled to a granular<br />

oxide CoPtCr: SiO 2TiO 2Ta 2O 5 layer) exhibited improvement of SNR, thermal stability and switching<br />

field distributi<strong>on</strong> (SFD)[1, 2]. TEM images together with intrinsic SFD for capped structure are studied to<br />

investigate the mechanism of the SFD reducti<strong>on</strong> in CGC media. We find out that in the bottom part, CoPtCr<br />

magnetic grains are separated by n<strong>on</strong>magnetic oxide grain boundaries. The amorphous grain boundary<br />

phase in the granular layer propagates to the top surface of the capped layer. The grain size increases with<br />

capped layers thickness. A critical capped thickness exists. At thinner capped thickness, capped layer inherits<br />

structural irregularity from the granular layer, while at thicker layer, the upper porti<strong>on</strong> of capped layer is less<br />

influenced by the granular layer. ReportedΔH (M, ΔM) method[3] is used to calculate intrinsic SFD. Both<br />

intrinsic and macroscopic SFD decrease linearly with capped layer thickness. As we know, the intrinsic<br />

SFD is due to the local variati<strong>on</strong>s of the grains properties. The reducti<strong>on</strong> of macroscopic SFD is caused by<br />

homogenous grains and uniform exchange coupling at thicker capped layer.<br />

1. H. S. Jung, E. M. T. Velu, S. S. Malhotra, U. Kw<strong>on</strong>, D. Suess and G. Bertero, Magnetics, IEEE Transacti<strong>on</strong>s <strong>on</strong> 43 (6), 2088-<br />

2090 (2007). 2. H. Nemoto, I. Takekuma, H. Nakagawa, T. Ichihara, R. Araki and Y. Hosoe, Journal of <strong>Magnetism</strong> and Magnetic<br />

Materials 320 (22), 3144-3150 (2008). 3. A. Berger, B. Lengsfield and Y. Ikeda, Journal of Applied Physics 99 (8), 08E705-706 (2006).<br />

QP23<br />

The effect of magnetic field <strong>on</strong> FePt nanoparticles during annealing<br />

process<br />

A. Khajehnezhad 1 , S. A. Sebt 1 , R. S. Dariani 2 and M. Akhavan 3 *<br />

1<br />

Physics Research Center, Science and Research Branch, Islamic Azad University,<br />

Tehran, Iran, Iran<br />

2<br />

Physics, Alzahra University, Tehran, Iran<br />

3<br />

Physics, Sharif University of Technology, Iran<br />

FePt, L10 nanocrystals are expected as <strong>on</strong>e of promising candidates for the magnetic recording media with<br />

ultrahigh densities. The 3nm FePt NPs have been synthesized by the polyol method and analysed by TEM<br />

analysis. The compositi<strong>on</strong> of the films was estimated to be approximately Fe 62.40Pt 37.60 by EDXS. Surface of<br />

Si and SiO 2 wafers have been covered by FePt nanoparticles and heated in 600°C for 1h to form L10 phase<br />

nanoparticles [1]. FE-SEM and XRD analyses show uniform surface distributi<strong>on</strong>s of FePt, L10 nanoparticles.<br />

The SiO 2 [2] substrate prevents nanoparticles from coalescence during annealing and prevents them from<br />

growth [3], hence, causing their size not to become more than 40nm. SiO 2 wafer is more suitable than Si wafer<br />

in separating the nanoparticles, which may be due to oxygen of surface b<strong>on</strong>ding with nanoparticles. Presence<br />

of 30mT magnetic field c<strong>on</strong>trols the size of nanoparticles around 25nm, which can be related to the reducti<strong>on</strong><br />

of random mobility in magnetic field and causes the nanoparticles to self-organize directi<strong>on</strong>ally. The larger<br />

I(001)/I(111) for perpendicular magnetic field indicates that the easy axis of nanoparticles is aligned in this<br />

directi<strong>on</strong> [4]. The magnetic field also c<strong>on</strong>trols the surface distributi<strong>on</strong> during heating process.<br />

1. S. Sun, Adv Matter 18, 393-403 (2006). 2. T. Ichitsubo, S. Tojo, T. Uchihara and E. Matsubara, Phys.<br />

Rev. B 77, 094114 (2008). 3. Y. C. Wu, L. W. Wang, and C. H. Lai, Appl. Phys. Lett. 93, 242501 (2008). 4. M.<br />

I. J. Beale, N. G. Chew, M. J. Uren, A.G. Cullis, and J.D. Benjamin, Appl. Phys. Lett. 46, 86(1985).<br />

QP24<br />

Novel soft lithography technique for fabricati<strong>on</strong> of Ni nanodots for use<br />

as bit patterned media<br />

Shivaraman Ramaswamy<br />

Nanotechnology Research Center, SRM University, India<br />

Magnetic disk drive technology has successfully reduced the size of multi-grain bits<br />

to ~30 nm, and there are intensive industrial efforts to shrink the bit size further. This<br />

work reports the development of a cheap, scalable polymer template lithography<br />

technique of fabricating large arrays of magnetic nanostructures towards use as bit<br />

patterned media, <strong>on</strong>e of the prominent next generati<strong>on</strong> data storage technologies.<br />

The technique has been standardized and physical properties such as bit sizes, pitch<br />

sizes and the storage densities have been calculated. Critical magnetic properties<br />

such as magnetizati<strong>on</strong> reversal have also been studied and discussed to ascertain the<br />

plausibility of its use in futuristic high density magnetic data storage devices<br />

[1] Park. S, Lee. D.H, Xu. J, Kim. B, H<strong>on</strong>g. S. W, Je<strong>on</strong>g. U, Xu. T, and Russell. T.P, 2009,<br />

“Macroscopic 10-Terabit-per-Square-Inch Arrays from Block Copolymers with Lateral Order,”<br />

Science, vol. 323, pp. 1030-1033. [2] Kikitsu. A, Kamata. Y, Sakurai. M and Naito. K, 2007,<br />

“Recent progress of patterned media,” IEEE Transacti<strong>on</strong>s <strong>on</strong> Magnetics, vol. 43,pp. 3685-3688. [3]<br />

Speliotis. D, 1984,'Media for high density magnetic recording', IEEE Transacti<strong>on</strong>s <strong>on</strong> Magnetics,<br />

20, 5, 669 - 674.<br />

RA01<br />

RA02<br />

RA03<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic res<strong>on</strong>ance and ferroelectricity of BaTi 1-xFe xO 3<br />

Dianta Ginting 1 , N. V. Dang 2 , V. D. Lam 2 , S. C. Yu 1 and T. L. Phan 1 *<br />

1 Phyisch, Bk 21, chungbuk nati<strong>on</strong>al university, Korea<br />

2 Institute of Materials Science, Vietnamese Academy of Science and Technology,<br />

Hanoi, Viet Nam<br />

BaTiO 3 is known as an excellent candidate for multiferroics. In this work, we present magneticres<strong>on</strong>ant<br />

and ferroelectric properties of polycrystalline BaTi 1-xFe xO 3 ceramics (0 ≤ x ≤0.12) prepared<br />

by c<strong>on</strong>venti<strong>on</strong>al solid-state reacti<strong>on</strong>. Measurements have been based <strong>on</strong> an X-ray diffractometer,<br />

electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) spectroscopy, and Precisi<strong>on</strong> Premier-Radiant. X-ray diffracti<strong>on</strong><br />

patterns reveal the tetrag<strong>on</strong>al-hexag<strong>on</strong>al phase transformati<strong>on</strong> as increasing Fe-doping c<strong>on</strong>tent. ESR<br />

spectra prove that many samples to be ferromagnetic, excepting for the x = 0.02-0.06 samples, which<br />

are paramagnetic. Such the results are in good agreement with the previously report <strong>on</strong> the magnetic<br />

behavior. Room-temperature P-E hysteresis loops of BaTi 1-xFe xO 3 reveal that with increasing Fe<br />

c<strong>on</strong>centrati<strong>on</strong>, the feature of ferroelectric P-E loops changes in the shape to the paraelectric regime,<br />

indicating the decrease in ferroelectricity. C<strong>on</strong>sequently, the values of the remnant polarizati<strong>on</strong> Pr and<br />

the coercive field Ec gradually are also decreased. Keywords: Fe-doped BaTiO 3; Magnetic phase<br />

separati<strong>on</strong>; Ferroelectricity *Electr<strong>on</strong>ic mail: ptl<strong>on</strong>g2512@yahoo.com Ph<strong>on</strong>e:<br />

Daniel Khomskii, Physics,2.20 (2009) W. Eerenstein, N.D. Mathur & J.F. Scott, Nature 442(17) (2006) N.V Dang,<br />

Thanh, L.V.H<strong>on</strong>g, V.D Lam, The-L<strong>on</strong>g Phan, Applied Physics 110, 043914, (2011). QIU Shen-Yu, LI Wang, LIU<br />

YU, LIU GUi Hua, WU Yi-Qiang, Chen Nan, Trans. N<strong>on</strong>ferrous Met.Sos. China 20,1911-1915(2010). Manfred<br />

Fiebig, J. Phys. D: Apply.Phys.38, R123-R152. S.Angappane, G Rangarajan, and K.Sethupathi, J. Apply.<br />

Phys.93,8334 (2003).F. Lin, D. Jiang, X. Ma, and W. Shi, Physica B 403, 2525 (2008). S. Ray, P. Mahadevan, S.<br />

Mandal, S. R. Krishnakumar, C. S. Kuroda, T. Sasaki, T. Taniyama, and M. Itoh, Phys. Rev. B 77, 104416 (2008).<br />

Growth of high pure BiFeO3 single crystals<br />

Kai Feng 1 , Jun Lu 2 * and Yicheng Wu 1<br />

1<br />

Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing<br />

100190, China, China<br />

2<br />

State Key Laboratory of <strong>Magnetism</strong>, Technical Institute of Physics and Chemistry,<br />

Chinese Academy of Sciences, Beijing 100190, China, China<br />

BiFeO 3(BFO) is a heavily beaten compound in recent publicati<strong>on</strong>s. BFO exhibits<br />

simultaneous polar and magnetic order at room temperature, promising important<br />

applicati<strong>on</strong>s, but growth of pure BFO single crystals is really a great challenge. To<br />

grow extremely pure BFO single crystals, we have systematically investigated Bi 2O 3-<br />

Fe 2O 3 pseudo-binary system from the l<strong>on</strong>g-term crystal growth experiments, high<br />

performance powder X-ray diffracti<strong>on</strong> analysis and high temperature differential<br />

thermal analysis instrument. The peritectic transiti<strong>on</strong> temperature of BFO was<br />

determined to be 852±5˚C and Other typical characteristic temperatures in Bi 2O 3-Fe 2O 3<br />

pseudo-binary phase diagram were reevaluated. It has been found that purity of grown<br />

BFO single crystals depends greatly <strong>on</strong> crucible materials. When suitable kind of<br />

crucibles were used, extremely high pure BFO single crystals could be easily obtained<br />

with maximum size above <strong>on</strong>e centimeter.<br />

[1] J. Lu et al., Eur. Phys. J. B, 75(4), 451-60(2010) (as cover story) [2] J. Lu et al., J. Cryst.<br />

Growth,318, 936-41(2011) [3] J. Lu et al., A method of growing centimeter pure BiFeO3 single<br />

crystals, Chinese Patent, 201110252660.5<br />

Structural, electrical and magnetic properties of La-doped BiFeO 3<br />

ceramics.<br />

M. Roy, S. Jangid, S. K. Barbar and Indu Bala Thakur<br />

Department of Physics, M. L. Sukhadia University, Udaipur, India<br />

Polycrystalline ceramic samples of Bi 1-xLa xFeO 3 (x=0.0, 0.1 and 0.2) have been<br />

prepared by standard solid state reacti<strong>on</strong> method using high purity oxides and<br />

carb<strong>on</strong>ates. The structure and formati<strong>on</strong> of the compounds have been checked by X-ray<br />

diffracti<strong>on</strong> followed by energy dispersive X-ray microanalysis (EDAX) techniques.<br />

There is a good agreement between observed and calculated X-ray diffracti<strong>on</strong> patterns<br />

obtained by performing the Rietveld refinement with a structural model using the n<strong>on</strong>centrosymmetric<br />

space group R3c. The lattice parameters have been refined but the<br />

over all structure remained the same. The microstructural studies have been carried<br />

out using scanning electr<strong>on</strong> microscopy. The dc c<strong>on</strong>ductivity of all the samples has<br />

been measured and their activati<strong>on</strong> energies were calculated from logσ vs 103/T<br />

curves. Vibrating sample magnetometer (VSM) has been used to study the magnetic<br />

behaviour of the compounds. It has been observed that with the increase of substituti<strong>on</strong><br />

c<strong>on</strong>centrati<strong>on</strong> of La, the insulating behaviour of the materials have been improved<br />

and showing the antiferromagnetic to weak ferromagnetic behaviour. The results are<br />

discussed in detail.<br />

July 8 - 13, 2012 Busan, Korea 135<br />

Poster Tuesday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RA04<br />

In situ X-ray absorpti<strong>on</strong> spectroscopy study <strong>on</strong> BaTiO 3<br />

J.-s. Lee* and C.-c. Kao<br />

SSRL, SLAC Nati<strong>on</strong>al Accelerator Laboratory, USA<br />

Ferroelectric systems are under intensive study for both the point of view of<br />

fundamental materials physics and the potential applicati<strong>on</strong>s such as memories, sensors,<br />

and transducers. The Ti 4+ (d0-ness) systems which are the generally well known<br />

ferroelectric as form ATiO 3 structure (A=Ba and Pb), inter alia, have been extensively<br />

investigated. To understand this system, both of structural and electr<strong>on</strong>ic investigati<strong>on</strong>s<br />

must be completed together. Structurally, Ti i<strong>on</strong>s in the TiO 6 octahedra are moved<br />

al<strong>on</strong>g the applied electric (E)-field, resulting in a symmetry lowing. However, we still<br />

do not understand much about a change in the electr<strong>on</strong>ic structure between Ti 3d and<br />

O 2p states. Although the soft x-ray spectroscopy study at the oxygen absorpti<strong>on</strong> edge<br />

that is regarded as a good approach for exploring the electr<strong>on</strong>ic structure, such study<br />

accompanies an experimental difficulty; electr<strong>on</strong> moti<strong>on</strong> distorti<strong>on</strong> under in situ E-field<br />

c<strong>on</strong>diti<strong>on</strong>. In this work, we introduce an approach for overcoming such difficulty in<br />

c<strong>on</strong>venti<strong>on</strong>al x-ray absorpti<strong>on</strong> spectroscopy (XAS) measurement. By looking at the O<br />

K-edge XAS of BaTiO 3 via a fluorescence yield, we studied electr<strong>on</strong>ic structure and<br />

reveal that the observed spectra features are related with the structural changes under<br />

the applied E-field.<br />

RA05<br />

Chiral skyrmi<strong>on</strong>s and magnetic bubbles in multiferroic materials<br />

Xiuzhen Yu 1 *, Y. Tokunaga 1 , S. Seki 2 , Y. Kaneko 3 , S. Ishiwata 2 , M. Mostovoy 4 , N.<br />

Nagaosa 5 and Y. Tokura 6<br />

1<br />

The Institute of Physical and Chemical Research, Japan<br />

2<br />

University of Tokyo, Japan<br />

3<br />

Japan Science and Technology Agency, Japan<br />

4<br />

University of Gr<strong>on</strong>ingen, Netherlands<br />

5<br />

University of Tokyo, The Institute of Physical and Chemical Research, Japan<br />

6<br />

University of Tokyo, The Institute of Physical and Chemical Research, JST, Japan<br />

Nanometric chiral skyrmi<strong>on</strong>s and magnetic bubbles have been successfully realized in multiferroic<br />

materials Cu 2OSeO 3 and Sc-doped barium ferrite by means of Lorentz transmissi<strong>on</strong> electr<strong>on</strong> microscopy.<br />

Under the normal magnetic fields, chiral skyrmi<strong>on</strong>s with a topological number of -1 and a unique chirality, 50<br />

nm in diameter, emerge in a n<strong>on</strong>-centrosyemmetric helimagnet Cu 2OSeO 3. In analogy with the transiti<strong>on</strong><br />

from a helical spin structure to chiral skyrmi<strong>on</strong>s, a normal magnetic field turns the magnetic stripes into<br />

a bubble lattice with a positi<strong>on</strong>al order and random chiralities in a hexaferrite BaFe 0.79Sc 0.16Mg 0.05O 19<br />

with uniaxial anisotropy. By systematically investigating the dependences of magnetic c<strong>on</strong>figurati<strong>on</strong>s <strong>on</strong><br />

magnetic field, temperature and sample thickness, we reveal the differences between the spin textures of<br />

chiral skyrmi<strong>on</strong>s and magnetic bubbles. First, the magnetic bubbles determined by the ratio of dipolar and<br />

exchange interacti<strong>on</strong>s show str<strong>on</strong>g size dependence <strong>on</strong> magnetic field and sample thickness. The chiral<br />

skyrmi<strong>on</strong>s induced by Dzyaloshinskii-Moriya interacti<strong>on</strong>, however, show less size dependence <strong>on</strong> the<br />

external factors. Sec<strong>on</strong>d is a difference in chirality. The chiral skyrmi<strong>on</strong>s have a unique chirality determined<br />

by the crystal chirality, while magnetic bubbles have two opposite chiralities, resulting in a variety of<br />

zoological magnetic structure with varying external magnetic field.<br />

RA06<br />

Studies <strong>on</strong> Bi 1-xLa xFeO 3 crystals in pulsed high magnetic fields<br />

Masashi Tokunaga 1 , Mitsuru Akaki 2 , Hideki Kuwahara 2 , Kengo Oka 1 and Takumi<br />

Kihara 1<br />

1 The Institute for Solid State Physics, The University of Tokyo, Japan<br />

2 Department of Physics, Sophia University, Japan<br />

BiFeO 3 is known as the unique material that shows multiferroic nature at room temperature [1,2].<br />

Applicati<strong>on</strong> of high magnetic fields to this material induces a magnetic transiti<strong>on</strong> accompanied by a<br />

significant change in the electric polarizati<strong>on</strong> [3-5]. Although the occurrence of this transiti<strong>on</strong> is explained<br />

in the framework of the Ginzburg-Landau theory, in detail study is highly desirable to understand the<br />

microscopic origin of the magnetoelectric effects in this material. In this work, we synthesized crystals<br />

of Bi 1-xLa xFeO 3 with using the flux method, and studied their magnetic and dielectric properties in<br />

pulsed magnetic fields up to 55 T. Early experiments <strong>on</strong> the polycrystalline samples showed that partial<br />

substituti<strong>on</strong> of La for Bi reduces the magnetic field needed to cause the magnetic transiti<strong>on</strong> [6]. Our<br />

isothermal magnetizati<strong>on</strong> measurements showed that the transiti<strong>on</strong> field at 4.2 K changes from 18 T to 15<br />

T by La substituti<strong>on</strong>. Our dielectric study revealed that the electric polarizati<strong>on</strong> shows significant change<br />

accompanied with this magnetic transiti<strong>on</strong>. Therefore, the phenomena observed in BiFeO 3 are reproduced<br />

in the reduced field scale in the La substituted system, which enables us more systematic studies to clarify<br />

the microscopic origin of the magnetoelectric effects associated with the magnetic transiti<strong>on</strong>.<br />

[1] J. Wang et al., Science 299, 1719 (2003). [2] G. Catalan and J. F. Scott, Adv. Mater. 21, 2463<br />

(2009). [3] Yu. F. Popov et al., JETP Lett. 57, 69 (1993). [4] A. M. Kadomtseva, et al., JETP Lett.<br />

79, 571 (2004). [5] M. Tokunaga et al., J. Phys. Soc. Jpn. 79, 064713 (2010). [6] G. Le Bras et al.,<br />

Phys. Rev. B 80, 134417 (2009).<br />

136 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RA07<br />

Enhanced magnetic properties of Ni-doped BiFeO 3 compounds<br />

Y. J. Yoo 1 , J. S. Park 1 , J. H. Kang 2 , J. Kim 3 , B. W. Lee 3 , M. S. Seo 4 and Y. P. Lee 1 *<br />

1 Physics, Hanyang University, Korea<br />

2 Nano & Electr<strong>on</strong>ic Physics, Kookmin University, Korea<br />

3 Physics, Hankuk University of Foreign Studies, Korea<br />

4 Divisi<strong>on</strong> of Materials Science, Korea Basic Science Institute, Korea<br />

The structure and the magnetic properties of polycrystalline BiFeO 3 and BiFe 0.95Ni 0.05O 3<br />

bulk ceramic compounds, which were prepared by solid-state reacti<strong>on</strong> and rapid sintering,<br />

were investigated. High-purity Bi 2O 3, Fe 3O 4 and NiO powders were mixed with the<br />

stoichiometric proporti<strong>on</strong>s, and calcined at 450°C for 24 h to produce BiFe 1-xNi xO 3. The<br />

crystalline structure of samples was investigated at room temperature by using a Rigaku<br />

Miniflex powder diffractometer. The field-dependent and the temperature-dependent<br />

at high temperatures magnetizati<strong>on</strong> measurements were performed with a vibratingsample<br />

magnetometer. The temperature-dependent magnetizati<strong>on</strong> at low temperatures<br />

was analyzed with Quantum Design superc<strong>on</strong>ducting quantum-interference-device<br />

(SQUID) magnetometer. The x-ray diffracti<strong>on</strong> study dem<strong>on</strong>strates the compressive stress<br />

due to the Ni substituti<strong>on</strong> at the Fe site. The lattice c<strong>on</strong>stant of BiFe 0.95Ni 0.05O 3 is smaller<br />

than of BiFeO 3 because of the smaller i<strong>on</strong>ic radius of Ni 3+ than that of Fe 3+ . The fielddependent<br />

magnetizati<strong>on</strong> of BiFe 0.95Ni 0.05O 3 exhibits a clear hysteresis loop at 300 K. The<br />

magnetic properties of BiFe 0.95Ni 0.05O 3 were improved at room temperature because of the<br />

existence of structurally compressive stress. The zero-field-cooled temperature-dependent<br />

magnetizati<strong>on</strong> reveals that the magnetic transiti<strong>on</strong> temperature and the magnetic moment<br />

of BiFe 0.95Ni 0.05O 3 are higher than those of BiFeO 3.<br />

RA08<br />

Magnetic modulati<strong>on</strong> of electrical impedance in Bi-doped<br />

La 0.7Sr 0.3MnO 3<br />

Sujit Kumar Barik, M Aparnadevi and Ramanathan Mahendiran*<br />

Physics, Nati<strong>on</strong>al University of Singapore, Singapore<br />

In recent years, magnetic c<strong>on</strong>trol of dielectric polarizati<strong>on</strong> in multiferroics and<br />

magnetoelectrica has become a topic of c<strong>on</strong>siderble interest. Dielectric studies in these<br />

materials are often d<strong>on</strong>e using an impedance analyzer in the frequency range f = 10<br />

to 10 kHz. As the frequency increase, dieletric permitivity decreses. Here, we show<br />

that an interesting phenomen<strong>on</strong> occurs in MHz range in Bi doped La 0.7Sr 0.3MnO 3.<br />

With increasing freqeuncy of the ac current or ac voltage, both in- and out-of phase<br />

compnents of electrical impedance show an abrupt increase that is accompanied by a<br />

peak around the Curie temperature. The peak decreases in magnitude and is suppressed<br />

in a field of 1 kOe. This results in a huge ac magnetoresistance (30-35 % for H = 1<br />

kOe) and magnetoreactance (= 30-40 %). The origin of the magnetoreactance is not<br />

necessarity due to change in capacitance but but it is suggested to magnetoindutance<br />

effect, which has not been seriously c<strong>on</strong>sidered so far. The combinati<strong>on</strong> of huge ac<br />

magneoresistance and magnet<strong>on</strong>ductance in a single material provides multifuncti<strong>on</strong>al<br />

capabilities. Results from our studies are compared to magnetocapacitance behavior<br />

found in BiMnO 3[1]<br />

[1] T. Kimura, S. Kawamoto,I. Yamada, M. Azuma, M.Takano, Y. Tokura, Phys. Rev. B 2003, 67,<br />

R180401 2003<br />

RA09<br />

Theoretical study of PCAR measurement with d-wave<br />

superc<strong>on</strong>ductors.<br />

Hiroyuki Ohtori 1 and Hiroshi Imamura 2 *<br />

1 Univ. of Tsukuba, NRI-AIST, Japan<br />

2 NRI-AIST, Japan<br />

High spin polarizati<strong>on</strong> ferromagnetic metals are essential for creating high<br />

performance spintr<strong>on</strong>ics devices, therefore it is important to estimate the value of<br />

spin polarizati<strong>on</strong> quickly and efficiently. Point c<strong>on</strong>tact Andreev reflecti<strong>on</strong> (PCAR)<br />

spectroscopy is a powerful method for measuring spin polarizati<strong>on</strong> of ferromagnetic<br />

metals. However, most PCAR measurement were performed at very low temperatures,<br />

around 1.5 K, since the c<strong>on</strong>venti<strong>on</strong>al s-type superc<strong>on</strong>ductor is used. If we use high-<br />

Tc superc<strong>on</strong>ductors, PCAR measurement can be performed at higher temperature. In<br />

this study, we theoretically analyze the Andreev reflecti<strong>on</strong> in the ferromagnetic metal<br />

(FM) / insulator (I) / d-wave superc<strong>on</strong>ductor (dS) juncti<strong>on</strong>s. The superc<strong>on</strong>ducting<br />

gap in momentum space is not uniform in the d-wave superc<strong>on</strong>ductor, therefore<br />

the c<strong>on</strong>ductance suppressi<strong>on</strong> due to the insulator is affected by the difference of the<br />

Fermi wave number between the ferromagnetic metal and superc<strong>on</strong>ductor. Especially,<br />

in the case of d x2-y2 model, we found that the bias voltage at which the normalized<br />

c<strong>on</strong>ductance of the FM/I/dS juncti<strong>on</strong> drops is expressed as a functi<strong>on</strong> of the exchange<br />

field of the ferromagnetic metal.


RA10<br />

T C Evoluti<strong>on</strong> of Bulk and Optical Spectra of Nanocolloidal Fe-doped<br />

Manganate CaMn 1-xFe xO 3 (x = 0, 0.01, 0.03, 0.05)<br />

Huyen-yen Duc Pham, Duc-thang Pham, Nam-nhat Hoang* and Duc-tho Nguyen<br />

Faculty of Technical Physics and Nanotechnology, Vietnam Nati<strong>on</strong>al University,<br />

University of Engineering and Technology, Viet Nam<br />

Recently, the effect of magnetic reversal at low magnetic field was observed with the<br />

multiferroic Fe-doped CaMnO 3 [Sol. Stat. Commun. 142 (2007) 525]. We report here the<br />

optical behaviors of this class of compounds (CaMn 1-xFe xO 3, x = 0, 0.01, 0.03, 0.05) which<br />

were prepared by using traditi<strong>on</strong>al ceramic method with parent oxides as precursors. The<br />

analysis of structure showed the predominant orthorhombic phase with slight increased<br />

cell c<strong>on</strong>stants according to doping c<strong>on</strong>tent (from 3.743 to 3.746 Å). The investigati<strong>on</strong> of<br />

the Raman spectra also agreed with the increased Mn-O b<strong>on</strong>d length according to doping,<br />

therefore suggested the weakening of ferromagnetic exchange between Mn 3+ and Mn 4+<br />

cati<strong>on</strong>s (exactly, from 0.61 to 0.52 eV). This weakening also developed together with<br />

the reducti<strong>on</strong> of Curie temperature (T C) (from 155 to 135 K), the shifts of infra-red (IR)<br />

absorpti<strong>on</strong> maxima towards the l<strong>on</strong>ger wavelengths and the narrowing of band-gaps (from<br />

0.45 to 0.14 eV). The absorpti<strong>on</strong> spectra also showed a clear absorpti<strong>on</strong> line near 1.2 eV<br />

which is characteristic for Fe, and is composed mainly from 3d electr<strong>on</strong> transiti<strong>on</strong> with a<br />

change in spin.<br />

PACS number: 75.47.Lx; 75.50.Ee; 74.25.Fy; 75.30.Kz<br />

Keywords: perovskite, manganate, structure, optical<br />

RA11<br />

Evidence of magnetic phase separati<strong>on</strong> in LuFe2O4 Julie Bourgeois 1 , Gilles Andre 2 , Sylvain Petit 2 , Julien Robert 2 , Maria Poienar 3 , Jerome<br />

Rouquette 3 , Erik Elkaim 4 , Maryv<strong>on</strong>ne Hervieu 1 , Christine Martin 1 , Antoine Maignan 1<br />

and Francoise Damay 2<br />

1<br />

Laboratoire CRISMAT, CNRS UMR 6508, 6 bvd Marechal Juin, 14050 CAEN CEDEX, France<br />

2<br />

Laboratoire Le<strong>on</strong> Brillouin, CEA-CNRS UMR 12, 91191 GIF-SUR-YVETTE CEDEX, France<br />

3<br />

Institut Charles Gerhardt, UMR CNRS 5253, Place Eugene Bataill<strong>on</strong>, cc1503, 34095 MONTPELLIER<br />

CEDEX 5, France<br />

4<br />

Synchrotr<strong>on</strong> Soleil, L'Orme des Merisiers, Saint-Aubin BP 48, 91192 GIF-SUR-YVETTE CEDEX, France<br />

The magnetic properties of a polycrystalline sample of multiferroic LuFe 2O 4 [1] have been investigated<br />

by means of magnetizati<strong>on</strong> measurements combined with neutr<strong>on</strong> scattering, between 1.5 and 300K<br />

[2]. Magnetic Bragg peaks appear below T N = 240K, and can be indexed using two propagati<strong>on</strong> vectors,<br />

corresp<strong>on</strong>ding to either a ferromagnetic or an antiferromagnetic stacking of the ir<strong>on</strong> bilayers. The magnetic<br />

arrangement in the ab plane follows a 1:2 pattern, which obeys the charge ordering <strong>on</strong>e observed in<br />

transmissi<strong>on</strong> electr<strong>on</strong> microscopy [3]. Neutr<strong>on</strong> inelastic scattering data c<strong>on</strong>firm the str<strong>on</strong>g easy-axis<br />

single-i<strong>on</strong> anisotropy of the ir<strong>on</strong> spin in its trig<strong>on</strong>al envir<strong>on</strong>ment, of about 8 meV at 5 K. Modeling of the<br />

diffracti<strong>on</strong> data, based <strong>on</strong> a CO-type modulati<strong>on</strong> of the spin ordering, shows coexisting magnetic phases<br />

with opposite signs of the intra-bilayer interacti<strong>on</strong>, corresp<strong>on</strong>ding to two distinct magnetic transiti<strong>on</strong><br />

temperatures. Coexisting antiferromagnetic and ferrimagnetic phases, al<strong>on</strong>g with the enlarged axial<br />

magnetic anisotropy, are necessary to describe the macroscopic magnetic properties of this compound.<br />

[1] N. Ikeda et al., Nature (L<strong>on</strong>d<strong>on</strong>) 436, 1136 (2005) [2] J. Bourgeois et al., submitted to Phys. Rev.<br />

B (2012) [3] J. Bourgeois et al., to appear in Phys. Rev. B (2012)<br />

RA12<br />

Magnetoelectric effect in mechanically mediated structure of TbFe 2,<br />

Pb(Zr,Ti)O 3, and n<strong>on</strong>magnetic flakes<br />

Yin-gang Wang* and Ke Bi<br />

Nanjing University of Aer<strong>on</strong>autics and Astr<strong>on</strong>autics, China<br />

For most investigati<strong>on</strong>s <strong>on</strong> layered ME composites with excellent ME effect compared<br />

to single phase materials and multiphase bulk composites, the classical structure is<br />

c<strong>on</strong>structed layer by layer through interface b<strong>on</strong>ding. In this work, the proposed ME<br />

structure is made up of two magnetostrictive TbFe 2 alloys, <strong>on</strong>e piezoelectric PZT<br />

ceramic and two n<strong>on</strong>magnetic glass flakes. When an external ac magnetic field Hac is<br />

applied al<strong>on</strong>g the length directi<strong>on</strong> of magnetostrictive TbFe 2 flakes, the TbFe 2 flakes<br />

will produce an extensi<strong>on</strong>al strain. The strain then transfer to the PZT flake because<br />

of the end parts of PZT and TbFe 2 flakes b<strong>on</strong>ded with glass slides in a vertical plane.<br />

Due to the piezoelectric effect, the PZT flake will induce a charge output. The interface<br />

between magnetostrictive and piezoelectric phases is not required to achieve ME<br />

coupling. Increasing H dc from zero, α E,31 increases linearly until a maximum value is<br />

reached at 350 Oe, and then decreases subsequently. With further increase in Hdc,<br />

α E,31 reaches a maximum value, and then decreases subsequently. There are several<br />

res<strong>on</strong>ance peaks at 200 Oe and 1


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RA16<br />

Enhancement of multiferroic properties of solid state prepared La<br />

doped BiFeO 3.<br />

Suresh P and Srinath S*<br />

School of Physics, University of Hyderabad, India<br />

BiFeO 3 (BFO) has generated widespread interest since it is a room-temperature<br />

multiferroic. La xBi 1-xFeO 3 (x= 0.05-0.4) are prepared through solid state reacti<strong>on</strong><br />

method. X-ray diffracti<strong>on</strong> for x ≤ 0.15 shows R3c and for x> 0.15 the structure<br />

changes to Pbnm. The percentage of these phases present is estimated through Rietveld<br />

analysis. Raman spectra for x ≤ 0.15 exhibit 8 peaks (4A+4E modes). There is no<br />

shift in Raman modes indicating that La substitutes Bi in BFO. The dielectric c<strong>on</strong>stant<br />

increases and leakage current decreases with x. The enhanced polarizati<strong>on</strong> may be due<br />

to the distorti<strong>on</strong> of the crystal lattice with La doping. With increase in La doping the<br />

T N decreases. The magnetizati<strong>on</strong> (M) decreases up to 250 K and increases <strong>on</strong> further<br />

cooling indicating the spin reorientati<strong>on</strong>. A cusp in M-T is observed close to 50 K<br />

indicating the spin glass behavior. M-H loops do not saturate even for field up to 6 T.<br />

With La doping, H C and the magnetizati<strong>on</strong> increases dramatically in comparis<strong>on</strong> to<br />

x=0. Both Hc (~ 1.6 T) and Mr (0.27 emu/g) have maximum values for x =0.2 at 5 K.<br />

The increase in the magnetic parameters is attributed to the break in the spin cycloid<br />

structure.<br />

(1) H. Fukamura et.al. J. Magn.Magn. Mater. 310, e367 (2007) (2) Manoj K. Singh et.al. Phys. Rev.<br />

B. 77, 144403 (2008)<br />

RA17<br />

Magnetostructural coupling at the metal-insulator transiti<strong>on</strong> in<br />

YBaCo 2O 5.5 as seen by synchrotr<strong>on</strong> x-ray diffracti<strong>on</strong> and absorpti<strong>on</strong><br />

Jessica Padilla-pantoja, Javier Herrero-martin, Carlos Fr<strong>on</strong>tera and Jose Luis Garciamunoz<br />

Institut de Ciencia de Materials de Barcel<strong>on</strong>a, ICMAB-CSIC, Spain<br />

In LnBaCo 2O 5.5 (Ln: lanthanide) cobaltites Ln and Ba cati<strong>on</strong>s order in alternating planes al<strong>on</strong>g the<br />

c-axis yielding an ordered arrangement of CoO 5 pyramids and CoO6 octahedra. The presence of two<br />

local envir<strong>on</strong>ments for Co may be at the origin of proposed Co spin-state changes whose interplay<br />

with the structural and electr<strong>on</strong>ic changes at metal-insulator transiti<strong>on</strong>s (MIT) are currently attracting<br />

much attenti<strong>on</strong> [1-5]. We present a study of the magnetic, structural and thermoelectric properties of<br />

YBaCo 2O 5.5 as a functi<strong>on</strong> of temperature. Our results evidence the presence of three magnetic transiti<strong>on</strong>s<br />

with a str<strong>on</strong>g magnetostructural coupling. We have used synchrotr<strong>on</strong> x-ray powder diffracti<strong>on</strong> to show<br />

that the Pmmm orthorhombic structure transforms (<strong>on</strong> cooling) into a m<strong>on</strong>oclinic (P112/a) phase<br />

below T MI ~ 295 K by doubling the a-axis [6]. C<strong>on</strong>comitantly a ferromagnetic moment appears and<br />

the Seebeck coefficient is enhanced. A further cooling leads to the successive appearance of Co AFM<br />

structures (T N1 ~ 267 K, T N2 ~ 231 K), the crystal structure becoming again orthorhombic. Finally, we<br />

present temperature dependent soft x-ray absorpti<strong>on</strong> data at the Co L 3 edge. They discard the possibility<br />

of a high to low spin state change in Co i<strong>on</strong>s at octahedral sites across the MIT [7].<br />

[1] A. Maignan et al., J. Solid State Chem. 142, 247 (1999). [2] E. Suard et al., Phys. Rev. B 61, R11871<br />

(2000). [3] C. Fr<strong>on</strong>tera et al., Phys. Rev B 74, 054406 (2006). [4] V.P. Plakhty et al., Phys. Rev. B 71,<br />

214407 (2005). [5] M. Soda et al., J. Phys. Soc. Jpn. 72, 1729 (2003). [6] J. Padilla-Pantoja et al., Phys.<br />

Rev. B 81, 132405 (2010). [7] J. Padilla-Pantoja et al., J. Appl. Phys. 111, 234291 (2012) (In press).<br />

RA18<br />

Magnetic field dependence of dielectric properties in LuFe 2O 4<br />

Takashi Kambe*, Yukimasa Fukada, Tomoko Nagata and Naoshi Ikeda<br />

Physics, Okayama university, Japan<br />

The multiferroic properties in LuFe 2O 4 are of interest, in which c<strong>on</strong>tains equal amount<br />

of Fe 2+ and Fe 3+ in triangular lattice. This material shows a ferri-magnetic transiti<strong>on</strong> at<br />

240K and three-dimensi<strong>on</strong>al charge ordering at around 320K. The dielectric property<br />

of this material is suggested with a valence fluctuati<strong>on</strong> process of ir<strong>on</strong> i<strong>on</strong>s in the polar<br />

charge ordered domain. Here we report a magnetic field variati<strong>on</strong> of the dielectric<br />

c<strong>on</strong>stant of single crystal LuFe 2O 4, and discuss with the valence fluctuati<strong>on</strong> process of<br />

ir<strong>on</strong> charges in the magnetic domain wall.<br />

138 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RA19<br />

Pressure studies of LaAgSb 2 utilizing new integrated pressure cell<br />

Sven Friedemann 1 *, Zhou Feng 1 , Takao Ebihara 2 , Christophe Thessieu 3 and F Malte<br />

Grosche 1<br />

1 Cavendish Laboratory, University of Cambridge, United Kingdom<br />

2 Department of Physics, Shizuoka University, Shizuoka 422-8529, Japan<br />

3 easyLab Technologies Ltd., Earley Gate, Whiteknights Road, Reading, RG6 6BZ,<br />

United Kingdom<br />

RA20<br />

Crystal & Magnetic structure studies of doped BiFeO 3 multiferroic<br />

compound<br />

Se<strong>on</strong>gsu Lee<br />

Neutr<strong>on</strong> Science Divisi<strong>on</strong>, KAERI, Korea<br />

Multiferroics, materials combining multiple order parameters, offer an exciting way of coupling<br />

phenomena such as electr<strong>on</strong>ic and magnetic order. The coexistence of different order parameter<br />

permits potential applicati<strong>on</strong>s in informati<strong>on</strong> storage, spintr<strong>on</strong>ics, and magnetic or electric field<br />

sensors. The perovskite BiFeO 3(BFO) is known to be antiferromagnetic below the Neel temperature<br />

of 640 K and ferroelectric with a high Curie temperature of 1100 K. According to the previous<br />

doping studies of BFO, it is likely that n<strong>on</strong>-stoichiometry and sec<strong>on</strong>d-phase formati<strong>on</strong> are the factors<br />

resp<strong>on</strong>sible for leakage current in BFO. It has been suggested that oxygen n<strong>on</strong>stoichiometry leads<br />

to valence fluctuati<strong>on</strong>s of Fe i<strong>on</strong>s in BFO, resulting in high c<strong>on</strong>ductivity. To reduce the large leakage<br />

current of BFO, <strong>on</strong>e attempt is to make d<strong>on</strong>or-doped BFO compounds. In this study, we have tried to<br />

generate the new multiferroric material functi<strong>on</strong>ing <strong>on</strong> at room temperature. The candidate systems<br />

are BiFeO 3+ BaMnO 3 and BiFeO 3+ BaTiO 3. These system have been fabricated by a solid-state<br />

reacti<strong>on</strong> method and flux method, respectively. The crystal and magnetic structure of these systems<br />

are studied using XRD and neutr<strong>on</strong> powder diffracti<strong>on</strong> as functi<strong>on</strong>s of temperature. We will discuss<br />

the magnetic and electric property of new multiferroic system working <strong>on</strong> at room temperature.<br />

1. T. Choi, S. Lee, Y. J. Choi, V. Kiryukhin, and S-W. Che<strong>on</strong>g Science 324, 63 (2009) 2. Junghwan<br />

PARK, Sang-Hyun LEE, Se<strong>on</strong>gsu LEE, Fabia GOZZO,Hiroyuki KIMURA, Yukio NODA, Young Jai<br />

CHOI, Valery KIRYUKHIN, Sang-Wook CHEONG, Younjung JO, Eun Sang CHOI, Luis BALICAS,<br />

Gun Sang JEON, and Je-Geun PARK Journal of the Physical Society of Japan 80, 114714(2011)<br />

RA21<br />

WITHDRAWN<br />

The analysis of structure, magnetic and ferroelectric properties of Ba1 xBixTi0.95Fe0.05O3 Widi Yansen 1 , Kadek Juliana Parwanta 1 , Jaeye<strong>on</strong>g Kim 1 , Min Gyu Kang 2 , Ch<strong>on</strong>g Yun<br />

Kang 2 and Bo Wha Lee 1 *<br />

1<br />

Physics, Hankuk University of Foreign Studies, Korea<br />

2<br />

Physics, Korea Institute of Science and Technology, Korea<br />

The multiferroic material is a material which shows more than <strong>on</strong>e primary ferroic order parameter<br />

simultaneously and can be made by introducing the magnetic impurities into ferroelectric material<br />

[1]. BaTiO 3 is known as a classical ferroelectric material, whereas the Fe-doped BaTiO 3 is reported<br />

to have a magnetic ordering. Although the Fe doping can induce the ferromagnetism in BaTiO 3,<br />

the ferroelectricity of this material is suppressed. In this report, we analyze the structure, magnetic<br />

and ferroelectric properties of Ba 1-xBi xTi 0.95Fe 0.05O 3 (0 ≤ x ≤ 0.05). XRD results indicate that the<br />

tetrag<strong>on</strong>al phase is merged with the hexag<strong>on</strong>al phase for x < 0.05. At x = 0.05, the pure tetrag<strong>on</strong>al<br />

phase is observed. The magnetic field dependence of magnetizati<strong>on</strong> at room temperature for x<br />

= 0 shows a kind of antiferromagnetism. Introducing 2 % Bi doping, it shows the ferrimagnetic<br />

properties. However, with the 5 % doping of Bi, the ferrimagnetic loop is disappeared and<br />

becomes paramagnetic. It suggests that the superexchange between Fe 3+ i<strong>on</strong>s in octahedral<br />

and pentrahedral sites associated with oxygen vacancy produces the ferromagnetism [2]. The<br />

ferroelectric hysteresis loop with low leakage current is <strong>on</strong>ly observed for x = 0.02. These results<br />

indicate that the multiferroic properties are observed in Ba 0.98Bi 0.02Ti 0.95Fe 0.05O 3 sample.<br />

[1] Y. Shuai, S. Zhou, D. Burger, H. Reuther, and I. Skorupa, J. Appl. Phys. 109, 084105 (2011). [2] F.<br />

Lin, D. Jiang, X. Ma, and W. Shi, J. Magn. Magn. Mater. 320, 691-694 (2008).


RA22<br />

Spin dynamics of multiferroic BiFeO 3 single crystal<br />

Jaeh<strong>on</strong>g Je<strong>on</strong>g 1 , E. A. Goremychkin 2 , T. Guidi 2 , K. Nakajima 3 , Gun Sang Je<strong>on</strong> 4 , Shin-ae Kim 5 , S.<br />

Furukawa 6 , Y<strong>on</strong>g Baek Kim 6 , Se<strong>on</strong>gsu Lee 5 , V. Kiryukhin 7 , S-w. Che<strong>on</strong>g 7 and Je-geun Park 1 *<br />

1 FPRD Department of Physics & Astr<strong>on</strong>omy, Center for Str<strong>on</strong>gly Correlated Materials<br />

Research, Seoul Nati<strong>on</strong>al University, Seoul 151-747, Korea<br />

2 ISIS Facility, STFC Rutherford Applet<strong>on</strong> Laboratory, Oxfordshire OX11 0QX, United Kingdom<br />

3 Neutr<strong>on</strong> Science Secti<strong>on</strong>, MLF Divisi<strong>on</strong>, J-PARC Center, Tokai, Ibaraki 319-1106, Japan<br />

4 Department of Physics, Ewha Womans University, Seoul 120-750, Korea<br />

5 Neutr<strong>on</strong> Science Divisi<strong>on</strong>, Korea Atomic Energy Research Institute, Daeje<strong>on</strong> 305-353, Korea<br />

6 Department of Physics, University of Tor<strong>on</strong>to, Tor<strong>on</strong>to M5S 1A7, Canada<br />

7 Rutgers Center for Emergent Materials and Department of Physics and Astr<strong>on</strong>omy, Rutgers<br />

University, Piscataway NJ 08854, USA<br />

Multiferroic compounds are <strong>on</strong>e of most challenging topics in the c<strong>on</strong>densed matter physics [1] not <strong>on</strong>ly for<br />

its fundamental importance but also for huge future applicati<strong>on</strong>s. Although several systems are known to have<br />

multiferroic behavior, there are few multiferroic materials that have both magnetic and ferroelectric transiti<strong>on</strong><br />

temperatures above room temperature. BiFeO 3 is probably the <strong>on</strong>ly excepti<strong>on</strong> with Neel temperature at T N=650<br />

K and Curie temperature at T C=1100 K [2]. In order to understand the spin dynamics of BiFeO 3, we have carried<br />

out inelastic neutr<strong>on</strong> scattering experiments <strong>on</strong> ten co-aligned single crystals of BiFeO 3 using AMATERAS<br />

beamline at J-PARC and MERLIN beamline at ISIS. In particular, we used a so-called sample rotati<strong>on</strong> method <strong>on</strong><br />

MERLIN to map out the full three-dimensi<strong>on</strong>al spin wave [3]. We have also calculated the spin wave dispersi<strong>on</strong><br />

using Heisenberg Hamilt<strong>on</strong>ian with two exchange parameters between the nearest and next nearest neighbors.<br />

A Dzyaloshinskii-Moriya term that arises from the spiral magnetic structure of BiFeO 3 was also examined. By<br />

carefully examining the AMATERAS and MERLIN data, we could find, for the first time, the full spin wave<br />

dispersi<strong>on</strong> of BiFeO 3 and determine the exchange parameters that are c<strong>on</strong>sistent with the experimental results.<br />

1) S-W. Che<strong>on</strong>g and M. Mostovoy, Nature Materials 6,13 (2007) 2) I. Sosnowska et al., J. Phys. C: Solid<br />

State Phys. 15, 4835 (1982) 3) Jaeh<strong>on</strong>g Je<strong>on</strong>g et al., Phys. Rev. Lett. 108, 077202 (2012)<br />

RA23<br />

Magnetic and dielectric properties of the single crystals Sm 1xHo<br />

xFe 3(BO 3) 4 and Sm 1-xLa xFe 3(BO 3) 4<br />

Evgeniy Eremin*, Irina Gudim, Vladislav Temerov and Alexander Eremin<br />

Kirensky Institute of Physics SB RAS, Russia<br />

The trig<strong>on</strong>al rare-earth ferroborates with hantit ctructures is interested due to very<br />

str<strong>on</strong>g of the electric polarizati<strong>on</strong> induced by magnetic field. The research of single<br />

crystals with double rare-earth subsystems such as Sm 1-xR xFe 3(BO 3) 4 (R = Ho, La) is<br />

important for analysis microscopic mechanism of magnetoelectric interacti<strong>on</strong>. The<br />

single crystals of Sm 1-xHo xFe 3(BO 3) 4 with x = 0; 0.3; 0.5 and Sm 1-xLa xFe 3(BO 3) 4. with<br />

х = 0.25; 0.5 were grown by a flux method. The magnetic and magnetodielectric<br />

properties have been investigated. It has been revealed what magnetic behaviour and<br />

magnetodielectric effect essential depended <strong>on</strong> x. The magnetic field influence <strong>on</strong> the<br />

change in degree of dielectric penetrability is decreased with increasing x for both<br />

under study families. The decreasing of magnetodielectric effect is probably related<br />

with influence of the racemic twinning.<br />

RA24<br />

Far infrared spectroscopy of EuFe 3(BO 3) 4<br />

Kirill N. Boldyrev 1 *, Taras N. Stanislavchuk 2 , Marina N. Popova 1 and Sergey A.<br />

Klimin 1<br />

1 Solid State Spectroscopy, Institute of spectroscopy RAS, Russia<br />

2 Physics, New Jersey Institute of Technology, USA<br />

We present the results <strong>on</strong> the polarized far infrared absorpti<strong>on</strong> spectra of EuFe 3(BO 3) 4<br />

crystal in a wide range of temperature (3.5 - 300K). Rare-earth ir<strong>on</strong> borates RFe 3(BO 3) 4<br />

undergo the antiferromagnetic phase transiti<strong>on</strong> at temperatures below 40 K, and some<br />

of them exhibit a significant magnetoelectric and magnetoelastic effect. EuFe 3(BO 3) 4<br />

is known to exhibit two phase transiti<strong>on</strong>s, the structural <strong>on</strong>e at T C = 58 K [1], and the<br />

antiferromagnetic ordering at T N = 34 K [2]. The ph<strong>on</strong><strong>on</strong> frequencies dem<strong>on</strong>strate<br />

pr<strong>on</strong>ounced changes at T C, c<strong>on</strong>sistent with the observed peculiarities in the dielectric<br />

c<strong>on</strong>stant and thermal expansi<strong>on</strong> [3]. Smaller but clearly visible ph<strong>on</strong><strong>on</strong> shift were<br />

registered below T N, thus evidencing the spin-lattice interacti<strong>on</strong> in the title compound.<br />

[1] M.N. Popova, Journal of Rare Earths, 27, 607 (2009). [2] M.N. Popova, Journal of <strong>Magnetism</strong><br />

and Magnetic Materials, 321, 716 (2009). [3] A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev, A.P.<br />

Pyatakov, S.S. Krotov, K.I. Kamilov, J. Low Temp. Phys., 36(6), 640 (2010).<br />

RA25<br />

RA26<br />

RA27<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Electric polarizati<strong>on</strong>, toroidal moments, spin chirality, spin canting at<br />

avoided level crossing induced by Dzyaloshinsky-Moriya interacti<strong>on</strong> in<br />

V 3 nanomultiferroics in transverse magnetic field<br />

Moisey Belinsky<br />

School of Chemistry, Tel-Aviv University, Tel Aviv, Israel<br />

The spin-frustrated V 3 and Cu 3 nanomagnets with the Dzialoshinsky-Moriya (DM) interacti<strong>on</strong> have<br />

received great attenti<strong>on</strong> for potential applicati<strong>on</strong> in quantum computati<strong>on</strong> [1-8]. V 3 with the out-of-plane<br />

Dz and in-plane Dn DM interacti<strong>on</strong>s dem<strong>on</strong>strates the multiferroic behavior in l<strong>on</strong>gitudinal magnetic field<br />

Bz||Z: field-induced polarizati<strong>on</strong> Pz(Bz) and toroidal moments Tz(Bz), which depend <strong>on</strong> the vector Κz(Bz)<br />

[scalar χ(Bz)] chirality, and complicated individual spin dynamics at avoided level crossing (ALC) [7].<br />

In order to investigate the multiferroic behavior in transverse field Bx┴Z and B-reversal/rotati<strong>on</strong> effects,<br />

P(Bx), Tn(Bx), M(Bx)magnetizati<strong>on</strong>, Κz(Bx), χ(Bx) and spin canting were calculated for B┴Z. The spin<br />

current P~Is mechanism [9] is the driving force of Pz(Bx) with a maximum at ALC that corresp<strong>on</strong>ds to<br />

Is(max). The in-plane DM leads to the in-plane Tn(Bx) which exhibits T-flop under B-rotati<strong>on</strong>/reversal.<br />

Tn(B), χ(B), orbital moment M'(B), circular orbital current Io~χ [Pz(B), Κz(B), Is] show the switch <strong>on</strong>/off<br />

[reducti<strong>on</strong>] under B-rotati<strong>on</strong> within vertical XZ plane. Field behavior Pz(Bx), Tn(Bx) , M(Bx), Κz(Bx),<br />

Is, Io, and individual spin dynamics for Bx┴Z str<strong>on</strong>gly differ from that for Bz||Z. V 3 exhibits n<strong>on</strong>-linear<br />

reducti<strong>on</strong> of Κz(Bx)vector chirality, χ(Bx)=0, and the entanglement effect. The V 3 nanomultiferroics<br />

dem<strong>on</strong>strate magnetically c<strong>on</strong>trolled anisotropic Pz(B), Tn(B), M(B), Κz(B), χ(B), M', Is, Io characteristics.<br />

1. T. Yamase et al., Inorg. Chem. 43, 8150 (2004). 2. Y. Kohama et al., J. Solid. State. Chem. 182, 1468 (2009). 3. K.-Y. Choi et<br />

al., Phys.Rev.Lett. 96, 107202 (2006); Phys. Rev. B 77, 024406 (2008). 4. M. Trif et al., Phys.Rev Lett. 101, 217201 (2008). 5. M.<br />

Trif et al., Phys.Rev. B 82, 045429 (2010). 6. M. F. Islam et al., Phys. Rev. B 82, 155446 (2010). 7. M.I. Belinsky, Phys. Rev. B<br />

84, 064425 (2011). 8. M.I. Belinsky, Chem. Phys. 361, 137, 152 (2009). 9. H. Katsura et al ., Phys. Rev. Lett. 95, 057205 (2005).<br />

Mössbauer studies of bismuth ferrite<br />

Seungkyu Han, Y<strong>on</strong>g Hui Li, Minse<strong>on</strong> Kim, Sam Jin Kim and Chul Sung Kim*<br />

Physics, Kookmin University, Korea<br />

Perovskite bismuth ferrite (BiFeO 3) is a multiferroic material, having ferroelectric order<br />

(T C = 1,103 K) and antiferromagnetic order (T N = 643 K) [1]. It is a possible candidate for<br />

informati<strong>on</strong> storage, spintr<strong>on</strong>ics, and sensors applicati<strong>on</strong>s [2]. Here, we have measured the<br />

magnetic properties of BiFeO 3 using x-ray diffractometer, field emissi<strong>on</strong> scanning electr<strong>on</strong><br />

microscope (FE-SEM), vibrating sample magnetometer, and Mössbauer spectroscopy.<br />

Single phased BiFeO 3 was synthesized by a low-temperature hydrothermal method. FE-<br />

SEM results showed that the grain sizes of microsphere and microcube were about 80 μm<br />

and 50 μm, respectively. BiFeO 3 powder showed weak-ferromagnetic behavior with a small<br />

magnetizati<strong>on</strong> value (Ms ~ 100 memu/g) at 295K. Rietveld refinement analysis showed that<br />

Fe-site and O-site splits into two pairs, respectively. The Mossbauer spectra of BiFeO 3 were<br />

analyzed with 2-set sextet. Isomer shift (δ) values showed that Fe 3+ i<strong>on</strong>s existed in octahedral<br />

site. Electric quadrupole shift (EQ) values suggested different lattice distributi<strong>on</strong> at octahedral<br />

site. Based <strong>on</strong> EQ values (0.02 ~ 0.1 mm/s), splitting into two partially occupied sites results<br />

in a distorted FeO 6 octahedral. The weak ferromagnetism observed in the hydrothermallyprepared<br />

BiFeO 3 particles comes from distorted FeO 6 octahedral, leading to incomplete<br />

counterbalance between the antiferromagnetic sublattices of the Fe i<strong>on</strong>s.<br />

[1] G. A. Smolenskii and I. chupis, Sov. Phys. Usp. 25, 475 (1982). [2] J. Wang, J. B. Neat<strong>on</strong>,<br />

H. Zheng, V. Nagarajan, S. B. Ogale, B. Liu, D. Viehland, V. Vaithyanathan, D. G. Schlom, U. V.<br />

Waghmare, N. A. Spaldin, K. M. Rabe, M. Wuttig, and R. Ramesh, Science 299, 1719 (2003).<br />

Synthesis and electrical characterizati<strong>on</strong> of Bi 1-xY xFeO 3 ceramics<br />

Vikash Singh*, Manoj Kumar and R. K. Dwivedi<br />

Physics & materials science & engg., Jaypee institute of informati<strong>on</strong> technology,<br />

India<br />

Compositi<strong>on</strong>s within range 0.05 ≤ x ≤ 0.20 in the system Bi 1-xY xFeO 3 (BYFO) have<br />

been synthesized by solid state reacti<strong>on</strong> method. Structural and electrical properties of<br />

yttrium doped bismuth ferrite ceramics have been investigated. Single-phase formati<strong>on</strong><br />

has been c<strong>on</strong>firmed by x-ray diffracti<strong>on</strong>, which has shown rhombohedral symmetry<br />

with R3c space group at room temperature. Temperature dependent dielectric behavior<br />

of BYFO ceramics with in compositi<strong>on</strong> range 0.05 ≤ x ≤ 0.20 at few frequencies<br />

have shown an anomaly near the temperature which corresp<strong>on</strong>ds to magnetic phase<br />

transiti<strong>on</strong> ‘T N’ for pure BiFeO 3 material (i.e.370 o C). Substituti<strong>on</strong> of yttrium in BFO has<br />

shown a shift in T N. The temperature dependence of ac c<strong>on</strong>ductivity indicates that the<br />

c<strong>on</strong>ducti<strong>on</strong> process may be influence by defects which occurs due to oxygen vacancies.<br />

1. N. A. Hill, Why are there so few magnetic ferroelectrics, J. Phys. Chem. B 104, 669 (2000). 2.<br />

H. Singh, K.L. Yadav, Dielectric, magnetic and magnetoelectric properties of La and Nb codoped<br />

bismuth ferrite, J. Phys.: C<strong>on</strong>dens. Matter 23, 385901 (2011).<br />

July 8 - 13, 2012 Busan, Korea 139<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RA28<br />

Lattice engineering <strong>on</strong> transiti<strong>on</strong> metal oxide thin film<br />

Chang Uk Jung*<br />

Department of Physics, Hankuk University of Foreign Studies, Korea<br />

Transiti<strong>on</strong> metal oxide having a perovskite structure showed a large spectrum of<br />

physical properties. YBa2Cu3O7 showed high temperature superc<strong>on</strong>ductivity,<br />

(La,Ca,Sr)MnO3 showed ferromagnetism with half metallicity, Pb(Zr,Ti)O3 showed<br />

Ferroelectricity, and BiFeO3 showed coexistence of antiferromagnetism and<br />

ferroelectricity. Recent advance in interface c<strong>on</strong>trol revealed a 2d electr<strong>on</strong> gas, interface<br />

superc<strong>on</strong>ductivity, interface magnetism, oribital reordering, interface thermoelectric<br />

effect at the interface of transiti<strong>on</strong> metal oxide. The effect of lattice distorti<strong>on</strong> has been<br />

studied for a l<strong>on</strong>g time and recently showed that lattice distorti<strong>on</strong> during thin film<br />

growth can create new ground state. Especially ATiO3, (A=Sr, Y, Eu) was interesting. [In<br />

bulk state, YTiO3 and EuTiO3 are magnetic insulator, and SrTiO3 is not ferroelectric.]<br />

I will introduce the some current research <strong>on</strong> the progress <strong>on</strong> these materials In this<br />

case, <strong>on</strong>ly lattice mismatch between substrate and film was used. On the c<strong>on</strong>trary<br />

the available substrate is rather narrow. I will also introduce efforts to overcome this<br />

problem.<br />

[1] A. Ohtomo & H. Y. Hwang, Nature 427, 423 (2004), [2] N. Reyren et al., Science 317, 1196<br />

(2007). [3] J. Chakhalian et al., Science 318, 1115 (2007). [4] S. C. Chae,et al., Appl. Phys. Lett. 89,<br />

182512 (2006). [5] J. H. Haeni et al., om, Nature 430, 758 (2004). [6] June Hyuk Lee et al., Nature<br />

466, 954 (2010). [7] C. U. Jung et al.,, Appl. Phys. Lett., 84, 2590 (2004). [8] B. W. Lee et al., J. of<br />

Appl. Phys., 104, 103909 (2008). [9] B. W. Lee et al.,, APL 96, 102507 (2010).<br />

RB01<br />

Structural and magnetic properties of doped ir<strong>on</strong> oxo-selenides<br />

Sven Landsgesell 1 , Karel Prokes 1 and Dimitri Argyriou 2<br />

1 M-I1, Helmholtz-Zentrum Berlin, Germany<br />

2 European Spallati<strong>on</strong> Source, Sweden<br />

In the Cu oxide superc<strong>on</strong>ductors the Cu resides in a square planar geometry[1], while in the<br />

Fe pnictide superc<strong>on</strong>ductors the Fe i<strong>on</strong> resides in a tetrahedrally coordinated positi<strong>on</strong>[2].<br />

Both compounds may show a separating LaO layer between the superc<strong>on</strong>ducting sheets.<br />

La 2O 3Fe 2Se 2 shows square planar Fe O sheets and offers a direct super exchange pathway<br />

to the next nearest Fe neighbour via the Se, comparable to the ir<strong>on</strong> arsenides[3]. These super<br />

exchange pathways are similar to the superc<strong>on</strong>ductors despite the difference and provide<br />

a similar local envir<strong>on</strong>ment for the Fe as is known for the Fe-superc<strong>on</strong>ductors[4]. We<br />

investigated the changes in the physical properties in the ir<strong>on</strong> oxo-selenides by varying the<br />

electr<strong>on</strong> density and structural comp<strong>on</strong>ents. We doped the parent compound with F, Cd and<br />

rare earths with smaller radii (La 2O 3-xFxFe 2Se 2, and La 2-x(Cd/RE) xO 3Fe 2Se 2, respectively).<br />

Temperature dependent neutr<strong>on</strong> diffracti<strong>on</strong> of the samples mostly show an antiferromagnetic<br />

order al<strong>on</strong>g the a-directi<strong>on</strong> with a propagati<strong>on</strong> of (0.5 0 0.5). We find indicati<strong>on</strong>s for an<br />

evolving transiti<strong>on</strong> in the physical properties, as decreasing TN for fluorine and rare earth<br />

samples. This is comparable to the known doped ir<strong>on</strong> superc<strong>on</strong>ductors and in c<strong>on</strong>trast to the<br />

electr<strong>on</strong> deficient Cd doped samples that show an in creasing TN.<br />

1 D. Vaknin et al., Phys. Rev. Lett. 58, 2802 (1987) 2 Y. Kamihara et al., J. Am. Chem. Soc. 130,<br />

3296 (2008) 3 E. Manousakis et al., Solid State Comm. 150, 62 (2010) 4 D.G. Free and J.S.O.<br />

Evans, Phys. Rev. B 81, 214433 (2010)<br />

RB02<br />

Phase separati<strong>on</strong> of antiferromagnetism and superc<strong>on</strong>ductivity in<br />

Rb xFe 2-ySe 2 observed by Rb NMR<br />

Yoshiaki Kobayashi 1 *, Shunsuke Saiki 1 , Shouhei Kototani 1 , Masayuki Itoh 1 and<br />

Masatoshi Sato 2<br />

1 Department of Physics, Graduate School of Science, Nagoya University, Japan<br />

2 Research Center For Neutr<strong>on</strong> Science And Technology, CROSS, Japan<br />

The observati<strong>on</strong> of the superc<strong>on</strong>ducting (SC) transiti<strong>on</strong> in A xFe 2-ySe 2 (A: alkali metal<br />

elements; Tc of ~30K) has been <strong>on</strong>e of surprising things, because the transiti<strong>on</strong> was<br />

found in the antiferromagnetic (AF) system with a large AF moment of ~3.3 μB/<br />

Fe. Moreover, their electrical resistivity just above Tc is too large to c<strong>on</strong>ceive the<br />

occurrence of the superc<strong>on</strong>ductivity. Here, to clarify whether the AF and SC states<br />

are microscopically coexistent or just phase-separated, we have carried out NMR<br />

measurements <strong>on</strong> both crystals with and without SC transiti<strong>on</strong>. The Rb-NMR spectra<br />

below 300 K observed for these crystals are clearly separable into two parts with<br />

different widths. The broader spectrum can be explained by the presence of the<br />

regi<strong>on</strong> with the “blocked” antiferromagnetic spins proposed by the neutr<strong>on</strong> magnetic<br />

scattering studies [1]. The narrower spectrum for the crystal with SC transiti<strong>on</strong> can<br />

be understood from its temperature dependence and spectral shape to stem from<br />

the superc<strong>on</strong>ducting regi<strong>on</strong> without Fe-vacancy ordering [1]. Thus, we can clearly<br />

c<strong>on</strong>clude that the superc<strong>on</strong>ductivity and the antiferromagnetism in the present system<br />

are phase-separated.<br />

[1] W. Bao, et al., Chin. Phys. Lett. 28, No. 8 (2011) 086104.<br />

140 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RB03<br />

Superc<strong>on</strong>ductivity of EuFe 2As 2 under high pressure<br />

Shugo Ikeda and Hisao Kobayashi<br />

Graduate School of Material Science, University of Hyogo, Japan<br />

EuFe 2As 2 with the tetrag<strong>on</strong>al ThCr 2Si 2-type structure exhibits a spin density wave<br />

(SDW) transiti<strong>on</strong> at 190 K, with a simultaneous structural change [1]. The SDW<br />

transiti<strong>on</strong> is suppressed by applied pressure and bulk superc<strong>on</strong>ductivity appears around<br />

2.5 GPa [1-3]. Furthermore, magnetic moments of Eu sublattice order magnetically<br />

at To = 19 K. The value of To reveals no changes at pressures of up to 3 GPa [1-3].<br />

We have studied the superc<strong>on</strong>ductivity and the magnetism of EuFe 2As 2 by measuring<br />

dc magnetizati<strong>on</strong> and 57Fe nuclear forward scattering (NFS) under high pressure.<br />

Magnetizati<strong>on</strong> at 2.6 GPa rapidly increases below 24 K and then gradually decreases<br />

by the appearance of superc<strong>on</strong>ductivity. The size of the drop at low temperatures is<br />

c<strong>on</strong>sistent with nearly 100 % shielding. Namely, bulk superc<strong>on</strong>ductivity appears under<br />

the magnetic ordered state of Eu sublattice. The pressure dependence of 57Fe NFS<br />

spectra shows the decrease of the hyperfine field Bhf of Fe sublattice with increasing<br />

pressure. Furthermore, it is found that the directi<strong>on</strong> of Bhf varies around 2.6 GPa,<br />

implying the changes of magnetic structure. In this presentati<strong>on</strong>, we will discuss the<br />

relati<strong>on</strong> between the superc<strong>on</strong>ductivity and the magnetism of EuFe 2As 2, c<strong>on</strong>sidering<br />

these results.<br />

[1] K. Matsubayashi et. al : Phys. Rev. B 84 (2011) 024502. [2] N. Kurita et. al : arXiv:<br />

1103.4209v1. [3] T. Terashima et. al : J. Phys. Soc. Jpn. 78 (2009) 083701.<br />

RB04<br />

Superc<strong>on</strong>ductivity in 4d, 5d pnictides<br />

Tomohiro Takayama 1 *, Daigorou Hirai 1 , Keisuke Kuwano 1 and Hidenori Takagi 2<br />

1 Department of Advanced Materials, University of Tokyo, Japan<br />

2 Department of Physics, University of Tokyo, Japan<br />

After the discovery of the ir<strong>on</strong> arsenide superc<strong>on</strong>ductors, a tremendous effort has<br />

g<strong>on</strong>e into the search for new high-Tc superc<strong>on</strong>ductors. We explored 4d, 5d pnictides,<br />

hoping to find superc<strong>on</strong>ductors which share important characteristics with Febased<br />

superc<strong>on</strong>ductors. We report two new superc<strong>on</strong>ducting systems with such<br />

characteristics, but sufficiently different from Fe pnictides. (i) APt 3P (A = Ca, Sr and<br />

La) The new compounds APt 3P crystallize in an antiperovskite structure with distorted<br />

PPt6 octahedra. All of them display superc<strong>on</strong>ductivity below 6.6, 8.4 and 1.5 K for<br />

Ca-, Sr- and LaPt 3P, respectively. The highest-Tc compound SrPt 3P exhibits str<strong>on</strong>gcoupling<br />

s-wave superc<strong>on</strong>ductivity. The presence of multiple pocket Fermi surface<br />

was inferred in SrPt 3P, which might enhance the coupling with low-energy ph<strong>on</strong><strong>on</strong>s.<br />

(ii) RuPn (Pn = P, As) Binary RuPn crystallize in an orthorhombic MnP-type structure.<br />

RuP and RuAs were found to show a metal to n<strong>on</strong>-magnetic insulator transiti<strong>on</strong> at 270<br />

and 200 K, respectively. The structural analysis evidenced another phase transiti<strong>on</strong> at<br />

higher temperatures, indicative of pseudogap formati<strong>on</strong>. The two transiti<strong>on</strong>s can be<br />

suppressed by Rh-doping. We discovered superc<strong>on</strong>ductivity with a maximum Tc = 3.7<br />

K and 1.8 K at the critical doping level for suppressing the pseudogap-phase in Ru1xRhxP<br />

and Ru1-xRhxAs, respectively.<br />

D. Hirai et al., arXiv:1112.0604<br />

RB05<br />

Elastic softening and electric quadrupole in ir<strong>on</strong> pnictide<br />

superc<strong>on</strong>ductor Ba(Fe 1-xCo x) 2As 2<br />

Ryosuke Kurihara 1 , Koji Araki 1 , Keisuke Mitsumoto 1 , Mitsuhiro Akatsu 1 , Yuichi<br />

Nemoto 2 , Terutaka Goto 2 , Yoshiaki Kobayashi 3 and Masatoshi Sato 4<br />

1 Graduate School of Science and Technology, Niigata University, Japan<br />

2 Graduate School of Science and Technology, Niigata University, JST-TRIP, Japan<br />

3 Department of Physics, Nagoya University, JST-TRIP, Japan<br />

4 Department of Physics, Nagoya University, CROSS, JST-TRIP, Japan<br />

We have performed ultras<strong>on</strong>ic measurements <strong>on</strong> ir<strong>on</strong> based superc<strong>on</strong>ductor Ba(Fe 1-xCo x) 2As 2 in order<br />

to investigate the mechanism of the superc<strong>on</strong>ductivity. The end-material BaFe 2As 2 shows structural and<br />

antiferromagnetic simultaneous transiti<strong>on</strong>s at~140K. With increasing Co c<strong>on</strong>centrati<strong>on</strong> x, the temperatures of<br />

these transiti<strong>on</strong> are lowered and separated from each other. The superc<strong>on</strong>ductivity appears at x>0.03. In our<br />

recent work [1], the softening of the elastic c<strong>on</strong>stant C66 as large as 21% was observed for optimized samples<br />

Ba(Fe 0.9Co 0.1) 2As 2 with decreasing temperature from 300K down to superc<strong>on</strong>ducting transiti<strong>on</strong> temperature<br />

of TSC=23 K, while other elastic c<strong>on</strong>stants do not show softening. Here, we have measured elastic c<strong>on</strong>stants<br />

of Ba(Fe 1-xCo x) 2As 2 samples with x=0,0.03 and 0.07, where <strong>on</strong>ly the C66 shows huge softening larger than<br />

70% with decreasing temperature down to the structural transiti<strong>on</strong> temperature. The large softening of C66<br />

in Ba(Fe 1-xCo x) 2As 2 with several Co c<strong>on</strong>centrati<strong>on</strong> x≤0.10 has been reported by other groups [2,3]. This huge<br />

elastic softening of C66 is caused by the quadrupole fluctuati<strong>on</strong> associated with the degenerate dy’z and dzx’<br />

band aslant Γ and X points of the Brillouin z<strong>on</strong>e. Quadrupole effects <strong>on</strong> the superc<strong>on</strong>ductivity in the present<br />

system are discussed in relati<strong>on</strong> to the s++ type symmetry of the superc<strong>on</strong>ductivity [4,5,6].<br />

[1] T. Goto, et al., JPSJ 80 (2011) 073702. [2] R. M. Fernandes et al., PRL 105 (2010) 157003. [3]<br />

M. Yoshizawa et al., JPSJ 81 (2012) 024604. [4] Y. Yanagi et al., JPSJ 79 (2010) 123707. [5] H.<br />

K<strong>on</strong>tani et al., PRB 84 (2011) 024528. [6] T. Kawamata et al JPSJ 80 (2011) 084720.


RB06<br />

C<strong>on</strong>centrati<strong>on</strong> dependence of magnetic and transport characteristics<br />

in EuFe 2As 2-xP x single crystals<br />

Takanari Kashiwagi*, Takuya Ishikawa, Tomoki Goya, Youhei J<strong>on</strong>o, Akihiko<br />

Nozawa, Kasumi Tashima and Kazuo Kadowaki<br />

Univ. of Tsukuba, WPI-MANA, JST-CREST, Japan<br />

EuFe 2As 2 exhibits the spin-density wave of Fe spins at TSDW=190 K and<br />

subsequently magnetic order of Eu 2+ moment at TN=19 K. It is also known that this<br />

compound shows the superc<strong>on</strong>ductivity by isovalent substituti<strong>on</strong> of As to P and the<br />

Tc value increases up to 28 K. We have studied magnetic and transport properties in<br />

single crystal of the EuFe 2As 2-xP x system grown by the self-flux method. From the<br />

magnetizati<strong>on</strong> measurements at 5 K, we observed a saturati<strong>on</strong> of magnetizati<strong>on</strong> of Eu 2+<br />

at HM ~ 1 T and a spin-flop like behavior at Hsf ~ 0.6 T for H||ab-plane. These fields<br />

seem to decrease as x is increased, indicating reducti<strong>on</strong> of the exchange interacti<strong>on</strong> and<br />

the uniaxial anisotropy. We also performed electr<strong>on</strong> spin res<strong>on</strong>ance measurements at<br />

X-band <strong>on</strong> single crystals of EuFe 2As 2-xP x. The result shows that the res<strong>on</strong>ance field<br />

increases with decreasing temperature toward to TN=19 K below which a new line was<br />

observed. We will discuss these results including electr<strong>on</strong> spin res<strong>on</strong>ance experiments<br />

with emphasis <strong>on</strong> the phase diagram of magnetism and superc<strong>on</strong>ductivity in EuFe 2As 2xP<br />

x.<br />

RB07<br />

Res<strong>on</strong>ance-like resp<strong>on</strong>se in antiferromagnetically ordered<br />

Fe 1.02Te 0.95Se 0.05, studied by polarized inelastic neutr<strong>on</strong> scattering<br />

Karel Prokes 1 *, Arno Hiess 2 , Wei Bao 3 , Sven Landsgesell 1 , Elisa Wheeler 4 and Dimitri Argyriou 2<br />

1 M-I1, Helmholtz Zentrum Berlin, Germany<br />

2 European Spallati<strong>on</strong> Source ESS AB, 22100 Lund, Sweden<br />

3 Renmin University of China, 100872 Beijing, China, China<br />

4 M-I1, Institut Laue-Langevin, 38042 Grenoble Cedex, France<br />

Unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity in ir<strong>on</strong> pnictides and chalcogenides [1] shows intriguing similarities with<br />

both copper-oxide- and rare-earth-based superc<strong>on</strong>ductors. Comm<strong>on</strong> is a proximity to a magnetic order and an<br />

existence of magnetic fluctuati<strong>on</strong>s [2]. Magnetic fluctuati<strong>on</strong>s change below the superc<strong>on</strong>ducting transiti<strong>on</strong> and<br />

are readily detectable by neutr<strong>on</strong> inelastic scattering. The character of these has been shown to be related to the<br />

pairing mechanism and gap symmetry [3]. In all superc<strong>on</strong>ducting pnictides and chalcogenides <strong>on</strong>e finds welldefined<br />

magnetic excitati<strong>on</strong>s centered close to the Q = (0.5, 0.5, 0) reciprocal positi<strong>on</strong> that str<strong>on</strong>gly disperse<br />

with increasing energy and peaking in the 6.5-9.8 meV range [2]. Polarizati<strong>on</strong> neutr<strong>on</strong> experiment allows for a<br />

determinati<strong>on</strong> of the in-plane and out-of-plane inelastic resp<strong>on</strong>ses that are proporti<strong>on</strong>al to the relevant imaginary<br />

parts of the dynamical susceptibility. While the fluctuati<strong>on</strong>s in FeTe 1-xSe x, x = 0.40 are nearly isotropic with a<br />

slightly enhanced comp<strong>on</strong>ent al<strong>on</strong>g the c axis [4,5], in BaFe 1.9Ni 0.1As 2 they are have an in-plane 2D character<br />

[6]. In this c<strong>on</strong>tributi<strong>on</strong> we report <strong>on</strong> a polarized neutr<strong>on</strong> study showing that similar fluctuati<strong>on</strong>s also exist also in<br />

antiferromagnetically ordered Fe 1.02Te 0.95Se 0.05 above the magnetic phase transiti<strong>on</strong>.<br />

[1] F.-C. Hsu, et al., Proc. Nat Acad. Sci. USA 105, 14262 (2008). [2] D. C. Johnst<strong>on</strong>, Advances in Physics 59, 803<br />

(2010). [3] M. M. Korshunov and I. Eremin, Phys. Rev. B 78, 140509 (R) (2008). [4] P. Babkevich, et al., Phys. Rev. B<br />

83, 180506 (R) (2011). [5] K. Prokes et al., to be published [6] O. J. Lipscombe, et al., Phys. Rev. B 82, 064515(2010).<br />

RB08<br />

Influence of filament diameter <strong>on</strong> superc<strong>on</strong>ducting properties of MgB 2<br />

multi-core wires<br />

Michael Reissner 1 *, Lukas Bulla 1 , I Husek 2 , T Melisek 2 and P Kovac 2<br />

1 Institute of Solid State Physics, Vienna Universtity of Technology, Austria<br />

2 Institute of Electrical Engineering, Slovak Academy of Sciences, Slovak<br />

Multi-core MgB 2 wires with 19 filaments of different diameter were produced [1]. The<br />

filaments are covered by a Ti shell and embedded in a Cu matrix. From outside the<br />

wires are stabilized by stainless steel tubes. Critical current densities were determined<br />

from hysteresis loops using Bean's model [2]. Magnetic relxati<strong>on</strong> measurements were<br />

performed at 1, 3, and 5 T both in increasing and decreasing field for up to 30 min.<br />

From these measurements mean effective activati<strong>on</strong> energies were determined within<br />

the flux creep theory of Anders<strong>on</strong> [3]. All samples were prepared in identical way. They<br />

<strong>on</strong>ly differ in diameter of the filaments, which ranges between 30 and 15 μm. Influence<br />

of the filament diameter <strong>on</strong> the superc<strong>on</strong>ducting properties, like critical current density,<br />

irreversibility line and activati<strong>on</strong> energies are discussed.<br />

[1] P Kovac, I Husek, T Melisek, L Kopera, M Reissner Superc<strong>on</strong>d. Sci. Technol 23 (2010) 065010 [2]<br />

C P Bean Phys. Rev. Lett. 9 (1962) 250 [3] P W Anders<strong>on</strong> Phys. Rev. Lett. 9 (1962) 309<br />

RB09<br />

RB10<br />

RB11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Kinetic energy density of cooper pairs in Sr doped YBa 2Cu 3O 7-δ single<br />

crystals<br />

Ana Paula Aguiar De Mend<strong>on</strong>ca 1 *, Rovan Fernandes Lopes 1 , Valdemar Das Neves<br />

Vieira1, Fabio Teixeira Dias 1 , Douglas Langie Da Silva 1 , Paulo Pureur 2 , Jacob Schaf 3 ,<br />

Mauro Melchiades Doria 4 and Frederik Wolff-fabris 5<br />

1 Universidade Federal de Pelotas, Brazil<br />

2 Universidade Federal do Rio Grande do Sul, Brazil<br />

3 Universidade Federal do Rio Grande so Sul, Brazil<br />

4 Universidade Federal do Rio de Janeiro, Brazil<br />

5 HZ Dresden-Rossendorf, Germany<br />

The kinetic energy, K(T) is a relevant tool to sort the distinct proposal for the normal state and their<br />

c<strong>on</strong>sequent paring mechanisms in HTSC.[1,2] Motivated by this potential we report <strong>on</strong> reversible DC<br />

magnetizati<strong>on</strong>s as a functi<strong>on</strong> of temperature of a series of YBa 2-xSr xCu 3O 7-δ (x = 0, 0.02, 0.10, 0.25, 0.37<br />

and 0.50) single crystals with the purpose to study the role of i<strong>on</strong> size chemical introduced disorder <strong>on</strong> the<br />

average kinetic energy density (AKED) of Cooper pairs in the YBa 2Cu 3O 7-δ superc<strong>on</strong>ducting state.[3] The<br />

Sr i<strong>on</strong> size chemical disorder is introduced in YBa 2Cu 3O7-? structure by lattice distorti<strong>on</strong>. The valuati<strong>on</strong><br />

of the AKED from reversible dc magnetizati<strong>on</strong> data is supported by viral theorem of superc<strong>on</strong>ductivity.<br />

[1,2,4] The AKED preliminary results of the YBa 1.9Sr 0.1Cu 3O 7-δ single crystal show that the series of the<br />

isofield K(T) curves, obtained to the H = 10 kOe, scales in a comm<strong>on</strong> behavior that smoothly develops as<br />

the temperature is increasing toward to the Tc, disappearing inside a comm<strong>on</strong> background for T > Tc. This<br />

interested AKED behavior str<strong>on</strong>gly suggests an existence of a unique superc<strong>on</strong>ducting c<strong>on</strong>densate state. At<br />

this time the dc magnetizati<strong>on</strong> measurements in additi<strong>on</strong>al samples are in progress.<br />

1. S. Salem-Sugui, Jr., M. M. Doria, A. D. Alvaraga, V. N. Vieira, P. F. Farinas and J. P. Sinnecker, Phys. Rev. B 76, 132502<br />

(2007). 2. M. M. Doria, S. Salem-Sugui, I. G. de Oliveira, L. Ghivelder and E. H. Brandt, Phys. Rev. B 65, 144509 (2002). 3. V. N.<br />

Vieira and J. Schaf , Phys. Rev. B 65, 144531 (2002). 4. M. M. Doria, J. E. Gubernatis and D. Rainer Phys. Rev. B 39, 9573 (1989).<br />

Interplay between superc<strong>on</strong>ductivity and antiferromagnetism in BaFe 2xNi<br />

xAs 2 single crystals studied by 57Fe Mossbauer spectroscopy<br />

Julian Andres Munevar Cagigas 1 , Hans Micklitz 2 , Chenglin Zhang 3 , Hui Quian Luo 4 ,<br />

Pengcheng Dai 5 and Elisa Baggio-saitovitch 1 *<br />

1 Brazilian Center for Research in Physics, Brazil<br />

2 Centro Brasileiro de Pesquisas Fisicas, Brazil<br />

3 Department of Physics, University of Tennessee, USA<br />

4 Beijing Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics, China<br />

5 Department of Physics and Astr<strong>on</strong>omy, University of Tennessee, USA<br />

We have performed magnetic susceptibility and 57Fe Mossbauer spectroscopy measurements <strong>on</strong> single<br />

crystal mosaics of BaFe 2-xNi xAs 2 (x=0.065, 0.075, 0.085). Our findings show antiferromagnetic order below<br />

TN obtained from magnetic hyperfine field phase diagram, with superc<strong>on</strong>ductivity below TC obtained by<br />

susceptibility measurements. Careful analysis of our Mossbauer data show that a decrease in the magnetic<br />

hyperfine field is observed below TC and the effect is proporti<strong>on</strong>al to the difference between TN and TC, being<br />

the largest when both temperatures become close. We argue this is caused by coexistence of superc<strong>on</strong>ductivity<br />

and magnetism, since both phenomena come from the same Fe 3d electr<strong>on</strong>s, and two possible scenarios are<br />

presented. Magnetic volume fracti<strong>on</strong> does not show any variati<strong>on</strong> at or below TC, but a str<strong>on</strong>g dependence<br />

with doping level, most likely due to short range magnetic order that cannot be sensed by our 57Fe local probe,<br />

probably caused by local inhomogeneities. A phase diagram is shown to illustrate how the variati<strong>on</strong> of the<br />

magnetic volume fracti<strong>on</strong> and the crossover between magnetism and superc<strong>on</strong>ductivity are related.<br />

M. Wang, H. Luo, J. Zhao, C. Zhang, M. Wang, K. Marty, S. Chi, J. W. Lynn, A. Schneidewind, S. Li and P. Dai,<br />

Physical Review B 81, (2010) 174524. M. Alzamora, J. Munevar, E. Baggio-Saitovitch, S. L. Bud'ko, Ni Ni, P. C.<br />

Canfield and D. R. Sanchez, Journal of Physics: C<strong>on</strong>densed Matter 23, (2011) 145701. arXiv:1111.5853<br />

<strong>Magnetism</strong> in superc<strong>on</strong>ducting Ba0.78K. 22Fe2As2 and EuFe2As1.4P0.6 single crystals studied by Mossbauer spectroscopy<br />

Elisa Baggio-saitovitch 1 , Julian Munevar 1 , Hans Micklitz 1 , Genfu Chen 2 , Chenglin<br />

Zhang 3 , Huiqian Luo 4 and Pengcheng Dai 5<br />

1<br />

Brazilian Center for Research in Physics, Brazil<br />

2<br />

Renmin University of China, China<br />

3<br />

Department of Physics and Astr<strong>on</strong>omy, University of Tennessee, USA<br />

4<br />

Beijing Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics,, China<br />

5<br />

Department of Physics and Astr<strong>on</strong>omy, University of Tennessee Neutr<strong>on</strong> Scattering Divisi<strong>on</strong>, ORNL, USA<br />

We studied magnetism in superc<strong>on</strong>ducting Fe-pnictide single crystals using 151Eu and 57Fe Mossbauer<br />

Spectroscopy. Neutr<strong>on</strong> studies <strong>on</strong> Ba 1-xK xFe 2As 2 single crystals revealed a decrease in Bragg peak intensity due<br />

to ir<strong>on</strong> moment or magnetic volume fracti<strong>on</strong> reducti<strong>on</strong>. 57Fe Mossbauer measurements <strong>on</strong> Ba 0.78K 0.22Fe 2As 2<br />

single crystal mosaics were performed down to 1.5 K, revealing a decrease in the magnetic hyperfine field<br />

below Tc, without change in magnetic volume fracti<strong>on</strong>. Our data c<strong>on</strong>firm a reducti<strong>on</strong> of Fe magnetic moment<br />

below Tc explaining also the neutr<strong>on</strong> results. Such a decrease is caused by a spectral weight transfer when<br />

entering the superc<strong>on</strong>ducting state. For EuFe 2As 1.4P 0.6 compound, magnetism originates from Eu 2+ moments.<br />

Mossbauer spectra reveal magnetic hyperfine fields below TM = 18 K of Eu 2+ moments. Data analysis<br />

shows coexistence of ferromagnetism, from Eu 2+ moments ordered al<strong>on</strong>g crystallographic c-axis, and<br />

superc<strong>on</strong>ductivity below TSC ~ 15 K. We find indicati<strong>on</strong>s for a change of small Fe magnetic moment dynamics<br />

(~ 0.07 μB) at superc<strong>on</strong>ductivity <strong>on</strong>set: below TSC the Fe magnetic moments seem to be “frozen” within the<br />

a,b-plane. In both compounds we show a change in the Fe magnetic moment state when entering the SC state,<br />

and discussi<strong>on</strong> about coexistence of magnetism and superc<strong>on</strong>ductivity will be provided.<br />

[1] Z. Ren et al., Chin. Phys. Lett. 25, 2215 (2008) [2] M. Lumsden et al., J. Phys: C<strong>on</strong>d. Mat. 22<br />

(2010) 203203. [3] H.H. Luetkens et al., Nat. Mater. 8 (2009) 305.<br />

July 8 - 13, 2012 Busan, Korea 141<br />

Poster Thursday


Poster Thursday<br />

RB12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Doping evoluti<strong>on</strong> of the in-plane L<strong>on</strong>d<strong>on</strong> penetrati<strong>on</strong> depth in<br />

Fe1+y(Te1-xSex) single-crystals<br />

Andrei Diac<strong>on</strong>u 1 , Jin Hu 2 , Tijiang Liu 2 , Bin Qian 2 , Zhiqiang Mao 2 and Le<strong>on</strong>ard Spinu 1<br />

1<br />

Advanced Materials Research Institute and Physics Department, University of New<br />

Orleans, USA<br />

2<br />

Department of Physics, Tulane University, USA<br />

Our work focuses <strong>on</strong> the doping evoluti<strong>on</strong> of the superc<strong>on</strong>ducting properties as derived<br />

from penetrati<strong>on</strong> depth measurements as a functi<strong>on</strong> of temperature in single crystals<br />

of Fe 1+y(Te 1-xSe x) with y


RB18<br />

M<strong>on</strong>te Carlo study of the magneto-elastic effects in Fe pnictides<br />

Cesar Jose Calder<strong>on</strong> Filho 1 *, Alex Ant<strong>on</strong>elli 1 , David Vaknin 2 and Gast<strong>on</strong> Eduardo<br />

Barberis 1<br />

1 IFGW, State University of Campinas - UNICAMP, Brazil<br />

2 Ames Nati<strong>on</strong>al Laboratory and Department of Physics, Iowa State University, USA<br />

A (J1, J2) model of the infinite square lattice of classical spins coupled by Heisenberg<br />

exchange interacti<strong>on</strong>s that includes a spin-lattice interacti<strong>on</strong> of the form A (Exx - Eyy)<br />

(Sx2- Sy2) is used in M<strong>on</strong>te-Carlo simulati<strong>on</strong>s to determine a phase diagram in the<br />

J1, J2, and A parameter-space. To facilitate phase transiti<strong>on</strong>s in the 2D system, we<br />

also include a weak out-of-plane coupling to spins in adjacent planes (Jz). This phase<br />

diagram is relevant to the parent materials of the newly discovered ir<strong>on</strong>-pnictides<br />

superc<strong>on</strong>ductors. Using first principles band calculati<strong>on</strong>s, both for the low and high<br />

temperatures, we obtain realistic parameters to the model that allow the predicti<strong>on</strong> of<br />

pressure induced magnetic transiti<strong>on</strong>s.<br />

RB19<br />

Geometrical Vortex Transiti<strong>on</strong> in the ir<strong>on</strong> pnictide SmFeAs(O,F)<br />

Philip J.w. Moll 1 *, Luis Balicas 2 , Janusz Karpinski 3 , Nikolai Zhigadlo 4 and Batlogg<br />

Bertram 5<br />

1 Solid State Physics Laboratory, ETH Zurich, Switzerland<br />

2 Nati<strong>on</strong>al High Magnetic Field Laboratory, Florida State University, USA<br />

3 Solid State Physics, ETH Zurich, Switzerland<br />

4 Solid State Laboratory, ETH Zurich, Switzerland<br />

5 Solid State Theory, ETH Zurich, Switzerland<br />

We have observed a distinct vortex matter transiti<strong>on</strong> in SmFeAs(O,F) (Tc~50K) up<strong>on</strong><br />

cooling below T*~41K(=0.81Tc) into a highly mobile state for fields well aligned with the<br />

FeAs layers. Below T*, the vortex core is c<strong>on</strong>fined between two adjacent FeAs planes by<br />

periodic modulati<strong>on</strong>s of the superc<strong>on</strong>ducting order parameter within the unit cell. Vortex<br />

moti<strong>on</strong> parallel to the planes is even more pr<strong>on</strong>ounced at lowest temperatures, well below<br />

Tc and Hc2, as the vortex cores avoid the highly effective pinning sites located in the FeAs<br />

layers. For fields slightly out-of-plane (10 6 A/cm 2<br />

@5K, 14T[1]). These results indicate str<strong>on</strong>g pinning localized in the FeAs layer to be the<br />

dominant factor for the highly effective pinning and thus show the pathway to improve the<br />

technological prospect of the pnictides.<br />

[1] P.J.W. Moll et al., 'High magnetic field scales and critical currents in SmFeAs(O,F) crystals.<br />

Nature Materials 9, 628 (2010)<br />

RB20<br />

SmFeAsO 1-xF x: Raman scattering and x-ray diffracti<strong>on</strong> study under<br />

low temperature and high pressure c<strong>on</strong>diti<strong>on</strong>s<br />

Sofia Michaela Souliou 1 *, Mathieu Le Tac<strong>on</strong> 1 , Andrew C. Walters 1 , Chengtian Lin 1 ,<br />

Karl Syassen 1 , Bernhard Keimer 1 , Gast<strong>on</strong> Garbarino 2 , Michael Hanfland 2 , Wils<strong>on</strong><br />

Cricht<strong>on</strong> 2 , Janusz Karpinski 3 and Nicolai Zhigaldo 3<br />

1 Max-Planck-Institut fur Festkorperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany, Germany<br />

2 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, BP 220, F-38043 Grenoble Cedex, France, France<br />

3 Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland, Switzerland<br />

We present a comparative low-temperature Raman study <strong>on</strong> single crystals of the parent n<strong>on</strong>-superc<strong>on</strong>ducting<br />

SmFeAsO and the fluorine-doped superc<strong>on</strong>ducting SmFeAsO 0.6F 0.35 [1]. As in the compounds from the 122<br />

family [2], clear renormalizati<strong>on</strong> of the c-axis polarized A1g(Sm) and the B1g(Fe) Raman-active modes<br />

are observed through the magneto-structural transiti<strong>on</strong> in the parent compound. Splitting of the in-plane<br />

Eg modes is also observed (like the reported in [3,4]). In the fluorine-doped compound, x-ray diffracti<strong>on</strong><br />

measurements reveal the retenti<strong>on</strong> of the structural transiti<strong>on</strong> (similar to the <strong>on</strong>e reported in [5]). Despite the<br />

absence of a coupled magnetic transiti<strong>on</strong>, a renormalizati<strong>on</strong> of the c-axis polarized modes similar to the <strong>on</strong>e<br />

seen in the parent compound is observed, followed at lower temperature by an anomalous increase of the<br />

linewidth of these ph<strong>on</strong><strong>on</strong>s below the superc<strong>on</strong>ducting transiti<strong>on</strong> temperature. The effects of the structural<br />

transiti<strong>on</strong> <strong>on</strong> the ph<strong>on</strong><strong>on</strong> modes are further investigating by applying high pressure <strong>on</strong> the parent compound,<br />

allowing a direct comparis<strong>on</strong> of the effect of pressure and doping <strong>on</strong> the lattice dynamics of the system.<br />

[1] Z.-A. Ren et al., Chinese Physics Letters 25 (6), 2215 (2008) [2] M. Rahlenbeck et al., Phys.<br />

Rev. B 80, 064509 (2009) [3] T. Yildirim, Phys. Rev. Let. 101, 057010 (2008) [4] L. Chauviere et al.,<br />

Phys. Rev. B 80, 094504 (2009) [5] A. Martinelli et al., Phys. Rev. Let. 106, 277001 (2011)<br />

RB21<br />

RB22<br />

RB23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Mass renormalizati<strong>on</strong> in isostructural Ru- and Fe-pnictides<br />

Philip J.w. Moll 1 *, Jakob Kanter 1 , Ross Mc.d<strong>on</strong>ald 2 , Fedor Balakirev 2 , Peter Blaha 3 ,<br />

Karlheinz Schwarz 3 , Zbigniew Bukowski 1 , Nikolai D. Zhigadlo 1 , Sergiy Katrych 1 ,<br />

Kurt Mattenberger 1 , Janusz Karpinski 1 and Bertram Batlogg 1<br />

1 Solid State Physics Laboratory, ETH Zurich, Switzerland<br />

2 Nati<strong>on</strong>al High Magnetic Field Laboratory, Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

3 Institute of Materials Chemistry, Vienna University of Technology, Austria<br />

We have studied the angular-dependent de Haas-van Alphen oscillati<strong>on</strong>s of LaRu 2P 2 using<br />

magnetic torque in pulsed magnetic fields up to 60 T. The observed oscillati<strong>on</strong> frequencies are<br />

in excellent agreement with the geometry of the calculated Fermi surface. The temperature<br />

dependence of the oscillati<strong>on</strong> amplitudes reveals effective masses m*(α) = 0.71 and m*(β) =<br />

0.99 me, which are enhanced over the calculated band mass by λcyc of 0.8. We find a similar<br />

enhancement of λγ ~ 1 in comparing the measured electr<strong>on</strong>ic specific heat (γ =11.5mJ/mol<br />

K 2 ) with the total density of states from band-structure calculati<strong>on</strong>s. Remarkably, very similar<br />

mass enhancements have been reported in other pnictides, LaFe 2P 2, LaFePO (Tc ~ 4 K), and<br />

LaRuPO, independent of whether they are superc<strong>on</strong>ducting or not. This is c<strong>on</strong>trary to the<br />

comm<strong>on</strong> percepti<strong>on</strong>s that the normal-state quasiparticle renormalizati<strong>on</strong>s reflect the strength<br />

of the superc<strong>on</strong>ducting pairing mechanism. To separate mass enhancement due to electr<strong>on</strong><br />

correlati<strong>on</strong>s from e.g. electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> interacti<strong>on</strong>s, high energy bandwidth measurements such<br />

as ARPES would be highly desirable, thus leading to new questi<strong>on</strong>s about competing pairing in<br />

isostructural and isoelectr<strong>on</strong>ic Ru- and Fe-pnictide superc<strong>on</strong>ductors.<br />

PHYSICAL REVIEW B 84, 224507 (2011)<br />

The role of spin fluctuati<strong>on</strong> for the high Tc superc<strong>on</strong>ductivity in<br />

LiFeAs, LiFeP, NaFeAs<br />

Geunsik Lee, Hyo Seok Ji and Ji Ho<strong>on</strong> Shim*<br />

Chemistry, POSTECH, Korea<br />

Based <strong>on</strong> fully self-c<strong>on</strong>sistent density functi<strong>on</strong>al theory and dynamical mean field<br />

theory (DMFT) methods, we have studied the electr<strong>on</strong>ic spectrum of three isovalent<br />

111 compounds, LiFeAs, LiFeP, NaFeAs. It has been known that while both LiFeAs<br />

and LiFeP are intrinsic superc<strong>on</strong>ductors with the nodeless and nodal gap symmetries<br />

respectively, NaFeAs exhibits spin density wave phase where superc<strong>on</strong>ducting<br />

transiti<strong>on</strong> occurs with chemical doping. With our simulated electr<strong>on</strong>ic spectrums, we<br />

examine the spin fluctuati<strong>on</strong> mechanism for the high Tc superc<strong>on</strong>ductivity.<br />

DFT+DMFT study <strong>on</strong> the electr<strong>on</strong>ic structure and anisotropy of<br />

Sr 2VO 3FeAs superc<strong>on</strong>ductor.<br />

Hyo Seok Ji and Ji Ho<strong>on</strong> Shim*<br />

Chemistry, POSTECH, Korea<br />

Electr<strong>on</strong> correlati<strong>on</strong> effect <strong>on</strong> Fe 3d orbital has very important role in describing<br />

electr<strong>on</strong>ic structure and anisotropy of ir<strong>on</strong>-based superc<strong>on</strong>ductors.[1] By using<br />

combinati<strong>on</strong> of the density functi<strong>on</strong>al theory (DFT) and dynamical mean field theory<br />

(DMFT), the electr<strong>on</strong> correlati<strong>on</strong> effect can be described well. In this study, we have<br />

investigated the electr<strong>on</strong>ic structure and anisotropy of Sr 2VO 3FeAs superc<strong>on</strong>ductor.<br />

Simple DFT result shows mixed band structures of Fe 3d and V 3d orbital, but the<br />

experimental result shows <strong>on</strong>ly Fe 3d band near the Fermi level.[2] The DFT+U<br />

method explains insulating V layer structure correctly[2, 3] but it cannot describe<br />

whole electr<strong>on</strong>ic structure such as renormalized Fe 3d bands. So we apply the electr<strong>on</strong><br />

correlati<strong>on</strong> effect <strong>on</strong> the V 3d orbital as well as the Fe 3d orbital using DFT+DMFT.<br />

With antiferromagnetic(AFM) ordering, V 3d bands split into -1 eV and 1 eV regi<strong>on</strong>,<br />

which is c<strong>on</strong>sistent with experimental ARPES result.[2] Also we calculate electrical<br />

anisotropy γ=σ_xx/σ_zz which is important for determining dimensi<strong>on</strong>ality effect in<br />

ir<strong>on</strong>-based superc<strong>on</strong>ductors. Calculated anisotropy value is much smaller than simple<br />

DFT result and the result is well c<strong>on</strong>sistent with recent experimental result. This trend<br />

is also c<strong>on</strong>sistent with the trend of previous work[1].<br />

[1] H. S. Ji, G. Lee, and J. H. Shim, Phys. Rev. B 84, 054542 (2011). [2] T. Qian et al., Phys. Rev. B<br />

83, 140513(R) (2011). [3] H. Nakamura and M. Machida, Phys. Rev. B 82, 094503 (2010).<br />

July 8 - 13, 2012 Busan, Korea 143<br />

Poster Thursday


Poster Thursday<br />

RB24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Behaviour of Magnetic and structural transiti<strong>on</strong>s up<strong>on</strong> Sr doping in<br />

CaFe 2As 2 and EuFe 2As 2<br />

Neeraj Kumar*, Ruta Kulkarni, Sudesh Kumar Dhar and Arumugam Thamizhavel<br />

C<strong>on</strong>densed Matter Physics and Materials Science, Tata Institute of Fundamental<br />

Research, Mumbai, India, India<br />

We have grown single crystals of Ca 1-xSr xFe 2As 2 and Eu 1-xSr xFe 2As 2. Our aim was to<br />

study the progressi<strong>on</strong> of SDW transiti<strong>on</strong> and the effect of diluti<strong>on</strong> <strong>on</strong> Eu magnetism<br />

in EuFe 2As 1-xSr xFe 2As 2. CaFe 2As 2 and SrFe 2As 2 undergo magneto-structural transiti<strong>on</strong><br />

at 170 K and 205 K respectively[1,2]. With introducti<strong>on</strong> of Sr in the CaFe 2As 2,<br />

magneto-structural transiti<strong>on</strong> temperature increases, and it reaches 200 K in nominal<br />

Sr 0.5Ca 0.5Fe 2As 2 indicating that Sr dominates Ca in determining the SDW and structural<br />

transiti<strong>on</strong>. Doping Fe with Co induces superc<strong>on</strong>ductivity in Ca 0.5Sr 0.5Fe 2As 2 below 12 K,<br />

which surprisingly shows a signature of SDW transiti<strong>on</strong> at a high temperature of 170<br />

K. In Eu 1-xSr xFe 2As 2 series the AFM ordering temperature of Eu sublattice decreases<br />

with increasing x while the structural/SDW transiti<strong>on</strong> temperature gradually varies<br />

from 190 K to 200 K. Field induced ferromagnetic behaviour of the parent EuFe 2As 2<br />

is also observed in the Sr doped compounds, the magnetic field needed to induce<br />

ferromagnetism decreases with increasing Sr.<br />

[1] Neeraj et. al. Phys. Rev. B, 79, 012504 (2009). [2] Krellner et al, Phys. Rev. B, 78, 100504(R)<br />

(2008)<br />

RB25<br />

Specific heat of the vortex lattice in ir<strong>on</strong>-pnictide superc<strong>on</strong>ductors<br />

Miguel Araujo 1 and Pedro Sacramento 2<br />

1<br />

CFIF, Instituto Superior Tecnico, TU Lisb<strong>on</strong> and Department of Physics, Universitiy<br />

of Evora, Portugal<br />

2<br />

CFIF, Instituto Superior Tecnico, TU Lisb<strong>on</strong>, Portugal<br />

We study a vortex lattice in a three-orbital model for ir<strong>on</strong>-pnictide superc<strong>on</strong>ductors. A<br />

gauge transformati<strong>on</strong>, first introduced by Vafek-Tesanovic [1], is employed in order<br />

to obtain an effective spatially periodic Hamilt<strong>on</strong>ian that produces a spectrum of<br />

Bloch states and automatically includes quantum effects, such as the Berry phase and<br />

Doppler shift of quasi-particles, without resorting to semi-classical approximati<strong>on</strong>s. We<br />

calculate the energy spectrum and specific heat as functi<strong>on</strong> of applied magnetic field.<br />

The effect of disorder due to impurities and positi<strong>on</strong>al disorder of the vortices is also<br />

addressed.<br />

[1] O. Vafek, A. Melikyan, M. Franz and Z. Tesanovic, Physical Review B 63, 134509 (2001)<br />

RB26<br />

Hexag<strong>on</strong>al superc<strong>on</strong>ducting pnictide SrPtAs: an ab initio study<br />

S<strong>on</strong>ny S. H. Rhim 1 , S. J. Youn 2 , Daniel Agterberg 3 , Michael Weinert 3 and Arthur J<br />

Freeman 1<br />

1 Physics and Astr<strong>on</strong>omy, Northwestern University, USA<br />

2 Physics Educati<strong>on</strong> and Research Institute of Natural Science, Gye<strong>on</strong>g Sang Nati<strong>on</strong>al<br />

University, Korea<br />

3 Physics, U. Wisc<strong>on</strong>sin-Milwaukee, USA<br />

We present an ab initio study <strong>on</strong> SrPtAs, a recently discovered hexag<strong>on</strong>al pnictide<br />

superc<strong>on</strong>ductor. SrPtAs is distinct from other pnictides: (i) it has a hexag<strong>on</strong>al structure<br />

and (ii) a large spin-orbit interacti<strong>on</strong>, whose c<strong>on</strong>sequence is not trivial. Based <strong>on</strong><br />

electr<strong>on</strong>ic structure calculati<strong>on</strong>s, a tight-binding Hamilti<strong>on</strong>ian is c<strong>on</strong>structed to analyze<br />

the character of the spin-orbit interacti<strong>on</strong> associated with the crystal structure. Further,<br />

the pairing mechanism by ph<strong>on</strong><strong>on</strong> and spin fluctuati<strong>on</strong> are analyzed from ph<strong>on</strong><strong>on</strong><br />

dispersi<strong>on</strong> and susceptiblity with matrix element fully taken into account. Finally,<br />

based <strong>on</strong> the band structure, we propose that electr<strong>on</strong> doping could increase TC.<br />

144 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RB27<br />

Josephs<strong>on</strong> effect in BaKFeAs inter-grain boundary juncti<strong>on</strong>s<br />

Sung-hak H<strong>on</strong>g 1 , Sung Ho<strong>on</strong> Lee 1 , So<strong>on</strong>-gul Lee 1 *, So<strong>on</strong>-gil Jung 2 , Nam Ho<strong>on</strong> Lee 2<br />

and W<strong>on</strong> Nam Kang 2<br />

1 Department of Display and Semic<strong>on</strong>ductor Physics, Korea University, Korea<br />

2 BK21 Physics Divisi<strong>on</strong> and Department of Physics, Sungkyunkwan University,<br />

Korea<br />

We have studied superc<strong>on</strong>ducting transiti<strong>on</strong> properties of Ba 0.6K 0.4Fe 2As 2 intergrain<br />

juncti<strong>on</strong>s. The juncti<strong>on</strong>s were fabricated by focused i<strong>on</strong> beam (FIB). Prior to FIB<br />

patterning, films were prepatterned into microbridges by a standard photolithography<br />

and arg<strong>on</strong> i<strong>on</strong> milling technique. The lowest-possible beam current of 1.5 pA was<br />

used for the FIB pattern to minimize the etching damage to the bridge. The nominal<br />

dimensi<strong>on</strong>s were 200 nm in width and 100 nm in length. Resistive transiti<strong>on</strong>, currentvoltage<br />

(I-V) characteristics, the temperature-dependent critical current (Ic), and the<br />

normal state resistance (Rn) were measured. Measured transiti<strong>on</strong> properties indicated<br />

that the juncti<strong>on</strong>s were dominated mainly by Josephs<strong>on</strong> coupling, showing resistivelyshunted-juncti<strong>on</strong><br />

(RSJ) behaviors. At higher currents, multiple transiti<strong>on</strong>s were<br />

observed, which might be due to dynamics of Josephs<strong>on</strong> vortices driven by transport<br />

currents. Details of the measurement results will be discussed.<br />

RB28<br />

Coexistence of different electr<strong>on</strong>ic phases in the K 0.8Fe 1.6Se 2<br />

superc<strong>on</strong>ductor: a bulk-sensitive hard x-rays spectroscopy study.<br />

Laura Sim<strong>on</strong>elli 1 *, Naurang L. Saini 2 , Marco Moretti Sala 1 , Y. Mizuguchi 3 , Y.<br />

Takano 3 , H. Takeya 3 , T. Mizokawa 4 and Giulio M<strong>on</strong>aco 1<br />

1 ESRF, France<br />

2 Dipartimento di Fisica, Universit´a di Roma “La Sapienza” - P. le Aldo Moro 2, 00185 Roma, Italy<br />

3 Nati<strong>on</strong>al Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan and JST-TRIP, 1-2-1, Japan<br />

4 Department of Physics, and Department of Complexity Science and Engineering, University of Tokyo, Japan<br />

In A xFe 2-ySe 2 (11)-type chalcogenides superc<strong>on</strong>ductivity appears to occur <strong>on</strong>ly in Fe-deficient samples,<br />

where the alkali metals are intercalated between the FeSe layers [1-3]. It has been dem<strong>on</strong>strated how<br />

the ordering of the Fe vacancies can be correlated to superc<strong>on</strong>ductivity and how it can be c<strong>on</strong>trolled<br />

by temperature treatments [2-6]. In particular the superc<strong>on</strong>ductivity can be tuned <strong>on</strong> a single sample<br />

from an insulating state by post-annealing and fast quenching, and it is tempting to c<strong>on</strong>clude that the<br />

superc<strong>on</strong>ductivity is achieved when the Fe-vacancies are in a disordered state [6]. Here we report <strong>on</strong> the<br />

electr<strong>on</strong>ic and magnetic structure of K 0.8Fe 1.6Se 2 superc<strong>on</strong>ductor by x-ray emissi<strong>on</strong> and high resoluti<strong>on</strong><br />

absorpti<strong>on</strong> spectroscopy. We report a study where the electr<strong>on</strong>ic and magnetic properties are investigated<br />

at the same time as a functi<strong>on</strong> of temperature in several c<strong>on</strong>sistent thermal cycles. We discuss the<br />

effects of ordered and disordered Fe vacancies <strong>on</strong> the electr<strong>on</strong>ic and magnetic structure, the existence<br />

of memory effects <strong>on</strong> thermal cycles, and the relati<strong>on</strong> between electr<strong>on</strong>ic and magnetic properties and<br />

superc<strong>on</strong>ductivity. The results obtained are finally compared with the electr<strong>on</strong>ic and magnetic properties of<br />

(11)-type chalcogenides [7].<br />

[1] Jing Guo, et al, arXiv: 1101.0092; Y. Kawasaki, et al, arXiv: 1101.0896; J J Ying et al., New J. Phys. 13, 033008 (2011). [2] D.<br />

M.Wang, et al, arXiv: 1101.0789 . [3] A. M. Zhang, et al, arXiv: 1101.2168v1. [4] Ricci et al. Superc<strong>on</strong>d. Sci. Technol. 24, 082002 (2011).<br />

[5] Bao Wei et al., Chin. Phys. Lett. 28, 086104 (2011) . [6] F. Han et al., arXiv :11031347. [7] L.Sim<strong>on</strong>elli et al., submitted to PRB.<br />

RB29<br />

Step towards a ferromagnetic Josephs<strong>on</strong> juncti<strong>on</strong> in YBCO/LCMO<br />

heterostructures<br />

Soltan Soltan 1 *, Magdy El-hagary 2 , Hanns-ulrich Habermeier 3 and Nasser Alzayed 4<br />

1<br />

Physics Department, Faculty of Science, Helwan University, 11792 Helwan, Cairo,<br />

Egypt<br />

2<br />

Physics Department, College of Science,Qassim University, P.O. Box 6644 Buraidah<br />

51452, Saudi Arabia<br />

3<br />

Max-Planck-Institute FKF, Heisenbergstrasse 1, 70569-Stuttgart,, Germany<br />

4<br />

Physics Department, King Saud University, Saudi Arabia<br />

High quality high-Tc superc<strong>on</strong>ductor/half metal ferromagnet/high-Tc superc<strong>on</strong>ductor<br />

YBCO/LCMO/YBCO trilayers (SFS) with different orientati<strong>on</strong> of CuO 2 planes in<br />

superc<strong>on</strong>ducting electrodes and different thicknesses of LCMO layers have been<br />

successfully fabricated by employing pulsed laser depositi<strong>on</strong> techniques. It has been<br />

found that a LCMO barrier with thickness of 2-3 unit cells is ferromagnetic with a<br />

Curie temperature close to the bulk value. The str<strong>on</strong>g difference in magnetizati<strong>on</strong> loops<br />

for different SFS-structures measured at T = 5K and the magnetic field parallel to the<br />

F-layers is caused by the presence of a superc<strong>on</strong>ducting current across the ferromagnet<br />

in the (110) oriented SFS-structure with a thickness of the ferromagnetic layer =1nm.<br />

This has been c<strong>on</strong>firmed by measuring current-voltage characteristics in patterned<br />

structures. This sample structure fulfils all prerequisites for the realizati<strong>on</strong> of high-Tc<br />

SFS-Josephs<strong>on</strong> juncti<strong>on</strong>s.


RC01<br />

DMFT study of the correlati<strong>on</strong> effects <strong>on</strong> a topological insulator<br />

Tsuneya Yoshida*, Satoshi Fujimoto and Norio Kawakami<br />

Department of Physics, Kyoto University, Japan<br />

Recently, topological insulators are theoretically proposed in correlated electr<strong>on</strong><br />

systems (e.g. Iridium oxides, Heusler compounds, and filled skutterudites)[1]. The<br />

correlati<strong>on</strong> effects <strong>on</strong> the topological insulators are expected to produce exotic states [2]<br />

and are extensively studied. The str<strong>on</strong>g Coulomb interacti<strong>on</strong> could drive the n<strong>on</strong>-trivial<br />

band insulator into a Mott insulator. In this paper, we study an extended Bernevig-<br />

Hughes-Zhang model[3] including the <strong>on</strong>-site Coulomb interacti<strong>on</strong> with DMFT.<br />

We calculate the double occupancy at each orbital and the spin-Hall c<strong>on</strong>ductivity<br />

which clearly distinguishes the trivial and n<strong>on</strong>-trivial phases in our model. From the<br />

analysis of these quantities, it is c<strong>on</strong>cluded that the topological insulator changes into<br />

a trivial n<strong>on</strong>magnetic Mott insulator via a first-order transiti<strong>on</strong> [4]. Therefore, the<br />

gap closing does not occur at the transiti<strong>on</strong>. In the presentati<strong>on</strong>, we also address the<br />

antiferromagnetic instability.<br />

[1] A. Shitade et al., Phys. Rev. Lett. 102, 256403 (2009), S. Chadov et al., Nature Materials 9 541-<br />

545 (2010), B. Yan et al., arXiv 1104.0641. [2] D. A. Pesin et al., Nature Physics 6, 376 - 381 (2010)<br />

. [3] B. A. Bernevig et al., Science 314 1757 (2006). [4] T. Yoshida et al., arXiv 1111.6250.<br />

RC02<br />

Self-c<strong>on</strong>sistent treatment of fully relativistic effect in the small bismuth<br />

clusters Bin (2≤ n ≤ 7)<br />

Ely Aprilia 1 *, Haruki Katou 2 , Junpei Gotou 2 , Shinya Haraguchi 2 , Suprijadi Hary<strong>on</strong>o 3<br />

and Tatsuki Oda 4<br />

1<br />

Double Degree Program of Kanazawa university-Bandung Institute of Technology,<br />

Ind<strong>on</strong>esia<br />

2<br />

Graduate School of Natural Sciences and Technology, Kanazawa University, Japan<br />

3<br />

Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Ind<strong>on</strong>esia<br />

4<br />

Institute of Science and Engineering, Kanazawa University, Japan<br />

The energy scale of spin-orbit (SO) interacti<strong>on</strong> reaches to the order of 0.1-1eV at the elements in the fifth low<br />

of periodic table. Such interacti<strong>on</strong> could cause effects <strong>on</strong> structural properties as well as <strong>on</strong> electr<strong>on</strong>ic <strong>on</strong>es.<br />

Bismuth has been investigated by many researchers due to its largeness of SO coupling. Rashba effect, which<br />

appears as the spin state splitting of surface bands, has been discussed intensively in the system which c<strong>on</strong>sists of<br />

bismuth [1]. The phenomena which are related with new physics of topological insulator have been investigated<br />

in a lot of bismuth systems [2]. In this c<strong>on</strong>text, bismuth clusters are interesting to investigate including relativistic<br />

effects. In this work, we have studied structural and electr<strong>on</strong>ic properties in small bismuth clusters; Bi_n (2 ≤ n<br />

≤7). The Car-Parrinello molecular dynamics [3] and self-c<strong>on</strong>sistent fully relativistic calculati<strong>on</strong>s [4,5] have been<br />

employed to investigate effects of SO coupling effects. It has been found that the clusters of odd number atoms<br />

were found to carry magnetic moment with n<strong>on</strong>-collinear magnetic c<strong>on</strong>figurati<strong>on</strong>.<br />

[1] Yu. M. Koroteev et al., Phys. Rev. Lett. 93, 046403 (2004). [2] Hsieh et al., Nature 452, 970 (2008).<br />

[3] R. Car and M. Parrinello, Phys. Rev. Lett. 55, 2471 (1985). [4] T. Oda, A. Pasquarello, and R.<br />

Car, Phys. Rev. Lett. 80, 3622 (1998). [5] T. Oda and A. Hosokawa, Phys. Rev. B 72, 224428 (2005).<br />

RC03<br />

Hidden topological order in URu 2Si 2<br />

Tanmoy Das<br />

Theoretical Divisi<strong>on</strong>, Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

UPGRADED<br />

RC04<br />

RC05<br />

RC06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ground-state properties of a two-dimensi<strong>on</strong>al correlated topological<br />

insulator<br />

Yuto Takenaka* and Norio Kawakami<br />

Department of Physics, Kyoto University, Japan<br />

Recently, the topological band insulator (TBI) has attracted much interest in c<strong>on</strong>densed<br />

matter physics. The TBI is characterized by a n<strong>on</strong>trivial band structure, which has a<br />

full insulating gap in the bulk and gapless edge states <strong>on</strong> the boundaries. While the<br />

essential features of the TBI can be described as a <strong>on</strong>e-body problem, there is much<br />

interest in the correlati<strong>on</strong> effects <strong>on</strong> the TBI. In this study, we investigate a generalized<br />

Bernevig-Hughes-Zhang model having electr<strong>on</strong> correlati<strong>on</strong>s with the variati<strong>on</strong>al<br />

M<strong>on</strong>te Carlo (VMC) method. In order to study how interacti<strong>on</strong>s affect the edge states<br />

and bulk states, it is important to c<strong>on</strong>sider inhomogeneous nature due to the lack of<br />

translati<strong>on</strong>al symmetry perpendicular to the boundaries. For this purpose, we introduce<br />

spatially-dependent variati<strong>on</strong>al parameters. We calculate the ground-state energy and<br />

the momentum distributi<strong>on</strong> to discuss how the correlati<strong>on</strong> effects affect electr<strong>on</strong>ic<br />

properties in the TBI.<br />

[1] B. A. Bernevig, T. L. Hughes and S. C. Zhang, Science 314, 1757 (2006).<br />

Magnetic impurity doping effect <strong>on</strong> bulk Rashiba spin splitting system<br />

BiTeI<br />

Je<strong>on</strong>gdae Seo and J<strong>on</strong>g- Soo Rhyee*<br />

Applied Physics, Kyung Hee Universty, Korea<br />

WITHDRAWN<br />

Topological charge pumping effect by the magnetizati<strong>on</strong> dynamics <strong>on</strong><br />

the Surface of 3D Topological Insulators<br />

Hiroaki T Ueda 1 *, Akihito Takeuchi 1 , Gen Tatara 1 and Takehito Yokoyama 2<br />

1 Department of Physics, Tokyo Metropolitan University, Japan<br />

2 Department of Physics, Tokyo Institute of Technology, Japan<br />

We discuss a current dynamics <strong>on</strong> the surface of a 3-dimensi<strong>on</strong>al topological insulator<br />

induced by magnetizati<strong>on</strong> precessi<strong>on</strong> of a ferromagnet attached. It is found that the<br />

magnetizati<strong>on</strong> dynamics generates a direct charge current when the precessi<strong>on</strong> axis is<br />

within the surface plane. This rectificati<strong>on</strong> effect is due to a quantum anomaly and is<br />

topologically protected. The rectified current is useful in the sense that a direct current<br />

is easy to detect experimentally. To see the effect of the fast-varying exchange field, we<br />

study the current dynamics by the topological field theory. We adopt the dimensi<strong>on</strong>al<br />

regularizati<strong>on</strong> to regularize the ultraviolet divergence, which is inevitable to study an<br />

electromagnetic resp<strong>on</strong>se of a topological insulator. As a result, the robustness of the<br />

rectificati<strong>on</strong> to the fast-varying exchange field is c<strong>on</strong>firmed.<br />

July 8 - 13, 2012 Busan, Korea 145<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RC07<br />

Tuning of carrier type in Mn-doped Bi 2Se 3<br />

Young Ha Choi 1 , Nahyun Jo 1 , Kyujo<strong>on</strong> Lee 1 , Jumpei Kajino 2 , Toshiro Takabatake 2<br />

and Myung- Hwa Jung 1 *<br />

1 Department of Physics, Sogang University, Korea<br />

2 ADSM, Hiroshima University, Japan<br />

Bi 2Se 3 is a good candidate for studying thermoelectric material as well as topological insulator.<br />

[1] In order to promote the thermoelectric performance, it is good to c<strong>on</strong>nect two materials in<br />

series with different charge carrier type. In Bi 2Se 3, the Se vacancies are dominant, which leads<br />

to n-type charge carriers.[2] In order to tune the carrier type and carrier density, we have doped<br />

Mn into Bi 2Se 3 and have studied their physical properties, mainly focusing <strong>on</strong> the thermoelectric<br />

properties. The single crystals of MnxBi 2-xSe 3 (x=0.03, 0.05, 0.09 and 0.15) were grown by<br />

melting the stoichiometric elements in an evacuated quartz ampoule. The Hall and thermoelectric<br />

measurements illustrate the change of carrier type from n to p type between x=0.03 and 0.05. The<br />

transport measurements have shown the metallic behavior for x≤0.03 and n<strong>on</strong>metallic behavior for<br />

x≥0.05 at low temperatures. This supports that the Fermi level of p-type samples lies in the surface<br />

state between the bulk valence band maximum and the bulk c<strong>on</strong>ducti<strong>on</strong> band minimum.[3] The<br />

Seebeck coefficient increases linearly up to ~100μV/K at room temperature both n- and p-type<br />

samples. This implies that Mn-doped Bi 2Se 3 is possible materials for thermoelectric applicati<strong>on</strong>.<br />

[1] D.M. Rowe, in : D.M. Rowe (Ed.), CRC Handbook of Thermoelectrics, CRC Press, Boca Rat<strong>on</strong>, FL, 1995, p 90. [2] N.<br />

P. Butch, K. Kirshenbaum, P. Syers, A. B. Sushkov, G. S. Jenkins, H. D. Drew, and J. Pagli<strong>on</strong>e, Phys. Rev. B. 81, 241301(R)<br />

(2010). [3] Y. L. Chen, J.-H. Chu, J. G. Analytis, Z. K. Liu, K. Lgarashi, H.-H. Kuo, X. L. Qi, S. K. Mo, R. G. Moore, D. H.<br />

Lu, M. Hashimoto, T. Sasagawa, S. C. Zhang, I. R. Fisher, Z. Hussain, and Z. X. Shen, Science 329, 659 (2010).<br />

RC08<br />

Magnetic edge profile in the Kane-Mele-Hubbard model<br />

Hye<strong>on</strong>g Jun Lee 1 , Moo Young Choi 1 and Gun Sang Je<strong>on</strong> 2 *<br />

1<br />

Department of Physics and Astr<strong>on</strong>omy and Center for Theoretical Physics, Seoul<br />

Nati<strong>on</strong>al University, Korea<br />

2<br />

Department of Physics, Ewha Womans University, Korea<br />

We investigate the magnetic state <strong>on</strong> the edge of the Kane-Mele-Hubbard model. The<br />

ferromagnetic edge states are induced in a graphene nanoribb<strong>on</strong> by electr<strong>on</strong>-electr<strong>on</strong><br />

interacti<strong>on</strong>s while certain spin-orbit interacti<strong>on</strong>s are known to give rise to a gapless<br />

current-flowing state <strong>on</strong> the edge without electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong>s. We use the<br />

Hartree-Fock approximati<strong>on</strong> to examine the nature of edge states in the presence of<br />

the Hubbard interacti<strong>on</strong> in the Kane-Mele model. Computing the local magnetizati<strong>on</strong><br />

of a nanoribb<strong>on</strong> with various widths, we obtain the edge phase diagram with four<br />

different phases for the ribb<strong>on</strong>s of finite width and study how the magnetic properties<br />

are affected by electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong>s. In particular, we show that the edge<br />

magnetic order survives for weak spin-orbit interacti<strong>on</strong>s in the thermodynamic limit.<br />

The edge magnetic order penetrates towards the ribb<strong>on</strong> center. The resulting magnetic<br />

profile gives its characteristic length which is found to be str<strong>on</strong>gly affected by both<br />

electr<strong>on</strong>-electr<strong>on</strong> and spin-orbit interacti<strong>on</strong>s. Variati<strong>on</strong>s of its characteristic length turn<br />

out to be closely related to the phase transiti<strong>on</strong> between the topological insulator and<br />

the antiferromagnetic insulator. Electr<strong>on</strong> dispersi<strong>on</strong>s are also discussed.<br />

RC09<br />

Theoretical study of spin texture in the Bi thin film<br />

Hiroki Kotaka 1 *, Fumiyuki Ishii 2 and Mineo Saito 2<br />

1 Graduate School of Natural Science and Technology, Kanazawa University, Japan<br />

2 Faculty of Mathematics and Physics, Kanazawa University, Japan<br />

The Spin-Orbit interacti<strong>on</strong> (SOI) is very important effect for heavy atom like Bismuth.<br />

Recently, first-principles study revealed that significant SOI effects <strong>on</strong> the electr<strong>on</strong>ic<br />

structure and lattice bistability of Bi nanofilms.[1] In this study, we perform firstprinciples<br />

electr<strong>on</strong>ic structure calculati<strong>on</strong>s under the electric field for Bismuth thin film<br />

and Bi (001) multi-layer surface. We revealed that the SOI combined with electric field<br />

(so called Rashba effect) is very important in Bi surface state and Bi edge state.[2] We<br />

calculate spin polarizati<strong>on</strong> and spin directi<strong>on</strong> for each band and k-points. Recently,<br />

giant out-of-plane spin comp<strong>on</strong>ent <strong>on</strong> Bi (001) surface is discovered SR-ARPES<br />

experiment.[3] We also calculate the spin structure of multi-layer Bi (001) surface, and<br />

our calculated result shows the detail of spin features at each k-point.<br />

[1] H. Kotaka et al., e-JSSNT, Vol.7, pp.13-16, (2009). [2] H. Kotaka, F. Ishii, M. Saito, T. Nagao,<br />

and S. Yaginuma, JJAP (2012). [3] A. Takayama et al., Phys. Rev. Lett. 106, 166401 (2011).<br />

146 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RC10<br />

A recipe for new Topological Insulators based <strong>on</strong> b<strong>on</strong>ds, bands,<br />

symmetry and heavy atoms<br />

Lukas Muechler 1 , Binghai Yan 2 , Stanislav Chadov 3 , Haijun Zhang 4 , Frederick Casper 1 ,<br />

Shoucheng Zhang 4 and Claudia Felser 3 *<br />

1 Inst. fuer Anorg. Chemie, Johannes Gutenberg - Universitaet Mainz, Germany<br />

2 Bremen Center for Computati<strong>on</strong>al Materials Science, Germany<br />

3 Max-Planck-Institut fur Chemische Physik fester Stoffe, Germany<br />

4 Department of Physics, Stanford University, USA<br />

In this work we will present a recipe to find new Topological Insulators (TIs) based<br />

<strong>on</strong> b<strong>on</strong>ds, bands, symmetry and heavy atoms. A big issue c<strong>on</strong>cerning the compounds<br />

known up to now is the c<strong>on</strong>trol of the bulk carrier density to produce truly insulating<br />

samples in the bulk. Using c<strong>on</strong>cepts from chemistry and supported by densityfuncti<strong>on</strong>al<br />

calcu- lati<strong>on</strong>s, we want to motivate an extended search for new compounds<br />

with tunable bulk properties.<br />

RC11<br />

Optimizing the Bi 2-xSb xTe 3-ySe y solid soluti<strong>on</strong>s to approach the intrinsic<br />

topological insulator regime<br />

Zhi Ren*, Alexey Taskin, Satoshi Sasaki, Kouji Segawa and Yoichi Ando<br />

ISIR, Osaka University, Japan<br />

Three dimensi<strong>on</strong>al (3D) topological insulators represent a new quantum state of mater<br />

realized in band insulators, which are predicted to present novel surface transport phenomena.<br />

In reality, while a number of materials have been identified to be 3D TIs, most of them are<br />

poor insulators in the bulk. Given this situati<strong>on</strong>, search for new TI materials better suited for<br />

achieving the bulk insulating state is of obvious importance. In this presentati<strong>on</strong>, we show<br />

that there exist a series of “intrinsic” compositi<strong>on</strong>s for Bi 2-xSb xTe 3-ySe y solid soluti<strong>on</strong>s where<br />

the acceptors and d<strong>on</strong>ors compensate each other and present a maximally bulk-insulating<br />

behavior. At such compositi<strong>on</strong>s, the resistivity can become as large as several Ωcm at low<br />

temperature, and <strong>on</strong>e can infer th role of the surface-transport channel in the n<strong>on</strong>linear<br />

Hall effect[1]. In particular, in the compositi<strong>on</strong> of Bi 1.5Sb 0.5Te 1.7Se 1.3, <strong>on</strong>e can achieve a<br />

surface-dominated transport where the surface channel c<strong>on</strong>tributes up to 70% of the total<br />

c<strong>on</strong>ductance[2]. In additi<strong>on</strong>, angle-resolved photoemissi<strong>on</strong> spectroscopy reveal that the Dirac<br />

c<strong>on</strong>e dispersi<strong>on</strong> changes systematically so that the Dirac point moves up in energy with<br />

increasing x, leading to a sign change of the Dirac carriers at x~0.9[3].<br />

[1] Z Ren, A.A. Taskin, S. Sasaki, K. Segawa, and Y. Ando, Phys. Rev. B 84, 165311 (2011). (Editors’<br />

Suggesti<strong>on</strong>) [2] A.A. Taskin, Z. Ren, S. Sasaki, K. Segawa, and Y. Ando, Phys. Rev. Lett. 107, 016801<br />

(2011). [3] T. Arakane, T. Sato, S. Souma, K. Kosaka, K. Nakayama, M. Komatsu, T. Takahashi, Z.<br />

Ren, K. Segawa, and Y. Ando, Nat. Commun., in press.<br />

RC12<br />

Explorati<strong>on</strong> of Three-dimensi<strong>on</strong>al Rashba Materials<br />

Manabu Kanou* and Sasagawa Takao<br />

Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

Str<strong>on</strong>g spin-orbit interacti<strong>on</strong>s under the broken space inversi<strong>on</strong> symmetry can induce<br />

sp<strong>on</strong>taneous spin polarizati<strong>on</strong> without external magnetic fields, which is known as<br />

the (surface/interface) Rashba effect. On the other hand, due to the lack of a model<br />

compound, the Rashba effect in three-dimensi<strong>on</strong>s (bulk) has been poorly explored.<br />

In this study, it is dem<strong>on</strong>strated that ternary compounds of bismuth tellurohalides,<br />

BiTeX (X = Cl, Br, and I), are promising candidate compounds as ideal threedimensi<strong>on</strong>al<br />

Rashba materials. As the essential backb<strong>on</strong>e for both fundamental and<br />

applied research, this study established the growth of their sizable single crystals (><br />

1 × 1 × 0.2 mm 3 ). Furthermore, it was found that, for BiTeI, that electr<strong>on</strong>ic state (the<br />

carrier c<strong>on</strong>centrati<strong>on</strong>) can be adjusted from metallic to insulating <strong>on</strong>es by the choice<br />

of the growth techniques. Realizati<strong>on</strong> of the 3D Rashba states, including the Fermi<br />

surface topology for the corresp<strong>on</strong>ding carrier c<strong>on</strong>centrati<strong>on</strong>s of the obtained crystals,<br />

was c<strong>on</strong>firmed by relativistic first-principles calculati<strong>on</strong>s. We will discuss that our<br />

3D Rashba materials can be a leading player in spin-involved novel phenomena,<br />

ranging from the metallic extreme (unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity) to the transport<br />

intermediate (spin Hall effects) to the novel insulating variant (3D topological<br />

insulating states).


RC13<br />

Quantum phase transiti<strong>on</strong> from normal to topological insulator phase<br />

in Na 2IrO 3<br />

Cho<strong>on</strong>g H. Kim 1 , Heung Sik Kim 1 , Hogyun Je<strong>on</strong>g 2 , Hosub Jin 3 and Jaejun Yu 1 *<br />

1 Department of Physics and Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Korea<br />

2 Korea Institute of Science and Technology Informati<strong>on</strong>, Korea<br />

3 Department of Physics and Astr<strong>on</strong>omy, Northwestern University, USA<br />

Na 2IrO 3 has been suggested to have a possible quantum spin Hall effect based <strong>on</strong><br />

the novel jeff=1/2 state arising from the 5d Ir states. From the electr<strong>on</strong>ic structure<br />

calculati<strong>on</strong> analysis of the band topology of Na 2IrO 3, however, it turns out that Na 2IrO 3<br />

as it is should be a trivial insulator. We investigated the electr<strong>on</strong>ic structure of by<br />

employing a tight-binding model for the layered iridium oxides with h<strong>on</strong>eycomb<br />

lattice. Our analysis for the layered iridates reveals that the topological nature of the<br />

spin-orbit coupled ground state depends <strong>on</strong> the trig<strong>on</strong>al crystal field and l<strong>on</strong>g-range<br />

hoppings. From the first-principles-derived tight-binding Hamilt<strong>on</strong>ian we determine<br />

the phase boundary through the parity analysis and predict a quantum phase transiti<strong>on</strong><br />

from normal to topological insulator. It is suggested that Na 2IrO 3 can be a candidate<br />

material which can have both n<strong>on</strong>-trivial topology of bands and str<strong>on</strong>g electr<strong>on</strong><br />

correlati<strong>on</strong>s.<br />

RC14<br />

Self-assembled nanowire with giant Rashba spin splitting<br />

Jewook Park, Min-cherl Jung, Sung W<strong>on</strong> Jung and Han Wo<strong>on</strong>g Yeom*<br />

Department of physics, POSTECH, Center for atomic wires and layers(CAWL),<br />

Korea<br />

We found gaint Rashba-type split bands for Pt-induced nanowires <strong>on</strong> the Si(110)<br />

surface by angle resolved photoemissi<strong>on</strong> spectroscopy (APRES) measurements. The<br />

observed Rashba parameter is about 2.1eVA, which is am<strong>on</strong>g the largest ever reported<br />

for Rashba systems and is unique in <strong>on</strong>e-dimensi<strong>on</strong>al systems. Pt-induced nanowires<br />

were also investigated by scanning tunneling microscopy (STM) and scanning<br />

tunneling spectroscopy (STS) at low temperature (78K). High resoluti<strong>on</strong> STM<br />

topography images show that the wire has a width of 1.6nm and a X3 superstructure<br />

al<strong>on</strong>g the wire. On the other hands, the STS measurements reveal well resolved local<br />

density of states (LDOS) with a peak at -200meV and a characteristic dip at -300meV<br />

<strong>on</strong> the nanowire. These peak and dip energies corresp<strong>on</strong>ds well to the ARPES data; the<br />

top edge and the Dirac-like crossing point energy of the Rashba-type spin split bands,<br />

respectively. Furthermore, based <strong>on</strong> the dI/dV spectroscopic mapping, we c<strong>on</strong>firmed<br />

noticeable <strong>on</strong>e-dimensi<strong>on</strong>al electr<strong>on</strong> channels al<strong>on</strong>g the nanowire edges, which are<br />

related to the gaint Rashba band. This implies a future applicati<strong>on</strong> of the Pt-induced<br />

nanowire structure in silic<strong>on</strong>-based spintr<strong>on</strong>ics devices.<br />

RC15<br />

Ab initio study of topological surface state <strong>on</strong> Sb (111) surface with<br />

ir<strong>on</strong> impurities<br />

Jinhee Han, Hyungjun Lee and Hyoung Jo<strong>on</strong> Choi*<br />

Department of Physics and IPAP, Y<strong>on</strong>sei University, Korea<br />

We study ir<strong>on</strong> impurities <strong>on</strong> Sb (111) surface and their effects <strong>on</strong> topological surface<br />

state by using an ab-initio pseudopotential density-functi<strong>on</strong>al method. We implemented<br />

the spin-orbit interacti<strong>on</strong> into the SIESTA in a form of additi<strong>on</strong>al fully n<strong>on</strong>-local<br />

projectors. To calculate electr<strong>on</strong>ic structure of topological surface states, we c<strong>on</strong>sider<br />

a slab of Sb using a supercell c<strong>on</strong>taining 20 atomic layers with experimental bulk Sb<br />

lattice parameters. We determine atomic positi<strong>on</strong>s of Fe impurities <strong>on</strong> Sb (111) surface<br />

by minimizing the total energy, and calculate surface band structures near the Fermi<br />

level. To find the impurity effects <strong>on</strong> the electr<strong>on</strong>ic structure of the surface states, we<br />

simulate ARPES spectra as a functi<strong>on</strong> of impurity density <strong>on</strong> the surface and calculate<br />

local density of states (LDOS) near the Fermi level. From the results, we find that Fe<br />

impurity states are present near Fermi level and they str<strong>on</strong>gly interact with the surface<br />

states and produce a characteristic feature in LDOS <strong>on</strong> the top surface Sb layer. This<br />

work was supported by the NRF of Korea (Grant No. 2011-0018306) and KISTI<br />

Supercomputing Center (Project No. KSC-2011-C3-06).<br />

RC16<br />

RC17<br />

RC18<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Topological insulating phase in cubic system: tight-binding approach<br />

Hosub Jin, Jino Im and Arthur J. Freeman<br />

Department of Physics and Astr<strong>on</strong>omy, Northwestern University, USA<br />

Recently, much attenti<strong>on</strong> has focused <strong>on</strong> three-dimensi<strong>on</strong>al str<strong>on</strong>g topological<br />

insulators as a new quantum state of matter, such as Bi 2Se 3 and Bi 2Te 3. Here we suggest<br />

topologically n<strong>on</strong>-trivial electr<strong>on</strong>ic structures in cubic systems based <strong>on</strong> the tightbinding<br />

analysis. Assuming the well separated s and p states and hopping parameters,<br />

we can set up an 8x8 tight-binding Hamilt<strong>on</strong>ian, and the trivial to n<strong>on</strong>-trivial<br />

topological phase transiti<strong>on</strong> occurs by tuning the hopping parameters or spin-orbit<br />

coupling strength. Our tight-binding Hamilt<strong>on</strong>ian is reduced to a 4x4 c<strong>on</strong>tinuum model<br />

which is the minimal model to describe the topological phase transiti<strong>on</strong>. Topologically<br />

protected surface states in the slab geometry are also shown within our model.<br />

Supported by the U.S. D.O.E.<br />

Topological insulator phase and Kitaev-like anisotropic exchange<br />

interacti<strong>on</strong>s in Li 2IrO 3<br />

Heung-sik Kim 1 , Cho<strong>on</strong>g H. Kim 1 , Hogyun Je<strong>on</strong>g 2 , Hosub Jin 3 and Jaejun Yu 1 *<br />

1 Department of Physics and Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Korea<br />

2 Korea Institute of Science and Technology Informati<strong>on</strong>, Korea<br />

3 Department of Physics and Astr<strong>on</strong>omy, Northwestern University, USA<br />

From first-principles electr<strong>on</strong>ic structure calculati<strong>on</strong>s results, we set up an effective<br />

tight-binding Hamilt<strong>on</strong>ian for Li 2IrO 3 by c<strong>on</strong>structing Wannier orbitals of lowenergy<br />

states near the Fermi level. The Wannier orbitals are found to be quite close<br />

to the $j_{eff}=1/2$ state, which are recently suggested to exist in many other iridate<br />

compounds. The model Hamilt<strong>on</strong>ian is characterized bythe n<strong>on</strong>trivial sec<strong>on</strong>d and third<br />

nearest neighbor hopping inside Ir h<strong>on</strong>eycomb lattice as well as relatively small but<br />

significant inter-layer hopping terms. It is shown that the ratio between the nearest and<br />

third nearest neighbor hopping determines the $Z_2$-invariant of this material, and<br />

that it can be c<strong>on</strong>trolled by the lattice strain in our first-principles calculati<strong>on</strong>s. We also<br />

suggest realistic exchange interacti<strong>on</strong>s from effective Hamilt<strong>on</strong>ian, which has various<br />

n<strong>on</strong>trivial terms including the most str<strong>on</strong>g Kitaev-type anisotropic exchange terms<br />

within the same sublattice, rather small but significant Dzyaloshinskii-Moriya terms,<br />

and Heisenberg exchange interacti<strong>on</strong>s.<br />

Structural and electrical properties of (111) oriented half-Heusler La-<br />

Pt-Bi thin films<br />

Nozomi Sugimoto 1 *, Yohei Niimi 1 , Tetsuya Miyawaki 1 , Tatsuhiko Yoshihara 1 , Naoto<br />

Fukatani 1 , Kenji Ueda 1 , Nobuo Tanaka 2 and Hidefumi Asano 1<br />

1 Department of Crystalline Materials Science, Nagoya University, Japan<br />

2 EcoTopia Institute, Nagoya University, Japan<br />

Topological insulators are candidate materials for low-power and high-speed spintr<strong>on</strong>ics<br />

devices, due to the dissipati<strong>on</strong> less and spin-polarized electr<strong>on</strong>s <strong>on</strong> the surface state.<br />

Recently, we have reported structural properties of LaPtBi(001) thin films, <strong>on</strong>e of<br />

candidate materials of half-Heusler topological insulator[1-2], grown by three-target<br />

co-sputtering[3]. In this paper, we report preparati<strong>on</strong> and properties of LaPtBi with<br />

different crystalline orientati<strong>on</strong>.By optimizing depositi<strong>on</strong> rate for each element, (111)<br />

oriented LaPtBi thin films were obtained below 500°C <strong>on</strong> Sapphire-C substrates. On<br />

the other hand, for films <strong>on</strong> YAlO 3 substrates, both (001) and (111) orientati<strong>on</strong>s were<br />

observed below 500°C. X-ray photoelectr<strong>on</strong> spectroscopy study is revealed that (111)<br />

oriented films exhibited chemical shifts and appearance of satellite peaks of La 3d,<br />

which are attributed to charge transfer from Bi p and Pt d states to La d and f states due<br />

to the mixture of these states in the valence band. Investigati<strong>on</strong> and comparis<strong>on</strong> of the<br />

behaviors of LaPtBi thin films with different orientati<strong>on</strong>s will enable us to uncover the<br />

electr<strong>on</strong> and spin transport properties in the surface state due to the topological nature.<br />

[1] S. Chadov et al., Nat. Mater. 9, 541 (2010). [2] H. Lin et al., Nat. Mater. 9, 546 (2010). [3] T.<br />

Miyawaki et al., J. Appl. Phys., accepted.<br />

July 8 - 13, 2012 Busan, Korea 147<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RC19<br />

First-principles study of spin texture in the multilayer graphene <strong>on</strong><br />

Ni(111)<br />

Fumiyuki Ishii 1 *, Hiroki Kotaka 2 , Keisuke Sawada 3 and Mineo Saito 1<br />

1 Faculty of Mathematics and Physics, Kanazawa University, Japan<br />

2 Graduate School of Natural Science and Technology, Kanazawa University, Japan<br />

3 Graduate School of Natural Science and Technology,, Kanazawa University, Japan<br />

Graphene, a two-dimensi<strong>on</strong>al h<strong>on</strong>eycomb lattice c<strong>on</strong>sisting of C atoms, shows useful<br />

properties for spintr<strong>on</strong>ics applicati<strong>on</strong>s. Recently, spin-split electr<strong>on</strong>ic states in the<br />

graphene <strong>on</strong> Ni(111) is discussed extensively [1-3]. By using n<strong>on</strong>collinear spindensity<br />

functi<strong>on</strong>al theory implemented in openmx code[4], we predict spin-polarized<br />

electr<strong>on</strong>ic states of the graphene <strong>on</strong> Ni(111) in real- and momentum-space. The Diracc<strong>on</strong>e<br />

shaped band structure was broken by str<strong>on</strong>g hybridizati<strong>on</strong> between m<strong>on</strong>olayer<br />

graphene and substrate Ni(111). On the other hand in the bilayer graphene <strong>on</strong> Ni(111),<br />

the Dirac-c<strong>on</strong>e shaped band recover <strong>on</strong>ly in minority spin. The relativistic spin-orbit<br />

effect make n<strong>on</strong>-collinear spin vortex (Rashba Effect) in the momentum space. This<br />

spin n<strong>on</strong>collinearity in momentum space may make significant effects <strong>on</strong> the electrical<br />

transport properties of the graphene/Ni(111).<br />

[1] Yu. S. Dedkov, M. F<strong>on</strong>in, U. Rudiger, and C. Laubschat, Phys. Rev. Lett. 100, 107602 (2008). [2]<br />

O. Rader, A. Varykhalov, and J. Sanchez-Barriga, D. Marchenko, A. Rybkin, and A. M. Shikin, Phys.<br />

Rev. Lett. 102, 057602 (2009). [3] K. Sawada, F. Ishii, M. Saito, Phys. Rev. B 82, 245426 (2010). [4] T.<br />

Ozaki, H. Kino, J. Yu, M. J. Han, N. Kobayashi, M. Ohfuti, F. Ishii, T. Ohwaki, H. Weng, M. Toyoda,<br />

and K. Terakura, http:// www.openmx-square.org/<br />

RD01<br />

Single Crystal Growth, Electrical and Magnetic Properties in ROs 2Al 10<br />

(R=rare earth)<br />

Masahito Sakoda 1 *, Kazuhiro Kubota 1 , Eiichi Matsuoka 1 , Hitoshi Sugawara 1 ,<br />

Takahiro Sakurai 2 , Hitoshi Ohta 3 , Tatsuma D. Matsuda 4 and Yoshinori Haga 4<br />

1 Department of Physics, Kobe University, Kobe 657-8501, Japan, Japan<br />

2 Center for Supports to Research and Educati<strong>on</strong> Activities, Kobe University, Kobe 657-8501, Japan, Japan<br />

3 Molecular Photosciece Research Center, Kobe University, Kobe 657-8501, Japan, Japan<br />

4 Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan, Japan<br />

The ternary rare-earth compounds ROs 2Al 10 (R = rare earth) crystallize with orthorhombic structure<br />

[1]. Am<strong>on</strong>g them, CeOs 2Al 10 have attracted much attenti<strong>on</strong> because of the heavy-fermi<strong>on</strong> behavior<br />

accompanied by a novel l<strong>on</strong>g-range order (LRO) at 28.7 K [2]. In order to understand the mechanisms<br />

of LRO, the informati<strong>on</strong> of physical properties of the reference compounds LaOs 2Al 10 and PrOs 2Al 10<br />

is required. In this work, we have succeeded in growing single crystals of LaOs 2Al 10 and PrOs 2Al 10<br />

by Al self-flux method, and investigated the physical properties by the X-ray diffracti<strong>on</strong>, electrical<br />

resistivity, Hall effect and magnetic susceptibility. Both of LaOs 2Al 10 and PrOs 2Al 10 show the typical<br />

metallic temperature dependence of electrical resistivity without any indicati<strong>on</strong> of phase transiti<strong>on</strong>s.<br />

LaOs 2Al 10 exhibits the Pauli paramagnetism with small temperature dependence, while PrOs 2Al 10<br />

exhibits the Van Vleck paramagnetism with the Curie-Wiess behavior at high temperature with a large<br />

magnetic anisotropy, which is most probably due to the crystalline electric field effect. All of these<br />

results indicate that the electr<strong>on</strong>ic structure of CeOs 2Al 10 is different from those of LaOs 2Al 10 and<br />

PrOs 2Al 10, and suggest that the 4f-electr<strong>on</strong>s in CeOs 2Al 10 are related to the unusual ordering.<br />

[1] V. M. T. Thieder et al., J. Mater. Chem. 8 (1998) 125. [2] T. Nishioka et al., J. Phys. Soc. Jpn. 78 (2009) 123705.<br />

RD02<br />

Anisotropic transport and magnetic properties of CeZn 11 single<br />

crystals^1$<br />

H. Hodovanets, S. L. Bud'ko and P. C. Canfield*<br />

Department of Physics and Astr<strong>on</strong>omy, Ames Laboratory/Iowa State University, Ames<br />

IA, USA<br />

Anisotropic measurements of the magnetic and transport properties have been<br />

performed <strong>on</strong> single crystals of CeZn 11 in three different crystallographic directi<strong>on</strong>s.<br />

M(H) for H$\perp c$ shows a broad metamagnetic transiti<strong>on</strong> at about 1.9 T with<br />

Ms~ 1.6 $\mu_B$ per Ce. Analysis of the temperature dependence of M/H indicates<br />

str<strong>on</strong>g magnetic anisotropy. Zero-field resistivity of CeZn 11 shows a broad maximum,<br />

characteristic of that of K<strong>on</strong>do compounds, at around 10 K followed by a sharp<br />

change of the slope and a kink corresp<strong>on</strong>ding to antiferromagnetic (AF) transiti<strong>on</strong><br />

at 2.0 K. Anisotropic temperature and field dependent magnetoresistance and H-T<br />

phase diagrams will be discussed. $^1$ Work at the Ames Laboratory was supported<br />

by the Department of Energy, Basic Energy Sciences under C<strong>on</strong>tract No. DE-AC02-<br />

07CH11358.<br />

148 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RD03<br />

Shubnikov-de Haas oscillati<strong>on</strong> in PuIn 3<br />

Yoshinori Haga 1 , Oscar Ayala-valenzuela 2 , Ross Mcd<strong>on</strong>ald 2 , Chuck Mielke 2 , Eric D.<br />

Bauer 2 , J N Mitchell 2 , P. H. Tobash 2 , Joe D. Thomps<strong>on</strong> 2 and Zachary Fisk 1<br />

1 Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

2 Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

RD04<br />

Quadrupolar ordering in a caged compound PrOs 2Zn 20<br />

Kazuhei Wakiya 1 , Naohiro Nagasawa 1 , Keisuke T Matsumoto 1 , Takahiro Onimaru 1 ,<br />

Kazunori Umeo 2 and Toshiro Takabatake 1<br />

1 AdSM, Hiroshima University, Higashi-Hiroshima, Japan<br />

2 N-BARD, Hiroshima University, Higashi-Hiroshima, Japan<br />

Pr-based intermetallic compounds with cubic crystal structures are expected to<br />

show various phenomena arising from quadrupolar degrees of freedom, when the<br />

crystal electric field (CEF) ground state of Pr 3+ i<strong>on</strong> is the n<strong>on</strong>magnetic Γ3 doublet.<br />

Recently, it has been found that a caged compound PrIr 2Zn 20 with the Γ3 doublet<br />

ground state undergoes a superc<strong>on</strong>ducting transiti<strong>on</strong> at Tc=0.05 K in the presence of<br />

antiferroquadrupolar order below TQ=0.11 K [1, 2]. We have studied the isostructural<br />

compound PrOs 2Zn 20, with 5d electr<strong>on</strong> <strong>on</strong>e less than in PrIr 2Zn 20, by the measurement<br />

of the electrical resistivity ρ, magnetic susceptibility χ, and specific heat C in the<br />

temperature range from 0.4 K to 300 K. On cooling below 5 K, χ(T ) approaches a<br />

c<strong>on</strong>stant value, indicating a n<strong>on</strong>magnetic CEF ground state. C(T ) shows a peak at<br />

To=0.6 K, where no anomaly appears in the χ(T ). These findings str<strong>on</strong>gly suggest a<br />

n<strong>on</strong>magnetic phase transiti<strong>on</strong> at To arising from the quadrupolar degrees of freedom.<br />

Furthermore, the To is five times higher than TQ in PrIr 2Zn 20, which is possibly<br />

attributed to enhancement of quadrupolar exchange interacti<strong>on</strong>.<br />

[1] T. Onimaru et al., J. Phys. Soc. Jpn. 79 033704 (2010). [2] T. Onimaru et al., Phys. Rev. Lett.<br />

106 177001 (2011).<br />

RD05<br />

UPGRADED<br />

Spin-triplet superc<strong>on</strong>ductivity induced by ferromagnetic fluctuati<strong>on</strong>s<br />

in UCoGe<br />

Taisuke Hattori 1 *, Yoshihiko Ihara 1 , Kosuke Karube 1 , Yusuke Nakai 2 , Kenji Ishida 2 , Yasuhiro Tada 1 ,<br />

Satoshi Fujimoto 1 , Norio Kawakami 1 , Kazuhiko Deguchi 3 , Noriaki K Sato 3 and Isamu Satoh 4<br />

1 Department of Physics, Graduate School of Science, Kyoto University, Japan<br />

2 Department of Physics, Graduate School of Science, Kyoto University. TRIP, JST, Japan<br />

3 Department of Physics, Graduate School of Science, Nagoya University, Japan<br />

4 Institute for Materials Research, Tohoku University, Japan<br />

After the discovery of superc<strong>on</strong>ductivity in the ferromagnetic (FM) UGe 2 under pressure, FM<br />

superc<strong>on</strong>ductors have attracted much interest, since in an itinerant FM superc<strong>on</strong>ductor with the presence<br />

of a large energy splitting between the majority and minority spin Fermi surfaces, exotic spin-triplet<br />

superc<strong>on</strong>ductivity has been anticipated. Am<strong>on</strong>g such FM superc<strong>on</strong>ductors, UCoGe [1] is <strong>on</strong>e of the most<br />

readily explored experimentally, because of its high superc<strong>on</strong>ducting transiti<strong>on</strong> temperature ~ 0.7 K and low<br />

Curie temperature ~ 2.5 K at ambient pressure. Large anisotropic behaviors of superc<strong>on</strong>ductivity [2, 3] and<br />

l<strong>on</strong>gitudinal FM fluctuati<strong>on</strong>s al<strong>on</strong>g the c axis (directi<strong>on</strong> of the ordered moment) [4] are thought to link with<br />

the mechanism of the superc<strong>on</strong>ductivity. From precise angle-resolved NMR and Meissner measurements<br />

we found that the magnetic field al<strong>on</strong>g the c axis str<strong>on</strong>gly suppresses the FM fluctuati<strong>on</strong>s and that the<br />

superc<strong>on</strong>ductivity is observed in the limited magnetic field regi<strong>on</strong> where the FM spin fluctuati<strong>on</strong>s are active.<br />

These results combined with model calculati<strong>on</strong>s str<strong>on</strong>gly suggest that the l<strong>on</strong>gitudinal FM spin fluctuati<strong>on</strong>s<br />

tuned by H || c induce the unique spin-triplet superc<strong>on</strong>ductivity in UCoGe. As far as we know, this is the first<br />

clear experimental example that FM fluctuati<strong>on</strong>s are intimately related with superc<strong>on</strong>ductivity.<br />

[1] N. T. Huy et al., Phys. Rev. Lett. 99 (2007) 067006. [2] N. T. Huy et al., Phys. Rev. Lett. 100 (2008) 077002. [3]<br />

D. Aoki et al., J. Phys. Soc. Jpn. 78 (2009) 113709. [4] Y. Ihara et al., Phys. Rev. Lett. 105 (2010) 206403.


RD06<br />

Competitive magnetic properties between the different anisotropic<br />

SDW phases in heavy-fermi<strong>on</strong> system Ce 0.87La 0.13(Ru 1-xRh x) 2Si 2<br />

Hiroaki Okamoto 1 , Eiichiro Harada 1 , Yusuke Amakai 1 , Shigeyuki Murayama 1 *,<br />

Hideaki Takano 1 , Naoki Mom<strong>on</strong>o 1 , Kazuyuki Matsubayashi 2 and Yoshiya Uwatoko 2<br />

1 Graduate School of Engineering, Muroran Institute of Technology, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

Typical heavy-fermi<strong>on</strong> compound CeRu 2Si 2 shows an SDW transiti<strong>on</strong> by the<br />

substituti<strong>on</strong> of La at the Ce site with the gap perpendicular to the c-axis and the moment<br />

al<strong>on</strong>g the c-axis(1). It shows another SDW transiti<strong>on</strong> with the gap and moment both<br />

parallel to the c-axis by the substituti<strong>on</strong> of Rh at the Ru site(2). In order to investigate<br />

the two different SDW phases, we have measured the susceptibility χ and resistivity ρ<br />

<strong>on</strong> single-crystalline Ce 0.87La 0.13(Ru 1-xRh x) 2Si 2 for 0 ≤ x ≤ 0.4 in directi<strong>on</strong>s perpendicular<br />

(∠) and parallel (//) to the c-axis(3). The ρ∠ for 0 ≤ x < 0.05 shows a gap-type anomaly<br />

at TN, whereas the ρ// for 0 ≤ x < 0.05 indicates a downward inflecti<strong>on</strong> or a shoulder<br />

at around TN, suggesting the transverse SDW transiti<strong>on</strong>. For 0.05 ≤ x ≤ 0.075 these<br />

anomalies become very small and a hysteresis is further seen between temperature<br />

decreasing and increaseing process below TN. For 0.075 < x ≤ 0.3 the gap-type anomaly<br />

in ρ∠ disappears and a clear gap-type jump has been detected in ρ// at TN, suggesting<br />

the l<strong>on</strong>gitudinal SDW transiti<strong>on</strong>. These behaviors would suggest that a competitive<br />

magnetic phase occurs between the two anisotropic SDW phases.<br />

(1) S. Quezel et. al., J. Magn. & Magn. Mater., 76 & 77, 403 (1988). (2) S. Murayama et. al., Phys.<br />

Rev. B 56, 11092 (1997). (3) Y. Amakai et. al., J. Phys. Soc. Jpn. 80, SA062 (2011).<br />

RD07<br />

Elastic c<strong>on</strong>stant of SmOs 4Sb 12 under high magnetic field<br />

Tatsuya Yanagisawa 1 *, Shota Mombetsu 1 , Mitsuhiro Akatsu 2 , Yuichi Nemoto 2 , Shadi<br />

Yashin 3 , Sergei Zherlitsyn 3 and Joachim Wosnitza 3<br />

1 Department of Physics, Hokkaido University, Japan<br />

2 Graduate School of Science and Technology, Niigata University, Japan<br />

3 Dresden High Magnetic Field Laboratory, Forschungszentrum Dresden-Rossendorf,<br />

Germany<br />

The filled skutterudite compound SmOs 4Sb 12 exhibits a large electr<strong>on</strong>ic specific heat coefficient Υ<br />

~ 820 mJ K -2 mol -1 , which is insensitive to an applied magnetic field H || , and also shows a<br />

phase transiti<strong>on</strong> at 2.5 K with tiny ferromagnetic moment. The origin of the magnetically robust<br />

heavy fermi<strong>on</strong> state and an exotic phase transiti<strong>on</strong> are unsolved issues. The crystalline electric field<br />

(CEF) ground state of this compound has also not been settled, thus far. Owing to clarified whether<br />

the CEF ground state is the Γ_8 quartet or Γ_7 doublet for Sm 3+ i<strong>on</strong>ic c<strong>on</strong>figurati<strong>on</strong>s, we have<br />

measured the elastic c<strong>on</strong>stant C_11 <strong>on</strong> single crystalline SmOs 4Sb 12 by using pulsed magnetic<br />

fields up to 62 T. As a result, C_11 shows a minimum at around 10 T and gradually increase with<br />

increasing magnetic field at 4.2 K. In the cubic symmetry, C_11 can be described as the sum of<br />

the bulk modulus C_B and the Γ_3-type quadrupole susceptibility. Assuming that C_B is <strong>on</strong>ly<br />

dominated by magneto-elastic effects of the weak ferromagnetic moment in the low magnetic<br />

field regi<strong>on</strong>, the increasing tendency of C_11 at high magnetic field regi<strong>on</strong> could be explained by a<br />

quadrupole susceptibility with Γ_8 quartet CEF ground state.<br />

[1] S. Sanada et al., J. Phys. Soc. Jpn. 74 (2005) 246, [2] W. M. Yuhasz et al., Phys. Rev. B 71 (2005) 104402, [3]<br />

Y. Aoki et al., Physica B 378-380 (2006) 54, [4] T. Yanagisawa et al., J. Phys. Soc. Jpn. 80 (2011) 043601.<br />

RD08<br />

27Al-NMR study for critical phenomena of metamagnetic transiti<strong>on</strong> in<br />

UCoAl<br />

Kosuke Karube 1 *, Taisuke Hattori 1 , Kenji Ishida 1 , Takuya Asai 2 , Takemi<br />

Komatsubara 3 and Noriaki Kimura 2<br />

1 Department of Physics, Graduate School of Science, Kyoto University, Japan<br />

2 Department of Physics, Graduate School of Science, Tohoku University, Japan<br />

3 Center for Low Temperature Science, Tohoku University, Japan<br />

UCoAl shows a first-order paramagnetism (PM)-ferromagnetism (FM) transiti<strong>on</strong> (metamagnetic<br />

transiti<strong>on</strong>) in small external magnetic field about 0.6 T applied <strong>on</strong>ly al<strong>on</strong>g its easy magnetizati<strong>on</strong><br />

axis, c-axis [1]. This first order transiti<strong>on</strong> line terminates at a “critical-end-point” at Tcr ~ 13 K.<br />

Above Tcr the first order transiti<strong>on</strong> from PM to FM changes to crossover. This feature is apparently<br />

similar to gas-liquid transiti<strong>on</strong>, where the order parameter and the tuning parameter are density of<br />

molecules and pressure, respectively. In fact, a gas-liquid transiti<strong>on</strong> is regarded to be mathematically<br />

equivalent to 3D-Ising FM transiti<strong>on</strong> [2], therefore we expect the metamagnetic transiti<strong>on</strong> in<br />

UCoAl has the same physical framework as a gas-liquid transiti<strong>on</strong>. In order to investigate static and<br />

dynamic properties in the critical phenomena <strong>on</strong> UCoAl, we performed 27Al-NMR measurement<br />

for a single-crystal UCoAl and measured Knight-shift K and nuclear spin-lattice relaxati<strong>on</strong> rate 1/<br />

T1 by varying temperature T and c-axis magnetic field Hc. In the poster presentati<strong>on</strong>, I will show<br />

the result of c-axis magnetizati<strong>on</strong> Mc (order parameter) and c-axis dynamical susceptibility Sc<br />

(fluctuati<strong>on</strong>s of order parameter) calculated from K and 1/T1T, as a functi<strong>on</strong> of (T, Hc) and discuss<br />

similarities and differences from comparis<strong>on</strong> with gas-liquid transiti<strong>on</strong>.<br />

[1] N. V. Mushinikov et al., Phys. Rev. B 59, 6877 (1999). [2] T. D. Lee et al., Phys. Rev. 87, 410 (1952).<br />

RD09<br />

RD10<br />

RD11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Hybridizati<strong>on</strong> gap and the hidden order in the heavy fermi<strong>on</strong> K<strong>on</strong>do<br />

lattice URu 2Si 2<br />

Wan Kyu Park 1 *, Paul H. Tobash 2 , Filip R<strong>on</strong>ning 2 , Eric D. Bauer 2 , John L. Sarrao 2 ,<br />

Joe D. Thomps<strong>on</strong> 2 and Laura H. Greene 1<br />

1 University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA<br />

2 Los Alamos Nati<strong>on</strong>al Laboratory, Los Alamos, NM 87545, USA<br />

What drives the sec<strong>on</strong>d order phase transiti<strong>on</strong> that occurs at 17.5 K in the K<strong>on</strong>do lattice<br />

heavy fermi<strong>on</strong> URu 2Si 2 remains unknown after two and half decades of research despite<br />

ubiquitous observati<strong>on</strong> of gap-like behaviors. Determining the nature of the extracted<br />

gaps, whether they are the order parameter or not, is a crucial task to resolving this hidden<br />

order enigma. Quasiparticle scattering spectroscopy (QPS), better known as pointc<strong>on</strong>tact<br />

spectroscopy, is a powerful technique to probe the bulk electr<strong>on</strong>ic properties by<br />

exploiting a ballistic juncti<strong>on</strong> between two electrodes. Employing QPS, we have carried<br />

out c<strong>on</strong>ductance measurements <strong>on</strong> URu 2Si 2 [1]. The differential c<strong>on</strong>ductance data exhibit<br />

a distinct double-peak structure with pr<strong>on</strong>ounced asymmetry, a signature for a Fano<br />

res<strong>on</strong>ance in a K<strong>on</strong>do lattice [2]. The extracted gap, a hybridizati<strong>on</strong> gap between the<br />

renormalized bands, opens well above the hidden order transiti<strong>on</strong> temperature, indicating<br />

this hybridizati<strong>on</strong> gap is not the hidden order parameter. Our results place severe<br />

c<strong>on</strong>straints <strong>on</strong> the origin of the hidden order transiti<strong>on</strong> in URu 2Si 2. The work at UIUC is<br />

supported by the U.S. DOE under Award No. DE-FG02-07ER46453. The work at LANL<br />

is carried out under the auspices of the U.S. DOE, Office of Science.<br />

[1] W. K. Park et al., PRL 108, 246403 (2012) [2] M. Maltseva, M. Dzero, P. Coleman, PRL 103, 206402 (2009).<br />

Res<strong>on</strong>ant Raman effect <strong>on</strong> LaRu2Al10 and CeRu2Al10 Katsuaki Nagano 1 , Takumi Hasegawa 1 , Norio Ogita 1 , Masayuki Udagawa 1 , Hiroshi<br />

Tanida 2 , Daiki Tanaka 2 , Masafumi Sera 2 , Takashi Nishioka 3 and Masahiro Matsumura 3<br />

1<br />

Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-<br />

Hiroshima 739-8521, Japan, Japan<br />

2<br />

Institute for Advanced Material Research, Hiroshima University, Higashi-Hiroshima<br />

739-8530, Japan, Japan<br />

3<br />

Graduate School of Advanced Sciences of Matter, Kouchi University, Kochi 780-<br />

8520, Japan, Japan<br />

LaRu 2Al 10 and CeRu 2Al 10 with space group Cmcm have the orthorhombic YbFe 2Al 10 type structure [1], where<br />

the number of Raman active ph<strong>on</strong><strong>on</strong>s is estimated as 10Ag + 9B1g + 6B2g + 8B3g by group theory. CeRu 2Al 10<br />

shows the transiti<strong>on</strong> at T0 = 27 K [2, 3, 4], while LaRu 2Al 10 shows no anomaly. We reported the temperature<br />

dependence of the ph<strong>on</strong><strong>on</strong> Raman spectra at the SCES 2011, where we could not observe all ph<strong>on</strong><strong>on</strong> modes by<br />

<strong>on</strong>ly 514.5 nm excitati<strong>on</strong> and no anomaly at T0 in CeRu 2Al 10. We c<strong>on</strong>cluded that the transiti<strong>on</strong> at T0 does not<br />

accompany with the structural change. Recently we have employed several excitati<strong>on</strong>s light at 488.0 nm, 514.5<br />

nm, 568.2 nm, and 647.1nm. We have observed the B1g mode missed by <strong>on</strong>ly 514.5 nm, that is, we observe all<br />

ph<strong>on</strong><strong>on</strong> modes by changing the excitati<strong>on</strong> energy. In the guest atoms modes, the vibrati<strong>on</strong> al<strong>on</strong>g b axis shows<br />

the intensity enhancement at 647.1 nm, but that al<strong>on</strong>g a or c axis does not show the case. Remarkable difference<br />

between LaRu 2Al 10 and CeRu 2Al 10 is observed for the ph<strong>on</strong><strong>on</strong>s at around 100 cm-1 in (y, z) polarizati<strong>on</strong>. These<br />

differences are originated by the difference of the electr<strong>on</strong>ic states between them.<br />

[1] Thieda V M T, et al, 1998 J. Mater. Chem. 8 125. [2] Strydom A M 2009 Physica B 404 2981 [3]<br />

Nishioka T, et al 2009 J. Phys. Soc. Jpn. 78 123705 [4] Muro Y, et al 2010 J. Phys.: C<strong>on</strong>f. Series 200 012136<br />

Magnetic properties of β-US2 single crystals<br />

Etsuji Yamamoto 1 *, Shugo Ikeda 2 , Hir<strong>on</strong>ori Sakai 1 , Tatsuma D. Matsuda 1 , Naoyuki<br />

Tateiwa 1 , Yoshinori Haga 1 , Yoshichika Onuki 3 and Zachary Fisk 4<br />

1 ASRC, Japan Atomic Energy Agency, Japan<br />

2 Graduate School of Material Science, University of Hyogo, Japan<br />

3 Graduate School of Science, Osaka University, Japan<br />

4 University of California, USA<br />

Uranium chalcogenides compounds UXS (X:S, Se and Te) have the same orthorhombic<br />

(Pnma) structure and those electr<strong>on</strong>ic state can easily be modified by changing the<br />

c<strong>on</strong>stituting elements. UTeS is an Ising-type ferromagnet with a Curie temperature 87<br />

K and shows metallic c<strong>on</strong>ductivity at all temperatures. USeS shows a semimetallic<br />

resistivity. Electrical resistivity of USeS decreases with decreasing temperature<br />

but increases steeply below 50 K, with an anomaly at the ferromagnetic ordering<br />

temperature 24 K.US2 is similar to USeS at high temperature and the electrical<br />

resistivity of US2 decreases with decreasing temperature and increases steeply below<br />

about 80 K, but US2 does not order magnetically. The electrical resistivity of US2 at<br />

low temperature suppresses under a high pressure or a high magnetic field [1]. We<br />

study the magnetic properties of US2 in detail by measuring magnetic susceptibility<br />

and electric resistivity under a magnetic field.<br />

[1] S. Ikeda et al., J. Phys. Soc. Jpn.76 (2009) 114704.<br />

July 8 - 13, 2012 Busan, Korea 149<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RD12<br />

Evidence of nodal gap structure in the skutteride superc<strong>on</strong>ductor<br />

PrPt 4Ge 12<br />

Jing Lei Zhang 1 , Lin Jiao 1 , Michael Nicklas 2 , Roman Gumeniuk 2 , Ye Chen 1 , Lu Kai<br />

Guo 1 , Li Na Wang 1 , Bin Hao Fu 1 , Walter Schnelle 2 , Helge Rosner 2 , Andreas Leithejasper<br />

2 , Yuri Grin 2 , Frank Steglich 2 and Hui Qiu Yuan 1 *<br />

1 Department of Physics, Zhejiang University, China<br />

2 Max Planck Institute for Chemical Physics of Solid, Germany<br />

In order to study the gap functi<strong>on</strong> of the newly discovered skutterudite superc<strong>on</strong>ductor<br />

PrPt 4Ge 12 (T_{c}=7.9K), we have measured the L<strong>on</strong>d<strong>on</strong> penetrati<strong>on</strong> depth Δλ(T) of the<br />

single crystalline PrPt 4Ge 12 down to 0.05Tc by using a tunnel diode oscillati<strong>on</strong> (TDO)<br />

based technique. Observati<strong>on</strong> of a quadratic temperature dependence of Δλ below<br />

0.3Tc indicates the existence of point nodes in the superc<strong>on</strong>ducting gap. The derived<br />

superfluid density ρ_{s}(T) can be nicely fitted by the A-phase gap functi<strong>on</strong> of 3He<br />

(Δ(θ,φ)=Δ_{0} |K_{x}+iK_{y}|) with a fitting parameter of Δ_{0}=2.2k_{B}T_{c},<br />

providing new evidence for a possible p-wave superc<strong>on</strong>ductivity in PrPt 4Ge 12.<br />

RD13<br />

Mossbauer spectroscopy of Fe doping valence fluctuating α-YbAlB 4<br />

Yui Sakaguchi1*, Shugo Ikeda1, Kentaro Kuga2, Keita S<strong>on</strong>e2, Satoru Nakatsuji2 and<br />

Hisao Kobayashi1<br />

1 Graduate School of Material Science, University of Hyogo, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

Valence fluctuating YbAlB 4 compounds have two different crystal structures; α-YbAlB 4<br />

andβ-YbAlB 4 [1].β-YbAlB 4 is the first compound which shows a Yb-based heavy fermi<strong>on</strong><br />

superc<strong>on</strong>ductor with Tc = 80mK [2] and exhibits a pr<strong>on</strong>ounced n<strong>on</strong>-Fermi-liquid behavior<br />

above Tc. Meanwhile, α-YbAlB 4 shows normal metallic behaviorsat low temperature.<br />

Recently, the small substituti<strong>on</strong> of Al by Fe in α-YbAlB 4 revealed a breakdown of<br />

the Fermi-liquid behavior with an antiferromagnetic order. We have studied magnetic<br />

properties of α-Yb(Al 0.75Fe 0.25)B 4 at low temperatures using 57Fe Mossbauer spectroscopy.<br />

The observed Mossbauer spectrum at room temperature using single crystalline samples<br />

is typical for a paramagnetic state. We analyzed the spectrum using a doublet. From<br />

the intensity rati<strong>on</strong> of the doublet, the principle z-axis of the diag<strong>on</strong>alized electric-field<br />

gradient tensor is perpendicular to the c-axis. We observed a small magnetic hyperfine<br />

field at 4.5K whitch comes from the antiferromagnetic ordering of Yb magnetic moments.<br />

This small magnetic hyperfine field disappears around TN (~ 9K). These results indicate<br />

that the magnetic structure is not simple in α-Yb(Al 0.75Fe 0.25)B 4. Above TN, the observed<br />

spectra change drastically with increasing temperature. Some of changes in the spectra<br />

were related to anomalies in the temperature dependence of magnetizati<strong>on</strong>.<br />

[1] R. T. Macaluso et al., Chem. Mater. 19. 1918 (2007) [2] S. Nakatsuji et al., Nature Phys. 4, 603 (2008)<br />

RD14<br />

Neutr<strong>on</strong> scattering study <strong>on</strong> f-electr<strong>on</strong> states of PrCu 4Au<br />

Hiroki Kobayashi 1 , Kazuaki Iwasa 1 *, Kotaro Saito 1 , Keisuke Tomiyasu 1 , Daichi<br />

Kawana 2 , Shuai Zhang 3 , Yosikazu Isikawa 4 , Jean - Michel Mignot 5 , Gilles Andre 5 ,<br />

Alexander I. Kolesnikov 6 , Andrei T. Savici 6 and Garrett E. Granroth 6<br />

1 Department of Physics, Tohoku University, Sendai 980-8578, Japan<br />

2 C<strong>on</strong>densed Matter Research Center and Phot<strong>on</strong> Factory, Institute of Materials Structure<br />

Science, KEK, Tsukuba 305-0801, Japan<br />

3 Department of Applied Chemistry, Hiroshima University, Higashi-Hiroshima 739-8527, Japan<br />

4 Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan<br />

5 Laboratoire Le<strong>on</strong> Brillouin, CEA-CNRS, CEA/Saclay, 91191 Gif sur Yvette, France<br />

6 Neutr<strong>on</strong> Sciences D., Oak Ridge Nati<strong>on</strong>al Laboratory, Oak Ridge, TN 37831, USA<br />

Pr-based compounds have recently been studied for heavy electr<strong>on</strong> properties originating from 4f 2<br />

electr<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong>, as in PrFe 4P 12 [1]. We extracted a large electr<strong>on</strong>ic-specific-heat-coefficient of<br />

0.77 J/mol K 2 from specific heat measurements <strong>on</strong> PrCu 4Au [2]. This material is expected to undergo<br />

an antiferromagnetic transiti<strong>on</strong> below 2.4 K. We investigate the role that f-electr<strong>on</strong> states play in these<br />

properties using neutr<strong>on</strong> scattering techniques. We used the spectrometers SEQUOIA at ORNL, 4F1 at<br />

LLB, and TOPAN at JAEA to measure the temperature dependence, between 1.6 K and 100 K, of the<br />

magnetic excitati<strong>on</strong>s in PrCu 4Au. The spectra are composed of several inelastic peaks. The crystal-fieldsplitting<br />

scheme with the triplet ground state, as suggested from the magnetizati<strong>on</strong> result [2], is a fair match<br />

to the observed spectra. A quasielastic comp<strong>on</strong>ent was also detected. The temperature dependences of the<br />

spectral intensity and width are similar to those in other heavy electr<strong>on</strong> systems. Diffracti<strong>on</strong> experiments<br />

for the powdered sample <strong>on</strong> the diffractometer G4-1 at LLB reveal antiferromagnetic peaks characterized<br />

by the wave vector (1/2, 1/2, 1/2). This result can be interpreted as the type-II magnetic ordering <strong>on</strong> the fcc<br />

sub-lattice of Pr i<strong>on</strong>s. To summarize, PrCu 4Au exhibits localized and str<strong>on</strong>gly-hybridized f-electr<strong>on</strong> states.<br />

[1] H. Sugawara et al.: Phys. Rev. B 66 (2002) 134411. [2] S. Zhang et al.: J. Phys.: C<strong>on</strong>dens. Matter 21 (2009) 205601.<br />

150 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RD15<br />

Effect of pressure <strong>on</strong> the YbNi 3Ga 9 single crystal<br />

T. Hirayama 1 , K. Matsubayashi 1 , T. Yamashita 2 , S. Ohara 2 and Y. Uwatoko 1 *<br />

1 University of Tokyo, Japan<br />

2 Nagoya Institute of Technology, Japan<br />

We have investigated the effect of pressure <strong>on</strong> the physical properties of singlecrystalline<br />

YbNi 3Ga 9. This compounds crystallize in a trig<strong>on</strong>al ErNi 3Al 9-type structure<br />

(space group R32). From the thermal, magnetic and transport study, YbNi 3Al 9 turns<br />

out to be an intermediate valence compound with r = 30 mJ/molK [1]. The electrical<br />

resistivity and ac susceptibility of n<strong>on</strong>magnetic heavy fermi<strong>on</strong> compound YbNi 3Al 9<br />

have been measured under hydrostatic pressure up to 11 GPa. With increasing pressure,<br />

the ferromagnetic ordering state was appeared over 9 GPa. These results suggested<br />

that n<strong>on</strong>magnetic Yb state change to the localized magnetic state, via quantum critical<br />

point, by tuning the pressure. In this paper, we will discuss the electrical state of<br />

YbNi 3Al 9 under pressure.<br />

[1]T. Yamashita and S. Ohara; submitted to J. Phys. Soc. Jpn.<br />

RD16<br />

Fermi surfaces in the mixed valent Yb system<br />

Hisatomo Harima*<br />

Department of Physics, Kobe University, Japan<br />

Many Yb-compounds have been crystalized recently in good quality, so that the de<br />

Haas-van Alphen effect is detected in those including the Yb-based heavy fermi<strong>on</strong><br />

compounds, i.e., YbCu 2Si 2, YbAlB 4. N<strong>on</strong>-magnetic Yb compounds are regarded<br />

mostly as divalent Yb system, in which Fermi surfaces are well reproduced by using<br />

c<strong>on</strong>venti<strong>on</strong>al band structure calculati<strong>on</strong>s. In some of n<strong>on</strong>-magnetic Yb compounds,<br />

such as YbAl 3, the valence of Yb-i<strong>on</strong> is diverted from Yb 2+ . Actually, the Fermi<br />

surfaces of YbAl 3 are very different in topology from those of divalent YbIn 3. This is<br />

the clear evidence of the 4f electr<strong>on</strong>s really affect the formati<strong>on</strong> of the Fermi surfaces<br />

in YbAl 3[1]. In Yb compounds, the dispersi<strong>on</strong> of the 4f bands are very flat, then the<br />

Fermi surfaces are very sensitive to the role of the 4f electr<strong>on</strong>s. Recently the LDA+U<br />

approach has shown that <strong>on</strong>ly the doublet ground states participate the Fermi surfaces<br />

in YbCu 2Si 2[2]. The role of 4f electr<strong>on</strong>s in mixed valent Yb system is discussed, for<br />

YbAlB 4 , YbCoGa 5 and the related compounds.<br />

[1] T. Ebihara, et.. al., J. Phys. Soc. Jpn. 69 (2000) 895. [2] Nguyen Duc Dung, et. al., J. Phys. Soc.<br />

Jpn. 78 (2009) 084711.<br />

RD17<br />

Unusual heavy fermi<strong>on</strong> behavior in PrTr 2Al 20 (T = Nb, Ta) associated<br />

with Γ_3 quadrupolar degrees of freedom<br />

Ryuji Higashinaka, Akihiro Nakama, Ryoichi Miyazaki, Yuji Aoki and Hideyuki Sato<br />

Department of Physics, Tokyo Metropolitan University, Japan<br />

Recently, PrTr 2X 20 (Tr = transiti<strong>on</strong> metal, X = Zn, Al) compounds have attracted<br />

much attenti<strong>on</strong> as a new candidate for investigating the quadrupolar K<strong>on</strong>do effect<br />

because PrTr 2Al 20 (Tr = Ti, V) show n<strong>on</strong> Fermi liquid behaviors and multipolar<br />

orderings attributed to n<strong>on</strong>magnetic Γ_3 doublet ground state[1]. Recently, we found<br />

that PrNb 2Al 20 also has a n<strong>on</strong>magnetic Γ_3 doublet ground state and does not show<br />

any phase transiti<strong>on</strong>s down to 0.15 K[2]. In additi<strong>on</strong>, this compound has a large<br />

Sommerfeld coefficient γ(~ 1.2 J/molK 2 ). This result suggests a possibility of the<br />

formati<strong>on</strong> of unusual heavy fermi<strong>on</strong> state attributed to the quadrupole moments of<br />

Γ_3 state. In order to investigate the quadrupole-induced str<strong>on</strong>gly correlated electr<strong>on</strong>ic<br />

properties in PrTr 2Al 20 systematically we have grown single crystals of other Pr based<br />

compound, PrTa 2Al 20, and performed specific heat, magnetizati<strong>on</strong> and electr<strong>on</strong>ic<br />

transport measurements. In C/T, PrTa 2Al 20 shows a peak around 0.6 K attributed to<br />

the ordring of quadrupole moment and has a large gamma value of 1.6 J/molK 2 at low<br />

temperatures with little field dependence. In this presentati<strong>on</strong>, we show recent results<br />

for PrT 2Al 20 (T = Nb, Ta) and discuss the possibility of the formati<strong>on</strong> of heavy fermi<strong>on</strong><br />

formati<strong>on</strong> induced by quadrupolar degrees of freedom.<br />

[1] A. Sakai and S. Nakatsuji: J. Phys. Soc. Jpn. 71 063701 (2011). [2] R. Higashinaka et al.: JPS<br />

Autumn meeting 23pPSA-37 (2010), JPS Spring meeting 28aEC-11 (2011).


RD18<br />

Tuning of the heavy-fermi<strong>on</strong> ground state in YbNi 3X 9 (X=Al, Ga) by<br />

substituti<strong>on</strong><br />

Shigeo Ohara*, Hiroshi K<strong>on</strong>o and Tetsuro Yamashita<br />

Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555,<br />

Japan<br />

We have succeeded in synthesizing new Yb-based K<strong>on</strong>do lattice systems YbNi 3X 9 (X =Al, Ga)<br />

which crystallizes in the trig<strong>on</strong>al ErNi 3Al 9-type structure [1]. YbNi 3Al 9 shows typical features<br />

of a heavy-fermi<strong>on</strong> antiferromagnet with Neel temperature of TN=3.4K and Sommerfeld<br />

coefficient γ~100mJ/(molK2). In c<strong>on</strong>trast, YbNi 3Ga 9 is an intermediate valence compound with<br />

γ=30mJ/(molK2) and a high characteristic temperature of TK~600K. YbNi 3X 9 (X =Al, Ga)<br />

is a great opportunity to investigate the tunability of heavy-fermi<strong>on</strong> ground states in Yb-based<br />

compound for using external c<strong>on</strong>trol parameters such as pressure or doping. In this regard, we<br />

are investigating physical properties of mixed crystals of YbNi 3Al 9-YbNi 3Ga 9, doping system of<br />

Yb(Ni 1-xM x) 3X 9 (M=3d transiti<strong>on</strong>-metal) and dilute system of (Yb 1-xLu x)Ni 3X 9. Here we report<br />

Ni-site substituti<strong>on</strong> effects <strong>on</strong> the antiferromagnetism of YbNi 3Al 9. For YbNi 3Al 9, the resistivity<br />

shows a -logT dependence below 100K and a broad peak at about 40 K arising due to the K<strong>on</strong>do<br />

effect combined with the CEF excited state. In the lower-temperature regi<strong>on</strong>, a str<strong>on</strong>g reducti<strong>on</strong><br />

in the extent of magnetic scattering associated with the antiferromagnetic ordering was observed<br />

below TN=3.4 K. By Fe-substituti<strong>on</strong> TN is decreased, while is increased by Cu-substituti<strong>on</strong>. The<br />

tunability of TN in Yb(Ni 1-xM x) 3X 9 will be discussed.<br />

[1] S. Ohara et al., J. Phys.: C<strong>on</strong>f. Series 273, 012048 (2011); T. Yamashita et al., to be published in<br />

J. Phys. Soc. Jpn.<br />

RD19<br />

Pressure effect studies in Ce 2T 3Ge 5 (T=Rh, Pd, Ir) by electrical<br />

resistivity<br />

Miho Nakashima 1 , Toshiyuki Uchiyama 1 , Toru Kawata 1 , Yasushi Amako 1 , Yusuke<br />

Hirose 2 , H<strong>on</strong>da Fuminori 2 , Rikio Settai 2 and Onuki Yoshichika 2<br />

1 Department of Physics, Faculty of Science, Shinshu University, Japan<br />

2 Graduate School of Science, Osaka University, Japan<br />

In the Ce 2T 3Ge 5 system (T: transiti<strong>on</strong> metal) with the orthorhombic crystal structure, Ce 2Ni 3Ge 5<br />

is an antiferromagnet with a Neel temperature T N = 5.2 K. T N decreases with increasing pressure<br />

and becomes zero at a critical pressure P c = 3.9 GPa. The A and ρ 0 values in the Fermi liquid<br />

relati<strong>on</strong> (the low-temprature electrical resistivity ρ = ρ 0 + AT 2 ) increase steeply above 3 GPa.<br />

It seems to be the heavy fermi<strong>on</strong> state around Pc, in which pressure regi<strong>on</strong> superc<strong>on</strong>ductivity<br />

was found below 0.26 GPa [1]. We measured temperature dependence of electrical resistivity<br />

of Ce 2Rh 3Ge 5, Ce 2Ir 3Ge 5 and Ce 2Pd 3Ge 5 under pressure in this study. These theree compounds<br />

are all antiferromagnets at ambient pressure, showing kinks of resistivity at T N (=4.7, 9.5 and<br />

3.8 K respectively)[2, 3, 4]. In Ce 2Rh 3Ge 5 and Ce 2Ir 3Ge 5 T N decreases with increasing pressure<br />

and seems to be zero at a critical pressure P c=0.4 and 2.0 GPa, while T N increases in Ce 2Pd 3Ge 5<br />

by pressure. We also found another anomaly at lower temperature, indicating T N splits into<br />

two ordering T N1 and T N2 under pressure more than 0.2 GPa. T N 1 and T N 2 are both increasing<br />

m<strong>on</strong>ot<strong>on</strong>ously with increasing pressure up to 2.3 GPa.<br />

[1] M. Nakashima, et al., J. Phys.: C<strong>on</strong>dens. Matter 17 (2005) 4539. [2] C. Godart, et al., Solid<br />

State Commun. 67 (1988) 677. [3] B. Becker, et al., Phys. B 230-232 (1997) 253. [4] Z. Hossain, et<br />

al., Phys. Rev. B 60 (1999) 10383.<br />

RD20<br />

Photoemissi<strong>on</strong> study <strong>on</strong> new K<strong>on</strong>do lattice compounds YbNi 3(Ga 1-xAl x) 9<br />

Yuki Utsumi 1 , Hitoshi Sato 2 , Shigeo Ohara 3 , Tetsuro Yamashita 3 , Kojiro Mimura 4 ,<br />

Satoru Mot<strong>on</strong>ami 4 , Masashi Arita 2 , Shigenori Ueda 5 , Keisuke Kobayashi 5 , Kenya<br />

Shimada 2 , Hirofumi Namatame 2 and Masaki Taniguchi 2<br />

1 Graduate School of Science, Hiroshima University, Japan<br />

2 Hiroshima Synchrotr<strong>on</strong> Radiati<strong>on</strong> Center, Hiroshima University, Japan<br />

3 Graduate School of Engineering, Nagoya Institute of Technology, Japan<br />

4 Graduate School of Engineering, Osaka Prefecture University, Japan<br />

5 NIMS Beamline Stati<strong>on</strong> at SPring-8, Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

Recently, new K<strong>on</strong>do lattice compounds YbNi 3X 9 (X=Al, Ga) were discovered [1]. YbNi 3Al 9 is a heavyfermi<strong>on</strong><br />

antiferromagnetic compound (TN=3.4 K), while YbNi 3Ga 9 is a valence fluctuating compound from<br />

the magnetic susceptibility measurements. These compounds are c<strong>on</strong>sidered to be very suitable for research<br />

of Yb-based K<strong>on</strong>do lattice systems because they both possess the ErNi 3Al 9-type crystal structure, and the Al<br />

and Ga i<strong>on</strong>s are isovalent. In this study, we have carried out hard x-ray (hν~6 keV) and low energy (hν~7 eV)<br />

excited photoemissi<strong>on</strong> spectroscopy (HAXPES and LEPES) <strong>on</strong> YbNi 3X 9 and mixed crystals YbNi 3(Ga 1-xAl x) 9<br />

to investigate the Yb valence and the K<strong>on</strong>do res<strong>on</strong>ance behavior. The Yb 3d HAXPES experiments revealed<br />

that the Yb i<strong>on</strong> in YbNi 3Al 9 exists with almost trivalent state while that in YbNi 3Ga 9 str<strong>on</strong>gly fluctuates with<br />

the averaged Yb valence of ~2.5. The Al substituti<strong>on</strong> for YbNi 3Ga 9 (x~0.1) changes the Yb i<strong>on</strong> toward trivalent<br />

state. The LEPES spectra of YbNi 3Ga 9 clearly exhibit the K<strong>on</strong>do res<strong>on</strong>ance peak near the Fermi level (EF),<br />

and the peak is shifted toward EF and the intensity increases with lowering temperature. The extrapolated peak<br />

energy at zero temperature provides TK~600 K for YbNi 3Ga 9 and the Al substituti<strong>on</strong> lowers TK.<br />

[1] S. Ohara et al., J. Phys.: C<strong>on</strong>f. Series 273, 012048 (2011); T. Yamashita et al., to be published in J. Phys. Soc. Jpn.<br />

RD21<br />

RD22<br />

RD23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Heavy-fermi<strong>on</strong> properties of YbCu5-xAux (x = 0.5, 0.6, 0.7)<br />

Ivan Curlik 1 *, Mauro Giovannini 2 , Mariana Zapotokova 3 and Marian Reiffers 1<br />

1<br />

Institute of Experimental Physics, Slovak Academy of Science, Wats<strong>on</strong>ova 47, 040<br />

01, Kosice, Slovakia, Slovak<br />

2<br />

CNR-SPIN and Department of Chemistry, University of Genoa, Via Dodecaneso 31,<br />

16 146, Genoa, Italy, Italy<br />

3<br />

Institute of Experimental Physics, Slovak Academy of Science, Wats<strong>on</strong>ova 47, 040<br />

01, Kosice, Slovakia, Slovak<br />

Yb compounds are very attractive for research because of their low temperature<br />

anomalous behaviour. Recently, emphasis was given to the investigati<strong>on</strong> of the solid<br />

soluti<strong>on</strong> YbCu 5-xM x (M = Ag, Au, In) crystallizing in the cubic AuBe 5-type structure.<br />

The substituti<strong>on</strong> of Cu by M offers the possibility of studying the different evoluti<strong>on</strong>s<br />

of the ground state depending <strong>on</strong> the M element (e.g. a valence transiti<strong>on</strong> in M = In,<br />

K<strong>on</strong>do-lattice behavior in M = Ag, magnetic ordering in M = Au) [1,2,3]. Here we<br />

present the measurements of heat capacity and resistivity in the temperature scale 0.4<br />

-300 K for different applied magnetic fields 0 - 9 T of the YbCu 5-xAu x (x = 0.5, 0.6, 0.7)<br />

system. The polycrystalline samples were prepared by inducti<strong>on</strong>-melting method, heattreated<br />

and then quenched in cold water. Phase purity was checked by electr<strong>on</strong> probe<br />

microanalysis (EPMA) and X-ray diffracti<strong>on</strong> (XRD)<br />

[1] K. Yoshimura et al., J. Alloys Comp 262-263 (1997) 118 [2] M. Galli, E.Bauer, St. Berger, Ch.<br />

Dusek et al. Physica B 312-313 (2002) 489 [3] J. He, N. Tsujii et al., J. Phys. Soc. Jpn 66 (1997)<br />

2481<br />

Magetic properties of heavy-fermi<strong>on</strong> compounds Ce 1-xLu xRu 2Si 2<br />

Toru Sekiguchi 1 , Yusuke Amakai 1 , Shigeyuki Murayama 1 *, Hideaki Takano 1 , Naoki<br />

Mom<strong>on</strong>o 1 , Kazuyuki Matsubayashi 2 and Yoshiya Uwatoko 2<br />

1 Graduate School of Engineering, Muroran Institute of Technology, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

Typical heavy-fermi<strong>on</strong> compound CeRu 2Si 2 with a tetrag<strong>on</strong>al structure shows an<br />

antiferromagnetic transiti<strong>on</strong> by the substituti<strong>on</strong> of La at the Ce site due to the negative<br />

chemical pressure by the larger La i<strong>on</strong>(1). The substituti<strong>on</strong> of Y introduces a decrease<br />

of the specific heat coefficient γ and an increase of the K<strong>on</strong>do temperature TK due to<br />

the positive chemical pressure by the smaller Y i<strong>on</strong>(2). In order to study substituti<strong>on</strong><br />

effect of Lu with the closed f-electr<strong>on</strong> shell and the i<strong>on</strong> smaller than Y, we have<br />

measured the susceptibility χ and resistivity ρ <strong>on</strong> single-crystalline Ce 1-xLu xRu 2Si 2 for<br />

0≤x≤0.2 perpendicular (∠) and parallel (//) to the c-axis.The χ// shows a maximum<br />

and the Tmax increases with x. Since the Tmax is supposed to be the heavy-fermi<strong>on</strong><br />

formati<strong>on</strong> temperature proporti<strong>on</strong>al to 1/γ, the effective mass meff is c<strong>on</strong>sidered<br />

to increase with x. The resistivity ρ shows a shoulder by the K<strong>on</strong>do effect and the<br />

Tshoulder increases with x. This indicates an increase of TK due to the positive<br />

chemical pressure by Lu. The low temperature resistivity follows the T 2 law and the<br />

coefficient A decreases with x. Since A is proporti<strong>on</strong>al to γ 2 , meff is again c<strong>on</strong>sidered to<br />

increase with x.<br />

(1) S. Quezel et. al., J. Magn. & Magn. Mater., 76 & 77, 403 (1988). (2) M.J. Besnus et. al., J. Magn.<br />

& Magn. Mater., 63 & 64, 323 (1987).<br />

Moment-bearing Tb substituti<strong>on</strong> in CePt 2Si 2<br />

Moise Bertin Tchoula Tchok<strong>on</strong>te 1 *, Zwelithini Melford Mahlubi 1 , Paul De Villiers Du<br />

Plessis 2 , Andre Michael Strydom 2 and Dariuzs Kaczorowski 3<br />

1 Physics, University of the Western Cape, South Africa<br />

2 Physics, University of Johannesburg, South Africa<br />

3 Physics, Institute of Low Temperature and Structure Research, Polish Academy of<br />

Sciences., Poland<br />

The effects of substituting moment-bearing Tb in CePt 2Si 2 are reported through X-ray<br />

diffracti<strong>on</strong> (XRD), electrical resistivity (ρ(T)), magnetic susceptibility (χ(T)) and<br />

magnetizati<strong>on</strong> (σ(μ0H)) measurements. XRD results for all compositi<strong>on</strong>s of the (Ce 1xTb<br />

x)Pt 2Si 2 system indicate a tetrag<strong>on</strong>al CaBe 2Ge 2-type structure with space group P4/<br />

nmm. ρ(T) results indicate the evoluti<strong>on</strong> from a coherent K<strong>on</strong>do lattice to incoherent<br />

single-i<strong>on</strong> K<strong>on</strong>do behavior up to 90% Ce substituti<strong>on</strong>. χ(T) data at higher temperatures<br />

follow the Curie-Weiss relati<strong>on</strong> for all alloy compositi<strong>on</strong>s and given effective moment<br />

values μeff which increase gradually from the expected value of 2.54 μB for the Ce 3+<br />

-i<strong>on</strong> to the expected value of 9.72 μB for the Tb 3+ -i<strong>on</strong>. At low temperature χ(T) data<br />

exhibit antiferromagnetism in the c<strong>on</strong>centrati<strong>on</strong> range 0.7≤ x ≤ 1. No evidence of<br />

metamagnetic behavior was observed from σ(μ0H) data for all compositi<strong>on</strong>s.<br />

July 8 - 13, 2012 Busan, Korea 151<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RD24<br />

Heavy Fermi<strong>on</strong> Behavior of Yb 2Ni 12P 7 Studied by 31P NMR<br />

Takehide Koyama 1 , Kyohei Sugiura 1 , Koichi Ueda 1 , Takeshi Mito 1 , Takao Kohara 1 ,<br />

Tomohito Nakano 2 , Ryohei Satoh 3 , Katsuhiko Tsuchiya 3 and Naoya Takeda 2<br />

1 Graduate School of Material Science, University of Hyogo, Japan<br />

2 Faculty of Engineering, Niigata University, Japan<br />

3 Graduate School of Science and Technology, Niigata University, Japan<br />

We present results of the nuclear magnetic res<strong>on</strong>ance measurement (NMR) of Ybbased<br />

intermetallic compound Yb 2Ni 12P 7, which crystallizes in the hexag<strong>on</strong>al Zr 2Fe 12P 7type<br />

structure [1]. Yb 2Ni 12P 7 does not order magnetically down to 50 mK and forms the<br />

heavy fermi<strong>on</strong> state. The electr<strong>on</strong>ic specific heat of Yb 2Ni 12P 7 is markedly enhanced at<br />

low temperatures (200 mJ/K2 mol-Yb). The magnetic susceptibility shows the Curie-<br />

Weiss like behavior at high temperatures and has a noticeable hump at around 50 K.<br />

We have performed NMR measurement to investigate the electr<strong>on</strong>ic properties of<br />

Yb 2Ni 12P 7. The observed NMR line shows a complicated shape, reflecting the presence<br />

of three n<strong>on</strong>-equivalent P sites and local symmetries around them. The nuclear-spin<br />

lattice relaxati<strong>on</strong> rate (1/T1) shows nearly T1T=c<strong>on</strong>st. behavior, which is c<strong>on</strong>sistent<br />

with the delocalizati<strong>on</strong> of the 4f electr<strong>on</strong>s.<br />

K. Zeppenfeld and W. Jeitschko, J. Phys. Chem. Solids, 54 (1993) 1527.<br />

RD25<br />

Electr<strong>on</strong>ic structure of RCu2Si2 (R=Yb, Y) studied by soft x-ray angleresolved<br />

photoemissi<strong>on</strong> spectroscopy<br />

Akira Yasui 1 , Shin-ichi Fujimori 1 , Ikuto Kawasaki 2 , Tetsuo Okane 1 , Yukiharu<br />

Takeda 1 , Yuji Saitoh 1 , Hiroshi Yamagami 3 , Akira Sekiyama 4 , Rikio Settai 5 , Tatsuma D<br />

Matsuda 6 , Yoshinori Haga 6 and Yoshichika Onuki 5<br />

1<br />

C<strong>on</strong>densed Matter Science Divisi<strong>on</strong>, Japan Atomic Energy Agency, Japan<br />

2<br />

Advanced Mes<strong>on</strong> Science Laboratory, RIKEN Nishina Center for Accelerator-Based Science, Japan<br />

3<br />

Department of Physics, Kyoto Sangyo University, Japan<br />

4<br />

Divisi<strong>on</strong> of Materials Physics, Osaka University, Japan<br />

5<br />

Department of Physics, Osaka University, Japan<br />

6<br />

Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

In recent years, electr<strong>on</strong>ic structure of YbCu 2Si 2, which is a classical example of Yb-based valence fluctuati<strong>on</strong><br />

compounds, has been studied by various experimental methods such as a quantum oscillati<strong>on</strong> measurement<br />

[1] and an angle-integrated photoemissi<strong>on</strong> spectroscopy (AIPES) [2]. However, these results are inc<strong>on</strong>sistent<br />

each other. In fact, the band structure calculati<strong>on</strong> which well describes the results of the quantum oscillati<strong>on</strong><br />

measurement [1] cannot explain the AIPES spectrum. In the present study, we have performed the soft x-ray<br />

angle-resolved photoemissi<strong>on</strong> spectroscopy (SX-ARPES) for YbCu 2Si 2 to understand the valence band<br />

structure and the Fermi surface (FS) in a unified way. The SX-ARPES measurements were recorded in<br />

BL23SU of SPring-8. We have observed that hybridized bands of Yb 4f electr<strong>on</strong>s and c<strong>on</strong>ducti<strong>on</strong> states cross<br />

the Fermi level at 20 K, which is well below the K<strong>on</strong>do temperature of TK = 50 K, in line with the valencefluctuating<br />

state of YbCu 2Si 2. We will discuss effects of Yb 4f electr<strong>on</strong>s <strong>on</strong> its band structure by comparing<br />

the ARPES spectra with those of a n<strong>on</strong>-4f reference compound YCu 2Si 2.<br />

[1] N. D. Dung et al., J. Phys. Soc. Jpn. 78, 084711 (2009). [2] M. Matsunami et al., Phys. Rev. B 78, 195118 (2008).<br />

RD26<br />

Anomalous increase of TC in UGa 2 under pressure<br />

Ladislav Havela 1 , A. Kolomiets 2 , J. Prchal 1 and A. V. Andreev 3<br />

1 Department of C<strong>on</strong>densed Matter Physics, Charles University, Czech Republic<br />

2 Department of Physics, Lviv Polytechnic Nati<strong>on</strong>al University, Ukraine<br />

3 Institute of Physics, Academy of Sciences of the Czech Pepublic, Czech Republic<br />

UGa 2 bel<strong>on</strong>gs to compounds quite thoroughly studied, although there is still no<br />

c<strong>on</strong>sensus about the character of the 5f states. In particular, 5f 2 or 5f 3 localized and<br />

band-like 5f states were c<strong>on</strong>sidered, n<strong>on</strong>e of those being able to explain all its features<br />

[1]. Resp<strong>on</strong>se of magnetic properties to external pressure is an important indicator of<br />

the situati<strong>on</strong> of the 5f states. While band systems tend to a suppressi<strong>on</strong> of magnetic<br />

moments and their ordering, magnetism based <strong>on</strong> localized states has insensitive size<br />

of moments and their ordering temperatures can weakly increase. Previous experiments<br />

[2] indicated a quite rapid increase (approx. 3 K/GPa) of the Curie temperature from<br />

TC = 126 K up to p = 0.8 GPa. New resistivity experiments <strong>on</strong> UGa 2 single crystal,<br />

extending the pressure range up to 8 GPa, reveal a c<strong>on</strong>tinuous linear increase, reaching<br />

160 K without any sign of saturati<strong>on</strong>. Such anomalously large increase can be <strong>on</strong>ly<br />

understood in the framework of a two-band model, in which the compressi<strong>on</strong> leads to a<br />

str<strong>on</strong>ger hybridizati<strong>on</strong> of the 5f and other c<strong>on</strong>ducti<strong>on</strong>-electr<strong>on</strong> states.<br />

[1] T. H<strong>on</strong>ma et al., J. Phys. Soc. Japan 69 (2000) 2647. [2] A.V. Kolomiets et al., Physica B 259-<br />

261 (1999) 238.<br />

152 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RE01<br />

Engineered p-d exchange interacti<strong>on</strong> of coupled double diluted<br />

magnetic quantum dots<br />

Eun-young Kim<br />

Seoul Nati<strong>on</strong>al University, Korea<br />

This paper presents the effects of inserting a thick InGaN layer which was grown<br />

between n-GaN and active layer by MOCVD. By adding the thick InGaN layer, we<br />

expected the compensati<strong>on</strong> of lattice mismatch between n-GaN and active layer. From<br />

AFM results, QDs (Quantum Dots) were formed at around 200 A InGaN thickness<br />

by TD (Threading Dislocati<strong>on</strong>) terminati<strong>on</strong> effect. According to the result of TD<br />

terminati<strong>on</strong>, the electrical and optical properties were improved due to the decrease<br />

of n<strong>on</strong>-radiative recombinati<strong>on</strong> area in active layer. The result of PL data shows PL<br />

intensity increased by inserting the thick InGaN layer.<br />

RE02<br />

Quasi-particle localizati<strong>on</strong> by disorder in an incompressible fracti<strong>on</strong>al<br />

quantum Hall state<br />

Partha Goswami*<br />

Physics department, D.B.College(University of Delhi),New Delhi, India, India<br />

The str<strong>on</strong>gly correlated electr<strong>on</strong>s, together with disorder, organize themselves in a n<strong>on</strong>trivial<br />

way to form incompressible collective states for the filling fracti<strong>on</strong> ν = 5/2 in<br />

a dirty bi-layer semi-c<strong>on</strong>ductor quantum well system. The theoretical analysis of the<br />

quantum phase transiti<strong>on</strong>(QPT) exhibited by this system has been carried out including<br />

the single-particle quantum lifetime sensitive to the l<strong>on</strong>g range scattering and the usual<br />

zero field short-range Drude scattering (transport lifetime). Since the tunneling terms<br />

can be c<strong>on</strong>trolled by changing gate voltages, we find that, in principle, a completely<br />

reversible sequence of events, viz. a crossover from the bi-layer fracti<strong>on</strong>al quantum<br />

Hall state to the single-layer <strong>on</strong>e followed by an entry to quantum critical state (and<br />

the QPT to the bi-layer state bey<strong>on</strong>d) and eventually a crossover to the single-layer<br />

state, could be realized with the increase in inter-layer tunneling. The sequence, which<br />

is manifestati<strong>on</strong> of quasi-particle localizati<strong>on</strong> by disorder, could prove to be useful in<br />

performing memory functi<strong>on</strong> and gating operati<strong>on</strong>.<br />

RE03<br />

NpCoGe, near quantum criticality?<br />

Eric Colineau*, Rachel Eloirdi, Jean-christophe Griveau, Piotr Gaczynski and<br />

Alexander Shick<br />

European Commissi<strong>on</strong>, Joint Research Centre, Institute for Transuranium Elements,<br />

Germany<br />

The orthorhombic isostructural series AnTGe (An = actinide ; T = transiti<strong>on</strong> metal)<br />

offers a unique opportunity to study the properties and trends of a system where<br />

ferromagnetism and superc<strong>on</strong>ductivity coexist at ambient pressure in URhGe (TC =<br />

9.5K, TSC = 0.26K) [1] and UCoGe (TC = 3K, TSC = 0.7K) [2]. However, due to<br />

the difficulty to handle them, transuranium systems are much less documented. In an<br />

effort to bridge this gap, we have undertaken the study of the neptunium analogues<br />

and have previously reported that NpRhGe exhibits an antiferromagnetic ground<br />

state (TN = 21K, μNp = 1.14μB) [3]. In the present work, we have investigated<br />

NpCoGe by dc magnetizati<strong>on</strong>, ac susceptibility, specific heat, electrical resistivity,<br />

237Np Mossbauer spectroscopy and LSDA calculati<strong>on</strong>s. We find that NpCoGe orders<br />

antiferromagnetically at TN=13K with an average ordered moment = 0.8 μB.<br />

The weak antiferromagnetic interacti<strong>on</strong>s (θp = -5.5K) are overcome by the applicati<strong>on</strong><br />

of a moderate magnetic field (B ~ 3T) that induces a metamagnetic phase. NpCoGe<br />

appears as a more delocalized antiferromagnet than NpRhGe, which is c<strong>on</strong>sistent<br />

with the trend observed in UTGe analogues. The proximity of NpCoGe to a quantum<br />

critical point and its implicati<strong>on</strong>s will be discussed.


RE04<br />

Pressure and magnetic-field induced n<strong>on</strong>-Fermi-liquid behavior in<br />

YbCo 2Zn 20<br />

Kazuyuki Matsubayashi 1 *, Rina Yamanaka 1 , Yuta Saiga 2 , Tatsuya Kawae 3 and<br />

Yoshiya Uwatoko 1<br />

1 Institute for Solid State Physics, The University of Tokyo, Japan<br />

2 Institute for Advanced Materials Research, Hiroshima University, Japan<br />

3 Department of Applied Quantum Physics, Faculty of Engineering, Kyushu<br />

University, Japan<br />

In heavy fermi<strong>on</strong> systems, applying pressure and magnetic field c<strong>on</strong>trols the electr<strong>on</strong>ic<br />

c<strong>on</strong>figurati<strong>on</strong>, and thus anomalous behaviors appear at around magnetic quantum critical point<br />

(QCP), such as an unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity and N<strong>on</strong>-Fermi-liquid behavior. Recently,<br />

YbCo 2Zn 20 have attracted much attenti<strong>on</strong> because of their heavy fermi<strong>on</strong> state and proximity to<br />

the pressure-induced QCP [1]. It is worth noting that the critical pressure of YbCo 2Zn 20 is lower<br />

than that of other Yb based compounds. Therefore YbCo 2Zn 20 has an advantage of investigating<br />

the behavior of Yb- based compounds near QCP. More interestingly, it is reported that a<br />

metamagnetic crossover appears at H ~ 0.6 T [2], however, the origin of this metamagnetic<br />

behavior remains unclear. In order to shed light <strong>on</strong> the nature of the pressure- and field-induced<br />

quantum critical behavior, we have measured the specific heat of YbCo 2Zn 20 under pressure<br />

and magnetic field. We found that the low temperature specific heat in the vicinity of the critical<br />

regi<strong>on</strong> exhibits the power-law divergence. The temperature-pressure-magnetic field phase<br />

diagram will be presented to sum up the physical properties.<br />

[1] Y. Saiga et al., J. Phys. Soc. Jpn 77 (2008) 053710 [2] M. Ohya et al., J. Phys. Soc. Jpn 79 (2010) 083601<br />

RE05<br />

Relati<strong>on</strong>ship between single-particle excitati<strong>on</strong> and spin excitati<strong>on</strong> at<br />

the Mott transiti<strong>on</strong><br />

Masanori Kohno*<br />

WPI Center for Materials Nanoarchitect<strong>on</strong>ics, Nati<strong>on</strong>al Institute for Materials<br />

Science, Japan<br />

The Mott transiti<strong>on</strong> in the <strong>on</strong>e- and two-dimensi<strong>on</strong>al Hubbard models is investigated<br />

using the Bethe ansatz, dynamical density-matrix renormalizati<strong>on</strong> group method,<br />

cluster perturbati<strong>on</strong> theory, and random-phase approximati<strong>on</strong>. I will show that the<br />

dispersi<strong>on</strong> relati<strong>on</strong> of single-particle excitati<strong>on</strong> in a metallic phase leads c<strong>on</strong>tinuously<br />

to that of spin excitati<strong>on</strong> of the Mott insulator.<br />

RE06<br />

Quantum criticality in K<strong>on</strong>do quantum dot coupled to 2D topological<br />

insulator<br />

Chung-hou Chung* and Salman Silotri<br />

Electrophysics Dept.,, Nati<strong>on</strong>al Chiao-Tung University, HsinChu, Taiwan, R.O.C.,<br />

Taiwan<br />

We investigate theoretically the quantum phase transiti<strong>on</strong> between the <strong>on</strong>e-channel<br />

K<strong>on</strong>do (1CK) and two-channel K<strong>on</strong>do (2CK) fixed points in a quantum dot coupled<br />

to edge states of interacting 2D topological insulators (2DTI) with Luttinger parameter<br />

0


Poster Thursday<br />

RE10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic phase diagram of UCoAl<br />

Tatsuma D. Matsuda 1 , Dai Aoki 2 , Naoyuki Tateiwa 1 , Etsuji Yamamoto 1 , Yoshinori<br />

Haga 1 , Yoshichika Onuki 3 , Jacques Flouquet 2 and Zachary Fisk 4<br />

1<br />

ASRC, JAEA, Japan<br />

2<br />

INAC/SPSMS, CEA-Grenoble, France<br />

3<br />

Graduate School of Science, Osaka University, Japan<br />

4<br />

University of California, USA<br />

Heavy fermi<strong>on</strong> UCoAl is known to be a unique system with metamagnetic transiti<strong>on</strong><br />

from paramagnetic to ferromagnetic ground states in uranium-based compounds. This<br />

kind of metamagnetism and quantum criticality in str<strong>on</strong>gly correlated electr<strong>on</strong> systems<br />

have attracted much attenti<strong>on</strong> because of expectati<strong>on</strong> of new quantum phases. Recently,<br />

we succeeded to grow a high quality single crystal of UCoAl by the Czochralski<br />

pulling method and performed the magnetic measurements. In this presentati<strong>on</strong>, we<br />

will show the magnetic phase diagram of UCoAl in detail.<br />

RE11<br />

Renormalizati<strong>on</strong>-group exp<strong>on</strong>ents for competiti<strong>on</strong>s between interelectr<strong>on</strong>ic<br />

and ph<strong>on</strong><strong>on</strong>-mediated interacti<strong>on</strong>s in ladder systems<br />

Wen-min Huang 1 *, Yiwei Cai 2 and Hsiu-hau Lin 2<br />

1 Physics Divisi<strong>on</strong>, Nati<strong>on</strong>al Center for Theoretical Sciences, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al Tsing Hua University, Taiwan<br />

After developing a scaling ansatz for electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong>s under<br />

renormalizati<strong>on</strong> group transformati<strong>on</strong>[1], we show that, with the inclusi<strong>on</strong> of ph<strong>on</strong><strong>on</strong>mediated<br />

interacti<strong>on</strong>s the ansatz, characterized by the divergent logarithmic length and<br />

a set of renormalizati<strong>on</strong>-group exp<strong>on</strong>ents, also works rather well. The superc<strong>on</strong>ducting<br />

phases in a doped two-leg ladder are studied and classified by these renormalizati<strong>on</strong>group<br />

exp<strong>on</strong>ents as dem<strong>on</strong>strati<strong>on</strong>. Finally, n<strong>on</strong>trivial c<strong>on</strong>straints am<strong>on</strong>g the exp<strong>on</strong>ents<br />

are derived and explained.<br />

[1] H.-Y. Shih, W.-M. Huang, S.-B. Hsu and H.-H. Lin, Phys. Rev. B 81, 121107(R) (2010).<br />

RE12<br />

Crystal Growth and Magnetic Order of Ni-doped CePdAl<br />

Ver<strong>on</strong>ika Fritsch 1 *, Sarah Woitschach 2 , Oliver Stockert 2 , Michael M. Koza 3 , Silvia<br />

Capelli 3 and Hilbert V. Loehneysen 4<br />

1<br />

Physikalisches Institut, Karlsruher Institut fuer Technologie, 76131 Karlsruhe,<br />

Germany<br />

2<br />

Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden, Germany<br />

3<br />

Institut Laue-Langevin, 38042 Grenoble, France<br />

4<br />

Physikalisches Institut and Institut fuer Festkoerperphysik, Karlsruher Institut fuer<br />

Technologie, 76131 Karlsruhe, Germany<br />

CePdAl is a stoichiometric, antiferromagnetic compound (Neel temperature = 2.7 K) which<br />

can be tuned to a quantum critical point (QCP) by hydrostatic [T. Goto et al., J. Phys. Chem. of<br />

Solids 63, 1159 (2002)] or chemical pressure [Y. Isikawa et al., J. Phys. Soc. Jpn. 65, 117 (1996)].<br />

The latter can be achieved by substituting Ni for Pd. Neutr<strong>on</strong>-scattering experiments [A. Doenni<br />

et al., J. Phys.: C<strong>on</strong>dens. Matter 8, 11213 (1996)] pointed towards a partial frustrati<strong>on</strong> of the Ce<br />

moments in CePdAl, making this system a promising candidate for investigating the influence<br />

of frustrati<strong>on</strong> <strong>on</strong> quantum criticality. We have grown large single crystals of Ni-doped CePdAl<br />

by the Czochralski method. The samples were characterized by x-ray powder diffracti<strong>on</strong>, atomic<br />

absorpti<strong>on</strong> spectroscopy and x-ray Laue diffracti<strong>on</strong>. Specific heat and inelastic neutr<strong>on</strong> scattering<br />

data of CePdAl yield a K<strong>on</strong>do temperature of approximately 5 K. Magnetizati<strong>on</strong> measurements<br />

display a str<strong>on</strong>g magnetic anisotropy which is preserved in the Ni-doped compounds, where<br />

the magnetic order is suppressed. Neutr<strong>on</strong>-diffracti<strong>on</strong> experiments indicate that short-range<br />

correlati<strong>on</strong>s are present well above the Neel temperature. Below the Neel temperature, <strong>on</strong>e third<br />

of the Ce moments display short-range order <strong>on</strong>ly, c<strong>on</strong>firming the frustrati<strong>on</strong> in this system.<br />

154 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RE13<br />

Transport properties of Ho 1-XLu XB 12 solid soluti<strong>on</strong>s<br />

Slavomir Gabani1*, Ivan Batko1, Marianna Batkova1, Karol Flachbart1, Emil Gazo1,<br />

Gabriel Pristas1, Iveta Takacova1, Alexey Bogach2, Nickolay Sluchanko2 and<br />

Natalya Shitsevalova 3<br />

1 Centre of Low Temperature Physics, Institute of Experimental Physics SAS, Slovak<br />

2 General Physics Institute RAS, Russia<br />

3 Institute for Problems of Materials Science NASU, Ukraine<br />

Recent studies of Ho 1-xLu xB 12 solid soluti<strong>on</strong>s have shown [1] that the antiferromagnetic<br />

(AF) order in geometrically frustrated system of HoB 12 (x = 0, TN = 7.4 K) is linearly<br />

suppressed to zero temperature, i.e. TN → 0, as lutetium c<strong>on</strong>centrati<strong>on</strong> increases to<br />

x → xC 0.9. In this c<strong>on</strong>tributi<strong>on</strong>, we present original results of electrical resistivity<br />

measurements <strong>on</strong> Ho 1-xLu xB 12 single crystalline samples with x = 0, 0.2, 0.5, 0.7, 0.9, 1<br />

in the temperature range 0.05 - 300 K and in magnetic fields (B) up to 8 T. Complex B<br />

vs TN phase diagrams were received from precise temperature and field dependences<br />

of resistivity with more AF phases for x ≥ 0.5 pointing to a possible quantum critical<br />

point at xC 0.9. The scattering of c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s in the AF phase and in the<br />

paramagnetic phase as well as Hall effect results are analyzed and discussed for various<br />

c<strong>on</strong>centrati<strong>on</strong>s x, when magnetic diluti<strong>on</strong> increases with the increasing c<strong>on</strong>tent of<br />

n<strong>on</strong>magnetic Lu i<strong>on</strong>s in the Ho 1-xLu xB 12 system.<br />

[1] S. Gabani, I. Batko, M. Batkova, K. Flachbart, E. Gazo, M. Reiffers, N. Shitsevalova, K.<br />

Siemensmeyer and N. Sluchanko, 17th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> symposium <strong>on</strong> bor<strong>on</strong>, borides and related<br />

materials, Sept 11-17, 2011, Istanbul, Turkey.<br />

RE14<br />

Low temperature thermal and electrical transport properties of ZrZn 2<br />

in high magnetic field<br />

Yang Zou 1 *, Michael Sutherland 1 , Stephen Hayden 2 and F. Malte Grosche 1<br />

1 Department of Physics, University of Cambridge, United Kingdom<br />

2 Department of Physics, University of Bristol, United Kingdom<br />

RE15<br />

WITHDRAWN<br />

N<strong>on</strong> fermi liquid behaviour in YFe 2Ge 2<br />

Yang Zou*, Zhuo Feng, Sven Friedemann and F. Malte Grosche<br />

Department of Physics, University of Cambridge, United Kingdom<br />

WITHDRAWN


RF01<br />

Magnetic orderings at the interface between Mott insulator and band<br />

insulator<br />

Suguru Ueda 1 *, Norio Kawakami 1 and Manfred Sigrist 2<br />

1 Department of Physics, Kyoto University, Japan<br />

2 Theoretische Physik, ETH Zurich, Switzerland<br />

Recent experimental progress in crystal growth techniques enables us to investigate the complex oxide<br />

hetrostructures as a new fr<strong>on</strong>tier for studies of str<strong>on</strong>gly correlated electr<strong>on</strong> systems. In such systems,<br />

the main interest is put toward the metallic state around the interface, which is realized between<br />

two different insulating compounds, such as SrTiO 3/LaTiO 3 and SrTiO 3/LaAlO 3 [1]. Intriguingly,<br />

magnetism and superc<strong>on</strong>ductivity are also reported in such metallic interfaces [2]. Stimulated by these<br />

findings, we theoretically study the magnetic properties of the str<strong>on</strong>gly correlated heterostructure<br />

composed a Mott insulator and band insulators. For this purpose, the single-band Hubbard model<br />

with l<strong>on</strong>g-range Coulomb interacti<strong>on</strong> is investigated using the Hartree-Fock approximati<strong>on</strong> [3]. We<br />

find the electr<strong>on</strong>ic and magnetic phases specific to the interface, including a canted anttiferromagnetic<br />

state and a charge-ordered state with checkerboard charge distributi<strong>on</strong>. We elucidate the origin of<br />

these phases is closely related to the spatial inhomogeneity which induces unc<strong>on</strong>venti<strong>on</strong>al couplings<br />

between spin and charge degrees of freedom. Additi<strong>on</strong>ally, the applied magnetic fields also reveal<br />

other aspects of correlated heterostructures; a first order metamagnetic transiti<strong>on</strong> and field-induced<br />

checkerboard charge-ordered state, which are also driven by the n<strong>on</strong>-uniform charge distributi<strong>on</strong>.<br />

[1] A. Ohtomo, et al., Nature 419, 378 (2002), A. Ohtomo, and H. Y. Hwang, Nature 427, 423 (2004).<br />

[2] A. Brinkman, et al., Nat. Mater. 6, 493 (2006), J. Biscaras, et al., Nat. Commun. 1, 89 (2010). [3]<br />

Okamoto, and Millis, Phys. Rev. B 70, 075101 (2004).<br />

RF02<br />

Str<strong>on</strong>g Electr<strong>on</strong> Correlati<strong>on</strong> in Cu-doped CaO Nanocolloid<br />

Nguyen Thuy Trang 1 , Pham Thanh C<strong>on</strong>g 2 , Hoang Nam Nhat 3 *<br />

1<br />

Faculty of Physics, Vietnam Nati<strong>on</strong>al University, University of Natural Sciences, Viet<br />

Nam<br />

2<br />

Physikalisches Institut, Goethe-Universitat Frankfurt, Germany<br />

3<br />

Faculty of Technical Physics and Nanotechnology, Vietnam Nati<strong>on</strong>al University,<br />

University of Engineering and Technology, Viet Nam<br />

Theoretical predicti<strong>on</strong> of magnetism induced by defects or doping in n<strong>on</strong>-metallic<br />

colloids has gained a renewed interests recently. In this work, we investigated the<br />

possible appearance of magnetism in Cu doped CaO nanocolloids activated by<br />

SPAN-80 in the framework of density functi<strong>on</strong>al theory (DFT). Despite of str<strong>on</strong>g<br />

antiferromagnetic super-exchange interacti<strong>on</strong> between Cu2+ i<strong>on</strong>s, the local magnetic<br />

moment of Cu may appear due to colloidal agent attachment <strong>on</strong>to the surface of CaO<br />

nanocluster (surface modificati<strong>on</strong>). The ferromagnetism attributes to the degenerati<strong>on</strong><br />

of Cu 3d orbitals in CaO crystal fields, the aspects of electr<strong>on</strong> correlati<strong>on</strong> and quantum<br />

spin fluctuati<strong>on</strong>.<br />

PACS number: 42.30.R, 42.40.Ht, 42.30.Kq<br />

Keywords: DFT, band-gap, CaO, calcium-oxide, mBJ, PBE, functi<strong>on</strong>al<br />

RF03<br />

The book-keeping fermi<strong>on</strong> analysis of the double exchange model with<br />

antiferromagnetic background<br />

Kyohei Nakano 1 *, Robert Eder 2 , Yukinori Ohta 1 and Piotr Wrobel 3<br />

1 Department of Physics, Chiba university, Japan<br />

2 Institute for Solid State Physics, Karlsruhe Institute of Technology, Germany<br />

3 Institute for Low Temperature and Structure Research, Poland<br />

We analyse the double exchange model with antiferromagnetic background by the<br />

book-keeping fermi<strong>on</strong> method. First, we c<strong>on</strong>sider the moti<strong>on</strong> of a single c<strong>on</strong>ducti<strong>on</strong><br />

electr<strong>on</strong>. We assume that the localized spins form the Neel state and the added<br />

c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong> forms <strong>on</strong>ly three types of states under the str<strong>on</strong>g Hund-coupling<br />

assumpti<strong>on</strong> and we regard these states as the book-keeping fermi<strong>on</strong>. Under these<br />

assumpti<strong>on</strong>s, we calculate the spectral functi<strong>on</strong>s which show good agreement with the<br />

results given by the exact diag<strong>on</strong>alizati<strong>on</strong>s for finite size clusters. We also study the<br />

relati<strong>on</strong> between the strength of the Hund coupling and the bandwidth in the lowerenergy<br />

regi<strong>on</strong>. The results show that the bandwidth approaches a finite value as the<br />

Hund-coupling c<strong>on</strong>stant becomes close to infinity. The bandwidth even increases with<br />

increasing the Hund coupling, which is in str<strong>on</strong>g c<strong>on</strong>trast to the expectati<strong>on</strong> from the<br />

semi-classical theory. Next, we c<strong>on</strong>sider the situati<strong>on</strong> where there are finite numbers of<br />

spin flips occurring in the down-spin sublattice in the Neel ordered state. C<strong>on</strong>sidering<br />

the effects of the spin defects, we add a new book-keeping fermi<strong>on</strong> and estimate the<br />

energy of the spin defects by a perturbati<strong>on</strong> theory. This theory gives the phase diagram<br />

comparable with the numerical results.<br />

RF04<br />

RF05<br />

RF06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ph<strong>on</strong><strong>on</strong> Induced Thermodynamic Properties of La 1-xCa xCoO 3<br />

Rasna Thakur*, Rajesh K. Thakur and N.k. Gaur<br />

Department of Physics, Barkatullah University, Bhopal, India<br />

Perovskite type cobaltate, La 1-xCaxCoO 3 (0 ≤ x ≤ 0.3) have been studied intensively<br />

because of their wide range of unique physical properties. The fact that rare-earth<br />

perovskite-type cobaltate are most suitable as a cathode material in solid oxide fuel<br />

cells (SOFC), makes the thermal behavior of these compounds highly important. As<br />

these compounds are predominantly i<strong>on</strong>ic in nature hence the lattice c<strong>on</strong>tributi<strong>on</strong>s to<br />

the specific heat at c<strong>on</strong>stant volume (C v(lattice)) of pure and Ca doped LaCoO 3 has been<br />

studied and thereby thermal expansi<strong>on</strong> is computed as functi<strong>on</strong> of temperature by<br />

means of Rigid I<strong>on</strong> Model (RIM). We have systematically investigated the effect of<br />

ph<strong>on</strong><strong>on</strong>s <strong>on</strong> thermal properties, Debye temperature (θ D), molecular force c<strong>on</strong>stant (f),<br />

Reststrahlen frequency (υ), cohesive energy (φ), and gruneisen parameter (γ) for La 1xCaxCoO<br />

3 (0 ≤ x ≤ 0.3). Also the effect of ph<strong>on</strong><strong>on</strong>s <strong>on</strong> the bulk modulus is studied<br />

using the atoms in molecules (AIM) theory for pure and ca doped LaCoO 3. We have<br />

found that the computed properties reproduce well with the available experimental<br />

data, implying that RIM represents properly the perovskite cobaltate La 1-xCa xCoO 3 (0<br />

≤ x ≤ 0.3). To our knowledge some of the properties for these complicated compounds<br />

are reported for the first time.<br />

Dynamical antiferromagnetic phase transiti<strong>on</strong> after the quantum<br />

quench in the fermi<strong>on</strong>ic Hubbard model<br />

Naoto Tsuji* and Philipp Werner<br />

Institute for Theoretical Physics, ETH Zurich, Switzerland<br />

Sp<strong>on</strong>taneous symmetry breaking is a universal c<strong>on</strong>cept in physics that stretches widely<br />

from c<strong>on</strong>densed matter to cosmology. Recently it is getting feasible to study in detail<br />

how symmetry is dynamically broken in correlated electr<strong>on</strong> systems using an ultrafast<br />

optical spectroscopy technique [1], which works as a key probe for electr<strong>on</strong> correlati<strong>on</strong><br />

and fluctuati<strong>on</strong>s. Theoretically the phenomen<strong>on</strong> has been discussed with the Ginzburg-<br />

Landau (GL) theory, a macroscopic phenomenology. To capture the evoluti<strong>on</strong> of<br />

the electr<strong>on</strong>ic structure, however, <strong>on</strong>e needs a microscopic descripti<strong>on</strong>, which is not<br />

well understood. Here we take the fermi<strong>on</strong>ic Hubbard model, a typical microscopic<br />

model for correlated electr<strong>on</strong>s, and study how the antiferromagnetic order develops<br />

from a paramagnetic initial state after the quantum quench using the n<strong>on</strong>equilibrium<br />

dynamical mean-field theory. The system shows a multistep time evoluti<strong>on</strong>: (i) a fast<br />

thermalizati<strong>on</strong> within the paramagnetic phase, (ii) an exp<strong>on</strong>ential growth of the order<br />

parameter, and (iii) decay of collective excitati<strong>on</strong>s. We show how these features are<br />

reflected in the single-particle and optical-c<strong>on</strong>ductivity spectrum, and discuss the<br />

nature of antiferromagnetic fluctuati<strong>on</strong>s.<br />

[1] R. Yusupov et al., Nat. Phys. 6, 681 (2010).<br />

Itinerant magnetism in the hubbard model within the dynamical<br />

cluster approximati<strong>on</strong><br />

Unj<strong>on</strong>g Yu*<br />

GIST college, Gwangju Institute of Science and Technology, Korea<br />

There have been a lot of efforts to understand the itinerant magnetism because<br />

ferromagnetism in many metallic magnets like ir<strong>on</strong>, cobalt, and nickel is due to the<br />

itinerant magnetism. However, the mechanism and the stability of the itinerant magnetism<br />

are not clear yet because the str<strong>on</strong>g quantum mechanical correlati<strong>on</strong> in time and space is<br />

crucial in the itinerant magnetism. The St<strong>on</strong>er model, which is the most popular model for<br />

the itinerant magnetism, ignores those correlati<strong>on</strong> effects and so is inadequate [1]. In this<br />

paper, we studied the itinerant magnetism within the dynamical mean-field theory (DMFT)<br />

and its cluster extensi<strong>on</strong>, dynamical cluster approximati<strong>on</strong> (DCA). These two methods<br />

are n<strong>on</strong>-perturbative and fully include str<strong>on</strong>g correlati<strong>on</strong> effects [2]. Particularly, the DCA<br />

incorporates spatial correlati<strong>on</strong> (n<strong>on</strong>local effects) systematically and gives numerically<br />

exact soluti<strong>on</strong> for the many-body problem [3]. We applied these two methods to study the<br />

ferromagnetic and antiferromagnetic instability of the Hubbard model in the 2-dimensi<strong>on</strong>al<br />

square lattice, the 3-dimensi<strong>on</strong>al cubic lattice, and the face-centered-cubic (fcc) lattice. We<br />

show that the correlati<strong>on</strong> in time and space reduces the critical temperature remarkably<br />

and is essential to understand the itinerant magnetism.<br />

[1] N. Majlis, The Quantum Theory of <strong>Magnetism</strong>, 2nd ed. (World Scientific Publishing, Singapore,<br />

2007), pp. 195-237. [2] D. Vollhardt et al., in Band-Ferromagnetism, edited by K. Baberschke et al.<br />

(Springer-Verlag, Berlin, 2001), p. 191. [3] U. Yu et al., Phys. Rev. Lett. 104, 037201 (2010).<br />

July 8 - 13, 2012 Busan, Korea 155<br />

Poster Thursday


Poster Thursday<br />

RF07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

First Principles DFT+U Method for Str<strong>on</strong>gly Correlating Electr<strong>on</strong>ic<br />

Structure Systems<br />

Tomoyuki Hamada 1 , Takahisa Ohno 2 and Sadamichi Maekawa 3<br />

1 Central Research Laboratory, Hitachi Ltd., JST-CREST, Japan<br />

2 Nati<strong>on</strong>al Institute of Materials Research, Japan<br />

3 ASRC, JAEA, JST-CREST, Japan<br />

First principles density functi<strong>on</strong>al+U pseudopotential (DFT+U PP) method free<br />

from any empirical parameters has been developed and applied to the electr<strong>on</strong>ic<br />

structure calculati<strong>on</strong>s of str<strong>on</strong>gly correlating electr<strong>on</strong>ic structure systems such as<br />

FeO and LaVO 3. The method can calculate the electr<strong>on</strong>ic structure of the systems<br />

from first principles, being c<strong>on</strong>trary to the c<strong>on</strong>venti<strong>on</strong>al DFT+U PP method, which<br />

uses empirical Ueff paramaters. The method primary calculates the Hubbard <strong>on</strong>-site<br />

interacti<strong>on</strong> parameter Ueff for localized electr<strong>on</strong>s, using an approximate c<strong>on</strong>strained<br />

DFT technique, and then uses the calculated parameter in the DFT+U PP electr<strong>on</strong>ic<br />

structure calculati<strong>on</strong>. Examples of calculati<strong>on</strong>s resulted in Ueff of Fe 3d electr<strong>on</strong>s of<br />

anti-ferromagnetic FeO to be 5.11 eV (the empirical value is 5eV) and Ueffs of La<br />

4f and V 3d electr<strong>on</strong>s of paramagnetic LaVO 3 to be 15.6 and 0.47 eV, respectively<br />

(the empirical values are 20.0 and 0 eV, respectively). The band gap structure of<br />

these materials was correctly described. Our method seems to be a promising tool<br />

for investigating str<strong>on</strong>gly correlating electr<strong>on</strong>ic structure systems for spintr<strong>on</strong>ics<br />

applicati<strong>on</strong>s, correctly describing the localized and itinerant nature of electr<strong>on</strong>s of the<br />

systems from first principles.<br />

RF08<br />

Correlati<strong>on</strong> effect in ferromagnetic 3d transiti<strong>on</strong> metals<br />

Muneyuki Nishishita 1 , Sudhakar Pandey 2 and Dai Hirashima 1 *<br />

1 Nagoya University, Japan<br />

2 APTPC, Korea<br />

RF09<br />

MOVED<br />

Mott transiti<strong>on</strong> in frustrated Hubbard model with spatial anisotropy: Cellular<br />

dynamical mean field study<br />

Tomoko Kita 1*, Yuta Furukawa 1, Takuma Ohashi 2 and Norio Kawakami 1<br />

1 Department of Physics, Kyoto University, Japan<br />

2 Department of Physics, Osaka University, Japan<br />

Geometrical frustrati<strong>on</strong> has attracted much interest in the field of str<strong>on</strong>gly correlated<br />

electr<strong>on</strong> systems. In the frustrated systems, a lot of intriguing phenomena such as<br />

the heavy fermi<strong>on</strong> behavior in LiV 2O 4, spin liquid ground state in organic materials,<br />

etc. have been observed and they have stimulated theoretical investigati<strong>on</strong>s of<br />

frustrated electr<strong>on</strong> systems. In particular, the reentrant behavior in the Mott transiti<strong>on</strong><br />

in moderately frustrated systems, the heavy Fermi-liquid behavior around the Mott<br />

transiti<strong>on</strong>, etc. are new aspects of the Mott transiti<strong>on</strong> and very interesting. In our recent<br />

study <strong>on</strong> the kagome lattice system with spatial anisotropy [1] and also Ref. [2], it has<br />

been found that the anisotropy is str<strong>on</strong>gly enhanced around the Mott transiti<strong>on</strong>, which<br />

stabilizes antiferromagnetic spin c<strong>on</strong>figurati<strong>on</strong>s. In this study, we apply the cellular<br />

dynamical mean field theory combined with a c<strong>on</strong>tinuous-time quantum M<strong>on</strong>te Carlo<br />

solver [3] to the Hubbard model <strong>on</strong> the anisotropic kagome and triangular lattices.<br />

We systematically investigate the effects of the enhanced anisotropy around the Mott<br />

transiti<strong>on</strong> <strong>on</strong> the quasiparticle spectra and spin correlati<strong>on</strong> functi<strong>on</strong>s.<br />

[1] Y. Furukawa et al.: Phys. Rev. B 82 (2010) 161101. [2] A. Yamada et al.: Phys. Rev. B 83 (2011)<br />

195127. [3] G. Kotliar et al.: Phys. Rev. Lett. 87 (2001) 186401; P. Werner et al.: Phys. Rev. Lett. 97<br />

(2006) 076405.<br />

156 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RF10<br />

Spin-nematic and -singlet states in the Mott insulator phase of the S=1<br />

two-dimensi<strong>on</strong>al Bose-Hubbard model<br />

Yuta Toga 1 , Hiroki Tsuchiura 1 , Makoto Yamashita 2 and Hisatoshi Yokoyama 3<br />

1 Department of Applied Physics, Tohoku University, Japan<br />

2 NTT Basic Research Laboratories, NTT Corporati<strong>on</strong>, Japan<br />

3 Department of Physics, Tohoku University, Japan<br />

Because of the recent development in experimental cold-atom physics, a quantum gas microscope technique<br />

has opened the door for detecting and manipulating single bos<strong>on</strong>ic atoms at single site level in an optical<br />

lattice, just like scanning tunneling microscopy in solid-state physics. Quite recently, Endres et al [1]. used this<br />

technique to track the superfluid-Mott insulator (SF-MI) transiti<strong>on</strong> of spinless bos<strong>on</strong>ic-atoms <strong>on</strong> an optical<br />

lattice in more detail, and found that correlated pairs of a doubly populated site and an unpopulated site which<br />

representing the excitati<strong>on</strong>s in the MI, fundamentally determine the properties of the SF-MI transiti<strong>on</strong>, which<br />

is c<strong>on</strong>sistent with recent numerical studies [2,3]. Theoretically, spin-1 bos<strong>on</strong>ic atoms <strong>on</strong> a two-dimensi<strong>on</strong>al<br />

lattice is also of prime importance because it is a bos<strong>on</strong>ic analogue of the two-dimensi<strong>on</strong>al fermi<strong>on</strong>ic (S=1/2)<br />

Hubbard model, which has been exhaustively studied in the c<strong>on</strong>text of magnetism and high-temperature<br />

superc<strong>on</strong>ductivity. Thus in this work, we study the ground state properties and quantum phase transiti<strong>on</strong>s of<br />

S=1 two-dimensi<strong>on</strong>al Bose-Hubbard model, focusing <strong>on</strong> correlated pairs excitati<strong>on</strong>s based <strong>on</strong> a variati<strong>on</strong>al<br />

M<strong>on</strong>te Carlo approach. We discuss the spin-structures in the MI, and present a c<strong>on</strong>sistent descripti<strong>on</strong> of the<br />

transiti<strong>on</strong> from the spin-nematic state to the spin-singlet state bey<strong>on</strong>d mean-field theory.<br />

[1]M. Endres, M. Cheneau, T. Fukuhara, C. Weitenberg, P. Schauß, C. Gross, L. Mazza, M. C. Banuls, L. Pollet, I.<br />

Bloch, and S. Kuhr, Science 334 (2011) 200. [2] M. Capello, F. Becca, M. Fabrizio, and S. Sorella, Phys. Rev.<br />

Lett. 99 (2007) 056402; Phys. Rev. B 77 (2008) 144517. [3] H. Yokoyama and M. Ogata, J. Phys. Chem. Solids<br />

69 (2008) 3356; H. Yokoyama, T. Miyagawa, and M. Ogata, J. Phys. Soc. Jpn 80 (2011) 084607.<br />

RF11<br />

Dynamical instability in two-comp<strong>on</strong>ent bos<strong>on</strong>ic systems in an optical<br />

lattice<br />

Rui Asaoka 1 , Yuta Toga 1 , Hiroaki Tsuchiura 1 and Makoto Yamashita 2<br />

1 Depertment of Applied Physics, Tohoku University, Japan<br />

2 NTT Basic Research Laboratories, NTT Corporati<strong>on</strong>, Japan<br />

Because of the recent development in experimental technique, there has been an emerging<br />

interest in dynamical properties of Bose-Einstein c<strong>on</strong>densates (BEC) <strong>on</strong> an optical lattice.<br />

In particular, quantum gas microscope technique has opened the door for real-time<br />

observati<strong>on</strong> of single bos<strong>on</strong>ic atoms at single site level in an optical lattice, which can act<br />

as scanning tunneling microscopy in solid state physics. Quite recently, Greiner and his<br />

co-workers used this technique to track the superfluid-Mott insulator (SF-MI) transiti<strong>on</strong><br />

of bos<strong>on</strong>ic-atoms in real-space and time [1,2]. Further studies for dynamical properties<br />

of BEC may be <strong>on</strong>ly a matter in time. Dynamical analysis of BEC in str<strong>on</strong>gly correlated<br />

bos<strong>on</strong>ic systems is also of interest in theoretical point of view. In particular, the dynamical<br />

instability of SF in multi-comp<strong>on</strong>ent bos<strong>on</strong>ic systems is of prime importance because<br />

there would be entangled interplay am<strong>on</strong>g superfluidity, Mott physics, and possibly also<br />

Anders<strong>on</strong> localizati<strong>on</strong>. Thus, in this work, we study the dynamical instability of the SF<br />

phase of the two-comp<strong>on</strong>ent Bose-Hubbard model based <strong>on</strong> the dynamical Gutzwiller<br />

approximati<strong>on</strong>. We mainly focus <strong>on</strong> the effects of the dispersive current of <strong>on</strong>e-comp<strong>on</strong>ent<br />

<strong>on</strong> the stability of SF current of another comp<strong>on</strong>ent.<br />

[1] W. S. Bakr et al., Science 329, 547 (2010). [2] M. Endres et al., Science 334, 200 (2011).<br />

RF12<br />

Mechanism for the high Neel temperature in SrTcO3<br />

Ashis Kumar Nandy 1 , S. Middey 1 , Priya Mahadevan 2 * and D. D. Sarma 3<br />

1<br />

Centre for Advanced Materials, Indian Associati<strong>on</strong> for the Cultivati<strong>on</strong> of Science,<br />

India<br />

2<br />

S.N. Bose Nati<strong>on</strong>al Centre for Basic Sciences, India<br />

3<br />

Solid State and Structural Chemistry Unit, Indian Institute of Science, India<br />

The microscopic origin [1] of the high Neel temperature observed experimentally<br />

in SrTcO 3 [2] and CaTcO 3 [3] has been examined using a combinati<strong>on</strong> of ab-initio<br />

electr<strong>on</strong>ic structure calculati<strong>on</strong>s and mean-field soluti<strong>on</strong>s of a multi-band Hubbard<br />

model. The G-type anti-ferromagnetic state is found to be robust for a large regi<strong>on</strong><br />

of parameter space, with large stabilizati<strong>on</strong> energies found, surprisingly, for small<br />

values of intra-atomic exchange interacti<strong>on</strong> strength as well as large bandwidths.<br />

The microscopic origin of this is traced to specific aspects associated with the d3<br />

c<strong>on</strong>figurati<strong>on</strong> at the transiti<strong>on</strong>-metal site. C<strong>on</strong>sidering values of interacti<strong>on</strong> strengths<br />

appropriate for SrTcO 3 and the corresp<strong>on</strong>ding 3d oxide SrMnO 3, we find a ratio of 4:1<br />

for the Neel temperatures as well as magnitudes c<strong>on</strong>sistent with experiment.<br />

1. S. Middey, Ashis Kumar Nandy, Priya Mahadevan, D.D. Sarma, arXiv:1112.5587 2. E. E.<br />

Rodriguez et. al., Phys. Rev. Lett. 106, 067201 (2011). 3. M. Avdeev et. al., J. Am. Chem. Soc. 133,<br />

1654 (2011).


RF13<br />

Spin-spectral-weight distributi<strong>on</strong> and energy range of the parent<br />

compound La 2CuO 4<br />

Jose Carmelo 1 , Miguel Araujo 2 , Steven White 3 and Maria Sampaio 1<br />

1 Departament of Physics, University of Minho, Portugal<br />

2 Departament of Physics, University of Evora, Portugal<br />

3 Departament of Physics, University of California, USA<br />

The spectral-weight distributi<strong>on</strong> in recent neutr<strong>on</strong> scattering experiments <strong>on</strong> the parent<br />

compound La 2CuO 4 (LCO) [1], which are limited in energy range to about 450 meV,<br />

is studied in the framework of the Hubbard model <strong>on</strong> the square lattice [2]. We find<br />

that the higher-energy weight extends to about 566 meV and is located at and near<br />

the momentum [pi,pi]. Our results c<strong>on</strong>firm that the U/t value suitable to LCO is in the<br />

range between U/t=6 and U/t=8. The c<strong>on</strong>tinuum weight energy-integrated intensity<br />

vanishes or is extremely small at momentum [pi,0]. This behavior of the intensity is<br />

c<strong>on</strong>sistent with that of spin waves, which are damped at [pi,0]. Our study combines<br />

a number of theoretical and numerical approaches, including, in additi<strong>on</strong> to standard<br />

treatments [3], a new spin<strong>on</strong> approach for the spin excitati<strong>on</strong>s [4,5] and density matrix<br />

renormalizati<strong>on</strong> group (DMRG) calculati<strong>on</strong>s for Hubbard cylinders [6].<br />

[1] - N. S. Headings, S. M. Hayden, R. Coldea, and T. G. Perring, Phys. Rev. Lett. 105, 247001 (2010).<br />

[2] - M. A. N. Araujo, J. M. P. Carmelo, M. J. Sampaio, and S. R. White, c<strong>on</strong>d-mat.str-el.1201.5940.<br />

[3] - N. M . Peres and M. A. N. Araujo, Phys. Rev. B 65, 132404 (2002). [4] - J. M. P. Carmelo,<br />

Nucl. Phys. B 824, 452 (2010); Nucl. Phys. B 840, 553 (2010), Erratum. [5] - J. M. P. Carmelo,<br />

Ann. Phys. 327, 553 (2012). [6] - S. Yan, D. A. Huse, and S. R. White, Science 332, 1173 (2011).<br />

RF14<br />

J 1J 2 anti-ferromagnetic heisenberg model <strong>on</strong> bilayer h<strong>on</strong>eycomb lattice<br />

Mojtaba Shoja Shabankah and Farhad Shahbazi<br />

Physics, Isfahan University Of Technology, Iran<br />

Recent experiment <strong>on</strong> spin-3/2 bilayer h<strong>on</strong>eycomb lattice antiferromagnet Bi 3 Mn 4<br />

O 12 (NO 3) shows a spin liquid behavior down to very low temperatures. This behavior<br />

can be ascribed to the frustrati<strong>on</strong> effect due to competiti<strong>on</strong>s between first and sec<strong>on</strong>d<br />

nearest neighbor antiferromagnet interacti<strong>on</strong>. Motivated by the experiment, we study<br />

J 1J 2Antiferromagnet Heisenberg model, using Mean field theory and M<strong>on</strong>te Carlo<br />

simulati<strong>on</strong>. This calculati<strong>on</strong> shows highly degenerate ground state. We also calculate<br />

the effect of sec<strong>on</strong>d nearest neighbor through z directi<strong>on</strong> and show these neighbors<br />

also increase frustrati<strong>on</strong> in these systems. In additi<strong>on</strong> calculati<strong>on</strong> of the effect of third<br />

nearest neighbor shows that this interacti<strong>on</strong> can lift the degenerate ground state to four<br />

discrete states. The next step of these calculati<strong>on</strong>s is to c<strong>on</strong>sider quantum effect of these<br />

interacti<strong>on</strong>s by Word line quantum M<strong>on</strong>te Carlo method.<br />

[1] S. Okumura, H. Kawamura, T. Okubo, Y. Motome J. Phys. Soc. Jpn. 79, 114705 (2010) [2] J.<br />

N. Reimers, A. J. Berlinsky, and A.-C. Shi , Phys. Rev. B 43, 865-878 (1991) [3] Hem C. Kandpal<br />

and Jeroen van den Brink, PHYSICAL REVIEW B 83, 140412(R) (2011) [4] M Azuma, M Matsuda,<br />

N Onishi, S Olga, Y Kusano, M Tokunaga, Y Shimakawa and N Kumada, Journal of Physics:<br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series 320 (2011) 012005. [5] L. Balents, Nature (L<strong>on</strong>d<strong>on</strong>) 464, 199 (2010).<br />

RF15<br />

A hybrid exchange density functi<strong>on</strong>al study of La 1-xCa xMnO 3<br />

Romi Kaur Korotana 1 , Leandro Liborio 1 , Giuseppe Mallia 1 , Zsolt Gercsi 2 and<br />

Nicholas Harris<strong>on</strong> 1<br />

1 Chemistry, Imperial College L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

2 Physics, Imperial College L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

Manganites exhibit a rich variety of crytallographic, electr<strong>on</strong>ic and magnetic properties<br />

[1] manifested in ferromagnetic-, antiferromagnetic (collinear and canted)-, metallic-,<br />

insulating-,charge- and orbital-ordered states. An insight into the competiti<strong>on</strong> and coupling<br />

between various degrees of freedom in doped manganites is of interest for the optimisati<strong>on</strong><br />

of the magnetocaloric effect [2, 3] in such materials. In this work, hybrid-exchange density<br />

functi<strong>on</strong>al theory (DFT) calculati<strong>on</strong>s have been carried out to determine the effects of A-site<br />

doping <strong>on</strong> the structural, electr<strong>on</strong>ic and magnetic properties of perovskite-type manganites<br />

La 1-x A x MnO 3 , where A=Ca and x=0, 0.25, 0.50, 0.75 and 1. A magnetic stability plot for<br />

La 1-x Ca x MnO 3 is complied, in which the ferromagnetic (F), antiferromagnetic A-type (A-AF),<br />

G-type (G-AF) and C-type (C-AF) c<strong>on</strong>figurati<strong>on</strong>s are c<strong>on</strong>sidered. At this level of theory, the<br />

structural, magnetic ground states and electr<strong>on</strong>ic states at each of the compositi<strong>on</strong>s studied<br />

are compared to available experimental data. This provides a basis for a first principles<br />

descripti<strong>on</strong> of the magnetocaloric effect in La 1-x Ca x MnO 3 systems.<br />

[1] J. B. Goodenough, in Handbook <strong>on</strong> the Physics and Chemistry of Rare Earths, vol 33, edited by K. A.<br />

Gschneidner, Jr. et al. (Elsevier 2003), p. 249. Elsevier, Amsterdam (2003). [2] V. K. Pecharsky and K. A.<br />

Gschneidner, Jr., J. Magn. Magn. Mater., 200, 44 (2002). [3] A. M. Tishin, in Handbook of Magnetic<br />

Materials, edited by K. H. J. Buschow (North Holland, Amsterdam, 1999), Vol. 12, pp. 395-524.<br />

RF16<br />

RG01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of GdFe 11Ti via first principal calculati<strong>on</strong>s.<br />

E. E. Kokorina*, M. V. Medvedev and I. A. Nekrasov<br />

Laboratory of Theoretical Physics, Institute of Electrophysics, Russia<br />

RF17<br />

WITHDRAWN<br />

Mott transiti<strong>on</strong> of ultracold Fermi-Fermi mixtures in optical lattices<br />

Takahiro Ooi* and Seiichiro Suga<br />

University of Hyogo, Japan<br />

WITHDRAWN<br />

Anisotropy in a high Landau level due to effective electr<strong>on</strong>-electr<strong>on</strong><br />

interacti<strong>on</strong>s<br />

Ori<strong>on</strong> Ciftja<br />

Prairie View A&M University, USA<br />

Quantizati<strong>on</strong> of Hall resistivity in str<strong>on</strong>gly correlated two-dimensi<strong>on</strong>al electr<strong>on</strong>ic<br />

systems at high magnetic fields generally indicates the stabilizati<strong>on</strong> of novel electr<strong>on</strong>ic<br />

quantum liquid phases of matter. This is the nature of the integer and fracti<strong>on</strong>al<br />

quantum Hall states that stabilize at integer and fracti<strong>on</strong>al odd-denominator (not<br />

always, though) filling factors of the Landau level. Away from certain filling factors<br />

that represent quantum Hall liquid states, different phases, some of them with<br />

unusually high magneto-transport anisotropy have been known to stabilize specially in<br />

high Landau levels. In this work, we try to understand the anisotropy of such quantum<br />

phases in terms of effective electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong> potentials. To this effect, we<br />

implement a full projecti<strong>on</strong> of the original Coulomb interacti<strong>on</strong> potential in the suitable<br />

Landau level. We find out that, in high Landau levels, thus for relatively weak magnetic<br />

fields, a semi-classical descripti<strong>on</strong> of the interacti<strong>on</strong> potential between electr<strong>on</strong>s appear<br />

to be an adequate choice. The features of this semi-classical interacti<strong>on</strong> potential in<br />

this limit suggest ways how the energetic balance between density waves and/or liquid<br />

crystalline phases might be sensitively affected.<br />

[1] R. B. Laughlin, Phys. Rev. Lett. 50, 1395 (1983). [2] P. K. Lam and S. M. Girvin, Phys. Rev. B.<br />

30, R473 (1984). [3] O. Ciftja and C. Wexler, Phys. Rev. B 67, 075304 (2003).<br />

July 8 - 13, 2012 Busan, Korea 157<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RG02<br />

Bipolar<strong>on</strong>-Bipolar<strong>on</strong> interacti<strong>on</strong> in many electr<strong>on</strong> Holstein-Hubbard<br />

model<br />

M<strong>on</strong>odeep Chakraborty and B. I. Min<br />

Department of Physics, Pohang University of Science and Technology, Korea<br />

Polar<strong>on</strong>s and bipolar<strong>on</strong>s have been l<strong>on</strong>g-term subjects of interest in many areas<br />

of c<strong>on</strong>densed matter. The Holstein model describing the str<strong>on</strong>g electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong><br />

interacti<strong>on</strong> and the Hubbard model describing the str<strong>on</strong>g electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong><br />

have played pivotal roles in various important physical systems, such as high Tc<br />

superc<strong>on</strong>ductors and the CMR manganites. In real systems, the polar<strong>on</strong>-polar<strong>on</strong> and<br />

polar<strong>on</strong>-bipolar<strong>on</strong> interacti<strong>on</strong>s might be of crucial importance. In order to investigate<br />

the physics of polar<strong>on</strong> and bipolar<strong>on</strong> systematically, we have studied the combined<br />

Holstein-Hubbard model treating both the electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> and the electr<strong>on</strong>-electr<strong>on</strong><br />

interacti<strong>on</strong> <strong>on</strong> an equal footing. We present our study <strong>on</strong> polar<strong>on</strong>-bipolar<strong>on</strong> and<br />

bipolar<strong>on</strong>-bipolar<strong>on</strong> interacti<strong>on</strong>s as a functi<strong>on</strong> of the electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> coupling strength<br />

and the electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong> U . We have calculated the ground state energy<br />

and wave functi<strong>on</strong>s of the system by applying the c<strong>on</strong>jugate-gradient technique <strong>on</strong><br />

a variati<strong>on</strong>ally c<strong>on</strong>structed basis. The obtained correlati<strong>on</strong> functi<strong>on</strong>s, the bipolar<strong>on</strong><br />

binding energy, and the effective mass enables us to capture the intricate mechanisms<br />

at play and their c<strong>on</strong>sequences.<br />

RG03<br />

Partial disorder in an Ising-spin K<strong>on</strong>do lattice model <strong>on</strong> a triangular<br />

lattice<br />

Hiroaki Ishizuka* and Yukitoshi Motome<br />

Department of Applied Physics, University of Tokyo, Japan<br />

Partial disorder, that is coexistence of paramagnetic and magnetically ordered sites,<br />

is an intriguing example of exotic orders induced by geometrical frustrati<strong>on</strong> [1].<br />

Experimentally, several metallic magnets with a triangular lattice structure, such as<br />

UNi 4B and Ag 2CrO 2, were reported to present such unique order. On the other hand,<br />

theoretical attempts to explore the partial disorder in two-dimensi<strong>on</strong>al localized spin<br />

systems turned out to be unsuccessful so far; it is fragile against thermal fluctuati<strong>on</strong>s<br />

[2] and <strong>on</strong>ly exists as a quasi-l<strong>on</strong>g-range order at most [3]. To explore the possible<br />

realizati<strong>on</strong> of the true l<strong>on</strong>g-range partially disordered phase in two dimensi<strong>on</strong>s, here<br />

we theoretically investigate the effect of the coupling of localized moments to itinerant<br />

electr<strong>on</strong>s in an Ising-spin K<strong>on</strong>do lattice model <strong>on</strong> a triangular lattice. We study the<br />

low-temperature magnetic phases by a real-space M<strong>on</strong>te Carlo technique. As a result,<br />

we obtained a l<strong>on</strong>g-range order of the partially disordered state at finite temperatures<br />

in the vicinity of electr<strong>on</strong> density n=1/3, where a two-sublattice stripe-type order and<br />

three-sublattice ferrimagnetic order compete with each other and an electr<strong>on</strong>ic phase<br />

separati<strong>on</strong> takes place at a lower temperature. Further details <strong>on</strong> the phase diagram and<br />

the partially disordered phase will be given in the presentati<strong>on</strong>.<br />

[1] M. Mekata, J. Phys. Soc. Jpn. 42, 76 (1977). [2] S. Fujiki et al., J. Phys. Soc. Jpn. 53, 1371 (1984).<br />

[3] T. Takagi and M. Mekata, J. Phys. Soc. Jpn. 64, 4609 (1995).<br />

RG04<br />

Basis reducti<strong>on</strong> in the exact diag<strong>on</strong>alizati<strong>on</strong> method for the dynamical<br />

mean-field theory<br />

Hye<strong>on</strong>g-do Kim*<br />

Beamline Divisi<strong>on</strong>, Pohang Accelerator Laboratory, Korea<br />

The exact diag<strong>on</strong>alizati<strong>on</strong> (ED) method for the dynamical mean-field theory is nearly<br />

the <strong>on</strong>ly method to calculate electr<strong>on</strong> spectra involving core levels, such as core-level<br />

photoemissi<strong>on</strong> spectra, x-ray absorpti<strong>on</strong>/emissi<strong>on</strong> spectra, res<strong>on</strong>ant inelastic x-ray<br />

scattering, etc., in a str<strong>on</strong>gly correlated electr<strong>on</strong> systems. In order to overcome the<br />

problem of the exp<strong>on</strong>entially increasing Hilbert-space dimensi<strong>on</strong> by the number of<br />

sites, the number of c<strong>on</strong>figurati<strong>on</strong>al bases for the ED method for the single-impurity<br />

Anders<strong>on</strong> model is systematically reduced by their perturbative expansi<strong>on</strong> starting<br />

from the lowest-energy c<strong>on</strong>figurati<strong>on</strong> and c<strong>on</strong>secutively allowing the hopping between<br />

an impurity level and a c<strong>on</strong>ducti<strong>on</strong> band. Comparis<strong>on</strong> of resulting Green's functi<strong>on</strong>s<br />

with exact <strong>on</strong>es in an imaginary frequency axis shows that bases up to the fourth<br />

order is enough to render reliable results. Since the reduced Hilbert-space dimensi<strong>on</strong><br />

increases according to the power law, the available size of involved sites could be<br />

greatly enhanced to simulate core-level-related spectra with a large spin-orbital degree<br />

of freedom.<br />

158 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RG05<br />

Electr<strong>on</strong>ic Structure of ternary stannides RRu4Sn6 (R=Y, La, Pr, Ce,<br />

and Gd) compounds<br />

Saad Elgazar 1, A. M. Strydom 1 and P. M. Oppeneer 2<br />

1 Physics, Johannesburg University, South Africa<br />

2 Physics, Uppsala University, Sweden<br />

We report density functi<strong>on</strong>al calculati<strong>on</strong>s of the band structure and density of states<br />

of the RRu4Sn6 (M=Y, La, Ce, and Gd) compounds. Our investigati<strong>on</strong> is carried<br />

out within the framework of the local density approximati<strong>on</strong>, using a relativistic,<br />

full-potential band-structure method. For the Ce-146 compound we find that LSDA<br />

calculati<strong>on</strong>s predict a semic<strong>on</strong>ducting ordered ground state whereas the other<br />

compounds ordered in metallic states, in accordance with available experimental<br />

measurements<br />

RG06<br />

Local correlati<strong>on</strong> effects in Mn doped GaAs<br />

Igor Di Marco*, Olle Erikss<strong>on</strong> and Patrik Thunstrom<br />

Physics and Astr<strong>on</strong>omy - Materials Theory, Uppsala University, Sweden<br />

RG07<br />

WITHDRAWN<br />

First-principles study <strong>on</strong> n<strong>on</strong>collinear magnetism and effects of spinorbit<br />

coupling in 5d pyrochlore oxide Cd 2Os 2O 7<br />

Hiroshi Shinaoka, Takashi Miyake and Shoji Ishibashi<br />

Nanosystem Research Institute, Nati<strong>on</strong>al Institute of Advanced Industrial Science and<br />

Technology, Japan<br />

Recently, increasing attenti<strong>on</strong> has been focused <strong>on</strong> 5d pyrochlore oxides A 2B 2O 7 (B=Ir, Os, etc.) in search<br />

for unc<strong>on</strong>venti<strong>on</strong>al phenomena induced by str<strong>on</strong>g spin-orbit coupling. Cd 2Os 2O 7 is a typical member of<br />

these compounds. Experimentally, it exhibits a metal-insulator transiti<strong>on</strong> at 227 K, below which a Neel order<br />

appears [1]. Despite many experimental attempts, the nature of the low-temperature phase remains to be<br />

clarified; e.g., the magnetic structure is unknown. Furthermore, several peculiar properties have been reported<br />

experimentally: (1) The transiti<strong>on</strong> temperature is the highest am<strong>on</strong>g pyrochlore oxides. (2) No clear charge<br />

gap is seen in the temperature dependence of the resistivity despite the high transiti<strong>on</strong> temperature. Motivated<br />

by these experiments, we investigate electr<strong>on</strong>ic structure of Cd 2Os 2O 7 [2] using the local spin density<br />

approximati<strong>on</strong> + U method. We use a fully relativistic two-comp<strong>on</strong>ent first-principles computati<strong>on</strong>al code<br />

[3] based <strong>on</strong> the projector augmented-wave method. We show that the so-called all-in/all-out magnetic order<br />

is the most stable in a wide range of U. By analyzing an effective spin model, we show that the local <br />

easy-axis anisotropy removes geometrical frustrati<strong>on</strong> to stabilize this n<strong>on</strong>-collinear magnetic order. We also<br />

compute the density of states and the electr<strong>on</strong>ic band structure and compare the results with experiments.<br />

[1] A. Sleight et al., Solid State Comm. 14, 357 (1974); D. Mandrus et al., Phys. Rev. B 63, 195104<br />

(2001); A. Koda et al., J. Phys. Soc. Jpn. 76, 063703 (2007); Y. H. Matsuda et al., Phys. Rev. B 84,<br />

174431 (2011). [2] H. Shinaoka, T. Miyake, and S. Ishibashi, arXiv:1111.6347. [3] QMAS (Quantum<br />

MAterials Simulator) [http://qmas.jp/].


RG08<br />

N<strong>on</strong>equilibrium states and I-V characteristics in <strong>on</strong>e-dimensi<strong>on</strong>al band<br />

and Mott insulators attached to electrodes<br />

Yasuhiro Tanaka* and Kenji Y<strong>on</strong>emitsu<br />

Institute for Molecular Science, Japan<br />

N<strong>on</strong>equilibrium states induced by an applied bias voltage (V) and the corresp<strong>on</strong>ding<br />

current-voltage characteristics of <strong>on</strong>e-dimensi<strong>on</strong>al models describing band and Mott<br />

insulators are investigated theoretically by using n<strong>on</strong>equilibrium Green's functi<strong>on</strong>s[1].<br />

We attach the models to metallic electrodes whose effects are incorporated into the<br />

self-energy. Modulati<strong>on</strong> of the electr<strong>on</strong> density and the scalar potential coming from<br />

the additi<strong>on</strong>al l<strong>on</strong>g-range interacti<strong>on</strong> are calculated self-c<strong>on</strong>sistently within the Hartree<br />

approximati<strong>on</strong>. For both models of band and Mott insulators with length L_C, the bias<br />

voltage induces a breakdown of the insulating state, whose threshold shows a crossover<br />

depending <strong>on</strong> L_C[2]. It is determined basically by the bias V_{th}~Δ for L_C smaller<br />

than the correlati<strong>on</strong> length ξ=W/Δ where W denotes the bandwidth and Δ the energy<br />

gap. For systems with L_C ξ, the threshold is governed by the electric field, V_{th}/<br />

L_C, which is c<strong>on</strong>sistent with a Landau-Zener-type breakdown, V_{th}/L_C Δ^2/<br />

W. We dem<strong>on</strong>strate that the spatial dependence of the scalar potential is crucially<br />

important for this crossover by showing the case without the scalar potential, where the<br />

breakdown occurs at V_{th} Δ regardless of the length L_C.<br />

[1] K. Y<strong>on</strong>emitsu, J. Phys. Soc. Jpn. 78 (2009) 054705. [2] Y. Tanaka and K. Y<strong>on</strong>emitsu, Phys. Rev.<br />

B 83 (2011) 085113.<br />

RG09<br />

Enhancement of charge ordering by Zeeman effect in <strong>on</strong>e-dimensi<strong>on</strong>al<br />

molecular c<strong>on</strong>ductors<br />

Hideo Yoshioka 1 , Hitoshi Seo 2 and Yuichi Otsuka 3<br />

1 Department of Physics, Nara Women's University, Japan<br />

2 C<strong>on</strong>densed Matter Theory Laboratory, RIKEN, Japan<br />

3 Advanced Institute for Computati<strong>on</strong>al Science, RIKEN, Japan<br />

A recent experiment observes increase of resistance with increasing the external<br />

magnetic field in <strong>on</strong>e-dimensi<strong>on</strong>al molecular c<strong>on</strong>ductor TPP[Co(Pc)(CN)_2]_2 [1]. The<br />

positive magnetoresistance is independent of the directi<strong>on</strong> of the magnetic field, and<br />

then the origin of it is c<strong>on</strong>sidered to be the Zeeman effect. Therefore, the experiment<br />

indicates that charge ordering (CO) is enhanced by the Zeeman effect. Stimulated by<br />

the experiment, we theoretically investigate effect of uniform magnetic field <strong>on</strong> CO<br />

in <strong>on</strong>e-dimensi<strong>on</strong>al extended Hubbard model. In a previous study, the ground state<br />

with coexistence of CO and 2k_F-SDW was investigated, but the amplitude of CO<br />

does not show noticeable enhancement under the uniform magnetic field [2]. In the<br />

present study, the parameter regi<strong>on</strong> where <strong>on</strong>ly CO appears is studied. We find the<br />

following results; (1) The amplitude of CO shows c<strong>on</strong>tinuous enhancement under the<br />

external magnetic field. (2) Enhancement of CO is accompanied by both uniform and<br />

staggered (4 k_F) comp<strong>on</strong>ent of magnetic moment. Our c<strong>on</strong>clusi<strong>on</strong> is c<strong>on</strong>sistent with<br />

experimental finding in TPP[Co(Pc)(CN)_2]_2.<br />

[1] N. Hanasaki et al., J. Phys. Soc. Jpn. 75 (2006) 104743. [2] K. Kishigi and Y. Hasegawa, J.<br />

Phys. Soc. Jpn. 69 (2000) 2145.<br />

RG10<br />

C<strong>on</strong>tributi<strong>on</strong> of electr<strong>on</strong>-lattice and spin-orbit coupling to the<br />

insulator-metal transiti<strong>on</strong> in VO2 and Sr2IrO4 J<strong>on</strong>gseok Lee 1 , K. Shibuya 2 , Y. Krockenberger 2 , K. S. Takahashi 2 , M. Kawasaki 3 and Y.<br />

Tokura 3<br />

1<br />

Department of Phot<strong>on</strong>ic and Applied Physics, Gwangju Institute of Science and<br />

Technology, Korea<br />

2<br />

Cross-Correlated Materials Research Group (CMRG) and Correlated Electr<strong>on</strong><br />

Research Group (CERG), RIKEN, Japan<br />

3<br />

Department of Applied Physics, University of Tokyo, Japan<br />

Mott insulating state in the str<strong>on</strong>gly correlated electr<strong>on</strong> system is often realized in<br />

competiti<strong>on</strong> and/or cooperati<strong>on</strong> with interacti<strong>on</strong>s other than the <strong>on</strong>-site Coulomb<br />

repulsi<strong>on</strong> energy, such as the electr<strong>on</strong>-lattice coupling and the spin-orbit coupling<br />

One of representative examples is VO 2 where the electr<strong>on</strong> correlati<strong>on</strong> and the Peierls<br />

instability have been debated as a driving force to realize its metal-insulator transiti<strong>on</strong><br />

near room temperature. Another example is Sr 2IrO 4 which is now believed to have a<br />

spin-orbit-induced Mott insulator ground state. In this presentati<strong>on</strong>, we discuss based<br />

<strong>on</strong> optical spectroscopy of thin films how the insulating ground states of each system<br />

evolve into the metallic states with a decrease of Peierls instability and the spin-orbit<br />

coupling strength which together can give an insight in to the complex phases in<br />

str<strong>on</strong>gly correlated electr<strong>on</strong> system [1,2].<br />

[1] J. S. Lee, Y. Krockenberg, K. Takahashi, M. Kawasaki, and Y. Tokura, Phys. Rev. B 85, 035101<br />

(2012). [2] J. S. Lee, K. Shibuya, M. Kawasaki, and Y. Tokura, submitted.<br />

RG11<br />

RG12<br />

RG13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Multipole moments at Pr-site and electric field gradients at Sb-site in<br />

PrOs_4Sb_12_<br />

Takeshi Goho* and Hisatomo Harima<br />

Department of Physics, Kobe University , Nada , Kobe 657-8501, Japan<br />

PrOs_4Sb_12_ is well known as an unusual superc<strong>on</strong>ductor with Tc = 1.85 K [1].<br />

The superc<strong>on</strong>ductivity might be related with the multipole moments of 4f^2 electr<strong>on</strong>s<br />

of Pr, because the antiferro-quadrupole ordering is realized under applied magnetic<br />

fields [2]. So, it is important to study a role of the multipole moments of Pr to make<br />

clear the system of unusual superc<strong>on</strong>ductor PrOs_4Sb_12_. The NQR frequency at<br />

Sb site shows temperature dependence corresp<strong>on</strong>ding to the crystalline electric field<br />

splitting below 10 K, associated with the Pr^3+^(4f^2)-derived ground state [3].<br />

This experimental result suggests that the change of multipole comp<strong>on</strong>ents affect the<br />

electr<strong>on</strong>ic field gradients (EFG) at Sb-site. The LDA + U calculati<strong>on</strong>s have described<br />

the Fermi surfaces of PrOs_4Sb_12_ well [4]. It has been shown that EFG at Sb-site<br />

can be calculated by using an FLAPW method and the calculated EFG reproduce well<br />

the experimental NQR frequency [5]. Moreover, the multipole moments of Pr can be<br />

classified from the density matrix, which is used in the LDA + U method. we have<br />

analyzed how each multipole comp<strong>on</strong>ent affects the EFG at Sb-site. Then we discuss<br />

the relati<strong>on</strong>ship between multipole moments at Pr-site and EFG at Sb-site.<br />

[1] E. D. Bauer et al., Phys. Rev. B 65 (2002) 100506. [2] M. Kohgi et al., J. Phys. Soc. Jpn. 72 (2003)<br />

1002. [3] M. Yogi et al., Phys. Rev. B 67 (2003) 180501(R). [4] H. Sugawara et al., Phys. Rev. B 66<br />

(2002) 220504(R). [5] H. Harima, Physica B 378-380 (2006) 246.<br />

The effect of pairing fluctuati<strong>on</strong>s and disorder <strong>on</strong> the BCS-BEC<br />

crossover<br />

Pinaki Majumdar<br />

Harish-Chandra Research Institute, India<br />

A fermi liquid with weak attractive interacti<strong>on</strong> undergoes a BCS transiti<strong>on</strong> to a<br />

superc<strong>on</strong>ductor with reducing temperature. With increasing interacti<strong>on</strong> strength the<br />

transiti<strong>on</strong> temperature displays n<strong>on</strong>-m<strong>on</strong>ot<strong>on</strong>ic behaviour as the system heads towards<br />

Bose c<strong>on</strong>densati<strong>on</strong> of preformed pairs. We use a new M<strong>on</strong>te Carlo tool, incorporating<br />

amplitude and phase fluctuati<strong>on</strong>s of the pairing field, to map out this BCS-BEC<br />

crossover in the attractive Hubbard model <strong>on</strong> large (40 X 40) two dimensi<strong>on</strong>al lattices.<br />

Havingestablished this benchmark we discuss the role of disorder in this system. This<br />

includes (i) the role of n<strong>on</strong>-magnetic impurities where we track the superc<strong>on</strong>ductor<br />

to insulator transiti<strong>on</strong> with increasing disorder, and (ii) the emergence of `gapless'<br />

superc<strong>on</strong>ductivity, the suppressi<strong>on</strong> of T_c, and the induced correlati<strong>on</strong> between<br />

scatterers themselves, in the case of magnetic impurities. Our method reproduces the<br />

standard results in all these cases but allows unprecedented spatial resoluti<strong>on</strong>, and<br />

access to the dynamical resp<strong>on</strong>se. We compare the results to imaging experiments <strong>on</strong><br />

disordered films.<br />

Transport properties of ferromagnetic material with Anders<strong>on</strong>-<br />

Hubbard centers<br />

Yuriy Skorenkyy*, Oleksandr Kramar and Le<strong>on</strong>id Didukh<br />

Physics Department, Ternopil Nati<strong>on</strong>al Technical University, Ukraine<br />

A competiti<strong>on</strong> between itinerant behavior and localizati<strong>on</strong> effects in str<strong>on</strong>gly<br />

correlated electr<strong>on</strong> system of periodically spaced Anders<strong>on</strong>-Hubbard centers<br />

introduced into narrow-band metal is studied. The c<strong>on</strong>figurati<strong>on</strong>al representati<strong>on</strong> for<br />

localized subsystem is used and the effective Hamilt<strong>on</strong>ian is obtained by can<strong>on</strong>ical<br />

transformati<strong>on</strong>. Besides the spin-spin interacti<strong>on</strong>s and str<strong>on</strong>g <strong>on</strong>-site Coulomb<br />

interacti<strong>on</strong>, the model takes into account the hybridizati<strong>on</strong> with c<strong>on</strong>ducti<strong>on</strong> band which<br />

results in the indirect hopping and indirect exchange interacti<strong>on</strong>s. Lattice deformati<strong>on</strong><br />

under the external pressure is taken into account and equilibrium value of lattice<br />

strain is found, having effect <strong>on</strong> both electrical and magnetic properties of the system.<br />

Green functi<strong>on</strong>s for band and localized electr<strong>on</strong>s are calculated. On this base, the<br />

energy spectrum and magnetizati<strong>on</strong> are investigated as functi<strong>on</strong> of model parameters,<br />

temperature and external pressure. For temperatures close to Curie temperature and<br />

partial filling of c<strong>on</strong>ducti<strong>on</strong> band the peculiarities of electr<strong>on</strong>ic c<strong>on</strong>ductivity are studied.<br />

C<strong>on</strong>centrati<strong>on</strong> dependence of static c<strong>on</strong>ductivity exhibits different transport regimes.<br />

Our results show that in the c<strong>on</strong>sidered model the effects of localizati<strong>on</strong> are enhanced<br />

even if external pressure promotes electrical c<strong>on</strong>ductivity.<br />

July 8 - 13, 2012 Busan, Korea 159<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RG14<br />

First principles studies of organic charge transfer salts<br />

Harald O. Jeschke, Anth<strong>on</strong>y Jacko and Roser Valenti<br />

Institut fur Theoretische Physik, Universitat Frankfurt, Germany<br />

We study a number of BEDT-TTF based charge transfer salts in the framework of ab<br />

initio density functi<strong>on</strong>al theory and determine the parameters of the effective Hubbard<br />

Hamilt<strong>on</strong>ian describing the low energy excitati<strong>on</strong>s[1]. For the spin liquid candidate<br />

kappa-(BEDT-TTF)2Cu 2(CN) 3, we investigate the questi<strong>on</strong> if the structures determined<br />

at various temperatures lead to different effective Hamilt<strong>on</strong>ian representati<strong>on</strong>s[2]. For<br />

the Fabre salts (TMTTF)2X, we compare the properties of the underlying Hamilt<strong>on</strong>ian<br />

for a series of different ani<strong>on</strong>s X.<br />

[1] H.C. Kandpal, I. Opahle, Y.-Z. Zhang, H. O. Jeschke, R. Valenti, Phys. Rev. Lett. 103, 067007<br />

(2009). [2] H. O. Jeschke, M. de Souza, R. Valenti, R. S. Manna, M. Lang, J. A. Schlueter, Phys. Rev.<br />

B 85, 035125 (2012)<br />

RG15<br />

Dynamics of str<strong>on</strong>gly correlated Fermi systems: The efffects of pairexcitati<strong>on</strong>s<br />

and exchange<br />

Martin Panholzer 1 *, Eckhard Krotscheck 2 , Helga M Boehm 2 , Robert Holler 2 and<br />

Thomas Lichtenegger 2<br />

1 Johannes Kepler University Linz, Austria<br />

2 Institut for Theoretical Physics, Johannes Kepler University Linz, Austria<br />

Understanding the emergent properties of many body systems from the underlying microscopic<br />

interacti<strong>on</strong>s is the major goal of c<strong>on</strong>densed matter physics. Recent progress, in the understanding<br />

of the dynamics of str<strong>on</strong>gly correlated systems, has been made by approximating the excited<br />

wave functi<strong>on</strong> by a superpositi<strong>on</strong> of correlated particle-hole and 2-particle-2-hole excitati<strong>on</strong>s.<br />

The amplitudes, describing these excitati<strong>on</strong>s, are obtained by minimizing the acti<strong>on</strong> integral. A<br />

surprising result of this approach is the c<strong>on</strong>firmati<strong>on</strong>/predicti<strong>on</strong> of the reemergence of collective<br />

mode below the PHB in two dimensi<strong>on</strong>al 3He for density fluctuati<strong>on</strong>s. By including exchange the<br />

agreement of the calculated spectrum with the experiment was further improved for 3He. The next<br />

step is to apply this tool to spin-density fluctuati<strong>on</strong>s, which are of inherent exchange character. Due<br />

to the proximity of the ferromagnetic phase transiti<strong>on</strong> the fluctuati<strong>on</strong>s are at very low energies for<br />

l<strong>on</strong>g wavelenth. This experimental finding is also present in a first implementati<strong>on</strong> of our theory.<br />

The presented approach is also applicable to other correltated fermi systems e.g. electr<strong>on</strong>s and<br />

dipols in two dimensi<strong>on</strong>s. We predict this transiti<strong>on</strong> of the collective mode seen in 3He also for two<br />

dimensi<strong>on</strong>al electr<strong>on</strong>s. The capability in describing these systems is investigated.<br />

Bohm, H. M., Holler, R., Krotscheck, E. & Panholzer, M. Dynamic many-body theory: Dynamics of<br />

Str<strong>on</strong>gly Correlated Fermi Fluids. Phys. Rev. B 22, 224505 (2010).<br />

RG16<br />

The induced effects of the Dzyaloshinskii-Moriya interacti<strong>on</strong> <strong>on</strong> the<br />

thermal entanglement<br />

Saeed Mahdavifar*<br />

Department of Physics, University of Guilan, Iran<br />

The pairwise thermal entanglement in <strong>on</strong>e-dimensi<strong>on</strong>al (1D) spin-1/2 XX model with<br />

added Dzyaloshinskii-Moriya interacti<strong>on</strong> and transverse magnetic field is studied<br />

through fermi<strong>on</strong>izati<strong>on</strong> technique. We have showed that, for fields less than quantum<br />

critical point, the thermal entanglement decreases by increasing the temperature and<br />

vanishes at a field-independent critical temperature. On the other hand for fields<br />

more than quantum critical value of the magnetic field (Fig. (1)(b)), NN spins are<br />

not entangled at $T=0$. By increasing the temperature from zero, NN spins remain<br />

unentangled up to the first critical temperature $T_{c_{1}}(h)$. As so<strong>on</strong> as the<br />

temperature increases from $T_{c_{1}}$, the thermal entanglement regain and<br />

takes a maximum value and then decrease and reaches to zero at the sec<strong>on</strong>d critical<br />

temperature $T_{c_{2}}(h)$.<br />

160 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RG17<br />

Magneto-polar<strong>on</strong>ic effects in molecular transistors as the c<strong>on</strong>sequence<br />

of quantum uncertainty of the displacement of vibrating quantum dot.<br />

Glib A(alexandrovich) Skorobagatko 1 *, Sergey I. Kulinich 2 , Ilya V. Krive 3 and Robert<br />

I. Shekhter 4<br />

1<br />

Department of Theoretical Physics, B.Verkin ILTPE of NAS of Ukraine, Kharkov,<br />

Ukraine, Ukraine<br />

2<br />

Department of Theoretical Physics, B.Verkin ILTPE of NAS of Ukraine, Kharkov,<br />

Ukraine, Ukraine<br />

3<br />

Department of Theoretical Physics, B.Verkin ILTPE of NAS of Ukraine, Ukraine<br />

4<br />

Department of Physics,, University of Gothenburg, SE-41296, Gothenburg, Sweden,<br />

Sweden<br />

The influence of magneto-polar<strong>on</strong>ic effects induced by the quantum uncertainty of<br />

the displacement of quantum dot <strong>on</strong> electr<strong>on</strong> transport through a single-level vibrating<br />

quantum dot subjected to a transverse (to the current flow) magnetic field is c<strong>on</strong>sidered<br />

. It is shown that the effects are most pr<strong>on</strong>ounced in the regime of sequential electr<strong>on</strong><br />

tunneling, where a polar<strong>on</strong>ic blockade of the current at low temperatures and an<br />

anomalous temperature dependence of the magnetoc<strong>on</strong>ductance are predicted.<br />

1. G. A. Skorobagatko, S. I. Kulinich, I. V. Krive, R. I. Shekhter, and M. J<strong>on</strong>s<strong>on</strong>, Low Temp. Phys. 37,<br />

1032 (2011).<br />

RG18<br />

Defect states and electr<strong>on</strong> correlati<strong>on</strong>s in multi-orbital Mott insulators<br />

Adolfo Avella 1 *, Peter Horsch 2 and Andrzej Oles 3<br />

1 Dipartimento di Fisica 'E.R. Caianiello', Universita degli Studi di Salerno, Italy<br />

2 Max Planck Institute for Solid State Research, Stuttgart, Germany<br />

3 Jagell<strong>on</strong>ian University, Krakow, Poland<br />

We address the role played by defects in doped Mott insulators with active orbital<br />

degrees of freedom. We observe that defects are characterized by rather complex<br />

and rich physics which is well captured by a degenerate Hubbard model extended by<br />

several terms that describe crystal-field splittings, the orbital-lattice coupling, as well<br />

as local terms generated by defects such as the Coulomb potential terms that act both<br />

<strong>on</strong> a doped hole and orbitals of undoped sites (orbital polarizati<strong>on</strong>). We show that<br />

the multiplet structure of excited states generated in such systems by str<strong>on</strong>g electr<strong>on</strong><br />

interacti<strong>on</strong>s is well described in an optimized unrestricted Hartree-Fock approximati<strong>on</strong>,<br />

taking into account the usual symmetry breaking by the <strong>on</strong>set of magnetic and orbital<br />

order. More importantly, we show that defect states are resp<strong>on</strong>sible for new features<br />

that arise within the Mott-Hubbard gap and in the multiplet spectrum at high energy.<br />

These states involve active orbital flavors at atoms b eing nearest neighbors of the<br />

defect state, which are modified by the local defect-orbital Coulomb interacti<strong>on</strong>s.<br />

The present study suggests a new mechanism for the Coulomb gap realized in the<br />

presence of defect states and investigates the dependence of the orbitals <strong>on</strong> the orbital<br />

polarizati<strong>on</strong>.<br />

RH01<br />

<strong>Magnetism</strong> of the n<strong>on</strong>centrosymmetric compound CeNiC 2-pressure<br />

effects<br />

Susumu Katano*, Toshiaki Kobayashi and Tohru Yoshida<br />

Graduate School of Science and Engneering, Saitama University, Japan<br />

The system RNiC 2 (R=Rare-earth element) has a simple but a characteristical<br />

n<strong>on</strong>centrosymmetric crystal structure, and shows various novel physical properties such<br />

as charge density waves (CDW) and complex magnetic structures. In the system the<br />

compound of R=La shows unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity, and has been intensively<br />

studied very recently. For CeNiC 2 a few reports indicated that the incommensurate<br />

antiferromagnetic state (ICAF) appears at around 20 K and this changes to the<br />

commensurate antiferromagnetic structure (CAF) at about 10 K, then a ferromagnetic<br />

state (F) takes place at around 2 K [1, 2]. However, since there are some clear<br />

discrepancies in these studies the magnetism of this compound has been reinvestigated<br />

in detail using a carefully prepared polycrystalline sample. It is found that there are<br />

definite magnetic moments in the paramagnetic state. With these moments the complex<br />

antiferromagnetic states undergo, which replaces to a ferromagnetic state at low<br />

temperatures. To investigate these magnetic states further, their pressure effects have<br />

been studied up to 2.5 GPa. The results show that the IC and CAF states at the higher<br />

temperatures is fairly stable, whose transiti<strong>on</strong> temperatures increase at a rate of about 2<br />

K/GPa. On the other hand the F state is changed little.<br />

[1] K. Motoya, et al. J. Phys.Soc. Jpn. 66 (1997) 1124. [2] V.K. Pecharsky, et al. Phys. Rev. B 58<br />

(1998) 497.


RH02<br />

Atomic scale disorder driven bicritical regi<strong>on</strong> in Sm0.5(Ca 1xSrx)0.5MnO<br />

3<br />

Saurav Giri 1 *, Sk. Sabyasachi 1 , S. Majumdar 1 , S. Das 2 and V. S. Amaral 3<br />

1 Solid State Physics, Indian Associati<strong>on</strong> for the Cultivati<strong>on</strong> of Science, India<br />

2 Department of Physics and CICECO, University of Aveiro, Portugal<br />

3 Department of Physics and CICECO, University of Aveiro, India<br />

On the verge of collapse of charge and orbital ordering a bicritical regi<strong>on</strong> occurs in hole doped<br />

manganites which displays rich electr<strong>on</strong>ic phase diagrams in R0.5(Ca,Sr)0.5MnO 3 [1]. Here,<br />

we dem<strong>on</strong>strate a fascinating c<strong>on</strong>sequence of A-site disorder in intermediate members of a<br />

new series Sm0.5(Ca 1-xSrx)0.5MnO 3. The Rietveld refinement of X-ray diffracti<strong>on</strong> studies<br />

reveal maximum structural distorti<strong>on</strong>s at x = ½. This is indicated by the highest value of ε [=<br />

√2b/(a+c), a, b, c being lattice c<strong>on</strong>stants] and most deviati<strong>on</strong> of Mn-O-Mn b<strong>on</strong>d-angle from<br />

180° compared to end compounds. An unusual behaviour in magnetic field-induced ultrasharp<br />

transiti<strong>on</strong> to ferromagnetic metallic (FMM) state and collapse of charge ordering is<br />

observed both in magnetizati<strong>on</strong> and magnetoresistance curves for intermediate compositi<strong>on</strong>s<br />

at much lower field compared to end compounds. When magnetic field is applied above<br />

a critical field, FMM state appears and it retains high-field state, although magnetic field<br />

decreased to zero. With decreasing field sweep rate, the transiti<strong>on</strong> shifts to higher field<br />

indicating a meta-magnetic transiti<strong>on</strong>. The atomic-scale local inhomogeneity/distorti<strong>on</strong> arising<br />

from the difference in i<strong>on</strong>ic radii and/or the random Coulomb potential from i<strong>on</strong> mixture is<br />

supposed to be critical behind such striking phenomena.<br />

[1] Y. Takura, Rep. Prog. Phys. 69, 797 (2006).<br />

RH03<br />

11B-NMR study <strong>on</strong> Shastry Sutherland system TbB4 Tomoki Muto 1 , Takayuki Goto 1 , Akira Oosawa 1 , Shunsuke Yoshii 2 , Takahiko Sasaki 3 , Shinji<br />

Michimura 4 , Fumitoshi Iga 4 and Toshiro Takabatake 4<br />

1<br />

Department of Physics, Sophia University, Japan<br />

2<br />

CINTS Tohoku University, Japan<br />

3<br />

Institute for Materials Research, Tohoku University, Japan<br />

4<br />

ADSM, Hiroshima University, Japan<br />

In TbB 4, the arrangement of Tb i<strong>on</strong>s within the c-plane is topologically equivalent to the<br />

Shastry Sutherland (S-S) lattice with geometrical frustrati<strong>on</strong> [1]. A well-known example<br />

of S-S lattice is SrCu 2(BO 3) 2 which shows the characteristic magnetizati<strong>on</strong> plateaus<br />

caused by the frustrati<strong>on</strong>. However, in TbB 4, due to the quadrupole interacti<strong>on</strong> and<br />

RKKY interacti<strong>on</strong> between classical spins, the appearance of the novel magnetism quite<br />

different from SrCu 2(BO 3) 2 is expected. The magnetizati<strong>on</strong> of TbB 4 for H // c-axis shows<br />

field-induced multi-step jump while the magnetizati<strong>on</strong> in the c-plane <strong>on</strong> which we focus<br />

attenti<strong>on</strong> shows <strong>on</strong>ly <strong>on</strong>e large jump at Hc = 15.9 and 12 T for H//[100] and H//[110]<br />

respectively [2]. In order to investigate the magnetic structure in high magnetic fields for<br />

H//[100], we performed 11B-NMR experiments up to 17.5T for the single crystalline<br />

TbB 4. 11B-NMR spectra observed at low magnetic field changes drastically at Hc = 15.9<br />

T, where the magnetizati<strong>on</strong> jump occurs. This result indicates the change of the magnetic<br />

structure at the field-induced magnetic phase transiti<strong>on</strong>. In order to determine the<br />

magnetic structure, we have compared the observed NMR spectra with the calculati<strong>on</strong><br />

based <strong>on</strong> the classical dipole-dipole interacti<strong>on</strong>.<br />

[1] B.S.Shastry et al., Physica B 208 (1981) 1069. [2] S.Yoshii et al., Phys. Rev. Lett. 101 (2008) 087202.<br />

RH04<br />

Magnetotransport Property of the Hole-doped Delafossite<br />

CuCr 0.97Mg 0.03O 2 with a Spin-3/2 Antiferromagnetic Triangular<br />

Sublattice<br />

Tetsuji Okuda 1 *, Satoshi Ooz<strong>on</strong>o 1 , Takumi Kihara 2 and Masashi Tokunaga 2<br />

1 Kagoshima University, Japan<br />

2 The University of Tokyo, ISSP, Japan<br />

Magnetotransport property of a hole-doped delafossite CuCr 0.97Mg 0.03O 2 with a spin-<br />

3/2 antiferromagnetic (AF) triangular sublattice was investigated by a pulsed high<br />

magnetic field up to about 56 Tesla. [1] A dramatic change of magnetoresistance (MR)<br />

was observed with a variati<strong>on</strong> of temperature (T), which is due to a development of<br />

an AF correlati<strong>on</strong> with a decrease in T. A negative MR is observed and the ratio is<br />

well proporti<strong>on</strong>al to a square of magnetizati<strong>on</strong> above a Curie-Weiss temperature (θ),<br />

which seems to suggest that the magnetic state above θ is well explained by a K<strong>on</strong>dolattice<br />

model [2] with a weak ferromagnetic Hund’s coupling between itinerant holes<br />

and localized spins. However, below θ, the negative MR gradually deviates from the<br />

scaling relati<strong>on</strong> with a decrease in T and is much enhanced around an AF transiti<strong>on</strong><br />

temperature (TN). Furthermore, a comp<strong>on</strong>ent of positive MR appears around TN. Such<br />

a MR behavior is due to a critical enhancement of spin fluctuati<strong>on</strong> around TN, which<br />

may cause a n<strong>on</strong>trivial promoti<strong>on</strong> of a 120° AF state by the Mg substituti<strong>on</strong> [3,4].<br />

[1] T. Okuda, S. Ooz<strong>on</strong>o, T. Kihara, and M. Tokunaga, in preparati<strong>on</strong>. [2] N. Furukawa, J. Phys. Soc.<br />

Jpn. 63, 3214 (1994). [3] T. Okuda, N. Jufuku, S. Hidaka, and N. Terada, Phys. Rev. B 72, 144403 (2005).<br />

[4] T. Okuda, Y. Beppu, Y. Fujii, T. Onoe, N. Terada, S. Miyasaka, Phys. Rev. B 77, 134423 (2008).<br />

RH05<br />

RH06<br />

RH07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Lifshitz transiti<strong>on</strong> with interacti<strong>on</strong>s in high magnetic fields: applicati<strong>on</strong><br />

to CeIn 3<br />

Pedro Schlottmann*<br />

Department of Physics, Florida State University, USA<br />

MOVED<br />

Novel colossal magnetoresistance in NaCr 2 O 4<br />

Hiroya Sakurai 1 *, Taras Kolodiazhnyi 1 , Yuichi Michiue 2 and Eiji Takayamamuromachi<br />

2<br />

1 Superc<strong>on</strong>ducting Properties Unit, Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

2 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

We recently discovered new chromium oxide, NaCr 2 O 4 , to have calcium ferrite<br />

type structure, in which spin frustrati<strong>on</strong> is expected. The compound shows cantedantiferromagentic<br />

transiti<strong>on</strong> at TN = 125 K and Arrhenius-type temperature dependence<br />

of electrical resistivity. The resistivity below TN is greatly suppressed by magnetic field<br />

and it remains to be a finite value at 0 K under H = 9 T. Thus, the magnetoresistance<br />

ratio, {rho(H)-rho(0)}/rho(0), becomes closer to -100% at low temperatures. The<br />

similar behavior has been observed in some manganites, such as Pr 0.7Ca 0.3MnO 3 and<br />

Nd 0.5Sr 0.5MnO 3, for which the competiti<strong>on</strong> between charge-ordered insulating phase<br />

and ferromagnetic metallic phase causes colossal magnetoresistance (CMR) through<br />

the first-order transiti<strong>on</strong>. Unlike them, however, NaCr2O4 shows no thermal or field<br />

hysteresis in its physical properties, and there is no ferromagnetic metallic phase<br />

compositi<strong>on</strong>ally close to NaCr 2O 4. Therefore, CMR of the compound is c<strong>on</strong>sidered to<br />

be caused by a new mechanism. The magnetism of Ca1-xNaxCr 2O 4 str<strong>on</strong>gly suggests<br />

unusual electr<strong>on</strong>ic state of Cr 4+ i<strong>on</strong>s. We will present a possible mechanism of CMR in<br />

NaCr 2O 4, in which spin frustrati<strong>on</strong> and the electr<strong>on</strong>ic state of Cr 4+ i<strong>on</strong>s play a key role.<br />

Low field study of Hall effect in GdB6 M. A. Anisimov 1 *, A. V. Bogach 1 , V. V. Glushkov 1 , S. V. Demishev 1 , N. A. Samarin 1 , N.<br />

Yu. Shitsevalova 2 , A. V. Levchenko 2 , V. B. Filipov 2 and N. E. Sluchanko 1<br />

1<br />

Low Temperatures and Cryogenic Engineering Dept., A.M.Prokhorov General<br />

Physics Institute of RAS, Russia<br />

2<br />

Institute for Problems of Materials Science NAS, Ukraine<br />

GdB 6 plays the important role for understanding of the mechanisms resp<strong>on</strong>sible for the<br />

antiferromagnetic (AF) state formati<strong>on</strong> in the rare earth hexaborides. However the magnetic<br />

structure of GdB 6 which is characterized by two successive AF transiti<strong>on</strong>s (AF(I) ordering<br />

below T_N~15.5K, and AF(II) phase at T^*~4.7K) is still the subject of discussi<strong>on</strong> [1]. In<br />

current work we present the comprehensive study of Hall effect <strong>on</strong> the high quality single<br />

crystals of GdB 6 in the wide temperature interval (2-120K) at low magnetic fields (H≤1T). In<br />

paramagnetic state Hall coefficient R_H is practically temperature independent and value of<br />

R_H~-4•10^{-4}cm^3/C detected with the high accuracy is in accord with the results of light<br />

hexaborides RB 6 (R-La, Ce, Pr, Nd) published previously [2],[3]. The temperature decrease<br />

below T_N induces the drastic enhancement of negative Hall coefficient (ΔR_H/R_H~ 64%).<br />

The magnetic ordering at T^* (AF(I)-AF(II) transiti<strong>on</strong>) is accompanied by the appearance of<br />

anomalous Hall effect which is detected in GdB 6 for the first time. The complex analysis of<br />

charge transport parameters suggests the possible effect of 5d-states spin density polarizati<strong>on</strong><br />

in AF and PM states of GdB 6.<br />

[1] M.Amara, S.E.Luca et al., Phys. Rev. B v. 72, p. 064447 (2005). [2] Y. Onuki, A.Umezawa et al., Phys. Rev. B v.<br />

40, p. 11195 (1989). [3] M.A.Anisimov, A.V.Bogach, V.V.Glushkov et al., arxiv c<strong>on</strong>d-mat:1006.0124v1<br />

July 8 - 13, 2012 Busan, Korea 161<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RH08<br />

Theoretical study of structures and mechanical properties of M-type<br />

hexag<strong>on</strong>al ferrites BaFe 12O 19<br />

W<strong>on</strong>ha Mo<strong>on</strong>*, Soye<strong>on</strong> Kim, Heejung Lee, Jaeho<strong>on</strong> Yeom, Sangw<strong>on</strong> Lee and Seok<br />

Bae<br />

LG innotek, Korea<br />

M-type hexag<strong>on</strong>al ferrite, BaFe 12O 19, has extensively studied in a wide range of<br />

applicati<strong>on</strong>s such as microwave devices and permanent magnets due to high Curie<br />

temperature, large saturati<strong>on</strong> magnetizati<strong>on</strong> and good chemical stability. In this paper,<br />

we have investigated the structure and elastic modulus of BaFe 12O 19 using atomistic<br />

simulati<strong>on</strong>s. An interatomic potential based <strong>on</strong> the shell model is used for the structure<br />

and properties of BaFe 12O 19. The shell model has been extensively used to a wide range<br />

of oxide materials since it is a simple and useful potential with the Coulomb interacti<strong>on</strong><br />

incorporated with the short-ranged term for i<strong>on</strong>ic characteristics, though it is incapable<br />

of describing the elemental comp<strong>on</strong>ents. The calculated results are in agreement<br />

with experiments and previous theoretical studies. To our knowledge, although many<br />

theoretical investigati<strong>on</strong>s have so far played an important role in understanding the<br />

properties of magnetic materials, there have been few theoretical studies using the<br />

interatomic potential for the structure and properties of BaFe 12O 19. The interatomic<br />

potential employed has been shown to be capable of describing the Ba-based hexag<strong>on</strong>al<br />

ferrites.<br />

1. P. Shepherd, K. K. Mallick and R. J. Green, J. Magn. Magn. Mater. 311 (2007) 683. 2. G. V. Lewis and C. R. A.<br />

Catlaw, J. Phys. C: Solid State Phys. 18 (1985) 1149. 3. P. Novak and J. Rusz, Phys. Rev. B 71 (2005) 184433.<br />

RH09<br />

N<strong>on</strong>linear susceptibility of gadolinium near curie temperature<br />

Takashi Shirane* and Shohei Sakurai<br />

Sendai Nati<strong>on</strong>al College of Technology, Japan<br />

The ac linear and n<strong>on</strong>linear susceptibilities of an elemental ferromagnetic gadolinium<br />

have been studied near the Curie temperature, to clarify the feature of the magnetic<br />

phase transiti<strong>on</strong> with special emphasis <strong>on</strong> the behavior below the Curie temperature.<br />

The temperature dependence of linear susceptibility is in good agreement with that of<br />

an experimental result reported in ref. [1]. The first observati<strong>on</strong> for the critical behavior<br />

of the n<strong>on</strong>linear susceptibility in gadolinium has been made at various field amplitudes.<br />

The behavior of the n<strong>on</strong>linear susceptibility is very sensitive to the field amplitude. The<br />

field dependence of the susceptibilities are explained <strong>on</strong> the basis of a mean field theory<br />

taken into account the domain structure[2]. The detailed discussi<strong>on</strong> will be shown the<br />

full paper in comparis<strong>on</strong> with magnetizati<strong>on</strong> curves at various temperature below the<br />

Curie temperature.<br />

[1] J. M. D. Coey, K. Gallangher, and V. Skumryev, J. Appl. Phys. 87 (2000) 7028. [2] T. Shirane,<br />

Statistical and C<strong>on</strong>densed Matter Physics: Over the Horiz<strong>on</strong>, ed. S. Fujita, T. Obata, and A. Suzuki<br />

(New York: Nova Science), p. 189-197, (2007).<br />

RH10<br />

Electr<strong>on</strong> correlati<strong>on</strong> and dynamical Jahn-Teller effect in orbitally<br />

degenerate system<br />

Joji Nasu and Sumio Ishihara*<br />

Department of Physics, Tohoku University, Japan<br />

Quantum spin liquid state is <strong>on</strong>e of the attractive subjects in correlated electr<strong>on</strong><br />

systems. Recently, a possibility of the quantum spin liquid state is experimentally<br />

reported in a layered copper oxide Ba 3CuSb 2O 9 where the orbital degree of freedom<br />

in a Cu i<strong>on</strong> and the dynamical Jahn-Teller effect (DJTE) are suggested to play some<br />

roles <strong>on</strong> an origin of the spin liquid state. Motivated from these recent experimental<br />

results, we study the DJTE in a spin-orbital coupled system. In particular, we focus<br />

<strong>on</strong> competitive or cooperative phenomena between the superexchange interacti<strong>on</strong> and<br />

the DJTE. A superexchange interacti<strong>on</strong> part is derived from the d-p model and the<br />

DJTE part for the low lying vibr<strong>on</strong>ic states is described by the orbital pseudo-spin and<br />

the lattice vibrati<strong>on</strong>. We analyze the model which combines the two interacti<strong>on</strong>s <strong>on</strong><br />

a h<strong>on</strong>eycomb lattice by using the Bethe approximati<strong>on</strong> and the exact diag<strong>on</strong>alizati<strong>on</strong><br />

method. We find that the magnetic order is unstable in a wide parameter regi<strong>on</strong> and a<br />

spin-singlet dimer state associated with an orbital order is realized. With increasing the<br />

DJTE, furthermore, the orbital order is str<strong>on</strong>gly suppressed and a res<strong>on</strong>ance state of the<br />

spin-orbital dimers appears.<br />

H. D. Zhou, et.al., Phys. Rev. Lett., 106 (2011) 147204.<br />

162 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RH11<br />

High-field NMR study <strong>on</strong> the charge in stability in quantum spin<br />

system Cu 3Mo 2O 9<br />

Keita Misoka 1, Takayuki Goto 1*, Haruhiko Kuroe 1, Tomoyuki Sekine 1, Takahiko Sasaki 2, Masashi<br />

Hase 3, Kunihiko Oka 4, Toshimitsu Ito 4 and Hiroshi Eisaki 4<br />

1 Department of Phisics, Sophia University, Japan<br />

2 Institute for Materials Research, Tohoku University, Japan<br />

3 Department of Phisics, Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

4 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology, Japan<br />

The quasi-<strong>on</strong>e-dimensi<strong>on</strong>al quantum spin system Cu 3Mo 2O 9 with the two spin-degrees of<br />

freedom, antiferromagnetic chain and dimer-like sites clinging around the chain undergoes<br />

the l<strong>on</strong>g-range antiferromagnetic order at 7.9 K, associated with a weak ferromagnetic<br />

moment. The system shows a small magnetizati<strong>on</strong> jump of 0.0033 μB at H* = 8.2 T, where<br />

the anomalous charge instability appears [1], suggesting an existence of tight coupling<br />

between spin and charge. In order to inverstigate the microscopic spin and charge states in<br />

the high magnetic field, we have utilized Cu-NMR technique, which separately probes the<br />

spin and charge in the chain site Cu 1, the dimer like sites Cu 2 and Cu 3 through hyperfine<br />

coupling and electric quadruple interacti<strong>on</strong> respectively. In this presentati<strong>on</strong>, we show by<br />

detailed analyses of spectra taken under a wide range of filed up to 17.5 T that the ordered<br />

antiferromagnetic moment is dominated by Cu 1, while the dimer-like sites <strong>on</strong>ly feel a<br />

uniform hyperfine field but staggered <strong>on</strong>e, and that the change inhomogenizati<strong>on</strong> takes<br />

place in Cu 2 and Cu 3 in the vicinity of the field of magnetizati<strong>on</strong> jump H*.<br />

1 T. Hamasaki et al., Phys. Rev. B77 134419 (2007).<br />

RH12<br />

Anisotropic spin excitati<strong>on</strong>s in spin-Peierls CuGeO3 Kazuhiko Ikeuchi 1 , Fumio Mizuno 2 , Ryoichi Kajimoto 1 , Yasuhiro Inamura 3 , Mitsutaka Nakamura 3 ,<br />

Kenji Nakajima 3 , Masaki Fujita 4 , Kazuya Aizawa 3 and Masatoshi Arai 3<br />

1<br />

Research Center for Neutr<strong>on</strong> Science and Technology, Comprehensive Research Organizati<strong>on</strong> for<br />

Science and Society, Japan<br />

2<br />

Department of Physics, Tohoku University, Japan<br />

3<br />

Neutr<strong>on</strong> Science Secti<strong>on</strong>, J-PARC Center, Japan<br />

4<br />

Institute for Material Research, Tohoku University, Japan<br />

Even though CuGeO 3 is a well-known 1-dimensi<strong>on</strong>al quantum spin system that shows magnetic<br />

transiti<strong>on</strong> into a dimerized state with a sp<strong>on</strong>taneous lattice distorti<strong>on</strong>, it is not clear whether it is<br />

an archetypal material of a spin-Peierls system. In fact, neutr<strong>on</strong> scattering experiment has still not<br />

succeeded in assignment of the soft ph<strong>on</strong><strong>on</strong> mode accompanying the magnetic transiti<strong>on</strong>. Actually,<br />

due to an antiferromagnetic coupling between the neighboring spin chains, the dimerizati<strong>on</strong> in the<br />

spin chain is close to the critical state [1][2][3], and it should not have a str<strong>on</strong>g effect <strong>on</strong> a ph<strong>on</strong><strong>on</strong>. In<br />

this time, we performed inelastic neutr<strong>on</strong> scattering experiment <strong>on</strong> CuGeO 3 with the Fermi chopper<br />

spectrometer 4SEASONS at MLF/J-PARC in Japan. In order to further understand the inter-chain<br />

coupling, we measured intensity-maps in a 4-dimensi<strong>on</strong>al (q,ω) space including the inter-chain<br />

directi<strong>on</strong> due to rotati<strong>on</strong> of the aligned 17.2 g CuGeO 3 single crystals in horiz<strong>on</strong>tal plane. In this<br />

experiment, we have clarified an anisotropy of the magnetic excitati<strong>on</strong>s below the spin-Peierls<br />

transiti<strong>on</strong> temperature. This result suggests the inter-chain coupling correlates with the dimerizati<strong>on</strong><br />

in the spin-Peierls state <strong>on</strong> CuGeO 3. We will present the detail of the magnetic excitati<strong>on</strong>s together<br />

with new other features recently discussed in several theoretical models.<br />

[1] M. Nishi et al., PRB, 50,6508 (1994). [2] J. Riera et al., PRB, 51,16098 (1995). [3] M. C. Martin et al., PRB, 56, 3173 (1997).<br />

RH13<br />

Neutr<strong>on</strong> inelastic scattering <strong>on</strong> spin-peierls system TiOBr<br />

Tetsuya Yokoo 1 , Shinichi Itoh 1 , Daichi Kawana 1 and Jun Akimitsu 2<br />

1 High Energy Accelerator Research Organizati<strong>on</strong>, Japan<br />

2 Aoyama Gakuin University, Japan<br />

Newly proposed spin-Peierls system TiOX (X: Cl, Br) has been revealed showing<br />

exotic structural and magnetic properties such as a successive phase transiti<strong>on</strong>, <strong>on</strong>edimensi<strong>on</strong>al<br />

(1D) nature associated with orbital ordering of Ti i<strong>on</strong>s and super-lattice<br />

structure being related to the Peierls instability. It is pointed out that resulting <strong>on</strong>ly from<br />

an arrangement of Ti dxy orbital, the formati<strong>on</strong> of 1D spin chains and the spin-Peierls<br />

transiti<strong>on</strong> will be realized. Recently, it has been dem<strong>on</strong>strated that TiOBr also exhibits<br />

two successive phase transiti<strong>on</strong>s similar to TiOC l at Tc1=27K and Tc 2=47K. Here we<br />

carried out inelastic neutr<strong>on</strong> experiments in order to see the evidence of spin-Peierls<br />

transiti<strong>on</strong>. The inelastic spectrum with a large amount of poly crystalline sample of<br />

TiOBr shows the localized signal in the vicinity of the magnetic z<strong>on</strong>e center Q=0.9A-1.<br />

Observed spin gap like signal lies at energy of ΔE=10meV. The gap energy in TiOBr is<br />

expected much higher from measured thermodynamic properties and by analogy with<br />

TiOCl. C<strong>on</strong>stant Q cuts of the observed S(Q,E) map show some Q-dependent structure<br />

in its intensity indicating the signal is sample oriented. The Q structure quite reveals<br />

the intensity is well explained by the powder averaged dynamical structure.


RH14<br />

Physical properties of the novel triangular-lattice silver oxides Ag 2MO 2<br />

(M = Co, Ga, Rh)<br />

Hiroyuki Yoshida and Masaaki Isobe<br />

Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

Triangular antiferromagnets have been extensively studied by many scientists in terms<br />

of geometrical frustrati<strong>on</strong>. According to current theories, triangular antiferromagnets<br />

show various exotic magnetic properties, e.g. chirality order, Kosterlitz-Thouless<br />

transiti<strong>on</strong>, a partially disordered state, etc. A series of layered Ag 2MO 2 compounds,<br />

where M is a transiti<strong>on</strong> metal, are possible model compounds of triangular<br />

antiferromagnets. The crystal structure of Ag 2MO 2 c<strong>on</strong>sists of alternate stacks of an<br />

M 3+ O 2 layer and a (Ag 2)+ layer. The former includes a triangular lattice of the M 3+ i<strong>on</strong>s,<br />

while the latter provides itinerant electr<strong>on</strong>s from the quarter-filled Ag 5s band. The<br />

triangular lattices are well separated from each other by the n<strong>on</strong>-magnetic double Ag<br />

layer. A path does not exist for superexchange interacti<strong>on</strong> between the M 3+ spins <strong>on</strong> the<br />

adjacent triangular lattices. In additi<strong>on</strong>, no cati<strong>on</strong> disorder is expected between the M<br />

and Ag i<strong>on</strong>s. Ag 2MO 2 is, therefore, c<strong>on</strong>sidered a suitable system to study the magnetic<br />

properties of triangular antiferromagnets. We recently succeeded in synthesizing<br />

Ag 2MO 2, M = Co, Ga, Rh, for the first time using a high-pressure technique. The<br />

details of physical properties of Ag 2MO 2 will be reported.<br />

RH15<br />

Electrical and thermal transport properties of the polycrystalline<br />

(Cr 86Ru 14)1-xVx alloy system<br />

Leelakrishna Reddy, Aletta Roletta Prinsloo, Charles Johannes Sheppard and Andre<br />

Micheal Strydom<br />

Physics, University of Johannesburg, South Africa<br />

Thermopower (S) and electrical resistivity (ρ) measurements <strong>on</strong> the (Cr 86Ru 14)1xVx<br />

alloy system with 0≤x≤0.144 reveal unique behaviour[1,2,3]. The <strong>on</strong>set of a<br />

commensurate (C) itinerant-electr<strong>on</strong> antiferromagnetic spin-density-wave (SDW)<br />

structure is marked by anomalies in ρ(T) and S(T), associated with the Neel temperature.<br />

Focus is <strong>on</strong> the thermopower as it is more sensitive to the changes in the electr<strong>on</strong>ic<br />

structure and scattering mechanisms that are of importance at the SDW transiti<strong>on</strong>[2].<br />

For this series S(T) shows a broad valley for x≤0.032. The valley gradually becomes<br />

more shallow with increasing x and is eventually replaced by a surplus of positive<br />

thermopower for x=0.074, for which parallelism is seen between ρ(T) and S(T) as<br />

in the case of Cr-V[2]. The size of the magnetic c<strong>on</strong>tributi<strong>on</strong>s to S and ρ str<strong>on</strong>gly<br />

correlates and decreases with increasing x; attributed to the additi<strong>on</strong> of V to the system<br />

that destabilizes the CSDW structure. The effect of the additi<strong>on</strong> of V will be explained<br />

in terms of a model that relates the behaviour of S(T) to the energy dependence of the<br />

decrease in the scattering rate of electr<strong>on</strong>s by ph<strong>on</strong><strong>on</strong>s and an increase in the resistivity<br />

<strong>on</strong> decreasing temperature due to a decrease in the Fermi surface area[3].<br />

[1] L. Reddy et al., J. Appl. Phys. 103 (2008) 07C903-1. [2] E. Fawcett et al., Rev. Mod. Phys. 66<br />

(1994) 25. [3] A. L. Trego et al., Phys. Rev. 166 (1968) 495.<br />

RH16<br />

Magnetic properties of the layered triangular-lattice antiferromagnets<br />

CsM(MoO 4)2 (M=V, Fe)<br />

Masahiko Isobe and Yutaka Ueda<br />

ISSP, Univ. of Tokyo, Japan<br />

Two-dimensi<strong>on</strong>al triangular lattice antiferromagnets are of great interest c<strong>on</strong>cerning<br />

the ordering in frustrated spin system. We have prepared powder samples of the<br />

layered triangular-lattice antiferromagnets CsFe(MoO 4)2 and CsV(MoO 4)2 and have<br />

investigated the magnetic properties. In CsFe(MoO 4)2, a structural phase transiti<strong>on</strong> at<br />

around 365K from P3m1 to P3 was detected. Also we observed the magnetic transiti<strong>on</strong><br />

at 4.4 K for CsFe(MoO 4)2 and 26 K for CsV(MoO 4)2. The magnetic properties of<br />

CsFe(MoO 4)2 are similar to that of the multiferroic RbFe(MoO 4)2.<br />

RH17<br />

RH18<br />

RH19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Kitaev-Heisenberg magnetism in h<strong>on</strong>eycomb iridates A 2IrO 3(A=Li,Na)<br />

Akihiko Kato 1, Tomohiro Takayama 2* and Hidenori Takagi 3<br />

1 Department of Applied Chemistry, University of Tokyo, Japan<br />

2 Department of Advanced Materials Science, University of Tokyo, Japan<br />

3 Department of Physics, University of Tokyo, Japan<br />

5d transiti<strong>on</strong>-metal oxides can have unique properties because of the str<strong>on</strong>g spin-orbit coupling and<br />

relatively weak electr<strong>on</strong> correlati<strong>on</strong>s. Layered perovskite iridate Sr 2IrO 4, for example, was revealed<br />

to be Jeff=1/2 Mott-insulator where spin and orbital degrees of freedom are entangled with including<br />

complex phase i[1]. The magnetism of such Jeff=1/2 Mott-insulator might be different from 3d<br />

transiti<strong>on</strong>-metal Mott-insulator.Indeed in iridates, the superexchange coupling between Ir-O-Ir was<br />

proposed to be anisotropic ferromagnetic when IrO 6 octahedra form edge-sharing network, due<br />

to the complex phase[2]. As a c<strong>on</strong>sequence, the spin-liquid state based <strong>on</strong> the Kitaev-model was<br />

theoretically predicted when such edge-shared IrO 6 octahedra compose a h<strong>on</strong>eycom network. Such<br />

unique lattice topology can be found in layered iridatesA 2IrO 3(A=Li,Na). Na 2IrO 3 is a frustrated<br />

antiferromagnet with Tn=17K, and the θw=-125K. The str<strong>on</strong>g antiferromagnetic interacti<strong>on</strong> is<br />

likely due to direct interacti<strong>on</strong> between Ir 5d electr<strong>on</strong>s. Meanwhile, Li 2IrO 3 exhibited less frustrated<br />

magnetism with Tn=12K and θw=-12K, even with the similar structure. We argue that this seemingly<br />

n<strong>on</strong>-frustrated magnetism of Li 2IrO 3 likely originates from a coexistence of direct antiferromagnetic<br />

and ferromagnetic superexchange interacti<strong>on</strong>, exemplifying the Kitaev-Heisenberg model[3]. The<br />

difference might come from the local structure, the h<strong>on</strong>eycomb of Na 2IrO 3 is distorted but that of<br />

Li 2IrO 3 is closer to ideal h<strong>on</strong>eycomb.<br />

[1] B.J.Kim et al., Science 323,1329(2009) [2]G.Jackeli and G.Khaliullin, Phys.Rev.Lett. 102,017205(2009) [3]<br />

J.Chaloupka et al., Phys.Rev.Lettt. 105,027204 (2010)<br />

Effects of the annealing c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the magneto-transport<br />

properties of La 0.7Sr 0.3Mn 1+dO 3-manganese oxide composites<br />

Sang-im Yoo 1 * and Hyo-jin Kim 2<br />

1 Department of Materials Science and Engineering, Seoul nati<strong>on</strong>al university, Korea<br />

2 Department of Materials Science and Engineering, Seoul Nati<strong>on</strong>al University, Korea<br />

The effects of the annealing c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the magneto-transport properties of<br />

the pure La 0.7Sr 0.3MnO 3(LSMO) and LSMO-manganese oxide composites were<br />

carefully investigated in this study. While the ferromagnetic-paramagnetic transiti<strong>on</strong><br />

temperatures of all polycrystalline samples were insignificantly varied in the range<br />

of 359~368 K, low field magnetoresistance (LFMR) properties and dMR/dH values<br />

were remarkably improved for the composite samples annealed at relatively high<br />

temperature. For instance, with increasing the annealing temperature from 1300 to<br />

1450°C, the LFMR ratios of 95 mol% LSMO - 5 mol% Mn2O3 composite sample<br />

were increased from 0.8 % to 1.1 % at 300 K in 0.5 kOe, suggesting that a magnetic<br />

disorder at the LSMO grain boundary, known as a key factor suppressing effective<br />

spin-dependent scattering, could be greatly improved by high temperature annealing<br />

process. Detailed annealing effects <strong>on</strong> the magneto-transport properties of samples<br />

will be presented for a discussi<strong>on</strong>. This work was supported by the Korea Research<br />

Foundati<strong>on</strong> Grant funded by the Korean Government (MOEHRD, Basic Research<br />

Promoti<strong>on</strong> Fund) (KRF-0417-20100021)<br />

Temperature dependence of spin lattice relaxati<strong>on</strong> time of prot<strong>on</strong><br />

NMR in mixed antiferromagnets A 1-xBxC l2-2H 2O<br />

Tatsuichi Hamasaki 1 , Kazuko Zenmyo 2 and Hidenori Kubo 2<br />

1 Physics Department, Kyushu Sangyo University, Japan<br />

2 Fukuoka Institute of Technology, Japan<br />

In the mixed antiferromagnet systems Ni 1-xCoxC l2_2H 2O and Ni1-xMnxC l2_2H 2O,<br />

the Co substituti<strong>on</strong> increases a little the transiti<strong>on</strong> temperature and the Mn substituti<strong>on</strong><br />

decreases the transiti<strong>on</strong> temperature rapidly. In Ni-Co system, the c<strong>on</strong>centrati<strong>on</strong><br />

dependence of the phase transiti<strong>on</strong> temperature is well explained by simple molecular<br />

field theory. But, in Ni-Mn system, molecular field theory cannot explain it sufficiently.<br />

Thus Mn spins in NiC l2_2H 2O crystal show the peculiar behavior. Then, we have<br />

measured the temperature dependence of the spin-lattice relaxati<strong>on</strong> time of prot<strong>on</strong><br />

NMR, in order to understand the specificity of the Mn spins. We have prepared the<br />

mixed antiferromagnets A 1-xBxC l2-2H 2O (A, B=Co, Mn, Ni). In Co-M (M=Ni,<br />

Mn) system, in comparis<strong>on</strong> with the Ni substituti<strong>on</strong>, the Mn substituti<strong>on</strong> induces a<br />

significant impact <strong>on</strong> the relaxati<strong>on</strong> time. In Mn-M (M=Ni, Co) system, the relaxati<strong>on</strong><br />

time is affected by a small amount of substituti<strong>on</strong>. In Mn-Co system, the reentrant<br />

spin-glass phase appears at low temperature. The strange behavior of the relaxati<strong>on</strong><br />

time at low temperature is believed to reflect that. A similar trend is seen at the low<br />

temperatures in the case of Ni substituti<strong>on</strong>, too. We suppose that this may be attributed<br />

to a kind of the instability of Mn spins.<br />

July 8 - 13, 2012 Busan, Korea 163<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RH20<br />

Electr<strong>on</strong>ic Structure and magneto-optical properties of Co 2MnX alloys<br />

where X = Ge, Sn and Pb: a first-principles investigati<strong>on</strong> in LDA+U<br />

approach<br />

Tran Van Quang 1 , Jae Il Lee 2 and Miyoung Kim 3<br />

1 Dept. of Physics, Ajou University, Suw<strong>on</strong> 443-749, Korea<br />

2 Dept of Physics, Inha University, Inche<strong>on</strong> 402-751, Korea<br />

3 Divisi<strong>on</strong> of Energy System Research, Ajou University, Suw<strong>on</strong> 443-749, Korea<br />

We report our ab initio calculati<strong>on</strong>al results <strong>on</strong> the electr<strong>on</strong>ic structures and magnetooptical<br />

(MO) properties of the ferromagnetic Co 2MnX alloys where X= Ge, Sn and<br />

Pb. Employing the +U correcti<strong>on</strong>s for the 3d valence bands of transiti<strong>on</strong> metal atoms<br />

in additi<strong>on</strong> to the c<strong>on</strong>venti<strong>on</strong>al local density approximati<strong>on</strong> (LDA), we investigate the<br />

correlati<strong>on</strong> effect <strong>on</strong> the MO spectra in polar geometry as well as the detailed electr<strong>on</strong>ic<br />

structures using the all-electr<strong>on</strong> FLAPW [1] method. Results show that the correlati<strong>on</strong><br />

effect results in a blue-shift of the peak positi<strong>on</strong>s and the large enhancement of the MO<br />

spectra compared to the LDA results. We find that our results can be attributed to the<br />

increased t2g-eg splitting of spin minority d-bands of both Co and Mn atoms, which<br />

indicates the suppressi<strong>on</strong> of diag<strong>on</strong>al elements of optical c<strong>on</strong>ductivity at energy regi<strong>on</strong><br />

of 1~2 eV where the interband transiti<strong>on</strong>s are forbidden.[2]<br />

[1] E. Wimmer, K. Krakauer, M. Weinert, and A. J. Freeman, Phys. Rev. B 24, 864 (1981). [2]<br />

Support by Basic Science Research Program (NRF-2010-0005387) and Priority Research Centers<br />

(2010-0029617) through the Nati<strong>on</strong>al Research Foundati<strong>on</strong> of Korea.<br />

RH21<br />

2D Heisenberg antiferromagnetism in spin-orbit Mott insulator Sr 2IrO 4<br />

Akiyo Matsumoto 1 , Tomohiro Takayama 1 and Hide Takagi 2 *<br />

1 Department of Advanced Materials, The University of Tokyo, Japan<br />

2 Department of Physics, The University of Tokyo, Japan<br />

In 5d iridates, the interplay between spin-orbit coupling and modest electr<strong>on</strong> correlati<strong>on</strong><br />

produces novel electr<strong>on</strong>ic phases. Sr 2IrO 4 was recently found to be a Jeff =1/2 Mott<br />

insulator where spin and orbital degrees of freedom are entangled[1]. The magnetic<br />

coupling between such Jeff = 1/2 state, which could be critically different from that in<br />

3d-based Mott insulators, is of particular interest. For example, the magnetic coupling<br />

between Ir was theoretically proposed to be isotropic Heisenberg-type when IrO 6 octahedra<br />

form corner-sharing network[2]. We focused <strong>on</strong> Sr 2IrO 4 to reveal the magnetism of such<br />

spin-orbit Mott insulator. Sr 2IrO 4 crystallizes in a K2NiF4-type perovskite structure, and<br />

magnetically orders at 240K. We investigated the detailed magnetic susceptibilities <strong>on</strong><br />

the single crystals. The ground state was found to be antiferromagnetism, and the inplane<br />

susceptibility steeply increases just above the transiti<strong>on</strong> temperature likely due to<br />

Dzialloshinski-Moriya interacti<strong>on</strong>. Meanwhile, at higher temperatures, the in- and out-ofplane<br />

susceptibilities were almost isotropic. By analyzing the susceptibilities, we found that<br />

they can be well described by the 2D Heisenberg antiferromagnetism. This indicates that<br />

even in the limit of str<strong>on</strong>g spin-orbit coupling, Sr 2IrO 4 displays the isotropic Heisenberg<br />

magnetism. This situati<strong>on</strong> c<strong>on</strong>trast with the 3d oxides, where spin-orbit coupling is<br />

resp<strong>on</strong>sible for magnetic anisotropy.<br />

[1] B. J. Kim et al., Science 323,1329 (2009) [2] G.Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009)<br />

RH22<br />

Magnetoresistance and magnetic properties of oxygen deficient (Sr,Y)<br />

(Fe,Co)O3 perovskites<br />

Jean-marie Le Bret<strong>on</strong> 1 *, Youssef Rizki 1 , Yohann Breard 2 , Luc Lechevallier 1 and<br />

Antoine Maignan 2<br />

1<br />

Groupe de Physique des Materiaux - UMR 6634, CNRS - Universite de Rouen,<br />

France<br />

2<br />

CRISMAT, UMR 6508 CNRS, ENSICAEN - Universite de Caen, France<br />

The magnetic and magnetoresistive properties of oxygen deficient (Sr,Y)(Co,Fe)<br />

O 3 perovskites have been investigated in relati<strong>on</strong> with the compositi<strong>on</strong>. The valence<br />

state of Fe has been probed by 57Fe Mossbauer spectrometry. Sr 1-xYxFe 0.8Co 0.2O 3-d<br />

and Sr 0.8Y 0.2Co 1-xFexO 3-d series were more particularly investigated. It appears that the<br />

progressive replacement of Sr2+ by Y3+ and the Co/Fe substituti<strong>on</strong> lead to a change<br />

of the valence state of Fe and to a drastic change of the magnetic and magnetoresistive<br />

properties, in relati<strong>on</strong> with the variati<strong>on</strong> of the Fe4+/Fe3+ ratio and the change in<br />

the oxygen c<strong>on</strong>tent. It is shown that the Sr 0.8Y 0.2Co 0.5Fe 0.5O 3-d reveals the highest<br />

magnetoresistance effect, in relati<strong>on</strong> with the fact that the magnetic field induced<br />

ferromagnetic alignement of the Fe/Co magnetic moments allows more metallic<br />

pathaways to be created. This work was supported by the French Agence Nati<strong>on</strong>ale de<br />

la Recherche (project ANR-08-BLAN-0005-01).<br />

164 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RH23<br />

High field element selective magnetometry in erbium ir<strong>on</strong> garnet<br />

Cornelius Strohm*, Thomas Roth, Peter J. E. M. Van Der Linden, Olivier Math<strong>on</strong> and<br />

Sakura Pascarelli<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, 6 rue Jules Horowitz 38000 Grenoble,<br />

France<br />

Ferrimagnets play an important role for applicati<strong>on</strong>s as well as from a fundamental point<br />

of view. The rare earth ir<strong>on</strong> garnets for example were at the heart of the dem<strong>on</strong>strati<strong>on</strong><br />

of the local molecular field theory [1] and later used for bubble memories, microwave<br />

devices and optival isolators. The ferrimagnetic superexchange between the rare earth<br />

and ir<strong>on</strong> cati<strong>on</strong>s being mainly determined by b<strong>on</strong>d angles and distances in the oxygen<br />

polyhedra, results in molecular fields of the order of tens of Tesla [2, 3]. We have perfomed<br />

element selective magnetometry <strong>on</strong> samples of Erbium Ir<strong>on</strong> Garnet, using energy<br />

dispersive x-ray magnetic circular dichroism at the Fe K-edge and the Erbium L-edges.<br />

Pulsed fields of 30 T were generated by a high duty cycle miniature coil [4] and the signal<br />

was acquired using a multiframe detecti<strong>on</strong> scheme exploiting the entire pulse durati<strong>on</strong> of<br />

1 ms [5]. Here we discuss mainly the results obtained at the Fe K-edge. At 65 K, below<br />

the compensati<strong>on</strong> point, two successive field induced phase transiti<strong>on</strong>s and the reversal of<br />

the net magnetizati<strong>on</strong> of the Fe sublattices in the intermediate canted phase were observed,<br />

while the Fe signal remains unchanged at 100 K, above the compensati<strong>on</strong> point.<br />

[1] L. Neel Science 174, 985 (1971). [2] A. E. Clark and E. Callen J. Appl. Phys. 39, 5972, (1968). [3] K.<br />

Nakao, T. Goto and N. Miura J. of Magn. Magn. Mat. 54, 1363, (1986). [4] P. J. E. M. van der Linden<br />

et al. Rev. Sci. Instrum. 79, 075104, (2008). [5] C. Strohm et al. J. of Synchrotr<strong>on</strong> Rad. 18, 224, (2011).<br />

RH24<br />

THz and infrared excitati<strong>on</strong> spectrum below the Jahn-Teller transiti<strong>on</strong><br />

in Sr 3Cr 2O 8<br />

Zhe Wang 1 *, Michael Schmidt 1 , Franz Mayr 1 , Diana Quintero-castro 2 , A. T. M.<br />

Nazmul Islam 2 , Bella Lake 2 , Hans-albrecht Krug V<strong>on</strong> Nidda 1 , Alois Loidl 1 and<br />

Joachim Deisenhofer 1<br />

1 Experimental Physics 5, Intitute for Physics, Augsburg University, Germany<br />

2 Helmholtz-Zentrum Berlin fur Materialien und Energie, Germany<br />

We report <strong>on</strong> optical excitati<strong>on</strong>s observed recently in Sr 3Cr 2O 8 by THz and infrared<br />

spectroscopy. Low-energy excitati<strong>on</strong>s below 3 THz are detected by THz time domain<br />

spectroscopy including the spin singlet to triplet excitati<strong>on</strong>s.[1] These excitati<strong>on</strong>s<br />

can be divided into two different classes according to the temperaturedependent<br />

properties. One is emergent right below the Jahn-Teller transiti<strong>on</strong> temperature, which<br />

is determined by specific heat measurement to occur at 285 K. [1,2] The other appears<br />

<strong>on</strong>ly below 100 K, where the fluctuati<strong>on</strong>s are sufficiently suppressed, c<strong>on</strong>sistent with<br />

the temperature dependence of low-energy Raman modes. [3] Infrared transmissi<strong>on</strong><br />

measurements reveal a broad crystal-field excitati<strong>on</strong>, which can be associated with an<br />

electr<strong>on</strong>ic transiti<strong>on</strong> from E to T 2 orbital states.<br />

[1] Zhe Wang et al., Phys. Rev. B 83, 201102 (2011) [2] D. L. Quintero-Castro et al., Phys. Rev. B<br />

81, 014415 (2010) [3] D. Wulferding et al., Phys. Rev. B 84, 064419 (2011)<br />

RH25<br />

High-field multi-frequency ESR in the S=2 Heisenberg<br />

antiferromagnetic chain compound MnCl3(bpy) Masayuki Hagiwara 1 *, Shojiro Kimura 2 , Yuichi Idutsu 1 and Zentaro H<strong>on</strong>da 3<br />

1<br />

KYOKUGEN, Osaka University, Japan<br />

2<br />

IMR, Tohoku University, Japan<br />

3<br />

Graduate School of Science and Engineering, Saitama University, Japan<br />

We report the results of high-field multi-frequency ESR experiments at 1.3 K <strong>on</strong> a<br />

powder sample of MnCl 3 (bpy) (bpy=2, 2'-bipyridine). This compound is <strong>on</strong>e of the<br />

rare examples of the spin 2 quasi-<strong>on</strong>e-dimensi<strong>on</strong>al Heisenberg antiferromagnets, and<br />

the magnetic properties <strong>on</strong> tiny single crystal samples were reported previously [1].<br />

In our previous paper <strong>on</strong> this compound [2], we attained good agreement between<br />

experiment and calculati<strong>on</strong> <strong>on</strong> the temperature dependence of magnetic susceptibility<br />

and the high-field magnetizati<strong>on</strong> process at 1.3 K. In this work, we have observed<br />

some high-frequency res<strong>on</strong>ance modes with a zero-field gap of about 800 GHz that<br />

may corresp<strong>on</strong>d to the excitati<strong>on</strong> modes at q=0 in the energy dispersi<strong>on</strong> higher than the<br />

triplet excitati<strong>on</strong> mode of about 50 GHz at q=pi expected from the evaluated exchange<br />

c<strong>on</strong>stant and the g-value.<br />

[1] G.E. Granroth et al., Phys. Rev. Lett. Vol. 77 (1996) 1616. [2] M. Hagiwara et al., to be<br />

published in J. Phys.: C<strong>on</strong>f. Ser.


RI01<br />

Distributi<strong>on</strong> of magnetizati<strong>on</strong> in the random ising models.<br />

Kazuyuki Matsumoto 1 , Tatsuya Yoshimoto 1 , Hiroki Mizuno 1 , Takuya Okada 1 , Yosuke<br />

Ishikawa 1 and Yasuhiro Akutsu 2<br />

1 Department of Applied Sciences, Muroran Institute of Technology, Japan<br />

2 Department of Physics, Graduate School of Sciences, Osaka University, Japan<br />

We investigate the two- and three-dimensi<strong>on</strong>al random Ising models by the M<strong>on</strong>te<br />

Carlo method. The integrated distributi<strong>on</strong> functi<strong>on</strong>s of site-magnetizati<strong>on</strong> are calculated<br />

above and below the lower Griffith temperature. It is found that these functi<strong>on</strong>s have<br />

distinct character above or below this temperature for the two-dimensinal random Ising<br />

model. However, for the three-dimensi<strong>on</strong>al random Ising model, this distincti<strong>on</strong> cannot<br />

be observed <strong>on</strong> c<strong>on</strong>trast to the two-dimensi<strong>on</strong>al random Ising model. This behavior<br />

may be explained by the percolati<strong>on</strong> theory.<br />

RI02<br />

Berezinskii-Kosterlitz-Thouless trasiti<strong>on</strong> in two-dimensi<strong>on</strong>al p-state<br />

clock model<br />

Yuta Kumano*, Yusuke Tomita and Masaki Oshikawa<br />

ISSP, Japan<br />

In two dimensi<strong>on</strong>s, the Berezinskii-Kosterlitz-Thouless (BKT) transiti<strong>on</strong> occurs in<br />

models with the U(1) symmetry. The helicity modulus, which measures the rigidity<br />

against a global twist across the system, is useful for a detecti<strong>on</strong> of the transiti<strong>on</strong><br />

because of its distinctive feature, the universal jump at the transiti<strong>on</strong> point. Meanwhile,<br />

in the p-state clock model which has the Z_p symmetry, it is believed that the BKT<br />

transiti<strong>on</strong> occurs when p is greater than 4 since the study by Jose et al. in 1977[1].<br />

However, a recent numerical study by Baek et al. in 2010[2] detects an absence of the<br />

universal jump in the helicity modulus for p=5. This c<strong>on</strong>tradicts the Jose’s result. In this<br />

study, we show that the helicity modulus as defined by Baek (HMB) remains finite for<br />

any p with the high-temperature expansi<strong>on</strong>. Therefore, the universal jump in the HMB<br />

cannot be observed whether the transiti<strong>on</strong> is the BKT or not. This casts a questi<strong>on</strong> <strong>on</strong><br />

the physical meaning of the HMB. We will present a systematic study of the helicity<br />

modulus to clarify the universality class of the transiti<strong>on</strong> for p=5.<br />

[1] J. V. Jose, L. P. Kadanoff, S. Kirkpatrick and D. R. Nels<strong>on</strong>, Phys. Rev. B 16, 1217 (1977) [2] S. K.<br />

Baek and P. Minnhagen, Phys. Rev. E 82, 031102 (2010)<br />

RI03<br />

Influence of interplanar coupling <strong>on</strong> the entropy and specific heat of<br />

the bilayer ferromagnet<br />

Karol Szalowski and Tadeusz Balcerzak*<br />

Department of Solid State Physics, University of Lodz, Poland<br />

The Ising-Ising and Ising-Heisenberg bilayer with a simple quadratic lattice in<br />

each plane is studied using the pair approximati<strong>on</strong> (PA) method. The foundati<strong>on</strong><br />

of formalism used has been developed in [1], where the phase diagrams for the<br />

anisotropic bi- and multilayer system have been obtained. In this paper the method<br />

(leading to a complete self-c<strong>on</strong>sistent thermodynamics) is adopted for the entropy<br />

and magnetic specific heat calculati<strong>on</strong>s. An interesting case is dem<strong>on</strong>strated when the<br />

exchange integrals in both planes are of unequal strength, and the interplanar coupling<br />

(Ising or Heisenberg) is relatively weak. In such a case, two peaks in the temperature<br />

dependence of the specific heat can be observed. The isothermal change of the entropy<br />

caused by applicati<strong>on</strong> of the external magnetic field has been additi<strong>on</strong>ally calculated<br />

for a wide temperature range. The entropy change in the field also shows a double<br />

peak structure, similarly to the specific heat. Such a phenomen<strong>on</strong> may be of potential<br />

interest for investigati<strong>on</strong>s of the magnetocaloric effect. The results of the PA method<br />

have been compared with those obtained for two Ising-type planes by means of exact<br />

diag<strong>on</strong>alizati<strong>on</strong> for finite clusters.<br />

[1] K. Szalowski, T. Balcerzak, Physica A 391 (2012) 2197-2208.<br />

RI04<br />

RI05<br />

RI06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

N<strong>on</strong>trivial ferrimagnetism of the heisenberg model <strong>on</strong> the uni<strong>on</strong> jack<br />

strip lattice<br />

Tokuro Shimokawa* and Hiroki Nakano<br />

University of Hyogo, Japan<br />

In low-dimensi<strong>on</strong>al quantum spin systems with frustrati<strong>on</strong>, n<strong>on</strong>trivial magnetic<br />

phenomena occur due to str<strong>on</strong>g quantum fluctuati<strong>on</strong>. One of the phenomena is a n<strong>on</strong>-<br />

Lieb-Mattis (NLM) ferrimagnetism[1][2], which is different from the well-known<br />

Lieb-Mattis (LM) ferrimagnetism[3][4]. In c<strong>on</strong>trast to the LM ferrimagnetism,<br />

the sp<strong>on</strong>taneous magnetizati<strong>on</strong> of the NLM ferrimagnetism changes gradually<br />

with respect to the strength of frustrati<strong>on</strong>. Incommensurate modulati<strong>on</strong> with l<strong>on</strong>gdistance<br />

periodicity in local magnetizati<strong>on</strong>s is also a characteristic behavior of the<br />

NLM ferrimagnetism. However, there are <strong>on</strong>ly a few cases revealing the NLM<br />

ferrimagnetism, which prevents us with understanding the mechanism of the<br />

occurrence of the NLM ferrimagnetism. In this study, we examine the ground-state<br />

properties of the S=1/2 Heisenberg model <strong>on</strong> the Uni<strong>on</strong> Jack strip lattice. We find the<br />

existence of the NLM ferromagnetism by the numerical diag<strong>on</strong>alizati<strong>on</strong> and density<br />

matrix renormalizati<strong>on</strong> group methods. We also discuss the relati<strong>on</strong>ship between the<br />

NLM ferromagnetic state of this strip lattice and the intermediate canted state of the<br />

S=1/2 Heisenberg model <strong>on</strong> the two-dimensi<strong>on</strong>al Uni<strong>on</strong> Jack lattice[5].<br />

[1] S. Yoshikawa and S. Miyashita: J. Phys. Soc. Jpn. 74 (2005) Suppl. 71. [2] K. Hida: J. Phys.: C<strong>on</strong>dens. Matter<br />

19 (2007) 145225. [3] W. Marshall: Proc. Roy. Soc. A 232 (1955) 48. [4] E. Lieb and D. Mattis: J. Math. Phys. 3<br />

(1962) 749. [5] R. F. Bishop, P. H. Y. Li, D. J. J. Farnell, and C. E. Campbell: Phys. Rev. B 82 (2010) 024416.<br />

C<strong>on</strong>trol of quantum critical points in b<strong>on</strong>d disordered spin ladder<br />

materials<br />

S Ward 1 *, H Ryll 2 , D Biner 3 , K W Kramer 3 , K Kiefer 2 , D F Mcmorrow 1 and Ch Ruegg 4<br />

1<br />

L<strong>on</strong>d<strong>on</strong> Centre for Nanotechnology, University College L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

2<br />

Helmholtz Zentrum Berlin, Germany<br />

3<br />

Chemistry and Biochemistry, University of Bern, Switzerland<br />

4<br />

Laboratory for Neutr<strong>on</strong> Scatering, Paul Scherrer Institut, Switzerland<br />

Spin ladders are model systems of low dimensi<strong>on</strong>al quantum spins. There is now<br />

c<strong>on</strong>siderable interest in materials which realise these ideal systems with solvable<br />

Hamilt<strong>on</strong>ians and rich phase diagrams. An archetypal spin ladder material in the lowenergy<br />

regime is (C 5H 12N)2CuBr 4 whose phase diagram is completely accessible in<br />

laboratory magnetic fields. The rung (Jr) and leg (Jl) exchange are 12.8 K and 3.4<br />

K, respectively, and two field-c<strong>on</strong>trolled quantum critical points (QCPs) exist at 6.9<br />

T and 14.5 T. (C 5H 12N)2CuC l4 is a related spin ladder material. The superexchange<br />

between quantum Cu 2+ spins is c<strong>on</strong>trolled by the halide atoms and is lowered to<br />

Jr=3.4 K and Jl=1.3 K. The QCPs appear at the lower fields of 1.7 T and 4.3 T. A<br />

comm<strong>on</strong> structure and rich chemical flexibility in the superexchange pathways allows<br />

for partial halide substituti<strong>on</strong> to create the b<strong>on</strong>d disordered spin ladder materials<br />

(C 5H 12N)2CuBr 4(1-x)Cl4x, while retaining ideal spin ladder geometry. We present<br />

recent neutr<strong>on</strong> scattering work and measurements of the magnetic and thermodynamic<br />

properties <strong>on</strong> the substituti<strong>on</strong> series, and dem<strong>on</strong>strate explicitly substituti<strong>on</strong>-c<strong>on</strong>trolled<br />

modificati<strong>on</strong> of exchange interacti<strong>on</strong>s as well as the effects of b<strong>on</strong>d disorder <strong>on</strong> the<br />

spin ladder physics and QCPs.<br />

Triangular spin tubes with b<strong>on</strong>d randomness<br />

Yoko Miura 1 * and Hirotaka Manaka 2<br />

1 Suzuka Nati<strong>on</strong>al College of Technology, Japan<br />

2 Department Graduate School of Science and Engineering, Kagoshima University,<br />

Japan<br />

We studied X-ray diffracti<strong>on</strong> and magnetic susceptibility experiments <strong>on</strong> n<strong>on</strong>equilateral<br />

triangular spin tubes composed of α-KCr 1-xFexF 4 (x=0-0.13), which<br />

c<strong>on</strong>sists of <strong>on</strong>e-dimensi<strong>on</strong>al Heisenberg antiferromagnets coexisting with geometrically<br />

frustrated spin systems with b<strong>on</strong>d randomness. For x=0, an antiferromagnetic l<strong>on</strong>grange<br />

order occurred at TN1 = 2.5(1) K and another phase transiti<strong>on</strong> occurred at TN 2<br />

= 4.0(1) K, because superexchange interacti<strong>on</strong>s through the three Cr-F-Cr paths in<br />

each n<strong>on</strong>-equilateral triangle lost their equilibrium at low temperatures [1]. As a result,<br />

the values of spin-flop transiti<strong>on</strong> field drastically decreases with increasing x. This is<br />

probably due to the close correlati<strong>on</strong> between the spin structure in the antiferromagnetic<br />

ordered state and the crystal structure as theoretically predicted by Nenert and Palstra,<br />

i.e., a magnetoelectric linear effect in which a magnetic field in an antiferromagnetic<br />

ordered state induces electrical polarizati<strong>on</strong>. Thus we carefully verified the crystal<br />

structure for x = 0-0.13.<br />

[1] H. Manaka et al., J. Phys. Soc. Jpn. 80, 084714 (2011). [2] G. Nenert and T. T. M. Palstra, J.<br />

Phys.: C<strong>on</strong>dens. Matter 19, 406213 (2007).<br />

July 8 - 13, 2012 Busan, Korea 165<br />

Poster Thursday


Poster Thursday<br />

RI07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A new approach to the characterizati<strong>on</strong> of aging, rejuvenati<strong>on</strong>, and<br />

memory effects in magnetic systems<br />

Hiroaki Mamiya* and Shigeki Nimori<br />

Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

We introduce a new approach to study n<strong>on</strong>-equilibrium dynamics in magnetic systems. We<br />

found that simple ferromagnets such as pure terbium and nickel aluminide foils actually<br />

resembles typical spin glasses such as Cu 97Mn 3 and Cd 55Mn 45Te, in behavior of out-of-phase<br />

comp<strong>on</strong>ent of ac susceptibility and magnetic viscosity, when they are thermally perturbed<br />

after isothermal aging. Briefly, it is not enough to c<strong>on</strong>venti<strong>on</strong>ally measure such dissipative<br />

properties for characterizing the n<strong>on</strong>-equilibrium dynamics of these systems. In c<strong>on</strong>trast,<br />

in the spin glasses, the relaxati<strong>on</strong>s of the uniform magnetizati<strong>on</strong> were accelerated at a<br />

c<strong>on</strong>stant magnetic field, when the spin glasses were cooled/heated after the isothermal aging.<br />

Surprisingly, such relaxati<strong>on</strong>s were reversed when they were subsequently reheated/recooled<br />

to the original temperature, despite the persistence of the magnetic field. Because the uniform<br />

magnetizati<strong>on</strong> mirrors the global evoluti<strong>on</strong> of the spin c<strong>on</strong>figurati<strong>on</strong>, these reversi<strong>on</strong>s<br />

indicate that the spin c<strong>on</strong>figurati<strong>on</strong>s are sp<strong>on</strong>taneously restored to the original [1,2]. On the<br />

other hand, such reversi<strong>on</strong>s were never observed in the ferromagnets. This fact indicates that<br />

ferromagnetic correlati<strong>on</strong>s are unaffected by the thermal perturbati<strong>on</strong>s, unlike rejuvenati<strong>on</strong> in<br />

spin glasses. Thus, the observati<strong>on</strong>s of the uniform magnetizati<strong>on</strong> would be an additi<strong>on</strong>al key<br />

to clarifying the features of n<strong>on</strong>-equilibrium dynamics in magnetic systems.<br />

[1] H. Mamiya and S. Nimori, New J. Phys. 12 (2010) 083007. [2] H. Mamiya and S. Nimori, J.<br />

Appl. Phys, in press.<br />

RI08<br />

The linear solit<strong>on</strong> generated by Z 2 vortex in quantum antiferromagnet<br />

Pawel Rusek<br />

Institute of Physics, Wroclaw University of Technology, PL, Poland<br />

The order parameter of n<strong>on</strong>collinear Heisenberg antiferromagnet is a triad of<br />

orth<strong>on</strong>ormal vectors,i.e. the space of available states is isomorphic to SO 3 group. The<br />

topology of SO 3 manifold allows the existence Z 2 vortices in a system. We show that<br />

the anisotropy essentially changes the structure of Z 2 vortex in 2D spin system. On<br />

the scale larger than the scale la defined by weak anisotropy energy the Z 2 vortex is a<br />

terminati<strong>on</strong> of a linear solit<strong>on</strong> with the topological charge π1 (R) = Z 2 . In the soft core<br />

of this solit<strong>on</strong> the rotati<strong>on</strong> angle of triad θ rapidly changes from the anisotropy locked<br />

value θa to θ = π, jumps <strong>on</strong> the line to θ = -π, and then decreases to the value θa <strong>on</strong> the<br />

la distance from the line. The linear solit<strong>on</strong> can terminate <strong>on</strong> the other Z 2 vortex or it<br />

should go out to surface sample. The rapid change of θ in the soft core of linear solit<strong>on</strong><br />

causes the change of plaquette chirality there- the chirality change the sign <strong>on</strong> the line<br />

initiating the creati<strong>on</strong> of the chirality domain.<br />

RI09<br />

Exact results of a mixed spin-1/2 and spin-1 Ising model with bilinear<br />

and three-site four-spin interacti<strong>on</strong>s <strong>on</strong> decorated planar lattices<br />

Michal Jascur 1 *, Viliam Stubna 1 , Karol Szalowski 2 and Tadeusz Balcerzak 2<br />

1 Institute of Physics, P.J. Safarik University in Kosice, Park Angelinum 9, 040 13 Kosice, Slovak<br />

2 Department of Solid State Physics, University of Lodz, ul. Pomorska 149/153, 90-236 Lodz, Poland<br />

A mixed spin-1/2 and spin-1 Ising model <strong>on</strong> decorated planar lattices is investigated<br />

using a generalized decorati<strong>on</strong>-iterati<strong>on</strong> transformati<strong>on</strong> technique [1]. In additi<strong>on</strong> to the<br />

standard bilinear nearest-neighbor interacti<strong>on</strong>s, we also c<strong>on</strong>sider three-site four-spin<br />

interacti<strong>on</strong>s and the crystal field effects. In this c<strong>on</strong>tributi<strong>on</strong>, exact expressi<strong>on</strong>s for the<br />

partiti<strong>on</strong> functi<strong>on</strong>, critical temperatures and other thermodynamic quantities are obtained<br />

and analyzed. Performing numerical calculati<strong>on</strong>s, we have found that in additi<strong>on</strong> to the<br />

standard ferromagnetic and paramagnetic phases there exists in the system also a peculiar<br />

partly ordered phase, which possesses n<strong>on</strong>-zero entropy at T = 0 and appears <strong>on</strong>ly for zero<br />

bilinear exchange interacti<strong>on</strong>. In this phase, the decorating atoms occupy spin states ±1 and<br />

0 with equal probability at all temperatures, while the nodal spins-1/2 are perfectly aligned<br />

al<strong>on</strong>g easy axis and generate n<strong>on</strong>-zero magnetizati<strong>on</strong>. Our calculati<strong>on</strong>s primarily clarify<br />

the influence of many-body interacti<strong>on</strong>s in localized spin systems, which is apparently very<br />

different from the standard pair interacti<strong>on</strong>s due to the different symmetries of relevant<br />

terms in Hamilt<strong>on</strong>ian. However, the presented results may be of wider interest since the<br />

origin of the three-site four-spin interacti<strong>on</strong> is related to the magnetoelastic effect [2].<br />

This work has been supported under grant VEGA No. 1/0234/12. [1] M. Jascur, Physica A 252 (1998)<br />

217. [2] T. Iwashita, N. Uryu, J. Phys. C: Solid State Phys. 17 (1984) 855.<br />

166 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RI10<br />

Anomalous spin diffusi<strong>on</strong> <strong>on</strong> the two-dimensi<strong>on</strong>al percolating network<br />

in Rb 2Mn 0.6Mg 0.4F 4<br />

Shinichi Itoh*<br />

Institute of Materials Structure Science, High Energy Accelerator Research<br />

Organizati<strong>on</strong>, Japan<br />

Inelastic neutr<strong>on</strong> scattering experiments were performed <strong>on</strong> a two-dimensi<strong>on</strong>al dilute<br />

antiferromagnet, Rb 2Mn 0.6Mg 0.4F 4, with the magnetic c<strong>on</strong>centrati<strong>on</strong> being close to the<br />

percolati<strong>on</strong> c<strong>on</strong>centrati<strong>on</strong>, c_p = 0.593, well above the Neel temperature, and with<br />

a high energy-resoluti<strong>on</strong> of ΔE = 17.5 μeV. The energy spectrum obtained from the<br />

observed dynamical structure factor S(q,E) integrated over wave number, q, throughout<br />

almost the entire Brillouin z<strong>on</strong>e, showed a power law dependence, S(E) ~ E^{-x}.<br />

The diffusi<strong>on</strong> <strong>on</strong> a percolating network is anomalous and it has been predicted that the<br />

mean square displacement of a random walker is described by ~ t^{2/(2+θ)}<br />

with an exp<strong>on</strong>ent, θ, as a functi<strong>on</strong> of the time, t. The exp<strong>on</strong>ent in S(E) is described as<br />

x = 1 - Df/(2+θ) with Df being the fractal dimensi<strong>on</strong> of the medium. The observed<br />

exp<strong>on</strong>ent, x, was in good agreement with a theoretical value.<br />

RI11<br />

Quantum phase transiti<strong>on</strong>s in 1/3 plateau of the quantum spin tube<br />

Kouichi Okunishi 1 *, Masahiro Sato 2 , Toru Sakai 3 , Kiyomi Okamoto 4 and Chigaku<br />

Itoi 5<br />

1 Department of Physics, Niigata University, Japan<br />

2 Department of Physics and Mathematics, Aoyama Gakuin University, Japan<br />

3 Japan Atomic Energy Agency, SPring-8 and University of Hyogo, Japan<br />

4 Department of Physics, Tokyo Institute of Technology, Japan<br />

5 Department of Physics, Nih<strong>on</strong> University, Japan<br />

We study quantum phase transiti<strong>on</strong>s in the 1/3 plateau state of the three-leg spin-1/2<br />

tube, where the low-energy effective chirality degree of freedom plays an essential<br />

role. Using density matrix renormalizati<strong>on</strong> group and the effective chirality model,<br />

we find that the chirality liquid, a novel spin imbalance phase and the vector-spinchirality<br />

ordered phase emerge without closing the plateau spin gap, as the leg coupling<br />

increases. We also report the role of S_3-symmetry of the spin tube behind these<br />

quantum phase transiti<strong>on</strong>s in detail.<br />

K. Okunishi, M. Sato, T. Sakai, K. Okamoto and C. Itoi, arXiv:1109.0063<br />

RI12<br />

Cs 2CoC l4 - an effective XY-spin-½ compound in transverse magnetic<br />

fields<br />

Oliver Breunig 1 *, Eran Sela 2 , Benjamin Buldmann 2 , Markus Garst 2 , Petra Becker 3 ,<br />

Ladislav Bohaty 3 , Ralf Muller 1 and Thomas Lorenz 1<br />

1 II. Physikalisches Institut, University of Cologne, Germany<br />

2 Institut fur Theoretische Physik, University of Cologne, Germany<br />

3 Institut fur Kristallographie, University of Cologne, Germany<br />

Cs 2CoCl 4 is a model system for studying the magnetism of <strong>on</strong>e-dimensi<strong>on</strong>al spin<br />

chains with XY anisotropy. It c<strong>on</strong>tains CoCl 4 tetrahedra, which form <strong>on</strong>e-dimensi<strong>on</strong>al<br />

chains al<strong>on</strong>g the crystallographic b-axis. The orbital groundstate of Co 2+ is split by<br />

the crystal field into doublets and an easy-plane anisotropy of the magnetizati<strong>on</strong> is<br />

established. The ground-state doublet is separated from the first excited doublet state<br />

by approximately 15 K, such that at temperatures between 0.3 and 4 K the compound<br />

is well described by the <strong>on</strong>e-dimensi<strong>on</strong>al XXZ model. We compare experimental data<br />

of specific heat and thermal expansi<strong>on</strong> to numerical calculati<strong>on</strong>s of the XXZ model<br />

for transverse magnetic fields; i.e., fields applied within the XY planes. Decreasing<br />

temperature below 0.3 K, magnetic order arises at field-dependent temperatures<br />

TC(H). Measuring thermodynamic properties with a magnetic field applied al<strong>on</strong>g the<br />

crystallographic b-axis, we observe a series of magnetic transiti<strong>on</strong>s within the ordered<br />

state. This work was supported by the DFG through SFB 608.


RI13<br />

Critical phenomena at the antiferromagnetic phase transiti<strong>on</strong> of<br />

Azurite Cu 3(CO 3)2(OH)2<br />

Pham Thanh C<strong>on</strong>g, Bernd Wolf*, Rudra Sekhar Manna, Andreas Bruhl, Sebastian<br />

Kohler and Michael Lang<br />

Physics Institute, Goethe-University Frankfurt (M), SFB/TR 49, D-60438 Frankfurt<br />

(M), Germany, Germany<br />

The natural mineral Azurite, Cu3(CO3)2(OH)2, has been c<strong>on</strong>sidered as a model substance<br />

for the 1D distorted diam<strong>on</strong>d chain, where unc<strong>on</strong>venti<strong>on</strong>al magnetic properties result<br />

from the interplay of str<strong>on</strong>g quantum fluctuati<strong>on</strong>s, low dimensi<strong>on</strong>ality and frustrating<br />

interacti<strong>on</strong>s. The system exhibits 3D l<strong>on</strong>g-range antiferromagnetic order at TN = 1.88 K.<br />

Our measurements of the sound velocity, ultras<strong>on</strong>ic attenuati<strong>on</strong> and thermal expansi<strong>on</strong> show<br />

pr<strong>on</strong>ounced signatures at TN indicating a str<strong>on</strong>g coupling to the lattice degrees of freedom.<br />

We present a detailed investigati<strong>on</strong> of the critical behavior of the sound velocity v22 and<br />

ultras<strong>on</strong>ic attenuati<strong>on</strong> α in the vicinity of TN. Our analyses reveal a power-law behavior<br />

of the critical c<strong>on</strong>tributi<strong>on</strong>s v22cr ~ t-ζ and αcr ~ t-η over a decade of reduced temperature<br />

t = (T - TN)/TN both above and below TN. While the value of η = 1.21, obtained above<br />

TN, is close to the theoretical predicti<strong>on</strong> for an anisotropy 3D Heisenberg antiferromagnet,<br />

the critical exp<strong>on</strong>ent derived from the sound velocity of ζ = 0.056, being identical for<br />

temperatures above and below TN, is at odds with this universality class. However, this value<br />

is c<strong>on</strong>sistent with the critical exp<strong>on</strong>ent observed in recent neutr<strong>on</strong> scattering measurements [1].<br />

[1] M. C. R. Gibbs et al., PRB 81, 140406(R), 2010<br />

RI14<br />

Dynamical Properties of Supersolid States in Spin Systems<br />

Yuta Murakami*, Takahi Oka and Hideo Aoki<br />

Physics, University of Tokyo, Japan<br />

It has been recognized that spin systems can be effectively thought of as bos<strong>on</strong> models<br />

as in magn<strong>on</strong> BEC[1]. Specifically, a possibility to realize supersolid(SS) states (in<br />

the bos<strong>on</strong> language) in spin systems is attracting recent attenti<strong>on</strong>, where a candidate is<br />

a frustrated spin-1/2 dimer model[2]. Here we study how the SS state accommodates<br />

collective excitati<strong>on</strong>s with the spin-wave theory. [3] We find that the excitati<strong>on</strong><br />

spectrum changes disc<strong>on</strong>tinuously as we go from a superfluid phase to an SS phase (that<br />

accompanies an SDW; CDW in bos<strong>on</strong> language). Quantitatively, an analytic relati<strong>on</strong><br />

between the velocity of the Goldst<strong>on</strong>e mode and the superfluid density is given. We<br />

also calculate the spin-spin correlati<strong>on</strong> functi<strong>on</strong>, Szz(q, ω), which translates to the<br />

dynamical structure factor in cold-atom systems. We find the intensity of the mode as<br />

estimated from the peaks in Szz(q, ω) sharply blows up toward the boundary of SS,<br />

which is accompanied by a drastic change in the character of the rot<strong>on</strong> mode. We also<br />

menti<strong>on</strong> the possibility to enlarge the SS phase regi<strong>on</strong>. These results obtained in the<br />

effective bos<strong>on</strong> model should also be directly applicable to cold bos<strong>on</strong>ic atoms.<br />

[1] T. Giamarchi, C. Ru egg, and O. Tchernyshyov, Nat. Phys. 4, 198 (2008). [2] P. Chen, C. -Y. Lai,<br />

and M.-F. Yang, Phys. Rev. B(R) 81, 020409 (2010). [3]T. Sommer, M. Vojta, and K.W. Becker Eur.<br />

Phys. J. B 23, 329-339 (2001).<br />

RI15<br />

Magnetic phase transiti<strong>on</strong> of antiferromagnetic Cs 3V 2Cl 9<br />

Hikomisu Kikuchi 1 , Takashi Tanaka 1 , Yutaka Fujii 2 , Akira Matsuo 3 and Koichi Kindo 3<br />

1 Department of Applied Physics, University of Fukui, Japan<br />

2 Research Center for Development of Far-Infrared Regi<strong>on</strong>, University of Fukui,<br />

Japan<br />

3 ISSP, The University of Tokyo, Japan<br />

Cs3V2Cl9 bel<strong>on</strong>gs to the family of hexag<strong>on</strong>al compounds A3M2X9 (A=Cs, Rb,<br />

3-<br />

M=transiti<strong>on</strong> metal i<strong>on</strong>s, X=Cl, Br) in which M2X9 dimers are oriented al<strong>on</strong>g<br />

crystallographic c-axis. Former work 1) <strong>on</strong> polycrystalline sample of Cs3V2Cl9 reported<br />

that intradimer interacti<strong>on</strong> is ferromagnetic although ground state is n<strong>on</strong>magnetic<br />

because of relatively large zero-field-splitting. Dimers of Cs3V2Cl9 form triangular<br />

lattice in their c-plane so that the geometrical spin frustrati<strong>on</strong> effect is expected to occur<br />

if interdimer interacti<strong>on</strong>s are antiferromagnetic. We measured magnetic susceptibility,<br />

specific heat, high field magnetizati<strong>on</strong> and 133 Cs-NMR using single crystal to study<br />

magnetic properties of Cs3V2Cl9. The specific heat shows two anomalies at around 15<br />

and 4 K suggesting successive phase transiti<strong>on</strong>s. Results will be discussed in terms of<br />

the spin frustrati<strong>on</strong>.<br />

1) B. Leuenberger et al. Inorg. Chem. 25, (1986) 2930.<br />

RI16<br />

RI17<br />

RI18<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Novel Field-Induced Quantum Phase Transiti<strong>on</strong> of the Kagome-<br />

Lattice Antiferromagnet<br />

Toru Sakai 1 * and Hiroki Nakano 2<br />

1 SPring-8, Japan Atomic Energy Agency, Japan<br />

2 Graduate School of Material Science, University of Hyogo, Japan<br />

The kagome-lattice antiferromagnet is investigated using the numerical exact diag<strong>on</strong>alizati<strong>on</strong><br />

up to 42-spin clusters. From our investigati<strong>on</strong> of the magnetizati<strong>on</strong> process, we found a<br />

novel field-induced quantum phase transiti<strong>on</strong>, called the ``magnetizati<strong>on</strong> ramp'', at 1/3 of<br />

the saturati<strong>on</strong> magnetizati<strong>on</strong> [1]. The finite-size scaling analysis of the critical exp<strong>on</strong>ents[2]<br />

indicated a significant difference of the magnetizati<strong>on</strong> ramp from the magnetizati<strong>on</strong> plateau<br />

observed in the triangular-lattice antiferromagnet. The critical magnetizati<strong>on</strong> behavior at<br />

lower-field side of the magnetizati<strong>on</strong> ramp is same as that of the <strong>on</strong>e-dimensi<strong>on</strong>al spin liquid.<br />

In order to clarify a difference between the magnetizati<strong>on</strong> ramp and plateau, we study a<br />

generalized anisotropic triangular-lattice model including the regular-triangular- and the<br />

kagome-lattice antiferromagnets in the parameter space. It revealed a quantum phase transiti<strong>on</strong><br />

between the triangular- and kagome-lattices at 1/3 of the saturati<strong>on</strong> magnetizati<strong>on</strong>. It means<br />

that the magnetizati<strong>on</strong> ramp of the kagome-lattice antiferromagnet is an essentially different<br />

phenomen<strong>on</strong> from the magnetizati<strong>on</strong> plateau of the triangular-lattice <strong>on</strong>e. The relati<strong>on</strong> to the<br />

recent magnetizati<strong>on</strong> measurements <strong>on</strong> the volborthite and vesignieite[3] is also c<strong>on</strong>sidered. In<br />

additi<strong>on</strong> we discuss about the spin gap issue of the kagome-lattice antiferromagnet [4].<br />

[1]H. Nakano and T. Sakai: J. Phys. Soc. Jpn. 79 (2010) 053707. [2]T. Sakai and H. Nakano: Phys. Rev. B 83 (2011)<br />

100405(R). [3]Y. Okamoto, M. Tokunaga, H. Yoshida, A. Matsuo, K. Kindo and Z. Hiroi: Phys. Rev. B 83 (2011)<br />

180407(R). [4]H. Nakano and T. Sakai: J. Phys. Soc. Jpn. 80 (2011) 053704.<br />

Antiferromagnetic phase transiti<strong>on</strong> of K-Rb alloy nanoclusters<br />

incorporated in sodalite<br />

Takehito Nakano*, Yuko Ishida, Atsufumi Hanazawa and Yasuo Nozue<br />

Department of Physics, Graduate School of Science, Osaka University, Japan<br />

Aluminosilicate sodalite possesses a bcc arrangement of nanospaces (beta-cages).<br />

Alkali-metal nanocluster (A4)3+ can be formed in each beta-cage, where an s-electr<strong>on</strong><br />

is shared by four alkali cati<strong>on</strong>s. (Na4)3+ clusters in sodalite are known to show<br />

antiferromagnetism below the Neel temperature of 48 K [1]. By substituting heavier<br />

alkali atoms for Na <strong>on</strong>es, the Neel temperature systematically increases, namely, 72 K<br />

in (K4)3+ and 80 K in (K3Rb)3+ clusters [2]. In the present work, we have succeeded<br />

in preparing K-Rb alloy clusters with a higher Rb c<strong>on</strong>centrati<strong>on</strong>, (K1.5Rb2.5)3+.<br />

Magnetic susceptibility obeys Curie-Weiss law and shows a peak at ~ 100 K. ESR<br />

spectrum is suddenly broaden below ~ 90 K to be an asymmetric shape which can<br />

be explained by powder pattern of antiferromagnetic res<strong>on</strong>ance. These results clearly<br />

indicate that the present sample exhibits an antiferromagnetic phase transiti<strong>on</strong> at<br />

approximately 90 K which is higher than that in (K3Rb)3+. Substituting Rb for K<br />

makes the size of s-electr<strong>on</strong> wave functi<strong>on</strong> of the cluster larger because of the larger i<strong>on</strong><br />

size and the lower i<strong>on</strong>izati<strong>on</strong> energy of Rb. This reduces the U/t in the Mott-Hubbard<br />

insulating state resulting in an increase in the kinetic exchange coupling between the<br />

adjacent clusters.<br />

[1] V.I. Srdanov et al., Phys. Rev. Lett. 80, 2449 (1998). [2] T. Nakano et al., J. Phys. Soc. Jpn. 79,<br />

073707 (2010).<br />

A novel scaling method for critical phenomena studies: finite size<br />

effects<br />

Joao S Amaral 1 *, Jouke R Heringa 2 , Ekkes Bruck 2 and Vitor S Amaral 1<br />

1 CICECO and Dept. of Physics, Universidade de Aveiro, Portugal<br />

2 Delft University of Technology, Faculty of Applied Sciences, 2626 Delft, Netherlands<br />

We present a novel approach for critical phenomena studies. By quantifying scaling plot<br />

data overlap, we introduce a ‘goodness of scaling’ parameter, allowing an iterative search for<br />

the ‘best’ critical exp<strong>on</strong>ent values for a given set of magnetizati<strong>on</strong> data. The main advantage<br />

of this method is going bey<strong>on</strong>d the usual power-law fits of the critical isotherm or low field<br />

susceptibility curve, by c<strong>on</strong>sidering the complete equati<strong>on</strong> of state and all data within the critical<br />

regi<strong>on</strong>. We c<strong>on</strong>sider M<strong>on</strong>te-Carlo simulated data of the 3D Ising model, and evaluate finitesize<br />

effects using our scaling method. Our results are in good agreement with the bibliography,<br />

including the dependence of pseudo-critical exp<strong>on</strong>ents <strong>on</strong> system size [1]. Interestingly, we<br />

have found that even with a str<strong>on</strong>g dependence of these pseudo-critical exp<strong>on</strong>ents <strong>on</strong> system<br />

size, the equati<strong>on</strong> of state is not affected by finite-size effects. The resulting scaling functi<strong>on</strong> is<br />

in good agreement with recent theoretical predicti<strong>on</strong>s for both exp<strong>on</strong>ent values and equati<strong>on</strong><br />

of state [2,3]. Our results suggest that while some effects may change the values of observed<br />

critical exp<strong>on</strong>ents of a given magnetic system, the state equati<strong>on</strong> may retain its identity. In a<br />

sense, the state equati<strong>on</strong> can be more universal than exp<strong>on</strong>ent values.<br />

[1] Haggkvist R., Rosengren A., Lundow P. H., Markstrom K., Andren D., Kundrotas P., Adv. Phys.<br />

56, 653-755 (2007). [2] Campostrini M., Pelissetto A., Rossi P., E. Vicari, Phys. Rev. E 65, 066127<br />

(2002). [3] D. O'C<strong>on</strong>nor, J. A. Santiago, and C. R. Stephens, J. Phys. A 42, 045003 (2009).<br />

July 8 - 13, 2012 Busan, Korea 167<br />

Poster Thursday


Poster Thursday<br />

RI19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The transverse-field quantum Ising model <strong>on</strong> infinite-dimensi<strong>on</strong>al<br />

structures using quantum M<strong>on</strong>te Carlo method and finite-size scaling<br />

Su Do Yi 1 , Seung Ki Baek 2 , Jaeg<strong>on</strong> Um 2 and Beom Jun Kim 1 *<br />

1 1<br />

Department of Physics and BK2 Physics Research Divisi<strong>on</strong>, Sungkyunkwan<br />

University, Suw<strong>on</strong> 440-746, Korea<br />

2<br />

School of Physics, Korea Institute of Advanced Study, Seoul 130-722, Korea<br />

In a number of classical statistical-physical models, there exists a characteristic<br />

dimensi<strong>on</strong>ality called the upper critical dimensi<strong>on</strong> above which <strong>on</strong>e observes the meanfield<br />

critical behavior. Instead of c<strong>on</strong>structing high-dimensi<strong>on</strong>al lattices, however,<br />

<strong>on</strong>e can also c<strong>on</strong>sider infinite-dimensi<strong>on</strong>al structures, and the questi<strong>on</strong> is whether<br />

this mean-field character extends to quantum-mechanical cases as well. We therefore<br />

investigate the transverse-field quantum Ising model <strong>on</strong> the globally coupled network<br />

and <strong>on</strong> the Watts-Strogatz small-world network by means of quantum M<strong>on</strong>te Carlo<br />

simulati<strong>on</strong>s and the finite-size scaling analysis. We c<strong>on</strong>firm that both of the structures<br />

exhibit critical behavior c<strong>on</strong>sistent with the mean-field descripti<strong>on</strong>. In particular,<br />

we show that the existing cumulant method has difficulty in estimating the correct<br />

dynamic critical exp<strong>on</strong>ent and suggest that an order parameter based <strong>on</strong> the quantummechanical<br />

expectati<strong>on</strong> value can be a practically useful numerical observable to<br />

determine critical behavior when there is no well-defined dimensi<strong>on</strong>ality.<br />

RI20<br />

Study of cluster heterogeneity scaling in the two-dimenti<strong>on</strong>al Ising<br />

model.<br />

Woo Se<strong>on</strong>g Jo 1 , Su Do Yi 1 , Seung Ki Baek 2 and Beom Jun Kim 1 *<br />

1<br />

Department of Physics and BK21 Physics Research Divisi<strong>on</strong>, Sungkyunkwan<br />

University, Suw<strong>on</strong> 440-746, Korea<br />

2<br />

School of Physics, Korea Institute of Advanced Study, Seoul 130-722, Korea<br />

The cluster heterogeneity, defined as the number of distinct cluster sizes, was suggested<br />

in [1] as an indicator of the phase transiti<strong>on</strong> in the percolati<strong>on</strong> model. Noh et al. [2]<br />

found that the c<strong>on</strong>venti<strong>on</strong>al finite-size scaling(FSS) form using the correlati<strong>on</strong>-length<br />

exp<strong>on</strong>ent ν does not describe the scaling of the cluster heterogeneity in the percolati<strong>on</strong><br />

model and that the other exp<strong>on</strong>ent ν_H should be used instead. We apply the FSS form<br />

suggested in [2] for cluster heterogeneity in the Ising model. Since there are two types<br />

of clusters, (+) and (-) spin clusters, we calculate the heterogeneity of each type (H+<br />

and H-, respectively), and carry out FSS near critical temperature. We find that total<br />

heterogeneity (H ≡ H+ + H-) scales with the exp<strong>on</strong>ent ν_H, as expected from [2] for<br />

the percolati<strong>on</strong> model.<br />

[1] H.K. Lee, B.J. Kim, and H. Park, Phys. Rev. E 84, 020101(R) (2011). [2] J.D. Noh, H.K. Lee,<br />

and H. Park, Phys. Rev. E 84, 010101(R) (2011).<br />

RI21<br />

Zero-temperature phase transiti<strong>on</strong> in a <strong>on</strong>e-dimensi<strong>on</strong>al Ising<br />

ferromagnet using Glauber dynamics with a synchr<strong>on</strong>ous update<br />

Il Gu Yi and Beom Jun Kim*<br />

Physics, Sungkyunkwan University, Korea<br />

Resently Glauber dynmaics for the <strong>on</strong>e-dimensi<strong>on</strong>al Ising spin system at lowtemperature<br />

is studied variously not <strong>on</strong>ly experimentlly but also theoritically in the<br />

nano molecular system. Sznajd-Wer<strong>on</strong> [Phys. Rev. E 82, 031120 (2010)] study the<br />

ferro anti-ferro phase transiti<strong>on</strong> of the density of active b<strong>on</strong>ds, and the behavior<br />

of the relaxti<strong>on</strong> time which means the time needed to reach to steady state in the<br />

generalized zero temperature Glauber dynamcis. They suggested in that paper that the<br />

<strong>on</strong>e-dimensi<strong>on</strong>al Ising model subject to the zero-temperature synchr<strong>on</strong>ous Glauber<br />

dynamics exhibits a disc<strong>on</strong>tinuous phase transiti<strong>on</strong>. We show here that the phase<br />

transiti<strong>on</strong> instead of a c<strong>on</strong>tinuous nature, and we identify critical exp<strong>on</strong>ents, \beta<br />

\approx 0, \nu \approx 1, and z \approx 2 via a systematic finite-size scaling analysis.<br />

1. K. Sznajd-Wer<strong>on</strong>, Phys. Rev. E 82, 031120 (2010). 2. N. Goldenfeld, Lectures <strong>on</strong> Phase<br />

Transiti<strong>on</strong>s and the Renormalizati<strong>on</strong> Group (Addis<strong>on</strong>-Wesley, Bost<strong>on</strong>, 1992).<br />

168 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RI22<br />

Stochastic treatment of magnetic moment relaxati<strong>on</strong> in spin echo<br />

models<br />

Maxim Pavlovich Shlykov<br />

Nati<strong>on</strong>al Research Centre 'Kurchatov Institute', Russia<br />

The method of nuclear spin-echo amplitude calculati<strong>on</strong> based <strong>on</strong> the density matrix technique is<br />

improved. Spin echo model [1] was supplemented with stochastic c<strong>on</strong>siderati<strong>on</strong> of the magnetic<br />

moment relaxati<strong>on</strong> provided by the interacti<strong>on</strong> nuclear spin with fluctuating magnetic field. The<br />

theory of reducible systems [2] was applied for solving stochastic differential equati<strong>on</strong>s. This<br />

mathematical approach was adapted to find the soluti<strong>on</strong> of the Schrodinger equati<strong>on</strong> for the timeevoluti<strong>on</strong><br />

operator which describes behavior of a nuclear spin in the presence of a radiofrequency<br />

pulsed magnetic field and fluctuating magnetic field. NMR spin echo for I = 1/2 is c<strong>on</strong>sidered as<br />

the simplest illustrati<strong>on</strong> of the method. Unlike classical approaches [3,4], It allows to calculate<br />

spin-echo amplitude correctly over whole period of relaxati<strong>on</strong> without any estimates. The<br />

possibility of applicati<strong>on</strong> of well-known Ito calculus [5] is also discussed. It was obtained more<br />

accurate formulae for spin-lattice relaxati<strong>on</strong> time T1 and spin-spin relaxati<strong>on</strong> time T2 .<br />

[1] Kravchenko E. A., Orlov V. G., Shlykov M. P., Magnetic properties of bismuth(III) oxy<br />

compounds, Russian Chemical Reviews, 2006, 75 (1), 77-93 [2] Erougin N., Reducible systems,<br />

Travaux Inst. Math. Stekloff, 1946, 13, 3-96 [3] Redfield A.G., On The Theory of Relaxati<strong>on</strong><br />

Processes, IBM Journ. Res. Develop., 1957, 1, 19-31 [4] Bloembergen N., Purcell E. M., Pound R.V.,<br />

Relaxati<strong>on</strong> Effects in Nuclear Magnetic Res<strong>on</strong>ance Absorpti<strong>on</strong>, Phys. Rev., 1948, 73, 679-712 [5]<br />

Gardiner, C. W., Handbook of stochastic methods for physics, chemistry and the natural sciences,<br />

Springer, 1994, 13, 442<br />

RJ01<br />

Vortex core switching <strong>on</strong> notched circular disks<br />

Tom<strong>on</strong>ori Sato* and Yoshinobu Nakatani<br />

University of Electro-Communicati<strong>on</strong>s, Japan<br />

The vortex core manipulati<strong>on</strong> by field has been frequently reported. However, the<br />

minimizati<strong>on</strong> of switching field is still being debated. In general, the vortex core<br />

switching is performed by annihilati<strong>on</strong> of vortex and anti-vortex, however the<br />

nucleati<strong>on</strong> of the pair requires large magnetic field. In this report, we proposed the<br />

new switching mechanism to decrease switching field by using circular disks with<br />

V-shaped notch. When the in-plane pulse field is applied, the vortex core moves to the<br />

notch and annihilates automatically. After the field is switched off, the vortex core gets<br />

back by demagnetizing field. The vortex core polarity is c<strong>on</strong>trolled by the external field<br />

perpendicular to the disk. In this switching mechanism, the vortex core switching is<br />

performed by <strong>on</strong>ly the annihilati<strong>on</strong> and nucleati<strong>on</strong> of the vortex, therefore the switching<br />

field is decreased compared with the circular disks without notch. We investigated the<br />

vortex core switching by micromagnetic simulati<strong>on</strong>. A Permalloy disk with 200nm<br />

diameter and 40nm thickness is used in the simulati<strong>on</strong>. The field perpendicular to the<br />

disk was fixed at 50 Oe. The result reveals that the minimum switching field decreases<br />

60% compared with the case using the circular disk without notch.<br />

RJ02<br />

Effect of oersted field <strong>on</strong> magnetic vortex core gyrati<strong>on</strong><br />

Tom<strong>on</strong>ori Sato 1 *, Yoshinobu Nakatani 1 and Teruo Ono 2<br />

1 University of Electro-Communicati<strong>on</strong>s, Japan<br />

2 Kyoto University, Japan<br />

Recently, the vortex core manipulati<strong>on</strong>s by spin current are studied intensively.<br />

Because spin current creates the Oersted field, there are some reports, which study<br />

the effect of the field <strong>on</strong> the vortex core moti<strong>on</strong>. When the vortex core is manipulated<br />

by the current, the electrodes are usually attached <strong>on</strong> top of the disk. Therefore, the<br />

current goes in and out from the top surface of the disk mainly. It makes the current<br />

n<strong>on</strong>-uniform, and it makes the Oersted field complex. In this work, we report the effect<br />

of the Oersted field and the current distributi<strong>on</strong> <strong>on</strong> the vortex core gyrati<strong>on</strong> by AC<br />

current by micromagnetic simulati<strong>on</strong>. A Permalloy circular disk with 1.5μm diameter<br />

and 40nm thickness is used in the simulati<strong>on</strong>. The AC current density is 2.66x1011A/<br />

m2 mainly. The current frequency is varied around the res<strong>on</strong>ant frequency of the<br />

disk. The result reveals that the effect of the Oerstead field changes by the current<br />

density, however the percentage of the effect of the Oersted field <strong>on</strong> the driving force<br />

is 8% in maximum. Furthermore, the vortex core is affected by not <strong>on</strong>ly the in-plane<br />

comp<strong>on</strong>ents but also the out-of-plane comp<strong>on</strong>ent.


RJ03<br />

Mutual spin-transfer torque in vortex nano-oscillators<br />

Xiaolei Wang, Ning Wang and Ant<strong>on</strong>io Ruotolo<br />

Department of Physics and Materials Science, City University of H<strong>on</strong>g K<strong>on</strong>g, H<strong>on</strong>g<br />

K<strong>on</strong>g<br />

We studied the emissi<strong>on</strong> resp<strong>on</strong>se of spin transfer vortex oscillators with dynamic<br />

polarizer. In these systems, mutual spin transfer torque between the two ferromagnetic<br />

layers is at the origin of a very rich dynamics. By changing the injected current, we<br />

could gain access to up to three dynamic modes. At high currents, mutual spin transfer<br />

torque is at play and high-frequency dynamics is simultaneously excited in both layers.<br />

The detected mode corresp<strong>on</strong>ds to a Sl<strong>on</strong>ckzewski’s windmill-like mode, which is<br />

stable in a large range of experimental c<strong>on</strong>diti<strong>on</strong>s. The mode observed at low currents<br />

corresp<strong>on</strong>ds to the comm<strong>on</strong>ly observed dynamics in nano-c<strong>on</strong>tact vortex oscillators, in<br />

which the vortex core is far away from the c<strong>on</strong>tact and current-in-plane spin-transfer<br />

torque is at play. Surprisingly, we could gain access to a third mode at intermediate<br />

currents, which we ascribe to the precessi<strong>on</strong> of a vortex in the thin ferromagnetic layer<br />

under the c<strong>on</strong>tact area. This mode is of particular scientific interest because it allows<br />

<strong>on</strong>e to experimentally study the vortex dynamics in the small amplitude limit.<br />

RJ04<br />

Key role of temperature in ferromagnetic bloch point simulati<strong>on</strong>s<br />

Kristof M. Lebecki 1 *, Denise Hinzke 1 , Oksana Chubykalo-fesenko 2 and Ulrich<br />

Nowak 1<br />

1 Department of Physics, University of K<strong>on</strong>stanz, Germany<br />

2 Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid,<br />

Spain<br />

A Bloch point (BP) is known to play a crucial role during vortex core switching process [1].<br />

Vortices themselves attract recently much attenti<strong>on</strong> since it was suggested to use them as a<br />

magnetic storage medium. For such an applicati<strong>on</strong> BP-related vortex core properties like the<br />

switching speed or stability of the final state are essential. This makes the BP an important<br />

object of study. We present here results of numerical simulati<strong>on</strong>s, where the BP at elevated<br />

temperature is investigated. Our approach makes it possible to model its behavior without<br />

problems related to its singular character [1,2] - as opposed to all BP simulati<strong>on</strong>s presented<br />

in the literature so far. We have included temperature effects via Landau-Lifshitz-Bloch<br />

equati<strong>on</strong> [3]. Our implementati<strong>on</strong>, basing <strong>on</strong> the OOMMF code, allow us to compare results<br />

of analytical theories with modern numerical approach. We focus our attenti<strong>on</strong> <strong>on</strong> permalloy<br />

and c<strong>on</strong>duct studies in the full temperature range. Firstly, we will present results of modeling<br />

an artificially pinned BP. This reveals details of its geometry, including its temperaturedependent<br />

radius. Sec<strong>on</strong>dly, we will present results of dynamical studies, where the vortex<br />

core switches via nucleati<strong>on</strong>, propagati<strong>on</strong> and annihilati<strong>on</strong> of a BP.<br />

1. S. Gliga, Y. Liu, and R. Hertel, J. Phys.: C<strong>on</strong>f. Ser., 303, 012005 (2011). 2. A. Thiaville, J. M. Garcia, R.<br />

Dittrich, J. Miltat, and T. Schrefl, Phys. Rev. B 67, 094410 (2003). 3. D. A. Garanin, Phys. Rev. B 55, 3050 (1997).<br />

RJ05<br />

Polarizati<strong>on</strong>-selective signal propagati<strong>on</strong> in a chain of vortices<br />

Andreas Vogel 1 *, Michael Martens 1 , Markus Weigand 2 and Guido Meier 1<br />

1<br />

Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung,<br />

Universitaet Hamburg, Germany<br />

2<br />

Max-Planck-Institut fuer Intelligente Systeme, Germany<br />

Dynamics <strong>on</strong> the subnanosec<strong>on</strong>d time scale and potential technological applicati<strong>on</strong>s give rise to<br />

a broad scientific interest in the dynamic properties of ferromagnetic microstructures with vortex<br />

magnetizati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong>. An excitati<strong>on</strong> of the low frequency mode of gyrati<strong>on</strong> can be transferred<br />

via dipolar interacti<strong>on</strong> between neighboring ferromagnetic elements with the transfer efficiency<br />

str<strong>on</strong>gly depending <strong>on</strong> their separati<strong>on</strong> and the relative c<strong>on</strong>figurati<strong>on</strong> of the vortex-core polarizati<strong>on</strong>s [1].<br />

The dependence <strong>on</strong> the core polarizati<strong>on</strong>s can be understood c<strong>on</strong>sidering the time-dependent shape<br />

of the external stay field. We employ time-resolved scanning transmissi<strong>on</strong> x-ray microscopy to study<br />

the vortex-core dynamics in a chain of three stray-field coupled permalloy squares. After exciting the<br />

first element via a short in-plane magnetic field pulse, the excitati<strong>on</strong> can be transferred through the<br />

chain. No resp<strong>on</strong>se is observed in the third square for equal core polarizati<strong>on</strong>s of all elements but the<br />

excitati<strong>on</strong> can be transferred through the chain just by changing the polarizati<strong>on</strong> in the central element.<br />

For alternating polarizati<strong>on</strong>s, a transfer efficiency of about 56% to the third square is achieved. The<br />

chain can be switched back and forth between the transmitting and a locking state [2].<br />

[1] A. Vogel, T. Kami<strong>on</strong>ka, M. Martens, A. Drews, K. W. Chou, T. Tyliszczak, H. Stoll, B. Van<br />

Waeyenberge, and G. Meier, Phys. Rev. Lett. 106, 137201 (2011); H. Jung, K.-S. Lee, D.-E. Je<strong>on</strong>g, Y.-S.<br />

Choi, Y.-S. Yu, D.-S. Han, A. Vogel, L. Bocklage, G. Meier, M.-Y. Im, P. Fischer, and S.-K. Kim, Sci. Rep. 1,<br />

59 (2011). [2] A. Vogel, M. Martens, M. Weigand, and G. Meier, Appl. Phys. Lett. 99, 042506 (2011).<br />

RJ06<br />

RJ07<br />

RJ08<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Theoretical study <strong>on</strong> frequency of vortex-antivortex pairs rotati<strong>on</strong> in a<br />

magnetic thin-film with multi-c<strong>on</strong>tacts<br />

Hiroshi Tsukahara, Hiroko Arai and Hiorshi Imamura*<br />

AIST, Japan<br />

Spin transfer torque (SST) induced magnetizati<strong>on</strong> dynamics is <strong>on</strong>e of the key c<strong>on</strong>cepts<br />

in spintr<strong>on</strong>ics and intensive studies have been c<strong>on</strong>ducted in the last two decades to<br />

realize STT based memories (Spin-RAM) and microwave oscillators. Finocchio et<br />

al. studied the STT induced magnetizati<strong>on</strong> dynamics in magnetic thin-film nanopillar<br />

which has <strong>on</strong>e aperture and found that the rotati<strong>on</strong>al dynamics of a vortex-antivortex<br />

(VA) pair produces the resistance oscillati<strong>on</strong> [1]. Therefore, it is interesting to study<br />

how the VA-pair dynamics in a multi-c<strong>on</strong>tacts system is influenced by the distance<br />

between c<strong>on</strong>tacts. We performed micromagnetic simulati<strong>on</strong>s of a magnetic thin-film<br />

where the spatially localized spin-polarized current was injected through two nanoc<strong>on</strong>tacts<br />

and found the rotati<strong>on</strong> of VA pairs. If the distance between two c<strong>on</strong>tacts is<br />

so large that the VA pair cannot interfere with each other, they independently rotate<br />

around each c<strong>on</strong>tact. In c<strong>on</strong>trast, when the distance becomes small, the single VA pair<br />

rotates around a large area in which the two c<strong>on</strong>tacts are included and the rotati<strong>on</strong><br />

frequency drops down to about 60% of that of a single c<strong>on</strong>tact. Our results show that<br />

we can c<strong>on</strong>trol the frequency of the VA pair rotati<strong>on</strong> by changing the distance between<br />

the c<strong>on</strong>tacts.<br />

[1] G. Finocchio, O. Ozatay, L. Torres, R. A. Buhrman, D. C. Ralph and B. Azzerb<strong>on</strong>i, Phys. Rev. B<br />

78 174408 (2008)<br />

Parametric excitati<strong>on</strong> and subcritical phase-locking in spin-transfer<br />

vortex oscillators<br />

Paolo Bortolotti 1 *, C. Serpico 2 , E. Grimaldi 1 , J. Grollier 1 , V. Cros 1 , A. Fukushima 3 , H.<br />

Kubota 3 , K. Yakushiji 3 , S. Yuasa 3 , K. Ando 3 and A. Fert 1<br />

1 Unite Mixte de Physique CNRS/Thales, France<br />

2 Dipartimento di Ingegneria Elettrica,Universita di Napoli 'Federico II', Italy<br />

3 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology (AIST), Japan<br />

In the last decade several systems have been proposed to design low power c<strong>on</strong>suming nano-oscillators.<br />

One promising example is a MgO tunnel juncti<strong>on</strong> with a vortex free layer[1,2] (STVO). Classically,<br />

oscillati<strong>on</strong>s at its natural frequency f_0 are obtained for currents larger than a critical value Ic. However, by<br />

applying a rf-excitati<strong>on</strong> current at 2f_0, i.e., parametric excitati<strong>on</strong>[3,4], it is possible to force the system into<br />

oscillati<strong>on</strong> even in the subcritical current regime (I


Poster Thursday<br />

RJ09<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Stability of the vortex structure <strong>on</strong> the core switching by AC current<br />

Tom<strong>on</strong>ori Sato* and Yoshinobu Nakatani<br />

University of Electro-Communicati<strong>on</strong>s, Japan<br />

Recently, magnetic disks with a vortex core have been c<strong>on</strong>sidered as <strong>on</strong>e of the<br />

candidates for the storage devices, and many reports relating to the core switching by<br />

spin current have been reported. Because the storage capacity depends <strong>on</strong> the magnetic<br />

disk size, it is important to investigate the stability of the vortex structure <strong>on</strong> its size.<br />

Until now, the disk size that the core can switch stable has not been reported. In this<br />

work, we investigate the stability <strong>on</strong> the core switching by micromagnetic simulati<strong>on</strong>.<br />

In the simulati<strong>on</strong>, two methods are used, the method by the core switching simulati<strong>on</strong><br />

by AC spin current and the method by the evaluati<strong>on</strong> of the magnetic energy. The<br />

switching simulati<strong>on</strong> reveals that the core does not switch around the transiti<strong>on</strong><br />

dimensi<strong>on</strong> of magnetic disks between single-domain structure and the vortex structure<br />

<strong>on</strong> a remanent state, and the disk diameter needs to be increased about 20 to 80 nm<br />

for the stable core switching compared with the stability limit <strong>on</strong> the remanent state.<br />

Furthermore, the result of the energy evaluati<strong>on</strong> agreed with the result obtained by the<br />

switching simulati<strong>on</strong>. Therefore, the stability <strong>on</strong> the core switching can be estimated by<br />

the magnetic energy.<br />

RJ10<br />

Time-averaged observati<strong>on</strong> of magnetic vortex res<strong>on</strong>ated in squareshaped<br />

NiFe films<br />

Motoi Kodama 1 , Koji Sekiguchi 2 and Yukio Nozaki 3 *<br />

1 Department of Physics, Keio University, Japan<br />

2 Department of Physics, Keio University, JST PRESTO, Japan<br />

3 Department of Physics, Keio University, JST CREST, Japan<br />

A dynamics of magnetic vortex c<strong>on</strong>fined in a patterned ferromagnetic thin film attracts<br />

much attenti<strong>on</strong> for both the fundamental and the technological points of view. The<br />

observati<strong>on</strong> of the trajectory of magnetic vortex core excited with an applicati<strong>on</strong> of<br />

ac magnetic field or ac current is significant for the quantitative understanding of spin<br />

dynamics. In this study, a time-averaged observati<strong>on</strong> of magnetic vortex res<strong>on</strong>ated<br />

in square-shaped NiFe thin film was dem<strong>on</strong>strated by means of magnetic force<br />

microscopy (MFM) to obtain the trajectory. A 30 nm-thick NiFe film with the lateral<br />

size of 1x1um 2 was fabricated <strong>on</strong> a coplanar waveguide that generates an ac magnetic<br />

field of 1mT in amplitude. The res<strong>on</strong>ant frequency of the magnetic vortex formed in the<br />

NiFe film was calculated to 260 MHz that is much higher than the sampling frequency<br />

of MFM. When the ac magnetic field with a frequency of 260 MHz was applied, a<br />

circular pattern with a uniform magnetic c<strong>on</strong>trast appeared in the vicinity of center of<br />

the NiFe film. The diameter of the circle is comparable with that of the trajectory of<br />

magnetic vortex core calculated with micromagnetic simulati<strong>on</strong>.<br />

RJ11<br />

Diverging-c<strong>on</strong>verging spin vortex pairs in biquadratically interlayer<br />

exchange coupled elements<br />

Sebastian Wintz 1 *, Christopher Bunce 1 , Anja Banholzer 1 , Michael Koerner 1 , Sibylle<br />

Gemming 1 , Artur Erbe 1 , Joerg Raabe 2 , Christoph Quitmann 2 and Juergen Fassbender1<br />

1 Helmholtz-Zentrum Dresden-Rossendorf, Germany<br />

2 SLS, Paul Scherrer Institut, Switzerland<br />

Spin structures have been an interesting topic of magnetism research for many years.<br />

Within this field, magnetic vortices have attracted much attenti<strong>on</strong>, due to their n<strong>on</strong>trivial<br />

topology and the various dynamic modes they exhibit [1]. A magnetic vortex<br />

c<strong>on</strong>sists of a planar, flux-closing magnetizati<strong>on</strong> curl that turns out of the plane in the<br />

central nanoscopic core regi<strong>on</strong>. In a single layer structure, the curl’s radial comp<strong>on</strong>ents<br />

typically cancel each other out. Recent investigati<strong>on</strong>s show that this also holds true<br />

for multilayer vortex systems with bilinear interlayer exchange coupling [2]. Here<br />

we report <strong>on</strong> pairs of diverging-c<strong>on</strong>verging spin vortices occurring in biquadratically<br />

coupled systems. Using magnetic scanning transmissi<strong>on</strong> x-ray microscopy (STXM)<br />

we directly observe that the individual vortices of such pairs possess a residual radial<br />

magnetizati<strong>on</strong> comp<strong>on</strong>ent, i.e. ∇Mxy≠0. This implies an additi<strong>on</strong>al perpendicular<br />

magnetizati<strong>on</strong> divergence ∇Mz, for which we compare a c<strong>on</strong>tinuous model with<br />

discrete micromagnetic simulati<strong>on</strong>s.<br />

[1] S.-B. Choe et al., Science 304, 420 (2004). [2] S. Wintz et al., Appl. Phys. Lett. 98, 232511 (2011).<br />

170 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RJ12<br />

Magnetic vortex dynamics in exchange-biased micr<strong>on</strong>-sized structures<br />

Sofia De Oliveira Parreiras 1 *, Flavio Garcia 2 and Maximiliano Delany Martins 1<br />

1 Applied Physics Laboratory, CDTN/CNEN, Brazil<br />

2 Laboratorio Naci<strong>on</strong>al de Luz Sincrotr<strong>on</strong>, Brazil<br />

The study of magnetic dots with magnetic vortex spin c<strong>on</strong>figurati<strong>on</strong> has recently<br />

attracted great scientific interest [1]. The great potential of applicati<strong>on</strong>s of magnetic<br />

vortices (as for example magnetic memories and nanoparticles for cancer treatment)<br />

draws attenti<strong>on</strong> for the investigati<strong>on</strong> of vortex proprieties. In this work, we studied the<br />

dynamics proprieties of exchange-biased vortex using the code OOMMF (NIST) [2]<br />

that applies the Landau-Lifshitz-Gilbert equati<strong>on</strong> to simulate the spin c<strong>on</strong>figurati<strong>on</strong> and<br />

compute the energy and magnetizati<strong>on</strong> of microstructures. A series of micromagnetic<br />

simulati<strong>on</strong>s for Permalloy/Fe 50Mn 50 disks with 0.5 ?m of diameter was d<strong>on</strong>e varying<br />

the magnetic coupling c<strong>on</strong>stant between the layers. We had observed that the vortex<br />

gyrotropic movement has a variable frequency that increases with the time, which is<br />

not observed when exchange bias is absent. Under a rotating magnetic field acting in<br />

the disks, the critical velocity for vortex polarity reversi<strong>on</strong> increases with the coupling<br />

c<strong>on</strong>stant and frequency. Our results show that the critical velocity can be adjusted in a<br />

wide range by selecting the magnetic coupling c<strong>on</strong>stant and the oscillating frequency,<br />

i.e., it is possible to c<strong>on</strong>trol the critical velocity for vortex polarity inversi<strong>on</strong> through<br />

the exchange bias coupling.<br />

[1] C. L. Chien, F. Q. Zhu, and J.-G. Zhu, Physics Today 60, 40 (June, 2007) [2] M. J. D<strong>on</strong>ahue and<br />

D. G. Porter, http://math.nist.gov/oommf/<br />

RJ13<br />

Magnetic Vortex Echo<br />

Flavio Garcia1*, Joao Paulo Sinnecker2, Erico Novais2 and Alberto Passos<br />

Guimaraes2<br />

1 Brazilian Sinchrotr<strong>on</strong> Light Laboratory, Brazil<br />

2 Centro Brasileiro de Pesquisas Fisicas, Brazil<br />

The interest of magnetic vortices has greatly grown in the last years since these systems<br />

present a myriad of promising applicati<strong>on</strong>s, which are mainly related <strong>on</strong> their dynamics<br />

aspects. When the vortex core is excited from its equilibrium positi<strong>on</strong>, it relaxes in<br />

a spiral moti<strong>on</strong>, with a very well defined frequency, which is inversely proporti<strong>on</strong>al<br />

to the disk aspect ratio. The sense of the gyrotropic moti<strong>on</strong> is determined by the core<br />

polarity. So, c<strong>on</strong>trolling the polarity, it is easy to c<strong>on</strong>trol the sense of gyrotropic moti<strong>on</strong>.<br />

In this work, we analytically shown that, properly manipulating the dynamic properties<br />

of the vortex, namely its polarity, in an analogous way as it is d<strong>on</strong>e in Nuclear<br />

Magnetic Res<strong>on</strong>ance, it is possible to generate a magnetic vortex echo (MVE). This<br />

echo is similar to the spin echo, and it may provide fundamental informati<strong>on</strong> about the<br />

dynamic properties of real arrays of vortices, e.g., magnetic coupling, inhomogeneities,<br />

magnetic stability etc. To illustrate the MVE, we performed micromagnetic simulati<strong>on</strong><br />

of arrays of nanodisks, where it has been varying their most significant parameters to<br />

prove that the MVE can give significant informati<strong>on</strong> about the dynamic properties of<br />

the real array of disks.<br />

ArXiv:1201.3553<br />

RJ14<br />

Origin of the dipolar coupling between vortex-state disks<br />

Ki-suk Lee and Sang-koog Kim*<br />

Seoul Nati<strong>on</strong>al University, Korea<br />

Coupled vortex gyrati<strong>on</strong>s in spatially separated nanodisks have been studied theoretically[1,2],<br />

experimentally[3-8], and numerically[9] owing to their possible applicati<strong>on</strong>s as an alternative to current<br />

signal processing devices with the advantage of negligible energy loss[7]. Fundamental phenomena<br />

such as eigenfrequency splitting and its dependence <strong>on</strong> dot-to-dot interdistance[3,4,7] have been verified<br />

experimentally and explained well by the normal mode representati<strong>on</strong>[7,9]. In this work, we studied dynamic<br />

dipole interacti<strong>on</strong> of coupled vortex gyrati<strong>on</strong>s observed in two disks by micromagnetic simulati<strong>on</strong> and<br />

analytical approaches. Shibata et al.[1] reported that, based <strong>on</strong> rigid vortex model [10], the dynamic dipolar<br />

interacti<strong>on</strong> of the coupled vortex gyrati<strong>on</strong>s originates from the magnetostatic interacti<strong>on</strong> that is induced by the<br />

side surface charges of each disk during the gyrati<strong>on</strong>s [1,2]. We extracted the interacti<strong>on</strong> energies of the two<br />

dipolar-coupled disks and compared those that are obtained directly from the micromagnetic simulati<strong>on</strong>s and<br />

obtained from spin c<strong>on</strong>figurati<strong>on</strong>s based <strong>on</strong> two different side-charge-free[10] and rigid-vortex models. The<br />

simulati<strong>on</strong> result is in better agreement with the side-charge-free-model-based spin c<strong>on</strong>figurati<strong>on</strong>s than the<br />

rigid-vortex-model <strong>on</strong>e. These results imply that the dipolar energy of the coupled gyrati<strong>on</strong>s of neighboring<br />

vortex-state disks originates dominantly from not the side surface charges of each disk, but the volume charges.<br />

This work was supported by Basic Science Research Program through the Nati<strong>on</strong>al Research Foundati<strong>on</strong> of Korea(NRF) funded<br />

by the Ministry of Educati<strong>on</strong>, Science and Technology(No. 20110000441). [1] J. Shibata et al.,Phys. Rev.B 67,224404(2003).<br />

[2] O.V. Sukhostavets, et al.,Appl. Phys. Express 4,065003(2011). [3] A. Vogel et al.,Phys. Rev. Lett.105,037201(2010). [4] S.<br />

Sugimoto et al.,Phys. Rev. Lett.106,197203(2011). [5] A. Barman et al.,J. Phys. D.43,422001(2010). [6] H. Jung et al.,Appl.<br />

Phys. Lett.97,222502(2010). [7] H. Jung et al.,Sci. Rep. 1,59;DOI:10.1038/srep00059(2011). [8] A. Vogel et al.,Phys. Rev.<br />

Lett.106,137201(2011). [9] K.-S. Lee et al.,J. Appl. Phys.110,113903(2011). [10] K. Y. Guslienko et al.,J. Appl. Phys.91,8037(2002).


RJ15<br />

Switching dynamics of vortex cores in nanodots by azimuthal-spinwave-mode<br />

excitati<strong>on</strong><br />

Myoung-woo Yoo, Jehyun Lee and Sang-koog Kim*<br />

Nati<strong>on</strong>al Creative Research Initiative Center for Spin Dynamics & Spin-Wave Devices & Nanospinics<br />

Lab, Research Institute of Adv. Materials, Dep. of Materials Sci. & Eng., Seoul Nat'l Univ., Seoul, Korea<br />

Owing to a possibility of implementati<strong>on</strong>s of magnetic vortices in future informati<strong>on</strong>-storage devices,<br />

vortex-core reversals have attracted much attenti<strong>on</strong> [1]. Very recently, ultrafast, low-power-driven core<br />

switching by azimuthal spin-wave mode was experimentally dem<strong>on</strong>strated [2]. Since their quantitative<br />

interpretati<strong>on</strong> and deeper understanding remain elusive, we start to elucidate the underlying physics of the<br />

switching dynamics. In this study, we performed micromagnetic simulati<strong>on</strong>s <strong>on</strong> a Permalloy disk of 302<br />

nm diameter and 50 nm thickness. We correlate the critical velocities (vc) and gyrofields (hz,cri) to the core<br />

switching driven res<strong>on</strong>antly by azimuthal mode excitati<strong>on</strong>s. For given disk’s dimensi<strong>on</strong>s and geometry<br />

used here, the vc increases to ~400 and ~700 m/s for m = -1 (clockwise) and +1 (counter-clockwise)<br />

modes, respectively, although vc is known to be ~330 m/s for the gyrati<strong>on</strong>-mode-assisted-core-switching<br />

mechanism [3]. This difference originates from the difference of hz,cri between the gyrati<strong>on</strong> mode and<br />

azimuthal mode driven core switching mechanisms because the magnetizati<strong>on</strong> dip of mz = -1 is necessary<br />

for the switching. From our calculati<strong>on</strong>s, hz,cri are estimated to be ~7 kOe and ~11 kOe for CW and CCW<br />

azimuthal mode excitati<strong>on</strong>s, compared to the value of hz,cri = 3.3 kOe for the gyrati<strong>on</strong> mode excitati<strong>on</strong> [4].<br />

*Corresp<strong>on</strong>ding author: sangkoog@snu.ac.kr [1] B. Van Waeyenberge et al., Nature (L<strong>on</strong>d<strong>on</strong>) 444, 461 (2006);<br />

S. -K. Kim et al., Appl. Phys. Lett. 92, 022509 (2008). [2] M. Kammerer et al., Nat. Commn. 2:279 doi: 10.1038/<br />

ncomms1277 (2011). [3] K.-S. Lee et al., Phys. Rev. Lett., 101, 267206 (2008). [4] M.-W. Yoo et al., Phys. Rev. B, 82,<br />

174437 (2010). [5] This work was supported by the Basic Science Research Program through the Nati<strong>on</strong>al Research<br />

Foundati<strong>on</strong> of Korea (NRF), funded by the Ministry of Educati<strong>on</strong>, Science and Technology (No. 20110000441).<br />

RJ16<br />

Logic operati<strong>on</strong>s based <strong>on</strong> magnetic-vortex-state networks<br />

Hyunsung Jung 1 , Youn-seok Choi 1 , D<strong>on</strong>g-soo Han 1 , Young-sang Yu 1 , Ki-suk Lee 1 ,<br />

Mi-young Im 2 , Peter Fischer 2 and Sang-koog Kim 1 *<br />

1 Nati<strong>on</strong>al Creative Research Initiative Center for Spin Dynamics & Spin-Wave<br />

Devices & Nanospinics Lab, Research Institute of Adv. Materials, Dep. of Materials<br />

Sci. & Eng., Seoul Nat'l Univ., Seoul, Korea<br />

2 Center for X-ray Optics, Lawrence Berkeley Nati<strong>on</strong>al Laboratory, Berkeley, CA<br />

94720, USA<br />

Logic operati<strong>on</strong>s based <strong>on</strong> coupled magnetic vortices were experimentally dem<strong>on</strong>strated. We utilized a<br />

simple chain structure c<strong>on</strong>sisting of three physically separated but dipolar-coupled vortex-state Permalloy<br />

disks as well as two electrodes for applicati<strong>on</strong> of the logical inputs. We directly m<strong>on</strong>itored the vortex<br />

gyrati<strong>on</strong>s in the middle disk, as the logical output, by time-resolved full-field soft X-ray microscopy<br />

measurements. By manipulating the relative polarizati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong>s of both end disks, two different<br />

logic operati<strong>on</strong>s are programmable: the XOR operati<strong>on</strong> for the parallel polarizati<strong>on</strong>, and the OR operati<strong>on</strong><br />

for the antiparallel polarizati<strong>on</strong>. This work paves the way for new-type programmable logic gates based<br />

<strong>on</strong> the coupled vortex-gyrati<strong>on</strong> dynamics achievable in vortex-state networks. The advantages are as<br />

follows: a low-power input signal by means of res<strong>on</strong>ant vortex excitati<strong>on</strong>, low-energy dissipati<strong>on</strong> during<br />

signal transportati<strong>on</strong> by selecti<strong>on</strong> of low-damping materials, and a simple patterned-array structure.<br />

*Corresp<strong>on</strong>ding author: sangkoog@snu.ac.kr This research was supported by the Basic Science Research Program through<br />

the Nati<strong>on</strong>al Research Foundati<strong>on</strong> of Korea (NRF), funded by the Ministry of Educati<strong>on</strong>, Science, and Technology (grant<br />

no. 20110000441). The operati<strong>on</strong> of the microscope was supported by the Director, Office of Science, Office of Basic Energy<br />

Sciences, Materials Sciences and Engineering Divisi<strong>on</strong>, U.S. Department of Energy, under c<strong>on</strong>tract no. DE-AC02-05-CH11231.<br />

RJ17<br />

Vortex-gyrati<strong>on</strong>-mediated magn<strong>on</strong>ic crystals<br />

D<strong>on</strong>g-soo Han and Sang-koog Kim*<br />

Nati<strong>on</strong>al Creative Research Initiative Center for Spin Dynamics & Spin-Wave Devices<br />

& Nanospinics Lab, Research Institute of Adv. Materials, Dep. of Materials Sci. &<br />

Eng., Seoul Nat'l Univ., Seoul, Korea<br />

Recently, mutual energy transfer between spatially separated magnetic disks has been studied and interpreted<br />

based <strong>on</strong> a coupled-vortex-oscillator model [1-5]. This novel energy-transfer mechanism provides the<br />

advantages of tunable energy transfer rate, low-power input signal, and extremely low energy dissipati<strong>on</strong><br />

for the case of using negligible damping materials. Here, we extended this study into magn<strong>on</strong>ic crystals of<br />

<strong>on</strong>e-dimensi<strong>on</strong>al (1D) and 2D arrays of dipolar-coupled magnetic disks. We analytically and numerically<br />

explored the fundamental modes of collective vortex-gyrati<strong>on</strong> excitati<strong>on</strong>s in such 1D and 2D disk-array<br />

magn<strong>on</strong>ic crystals of four different ordering of vortex polarizati<strong>on</strong> (p) and chirality (C) states. Both the<br />

analytical and numerical calculati<strong>on</strong>s show excellent quantitative agreement <strong>on</strong> c<strong>on</strong>trasting dispersi<strong>on</strong><br />

branches for different orderings of p and C states. Such collective vortex-gyrati<strong>on</strong> modes can be understood<br />

in terms of the energy variati<strong>on</strong> of dynamic dipolar interacti<strong>on</strong> between the neighboring vortex-state disks.<br />

These results provide for the possibility of vortex-gyrati<strong>on</strong>-mediated magn<strong>on</strong>ic crystals as applicati<strong>on</strong>s for<br />

future signal processing devices, offering the advantages of low energy dissipati<strong>on</strong> and low power input.<br />

This work was supported by Basic Science Research Program through the Nati<strong>on</strong>al Research Foundati<strong>on</strong> of<br />

Korea (NRF) funded by the Ministry of Educati<strong>on</strong>, Science and Technology (No. 20110000441).<br />

*Corresp<strong>on</strong>ding author: sangkoog@snu.ac.kr [1] J. Shibata et al., Phys. Rev. B 67, 224404 (2003). [2] J.<br />

Shibata et al., Phys. Rev. B 70, 012404 (2004) [3] S. Barman et al., IEEE Trans. Mag. 46, 1342 (2010) [4] H.<br />

Jung et al., Appl. Phys. Lett. 97, 222502 (2010); H. Jung et al., Sci. Rep. 1, 59 ; DOI:10.1038/srep00059 (2011);<br />

A. Vogel et al. Phys. Rev. Lett. 106, 137201 (2011); S. Sugimoto et al. Phys. Rev. Lett. 106, 197203 (2011). [5]<br />

K.-S. Lee et al., J. Appl. Phys. 110, 113903 (2011); O.V. Sukhostavets, Appl. Phys. Express 4, 065003 (2011).<br />

RJ18<br />

RJ19<br />

RJ20<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Vortex-gyrati<strong>on</strong> transfer rate and energy attenuati<strong>on</strong> in coupled<br />

nanodisks<br />

Ji-hye Kim, Ki-suk Lee, Hyunsung Jung, D<strong>on</strong>g-soo Han and Sang-koog Kim*<br />

Nati<strong>on</strong>al Creative Research Initiative Center for Spin Dynamics & Spin-Wave Devices<br />

& Nanospinics Lab, Research Institute of Adv. Materials, Dep. of Materials Sci. &<br />

Eng., Seoul Nat'l Univ., Seoul, Korea<br />

One of the most important research goals in current informati<strong>on</strong>-signal processing technologies is to enhance<br />

signal-processing speed and to reduce energy loss[1]. In recent electr<strong>on</strong>ic devices, informati<strong>on</strong>-signal transports<br />

are based <strong>on</strong> the moti<strong>on</strong> of electr<strong>on</strong> charges. Interestingly, coupled vortex oscillati<strong>on</strong>s in nanodots can be used<br />

as an alternative mechanism of informati<strong>on</strong>-signal processing[2-4]. Here, we report a study of, by analytical<br />

and micromagnetic numerical calculati<strong>on</strong>s, informati<strong>on</strong>-signal transfer in vortex-state nanodisks that is<br />

available with assistance of vortex-gyrati<strong>on</strong> transfer through the dynamic dipolar interacti<strong>on</strong>. We analytically<br />

derived the vortex-gyrati<strong>on</strong> transfer rate and energy attenuati<strong>on</strong> that are both technologically essential<br />

parameters for c<strong>on</strong>trolling signal processing speed and energy loss in signal processing devices. It is found that<br />

the transfer rate can be c<strong>on</strong>trolled by the relative polarizati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong> p1p2, the saturati<strong>on</strong> magnetizati<strong>on</strong><br />

Ms, and the radius (R)-to-thickness (L) ratio R/L of given magnetic disks as well as interdistance. The energy<br />

attenuati<strong>on</strong> is governed by not <strong>on</strong>ly the intrinsic damping c<strong>on</strong>stant of a given material, but also the values of<br />

Ms, L, and R. The analytical results are in reas<strong>on</strong>able agreements with micromagnetic simulati<strong>on</strong> results. This<br />

work provides a foundati<strong>on</strong> of manipulating informati<strong>on</strong>-signal processing between vortex-state networks.<br />

* Corresp<strong>on</strong>ding author : sangkoog@snu.ac.kr. [1] K. Bernstein et al., Proc. IEEE 98, 2169 (2010). [2] H. Jung et al., Appl. Phys.<br />

Lett. 97, 222502 (2010). [3] H. Jung et al., Sci. Rep. 1, 59; DOI:10.1038/srep00059 (2011). [4] S. Barman et al., IEEE Trans. Magn.<br />

46, 1342 (2010). [5] A. Vogel et al., Phys. Rev. Lett. 106, 137201 (2011). [6] This work was supported by the Basic Science Research<br />

Program through the NRF of Korea funded by the Ministry of Educati<strong>on</strong>, Science and Technology (Grant No. 20110000441).<br />

Effect of spin-motive force and spin-diffusi<strong>on</strong> <strong>on</strong> a vortex dynamics<br />

Jung-hwan Mo<strong>on</strong> 1 , Aurelien Manch<strong>on</strong> 2 and Kyung-jin Lee 1 *<br />

1<br />

Department of Materials Science and Engineering, Korea University, Seoul 136-<br />

713, Korea, Korea<br />

2<br />

Materials Science and Engineering, Divisi<strong>on</strong> of Physical Science and Engineering,<br />

KAUST, Thuwal 23955, Saudi Arabia, Saudi Arabia<br />

Theoretically, it is known that the dynamics of magnetic texture highly depends <strong>on</strong><br />

damping (α) and n<strong>on</strong>-adiabatic parameter (β). However, the value of β is c<strong>on</strong>troversial<br />

both theoretically and experimentally. Moreover, it was recently reported that α and β are<br />

also affected by the spin c<strong>on</strong>figurati<strong>on</strong>. The former comes from spin-motive force(SMF)<br />

[1, 2] and the latter comes from torque which is exerted from spin-diffusi<strong>on</strong> [3]. In order<br />

to understand the spin dynamics under complex spin texture, it is needed to study the<br />

effect of SMF and spin-diffusi<strong>on</strong> <strong>on</strong> α and β. In this work, we performed micromagnetic<br />

simulati<strong>on</strong> using LLG equati<strong>on</strong> with spin torque term, SMF, and spin-diffusi<strong>on</strong>. The currentinduced<br />

dynamics of a vortex core is micromagnetically modeled using a computati<strong>on</strong>al<br />

framework based <strong>on</strong> the fourth-order Runge-Kutta method. The model system is a circular<br />

Permalloy disk with the thickness of 20 nm and the diameter of 270 nm which is vortex<br />

favored dimensi<strong>on</strong>. Initial trajectory with spin-diffusi<strong>on</strong> was shifted al<strong>on</strong>g y-axis directi<strong>on</strong><br />

compared to that without spin-diffusi<strong>on</strong>. It is because that the initial moti<strong>on</strong> of a core moti<strong>on</strong><br />

is governed by n<strong>on</strong>-adiabaticity [4]. The further studies will be discussed in detail.<br />

[1] S. Zhang and S.-L. Zhang, Phys. Rev. Lett. 102, 086601 (2009). [2] J.-H. Mo<strong>on</strong>, S,-M. Seo, and K.-J. Lee, IEEE Trans. Magn.,<br />

vol. 46, p.2167 (2010) [3] A. Manch<strong>on</strong>, W.-S. Kim, and K.-J. Lee, unpublished. [4] J.-H. Mo<strong>on</strong> et al., Phys. Rev. B 79, 134410 (2009).<br />

Soft X-ray microscopy of n<strong>on</strong>-linear magnetic vortex core moti<strong>on</strong><br />

Peter Fischer 1 , Brooke Mesler 1 , Mi-young Im 1 and Kristen Buchanan 2<br />

1 CXRO, LBNL, USA<br />

2 Colorado State U, USA<br />

<strong>Magnetism</strong> <strong>on</strong> the nanometer length scale and its fast spin dynamics is a scientfically<br />

highly attractive and technologically relevant topic. It addresses fundamental magnetic<br />

length scales e.g. magnetic exchange lengths in the sub-10nm range and fast time<br />

scales in the sub-ns regime where precessi<strong>on</strong>al and relaxati<strong>on</strong> phenomena, domain<br />

wall moti<strong>on</strong> and vortex dynamics occur [1,2]. New technological c<strong>on</strong>cepts such as<br />

spintr<strong>on</strong>ics require precise c<strong>on</strong>trol the electr<strong>on</strong> spin <strong>on</strong> a nanoscale with psec timing.<br />

We use time magnetic soft X-ray microscopy providing a spatial resoluti<strong>on</strong> down<br />

to 10nm and a temporal resoluti<strong>on</strong> below 100ps [3]. As <strong>on</strong>e example, we report<br />

experimental results showing n<strong>on</strong>-linear behavior in the res<strong>on</strong>ant excitati<strong>on</strong> of<br />

magnetic vortex cores with increasing amplitude of the exciting magnetic AC fields<br />

[4]. Supported by the Director, Office of Science, Office of Basic Energy Sciences,<br />

Materials Sciences and Engineering Divisi<strong>on</strong>, of the U.S. Department of Energy.<br />

[1] L. Bocklage, et al. Phys Rev B 81, 054404 (2010) [2] S. Kasai, et al Phys Rev Lett 101, 237203<br />

(2008) [3] P. Fischer, Materials Today 13(9) 14 (2010) [4] B. Mesler et al J.Appl. Phys. (2012) in<br />

print<br />

July 8 - 13, 2012 Busan, Korea 171<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RK01<br />

Dynamics of Successive Minor Hysteresis Loops<br />

Alexander Gerber and Yoav W Windsor<br />

School of Physics and Astr<strong>on</strong>omy, Tel Aviv University, Israel<br />

Cumulative growth of successive minor hysteresis loops in Co/Pd multilayers with<br />

perpendicular anisotropy was studied in the c<strong>on</strong>text of time dependent magnetizati<strong>on</strong><br />

reversal dynamics. We show that in disordered ferromagnets, where magnetizati<strong>on</strong><br />

reversal involves nucleati<strong>on</strong>, domains’ expansi<strong>on</strong> and annihilati<strong>on</strong>, differences between<br />

the time dependencies of these processes are resp<strong>on</strong>sible for accumulati<strong>on</strong> of nuclei for<br />

rapid domain expansi<strong>on</strong>, for the asymmetry of forward and backward magnetizati<strong>on</strong><br />

reversals and for the respective cumulative growth of hysteresis loops. Loops stop<br />

changing and become macroscopically reproducible when populati<strong>on</strong>s of upward<br />

and downward nucleati<strong>on</strong> domains balance each other and the respective upward and<br />

downward reversal times stabilize.<br />

RK02<br />

Gilbert damping c<strong>on</strong>stants of exchange biased NiFe/FeMn bilayers<br />

Jungbum Yo<strong>on</strong>, Hyeok-cheol Choi and Chun-yeol You*<br />

Department of Physics, Inha Universirty, Korea<br />

The physics of exchange bias effect has been studied intensively for the past decades,<br />

however, a few experiments have been reported about the spin dynamics and damping<br />

mechanism for the exchange biased systems. Recently, the vector network analyzer<br />

ferromagnetic res<strong>on</strong>ance (VNA-FMR) is employed to research the spin dynamics of<br />

ferromagnetic thin films with wide range microwave frequencies. In this study, the<br />

dynamics magnetic properties of the NiFe/FeMn bilayers is investigated by VNA-FMR<br />

with various external static field. The exchange bias is verified by vibrating sample<br />

magnetometer and VNA-FMR with varying the thickness of FeMn. Spin dynamics and<br />

the Gilbert damping c<strong>on</strong>stants of exchange biased NiFe/FeMn bilayers are investigated<br />

by the analysis of FMR spectra. The exchange bias field induced asymmetry in the<br />

magnetizati<strong>on</strong> hysteresis loops. It implies the spin dynamics must be asymmetry<br />

for positive and negative field regi<strong>on</strong>. We perform VNA-FMR measurement for<br />

positive and negative fields. In results, we find that the apparent damping parameters<br />

are different in the both field directi<strong>on</strong>s in the exchange biased NiFe/FeMn bilayers.<br />

Therefore, we c<strong>on</strong>jecture that the exchange bias layer acts differently, depends <strong>on</strong> the<br />

relative directi<strong>on</strong> of the ferromagnetic layer magnetizati<strong>on</strong> to the exchange bias field.<br />

RK03<br />

N<strong>on</strong>-linear susceptibility and influence of the applied magnetic field <strong>on</strong><br />

ZFC/FC curves<br />

Florent Tournus*, Arnaud Hilli<strong>on</strong>, Alexandre Tami<strong>on</strong> and Ver<strong>on</strong>ique Dupuis<br />

LPMCN, CNRS & Univ. Ly<strong>on</strong> 1 , France<br />

ZFC/FC curves are widely used to characterize assemblies of magnetic nanoparticles.<br />

They reflect the crossover between the blocked and superparamagnetic (SP) regime<br />

with increasing temperature. With a low applied field a linear resp<strong>on</strong>se can be assumed,<br />

the shape of the curves is then independent of the applied field H, and a simple<br />

theoretical modeling is possible: this allows efficient theoretical fits of experimental<br />

curves. We have studied the influence of the applied field magnitude <strong>on</strong> the ZFC/<br />

FC curves shape, both theoretically and experimentally. While the effect of H <strong>on</strong> the<br />

energy barriers has already been discussed, its effect <strong>on</strong> the resp<strong>on</strong>se of SP particles<br />

has not been c<strong>on</strong>sidered. However, this n<strong>on</strong>-linearity manifests itself much before<br />

the modificati<strong>on</strong> of the switching energy distributi<strong>on</strong>. In additi<strong>on</strong> to experimental<br />

measurements <strong>on</strong> a diluted Co nanoparticle assembly, we have simulated ZFC/FC<br />

curves for different applied fields, including the third-order susceptibility in the SP<br />

resp<strong>on</strong>se. The later depends <strong>on</strong> the anisotropy and does not at all corresp<strong>on</strong>d to a<br />

Langevin functi<strong>on</strong> around the blocking temperature. We find that the curves can be<br />

significantly affected (in particular the low temperature limit of the FC) for quite low<br />

applied fields, which are usually used in experiments.<br />

172 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RK04<br />

On the relati<strong>on</strong> between the magnetoelastic effect and the damping<br />

c<strong>on</strong>stants of (Ni-Fe) 1-xM x (M = Ag, Cr, Ga, Au, Pd, and Pt) films<br />

Yasushi Endo*, Yoshio Mitsuzuka, Yutaka Shimada and Masahiro Yamaguchi<br />

ECEI, Graduate School of Engineering, Tohoku University, Japan<br />

The dynamics of magnetic thin films have received attenti<strong>on</strong> in magnetic device<br />

applicati<strong>on</strong>s such as recording heads, media, and MRAM. Although the dynamics<br />

significantly depend <strong>on</strong> the damping c<strong>on</strong>stant α, which determines the strength of<br />

damping torque in magnetic thin films, details about their damping mechanism,<br />

especially the magnetoelastic effect <strong>on</strong> damping remain unclear. Herein to clarify the<br />

effect of λs <strong>on</strong> α in (Ni-Fe) 1-xM x films in detail, we evaluated α and λs in these films.<br />

For M= Au, Pd, and Pt, α increases linearly and negative λs increases as x increases. In<br />

c<strong>on</strong>trasts, α and positive λs tend to increase almost linearly with x when M=Ag, Cr, and<br />

Ga. These results provide clear evidence that α is correlated with λs in (Ni-Fe)-M films.<br />

Furthermore, increments of α and the absolute value of λs to x are markedly enhanced<br />

in the order of M = Pt, Au, Pd, Cr, Ag, and Ga, suggesting that 5d transiti<strong>on</strong> metal<br />

dopants are more influential <strong>on</strong> both α and λs than 3d and 4d transiti<strong>on</strong> metal dopants<br />

due to the str<strong>on</strong>g spin-orbit interacti<strong>on</strong> of 5d dopants. C<strong>on</strong>sequently, these results<br />

dem<strong>on</strong>strate that a change in magnetostricti<strong>on</strong> energy via transiti<strong>on</strong> metal dopants can<br />

effectively c<strong>on</strong>trol α.<br />

This work is partly supported by KAKENHI (No. 23686047) from MEXT, Japan, A-STEP from JST,<br />

Japan, and SRC.<br />

RK05<br />

Ultrafast magnetizati<strong>on</strong> dynamics of ferromagnetic systems induced<br />

by mid infrared laser pulses<br />

Amani Zagdoud, Mircea Vomir, Michele Albrecht and Jean-yves Bigot<br />

IPCMS, France<br />

The aim of the present study is to show how the ultrafast demagnetizati<strong>on</strong> and the<br />

subsequent rapid re-magnetizati<strong>on</strong> occur when exciting a ferromagnetic material with<br />

low energy infrared pulses. We have used mid-infrared femtosec<strong>on</strong>d laser pulses (λ=<br />

[3-10 μm]) to excite CoPt3, Ni and Co ferromagnetic thin films. The magneto-optical<br />

resp<strong>on</strong>se is then probed in the visible (λ = 798nm). Our results show that even though<br />

<strong>on</strong>ly intraband transiti<strong>on</strong>s occur, the demagnetizati<strong>on</strong> process and its subsequent<br />

relaxati<strong>on</strong> to the lattice and to the envir<strong>on</strong>ment are still the dominant processes<br />

involved in the magnetizati<strong>on</strong> dynamics. We also show that the material band structure<br />

is important to interpret the thermalizati<strong>on</strong> dynamics of the spins that occur before<br />

the heating of the lattice. For specific experimental c<strong>on</strong>figurati<strong>on</strong>s, we show that it is<br />

possible to induce a moti<strong>on</strong> of precessi<strong>on</strong> of the magnetizati<strong>on</strong> around the effective<br />

magnetic field and observe it while it is damped. The magnetizati<strong>on</strong> dynamics induced<br />

at 6.5 μm in nickel shows an oscillatory behaviour with a period of 2 ps. We attribute<br />

this result to the excitati<strong>on</strong> of a two-magn<strong>on</strong>s mode <strong>on</strong> the NiO by an acoustic mode<br />

generated in nickel.<br />

RK06<br />

Ferromagnetic res<strong>on</strong>ance of bilayer CoFeB/NiFeSiB thin film<br />

Sangho<strong>on</strong> Jung 1 , Chang Ho Choi 1 , Jungbum Yo<strong>on</strong> 2 , Chun-yeol You 2 , Seung Hyun<br />

Kim 3 , Young Keun Kim 3 and Myung-hwa Jung 1<br />

1 Sogang University, Korea<br />

2 Inha University, Korea<br />

3 Korea University, Korea<br />

Spin transfer torque magnetic random access memory (STT-MRAM) is <strong>on</strong>e of the<br />

candidates for next generati<strong>on</strong> random access memory. For practical applicati<strong>on</strong>, the<br />

device should have high thermal stability and low critical current density. They have<br />

str<strong>on</strong>g correlati<strong>on</strong> with saturati<strong>on</strong> magnetizati<strong>on</strong> (Ms) and damping c<strong>on</strong>stant (α) so that<br />

we need to determine Ms and α. To study the damping mechanism of the thin films, we<br />

have performed ferromagnetic res<strong>on</strong>ance (FMR) experiments through vector network<br />

analyzer with bilayer thin films of CoFeB(10-x nm)/NiFeSiB(x nm) (x=0,1,2,….,10).<br />

We have fitted the FMR data with Lorentz functi<strong>on</strong> to get the informati<strong>on</strong> of res<strong>on</strong>ance<br />

frequency and line width. From these two fitting parameters, we could get Ms and α by<br />

Kittel formula and Full Width at Half Maximum. As increasing x values, the Ms tends<br />

to increase, whereas the α suddenly decrease and then saturate. This implies that the<br />

added NiFeSiB layer in CoFeB plays a role to prevent the spins align al<strong>on</strong>g the field<br />

directi<strong>on</strong>.


RK07<br />

Observati<strong>on</strong> of n<strong>on</strong>-kittel ferromagnetic res<strong>on</strong>ance in Co/Cu<br />

multilayer system<br />

Faris B. Abdul Ahad 1 , Yu-che Chiu 1 , Shang-fan Lee 2 * and Dung S Hung 3<br />

1 Institute of Physics, Academia Sinica, Taiwan<br />

2 Institute o Physics, Academia Sinica, Taiwan<br />

3 Informati<strong>on</strong> and Telecommunicati<strong>on</strong>s Engineering, Ming Chuan University, Taiwan<br />

In this research, we study the ferromagnetic res<strong>on</strong>ance behavior (FMR) of Co/Cu multilayer system.<br />

The samples stacking Ta (5nm) / [Co (4nm) / Cu (t)]*10 / Ta (5nm) with t = 0.5 ? 6 nm were prepared<br />

by dc magnetr<strong>on</strong> sputtering in a multitarget sputtering chamber at room temperature and 1 mTorr of pure<br />

Ar-pressure. The magnetoresistance (MR) was measured by the standard four point measurement with<br />

current in plane (CIP) c<strong>on</strong>figurati<strong>on</strong> using Quantum Design Physical Properties Measurement System<br />

(PPMS). The magnetic hysteresis loops were recorded using a Vibrating Sample Magnetometer (VSM).<br />

FMR resp<strong>on</strong>ses were measured at microwave frequencies by means of a Vector Network Analyzer (VNA)<br />

equipped with a low pass filter circuit. Clear FMR resp<strong>on</strong>ses were recorded for all samples, however,<br />

the noise increased for samples with thicker spacer. Then res<strong>on</strong>ance frequencies (fr) acquired from FMR<br />

resp<strong>on</strong>ses. Theoretically, this FMR should follow Kittel frequency given by: fr=(γ/2π)√H(H+4πM).<br />

However, our results shows that the res<strong>on</strong>ace linewidth and the deviati<strong>on</strong> of res<strong>on</strong>ance frequency from<br />

kittel behavior will increases as the spacer thickness increased. This behavior is the result of RKKY<br />

interacti<strong>on</strong> evident by the increased GMR and will be dicussed within the manuscript.<br />

1. N. Smith and P. Arnett, Appl. Phys. Lett. 78, 1448 (2001). 2. N. Smith, J. Appl. Phys. 90, 5768 (2001). 3. J. C. Jury, et.al,<br />

IEEE Trans. Magn. 38, 3545 (2002). 4. Z. Jin and H. N. Bertram, IEEE Trans. Magn. 38, 2265 (2003). 5. Abdul Ahad F.<br />

B., Hung D. S., Chiu C. Y. and Lee S. F., IEEE Trans. Mag. 47, 4227 (2011). 6. Hung, D. S.; Fu, Y. P.; Lee, S. F.; Yao, Y. D.;<br />

Abdul Ahad, Faris B, J. Appl. Phy. 107, 09A503 (2010). 7. B. Heinrich and J.F. Cohran, Adv. Phys. 42, 523 (1993).<br />

RK08<br />

Neighboring layer dependence of ultrafast thermo-magnetic property<br />

in GdFeCo films<br />

Arata Tsukamoto*, Tetsuya Sato, Shingo Toriumi, Ryutarou Shimizu and Akiyoshi Itoh<br />

Electr<strong>on</strong>ics & Computer Science, College of Science and Technology Nih<strong>on</strong><br />

University, Japan<br />

Femtosec<strong>on</strong>d pulsed laser light allow excitati<strong>on</strong> of magnetic systems much shorter than the time scale of<br />

thermal diffusi<strong>on</strong> represented by c<strong>on</strong>venti<strong>on</strong>al Fourier's law. In this time scale, heating and demagnetizati<strong>on</strong><br />

phenomena arise via str<strong>on</strong>gly n<strong>on</strong>-equilibrium n<strong>on</strong>-adiabatic way, and cannot be explained by c<strong>on</strong>venti<strong>on</strong>al<br />

equilibrium thermo dynamics descripti<strong>on</strong>[1]. In this study, we investigated the neighboring layer dependence<br />

of ultrashort laser-induced thermal/magnetic resp<strong>on</strong>se in layered GdFeCo films by all-optical pumpprobe<br />

method. Simultaneously, change of normalized reflectivity was measured for m<strong>on</strong>itoring the time<br />

evoluti<strong>on</strong> of electr<strong>on</strong> temperature Te. We designed layered structures as same 20 nm thick GdFeCo with<br />

different neighboring layers (c<strong>on</strong>ductive AlTi and insulating SiN). We found two characteristic time regi<strong>on</strong><br />

from magnetic behavior: (A) rapid step-like demagnetizati<strong>on</strong> and (B) following recovering process with<br />

precessi<strong>on</strong>al moti<strong>on</strong>. The time scale of (A) is c<strong>on</strong>formed as within picosec<strong>on</strong>ds range (time c<strong>on</strong>stant ~100<br />

fs) independently with film structure, which is much shorter than ferromagnetic res<strong>on</strong>ance (period ~0.1 ns at<br />

10 GHz ) and hundreds fs delayed with respect to the increase of Te. Following regime (B), film structural<br />

dependency of precessi<strong>on</strong>al magnetic moti<strong>on</strong> was appeared. The difference of precessi<strong>on</strong> frequency and<br />

damping properties indicate the different time evoluti<strong>on</strong> of lattice temperature in magnetic layer.<br />

[1] I. Radu, K. Vahaplar, C. Stamm, T. Kachel, N. P<strong>on</strong>tius, H. A. Durr, T. A. Ostler, J. Barker, R. F. L. Evans,<br />

R. W. Chantrell, A. Tsukamoto, A. Itoh, A. Kirilyuk, Th. Rasing and A. V. Kimel, Transient ferromagnetic-like<br />

state mediating ultrafast reversal of antiferromagnetically coupled spins, Nature, 472 (2011) 205.<br />

RK09<br />

Magnetizati<strong>on</strong> dynamics in perpendicular magnetic anisotropy CoFeB/<br />

MgO system<br />

Je<strong>on</strong>g Woo Sohn 1 , Ji-wan Kim 1 , Kye<strong>on</strong>g-d<strong>on</strong>g Lee 1 , Hy<strong>on</strong>-seok S<strong>on</strong>g 1 , Il-jae Shin 2 ,<br />

Byoung-chul Min 2 , Chun-yeol You 3 and Sung-chul Shin 4 *<br />

1<br />

Department of Physics, Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST,<br />

Korea<br />

2<br />

Center for Spintr<strong>on</strong>ics Research, KIST, Korea<br />

3<br />

Department of Physics, Inha University, Korea<br />

4<br />

Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST, Department of Emerging<br />

Materials Science, DGIST, Korea<br />

We study the ultrafast magnetizati<strong>on</strong> dynamics of perpendicularly magnetized MgO/CoFeB/Ta<br />

and Ta/CoFeB/MgO stack structures which gains wide attenti<strong>on</strong> from a viewpoint of perpendicular<br />

magnetic tunnel juncti<strong>on</strong>s. An all-optical time-resolved magneto-optical Kerr effect measurement<br />

reveals that effective Gilbert damping α stays unchanged at ~0.02 in high external field regardless<br />

of pump fluence, but it declines drastically with the increase of pump fluence in weak external field.<br />

This can be explained by the enlarged apparent relaxati<strong>on</strong> time due to slow remagnetizati<strong>on</strong>. Genuine<br />

damping tends to attract the precessing magnetizati<strong>on</strong> vector towards the effective equilibrium axis,<br />

while the tip of the reduced magnetizati<strong>on</strong> vector after pump pulse heating recovers growing away<br />

from the effective axis. These two competing c<strong>on</strong>tributi<strong>on</strong>s determine the apparent relaxati<strong>on</strong> time.<br />

In a weak field regime, slow recovery of the magnetizati<strong>on</strong> vector results in the increased relaxati<strong>on</strong><br />

time and low effective Gilbert damping. We believe that low Gilbert damping found in CoFeB/MgO<br />

structure will be expected to reduce the critical current for current-induced magnetizati<strong>on</strong> switching.<br />

RK10<br />

RK11<br />

RK12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Compositi<strong>on</strong> dependence of the gilbert damping c<strong>on</strong>stant for co-based<br />

heusler alloy<br />

Yuichi Kasatani 1 , Shinya Yamada 2 , Masanobu Miyao 3 , Kohei Hamaya 4 , Hiroyoshi Ito 5 and Yukio Nozaki 6 *<br />

1 Department of Physics, Keio University, Japan<br />

2 Department of Electr<strong>on</strong>ics, Kyushu University, Japan<br />

3 Department of Electr<strong>on</strong>ics, Kyushu University / CREST, JST, Japan<br />

4 Department of Electr<strong>on</strong>ics, Kyushu University / PREST, JST, Japan<br />

5 Department of Pure and Applied Physics, Kansai University / CREST, JST, Japan<br />

6 Department of Physics, Keio University / CREST JST, Japan<br />

Spin polarized current attracts much attenti<strong>on</strong> to operate the magnetic memory devices. To reduce the<br />

spin current density, the materials with small Gilbert damping are needed. Recently, it is reported that the<br />

Gilbert damping c<strong>on</strong>stant of Co-based Heusler alloy known as half-metallic ferromagnet is less than 0.01[1],<br />

although the Gilbert damping factor of Co-based Heusler alloy are closely related to crystalline structure<br />

and c<strong>on</strong>centrati<strong>on</strong> ratio. In this study, to understand the damping mechanism in high-quality L 21-type Cobased<br />

Heusler alloy we measured ferromagnetic res<strong>on</strong>ance (FMR) and estimated the Gilbert damping<br />

factor. 25 nm thick L2 1-type Co 2-xFe xSi (x=0, 1, 1.5) films for which degree of crystalline order were found<br />

to be about 70%[2] were grown <strong>on</strong> Si(111) substrates. The saturati<strong>on</strong> magnetizati<strong>on</strong> of Co 2-xFe xSi with<br />

x=0, 1, 1.5 are 1106, 1023 and 980 emu/cm 3 , respectively. SiO 2 insulating layer and coplanar waveguides<br />

(CPW) which c<strong>on</strong>sists of Ti (5 nm)/Au (60 nm) were prepared. Following that, FMR was measured<br />

using a vector network analyzer. The results show the Gilbert damping c<strong>on</strong>stant inversely proporti<strong>on</strong>al<br />

to saturati<strong>on</strong> magnetizati<strong>on</strong>. C<strong>on</strong>sidering the electr<strong>on</strong> density of state from the ab initio calculati<strong>on</strong>, the<br />

broadening of FMR spectra is c<strong>on</strong>sidered to be related to the electr<strong>on</strong> density of state.<br />

[1] T. Kubota, S. Tsunegi, M. Oogane, S. Mizukami, T. Miyazaki, H. Naganuma and Y. Ando, Appl. Phys. Lett., 94 122504<br />

(2009). [2] S. Yamada, K. Hamaya, K. Yamamoto, T. Murakami, K. Mibu and M. Miyao, Appl. Phys. Lett., 96, 082511 (2010).<br />

Detecti<strong>on</strong> of picosec<strong>on</strong>d magnetizati<strong>on</strong> dynamics of 50 nm magnetic<br />

dots down to the single nanodot regime<br />

Bivas Rana, Dheeraj Kumar, Saswati Barman, Semanti Pal, Yasuhiro Fukuma,<br />

Yoshichika Otani and Anjan Barman*<br />

C<strong>on</strong>densed Matter Physics and Material Sciences, S. N. Bose Nati<strong>on</strong>al Centre For<br />

Basic Sciences, India<br />

We present the detecti<strong>on</strong> of the picosec<strong>on</strong>d dynamics in arrays of 50 nm permalloy dots<br />

down to the single nanodot regime by an all-optical time-resolved magneto-optical Kerr<br />

effect microscope. The inter-dot separati<strong>on</strong> (S) varies from 200 to 50 nm and simulated<br />

magnetostatic fields shows a transiti<strong>on</strong> from magetostatically isolated to str<strong>on</strong>gly coupled<br />

regime as S decreases. C<strong>on</strong>sequently, we observe a single precessi<strong>on</strong>al mode for S down to<br />

75 nm, whose frequency increases with the decrease in S. At the smallest separati<strong>on</strong> S = 50<br />

nm, we observe a mode splitting. The simulated mode profile reveals that the dynamics of<br />

a single 50 nm dot is dominated by the edge mode. In sparsely packed arrays we primarily<br />

observe the isolated dynamics of the c<strong>on</strong>stituent dots in phase. For S = 50 nm, we observe an<br />

additi<strong>on</strong>al backward volume magnetostatic mode of the array. The damping is minimum for<br />

S = 200 nm but increases linearly with the decrease in S as a result of the dynamic dephasing<br />

of the precessi<strong>on</strong> of the weakly interacting dots. At S = 50 nm, the dephasing due to the<br />

superpositi<strong>on</strong> of two res<strong>on</strong>ant modes results in a sudden increase in the apparent damping.<br />

1. B. Rana, S. Pal, S. Barman, Y. Fukuma, Y. Otani, and A. Barman, Appl. Phys. Express 4, 113003 (2011). 2. A.<br />

Barman, S. Wang, J. D. Maas, A. R. Hawkins, S. Kw<strong>on</strong>, A. Liddle, J. Bokor, H. Schmidt, Nano Lett. 6, 2939 (2006).<br />

3. B. Rana, D. Kumar, S. Barman, S. Pal, Y. Fukuma, Y. Otani, and A. Barman, ACS Nano 5, 9559 (2011).<br />

Femtosec<strong>on</strong>d demagnetizati<strong>on</strong> in Ni: Electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> spin flip<br />

scattering from first principles<br />

Karel Carva 1 , Marco Battiato 2 and Peter M Oppeneer 2<br />

1 DCMP, Charles University in Prague, Czech Republic<br />

2 Uppsala University, Sweden<br />

The femtosec<strong>on</strong>d demagnetizati<strong>on</strong> discovered in 1996 [1] represents a critical test of magnetizati<strong>on</strong><br />

dynamics theories and may lead to many interesting applicati<strong>on</strong>s. It is still far from being understood<br />

<strong>on</strong> a microscopic level. Electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> spin-flip scattering in Ni was suggested to be the microscopic<br />

explanati<strong>on</strong> of its femtosec<strong>on</strong>d laser-induced demagnetizati<strong>on</strong> [2]. We have calculated the spin-flip<br />

Eliashberg functi<strong>on</strong> [3] based <strong>on</strong> ab initio electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> coupling matrix elements, which allows us<br />

to obtain the spin-flip probability with much higher accuracy. We extend this method also to the regime<br />

of n<strong>on</strong>-equilibrated electr<strong>on</strong> distributi<strong>on</strong>s relevant for ultrafast processes. We have found that the spinflip<br />

probability depends str<strong>on</strong>gly <strong>on</strong> electr<strong>on</strong> energy. We c<strong>on</strong>sider two cases for system excited by a laser:<br />

thermalized very hot electr<strong>on</strong> distributi<strong>on</strong>s, as well as highly n<strong>on</strong>-equilibrium electr<strong>on</strong> distributi<strong>on</strong>s that are<br />

expected to be present immediately after the fs laser excitati<strong>on</strong>. Employing this approach we compute the<br />

electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> SF rates. We find that the demagnetizati<strong>on</strong> rate is very low for any thermalized electr<strong>on</strong><br />

distributi<strong>on</strong> as compared to n<strong>on</strong>-equilibrium distributi<strong>on</strong>s present within first femtosec<strong>on</strong>ds following the<br />

pump laser [3]. This is due to the density of states and the specific energy-dependence of SF probability.<br />

[1] E. Beaurepaire, J.-C. Merle, A. Daunois J.-Y. Bigot, Phys. Rev. Lett. 76, 4250 (1996). [2] B. Koopmans,<br />

G. Malinowski, F. Dalla L<strong>on</strong>ga, D. Steiauf, M. Fahnle, T. Roth, M. Cinchetti, M. Aeschlimann, Nature<br />

Mater. 9, 259 (2010). [3] K. Carva, M. Battiato, P. M. Oppeneer, Phys. Rev. Lett., 107, 207201 (2011)<br />

July 8 - 13, 2012 Busan, Korea 173<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RK13<br />

Ultrafast magneto-acoustic pulses in a nickel film<br />

Jiwan Kim, Mircea Vomir and Jean-yves Bigot*<br />

Physics, IPCMS, CNRS, France<br />

We report about the ultrafast magnetizati<strong>on</strong> dynamics induced by magneto-acoustic<br />

pulses in a 200-nm-thick Ni film generated with femtosec<strong>on</strong>d laser pulses. The<br />

magneto-acoustic pulses result from the coupling between the magnetizati<strong>on</strong> and<br />

the acoustic waves generated by the laser pulses. In order to distinguish between<br />

dynamical magnetic effects induced either by the thermal excitati<strong>on</strong> or by the magnetoacoustic<br />

pulse, the spin dynamics is measured from both the fr<strong>on</strong>t and rear sides of the<br />

film via the magneto-optical Kerr technique. It is found that the acoustic pulses excite<br />

the magnetizati<strong>on</strong> <strong>on</strong> both sides of the film and the perturbati<strong>on</strong> of the magnetizati<strong>on</strong><br />

is very efficient at the rear side (10% of the static <strong>on</strong>e). Using a detailed modeling<br />

of magneto-acoustic pulses combining the c<strong>on</strong>cepts of acoustic pulse propagati<strong>on</strong><br />

and ultrafast magnetizati<strong>on</strong> dynamics, we reproduce the magnetizati<strong>on</strong> dynamics <strong>on</strong><br />

both sides of the film. In additi<strong>on</strong>, our results imply that the magnitude of magnetoacoustic<br />

pulses can be c<strong>on</strong>trolled and maximized by selecting proper substrates with<br />

same ferromagnetic materials. We forecast that our results will have a str<strong>on</strong>g impact<br />

for making ultrafast magneto-acoustic devices, with the capability of sensing the<br />

magnetizati<strong>on</strong> at relatively l<strong>on</strong>g distances from acoustic pulses generated by the laser<br />

pulses.<br />

RK14<br />

Minimal precessi<strong>on</strong>al and switching currents for relaxing-precessi<strong>on</strong>al<br />

magnetizati<strong>on</strong> reversal within a spin valve<br />

Jui-hang Chang*, Hao-hsuan Chen and Ching-ray Chang<br />

Physics, Nati<strong>on</strong>al Taiwan University, Taiwan<br />

The relaxing-precessi<strong>on</strong>al magnetizati<strong>on</strong> reversal [1] is studied from the point of view<br />

of n<strong>on</strong>linear dynamics. The soluti<strong>on</strong> of the Landau-Lifshitz-Gilbert equati<strong>on</strong> with<br />

spin-transfer toque [2] shows that there are two critical values, α_cs and α_cp, for the<br />

damping c<strong>on</strong>stant, and α_cs < α_cp. Above α_cs the minimal switching current a_<br />

s is the same as the modified St<strong>on</strong>er-Wolfarth (SW) limit [3] a_cs for the switching,<br />

and above α_cp the minimal precessi<strong>on</strong>al current a_p is the same as the modified SW<br />

limit a_cp for the <strong>on</strong>set of precessi<strong>on</strong>. For a given magnetic anisotropy and an arbitrary<br />

in-plane bias field, c<strong>on</strong>diti<strong>on</strong> a_s < a_cs < a_p < a_cp always happen, where a_s, a_<br />

p are functi<strong>on</strong>s of α_s, α_p, respectively. These investigati<strong>on</strong>s will be of importance<br />

for the design of spin-torque-transfer magnetic random access memories [4] and nano<br />

oscillators [5].<br />

[1] H. Morise and S. Nakamura, J. Magn. Magn. Mater. 306, 260 (2006). [2] J. C. Sl<strong>on</strong>czewski,<br />

J. Magn. Magn. Mater. 159, L1 (1996). [3] J. H. Chang, H. H. Chen, and C. R. Chang, Phys. Rev.<br />

B 83, 054425 (2011). [4] U. Ebels, D. Houssameddine, I. Firastrau, D. Gusakova, C.Thiri<strong>on</strong>, B.<br />

Dieny, and L. D. Buda- Prejbeanu, Phy. Rev. B 78, 024436 (2008). [5] D. Houssameddine, U.<br />

Ebels, B. Dela¨et, B. Rodmacq, I. Firastrau, F. P<strong>on</strong>thenier, M. Brunet, C. Thiri<strong>on</strong>, J. -P. Michel, L.<br />

Prejbeanu-Buda, M. -C. Cyrille, O. Red<strong>on</strong>, and B. Diney, Nature Mater. 6, 447 (2007).<br />

RK15<br />

Time dependent dichroism induced near the Surface Plasm<strong>on</strong> of Au<br />

nanoparticles<br />

Jean-yves Bigot 1 * and Minji Gw<strong>on</strong> 2<br />

1 Institute de Physique et Chimie des Materiaux de Strasbourg, CNRS, Universite de<br />

Strasbourg, Korea<br />

2 Ewha Womans University, Korea<br />

We have studied the Surface Plasm<strong>on</strong> (SP) dynamics of Au Nanoparticles, with a<br />

diameter of 50 nm, excited by circularly polarized femtosec<strong>on</strong>d laser pulses. We report<br />

about a new effect observed in a time resolved pump-probe experiment, analyzing<br />

the polarizati<strong>on</strong> state of the probe pulses. It manifests as a circular dichroism and an<br />

optical rotati<strong>on</strong> induced in the vicinity of the SP when pumping with left (σ+) or right<br />

(σ-) circularly polarized pulses. We attribute this effect to a time dependent change of<br />

the orbital momentum of c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s as the effect is more pr<strong>on</strong>ounced when<br />

the nanoparticles are excited with a pump wavelength -pump = 800 nm as compared to<br />

400 nm. Indeed, in that case the interband transiti<strong>on</strong>s from the d-band to the c<strong>on</strong>ducti<strong>on</strong><br />

band are minimized with respect to the Drude electr<strong>on</strong>s. The induced dichroism is<br />

res<strong>on</strong>ant <strong>on</strong> the SP (560 nm). Its lifetime is comparable to the energy relaxati<strong>on</strong> time<br />

of the quasiparticles to the lattice. It suggests that the electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> interacti<strong>on</strong><br />

is the main mechanism for the dissipati<strong>on</strong> of this pump induced orbital momentum.<br />

The detailed behavior of the SP dynamics as a functi<strong>on</strong> of probe wavelength, pump<br />

polarizati<strong>on</strong> and pump-probe delay will be discussed.<br />

174 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RK16<br />

The effect of surface anisotropy <strong>on</strong> the switching of a particle magnetic<br />

moment<br />

Shuang Guo and An Du*<br />

Physical department, Northeastern University, China<br />

The effect of surface anisotropy <strong>on</strong> the switching of a particle magnetic moment<br />

Shuang Guo, An Du* College of Sciences, Northeastern University, Shenyang 110004,<br />

China * Corresp<strong>on</strong>ding author(du_an_neu@126.com) The dynamic precessi<strong>on</strong><br />

of the moment for a spherical particle in a microwave field was studied by using<br />

Landau-Lifshitz-Gilbert (LLG) equati<strong>on</strong>. The spins inside the particle have singlei<strong>on</strong><br />

anisotropy and the <strong>on</strong>es <strong>on</strong> the surface of the particle have the surface anisotropy<br />

normal to the surface. The switching field threshold was calculated for different surface<br />

anisotropy with definite microwave frequency. It is found that the surface anisotropy<br />

influences the switching field threshold, with the increase of the surface anisotropy, the<br />

threshold increases, the switching speed of the magnetic moment increases obviously.<br />

1. K. Rivkin, and J. B. Ketters, Appl. Phys. Lett. 89, 252507(2006). 2. J.G. Zhu, X. Zhu, and Y.<br />

Tang, IEEE Trans. Magn. 44, 125(2008). 3. S. Okamoto, N. Kikuchi et al, Appl. Phys. Lett. 93,<br />

102506(2008). 4. S. Okamoto, N. Kikuchi, and O. Kitakami, Appl. Phys. Lett. 93, 142501(2008). 5. M.<br />

Lgarashi, Y. Suzuki et al, J. Appl. Phys. 105, 07B907(2009).<br />

RK17<br />

Magnetizati<strong>on</strong> dynamics of GdFeCo nanostructures revealed with<br />

PEEM<br />

Souliman El Moussaoui 1 *, Loic Le Guyader 1 , Michele Buzzi 1 , Elena Mengotti 1 ,<br />

Laura J. Heyderman 1 , Frithjof Nolting 1 , Thomas A. Ostler 2 , Joe Barker 2 , Richard F.<br />

L. Evans 2 , Roy Chantrell 2 , Arata Tsukamoto 3 , Akiyoshi Itoh 3 , Andrei Kirilyuk 4 , Theo<br />

Rasing 4 and Alexey V. Kimel 4<br />

1<br />

Paul Scherrer Institut, Switzerland<br />

2<br />

Department of Physics, University of York, United Kingdom<br />

3<br />

Nih<strong>on</strong> University, Japan<br />

4<br />

Radboud University Nijmegen, Institute for Molecules and Materials, Netherlands<br />

The manipulati<strong>on</strong> of spins is a very exciting topic from fundamental point of view as well as for practical<br />

applicati<strong>on</strong>s. Combining experiments and simulati<strong>on</strong>, we have been able to dem<strong>on</strong>strate that a fs-optical<br />

excitati<strong>on</strong> is sufficient to trigger magnetizati<strong>on</strong> reversal in GdFeCo nanostructures <strong>on</strong> very short timescales.<br />

Employing a photoemissi<strong>on</strong> electr<strong>on</strong> microscope (PEEM) at the SIM beamline, we have proved that we can<br />

manipulate the magnetizati<strong>on</strong> of nanostructures by using a heat pulse <strong>on</strong>ly. Performing time resolved X-ray<br />

magnetic circular dichroism (TR-XMCD) measurement we have observed that the magnetizati<strong>on</strong> reversal<br />

within the structures occurs <strong>on</strong> a timescale faster than 100 ps and evidenced that the reversal occurs against<br />

an external applied magnetic field. In our experiment the reversal happens <strong>on</strong>ly by heating the system <strong>on</strong> the<br />

time scale of the exchange interacti<strong>on</strong> of the two sublattices and does not require any other external stimulus.<br />

'Ultrafast heating as a sufficient stimulus for magnetizati<strong>on</strong> reversal' T. A. Ostler, J. Barker, R. F. L. Evans, R. Chantrell, U. Atxitia, O.<br />

Chubykalo-Fesenko, S. El Moussaoui, L. Le Guyader, E. Mengotti, L. J. Heyderman, F. Nolting, A. Tsukamoto, A. Itoh, D. Afanasiev,<br />

B. A. Ivanov, A. M. Kalashnikova, K. Vahaplar, J. Mentink, A. Kirilyuk,Th. Rasing and A. V. Kimel, Nature Comm. 3, 666 (2012).<br />

RK18<br />

A study of magnetic domain and magnetizati<strong>on</strong> reversal in L-shaped<br />

Py<br />

S.s. Lee, W<strong>on</strong>d<strong>on</strong>g Kim, By<strong>on</strong>g Sun Chun and Chany<strong>on</strong>g Hwang*<br />

Korea Research Institute of Standards and Science, Korea<br />

The evaluati<strong>on</strong> of characteristic of nanometer-sized magnetic domain is <strong>on</strong>e of the<br />

most important issues in the fields of spintr<strong>on</strong>ics. We made the Py stripe with and<br />

without the L-shaped edge structure. First, magnetic domain and its reversal reversal<br />

behavior were simulated with the use of OOMMF program. Depending <strong>on</strong> the<br />

thickness, width of this L-shaped structure, magnetic domain and its reversal behavior<br />

could be classified in several groups. We also used scanning electr<strong>on</strong> microscope with<br />

polarizati<strong>on</strong> analysis(SEMPA, or spin-SEM) to probe the magnetic domain pattern<br />

predicted in the simulati<strong>on</strong>.


RK19<br />

Ultrafast dynamics of ferromagnetic copd thin film by various<br />

polarized probe beam<br />

S. H. Jung 1 , M. H. Jung 1 , Jin Pyo H<strong>on</strong>g 2 , W<strong>on</strong> D<strong>on</strong>g Kim 3 , Chany<strong>on</strong>g Hwang 3 * and<br />

Joo In Lee 3<br />

1 Department of Physics, Sogang University, Korea<br />

2 Department of Pysics, Hanyang University, Korea<br />

3 Center for Nano-imasing Technology, Korea Research Institute of Standards and<br />

Science, Korea<br />

We study ultrafast dynamics of the ferromagnetic CoPd thin film by using timeresolved<br />

magneto-optical Kerr effect. In the case of using linearly polarized probe<br />

beam, the spin precessi<strong>on</strong> is observed in the frequency of about 14 GHz in the range<br />

of large time scale. On the other hand, when the probe beam changes to circular<br />

polarizati<strong>on</strong>, the large time scale precessi<strong>on</strong> disappears, and ultrafast precessi<strong>on</strong><br />

(~100GHz) is observed in short time scale. We suppose that these result from the<br />

momentum change of probe beam from 0 to 1, and the ultrafast precessi<strong>on</strong> is related to<br />

interacti<strong>on</strong> between spin and circularly polarized phot<strong>on</strong>.<br />

1. J.-Y. Bigot, Physics 5, 11 (2012) 2. J.-Y. Bigot, M. Vomir, E. Beaurepaire, Nature Physics 5, 515<br />

(2009)<br />

RK20<br />

Low temperature time domain THz spectroscopy of terbium gallium<br />

garnet crystals<br />

Rostislav V. Mikhaylovskiy*, Euan Hendry, Feodor Y. Ogrin and Volodymyr V.<br />

Kruglyak<br />

School of Physics, University of Exeter, United Kingdom<br />

We have used the terahertz (THz) time domain spectroscopy to study high frequency<br />

magnetic excitati<strong>on</strong>s in terbium gallium garnet (TGG) crystals cut al<strong>on</strong>g <br />

and crystallographic planes. We dem<strong>on</strong>strate that a THz bandwidth transient<br />

electromagnetic pulse can efficiently couple to magnetic moments in TGG. By<br />

comparing the spectrum of the pulse before and after transmissi<strong>on</strong> through the crystal,<br />

we are able to isolate the absorpti<strong>on</strong> corresp<strong>on</strong>ding to magnetic res<strong>on</strong>ance modes<br />

of TGG. We measure and discuss the dependence of the observed modes up<strong>on</strong> the<br />

temperature and the strength and orientati<strong>on</strong> of the bias magnetic field with respect<br />

to the crystallographic axes of the crystals. The magnetic modes are present at<br />

temperatures above the Neel point, which is interpreted in terms of the field-induced<br />

magnetic ordering. The illuminati<strong>on</strong> of the crystal with intense optical pulses with<br />

wavelength close to the TGG absorpti<strong>on</strong> band destroys the magnetic ordering. Thus,<br />

the light induced demagnetizati<strong>on</strong> of TGG is observed. Our findings dem<strong>on</strong>strate that<br />

the time domain THz spectroscopy can be a powerful tool by which to study high<br />

frequency properties of dielectric magnetic materials.<br />

RK21<br />

Ferromagnetic res<strong>on</strong>ance of a single micr<strong>on</strong> dot using vector network<br />

analyzer<br />

Kazuto Yamanoi 1 , Satoshi Yakata 2 , Takashi Kimura 2 and Takashi Manago 1 *<br />

1 Department of Applied Physics, Fukuoka University, Japan<br />

2 Inamori Fr<strong>on</strong>tier Research Center, Kyusyu University, Japan<br />

Magnetizati<strong>on</strong> dynamics of small ferro-magnets in the gigahertz regi<strong>on</strong> have been<br />

investigated intensively for the applicati<strong>on</strong>s in microwave devices. It is based <strong>on</strong> the<br />

precessi<strong>on</strong>al moti<strong>on</strong> of magnetizati<strong>on</strong> and it is necessary to c<strong>on</strong>trol <strong>on</strong>e of each small<br />

magnets in devices. In this paper, we investigated ferromagnetic res<strong>on</strong>ance (FMR) of<br />

a single mic<strong>on</strong>scale dot of permalloy (Py) using a vector network analyzer (VNA). A<br />

micr<strong>on</strong>-scale Py dot and a coplanar wave guide were fabricated using electr<strong>on</strong> beam<br />

lithography, electr<strong>on</strong> beam evaporati<strong>on</strong> and lift off technique. The thickness of the Py<br />

dots was 30 nm, and the shapes were square and rectangle with a width and length of<br />

1~10 um and 1~40 um, respectively. The FMR measurement was performed using<br />

the VNA and probe stati<strong>on</strong>. In the square shape dot of 10 um, the res<strong>on</strong>ant frequency<br />

depends <strong>on</strong> magnetic fields, which was good agreement with the Kittel’s equati<strong>on</strong><br />

of a thin film. In the rectangle shape dots, the res<strong>on</strong>ant frequency shifted to higher<br />

frequency with increasing length. This tendency was remarkable for 1 um-width dots.<br />

It means that demagnetizati<strong>on</strong> effect becomes large when the width is less than 1 um<br />

for a thin film.<br />

RK22<br />

RK23<br />

RK24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Relati<strong>on</strong> between gilbert damping c<strong>on</strong>stants and perpendicular<br />

magnetic anisotropy in Ti buffered Co/Ni multilayers<br />

Hy<strong>on</strong>seok S<strong>on</strong>g 1 , Kye<strong>on</strong>g-d<strong>on</strong>g Lee 1 , Je<strong>on</strong>g-woo Sohn 1 , See-hun Yang 2 , Stuart S.p.<br />

Parkin 2 , Chun-yeol You 3 and Sung-chul Shin 4 *<br />

1 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST, Daeje<strong>on</strong> 305-701, Korea<br />

2 IBM Research Divisi<strong>on</strong>, Almaden Research Center, San Jose, California 95120, USA<br />

3 Department of Physics, Inha University, Inche<strong>on</strong> 402-751, Korea<br />

4 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST, Daeje<strong>on</strong> 305-701,<br />

Department of Emerging Materials Science, DGIST, Daegu 711-873, Korea<br />

Recently, there has been a growing interest in spin-transfer-torque magnetic random access memory utilizing<br />

perpendicularly magnetic anisotropy (PMA) materials in order to overcome thermal stability problems.<br />

Since the critical current density depends <strong>on</strong> the Gilbert damping parameter, it has been an important<br />

issue to understand and manipulate the Gilbert damping parameter in the PMA materials. In this work,<br />

we have investigated PMA [Co/Ni] multilayers with Ti buffer layers by an all-optical pump-probe time<br />

resolved magnetic optical Kerr effect (TR-MOKE). In particular, we have studied the variati<strong>on</strong> of Gilbert<br />

damping c<strong>on</strong>stant (α) and PMA as a functi<strong>on</strong> of the thickness of Ti buffer layer thickness (t). Since the PMA<br />

and damping c<strong>on</strong>stant are str<strong>on</strong>gly related with the spin-orbit coupling, both physical quantities must be<br />

correlated. Clear damped oscillati<strong>on</strong>s of the magnetizati<strong>on</strong> are observed in TR-MOKE measurements. After<br />

background subtracti<strong>on</strong>, the signal is fitted with a damped harm<strong>on</strong>ic functi<strong>on</strong>, from which the precessi<strong>on</strong><br />

frequency (f) and the decay time (τ) are deduced. We obtained f and τ by fitting with Landau-Lifshitz-<br />

Gilbert equati<strong>on</strong>, and we could be estimated α. We find that The α and PMA values increased m<strong>on</strong>ot<strong>on</strong>ically<br />

with increasing of t. This result clearly shows close relati<strong>on</strong>ship between PMA and α.<br />

Chaotic moti<strong>on</strong> of magnetic domain structure under alternate field<br />

Michinobu Mino* and Yousuke Yamamoto<br />

Department of Physics, Okayama University, Japan<br />

Magnetic domain moti<strong>on</strong> in a garnet thin film under alternate magnetic fields up to<br />

5000 Hz has been investigated at room temperature. Domain structures and moti<strong>on</strong>s are<br />

observed by using a high-speed video camera with the help of magneto-optical Faraday<br />

effect. When a field frequency is low, the magnetizati<strong>on</strong> changes periodically and a<br />

domain pattern has a labyrinth structure. By increasing the field amplitude and driving<br />

frequency, irregular oscillati<strong>on</strong>s of a magnetizati<strong>on</strong> appear. Under a rapidly oscillating<br />

field, chaotic moti<strong>on</strong>s of domain are observed. In this regi<strong>on</strong>, domain structures have<br />

a disk-like shape. These disks grow from some crystal defects. And a growing point<br />

shows a branch-like form.<br />

Demagnetizati<strong>on</strong> dynamics observed by spin-resolved ultrafast x-ray<br />

photoemissi<strong>on</strong><br />

Thomas Michlmayr<br />

Physics, ETH Zurich, Switzerland<br />

We report <strong>on</strong> the experiment and the results of time- and spin-resolved photoemissi<strong>on</strong>.<br />

Ultrafast demagnetizati<strong>on</strong> was first observed by Beaurepaire et al. in 1996 and many<br />

approaches where d<strong>on</strong>e to support these findings. Our method allows for measuring<br />

the whole valence band mediated by the cascade electr<strong>on</strong>s emerging from the<br />

sample and therefore gives a direct measure of the sample's magnetizati<strong>on</strong>. Ultrafast<br />

demagnetizati<strong>on</strong> is observed <strong>on</strong> thin films of Fe <strong>on</strong> W(110) by optical pumping at 800<br />

nm and x-ray probing at 7 nm. The measured demagnetizati<strong>on</strong> time of 450 fs is limited<br />

by the experiment. Although space charge effects limits the photoelectr<strong>on</strong> gain the<br />

measured spin asymmetry stays almost c<strong>on</strong>stant with increasing x-ray flux and <strong>on</strong>ly<br />

drops at very high x-ray fluxes (> 4 nJ/pulse). We also show the feasibility of single<br />

shot magnetic measurement. The experimental setup c<strong>on</strong>sists of a completely mobile<br />

two chambers ultra-high vacuum system (preparati<strong>on</strong> and measurement chamber) with<br />

Mott-polarimeter which can be brought to the free electr<strong>on</strong> laser FLASH, Hamburg.<br />

July 8 - 13, 2012 Busan, Korea 175<br />

Poster Thursday


Poster Thursday<br />

RL01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Synchr<strong>on</strong>ized modes of in-plane/out-of-plane spin-torque oscillators in<br />

MTJ with synthetic ferrimagnetic free layer<br />

Masahiko Ichimura 1 *, Ryoko Sugano 1 , Saburo Takahashi 2 and Sadamichi Maekawa 3<br />

1 Central Research Lab., Hitachi, Ltd. and JST-CREST, Japan<br />

2 IMR, Tohoku University and JST-CREST, Japan<br />

3 Advanced Science Research Center, Japan Atomic Energy Agency and JST-CREST,<br />

Japan<br />

There has been c<strong>on</strong>siderable interest in the phenomena of spin-torque oscillators (STO) in<br />

magnetic tunnel juncti<strong>on</strong>s (MTJs) for device applicati<strong>on</strong>s, as well as the current induced<br />

magnetizati<strong>on</strong> switching (CIMS) resulting from the spin transfer torque (STT). In particular,<br />

the MTJs with synthetic ferrimagnetic (SyF) free layer is important since we can expect<br />

the cooperati<strong>on</strong> and/or competiti<strong>on</strong> of the magnetizati<strong>on</strong> dynamics due to the interlayer<br />

coupling between magnetizati<strong>on</strong>s in the ferromagnetic bilayer. We analyze the magnetizati<strong>on</strong><br />

dynamics self-c<strong>on</strong>sistently in the MTJs with SyF layer by iterative calculati<strong>on</strong> following<br />

two steps. The STT in the ballistic regime is estimated, and the magnetizati<strong>on</strong> reversal is<br />

simulated by the LLG method at the finite temperature. We discuss the effect of the interlayer<br />

coupling <strong>on</strong> the STO. As the interlayer coupling increases, the change of the STO mode is<br />

observed, where the STO mode moved from the out-of-plane precessi<strong>on</strong> (OPP) to in-plane<br />

precessi<strong>on</strong> (IPP). From the mapping of the STO behavior <strong>on</strong> the plane with applied current<br />

and interlayer coupling, synchr<strong>on</strong>ized mode of STO appears in the regi<strong>on</strong> where the effective<br />

filed corresp<strong>on</strong>ding to the interlayer coupling is larger than the anisotropy field. These results<br />

suggest that the STO appears even without external magnetic field.<br />

RL02<br />

Interface material effects <strong>on</strong> magnetic anisotropy and its electric field<br />

induced variati<strong>on</strong> in thin films<br />

Yuusaku Taguchi 1 *, Haruki Kato 1 , Shinya Haraguchi 1 , Masahito Tsujikawa 2 ,<br />

Masafumi Shirai 3 and Tatsuki Oda 4<br />

1<br />

Graduate School of Natural Sciences and Technology, Kanazawa University, Japan<br />

2<br />

CSIS, Tohoku University, Japan<br />

3<br />

CSIS, Tohoku University & RIEC, Tohoku University, Japan<br />

4<br />

Institute of Science and Engineering, Kanazawa University, Japan<br />

The spintr<strong>on</strong>ics has grown up intensively to realistic applicati<strong>on</strong>s in the technology of magnetic random access<br />

memory (MRAM) development. Such development has been remarkable in memory density, reading-writing<br />

speed, and n<strong>on</strong>-volatile property in cooperati<strong>on</strong> with the technologies of spin-injecti<strong>on</strong> and physics of spin<br />

transfer torque. The basic physics about magnetism has been developing in the resp<strong>on</strong>se to electric field (EF).<br />

This has emerged as the c<strong>on</strong>necti<strong>on</strong> with low power c<strong>on</strong>sumpti<strong>on</strong> device and small energy scale of magnetoelectric<br />

effects. For the thin films [1,2] as a memory, sensitivity and large resp<strong>on</strong>se may be required in device<br />

applicati<strong>on</strong>s. Due to the limitati<strong>on</strong> of EF penetrati<strong>on</strong> into the thin film, interface with a few metallic layers is<br />

critical to determine the resp<strong>on</strong>se to the EF. We have investigated MgO/Fe/M(001) (M = Au, Pt) [3,4] with using<br />

the density functi<strong>on</strong>al calculati<strong>on</strong>, in which the substrate of Pt was found to enhance the EF effect <strong>on</strong> magnetic<br />

anisotropy. In this work, in order to investigate influences of stacking structure for the interface, we investigate<br />

MgO/Fe/Pt/Au(001) and MgO/Fe/Pd/Au(001). In additi<strong>on</strong>, results in MgO/Au/Fe/Au(001) are also discussed<br />

in the c<strong>on</strong>necti<strong>on</strong> with segregati<strong>on</strong> effects of film preparati<strong>on</strong>, which may be expected in experiments.<br />

[1] Y. Shiota et al., Appl. Phys. Express 2, 063001 (2009). [2] T. Nozaki et al., Appl. Phys. Lett. 96, 022506 (2010).<br />

[3] M. Tsujikawa et al., J. Appl. Phys., 109, 07C107 (2011). [4] M. Tsujikawa et al., submitted for publicati<strong>on</strong>.<br />

RL03<br />

Effect of spin relaxati<strong>on</strong> rate <strong>on</strong> the interfacial spin depolarizati<strong>on</strong> in<br />

ferromagnet/oxide/semic<strong>on</strong>ductor c<strong>on</strong>tacts<br />

Kun-rok Je<strong>on</strong> 1 , Byoung-chul Min 2 , Youn-ho Park 2 , Young-hun Jo 3 , Hun-sung Lee 1 ,<br />

Chang-yup Park 1 and Sung-chul Shin 1 *<br />

1 Korea Advanced Institute of Science and Technology (KAIST), Korea<br />

2 Korea Institute of Science and Technology (KIST), Korea<br />

3 Korea Basic Science Institute (KBSI), Korea<br />

The electrical injecti<strong>on</strong> and detecti<strong>on</strong> of spin-polarized carriers in semic<strong>on</strong>ductors (SCs) has been<br />

successfully achieved by employing spin tunnel c<strong>on</strong>tacts and the Hanle effects. However, many aspects<br />

of the spin phenomena in these systems, e.g., (i) the locati<strong>on</strong>, magnitude, and sign of the induced<br />

spin accumulati<strong>on</strong>, (ii) the unusual bias and temperature-dependence of the spin signal, and (iii) the<br />

unexpected short spin lifetime and its weak variati<strong>on</strong> with temperature, require additi<strong>on</strong>al investigati<strong>on</strong>.<br />

Here, we report the effect of spin relaxati<strong>on</strong> rate <strong>on</strong> the interfacial spin depolarizati<strong>on</strong> (ISD) from<br />

the local fields in ferromagnet (FM)/oxide/SC c<strong>on</strong>tacts [1]. The combined measurements of normal<br />

and inverted Hanle effects reveal the effect of spin relaxati<strong>on</strong> rate <strong>on</strong> the ISD [2] in CoFe/MgO/<br />

Si and CoFe/MgO/Ge c<strong>on</strong>tacts. We have observed, despite the similar amplitudes of the interfacial<br />

roughness and local magnetic fields, significant differences of the ISD [2] depending <strong>on</strong> the host SC;<br />

the spin accumulati<strong>on</strong> exposed to similar local fields in different SCs give rise to a clearly different<br />

ratio of the inverted Hanle signal to the normal <strong>on</strong>e. This can be understood in terms of two competing<br />

mechanisms in the host SCs, namely the spin relaxati<strong>on</strong> and spin precessi<strong>on</strong> due to the local fields.<br />

[1] K. R. Je<strong>on</strong> et al., arXiv:1110.5978v1. [2] S. P. Dash et al., Phys. Rev. B 84, 054410 (2011).<br />

176 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RL04<br />

Spin-pumping and revelati<strong>on</strong> of inverse spin-Hall effect in n-type Si at<br />

room temperature<br />

Mariko Koike*, Eiji Shikoh, Teruya Shinjo and Masashi Shiraishi<br />

Osaka University, Japan<br />

Since spin-orbit interacti<strong>on</strong> in n-type Si is very week due to its band structure and<br />

lattice inversi<strong>on</strong> symmetry, observati<strong>on</strong> of the spin-Hall effect in n-type Si has been<br />

believed to be difficult. Here, we report successful observati<strong>on</strong> of the inverse spin-Hall<br />

effect (ISHE) in n-type Si at room temperature. The sample composes of a Ni 80Fe 20/<br />

n-type Si film with a doping c<strong>on</strong>centrati<strong>on</strong> of 1.0×10 19 1/cm 3 . The n-type Si surface<br />

was etched by hydrofluoric acid to remove the naturally-oxidized Si. A ferromagnetic<br />

Ni 80Fe 20 was formed by using electr<strong>on</strong> beam lithography and depositi<strong>on</strong> methods <strong>on</strong><br />

the n-type Si. Two electrode-pads were attached to the n-type Si layer to detect the<br />

electromotive force in the Si. In a ferromagnetic res<strong>on</strong>ance c<strong>on</strong>diti<strong>on</strong> of the Ni 80Fe 20,<br />

a pure spin current was injected into the n-type Si layer by the spin pumping. If ISHE<br />

is induced in the n-type Si, the spin current is c<strong>on</strong>verted to a charge current. Here, the<br />

ISHE in the n-Si was observed. The output voltage due to the ISHE was estimated to<br />

be 0.4μV. The voltage sign was inverted by the magnetizati<strong>on</strong> reversal of the Ni 80Fe 20.<br />

In this presentati<strong>on</strong>, we discuss details of the inverse spin-Hall effect in the n-type Si.<br />

RL05<br />

Critical current density and domain wall mobility in nanowires with<br />

exchange coupled hard-soft magnetic layers<br />

Xiaoxi Liu 1 *, Liangqiu Gao 2 and Akimitsu Morisako 2<br />

1 Department of Informati<strong>on</strong> Engineering, Shinshu University, Japan<br />

2 Shinshu University, Japan<br />

In this study, critical current density and domain wall mobility of current driven<br />

domain wall moti<strong>on</strong> in nanowires composed of TbFeCo and NiFe layers have been<br />

studied. TbFeCo layer has perpendicular magnetic anisotropy. Wires and electrode are<br />

fabricated by photolithographic method. Current pulses with width less than 100 ns<br />

are applied to drive the domain wall in the wires. The domain structure is observed by<br />

a high resoluti<strong>on</strong> Kerr microscope. We found critical current density decreases in the<br />

soft-hard bi-layered structure compared to a single TbFeCo layer. Nanowires of single<br />

TbFeCo layer have critical current density of 5×10 6 A/cm 2 ; however, the critical current<br />

density in bi-layered structure has critical current density as small as 2 ×10 6 A/cm 2 . The<br />

domain wall mobility is deduced from the dependence of domain wall velocity <strong>on</strong> the<br />

applied current density. We found that the domain wall mobility improved by almost<br />

two times with the introducing of the NiFe layer. Of particular interesting is that,<br />

micromagnetic simulati<strong>on</strong>s show that the Bloch walls in perpendicular TbFeCo wires<br />

change to Neel walls with the introducing of NiFe layer. Our experimental results<br />

suggest nano-wires composing of soft-hard layers suitable for race track memory.<br />

RL06<br />

Spin Seebeck Effect in SiO2/Py structures<br />

Sang-il Kim 1 , Seung-young Park 2 , Byoung-chul Min 3 , Younghun Jo 2 , Kyung-jin Lee 1 *<br />

and Kyung-ho Shin 3<br />

1<br />

Department of Materials Science and Engineering, Korea University, Seoul 136-<br />

713, Korea, Korea<br />

2<br />

Nano Material Research Team, Korea Basic Science Institute, Daeje<strong>on</strong> 305-333,<br />

Korea, Korea<br />

3<br />

Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea, Korea<br />

Recently, spin versi<strong>on</strong> of Seebeck effect, the spin-Seebeck effects (SSE) was observed<br />

experimentally at room temperature[1]. For the SSE, it is expected that the voltage sign at the<br />

hot end is opposite to that at the cold end and the absolute magnitudes of the voltages at the<br />

hot and cold ends are the same. However, it is often observed that an asymmetric magnitude<br />

of the voltage at the hot and cold ends [2]. The origin of this asymmetric behavior is<br />

attributed to an additi<strong>on</strong>al temperature gradient al<strong>on</strong>g the thickness directi<strong>on</strong>, which generates<br />

an additi<strong>on</strong>al voltage signal due to the anomalous Nernst-Ettingshausen effect(ANE) [2]. In<br />

this study, we investigated the dependence of the SSE and the ANE <strong>on</strong> the thickness of the<br />

ferromagnetic layer in SiO 2/Py samples. In our results, the sign change in the voltage signal<br />

between the hot and cold ends was not observed. Instead, we obtained an offset voltage<br />

due to the mixture of SSE and ANE signals. We attribute this offset to the l<strong>on</strong>gitudinal SSE<br />

caused by an additi<strong>on</strong>al temperature gradient al<strong>on</strong>g the thickness directi<strong>on</strong> of Py layer. A<br />

possible origin of the dependence of offset voltage <strong>on</strong> Py thickness will be discussed in detail.<br />

[1] K. Uchida et al., Nature, 455, 778-781 (2008). [2] S. Bosu et al., Phy. Rev. B 83, 224401 (2011).


RL07<br />

Domain wall pinning by stray field from NiFe <strong>on</strong> Co/Ni nano-wire<br />

Ryo Hiramatsu 1 , T. Koyama 1 , D. Chiba 1 , S. Fukami 2 , N. Ishiwata 2 , Y. Nakatani 3 and T.<br />

Ono 1 *<br />

1 Institute for Chemical Research, Kyoto University, Japan<br />

2 Green Innovati<strong>on</strong> Research Laboratories, NEC Corporati<strong>on</strong>, Japan<br />

3 University of Electro-communicati<strong>on</strong>s, Japan<br />

C<strong>on</strong>trol of a magnetic domain wall (DW) displacement in a ferromagnetic nano-wire<br />

is essential in its potential applicati<strong>on</strong> for n<strong>on</strong>volatile magnetic memories. Parkin et<br />

al. dem<strong>on</strong>strated a race track memory device by c<strong>on</strong>trolling DW displacement in a<br />

NiFe nano-wire with notch structure [1]. However, the structure with notch has two<br />

problems such as i) transformati<strong>on</strong> of DW structure and ii) increase of current density<br />

due to the change of the wire width between notch and wire part. Here, to make new<br />

DW pinning method without the change of wire width, we focus <strong>on</strong> the DW pinning<br />

in Co/Ni nano-wire by the stray field from ferromagnetic stack.We prepared two types<br />

of devices; <strong>on</strong>e was a simple wire of Ta/Pt/[Co(0.2 nm)/Ni(0.6 nm)] 4/Co(0.2 nm)/Pt/<br />

Ta, and the other was a wire of Ta/Pt/[Co(0.2 nm)/Ni(0.6 nm)] 4/Co(0.2 nm)/Pt/Ta <strong>on</strong><br />

which NiFe/SiO 2 was stacked partly. To investigate an influence of the stray field from<br />

the NiFe stack, DW depinning field (H dep) was measured for both types of wires. H dep<br />

of the wire without the NiFe stack was 200 Oe, while the wire with that had larger H dep<br />

of 700 Oe, indicating the effectiveness of the use of the stray field to c<strong>on</strong>trol the DW<br />

positi<strong>on</strong>.<br />

[1] S. S. P. Parkin, et al., Science 320, 190 (2008).<br />

RL08<br />

Compositi<strong>on</strong>al dependence of critical current density for spin transfer<br />

torque switching of amorphous GdFeCo for thermally assisted MRAM<br />

Bing Dai 1 *, Takeshi Kato 1 , Satoshi Iwata 1 and Shigeru Tsunashima 2<br />

1 Department of Quantum Engineering, Nagoya University, Nagoya 464-8603, Japan<br />

2 Department of Research, NISRI, Yotsuya-dori 1-13, Chikusa-ku, Nagoya, 464-0819,<br />

Japan<br />

Spin transfer torque (STT) switching has been dem<strong>on</strong>strated in magnetic tunneling juncti<strong>on</strong>s<br />

(MTJ) with perpendicular magnetic anisotropy (PMA), which exhibits a low critical current<br />

density compared to their in-plane counterparts [1]. In this paper, we fabricated giant magnetoresistance<br />

(GMR) devices c<strong>on</strong>sisting of bottom electrode/ [Pd (1.6)/Co (0.4)] 6/Co 40Fe 40B 20<br />

(0.5)/Cu (3)/ Gd x(Fe 90Co 10)100-x (10)/Cu (5)/top electrode (thickness in nanometer). The R-I<br />

loops were measured for 120×180 nm 2 cell with Gd x(Fe 90Co 10) 100-x memory layers, and the<br />

STT switching property of these devices was estimated from the resistance measurement after<br />

applying current pulses with a durati<strong>on</strong> of 100 ms. In TM-rich compositi<strong>on</strong>s, the average value<br />

of the critical current density Jc increased from 2.0×10 7 A/cm 2 for x = 22.3 at.% to 4.5×10 7 A/<br />

cm 2 for x = 24.0 at.% with increasing x, while the Jc reduced to 1.4×10 7 A/cm 2 for RE-rich<br />

Gd 28.9(Fe 90Co 10) 71.1. It is noted that the values of Jc are comparable to the results in c<strong>on</strong>venti<strong>on</strong>al<br />

MTJs[2]. The difference of Jc values may be due to the difference of the effective perpendicular<br />

anisotropy and/or the Curie temperature of the GdFeCo layer. The dependence of Jc <strong>on</strong> the<br />

current pulse width and temperature will be discussed in the presentati<strong>on</strong>.<br />

[1]S. Ikeda, et al. Nature Materials 9, 721-724 (2010). [2]Y. Huai, et al. Appl.Phys.Lett. 82, 222510 (2005).<br />

RL09<br />

Microscopic theory of magn<strong>on</strong>-drag thermodynamic transport in<br />

ferromagnetic metals<br />

Daisuke Miura* and Akimasa Sakuma<br />

Department of Applied Physics, Tohoku University, Japan<br />

We study the thermodynamic transport carried by magn<strong>on</strong>s in ferromagnetic metals.<br />

In this study, the Peltier effect caused by a magn<strong>on</strong> heat current (magn<strong>on</strong>-drag Peltier<br />

effect) is described in a microscopic model. Magn<strong>on</strong>s can indirectly interact with<br />

electric fields via electr<strong>on</strong>-magn<strong>on</strong> interacti<strong>on</strong>; we evaluate the magn<strong>on</strong> heat current<br />

perturbatively with respect to the electr<strong>on</strong>-magn<strong>on</strong> interacti<strong>on</strong> in the 2nd order. As a<br />

c<strong>on</strong>sequence, we found out that the magn<strong>on</strong> heat current is proporti<strong>on</strong>al to the spin<br />

current carried by the spin polarized electric current drifted by the electric filed, that is,<br />

the magn<strong>on</strong>-drag Peltier coefficient is governed by the spin polarizati<strong>on</strong> of the electric<br />

current. This is in c<strong>on</strong>trast to the phenomenological result derived by Grannemann and<br />

Berger [1] in which the coefficient is proporti<strong>on</strong>al to the electric current directly. In<br />

additi<strong>on</strong>, we show the temperature dependence of the Peltier coefficient is T 5/2 in low<br />

temperature. These results indicate that, in the inverse effect (Seebeck effect) of the<br />

Peltier effect, the magn<strong>on</strong> heat current caused by a temperature difference induces the<br />

spin current, and the temperature dependence of the Seebeck coefficient is T 3/2 .<br />

[1] G. N. Grannemann and L. Berger, Phys. Rev. B 13, 2072 (1976).<br />

RL10<br />

RL11<br />

RL12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Electric-field c<strong>on</strong>trol of magnetic properties in cobalt by means of electric double layer<br />

Kazutoshi Shimamura 1 , Daichi Chiba 2 , Masashi Kawaguchi 1 , Shimpei Ono 4 , Shunsuke Fukami 5 ,<br />

Nobuyuki Ishiwata 5 , Kensuke Kobayashi 3 and Teruo 1 *<br />

1 Institute for Chemical Research, Kyoto University, Japan<br />

2 Institute for Chemical Research, Kyoto University and PRESTO JST, Japan<br />

3 Institute for Chemical Research, Kyoto University and Osaka University, Japan<br />

4 Central Research Institute of Electric Power Industry, Japan<br />

5 NEC Corporati<strong>on</strong>, Japan<br />

Electric-field effect <strong>on</strong> magnetism using a capacitance structure (gate electrode/insulator/ferromagnetic)<br />

has actively investigated to open up a new technology for an electrically manipulati<strong>on</strong> of magnetizati<strong>on</strong> [1-<br />

10]. Here, we show electric field c<strong>on</strong>trol of magnetic properties in Co using an electrical double layer (EDL)<br />

formed at the interface between the Co layer and a polymer film c<strong>on</strong>taining an i<strong>on</strong>ic liquid. The polymer<br />

film c<strong>on</strong>taining the i<strong>on</strong>ic liquid was put <strong>on</strong> a 0.4-nm-thin-Co-film and Pt-thin-film was placed <strong>on</strong> the top<br />

of the polymer film as a gate electrode. For the direct detecti<strong>on</strong> of the magnetizati<strong>on</strong> under the gate-voltage<br />

(Vg), superc<strong>on</strong>ducting quantum interference device [6] was used. Magnetizati<strong>on</strong> curves were measured<br />

at 300 K under the applicati<strong>on</strong> of Vg from -2.0 V to +2.0 V. Dramatic change of coercivity was observed<br />

depending <strong>on</strong> Vg. To investigate the mechanism of this, we measured temperature dependences of the<br />

remanent magnetizati<strong>on</strong> under the different Vg. The significant increase of Curie temperature from ~320 K<br />

at Vg = 0 V to ~370 K at 2.0 V was observed. Thus, the dramatic change in corecivity at 300 K presented<br />

here is attributed to this large modulati<strong>on</strong> of Curie temperature [10].<br />

[1] H. Ohno et al., Nature 408, 944, (2000). [2] D. Chiba, M. Yamanouchi, F. Matsukura and H. Ohno, Science 301, 943 (2003). [3] M.<br />

Weisheit et al., Science 315, 349 (2007). [4] D. Chiba et al., Nature 455, 515 (2008). [5] T. Maruyama et al., Nature Nanotechnol.<br />

4, 158 (2009). [6] M. Sawicki et al., Nature Phys. 6, 22 (2009). [7] M. Endo et al., Appl. Phys. Lett. 96, 22515 (2010). [8] H. Ohno,<br />

Nature Mater. 9, 952 (2010). [9] Y. Yamada et al., Science 332, 1065 (2011). [10] D. Chiba et al., Nature Mater. 10, 853 (2011).<br />

Spin-torque magnetic res<strong>on</strong>ance of superparamagnetic Fe nanoparticles<br />

in Fe/MgO/Fe magnetic tunnel juncti<strong>on</strong>s<br />

Shinji Miwa, Norikazu Mizuochi, Teruya Shinjo and Yoshishige Suzuki<br />

Graduate School of Engineering Science, Osaka University, Japan<br />

During the past decade, electric detecti<strong>on</strong> and manipulati<strong>on</strong> of submicr<strong>on</strong>-scale<br />

magnet have been c<strong>on</strong>ducted by using magnetoresistance (MR) effect and spin-torque.<br />

Now, a great deal of interests in manipulating nano-scale magnets (or single-spin)<br />

and physics of spin-torque in such a small system are taken. In this study, we employ<br />

superparamagnetic Fe nano-particles and the single-crystal MgO based magnetic tunnel<br />

juncti<strong>on</strong>s (MTJs) [1]. The magnetic res<strong>on</strong>ance of super-paramagnetic Fe nano-particles<br />

is electrically excited by spin-torque and detected by the spin-torque diode effect [2,3].<br />

The structure of the MTJs is as follows: MgO(100) substrate/Fe film (50 nm)/MgO<br />

(1.35 nm)/Fe nano-particles (2.1 nm)/capping layer. All of the layers were grown by<br />

molecular beam epitaxy. The RF detecti<strong>on</strong> mechanism is explained as the homodyne<br />

detecti<strong>on</strong> of the applied RF current because of the oscillati<strong>on</strong> of resistance at the same<br />

frequency. In the measurements, the res<strong>on</strong>ant peak was observed around 5 GHz under<br />

a magnetic field of 5 kOe at room temperature, for example. This represents that the<br />

magnetic res<strong>on</strong>ance of superparamagnetic Fe nano-particles was electrically excited and<br />

detected. We thank Y. Shiota, H. Tomita, G. Shiomi for valuable discussi<strong>on</strong>s. This work<br />

is supported by Grant-in-Aid for Scientific Research (S), MEXT, Japan. (No. 23226001)<br />

[1] S. Yuasa et al., Nature Mater. 3, 868 (2004). [2] A. A. Tulapurkar et al., Nature 438, 339 (2005).<br />

[3] S. Ishibashi, S. Miwa et al., submitted.<br />

Spin Coulomb drag and optical excitati<strong>on</strong>s in low dimensi<strong>on</strong>al systems<br />

Irene D'amico 1 and Carsten A. Ullrich 2<br />

1 Physics, University of York, United Kingdom<br />

2 Physics, University of Missouri-Columbia, USA<br />

Within the remit of new quantum technologies, an intense effort is devoted to<br />

improving our understanding of spin dynamics, with the aim of building novel<br />

spintr<strong>on</strong>ics devices. In this c<strong>on</strong>text the theory of spin Coulomb drag (SCD) was<br />

recently developed. It shows that Coulomb interacti<strong>on</strong>s are an intrinsic decay<br />

mechanism for spin currents. As c<strong>on</strong>firmed by experiments, SCD can be substantial<br />

in semic<strong>on</strong>ductors, and it is bound to become <strong>on</strong>e of the most serious issues in spin<br />

polarized transport, since, due to its intrinsic nature, it cannot be avoided even in the<br />

purest material. More recently the influence of SCD <strong>on</strong> optical spin-injecti<strong>on</strong> and spinresolved<br />

optical experiments has been c<strong>on</strong>sidered. Here we report <strong>on</strong> SCD effects<br />

<strong>on</strong> intersubband optical spin excitati<strong>on</strong>s in III-V quantum wells, where SCD may<br />

c<strong>on</strong>tribute substantially to the linewidth of spin plasm<strong>on</strong>s. By going bey<strong>on</strong>d the usual<br />

local density functi<strong>on</strong>al approximati<strong>on</strong> and properly including the effects due to the<br />

inhomogeneity of the system in the growth directi<strong>on</strong>, we show that the quantizati<strong>on</strong> of<br />

states in the growth directi<strong>on</strong> may str<strong>on</strong>gly reduce the intrinsic plasm<strong>on</strong> linewidth.<br />

July 8 - 13, 2012 Busan, Korea 177<br />

Poster Thursday


Poster Thursday<br />

RL13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Perpendicular magnetic property and magnetic damping of very thin<br />

CoFeB films<br />

Mikihiko Oogane*, Miho Kubota, Kei Sato, Hiroshi Naganuma and Yasuo Ando<br />

Applied Physics, Tohoku University, Japan<br />

A very thin CoFeB film with a perpendicular magnetic anisotropy is a promising material<br />

for applicati<strong>on</strong>s of spintr<strong>on</strong>ics devices, such as Spin-RAM and spin-logic circuit [1].<br />

Development of materials with high magnetic anisotropy and low magnetic damping<br />

is an important issue to achieve high thermal stability and low power c<strong>on</strong>sumpti<strong>on</strong><br />

in the spintr<strong>on</strong>ics devices. However, the relati<strong>on</strong>ship between magnetic damping and<br />

perpendicular anisotropy has not been systematically investigated. In this work, we have<br />

investigated capping layer dependence of perpendicular magnetic property and magnetic<br />

damping in very thin CoFeB films. The films were prepared by sputtering system. The<br />

structure of the films were SiO 2-sub./Ta(5)/MgO(0.9)/CoFeB(d)/X(5 nm), (X = Ta, Pd,<br />

Cu, Ru, V, MgO). After the depositi<strong>on</strong> of the films, annealing process was carried out at<br />

250 - 350 o C. Magnetic property and magnetic damping were respectively characterized by<br />

SQUID and FMR [2]. Perpendicular magnetic anisotropy and damping str<strong>on</strong>gly depends<br />

<strong>on</strong> the capping layer material. For the Ta capping layer, CoFeB film below 1.4 nm showed<br />

a perpendicular anisotropy. However, magnetic damping was drastically enhanced for<br />

the films with perpendicular anisotropy. Similar behavior was observed in the films with<br />

capping layers of Pd and Ru. This work was supported by the FIRST program.<br />

[1] S. Ikeda et al., Nature Material 9, 721 (2010). [2] S. Mizukami et al., Jpn. J. Appl. Phys. 40, 580 (2001).<br />

RL14<br />

Perpendicular magnetic tunnel juncti<strong>on</strong>s with TbFeCo-based pinned<br />

layer and CoFeB-MgO free layer<br />

Jungmin Han 1 *, Byoung-chul Min 1 , Kyung-jin Lee 2 and Kyung-ho Shin 1<br />

1<br />

Spin Device Research Center, Korea Institute of Science and Technology, Seoul 136-<br />

791, Korea<br />

2<br />

Department of Materials Science, Korea University, Seoul 136-701, Korea<br />

We have fabricated perpendicular magnetic tunnel juncti<strong>on</strong>s (pMTJs) with a CoFeB/<br />

TbFeCo pinned layer and Ta/ CoFeB/ MgO free layer using in-situ annealing<br />

process. The TbFeCo-based hybrid pinned layer is a useful approach to obtain a high<br />

perpendicular magnetic anisotropy (PMA). However, a high temperature annealing,<br />

often required for MgO-based MTJs to obtain a high tunneling magnetoresistance<br />

(TMR), may deteriorate the PMA of TbFeCo films. Our experimental results show a<br />

possibility to obtain a reas<strong>on</strong>able TMR and high PMA simultaneously by c<strong>on</strong>ducting<br />

an annealing process to achieve a grain-to-grain epitaxy in CoFeB/MgO/CoFeB layers<br />

before depositing the TbFeCo layer. The pMTJs prepared by this process show a<br />

tunneling magnetoresistance (TMR) ratio of 15% to 19 % at room temperature.<br />

[1] S. Ikeda, K. Miura, H. Yamamoto, K. Mizunuma, H. D. Gan, M. Endo, S. Kanai, J. Hayakawa, F.<br />

Matsukura & H. Ohno, Nature Materials 9, 721-724 (2010). [2] N. Nishimura,T. Hirai, A. Koganei,<br />

T. Ikeda, K. Okano, Y. Sekiguchi, and Y. Osada J. Appl. Phys. 91, 5246 (2002). [3] Il-Jae Shin,<br />

Byoung-Chul Min, Jin Pyo H<strong>on</strong>g, and Kyung-Ho Shin, Appl. Phys. Lett. 95, 222501 (2009).<br />

RL15<br />

Thickness and magnetic anisotropy dependence of anomalous Nernst<br />

effect in L1 0-FePt films<br />

Kota Hasegawa, Masaki Mizuguchi*, Ken-ichi Uchida, Eiji Saitoh and Koki<br />

Takanashi<br />

Institute for Materials Research (IMR), Tohoku University, Japan<br />

The anomalous Nernst effect (ANE) is a thermomagnetic effect which gives rise to an<br />

electric field perpendicular to both temperature gradient and saturati<strong>on</strong> magnetizati<strong>on</strong>.<br />

Although ANE has been known phenomenologically for a l<strong>on</strong>g time, <strong>on</strong>ly a few<br />

studies have been reported, and the mechanism has not fully been understood. L1 0-<br />

FePt with high magnetic anisotropy (K u) attracted much attenti<strong>on</strong> for recent years as a<br />

promising material for “spin caloritr<strong>on</strong>ics” [1]. In this paper, we have made systematic<br />

investigati<strong>on</strong> <strong>on</strong> the thickness and Ku dependence of ANE in perpendicularly<br />

magnetized FePt(001) films. FePt(001) films were deposited <strong>on</strong> MgO(001) single<br />

crystal substrates at 500°C. The thickness was varied in the range from 7 to 40 nm.<br />

Ku was changed in the range from 3.0×10 6 to 2.7×10 7 erg/cc, depending <strong>on</strong> the degree<br />

of L10 order which was c<strong>on</strong>trolled by the depositi<strong>on</strong> temperature from 300 to 500°C.<br />

It is found that the anomalous Nernst coefficient (Q s) does not depend <strong>on</strong> the film<br />

thickness. On the other hand, Qs increases with decreasing K u. These results suggest a<br />

c<strong>on</strong>tributi<strong>on</strong> of spin wave in ANE.<br />

[1] T. Seki et al., Solid State Comm., Vol. 50, 496 (2010).<br />

178 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RL16<br />

Spin-torque efficiency and magnetizati<strong>on</strong> reversal in three-dimensi<strong>on</strong>al<br />

Rashba materials<br />

Kazuhiro Tsutsui and Shuichi Murakami*<br />

Dept. of Physics, School of Science, Tokyo Institute of Technology, Japan<br />

In additi<strong>on</strong> to the magnetizati<strong>on</strong> reversal by the spin-transfer torque, the magnetizati<strong>on</strong><br />

reversal driven by a str<strong>on</strong>g spin-orbit coupling has been intensely investigated<br />

experimentally and theoretically [1,2]. In this presentati<strong>on</strong>, we focus <strong>on</strong> 3D Rashba<br />

models coupled with localized spins, and study the spin torque theoretically. This is<br />

motivated by the recent discovery of BiTeI as 3D Rashba systems [3]. As a result,<br />

we find that the spin torque in 3D Rashba models is largely enhanced in the highcarrier-density<br />

regime compared with 2D Rashba models. We also find that the spintorque<br />

efficiency defined as the ratio between the spin torque and the electric current is<br />

enhanced when the Fermi energy lies <strong>on</strong> <strong>on</strong>ly lower band, both in 3D and 2D. As we<br />

change the Rashba spin-orbit coupling, the spin-torque efficiency becomes maximum<br />

when the Rashba spin-orbit coupling is comparable to the exchange coupling to the<br />

localized spins. The optimum spin-torque efficiency becomes large when the Rashba<br />

spin-orbit coupling is large, and it is preferable for the magnetizati<strong>on</strong> reversal with<br />

smaller amount of current injecti<strong>on</strong>.<br />

[1] A. Manch<strong>on</strong> and S. Zhang, Phys. Rev. B 78, 212405 (2008). [2] I. M. Mir<strong>on</strong> et al., Nature Mater.<br />

9, 230 (2010). [3] K. Ishizaka et al., Nature Mater. 10, 521 (2011).<br />

RL17<br />

A new circuit model for spin-torque oscillator including the<br />

perpendicular torque of magnetic tunnel juncti<strong>on</strong><br />

Hyein Lim, Sora Ahn, Mirye<strong>on</strong> Kim, Jihye Shin, Jinju Lee, Seungjun Lee and<br />

Hyungso<strong>on</strong> Shin*<br />

Electr<strong>on</strong>ic Engineering, Ewha Womans University, Korea<br />

Spin-torque oscillator (STO) is a promising new technology for the future RF oscillator, which is<br />

based <strong>on</strong> the spin transfer torque (STT) effect in magnetic multilayered nanostructure. It is expected<br />

to overcome the limitati<strong>on</strong>s of the semic<strong>on</strong>ductor-based device technology. In our previous work,<br />

we have proposed a circuit-level model of the Giant Magneto-Resistance (GMR) STO. In this paper,<br />

we present a physics-based circuit-level model of the Magnetic Tunnel Juncti<strong>on</strong> (MTJ)-based STO.<br />

The new model includes the effect of perpendicular torque that has been ignored in the GMR STO<br />

model. The variati<strong>on</strong>s of three major characteristics, generati<strong>on</strong> frequency, mean oscillati<strong>on</strong> power,<br />

and generati<strong>on</strong> linewidth of an MTJ STO are investigated by changing the amount of perpendicular<br />

torque. The model is fully compatible with circuit-level simulators such as SPICE. The accuracy of<br />

new model was verified by HSPICE simulati<strong>on</strong>. The simulati<strong>on</strong> results show an excellent agreement<br />

with the experimental data. With our circuit model, we could compose a current mirror circuit that<br />

c<strong>on</strong>tains an STO element and a multi-stage amplifier for signal amplificati<strong>on</strong>, such that a full circuitlevel<br />

simulati<strong>on</strong> of MJT STO was accomplished for the first time.<br />

1. HyeIn Lim, Sora Ahn, Seungjun Lee, and Hyungso<strong>on</strong> Shin: SSDM (2011) p. 1466. 2. A. Slavin, and V. Tiberkevich: IEEE<br />

Trans. Magn. 45 (2009) 1875. 3. P. Villard, U. Ebels, D. Houssameddine J. Katine, D. Mauri, B. Delaet, P. Vincent, M.-C. Cyrille, B.<br />

Viala, J.-P. Michel, J. Prouvee, and F. Badets: IEEE J. Solid-State Circuits 45 (2010) 214. 4. Z. M. Zeng, P. Upadhyaya, P. Khalili<br />

Amiri, K. H. Cheung, J. A. Katine, J. Langer, K. L. Wang, and H. W. Jiang: Appl. Phys. Lett. 99 (2011) 032503.<br />

RL18<br />

Current induced localized domain wall oscillators in NiFe /Cu /NiFe<br />

nano-stripe<br />

Liang-juan Chang 1 , Pang Lin 2 and Shang-fan Lee 1 *<br />

1 Institute of Physics, Academia Sinica, Taiwan<br />

2 Department of Materials Science & Engineering, Nati<strong>on</strong>al Chiao Tung University,<br />

Taiwan<br />

We study domain wall (DW) oscillati<strong>on</strong>s induced by the injecti<strong>on</strong> of a dc current through<br />

a nanowires c<strong>on</strong>taining artificial symmetric protrusi<strong>on</strong>s with Permalloy based pseudo<br />

spin valve (NiFe 12 nm/Cu 8 nm/NiFe 24 nm). An experimental analysis was carried out<br />

to describe the variati<strong>on</strong> of differential resistance dV/dI by applying in-plane dc current<br />

with pinned DWs. When the DWs are pinned at the traps, we have observed a reversible<br />

moti<strong>on</strong> of the DWs by changing the applied in-plane dc current. The peak in dV/dI<br />

associated with the reversible change of magnetoresistance has been taken as evidence of<br />

current induced coherent DW oscillati<strong>on</strong> between the pinned regimes which gives rise to<br />

the peak. The excited critical current shifts symmetrically with respect to H. It is expected<br />

from the DW trap with symmetrical potential landscape. The dynamics of localized DW<br />

oscillati<strong>on</strong>s under applicati<strong>on</strong> of dc current was examined by micromagnetic simulati<strong>on</strong>s<br />

(OOMMF). The frequency f of DW oscillati<strong>on</strong> decreases from 1.5 GHz to 0.95 GHz as H<br />

increasing. This simple c<strong>on</strong>cept of DW based oscillators could be used as radio frequency<br />

assisted writing in magnetic recording technology.<br />

* Corresp<strong>on</strong>ding author e-mail: leesf@phys.sinica.edu.tw


RL19<br />

Current induced transverse field versus Joule heating in Co/Pd<br />

nanowires<br />

Mahdi Jamali, Xuepeng Qiu, Kulothungasagaran Narayanapillai and Hyunsoo Yang*<br />

Electrical and Computer Engineering, Nati<strong>on</strong>al University of Singapore, Singapore<br />

There has been a tremendous effort in understanding of the electric current effect in<br />

the ultra thin film of ferromagnetic materials[1, 2]. We have recently found that in the<br />

nanowire made of a multilayer structure of Co/Pd, there is a current induced transverse<br />

magnetic field[3]. Electric current could also cause Joule heating especially in the high<br />

current densities. The Hall resistance has been measured at different current densities<br />

for the magnetic fields in the easy axis directi<strong>on</strong>. By increasing the current density,<br />

there is a reducti<strong>on</strong> in the switching field of the nanowire. We further performed the<br />

measurement at different angles of the magnetic field with respect to the easy axis<br />

of the sample. From the asymmetry of the switching fields, <strong>on</strong>e can approximate the<br />

current induced transverse field. Furthermore, by using four-probe measurements, the<br />

nanowire resistance has been measured at different temperatures and the temperature<br />

coefficient of the Co/Pd nanowire has been extracted. By measuring the resistance<br />

of the nanowire at different current densities, we can approximate the nanowire<br />

temperature during the measurement and its effect <strong>on</strong> the switching dynamics.<br />

[1] I. M. Mir<strong>on</strong>, G. Gaudin, S. Auffret, B. Rodmacq, A. Schuhl, S. Pizzini, J. Vogel, and P.<br />

Gambardella, Nat. Mater. 9, 230 (2010). [2] T. Suzuki, S. Fukami, N. Ishiwata, M. Yamanouchi,<br />

S. Ikeda, N. Kasai, and H. Ohno, Appl. Phys. Lett. 98, 142505 (2011). [3] K. Narayanapillai, M.<br />

Jamali, and H. Yang, MMM c<strong>on</strong>ference, Ariz<strong>on</strong>a (2011).<br />

RL20<br />

Improvement of generati<strong>on</strong> efficiency of pure spin current using multiterminal<br />

spin injecti<strong>on</strong><br />

Shaojie Hu, Tatsuya Nomura, Seiji N<strong>on</strong>oguchi and Takashi Kimura*<br />

Advanced Electr<strong>on</strong>ics Research Divisi<strong>on</strong>, INAMORI Fr<strong>on</strong>tier Research Center,<br />

Kyushu University., Japan<br />

Lateral spin valve structures have several advantages for the generati<strong>on</strong>, manipulati<strong>on</strong><br />

and injecti<strong>on</strong> of the spin current because of their flexible probe c<strong>on</strong>figurati<strong>on</strong>s.<br />

Particularly, n<strong>on</strong>local spin injecti<strong>on</strong> techniques enable us to create a pure spin current<br />

which carries the spin informati<strong>on</strong> with extremely low propagati<strong>on</strong> loss. However, in<br />

general, the generati<strong>on</strong> efficiency of the pure spin current is quite low. To solve this<br />

serious obstacle, we propose a n<strong>on</strong>local spin injecti<strong>on</strong> with multi spin injectors. In<br />

the present study, we fabricated the lateral valve structure c<strong>on</strong>sisting of a quadruple<br />

Permalloy spin injectors and n<strong>on</strong>magnetic Cu strip and show that the developed device<br />

has two advantages. One is that the maximum generated spin current is str<strong>on</strong>gly<br />

enhanced. The other <strong>on</strong>e is that the efficiency for generating a certain quantity of the<br />

spin current is significantly improved. We also show that the optimizati<strong>on</strong> of the device<br />

dimensi<strong>on</strong> yields the further enhancement of the maximum generating spin current.<br />

M. Johns<strong>on</strong> and R. H. Silsbee, Phys. Rev. Lett. 55, 1790 (1985). T. Kimura, T. Sato, and Y. Otani,<br />

Phys. Rev. Lett. 100, 066602 (2008). T. Kimura et al., Appl. Phys. Lett. 85, 3501 (2004).<br />

RL21<br />

Electrical transport properties of Co2MnSi Schottky diode<br />

In-bok Baek 1 , Xianh<strong>on</strong>g Li 1 , Se<strong>on</strong>gjae Lee 1 *, Chil Se<strong>on</strong>g Ah 2 , J<strong>on</strong>g-he<strong>on</strong> Yang 2 , Chan<br />

Woo Park 2 , Han Young Yu 2 , Mo<strong>on</strong>gyu Jang 2 and Gun Y<strong>on</strong>g Sung 2<br />

1<br />

Department of Physics, Research Institute for Natural Sciences,, Hanyang University,<br />

Seoul, 133-791,, Korea<br />

2<br />

Electr<strong>on</strong>ics and Telecommunicati<strong>on</strong>s Research Institute (ETRI), Daej<strong>on</strong>, 305-700,, Korea<br />

Recently, the spintr<strong>on</strong>ic device has attracted c<strong>on</strong>siderable attenti<strong>on</strong>s due to its possibility to lead a new<br />

generati<strong>on</strong> of electr<strong>on</strong>ic devices by utilizing spin degree-of-freedom. Especially, silic<strong>on</strong> is a very attractive<br />

material for the spin channel of spintr<strong>on</strong>ic devices due to a weak spin-orbit coupling [1] and a l<strong>on</strong>g spin<br />

lifetime of ~ 10 ns [2, 3], while Co 2MnSi being a half-metallic Heusler compound is regarded as a promising<br />

candidate for the spin injecti<strong>on</strong>/detecti<strong>on</strong> electrodes due to a possible complete spin polarizati<strong>on</strong>. [4, 5] In this<br />

work, the elect<strong>on</strong>ic transport chracteristics of Co 2MnSi/Si Schottky diodes are studied for the investigati<strong>on</strong> of<br />

spin electrode/channel interface quality, in which Co 2MnSi was prepared under various process c<strong>on</strong>diti<strong>on</strong>s.<br />

We found that the Schottky barrier height of Co 2MnSi decreased from 0.56 to 0.52 eV and 0.44 to 0.36 eV<br />

for electr<strong>on</strong> and hole, respectively, with increasing RTA temperature from 450 to 550°C. Also, the ideality<br />

factor close to unity for RTA temperature of 450°C significantly degraded as it changed to 550°C, indicating<br />

the increase of interface trap density. Deduced from our electrical results, the manufactured Co 2MnSi is<br />

expected as a promising ferromagnetic material for the applicati<strong>on</strong>s in silic<strong>on</strong> spintr<strong>on</strong>ic devices.<br />

[1] I. Zutic, J. Fabian, and S. C. Erwin, Phys. Rev. Lett. 97, 026602 (2006). [2] G. Lancaster, J. A. V. Wyk and E. E.<br />

Schneider, Proc. Phys. Soc. L<strong>on</strong>d<strong>on</strong> 84, 19 (1964). [3] J. Fabian, A. Mathos-Abiague, C. Ertler, P. Stano, and I. Zutic,<br />

Acta Phys. Slov. 57, 565 (2007). [4] Y.ohdaira, M. Oogane, H. Naganuma, and Y. Ando Appl. Phys. Lett. 99, 132513<br />

(2011). [5] P. J. Brown, K. U. Neumann, P. J. Webster and K. R. A. Ziebeck, J. Phys.: C<strong>on</strong>dens. Matter 12, 1827 (2000).<br />

RL22<br />

RL23<br />

RL24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Negative electr<strong>on</strong>-beam resist hard mask i<strong>on</strong> beam etching process for<br />

the fabricati<strong>on</strong> of nanoscale spin transfer torque magnetic random<br />

access memory device<br />

Hyungyu Lee 1 , Daeh<strong>on</strong>g Kim 1 , B<strong>on</strong>gho Kim 1 , Sungwoo Chun 1 , Se<strong>on</strong>jun Choi 1 and<br />

Seung-beck Lee 2 *<br />

1 Department of Electr<strong>on</strong>ic Engineering, Hanyang University, Korea<br />

2 Institute of Nano Science and Technology, Hanyang University, Korea<br />

To c<strong>on</strong>duct MTJs etching process, Ta[1] hard masks are generally used for reactive<br />

i<strong>on</strong> etching and i<strong>on</strong> beam etching (IBE) process due to relatively good selectivity over<br />

magnetic metals. However, tapering of the Ta mask is unavoidable which results in the<br />

underlying MTJ to become trapezoidal. Here we utilized negative electr<strong>on</strong>-beam resist<br />

(NER) hard mask process to overcome the hard mask induced nano-patterning difficulties.<br />

Arrays of 30 nm dot patterns 200 nm apart were defined by electr<strong>on</strong> beam lithography<br />

with a NER thickness of 90 nm. The IBE was performed using the NER as the hard mask<br />

layer. During the IBE process, The IBE etch rate of the NER was 3 nm/min and since the<br />

total MTJ etching thickness was 36 nm with 2.1 nm/min etch rate, a 30 nm diameter NER<br />

pillar with 90 nm thickness was enough to produce the 30 nm diameter MTJ nanopillars.<br />

And redepositi<strong>on</strong> of the etched material <strong>on</strong> side walls of the NER protects the resist from<br />

tapering, resulting in vertical side profiles in the etched MTJs.<br />

[1] X. Peng, S. Wakeham, A. Morr<strong>on</strong>e, S. Axdal, M. Feldbaum, J. Hwu, T. Bo<strong>on</strong>stra, Y. Chen, J.<br />

Ding, Vacuum. 83. 1007 (2009)<br />

Magnetizati<strong>on</strong> reversal process of a Py nanodot under pure spin<br />

current injecti<strong>on</strong><br />

Tatsuya Nomura, Seiji N<strong>on</strong>oguchi and Takashi Kimura*<br />

Kyushu University, Japan<br />

A new type lateral spin valve structure based <strong>on</strong> a pair of closely located Permalloy<br />

nanopillars has been developed. This structure enables us to flow a large amount of<br />

current, resulting in the injecti<strong>on</strong> of a large pure spin current into a ferromagentic<br />

nanodot entirely. We investigated the magnetizati<strong>on</strong> reversal process of the Permalloy<br />

nanodot under dc pure spin current injecti<strong>on</strong> from the field dependence of the n<strong>on</strong>local<br />

spin valve signal. The dc pure spin current was generated by flowing the dc current<br />

with an ac excitati<strong>on</strong> current in the n<strong>on</strong>local current terminal. The n<strong>on</strong>local spin valve<br />

signal without the dc current exhibits a clear bipolar signal typically observed in the<br />

c<strong>on</strong>venti<strong>on</strong>al lateral spin valve.[1,2] The n<strong>on</strong>local signal curve shows the systematic<br />

changes with increasing the dc pure spin current and its variati<strong>on</strong> str<strong>on</strong>gly depends <strong>on</strong><br />

the current intensity and polarity. This means that the reversal process of the Py dot is<br />

str<strong>on</strong>gly modified by the pure spin current injecti<strong>on</strong>.<br />

[1] F.J.Jedema,A.T.Filip,B.J.vanWees,Nature410(2001)345. [2] T. Kimura et al. Appl. Phys. Lett.<br />

85, 3501~3503 (2004)<br />

Spin transfer effect in FePt nanowires: c<strong>on</strong>trolling the stochasticity of<br />

domain wall depinning using c<strong>on</strong>stricti<strong>on</strong>s<br />

Jean-philippe Attane 1 , Van Dai Nguyen 1 , Alain Marty 1 , Lucien Notin 1 , Cyrille Beigne 1 ,<br />

Juan Carlos Rojas-sanchez 1 , Stefania Pizzini 2 and Laurent Vila 1<br />

1<br />

Universite Joseph Fourier, BP 53, 38041, Grenoble and INAC/ CEA Grenoble, 17<br />

avenue des Martyrs, France<br />

2<br />

Institut Neel, CNRS, 25 avenue des Martyrs, 38042 Grenoble, France<br />

In this c<strong>on</strong>tributi<strong>on</strong>, we present dynamic measurements of domain wall (DW) depinning from structural<br />

defects, in nanowires processed from single FePt layers and FePt/Pd(Pt)/FePt spin-valves. Statistical<br />

analysis reveals that in such systems, the DW depinning is stochastic, and that this stochasticity has two<br />

origins. The first <strong>on</strong>e is thermal activati<strong>on</strong>, which helps the wall to cross the energy barrier associated<br />

to the defect. The sec<strong>on</strong>d <strong>on</strong>e originates from the ability of the DW to get pinned randomly al<strong>on</strong>g<br />

different micromagnetic c<strong>on</strong>figurati<strong>on</strong>s, each <strong>on</strong>e corresp<strong>on</strong>ding to a given depinning fields. We study<br />

the influence of different c<strong>on</strong>stricti<strong>on</strong> types <strong>on</strong> the dynamic of DW depinning, using spin-valve-based<br />

nanowires. The depinning probability functi<strong>on</strong> is found to exhibit very different behaviors, which depend<br />

<strong>on</strong> the types of c<strong>on</strong>stricti<strong>on</strong>: it is partially possible to c<strong>on</strong>trol the stochastic behavior of DW depinning by<br />

tuning the shape of c<strong>on</strong>stricti<strong>on</strong>s. Additi<strong>on</strong>ally, we showed that the probability functi<strong>on</strong> of DW depinning<br />

can be varied by applying a DC current, the effect of the spin torque <strong>on</strong> thermal and c<strong>on</strong>figurati<strong>on</strong>al<br />

stochasticities being similar to those of a field. The measured spin transfer torque efficiency is very high<br />

(~10-13T.m 2A -1 ), and is similar for single FePt layers and FePt-based spin-valves.<br />

C. Burrowes et al., Nat. Phys. 6, 17 (2010) A. Mihai et al., Phys. Rev. B 84, 014411 (2011)<br />

July 8 - 13, 2012 Busan, Korea 179<br />

Poster Thursday


Poster Thursday<br />

RL25<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Electric field effect <strong>on</strong> magnetic coercivity of Fe3O4/BaTiO3<br />

heterostructures<br />

Tomoyasu Taniyama*, Taiichiro Nozaki, Yasuhiro Shirahata, Gorige Venkataiah and<br />

Mitsuru Itoh<br />

Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

Electric field c<strong>on</strong>trol of the magnetic coercivity of half metallic Fe 3O 4 epitaxial thin films<br />

<strong>on</strong> BaTiO 3(001) is dem<strong>on</strong>strated at room temperature, with a view to developing a new<br />

type of highly spin polarized electr<strong>on</strong> source, where the magnetizati<strong>on</strong> orientati<strong>on</strong> of the<br />

spin source can be c<strong>on</strong>trolled by electric field. Fe 3O 4 films were grown <strong>on</strong> BaTiO 3(001)<br />

substrates by reactive molecular beam epitaxy in an oxygen atmosphere at a pressure of<br />

1×10 -6 Torr. The Fe 3O 4 films show a clear Verwey transiti<strong>on</strong> at ~120 K, ensuing the high<br />

quality of the films grown. The electric field variati<strong>on</strong> of the in-plane magnetic coercivity<br />

of Fe 3O 4 films was measured using Kerr effect, exhibiting a hysteretic behavior, where the<br />

magnetic coercivities for positive and negative electric fields at ±10 kV/cm show distinct<br />

values. Since a possible strain effect due to ferroelectric domain switching of BaTiO 3<br />

should be equivalent for both electric field polarities over the switching field, another<br />

possible mechanism such as polarizati<strong>on</strong> charge accumulati<strong>on</strong> at the interface likely has<br />

its origin in the electric field effect, associated with carrier induced modulati<strong>on</strong> of the<br />

electr<strong>on</strong>ic states of Fe 3O 4. Work supported in part by Industrial Technology Research<br />

Grant Program in 2009 from NEDO, Japan.<br />

[1] G. Venkataiah, Y. Shirahata, M. Itoh, and T. Taniyama, Appl. Phys. Lett. 99, 102506 (2011).<br />

RL26<br />

Dependence of current-induced effective rashba field and<br />

perpendicular magnetic anisotropy <strong>on</strong> annealing temperature<br />

Ki-seung Lee 1 , Byung Chul Min 1 , Kyung Jin Lee 2 * and Kyung-ho Shin 1<br />

1<br />

Spin C<strong>on</strong>vergence Research Center, Korea Institute of Science and Technology,<br />

Korea<br />

2<br />

Departments of Materials Science and Engineering, Korea University, Korea<br />

Manipulati<strong>on</strong> of local magnetizati<strong>on</strong> using electrical current has attracted c<strong>on</strong>siderable interest<br />

due to its rich physics and potential applicati<strong>on</strong>s for a new class of spintr<strong>on</strong>ic devices. It was<br />

theoretically proposed that Rashba-type spin-orbit coupling (SOC) caused by inversi<strong>on</strong> symmetry<br />

breaking yields a new type of current-induced effective magnetic field [1], i.e. Rashba field of<br />

which directi<strong>on</strong> is perpendicular to both the directi<strong>on</strong> of current-flow and that of the inversi<strong>on</strong><br />

symmetry breaking. The existence of this Rashba field in the structure c<strong>on</strong>sisting of n<strong>on</strong>-magnetic<br />

metal | ferromagnetic metal | oxide was recently c<strong>on</strong>firmed experimentally [2]. We previously<br />

investigated the effect of the ferromagnetic film thickness <strong>on</strong> the Rashba spin transfer torque<br />

(STT), as well as its effect <strong>on</strong> the perpendicular magnetic anisotropy. The magnetic anisotropy<br />

clearly showed surface properties, while the surface nature of the Rashba field remained elusive.<br />

In this work, we further investigate the dependence of current-induced effective Rashba field and<br />

perpendicular magnetic anisotropy <strong>on</strong> annealing temperature. Experiments were carried out <strong>on</strong><br />

Pt(3nm)|Co(0.6nm)|MgO(2nm) samples with the annealing temperature from 300 O C up to 450<br />

O C. In this presentati<strong>on</strong>, the effect of annealing treatment will be discussed.<br />

[1] A. Manch<strong>on</strong> and S. Zhang, Phy. Rev. B 78, 212405 (2008) ; Phys. Rev. B 79, 094422 (2009). [2] I.<br />

M. Mir<strong>on</strong> et al., Nature Mater. 9, 230 (2010).<br />

RL27<br />

Spin motive force driven by magnetizati<strong>on</strong> dynamics<br />

Junichiro Ohe<br />

Toho University, Japan<br />

The current-induced magnetizati<strong>on</strong> dynamics realized in spintr<strong>on</strong>ics devices involve<br />

both of charge and spin degrees of freedom. Recently, it has been pointed out that the<br />

magnetizati<strong>on</strong> dynamics induces an effective electric field acting <strong>on</strong> the c<strong>on</strong>ducti<strong>on</strong><br />

electr<strong>on</strong>s through the spin Berry phase. The effective electric field, or a 'spin motive<br />

electric field', was investigated for a simple <strong>on</strong>e-dimensi<strong>on</strong>al domain wall. It is<br />

difficult to estimate analytically this effective electric field in actual systems, because<br />

the magnetizati<strong>on</strong> dynamics obeys the n<strong>on</strong>-linear Landau-Lifshitz equati<strong>on</strong>. In this<br />

report, we investigate the the spin motive force and the measurable voltage by solving<br />

Landau-Lifshitz-Gilbert equati<strong>on</strong> numerically. We propose several structures that<br />

show measurable spin motive force. We also compare the our numerical results and<br />

experimental results.<br />

J. Ohe and S. Maekawa, J. Appl. Phys. 105, 07C706 (2008) J. Ohe et al., Appl. Phys. Lett., 95,<br />

123110 (2009) Y. Yamane et al, Phys. Rev. Lett. 107, 236602 (2011) M. Hayashi et al, Phys. Rev.<br />

Lett. (2012) in press<br />

180 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RL28<br />

Electrical detecti<strong>on</strong> of the spin Hall effects in the InAs quantum well<br />

structure<br />

Tae Young Lee, Jo<strong>on</strong>ye<strong>on</strong> Chang*, Hyun Cheol Koo, Hyung-jun Kim and Suk Hee<br />

Han<br />

Korea Institute of Science and technology, Korea<br />

Spin Hall effect (SHE) becomes intriguing because it generates and manipulates carrier<br />

spins in n<strong>on</strong>-magnets without external magnetic field. Use of perpendicularly polarized<br />

spin currents for spin field effect transistor is a quite promising because precessi<strong>on</strong> of<br />

perpendicularly polarized spins can be manipulated by Rashba spin orbit coupling in the<br />

absence of the applied field al<strong>on</strong>g momentum directi<strong>on</strong> [1]. The SHEs are electrically<br />

measured for an InAs quantum well (QW) structure where Rashba field of 8.5 Tesla<br />

is induced. The device is composed of an InAs channel and Pd/CoFe multilayers with<br />

perpendicular magnetizati<strong>on</strong>, which allows to detecti<strong>on</strong> of spin Hall voltages. The spinpolarized<br />

electr<strong>on</strong>s with perpendicular orientati<strong>on</strong> cause a charge accumulati<strong>on</strong> at the<br />

edge of the InAs channel probed by spin Hall voltage. This charge accumulati<strong>on</strong> induces a<br />

transverse voltage. We observe large spin Hall resistance up to 9.3 mΩ and spin Hall angle<br />

is found to be about 0.01. According to the theoretical reports [2, 3], <strong>on</strong>e of its origins is<br />

spin-orbit scattering of c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s through side-jump or skew scattering. The<br />

SHEs are emerging from the side-jump scattering of flowing spins in the InAs QW and the<br />

scattering directi<strong>on</strong> is determined by spin orientati<strong>on</strong> with sp<strong>on</strong>taneous magnetizati<strong>on</strong>.<br />

REFERENCES [1] Koo et al., Science. 325, 1515 (2009). [2] J. E Hirsch, Phys. Rev. Lett. 83, 1834<br />

(1999). [3] J. Zhang, Phys. Rev. Lett. 85, 393 (2000).<br />

RL29<br />

Bias-voltage c<strong>on</strong>trolled tunneling resistance in a ferromagnet-metalinsulator-ferromagnet<br />

tunneling juncti<strong>on</strong><br />

Sui-pin Chen*<br />

Department of Electrophysics, Nati<strong>on</strong>al Chiayi University, Taiwan<br />

We adopt the spin-polarized free-electr<strong>on</strong> model [1-3] and extend our previous work [4]<br />

to study the tunneling resistance change in a ferromagnet/metal/insulator/ferromagnet<br />

magnetic tunneling juncti<strong>on</strong> [5], and find a method for changing the tunneling<br />

resistance. Unlike the traditi<strong>on</strong>al method of varying the magnetizati<strong>on</strong>s c<strong>on</strong>figurati<strong>on</strong><br />

between the two ferromagnetic layers, the proposed method uses the polarity of a<br />

bias voltage with a small strength to change the tunneling resistance. Under suitable<br />

c<strong>on</strong>diti<strong>on</strong>s, we show that both tunneling resistance changes resulting from the polarity<br />

of the bias voltage and from the magnetizati<strong>on</strong>s c<strong>on</strong>figurati<strong>on</strong> are equal in magnitude,<br />

and are larger than that in a c<strong>on</strong>venti<strong>on</strong>al ferromagnet/insulator/ferromagnet magnetic<br />

tunneling juncti<strong>on</strong>.<br />

[1] S. Zhang and P. M. Levy, Phys. Rev. Lett. 81, 5660 (1998). [2]J. Yang, J. Wang, Z. M. Zheng, D.<br />

Y. Xing and C. R. Chang, Phys. Rev. B 71, 214434 (2005). [3] S.-P. Chen and C.-R. Chang, IEEE<br />

Trans. Magn. 45, 2410 (2009). [4] S.-P. Chen, J. Appl. Phys. 107, 09C716 (2010). [5] S. Yuasa, T.<br />

Nagahama and Y. Suzuki, Science 297, 234 (2002).<br />

RL30<br />

A highly (001) textured Ge/MgO/bcc-ferromagnet system prepared by<br />

ultra-high vacuum sputtering<br />

Soogil Lee 1 , Sangho<strong>on</strong> Kim 1 , Jungho Ko 1 , Sangho Lee 1 , Jangyup S<strong>on</strong> 1 , Seung-he<strong>on</strong><br />

Chris Baek 2 , Seok-hee Lee 2 and J<strong>on</strong>gill H<strong>on</strong>g 1 *<br />

1 Materials Science and Engineering, Y<strong>on</strong>sei University, Seoul 120-749, Korea, Korea<br />

2 Dept. of Electrical Engineering, Korea Advanced Institute of Science and Technology<br />

(KAIST), Daeje<strong>on</strong>, 305-701, Korea, Korea<br />

Observati<strong>on</strong> of spin accumulati<strong>on</strong> in semic<strong>on</strong>ductor is very fascinating for fundamental physics and applicati<strong>on</strong>s<br />

as well. Many important progresses have recently been made in this field. For example, the inserti<strong>on</strong> of a tunnel<br />

barrier at the interface between ferromagnet (FM) and semic<strong>on</strong>ductor has increased the chemical potential<br />

difference at the interface [1]. Ge/MgO/bcc-FM has been intensively studied because of an epitaxial growth of<br />

MgO <strong>on</strong> a Ge substrate due to small lattice mismatch (~4%) between Ge(001)[100] and MgO(001)[110]. As<br />

a result, the symmetry-related spin-dependent tunneling is expected to occur at the Ge/MgO/bcc-FM juncti<strong>on</strong>.<br />

The successful growth of the single-crystal Ge(001)/MgO(001)/bcc-FM(001) stack has been reported [2,3].<br />

However, these results have been obtained using a molecular beam epitaxy technique which may not be<br />

suitable for applicati<strong>on</strong>s in the industry. Here, we show that a highly (001) textured Ge/MgO/CoFeB juncti<strong>on</strong><br />

can be achieved by an ultra-high vacuum sputtering technique. We will discuss the effect of various depositi<strong>on</strong><br />

c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the (001) texture of MgO/CoFeB deposited <strong>on</strong> (001) Ge. The quantitative and qualitative analyses<br />

of the structures of MgO/CoFeB layers will be presented based <strong>on</strong> the results of x-ray diffractometry and<br />

transmissi<strong>on</strong> electr<strong>on</strong> microscopy. Finally, we will examine the tunneling characteristics of the juncti<strong>on</strong>.<br />

[1] Abert Fert and Henry Jaffres, Physical Review B 64, 184420 (2001) [2] Wei Han, et al., Journal of<br />

Crystal Growth 312, 44 (2009) [3] Kun-Rok Je<strong>on</strong>, et al., Crystal Growth and Design 10, 1346 (2010)


RL31<br />

Electrical spin injecti<strong>on</strong> and detecti<strong>on</strong> in GaAs with ferromagnetic<br />

metal/MgO juncti<strong>on</strong>s<br />

Se<strong>on</strong>g Ho<strong>on</strong> Shim 1 , Kyung-ho Kim 1 , Hyung-jun Kim 1 , Yun-hi Lee 2 and Jo<strong>on</strong>ye<strong>on</strong><br />

Chang 1 *<br />

1<br />

Spin C<strong>on</strong>vergence Research Center, Korea Institute of Science and Technology,<br />

Korea<br />

2<br />

Department of Physics, Korea University, Korea<br />

The intrinsic c<strong>on</strong>ductance mismatch between ferromagnetic metals (FM) and<br />

semic<strong>on</strong>ductors is a critical obstacle in spin injecti<strong>on</strong>, and inserting a thin tunnel<br />

barrier, especially MgO, is expected to hurdle this problem. [1] In this study, we report<br />

electrical measurements of spin polarizati<strong>on</strong> in GaAs coming from efficient spin<br />

injecti<strong>on</strong> through MgO tunneling barrier. The whole epitaxial layers of FM/MgO/GaAs<br />

structures were prepared in-situ process using cluster MBE. To reduce the depleti<strong>on</strong><br />

layer of Schottky barrier, doping modulated GaAs layer has been inserted in the<br />

vicinity of the interface between GaAs and MgO layers. Large voltage drop (ΔV = 6.3<br />

mV at 10 K when I = -0.9 mA in Fe/MgO/GaAs structure) between the baseline and<br />

the dip of Hanle curve is observed at various temperatures up to 400 K in a 3-terminal<br />

Hanle measurement geometry. The Lorentzian fitting of the Hanle curve gives 234 ps<br />

spin lifetime of n-doped GaAs and 952 nm spin diffusi<strong>on</strong> length at 300 K.<br />

[1] G. Schmidt, D. Ferrand, L.W. Molenkamp, A.T. Filip and B.J. van WeesPhys. Rev. B 62, R4790<br />

(2000).<br />

RL32<br />

Transistorless 3D STT-MRAM Architecture<br />

Weizh<strong>on</strong>g Wang*<br />

University of Wisc<strong>on</strong>sin - Milwaukee, USA<br />

The MTJ based devices are fabricated through thin film depositi<strong>on</strong> and patterning<br />

which are intrinsically capable for 3D vertical multiple layers integrati<strong>on</strong>. However,<br />

current MRAM architecture requires at least <strong>on</strong>e isolati<strong>on</strong> transistor in each MRAM<br />

cell(1). Since there is no mature 3D CMOS technology available, isolati<strong>on</strong> transistor<br />

prevent the progress <strong>on</strong> developing 3D MRAM. Therefore the races <strong>on</strong> MRAM area<br />

density improvements are all based <strong>on</strong> aggressive horiz<strong>on</strong>tal cell size scaling. This<br />

paper introduces a new transistor-less MRAM architecture to enable vertical 3-D<br />

integrati<strong>on</strong>. Since the MTJ devices are essentially two terminal resistors, an array<br />

of MTJ devices form a c<strong>on</strong>nected resistor network. We introduce a 3D architecture<br />

with new read/write operati<strong>on</strong> to address individual MTJ cells. Comparing with<br />

c<strong>on</strong>venti<strong>on</strong>al STT-MTJs, our preliminary simulati<strong>on</strong> results show (1) little penalties <strong>on</strong><br />

both speed and power c<strong>on</strong>sumpti<strong>on</strong> during read operati<strong>on</strong>;(2) little penalty <strong>on</strong> writing<br />

speed; and (3) 2x to 3x penalty <strong>on</strong> writing power c<strong>on</strong>sumpti<strong>on</strong> depending <strong>on</strong> TMR ratio<br />

of MTJs. The proposed STT-MRAM architecture can greatly enhance the area density<br />

of STT-MRAM and beat CMOS or any single layer based memory technologies.<br />

(1) Tehrani, S.; Slaughter, J.M.; Deherrera, M.; Engel, B.N.; Rizzo, N.D.; Salter, J.; Durlam, M.;<br />

Dave, R.W.; Janesky, J.; Butcher, B.; Smith, K.; Grynkewich, G.; 'Magnetoresistive random access<br />

memory using magnetic tunnel juncti<strong>on</strong>s', Proceedings of the IEEE, Volume: 91 , Issue: 5, 2003 ,<br />

pp.703 - 714<br />

RM01<br />

Collisi<strong>on</strong> of cobalt atom with Alq3 molecule thin film: a molecule<br />

dynamics study<br />

Yun-peng Wang, Ling-ling Tao and Xiu-feng Han*<br />

Institute of Physics, Chinese Academy of Sciences, China<br />

Yun-Peng Wang, Xiu-Feng Han and Ling-Ling Tao Beijing Nati<strong>on</strong>al Laboratory<br />

of C<strong>on</strong>densed Matter Physics, Institute of Physics, Chinese Academy of Sciences,<br />

Beijing 100190, China Hai-Ping Cheng Department of Physics and Quantum Theory<br />

Project, University of Florida, Gainesville, Florida 32611, USA Molecular dynamics<br />

simulati<strong>on</strong>s <strong>on</strong> depositi<strong>on</strong> of cobalt atom <strong>on</strong>to tris(8-hydroxyquinoline) aluminum<br />

(Alq3) molecule thin film are presented. A Lennard-J<strong>on</strong>es potential calibrated by firstprinciple<br />

calculati<strong>on</strong>s was used to describe Alq3-Co interacti<strong>on</strong>s. Microscopic collisi<strong>on</strong><br />

process was analyzed by looking into <strong>on</strong>e trajectory. Statistics of final positi<strong>on</strong>s and<br />

penetrati<strong>on</strong> depths of cobalt atoms show that cobalt atoms with low initial energy<br />

penetrate little into Alq3 thin film and stay near the surface of Alq3 thin film while<br />

cobalt atom with high initial energy penetrates significantly into Alq3 thin film.<br />

C<strong>on</strong>sequently, thickness of Alq3/cobalt interface is equal to roughness of Alq3 surface<br />

if initial energies of cobalt atoms are small, but 1 nanometer larger than roughness of<br />

Alq3 thin film if initial energies of cobalt atoms are large. Injected cobalt atoms lose<br />

their kinetic energies via collisi<strong>on</strong> with 8-hydroxyquinoline ligands of Alq3 molecules.<br />

DFT calculati<strong>on</strong>s show hybridizati<strong>on</strong> of carb<strong>on</strong> and oxygen due to cobalt and sizable<br />

charge transferred from cobalt to nearest Alq3 molecule.<br />

RM02<br />

RM03<br />

RM04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

<strong>Magnetism</strong> and Electr<strong>on</strong>ic Structures of SiC nanoribb<strong>on</strong>s: Role of<br />

defects<br />

Gul Rahman 1 * and J. M. Morbec 2<br />

1 Department of Physics, Quaid-i-Azam University,Islamabad, Pakistan<br />

2 Instituto de Ciencias Exatas, Universidade Federal de Alfenas, 37130-000, Alfenas,<br />

MG, Brazil, Brazil<br />

<strong>Magnetism</strong> in diamagnetic materials such as defective SnO2, ZnO, or SiC got<br />

particular attenti<strong>on</strong> to probe and understand the source and nature of magnetism in<br />

these materials. Particularly, the role of intrinsic defects, e.g. a vacancy which is the<br />

main source of magnetism, motivated many scientists around the world. The defect<br />

formati<strong>on</strong> energies of vacancies in these diamagnetic materials are very large which<br />

limit its experimental synthesis. Here, we focused <strong>on</strong> SiC nanoribb<strong>on</strong>s (NRs) to probe<br />

the native defects and their interacati<strong>on</strong>s with the alien light element impurities, e.g.,<br />

B, N, in terms of magnetism. Using ab-initio calculati<strong>on</strong>s based <strong>on</strong> density-functi<strong>on</strong>al<br />

theory (DFT), our extensive results indicate that silic<strong>on</strong> or carb<strong>on</strong> vacancy per cell<br />

induces magnetic moment in SiCNRs, whereas SiCNR with Si+Si divacancy has<br />

almost zero magnetic moment. The half-metallic behavior, which is very important for<br />

spintr<strong>on</strong>ics devices, of SiC NRs is maintained in the presence of <strong>on</strong>e C or Si vacancy<br />

per cell. The Si or C vacancies have high defect formati<strong>on</strong> energies, howevere, we<br />

found that foreing impurities B or N significantly reduced the defect formati<strong>on</strong> energy<br />

of vacancies in SiCNRs.<br />

Bulk and surface half-metallic ferromagnetism in transiti<strong>on</strong>-metal<br />

chalcogenides with rocksalt phase from first-principles calculati<strong>on</strong>s<br />

Guoying Gao* and Kailun Yao<br />

School of Physics, Huazh<strong>on</strong>g University of Science and Technology, China<br />

In the past decade, most of transiti<strong>on</strong>-metal pnictides and chalcogenides with metastable zincblende<br />

structure were predicted to be half-metallic ferromagnets. So far, however, <strong>on</strong>ly four of<br />

them, zinc-blende CrAs, MnAs, CrSb, and CrTe, have been realized experimentally in the form<br />

of thin films or multilayers because of the instability of the zinc-blende phase. Here we predict<br />

with first-principles calculati<strong>on</strong>s that all three rocksalt CrTe, VPo, and CrPo are half-metallic<br />

ferromagnets with the half-metallic gaps of 0.03, 0.18, and 0.31 eV, respectively. Importantly,<br />

the rocksalt phases are approximately 0.19-0.33 eV per formula unit lower in energy than the<br />

corresp<strong>on</strong>ding zinc-blende phases for these three half-metallic compounds, which indicate it is<br />

more possible to fabricate these binary compounds with rocksalt phase than the zinc-blende phase<br />

in the form of thin films or multilayers. We also study the (111) surface properties of rocksalt CrTe<br />

and CrPo, and find the Te- (Po-)terminated (111) surface is more stable than the Cr-terminated (111)<br />

surface, and both Cr- and Te- (Po-)terminated (111) surfaces preserve the bulk half-metallicity.<br />

The present work will not <strong>on</strong>ly add to the understanding of these binary half-metals, but will also<br />

stimulate experimental efforts toward fabricati<strong>on</strong> and utilizati<strong>on</strong> of these systems in spintr<strong>on</strong>ics.<br />

[1] T. Graf, C. Felsler, and S. P. P. Parkin, Prog. Solid State Chem. 39, 1 (2011). [2] C. Felser, G. H. Fecher, and B. Balke,<br />

Angew. Chem. Int. Edn 46, 668 (2007). [3] M. I. Katsnels<strong>on</strong>, et al., Rev. Mod. Phys. 80, 315 (2008). [4] S. K. Bose and J.<br />

J. Kudrnovsky, Phys. Rev. B 81, 054446 (2010). [5] G. Y. Gao and K. L. Yao, Appl. Phys. Lett. 91, 082512 (2007). [6] J. J.<br />

Deng, et al., J. Appl. Phys. 99, 093902 (2006). [7] G.Y. Gao, K.L. Yao, N. Li, J. Phys.:C<strong>on</strong>dens. Matter 23, 075501 (2011).<br />

Magneto-transport properties of Fe thin films in an external electric<br />

field<br />

Kohji Nakamura 1 *, T. Akiyama 1 , T. Ito1, M. Weinert 2 and A. J. Freemnan 3<br />

1 Physics Engineering, Mie University, Japan<br />

2 Physics, University of Wisc<strong>on</strong>sin-Milwaukee, USA<br />

3 Physics and Astr<strong>on</strong>omy, Northwestern University, USA<br />

UPGRADED<br />

July 8 - 13, 2012 Busan, Korea 181<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RM05<br />

Role of interfacial B impurity in magnetocrystalline anisotropy at<br />

MgO/Fe interface<br />

Koji Hotta*, Kohji Nakamura, Toru Akiyama and Tom<strong>on</strong>ori Ito<br />

Mie University, Japan<br />

An interface induced-perpendicular magnetocrystalline anisotropy (MA), as observed<br />

in the MgO/CoFeB,[1] has attracted much attenti<strong>on</strong> in magnetic applicati<strong>on</strong>. From<br />

first-principles, previously, we dem<strong>on</strong>strated a perpendicular MA at the MgO/Fe<br />

interface due to a weak Fe d_z-O p_z hybridizati<strong>on</strong>[2], but it still need to discuss a<br />

role of interfacial B impurity. Here, we extend investigati<strong>on</strong> to include the interfacial B<br />

impurity. Calculati<strong>on</strong>s were carried out by using FLAPW method[2]. First, the phase<br />

stability at the MgO/Fe interface was determined based <strong>on</strong> calculated total energy with<br />

a model of an MgO m<strong>on</strong>olayer <strong>on</strong> a five-layer Fe, where the B were incorporated in<br />

interstitial positi<strong>on</strong>s at top, sec<strong>on</strong>d, and third Fe-interface-layers. Results indicate that<br />

the B favors to segregate to the interface so as to form an MgO/FeB/Fe interface. Then,<br />

the MA energy (E_(MA)) was calculated by using the sec<strong>on</strong>d variati<strong>on</strong> SOC method<br />

and the force theorem. The calculated E_(MA) has a large positive value of 0.69 eV for<br />

the ideal MgO/Fe, indicating a perpendicular MA. For the MgO/FeB/Fe, the E_(MA)<br />

turns out to be almost zero (-0.02 eV), which indicates no interface MA, due to an<br />

enlargement of the Fe-MgO interlayer distance by the interfacial B atoms.<br />

[1] S. Ikeda, et.al. , Nature Mater. 9, 721 (2010) . [2] K. Nakamura, et.al. , Phys. Rev. B81, 220409<br />

(2010) .<br />

RM06<br />

First-principles study <strong>on</strong> magnetic anisotropy of Co/Pt(111) film in<br />

electric field<br />

Sho Yasuda* and Shugo Suzuki<br />

Divisi<strong>on</strong> of Materials Science, Faculty of Pure and Applied Sciences, University of<br />

Tsukuba, Japan<br />

Electric field (EF) c<strong>on</strong>trol of magnetism is attractive for spintr<strong>on</strong>ics devices. In<br />

recent research, it has been shown that EF affects not <strong>on</strong>ly magnetic moment but also<br />

spin c<strong>on</strong>ducti<strong>on</strong> and magnetic anisotropy[1-4]. In particular, it has been found that<br />

combinati<strong>on</strong> of the 3d and 5d metals in EF causes large effects <strong>on</strong> magnetic anisotropy.<br />

In this study, we investigate the dependence of the magnetic anisotropy energy (MAE)<br />

and the magnetic moment of Co/Pt(111) <strong>on</strong> EF by first-principles calculati<strong>on</strong>s. We<br />

employ the fully relativistic full-potential linear-combinati<strong>on</strong>-of-atomic-orbitals method<br />

based <strong>on</strong> the density-functi<strong>on</strong>al theory within the local-spin-density approximati<strong>on</strong>.<br />

The exchange-correlati<strong>on</strong> energy functi<strong>on</strong>al is the Perdew-Wang parameterizati<strong>on</strong> of<br />

the Ceperley-Alder results. We have found that the magnetic moment of the Co atom<br />

is in proporti<strong>on</strong> to EF. The results of the calculati<strong>on</strong>s of the MAE and the other details<br />

will be shown at the c<strong>on</strong>ference.<br />

[1]T. Maruyama, Y, Shiota, T. Nozaki, K. Ohta, N. Toda, M. Mizuguchi, A. Tulapurkar, T. Shinjo, M.<br />

Shiraishi, S. Mizukami, Y. Ando and Y. Suzuki: Nature. Vol.4 (2008) 158 [2]D. Chiba, S. Fukami,<br />

K. Shimamura, N. Ishiwata, K. Kobayashi, and T. Ono: Nature Mater. Vol.10 (2011) 853. [3]M.<br />

Tsujikawa and T. Oda: Phys. Rev. Lett. Vol.102 (2009) 247203. [4]K. Nakamura, T. Akiyama, and T.<br />

Ito: Phys. Rev. B Vol.81 (2010) 220409.<br />

RM07<br />

Magnetic ground state of TM/Graphene/TM films<br />

D<strong>on</strong>gyoo Kim, Arqum Hashmi and Jisang H<strong>on</strong>g*<br />

Department of Physics, Puky<strong>on</strong>g Nati<strong>on</strong>al University, Korea<br />

Using the full potential linearized augmented plane wave (FLAPW) method, we have<br />

investigated the magnetic properties of transiti<strong>on</strong> metal (TM)/Graphene/transiti<strong>on</strong><br />

metal (TM) structure. We have explored magnetic properties of metal/grapheme/<br />

metla systems, which is Co(1 ML)/Graphene/Ni(1 ML). Co(1ML)/Graphen/Ni(1ML)<br />

film have the AFM ground state. The calculated magnetic moment of Ni is -0.22 μB,<br />

while the Co layer has 1.50 μB. In calculati<strong>on</strong> of optimized structure, we have that<br />

the distance between carb<strong>on</strong> and Co is 2.07 A and it is 2.04 A for carb<strong>on</strong> and Ni. The<br />

relative height difference between two carb<strong>on</strong> atoms in grapheme layer is 0.29 A.<br />

To understand the effect of buckling geometry of graphene, we have performed the<br />

calculati<strong>on</strong> whithout any buckling factor of graphene layer. The magnetic ground state<br />

is not changed, and calculated magnetic moment of Ni and Co are -0.60 and 1.70,<br />

respectively. This implies that the AFM coupling is an intrinsic property of Co(1ML)/<br />

Gr/Ni(1ML) system. Also, we will present the magnetic properties of Co(2ML)/Gr/<br />

Ni(1ML) and Co(1ML)/Gr/Ni(2ML) systems. This work was supported by KCAP<br />

located in Sogang University funded by the Ministry of Educati<strong>on</strong>, Science, and<br />

Technology (MEST) through the Nati<strong>on</strong>al Research Foundati<strong>on</strong> of Korea (NRF-2011-<br />

C1AAA001-2011-0030278) and by KOSEF (No. R01-2008-000-20014-0).<br />

182 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RM08<br />

A model of chain of ellipsoid-rings for magnetic nanotubes<br />

Sen Yang*, Junfeng G<strong>on</strong>g and Xiaoping S<strong>on</strong>g<br />

Department of Materials Physics, Xi'an Jiaot<strong>on</strong>g University, China<br />

Numerical calculati<strong>on</strong> of magnetic properties is a very effective way to understand the<br />

whole magnetic behavior of nanotubes. Currently, the most studies of calculati<strong>on</strong> of<br />

magnetic properties of nanotubes are mainly grounded <strong>on</strong> the St<strong>on</strong>er-Wohlfarth (S-W)<br />

model, starting from an el<strong>on</strong>gated prolate ellipsoid with single-domain. But, it is hard<br />

to imagine how such an ellipsoid is arranged in the hollow tubular structure and hence<br />

the realizati<strong>on</strong> of predicted magnetic properties has been hindered by the experimental<br />

difficulties. In the present article, an alternative model of chain of ellipsoid-rings is<br />

proposed to calculate the magnetic properties of nanotubes, where the chain of rings<br />

with ellipsoid particles is assumed to compose nanotube. Based <strong>on</strong> this new model,<br />

we calculate the magnetic properties of nanotube and further discuss the influence<br />

of tubular geometric parameters <strong>on</strong> the magnetic properties. All the results are well<br />

c<strong>on</strong>sistent with the experimental data of Ni nanotube and moreover are available for<br />

the Ni nanowire. C<strong>on</strong>sequently, our model provides an easy and general approach to<br />

both magnetic nanotubes and magnetic nanowires.<br />

RM09<br />

First-principles GGA+U calulati<strong>on</strong>s of half-metallicity in wurtzite<br />

NiO/ZnO(0001) superlattices<br />

X. H. Zhou<br />

Nati<strong>on</strong>al Laboratory for Infrared Physics,, Shanghai Institute of Technical Physics,<br />

Chinese Academy of Sciences, China<br />

Wurtzite NiO has been predicted to display half-metallicity and have <strong>on</strong>ly small<br />

lattice mismatch with wutzite ZnO [1]. It is interested to explore the possibillity of<br />

the so-called all oxides spintr<strong>on</strong>ics obtained by the hybrid structrues c<strong>on</strong>sisted of the<br />

wurtize NiO and ZnO [2]. In this c<strong>on</strong>tributi<strong>on</strong>, the structural, electr<strong>on</strong>ic, and magnetic<br />

properties of wurtzite NiO/ZnO(0001) superlattice were investigated by means of<br />

density functi<strong>on</strong>al calculati<strong>on</strong>s using spin-polarized generalized gradient approximati<strong>on</strong><br />

GGA and GGA+U schemes. We dem<strong>on</strong>strate that these superlattices retain their halfmetallic<br />

behavior leading to a complete, i.e., 100%, spin polarizati<strong>on</strong> of the c<strong>on</strong>ducti<strong>on</strong><br />

electr<strong>on</strong>s.This property makes the wurtzite NiO/ZnO(0001) heterostructures to be<br />

excellent candidates for high-efficiency magnetoelectr<strong>on</strong>ic devices.<br />

[1] R. Q. Wu, G. W. Peng, L. Liu, and Y. P. Feng, Appl. Phys. Lett. 89, 082504 (2006) [2] Z. Chen, L.<br />

Miao, and X. Miao, AIP ADVANCES 1,022124 (2011)<br />

RN01<br />

Magnetic properties of La doped nanocrystalline Z-type ferrite<br />

nanopowders synthesized via co-precipitati<strong>on</strong> method<br />

Mohamed M. Rashad 1 *, M. Rasly 1 , H. M. Elsayed 2 , A. A. Satter 2 and I. A. Ibrahim 1<br />

1<br />

Advanced Materials Department, Central Metallurgical Research and Development<br />

Institute, Egypt<br />

2<br />

Physics Department, Ain Shams University, Egypt<br />

Co2Z type hexag<strong>on</strong>al ferrites powders doped with La 3+ i<strong>on</strong>s (Ba 3-XLaXCo 2Fe 24O 41<br />

where X=0.0, 0.05, 0.10 and 0.15) were prepared using co-precipitati<strong>on</strong> method. The<br />

results revealed that single phase CO2Z type ferrite was formed from the precipitated<br />

precursor in presence of SDS as ani<strong>on</strong>ic surfactant and then preheated at 600oC<br />

for 4h and then post annealed at 1300oC for 6h. Moreover, the crystallite size and<br />

the porosity,% of the formed powders were increased whereas the unit cell volume<br />

were decreased by increasing the La 3+ substituti<strong>on</strong>. The microstructure of the formed<br />

powders appeared as hexag<strong>on</strong>al platelet like structure. The DC resistivity of the<br />

obtained CO2Z was decreased as La 3+ c<strong>on</strong>tent increased. The saturati<strong>on</strong> magnetizati<strong>on</strong><br />

(Ms= 53.7-55.5 emu/g) was slightly increased with substituti<strong>on</strong> of La 3+ . Moreover,<br />

two res<strong>on</strong>ance frequencies peaks are observed through the imaginary part of complex<br />

permeability meanwhile a decrease in the real part of magnetic permeability through<br />

X-band frequencies. The reas<strong>on</strong>s are discussed using electromagnetic theory.<br />

1- G. Shihai, Z. Yanghuan, F. Zekun, W. Xinlin, H. Huahui, J. Rare Earths 25(2007)220-225 2-X.Wang, L. Li, S. Su, Z.<br />

Gui, Z. Yue, J. Zhou, J. Eur. Ceram. Soc. 23(2003)715-720. 3- J. J. Xu, C. M. Yang, H. F. Zou, Y. H. S<strong>on</strong>g, G. M. Gao, B.C.<br />

An, S. C. Gan, J. Magn. Magn. Mater. 321(2009)3231-3235. 4-L. Qin, H. Verweij, Mater. Lett. 68(2012)143-145.


RN02<br />

Magnetic properties of Fe-doped NiO nanoparticles<br />

Akinobu Kurokawa*, Takuya Yanoh, Shinya Yano, Hiromasa Takeuchi, Kazuki<br />

Onuma, Takaya K<strong>on</strong>do, Kazunari Miike, Toshiki Miyasaka and Yuko Ichiyanagi<br />

Physics, Yokohama Nati<strong>on</strong>al University, Japan<br />

NiO is known as a P-type semic<strong>on</strong>ductor with wide band gap between 3.2 eV and<br />

3.5 eV, and expected as a new material of diluted magnetic semic<strong>on</strong>ductor. Magnetic<br />

properties of NiO nanoparticles with several nanometers were observed and blocking<br />

temperature(TB) was determined to be 17 K, while Neel temperature of NiO bulk<br />

crystal exhibits TN=523 K. In this study, Fe i<strong>on</strong>s were doped into NiO nanoparticles in<br />

order to obtain higher blocking temperature. Ni1-xFexO (x=0, 0.05, 0.1) nanoparticles<br />

with several nanometers encapsulated with amorphous SiO 2 were prepared by our<br />

novel preparati<strong>on</strong> method. NiO single phase structure was c<strong>on</strong>firmed from the x-ray<br />

diffracti<strong>on</strong> measurements. It is c<strong>on</strong>sidered that Ni i<strong>on</strong>s are replaced to Fe i<strong>on</strong>s exactly.<br />

This fact was also supported by X-ray absorpti<strong>on</strong> fine structure measurements.<br />

Magnetizati<strong>on</strong> measurements were performed by SQUID magnetometer for obtained<br />

samples. Temperature dependence of magnetizati<strong>on</strong> showed that TB shifted from 17<br />

K to 57 K as the amount of Fe i<strong>on</strong>s increased, and below TB, ferromagnetic behaviors<br />

were observed. Coercive force (HC) increased from 0.8 kOe to 1.5 kOe as the<br />

amount of Fe i<strong>on</strong>s increased. This phenomen<strong>on</strong> can be explained by characteristics of<br />

extremely small particles in this system.<br />

RN03<br />

Uniaxial strain effects <strong>on</strong> spinel ferrite nanoparticles c<strong>on</strong>taining Nd<br />

and B elements<br />

Masaki Mito 1 , Seiya Saisho 2 , Hiroyuki Deguchi 1 , Takashi Iwamoto 3 and Atsushi<br />

Takahara 4<br />

1<br />

Department of Basic Science, Kyushu Institute of Technology, Japan<br />

2<br />

Department of Applied Science for Integrated System Engineering, Kyushu Institute<br />

of Technology, Japan<br />

3<br />

Institute for Sustainability Research and Educati<strong>on</strong>, Hosei University, Japan<br />

4<br />

Institute for Materials Chemistry and Engineering, Kyushu University, Japan<br />

We studied the uniaxial strain effects <strong>on</strong> spinel ferrite nanoparticles that c<strong>on</strong>tainined Nd<br />

and B elements (Nd : Fe : B = 10.4 : 83.5 : 6.1) and had the particle size of 5.1 nm. In<br />

diffused magnetic nanoparticles, the magnetic easy-axis is distributed randomly, and it<br />

is impossible to add the strain al<strong>on</strong>g a specific structural axis of each particle. However,<br />

in order to c<strong>on</strong>trol the magnetic property of the magnetic nanoparticles, the applicati<strong>on</strong><br />

of the uniaxial strain for the particles with the uniform easy-axis vector is preferable<br />

to that of hydrostatic pressure for randaomly diffused particles. In this study, magnetic<br />

easy-axis of each particle was arranged by solidifying an epoxy resin c<strong>on</strong>taining the<br />

particle at the dc magnetic field of 1 T, resulting in creating an assembly of uniformly<br />

oriented nanoparticles. Afterward, the strain was applied al<strong>on</strong>g both the magnetic<br />

easy-axis and hard-axis. In both situati<strong>on</strong>s, the magnetic blocking temperature had<br />

the maxmimum at the strain of about 3-5 kbar. The difference between two strainexpeirments<br />

appeared at pressure of above 10 kbar.<br />

RN04<br />

The magnetic proximity effect in Fe 3O 4 core/γ-Mn 2O 3 shell<br />

nanoparticles<br />

S. M. Yusuf* and P. K. Manna<br />

SOLID STATE PHYSICS DIVISION, BHABHA ATOMIC RESEARCH CENTRE,<br />

MUMBAI 400085, India<br />

The phenomen<strong>on</strong> of ‘proximity effect’ is very popular in the c<strong>on</strong>text of superc<strong>on</strong>ductor/<br />

n<strong>on</strong>-superc<strong>on</strong>ductor heterostructures. In the present study, we report the magnetic<br />

proximity effect in a core-shell nanoparticle system by employing dc magnetizati<strong>on</strong><br />

and neutr<strong>on</strong> diffracti<strong>on</strong> techniques. In a heterostructure, the substrate, used for its<br />

depositi<strong>on</strong>, often modifies the magnetic properties of the deposited layers. However, a<br />

core-shell nanoparticle system, being substrate-free, rules out any such possibility. We<br />

have observed magnetic proximity effect in a Fe 3O 4 core/γ-Mn2O3 shell nanoparticle<br />

system, in terms of an enhancement of the Curie temperature (Tc) of the γ-Mn 2O 3 shell<br />

(~66K) compared to its bulk value (~40K), and the presence of magnetic ordering in<br />

its so-called paramagnetic regi<strong>on</strong> (i.e. above 66K). The origin of these two features has<br />

been ascribed to the proximity of the γ-Mn 2O 3 shell with a high-Tc Fe 3O 4 core (~858K<br />

in bulk form) and an interface exchange coupling between core and shell. Interestingly,<br />

no exchange bias effect is found due to a weak interface exchange coupling between<br />

core and shell. The present study brings out the importance of the relative strength of<br />

interface coupling in governing the simultaneous occurrence of the magnetic proximity<br />

effect and the exchange bias phenomen<strong>on</strong> in a single system.<br />

RN05<br />

RN06<br />

RN07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Covalent immobilizati<strong>on</strong> of biotin <strong>on</strong> superparamagnetic nanoparticles<br />

L<strong>on</strong>g Giang Bach 1 , Md. Rafiqul Islam 2 and Kw<strong>on</strong> Taek Lim 2 *<br />

1<br />

Department of Imaging System Engineering, Puky<strong>on</strong>g Nati<strong>on</strong>al University, 608-737,<br />

Busan, Korea, Korea<br />

2<br />

Department of Imaging System Engineering, Puky<strong>on</strong>g Nati<strong>on</strong>al University, Busan,<br />

Korea, Korea<br />

Am<strong>on</strong>g the magnetic materials, the nano-scale structured magnetite, Fe3O4 is<br />

widely applicable magnetic nanparticles (MNPs). MNPs offer attractive possibilities<br />

in biomedicine, biosensor, and separati<strong>on</strong> processes because of their unique<br />

properties of superparamagnetism, biocompatibility and low toxicity. The ease of<br />

synthesis and subsequent surface functi<strong>on</strong>alizati<strong>on</strong> of MNPs with a desired material<br />

improve biocompatibility which creates an avenue of delivering multimodal and<br />

multifuncti<strong>on</strong>al MNPs. In this study, a simple protocol of covalent immobilizati<strong>on</strong><br />

of biotin <strong>on</strong> the surface of MNPs for improving biocompatibility and cell viability of<br />

the original MNPs has been dem<strong>on</strong>strated. MNPs were prepared using a soluti<strong>on</strong> of<br />

ferrous and ferric i<strong>on</strong>s. The anchoring of 3-aminopropyltrimethoxysilane with MNPs<br />

resulted due to the formati<strong>on</strong> of Fe-O-Si covalent linkage which is quite str<strong>on</strong>g and<br />

having free amino group. The hydroxyl groups of the biotin were activated by N,N'disuccinimidyl<br />

carb<strong>on</strong>ate followed by c<strong>on</strong>jugati<strong>on</strong> with MNPs-NH2 to afford Biotin-<br />

MNPs. The c<strong>on</strong>jugati<strong>on</strong> of biotin to MNPs was c<strong>on</strong>firmed by FT-IR, XPS and EDX.<br />

The Biotin-MNPs showed superparamagnetic character as investigated by SQUID.<br />

Fabricati<strong>on</strong> of (Mn-Al)/Pd or Ni with Core-Satellite Structured<br />

Magnetic Particles<br />

Youn-kyoung Baek*, Jung-goo Lee and Chul-jin Choi<br />

Powder & Ceramic Divisi<strong>on</strong>, Korea Institute of Materials Science, Korea<br />

WITHDRAWN<br />

The effect of hydrostatic pressure <strong>on</strong> the Morin transiti<strong>on</strong> in hematite<br />

nanoparticles<br />

Luana Car<strong>on</strong>1*, Davide Peddis2, Lorenza Suber3, Dino Fiorani3 and Per Nordblad4<br />

1 Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, TU Delft Mekelweg<br />

15, 2629JB Delft, Netherlands<br />

2 Dipartimento di Scienze Chimiche, Universita degli Studi di Cagliari,, Cittadella Universitaria di<br />

M<strong>on</strong>serrato 09042 Cagliari, Italy<br />

3 Istituto di Struttura della Materia, Area della Ricerca di Roma, CNR Via Salaria km 29500, CP<br />

10-00016 M<strong>on</strong>terot<strong>on</strong>do Stazi<strong>on</strong>e, Rome, Italy<br />

4 Department of Engineering Sciences, Uppsala University Box 534, 751 21 Uppsala, Sweden<br />

Recently, hematite particles have been the subject of intensive studies in areas as diverse as magnetic storage<br />

media, photo electrodes and catalysis[1,2]. Hematite is an antiferromagnetic system that displays a spin<br />

reorientati<strong>on</strong> from uniaxial to canted antiferromagnetism at the Morin temperature[3]. Particle shape, size and<br />

microstructural defects have str<strong>on</strong>g influence <strong>on</strong> the Morin temperature and thus can be used to tune the system’s<br />

magnetic resp<strong>on</strong>se. It is known that the Morin transiti<strong>on</strong> temperature decreases al<strong>on</strong>g with particle size as a result<br />

of the increasing lattice spacing[4], whereas an increase of the Morin temperature under hydrostatic pressure is<br />

observed in the bulk material[5]. In a novel approach, we report <strong>on</strong> the effect of hydrostatic pressures <strong>on</strong> hematite<br />

rhombohedral nanoparticles of narrow size distributi<strong>on</strong> = 93 ± 2 nm[6]. Pressure was found to increase<br />

the Morin temperature at a rate of ~ 5 K/kbar and c<strong>on</strong>siderably decrease thermal hysteresis. These results str<strong>on</strong>gly<br />

c<strong>on</strong>trast with the effects of pressure <strong>on</strong> the bulk material where a milder influence of pressure <strong>on</strong> both the Morin<br />

temperature and thermal hysteresis is observed.<br />

[1] Zhih<strong>on</strong>g Jing, Shihua Wu, Mater. Lett. 58, 3637 (2004) [2] K. Sivula, F. Le Formal and M. Gratzel, ChemSusChem 4, 417 (2011) [3] F. J. Morin, Phys. Rev. 78, 819 (1950) [4] D.<br />

Schroeer and R. C. Nininger, Phys. Rev. Lett. 19, 632 (1967) [5] T. G. Worlt<strong>on</strong> and D. L. Decker, Phys. Rev. 171, 596 (1968) [6] L. Suber et al., Phys. Chem. Chem. Phys. 12, 6984 (2010)<br />

July 8 - 13, 2012 Busan, Korea 183<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RN08<br />

Ultra-thin MgO coating of superparamagnetic magnetite nanoparticles<br />

by combined co-precipitati<strong>on</strong> and sol-gel synthesis<br />

Laura De Matteis 1 , Laura Custardoy 1 , Rodrigo Fernandez-pacheco 2 , Cesar Magen 3 ,<br />

Jesus M De La Fuente 4 , M R Ibarra 5 and Clara Marquina 6 *<br />

1 Instituto de Nanociencia de Arag<strong>on</strong>- INA, Universidad de Zaragoza, Spain<br />

2 Laboratorio de Microscopias Avanzadas (LMA) - Instituto de Nanociencia de Arag<strong>on</strong> (INA,<br />

Universidad de Zaragoza, Spain<br />

3 Laboratorio de Microscopias Avanzadas (LMA) - Instituto de Nanociencia de Arag<strong>on</strong> (INA,<br />

Departamento de Fisica de la Materia C<strong>on</strong>densada Universidad de Zaragoza Fundaci<strong>on</strong> ARAID, Spain<br />

4 Instituto de Nanociencia de Arag<strong>on</strong>- INA, Universidad de Zaragoza Fundaci<strong>on</strong> ARAID, Spain<br />

5 Instituto de Nanociencia de Arag<strong>on</strong> (INA)- Laboratorio de Microscopias Avanzadas (LMA),<br />

Departamento de Fisica de la Materia C<strong>on</strong>densada Universidad de Zaragoza, Spain<br />

6 Instituto de Ciencia de Materiales de Arag<strong>on</strong>-ICMA, Departamento de Fisica de la Materia<br />

C<strong>on</strong>densada CSIC-Universidad de Zaragoza, Spain<br />

Superparamagnetic magnetite nanoparticles coated with an ultra-thin (~1 nm) magnesium oxide (MgO)<br />

layer have been synthesized by combining co-precipitati<strong>on</strong> and sol-gel methods. A thorough chemical and<br />

structural characterizati<strong>on</strong> has been carried out by means of HRTEM, XRD, EDS, DLS and TGA. Aberrati<strong>on</strong><br />

corrected HRTEM experiments with sub-angstrom spatial resoluti<strong>on</strong> have allowed us to distinguish the ultrathin<br />

MgO shell that grows epitaxially <strong>on</strong> the magnetic cores. The capability of the MgO shell to protect the<br />

magnetic nuclei from oxidati<strong>on</strong> up to 600ºC has been dem<strong>on</strong>strated. The magnetic properties of the material<br />

have been studied before and after the coating procedure. The superparamagnetism of the magnetite nuclei<br />

at room temperature is preserved even after calcinati<strong>on</strong>. The possibility of obtaining particles of c<strong>on</strong>trolled<br />

size coated with an isolating layer of nanometric thickness and high thermal stability makes the combinati<strong>on</strong><br />

of the two synthesis methods used in this work a starting procedure to obtain nanometric powders suitable<br />

for technological applicati<strong>on</strong>s, such as high-frequency electr<strong>on</strong>ics. These particles, after the appropriated<br />

functi<strong>on</strong>alizati<strong>on</strong>, are also potential candidates to be used in biomedical applicati<strong>on</strong>s<br />

RN09<br />

Synthesis and characterizati<strong>on</strong> of ultra-small magnetic FeNi/G and<br />

NiCo/G nanoparticles<br />

Mariana Castrill<strong>on</strong> 1 , Alvaro Mayoral 2 , Cesar Magen 3 , Johan G. Meier 1 , Clara<br />

Marquina 4 *, Silvia Irusta 5 and Jesus Santamaria 5<br />

1<br />

Technological Institute of Arag<strong>on</strong> (ITA), Zaragoza, Spain<br />

2<br />

Instituto de Nanociencia de Arag<strong>on</strong> (INA)- Laboratorio de Microscopias Avanzadas (LMA),<br />

Universidad de Zaragoza, Spain<br />

3<br />

Instituto de Nanociencia de Arag<strong>on</strong> (INA)- Laboratorio de Microscopias Avanzadas (LMA),<br />

Departamento de Fisica de la Materia C<strong>on</strong>densada Universidad de Zaragoza, Spain<br />

4<br />

Instituto de Ciencia de Materiales de Arag<strong>on</strong>-ICMA, CSIC-U. Zaragoza, Spain<br />

5<br />

Instituto de Nanociencia de Arag<strong>on</strong>- INA, Networking Research Center <strong>on</strong> Bioengineering,<br />

Biomaterials and Nanomedicine, CIBER-BBN U. Zaragoza, Spain<br />

Ultra-small magnetic nanoparticles c<strong>on</strong>sisting of NiCo and FeNi alloys coated by graphitic shells (NiCo/G<br />

and FeNi/G) have been synthesized by a procedure similar to that described by Seo et al. [1]. The cores, which<br />

retained the face-centered cubic (fcc) symmetry of the original bulk metals, together with the graphitic coating<br />

have been characterized by means of aberrati<strong>on</strong> corrected scanning transmissi<strong>on</strong> electr<strong>on</strong> microscopy (STEM).<br />

The particles have mean sizes of 2.6 nm and 6.2 nm for NiCo/G and FeNi/G, respectively. The samples c<strong>on</strong>tain<br />

a large fracti<strong>on</strong> of superparamagnetic nanoparticles at room temperature. The thermal stability of the particles<br />

is enhanced by the graphite shell, and the graphite coated FeNi and NiCo are stable under oxygen atmosphere<br />

up to 170 C. N<strong>on</strong>-coated bimetallic FeNi and NiCo have also been prepared. Their chemical characterizati<strong>on</strong><br />

revealed the massive oxidati<strong>on</strong> of the bimetallic nanoparticles in absence of the graphite coating (oxygen c<strong>on</strong>tent<br />

higher that 60 at. %). This fact c<strong>on</strong>firms the effectiveness of the graphite shell in preventing the magnetic cores<br />

from oxidati<strong>on</strong> and therefore preserving their magnetic properties even at high temepratures.<br />

1.- Seo W. S. et al., Nature Mater. 5 (2006) 971-6<br />

RN10<br />

Magnetizati<strong>on</strong> measurements and blocking temperature distributi<strong>on</strong><br />

in magnetic nanoparticle systems<br />

Taeho<strong>on</strong> Lee 1 , Seunghyun Kim 1 , Sungw<strong>on</strong> Yo<strong>on</strong> 2 , Byoung Jin Suh 2 *, Zeeho<strong>on</strong> Jang 1<br />

and Kyunghyun Kim 3<br />

1 Department of Physics, Kookmin University, Korea<br />

2 Department of Physics, The Catholic University of Korea, Korea<br />

3 Biotechnology & Bioinformatics, Korea University, Korea<br />

We present magnetizati<strong>on</strong> measurements <strong>on</strong> a variety of magnetic nanoparticle<br />

ensembles. The samples are; (1) Artificailly synthesized Helicobacter Pylori ferritin<br />

rec<strong>on</strong>stituted with three different Fe i<strong>on</strong>s/ferritin ratio, 160, 2000, and 4000. (2)<br />

Commercial horse spleen ferritin (3) CoPt nanoparticles with average particle size of<br />

2 nm. Temperature dependence of magnetizati<strong>on</strong> has been measured using a SQUID<br />

magnetometer. Measurement sequence has been modified from a typical field-cool<br />

sequence and the measurements have been performed with field “stop-resume” steps<br />

at the regular temperature interval. Using a phenomenological model, we could extract<br />

the moment weighted blocking temperature distributi<strong>on</strong>s in the samples from the<br />

experimental data. The model is based <strong>on</strong> the assumpti<strong>on</strong>s that; 1) the particles in the<br />

ensembles can be uniquely categorized in terms of the blocking temperature. 2) the<br />

particles with the same blocking temperature will have the same field and temperature<br />

dependence of the magnetizati<strong>on</strong>. 3) the particles are n<strong>on</strong>-interacting with each other.<br />

With the obtained distributi<strong>on</strong>s, the numerical simulati<strong>on</strong>s are performed to reproduce<br />

the field-cool magnetizati<strong>on</strong> data and zero-field-cool magnetizati<strong>on</strong> data.<br />

184 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RN11<br />

Structural and magnetic anomalies in CoAl2O4 nanocrystals<br />

Koichi Sato 1 , Takashi Naka 1 , Takayuki Nakane 1 , Minori Taguchi 1 , Dinesh Rangappa 2 ,<br />

Satoshi Ohara 3 and Tadafumi Adschiri 4<br />

1 Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

2 <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Advanced Research Centre for Powder Metallurgy & New Materials, India<br />

3 Joining and Welding Research Institute, Osaka University, Japan<br />

4 WPI, Advanced Institute for Materials Research, Tohoku University, Japan<br />

In this study, we investigated magnetic properties of spinel CoAl 2O 4 nanocrystals (NCs) synthesized by a<br />

supercritical hydrothermal synthesis. We c<strong>on</strong>firmed that all the samples are composed of the single phase<br />

CoAl 2O 4 by the X-ray diffracti<strong>on</strong> measurements. Crystalline sizes are c<strong>on</strong>trolled to be 4 ? 8 nm. We also<br />

found that the inversi<strong>on</strong> parameters of the samples, describing the cati<strong>on</strong> distributi<strong>on</strong> are more than 0.3 [1,2],<br />

being much higher than bulk specimens previously reported. We c<strong>on</strong>ducted magnetizati<strong>on</strong> and, dc- and acsusceptibility<br />

measurements. All the samples show paramagnetic behavior above 70 K. The effective Bohr<br />

magnet<strong>on</strong>s and the Weiss temperatures are 2.6 - 2.8 μB and -40 - -50 K. The effective Bohr magnet<strong>on</strong>s are<br />

smaller than 4.4 - 4.6 μB reported <strong>on</strong> specimens with the low inversi<strong>on</strong> parameters [3,4]. The susceptibilities<br />

deviate from Curie-Weiss law below 40 - 50 K. From the results of the magnetizati<strong>on</strong> measurements, it was<br />

found that sp<strong>on</strong>taneous magnetizati<strong>on</strong>, 0.1 μB/Co, emerges below 40 K in the samples with the size of 4<br />

nm. The reduced Bohr magnet<strong>on</strong>s and the emergence of the sp<strong>on</strong>taneous magnetizati<strong>on</strong> indicate that in our<br />

NC samples, a certain magnetic phase, being different from those of bulk specimens, appears below 40 K.<br />

[1] N. Tristan, J. Hemberger, A. Krimmel, H-A. Krug v<strong>on</strong> Nidda, V. Tsurkan, and A. Loid, Phys. Rev. B 72, 174404 (2005) [2] T.<br />

Suzuki, H. Nagai, M. Nohara, and H. Takagi, J. Phys. C<strong>on</strong>densed matter 19, 145265 (2007). [3] H. St. C. O'neill, Eur. J. Mineral. 6,<br />

603 (1994). [4] A. Nakatsuka, Y. Ikeda, Y. Yamasaki, N. Nakayama, and T. Mizota, Solid State Commun. 128, 85 (2003).<br />

RN12<br />

Preparati<strong>on</strong> of chains of single-domain Ni nanoparticles with collinear<br />

directi<strong>on</strong> of magnetizati<strong>on</strong><br />

S A Nepijko 1 *, D Kutnyakhov 1 , I E Protsenko 2 , H J Elmers 1 , R Wiesendanger 3 and G<br />

Schoenhense 1<br />

1 Institute of Physics, University of Mainz, Germany<br />

2 Department of Applied Physics, Sumy State University, Ukraine<br />

3 Institute of Applied Physics, University of Hamburg, Germany<br />

Networks of ferromagnetic nanoparticles have been proposed to form quantum cellular automata [1]. We<br />

present a fabricati<strong>on</strong> method based <strong>on</strong> self-organized growth <strong>on</strong> stepped surfaces for fairly regular nanoparticles<br />

arranged in a <strong>on</strong>e-dimensi<strong>on</strong>al chain, that are suitable for this applicati<strong>on</strong>. We studied Ni nanoparticles with<br />

sizes in the range 80-130 nm <strong>on</strong> a highly-ordered pyrolytic graphite (HOPG) substrate and succeeded to<br />

prepare <strong>on</strong>e-dimensi<strong>on</strong>al chains of these single-domain particles characterized by the same directi<strong>on</strong> of their<br />

magnetizati<strong>on</strong>. The nanoparticles were found to decorate atomic cleavage steps <strong>on</strong> the basal surface and their<br />

distances are small enough to give rise to str<strong>on</strong>g dipolar coupling. The necessary and sufficient c<strong>on</strong>diti<strong>on</strong>s are:<br />

(i) 3D growth mechanism al<strong>on</strong>g with n<strong>on</strong>-wetting behaviour, (ii) the dielectric substrate has atomic cleavage<br />

steps, (iii) the size of the ferromagnetic particles is smaller than the characteristic domain size but still above<br />

the transiti<strong>on</strong> into the superparamagnetic state and, finally, (iv) the distances between the particles are small<br />

enough for dipolar coupling. The study was carried out using atomic-force (AFM) and magnetic-force (MFM)<br />

microscopy. The approach of ordering ferromagnetic nanoparticles into <strong>on</strong>e-dimensi<strong>on</strong>al chains is of particular<br />

interest because chains are a basic block for storage and transport of informati<strong>on</strong>.<br />

[1] R.P. Cowburn, M.E. Welland, Science 287 (2000) 1466<br />

RN13<br />

Influence of the morphology <strong>on</strong> the magnetic properties of<br />

dodecanethiol-capped Au anoparticles<br />

Daniel Ortega 1 , Eider Goikolea 2 , Jose Javier Garita<strong>on</strong>andia 2 , Maite Insausti 2 , Hyodo<br />

Zhang 3 , Kiy<strong>on</strong>ori Suzuki 3 and Fernando Plazaola 2<br />

1 Department od Physics and Astr<strong>on</strong>omy, University College L<strong>on</strong>d<strong>on</strong> Gower Street<br />

WCIE 6BT L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

2 Zientzia eta Teknologia Fakultatea Euskal Herriko Unibertsitatea, Spain<br />

3 Department of Materials Engineering, M<strong>on</strong>ash University, Australia<br />

It has been proved that Au nanoparticles (NP) coated with certain molecules can present different magnetic<br />

characters, ranging from superparamagnetism to permanent magnetism at room temperature (RT) [1-3]. We have<br />

prepared ferromagnetic dodecanethiol-capped Au NPs with a high magnetic signal of 1.7 emu/gr and coercive<br />

field of 85 Oe at RT. An analysis by high resoluti<strong>on</strong> electr<strong>on</strong> microscopy reveals that the NPs are composed by ~<br />

200 atoms forming multi-twinned structured nanocrystals of ~ 2 nm with icosahedral or decahedral morphologies<br />

where well ordered fcc twinned entities are joined forming an <strong>on</strong>ly nanocrystal with a spatial 5-fold symmetry.<br />

The external morphology is c<strong>on</strong>diti<strong>on</strong>ed by the final stabilizati<strong>on</strong> of the NP and, with a surface to bulk atoms ratio<br />

up to ~ 75% and a magnetism located exclusively in the surface atoms, the morphology plays a crucial role in the<br />

definiti<strong>on</strong> of the magnetic character of the NP. In a comparative view with the multidomain structures presented<br />

in bulk materials, we argue that borders am<strong>on</strong>g the twinned nanosized entities would act as pinning centers,<br />

hindering the alignment of the magnetic moments between entities and promoting the coercive field.<br />

[1] Y. Yamamoto, T. Miura, M. Suzuki, N. Kawamura, H. Miyagawa, T. Nakamura, K. Kobayashi, T. Teranishi,<br />

and H. Hori, Phys. Rev. Lett. 93 116801 (2004). [2] P. Crespo, R. Litran, T. C. Rojas, M. Multigner, J. M. de la<br />

Fuente, J. C. Sanchez-Lopez, M. A. Garcia, A. Hernando, S. Penedes, and A. Fernandez, Phys. Rev. Lett. 93<br />

087204 (2004). [3] J. S. Garita<strong>on</strong>andia, M. Insausti, E. Goikolea, M. Suzuki, J. D. Cashi<strong>on</strong>, N. Kawamura, H.<br />

Ohsawa, I. Gil de Muro, K. Suzuki, F. Plazaola, and T. Rojo, Nanoletters 8 661 (2008).


RN14<br />

Structure effects <strong>on</strong> the magnetic behavior in Fe oxide based<br />

nanoparticles<br />

Amilcar Labarta*, Carlos Moya, Nicolas Perez, Arantxa Fraile, Oscar Iglesias and<br />

Xavier Batlle<br />

Fundamental Physics, University of Barcel<strong>on</strong>a, Spain<br />

A key questi<strong>on</strong> in magnetic nanoparticles (NP) is how the nanostructure modifies their magnetic and electr<strong>on</strong>ic<br />

properties. As the particle size is reduced, deviati<strong>on</strong>s from bulk behaviour have been widely reported and<br />

attributed to both the appearance of a magnetically disordered surface layer and finite-size effects, thus giving<br />

rise to a decrease in the particle magnetizati<strong>on</strong>, an exchange field acting <strong>on</strong> the core and an increase in the<br />

anisotropy. In order to elucidate those phenomena we have carried out STEM, XAS, XMCD and magnetizati<strong>on</strong><br />

measurements in Fe oxide based NP models, aiming at the real-space characterizati<strong>on</strong> at the sub-nanometer<br />

scale of a single NP to characterize the particle structure, surface magnetizati<strong>on</strong>, and the dependence of the<br />

latter <strong>on</strong> the strength of the surface b<strong>on</strong>d to a bio-molecule coating. We also aim at the quantificati<strong>on</strong> of the<br />

orbital and spin c<strong>on</strong>tributi<strong>on</strong>s to the NP magnetic moment. The key role of the crystal quality is thus suggested,<br />

because particlelike behaviour above about 5 nm in size is observed <strong>on</strong>ly when NP are structurally defective.<br />

These c<strong>on</strong>clusi<strong>on</strong>s are supported by M<strong>on</strong>te Carlo simulati<strong>on</strong>s. It is also shown that thermal decompositi<strong>on</strong> is a<br />

chemical route capable of producing high-crystal quality NP with bulklike properties.<br />

1. N. Perez, F. Bartolome, L.M. Garcia, J. Bartolome, M.P. Morales, C.J. Serna, A. Labarta and X. Batlle, Applied Physiscs Letters<br />

94, 093108 (2009). 2. P. Guardia, N. Perez, A. Labarta and X. Batlle, Langmuir , 26, 5843-5847 (2010). 3. X. Batlle, N. Perez,<br />

O. Iglesias, A. Labarta, F. Bartolome, L.M. Garcia, J. Bartolome, A.G. Roca, M.P. Morales, and C.J. Serna, Journal of Applied<br />

Physics 109, 07B524 (2011). 4. Work in collaborati<strong>on</strong> with: F. Bartolome, L.M. Garcia, J. Bartolome (ICMA-CSIC, Spain); M.P.<br />

Morales and C.J. Serna (ICMM-CSIC, Spain); M. Varela, J. Salafranca and J. Gazquez (OAK-Ridge Nati<strong>on</strong>al Laboratory, USA).<br />

RN15<br />

Magnetic properties of surface-functi<strong>on</strong>alized nano-particles<br />

Ann Kathrin Michel 1 , Mathias Kraken 1 , Jochen Litterst 1 *, Yannick Guari 2 , Joulia<br />

Lari<strong>on</strong>ova 2 , Lenaic Lartigue 2 , Jerome L<strong>on</strong>g 2 and Alessandro Lascialfari 3<br />

1 IPKM, TU Braunschweig, Germany<br />

2 Institut Charles Gerhardt, Universite M<strong>on</strong>tpellier II, France<br />

3 CNRNANO, Univ. Milano, Italy<br />

RN16<br />

WITHDRAWN<br />

Study of aqueous dispersi<strong>on</strong>s of magnetic nanoparticles by magnetic<br />

and rheological measurements<br />

Shalini M 1 , Mahesh Samant 2 , Radha S 3 * and D. C. Kothari 3<br />

1 Department of Physics and UM-DAE CBS, University of Mumbai, India<br />

2 Nati<strong>on</strong>al Center for Nanosciences and Nanotechnology, University of Mumbai, India<br />

3 Department of Physics, University of Mumbai, India<br />

The observed magnetic tunability of light transmissi<strong>on</strong> through a ferrofluid [1] can be effectively understood<br />

in terms of the inter-particle interacti<strong>on</strong> that can be estimated from the magnetic and rheological properties of<br />

these fluids. The present study reports complementary magnetic and rheological measurements of synthesized<br />

aqueous dispersi<strong>on</strong>s of ferrite nanoparticles, using a commercial ferrofluid as a standard. The aqueous<br />

dispersi<strong>on</strong>s of the ferrite nanoparticles were synthesized by co-precipitati<strong>on</strong> using suitable precursors and<br />

surfactants. The dispersi<strong>on</strong>s were stable for reas<strong>on</strong>ably l<strong>on</strong>g durati<strong>on</strong>s and the particle size was estimated<br />

to be 10-28 nm from XRD measurements. The room temperature magnetizati<strong>on</strong> measured in a SQUID<br />

magnetometer up to fields of 1 Tesla showed superparamagnetic behaviour of the powder and the dispersi<strong>on</strong><br />

with the background signal of the liquid varying from a diamagnetic to a paramagnetic behaviour. The room<br />

temperature rheological behaviour in zero magnetic field of both the standard and synthesized dispersi<strong>on</strong><br />

was investigated by measuring the viscosity as a functi<strong>on</strong> of shear rate from 1-1000s-1. The viscosity of<br />

the dispersi<strong>on</strong> increased with increasing shear rate reaching a c<strong>on</strong>stant value at higher shear rates; while the<br />

standard sample showed almost no change in viscosity with shear rate c<strong>on</strong>forming to a Newt<strong>on</strong>ian behaviour.<br />

[1] M. Shalini, D. Sharma, A. A. Deshpande, D. Mathur, Hema Ramachandran and N. Kumar, Eur. Phys. Jour. D 66 (2012) 30.<br />

RN17<br />

RN18<br />

RN19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetodielectric effect of Fe 2O 3 nanoparticles embedded in SiO 2<br />

glass matrix<br />

Hung-cheng Wu, Sudip Mukherjee and Hung-duen Yang*<br />

Department of Physics, Nati<strong>on</strong>al Sun Yat-sen University, Taiwan<br />

Magnetic ir<strong>on</strong>-oxide (doping 0.5 mole %) nanoparticles (NPs) have been synthesized<br />

in silica glass matrix, prepared by the sol-gel method with different annealing<br />

temperatures. XRD, TEM and XANES show the presence of NPs of Fe 2O 3 and Fe 3O 4<br />

crystalline phase (< 5 nm). An interesting colossal enhancement of dielectric c<strong>on</strong>stant<br />

with diffuse phase transiti<strong>on</strong> is observed around room temperature due to the thermally<br />

activated oxygen vacancies. The magnetodielectric effect observed in the glass<br />

composites is c<strong>on</strong>sidered to be associated with magnetoresistance changes, depending<br />

<strong>on</strong> NPs size.<br />

Tuning the c<strong>on</strong>centrati<strong>on</strong> of magnetic Co nanoparticles in In 2O 3 with<br />

oxygen pressure and c<strong>on</strong>centrati<strong>on</strong> of tin<br />

Marzook S. Alshammari 1 *, Mohammed S. Alqahtani 1 , Qi Feng 1 , S. Alfahad 2 , M. Alotibi 2 , A.<br />

Alyamani 2 , A. M. H. R. Hakimi 3 , S. M. Heald 4 , H. J. Blythe 1 , A. M. Fox 1 and G. A. Gehring 1<br />

1 Department of physics and astr<strong>on</strong>omy, University of Sheffield, United Kingdom<br />

2 Nanotechnology center, King Abdulaziz City for Science and Technology, Saudi Arabia<br />

3 Department of Materials Science and Metallurgy, University of Cambridge, United Kingdom<br />

4 Advanced Phot<strong>on</strong> Source, Arg<strong>on</strong>ne Nati<strong>on</strong>al Laboratory, USA<br />

This study shows the power of combining magnetic measurements with magnetic circular dichroism (MCD)<br />

to detect the c<strong>on</strong>tributi<strong>on</strong> to the magnetism from metallic Co nanoparticles, and the result that the formati<strong>on</strong><br />

of nanoparticles is suppressed by the inclusi<strong>on</strong> of tin. Thin films of (In 1-0.95Co 0.05) 2O 3 were deposited using<br />

pulsed laser depositi<strong>on</strong> (PLD) <strong>on</strong> sapphire substrates. The magnetism and the amount of cobalt in nanoparticles<br />

increased with the oxygen deficiency in the PLD chamber and also after annealing in vacuum as expected and<br />

as c<strong>on</strong>firmed using Extended X-ray Absorpti<strong>on</strong> Fine Structure. The MCD spectra show two features that are<br />

well fitted by a combinati<strong>on</strong> of the spectrum from the nanoparticles in the In 2O 3 matrix, as calculated using<br />

Maxwell-Garnett theory, and a c<strong>on</strong>tributi<strong>on</strong> from polarized carriers [1]. The changes in the magnetizati<strong>on</strong> and<br />

the MCD are used to get a quantitative estimate of the c<strong>on</strong>tributi<strong>on</strong> of the nanoparticles magnetizati<strong>on</strong> to the<br />

total magnetizati<strong>on</strong> in each sample. Adding 5% of Sn made little difference to the saturati<strong>on</strong> magnetizati<strong>on</strong><br />

but the signal due to Co nanoparticles was completely suppressed and that from polarized carriers enhanced<br />

str<strong>on</strong>gly. This indicates that, the magnetizati<strong>on</strong> of the carriers in Sn and Co co doped In 2O 3 is particularly high.<br />

Hakimi, et al, Physical Review B 84, 085201 (2011).<br />

Synthesis, structural, and magnetic properties of str<strong>on</strong>trium<br />

hexaferrite nanoparticles with La, Sm doping and core/shell structure<br />

by the sol-gel hydrothermal process<br />

Hue Thi Minh Dang 1 , Dien Xuan Lu<strong>on</strong>g 1 , Hoang Duc Tran 1 , Hu<strong>on</strong>g Manh Phan 2 and Chinh Dang Huynh 1 *<br />

1 Department of Inorganic Chemistry, Hanoi University of Science and Technology, Viet Nam<br />

2 Department of Physics, University of South Florida, USA<br />

SrFe 12O 19 nanoparticles have been prepared by the sol-gel hydrothermal method.<br />

These SrFe 12O 19 nanoparticles have been doped with La, Sm and coated with NiFe 2O 4,<br />

CoFe 2O 4 nanoparticles by the sol-gel and the self-assembly method, respectively.<br />

Properties of the nanoparticle samples were charaterized by powder X-ray diffracti<strong>on</strong><br />

with the Rietveld refinement, transmissi<strong>on</strong> electr<strong>on</strong> microscope, scanning electr<strong>on</strong><br />

microscopy with energy dispersive spectrometer, and vibrating sample magnetometry.<br />

SEM micrograhs of the samples showed the spherical shape of NiFe 2O 4, CoFe 2O 4<br />

nanoparticles located above <strong>on</strong> the surface of SrFe 12O 19 hexag<strong>on</strong>al platelet shape.<br />

TEM micrographs showed the particle size of core and shell. With the core/shell<br />

nanoparticles, the saturati<strong>on</strong> magnetizati<strong>on</strong> was decreased but coercivity was increased<br />

with SrFe 12O 19/CoFe 2O 4 sample.<br />

[1.] Alex Goldman, Modern Ferrite Technology, Springer; 2nd editi<strong>on</strong> (2005). [2.] Smit J., Wijn H.P.J, Ferrits-Physical<br />

properties of ferritmagnetic oxides in relati<strong>on</strong> to their technical applicati<strong>on</strong>, Philip Technical Library, Eindhoven, (1959). [3.] L.A.<br />

Garcia-Cerda, O.S. Rodriguez-Fernandez, P.J. Resendiz-Hernandez, Journal of Alloys and Compounds 369 (2004) 182-184. [4.]<br />

Malick Jean, Virginie Nachbaur, Julien Bran, Jean-Marie Le Bret<strong>on</strong>, Journal of Alloys and Compounds 496 (2010) 306-312.<br />

[5.] Xiaofeng Yang, Qiaoling Li, Jingxian Zhao, Baod<strong>on</strong>g Li, Y<strong>on</strong>gfei Wang, Journal of Alloys and Compounds 475 (2009) 312-<br />

315. [6.] T. T.V. Nga , N.P. Du<strong>on</strong>g, T.D. Hien, Journal of Alloys and Compounds 475 (2009) 55-59.<br />

July 8 - 13, 2012 Busan, Korea 185<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RN20<br />

A facial fabricati<strong>on</strong> of the superparamagnetic Fe 3O 4@TiO 2<br />

microspheres and its photocatalytic applicati<strong>on</strong><br />

Ky<strong>on</strong>g-ho<strong>on</strong> Choi 1 , Eun-mee Kim 2 , Seung-lim Oh 3 , Do-ye<strong>on</strong> Kim 4 and Jin-seung Jung 4 *<br />

1 Material R&D Divisi<strong>on</strong>, H & Global Co. Ltd., Korea<br />

2 Gangneung Center, korea Basic Science Institute, Korea<br />

3 Material R&D Divisi<strong>on</strong>, H & Global Co. Ltd., Korea<br />

4 Department of Chemistry, Gangneung-W<strong>on</strong>ju Nati<strong>on</strong>al University, Korea<br />

Over the past few decades, semic<strong>on</strong>ductor photocatalysts have attracted much attenti<strong>on</strong> because of their<br />

applicati<strong>on</strong>s in new energy fields where they represent a promising strategy for splitting water to provide<br />

clean hydrogen energy, and their use in the photocatalytic degradati<strong>on</strong> of polluted atmosphere and wastewater<br />

in envir<strong>on</strong>mental remediati<strong>on</strong>[1,2]. Am<strong>on</strong>g the reported photocatalysts, titanium dioxide (TiO 2 ) is <strong>on</strong>e of<br />

the most studied semic<strong>on</strong>ductors for photocatalytic reacti<strong>on</strong>s because of its high activity, chemical stability,<br />

robustness against photocorrosi<strong>on</strong>, low toxicity and availability at low cost, especially for the detoxificati<strong>on</strong> of<br />

water and air [3,4]. In this study, we have successfully synthesized of multifuncti<strong>on</strong>al core/shell (Fe 3O 4/TiO 2)<br />

submicr<strong>on</strong> particles with c<strong>on</strong>trolled shell thickness. In the first step, superparamagnetic Fe 3O 4 submicr<strong>on</strong><br />

particles were fabricated by <strong>on</strong>e-step hydrothermal method. In the sec<strong>on</strong>d step, the surface of Fe 3O 4 submicr<strong>on</strong><br />

particles was coated with TiO 2 by atomic layer depositi<strong>on</strong> (ALD) method. Through this method, the thickness<br />

of shell was accurately tunable. The recyclable Fe 3O 4@TiO 2 particles exhibit excellent catalytic properties for<br />

the oxidati<strong>on</strong> reacti<strong>on</strong> of 2,4,6-trichlorophenol (2,4,6-TCP) in aqueous soluti<strong>on</strong>.<br />

[1]. A. Fujishima, K. H<strong>on</strong>da, Nature, 238, 37 (1972) [2]. X. C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, G. M.<br />

Garlss<strong>on</strong>, K. Domen, M. Ant<strong>on</strong>ietti, Nat. Mater., 8, 76 (2009) [3]. T. L. Thomps<strong>on</strong>, J. T. Yates Jr., Chem. Rev. 106, 4428 (2006)<br />

[4].A. C. Rodrigues, M. Boroski, N. S. Shimada, J. C. Garcia, J. Nozaki, N. Hioka, J. Photochem. Photobiol. A 194, 1 (2008)<br />

RN21<br />

Synthesis of high moment magnetite (Fe 3O 4) nanoparticles by simple<br />

modified polyol method<br />

Mohamed Abbas Ali Ahmed and Cheolgi Kim*<br />

Material Science and Engineering, Chungnam Nati<strong>on</strong>al University, Korea<br />

(Synthesis of high moment magnetite (Fe 3O 4) nanoparticles by simple modified<br />

polyol method) Mohamed Abbas and CheolGi Kim Center for NanoBioEngineering<br />

and Spintr<strong>on</strong>ics, Department of Materials Science and Engineering, Chungnam<br />

Nati<strong>on</strong>al University, Daeje<strong>on</strong> 305-764, Korea Abstract Single phase magnetite with<br />

high saturati<strong>on</strong> magnetizati<strong>on</strong> and 50 nm as a medium range particles size has been<br />

synthesized by in expensive and surfactant-free simple modified polyol method using<br />

FeCl 2.4H 2O as a precursor of ir<strong>on</strong> and Poly Ethylene Glycol (PEG) as a solvent and<br />

reducing agent simultaneously. X-ray diffracti<strong>on</strong> (XRD) and EDS analysis indicated<br />

that, formati<strong>on</strong> of purely magnetite (Fe 3O 4) without presence of any other phase.<br />

Transmissi<strong>on</strong> electr<strong>on</strong> microscopy (TEM) also show that the synthesized nanoparticles<br />

are almost sphere in shape. The magnetic properties of the synthesized magnetite<br />

nanoparticles were measured by means Physical Property Measurement System<br />

(PPMS-VSM) at different temperature and shows that the as-synthesized NPs were<br />

ferromagnetic with high moment 91.7 emu/g at 5 K. Corresp<strong>on</strong>ding author. Tel:-<br />

+82428216236 E-mail address: cgkim@cnu.ac.kr (Prof/ CheolGi Kim)<br />

RN22<br />

Study of Structural, morphological and optical properties of SrFe 12-x<br />

Co x O 19 (x= 0, 0.1, 0.2) hexaferrite nanoparticles<br />

Morteza Zargar Shoushtari*, Ebrahim Mousavi Ghahfarokhi and Fereshte Ranjbar<br />

Physics, Shahid Chamran University of Ahvaz, Iran<br />

A series of M-type str<strong>on</strong>tium hexaferrite samples having nominal compositi<strong>on</strong> SrFe 12-x<br />

Co x O 19 (x = 0.0, 0.1 and 0.2) with different morphologies have been synthesized via<br />

sol gel method. For synthesis of samples, first a precursor gel was prepared using the<br />

sol-gel method. The mixture of KCl and dry-gel was calcined at 1000 ˚C for 2 h to<br />

obtain the needle-like nano- SrFe 12-x Co x O 19. The rod-like and bubble nano- SrFe 12-x<br />

Co x O 19 was prepared by calcining the mixture of KBr and dry-gel or KI and dry-gel,<br />

respectively, and spherical nano- SrFe 12-x Co x O 19 was prepared <strong>on</strong>ly by calcined drygel.<br />

The structure and morphology of samples were systematically characterized by X-<br />

ray diffracti<strong>on</strong> (XRD), scanning electr<strong>on</strong> microscopy (SEM). The optical properties<br />

of samples were investigated by UV-Vis. The result of XRD of samples showed that<br />

the M-type hexag<strong>on</strong>al structure can be maintained for all the samples without the<br />

segregati<strong>on</strong> of sec<strong>on</strong>dary phases. The FT- IR frequency bands in the range 560 - 580<br />

cm -1 and 430 - 470 cm -1 in the all of samples corresp<strong>on</strong>ds to the formati<strong>on</strong> of tetrahedral<br />

and octahedral clusters of metal oxides in ferrites, respectively.<br />

186 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RN23<br />

Light induced ferromagnetism of nanocrystalline CuCr 2Se 4 particles<br />

D<strong>on</strong>gsoo Kim*, Kookchae Chung and Choljin Choi<br />

Korea Institute of Materials Science, Korea<br />

A novel method to synthesize ternary chalcogenide nanoparticles was developed with<br />

microwave-assisted polyol reacti<strong>on</strong> in this study. Copper chloride, chromium acetate and<br />

metallic selenium were used as precursors with stoichiometric ratios in poly ethylene glycol. The<br />

system was purged with arg<strong>on</strong> and then the mixed reactants were irradiated for 60 minutes with<br />

60% of the instrument power. Products were collected, centrifuged, washed with ethyl alcohol<br />

in order to remove poly ethylene glycol and dried overnight under inert atmosphere. Magnetic<br />

moment of CuCr 2Se 4 nanoparticles was measured from 300 K to 750 K with external magnetic<br />

field of 500 Oe in arg<strong>on</strong> atmosphere and Curie temperature was calculated as 445 K. From<br />

the hysteresis loop, magnetic property was ferromagnetic and its saturati<strong>on</strong> magnetizati<strong>on</strong> and<br />

coercive force were measured to 15 emu/g and 80 Gauss respectively. Nanocrystalline CuCr 2Se 4<br />

particles were dispersed in the matrix of light transparent resin so as to investigate light induced<br />

effect <strong>on</strong> the magnetic properties. Er-laser with the wavelength of 1.5 µm was employed as light<br />

source. Light illuminati<strong>on</strong> in an external magnetic field increased the magnetizati<strong>on</strong> and this<br />

increment of magnetizati<strong>on</strong> (δJ) to initial magnetizati<strong>on</strong> (J) showed a maximum.<br />

1. Mingos D.M.P. The applicati<strong>on</strong> of microwaves in chemistry // Res. Chem. Intermed., 1994, V. 20, P. 85-91. 2.<br />

Baran M., Szymczak R., Szymczak H., Tsurkan V. Spin glass like behavior of magnetizati<strong>on</strong> in ani<strong>on</strong> substituted<br />

CuCr2Se4 magnetic semic<strong>on</strong>ductor // J. Magn. Magn. Mater., 1995, V. 140-144, P. 2043-2047. 3. Boukari H.,<br />

Kossacki P., Bertolini M., Ferrand D., Cibert J., Tatarenko S., Wasiela A., Gaj J.A., Dietl T. Light and electric<br />

field c<strong>on</strong>trol of ferromagnetism in magnetic quantum structures // Phys. Rev. Lett., 2002, V. 88, N. 20, P. 204-207.<br />

RN24<br />

Magnetite nanoparticles in hybrid aerogel and PEG encapsulated of<br />

magnetite nanoparticles for the hyperthermia applicati<strong>on</strong><br />

Eunhee Lee and Chang-yeoul Kim<br />

KICET, Korea<br />

Magnetite nanoparticles have received intensive attracti<strong>on</strong>s because of their<br />

applicati<strong>on</strong>s as magnetic carriers in drug targeting and hyperthermia in tumor<br />

treatment. However, magnetite nanoparticles with 10 nm in diameter easily aggregate<br />

themselves to form large sec<strong>on</strong>dary particles. To disperse magnetite nanoparticles,<br />

this research paper suggests the infiltrati<strong>on</strong> of magnetite nanoparticles into hybrid<br />

silica aerogels. The PEG encapsulate of magnetite is to disperse magnetite up in PBS<br />

soluti<strong>on</strong>. The well-dispersi<strong>on</strong> of magnetite is necessary for target the tumor cells<br />

and hyperthermia treatment. Methyltriethoxysilicate (MTEOS) based hybrid silica<br />

aerogels were synthesized by a supercritical drying method. To incorporate magnetite<br />

nanoparticles into the hybrid silica aerogels, we immersed it into magnetite precursor<br />

soluti<strong>on</strong>. The surfaces of magnetite nanoparticles were modified by PEG(polyethylene<br />

glycol). The infiltrati<strong>on</strong> and PEG coating of magnetite nanoparticles were identified<br />

by XRD, FT-IR and TEM. Vibrating Sample Magnetometer analysis showed that<br />

the composite of the magnetite and hybrid silica aerogel is superparamagnetic. The<br />

temperature behaviors of the magnetite composite and the surface coated magnetite<br />

nanoparticles were discussed in the c<strong>on</strong>text of the change of magnetite particles with<br />

PBS for Hyperthermia applicati<strong>on</strong>.<br />

RO01<br />

Effect of the Cu c<strong>on</strong>tent <strong>on</strong> the microstructural and magnetic<br />

properties of Nd-Fe-B sintered magnets<br />

Tae-ho<strong>on</strong> Kim 1 , Se<strong>on</strong>g-rae Lee 1 *, Seok Namkung 2 and Tae-suk Jang 2<br />

1 Korea University, Korea<br />

2 Sunmo<strong>on</strong> University, Korea<br />

The Cu additi<strong>on</strong> in the Nd-Fe-B sintered magnet improves the coercivity after the post-sintering<br />

annealing (PSA) because the c<strong>on</strong>tinuous Nd-rich grain boundary phase (GBP) and the metastable<br />

C-Nd 2O 3 phase were formed [1-3]. However, the magnetic properties of the commercial magnet<br />

were deteriorated when the Cu c<strong>on</strong>tent of the magnet is higher than 0.15 at.% (optimized Cu<br />

c<strong>on</strong>tent). In this study, we investigated the Cu c<strong>on</strong>tent effects <strong>on</strong> the microstructural and magnetic<br />

properties of sintered 12Nd-2.7Dy-(76.45-x)Fe-xCu-6B-2.65M (at.%, x=0.2, 0.3, 0.4, 0.5) magnets.<br />

The coercivity was decreased (28.7→26.1 kOe) with increasing the Cu c<strong>on</strong>tent, but the remanence<br />

was unchanged. Two kinds of Cu enriched Nd-rich triple juncti<strong>on</strong> phases (Cu-rich TJP), such as<br />

5~10 at.% Cu c<strong>on</strong>taining Nd-rich TJP (Culow-rich) and 35~45 at.% Cu c<strong>on</strong>taining Nd-rich TJP<br />

(Cuhigh-rich), were observed. The Culow-rich TJP was the stable h-Nd 2O 3, but the Cuhigh-rich TJP<br />

was the metastable C-Nd 2O 3 phase. The thickness and Fe c<strong>on</strong>tent of Nd-rich GBP was increased<br />

with increasing Cu c<strong>on</strong>tent because the oversaturated Cu atoms in the GBP substitutes with the Fe<br />

atoms near the GBP//Nd 2Fe 14B interfaces. As a result, the magnetic decoupling through the Nd-rich<br />

GBP was deteriorated and the coercivity was decreased when the Cu c<strong>on</strong>tent of the magnet is high.<br />

[1] F. Vial, F. Joly, E. Nevalainen, M. Sagawa, K. Hiraga, and K. T. Park,.J. Magn. Magn. Maters. 242-245,<br />

1329 (2002). [2] W. F. Li, T. Ohkubo, T. Akiya, H. Kato, K. H<strong>on</strong>o, J. Mater. Res. 24, 413 (2009). [3] M. Matsuura, S.<br />

Sugimoto, T. Fukada, R. Goto, N. Tezuka, Journal of Physics: <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series. 200, 082019 (2010).


RO02<br />

Effects of the D yH 3 and D y2O 3 powder additi<strong>on</strong> <strong>on</strong> the magnetic and<br />

microstructural properties of Nd-Fe-B sintered magnet<br />

Kyoung-ho<strong>on</strong> Bae 1 , Tae-ho<strong>on</strong> Kim 1 , Se<strong>on</strong>g-rae Lee 1 *, Seok Namkung 2 and Tae-suk<br />

Jang 2<br />

1 Korea University, Korea<br />

2 Sunmo<strong>on</strong> University, Korea<br />

Effective way for enhancing the magnetic properties as well as saving the Dy c<strong>on</strong>tent in the Nd-Fe-B based<br />

magnet is to develop the core-shell microstructure using the Dy 2O 3, DyF 3 or DyH3 powder doping [1, 2]. The<br />

DyH 3-doped magnet shows the most improved results [2]. However, the role of DyH 3 powder has not been<br />

identified yet. In this study, we investigated the magnetic and microstructural changes of the DyH 3-doped<br />

(2.4 wt.%) Nd 27.68Dy 4.89Febal.B 1.0M 2.4 (wt.%) sintered magnet comparing with those of the Dy 2O 3-doped (2.0<br />

wt.%) magnet. The coercivity of Dy 2O 3-doped magnet slightly increased (30.13→30.71 kOe) with a little<br />

remanence reducti<strong>on</strong> (11.59→11.56 kG) comparing with the undoped magnet. However, the coercivity of the<br />

DyH 3-doped magnet increased (30.13→31.9 kOe) without sacrificing remanence (11.59→11.6 kG). Coreshell<br />

microstructure was well developed when the DyH 3 powders were added comparing with the Dy 2O 3doped<br />

magnet. The hydride powder doping enhanced the diffusi<strong>on</strong> of Dy because the dissoluti<strong>on</strong> of the<br />

hydrogen in the Nd 2Fe 14B increased the lattice parameter and the point defects. The hydride was also known as<br />

a solid lubricant role at the grain boundaries [3]. As a result, the core-shell microstructure and the (00L) grain<br />

alignment of the DyH 3-doped magnet was more developed than those of Dy 2O 3-doped magnet.<br />

[1] S. E. Park, T. H. Kim, S. R. Lee, D. H. Kim, S. Namkung, and T. S. Jang, IEEE. Tran. Magn. 47, 10<br />

(2011). [2] G. Yan, P. J. McGuiness, J. P. G. Farr, and I. R. Harris, J. Alloys Compd. 491, L20 (2010). [3]<br />

S. Guo, R. J. Chen, Y. Ding, G. H. Yan, D. Lee, and A. R. Yan, J. Phys.: C<strong>on</strong>f. Ser. 266, 012030 (2011).<br />

RO03<br />

Magnetic properties of nano-composite Nd-Fe-B thick-film magnets<br />

prepared by vacuum arc depositi<strong>on</strong><br />

Tomoaki Tsutsumi 1 , Masaki Nakano 1 *, Takeshi Yanai 1 , Fumitoshi Yamashita 2 and<br />

Hirotoshi Fukunaga 1<br />

1 Nagasaki University, Japan<br />

2 MInebea Co. Ltd., Japan<br />

In order to upgrade the torque of the small motor comprising a multi-polarly magnetized<br />

rotor with isotropic thick-film magnets [1], enhancement in remanence of the isotropic thickfilm<br />

is indispensable. We, therefore, prepared nano-composite Nd-Fe-B/Alpha-Fe isotropic<br />

thick-films by using a vacuum arc depositi<strong>on</strong> method [2]. This c<strong>on</strong>tributi<strong>on</strong> reports the effect<br />

of the compositi<strong>on</strong> and the power of arc depositi<strong>on</strong> <strong>on</strong> the magnetic properties. Samples<br />

were prepared by using several targets with the compositi<strong>on</strong>s of NdXFe 14B + Nb 0.5 at.% (X<br />

=1.4~2.0). The voltage and capacitance varied in order to c<strong>on</strong>trol the power range between<br />

11 and 44 J. As the power was fixed at 44 J, use of a Nd 1.6Fe 14B + Nb 0.5 at. % target enabled<br />

us to obtain the highest (BH)max value. Although the depositi<strong>on</strong> rate decreased from<br />

approximately 20 to 5 micr<strong>on</strong>s per hour due to the power reducti<strong>on</strong> from 44 to 11 J, the value<br />

of (BH)max could be improved by approximately 15 kJ/m3 at the target compositi<strong>on</strong> of<br />

Nd 1.6Fe 14B + Nb 0.5 at. %. Resultantly, we succeeded in obtaining a 29 micr<strong>on</strong>-thick Nd-Fe-B<br />

thick-films with the remanence, coercivity and (BH)max values of 0.92 T, 390 kA/m and 79<br />

kJ/m3, respectively.<br />

[1] F. Yamashita et al., IEEE Trans. Magn. 46, 2012 (2010). [2] M. Nakano et al., J. Appl. Phys. 109, No.7, 07A755-1 (2011).<br />

RO04<br />

Corrosi<strong>on</strong> resistance and corrosi<strong>on</strong> behaviors of sintered rare-earth<br />

magnets in different corrosive envir<strong>on</strong>ments<br />

Anhua Li*, Wei Li, Jiajie Li, Haibo Feng, Zhaohui Guo and Minggang Zhu<br />

Divisi<strong>on</strong> of Functi<strong>on</strong>al Materials, Central Ir<strong>on</strong> & Steel Research Institute, China<br />

Sintered rare-earth magnets possessing outstanding magnetic properties are widely applied<br />

in many fields. However, corrosi<strong>on</strong> resistance has been a problem with the magnets owing<br />

to the high chemical activity of the phases rich in rare earth elements [1]. The Nd-rich<br />

phases of the Nd-Fe-B magnets can react with water vapor and oxygen in a damp and<br />

humid atmosphere. The electro-chemical corrosi<strong>on</strong> occurs for Nd-Fe-B magnets in a high<br />

humidity atmosphere because of the difference of corrosi<strong>on</strong> potential between the matrix<br />

Nd 2Fe 14B phase and the boundary Nd-rich phase [2]. In this article, Corrosi<strong>on</strong> resistance<br />

of sintered Nd-Fe-B and Sm-Co magnets was investigated in steady-state damp heat<br />

(HH), neutral salt spray (NSS) and pressure cooker (PCT) climates. The effects of alloy<br />

compositi<strong>on</strong> and different corrosive envir<strong>on</strong>ments <strong>on</strong> magnetic flux loss were discussed.<br />

It shows that the corrosi<strong>on</strong> rates of sintered Nd-Fe-B magnets in HH and NSS climates<br />

exhibit a obvious parabolic trend, flux loss in the above three kinds of climates have a<br />

approximate linear trend. The corrosi<strong>on</strong> resistance of sintered Nd-Fe-B magnets can be<br />

improved by Dy partially substituti<strong>on</strong> for Nd and minor Co additi<strong>on</strong>. The sintered Sm-Co<br />

magnets show very good corrosi<strong>on</strong> resistance in the above three kinds of climates.<br />

Sintered rare-earth magnets; corrosi<strong>on</strong> resistance; corrosi<strong>on</strong> behavior; different corrosive<br />

envir<strong>on</strong>ments<br />

RO05<br />

RO06<br />

RO07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Effects of grain size and interface state <strong>on</strong> the coercivity in Nd-Fe-B/<br />

Nd thin films<br />

Kunihiro Koike 1*, Takanao Kusano 1 , Daisuke Ogawa 1 , Mizuno Yoshiyuki 1 , Miyazaki<br />

Takamichi 2 , Yasuo Ando 2 and Hiroaki Kato 1<br />

1 Graduate School of Science and Engineering, Yamagta University, Japan<br />

2 Graduate School of Engineering, Tohoku University, Japan<br />

High coercivity in sintered Nd-Fe-B magnets is the crucial subject, especially in view of a<br />

high demand for developing Dy-saving magnets [1]. In order to approach this matter, the<br />

grain refinement and the interfacial microstructure c<strong>on</strong>trol are known l<strong>on</strong>g to be the promising<br />

methods [2, 3]. In this work, the effect of Nd coating <strong>on</strong> the coercivity has been investigated<br />

in the Nd 2Fe 14B thin films with different grain sizes. As the Nd 2Fe 14B layer thickness tNFB<br />

was decreased from 70 nm to 5 nm, the coercivity exhibited a gradual increase behavior from<br />

6.5 kOe to 16 kOe, and from 17.5 kOe to 26.2 kOe for the Nd-Fe-B and Nd-Fe-B/Nd films,<br />

respectively. It should be noted that the amount of Hc increase by the Nd coating was about 10<br />

kOe irrespective of Nd-Fe-B layer thickness tNFB. AFM observati<strong>on</strong>s showed that the average<br />

Nd2Fe14B particle size of the tNFB = 5 nm film is about 60 nm, which is much smaller than<br />

the critical size for the single domain in the Nd2Fe14B phase. These results therefore suggest<br />

that a proper interface state is extremely important to achieve high coercivity not <strong>on</strong>ly in larger<br />

grain system but also in smaller particle <strong>on</strong>e.<br />

[1] S. Sugimoto, Proc. <strong>on</strong> the 21th Int. Workshop <strong>on</strong> Rare-earth Permanent Magnet and their<br />

Applicati<strong>on</strong>s, Bled, Slovenia (2010) 103. [2] K. H. Muller, D. Eckert, A. Handstein, P. Nothnagel, and J.<br />

Schneider, J. Magn. Magn. Mater., 83, (1991) 195. [3] J. D. Livingst<strong>on</strong>, J. Appl. Phys., 57, (1985) 4137.<br />

Interface state and coercivity in Nd-Fe-B/Dy films<br />

Jin Umezawa 1 , Yoshiki Sakai 1 , Kunihiro Koike 1 *, Daisuke Ogawa 1 , Yoshiyuki<br />

Mizuno 1 , Takamichi Miyazaki 2 , Yasuo Ando 2 and Hiroaki Kato 1<br />

1 Graduate School of Science and Engineering, Yamagta University, Japan<br />

2 Graduate School of Engineering, Tohoku University, Japan<br />

It is believed that the Nd-rich phase plays an important role for the coercivity emhancement<br />

in the Nd-Fe-B magnets [1-2]. In the case of Dy-diffusi<strong>on</strong>-processed Nd-Fe-B magnets [3],<br />

however, it is still not clear whether <strong>on</strong>ly the Dy-rich shell or both Dy-shell and the Nd-rich<br />

phase is indispensible for the high coercivity. Therefore, we fabricated a model interface<br />

system, which c<strong>on</strong>sists of the Nd 2Fe 14B layer with the Dy and Nd overlayers in order to study<br />

the relati<strong>on</strong>ship between microstructure near the interface and the coercivity. Nd 2Fe 14B particles<br />

with the c-axis normal to the film plane were c<strong>on</strong>structed by using HV or UHV sputtering<br />

systems. We introduced high-melting-point bcc metals, Ta or Mo, as an underlayer <strong>on</strong> the<br />

heat-resistant glass or sapphire c-plane single-crystal substrates. When the temperature of the<br />

substrate during a depositi<strong>on</strong> of the 1 μm thick Nd-Fe-B layer was 620°C, the demagnetizati<strong>on</strong><br />

curve of this film without rare-earth overlayers exhibited a nice squareness with coercivity Hc =<br />

3.3 kOe. On the other hand, preliminary experiments <strong>on</strong> the post-annealed Nd-Fe-B films with<br />

the Dy overlayer showed a significant increase in Hc of up to above 15 kOe.<br />

[1] K. H. Muller, D. Eckert, A. Handstein, P. Nothnagel, and J. Schneider, J. Magn. Magn. Mater.,<br />

83, (1991) 195. [2] F. Vial, F. Joly, E. Nevalainen, M. Sagawa, K. Hiraga, and K.T. Park, J. Magn.<br />

Magn. Mater., 242-245, (2002) 1329. [3] H. Nakamura, K. Hirota, M. Shimao, T. Minowa, and M.<br />

H<strong>on</strong>shima, IEEE Trans. Magn., 41 (2005) 3844.<br />

Investigati<strong>on</strong> <strong>on</strong> the magnetic and crystalline structures of die-upset<br />

Nd-Fe-B magnets<br />

Yikun Fang 1 *, Wei Li 1 , Xiaolu Yin 2 , Zhaohui Guo 1 , Minggang Zhu 1 and Sy-hwang Liou 2<br />

1<br />

Divisi<strong>on</strong> of Functi<strong>on</strong>al Materials Research, Central Ir<strong>on</strong> and Steel Research<br />

Institute,Beijing 100081, China<br />

2<br />

Department of Physics and Astr<strong>on</strong>omy and Nebraska Center for Materials and<br />

Nanoscience, University of Nebraska- Lincoln, Lincoln, NE 68588, USA<br />

Die-upsetting is used to prepare anisotropic Nd-Fe-B magnets due to high magnetic texture in which the<br />

c-axis of Nd2Fe14B grains is parallel to the loading directi<strong>on</strong>. [1] Though many papers have reported <strong>on</strong> the<br />

structures of high-textured Nd-Fe-B magnets [2-5], there are still some issues needed to be clarified, such as<br />

how about the uniformity of the magnetic structures and how to improve the uniformity. In this paper, x-ray<br />

diffracti<strong>on</strong> (XRD) and magnetic force microscopy (MFM) are used to reveal the crystalline and magnetic<br />

structures of die-upset Nd 13.62Fe 75.70Co 4.45B 5.76Ga 0.47 magnets. It is found that the ratio of the XRD peak intensity<br />

I(006)/ I(105) from center to edge of the sample decreases from 1.86 to 1.35. The magnetic c<strong>on</strong>figurati<strong>on</strong>s of<br />

the central of the sample are typical interacti<strong>on</strong> domains. The interacti<strong>on</strong> domains are formed due to the str<strong>on</strong>g<br />

inter-granular exchange interacti<strong>on</strong> and magnetostatic interacti<strong>on</strong> between grains. However, <strong>on</strong> the edge of<br />

the sample the n<strong>on</strong>-interacti<strong>on</strong> domains present. The XRD and MFM results may relate to the n<strong>on</strong>-uniformity<br />

of the effective strain that generated during the die-upsetting process. This indicates we need to improve the<br />

uniformity of the strain distributi<strong>on</strong> for the development of high-performance magnets.<br />

[1] R. W. Lee, Appl. Phys. Lett. 46, 790 (1985). [2] K. Khlopkov, O. Gutfleisch, D. Hinz, K.-H. Muller, and L.<br />

Schultz, J. Appl. Phys. 102, 023912 (2007). [3] Y. G. Liu, L. Xu, Q.F. Wang, W. Li, and X. Y. Zhang, Appl. Phys.<br />

Lett. 94, 172502 (2009). [4]R. Zhao, W. C. Zhang, J. J. Li, H. J. Wang, M. G. Zhu, and W. Li, J. Magn.16, 294 (2011).<br />

[5] Y. K. Fang, X. L. Yin, R. Zhao, S. Valloppilly, W. Li, M. G. Zhu, S. H. Liou, J. Appl. Phys.(2012) in press.<br />

July 8 - 13, 2012 Busan, Korea 187<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RO08<br />

A novel approach -microwave assisted sintering - for preparati<strong>on</strong> of<br />

high performance permanent magnets<br />

Dimitrios G Niarchos 1 *, Margarit Gjoka 1 , Eam<strong>on</strong> Devlin 1 , George Hadjipanayis 2 ,<br />

Amparo Borrell Tomas 3 , Maria Dolores Salvador Moya 3 and Felipe L Penaranda-foix 4<br />

1 Institute of Materials Science, NCSR DEMOKRITOS, Greece<br />

2 Department of Physics and Astr<strong>on</strong>omy, U of Delaware, Newark, DE, USA<br />

3 Institute of Materials, Technology Polytechnic University of Valencia, Camino de Vera, s/n 46022, Spain<br />

4 School of Communicati<strong>on</strong>, 4 School of Telecommunicati<strong>on</strong>, Polytechnic University of Valencia, Camino<br />

de Vera, s/n 46022, Spain<br />

A large porti<strong>on</strong> of the cost for the fabricati<strong>on</strong> of permanent magnets is due to the energy needed for<br />

sintering. Any improvement for the sintering process with respect to time and energy will reduce the cost<br />

and will increase the market of permanent magnets c<strong>on</strong>siderably. Based <strong>on</strong> the most recent development in<br />

microwave applicati<strong>on</strong>s reported by R. Roy (1) , where it was dem<strong>on</strong>strated that sintering of metal powders-<br />

a surprising applicati<strong>on</strong>- is possible with microwaves (in view of the known fact that bulk metals reflect<br />

microwaves), we have employed microwaves to sinter Nd-Fe-B at a fracti<strong>on</strong> of time and energy, compared<br />

to the c<strong>on</strong>venti<strong>on</strong>al resistive/radiant heating in excess of 1000 0C for many hours, and in many cases<br />

homogenizing also at high temperatures. Microwave heating is a volumetric heating involving c<strong>on</strong>versi<strong>on</strong><br />

of electromagnetic energy into thermal energy, which is instantaneous, rapid and highly efficient. In this<br />

work, we will present the emerging possibilities for sintering Nd-Fe-B and Sm-Co permanent magnets as<br />

well as the opening of new possibilities for metal b<strong>on</strong>ded magnets by employing microwave radiati<strong>on</strong>, that<br />

is already used for ferrites by various groups. Supported by the project NANOPERMAG of the EU<br />

RERERENCES 1. R. Roy, D. Agrawal, J. Cheng and S. Gedevanishvili, Nature, 399, pp.668-670, 1999<br />

RO09<br />

Preparati<strong>on</strong> of Nd-Fe-B thin films with columnar structure and their<br />

structure and magnetic properties<br />

Shota Suzuki, Yuki Hatayama and Toshiyuki Shima<br />

Tohoku Gakuin University, Japan<br />

The additi<strong>on</strong> of heavy rare earth elements is essential for Nd-Fe-B sintered magnet<br />

to obtain high-performance characteristic at high temperature. However, a reducti<strong>on</strong><br />

of these additive elements is str<strong>on</strong>gly required since the price of these elements has<br />

increased in recent years. It was reported that the additive elements such as Cu and<br />

Ga were diffused and c<strong>on</strong>centrated into the grain boundary phase (GBP) [1, 2], and<br />

the magnetic coupling between the main phases is thought to reduce by the GBP.<br />

In order to improve the hard magnetic properties, therefore, the c<strong>on</strong>trol of the GBP<br />

is indispensable. In this study, the Nd-Fe-B thin films with well-defined columnar<br />

structure have been prepared and structure and magnetic properties have been also<br />

investigated. The samples were prepared by using an ultra-high vacuum sputtering<br />

system. The thickness of the Nd-Fe-B layer was varied in the range of 50 ~ 300 nm.<br />

From the X-ray diffracti<strong>on</strong> patterns, the peaks from Nd2Fe14B (004), (006), and (008)<br />

were observed for all the samples. This indicates that the films grew with a str<strong>on</strong>g (001)<br />

texture. A good magnetic squareness and relatively high coercivity of 8.3 kOe were<br />

obtained for the Nd-Fe-B films with t = 100 and 200 nm.<br />

[1] C. Y. You, Y. K. Takahashi, K. H<strong>on</strong>o, J. Appl. Phys., 108, (2010) 043901. [2] T. Sato, H. Kato, T.<br />

Shima, Y. K. Takahashi, K. H<strong>on</strong>o, J. Magn. Magn. Mater., 323 (2011) 163-166.<br />

RO10<br />

Microstructure of (Nd,Dy)-Fe-B permanent magnet by spark plasma<br />

sintering<br />

Sun Y<strong>on</strong>g S<strong>on</strong>g, Jin Woo Kim and Young Do Kim*<br />

Divisi<strong>on</strong> of Materials Science and Engineering, Hanyang University, Korea<br />

Sintered (Nd,Dy)-Fe-B magnets are widely used in various parts such as motor, generators,<br />

actuators, and so <strong>on</strong> because of their outstanding magnetic properties. (Nd,Dy)-Fe-B sintered<br />

magnets are generally composed of the Nd 2Fe 14B hard magnet phase as a matrix and a Ndrich<br />

phase at the triple juncti<strong>on</strong> [1,2]. However, typical sintered (Nd,Dy)-Fe-B magnets are<br />

limited in their applicati<strong>on</strong>s due to low curie temperature[3]. Many researchers have shown<br />

that the magnetic properties of (Nd,Dy)-Fe-B magnets are structure sensitive, and dependent<br />

<strong>on</strong> the distributi<strong>on</strong> of the rare-earth-rich phases, average grain size and size distributi<strong>on</strong>.<br />

Particularly the grain size of Nd 2Fe 14B was essentially important for high magnet properties.<br />

In this study, we focused <strong>on</strong> c<strong>on</strong>trolling of the grain size to enhance magnetic properties<br />

by the spark plasma sintering process. The starting powder with the compositi<strong>on</strong> of<br />

Nd 13Dy 2Fe 76.2TM 2.8B 6 was prepared by strip casting and jet milling process. The raw powder<br />

was pre-sintered for preventing collapsibility of anisotropy. After the pre-sintering, (Nd,Dy)-<br />

Fe-B magnet was fabricated by spark plasma sintering process under 30 MPa with various<br />

temperatures. C<strong>on</strong>sequently we had made the (Nd,Dy)-Fe-B sintered magnet with grain size<br />

of 5.9 μm. The grain size was effectively c<strong>on</strong>trolled by spark plasma sintering.<br />

[1] M.Sagawa,S.Fujimura,N.Togawa,H.Yamamoto,Y.Matsuura,J.Appl.Phys.55 (1984)2083-2087.<br />

[2] H.J.Wang,Z.H.Guo,A.H.Li,X.M.Li,W.Li,J.Magn.Magn.Mater.303(2006) e392-e395. [3] W.F.Li,T.<br />

Ohkubo,K.H<strong>on</strong>o,M.Sagawa,J.Magn.Magn.Mater.321(2009) 1100-1105.<br />

188 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RO11<br />

Effect of small Dy-alloy powder additi<strong>on</strong>s <strong>on</strong> the coercivity of NdFeB<br />

sintered magnets<br />

MINWOO LEE<br />

Sunmo<strong>on</strong> University, Korea<br />

Recently, demand of high performance NdFeB sintered magnets is rapidly increasing<br />

mostly due to expansi<strong>on</strong> of wind generators and hybrid electric vehicles. For tracti<strong>on</strong><br />

motors of hybrid electric vehicles, the coercivity of NdFeB sintered magnet is<br />

required to exceed 25 kOe. For such high coercivity, partial substituti<strong>on</strong> of Dy for Nd<br />

in Nd 2Fe 14B of NdFeB sintered magnet is practically inevitable, with the sacrifice of<br />

magnetizati<strong>on</strong> value and the increase of material cost. Because the price of Dy is very<br />

high and keeps increasing due to its scarcity, it is important to reduce the amount of Dy<br />

in NdFeB magnets as much as possible without losing coercivity. Recent researches <strong>on</strong><br />

NdFeB magnets, therefore, are mainly focused <strong>on</strong> Dy-saving methods. In this study, as<br />

an effort to develop a Dy-saving method, small Dy-TM alloy powder was mixed with<br />

NdFeB magnet powder and then a sintered magnet was fabricated by a c<strong>on</strong>venti<strong>on</strong>al<br />

process. When 1.9 wt% of DyCo powder was mixed, the coercivity of the sintered<br />

magnet increased about 4 kOe, indicating 20% of Dy saving effect. More experimental<br />

results will be discussed in this presentati<strong>on</strong>.<br />

RO12<br />

Coercivity of near single domain size Nd-Fe-B-type alloy particles<br />

Hae-wo<strong>on</strong>g Kw<strong>on</strong> 1 and J H Yu 2<br />

1 Puky<strong>on</strong>g Nati<strong>on</strong>al University, Korea<br />

2 KIMS, Korea<br />

Fine particles of Nd-Fe-B alloy in near single domain size have increasingly found new<br />

applicati<strong>on</strong>s for high performance micro-magnet. However, because of high oxygenaffinity<br />

and high specific surface area, the ultra-fine Nd-Fe-B-type particles are readily<br />

oxidized in air, hence causing a radical coercivity loss. In the present study, an ultrafine<br />

Nd-Fe-B-type particles in near single domain size was prepared by ball milling of<br />

HDDR-treated Nd12.5Fe80.6B6.4Ga0.3Nb0.2 alloy. The prepared near single domain<br />

size Nd-Fe-B-type powder ( 0.3 um) had high coercivity over 9 kOe. However, the<br />

coercivity was radically reduced as the temperature increased in air (< 2 kOe at 200<br />

°C). Room temperature l<strong>on</strong>g-term stability of coercivity of the fine powder in air was<br />

investigated for 1 m<strong>on</strong>th, and the coercivity was decreased by rate of 0.5 kOe/week.<br />

Feasibilty of surface nitrogenati<strong>on</strong> of the fine powder for improving the l<strong>on</strong>g-term<br />

stability of coercivity was studied. L<strong>on</strong>g-term stability of coercivity of the nitrogenated<br />

fine powder was improved markedly. The nitrogenated powder showed no coercvity<br />

reducti<strong>on</strong> even after 1 m<strong>on</strong>th in air at room temperature. In this article, the surface<br />

passivati<strong>on</strong> of near single domain size Nd-Fe-B-type particles by nitrogenati<strong>on</strong> for<br />

improving l<strong>on</strong>g-term stability of coercivity is to be discussed.<br />

RO13<br />

Effect of annealing temperature <strong>on</strong> microstructure, magnetic<br />

properties and corrosi<strong>on</strong> resistance of NdFeB/α-Fe nanocomposite<br />

magnets<br />

Minxiang Pan, Pengyue Zhang*, H<strong>on</strong>gliang Ge, Hangfu Yang and Qi<strong>on</strong>g Wu<br />

<strong>Magnetism</strong> key laboratory of Zhejiang Province, China Jiliang University, 310018<br />

Hangzhou, China, China<br />

REFeB based nanocomposite alloys have attracted much attenti<strong>on</strong> in both the scientific<br />

community and b<strong>on</strong>ded magnet industry. However, lower coercivity and poor corrosi<strong>on</strong><br />

resistance limit their applicati<strong>on</strong>s. Both the practical coercivity and corrosi<strong>on</strong> resistance<br />

are sensitive to the character of phase c<strong>on</strong>stitute in the microstructure. Sintered NdFeB<br />

magnet is the poor corrosi<strong>on</strong> resistance due to the presence of the highly corrosive Ndrich<br />

phase. As no Nd-rich phase is formed in the NdFeB/α-Fe nanocomposite magnets,<br />

these alloys should be more corrosi<strong>on</strong> resistant than the NdFeB sintered magnet. In this<br />

work, the effects of annealing temperature <strong>on</strong> the microstructure, magnetic properties<br />

and corrosi<strong>on</strong> resistance in NdFeB/α-Fe alloys were investigated. It is shown that<br />

after heat treatment, the alloys mainly c<strong>on</strong>sist of two phases: a hard magnetic phase of<br />

Nd 2Fe 14B (space group P 42/mnm) and a soft magnetic phase of α-Fe (Im3m), and that<br />

no other phases are identified. Moreover, the optimum corrosi<strong>on</strong> resistance of NdFeB/<br />

α-Fe magnets was observed with the annealing temperature at 610°C. Keywords:<br />

Nanocomposite, Magnetic property, corrosi<strong>on</strong> resistance<br />

*E-mail: Zhang_Pengyue@cjlu.edu.cn.


RO14<br />

Effect of magnetic heat-treatment <strong>on</strong> magnetic properties and<br />

corrosi<strong>on</strong> behavior of Nd 6Fe 72-xCo xB 22 (x=10, 20, 30) nanocomposite<br />

ribb<strong>on</strong>s<br />

Qi<strong>on</strong>g Wu, P.z. Zhang*, M.x. Pan, Z.s. Wang and H.l. Ge<br />

China Jiliang University, China<br />

Nanocomposite rare-earth magnets c<strong>on</strong>sisting of a hard and a soft magnetic phase have<br />

attracted c<strong>on</strong>siderable attenti<strong>on</strong> because the remanence enhancement in exchange coupled<br />

nanocomposite alloys has potential importance as a way to achieve high values of the<br />

maximum energy product (BH)max. It is well established that the magnetic properties of<br />

nanocrystalline two-phase magnets are str<strong>on</strong>gly dependent <strong>on</strong> its microstructure. A uniform<br />

microstructure and a well-coupled grain interface should be two essential c<strong>on</strong>diti<strong>on</strong>s<br />

for a well-performing nanocomposite. Magnetic annealing has been tried to perfect the<br />

microstructure and enhance the magnetic properties. In this paper, Nd 6Fe 72-xB 22(x=10,20,30)<br />

ribb<strong>on</strong>s were heat-treated with or without an external magnetic field of 3 kOe in arg<strong>on</strong><br />

atmosphere in the temperature range of 600-750°C for 10 min. It is found that magnetic heattreatment<br />

enhances both coercivity and remanence ratio of the Nd 6Fe 72-xCoxB 22(x=10,20,30)<br />

ribb<strong>on</strong>, and decrease the annealed temperature obtained the optimum magnetic properties<br />

due to the uniform distributi<strong>on</strong> and preferential orientati<strong>on</strong> of α-Fe and Nd 2Fe 14B grains. The<br />

corrosi<strong>on</strong> behavior of Nd 6Fe 72-xCoxB 22(x=10, 20, 30)nanocomposite ribb<strong>on</strong>s with or without<br />

an external magnetic field is discussed in detail.<br />

Q.G. Ji, B.X. Gu, S.L. Tang et al. J.Magn.Magn.Mater. 257 (2003) 146.<br />

RO15<br />

Study <strong>on</strong> magnetizati<strong>on</strong> reversal behavior for the annealed Nd2Fe14B/ α-Fe nancomposite alloys<br />

Pengyue Zhang 1 , Minxiang Pan 1 , H<strong>on</strong>gliang Ge 1 , Luke Yang 1 , Ming Yue 2 and<br />

Weiqiang Liu 2<br />

1<br />

College of Materials Science & Engineering, China Jiliang University, Hangzhou<br />

310018, China, China<br />

2<br />

College of Materials Science & Engineering, Beijing University of Technology,<br />

Beijing 100124, Chin, China<br />

Effect of thermal annealing <strong>on</strong> the magnetizati<strong>on</strong> reversal behavior of α-Fe/Nd 2Fe 14B<br />

alloys has been investigated. A drastic increase of the remanence Mr from 0.67T up<br />

to 0.87T and remanence ratio Mr/Ms from 0.66 up to 0.76, respectively, is observed<br />

in the α-Fe/Nd 2Fe 14B alloys annealed at 610 oC as compared with the as-quenched<br />

sample. Whereas the further annealing at 680 oC results in a str<strong>on</strong>gly increase of the<br />

corecivity Hc as high as 491 kA/m but a slight decrease in Mr. The analysis result of<br />

the magnetizati<strong>on</strong> reversal behavior shows that the maximum value of the integrated<br />

recoil loop area about 1.58 kJ/m 3 is obtained in the α-Fe/Nd 2Fe 14B alloys at the<br />

annealing temperature of 610 oC, significantly lower than other annealed samples.<br />

This indicates a significant advantage for the applicati<strong>on</strong> of this material as permanent<br />

magnets in electrical machines and generators due to a low energy loss. Keywords:<br />

Nanocomposite; Magnetizati<strong>on</strong> reversal behavior; Recoil loop<br />

*E-mail: Zhang_Pengyue@cjlu.edu.cn.<br />

RP01<br />

C<strong>on</strong>structi<strong>on</strong> of a versatile neutr<strong>on</strong>-scattering spectrometer<br />

HERMES-E using renovated Ge m<strong>on</strong>ochromator crystals<br />

Haruhiro Hiraka 1 *, Kenji Ohoyama 1 , Manabu Ohkawara 1 , Naoki Murakami 1 , Yasuo<br />

Yamaguchi 1 , Kazuma Okubo 2 , Michiro Furusaka 2 , Yoshiaki Kiyanagi 2 , Shin Ae Kim 3 ,<br />

Chang Hee Lee 3 , Kohei Morishita 4 , Kazuo Nakajima 4 and Kazuyoshi Yamada 5<br />

1<br />

Institute for Materials Research, Tohoku University, Japan<br />

2<br />

Divisi<strong>on</strong> of Quantum Science and Engineering, Graduate School of Engineering,<br />

Hokkaido University, Japan<br />

3<br />

HANARO, Korea Atomic Energy Research Institute, Korea<br />

4<br />

Graduate School of Energy Science, Kyoto University, Japan<br />

5<br />

Advanced Institute for Materials Research, WPI, Tohoku University, Japan<br />

We propose an efficient way, which increases a number of neutr<strong>on</strong> spectrometers<br />

in a research-reactor facility. The first key is to making use of a characteristic Gecrystal<br />

m<strong>on</strong>ochromator, which discretely emits Bragg reflecti<strong>on</strong>s to different scattering<br />

angles at the same time. The sec<strong>on</strong>d is to save the instrumental space by using curved<br />

and deformed Ge-wafer crystals as a m<strong>on</strong>ochromator or an analyzer. Indeed, we are<br />

planning to double a neutr<strong>on</strong>-powder diffractometer of Tohoku University (HERMES<br />

[1]) that is working at a research reactor JRR-3, Tokai, Japan; a versatile neutr<strong>on</strong>scattering<br />

spectrometer HERMES-E is now under c<strong>on</strong>structi<strong>on</strong> next to HERMES.<br />

[1] K. Ohoyama et al., Jpn. J. Appl. Phys. vol. 37 (1998) 3319.<br />

RP02<br />

NMR study of the phase transiti<strong>on</strong> behavior in Ce3Co4Sn13<br />

Chin Shan Lue, H. F. Liu and C. N. Kuo<br />

Physics, Nati<strong>on</strong>al Cheng Kung University, Taiwan<br />

RP03<br />

RP04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

We present a study of the phase transiti<strong>on</strong> behavior in Ce 3Co 4Sn 13 using 59Co nuclear<br />

magnetic res<strong>on</strong>ance (NMR) spectroscopy. The quadrupole splitting, Knight shift, and<br />

spin-lattice relaxati<strong>on</strong> rate (1/T1) below and above the phase transiti<strong>on</strong> temperature<br />

To have been identified. All measured NMR quantities exhibit pr<strong>on</strong>ounced features at<br />

around To=155 K except for the Knight shift. It thus excludes the magnetic origin for<br />

the observed transiti<strong>on</strong>. In additi<strong>on</strong>, the x-ray diffracti<strong>on</strong> results below and above To<br />

c<strong>on</strong>firm the absence of a crystal structural change, suggesting that the peculiar phase<br />

transiti<strong>on</strong> is possibly driven by the charge-density-wave (CDW) formati<strong>on</strong>. As a matter<br />

of fact, the double-peak feature in the 59Co NMR central line smears out below To<br />

which can be associated with the spatial modulati<strong>on</strong> of the electric field gradient (EFG)<br />

due to incommensurate CDW superlattices. Furthermore, a distinct peak found in the<br />

spin-lattice relaxati<strong>on</strong> rate near To can be accounted for by the thermally-driven normal<br />

modes of the CDW.<br />

Analysis of 1/f noise characteristics of magneto-optical Kerr effect<br />

measured from Co/Pt and NiFe/Pt multilayers thin film<br />

Djati Handoko, Sang-hyuk Lee and D<strong>on</strong>g-hyun Kim*<br />

Physics Department, Chungbuk Nati<strong>on</strong>al University, Korea<br />

We have investigated 1/f noise characteristic of the polar and l<strong>on</strong>gitudinal magnetooptical<br />

Kerr effect (MOKE). The hand-made MOKE measurement system was set<br />

using diode laser as a light source. Si photodetector was used as a detector where the<br />

bias has been systematically c<strong>on</strong>trolled. To increase a signal-to-noise ratio, the laser<br />

light was modulated with the lock-in amplificati<strong>on</strong> frequency referenced from the<br />

mechanical chopper in the frequency ranges up to 4 kHz. Noise characteristics of the<br />

optical/electrical/mechanical error were systematically examined. To separate the noise<br />

c<strong>on</strong>tributi<strong>on</strong> from the ferromagnetic layer and from the intrinsic measurement error,<br />

various c<strong>on</strong>figurati<strong>on</strong>al changes were made for the lock-in frequency as well as the bias<br />

voltage of the Si photodetector. Magnetic noise properties under a different magnetic<br />

field were systematically investigated as well. For a perpendicular anisotropy sample,<br />

Co/Pt multilayer film was investigated while for an in-plane anisotropy sample, NiFe/<br />

Pt bilayer film was investigated. The noise characteristics with respect to the multilayer<br />

thickness variati<strong>on</strong>s were examined as well. The 1/f noise characteristics observed for<br />

a wide range regardless of the lock-in frequency change or the film thickness change<br />

implies that there might be a universal characteristics in the MOKE signal noise,<br />

arising from the sample itself.<br />

Photoemissi<strong>on</strong> electr<strong>on</strong> microscopy of three-dimensi<strong>on</strong>al magnetizati<strong>on</strong><br />

c<strong>on</strong>figurati<strong>on</strong>s in core-shell nanostructures<br />

Judith Kimling 1 , Florian Kr<strong>on</strong>ast 2 , Stephan Martens 1 , Tim Boehnert 1 , Michael<br />

Martens 1 , Julia Herrero Albillos 2 , Logane Tati Bismaths 2 , Ulrich Merkt 1 , Kornelius<br />

Nielsch 1 and Guido Meier 1 *<br />

1 University of Hamburg, Germany<br />

2 Helmholtz-Zentrum Berlin fuer Materialien und Energie, Germany<br />

We present a photoemissi<strong>on</strong> electr<strong>on</strong> microscopy method that combines magnetic imaging of the<br />

surface and of the inner magnetizati<strong>on</strong> in three-dimensi<strong>on</strong>al core-shell nanostructures [1]. The<br />

structure investigated c<strong>on</strong>sists of a cylindrical nickel core that is completely surrounded by a shell of<br />

ir<strong>on</strong> oxide and silic<strong>on</strong> oxide layers. The method enables <strong>on</strong>e to image the magnetizati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong><br />

of the nickel core even though the shell is thicker than the mean-free path of the photoelectr<strong>on</strong>s.<br />

Characteristic L 3 and L 2 edges can be observed not <strong>on</strong>ly in the yield of the photoelectr<strong>on</strong>s emitted<br />

from the surface of the nanostructure but also in its shadow. X-ray magnetic circular dichroism in<br />

the electr<strong>on</strong> yield of the x rays absorbed and transmitted by the multilayered nanowire allows for the<br />

individual imaging of the magnetizati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong>s of the ir<strong>on</strong> oxide tube and the nickel core. The<br />

method suggests novel approaches for the characterizati<strong>on</strong> of the magnetic and material properties of<br />

complex three-dimensi<strong>on</strong>al nanostructures. Financial support by the DAAD via the Project 50725506<br />

and by DFG via the SFB 668 and the GrK 1286 as well as the Forschungs- und Wissenschaftsstiftung<br />

Hamburg via the Exzellenzcluster “Nano-Spintr<strong>on</strong>ik” is gratefully acknowledged.<br />

[1] J. Kimling, F. Kr<strong>on</strong>ast, S. Martens, T. Boehnert, M. Martens, J. Herrero-Albillos, L. Tati-<br />

Bismaths, U. Merkt, K. Nielsch, and G. Meier, Phys. Rev. B 84, 174406 (2011).<br />

July 8 - 13, 2012 Busan, Korea 189<br />

Poster Thursday


Poster Thursday<br />

RP05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Development of high-field ESR system using SQUID magnetometer<br />

and its applicati<strong>on</strong> to measurement under high pressure<br />

Takahiro Sakurai 1 *, Kohdai Fujimoto 2 , Susumu Okubo 3 , Hitoshi Ohta 3 and Yoshiya<br />

Uwatoko 4<br />

1 Center for Supports to Research and Educati<strong>on</strong> Acti, Kobe University, Japan<br />

2 Graduate School of Science, Kobe University, Japan<br />

3 Molecular Photoscience Research Center, Kobe University, Japan<br />

4 Institute of Solid State Physics, University of Tokyo, Japan<br />

We have developed high-field ESR system using commercial SQUID magnetometer, in<br />

which ESR is observed as a change of magnetizati<strong>on</strong>. [J. Phys.: C<strong>on</strong>f. Ser. 334 (2011)<br />

012058.] The advantage of this method as compared with c<strong>on</strong>venti<strong>on</strong>al high-field ESR is<br />

that the measurement can be d<strong>on</strong>e very easily. Moreover, the macroscopic magnetizati<strong>on</strong><br />

measurement can be made simultaneously. Although the sensitivity of this system is<br />

lower than that of ESR system using cavity, it is comparable with that of transmissi<strong>on</strong><br />

type ESR system. Recently, we have succeeded in performing ESR measurement under<br />

high pressure by this ESR system. The pressure is generated by a widely used clamped<br />

type pist<strong>on</strong>-cylinder pressure cell whose cylinder is made of n<strong>on</strong>-magnetic CuBe alloy.<br />

Since all inner parts are made of zirc<strong>on</strong>ium oxide, the electromagnetic wave can be<br />

introduced into the sample space. Therefore, we can measure the magnetic moment of<br />

sample and obtain ESR signal under pressure. The pressure is available up to 1.5 GPa.<br />

This is the easiest ESR system which gives us pressure dependence ESR spectra as far<br />

as we know. The setup of this system and several results will be shown in detail.<br />

RP06<br />

Alternating magnetic force microscopy: directi<strong>on</strong> detectable imaging<br />

of static and alternating magnetic field with high spatial resoluti<strong>on</strong><br />

Hitoshi Saito 1 , Ito Ryoichi 1 , Kodai Hatakeyama 1 , Zhenghua Li 2 , Genta Egawa 1 and<br />

Satoru Yoshimura 1<br />

1 Graduate School of Engineering and Resource Science, Akita University, Japan<br />

2 Venture Business Laboratory, Akita University, Japan<br />

We have developed a new functi<strong>on</strong>al MFM named as “Alternating Magnetic Force Microscopy<br />

(A-MFM)” which enables us to measure static and alternating magnetic fields with the polarity of<br />

field directi<strong>on</strong> [1-5]. A-MFM utilized the frequency modulati<strong>on</strong> of a cantilever oscillati<strong>on</strong> generated<br />

by an off-res<strong>on</strong>ance alternating magnetic force between a magnetic sample and a magnetic tip. The<br />

alternating magnetic force was extracted by a lock-in amplifier for the frequency demodulated signal<br />

of the cantilever oscillati<strong>on</strong>. For the static magnetic field from a sample, a soft magnetic tip which ware<br />

driven by an AC magnetic field was used to detect the static magnetic field with high sensitivity. On the<br />

other hand, for the alternating magnetic field from a sample, such as a magnetic writing head, a hard<br />

magnetic tip was used. A-MFM can measure a magnetic force without surface short-range forces and<br />

directly detect the directi<strong>on</strong> of perpendicular magnetic fields. When the tip-sample distance became<br />

short, spatial resoluti<strong>on</strong> was improved. In the c<strong>on</strong>ference, we will dem<strong>on</strong>strate high performance of<br />

A-MFM and show high-resoluti<strong>on</strong> magnetic field images with a resoluti<strong>on</strong> of less than 10 nm for highdensity<br />

recording media and magnetic writing heads. This study was supported by SENTAN, JST.<br />

[1] H. Saito et al. J. Appl. Phys. 105 (2009) 07D524, [2] H. Saito et al. J. Appl. Phys. 107 (2010)<br />

09D309, [3] W. Lu et al. Appl. Phys. Lett. 96 (2010) 143104, [4] W. Lu et al. IEEE Trans. Magn. 46<br />

(2010) 1479, [5] H. Saito et al. J. Appl. Phys. 109 (2011) 07E330<br />

RP07<br />

30 T pulsed-high-magnetic-field and element-selective magnetizati<strong>on</strong><br />

studies using soft x-ray magnetic circular dichroism<br />

Yasuo Narumi 1 *, Tetsuya Nakamura 2 , Misaki Hayashi 1 , Hiroyuki Nojiri 1 , Kenji Kodama 3 , Toko<br />

Hir<strong>on</strong>o 2 , Wataru Ito 4 , Rie Umetsu 1 , Ryosuke Kainuma 5 , Koichi Kindo 6 and Toyohiko Kinoshita 2<br />

1 Institute for Materials Research, Tohoku University, Japan<br />

2 Japan Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Institute/SPring-8, Japan<br />

3 Department of Mechanical Engineering, Nara Nati<strong>on</strong>al College of Technology, Japan<br />

4 Department of Materials and Envir<strong>on</strong>mental Engineering, Sendai Nati<strong>on</strong>al College of Technology, Japan<br />

5 Graduate School of Engineering, Tohoku University, Japan<br />

6 Institute for Solid State Physics, The University of Tokyo, Japan<br />

We dem<strong>on</strong>strate the applicability of 30 T pulsed-high-magnetic-field to observe magnetic circular dichroism<br />

(MCD) of antiferromagnetic compounds in soft x-ray energy regi<strong>on</strong>s, in which there are magnetically important<br />

transiti<strong>on</strong> energies, L-edge of 3d transiti<strong>on</strong> metal and M-edge of 4f rare earth elements. We have developed a<br />

specially designed pulse magnet equipped with an ultra-high-vacuum envir<strong>on</strong>ment and a portable capacitor<br />

bank for synchrotr<strong>on</strong> soft x-ray experiments [1]. A time-resolved total electr<strong>on</strong> yield method is used to record<br />

x-ray absorpti<strong>on</strong>s in synchr<strong>on</strong>izati<strong>on</strong> with pulsed-high-magnetic-fields and periodic switching of circularly<br />

polarized soft x-rays. We have measured elements-selective magnetizati<strong>on</strong>s of Ni, Co and Mn in the NiCoMnIn<br />

alloy which shows a large field-induced strain accompanied by a drastic change of the magnetizati<strong>on</strong> [2]. All 3d<br />

transiti<strong>on</strong> metal elements show steep n<strong>on</strong>-linear increases of the MCD intensities around 15 T corresp<strong>on</strong>ding to<br />

the metamagnetic transiti<strong>on</strong>. This high-magnetic-field soft x-ray MCD result directly evidences that all magnetic<br />

elements c<strong>on</strong>tribute to the field-induced shape memory effect in the NiCoMnIn alloy.<br />

[1] T. Nakamura et al., Appl. Phys. Express 4, 066602 (2011). [2] R. Kainuma et al., Nature 439, 957 (2006).<br />

190 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RP08<br />

Imaging magnetic resp<strong>on</strong>ses of nanomagnets by X-ray PhotoEmissi<strong>on</strong><br />

Electr<strong>on</strong> Microscopy<br />

Florian Kr<strong>on</strong>ast 1 *, Julia Herrero-albillos 2 , Oliver Sandig 1 , Julia Kurde 1 , T Noll 1 ,<br />

Florian Roemer 3 , Nina Friedenberger 3 and M Farle 3<br />

1<br />

Helmholtz Zentrum Berlin fur Materialien und Energie, Albert-Einstein-Str. 15,<br />

1<br />

2489 Berlin, Germany<br />

2<br />

Centro Universitario de la Defensa, Carretera Huesca s/n, Zaragoza, Spain<br />

3<br />

Universitat Duisburg-Essen, Lotharstr.1, 47048 Duisburg, Germany<br />

The Spin-resolved PhotoEmissi<strong>on</strong> Electr<strong>on</strong> Microscope (SPEEM) is a permanently installed setup at<br />

the X-ray synchrotr<strong>on</strong> radiati<strong>on</strong> source BESSY, Helmholtz-Zentrum Berlin. The capabilities of excellent<br />

spatial resoluti<strong>on</strong> and an energy- and polarizati<strong>on</strong>-tunable light source make this end-stati<strong>on</strong> ideal for<br />

magnetic imaging and micro-spectroscopy with quantitative analysis. The applicati<strong>on</strong> of magnetic fields<br />

while measuring significantly expands the technique of magnetic imaging. A dedicated magnetic sample<br />

holder incorporating both DC and AC magnetic field with additi<strong>on</strong>al temperature c<strong>on</strong>trol has recently<br />

been developed. The SPEEM end-stati<strong>on</strong>, in combinati<strong>on</strong> with this novel sample holder enables the insitu<br />

c<strong>on</strong>trol of the magnetic state and direct observati<strong>on</strong> of the corresp<strong>on</strong>ding magnetic resp<strong>on</strong>se. Two<br />

selected examples dem<strong>on</strong>strate these capabilities: magnetizati<strong>on</strong> curves of individual Fe nanocubes,<br />

and the local magnetic ac susceptibility in and microstructures as a functi<strong>on</strong> of temperature. In the latter<br />

example, a surprising <strong>on</strong>set of finite size effects at the micro-scale has been observed, with a significant<br />

reducti<strong>on</strong> of the ordering temperature in microstructures compared to the extended film. These results were<br />

observed specifically as a result of these improvements in the PEEM technique. In combinati<strong>on</strong> with other<br />

possibilities, such as depth resolved imaging, new insights to magnetic nanostructures can be realized.<br />

RP09<br />

Development of high-sensitivity cantilever-detected ESR measurement<br />

using a fiber-optic interferometer.<br />

Yuki Tokuda 1 , Eiji Ohmichi 2 * and Hitoshi Ohta 3<br />

1 Graduate School of Science, Kobe University, Japan<br />

2 Graduate School of Science,, Kobe University, Japan<br />

3 Molecular Photoscienece Research Center, Kobe University, Japan<br />

Cantilever-detected high-frequency electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) is a powerful method<br />

for terahertz ESR spectroscopy of a tiny magnetic sample at low temperature [1,2]. In this<br />

technique, a small magnetizati<strong>on</strong> change associated with ESR transiti<strong>on</strong> is detected as deflecti<strong>on</strong><br />

of a sample-mounted cantilever. So far, we have succeeded in ESR detecti<strong>on</strong> at 370 GHz using<br />

a commercial piezoresistive microcantilever. The spin sensitivity was estimated to ~1012 spins/<br />

gauss. In order to further increase the sensitivity, we adopt a fiber-optic-based detecti<strong>on</strong> system<br />

using a Fabry-Perot interferometer in place of piezoresistive system. Fabry-Perot cavity is<br />

formed between an optical-fiber end and microcantilever surface, and a change in interference<br />

signal, corresp<strong>on</strong>ding to the cantilever deflecti<strong>on</strong>, is sensitivity detected. This system is suitable<br />

for low-temperature and high-magnetic field experiments because of its compact setup and less<br />

heat dissipati<strong>on</strong>. We will combine our fiber-optic detecti<strong>on</strong> system with a 15 T superc<strong>on</strong>ducting<br />

magnet and BWO light sources covering a wide frequency range 200-1200 GHz. Test<br />

measurement with Co Tutt<strong>on</strong> salt is now in process to estimate the system performance. In the<br />

presentati<strong>on</strong>, details of our experimental setup and test results will be presented.<br />

[1] E.Ohmichi, N. Mizuno, M. Kimata, and H.Ohta, Rev. Sci. Instrum. 79, 103903 (2008) [2]<br />

E.Ohmichi, and T.Osada, Rev. Sci. Instrum 73, 3022 (2002)<br />

RP10<br />

Study of the epitaxial growth and perpendicular magnetic domain<br />

structure of ordered FePt thin film <strong>on</strong> MgO substrate using HRTEM<br />

and electr<strong>on</strong> holography<br />

W. H. Lee 1 , J. H. Yoo 2 , J. M. Yang 2 and J. K. Park 1 *<br />

1<br />

Department of Materials Science and Engineering, Korea Advanced Institute of<br />

Science and Technology, Korea<br />

2<br />

Measurement and Analysis Team, Nati<strong>on</strong>al Nanofab Center, Korea<br />

The epitaxial film of ordered FePt, showing the c-axis normal to the film plane, was<br />

successfully grown <strong>on</strong> top of MgO substrate using DC-magnetr<strong>on</strong> co-sputtering technique.<br />

The electr<strong>on</strong> holography study showed that a columnar epitaxial film displayed <strong>on</strong>ly a weak<br />

stray-field signal due to the presence of columnar boundaries. The growth of a c<strong>on</strong>tinuous<br />

(full) epitaxial film however revealed characteristic Lorentz TEM images for the perpendicular<br />

magnetic domains. The electr<strong>on</strong> hologram indicated the presence of the stray-fields of inducti<strong>on</strong><br />

originating from the perpendicular magnetizati<strong>on</strong>s. It was shown that the sense of stray fields<br />

and thus the sense of perpendicular magnetizati<strong>on</strong>s could be determined by analyzing the<br />

c<strong>on</strong>tracti<strong>on</strong> and expansi<strong>on</strong> behavior of hologram fringes which were parallel to the reference<br />

fringes. Furthermore, direct hologram informati<strong>on</strong> was detected in a thicker epitaxial film by<br />

applying high resoluti<strong>on</strong> electr<strong>on</strong> holography. Perpendicular magnetic domain structure was<br />

directly revealed in the unwrapped phase image and was c<strong>on</strong>firmed by the measurement of the<br />

line profile of phase-shift. The estimati<strong>on</strong> of the local strength indicated that the perpendicular<br />

inducti<strong>on</strong> strength was varying from about 0.33T to about 0.61T depending <strong>on</strong> the domain size.<br />

The variati<strong>on</strong> of inducti<strong>on</strong> strength was due to a weak ordering of the film.


RP11<br />

Asteroid curve of GMR films <strong>on</strong> the practical substrate under the<br />

stress<br />

Kazuhiko Okita 1 , Kazushi Ishiyama 2 and Hideo Miura 3<br />

1 Industrial Instrumentati<strong>on</strong> Divisi<strong>on</strong>, Tohoku Steel Co., L7td., Japan<br />

2 Research Institute of Electrical Communicati<strong>on</strong>, Tohoku University, Japan<br />

3 Department of Nanomechanics, Graduate School of Engineering, Tohoku University,<br />

Japan<br />

Magnetic thin films usually have some of magnetostricti<strong>on</strong> effect. After forming electric devices,<br />

this effect sometimes deteriorates the sensitivity of sensors such as read heads of hard disk drives,<br />

HDD, or the bit stability of memories such as magnetic random access memories, MRAM,<br />

through the inverse magnetostricti<strong>on</strong> phenomen<strong>on</strong>. We need, therefore, to understand the<br />

magnetostricti<strong>on</strong> effect <strong>on</strong> a film deposited <strong>on</strong> an actual wafer and the influence from the stress<br />

to it. In the previous paper, we showed the novel method of measuring the magnetostricti<strong>on</strong><br />

c<strong>on</strong>stant <strong>on</strong> the practical substrate [1]. In this paper, by using this method we measured the<br />

asteroid curves of the magnetic thin film of the giant magnetoresistance, GMR, <strong>on</strong> the practical<br />

wafer with varying applied stress <strong>on</strong> it. This result showed that the coercive force parallel to the<br />

easy axis, Hc, of a magnetic thin film with a negative sign of magnetostricti<strong>on</strong> c<strong>on</strong>stant was<br />

decreasing with increasing tensile stress and the coercive force parallel to the hard axis, Ha,<br />

was also decreasing. For the film with the positive sign <strong>on</strong>e, Hc and Ha were increasing with<br />

increasing tensile stress. And we showed the Hc was roughly proporti<strong>on</strong>al to the applied stress.<br />

[1] K. Okita, K. Ishiyama and H. Miura, 'Magnetostricti<strong>on</strong> Measurement of GMR Films <strong>on</strong> the<br />

practical substrate', Journal of Physics, <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series 200 (2010) 112008<br />

RP12<br />

Micromagnetic study <strong>on</strong> the perturbative effect of magnetic force<br />

microscopy probes <strong>on</strong> 90° asymmetric Neel walls in a soft magnetic material<br />

Hir<strong>on</strong>ori Asada 1 *, Hidenori Kubo 1 , Hazrina Abu Seman 1 , Takashi Manago 2 and<br />

Hiromi Kuramochi 3<br />

1<br />

Yamaguchi University, Japan<br />

2<br />

Fukuoka University, Japan<br />

3<br />

Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

It is important to clarify the dependence of perturbative effect of MFM probes up<strong>on</strong> probe parameters and<br />

experimental c<strong>on</strong>diti<strong>on</strong>s[1]. In this study, 3D micromagnetic simulati<strong>on</strong> has been performed to evaluate<br />

the perturbative effects <strong>on</strong> magnetizati<strong>on</strong> states and force gradient signals of 90° asymmetric Neel walls<br />

in a 100nm-thick patterned permalloy film. The signals are computed by varying the positi<strong>on</strong> of the probe<br />

assuming the stripe shape. The different signal distorti<strong>on</strong>s are observed depending up<strong>on</strong> the combinati<strong>on</strong><br />

of the out-of-plane comp<strong>on</strong>ent of the magnetizati<strong>on</strong> directi<strong>on</strong> of wall and the magnetizati<strong>on</strong> directi<strong>on</strong> of<br />

the probe. In the parallel case, signal asymmetry originated from the asymmetric wall structure is enhanced<br />

and the normalized c<strong>on</strong>trast defined as the difference of the maximum and minimum values of the signal<br />

divided by probe saturati<strong>on</strong> magnetizati<strong>on</strong>(Ms) is increased. In the antiparallel case, signal asymmetry<br />

is suppressed and the normalized c<strong>on</strong>trast is decreased. When probe Ms is increased further (antiparallel<br />

case), the out-of-plane comp<strong>on</strong>ent directi<strong>on</strong> of wall is reversed being accompanied by the jump of the<br />

Neel cap positi<strong>on</strong>s. The probe Ms dependences of signal distorti<strong>on</strong>s such as c<strong>on</strong>trast variati<strong>on</strong> and distance<br />

change between the signal peaks which corresp<strong>on</strong>d to the measured wall width are also presented.<br />

[1] J. M. Garcia, et al., Appl. Phys. Lett. 79, 656 (2001).<br />

RP13<br />

Development of a n<strong>on</strong>-c<strong>on</strong>venti<strong>on</strong>al ESR spectrometer with a<br />

composite antenna system and an electr<strong>on</strong>ically c<strong>on</strong>trolled tuning and<br />

matching circuit<br />

Alexey P<strong>on</strong>omaryov 1 , Kwang Y<strong>on</strong>g Choi 2 , Byoungjin Suh 3 and Zeeho<strong>on</strong> Jang 4 *<br />

1<br />

Physics, Chungang University, Korea<br />

2<br />

Physics, Chungang, Korea<br />

3<br />

Physics, The Catholic University of Korea, Korea<br />

4<br />

Physics, Kookmin University, Korea<br />

We present a new development of n<strong>on</strong>-c<strong>on</strong>venti<strong>on</strong>al Electr<strong>on</strong> Spin Res<strong>on</strong>ance (ESR) spectrometer, in which the<br />

sweeping frequency is available in the wide range of frequency. This is a modificati<strong>on</strong> of the previous system<br />

without using a cavity and with two antennas <strong>on</strong>e for the microwave transmissi<strong>on</strong> and the other for the ESR<br />

signal detecti<strong>on</strong>.[1] In c<strong>on</strong>trast to previous work[1], utilizati<strong>on</strong> of microstrip antenna as a transmitter provided<br />

us the capability of wide-frequency operati<strong>on</strong> between 0.8 and 10 GHz. On the other hand, the use of loop<br />

antenna as a detector with tuning and matching circuit enhanced ESR signal. In order to simplify tuning and<br />

matching circuit and make res<strong>on</strong>ance c<strong>on</strong>diti<strong>on</strong> easily reproducible, c<strong>on</strong>venti<strong>on</strong>al capacitors were replaced with<br />

varactor diodes. This allowed us to avoid any mechanical acti<strong>on</strong> during tuning and matching procedure, since the<br />

capacitance of the diodes was changed by applying different DC voltages. Compared to Ref.[1], such a scheme<br />

increased S/N ratio several times in a wide frequency range. For testing the developed system, a homemade<br />

magnet with water-cooling system was used. The efficiency of the ESR spectrometer was checked by measuring<br />

a signal of 1,1-diphenil-2-picrylhydrazyl (DPPH) sample at different frequencies at room temperature.<br />

[1] Z. H. Jang, B. J. Suh, M. Corti, L. Cattaneo, D. Hajny, F. Borsa, and M. Luban, Rev. Sci. Instrum. 79, 46101 (2008).<br />

RP14<br />

RP15<br />

RP16<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A new type of spin-polarized scanning tunneling microscopy for<br />

observing an in-plane magnetizati<strong>on</strong> comp<strong>on</strong>ent with high resoluti<strong>on</strong><br />

Daichi Nara 1 , Takuya Nakamura 1 , Atsuhiko Nakamoto 1 , Ryu Kageyama 1 , Elaiyaraju<br />

Srinivasan 2 , Kazuyuki Koike 1 and Hideo Matsuyama 1 *<br />

1 Department of Physics, Faculty of Science, Hokkaido University, Japan<br />

2 Creative Research Instituti<strong>on</strong> (CRIS), Hokkaido University, Japan<br />

To obtain a high resoluti<strong>on</strong> image routinely even from the rough surface of a ferromagnetic<br />

sample with a spin-polarized scanning tunneling microscope (SP-STM) operating in<br />

modulating tip magnetizati<strong>on</strong> mode [1], we have developed an SP-STM using a micrometersized<br />

magnetic tip integrated <strong>on</strong>to the magnetic recording head of a hard disk drive. The tip<br />

apex was formed into a round shape with a diameter of less than <strong>on</strong>e micrometer by using a<br />

focused i<strong>on</strong> beam instrument. Driving the recording head with a signal generator to switch<br />

the magnetizati<strong>on</strong> of the tip apex periodically generates an unnecessary artificial current flow<br />

into a current-to-voltage (IV) c<strong>on</strong>verter through stray capacitance, which prevents detecti<strong>on</strong><br />

of the spin-polarized tunneling current precisely. To reduce the artificial current, we added a<br />

homemade circuit that generates a countercurrent against the artificial current into the input<br />

of the IV c<strong>on</strong>verter. We tried to image both the topography and the spin polarizati<strong>on</strong> of an<br />

ir<strong>on</strong> thin film deposited <strong>on</strong> a magnetic recording medium whose local roughness was <strong>on</strong><br />

the order of several nanometers due to the crystal grains of the medium. This is the first spin<br />

image of a magnetic thin film having such a rough surface obtained with an SP-STM.<br />

[1] U. Schlickum, W. Wulfhekel, and J. Kirschner, Appl. Phys. Lett. 83, 2016 (2003).<br />

Violati<strong>on</strong> of Hund's third rule in structurally disordered ferromagnets<br />

Vassilios Kapaklis 1 *, Panagiotis Korelis 1 , Bjorgvin Hjorvarss<strong>on</strong> 1 , Athanasios Vlachos 2 ,<br />

Iossif Galanakis 3 , Panagiotis Poulopoulos 3 , K. Ozdogan 4 , Makis Angelakeris 5 , Fabrice<br />

Wilhelm 6 and Andrei Rogalev 6<br />

1 Department of Physics and Astr<strong>on</strong>omy, Uppsala University, Sweden<br />

2 Department Materials Science, University of Patars, Greece<br />

3 Department Materials Science, University of Patras, Greece<br />

4 Department of Physics, Yildiz Technical University, Turkey<br />

5 Department of Physics, Aristotle University of Thessal<strong>on</strong>iki, Greece<br />

6 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, France<br />

Violati<strong>on</strong> of Hund's third rule caused by structural disorder is observed for the induced<br />

magnetic moment of Zr, using x-ray magnetic circular dichroism. The induced spin<br />

and orbital magnetic moments are antiparallel in the crystalline state, but parallel in<br />

an amorphous state of the investigated Co- and Fe-based materials. First-principles<br />

calculati<strong>on</strong>s are used to provide physical insight into the dependency of the spin-orbit<br />

coupling <strong>on</strong> the interatomic distance and coordinati<strong>on</strong> number.<br />

V. Kapaklis, P. T. Korelis, B. Hjorvarss<strong>on</strong>, A. Vlachos, I. Galanakis, P. Poulopoulos, K. Ozdogan,<br />

M. Angelakeris, F. Wilhelm, and A. Rogalev, Violati<strong>on</strong> of Hund's third rule in structurally disordered<br />

ferromagnets, Phys. Rev. B 84, 024411 (2011).<br />

Bulk Cr tips with full spatial magnetic sensitivity for spin-polarized<br />

scanning tunneling microscopy<br />

Anika Schlenhoff, Andreas S<strong>on</strong>ntag*, Stefan Krause, Gabriela Herzog and Roland<br />

Wiesendanger<br />

University of Hamburg, Germany<br />

Spin-polarized scanning tunneling microscopy (SP-STM) is a powerful technique<br />

to access the magnetic properties of a surface <strong>on</strong> the atomic scale. Here, magnetic<br />

tips are usually prepared by extensive in-situ metal evaporati<strong>on</strong>, demanding for a tip<br />

exchange mechanism inside the microscope. Using magnetic bulk tips is an elegant<br />

way to circumvent these efforts. For example, bulk chromium tips are reported to be<br />

suitable for SP-STM, exhibiting an in-plane magnetic sensitivity [1]. Since they are<br />

antiferromagnetic, their influence <strong>on</strong> the sample magnetizati<strong>on</strong> in terms of stray field<br />

interacti<strong>on</strong> is negligible. We perform SP-STM experiments <strong>on</strong> the sample system<br />

of 1.8 atomic layers Fe/W(110) with the magnetizati<strong>on</strong> lying in the plane <strong>on</strong> the<br />

m<strong>on</strong>olayer and pointing perpendicular to the plane <strong>on</strong> the double layer [2]. Our study<br />

dem<strong>on</strong>strates that Cr bulk tips can be used to image the complete magnetic structure<br />

and hence are sensitive to both the in-plane as well as the out-of-plane-comp<strong>on</strong>ent of<br />

sample magnetizati<strong>on</strong> [3]. Analyzing magnetic SP-STM maps enables the full spatial<br />

characterizati<strong>on</strong> of the tip.<br />

[1] A. L. Bassi et al., Appl. Phys. Lett. 91, 173120 (2007). [2] M. Pratzer et al., Phys. Rev. Lett. 87,<br />

127201 (2001). [3] A. Schlenhoff et al., Appl. Phys. Lett. 97, 083104 (2010).<br />

July 8 - 13, 2012 Busan, Korea 191<br />

Poster Thursday


Poster Thursday<br />

RP17<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Polarizati<strong>on</strong> state of scattered light in apertureless reflecti<strong>on</strong>-mode<br />

magneto-optical scanning near-field optical microscopy<br />

Y<strong>on</strong>gfu Cai1, Mitsuharu Aoyagi 1 , Sanyalak Niratisairak 1 , Akira Emoto 2 , Tatsutoshi<br />

Shioda 3 and Takayuki Ishibashi 1 *<br />

1<br />

Department of materials science and technology, Nagaoka University of Technology,<br />

Japan<br />

2<br />

Nati<strong>on</strong>al institute of advanced industrial science and technology (AIST), Japan<br />

3<br />

Department of Electrical Engineering, Nagaoka University of Technology, Japan<br />

Magneto-optical scanning near-field optical microscopy (MO-SNOM) has attracted attenti<strong>on</strong> because of its<br />

high spatial resoluti<strong>on</strong> in magnetic imaging. We are developing a reflecti<strong>on</strong>-mode apertureless scanning nearfield<br />

optical microscopy (a-SNOM). The sample is a patterned Chromium film with a thickness of 20nm<br />

deposited <strong>on</strong> a glass substrate. The a-SNOM images are measured with Si tip that has an extremity’s radius<br />

of 7nm, and with an illuminati<strong>on</strong> of 408 nm with an incident angle of 45 degree. Scattered light caused by an<br />

interacti<strong>on</strong> between the near-field wave and the sample was measured as a signal for a-SNOM image. Finitedifference<br />

time-domain (FDTD) method was used to calculate the polarizati<strong>on</strong> state of the scattered light. The<br />

a-SNOM images of Cr patterns were successfully obtained with a spatial resoluti<strong>on</strong> of 30-40nm. In additi<strong>on</strong>,<br />

we found that the extincti<strong>on</strong> rati<strong>on</strong> of the scattered light back to the same directi<strong>on</strong> with the incidence was<br />

better than 100, which is an enough polarizati<strong>on</strong> property for obtaining MO images. FDTD simulati<strong>on</strong><br />

reproduced that the scattered light preserved its polarizati<strong>on</strong> state. These results showed that the a-SNOM is a<br />

promising technique to obtain high-resoluti<strong>on</strong> magnetic images with a resoluti<strong>on</strong> of several tens nm.<br />

[1] E. Betzig, et. al., Appl. Phys. Lett. 61,142(1992). [2] Y. Mitsuoka, et. al., J. Appl. Phys. 83,<br />

3998(1998). [3] T. Yoshida, et. al., J. Magn. Soc. Jpn. 23,1960(1999).<br />

RP18<br />

Applicati<strong>on</strong> of image processing to determine size distributi<strong>on</strong> of<br />

magnetic nanoparticles<br />

Udomchok Phromsuwan 1 *, Yaowarat Sirisathitkul 2 , Chitnar<strong>on</strong>g Sirisathitkul 1 and<br />

Bunyarit Uyyan<strong>on</strong>vara 3<br />

1 School of Science, Walailak University, Thailand<br />

2 School of Informatics, Walailak University, Thailand<br />

3 School of Informati<strong>on</strong>, Computer and Communicati<strong>on</strong> Technology (ICT), Sirindhorn<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Institute of Technology (SIIT), Thammasat University., Thailand<br />

Digital image processing has increasingly been implemented in analyzing micro- and<br />

nanostructured materials and would be an ideal tool to characterize the morphology and<br />

positi<strong>on</strong> of self-assembled magnetic nanoparticles for high density recording. In this<br />

work, magnetic nanoparticles were synthesized by the modified polyol process using<br />

Fe(acac) 3 and Pt(acac) 2 as starting materials. Transmissi<strong>on</strong> electr<strong>on</strong> microscopy (TEM)<br />

images of an as-synthesized product were taken with a resoluti<strong>on</strong> of 800 x 800 pixels,<br />

72 dot per inch and then inspected using image processing algorithms <strong>on</strong> MatLab.<br />

The grayscale image was c<strong>on</strong>verted to a binary image by using Otsu’s thresholding.<br />

An individual particle was then detected by using the closing algorithm with disk<br />

structuring elements and the canny edge detecti<strong>on</strong>. The areas of detected particles were<br />

filled and small objects were removed. A centroid, diameter and area of each particle<br />

were finally evaluated. The average diameter is 4.62 nm with a standard deviati<strong>on</strong> of<br />

0.52 nm. The degree of polydispersity of magnetic nanoparticles can then be compared<br />

using size distributi<strong>on</strong> from the image processing.<br />

RP19<br />

Microfabricati<strong>on</strong> of a MEMS cantilever for mechanically detected<br />

high-frequency ESR measurement<br />

Eiji Ohmichi 1 *, Yoshimasa Yasufuku 2 and Hitoshi Ohta 3<br />

1 Graduate School of Science, Kobe University, Japan<br />

2 Graduate School of Science, Kobe University, Japan<br />

3 Molecular Photoscience Research Center, Kobe University, Japan<br />

Mechanically detected high-frequency electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) is a promising<br />

tool for high-resoluti<strong>on</strong> terahertz (THz) ESR spectroscopy of tiny magnetic samples.<br />

So far we succeeded in multi-frequency ESR detecti<strong>on</strong> for 80-370 GHz and achieved<br />

a spin sensitivity <strong>on</strong> the order of 10 9 spins/Gauss[1,2]. In this study, a prototype<br />

microcantilever is fabricated in order to further improve the sensitivity and flexibility<br />

of our ESR measurement system. Microcantilevers are fabricated from silic<strong>on</strong>-<strong>on</strong>insulator<br />

(SOI) wafers using standard MEMS techniques such as lithography, wet<br />

etching, and RIE. By using commercial SOI wafers, fabricati<strong>on</strong> cost and the number<br />

of process can be substantially reduced. Two types of cantilevers for capacitive<br />

and optical detecti<strong>on</strong> are fabricated in this study. The former has lateral dimensi<strong>on</strong>s<br />

of 4 mm x 8 mm, and is anodically b<strong>on</strong>ded to a glass substrate to form capacitive<br />

electrodes. The latter has dimensi<strong>on</strong>s of 50 μm x 200 μm, and is equipped with a gold<br />

mirror for Fabry-Perot detecti<strong>on</strong>. Applicati<strong>on</strong> to high-frequency ESR measurement is<br />

now in progress and details will be reported in the presentati<strong>on</strong>.<br />

[1]E. Ohmichi, N. Mizuno, M. Kimata, and H. Ohta, Rev. Sci. Instrum. 79 (2008) 103903. [2]E.<br />

Ohmichi, N. Mizuno, S. Hirano, and H. Ohta, J. Low Temp. Phys. 159 (2010) 276.<br />

192 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RP20<br />

2D reflecti<strong>on</strong>-type electr<strong>on</strong> spin filter increasing the detecti<strong>on</strong> efficiency<br />

in spinresolved spectroscopy by 4 orders of magnitude<br />

D Kutnyakhov 1 , M Kolbe 1 , P Lushchyk 1 , M Jourdan 1 , K Medjanik 1 , S A Nepijko 1 ,<br />

H J Elmers 1 , C Tusche 2 , J Kirschner 2 , F Giebels 3 , H Gollisch 3 , R Feder 3 and G<br />

Schoenhense 1 *<br />

1 Institute of Physics, University of Mainz, Germany<br />

2 Max Planck Institute of Microstructure Physics, Germany<br />

3 Theoretische Festkoerperphysik, Universitaet Duisburg-Essen, Germany<br />

Spin-resolved electr<strong>on</strong> spectroscopy is characterized by a low figure of merit FoM= S²I/Io typically 10 -4 ; S<br />

spin sensitivity, I/Io reflectivity. Electr<strong>on</strong> diffracti<strong>on</strong> from W(001) in the (00) LEED spot facilitates parallel<br />

detecti<strong>on</strong> of 3800 data points in our imaging spin filter behind a PEEM [1], and 960 behind a hemispherical<br />

energy analyzer [2]. We achieved a “2D FoM” of 1.7 being four orders of magnitude higher than the previous<br />

value. We further studied the dependence of the spin sensitivity and reflectivity as a functi<strong>on</strong> of scattering<br />

energy and angle of incidence. The experimental setup includes a spin-polarized GaAs electr<strong>on</strong> source,<br />

hemispherical analyzer and a Delaylinedetector. Intensities, spin-orbit-coupling induced asymmetries and FoM<br />

were calculated via a relativistic layer KKR SPLEED code [3]. The superior performance of multichannel spin<br />

detecti<strong>on</strong> facilitates experiments <strong>on</strong> highly reactive surfaces like in-situ prepared Heusler films [4] or radiati<strong>on</strong>sensitive<br />

organic layers [5] and paves the way to single-shot experiments at ultra bright fs-sources like FELs.<br />

Funded by DFG (Scho341/9), Stiftung Innovati<strong>on</strong> (project 886) and centre of complex materials COMATT.<br />

[1] C. Tusche et al., APL 99 (2011) 032505; [2] M. Kolbe et al., PRL 107 (2011) 207601; [3] R.<br />

Feder, Polarized Electr<strong>on</strong>s in Surface Physics (World Scientific, Singapore, 1985); [4] M. Hahn et<br />

al., APL 98 (2011) 232503; [5] K. Medjanik et al., JACS 134 (2012) 4694<br />

RP21<br />

Element selective magnetizati<strong>on</strong> measurements under high magnetic<br />

field<br />

Andrei Rogalev* and Fabrice Wilhelm<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility, France<br />

X-ray Magnetic Circular Dichroism (XMCD) spectroscopy is a well-established<br />

experimental tool to study the microscopic origin of magnetism allowing <strong>on</strong>e to determine<br />

separately spin and orbital magnetic moments of each element in both amplitude and<br />

directi<strong>on</strong>. So far, XMCD has been extensively used to investigate mainly ferro- or<br />

ferrimagnetic materials, and <strong>on</strong>ly very few studies have been performed <strong>on</strong> paramagnetic<br />

compounds. In this presentati<strong>on</strong> we describe first a new experimental set-up dedicated to<br />

high field XMCD measurements that has been recently installed at the ESRF beamline<br />

ID12. Static magnetic field of up to 17 Tesla is generated by a superc<strong>on</strong>ducting solenoid.<br />

The sample is mounted <strong>on</strong> a cold finger of a He c<strong>on</strong>tinuous flow cryostat allowing to<br />

set the temperature in the range from 2.2 K to 300 K with a stability of about 100 mK.<br />

Performances of this set-up are illustrated with results of element selective magnetizati<strong>on</strong><br />

measurements in various systems: (i) Intrinsic magnetic moment in gold nanoparticles<br />

grown <strong>on</strong>to naturally thiol-c<strong>on</strong>taining proteinatious archaeal surface layer has been<br />

evidenced by field dependent XMCD at the Au L2,3-edges[1]; (ii) Extrinsic origin of<br />

room temperature ferromagnetism in diluted magnetic semic<strong>on</strong>ductors has been proven<br />

with field and temperature dependent XMCD measurements[2].<br />

[1] S. Selenska-Pobell et al., Nanomater. nanotechnol., 1 (2011), 8 [2] A. Ney et al., New J. Phys., 13 (2011) 103001<br />

RP22<br />

POLI: The new single crystal polarized neutr<strong>on</strong> diffractometer for<br />

investigati<strong>on</strong> complex magnetic structures at FRM-II<br />

Vladimir Hutanu*, Martin Meven, Gernot Heger and Georg Roth<br />

Institut fur Krystallographie, RWTH Aachen University, Germany<br />

POLI is a new single crystal polarized neutr<strong>on</strong> diffractometer [1] at the hot source<br />

of the 'Forschungsneutr<strong>on</strong>enquelle Heinz Maier-Leibnitz' (FRM-II) in Garching,<br />

Germany. It is designed to perform spherical neutr<strong>on</strong> polarimetry (SNP) in zero field<br />

as well as classical polarized neutr<strong>on</strong> diffracti<strong>on</strong> (PND) measurements (flipping ratio)<br />

under applied magnetic fields. Am<strong>on</strong>g the intended applicati<strong>on</strong>s of this instrument are:<br />

complex magnetic structures and magneto-electric coupling in multiferroics, magnetic<br />

structure and spatially resolved spin densities in molecular magnets, magnetically<br />

ordered superc<strong>on</strong>ductors, str<strong>on</strong>gly correlated transiti<strong>on</strong> metal oxides and spin<br />

chain compounds. The instrument is unique in the sense that it combines a variable<br />

wavelength focussing m<strong>on</strong>ochromator with the use of 3He spin-filter cells (SFC) to<br />

create polarized, short wavelength neutr<strong>on</strong>s. A new zero-field polarimeter Cryopad [2,<br />

3] has been built in cooperati<strong>on</strong> between RWTH and ILL. On the detector side, the<br />

polarisati<strong>on</strong>-analysis and detecti<strong>on</strong> unit DECPOL (again with 3He-spin filter cells) is<br />

used. This setup called 'POLI-HEIDI' is operati<strong>on</strong>al and open for users at FRM-II over<br />

JCNS proposal system. Its properties will be dem<strong>on</strong>strated in this talk.<br />

[1] V. Hutanu, M. Meven, E. Lelievre-Berna, G. Heger, Physica B 404, 2633 (2009). [2] F. Tasset,<br />

Physica B 156-157, 627 (1989). [3] E. Lelievre-Berna, “Novel polarized neutr<strong>on</strong> tools”, I. Anders<strong>on</strong><br />

& B. Guerard, Editors, Proceedings of SPIE 4785, 112-125 (2002).


RP23<br />

Observati<strong>on</strong> of the magnetic domain using scanning electr<strong>on</strong><br />

microscopy with polarizati<strong>on</strong> analysis<br />

Sang Sun Lee, Mo<strong>on</strong> Seob Bae, W<strong>on</strong>d<strong>on</strong>g Kim and Chany<strong>on</strong>g Hwang*<br />

Korea Research Institute of Standards and Science, Korea<br />

We have developed a scanning electr<strong>on</strong> microscope with polarizati<strong>on</strong> analysis(SEMPA<br />

or spin-SEM) for the nano-scale observati<strong>on</strong> of magnetic domain structure. A typical<br />

micro Mott type spin detector with 25 kV operating voltage, shows the effective<br />

Sherman functi<strong>on</strong> in the range between -0.3~-0.35, which is relatively low valued. In<br />

order to get higher Sherman functi<strong>on</strong>, we optimized all geometrical factors and the<br />

accelerating voltage. First, we tried M<strong>on</strong>te Carlo simulati<strong>on</strong> by increasing operating<br />

voltage from 25 kV to 50 kV. At 40 kV of accelerati<strong>on</strong> voltage with optimized 120<br />

degrees of scattering angle, a better effective Sherman functi<strong>on</strong> was obtained compared<br />

with the value operated at 25 kV(-0.5 : -0.3). Base <strong>on</strong> this simulati<strong>on</strong>, we have<br />

developed the high-efficiency Mott spin detector with 40 kV operating voltage. Also<br />

a sec<strong>on</strong>dary electr<strong>on</strong> deflector, and transfer lens system has been optimized. In order<br />

to test performance of the new spin detector, the thick Fe film sample was prepared <strong>on</strong><br />

Si substrate using an evaporati<strong>on</strong> method. We will show several different images of Fe<br />

films depending <strong>on</strong> the oxidati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>.<br />

RQ01<br />

Precisi<strong>on</strong> broadband ac measurement system for magnetotransport,<br />

magnetopolarizati<strong>on</strong> and magnetoelectric properties<br />

Jun Lu*, Baogen Shen and Xiaoping Shao<br />

State Key Laboratory of <strong>Magnetism</strong>, Institute of Physics, Chinese Academy of<br />

Sciences, China<br />

For complex or str<strong>on</strong>gly correlated magnetic materials, broadband ac measurements<br />

provide much richer dynamic informati<strong>on</strong> than static or quasistatic measurements,<br />

which would help <strong>on</strong>e to understand more clearly how magnetic materials of interest<br />

resp<strong>on</strong>d to various external excitati<strong>on</strong>s. After many-year researches, we have developed<br />

a suite of precisi<strong>on</strong> broadband ac magnetic measurement system based <strong>on</strong> novel<br />

broadband digital lock-in amplifier techniques, which can work from sub 1 Hz to above<br />

1 GHz. In additi<strong>on</strong> to multi-channel lock-in amplifier techniques, to realize broadband<br />

ac transporting and polarizability measurement from sub 1 Hz to above 100 MHz,<br />

transmissi<strong>on</strong>-line bridge compensati<strong>on</strong> techniques have been used so as to measure<br />

complex ac magnetoresistance and Hall coefficient simultaneously in a precisi<strong>on</strong> way.<br />

Broadband ac magnetoelectric measurement system has also been set up for evaluating<br />

complex magnetoelectric coupling coefficient, which including not <strong>on</strong>ly magnitude but<br />

also phase lag. For various magnetotransport and magnetoelectric measurements, we<br />

have developed measuring software which supports fully automatic tests.<br />

[1] J. Lu et al., Meas. Sci. Technol., 19, 045702-6(2008) [2] J. Lu et al., IEEE Trans. Magn., 44(9),<br />

2127-9(2008) [3] J. Lu et al., A kind of precisi<strong>on</strong> broadband anti-noise lock-in frequencymeter,<br />

Chinese Patent, 201110380805.X<br />

RQ02<br />

Detecti<strong>on</strong> of magnetic beads using an extraordinary magnetoresistance<br />

sensor fabricated with unpatterned semic<strong>on</strong>ductor substrate<br />

Jian Sun* and Jurgen Kosel<br />

King Abdullah University of Science and Technology, Saudi Arabia<br />

A str<strong>on</strong>g geometry dependent magnetoresistance effect, the so-called extraordinary<br />

magnetoresistance (EMR), has been observed in semic<strong>on</strong>ductor/metal hybrid<br />

structures. It is based <strong>on</strong> the redistributi<strong>on</strong> of the current from the metal shunt into<br />

the semic<strong>on</strong>ductor causes by the Lorentz force. A typical EMR device c<strong>on</strong>sists of a<br />

patterned semic<strong>on</strong>ductor mesa and metal shunt. When the dimensi<strong>on</strong>s of the device<br />

are reduced, for example, to increase the sensitivity, the alignment of the metal c<strong>on</strong>tact<br />

with the semic<strong>on</strong>ductor bar becomes more difficult. Furthermore, the patterning<br />

process inescapably causes some damage to the semic<strong>on</strong>ductor thereby reducing the<br />

performance. In this work, we report a new EMR device fabricati<strong>on</strong> process, which<br />

does not require patterning of the semic<strong>on</strong>ductor substrate reducing the complexity of<br />

the fabricati<strong>on</strong> and omitting any kind of damage of the semic<strong>on</strong>ductor. The sensitivity<br />

of this device is 0.58 μT/√Hz, which is twice as high as the <strong>on</strong>e of the patterned sensor.<br />

The device is employed to detect superparamagnetic beads of 2.8 μm in diameter,<br />

which is the first time this is dem<strong>on</strong>strated with an EMR sensor. Applying the beads to<br />

the sensor surface results in a voltage signal of 100 μV.<br />

RQ03<br />

RQ04<br />

RQ05<br />

Ac Calorimetry under Pulsed High Magnetic Field<br />

Yuji Inagaki 1 , Tatsuya Kawar 1 , Akira Matsuo 2 and Koichi Kindo 2<br />

1 applied quantum physics, kyushu university, Japan<br />

2 institute for solid state physics, the university of tokyo, Japan<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetizati<strong>on</strong> of single ferromagnetic-grain obtained from<br />

observati<strong>on</strong> of field-induced-translati<strong>on</strong> in a chamber-type μg system.<br />

Chiaki Uyeda 1 , Kenta Kuwada 2 and Keiji Hisayoshi 2<br />

1 Graduate School of Science, Osaka university, Japan<br />

2 Graduate school of Science, Osaka university, Japan<br />

A new principle to measure saturated magnetizati<strong>on</strong> Ms of a single ferromagnetic-grain<br />

is proposed, which is based <strong>on</strong> free translati<strong>on</strong> of the grain caused by field-gradient force.<br />

The moti<strong>on</strong>s were observed in a diffused (~10Pa) μG c<strong>on</strong>diti<strong>on</strong> (0.01G). It is c<strong>on</strong>firmed<br />

for the first time that a classical c<strong>on</strong>servati<strong>on</strong> rule between field-induced potential and<br />

kinetic energy is c<strong>on</strong>served for a translating magnetic-grain. Accordingly, Ms is obtained<br />

from the relati<strong>on</strong>ship between sample velocity and field intensity observed at different<br />

sample positi<strong>on</strong>s. The Ms value is obtained even for a nano-sized sample, provided that<br />

translati<strong>on</strong> is observed by an ultra-violet fluorescence microscope [1]. This is because the<br />

method does not require mass measurement; it is also free of the interfering signal emitted<br />

from a sample holder [1]. The above two factors has been the major problem in detecting<br />

magnetizati<strong>on</strong> of single grain in c<strong>on</strong>venti<strong>on</strong>al methods. A chamber-type drop shaft to<br />

produce μG, which can be introduced in an ordinary laboratory, was newly developed<br />

to realize routine Ms measurement. Here, size of drop capsule was reduced to 30cm in<br />

diameter by introducing a magnetic circuit composed of an NdFeB permanent magnet.<br />

[1] C.Uyeda et al: Jpn. Phys. Soc. Jpn. 79, 064709 (2010).<br />

applicati<strong>on</strong> of magnetoimpedance effect for protein biomarker<br />

detecti<strong>on</strong><br />

D.g. Park and Ho<strong>on</strong> S<strong>on</strong>g<br />

korea atomic energy research institute, Korea<br />

Ultra-low c<strong>on</strong>centrati<strong>on</strong> detecting of biomolecules, has gain increasing interest since<br />

various protein biomarkers for cancer or chr<strong>on</strong>ic diseases are present at very low levels<br />

at the early stages of the disease development [1].In this work, we present the results of<br />

the development of a sensor prototype working in a principle of label free for m<strong>on</strong>itoring<br />

the effects <strong>on</strong> the immobilizati<strong>on</strong> of the biomolecular using giant magnetoimpedance.<br />

Amorphous ribb<strong>on</strong>s were tested in different biomoleculars. The MI resp<strong>on</strong>se of the<br />

sensive elements made from ribb<strong>on</strong>s was measured with a various biomolecular in<br />

order to dem<strong>on</strong>strate the capacity of m<strong>on</strong>itoring the immobilizati<strong>on</strong> of biomolecule. To<br />

dem<strong>on</strong>strate the sensitivity and specificity of this GMI sensor platform for biomolecule<br />

detecti<strong>on</strong> and quantificati<strong>on</strong>, we have used this platform to successfully detect and<br />

quantify the biomolecules. To apply to the real biomarker and verify the sensitivity of<br />

GMI-based magnetic sensor, we used the biomarker scheme using the applied the real<br />

protein <strong>on</strong> the magnetic sensor surface. The capture antibodies (P21 m<strong>on</strong>o antibody)<br />

are first immobilized <strong>on</strong> the positive magnetic sensor surfaces. The advantage of this<br />

approach c<strong>on</strong>sists in the possibility to design a biosensor with enhanced sensitivity and<br />

the applicati<strong>on</strong> for detecti<strong>on</strong> of small amounts of biomolecules.<br />

[1] M. Gomez and G. Silvestri, “Lung cancer screening,” Am. J. Med. Sci., vol. 335, pp. 46-50,<br />

2008<br />

Ac calorimetry measurement adapted for use of the pulsed high magnetic field will be<br />

presented. This technique is quite useful to investigate the thermal properties under<br />

high magnetic field bey<strong>on</strong>d the steady magnetic field range. In additi<strong>on</strong>, it is also<br />

possible to capture a transient phenomena under fast sweep magnetic field. Resultant<br />

examples will be presented in detail.<br />

July 8 - 13, 2012 Busan, Korea 193<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RQ06<br />

Specific heat and thermal expansi<strong>on</strong> of Sr 1-xCa xRuO 3<br />

Rasna Thakur 1 *, Archana Srivastava 2 , Rajesh K. Thakur 1 and N.k. Gaur 1<br />

1 Department of Physics, Barkatullah University, Bhopal, India<br />

2 Department of Physics, Sri Satya Sai College for Women, Bhopal, India<br />

We have investigated the thermodynamic properties of perovskite ruthnate Sr 1xCa<br />

xRuO 3 (0≤ x ≤1) probably for the first time by means of Rigid I<strong>on</strong> Model (RIM).<br />

The lattice c<strong>on</strong>tributi<strong>on</strong>s to the specific heat and thermal expansi<strong>on</strong> of pure and Ca<br />

doped SrRuO 3 as a functi<strong>on</strong> of temperature (0 K≤ T ≤ 1000 K) are reported. The<br />

systematic trend of variati<strong>on</strong> of specific heat and the closer agreement with the<br />

experimental data reveal the suitability and appropriateness of RIM, for Sr 1-xCa xRuO 3<br />

(0≤ x ≤1) perovskite ruthnates. The calculated lattice specific heat gives Debye<br />

temperature (478.4 K) which is c<strong>on</strong>sistent with experimental value (480 K). Our<br />

calculated value of 494.4 K for CaRuO 3 is in very good agreement with the reported<br />

value of 495 K. The Atoms in Molecules (AIM) theory is used to determine the bulk<br />

modulus of these compounds. Further, the value of Gruneisen parameter is calculated<br />

which is within the range 2-3 as reported earlier for perovskite family. In additi<strong>on</strong>, the<br />

results <strong>on</strong> cohesive energy (φ), molecular force c<strong>on</strong>stant (f), restsrahlen frequency (υ),<br />

Debye temperature(θ D) and gruneisen parameter (γ) are also presented. Our results<br />

<strong>on</strong> cohesive and thermal properties revealed by using RIM reproduces well with the<br />

available experimental data.<br />

RQ07<br />

Voltage-current characteristics of superc<strong>on</strong>ductor-normal metal<br />

c<strong>on</strong>tact juncti<strong>on</strong>s measured by a picovoltmeter<br />

Wan-seop Kim*, Mun-seog Kim, Po Gyu Park, Kyu-tae Kim and Danbee Kim<br />

KRISS, Korea<br />

A picovoltmeter based <strong>on</strong> a DC SQUID has been developed for improvement of<br />

Josephs<strong>on</strong> voltage measurement uncertainty to better than ΔV/V = 50 x 10-12. An<br />

output to input ratio of 108 is achieved using a proper current feed-back system.<br />

The performance of the picovoltmeter dem<strong>on</strong>strated by the Voltage(V)-Current(I)<br />

measurements <strong>on</strong> a Cu-wire with a diameter of 0.25 mm and a length of 10 mm shows<br />

that a voltage resoluti<strong>on</strong> is of about 10-12 V (pV) and a corresp<strong>on</strong>ding resistance<br />

resoluti<strong>on</strong> is order of 10 μΩ. In additi<strong>on</strong>, the current sensitivity of the picovoltmeter<br />

was found to be 2x10-7 A/Φ0, where Φ0 is the magnetic flux quantum. Here we<br />

present voltage steps induced by magnetic flux trap in the V-I curve measurements<br />

for a bulk cylinder-type Pb wire with a diameter of 0.25 mm. The step height was<br />

observed to change abruptly in an irregular manner, but in multiple of 6 pV. Moreover,<br />

dissipati<strong>on</strong> behavior of the remnant voltage observed in the V-I curves for thick films<br />

of superc<strong>on</strong>ductor/normal metal/superc<strong>on</strong>ductor c<strong>on</strong>tact juncti<strong>on</strong>s will be discussed.<br />

RQ08<br />

Development of high resoluti<strong>on</strong> cryogenic particle detectors using a<br />

magnetic calorimeter<br />

W.S. Yo<strong>on</strong> 1,2 , Y.S. Jang 1 , S.J. Lee 1 , G.B. Kim 1 , H.J. Lee 1,2 , K.B. Lee 1 , M.K. Lee 1 , Y.N.<br />

Yuryev 1 , Y.H. Kim 1,2<br />

1 Korea Research Institute of Standards and Science<br />

2 University of Science and Technology<br />

Micro-calorimeters operating at low temperatures have become important tools in<br />

many aspects of science because of their high energy resoluti<strong>on</strong> much bey<strong>on</strong>d the limit<br />

of semic<strong>on</strong>ductor based detectors. These sensitive detectors measure the temperature<br />

dependent properties of sensor materials such as their resistance or magnetizati<strong>on</strong>.<br />

In metallic magnetic calorimeters, a small c<strong>on</strong>centrati<strong>on</strong> of erbium doped in gold<br />

host provides a paramagnetic system, in which the magnetizati<strong>on</strong> is inversely<br />

proporti<strong>on</strong>al to the temperature. A metallic film of the sensor material is fabricated <strong>on</strong><br />

a superc<strong>on</strong>ducting meander-type pickup coil c<strong>on</strong>nected to an input coil of a SQUID<br />

current sensor. An absorber, another gold foil, is employed to detect incident alpha<br />

particles. The gold foil absorber and the magnetic temperature sensor are thermally<br />

c<strong>on</strong>nected by gold b<strong>on</strong>ding wires. The kinetic energy of each particle is c<strong>on</strong>verted into<br />

a temperature increase of the absorber/sensor assembly. In the present report, the recent<br />

progress <strong>on</strong> high resoluti<strong>on</strong> alpha spectrometers using these detectors is discussed<br />

together with an applicati<strong>on</strong> to radi<strong>on</strong>uclide analysis.<br />

194 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RQ09<br />

High pressure inductive measurements using microcoils in anvil cells.<br />

Swee K. Goh 1 *, Thomas Meissner 2 , Patricia Alireza 1 and Juergen Haase 2<br />

1 University of Cambridge, United Kingdom<br />

2 University of Leipzig, Germany<br />

Diam<strong>on</strong>d or Moissanite anvil cells are routinely employed to reach pressures higher<br />

than 35 kbar. However, due to the presence of the gasket and the limited sample space,<br />

inductive type measurements have been challenging. To overcome these challenges,<br />

we place a microcoil inside the gasket hole of the anvil cell. With an increase in the<br />

filling factor and the close proximity between the sample and the coil, this arrangement<br />

has so far enabled us to perform AC susceptibility [1], the de Haas-van Alphen effect<br />

[2], tunnel-diode oscillator [3] and Nuclear Magnetic Res<strong>on</strong>ance [4,5] experiments.<br />

Technical aspects associated with the preparati<strong>on</strong> of these pressure cells will be<br />

presented, with particular emphasis placed <strong>on</strong> recent NMR experiments performed<br />

using this technique.<br />

[1] P. L. Alireza et al., Rev. Sci. Instrum. 74, 4728 (2003) [2] S. K. Goh et al., Curr. Appl. Phys. 8,<br />

304 (2008) [3] S. K. Goh et al., arXiv:1107.0689 (2011) [4] J. Haase, S. K. Goh et al., Rev. Sci.<br />

Instrum. 80, 073905 (2009) [5] T. Meissner, S. K. Goh et al., Phys. Rev. B 83, 220517(R) (2011)<br />

RQ10<br />

Microwave synthesis and characterizati<strong>on</strong> of the series of co 4-xfexsb 12<br />

high temperature thermoelectric materials<br />

Alexandra Ioannidou 1 *, Margarit Gjoka 2 , Dimitris G Niarchos 2 , A Borrell 3 , M D<br />

Salvador 4 and F L Penaranda-foix 5<br />

1 Institute of Materials Science, NCSR Demokritos, Athens, Greece<br />

2 Institute of Materials Science, NCSR DEMOKRITOS, Greece<br />

3 Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera,, Spain<br />

4 Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera, s/n,<br />

46022 Valencia, Spain<br />

5 Instituto de Aplicaci<strong>on</strong>es de las Tecnologias de la Informaci<strong>on</strong> y de las Comunicaci<strong>on</strong>es Avanzadas,<br />

Universidad Politecnica de Valencia, Camino de Vera, s/n, 46022 Valencia, Spain<br />

An alternative route has been followed for a rapid synthesis of skutterudites as it was suggested by Biswas et<br />

al. (1) using microwave assisted synthesis. Microwave heating and sintering (involve microwaves <strong>on</strong>ly at 2.45<br />

GHz and 915 MHz frequencies) is fundamentally different from the c<strong>on</strong>venti<strong>on</strong>al sintering, which involves<br />

radiant/resistance heating followed by transfer of thermal energy via c<strong>on</strong>ducti<strong>on</strong> to the inside of the body being<br />

processed. Microwave heating is a volumetric heating involving c<strong>on</strong>versi<strong>on</strong> of electromagnetic energy into<br />

thermal energy, which is instantaneous, rapid and highly efficient. The use of microwave energy for materials<br />

processing has major potential and real advantages over c<strong>on</strong>venti<strong>on</strong>al heating. These include: - Time and<br />

energy savings. - Rapid heating rates (volumetric heating vs. c<strong>on</strong>ducti<strong>on</strong>). - C<strong>on</strong>siderably reduced processing<br />

time and temperature. - Fine microstructures - Lower envir<strong>on</strong>mental impact. Using the microwave-assisted<br />

synthesis, here we report our effort to synthesize the series of Co4-xFexSb12 using this novel approach,<br />

which gave high quality materials with little or no impurity in a fracti<strong>on</strong> of time compared to the c<strong>on</strong>venti<strong>on</strong>al<br />

synthesis. We will present data for structural, microstructural and thermoelectric properties and compare with<br />

materials synthesized with c<strong>on</strong>venti<strong>on</strong>al approach. Supported by the project NEXTEC of the EU<br />

1. K. Biswas, et al. MRS Bulletin 46, pp. 2288-2290 (2011). 2288-229 2. R. Roy, et al. Nature 399, pp. 668-670 (1999).<br />

RQ11<br />

Development of SI-STM optimized for 3D(x,T,B) phase-diagram-wide<br />

FTSTS mapping <strong>on</strong> high Tc superc<strong>on</strong>ductors<br />

Seokhwan Choi 1 , Jimin Kim 1 , Chanhee Kim 1 , Jaewook Kim 1 , Hwansoo Suh 2 and<br />

Jhinhwan Lee 1 *<br />

1 Physics, KAIST, Korea<br />

2 FRL, SAIT, Korea<br />

We are c<strong>on</strong>structing an SI-STM optimized for 3D(x,T,B) phase-diagram-wide QPI<br />

mapping <strong>on</strong> high Tc superc<strong>on</strong>ductors, K<strong>on</strong>do systems and SCESs. It is based <strong>on</strong> Panstyle<br />

STM design for high magnetic field compatibility and yet has enough symmetry<br />

required for covering a wide temperature range with minimal drift. Also it has multiple<br />

sample storage at 4K for unlimited reuse of samples with various dopings. Its primary<br />

goal is to extend the SI-STM measurement coverage over the most significant regime<br />

of the 3D phase diagram for unique determinati<strong>on</strong> of the mechanisms of high Tc<br />

superc<strong>on</strong>ductivity using the fully-phased Green-functi<strong>on</strong>-based cross-secti<strong>on</strong>al FTSTS<br />

analysis method.


RQ12<br />

Homemade microcalorimetry equipment, with magnetic fields up to 9<br />

Teslas, for magnetocaloric measurements<br />

J. V. Leitao*, P. Van Dommelen, F. Naastepad and E. Bruck<br />

Delft University of Technology, Netherlands<br />

The magnetocaloric effect (MCE) has gains relevance as a cheap and envir<strong>on</strong>mentally<br />

friendly alternative to the current household vapor cycle refrigerators. The most<br />

comm<strong>on</strong> method for calculating the MCE of a material, due to its technical and<br />

mathematical practicality, is the applicati<strong>on</strong> of Maxwell’s thermodynamic equati<strong>on</strong><br />

to a set of magnetic isotherms so as to calculate the magnetic entropy change [1].<br />

The other current alternative for this calculati<strong>on</strong> is through the adiabatic temperature<br />

change. Unfortunately, even though a working magnetocaloric refrigerator should rely<br />

much more <strong>on</strong> an adiabatic (Brayt<strong>on</strong>) cycle [2], such calculati<strong>on</strong> is usually hindered<br />

by the lack of a proper measurement system that would allow for reliable specific heat<br />

measurements with an applied magnetic field. Our group has recently c<strong>on</strong>structed<br />

such a device, using a 9 Tesla cryostat, allowing for liquid helium temperatures, and<br />

microcalorimetry chips from the company Xensor Integrati<strong>on</strong>. This equipment, besides<br />

the usefulness in magnetocalorics research, is an invaluable tool in the study and<br />

investigati<strong>on</strong> of any form of phase transiti<strong>on</strong>s where the applicati<strong>on</strong> of a magnetic field<br />

may play a significant role. We now report the overall characteristics of this equipment<br />

and further illustrate it with a few early measurements performed <strong>on</strong> it.<br />

[1]Debye P, 1926, Some observati<strong>on</strong>s <strong>on</strong> magnetisati<strong>on</strong> at a low temperature, Ann. Phys. 81: 1154-1160; [2]<br />

Tishin A.M, Spichkin Y.I, 2003, The Magnetocaloric Effect and its Applicati<strong>on</strong>s, MPG Books Ltd., Bodmin, 2003;<br />

RQ13<br />

Nucleati<strong>on</strong> and development of clustered state in hole doped<br />

manganites and cobaltites<br />

A. V. Lazuta 1 , V. A. Ryzhov 1 , V. P. Khavr<strong>on</strong>in 1 , P. L. Molkanov 1 and Ya. M.<br />

Mukovskii 2<br />

1 Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg 188300, Russia<br />

2 Moscow Steel and Alloys Institute, Leninskii prosp. 4, Moscow 117936, Russia<br />

The originati<strong>on</strong> of the ferromagnetic (F) metallic (M) clusters in a paramagnetic (P) state of the hole<br />

doped manganites was well established [1-3]. Study of this state in the hole doped cobaltites is the<br />

topic of the current research activity [4,5]. It is found by measurements of the n<strong>on</strong>linear magnetic<br />

resp<strong>on</strong>ses (the sec<strong>on</strong>d and third orders) that an universality exists in the nucleati<strong>on</strong> and development of<br />

the clustered states (CS) in these systems which proceed into three stages. On cooling, during the first<br />

stage, the F clusters nucleate at the preferential sites that are likely produced by variati<strong>on</strong> in oxygen and<br />

doping stoichiometry. Sec<strong>on</strong>d stage is characterized by a sharp increasing c<strong>on</strong>centrati<strong>on</strong> of the isolated<br />

F clusters. A coalescence of the clusters into large-scale complexes c<strong>on</strong>taining some amount of the F<br />

domains is associated with the third stage that can end with formati<strong>on</strong> of a percolative FM network.<br />

This scenario is dem<strong>on</strong>strated by using the data obtained <strong>on</strong> the single-crystalline manganites Pr1-x<br />

CaxMnO 3 (x = 0.2, 0.25; the F insulators) and single-crystalline cobaltite La 0.7Sr 0.3CoO 3 (a F metal). A<br />

new effect is found in the latter, in which the CS in the P metallic regime is observed for the first time.<br />

[1] M. B. Salam<strong>on</strong>, M. Jaime, Rev. Mod. Phys.73 (2001) 583. [2] V.A. Ryzhov, A.V. Lazuta, I.D. Luzyanin<br />

et al., Zh. Eksp. Teor. Fiz. 121 (2002) 678. [3] A.V. Lazuta, V.A. Ryzhov, V. P. Khavr<strong>on</strong>in et al., Funct.<br />

Mater. 17 (2010) 11 and Ref. therein. [4] C. He, S. El-Khatib, S. Eisenberg et. al., Appl. Phys. Lett. 95 (2009)<br />

222511. [5] A. V. Lazuta, V.A. Ryzhov, A. I. Kurbakov et al., Solid State Phenom. 168-169 (2011) 457.<br />

RQ14<br />

Measurements and analysis of core loss including higher harm<strong>on</strong>ic<br />

inducti<strong>on</strong> waveforms using superpositi<strong>on</strong> principle and steinmetz’s law<br />

Duhyung Ye<strong>on</strong> and Derac S<strong>on</strong>*<br />

Physics, Hannam university, Korea<br />

N<strong>on</strong>-oriented electrical steels have been used in rotating electric machines. Magnetic<br />

inducti<strong>on</strong> waveforms of stator cores of inducti<strong>on</strong> motors have ac major hysteresis<br />

loop of driving frequency and ac minor loops due to the slip. Predicti<strong>on</strong> of core loss<br />

including higher harm<strong>on</strong>ic is <strong>on</strong>e of important task for high efficiency inducti<strong>on</strong><br />

motor design[1]. In this work, we have c<strong>on</strong>structed core loss measuring system which<br />

could c<strong>on</strong>trol waveform of magnetic inducti<strong>on</strong> the same as generated from waveform<br />

synthesizer using analog negative feed-back system and test specimen was used air<br />

flux compensated ring core. Using the developed measuring system, we can measured<br />

core losses of ac minor loops which depend <strong>on</strong> the peak amplitude and positi<strong>on</strong><br />

in major hysteresis loop and theses core losses obeyed Steinmetz’s law. Core loss<br />

including minor loops could be calculated superpositi<strong>on</strong> principle of the core loss from<br />

major hysteresis loop and the core losses from minor loops which come from higher<br />

harm<strong>on</strong>ic inducti<strong>on</strong>.<br />

[1] D. S<strong>on</strong> “AC hysteresis loop measurement of stator-tooth in inducti<strong>on</strong> motor”, IEEE Trans. <strong>on</strong><br />

Magn., Vol.35, No.5, p.3931~3933(1999)<br />

RQ15<br />

RQ16<br />

RQ17<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Highly sensitive cantilever magnetometryin static and dynamic modes<br />

for micro-scale samples<br />

He<strong>on</strong>hwa Choi 1 , Yun W<strong>on</strong> Kim 2 and Jae-hyuk Choi 1 *<br />

1<br />

Nano Science, University of Science and Technology ; Divis<strong>on</strong> of Physical metrology,<br />

KRISS, Deaje<strong>on</strong> 305-340, Korea<br />

2<br />

Display and Semic<strong>on</strong>ductor Physics, Korea University, Chungnam 339-800 ;<br />

Divis<strong>on</strong> of Physical metrology, KRISS, Deaje<strong>on</strong> 305-340, Korea<br />

Recently, dynamic modecantilever magnetometriesusing an ultra-soft cantilever with<br />

att<strong>on</strong>ewt<strong>on</strong> dynamic force sensitivity arebecoming a very powerfultool for measuring<br />

the magnetic properties of micrometer-sized samples. In spite of its high sensitivity, the<br />

dynamic mode measuring a cantilever’s res<strong>on</strong>ance frequency shifthas a limitati<strong>on</strong> that<br />

it requires anisotropic magnetic samples,andhigh or moderate external magnetic fields.<br />

Therefore, we suggest a new type of a cantilever magnetometry with no limitati<strong>on</strong> <strong>on</strong><br />

magnetic anisotropy and external magnetic field, a cantilever forcemagnetometrywhich<br />

measuresastatic displacement of a cantilever in a well-defined magnetic field gradient.<br />

Its principle and experimental details including the magnetometry’sstructure are<br />

presented, which are accompanied by the results of measurement at T = 3.5 K <strong>on</strong> a<br />

small magnetic moment of 1.84 x 10-14 A m 2 using both static and dynamic modes<br />

revealing the high sensitivity of the static mode.<br />

Pulsed high magnetic fields for synchrotr<strong>on</strong> and neutr<strong>on</strong> applicati<strong>on</strong>s<br />

Fabienne Duc*, Xavier Fabreges, Paul Frings, Marc Nard<strong>on</strong>e, Julien Billette, Jerome<br />

Beard, Abdelaziz Zitouni and Geert Rikken<br />

Laboratoire Nati<strong>on</strong>al des Champs Magnetiques Intenses - CNRS Grenoble-Toulouse,<br />

France<br />

As is well known, a magnetic field, together with temperature and pressure, is a very<br />

important and efficient thermodynamic parameter for the investigati<strong>on</strong> of c<strong>on</strong>densed<br />

matter. It can be used as an external variable to tune the ground and excited states<br />

properties of a given magnetic system. The last ten years have seen a growing interest<br />

for the combined use of pulsed high magnetic fields (up to 40 T) at synchrotr<strong>on</strong> and<br />

neutr<strong>on</strong> sources. Because of the larger flux of synchrotr<strong>on</strong> x-ray sources compared<br />

to neutr<strong>on</strong> facilities, the development efforts have been first focused <strong>on</strong> synchrotr<strong>on</strong><br />

methods. Neutr<strong>on</strong> diffracti<strong>on</strong> has complementary features to x-ray diffracti<strong>on</strong>, and<br />

unique capabilities for studying microscopically the magnetic properties of materials.<br />

Here, we will present the various devices developed by the LNCMI, Toulouse to<br />

combine pulsed high magnetic fields with synchrotr<strong>on</strong> and neutr<strong>on</strong> techniques. These<br />

developments are performed in close collaborati<strong>on</strong> with the ESRF, Grenoble for<br />

synchrotr<strong>on</strong> applicati<strong>on</strong>s and with the ILL and CEA, Grenoble for neutr<strong>on</strong> diffracti<strong>on</strong>.<br />

We will discuss the main limitati<strong>on</strong>s for the use of pulsed magnetic fields related to<br />

their low duty cycle. Those instrumental developments will be illustrated by some<br />

recent results.<br />

Characteristics of an SQUID system with a superc<strong>on</strong>ductive shield for<br />

biomagnetic measurements<br />

Kw<strong>on</strong> Kyu Yu, Kiwo<strong>on</strong>g Kim, Hyuckchan Kw<strong>on</strong>, Jin Mok Kim and Y<strong>on</strong>g Ho Lee<br />

Brain and Cogniti<strong>on</strong> Measurement Lab, KRISS(Korea Research Institute of Standards<br />

and Science), Korea<br />

We have fabricated a magnetoencephalography (MEG) system having a<br />

superc<strong>on</strong>ductive shield helmet. By using the perfect diamagnetic effect of the<br />

superc<strong>on</strong>ductor (Pb), superc<strong>on</strong>ducting quantum interference device (SQUID)<br />

magnetometers inside the Pb enclosure can be shielded from external magnetic<br />

disturbances, and this effect can be used to enhance the signal quality of biomagnetic<br />

signals. Al<strong>on</strong>g the surface of the helmet, the shielding factor (SF) was from 28 to 57<br />

dB, depending <strong>on</strong> the positi<strong>on</strong> of the SQUID from the edge. SF reduced rapidly as<br />

the distance from Pb surface increased. The shielded helmet-shape MEG system has<br />

a noise level of about 7 fT/Hz1/2 at 1 Hz, and 3 fT/Hz1/2 at 100 Hz. Auditory evoked<br />

brain signals were measured and were compared in the case of superc<strong>on</strong>ductive shield<br />

and without shield, and c<strong>on</strong>firmed big improvement of the signal quality by using<br />

superc<strong>on</strong>ductive shield.<br />

[1] Y. H. Lee, “A low noise multichannel magnetocardiogram system for the diagnosis of heart electric activity”, Korean society of<br />

medical and biological Eng., Vol. 27, pp. 154-163, 2006. [2] R. H. Kraus, “ First Results for a Superc<strong>on</strong>ducting Imaging-Surface<br />

Sensor Array for Magnetocardiography”, Recent Advances in Biomagentism Proceeding, pp. 43-46, 1999. [3] D. B. Hulsteyn, “<br />

Superc<strong>on</strong>ducting Imaging Surface Magnetometery”, Rev. Sci. Instrum., Vol. 66, pp. 3777-3784. [4] H. Ohta,“A 64-channel whole<br />

head SQUID system in a superc<strong>on</strong>ducting magnetic shield”, Superc<strong>on</strong>. Sci. Technol., Vol.12, pp. 762-765, 1999.<br />

July 8 - 13, 2012 Busan, Korea 195<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RQ18<br />

Radio-frequency atomic magnetometer for sensitive susceptibility<br />

detecti<strong>on</strong><br />

Hyun Jo<strong>on</strong> Lee 1 , Han Seb Mo<strong>on</strong> 1 , Y<strong>on</strong>g-ho Lee 2 , Se<strong>on</strong>g-joo Lee 2 , Kw<strong>on</strong>-kyo Yu 2 and<br />

Kiwo<strong>on</strong>g Kim 2 *<br />

1 Pusan Nati<strong>on</strong>al University, Korea<br />

2 Korea Research Institute of Standards and Science (KRISS), Korea<br />

Alkali-metal magnetometers use the coherence precessi<strong>on</strong> of polarized atomic spins to detect and<br />

measure magnetic fields. Previously, the interacti<strong>on</strong> between light and atoms allows magnetometers<br />

to detect and measure magnetic fields, with sensitivity of 10 fT/√Hz [1]. Atomic magnetometers<br />

such as spin-exchange relaxati<strong>on</strong> free (SERF) regime magnetometer and coherence populati<strong>on</strong><br />

trapping (CPT) magnetometer have been designed to detect of varying magnetic fields mainly at low<br />

frequency. Therefore, detecti<strong>on</strong> of weak fields at high frequencies up to several megahertz requires an<br />

alternative detecti<strong>on</strong> method. To observe the Nuclear magnetic res<strong>on</strong>ance (NMR) signals at several<br />

tens of kilohertz, RF (Radio-Frequency) atomic magnetometer can be used. RF magnetometer has a<br />

fundamental sensitivity limit <strong>on</strong> the order of 0.01 fT/√Hz [2, 3]. In RF magnetometer, the oscillating<br />

magnetic field causes the polarizati<strong>on</strong> of each spin to rotate al<strong>on</strong>g the pumping axis, with the transverse<br />

spin comp<strong>on</strong>ent increasing until the polarizati<strong>on</strong> is perpendicular to the pump axis. The res<strong>on</strong>ant RF field<br />

eventually makes all of the processing spins coherent. In this study, the measured SNR corresp<strong>on</strong>ded to<br />

a sensitivity of 50 fT/√Hz at 25 kHz and such results will be useful to atomic NMR detector.<br />

[1] J. C. Allred, R.N. Lyman, T.W. Kornack and M.V. Romalis, Phys. Rev. Lett. 89, 130801 (2002) [2]<br />

S.-K. Lee, K. L. Sauer, S. J. Seltzer, O. Alem, and M. V. Romalis, Appl. Phys. Lett. 89, 214106 (2006) [3]<br />

I.M. Savukov, S.J. Seltzer and M.V. Romalis, Journal of Magnetic Res<strong>on</strong>ance 185 (2007) 214-220<br />

RQ19<br />

Cancellati<strong>on</strong> coil allows precisi<strong>on</strong> magnetic measurements with str<strong>on</strong>g<br />

magnetizati<strong>on</strong> field inside a shielded enviroment<br />

Se<strong>on</strong>g-min Hwang, Kiwo<strong>on</strong>g Kim*, Chan Seok Kang, Se<strong>on</strong>g-joo Lee and Y<strong>on</strong>g-ho Lee<br />

Brain and Cogniti<strong>on</strong> Measurement Lab., Korea Research Institute of Standards and<br />

Science, Korea<br />

A great number of precisi<strong>on</strong> magnetic measurements can benefit significantly from, or in some<br />

cases, even require str<strong>on</strong>g prepolarizati<strong>on</strong> fields (B p) and magnetically shielded envir<strong>on</strong>ments.<br />

We devised a cancellati<strong>on</strong> coil (CC) to neutralize the B p <strong>on</strong> electrically c<strong>on</strong>ductive shield walls<br />

that may otherwise induce currents <strong>on</strong> the walls to produce a lingering transient residual field (B tr)<br />

inside the shielded envir<strong>on</strong>ment and disrupt the measurement operati<strong>on</strong>s. The CC was designed<br />

using the inverse problem method to effectively neutralize magnetic fields generated <strong>on</strong> the<br />

shield walls by the B p coil. The implemented CC was evaluated by measuring the resulting B tr<br />

after str<strong>on</strong>g pulsed B p using a fluxgate magnetometer at different magnetometer positi<strong>on</strong>s and<br />

cancellati<strong>on</strong> coil currents (ICC). We have c<strong>on</strong>ducted multi-mode comp<strong>on</strong>ent analysis <strong>on</strong> the<br />

B tr measurements to reveal two dominant comp<strong>on</strong>ents, where the comp<strong>on</strong>ent with shorter time<br />

c<strong>on</strong>stant comes from the current induced around the shield side walls and the other with l<strong>on</strong>ger<br />

time c<strong>on</strong>stant from the current induced <strong>on</strong> the ceiling and floor of the MSR. The analysis also<br />

allows optimizati<strong>on</strong> of ICC for each of the top, side, and bottom secti<strong>on</strong>s of the CC to enable<br />

significantly easier fine-tuning of individual secti<strong>on</strong>s of the CC to enhance CC performance.<br />

Se<strong>on</strong>g-min Hwang, Kiwo<strong>on</strong>g Kim, Chan Seok Kang, Se<strong>on</strong>g-Joo Lee, and Y<strong>on</strong>g-Ho Lee, Appl. Phys. Lett. 99, 132506 (2011)<br />

Se<strong>on</strong>g-min Hwang, Kiwo<strong>on</strong>g Kim, Chan Seok Kang, Se<strong>on</strong>g-Joo Lee, and Y<strong>on</strong>g-Ho Lee, submitted to J. Appl. Phys. 111,<br />

083916 (2012)<br />

RQ20<br />

Development of a SQUID based ultra-low-field MRI system<br />

Se<strong>on</strong>g-joo Lee, Kiwo<strong>on</strong>g Kim*, Chan Seok Kang, Se<strong>on</strong>g-min Hwang and Y<strong>on</strong>g-ho<br />

Lee<br />

Brain and Cogniti<strong>on</strong> Measurement Lab., Korea Research Institute of Standards and<br />

Science, Korea<br />

We obtained 2-dimensi<strong>on</strong>al Magnetic Res<strong>on</strong>ance Imaging (MRI) image of a phantom<br />

in fields of a few microtesla by using a dc Superc<strong>on</strong>ducting QUantum Interference<br />

Device (SQUID) based MRI system. Microtesla MRI technique is a challenging<br />

applicati<strong>on</strong> based <strong>on</strong> SQUID technology. The high sensitivity of the SQUID<br />

magnetometer enables measurement of very weak magnetic res<strong>on</strong>ance signals even<br />

for the low Larmor frequency in microtesla fields. Measuring the nuclear magnetic<br />

res<strong>on</strong>ance (NMR) signals at such a low field gives many benefits like development of<br />

an open-type low-cost surgery-m<strong>on</strong>itoring MRI system, high-c<strong>on</strong>trast cancer detector,<br />

etc. In this presentati<strong>on</strong>, we introduce experimental details for ultra-low-field (ULF)<br />

MRI.<br />

196 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RQ21<br />

26 T+ steady magnetic field for neutr<strong>on</strong> science at HZB Berlin<br />

P. Smeibidl, Karel Prokes*, H. Ehmler, O. Prokhnenko and A. Tennant<br />

M-I1, Helmholtz Zentrum Berlin, Germany<br />

The Helmholtz Zentrum Berlin is building in collaborati<strong>on</strong> with the Nati<strong>on</strong>al High<br />

Magnetic Field Laboratory, Tallahassee, FL, USA a new series-c<strong>on</strong>nected hybrid<br />

magnet system for neutr<strong>on</strong> scattering experiments [1]. Two c<strong>on</strong>ical endings of 30°<br />

opening angle enable neutr<strong>on</strong>s to hit the sample and to be detected either in the forward<br />

or backward directi<strong>on</strong>. To achieve a maximum field with the present technology, a<br />

13 T superc<strong>on</strong>ducting Nb 3Sn cable-in-c<strong>on</strong>duit coil is combined with resistive insert<br />

coils of 13 T to 19 T, depending <strong>on</strong> electric power, to give a maximum of 26 to 32<br />

T. The magnet that provides a 50 mm diameter room temperature bore in horiz<strong>on</strong>tal<br />

orientati<strong>on</strong> will be permanently mounted at the dedicated time-of-flight instrument<br />

ExED 76 m away from the neutr<strong>on</strong> source. The c<strong>on</strong>tributi<strong>on</strong> describes the most<br />

important design features of the system (the 20 kA, 8 MW power supply, the helium<br />

refrigerator system for cooling of the superc<strong>on</strong>ducting coil and the 4-8 MW water<br />

cooling system for cooling of the resistive coil), the status of the fabricati<strong>on</strong> of the<br />

comp<strong>on</strong>ents, the outline of the building for the technical infrastructure and the status of<br />

the installati<strong>on</strong> of the most important comp<strong>on</strong>ents.<br />

[1] P. Smeibidl et al., J. Low Temp. Phys. 159, 402 (2010).<br />

RQ22<br />

A simple method for measuring blocking temperatures<br />

Mansor Hashim 1 , Ghazaleh Bahmanrokh 2 and Ismayadi Ismail 1<br />

1 Institute of Advanced Technology, Universiti Putra Malaysia, Malaysia<br />

2 Physics Department, Faculty of Science, Universiti Putra Malaysia, Malaysia<br />

We describe a new method for measuring a blocking temperature, much simpler than<br />

that involving a SQUID. Nanoparticles of Co, Co coated with Au,Co-Pt and Co-Pt<br />

coated with Au were prepared by the reverse micelle microemulsi<strong>on</strong> method. The<br />

four magnetic powder specimens were each pressed to yield a disc. A Hall-effect<br />

probe blade surface was stuck intimately against <strong>on</strong>e flat surface of the disc. Properly<br />

analysed, this arrangement allows the probe to detect the normal comp<strong>on</strong>ent, BN,<br />

projecting from the disc since, at the interface, BN (air) = BN (disc). Use of this<br />

relati<strong>on</strong> led to the determinati<strong>on</strong> of a magnetic moment near the disc surface. By<br />

simply cooling this arrangement of disc + probe in a probe stati<strong>on</strong> to 15K, a graph of<br />

the magnetic moment was clearly peaked at a temperature which, unmistakably, was<br />

the blocking temperature, TB. For the four different samples TB lies between 40K and<br />

45K.<br />

RQ23<br />

Optimizati<strong>on</strong> of operati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> of orthog<strong>on</strong>al fluxgate sensor<br />

fabricated with Co based amorphous wire<br />

Y<strong>on</strong>gmin Kim 1 , Young-hak Kim 2 , Sang-ho Lim 3 , Cang-seob Yang 4 and Kwang-ho<br />

Shin 1 *<br />

1 Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Kyungsung University,<br />

Korea<br />

2 Puky<strong>on</strong>g Nati<strong>on</strong>al University, Korea<br />

3 Korea University, Korea<br />

4 Agency forDefense Development, Korea<br />

Orthog<strong>on</strong>al fluxgate (OFG) sensors have an additi<strong>on</strong>al advantage comparing with c<strong>on</strong>venti<strong>on</strong>al fluxgate sensors<br />

in their simple structure [1-2]. Because the sensitivity of an OFG is typically proporti<strong>on</strong>al to its winding number N,<br />

cross secti<strong>on</strong> area of its magnetic core A, and operati<strong>on</strong> frequency f, the f should be as high as possible to prevent<br />

reducti<strong>on</strong> of the sensitivity in the case of small-sized OFG sensors in which the N and A are restricted. The f is<br />

limited due to the LC res<strong>on</strong>ance occurred by inductance and stray-field capacitance of the pickup coil around the<br />

magnetic core and transmissi<strong>on</strong> line, coaxial line in this study, as well as performance of the signal c<strong>on</strong>diti<strong>on</strong>ing<br />

circuit in comm<strong>on</strong>. And the sensitivity could be also reduced according to increase of operati<strong>on</strong> frequency due<br />

to the skin effect if the sensor is operated in the frequency range of near MHz. We present how to optimize<br />

the operati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> including frequency of the OFG fabricated with a CoFeSiB amorphous wire with the<br />

diameter of 100 μm in this paper. The LC res<strong>on</strong>ance frequency according to external capacitances was calculated<br />

with an equivalent circuit and FEM analysis to calculate the magnetizati<strong>on</strong> distributi<strong>on</strong> in a high frequency.<br />

[1] E. Paperno, E. Weiss and A. Plotkin, IEEE Trans. Magn., 44, 4018 (2008). [2] I. Sasada, J. Appl. Phys., 91, 7789 (2002).


RR01<br />

Preparati<strong>on</strong> of γ-Fe4N and ε-Fe3N particles with high magnetizati<strong>on</strong><br />

for electromagnetic wave absorpti<strong>on</strong> applicati<strong>on</strong>s<br />

Ming-f<strong>on</strong>g Tai 1 *, Hsin-tzu Liu 2 , C. M. Lin 3 and Huan-chiu Ku 1<br />

1 Department of Physics, Nati<strong>on</strong>al Tsing Hua University, Taiwan<br />

2 Department of Chemical Engineer, Nati<strong>on</strong>al Tsing Hua University, Taiwan<br />

3 Department of Applied Science, Nati<strong>on</strong>al Hsingchu University of Educati<strong>on</strong>, Taiwan<br />

High-Ms ferromagnetic ir<strong>on</strong> nitrides have vast applicati<strong>on</strong>s <strong>on</strong> microwave absorbing<br />

and magnetic recording. In this study, we successfully used a simple nitrogen<br />

treatment to prepare cubic γ-Fe 4N and hexag<strong>on</strong>al ε-Fe 3N powder. Both kinds of<br />

powders are synthesized by the nitriding process of the commercial micro-scale Fe<br />

and Fe 2O 3 powders, at 550°C for 5 hours during a flowing mixture of NH 3 and H 2<br />

gas. Our pure γ-Fe 4N powder exhibits a high saturati<strong>on</strong> magnetizati<strong>on</strong> of 15.03 kG at<br />

room temperature, which is slightly lower than that of bulk Fe (22.0 kG @ 4 K) but is<br />

c<strong>on</strong>siderably higher than that of γ-Fe 2O 3 (4.0 kG @ 4 K). The ε-Fe 3N powder including<br />

a slight amount of γ-Fe 4N was also synthesized by heating the commercial Fe 2O 3<br />

powder with the same procedure. The chemical stabilities of both γ-Fe 4N and ε-Fe3N<br />

powder are superior to that of the pure Fe and have high level of mechanical hardness.<br />

The mircostructures and electr<strong>on</strong> spin res<strong>on</strong>ances of our ir<strong>on</strong> nitrides were also studied.<br />

This work was supported by the Nati<strong>on</strong>al Science Council, Taiwan under the NSC 98-2112-M-007-<br />

016-MY3 project.<br />

RR02<br />

Methods for determining the quality of magnetic fluids<br />

Viorica Chioran<br />

University Babes-Bolyai - Cluj Napoca / Romania, Romania<br />

The c<strong>on</strong>versi<strong>on</strong> parameter of the magnetic properties of magnetic fluids is a physical<br />

quantity describing the quality of those fluids from a technological point of view.<br />

This study determines the value of this parameter for three samples of magnetic<br />

fluid. Many technical applicati<strong>on</strong>s require magnetic fluids with specific magnetic<br />

properties such as very high magnetizati<strong>on</strong> at saturati<strong>on</strong> point or rheological properties<br />

involving high fluidity (very low viscosity). The sample with bigger density (1070 kg/<br />

m3) also has a larger solid volume fracti<strong>on</strong> (0, 059). Increasing the solid part/ fluid<br />

volume increases the density and viscosity of that fluid. A magnetic fluid with a larger<br />

magnetic part/ volume (0,031) has a higher magnetizati<strong>on</strong> at saturati<strong>on</strong> point (0,0138<br />

A/m). The parameter always has sub-unitary values because inside the volume of the<br />

magnetic fluid, the percentage of the solid part is larger then that of the magnetic part.<br />

Resp<strong>on</strong>sible for this is the n<strong>on</strong>magnetic layer at the surface of the particles. For the<br />

fluid samples studied, regardless of the magnetic and physic diameter, the n<strong>on</strong>magnetic<br />

layer of particles has the same value: a = 0,83 nm. Good quality of a magnetic fluid is<br />

indicated by a high value of the c<strong>on</strong>versi<strong>on</strong> parameter.<br />

RR03<br />

A study <strong>on</strong> magnetic fluid viscosity<br />

Viorica Chioran<br />

University Babes-Bolyai - Cluj Napoca / Romania, Romania<br />

This paper shows the results of a study of the parameters that the viscosity of magnetic<br />

fluids depends <strong>on</strong>, in the absence of magnetic fields. Viscosity’s and shearing tensi<strong>on</strong>’s<br />

dependence <strong>on</strong> the rheologic comp<strong>on</strong>ent and shearing speed was verified for several<br />

samples of kerosene based magnetic fluid with the same dimensi<strong>on</strong>al distributi<strong>on</strong><br />

but various c<strong>on</strong>centrati<strong>on</strong>s, at different temperatures. Experimental results show <strong>on</strong>e<br />

situati<strong>on</strong> where the sample P1 has a n<strong>on</strong>-Newt<strong>on</strong>ian character over a small interval of<br />

shearing speeds. An increase in fluid viscosity indicates that b<strong>on</strong>ds between particles<br />

are formed inside the fluid. As shearing speeds increase these b<strong>on</strong>ds disappear.<br />

Samples P and P 2 show Newt<strong>on</strong>ian character over the shearing speed interval where<br />

viscosity remains c<strong>on</strong>stant. By comparing viscosity values of samples at different<br />

temperatures and shearing speeds, decreasing viscosity while increasing temperature<br />

is observed due to the activati<strong>on</strong> energy of viscous flow. A linear increase of shearing<br />

tensi<strong>on</strong> with the increase of shearing speed was observed for the studied samples at<br />

different temperatures. The slope of this line can be used to determine the dynamic<br />

viscosity’s value. For the c<strong>on</strong>sidered samples, viscosity str<strong>on</strong>gly depends <strong>on</strong> several<br />

factors: density, c<strong>on</strong>centrati<strong>on</strong>, temperature (by Arrhenius’s Law) and shearing speed (by<br />

Newt<strong>on</strong>’s equati<strong>on</strong>).<br />

RR04<br />

RR05<br />

RR06<br />

Theoretical design of magnetic energy harvesting module<br />

Kunihisa Tashiro*, Hiroyuki Wakiwaka and Yu Uchiyama<br />

Shinshu University, Japan<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magneto-motive force and torque analysis of squirrel cage inducti<strong>on</strong><br />

motor with rotor or stator faults<br />

Cheol Soo Goo 1 , Seok-mye<strong>on</strong>g Jang 2 and Yu Seop Park 2<br />

1<br />

Insturmentati<strong>on</strong> and C<strong>on</strong>trol Assessment Department, Korea Institute of Nuclear<br />

Safety, Korea<br />

2<br />

Electrical Engineering, Chungnam Nati<strong>on</strong>al University, Korea<br />

Torque characteristics of high voltage inducti<strong>on</strong> motor are simulated under the<br />

c<strong>on</strong>diti<strong>on</strong> of under voltage and broken rotor bars. The motor is high voltage squirrel<br />

cage inducti<strong>on</strong> type for driving force of pumps and valves in nuclear power plant. In<br />

the simulati<strong>on</strong>, a rotor with health and broken bars, stator winding deteriorati<strong>on</strong> and<br />

voltage drop 25% al<strong>on</strong>e and combinati<strong>on</strong> with bar faults were used. Then the results<br />

were analyzed. The effects of rotor faults <strong>on</strong> the torque-speed curve were compared<br />

according to the number of the rotor faults. The results revealed that voltage drop and<br />

the number of the rotor fault at high speed span is directly proporti<strong>on</strong>al to its effect <strong>on</strong><br />

the curve, but the curve indicated the opposite at the low speed span due to the rotor<br />

impedance increase. In stator, winding faults made a distorti<strong>on</strong> of the phase magnetomotive<br />

force and reducti<strong>on</strong> of co-energy at the gap which cause vibrati<strong>on</strong>, harm<strong>on</strong>ics<br />

and total power decrease.<br />

Evaluati<strong>on</strong> of materials degradati<strong>on</strong> of ferromagnetic steels for various<br />

magnetized states using a hysteresis scaling law<br />

Satoru Kobayashi*, Yusuke Ishibashi and Ryo Baba<br />

Department of Materials Science and Engineering, Iwate University, Japan<br />

We have examined a hysteresis scaling behavior of magnetic minor hysteresis loops<br />

for ferromagnetic low carb<strong>on</strong> steels under DC-biased magnetic field and/or remanent<br />

magnetizati<strong>on</strong> state. For all minor loops with dominant c<strong>on</strong>tributi<strong>on</strong> of irreversible<br />

Bloch wall moti<strong>on</strong>, a scaling relati<strong>on</strong> between the hysteresis loss and maximum<br />

magnetizati<strong>on</strong> shows the same curve from very low to high magnetizati<strong>on</strong> regime,<br />

suggesting the invariant pinning mechanism for the irreversible wall moti<strong>on</strong>. In the<br />

intermediate magnetizati<strong>on</strong> regime, the relati<strong>on</strong> follows the usual Steinmetz law with<br />

a power-law exp<strong>on</strong>ent of about 1.5, whose coefficient increases with defect density.<br />

The method using a hysteresis scaling can be a useful technique of evaluating materials<br />

degradati<strong>on</strong> of ferromagnetic steels in an unknown magnetic state, which is comm<strong>on</strong>ly<br />

encountered <strong>on</strong> <strong>on</strong>-site measurements.<br />

Energy harvesting is a key technology to build a sustainable society. In previous<br />

paper, we focused <strong>on</strong> a magnetic power-line noise as a reusable energy. In this paper,<br />

we present a theoretical design method of magnetic energy harvesting module. This<br />

module c<strong>on</strong>sists of an air-core coil and res<strong>on</strong>ant capacitor. With a simple RLC circuit<br />

model, we derive a equati<strong>on</strong> of the harvesting energy as a functi<strong>on</strong> of coil size. In<br />

order to dem<strong>on</strong>strate the magnetic field, a uniform magnetic field is generated by our<br />

developed coil system. From the experimeted results, we successfully dem<strong>on</strong>strated the<br />

energy harvesting of 100 mW from a magnetic field of 0.09 mT at 60 Hz. This value<br />

is good in agreement with the estimated results. The harvested energy is proporti<strong>on</strong>al<br />

to the square of the magnetic flux density. However, ICNIRP2010 provide a guide<br />

line for human helth that an acceptable level in a public space is 0.2 mT at power-line<br />

frequency. We also reveal the required coil size to harvest a demanded energy.<br />

July 8 - 13, 2012 Busan, Korea 197<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RR07<br />

A study <strong>on</strong> detecting and determining the shape of small axial cracks<br />

by using magnetic flux leakage in ndt system of pipe<br />

Hui Min Kim and Gwan Soo Park*<br />

School of Electr<strong>on</strong>ic and Electrical Engineering, Pusan Nati<strong>on</strong>al University, Korea<br />

There is the source of energy that is used widely all over the world, which is oil and<br />

natural gas. Oil and gas is supplied for industries or home c<strong>on</strong>sumers through pipelines.<br />

Most pipelines are laid to underground and exposed the external envir<strong>on</strong>ment. By<br />

these c<strong>on</strong>diti<strong>on</strong>s pipelines have some bad effects like the metal loss, corrosi<strong>on</strong>s and<br />

any other damages. For preventing accidents, these defects have to be detected by the<br />

N<strong>on</strong>-destructive testing(NDT). The magnetic flux leakage(MFL) method am<strong>on</strong>g the<br />

NDT methods is suitable for testing pipelines which the magnetic characteristic of<br />

has high magnetic permeability. The system that MFL method applies to is called the<br />

pipeline inspecti<strong>on</strong> gauge, MFL PIG. The previous MFL PIG has high performance<br />

for detecting the metal loss and corrosi<strong>on</strong>s. But MFL PIG cannot detect the cracks<br />

which occurred by the difference of pressure between the inside and outside of<br />

pipelines and the shape of is l<strong>on</strong>g and very narrow. Cracks occures frequently in the<br />

pipelines and the risk of the accident from the cracks is higher than that from the metal<br />

loss and corrosi<strong>on</strong>s. The circumferential MFL(CMFL) PIG performs magnetic field<br />

circumferentially and can maximize the magnetic flux leakage at the cracks.<br />

RR08<br />

C<strong>on</strong>trol of working temperature of isothermal magnetic entropy<br />

change by hydrogen absorpti<strong>on</strong> into La 0.8Nd 0.2(Fe 0.88Si 0.12) 13 for magnetic<br />

refrigerant<br />

S Fujieda 1 *, A Fujita 2 , K Fukamichi 1 and S Suzuki 1<br />

1 Institute of Multidisciplinary Research for Advanced Materials, Tohoku Univ., Japan<br />

2 Dept. of Materials Science, Graduate School of Engineering, Tohoku Univ., Japan<br />

Hydrogen absorpti<strong>on</strong> into La 0.8Nd 0.2(Fe 0.88Si 0.12) 13 has been investigated to obtain large<br />

magnetocaloric effects (MCEs) near room temperature for applicati<strong>on</strong>s to magnetic<br />

refrigerati<strong>on</strong>. La(Fe 0.88Si 0.12) 13 exhibits large MCEs just above the Curie temperature<br />

T C = 195 K because of the itinerant-electr<strong>on</strong> metamagnetic (IEM) transiti<strong>on</strong> [1]. The<br />

MCEs due to the IEM transiti<strong>on</strong> are enhanced by the partial substituti<strong>on</strong> of Nd for La<br />

[2]. It was c<strong>on</strong>firmed that T C of La 0.8Nd 0.2(Fe 0.88Si 0.12) 13 is increased from 193 K to 318<br />

K by hydrogen absorpti<strong>on</strong> with keeping the IEM transiti<strong>on</strong> because the unit cell volume<br />

is expanded. Note that the isothermal magnetic entropy change ΔSm due to the IEM<br />

transiti<strong>on</strong> in a magnetic field change of 2 T for La 0.8Nd 0.2(Fe 0.88Si 0.12) 13H 1.1 was evaluated<br />

to be about -23 J/kg K at T C = 288 K, which is larger than ΔSm = -19 J/kg K at T C = 276<br />

K for La(Fe 0.88Si 0.12) 13H 1.0. The relative cooling power RCP = 179 J/kg of the former<br />

also is larger than 160 J/kg of the latter. Accordingly, it is c<strong>on</strong>cluded that the partial<br />

substituti<strong>on</strong> of Nd improves the MCEs near room temperature.<br />

[1] A. Fujita et al., Phys. Rev. B 67 (2003) 104416. [2] S. Fujieda et al., Mater. Sci. Forum 561-565 (2007) 1093.<br />

RR09<br />

Characteristic analysis of inducti<strong>on</strong> motor for electric vehicle<br />

according to electric loading and magnetic loading<br />

Ki Young Sung 1 and Ki-chan Kim 2 *<br />

1 SPG Co,. Ltd., Korea<br />

2 Hanbat nati<strong>on</strong>al university, Korea<br />

In the paper, an inductive motor for electric vehicle that was designed for compact<br />

car modificati<strong>on</strong> was selected as the basic model, and its performance change was<br />

examined according to the change in the electric and magnetic loading related to the<br />

rotor slot. The characteristic changes according to the change in the loading were<br />

analyzed for two speed ranges: the low speed (near the base speed) and the high speed<br />

(maximum speed with field weakening c<strong>on</strong>trol). To provide the characteristic analysis<br />

c<strong>on</strong>diti<strong>on</strong>s according to the change in the slot shape of the reference model, the rotor<br />

bar depth was changed with the rotor teeth width fixed to vary the electric loading, and<br />

the rotor teeth width was changed with the rotor bar area fixed to vary the magnetic<br />

loading. The characteristics of the inductive motor were analyzed via the analysis<br />

of the characteristics according to the parameters of the equivalent circuit based <strong>on</strong><br />

the magnetic circuit method and via the electromagnetic analysis based <strong>on</strong> the finite<br />

element method to c<strong>on</strong>sider the n<strong>on</strong>linear characteristic of the motor parameters.<br />

[1] Z.Zhang, F.profmo, a. tenc<strong>on</strong>i, 'Improved design for elelctric vehicle inducti<strong>on</strong> motors using an optimisati<strong>on</strong> procedure'.<br />

Electric Power Applicati<strong>on</strong>s, IEE Proceedings, vol, 143, pp.410-416, 1996 [2] T. Wang, P. Zheng, Q. Zhang, and S. Cheng,<br />

'Design Characteristics of the inducti<strong>on</strong> motor used for hybrid electric vehicle'. IEEE Tracnsacti<strong>on</strong> <strong>on</strong> Magnetics, vol. 41,<br />

pp. 505-508, 2005 [3] I. Boldea and S. A. Nasar, 'The inducti<strong>on</strong> machine handbook'. Boca Rat<strong>on</strong>, CRC Press, 2002<br />

198 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RR10<br />

Torque characteristics of interior permanent magnet synchr<strong>on</strong>ous<br />

motor for electrical hydraulic power steering system<br />

Su-jin Hwang 1 and Ki-chan Kim 2 *<br />

1 Daed<strong>on</strong>g movel company, Korea<br />

2 Hanbat nati<strong>on</strong>al university, Korea<br />

In the paper, a 12 V-DC interior permanent magnet synchr<strong>on</strong>ous motor for electric<br />

hydraulic power steering (EHPS) was designed for the purpose of improving its torque<br />

performance. The EHPS is a steering system that uses the battery power of the vehicle,<br />

which is weaker than the power of the hydraulic power steering system. Because of<br />

the spatial limitati<strong>on</strong>, the IPMSM, which has high-power characteristic and excellent<br />

performance within the field weakening area at a high rotating speed, is advantageous.<br />

To improve the torque performance, the average torque was increased by increasing<br />

the rotor size. In additi<strong>on</strong>, because the torque ripple is detected as vibrati<strong>on</strong> when<br />

the steering wheel is operated, the shape of the barrier was modified to change the<br />

inductance element of the axis and reduce the torque ripple. The optimally designed<br />

model characteristics were analyzed using the finite element method to comparatively<br />

analyze the parameters. It is expected that this study will be important reference data to<br />

understand the characteristics of the IPMSM as well as of the EHPS.<br />

[1] Tomy Sebastian, Vineeta Gangla, 'Analysis of Induced EMF Waveforms and Torque Ripple in a<br />

Brushless Permanent Magnet Machine,' IEEE Trans. <strong>on</strong> Industrial Applicati<strong>on</strong>s, Vol. 32, No. 1, 1996. [2]<br />

A. M. Elrefais, T. M. Jahns and D. W. Novotny, 'Analysis of Surface Permanent Magnet Machines with<br />

Fracti<strong>on</strong>al Slot C<strong>on</strong>centrated Windings', IEEE Trans <strong>on</strong> Energy C<strong>on</strong>versi<strong>on</strong>, vol. 21, no. 1, pp. 34-43, 2006<br />

RR11<br />

Edge auxiliary teeth design of stati<strong>on</strong>ary disc<strong>on</strong>tinuous armature PM-<br />

LSM with c<strong>on</strong>centrated winding<br />

Y<strong>on</strong>g-jae Kim 1 , Sung-jin Kim 1 * and Sang-y<strong>on</strong>g Jung 2<br />

1 Department of Electrical Engineering, Chosun University, Korea<br />

2 School of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Sungkyunkwan University, Korea<br />

Recently, in order to resolve the problem of high cost, we have proposed the stati<strong>on</strong>ary disc<strong>on</strong>tinuous armature<br />

PM-LSM in which the armature is engaged <strong>on</strong>ly when accelerated and decelerated operati<strong>on</strong>s are necessary,<br />

when PM-LSM is used with l<strong>on</strong>g-distance transportati<strong>on</strong> systems in factories [1]. As the armatures are<br />

arranged disc<strong>on</strong>tinuously in the PM-LSM, the number required is dramatically decreased. In this case, several<br />

stator blocks can be arranged at certain intervals within the overall running route. The space between the<br />

blocks without the stator is called the free-running secti<strong>on</strong>, and the mover in this secti<strong>on</strong> drives under its own<br />

inertia. However, the stati<strong>on</strong>ary disc<strong>on</strong>tinuous armature PM-LSM c<strong>on</strong>tains the edges which always exist as a<br />

result of the disc<strong>on</strong>tinuous arrangement of the armature [2]. For this reas<strong>on</strong>, cogging force generated between<br />

the “entrance end” and the “exit end” has become a problem. Therefore, we have examined the edge cogging<br />

force by installing the auxiliary teeth at the armature’s edge in order to minimize the cogging force generated<br />

when the armature is arranged disc<strong>on</strong>tinuously. We obtain the edge cogging force by using 2-D numerical<br />

analysis with a FEM and also by adjusting the width, height and the length of pitch of auxiliary teeth.<br />

[1] Y<strong>on</strong>g-Jae Kim, Masaya Watada, Susumu Torii and Daiki Ebihara, “C<strong>on</strong>stant Load Angle C<strong>on</strong>trol of the Disc<strong>on</strong>tinuous<br />

Primary Linear Synchr<strong>on</strong>ous Motor without Positi<strong>on</strong> Feedback”, The Fourth <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Symposium <strong>on</strong> LINEAR<br />

DRIVES FOR INDUSTRY APPLICATIONS, pp.113-116, 2003. [2]Y<strong>on</strong>g-Jae Kim, Masaya Watada, Susumu Torii, Hideo<br />

Dohmeki and Daiki Ebihara, “The Influence which Outlet edge of the Disc<strong>on</strong>tinuous Primary Linear Synchr<strong>on</strong>ous Motor<br />

Exerts <strong>on</strong> the Drive of Sec<strong>on</strong>dary Mover”, The 5th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Power Electr<strong>on</strong>ics <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, pp.859-864, 2005.<br />

RR12<br />

Inductively coupled LC res<strong>on</strong>ators as displacement sensor<br />

Y<strong>on</strong>gmin Kim and Kwang-ho Shin*<br />

Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Kyungsung University, Korea<br />

In this paper, we present novel displacement sensor composed of a pair of LC<br />

res<strong>on</strong>ators. The LC res<strong>on</strong>ator was formed by serial c<strong>on</strong>necti<strong>on</strong> of 300-turn Cu wire<br />

wound <strong>on</strong> a rectangular NiZn ferrite (20 × 3 × 4 mm) core and SMD capacitor (3.2 ×<br />

1.6 mm). The res<strong>on</strong>ance frequencies of two res<strong>on</strong>ators are adjusted to be identical with<br />

each other. By this, we could obtain the sensor output linearly dependent of distance<br />

between two LC res<strong>on</strong>ators, because the mutual inductance is proporti<strong>on</strong>al to distance<br />

between two res<strong>on</strong>ators in a few centimeters. The sensor was designed by a sequence<br />

of magnetic field simulati<strong>on</strong> with a FEM tool (COMSOL) and circuit calculati<strong>on</strong> with<br />

a SPICE. The sensitivity estimated by S = fr/D was about 480 kHz/m, where, fr and<br />

D are res<strong>on</strong>ance frequency and distance between two res<strong>on</strong>ators, respectively. The<br />

proposed sensor would be a promising displacement sensor when it takes an active part<br />

in an envir<strong>on</strong>ment surrounded by serious electrical/magnetic noise, since it could be<br />

operated in extremely narrow frequency range.


RR13<br />

Magnetic NDE for sensitizati<strong>on</strong> of Inc<strong>on</strong>el 600 alloy<br />

Hiroaki Kikuchi, Takaki Sumimoto, Yasuhiro Kamada and Satoru Kobayashi<br />

Faculty of Engineering, Iwate University, Japan<br />

Inc<strong>on</strong>el 600 alloy, Ni base alloy, is used as steam generators in nuclear power plants,<br />

and sensitizati<strong>on</strong> occurs al<strong>on</strong>g grain boundary with heat treatment <strong>on</strong> this material. The<br />

sensitizati<strong>on</strong> causes a degradati<strong>on</strong> of corrosi<strong>on</strong> resistance and generates stress corrosi<strong>on</strong><br />

crack [1], [2]. Therefore n<strong>on</strong>destructive evaluati<strong>on</strong> (NDE) technique for sensitizati<strong>on</strong><br />

of Inc<strong>on</strong>el alloy is quite important so as to keep the integrity of plants. Inc<strong>on</strong>el 600<br />

alloy has usually paramagnetic property, however, it shows ferromagnetic properties<br />

al<strong>on</strong>g grain boundary when sensitizati<strong>on</strong> occurs: this means NDE using magnetism<br />

is possible. Thus, in this study, Inc<strong>on</strong>el 600 alloys were heat treated at 873 K from 0<br />

to 400 hours and their magnetic properties were investigated in detail. Magnetizati<strong>on</strong><br />

increases with increasing time of heat treatment and takes a maximum. On the<br />

other hand, coercivity decreases with the increase in time. We c<strong>on</strong>firmed that <strong>on</strong>ly<br />

characteristics at the grain boundaries changes ferromagnetic by MFM observati<strong>on</strong>. As<br />

trial for industrial applicati<strong>on</strong>, heat treated Inc<strong>on</strong>el 600 alloy has scanned by magnetic<br />

field sensor, and the changes of magnetizati<strong>on</strong> n<strong>on</strong>destructively were successfully<br />

obtained. The result indicates the feasibility of magnetic NDE for sensitizati<strong>on</strong> of<br />

Inc<strong>on</strong>el 600 alloy.<br />

[1] M. Kowaka, H. Nagano, T. Kubo, Y. Okada, M. Yagi, O. Takaba, T. Y<strong>on</strong>ezawa and K. Arioka,<br />

Nuclear Technologies, Vol. 55, pp. 394-404 (1981). [2] J. D. Wang, D. Gan, Materials Chemistry<br />

and Physics, Vol. 70, pp. 124-128 (2001).<br />

RR14<br />

Comparis<strong>on</strong> of characteristics between the PM synchr<strong>on</strong>ous motor<br />

and the inducti<strong>on</strong> motor for electric vehicle<br />

Mi-jung Kim, Ik-sang Jang, Ki-doek Lee, Jae-jun Lee, Je<strong>on</strong>g-ho Han, Tae-chul Je<strong>on</strong>g<br />

and Ju Lee*<br />

Hanyang University, Korea<br />

This paper presents the characteristics over a wide speed range of the interior permanent magnet<br />

synchr<strong>on</strong>ous motor(IPMSM) and the inducti<strong>on</strong> motor(IM) for an applicati<strong>on</strong> of electric vehicle<br />

drive. In generally, IPMSM have higher performance than IM. The performance: torque,<br />

efficiency, power factor etc. are compared at rated speed of 2,843rpm and maximum speed of<br />

10,000rpm. The inducti<strong>on</strong> motor operating c<strong>on</strong>stant speed is not need to c<strong>on</strong>sider the c<strong>on</strong>trol<br />

property; however, the adjustable speed drive applicati<strong>on</strong>s such as tracti<strong>on</strong> motor are should<br />

be deliberated for c<strong>on</strong>trol. In this paper, the characteristics of IPMSM and IM c<strong>on</strong>trolled by<br />

space vector PWM are illustrated and verified by experiment. In case of IPMSM, the efficiency<br />

map was made up through driving simulati<strong>on</strong> c<strong>on</strong>sidering the actual c<strong>on</strong>trol. It was carried out<br />

MTPA c<strong>on</strong>trol until c<strong>on</strong>stant torque operating regi<strong>on</strong> and applied the field weakening c<strong>on</strong>trol<br />

under c<strong>on</strong>stant power regi<strong>on</strong>. In case of inducti<strong>on</strong> motor, V/f c<strong>on</strong>trol maintained a c<strong>on</strong>stant ratio<br />

of voltage versus current was carried out until c<strong>on</strong>stant torque operating regi<strong>on</strong> and applied<br />

the c<strong>on</strong>stant voltage variable frequency c<strong>on</strong>trol under c<strong>on</strong>stant power regi<strong>on</strong>. As illustrated in<br />

Figure 1, overall efficiency of IPMSM has high level than IM about 5%.<br />

[1] Z. Q. Zhu and David Howe, 'Electrical Machines and Drives for Electric, Hybrid, and Fuel cell Vehicles', Proceedings of the<br />

IEEE, Vol. 95, No. 4, pp 746-765, April 2007. [2] J. Herbst, J. Hahne, H. Jordan, H. Liu, A.Gattozzi and Ben Wu, 'Challenges in<br />

the Design of a 100 kW Inducti<strong>on</strong> Motor for a PHEV Applicati<strong>on</strong>', Vehicle Power and Propulsi<strong>on</strong> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, pp 408-413, 2009.<br />

RR15<br />

Comparis<strong>on</strong> of simultaneously measured pulse waveforms from both<br />

hands using permanent magnet-hall pulsimeter sensors<br />

Sang-suk Lee 1 , J<strong>on</strong>g-gu Choi 2 , Il-ho S<strong>on</strong> 1 , Keun-ho Kim 1 , Nam-kyu Lee 1 and Hyunsung<br />

Cho 1<br />

1 Oriental Biomedical Engineering, Sangji University, Korea<br />

2 Eastern-Western Biomedical Engineering, Sangji University, Korea<br />

Two radially arterial pulses of dual hands using the prototype of a clamping clip<br />

pulsimeter equipped with permanent magnet and Hall device are compared and<br />

analyzed. The phase difference of two pulse wave signals is dominantly presented<br />

from the simultaneous measuring clinical pulse wave signals for twenty two male<br />

participants at their 20’s. It is possible to analyze that the fast and slow pulse wave for<br />

right hand and left hand depend <strong>on</strong> the muscle property of arms rather than the total<br />

length of blood vessel due to cardiovascular circulatory system.<br />

[1] S. S. Lee, M. C. Ahn, and S. H. Ahn, J. Magnetics. 14, 132 (2009). [2] M. F. P. O’Rourke, R. P.<br />

Kelly, A. P. Avolio, 'The Arterial Pulse', 1st Ed.; Lea & Febiger: Philadelphia, PA, USA, 1992 [3] S. W.<br />

Kim, Y, G, Choi, H. S. Lee, D. H. Park, D. G. Hwang, S. S. Lee, G. W. Kim, S. G. Lee, and S. J. Lee, J.<br />

Appl. Phys. 99, R908 (2006).<br />

RR16<br />

RR17<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A study <strong>on</strong> new permanent magnet c<strong>on</strong>figurati<strong>on</strong> for high thrust<br />

density in permanent magnet synchr<strong>on</strong>ous linear motor<br />

Taewoo Kim and Junghwan Chang*<br />

Electrical Engineering, D<strong>on</strong>g-A University, Busan, 604-714, Korea, Korea<br />

WITHDRAWN<br />

Design of stati<strong>on</strong>ary pole pieces in a coaxial magnetic gear<br />

Daekyu Jang and Junghwan Chang*<br />

Electrical Engineering, D<strong>on</strong>a-A University, Saha-gu, Busan, 604-714, Korea, Korea<br />

Magnetic gears have been proposed by unique advantage compared with mechanical<br />

gears, such as c<strong>on</strong>tactless power transmissi<strong>on</strong>. In additi<strong>on</strong>, they can limit a torque<br />

under overloaded c<strong>on</strong>diti<strong>on</strong> and have excellent performances <strong>on</strong> noise, vibrati<strong>on</strong> and<br />

reliability [1]. However, their use in industries has been very limited due to poor torque<br />

density, low transmissi<strong>on</strong> ratio and transmitted toque performances. Of magnetic gears,<br />

a coaxial magnetic gear is a comm<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong> and extensively studied for its<br />

relative high performances [2]. It is c<strong>on</strong>sist of inner rotor, outer rotor and stati<strong>on</strong>ary<br />

pole pieces in between the rotors. The stati<strong>on</strong>ary pole pieces have an important role in<br />

torque transmissi<strong>on</strong> by modulating the air gap flux density distributi<strong>on</strong> adjacent to inner<br />

and outer rotor. However, they also generate unwanted harm<strong>on</strong>ics resulting in torque<br />

ripples and vibrati<strong>on</strong>. This paper proposes variants of stati<strong>on</strong>ary pole pieces to gain<br />

high performances in torque transmissi<strong>on</strong>. It also has mechanical and manufacturing<br />

advantages in transmitting torque by a structure combining each pole pieces. The finite<br />

element analysis shows the produced torque has reduced harm<strong>on</strong>ic comp<strong>on</strong>ents in both<br />

sides of rotors.<br />

[1] K.Atallah, S.D. Calverley and D. Howe, “Design, analysis and realizati<strong>on</strong> of a high performance<br />

magnetic gear”, IEEE proc.-Electr. Power Appl, vol. 151, No. 2, pp.135-143, March. 2004. [2]<br />

Noboru Niguchi, Katsuhiro Hirata, Masari Muramatsu and Yuichi Hayakawa, “Transmissi<strong>on</strong><br />

Torque Characteristics in a Magnetic Gear,” ICEM c<strong>on</strong>f, pp 1-6, sept. 2010.<br />

RR18<br />

Design techniques for reducing torque ripple in permanent magnet<br />

flux switching motor<br />

Daohan Wang 1 , Xiuhe Wang 2 and Sang-y<strong>on</strong>g Jung 1 *<br />

1 Sungkyunkwan University, Korea<br />

2 Shand<strong>on</strong>g University, China<br />

Permanent magnet flux switching motor (PMFSM) is a novel double salient machine<br />

which employ the PM instead of the field winding for excitati<strong>on</strong> and c<strong>on</strong>tains <strong>on</strong>ly <strong>on</strong>e set<br />

of armature winding so has the advantage of low cost power c<strong>on</strong>verter and extreme high<br />

efficiency. It has a potential for taking place of BLDC in some applicati<strong>on</strong>s, such as fans<br />

and air ventilati<strong>on</strong> machines. Due to the different structure and operati<strong>on</strong> principle from<br />

traditi<strong>on</strong>al permanent magnet machine, the generated torque ripple in PMFSM is very<br />

critical and rather unique compared to the comm<strong>on</strong> PM machines. In this paper, the design<br />

techniques of reducing the torque ripple in PMFSM has been presented. Different kinds<br />

of design approaches have been presented to reduce the torque ripple with comparing the<br />

mean output torque. Analytical method is first presented to investigate the influence and<br />

determine the design parameters thus reduce the computati<strong>on</strong>al effort. Then FEA simulati<strong>on</strong><br />

is employed to validate the analysis above. Finally, time stepped FEA simulati<strong>on</strong> is being<br />

employed to investigate the performance with different approaches adopted.<br />

[1] Z. Q. Zhu, A. S. Thomas, J. T. Chen, and G. W. Jewell, “Cogging Torque in Flux-Switching Permanent<br />

Magnet Machines,” IEEE Trans. Magn., vol. 45, no. 10, pp. 4708-4711, Oct. 2009. [2] Z. Q. Zhu, J. T. Chen,<br />

D. Howe, S. Iwasaki, and R. Deodhar, “Design of multi-tooth flux-switching permanent magnet brushless ac<br />

machines for low speed direct drives,” IEEE Trans. Magn., vol. 44, no. 11, pp. 4313-4316, 2008.<br />

July 8 - 13, 2012 Busan, Korea 199<br />

Poster Thursday


Poster Thursday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RR19<br />

The analysis of line-start permanent magnet machine with saliency<br />

ratio<br />

Kwang Hee Kim, Jian Li and Yun Hyun Cho*<br />

D<strong>on</strong>g-A University, Korea<br />

RR20<br />

RR21<br />

WITHDRAWN<br />

Analysis of n<strong>on</strong>-linear characteristics of linear compressor<br />

Park Daegeun and Cho Yunhyun*<br />

D<strong>on</strong>g-A University, Korea<br />

WITHDRAWN<br />

Torque harm<strong>on</strong>ics and reducti<strong>on</strong> design characteristics of inducti<strong>on</strong><br />

motor for electric vehicle propulsi<strong>on</strong><br />

Kyung-w<strong>on</strong> Je<strong>on</strong> 1 , Seungho Lee 1 , Y<strong>on</strong>g-jae Kim 2 and Sang-y<strong>on</strong>g Jung 1 *<br />

1 School of Electr<strong>on</strong>ic and Electrical Engineering, Sungkyunkwan Univ., Korea<br />

2 Dept. of Electrical Engineering, Chosun University, Korea<br />

This paper deals with torque harm<strong>on</strong>ic characteristics of inducti<strong>on</strong> motor for electric vehicle (EV).<br />

For calculate phase stator harm<strong>on</strong>ic leakage flux of a three phase inducti<strong>on</strong> motor, an analysis method<br />

is determine relati<strong>on</strong>ships with stator teeth design. In particular, torque harm<strong>on</strong>ics including EMF<br />

harm<strong>on</strong>ics at whole speed ranges are analyzed by the finite element method (FEM). Torque harm<strong>on</strong>ic<br />

comp<strong>on</strong>ents are identified with Fourier fast transform (FFT). Torque harm<strong>on</strong>ics are generated due<br />

to the different phase windings interacti<strong>on</strong> and they can be reduced by applying a stator teeth design.<br />

The electromagnetic field and corresp<strong>on</strong>ding harm<strong>on</strong>ics of an electrical machine are calculated using<br />

the FEM, the harm<strong>on</strong>ic winding factors show how the torque harm<strong>on</strong>ics can be reduced significantly<br />

by good stator teeth design. The novel design methods to compensate the specified torque harm<strong>on</strong>ics<br />

are proposed. Then, its effectiveness is clarified according to the representative c<strong>on</strong>trol strategies for<br />

inducti<strong>on</strong> motor such as maximum torque per ampere (MTPA) and flux-weakening c<strong>on</strong>trol.<br />

[1] Lee S., Kim Y.-J., Jung S.-Y., “Numerical Investigati<strong>on</strong> <strong>on</strong> Torque Harm<strong>on</strong>ics Reducti<strong>on</strong> of Interior PM Synchr<strong>on</strong>ous<br />

Motor With C<strong>on</strong>centrated Winding”, IEEE Trans <strong>on</strong>. Magnetics, vol.48, no.2, pp.927-930, Feb. 2012. [2] Yamazaki K.,<br />

Suzuki A., Ohto M., Takakura T., Nakagawa S., “Equivalent Circuit Modeling of Inducti<strong>on</strong> Motors C<strong>on</strong>sidering Stray<br />

Load Loss and Harm<strong>on</strong>ic Torques Using Finite Element Method”, IEEE Trans <strong>on</strong>. Magnetics, vol.47, no.5, pp.986-989,<br />

May. 2011. [3] Bianchi N., Alberti L., “MMF Harm<strong>on</strong>ics Effect <strong>on</strong> the Embedded FE Analytical Computati<strong>on</strong> of PM<br />

Motors”, IEEE Trans <strong>on</strong>. Industry Applicati<strong>on</strong>s, vol.46, no.2, pp.812-820, Mar-Apr. 2010.<br />

200 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

RR22<br />

Numerical analysis <strong>on</strong> ir<strong>on</strong> loss and pm loss of permanent magnet<br />

synchr<strong>on</strong>ous motor c<strong>on</strong>sidering the carrier harm<strong>on</strong>ics<br />

Yun-ho Je<strong>on</strong>g 1 , Kyung-w<strong>on</strong> Je<strong>on</strong> 1 , Y<strong>on</strong>g-jae Kim 2 and Sang-y<strong>on</strong>g Jung 1 *<br />

1 School of Electr<strong>on</strong>ic and Electrical Engineering, Sungkyunkwan Univ, Korea<br />

2 Dept. of Electrical Engineering, Chosun University, Korea<br />

In this paper, decisive influences of the inverter harm<strong>on</strong>ic <strong>on</strong> ir<strong>on</strong> loss characteristic for PMSM (Permanent<br />

Magnet Synchr<strong>on</strong>ous Motor) are numerically investigated with the FEM (Finite Element Method).<br />

Particularly, analysis is carried out based <strong>on</strong> a multi-layer buried PMSM, which is newly designed for EV<br />

drive system and its rotor c<strong>on</strong>tains ferrite magnets. First of all, not <strong>on</strong>ly the design criteria and the specificati<strong>on</strong><br />

of the designed PMSM but also the features of the motor like torque ripple, Back-EMF are represented. In<br />

additi<strong>on</strong>, the remarkable ir<strong>on</strong> loss analysis result, that is obtained using 3-D FEM c<strong>on</strong>sidering skewed stator<br />

structure, is covered in priority. Then its each harm<strong>on</strong>ic comp<strong>on</strong>ent is identified using the FFT (Fourier Fast<br />

Transform) and that is compared with ir<strong>on</strong> loss characteristic in case of sinusoidal input current which is<br />

not include harm<strong>on</strong>ic comp<strong>on</strong>ent. Finally, the efficiency at each operating point is calculated c<strong>on</strong>sidering<br />

loss analysis results. Meanwhile, entire analysis is performed through various operating c<strong>on</strong>diti<strong>on</strong>s using<br />

intrinsically real input current values implemented by testing performance of the manufactured model.<br />

[1] Z.Q.Zhu, Y.S.Chen, D.Howe, 'Ir<strong>on</strong> Loss in Permanent-Magnet Brushless AC Machines Under Maximum Torque<br />

Per Ampere and Flux Weakening C<strong>on</strong>trol', IEEE Trans. <strong>on</strong> Magnetics, vol. 38, No. 5,pp. 3285-3287, Set. 2002. [2]<br />

Katsumi Yamazaki, Shinjiro Watarim 'Loss Analysis of Permanent-Magnet Motor C<strong>on</strong>sidering Carrier Harm<strong>on</strong>ics<br />

of PWM Inverter Using Combinati<strong>on</strong> of 2-D and 3-D Finite-Element Method', IEEE Trans. <strong>on</strong> Magnetics, vol. 41,<br />

No. 5,pp. 3285-3287, May. 2005. [3] G. Ombach, J. Junak, 'Torque ripple optimizati<strong>on</strong> of skewed IPM motor for<br />

field weakening operati<strong>on</strong>', Electrical Machines and Systems (ICEMS) 2011, pp. 1-7, Aug. 2011.<br />

RR23<br />

Defect depth estimati<strong>on</strong> based <strong>on</strong> the analysis of interference defects<br />

<strong>on</strong> the underground gas pipelines<br />

Min-Ho Kim 1 , Bok-Jin Oh 1 , and Doo-Hyun Choi 2 *<br />

1<br />

Graduate School of Electrical Engineering and Computer Science, Kyungpook<br />

Nati<strong>on</strong>al Univ., Korea<br />

2<br />

School of Electr<strong>on</strong>ics Engineering, Kyungpook Nati<strong>on</strong>al Univ., Korea<br />

Underground gas pipelines have corrosi<strong>on</strong>s and deformati<strong>on</strong>s due to both the natural<br />

causes such as moisture and ground pressure and the artificial causes such as faulty<br />

c<strong>on</strong>structi<strong>on</strong>, etc. So, periodic pipeline inspecti<strong>on</strong> is essential. In NACE (nati<strong>on</strong>al<br />

associati<strong>on</strong> of corrosi<strong>on</strong> engineers) standard, it is advised to replace the pipeline when<br />

a defect’s depth is over 50% of the pipeline’s thickness. Therefore, the study to analyze<br />

the defect’s depth and its progress is meaningful. Especially when defects more than<br />

two are closely located, the interacti<strong>on</strong> am<strong>on</strong>g these defects accelerates the progress of<br />

defecti<strong>on</strong>. In this paper, the interference defects <strong>on</strong> underground pipelines are analyzed<br />

and their depths are estimated effectively. Experimental results show that the proposed<br />

method can effectively estimate the depth of the interference defects.<br />

RR24<br />

Comparis<strong>on</strong> <strong>on</strong> electromagnetic losses of super high speed PM motor/<br />

generator with slot and slotless stators<br />

Jin Hak Jang 1 , Jian Li 2 and Yun Hyun Cho 1 *<br />

1 D<strong>on</strong>g-A University, Korea<br />

2 D<strong>on</strong>g-A University, China<br />

WITHDRAWN


RR25<br />

A study <strong>on</strong> Voltage-PWM c<strong>on</strong>trol of switched reluctance generator at<br />

low speed<br />

Sun Ning 1 , Dawo<strong>on</strong> Choi 2 , Jian Li 1 and Yunhyun Cho 2 *<br />

1 D<strong>on</strong>gA-university, China<br />

2 D<strong>on</strong>gA-university, Korea<br />

This paper is a study <strong>on</strong> switched reluctance generator’s c<strong>on</strong>trol method---Voltage-<br />

PWM. It can be used to regulate the current to a desired value by varying the average<br />

applied voltage in the switched reluctance generator . The advantages of Voltage-<br />

PWM c<strong>on</strong>trol at low speed are more than high speed which may make the applicati<strong>on</strong><br />

of PWM difficult. The switched reluctance machine can operate as a generator as well<br />

as a motor by simply changing the firing angles. Some main c<strong>on</strong>trol methods we often<br />

used are Chopped Current C<strong>on</strong>trol (CCC), Angular Positi<strong>on</strong> C<strong>on</strong>trol (APC) and PWM<br />

C<strong>on</strong>trol . The c<strong>on</strong>troller could regulate c<strong>on</strong>trol variables, such as current level, turn-<strong>on</strong><br />

and turn-off angles, supply voltage and so <strong>on</strong>. Different c<strong>on</strong>trol methods will be carried<br />

out by regulating some variables in different c<strong>on</strong>diti<strong>on</strong>s. For example, at low speed, the<br />

d.c link voltage is c<strong>on</strong>trolled by varying the set-point current or the duty-cycle and at<br />

high speed by varying the c<strong>on</strong>trol angles. Because of excitati<strong>on</strong> current is closely linear<br />

relati<strong>on</strong> to duty cycle, so many applicati<strong>on</strong>s determine this c<strong>on</strong>trol method.<br />

[1]Miller, T.J.E. Electr<strong>on</strong>ic C<strong>on</strong>trol of Switched Reluctance Machines. MPG Books Ltd, Bodmin,<br />

Cornwall. 2001. [2]K.Kannan , Dr.S.Sutha. The 4th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Power Engineering and Optimizati<strong>on</strong><br />

<str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> (PEOCO2010), ShahAlam, Selangor, Malaysia.23-24 June 2010. [3] Jianzh<strong>on</strong>g Sun,<br />

Fengxian Bai, Special type electroc machine and c<strong>on</strong>trol China waterpub press, 2005.137-143.<br />

RR26<br />

The measurement procedure of the equivalent core loss in a PM motor<br />

Guo Jhih Yan 1 *, Ming-hung Jian 1 and Chia-sheng Huang 2<br />

1 Micro/Meso Mechanical Manufacturing R&D Secti<strong>on</strong>, Metal Industries Research &<br />

Development Centre, Taiwan<br />

2 Codent Tech Co. Ltd, Taiwan<br />

For the development of high efficiency motor, the core loss decrease is <strong>on</strong>e of the most important tasks.<br />

However, the calculated core loss in the design stage is not so accurate because the specificati<strong>on</strong> provided<br />

by material manufacturer usually obtained by ideal test c<strong>on</strong>diti<strong>on</strong> in simple geometry, i.e. single sheet tester<br />

and toroidal tester. Therefore, a method that can measure the core loss with the practical shape of motor<br />

stator/rotor core includes every aspect of the manufacturing effects is required. This paper proposed a<br />

refined procedure based <strong>on</strong> torque metric method. Am<strong>on</strong>g several proven measuring methods, it is a directly<br />

measuring method that can be applied to the actual motor. Typical torque method uses a motor driving a<br />

specimen at a specific speed and then measures the drag torque. However, it is time c<strong>on</strong>suming and requires<br />

higher precisi<strong>on</strong> torque meter. Instead, the proposed method measures the speed-power characteristic curve<br />

of the driving motor with/without the test motor. From the difference of the speed-power characteristic,<br />

the core loss at various speeds can be obtained. Several c<strong>on</strong>venti<strong>on</strong>al PM motors are taking as examples to<br />

dem<strong>on</strong>strate this procedure and to investigate the core loss influenced by manufacturing.<br />

[1]N. Stranges, and R. D. Findlay, “Measurement of Rotati<strong>on</strong>al Ir<strong>on</strong> Losses in Electrical Sheet,” IEEE<br />

TRANSACTIONS ON MAGNETICS, Vol. 36, No. 5, Sep, 2000, pp. 3457-3459. [2]W. Arshad, etc, “Incorporating<br />

laminati<strong>on</strong> processing and comp<strong>on</strong>ent manufacturing in electrical machine design tools,” in Industry<br />

Applicati<strong>on</strong>s <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, 2007. 42nd IAS Annual Meeting. <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Records, 2007, pp. 94-102. [3]Youguang<br />

Guo, etc, “Measurement and Modeling of Rotati<strong>on</strong>al Core Losses of Soft Magnetic Materials Used in Electrical<br />

Machines: A Review,” IEEE TRANSACTIONS ON MAGNETICS, Vol. 44, No. 2,Feb, 2008, pp. 279-291.<br />

RR27<br />

MFL signal enhancement based <strong>on</strong> exp<strong>on</strong>ential smoothing<br />

Su-ye<strong>on</strong> Je<strong>on</strong>g 1 , J<strong>on</strong>g-hwa Kim 2 and Doo-hyun Choi 2 *<br />

1<br />

Graduate School of Electrical Engineering and Computer Science, Kyungpook<br />

Nati<strong>on</strong>al Univ., Korea<br />

2<br />

School of Electr<strong>on</strong>ics Engineering, Kyungpook Nati<strong>on</strong>al Univ., Korea<br />

Nowadays, as industrializati<strong>on</strong> is in progress worldwide and ec<strong>on</strong>omy grows rapidly,<br />

demand for the energy supply of oil and gas has also increased. Currently, over milli<strong>on</strong>s<br />

of kilometers of underground gas pipeline has been established worldwide. The<br />

maintenance of pipeline is needed for the efficient supply of energy, but in reality, it is<br />

impossible for human experts to investigate all the underground pipelines in order to<br />

c<strong>on</strong>firm whether a pipe has deteriorati<strong>on</strong> or damage because of the pipe’s geographical<br />

positi<strong>on</strong>. So, automatic n<strong>on</strong>destructive testing methods by using MFL (magnetic<br />

flux leakage) signal are currently studied actively to detect and extract defects <strong>on</strong> the<br />

pipeline. The raw signals acquired from MFL sensors c<strong>on</strong>tain the signals of defects, as<br />

well as noise and distorti<strong>on</strong> caused by various underground envir<strong>on</strong>ments. In this paper,<br />

MFL signal is enhanced by using several smoothing techniques. Through experiments,<br />

it is c<strong>on</strong>firmed that the distorti<strong>on</strong> of raw signal by noise canceling can be reduced.<br />

RR28<br />

RR29<br />

RR30<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Electromagnetic separati<strong>on</strong> of the brown coal ash of thermal power<br />

stati<strong>on</strong>s<br />

Shavkat Malikov 1 , Valeriy Pikul 1 , Nuranya Mukhamedshina 1 , Vladimir Sandalov 2 and<br />

Elvira Ibragimova 2 *<br />

1 Muclear physics, Institute of Nuclear Physics, Uzbekistan<br />

2 Radiati<strong>on</strong> physics of solids and material science, Institute of Nuclear Physics,<br />

Uzbekistan<br />

Tens milli<strong>on</strong>s of brown coal ash have accumulated near thermal power stati<strong>on</strong>s (TPS) in<br />

Uzbekistan, so their utilizati<strong>on</strong> has become quite actual. So far the ash is used for cement.<br />

However the ash is well known to c<strong>on</strong>tain a large amount of valuable elements, including<br />

~3.13%Fe 2O 3 in Russian coal. Element analyses of the brown coal ash from Angren TPS<br />

were d<strong>on</strong>e with the neutr<strong>on</strong> activati<strong>on</strong> techniques and 3.6%Fe, 0.084%Mn, 0.063%Zr and<br />

also 0.023% of rare earth elements have been determined. The ash samples were underg<strong>on</strong>e<br />

to electromagnetic separati<strong>on</strong>, and the magnetic fracti<strong>on</strong> was 3.7%, where the c<strong>on</strong>tent of<br />

Fe increased to 58%. Then the magnetic fracti<strong>on</strong> was separated with the standard screen<br />

grader into 7 classes from 0.4 to 0.05mm. Two times increase of the c<strong>on</strong>tents of Fe and rare<br />

earth elements have been found in the fine fracti<strong>on</strong>s of 0.1-0.05mm. Optical absorpti<strong>on</strong><br />

spectroscopy of water soluti<strong>on</strong>s of the magnetic fracti<strong>on</strong>s has revealed the presence of Fe 2+<br />

and Fe 3+ i<strong>on</strong>s. Microscopic analysis of the fine fracti<strong>on</strong>s has shown that there are black ir<strong>on</strong><br />

microspheres of 0.02-0.05mm sizes, which can be used for cleaning of technological liquid<br />

waste by means of the high gradient magnetic field, and powder metallurgy.<br />

Studies <strong>on</strong> viscidity in ferrofluids of Fe3O4 Han Gu 1 , Zhaozhen Jiang 2 , Aimei Zhang 3 and Xiaoshan Wu 2<br />

1<br />

Advance Functi<strong>on</strong>al Materials Lab and Department of Physics, Changshu Institute<br />

of Technology, Changs, China<br />

2<br />

Lab of Solid State Microstructures, Dept Physics, Nanjing University, China<br />

3<br />

College of Science, Hohai University, China<br />

Fe 3O 4 nanoparticles with superparamagnetic properties are synthesized by sol-gel<br />

approach. Fe 3O 4 nanoparticles are coated using the amorphous silica. The viscidity<br />

of the coated Fe 3O 4 nanoparticles increases as the particles is incorporated in the<br />

impregnant, which may due to the magnetic interacti<strong>on</strong>s. At room temperature, the<br />

ferrofluid viscidity increases momot<strong>on</strong>ically with increasing the c<strong>on</strong>centrati<strong>on</strong> of<br />

Fe 3O 4 nanoparticles, the ratio of surface activity. With rising the temperature, the<br />

ferrofluid viscidity becomes larger. The applied magnetic field has also effects <strong>on</strong> the<br />

ferrofluid viscidity. The switching process of the applied magnetic field may increase<br />

the ferrofluid viscidity, although the ferrofluid viscidity increases with increasing the<br />

applied magnetic field. Dynamic properties of the magnetic particles in the impregnant<br />

are also discussed in the present.<br />

N<strong>on</strong>-c<strong>on</strong>tact magnetic evaluati<strong>on</strong> of ferromagnetic plate and its<br />

compensati<strong>on</strong> of unknown air gap<br />

Young-hak Kim 1 and Kwang-ho Shin 2 *<br />

1 Puky<strong>on</strong>g Nati<strong>on</strong>al University, Korea<br />

2 Dept. of Informati<strong>on</strong> and Communicati<strong>on</strong> Engineering, Kyungsung University,<br />

Korea<br />

This paper represents a magnetic hysteresis model-assisted measurement method<br />

for n<strong>on</strong>-c<strong>on</strong>tact evaluati<strong>on</strong> of ferromagnetic plates in the case of the air gap between<br />

the test sample and the sensor probe is unknown. Our method involves measuring<br />

hysteresis loops from a test sample using a sensor probe in close proximity to the<br />

sample and measuring inductance spectra according to the various air gap. The sensor<br />

outputs were simulated based <strong>on</strong> a magnetic hysteresis model (Jiles-Athert<strong>on</strong> model)<br />

to describe the magnetic property of the sample. In this study, the measurement was<br />

applied to characterize a series of Fe-C samples. However, it is hard to c<strong>on</strong>firm the<br />

permeability of a sample when the air gap is unknown, since the magnetic resistance<br />

of magnetic circuit composed of the sample and the sensor probe is affected by air<br />

gap size. The main idea of our study is that the frequency spectrum of inductance of<br />

the magnetic circuit is unaffected when the air gap is adequately small, even if the<br />

amplitude of inductance is directly dependent <strong>on</strong> air gap. The magnetic hysteresis<br />

measured with unknown air gap was compensated by measured inductance spectra,<br />

and was found to agree with n<strong>on</strong>linear FEM analysis.<br />

July 8 - 13, 2012 Busan, Korea 201<br />

Poster Thursday


Poster Friday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

RR31<br />

The several analysis techniques of high speed inducti<strong>on</strong> motor for<br />

copper die casting<br />

Do-kwan H<strong>on</strong>g 1 *, Jae-hak Choi 1 , Byung-chul Woo 1 , Dae-hyun Koo 1 and Chan-woo<br />

Ahn 2<br />

1 Korea Electrotechnology Research Institute, Korea<br />

2 D<strong>on</strong>g-A University, The department of mechanical engineering, Korea<br />

RR32<br />

SA01<br />

WITHDRAWN<br />

Effect of magnetic reynolds number variati<strong>on</strong> <strong>on</strong> MHD c<strong>on</strong>vecti<strong>on</strong><br />

inside an enclosure<br />

Mohsen Pirmohammadi*<br />

MAPNA Group, Iran<br />

Numerically investigati<strong>on</strong> is carried out for magnetohydrodynamics natural c<strong>on</strong>vecti<strong>on</strong><br />

in an enclosure. The vertical walls are maintained isothermal at different temperatures<br />

and the other walls are adiabatic. The magnetic field is applied horiz<strong>on</strong>tally. The n<strong>on</strong><br />

linear governing equati<strong>on</strong>s for the fluid flow and heat transfer are solved for three<br />

magnetic Reynolds numbers (10-5, 10-3 and 0.1). The Rayleigh number, the Hartmann<br />

number and the Prandtl number are c<strong>on</strong>sidered 105, 80 and 0.01, respectively. A<br />

finite volume code based <strong>on</strong> Patankar's SIMPLER method is utilized. It is found that<br />

when the magnetic Reynolds number (Rem) is very low (10-5 and 10-3) the magnetic<br />

field distributi<strong>on</strong> in the cavity is not affected by flow field and as Rem increases the<br />

magnetic field in x and y directi<strong>on</strong> is not c<strong>on</strong>stant. Also it is observed that as Rem<br />

increases the rate of heat transfer changes.<br />

Magnetic annealing effects <strong>on</strong> properties of the multilayer BaTiO3 /<br />

CoFe2O4 thin films<br />

Yuqiang Dai 1 , Jianming Dai 1 *, Xianwu Tang1 and Qiangchun Liu 2<br />

1<br />

Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese<br />

Academy of Sciences, China<br />

2<br />

School of Physics and Electr<strong>on</strong>ic Informati<strong>on</strong>, Huaibei Normal University, China<br />

Multilayer BaTiO 3/CoFe 2O 4 thin films are prepared via chemical soluti<strong>on</strong> depositi<strong>on</strong><br />

method with and without magnetic field annealing process, respectively. The<br />

microstructural, magnetic, dielectric and the ferroelectric properties of the films are<br />

investigated. It is observed that the dielectric c<strong>on</strong>stant, polarizati<strong>on</strong>s and magnetizati<strong>on</strong>s<br />

of the multilayer thin films are improved with magnetic field annealing process.<br />

Moreover, for the magnetic field annealing films, the saturati<strong>on</strong> magnetizati<strong>on</strong> with<br />

measuring magnetic field vertical to the film surface is much higher than that parallel<br />

to the film surface.<br />

202 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SA02<br />

Magnetoelectric CoFe2O4-PZT thin film composites grown by pulsed<br />

laser depositi<strong>on</strong><br />

Ioanna Giouroudi 1 *, Mohammed Alnassar 2 , Roland Groessinger 3 and Juergen Kosel 2<br />

1<br />

Institute of Sensor and Actuator Systems, Vienna University of Technology, Austria<br />

2<br />

Divisi<strong>on</strong> of Physical Sciences and Engineering, King Abdullah University of Science<br />

and Technology, Saudi Arabia<br />

3<br />

Institute of Solid State Physics, Vienna University of Technology, Austria<br />

SA03<br />

Synthesis and magnetic property of multiferroic DyMnO 3<br />

nanoparticles in mesoporous silica<br />

Takayuki Tajiri 1 *, Kenta Hamamoto 2 , Yuhki Ando 2 , Hiroyuki Deguchi 2 , Masaki Mito 2<br />

and Atsushi Kohno 1<br />

1 Faculty of Science, Fukuoka University, Japan<br />

2 Faculty of Engineering, Kyushu Institute of Technology, Japan<br />

Multiferroic compound DyMnO 3 shows antiferromagnetic ordering with T N ~ 40 K and<br />

Dy spin ordering below about 6 K. The ferroelectricity is attributed to lattice modulati<strong>on</strong><br />

accompanied by the antiferromagnetic order. We are interested in the size effect <strong>on</strong><br />

DyMnO 3 nanoparticles with particle size of a few nano-meters. We synthesized DyMnO 3<br />

nanoparticles and investigated their magnetic property. The DyMnO 3 nanoparticles were<br />

synthesized in the pores of a mesoporous silica SBA-15 with pore diameter of about 8<br />

nm. SBA-15 was used as a template to equalize the particle size in the fabricati<strong>on</strong> of the<br />

DyMnO 3 nanoparticles. The X-ray diffracti<strong>on</strong> pattern for DyMnO 3 nanoparticles shows<br />

some broad Bragg peaks corresp<strong>on</strong>ding to crystal structure of DyMnO 3 bulk crystals. The<br />

size of nanoparticles was estimated to be about 10 nm based <strong>on</strong> the Bragg peaks and using<br />

Scherrer’s equati<strong>on</strong>. The temperature dependence of DC magnetic susceptibilities for the<br />

nanoparticles exhibited a magnetic irreversibility between field-cooled susceptibility and<br />

zero-field-cooled <strong>on</strong>e below about 40 K and an increase in susceptibilities due to magnetic<br />

ordering am<strong>on</strong>g the Dy spins below about 5 K. The magnetizati<strong>on</strong> curves exhibited<br />

hysteresis loop below blocking temperature. DyMnO 3 nanoparticles were successfully<br />

synthesized with size of about 10 nm and showed superparamagnetic behaviors.<br />

SA04<br />

WITHDRAWN<br />

Magnetic properties of Co 1-xMn xFe 2O 4 (x=0-0.5) - PZT thin films<br />

fabricated by sol-gel spin coating method<br />

M. Khodaei, S. A. Seyyed Ebrahimi* and R. Vaghar<br />

Center of Excellence for Magnetic Materials, School of Metallurgy and Materials,,<br />

University of Tehran, Iran<br />

Co (1-x)Mn xFe 2O 4 (x=0-0.5) thin films were fabricated <strong>on</strong> PZT layer by sol-gel spin<br />

coating method in order to investigati<strong>on</strong> of influence of Mn-substituti<strong>on</strong> in C oFe 2O4<br />

<strong>on</strong> the magnetic properties. The films were fabricated <strong>on</strong> the PZT layer which was<br />

previously fabricated <strong>on</strong> Pt(111)/Ti/SiO 2/Si substrate using the same method. The phase<br />

identificati<strong>on</strong> of the samples was studied by X-ray diffractometry analysis. Magnetic<br />

properties of the samples were also measured using a vibrating sample magnetometer.


SA05<br />

M doping element localizati<strong>on</strong> by the molecular field theory in the<br />

Ga xFe 2-xO 3:M thin films<br />

Christophe Lefevre 1 *, Ran Hee Shin 2 , Ji Hye Lee 2 , Seol Hee Oh 2 , Alexandre<br />

Thomass<strong>on</strong> 1 , Francois Roulland 3 , Christian Meny 1 , William Jo 2 and Nathalie Viart 3<br />

1 CNRS, France<br />

2 Department of Physics, Ewha Womans University, Korea<br />

3 Universite de Strasbourg, France<br />

Magnetoelectric materials open the way towards new applicati<strong>on</strong>s through c<strong>on</strong>trolling<br />

magnetic or electric polarizati<strong>on</strong> with electric or magnetic field, respectively.<br />

Ga 0.6Fe 1.4O 3 is predicted magnetoelectric with n<strong>on</strong> zero magnetizati<strong>on</strong> at room<br />

temperature. High quality GFO thin films having similar magnetic properties to<br />

those of the bulk materials have been produced <strong>on</strong>ly recently. However their electric<br />

properties failed to be properly characterized until now because of important leakage<br />

currents originating from a hopping mechanism between Fe 2+ and Fe 3+ within the<br />

structure. Recently, we succeeded to str<strong>on</strong>gly lower the leakage currents of these films<br />

by chemical doping. The determinati<strong>on</strong> of the cati<strong>on</strong>ic distributi<strong>on</strong> within the structure<br />

is a key point for the knowledge of these phases, because it is at the origin of the<br />

evidenced magnetic and electrical properties of these materials. We present here an<br />

original approach to determine the localizati<strong>on</strong> of the M doping element based <strong>on</strong> the<br />

molecular field theory. Different modeling associated with the different substituti<strong>on</strong><br />

possibilities have been performed within the frame of this theory and are compared<br />

with the experimental values.<br />

SA06<br />

Interplay between magnetizati<strong>on</strong> and polarizati<strong>on</strong> in epitaxial<br />

(Ga,Fe) 2O3 thin films with additi<strong>on</strong>al i<strong>on</strong>-substituti<strong>on</strong>s into Fe sites<br />

R. H. Shin 1 , J. H. Lee 1 , S. H. Oh 2 , W. Jo 2 *, C. Lefevre 3 , F. Roulland 3 , A. Thomass<strong>on</strong> 3 , C.<br />

Meny 3 and N. Viart 3<br />

1<br />

Department of Physics and CNRS-EWHA <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Research Center, Ewha<br />

Womans University, Korea<br />

2<br />

Department of Physics, Ewha Womans University, Korea<br />

3<br />

Institute of Physics and Chemistry of Materials of Strasbourg, France<br />

(Ga,Fe) 2O 3 (GFO) is a promising material for room-temperature multiferroic because of high<br />

magnetic T C as 370 K when Ga = 0.6 and Fe = 1.4. However, multiferroic properties of GFO<br />

in thin film type is c<strong>on</strong>troversial because most of polarizati<strong>on</strong>-electric field hysteresis curves<br />

in GFO showed leaky behaviors due to large leakage current. In this research, we focused <strong>on</strong><br />

the improved magnetic and electric properties of GFO thin films as multiferroic by decreasing<br />

their leakage current. The main origin probably lies <strong>on</strong> electr<strong>on</strong> hopping between Fe 3+ and Fe 2+<br />

octahedr<strong>on</strong> sites which can co-exist due to charge neutrality by oxygen vacancy. Therefore, we<br />

tried to decrease leakage current by substituting Fe 2+ site with divalent cati<strong>on</strong>. The i<strong>on</strong>-substituted<br />

GFO thin films were epitaxially deposited al<strong>on</strong>g the b-axis by pulsed laser depositi<strong>on</strong> at 750°C<br />

for 15 min in oxygen partial pressure of 200 mTorr <strong>on</strong> SrRuO 3/SrTiO 3 (111) substrates. The<br />

films showed the str<strong>on</strong>gly reduced leakage current up to 5~6 order of magnitude. Magnetic<br />

properties of the doped GFO thin films were investigated by SQUID measurement. Ferroelectric<br />

polarizati<strong>on</strong> as a functi<strong>on</strong> of external field was measured in macroscopic and microscopic<br />

schemes. Magnetoelectric interacti<strong>on</strong>s of the epitaxial thin-films will be addressed in this talk.<br />

SA07<br />

Fabricati<strong>on</strong> and characterizati<strong>on</strong> of heusler-alloy/perovskite<br />

heterostructures<br />

Kohei Kobayashi, Keita Sakuma*, Naoto Fukatani, Tetsuya Miyawaki, Kenji Ueda<br />

and Hidefumi Asano<br />

Nagoya University, Japan<br />

Multiferroic heterostructures composed of ferromagnetic half-metal and ferroelectric materials have<br />

attracted significant interest due to the potential applicati<strong>on</strong>s for nanoscale devices. Heusler-alloy /<br />

perovskite heterostructures are expected to emerge the interface magnetoelectric1) and tunnel electroresistance<br />

effect. In this study, to explore the potential of Heusler-alloy / perovskite heterostructures, we<br />

have investigated multiferroic and transport properties of heterostructures composed of half-metallic<br />

Heusler-alloy Fe 2CrSi (FCS) and ferroelectric perovskite Ba 0.7Sr 0.3TiO 3 (BSTO). BSTO was firstly<br />

deposited <strong>on</strong> MgO and LaAlO 3 substrates by magnetr<strong>on</strong> sputtering, followed by the depositi<strong>on</strong> of<br />

FCS at 550-750°C. Structural characterizati<strong>on</strong> revealed that FCS grew epitaxially <strong>on</strong> BSTO with the<br />

relati<strong>on</strong>ship of BSTO(001)[100]||FCS(001)[110]. From M-H curve of the BSTO (100 nm) / FCS<br />

(150 nm) bilayer, saturated magnetizati<strong>on</strong> of 417 emu/cc was obtained. The ferroelectric properties<br />

of La 0.7Sr 0.3MnO 3 (LSMO) / BSTO (100 nm) / FCS (50 nm) were measured, and the maximum<br />

remaneant polarizati<strong>on</strong> was 73 μC/cm 2 . From these results, ferromagnetic and ferroelectric properties<br />

were preserved in BSTO/FCS heterostructures. From the analysis of I-V characteristics, Schottkyemissi<strong>on</strong><br />

was found to be a dominant leakage mechanism in LSMO / BSTO / FCS. The BSTO / FCS<br />

heterostructure is a promising candidate for fabricating multiferroic devices.<br />

1) K. Yamauchi et al., Appl. Phys. Lett. 91, 062506 (2007)<br />

SA08<br />

SA09<br />

Preperati<strong>on</strong> of hexag<strong>on</strong>al YFeO 3 powder and thin film<br />

Hanju Lee, Kyoungchul Kim, Sujin Lee, Sul A Choi and Kiejin Lee*<br />

physics, Department of physics, Sogang university, Korea<br />

SA10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Optical properties of (SrMnO3) n/(LaMnO3) 2n superlattices: An<br />

insulator-to-metal transiti<strong>on</strong> observed in the absence of disorder<br />

Andrea Perucchi 1 , Le<strong>on</strong>etta Baldassarre 1 , Alessandro Nucara 2 , Paolo Calvani2,<br />

Carolina Adamo 3 , Darrell G Schlom 3 , Pasquale Orgiani 4 , Luigi Maritato 4 and Stefano<br />

Lupi 5<br />

1<br />

Sincrotr<strong>on</strong>e Trieste, Italy<br />

2<br />

CNR-SPIN and University of Rome 'Sapienza', Italy<br />

3<br />

Cornell University, USA<br />

4<br />

CNR-SPIN and University of Salerno, Italy<br />

5<br />

CNR-IOM and University of Rome 'Sapienza', Italy<br />

We measure the optical c<strong>on</strong>ductivity, σ 1(ω), of (SrMnO 3) n/(LaMnO 3) 2n superlattices (SL)<br />

for n=1, 3, 5, and 8 and 10 < T < 400 K. Data show a T-dependent insulator to metal<br />

transiti<strong>on</strong> (IMT) for n=3, driven by the softening of a polar<strong>on</strong>ic mid-infrared band. At<br />

n=5 that softening is incomplete, while at the largest-period n=8 compound the MIR<br />

band is independent of T and the SL remains insulating. One can thus first observe the<br />

IMT in a Manganite system in the absence of the disorder due to chemical doping.<br />

Unsuccessful rec<strong>on</strong>structi<strong>on</strong> of the SL optical properties from those of the original bulk<br />

materials suggests that (SrMnO 3) n/ (LaMnO 3) 2n heterostructures give rise to a novel<br />

electr<strong>on</strong>ic state.<br />

A. Perucchi et al., Nano Letters 10 (12), 4819-4823 (2010)<br />

In the past few years, multiferroic materials, characterized by coexistence of two or<br />

more ferroicity, have attracted much attenti<strong>on</strong> due to their interesting properties. Am<strong>on</strong>g<br />

the magnetic ferroelectric materials, there is an important class, hexag<strong>on</strong>al manganese<br />

oxides (RMnO 3, R: rare-earth element), which have been extensively studied because<br />

of its unusual property. However, hexag<strong>on</strong>al ir<strong>on</strong> oxides (RFeO 3), which have a similar<br />

structure to RMnO 3, have been rarely reported due to a preferred formati<strong>on</strong> to the<br />

orthombic or garnet phase. Here, we report that the hexag<strong>on</strong>al phase can be easily<br />

prepared as a powder and thin film from chemical soluti<strong>on</strong> depositi<strong>on</strong> method (CSD).<br />

The crystallizati<strong>on</strong> temperature, crystal structure, magnetic and electric properties of<br />

the thin film and powder were investigated. The hexag<strong>on</strong>al phase was observed at<br />

750-800, and at higher temperature (>850) orthombic phase appeared. The observed<br />

structure bel<strong>on</strong>ged to the paraelectric P63/mmc phase, rather than ferroelectric phase.<br />

Samples showed paramagnetic property at room temperature caused by geometrically<br />

fluctuated magnetism in tri-angular spin lattice.<br />

Magnetic hysteretic effects in LaAlO 3 /SrTiO 3 Heterostructures<br />

Veerendra Kumar Guduru 1 , Alix Mccollam 1 , Sander Wenderich 2 , Michelle Kruize 2 ,<br />

Uli Zeitler 1 *, Alexander Brinkman 2 , Jan Kees Maan 1 , Mark Huijben 2 , Hans<br />

Hilgenkamp 2 , Gertjan Koster 2 , Guus Rijnders 2 and Dave Blank 2<br />

1 HFML/IMM,Radboud University Nijmegen, Netherlands<br />

2 MESA+ Institute for Nanotechnology, University of Twente, Netherlands<br />

A two-dimensi<strong>on</strong>al electr<strong>on</strong> system (2DES) with remarkable electr<strong>on</strong>ic properties can be<br />

realized at the interface between two band insulators LaAlO 3 and SrTiO 3 (1). Depending<br />

<strong>on</strong> growth c<strong>on</strong>diti<strong>on</strong>s, this 2DES has been found to show a superc<strong>on</strong>ducting ground state<br />

(2), magnetic ordering (3) and even co-existence of these two properties (4-5). The origin<br />

of the magnetic behaviour at the interface is still unclear, and to try to understand it we<br />

have performed magneto-transport studies <strong>on</strong> LaAlO 3/SrTiO 3 heterostructures in high<br />

magnetic fields up to 33 T, and low temperatures down to 0.3 K. We observed negative<br />

magnetoresistance (nMR) which is nearly identical for all field orientati<strong>on</strong>s in the temperature<br />

range from 4 K to 350 mK. This nMR could be related to reduced spin scattering due to the<br />

alignment of spins at the interface (3). At low magnetic fields, the nMR is very sensitive to<br />

temperature and at temperatures below 1 K an unusual time dependent magnetic hysteresis<br />

appears for field below 3 T. We propose a magnetocaloric effect model to explain the<br />

hysteretic behaviour, and propose that the possible underlying origin of the hysteresis is the<br />

co-existence of ferro- and antiferromagnetic phases in the spin system.<br />

1) A. Ohtomo and H.Y. Hwang, Nature 427, 423, 2004. 2) N. Reyren et al., Science 317, 1196, 2007. 3) A. Brinkman et al.,<br />

Nature Materials 6, 493, 2007. 4) L. Li et al., Nat Phys 7 (10), 762-766, 2011. 5) J.A.Bert et al., Nat Phys 7 (10), 767-771, 2011.<br />

July 8 - 13, 2012 Busan, Korea 203<br />

Poster Friday


Poster Friday<br />

SA11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Synthesis and magnetoelectric properties of multiferroic composites <strong>on</strong><br />

the cobalt ferrite - pzt system<br />

C. Miclea 1 *, L. Amarande 1 , L. Trupina 1 , M. Cioangher 1 , C. T. Miclea 2 and C. F.<br />

Miclea 1<br />

1 Nati<strong>on</strong>al Institute for Materials Physics, Bucharest, Romania<br />

2 Hyperi<strong>on</strong> University, Bucharest, Romania<br />

In the present study we prepared and investigated the properties of bulk particulate<br />

composites made from cobalt ferrite (COF) and a soft piezoelectric material (PZT).<br />

We chose COF and soft PZT due to their high magnetic and piezoelectric parameters<br />

respectively. Composite samples, according to the formula xCOF(1-x)PZT with 0 ≤ x ≤<br />

1 were prepared by mixing the COF and PZT powders, pressing them as discs and then<br />

sintered at 1200 C for 3 hours. Structural, magnetic, piezoelectric and magnetoelectric<br />

characteristics of the sintered composites were then determined as a functi<strong>on</strong> of the<br />

weight fracti<strong>on</strong> of COF into PZT and magnetic fields. The ME coefficient shows a<br />

maximum value about 70 mV/cmOe for composites c<strong>on</strong>taining 40 % COF and 60%<br />

PZT, in a DC magnetic field of 3 kOe at a frequency of 1KHz of the ac magnetic field.<br />

Some of the dielectric and piezoelectric properties of the composite samples, as a<br />

functi<strong>on</strong> of the weight fracti<strong>on</strong> x, were also determined. The results were discussed in<br />

terms of the recent theoretical cube model of different c<strong>on</strong>nectivities of particles of <strong>on</strong>e<br />

phase embedded into the matrix of the sec<strong>on</strong>d phase.<br />

SA12<br />

Detailed structural study of BiFeO 3/SrRuO 3 heteroestructures grown<br />

<strong>on</strong> SrTiO 3 (001) substrates<br />

Claribel Dominguez 1 , John Edward Ord<strong>on</strong>ez 1 , Maria Elena Gomez 1 , Wils<strong>on</strong> Lopera 1 and Pedro Prieto 2<br />

1 Thin Film Group, Department of Physics, Universidad del Valle, A.A. 25360, Cali, Colombia, Colombia<br />

2 Center of Excellence for Novel Material CENM, Calle 13 # 100-00 320-1026, Cali, Colombia, Colombia<br />

SA13<br />

WITHDRAWN<br />

Lattice engineering <strong>on</strong> transiti<strong>on</strong> metal oxide thin film<br />

Chang Uk Jung*<br />

Department of Physics, Hankuk University of Foreign Studies, Korea<br />

MOVED<br />

204 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SA14<br />

Magnetisati<strong>on</strong> in different multiferroic YMO (Yttrium Manganese<br />

Oxide) thin films<br />

Manish Kumar*, R.j. Choudhary and D.m Phase<br />

UGC-DAE CSR, UGC-DAE CSR Indore,Madhya Pradesh, India<br />

Recently Yttrium manganese oxides (YMO): hexag<strong>on</strong>al YMnO 3 and orthorhombic<br />

YMn 2O 5 have attracted c<strong>on</strong>siderable attenti<strong>on</strong> as both of these compounds exhibit<br />

multiferrocity but the microscopic origins are different. Here we stabilize thin films of<br />

different phases of YMO by pulsed laser depositi<strong>on</strong> from a single h-YMnO 3 target and<br />

characterize them with various techniques and perform magnetizati<strong>on</strong> measurements.<br />

It is observed that the phase stability and crystallinity of YMO thin films depend <strong>on</strong><br />

the substrate used and oxygen partial pressure (OPP). Oriented and polycrystalline<br />

growth of h-YMnO 3 and O-YMn 2O 5 phase film are observed <strong>on</strong> different substrates.<br />

ZFC,FC (Magnetisati<strong>on</strong> verses Temperature ) and MH magnetizati<strong>on</strong> measurements<br />

of these multiferroic films were performed. All the multiferroic thin films show<br />

the antiferromagnetic transiti<strong>on</strong> in ZFC measurements which is forbidden in FC<br />

measurements. MH behavior at both sides of magnetic transititi<strong>on</strong> is in good agreement<br />

in these multiferroic thin films.<br />

1. Bas B. Van Aken, Thomas T. M. Palstra, Alessio Filippetti and Nicola A. Spaldin,Nature<br />

Materials,Vol 3, 2004, pp.164-170 2 L. C. Chap<strong>on</strong>, P. G. Radaelli, G. R. Blake, S. Park and S.W.<br />

Che<strong>on</strong>g, Phys.Rev.Letter 96, 097601 (2006) 3. W. Prellier, M P Singh and P Murugavel, J. Phys.:<br />

C<strong>on</strong>dens. Matter 17 (2005) R803-R832 4. A Munoz et al 2002 J. Phys.: C<strong>on</strong>dens. Matter 14 3285<br />

SA15<br />

Dependence of magnetoelectric resp<strong>on</strong>se <strong>on</strong> magnetostrictive c<strong>on</strong>tent<br />

in composite multiferroics<br />

Mohsin Rafique 1 *, Syed Qamar Ul Hassan 1 , Muhammad Saifullah Awan 2 and Sadia<br />

Manzoor 1<br />

1<br />

Physics, COMSATS Institute of Informati<strong>on</strong> Technology, Islamabad, Pakistan,<br />

Pakistan<br />

2<br />

Center for Nano and Micro Devices (CNMD), COMSATS Institute of Informati<strong>on</strong><br />

Technology, Islamabad, Pakistan, Pakistan<br />

Magnetoelectric multiferroics exhibit a str<strong>on</strong>g coupling between ferromagnetic and ferroelectric<br />

ordering. The coupling between these two types of orderings may occur naturally or be mediated via<br />

mechanically. This coupling is very weak in single phase multiferroics. The design and investigati<strong>on</strong><br />

of composites of magnetostrictive and piezoelectric phases have shown magnetoelectric coupling<br />

orders of magnitude higher than that of single phase multiferroics. The mechanical deformati<strong>on</strong><br />

in magnetostrictive and piezoelectric phases results in the coupling between the two c<strong>on</strong>stituents.<br />

The multiferroic CoFe 2O 4-BaTiO 3 (CFO-BTO) composites with nanoscale mixture of the two<br />

c<strong>on</strong>stituents were prepared by solgel process. Four different compositi<strong>on</strong>s, with varying percentage<br />

of c<strong>on</strong>stituents, were investigated. X-ray diffracti<strong>on</strong> revealed the coexistence of the two phases.<br />

Magnetic properties of the CFO-BTO nanocomposites were examined which were c<strong>on</strong>sistent with<br />

the compositi<strong>on</strong>. The magnetoelectric coupling between CFO and BTO was dem<strong>on</strong>strated by an<br />

external magnetic field induced change in capacitance. The magnetoelectric coupling was found to<br />

be not <strong>on</strong>ly dependent <strong>on</strong> the applied magnetic field but also <strong>on</strong> the compositi<strong>on</strong> of the composites.<br />

It has a n<strong>on</strong>linear dependence <strong>on</strong> magnetostrictive c<strong>on</strong>tent.<br />

SA16<br />

Raman analyses of oxygen defects in hexag<strong>on</strong>al HoMnO 3 thin films<br />

Xiang-bai Chen 1 , Nguyen Thi Minh Hien 2 , D. Lee 3 , T. W. Noh 3 and In-sang Yang 2<br />

1 K<strong>on</strong>kuk University, Korea<br />

2 Ewha Womans University, Korea<br />

3 Seoul Nati<strong>on</strong>al University, Korea<br />

Oxygen defects are usually unavoidable in synthesizing oxide thin films. In this study,<br />

we investigated the origins of the oxygen defects in hexag<strong>on</strong>al manganites HoMnO 3<br />

epitaxial thin films through Raman spectroscopy. We found that the oxygen defects in<br />

hexag<strong>on</strong>al HoMnO 3 thin films have different effects <strong>on</strong> different ph<strong>on</strong><strong>on</strong> modes and<br />

<strong>on</strong> magn<strong>on</strong> scattering. Our analyses indicated that the oxygen defects in hexag<strong>on</strong>al<br />

HoMnO 3 thin films would be mainly correlated with the basal O 3 and/or O 4 oxygen<br />

i<strong>on</strong>s. Furthermore, our analyses of oxygen defects predicted that the Mn 3d orbitals<br />

would be more str<strong>on</strong>gly hybridized with the apical O 1 and/or O 2 2p orbitals than the<br />

basal O 3 and/or O 4 2p orbitals. This predicti<strong>on</strong> is c<strong>on</strong>sistent with our res<strong>on</strong>ant Raman<br />

scattering study and earlier first-principle calculati<strong>on</strong>s of electr<strong>on</strong>ic structures of<br />

hexag<strong>on</strong>al manganites.


SA17<br />

Preparati<strong>on</strong> and properties of inverse perovskite Mn 3GaN thin films<br />

Hiroki Tashiro, Ryosuke Suzuki*, Tetsuya Miyawaki, Kenji Ueda and Hidefumi<br />

Asano<br />

Department of engineering, Nagoya University, Japan<br />

There has been c<strong>on</strong>siderable interest in antiperovskite Mn 3GaN because of its intriguing<br />

physical properties such as negative thermal expansi<strong>on</strong>, magneto-volume effect and<br />

piezomagnetic effect(1). Mn 3GaN is expected to be advantageous to fabricate thin-film<br />

hybrid devices with various perovskite oxides, since it has a cubic antiperovskite structure<br />

virtually identical with the perovskite oxides. However, there is no report <strong>on</strong> growth<br />

of Mn 3GaN thin films and heterostructures. In this paper, we report <strong>on</strong> the preparati<strong>on</strong><br />

and properties of Mn 3GaN thin films as well as ferroelectric Ba 0.7Sr 0.3TiO 3/Mn 3GaN<br />

heterostructutes. Mn 3GaN films were deposited <strong>on</strong> (001) SrTiO 3 and LaAlO 3 substrates at<br />

450~650°C by i<strong>on</strong> beam sputtering of a sintered stoichiometric target. Ba 0.7Sr 0.3TiO 3films<br />

were prepared at 650~750°C by magnetr<strong>on</strong> sputtering. In-plane and out-of-plane<br />

X-ray diffracti<strong>on</strong> analysis revealed that <strong>on</strong> SrTiO 3 substrate Mn 3GaN films were grown<br />

coherently with the in-plane lattice parameter aMGN of 0.3903 nm. On LaAlO 3 substrate<br />

a Ba 0.7Sr 0.3TiO 3 layer and subsequently a Mn 3GaN layer were grown epitaxially with the<br />

relati<strong>on</strong>ship of LaAlO 3(001)[100]//Ba 0.7Sr 0.3TiO 3(001)[100]//Mn 3GaN (001)[100]. These<br />

Mn 3GaN thin films showed a metallic temperature dependence of resistivity with 0.8-0.9<br />

mΩcm at room temperature. It was found that the Ba 0.7Sr 0.3TiO 3/Mn 3GaN heterostructutes<br />

exhibited a colossal magnetocapacitance effect.<br />

(4) P. Lukashev, et al., Phys. Rev. B 78 184414 (2008)<br />

SA18<br />

Ferroelectric and magnetic properties of BiMnO 3 thin films<br />

Min-hwa Jung and Yo<strong>on</strong>-hee Je<strong>on</strong>g*<br />

Department of Physics, Pohang University of Science and Technology, Korea<br />

BiMnO 3 is heralded widely as a rare case of multiferroicity with simultaneous<br />

existence of both ferroelectricity and ferromagnetism. Ferroelectricity in BiMnO 3,<br />

however, still remains c<strong>on</strong>troversial as various results do not c<strong>on</strong>verge <strong>on</strong> a definite<br />

c<strong>on</strong>clusi<strong>on</strong> [1-3]. In order to shed light <strong>on</strong> this issue, we have synthesized BiMnO 3<br />

thin films <strong>on</strong> Nb:SrTiO 3 substrates by PLD method. Measurements of various physical<br />

properties such as dielectric properties, PE hysteresis loop, and piezoelectric d33 do<br />

not show any significant evidence of ferroelectricity for all films. Thus, we are led to<br />

c<strong>on</strong>clude that BiMnO 3 is not ferroelectric in accordance with a theoretical calculati<strong>on</strong><br />

[4-5]. Also of interest is the ferromagnetism of BiMnO 3 and, in particular, its magnetic<br />

easy directi<strong>on</strong>. We also investigate the magnetic properties of the films with in and out<br />

of the plane orientati<strong>on</strong>s. From these measurements, the magnetic easy directi<strong>on</strong> is<br />

inferred for the m<strong>on</strong>oclinic phase BiMnO 3. In c<strong>on</strong>clusi<strong>on</strong>, the present study offers a full<br />

characterizati<strong>on</strong> of the ferroelectric and magnetic properties of multiferroic BiMnO 3.<br />

[1] T. Kimura, S. Kawamoto, I. Yamada, M. Azuma, M. Takano, and Y. Tokura, Phys. Rev. B 67,<br />

180401 (2003) [2] M. Grizalez, E. Martinez, J. Caicedo, et al.,, Microelectr<strong>on</strong>ics Journal 39, 1308<br />

(2008) [3] A. A. Belik, S. likubo, T. Yokosawa, et al., J. Am. Chem. Soc. 129.971 (2007) [4] A.J. Hatt<br />

and N.A. Spaldin, Eur. Phys. J. B 71,435 (2009) [5] Shichidou T, Oguchi T (2006) Multiferroicity of<br />

BiMnO3 reexamined from first principles. Presented at APS meeting March Meeting, Baltimore, MD.<br />

SA19<br />

Ferroelectric polarizati<strong>on</strong> induced magnetic anisotropy in Co40Fe40B20/ YMnO3 multiferroic heterostructure<br />

Jiawei Wang 1 , Yanggang Zhao 1 *, Peisen Li 1 , Sen Zhang 1 , Syed Rizwan 2 , Xiufeng<br />

Han 2 , Xuefeng Sun 3 , Yuanjun Yang 4 , Qianping Chen 1 and Xin Zhang 1<br />

1<br />

Department of Physics and State Key Laboratory of Low-Dimensi<strong>on</strong>al Quantum Physics, Tsinghua<br />

University, China<br />

2<br />

Beijing Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics, Chinese Academy of Sciences, China<br />

3<br />

Hefei Nati<strong>on</strong>al Laboratory for Physical Sciences at the Microscale, University of Science and<br />

Technology of China, China<br />

4<br />

Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Laboratory, University of Science and Technology of China, China<br />

Multiferroic (MF) materials have attracted much attenti<strong>on</strong> due to their interesting new physics and potential<br />

for exploring novel multifuncti<strong>on</strong>al devices. The research of magnetic anisotropy in MF heterostucture is an<br />

important aspect. One of the key issues in the MF heterostructures is the effect of ferroelectric (FE) polarizati<strong>on</strong> <strong>on</strong><br />

magnetic anisotropy. So far, however, a lot of work has been carried out <strong>on</strong> MF heterostructures with crystalline<br />

ferromagnetic films. Actually, MF heterostructures involving amorphous ferromagnetic materials are also very<br />

interesting due to the absence of magnetocrystalline anisotropy and low coercive force Hc. We have studied the<br />

coupling between amorphous magnetic Co 40Fe 40B 20 (CFB) and YMnO 3 (YMO) in the heterostructure with CFB<br />

film grown <strong>on</strong> YMO (110) substrates. A large uniaxial magnetic anisotropy (UMA) was observed from room<br />

temperature to 10 K with magnetic easy axis (MEA) al<strong>on</strong>g the polarizati<strong>on</strong> directi<strong>on</strong> of YMO. More interestingly,<br />

the angular dependence of coercive force Hc shows a n<strong>on</strong>-m<strong>on</strong>ot<strong>on</strong>ous behavior. The results were discussed<br />

by c<strong>on</strong>sidering the coupling between the FE domain in YMO and magnetism in CFB. This work is helpful for<br />

understanding the effect of FE polarizati<strong>on</strong> <strong>on</strong> magnetic anisotropy in MF heterostuctures.<br />

SA20<br />

SA21<br />

SA22<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ferroelectric-domain-switching c<strong>on</strong>trolled magnetism in CoFeB/PMN-<br />

PT multiferroic heterostructure<br />

Peisen Li 1 , Y<strong>on</strong>ggang Zhao 1 *, Sen Zhang 1 , Lifeng Yang 1 , Syed Rizwan 2 , Qianping<br />

Chen 1 , Jiawei Wang 1 and Xiufeng Han 2<br />

1<br />

Department of Physics and State Key Laboratory of Low-Dimensi<strong>on</strong>al Quantum Physics,<br />

Tsinghua University, China<br />

2<br />

Beijing Nati<strong>on</strong>al Laboratory for C<strong>on</strong>densed Matter Physics, Chinese Academy of Sciences, China<br />

Multiferroic materials have attracted much attenti<strong>on</strong> due to their interesting new physics and potential<br />

applicati<strong>on</strong>s in new multifuncti<strong>on</strong>al devices. In multiferroic materials, the magnetizati<strong>on</strong> can be tuned by<br />

electric fields, which open a new way to reach high integrati<strong>on</strong> density and low power c<strong>on</strong>sumpti<strong>on</strong> in<br />

informati<strong>on</strong> storage. In the shorter term, niche applicati<strong>on</strong>s are more likely to emerge in the two-phase<br />

systems [1], so there have been lots of work <strong>on</strong> the electric-field c<strong>on</strong>trol of magnetism via the piezostrain<br />

in ferromagnet-ferroelectric heterostructures[2, 3]. However, the reports related to magnetoelectric<br />

(ME) effect via ferroelectric domain switching are still limited. Thus, we have studied the electric-field<br />

c<strong>on</strong>trol of magnetism in Co 20Fe 40B 20/Pb(Mg 1/3Nb 2/3) 0.7Ti 0.3O 3(PMN-PT)(001) two-phase-system. N<strong>on</strong>volatile<br />

and volatile changes of magnetizati<strong>on</strong> related to different types of ferroelectric domain switching<br />

were found and the ratio between them changes with temperature. The angular-dependence of electricfield<br />

c<strong>on</strong>trol of magnetism indicates that some magnetic domains rotate 90°, which is c<strong>on</strong>sistent with<br />

our in situ electric-field-dependent magnetic force microscopy data. The results were explained by<br />

c<strong>on</strong>sidering the ferroelectric domain switching induced magnetic anisotropy. This work is helpful for<br />

understanding the coupling between magnetism and ferroelectric domain switching.<br />

[1] W. Eerenstein et al., Nature 442, 759 (2006). [2] C. Thiele et al., Phys. Rev. B 75, 054408 (2007).<br />

[3] J. J. Yang et al., Appl. Phys. Lett. 94, 212504 (2009).<br />

Multiferroic properties of BaTiO 3 - Zn 1-xCo xO multilayer thin films<br />

Anuraj S 1 , Shivaraman Ramaswamy 1 *, Helen Annal Therese 1 , C Gopalakrishnan 1 and<br />

A Karthigeyan 2<br />

1 Nanotechnology Research Center, SRM University, India<br />

2 Department of Physics and Nanotechnology, SRM University, India<br />

Near room temperature ferroelectric and ferromagnetic hysteresis is observed<br />

in horiz<strong>on</strong>tal superlattice system of BaTiO 3 - Zn 1-xCo xO (x > 0.2) [BTO - ZCO]<br />

multilayered thin films. The multilayered thin films were prepared <strong>on</strong> Si substrate<br />

by alternate depositi<strong>on</strong> of BTO and ZCO layers to a thickness of 350 nm using<br />

pulsed laser depositi<strong>on</strong> technique. Analysis of the prepared thin film by x-ray powder<br />

diffracti<strong>on</strong> and electr<strong>on</strong> microscopic techniques c<strong>on</strong>firm the polycrystalline nature<br />

of the multilayered film. Dielectric and the magnetic properties studied <strong>on</strong> the<br />

multilayered thin film at different temperatures exemplified the coupling between their<br />

dual order parameters and it is mediated through an electric field effect at the interface.<br />

1. Multiferroic properties of Bi0.8La0.2FeO3/CoFe2O4 multilayer thin films. Shan-Tao Zhang, Yi<br />

Zhang, Zhen-Lin Luo, Ming-Hui Lu, Zheng-Bin Gu, Yan-Feng Chen., Applied Surface Science 255<br />

(2009) 5092-5095. 2. Multiferroic BaTiO3-CoFe2O4 Nanostructures., H. Zheng, J. Wang, S. E.<br />

Lofland, Z. Ma, L. Mohaddes-Ardabili, T. Zhao, L. Salamanca-Riba, S. R. Shinde, S. B. Ogale, F.<br />

Bai, D. Viehland, Y. Jia, D. G. Schlom, M. Wuttig, A. Roytburd, R. Ramesh. Science 303, (2004) 661.<br />

Study of structural phase transiti<strong>on</strong> and multiferroic properties of<br />

Samarium substituted BiFeO 3 thin films<br />

Mahdiyar Bagheri, Shivaraman Ramaswamy*, Helen Annal Therese and C<br />

Gopalakrishnan<br />

Nanotechnology Research Center, SRM University, India<br />

In this study we report the effect of samarium substituti<strong>on</strong> <strong>on</strong> the structure and<br />

multiferroic properties of BiFeO 3 thin films. The Bi 1-xSm xFeO 3 thin films of various<br />

thicknesses were sputter deposited <strong>on</strong> to Si substrates. Magnetic and electric properties<br />

of the thin films were studied by vibrating sample magnetometer, impedance analyzer<br />

and I-V characterizer. Samarium substituti<strong>on</strong>-driven structural phase transiti<strong>on</strong> was<br />

studied by x-ray diffracti<strong>on</strong> at room temperature. Samarium doping was found to<br />

modify structural properties of Bi 1-xSm xFeO 3 thin film. The phase transiti<strong>on</strong> was found<br />

to destruct cycloid spin structure of BiFeO 3 that resulted in amplified magnetoelectric<br />

interacti<strong>on</strong>s. The substituti<strong>on</strong> of Sm was found to be a promising way to c<strong>on</strong>trol the<br />

c<strong>on</strong>ductivity and leakage current of film by suppressing the formati<strong>on</strong> of oxygen<br />

vacancies.<br />

1. Hiroshi Uchida, Risako Ueno, Hiroshi Funakubo, and Seiichiro Koda, J. Appl. Phys.100, 014106<br />

(2006) 2. E. Ohshima, Y. Saya, M. Nantoh and M. Kawai Solid State Commun. 116 (2000), p.73.<br />

July 8 - 13, 2012 Busan, Korea 205<br />

Poster Friday


Poster Friday<br />

SA23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Study of ferroelectricity in Eu substituted BiMnO 3 films<br />

Shivaraman Ramaswamy*, Helen Annal Therese and C Gopalakrishnan<br />

Nanotechnology Research Center, SRM University, India<br />

In this paper, we report evidence of ferroelectricity in europium substituted manganite<br />

(Bi 1-xEu xMnO 3) thin films synthesized via sol gel synthesis and dip coating method<br />

<strong>on</strong> a single-crystal (1 0 0) substrates. The films were post treated by annealing at<br />

500°C. X-ray diffracti<strong>on</strong> measurements were used to analyze the crystal structure<br />

and phase purity of the thin films. AFM measurements were performed to investigate<br />

surface morphology; quantitative values of roughness and grain size which are in the<br />

range between 30 and 150 nm. Ferroelectric characterizati<strong>on</strong> was c<strong>on</strong>ducted at low<br />

temperatures and at 300 K. Hysteresis loops (polarizati<strong>on</strong> vs. voltage) were obtained,<br />

showing enhanced ferroelectricity at room temperature in the 10% Eu substituted<br />

BiMnO 3 film. Resistance vs. temperature measurements were performed, which<br />

indicated this to be very robust insulating material. Moreover, all films show small<br />

dielectric dispersi<strong>on</strong> and dielectric loss.<br />

SA24<br />

Experimental evidence for Exchange bias in polycristalline BiFeO 3 /<br />

Ni 81Fe 19<br />

T<strong>on</strong>y Hauguel, Souren P Pogossian, David Toyo Dekadjevi*, Jean-philippe Jay,<br />

Mikhail Indenbom, David Spenato and Jamal Ben Youssef<br />

Laboratoire de <strong>Magnetism</strong>e de Bretagne, CNRS-Universite Europeene de Bretagne,<br />

France<br />

Multiferroic (MF) materials have been the subject of extensive studies in the past decade since it<br />

allows a coupling of ferroelectric and magnetic orders in a single phase. Am<strong>on</strong>g all the multiferroic<br />

materials studied so far, BiFeO 3 (BFO) exhibits the coexistence of ferroelectric and antiferromagnetic<br />

orders at room temperature. Magnetic heterostructures with a ferromagnetic thin film exchange<br />

biased to an antiferromagnetic-BFO film may allow an electric field influence <strong>on</strong> the magnetic<br />

hysteresis properties of the bilayer. The exchange coupling and exchange bias involving MF/<br />

F systems has previously been obtained with either epitaxial BFO [1] or BFO bulk materials [2].<br />

However, the exchange coupling between a ferromagnetic film and a polycrystalline multiferroic was<br />

not studied. Furthermore, previous studies have shown that polycrystalline BFO exhibits multiferroic<br />

properties. We report experimental evidence for exchange bias in polycrystalline BiFeO 3/Ni 81Fe 19<br />

bilayers, grown by RF sputtering [3]. Our measured 17 Oe shift corresp<strong>on</strong>ds to exchange energy per<br />

unit area of interface coupling the two films of 11×10 -3 erg/cm 2 comparable with similar epitaxial<br />

grown systems. The azimuthal behavior of l<strong>on</strong>gitudinal and transverse comp<strong>on</strong>ents of magnetizati<strong>on</strong><br />

reveals the presence of induced unidirecti<strong>on</strong>al and biquadratic anisotropies.<br />

[1] H. Bea et al., Phys. Rev. Lett. 100, 017204 (2008) [2] J. Dho et al., J. Appl. Phys. 106, 073914<br />

(2009) [3] T. Hauguel et al., J. Appl. Phys. 110, 073906 (2011).<br />

SB01<br />

Parit variati<strong>on</strong> in the rectangular array of periodic holes <strong>on</strong><br />

superc<strong>on</strong>ducting thin film<br />

Kamran Muhammad 1 * and Qiu Xiang Gang 2<br />

1 Physics, COMSATS Institute of IT, Islamabad, Pakistan<br />

2 Institute of Physics, Chinese Academy of Sciences, Beijing, China<br />

Superc<strong>on</strong>ductivity has been full of surprises and w<strong>on</strong>der. One of the most elegant<br />

properties of superc<strong>on</strong>ductors is the quantizati<strong>on</strong> of magnetic flux in units of φ0=h/2e,<br />

where h is the Planck c<strong>on</strong>stant of quantum mechanics, and 2e the electr<strong>on</strong>-pair charge<br />

serving the fundamental building block of the superc<strong>on</strong>ducting c<strong>on</strong>densate. Here we<br />

report our discovery of a new twist of this phenomen<strong>on</strong> in a film geometry perforated<br />

with a periodic lattice of sub-micr<strong>on</strong> holes, a variati<strong>on</strong> of the flux quantizati<strong>on</strong> based <strong>on</strong><br />

the parity of the number of the flux quanta. Measured in terms of magneto-resistance<br />

at temperatures just below the transiti<strong>on</strong> temperature of the bulk superc<strong>on</strong>ductor, we<br />

find that superc<strong>on</strong>ductivity is most enhanced at odd multiples of the flux quantum.<br />

We explain the phenomen<strong>on</strong> by noting that thermal quasi-particles, which see the<br />

superc<strong>on</strong>ducting flux quantum <strong>on</strong>ly as half, are in fact suppressed at these flux values.<br />

In fields larger than the thermodynamic critical field, where quasi-particles dominate,<br />

magneto-resistance minima <strong>on</strong>ly occur at such odd values.<br />

206 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SB02<br />

Charge disproporti<strong>on</strong>, spin and orbital states in the tri-layered<br />

nickelate La 4Ni 3O 8 from first principles<br />

Hua Wu*<br />

Department of Physics, Fudan University, Shanghai, China<br />

Several mixed-valent layered nickelates were synthesized very recently [1,2], in<br />

the effort to search an analog to the hole doped cuprates. Here we have studied<br />

the electr<strong>on</strong>ic structure and the magnetism of the tri-layered La 4Ni 3O 8, using the<br />

c<strong>on</strong>figurati<strong>on</strong>-state c<strong>on</strong>strained LDA+U calculati<strong>on</strong>s. Our results show that La 4Ni 3O 8<br />

would be a charge homogeneous low-spin half metal in the ferromagnetic state. In<br />

c<strong>on</strong>trast, the C-type antiferromagnetic state is insulating and has a charge disproporti<strong>on</strong><br />

of the formal 2Ni + /Ni 2+ type, thus accounting for several experimental observati<strong>on</strong>s.<br />

The high-spin (S=1) Ni 2+ state and its orbital c<strong>on</strong>figurati<strong>on</strong> are found to be against<br />

the crystal-field level picture. We note that it would be interesting to explore, for<br />

novel magnetism and superc<strong>on</strong>ductivity, the Ni 2+ low-spin S=0 state and the partially<br />

occupied x 2-y 2 band structure of the Ni + /Ni 2+ mixed-valent nickelate.<br />

[1] V. V. Poltavets et al., Phys. Rev. Lett. 104, 206403 (2010). [2] V. V. Poltavets, M. Greenblatt, G. H.<br />

Fecher, and C. Felser, Phys. Rev. Lett. 102, 046405 (2009).<br />

SB03<br />

Carrier doping to the novel layered nickelate<br />

Yoshiki Sakurai, Yoshihide Kimishima and Masatomo Uehara*<br />

Yokohama nati<strong>on</strong>al university, Japan<br />

Recently a series of new layered nickelate (Ln n+1Ni nO 2n+2) (Ln=La, Nd) has been<br />

synthesized with using CaH 2 as a reducing agent or hydrogen gas. The crystal structure<br />

is the analogue of so-called Ruddlesden-Popper phase, and basically the same crystal<br />

structure with high-Tc superc<strong>on</strong>ducting cuprate, c<strong>on</strong>sisting of insulating block layer<br />

and two-dimensi<strong>on</strong>al NiO 2 layer. Interestingly Ni i<strong>on</strong>s in these materials can have the<br />

same electr<strong>on</strong>ic c<strong>on</strong>figurati<strong>on</strong> with Cu 2+ 3d 9 in high-Tc cuprate, suggesting that this is a<br />

promising candidate for another high-Tc material. Therefore, we have tried to carrierdope<br />

to Ln and Ni sites of (Ln n+1Ni nO 2n+2) (Ln=La, Nd) with n=2, 3, and ∞ using<br />

Ca, Cu, Co i<strong>on</strong>s in order to tune the electr<strong>on</strong>ic state of Ni. If the Ni electr<strong>on</strong>ic state<br />

is adjusted to 3d 9.15 or 3d 8.85 which are the same cases with those of optimum doping<br />

level for the emergence of high-Tc in cuprate. We will present the detailed result in the<br />

c<strong>on</strong>ference.<br />

SB04<br />

Occurrence of superc<strong>on</strong>ductivity and structural variati<strong>on</strong>s in the Sr 1-xT 2-<br />

2xGe 2 layer system (T = Ni, Pd, and Pt; x ≥ 0)<br />

H. C. Ku 1 , I. A. Chen 1 , C. H. Hung 1 , C. Y. Lin 1 , S. J. Wang 1 , Y. B. You 1 , M. F. Tai 1 and<br />

Y. Y. Hsu 2<br />

1 Department of Physics, Nati<strong>on</strong>al Tsing Hua University, Taiwan<br />

2 Department of Physics, Nati<strong>on</strong>al Taiwan Normal University, Taiwan<br />

Superc<strong>on</strong>ducting transiti<strong>on</strong> temperature Tc of the body-centered-tetrag<strong>on</strong>al (bct)<br />

122 Sr(Ni 1-yPdy) 2Ge 2 (0 ≤ y ≤ 1) layer system (space group I4/mmm) increases<br />

m<strong>on</strong>ot<strong>on</strong>ically from 0.87 K for 3d-Ni SrNi 2Ge2 to 3.12 K for 4d-Pd SrPd 2Ge 2.<br />

However, due to larger atomic radius of 5d-Pt, the bct stoichiometric Sr(Pd 1-yPty) 2Ge 2<br />

phase (I4/mmm) is unstable and a structural transformati<strong>on</strong> to a vacancy stabilized<br />

superstructure Sr 1-x(Pd 1-yPty) 2-2xGe 2 with orthorhombic space group Pmna may be<br />

formed. Trace of superc<strong>on</strong>ductivity with Tc ranging from 5-10 K in the Sr 1-xPt 2-2xGe 2<br />

system was observed but very difficult to be stablized. This structural transformati<strong>on</strong><br />

is very similar to the high temperature superc<strong>on</strong>ducting system K 1-xFe 2-2xSe 2 with I4/<br />

mmm and two superstructure space groups Pmna and I4/m, where superc<strong>on</strong>ductivity<br />

Tc up to 32 K was reported <strong>on</strong>ly in the bct I4/m system. This work was supported by<br />

Grant No. NSC98-2112-M-007-013-MY3 of Nati<strong>on</strong>al Science Council of Republic of<br />

China.


SB05<br />

Fermi surface study <strong>on</strong> the rattling-induced superc<strong>on</strong>ductor KOs2O6 Taichi Terashima 1 *, Nobuyuki Kurita 1 , Andhika Kiswandhi 2 , Eun-sang Choi 2 , James S.<br />

Brooks 2 , Kota Sato 3 , Jun-ichi Yamaura 3 , Zenji Hiroi 3 , Hisatomo Harima 4 and Shinya<br />

Uji 1<br />

1<br />

Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

2<br />

Nati<strong>on</strong>al High Magnetic Field Laboratory, USA<br />

3<br />

ISSP, Univ. of Tokyo, Japan<br />

4<br />

Graduate School of Scienece, Kobe Univ., Japan<br />

SB06<br />

Transient analysis of the current density and temperature distributi<strong>on</strong><br />

of the MgB2 superc<strong>on</strong>ductor in the He atmosphere<br />

H. M. Iftekhar Jaim 1 and Klaus Barner 2<br />

1<br />

Department of Mechanical, Material and Aerospace Engineering, University of<br />

Central Florida, USA<br />

2<br />

Department of Physics (4 Physik),, University of Gottingen, F. Hund Platz 1, 37077<br />

Gottingen, Germany<br />

SB07<br />

WITHDRAWN<br />

In this paper, the transient analysis is carried out for the type II superc<strong>on</strong>ductor material<br />

MgB 2 in liquid Helium atmosphere. The str<strong>on</strong>g n<strong>on</strong>linearity of the E-J relati<strong>on</strong>ship<br />

near critical current poses a challenge in such calculati<strong>on</strong>s for getting practical values<br />

in other models employed for Ohmic materials. For this reas<strong>on</strong>, the curl-curl equati<strong>on</strong><br />

and the variable magnetic field quantity are employed as the unknown in solving the<br />

PDE by the finite element method. The temperature distributi<strong>on</strong> by the generated heat<br />

in the superc<strong>on</strong>ductor is calculated by the coupled c<strong>on</strong>ducti<strong>on</strong> and c<strong>on</strong>vecti<strong>on</strong> module.<br />

Using the nominal experimental values for the exp<strong>on</strong>ential current fundamental<br />

characteristics like the magnetic flux, current distributi<strong>on</strong> density and temperature<br />

profile in the superc<strong>on</strong>ductor are calculated for 2D axis symmetric cylindrical cases.<br />

The study gives the limiting current values to avoid heat generati<strong>on</strong> and shows the<br />

development of the mixed state and finally the normal state with the time. Effect of<br />

changing the magnitude of current and time c<strong>on</strong>stant is also studied. Ripple effect at the<br />

surface is observed due to difference in the inner and outer magnetic flux distributi<strong>on</strong>.<br />

Meissner-like effect <strong>on</strong> normal- superfluid interface of imbalanced<br />

Fermi gas<br />

Neda Ebrahimian* and Mohammad Mehrafarin<br />

Physics Department, Amirkabir University of Technology,Tehran 15914, Iran<br />

The observati<strong>on</strong> of phase separati<strong>on</strong> between the superfluid (SF) core and a normal (N) shell around<br />

the core in ultra-cold Fermi gases has been reported by the new experiments of MIT and Rice<br />

groups[1-2]. Much researches have been d<strong>on</strong>e about the N-SF interface[3-5]. In this article, we<br />

examine the N-SF interface of a imbalanced Fermi gas with two spin species, in the presence of a<br />

weak magnetic field. In our analysis, we c<strong>on</strong>sider a c<strong>on</strong>stant magnetic field in the N side and anticipate<br />

the possibility of the Meissner-like effect in the SF side. We take into account the various scattering<br />

regi<strong>on</strong>s of the BCS regime and analytically obtain the transmissi<strong>on</strong> coefficients by using the perturbed<br />

Bogoliubov equati<strong>on</strong>s. It suffices to remark that the leading order term in transmissi<strong>on</strong> coefficients are<br />

independent of the energy of incident quasiparticles. Then, we calculate the heat c<strong>on</strong>ductivity across<br />

the interface at sufficiently low temperatures. We describe how the heat c<strong>on</strong>ductivity is affected by the<br />

Meissner effect and the species imbalance. Also the relati<strong>on</strong> between the additi<strong>on</strong>al heat c<strong>on</strong>ductivity<br />

and penetrati<strong>on</strong> depth is obtained. The corresp<strong>on</strong>ding graphs is also plotted and discussed.<br />

Furthermore, we show the dependence of the heat c<strong>on</strong>ductivity <strong>on</strong> average chemical potential.<br />

References: [1] G. B. Partridge, W. Li, R. I. Kamar, Y. A. Liao, and R. G. Hulet, Science 311, 503 (2006). [2] M.<br />

W. Zwerlein, A. Schirotzek, C. H. Schunck, and W. Ketterle, Science 311, 492 (2006). [3] B. Van Schaeybroeck<br />

and A. Lazarides, Phys. Rev. Lett. 98, 170402 (2007). [4] N. Ebrahimian, M. Mehrafarin, and R. Afzali,<br />

Physica B 407, 140 (2012). [5] N. Ebrahimian, M. Mehrafarin, and R. Afzali, To be published Physica C:<br />

Superc<strong>on</strong>ductivity (2012).<br />

SB08<br />

SB09<br />

SB10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties and structure evoluti<strong>on</strong> al<strong>on</strong>g R 2RhIn 8 series<br />

Petr Cermak 1 *, Marie Kratochvilova 1 , Jan Prokleska 1 , Marie-helene Lemee-cailleau 2 ,<br />

Bachir Ouladdiaf 2 and Pavel Javorsky 1<br />

1 Department of C<strong>on</strong>densed Matter Physics, Charles University in Prague, Czech<br />

Republic<br />

2 Institut Laue-Langevin, France<br />

Intermetallic compounds R 2RhIn 8 (R = rare earth) are structurally related to a class of Ce-based<br />

heavy-fermi<strong>on</strong> superc<strong>on</strong>ductors. Study of their magnetic structure and behavior is important for<br />

understanding mechanism of the unc<strong>on</strong>venti<strong>on</strong>al heavy-fermi<strong>on</strong> superc<strong>on</strong>ductivity. We have<br />

successfully grown single crystals of these compounds with R = Nd, Tb, Dy, Ho, Er and Tm<br />

from the melt in the In flux. We report the evoluti<strong>on</strong> of the magnetic properties of this series. All<br />

studied compounds exhibit antiferromagnetic behavior with the Neel temperatures up to 43 K<br />

for Tb compound. Magnetizati<strong>on</strong> and specific heat measurements have revealed metamagnetic<br />

transiti<strong>on</strong>s to another antiferromagnetic phase for Tb, Dy and Ho compounds. We show detailed<br />

magnetic phase diagrams for all these compounds and compare with results reported for<br />

Nd 2RhIn 8 [1]. Low temperature magnetic structures were studied by neutr<strong>on</strong> diffracti<strong>on</strong> at the<br />

Institute Laue-Langevin <strong>on</strong> VIVALDI Laue diffractometer and four-circle D 10 diffractometer.<br />

From these experiments, propagati<strong>on</strong> vector k = (1/2, 1/2, 1/2) and magnetic structure of studied<br />

compounds were determined. We present comparis<strong>on</strong> of our results with the magnetic structure<br />

of Ce 2RhIn 8 and other isostructural compounds from RRhIn5 [2] and R 2CoGa 8 [3] series.<br />

[1] J. G. S. Duquea, et al., J. Magn. Magn. Mater. 323 (2011) 954-956 [2] N. V. Hieu, et al., J. Phys.<br />

Soc. Japan 75 (2006) 074708 [3] D. A. Joshi Phys. Rev. B 77 (2008) 174420<br />

Sec<strong>on</strong>d magnetizati<strong>on</strong> peak and magnetic field distributi<strong>on</strong> in<br />

superc<strong>on</strong>ductor<br />

Denis Gokhfeld<br />

L.V. Kirensky Institute of Physics, Russia<br />

The peak effect <strong>on</strong> M-H loop of superc<strong>on</strong>ductors is analyzed within the framework<br />

of the extended critical state model (ECSM) [D. M. Gokhfeld, D. A. Balaev, S. I.<br />

Popkov, K. A. Shaykhutdinov, M. I. Petrov, Physica C 434, 135 (2006)]. The sec<strong>on</strong>d<br />

magnetizati<strong>on</strong> peak is referred to the vortex lattice transiti<strong>on</strong> or the normal phase rise<br />

occurred at a certain magnetic field value. According to ECSM, these processes extend<br />

from the surface of a sample (or a granule) to inside due to the magnetic field gradient.<br />

Any experimental M-H loops are fitted by assigning the appropriate distributi<strong>on</strong><br />

of the magnetic field in the sample and the field dependence of the critical current<br />

density. ECSM predicts that the asymmetry of M-H loop produces the mismatch of the<br />

peak positi<strong>on</strong>s in the field increasing and decreasing branches. The peak in the field<br />

increasing cycle is situated at lower H value than <strong>on</strong>e in the field decreasing cycle.<br />

Superc<strong>on</strong>ductivity in LuGe2 single crystals<br />

N. H. Sung 1 , A. I. Coldea 2 , S. K. Choi 2 , H. Kim 3,4 , R. Prozorov 3,4 , and B. K. Cho 1,5 *<br />

1<br />

School of Materials Science and Engineering, Gwangju Institute of Science and<br />

Technology (GIST), Gwangju 500-712, Korea<br />

2<br />

Clarend<strong>on</strong> Laboratory, Department of Physics, University of Oxford, Oxford OX1<br />

3PU, United Kingdom<br />

3<br />

The Ames Laboratory, Ames, Iowa 50011, USA<br />

4<br />

Department of Physics and Astr<strong>on</strong>omy, Iowa State University, Ames, Iowa 50011,<br />

USA<br />

5<br />

Department of Phot<strong>on</strong>ics and Applied Physics, Gwangju Institute of Science and<br />

Technology (GIST), Gwangju 500-712, Korea<br />

Superc<strong>on</strong>ducting binary germanide LuGe 2 single crystals were synthesized using a<br />

high-temperature metal flux method. Several shiny plate-like single crystals were<br />

obtained and the compound has the orthorhombic ZrSi 2-type structure (a = 3.9817 Å, b<br />

= 15.5573 Å, c = 3.8477 Å). Superc<strong>on</strong>ducting phase transiti<strong>on</strong> temperature at T c = 2.35<br />

K was c<strong>on</strong>firmed by temperature- and magnetic-field-dependent magnetizati<strong>on</strong>, and<br />

electrical resistivity measurement. In additi<strong>on</strong>, we observed anomalous phase transiti<strong>on</strong><br />

at around T = 4 K, and c<strong>on</strong>firmed the c<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity by heat capacity<br />

measurement. Including these results, we will discuss the nature of LuGe 2 single<br />

crystals in detail.<br />

July 8 - 13, 2012 Busan, Korea 207<br />

Poster Friday


Poster Friday<br />

SB11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Mutual interplay of magn<strong>on</strong> BEC and superc<strong>on</strong>ductivity<br />

Zygmunt Bak*<br />

Institute of Physics, Institute of Physics, Jan Dlugosz University, Czestochowa,<br />

Poland, Poland<br />

We present a theoretical study of the mutual interplay of magn<strong>on</strong> Bose-Einstein<br />

c<strong>on</strong>densate and superc<strong>on</strong>ductivity /SC/, provided that they are simultaneously present.<br />

As a rule these phenomena are treated separately but it is evident that , at least in the<br />

case of triplet SC, there arises coherence in the electr<strong>on</strong> as well as in the magnetic<br />

system. Therefore it is reas<strong>on</strong>able to assess whether magn<strong>on</strong> BEC can facilitate<br />

transiti<strong>on</strong> to the superc<strong>on</strong>ducting state. Such situati<strong>on</strong> should arise when the electr<strong>on</strong><br />

pairing arises due to the magnetic interacti<strong>on</strong>s . In this case electr<strong>on</strong> pair is accompanied<br />

by a cloud of magn<strong>on</strong>s and below critical temperature there arises composed electr<strong>on</strong>magn<strong>on</strong><br />

c<strong>on</strong>densate. We point out that there are experimental evidences that magnetic<br />

coherence reduces or even switches off the destructive effect of magnetic excitati<strong>on</strong>s<br />

<strong>on</strong> SC. We prove that in the case of triplet superc<strong>on</strong>ductivity there should appear the<br />

quadrupolar coherence and what’s more quadrupolar interacti<strong>on</strong>s c<strong>on</strong>tribute to the<br />

electr<strong>on</strong> pairing. We give arguments that Josephs<strong>on</strong> tunneling and “sec<strong>on</strong>d sound”<br />

experiments in magn<strong>on</strong> and electr<strong>on</strong> c<strong>on</strong>denstes with various juncti<strong>on</strong> and setups can<br />

serve as a cross-tests verifying/falsifying hypothesis that in some systems SC is based<br />

<strong>on</strong> magnetic interacti<strong>on</strong>s.<br />

SB12<br />

Studies of the absolute value of $lambda$ in unc<strong>on</strong>venti<strong>on</strong>al<br />

superc<strong>on</strong>ductors<br />

Jeeho<strong>on</strong> Kim*, Filip R<strong>on</strong>ning, N. Haberkorn, L. Civale, J. D. Thomps<strong>on</strong> and Roman<br />

Movshovich<br />

Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

The superc<strong>on</strong>ducting coherence length ($\xi$), magnetic penetrati<strong>on</strong> depth ($\lambda$), and<br />

their anisotropy are fundamental parameters that characterize superc<strong>on</strong>ducting materials. The<br />

value of $\xi$ can be estimated from the superc<strong>on</strong>ducting upper critical field ($H_{c2}$)<br />

using the Ginzburg-Landau theory. In c<strong>on</strong>trast to $\xi$, precise determinati<strong>on</strong> of the absolute<br />

$\lambda$ value is notoriously difficult. In this talk we present a simple, robust, and modelindependent<br />

technique to measure $\lambda$ using magnetic force microscopy (MFM),<br />

and discuss our recent results of the measurements of the absolute value of $lambda$ in a<br />

variety of unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors, such as MgB 2, borocarbides, and pnictides. In<br />

MgB 2 we will discuss the influence of the intra-band c<strong>on</strong>tributi<strong>on</strong>s <strong>on</strong> the superc<strong>on</strong>ducting<br />

properties and scattering effect between the two bands. In a recently discovered Ca 10(Pt 3As 8)<br />

[(Fe 1-xPt x) 2As 2] 5 (x=0.097) single crystal, we observed large $\lambda$. Large $\lambda$ and<br />

high anisotropy in this system enhance thermal fluctuati<strong>on</strong>, which leads to a liquid vortex<br />

phase in this low-temperature (T$_c$= 11 K) superc<strong>on</strong>ductor. Also, we will discuss the effect<br />

of irradiati<strong>on</strong> <strong>on</strong> the value of $\lambda$ in Ca 0.5Na 0.5Fe 2As 2. Finally, we will present our<br />

results <strong>on</strong> the anisotropy of $\lambda$ in a pnictide Ba-122 system, which shows a different<br />

temperature dependence from that of H$_{c2}$.<br />

SB13<br />

Self-c<strong>on</strong>sistent calculati<strong>on</strong>s of the effects of disorder in d- and s-wave<br />

superc<strong>on</strong>ductors<br />

L<strong>on</strong>g He and Yun S<strong>on</strong>g*<br />

Department of Physics, Beijing Normal University, China<br />

The kernel polynomial method (KPM) [1], as an approach for deriving highly accurate<br />

spectral properties of large sparse matrices, is very suitable for the numerical study<br />

<strong>on</strong> the Anders<strong>on</strong> localizati<strong>on</strong> problem. We investigate the effects of disorder in the<br />

two-dimensi<strong>on</strong>al inhomogeneous superc<strong>on</strong>ductors within the KPM by solving selfc<strong>on</strong>sistently<br />

the Bogoliubov-de Gennes equati<strong>on</strong>s [2, 3]. Comparing the behaviors<br />

of optical c<strong>on</strong>ductivity and the time evoluti<strong>on</strong>s of single particle Green’s functi<strong>on</strong> in<br />

superc<strong>on</strong>ducting phases with different pairing symmetries, we find that the delocalized<br />

screening effect <strong>on</strong> the localized quasiparticle states is sufficiently larger in the d-wave<br />

superc<strong>on</strong>ductor than that in the s-wave superc<strong>on</strong>ductor. Within a c<strong>on</strong>siderable large<br />

range of disorder strength, the disorder-induced pseudogap state is derived close to the<br />

s-wave superc<strong>on</strong>ductor-insulator transiti<strong>on</strong>.<br />

[1] A. Weisse, G. Wellein, A. Alvermann, and H. Fehske, Rev. Mod. Phys. 78, 275 (2006). [2] L.<br />

Covaci, F. M. Peeters, and M. Berciu, Phys. Rev. Lett. 105, 167006 (2010). [3] Y. Nagai, Y. Ota, and<br />

M. Machida, J. Phys. Soc. Jpn. 81, 024710 (2012).<br />

208 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SB14<br />

Superc<strong>on</strong>ductivity and structural transiti<strong>on</strong> of RPt 2Si 2 ( R = Y, La, Lu )<br />

Yutaro Nagano 1 *, Nobutaka Araoka 1 , Akihiro Mitsuda 1 , Hirofumi Wada 1 , Masaki<br />

Ichihara 2 , Masahiko Isobe 2 and Yutaka Ueda 2<br />

1 Department of Physics, Kyushu University, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

The RPt 2Si 2 compounds, where R stands for a rare-earth element, have a tetrag<strong>on</strong>al<br />

CaBe 2Ge 2-type structure. LaPt 2Si 2 and YPt 2Si 2 are superc<strong>on</strong>ductors with Tc~2<br />

K[1]. On the other hand, the compounds with R = La and Pr show anomalies in the<br />

temperature dependence of electrical resistivity[2,3]. These compounds are metallic<br />

but the resistivity shows a step at T* ~ 110 K, which is attributable to a charge density<br />

wave (CDW) transiti<strong>on</strong>. In order to detect a periodic lattice distorti<strong>on</strong> due to CDW,<br />

we performed selected area electr<strong>on</strong> diffracti<strong>on</strong> (SAED) and X-ray diffracti<strong>on</strong> (XRD)<br />

measurements at low temperatures. It was found that (2 2 0) reflecti<strong>on</strong> peak was split<br />

into two sub-peaks with equal intensity below T* in XRD measurements. This fact<br />

indicates that LaPt 2Si 2 has an orthorhombic symmetry at low temperatures. The SAED<br />

patterns show (n/3 0 0) superlattice reflecti<strong>on</strong>s with n = 1 and 2 below T*. These results<br />

str<strong>on</strong>gly support the formati<strong>on</strong> of CDW in LaPt 2Si 2. In c<strong>on</strong>trast, we did not observe<br />

any anomalies in the temperature dependence of resistivity except the superc<strong>on</strong>ducting<br />

transiti<strong>on</strong> for YPt 2Si 2 and LuPt 2Si 2. These results are suggestive of no significant<br />

relati<strong>on</strong> between CDW and superc<strong>on</strong>ductivity in the RPt 2Si 2 compounds.<br />

[1] R.N. Shelt<strong>on</strong> et al, Solid State Commun. 52 (1984) 797. [2] F C Ragel, et al , J. Phys. C<strong>on</strong>dens.<br />

Matter 20 (2008) 055218. [3] M. Kumar et al. Phys. Rev. B 81 (2010) 125107.<br />

SB15<br />

Magnetic property in ferromagnetic superc<strong>on</strong>ductor UGe 2 above<br />

ferromagnetic critical pressure<br />

Naoyuki Tateiwa 1 *, Yoshinori Haga 1 , Tatsuma D Matsuda 1 , Eetsuji Yamamoto 1 ,<br />

Yoshichika Onuki 2 and Zachary Fisk 3<br />

1 Advanced Science Research Center,, Japan Atomic Energy Agency, Japan<br />

2 Graduate School of Science, Osaka University, Japan<br />

3 University of California, USA<br />

UGe_2 is a ferromagnet with the Curie temperature of 54 K at ambient pressure.<br />

The ferromagnetic transiti<strong>on</strong> temperature decreases with increasing pressure. The<br />

superc<strong>on</strong>ductivity appears in the pressure regi<strong>on</strong> of 1.0-1.6 GPa where UGe_2 is in<br />

the ferromagnetic state. Ferromagnetic state disappears above P_c =1.6 GPa. Previous<br />

studies up to 2 GPa showed that the broad maximum appears in the temperature<br />

dependence of the ac magnetic susceptibility and that the ferromagnetic state is<br />

induced at metamagnetic field H_m above P_c. These phenomena are resemblance to<br />

weak ferromagnetic compound in the 3d electr<strong>on</strong> system such as ZrZn_2. In this study,<br />

we have measured the dc-magnetizati<strong>on</strong> up to 4.1 GPa using the ceramic anvil high<br />

pressure cell. We c<strong>on</strong>firmed the maximum at T_max in the temperature dependence of<br />

the dc magnetic susceptibility. With increasing pressure, T_max is increased from 24 K<br />

at 1.9 GPa to 32 K at 2.6 GPa. The peak structure around T_max becomes broader with<br />

increasing pressure and disappears above 4 GPa. The metamagnetic transiti<strong>on</strong> field H_<br />

m increases rapidly with increasing pressure. We discuss the experimental results with<br />

the phenomenological spin-fluctuati<strong>on</strong> theory.<br />

SB16<br />

Electr<strong>on</strong> and hole transmissi<strong>on</strong> through superc<strong>on</strong>ductor - normal<br />

metal interfaces<br />

Kurt Gloos* and Elina Tuuli<br />

Department of Physics and Astr<strong>on</strong>omy, University of Turku, Finland<br />

We have investigated the transmissi<strong>on</strong> of electr<strong>on</strong>s and holes through interfaces<br />

between superc<strong>on</strong>ducting aluminum (T_c = 1.2 K) and various normal metals (copper,<br />

gold, palladium, platinum, silver) using Andreev-reflecti<strong>on</strong> spectroscopy at T = 0.1 K.<br />

Most of the c<strong>on</strong>tacts had the typical Andreev reflecti<strong>on</strong> spectra and could be analyzed<br />

with the modified BTK theory. We included Dynes' lifetime as a fitting parameter<br />

Γ in additi<strong>on</strong> to superc<strong>on</strong>ducting energy gap 2Δ and normal reflecti<strong>on</strong> described<br />

by Z. For c<strong>on</strong>tact areas from 1 nm 2 to 10 000 nm 2 the BTK Z parameter was 0.5,<br />

corresp<strong>on</strong>ding to transmissi<strong>on</strong> coefficients of about 80%. This is c<strong>on</strong>siderably larger<br />

than estimated based <strong>on</strong> reports of other experimental methods (proximity effect<br />

and CPP resistance of multilayers) or expected theoretically. The small variati<strong>on</strong> of<br />

Z indicates that the interfaces have a negligible dielectric tunneling barrier and that<br />

Fermi surface mismatch does not depend <strong>on</strong> the normal metal. Our results c<strong>on</strong>tradict<br />

standard expectati<strong>on</strong>s and call for a revisi<strong>on</strong> of the interpretati<strong>on</strong> of the BTK theory<br />

and normal reflecti<strong>on</strong>. This is an especially important topic for applying Andreevreflecti<strong>on</strong><br />

spectroscopy to unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors or for measuring the local<br />

spin polarizati<strong>on</strong> of ferromagnets.


SB17<br />

Magnetic field-induced odd-frequency superc<strong>on</strong>ductivity in s-wave<br />

superc<strong>on</strong>ductors<br />

Masashige Matsumoto 1 *, Mikito Koga 2 and Hiroaki Kusunose 3<br />

1 Department of Physics, Fuclty of Science, Shizuoka University, Japan<br />

2 Department of Physics, Fuculty of Educati<strong>on</strong>, Shizuoka University, Japan<br />

3 Department of Physics, Ehime University, Japan<br />

The wavefuncti<strong>on</strong> of the Cooper pair of the c<strong>on</strong>venti<strong>on</strong>al BCS state is characterized<br />

by the even parity (s-wave) and spin singlet state. It is well known that an external<br />

magnetic field modifies the wavefuncti<strong>on</strong> of the Cooper pair and breaks the<br />

c<strong>on</strong>venti<strong>on</strong>al BCS superc<strong>on</strong>ducting state. We find that the wavefuncti<strong>on</strong> of the<br />

modified Cooper pair c<strong>on</strong>tains a spin triplet comp<strong>on</strong>ent with the s-wave orbital<br />

symmetry. While the spin triplet s-wave Cooper pair is forbidden owing to the fermi<strong>on</strong><br />

property, it is permitted in the generalized theoretical framework c<strong>on</strong>taining the oddfrequency<br />

dependence of the order parameter. We investigate this point <strong>on</strong> the basis of<br />

the self-c<strong>on</strong>sistent calculati<strong>on</strong> in the Eliashberg theory and find that the odd-frequency<br />

order parameter coexists with the even-frequency <strong>on</strong>e [1]. We also report how physical<br />

properties are affected by the induced odd-frequency superc<strong>on</strong>ducting order parameter<br />

[2].<br />

[1] M. Matsumoto, M. Koga, and H. Kusunose, J. Phys. Soc. Jpn. Vol. 81, 033702 (2012).<br />

[2] H. Kusunose, M. Matsumoto, and M. Koga, Phys. Rev. B Vol. 85, 174528 (2012).<br />

SB18<br />

Enhanced pinning properties and the zero-resistance state in melttextured<br />

high-Tc superc<strong>on</strong>ductors probed by pulsed magnetic fields<br />

Fabio Teixeira Dias 1 *, Valdemar Das Neves Vieira 1 , Douglas Langie Da Silva 1 , Sabrina Esperanca<br />

Nunes 1 , Frederik Wolff-Fabris 2 , Erik Kampert 2 , Jacob Schaf 3 and Joan Josep Roa Rovira 4<br />

1 Department of Physics, Universidade Federal de Pelotas, 96010-900, Pelotas, Brazil<br />

2 Dresden High Magnetic Field Laboratory, HZ Dresden-Rossendorf, 01314, Dresden, Germany<br />

3 Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, Brazil<br />

4 Universite de Poitiers, 86962, Poitiers, France<br />

Am<strong>on</strong>g several techniques to grow high-temperature superc<strong>on</strong>ductors, melt-textured techniques have emerged as an<br />

alternative way to produce materials with physical properties needed for some technological applicati<strong>on</strong>s. In this work<br />

we have studied the correlati<strong>on</strong> between the magnetic irreversibility line and the zero-resistance state in melt-textured<br />

YBaCuO samples (Y123) with inclusi<strong>on</strong>s of Y211 phase particles by performing magnetizati<strong>on</strong> and magnetotransport<br />

measurements in DC and pulsed magnetic fields up to 60 T and temperatures down to 1.5 K [1]. Our results show for inplane<br />

magnetic fields an irreversibility field higher than 40 T at 77 K which evidences a str<strong>on</strong>g pinning effect due to the<br />

interface of the Y211 particles embedded in the Y123 phase. We have observed effects of the intrinsic pinning due to the<br />

anisotropic superc<strong>on</strong>ductivity of the Y123 phase. Access to pulsed high magnetic fields reveals a suppressi<strong>on</strong> of the lowtemperature<br />

magnetic irreversibility field relative to BC 2. These results show experimental evidences for field-induced<br />

microscopic quantum fluctuati<strong>on</strong>s as observed in different high-Tc superc<strong>on</strong>ductors. Our findings in melt-textured<br />

YBCO samples exclude the possibility that the zero-resistance state and the magnetic irreversibility merge in this field<br />

range [2,3,4], showing evidences of weak granularity and providing a good candidate for technological applicati<strong>on</strong>s.<br />

[1] J. Schaf, P. Pureur, F. Dias, V. Vieira, P. Rodrigues Jr., and X. Obradors, Phys. Rev. B 77, 134503 (2008). [2] C. Ebner<br />

and D. Stroud, Phys. Rev. B 31, 165 (1985). [3] P. Pureur, R. Costa, J. Roa-Rojas, and P. Prieto, Phys. Rev. B 61, 12457 (2000).<br />

[4] J. Rosenblatt, P. Peyral, A. Raboutou, and C. Lebeau, Physica B 152, 95 (1988).<br />

SB19<br />

Phenomena of vortex pinning by composite pinning array <strong>on</strong> Nb films<br />

Sheng Hao Wang 1 *, Lance Horng 1 , T. C. Wu 2 , Chien-miao Chen 1 , R Cao 1 and J. C.<br />

Wu 1<br />

1 Dept. of Physics, Nati<strong>on</strong>al ChangHua University of Educati<strong>on</strong>, Taiwan<br />

2 Dept. of Electr<strong>on</strong>ic Engineering, Nati<strong>on</strong>al Formosa University, Taiwan<br />

In type II superc<strong>on</strong>ductor, magnetic fields can penetrate into the superc<strong>on</strong>ductor<br />

inhomogeneously as an array of vortices. The interacti<strong>on</strong> of these vortices and vortexpin<br />

interacti<strong>on</strong>s in the superc<strong>on</strong>ductor give rise to a rich variety of static and dynamical<br />

phases. In our study, smaller pinning sites at the center of every hexag<strong>on</strong>al cell were<br />

added when fabricating film with h<strong>on</strong>eycomb array to obtain films with composite<br />

pinning array. It has been prepared <strong>on</strong> Si 3N 4-coated Si wafers using electr<strong>on</strong>-beam<br />

lithography in c<strong>on</strong>juncti<strong>on</strong> with reactive i<strong>on</strong> etching. Then a dc sputtering completed<br />

the four-terminal geometry niobium films over the composite array. MR measurements<br />

were carried out by a four-probe technique. Special matching peaks of critical currents<br />

are exhibited at different temperatures in the measurements. The positi<strong>on</strong>s and structures<br />

of the matching peaks seem irregular and are very different from the structures of the<br />

matching peaks for previously explored films, such as films with triangular, square, or<br />

h<strong>on</strong>eycomb pinning arrays. C<strong>on</strong>sidering the multiple-vortex filling of different pinning<br />

sites, we can give a reas<strong>on</strong>able explanati<strong>on</strong> to this interesting phenomen<strong>on</strong>.<br />

T. C. Wu, R. Cao, T. J. Yang, L. Horng, J. C. Wu, Jan Kolacek, Solid State Commun. 143, 171 (2010) ,<br />

R Cao, Lance Horng, T. J. Yang, T. C. Wu, J. C. Wang, and J. C. Wu, J. Appl. Phys. 107, 09E129 (2010)<br />

,T. C. Wu, J. C. Wang, Lance Horng, J. C. Wu, and T. J. Yang1, J. Appl. Phys. 97, 10B102 (2005)<br />

SB20<br />

SB21<br />

SB22<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Superc<strong>on</strong>ducting fluctuati<strong>on</strong>s near the Mott critical point<br />

Mo<strong>on</strong>-sun Nam 1 , Cecile Meziere 2 , Patrick Batail 2 and Arzhang Ardavan 1<br />

1<br />

The Clarend<strong>on</strong> Laboratory, Department of Physics, University of Oxford, United<br />

Kingdom<br />

2<br />

Laboratoire MOLTECH-Anjou, UMR 6200 CNRS-Universite d'Angers, 2 Boulevard<br />

Lavoisier, F-49045 Angers, France<br />

The Nernst effect, the voltage that occurs transverse to crossed temperature gradient and<br />

magnetic field applied to a c<strong>on</strong>ductor, is a sensitive probe of superc<strong>on</strong>ducting fluctuati<strong>on</strong>s in<br />

unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors such as the high-Tc cuprates [1] and organic superc<strong>on</strong>ductors<br />

[2]. The isostructural kappa-phase organic compounds (BEDT-TTF)2X offer a series of<br />

materials ranging from weakly correlated superc<strong>on</strong>ductors (X = Cu(NCS) 2) through str<strong>on</strong>gly<br />

correlated superc<strong>on</strong>ductors (X = Cu[(N(CN) 2]Br) to Mott insulators (X = Cu[(N(CN) 2]<br />

Cl) as the bandwidth decreases and the importance of correlati<strong>on</strong>s increases. We previously<br />

showed that while there are no fluctuati<strong>on</strong>s significantly above Tc in the weakly correlated<br />

superc<strong>on</strong>ductor, there are str<strong>on</strong>g superc<strong>on</strong>ducting fluctuati<strong>on</strong>s at temperatures up to 50% above<br />

Tc in the str<strong>on</strong>gly correlated superc<strong>on</strong>ductor [2], suggesting that the proximity of the Mott state<br />

drives the fluctuating state. Here, by alloying the str<strong>on</strong>gly correlated and the Mott insulating<br />

materials, we tune the system towards the Mott critical point. Superc<strong>on</strong>ductors in the vicinity<br />

of the critical point exhibit a large and magnetic-field-dependent Nernst effect, characteristic of<br />

superc<strong>on</strong>ducting fluctuati<strong>on</strong>s, at even higher temperatures. The effect is apparent over the whole<br />

temperature range for which the c<strong>on</strong>ductivity is metallic, up to 50K, about six times Tc.<br />

[1] Y. Wang, et al., Phys. Rev. B 73, 024510 (2006) [2] M.-S. Nam et al., Nature 449, 584 (2007)<br />

Anomalous hall effect in superc<strong>on</strong>ductors with spin-orbit interacti<strong>on</strong><br />

Pedro D Sacramento 1 , M. A. N. Araujo 2 , V R Vieira 1 , V K Dugaev 3 and J Barnas 4<br />

1 Departamento de Fisica and CFIF, Instituto Superior Tecnico, TULisb<strong>on</strong>, Portugal<br />

2 Departamento de Fisica and CFIF, Universidade de Evora, Portugal<br />

3 Department of Physics, Rzeszow University of Technology, Poland<br />

4 Department of Physics, Adam Mickiewicz University, Poland<br />

WITHDRAWN<br />

Analysis of the local current density in HTS coated c<strong>on</strong>ductors using<br />

low-temperature scanning laser and hall probe microscopy<br />

Sang Kook Park, Bo Ram Cho, Hee Ye<strong>on</strong> Park and Hye<strong>on</strong>g-cheol Ri*<br />

Department of Physics, Kyungpook Nati<strong>on</strong>al University, Korea<br />

Local current density in HTS coated c<strong>on</strong>ductors was investigated using Lowtemperature<br />

Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared<br />

GdBCO and YBCO coated c<strong>on</strong>ductors to study the spatial distributi<strong>on</strong> of the current<br />

density in a single bridge. Inhomogeneity of the local critical temperature in the<br />

bridge was analyzed from experimental results of scanning laser microscopy near the<br />

superc<strong>on</strong>ducting transiti<strong>on</strong>. The local transport and screening current in the bridge were<br />

also investigated using scanning Hall probe microscopy. From experimental results<br />

of scanning laser and Hall probe microscopy, we have observed the redistributi<strong>on</strong> of<br />

current density and the critical temperature caused by defects of the HTS layer.<br />

July 8 - 13, 2012 Busan, Korea 209<br />

Poster Friday


Poster Friday<br />

SB23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Cooper pairing between c<strong>on</strong>ducti<strong>on</strong> and localized electr<strong>on</strong>s in heavyfermi<strong>on</strong><br />

systems<br />

Keisuke Masuda 1 * and Daisuke Yamamoto 2<br />

1 Department of Physics, Waseda University, Japan<br />

2 C<strong>on</strong>densed Matter Theory Laboratory, RIKEN, Japan<br />

We study the Cooper pairing between a c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong> (c electr<strong>on</strong>) and a localized<br />

f electr<strong>on</strong>, referred to as the c-f paring, as a mechanism of s-wave superc<strong>on</strong>ductivity<br />

in heavy-fermi<strong>on</strong> systems. To describe the physics of heavy-fermi<strong>on</strong> systems, we start<br />

from the periodic Anders<strong>on</strong> model. We apply the Schrieffer-Wolff transformati<strong>on</strong> to this<br />

model c<strong>on</strong>sidering the situati<strong>on</strong> where the f level is sufficiently deep and the Coulomb<br />

repulsi<strong>on</strong> is finite but large. The resulting effective Hamilt<strong>on</strong>ian includes direct and<br />

spin-exchange interacti<strong>on</strong>s between c and f electr<strong>on</strong>s, which can be the driving force<br />

for the formati<strong>on</strong> of the Cooper pairs. Within the mean-field approximati<strong>on</strong>, we show<br />

that the c-f pairing state with anisotropic s-wave symmetry appears in a large regi<strong>on</strong> of<br />

the phase diagram. Such a pairing state can be realized when the quasiparticle band of<br />

the f electr<strong>on</strong>s, which is formed by the str<strong>on</strong>g Coulomb repulsi<strong>on</strong>, is located near the<br />

energy level of the c<strong>on</strong>ducti<strong>on</strong> band. We also discuss the relati<strong>on</strong>ship between the c-f<br />

pairing proposed here and the s-wave superc<strong>on</strong>ductivity found in the experiments <strong>on</strong><br />

CeRu 2 and CeCo 2.<br />

SB24<br />

Low-temperature thermoelectric properties of the electr<strong>on</strong>-doped<br />

Perovskites Sr 1-xCaxTi 1-yNbyO 3<br />

Tetsuji Okuda 1 *, Junichi Fukuyado 1 , Kurahito Narikiyo 1 , Mitsuru Akaki 2 and Hideki<br />

Kuwahara 2<br />

1 Kagoshima University, Japan<br />

2 Sophia University, Japan<br />

Electr<strong>on</strong>-doped perovskite SrTiO 3 is known to be <strong>on</strong>e of candidates for an n-type<br />

thermoelectric (TE) oxide. [1] In this study, we tried to improve a TE property of a<br />

lightly-electr<strong>on</strong>-doped SrTiO 3 single crystal below room temperature by substituti<strong>on</strong>s<br />

of Ca and Nb for Sr and Ti. We found that SrTi 0.99Nb 0.01O 3 shows a large power factor<br />

of about 90 μW/K2 cm at 50 K and the largest dimensi<strong>on</strong>less TE figure-of-merit (ZT ~<br />

0.07) below 40 K am<strong>on</strong>g the ever-reported materials. The good n-type TE resp<strong>on</strong>se is<br />

due to a distinct electr<strong>on</strong>-ph<strong>on</strong><strong>on</strong> interacti<strong>on</strong> which could relate to the superc<strong>on</strong>ducting<br />

state [2], which enlarges a Seebeck coefficient not through an enhancement of effective<br />

mass, but through a change of relaxati<strong>on</strong> time. On the other hand, a Ca 2+ substituti<strong>on</strong><br />

for Sr 2+ increases the ZT at 300 K for Sr 1-xCaxTi 0.97Nb 0.03O 3 from 0.08 to 0.105. The<br />

enhancement of ZT originates not <strong>on</strong>ly in a large reducti<strong>on</strong> of a thermal c<strong>on</strong>ductivity<br />

due to an introduced randomness into the crystal structure, but also in an unexpected<br />

enhancement of Seebeck coefficient by the Ca substituti<strong>on</strong>.<br />

[1] T. Okuda, K. Nakanishi, S. Miyasaka, and Y. Tokura, Phys. Rev. B 63, 113104 (2001). [2] H. Suzuki, H.<br />

Bando, Y. Ootuka, I.H. Inoue, T. Yamamoto, K. Takahashi, and Y. Nishihara, J. Phys. Soc. Jpn. 65, 1529<br />

(1996). [3] J. Fukuyado, K. Narikiyo, M. Akaki, H. Kuwahara, and T. Okuda, Phys. Rev. B, to be published.<br />

SB25<br />

Evoluti<strong>on</strong> of pairing potential in ladder materials under<br />

renormalizati<strong>on</strong> group transformati<strong>on</strong>s<br />

Yen-chen Lee 1 *, Wen-min Huang 2 and Hsiu-hau Lin 1<br />

1 Department of Physics, Nati<strong>on</strong>al Tsing Hua University, Taiwan<br />

2 Physics Divisi<strong>on</strong>, Nati<strong>on</strong>al Center for Theoretical Sciences, Taiwan<br />

It is generally believed that electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong>s are resp<strong>on</strong>sible for pair<br />

formati<strong>on</strong> in unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors. However, how electr<strong>on</strong>s can form<br />

pairs in the presence of repulsive interacti<strong>on</strong>s remains counterintuitive and puzzling.<br />

Many studies suggest that spin fluctuati<strong>on</strong>s provides the “pairing glues” to account for<br />

the unc<strong>on</strong>venti<strong>on</strong>al pairing. Here we take a different route: finding effective pairing<br />

potential at different length scales by renormalizati<strong>on</strong> group approach. We focus <strong>on</strong><br />

the unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity in ladder materials and show how the profile<br />

of electr<strong>on</strong>-electr<strong>on</strong> interacti<strong>on</strong>s evolves under renormalizati<strong>on</strong> group transformati<strong>on</strong>.<br />

Starting with repulsive short-ranged interacti<strong>on</strong>, compelling evidence for spatially<br />

structured attractive interacti<strong>on</strong>s emerges in l<strong>on</strong>g-wavelength limit and explains the<br />

unc<strong>on</strong>venti<strong>on</strong>al pairing symmetry naturally. Comparis<strong>on</strong>s with other theoretical<br />

approaches and potential generalizati<strong>on</strong> to two dimensi<strong>on</strong>s are discussed at the end.<br />

210 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SB26<br />

Evidence for multiband order parameters in the st<strong>on</strong>g-coupling<br />

LaRu 4As 12 Skutterudite Superc<strong>on</strong>ductor<br />

Tomasz Cichorek 1, Lukasz Bochenek 1, Ryszard Wawryk 1, Roman Puzniak 2 and<br />

Zygmunt Henkie 1<br />

1 Institute of Low Temperature and Structure Research, Polish Academy of Sciences,<br />

Wroclaw, Poland<br />

2 Institute of Physics, Polish Academy of Sciences, Warsaw, Poland<br />

Superc<strong>on</strong>ducting properties of high-purity LaRu 4As 12 single crystals with the highest<br />

critical temperature Tc = 10.45 K am<strong>on</strong>g the fully filled-skutterudite superc<strong>on</strong>ductors<br />

were investigated by dc magnetizati<strong>on</strong>, electrical resistivity, torque, and specific heat<br />

measurements both as a functi<strong>on</strong> of temperature and magnetic field. At B = 0 and<br />

below about Tc/2, the electr<strong>on</strong>ic specific heat exhibits two-band features, as c<strong>on</strong>cluded<br />

from an α-model analysis. Multi-band effects are further inferred from a n<strong>on</strong>linear<br />

magnetic-field dependence of the electr<strong>on</strong>ic specific heat coefficient in the zerotemperature<br />

limit as well as from a positive curvature of the upper critical field in the<br />

vicinity of Tc. Our findings, combined with results of previous de Haas-van Alphen<br />

experiments, suggest that enhanced superc<strong>on</strong>ductivity in LaRu 4As 12appears al<strong>on</strong>g with<br />

a spherical Fermi-surface sheet enclosing a small volume in the center of the Brillouin<br />

z<strong>on</strong>e.<br />

SB27<br />

NMR Study of magnetic order and the FFLO state in CeCoIn 5<br />

Ken-ichi Kumagai 1 *, Hiroyuki Shishido 2 , Takasada Shibauchi 2 and Yuji Matsuda 2<br />

1 Department of Physics, Hokkaido University, Sapporo, 060-0810, Japan<br />

2 Department of Physics, Kyoto University, Kyoto 606-8502, Japan<br />

A str<strong>on</strong>gly-correlated superc<strong>on</strong>ductor, CeCoIn 5 is believed to host a Fulde-Ferrell-<br />

Larkin-Ovchinnkov (FFLO) state in a restricted regi<strong>on</strong> of high field and very low<br />

temperature. In additi<strong>on</strong> to the field evoluti<strong>on</strong> of NMR results for H//a-axis [1], we<br />

will report recent results of the angle,θ, dependence of external fields with respect to<br />

the ab planes down to ~50mK. Detail phase diagram for θ-, B-, and T-parameters is<br />

obtained. The NMR spectra change dramatically up<strong>on</strong> entering the novel SC phase.<br />

A well-separated peak structure at the In(2b) site suggests the occurrence of the<br />

magnetic order which is emerging <strong>on</strong>ly in the newly-discovered SC state. The structure<br />

of the spin density wave (SDW) is modified with angle and field. The Knight shift<br />

of CeCoIn 5 provides a direct evidence for the emergence of the spatially-distributed<br />

normal quasiparticle regi<strong>on</strong>. The quantitative analysis for the field evoluti<strong>on</strong> of the<br />

paramagnetic magnetizati<strong>on</strong> and low-lying energy quasiparticle density of state is<br />

c<strong>on</strong>sistent with the nodal plane formati<strong>on</strong>, which is characterized by an order parameter<br />

in the FFLO state.<br />

[1] K. Kumagai et al., Phys. Rev. Lett. 106, 137004 (2011).<br />

SB28<br />

MgB2 coated c<strong>on</strong>ductors grown at various temperatures by hybrid<br />

physical-chemical vapor depositi<strong>on</strong><br />

Mahipal Ranot 1 , K. H. Cho 1 , So<strong>on</strong>-gil Jung 1 , W<strong>on</strong> Nam Kang 1 *, S. Oh 2 and K. C.<br />

Chung 3<br />

1 Physics, Sungkyunkwan University, Suw<strong>on</strong>, Korea<br />

2 Nati<strong>on</strong>al Fusi<strong>on</strong> Research Institute, Korea<br />

3 Korea Institute of Machinery and Materials, Korea<br />

For practical applicati<strong>on</strong>s, MgB 2 superc<strong>on</strong>ductor (T c~39 K) in the form of wires and<br />

tapes are required to be produced in l<strong>on</strong>g lengths to replace the c<strong>on</strong>venti<strong>on</strong>al metallic<br />

superc<strong>on</strong>ductors, such as Nb-Ti and Nb 3Sn. In this work, we have grown MgB 2 coated<br />

c<strong>on</strong>ductors by depositing MgB 2 films directly <strong>on</strong> the flexible Hastelloy tapes at various<br />

temperatures ranging from 520 to 600 °C by using HPCVD. The MgB 2 coated c<strong>on</strong>ductors<br />

exhibit critical temperatures ranging from 37.5 to 38.5 K with superc<strong>on</strong>ducting transiti<strong>on</strong><br />

width (T c) of about 0.3?0.8 K. X-ray diffracti<strong>on</strong> analysis revealed that the MgB 2 coated<br />

c<strong>on</strong>ductors are polycrystalline in nature. It was found that the MgB 2 coated c<strong>on</strong>ductor<br />

grown at 520 °C had dense microstructure with good grain c<strong>on</strong>nectivity. However, up<strong>on</strong><br />

increasing the growth temperature from 520 to 600 °C deteriorati<strong>on</strong> of grain c<strong>on</strong>nectivity<br />

takes place and void formati<strong>on</strong>s were observed. The critical current density (Jc) of the<br />

order of Jc(5 K, 0 T) ~107 and Jc(5 K, 3 T) ~105 A/cm2 was obtained for the MgB 2 coated<br />

c<strong>on</strong>ductor fabricated at 520 °C. The fabricati<strong>on</strong> process, crystallographic orientati<strong>on</strong>s,<br />

surface morphologies and superc<strong>on</strong>ducting properties [T c, Jc (H)] of MgB 2 coated<br />

c<strong>on</strong>ductors grown at various temperatures will be discussed in detail.


SB29<br />

Low temperature properties of the weakly-coupled n<strong>on</strong>centrosymmetric<br />

superc<strong>on</strong>ductor LaNiC 2<br />

Jian Chen 1 , Jing Lei Zhang 1 , Lin Jiao 1 , Lin Yang 1 , Tian Shang 1 , Michael Nicklas 2 ,<br />

Frank Steglich 2 and Hui Qiu Yuan 1 *<br />

1 Physical Department, Zhejiang University, China<br />

2 Max Planck Institute for the Chemical Physics of Solids, Dresden, Germany<br />

In a n<strong>on</strong>-centrosymmetric (NCS) superc<strong>on</strong>ductor, an asymmetric potential gradient<br />

yields an antisymmetric spin-orbit coupling (ASOC), which splits the degeneracy of<br />

c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>, and allows the admixture of spin-singlet and spin-triplet pairing<br />

states, leading to accidental nodes in the energy gap [1,2]. It was shown that the timereversal<br />

symmetry is broken in the weakly correlated intermetallic compound LaNiC 2<br />

[3] but its pairing symmetry is still under debate. Here we present the low temperature<br />

specific heat C(T) and the magnetic penetrati<strong>on</strong> depth λ(T) for LaNiC 2. It is found<br />

that both λ(T) and Ce(T)/T can be well described by a phenomenological two-gap<br />

model. The Sommerfeld parameter, γ(H), increases steeply at low fields and eventually<br />

get saturated with increasing magnetic field, being also c<strong>on</strong>sistent with the behavior<br />

of two-gap superc<strong>on</strong>ductivity. We argue that the ASOC is weak in LaNiC 2 and the<br />

spin-singlet state dominates in the pairing states, giving rise to two-gap-like BCS<br />

superc<strong>on</strong>ductivity.<br />

[1] P. A. Frigeri, D. F. Agterberg, A. Koga, and M. Sigrist, Phys. Rev. Lett. 92, 097001 (2004). [2] H. Q.<br />

Yuan, D. F. Agterberg, N. Hayashi, P. Badica, D. Vandervelde, K. Togano, M. Sigrist, M. B. Salam<strong>on</strong>, Phys.<br />

Rev. Lett. 97, 017006 (2006). [3] A. D. Hillier, J. Quintanilla, R Cywinski, Phys. Rev. Lett. 102, 117007 (2009).<br />

SB30<br />

Magnetic penetrati<strong>on</strong> depth and $H$-$T$ phase diagram in SrPd 2Ge 2<br />

H. Kim 1 , N. H. Sung 2 , M. A. Tanatar 1 , B. K. Cho 2 and R. Prozorov 1 *<br />

1 The Ames Laboratory, USA<br />

2 School of Materials Science and Engineering, Gwangju Institute of Science and<br />

Technology, Korea<br />

In-plane magnetic penetrati<strong>on</strong> depth, $\lambda(T)$, was measured in single crystals of<br />

SrPd 2Ge 2 superc<strong>on</strong>ductor down to 50 mK and in magnetic fields up to $H_{dc} = 1$ T by<br />

using a self - oscillating tunnel diode res<strong>on</strong>ator operating at 16 MHz with amplitude of $H_{ac}<br />

≈ 20$ mOe. In the pure Meissner state, at $H_{dc}=0$, $ \lambda(T)$ saturates exp<strong>on</strong>entially<br />

approaching $T\rightarrow 0$ indicating fully gapped superc<strong>on</strong>ductivity in SrPd$_2$Ge$_2$.<br />

In a magnetic field, the measured penetrati<strong>on</strong> depth is given by $\lambda^2 = \lambda^2_L +<br />

\lambda^2_C$, where $\lambda^2_C ~ B/j^2_c$ is the Campbell penetrati<strong>on</strong> depth and $j_c$<br />

is the critical current density. For $H < 0.4$ T, the shortest $\lambda_C$ (str<strong>on</strong>gest pinning) is<br />

achieved not at the lowest, but at some intermediated temperature. Additi<strong>on</strong>ally, $Δ \lambda(T)$<br />

shows hysteresis between zero field cooling and field cooling measurements, which is an<br />

indicati<strong>on</strong> of n<strong>on</strong> - parabolic pinning potential. Another interesting feature is a pr<strong>on</strong>ounced<br />

finite diamagnetic resp<strong>on</strong>se above bulk superc<strong>on</strong>ducting transiti<strong>on</strong>, which could be related to<br />

superc<strong>on</strong>ducting fluctuati<strong>on</strong>s. Combining all measurements, the entire $H-T$ phase diagram<br />

of SrPd 2Ge 2 has been c<strong>on</strong>structed. Possible pairing mechanism and the superc<strong>on</strong>ducting gap<br />

structure, unusual vortex resp<strong>on</strong>se and field - and temperature dependent critical current density<br />

will be discussed.<br />

SB31<br />

Eliashberg functi<strong>on</strong> of the overdoped Bi 2212 superc<strong>on</strong>ductors deduced<br />

from the high resoluti<strong>on</strong> laser ARPES intensity<br />

Jin Mo Bok 1 *, Han-y<strong>on</strong>g Choi 1 , Junfeng He 2 , X. J. Zhou 3 and C. M. Varma 4<br />

1 Department of Physics, SungKyunKwan University, Suw<strong>on</strong> 440-746, Korea<br />

2 Institute of Physics, Chinese Academy of Sciences, Beijing 100190., China<br />

3 Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China<br />

4 Department of Physics and Astr<strong>on</strong>omy, University of California, Riverside, CA<br />

92521, USA<br />

We report the diag<strong>on</strong>al and off-diag<strong>on</strong>al Eliashberg functi<strong>on</strong>s a2F(+) and a2F(-) of<br />

overdoped Bi2212 superc<strong>on</strong>dcutors deduced from the high resoluti<strong>on</strong> laser APRES<br />

experiments. By fitting the momentum distributi<strong>on</strong> curves of the ARPES intensity<br />

employing the superc<strong>on</strong>ducting Green's functi<strong>on</strong>, the diag<strong>on</strong>al and off-diag<strong>on</strong>al selfenergies<br />

al<strong>on</strong>g several cuts in the Brillouin z<strong>on</strong>e are extracted. Then, the diag<strong>on</strong>al and<br />

off-diag<strong>on</strong>al Eliashberg functi<strong>on</strong>s are deduced by inverting the d-wave Eliashberg<br />

equati<strong>on</strong> using, respectively, the c<strong>on</strong>rresp<strong>on</strong>ding self-energies. We will present the<br />

momentum and frequency dependences of the Eliashberg functi<strong>on</strong> a2F(+) and a2F(-).<br />

We then compare these results with other experiment and calculati<strong>on</strong> results.<br />

SB32<br />

SC01<br />

SC02<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The momentum and frequency dependences of the self-energy induced<br />

by the spin fluctuati<strong>on</strong>s for the cuprate superc<strong>on</strong>ductors<br />

Seung Hwan H<strong>on</strong>g and Han-y<strong>on</strong>g Choi*<br />

Department of Physics, SungKyunKwan University, Korea<br />

We solve the momentum resolved d-wave Eliashberg equati<strong>on</strong> to investigate the<br />

c<strong>on</strong>sistency of the spin fluctuati<strong>on</strong> induced superc<strong>on</strong>ductivity theory for the cuprates.<br />

The effective interacti<strong>on</strong> between electr<strong>on</strong>s (Eliashberg functi<strong>on</strong>) is modeled in terms<br />

of the magnetic excitati<strong>on</strong> spectrum measured by the inelastic neutr<strong>on</strong> scattering <strong>on</strong> the<br />

LSCO superc<strong>on</strong>ductors reported by Vignolle et al[1]. The magnetic excitati<strong>on</strong> spectrum<br />

c<strong>on</strong>sists of three parts: the res<strong>on</strong>ance mode near 40-70 meV and the incommensurate<br />

parts above and below the res<strong>on</strong>ance mode. The res<strong>on</strong>ance mode has a peak at (π,π).<br />

The low energy incommensurate part makes a n<strong>on</strong>m<strong>on</strong>ot<strong>on</strong>ic momentum dependence<br />

of the diag<strong>on</strong>al and off-diag<strong>on</strong>al self-energies. On the other hand, the res<strong>on</strong>ance mode<br />

makes a m<strong>on</strong>ot<strong>on</strong>ic momentum dependence of the self-energy. The angle dependence<br />

of the superc<strong>on</strong>ducting gap is influenced by the effects of these two energy scales.<br />

These results are compared with the ARPES experiments.<br />

[1] B. Vignolle et al., Natrue Physics 3, 163 (2007)<br />

Novel n<strong>on</strong>-centrosymmetric superc<strong>on</strong>ductors in 113 and 111 crystal structures<br />

Friedrich Kneidinger 1 *, Ernst Bauer 1 , Herwig Michor 1 , Gerfried Hilscher 1 , Isolde Zeiringer 2 ,<br />

Peter Rogl 2 , Nataliya Melnychenko 3 , Le<strong>on</strong>id Salamakha 4 and Adrian Hillier 5<br />

1 Institute of solid state physics, Vienna University of Technology, Austria<br />

2 Institute of physical chemistry, University of Vienna, Austria<br />

3 Inorganic Chemistry Department, Ivan Franko Nati<strong>on</strong>al University of Lviv, Ukraine<br />

4 Ivan Franko Lviv Nati<strong>on</strong>al University, Ukraine<br />

5 ISIS facility, STFC Rutherford Applet<strong>on</strong> Laboratory, Harwell Science and Innovati<strong>on</strong><br />

Campus, United Kingdom<br />

Superc<strong>on</strong>ductivity (SC) in materials that d<strong>on</strong>’t possess a center of inversi<strong>on</strong> due to their crystal structure has<br />

been recently found in materials like CePt_3Si[1]. The lack of inversi<strong>on</strong>-symmetry gives rise to an electrical<br />

field and therefore leads to an antisymmetric spin-orbit coupling (ASOC) of the Rashba-type[2]. This causes<br />

a splitting of the Fermi surface, thereby leading to a superpositi<strong>on</strong> of spin-singlet and spin-triplet Cooper pairs<br />

in the SC c<strong>on</strong>densate. Intriguing features like nodes in the superc<strong>on</strong>ducting gap, as well as H_c2 exceeding<br />

the Pauli-Clogst<strong>on</strong> limit, may occur. However, besides Li_2Pt_3B[3], spin-triplet pairing seems <strong>on</strong>ly to be<br />

dominant in heavy fermi<strong>on</strong> systems. In order to study these features in further detail, new ternary compounds<br />

like BaPtSi_3[4], SrPdSi_3, SrPdGe_3[5], SrPtSi_3 and SrPtGe_3 of BaNiSn_3 type (space group I/4mm)<br />

as well as promising 111-types like LaPtSi[6,7] and LaIrSi[8] have been investigated, since there is a tuning<br />

possibility regarding the quadratic atomic number dependency (Z²) of the spin-orbit coupling. Measurements<br />

of the electrical resistivity and the specific heat have been c<strong>on</strong>ducted to analyze the superc<strong>on</strong>ducting ground<br />

state. Additi<strong>on</strong>ally, μSR measurements have been performed to proof the microscopic pairing mechanism of<br />

the Cooper pairs. The results obtained so far indicate s-wave fully gapped BCS SC.<br />

[1] E. Bauer et al., Phys. Rev. Lett. 92, 027003 (2004) [2] Y.A. Bychkov and E. I. Rashba, JETP Lett 39, 78 (1984)<br />

[3] M. Nishiyama et al., Phys. Rev. Lett. 98, 047002 (2007) [4] E. Bauer et al., Phys. Rev. B 80, 064504 (2009)<br />

[5] K. Miliyanchuk et al., Journal of Physics: <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series 273, 012078 (2011) [6] K. Klepp & E.Parthe,<br />

Acta Crystallogr. B38, 1105 (1982) [7] J. Evers, G. Oehlinger and A. Weiss, Solid State Communicati<strong>on</strong>s, Vol.<br />

50, No. 1, pp. 61-62, (1984) [8] K. Klepp & E.Parthe, Acta Crystallogr. B38, 1541 (1982)<br />

N<strong>on</strong>-fermi liquid behavior of d-wave superc<strong>on</strong>ductor<br />

Pankaj Singh*, Ajay Pratap Singh Gahlot, Manju Rani and Partho Goswami<br />

PHYSICS DEPARTMENT, DESHBANDHU COLLEGE, UNIVERSITY OF DELHI,<br />

India<br />

The d+id-density wave (Chiral DDW) order, at the anti-ferromagnetic wave vector<br />

Q = (π,π), is assumed to represent the pseudo-gap (PG) state of a hole-doped cuprate<br />

superc<strong>on</strong>ductor. The d-wave superc<strong>on</strong>ductivity (DSC), driven by an assumed attractive<br />

interacti<strong>on</strong>, is discussed within the BCS framework together with the d+id ordering.<br />

The single-particle excitati<strong>on</strong> spectrum in the CDDW + DSC state is characterized by<br />

the Bogoluibov quasi-particle bands-a characteristic feature of SC state. The coupled<br />

gap equati<strong>on</strong>s are solved self-c<strong>on</strong>sistently together with the equati<strong>on</strong> to determine<br />

the chemical potential (μ). With the pinning of the van Hove-singularities close to μ,<br />

<strong>on</strong>e is able to calculate the thermodynamic properties of the under-doped cuprates<br />

in a c<strong>on</strong>sistent manner. Apart from the known facts that PG and DSC represent<br />

two competing orders as the former brings about a depleti<strong>on</strong> of the spectral weight<br />

available for pairing in the anti-nodal regi<strong>on</strong> of momentum space and the depleti<strong>on</strong><br />

of the spectral weight below Tc at energies larger than the gap amplitude, we find<br />

a c<strong>on</strong>spicuous feature that the electr<strong>on</strong>ic specific heat displays n<strong>on</strong>-Fermi liquid<br />

behavior( anomalous temperature dependence) in the CDDW + DSC state.<br />

July 8 - 13, 2012 Busan, Korea 211<br />

Poster Friday


Poster Friday<br />

SC03<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Low temperature enhancement of the critical current in CeCoIn 5.<br />

Possible signature of magnetic order.<br />

C. F. Miclea 1 *, M. Nicklas 2 , A. C. Mota 3 , M. M. Altarawneh 4 , C. Miclea 1 , N.<br />

Harris<strong>on</strong> 4 , J. Thomps<strong>on</strong> 4 , F. Steglich 2 and R. Movshovich 4<br />

1 Nati<strong>on</strong>al Institute for Materials Physics, 077125 Bucharest-Magurele, Romania<br />

2 Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany<br />

3 Solid State Laboratory, ETH Zurich, Switzerland<br />

4 Los Alamos Nati<strong>on</strong>al Laboratory, Los Alamos, New Mexico 87545, USA<br />

We report <strong>on</strong> vortex dynamics, dc magnetizati<strong>on</strong> and RF penetrati<strong>on</strong> depth measurements in<br />

the heavy fermi<strong>on</strong> compound CeCoIn 5 down to low temperatures, T=50 mK. No str<strong>on</strong>g pining<br />

is observed as expected for a clean limit superc<strong>on</strong>ductor which does not break sp<strong>on</strong>taneously<br />

any additi<strong>on</strong>al symmetries besides the U(1)-gauge. CeCoIn 5 display clear logarithmic relaxati<strong>on</strong><br />

curves as expected from Kim-Anders<strong>on</strong> theory. The temperature dependence of the relaxati<strong>on</strong><br />

rate, S, with a small but finite residual value indicate that quantum tunneling plays a significant<br />

role in the vortex creep <strong>on</strong>ly at very low temperatures. Remarkably, a new phase transiti<strong>on</strong><br />

marked by a str<strong>on</strong>g increase in the remnant magnetizati<strong>on</strong>, Mrem is observed around T = 0.3 K<br />

in low magnetic fields just high enough to put the sample in the Bean critical state. Moreover,<br />

this anomaly is corroborated by the DC magnetizati<strong>on</strong> and RF measurements at very low fields.<br />

We extended the vortex dynamics investigati<strong>on</strong> to Pb irradiated CeCoIn 5. While the defects<br />

created by irradiati<strong>on</strong> have a clear effect <strong>on</strong> the relaxati<strong>on</strong> rates the enhancement of Mrem<br />

still takes place at the same temperature. Our findings are c<strong>on</strong>sistent with the existence of a<br />

magnetically ordered phase, deep inside the superc<strong>on</strong>ducting state.<br />

SC04<br />

Superc<strong>on</strong>ducting phase diagram in fcc phase of Cs 3C 60; A pressure<br />

dependence of resistivity<br />

Takashi Kambe*, Yuta Suzuki, Seizi Shibasaki, Keitaro Tomita and Yoshihiro<br />

Kuboz<strong>on</strong>o<br />

Physics, Okayama university, Japan<br />

Cs 3C 60 crystallizes three polymorphic phases; A 15, fcc and bco. Two polymorphs, A 15<br />

and fcc phases, show pressure induced superc<strong>on</strong>ducting transiti<strong>on</strong>s around 38 K and<br />

35 K, respectively. Here we report a resistivity for fcc phase of Cs 3C 60 as a functi<strong>on</strong> of<br />

pressure and present a dome-shaped superc<strong>on</strong>ducting phase diagram.<br />

SC05<br />

The superc<strong>on</strong>ducting phases of URu 2Si 2 from sound velocity<br />

measurements<br />

B S Shivaram 1 , V W Ulrich 1 and D G Hinks 2<br />

1 Physics, University of Virginia, USA<br />

2 Materials Science Divisi<strong>on</strong>, Arg<strong>on</strong>ne Nati<strong>on</strong>al Labs, USA<br />

High resoluti<strong>on</strong> measurements of the changes in the l<strong>on</strong>gitudinal sound velocity in<br />

a magnetic field have been performed in the zero temperature limit in high quality<br />

single crystals of URu 2Si 2. These measurements reveal two distinct signatures<br />

attributable to multiple superc<strong>on</strong>ducting phases. A step change in the sound velocity,<br />

for propagati<strong>on</strong> in the basal plane, is observed at the critical field, Bc 2. This step<br />

broadens c<strong>on</strong>siderably as T tends to Tc with a c<strong>on</strong>comitant decrease in magnitude. A<br />

sec<strong>on</strong>d step is observed at a field ~0.5 Bc 2 and it's magnitude remains c<strong>on</strong>stant at all<br />

temperatures. Inductive measurements of the transiti<strong>on</strong>s in a magnetic field, however,<br />

reveal <strong>on</strong>ly a single signature which coincides with the lower step change in the sound<br />

velocity. Measurements performed with B oriented at various angles between the a and<br />

c-axes reveal a weaker angular dependence of the lower step and c<strong>on</strong>firm the rapid fall<br />

off of Bc 2 close to B||c-axis. A multiple superc<strong>on</strong>ducting phase diagram for URu 2Si 2 is<br />

proposed.<br />

212 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SC06<br />

Electr<strong>on</strong>ic structure of a superc<strong>on</strong>ducting boride, ZrB12 Sangeeta Thakur 1 , Deep Narayan Biswas Biswas 2 , Nishaina Sahadev 3 , Geetha<br />

Balakrishnan 4 and Kalobaran Maiti 5 *<br />

1<br />

Department of C<strong>on</strong>densed Matter Physics and Materials' Science, Tata Institute of<br />

Fundamental Research Colaba, Mumbai - 400 005, India<br />

2<br />

Tata Institute of Fundamental Research Colaba, Mumbai - 400 005, India<br />

3<br />

Tata Institute of Fundamental Research, Colaba, Mumbai - 400 005, India<br />

4<br />

Department of Physics, University of Warwick, Coventry, CV4 7AL, UK, United<br />

Kingdom<br />

5<br />

Tata Institute of Fundamental Research Colaba Mumbai 400005, India<br />

Borides have attracted a great deal of attenti<strong>on</strong> followed by the finding of varied interesting<br />

properties. ZrB 12 is <strong>on</strong>e such compound exhibiting highest superc<strong>on</strong>ducting critical<br />

temperature (Tc = 6 K) in MB12 family. In order to probe the electr<strong>on</strong>ic states resp<strong>on</strong>sible<br />

for superc<strong>on</strong>ductivity in this compound, we studied the electr<strong>on</strong>ic structure of single<br />

crystalline ZrB 12 using high resoluti<strong>on</strong> photoemissi<strong>on</strong> spectroscopy and ab initio band<br />

structure calculati<strong>on</strong>s. Zr 3d core level spectra exhibit signature of satellite features indicating<br />

finite correlati<strong>on</strong> am<strong>on</strong>g the c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s. The B 1s spectra appears to be sharp with<br />

unusual asymmetry, presumably due to surface c<strong>on</strong>tributi<strong>on</strong>s as found in hexaborides. In<br />

the valence band spectra, the spectral density of states reveal a dip at the Fermi level, which<br />

gradually increases with the decrease in temperature down to 10 K. The band structure results<br />

indicate dominant c<strong>on</strong>tributi<strong>on</strong> from the B 2p electr<strong>on</strong>ic states in the valence band. However,<br />

the phot<strong>on</strong> energy dependence in the experimental spectra indicate large c<strong>on</strong>tributi<strong>on</strong> from<br />

the Zr 4d states near Fermi level suggesting their important role in the superc<strong>on</strong>ductivity.<br />

SC07<br />

On the nature of an energy barrier between (π,0) and (0,π) magnetic<br />

orders in Fe pnictides<br />

Alexander Yaresko 1 *, Lilia Boeri 2 , Vladimir Antropov 3 and Ole Krogh Andersen 2<br />

1 Andersen, Max Planck Institute for Solid State Research, Germany<br />

2 Max Planck Institute for Solid State Research, Germany<br />

3 Ames Laboratory, Ames, Iowa, USA<br />

As temperature is lowered most of undoped Fe arsenides, parent compounds for<br />

recently discovered Fe based superc<strong>on</strong>ductors, undergo a transiti<strong>on</strong> into a collinear<br />

state with stripe-like magnetic order in which anti-ferromagnetic (AFM) Fe chains<br />

are ferromagnetically ordered al<strong>on</strong>g the directi<strong>on</strong> perpendicular to the chains. Two<br />

such collinear magnetic structures, characterized by ordering vectors (π,0) or (0,π),<br />

are c<strong>on</strong>nected by infinite number of n<strong>on</strong>-collinear states with two AFM sublattices<br />

of sec<strong>on</strong>d Fe neighbors rotated by an arbitrary angle with respect to each other. In a<br />

classical Heisenberg model all these states are degenerate. Band structure calculati<strong>on</strong><br />

show, however, that the degeneracy is lifted already at the mean field LSDA level and<br />

that in Fe arsenides (π,0) and (0,π) magnetic orders are separated by an energy barrier<br />

comparable to the energy difference between Neel and stripe AFM orders. We discuss<br />

a microscopic origin of the energy barrier and dem<strong>on</strong>strate that it is caused by closely<br />

related to underlying band structure. The results for Fe arsenides are compared to<br />

BaMn 2As 2 and hypothetical KFe 2Se 2 for which we found that a n<strong>on</strong>-collinear 90-degree<br />

spin arrangement is more favorable than collinear <strong>on</strong>es. A doping dependence of the<br />

barrier is also discussed.<br />

SC08<br />

Electr<strong>on</strong>ic structures and magnetic properties of LnFeAsO<br />

Chang Hyun Yi, Ju Young Kim, Jae Kyung Chang, and Joo Yull Rhee<br />

Department of Physics, Sungkyunkwan University, Suw<strong>on</strong> 440-746, Korea<br />

Recently, high transiti<strong>on</strong>-temperature superc<strong>on</strong>ductivity was discovered in the<br />

ir<strong>on</strong>pnictide RFeAsO (R=rare-earths) family of materials. Am<strong>on</strong>g them, LaFeAsO<br />

undergoes a tetrag<strong>on</strong>al-to-orthorhombic phase transiti<strong>on</strong> at ~160 K followed by an<br />

antiferromagnetic ordering at ~145 K. This material has also been reported to undergo<br />

a spin-density wave transiti<strong>on</strong> near 150 K. Through first-principles calculati<strong>on</strong>s we<br />

tried to understand the electr<strong>on</strong>ic structures and magnetic properties of LaFeAsO. We<br />

used full-potential linearized-augmented-planewave method in the antiferromagnetic<br />

ground state with orthorhombic phase. The physical origin of the SDW formati<strong>on</strong> will<br />

be discussed.


SC09<br />

Phase transiti<strong>on</strong> of a heavy fermi<strong>on</strong> superc<strong>on</strong>ductor in a high magnetic<br />

field : entanglement analysis<br />

Reza Afzali 1 * and Neda Ebrahimian 2<br />

1 Physics Department, K. N. Toosi University of Technology, Tehran 15418, Iran<br />

2 Physics Department, Amirkabir University of Technology, Tehran 15914, Iran<br />

When the magnetic field is acting <strong>on</strong> the spin of electr<strong>on</strong>s <strong>on</strong>ly, a transiti<strong>on</strong> from a normal to a<br />

modulated superc<strong>on</strong>ducting state or FFLO superc<strong>on</strong>ductor state may occur at low temperatures[1-3].<br />

A FFLO superc<strong>on</strong>ducting state, accompany with an order parameter that oscillates spatially, may be<br />

stabilized by a high applied magnetic field or a molecular field. CeCoIn 5 is a sample of heavy-fermi<strong>on</strong><br />

superc<strong>on</strong>ductor[4]. Initially experiments <strong>on</strong> CeCoIn 5 indicate that in this substance a FFLO state in a<br />

exchange field is realized. Quantum multipartite entanglement is a new procedure for investigating<br />

quantum phase transiti<strong>on</strong>[5-6], which is <strong>on</strong>e of the interesting topics in c<strong>on</strong>densed matter. In this<br />

article, we deal with to the phase transiti<strong>on</strong> of FFLO state of CeCoIn 5 to the normal state by obtaining<br />

quantum multipartite entanglement of the system. For this purpose, using normal and anomalous Green<br />

functi<strong>on</strong>s and density matrix, c<strong>on</strong>currence, as a measure of bipartite entanglement, is obtained. Then,<br />

order parameter and magnetic field dependence of multipartite entanglement in momentum space is<br />

calculated. The phase transiti<strong>on</strong> is determined and the behavior of the system based <strong>on</strong> order parameter<br />

is discussed. Furthermore, the phase transiti<strong>on</strong>s of both BCS and FFLO states to the normal state are<br />

compared.<br />

References: [1]Fulde P and Ferrell R A 1964 Phys. Rev. A 135 550 [2]Larkin A I and Ovchinnikov Y N 1965<br />

Sov. Phys. JETP 20 762 [3]Takada S and Izuyama T 1969 Prog. Theor. Phys. 41 635 [4]Radovan H A, Fortune<br />

N A, Murphy T P, Hannahs S T, Palm E C, Tozer S W and Hall D 2003 Nature 425 51 [5] Amico L, Fazio R,<br />

Osterloh A and Vedral V 2008 Rev. Mod. Phys. 80 517 [6] Brandao F G S L 2005 New J. Phys. 7 254<br />

SC10<br />

Spin and charge excitati<strong>on</strong>s in antiferromagnetic metallic phase in<br />

multi-orbital systems: A case study of chromium<br />

Koudai Sugimoto 1 , Eiji Kaneshita 2 , Kenji Tsutsui 3 and Takami Tohyama 1 *<br />

1 Yukawa Institute for Theoretical Physics, Kyoto University, Japan<br />

2 Sendai Nati<strong>on</strong>al College of Technology, Japan<br />

3 C<strong>on</strong>densed Matter Science Divisi<strong>on</strong>, JAEA, Japan<br />

Since the discovery of Fe-based superc<strong>on</strong>ductors, it has been recognized that the<br />

interplay of spin, charge, and orbital degrees of freedom is the key to understanding<br />

the physics of multiband itinerant systems. Antiferromagnetic (AF) phase seen in<br />

the parent compounds of Fe-based superc<strong>on</strong>ductors is a good example to study the<br />

multi-orbital physics in the metallic phase. The AF metallic phase similar to the<br />

parent compounds is realized in a simple chromium metal with AF order. To make<br />

a unified view in the AF metallic phase of multi-orbital systems, we study spin and<br />

charge excitati<strong>on</strong>s in AF Cr. We calculate the optical c<strong>on</strong>ductivity, neutr<strong>on</strong> scattering<br />

spectra, and Cr L-edge res<strong>on</strong>ant X-ray scattering (RIXS) spectra based <strong>on</strong> the meanfield<br />

theory for the multi-band Hubbard model and the random-phase approximati<strong>on</strong>.<br />

The calculated results of the optical c<strong>on</strong>ductivity and neutr<strong>on</strong> scattering spectra are<br />

compared with corresp<strong>on</strong>ding experimental data. The d etailed polarizati<strong>on</strong> and<br />

momentum dependence in RIXS is also discussed with predicti<strong>on</strong>s for the experiments.<br />

SC11<br />

The dirty crossover - signature of a robust superfluid in the unitary<br />

regime.<br />

IIT Guwahati<br />

IIT Guwahati, India<br />

We perform a systematic study of the BCS-BEC crossover in an ultracold fermi<strong>on</strong>ic<br />

gas in presence of a weak white noise-like random disorder which is incorporated<br />

in our mean-field treatment via Gaussian fluctuati<strong>on</strong>s. A careful investigati<strong>on</strong> of<br />

different mean field quantities as a functi<strong>on</strong> of the interparticle interacti<strong>on</strong> reveals a<br />

n<strong>on</strong>m<strong>on</strong>ot<strong>on</strong>ic behavior in the the c<strong>on</strong>densate fracti<strong>on</strong> data as disorder is included<br />

in our calculati<strong>on</strong>s. The inflexi<strong>on</strong> point is seen to occur in the unitary regime, and<br />

afterwards there is a gradual depleti<strong>on</strong> of the c<strong>on</strong>densate density in the BEC side,<br />

thereby corroborating a robust paradigm of superfluidity in the unitary regime.<br />

Motivated by this result, we study the spectral gap and the density of states in the<br />

crossover regi<strong>on</strong> and their resp<strong>on</strong>ses to the disorder. We further include a comparative<br />

discussi<strong>on</strong> <strong>on</strong> the role of the pair and phase coherence lengths in this regi<strong>on</strong> in presence<br />

of disorder to assess how these results can be relevant to the <strong>on</strong>going discussi<strong>on</strong>. Due<br />

to tremendous progress taking place in the experimental fr<strong>on</strong>t in manipulating atoms<br />

<strong>on</strong> an optical lattice in presence of (speckle) disorder, a stable superfluid scenario in the<br />

unitary limit, as proposed here, may so<strong>on</strong> be realizable.<br />

Prof. S.S. Mandal, Indian Associati<strong>on</strong> for Cultivati<strong>on</strong> of Science, Kolkata, India Prof. Y. Yanase,<br />

Niigata University, Japan<br />

SC12<br />

SC13<br />

SC14<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Spin-orbit coupling and the superc<strong>on</strong>ductivity in simple-cubic<br />

pol<strong>on</strong>ium<br />

Chang-j<strong>on</strong>g Kang, Kyoo Kim and B. I. Min*<br />

Physics, POSTECH, Korea<br />

Pol<strong>on</strong>ium is the <strong>on</strong>ly element which has the simple-cubic (SC) structure in the<br />

periodic table. We have studied its structural stability based <strong>on</strong> the ph<strong>on</strong><strong>on</strong> dispersi<strong>on</strong><br />

calculati<strong>on</strong>s using the first-principles all-electr<strong>on</strong> full-potential band method. We have<br />

dem<strong>on</strong>strated that the str<strong>on</strong>g spin-orbit coupling (SOC) in SC-Po suppresses the Peierls<br />

instability and makes the SC structure stable. Further, we have investigated the possible<br />

superc<strong>on</strong>ductivity in SC-Po, and predicted that it becomes a superc<strong>on</strong>ductor with Tc<br />

~ 4 K at ambient pressure. The transverse soft ph<strong>on</strong><strong>on</strong> mode at q ~ 2/3 R, which is<br />

greatly affected by the SOC, plays an important role both in the structural stability and<br />

the superc<strong>on</strong>ductivity in SC-Po. We have explored effects of the SOC and the volume<br />

variati<strong>on</strong> <strong>on</strong> the ph<strong>on</strong><strong>on</strong> dispersi<strong>on</strong>s and superc<strong>on</strong>ducting properties of SC-Po.<br />

Stability of FFLO states in optical lattices with layered structure<br />

Akihisa Koga* and Yasuharu Okawauchi<br />

Department of Physics, Tokyo Institute of Technology, Japan<br />

Recently, ultracold fermi<strong>on</strong>s with spin-imbalanced populati<strong>on</strong>s have attracted much<br />

interest. One of the interesting questi<strong>on</strong>s is how the Fulde-Ferrell-Larkin-Ovchinnikov<br />

(FFLO) phase, where Cooper pairs are formed with a finite total momentum, is realized<br />

in the system. In the two dimensi<strong>on</strong>al optical lattice with a c<strong>on</strong>fining potential, it has<br />

been pointed out that two kinds of FFLO states are realized[1,2]. On the other hand,<br />

such FFLO states with a three-dimensi<strong>on</strong>al structure have not been studied so well<br />

although the interlayer coupling should be important for realistic optical lattice systems.<br />

Motivated by this, we investigate the stability of the superfluid state in a layered<br />

fermi<strong>on</strong>ic optical lattice system with a c<strong>on</strong>fining potential, using the Bogoliubov de-<br />

Gennes equati<strong>on</strong>s. It is clarified that in the imbalanced case, the introducti<strong>on</strong> of the<br />

interlayer hopping stabilizes the radial FFLO state, while makes the angular FFLO<br />

state unstable. We also discuss the system size dependence of the superfluid ground<br />

state. It is clarified that in a certain ring regi<strong>on</strong> the A-FFLO state is indeed realized in a<br />

large system.<br />

[1] Y. Chen, Z. D. Wang, F. C. Zhang, and C. S. Ting, Phys. Rev. B 79, 054512 (2009) [2] Y. Yanase,<br />

Phys. Rev. B 80, 220510 (2009)<br />

Flux quantizati<strong>on</strong> and its magnetic relaxati<strong>on</strong> in a micrometer-sized<br />

superc<strong>on</strong>ducting ring of niobium<br />

Jae-hyuk Choi 1 *, He<strong>on</strong>-hwa Choi 1 , Yun-w<strong>on</strong> Kim 2 , So<strong>on</strong>-gul Lee 2 and Mahn-soo<br />

Choi 3<br />

1<br />

Divisi<strong>on</strong> of Physical Metrology, Korea Reserach Institute of Standards and Science,<br />

Korea<br />

2<br />

Dep. of Display and Semic<strong>on</strong>ductor Physics, Korea University, Korea<br />

3<br />

Dep. of Physics, Korea University, Korea<br />

We developed a high-sensitivity cantilever force magnetometry, which is capable<br />

of direct measurement of the magnetic moment of micr<strong>on</strong>-scale samples at low<br />

magnetic fields and low temperatures, and studied magnetic properties of a 100 nmthick<br />

Nb superc<strong>on</strong>ducting ring with 4 micrometer radius and 2 micrometer width. At a<br />

temperature of 3.5 K, we observed flux quantizati<strong>on</strong> of h/2e period using ac torque and<br />

dc force magnetometries with att<strong>on</strong>ewt<strong>on</strong> and sub-pic<strong>on</strong>ewt<strong>on</strong> sensitivity, respectively,<br />

determining the magnetic moment of each flux quantum. First dem<strong>on</strong>strati<strong>on</strong> of<br />

magnetic relaxati<strong>on</strong> at single flux quantum level is also presented, which provides<br />

informati<strong>on</strong> about the dynamics of thermally-activated single flux quantums depending<br />

<strong>on</strong> their number.<br />

July 8 - 13, 2012 Busan, Korea 213<br />

Poster Friday


Poster Friday<br />

SC15<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Measurement of rat biomagnetic signals by using a HTS-SQUID<br />

system<br />

In-se<strong>on</strong> Kim* and San Ahn<br />

Divisi<strong>on</strong> of C<strong>on</strong>vergence Technology, Korea Research Institute of Standards and<br />

Science, Korea<br />

We have measured biomagnetic signals in rats by using a high-TC SQUID<br />

magnetometer system employing a small magnetically shielded box. For the rat cardiac<br />

magnetic field measurements, healthy Wistar Kyoto rat and sp<strong>on</strong>taneously hypertensive<br />

rat were anesthetized and fixed <strong>on</strong> a plastic xyz-stage in supine positi<strong>on</strong> inside the<br />

magnetically shielded box. Well defined P- , QRS- and T-waves were observed <strong>on</strong><br />

the rat cardiac magnetic field measurements. We investigated circular measurements<br />

based <strong>on</strong> the hexaxial reference system, i.e., 12 measurement points were determined<br />

al<strong>on</strong>gside the circumference of a circle centered at the heart positi<strong>on</strong>. These results<br />

were quite promising for use in biomedical applicati<strong>on</strong>s of heart disease rat model<br />

study by using the high-TC SQUID magnetometer system.<br />

SC16<br />

Evoluti<strong>on</strong> of the effective mass approaching the quantum critical point<br />

in the heavy fermi<strong>on</strong> superc<strong>on</strong>ductor CePt 2In 7<br />

Jakob Kanter 1 *, Philip J. W. Moll 1 , Filip R<strong>on</strong>ning 2 , Sven Friedemann 3 , Patricia L<br />

Alireza 3 , Michael Sutherland 3 , P. Tobash 2 , J. Thomps<strong>on</strong> 2 , Eric D. Bauer 2 and Bertram<br />

Batlogg 1<br />

1 Laboratory for Solid State Physics, ETH Zurich, Switzerland<br />

2 Los Alamos Nati<strong>on</strong>al Laboratory, Los Alamos, New Mexico, USA<br />

3 Cavendish Laboratory, University of Cambridge, United Kingdom<br />

We report Shubnikov-de Haas measurements <strong>on</strong> micro-structured CePt 2In 7 single<br />

crystals under high pressures. CePt 2In 7 bel<strong>on</strong>gs to the Ce mMnIn 3m+2n heavy fermi<strong>on</strong><br />

family and orders antiferromagnetically below 5.5 K. Applying pressure induces a<br />

superc<strong>on</strong>ducting phase and suppresses the AFM order with the Neel temperature<br />

extrapolating to a quantum critical point. The magnetic fluctuati<strong>on</strong>s associated with<br />

the QCP are thought to stabilize the unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ducting phase. The<br />

evoluti<strong>on</strong> of the effective electr<strong>on</strong>ic masses approaching the quantum critical point is<br />

essential to the understanding of the electr<strong>on</strong>ic correlati<strong>on</strong> leading to unc<strong>on</strong>venti<strong>on</strong>al<br />

superc<strong>on</strong>ductivity. To this end we have developed a method to c<strong>on</strong>tact micro-structured<br />

samples inside a diam<strong>on</strong>d anvil cell allowing for complex sample shapes and several<br />

electric c<strong>on</strong>tacts.<br />

SC17<br />

Thermal stability of an epoxy-impregnated HTS racetrack coil without<br />

turn-to-turn insulati<strong>on</strong> for rotating machines<br />

Oh Jun Kw<strong>on</strong>, Kwang Lok Kim, Yo<strong>on</strong> Hyuck Choi, Hyun-jin Shin and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

MOVED<br />

214 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SC18<br />

Design, fabricati<strong>on</strong>, and testing of a cooling system using solid nitrogen<br />

for a 3 T/60-mm RT bore superc<strong>on</strong>ducting HGMS<br />

Jung-bin S<strong>on</strong>g, Kwang Lok Kim, D<strong>on</strong>g Gyu Yang, Yo<strong>on</strong> Hyuck Choi, J<strong>on</strong>gseok Lee<br />

and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

SC19<br />

Purificati<strong>on</strong> of chemical mechanical polishing wastewater using a 2G<br />

HTS high gradient magnetic separati<strong>on</strong> system<br />

D<strong>on</strong>g Gyu Yang, Jung-bin S<strong>on</strong>g, Young-gyun Kim, J<strong>on</strong>gseok Lee, Ye<strong>on</strong>joo Park and<br />

Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

SC20<br />

MOVED<br />

MOVED<br />

Effect of liquid cryogen <strong>on</strong> a 2G HTS magnet using a mixed cryogen<br />

cooling system<br />

Kwang Lok Kim, Jung-bin S<strong>on</strong>g, Yo<strong>on</strong> Hyuck Choi, D<strong>on</strong>g Gyu Yang and Haigun<br />

Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

MOVED


SC21<br />

Removal of silica and copper i<strong>on</strong>s from CMP wastewater via magnetic<br />

seeding aggregati<strong>on</strong> using superc<strong>on</strong>ducting HGMS<br />

J<strong>on</strong>gseok Lee, Jung-bin S<strong>on</strong>g, D<strong>on</strong>g Gyu Yang, Ye<strong>on</strong>joo Park and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

SC22<br />

MOVED<br />

Removal of silica and copper i<strong>on</strong>s from CMP wastewater via magnetic<br />

seeding aggregati<strong>on</strong> using superc<strong>on</strong>ducting HGMS<br />

J<strong>on</strong>gseok Lee, Jung-bin S<strong>on</strong>g, D<strong>on</strong>g Gyu Yang, Ye<strong>on</strong>joo Park and Haigun Lee*<br />

Department of Materials Science and Engineering, Korea University, Korea<br />

SC23<br />

MOVED<br />

Powder neutr<strong>on</strong> diffracti<strong>on</strong> study of HoCoGa5 Riki Kobayashi 1 *, Koji Kaneko 1 , Shuichi Wakimoto 1 , Naoyuki Sanada 2 , Ryuta<br />

Watanuki 2 , Kazuya Suzuki 2 and S<strong>on</strong>gxue Chi 3<br />

1<br />

Quantum beam science directolate, Japan atomic energy agency, Japan<br />

2<br />

Department of Advanced Materials Chemistry, Yokohama Nati<strong>on</strong>al University,<br />

Japan<br />

3<br />

Quantum beam science directolate, Oak Ridge Nati<strong>on</strong>al Laboratory, USA<br />

Ternary compound ACoGa 5(A=rare earth or actinide) attracts a much attenti<strong>on</strong> due to high<br />

temperature superc<strong>on</strong>ductivity in PuCoGa 5 and related compounds. In additi<strong>on</strong>, recent<br />

study <strong>on</strong> TbCoGa 5 reveals another interesting aspects of this system ; successive transiti<strong>on</strong>s<br />

in TbCoGa 5 could be “comp<strong>on</strong>ents-separated orders” which may arise from a novel type<br />

of frustrati<strong>on</strong> between multipole. HoCoGa5 also exhibits successive transiti<strong>on</strong>s at TN1 = 9.6<br />

K and TN2 = 7.5 K. In order to investigate nature of these transiti<strong>on</strong>s in HoCoGa 5, neutr<strong>on</strong><br />

powder diffracti<strong>on</strong> experiment were carried out. Appearance of superlattice refracti<strong>on</strong>s<br />

was clearly observed below TN1. In additi<strong>on</strong>, we observed that both peak positi<strong>on</strong> and<br />

intensity of superlattice peaks abruptly change at TN2 <strong>on</strong> cooling. The observed peak in<br />

the phase I(T < TN2) and II(TN2 < T < TN1) can be described with q1=(1/2 0 1/2) and<br />

q2=(1/2 0 τ) with τ=0.35, respectively. The determined propagati<strong>on</strong> vector of the phase<br />

I is the same as that of TbCoGa5, whereas that of phase II is altered. Detailed magnetic<br />

structure analysis for both phases are in progress.<br />

[1] J. L. Sarrao et al., Nature 420, 297 (2002). [2] F. H<strong>on</strong>da et al., Physica B 359, 1147 (2005). [3] N.<br />

Sanada et al., J. Phys. Soc. Jpn. 78, 073709 (2009).<br />

SC24<br />

SC25<br />

SC26<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Evidence of two-band gap superc<strong>on</strong>ductivity in LaRu 2P 2<br />

Tetsuya Fujiwara 1 *, Harunobu Sagawa 1 , Kazuyuki Matsubayashi 2 , Yoshiya Uwatoko2<br />

and Toru Shigeoka 1<br />

1 Graduate School of Science and Engineering, Yamaguchi University, Japan<br />

2 Institute for Solid State Physics, University of Tokyo, Japan<br />

We investigate the electr<strong>on</strong>ic transport properties and the superc<strong>on</strong>ducting gap characteristics<br />

of LaRu 2P 2. Superc<strong>on</strong>ducting transiti<strong>on</strong> was recognized at Tc = 4.4 K in LaRu 2P 2 single<br />

crystal as reported in ref [1]. Values of upper critical field Hc 2 estimated from the electrical<br />

resistivity under magnetic field are isotropic in this system. These are good accordance with<br />

the results by Ying et al.[2]. However, they, although, claimed that LaRu 2P 2 is a c<strong>on</strong>venti<strong>on</strong>al<br />

superc<strong>on</strong>ductor, so called BCS type, it was revealed that LaRu 2P 2 single crystal obtained in<br />

this work shows a remarkably larger Hc 2 than that expected from GL theory at c<strong>on</strong>siderably<br />

low temperature. In additi<strong>on</strong>, we observed two clear disc<strong>on</strong>tinuities of specific heat at Tc 1<br />

= 4.4 K and Tc 2 = 4.0 K, respectively, in specific heat as a functi<strong>on</strong> of temperature. Each<br />

transiti<strong>on</strong> temperature vary obeying Hc 2(t)=Hc 2(0)(1-t2)/(1+t2), here, t = T/Tc, indicating<br />

that both disc<strong>on</strong>tinuities at Tc 1 and Tc 2 are attributed to superc<strong>on</strong>ducting transiti<strong>on</strong>s. So, we<br />

tried to analyze thermodynamic properties of LaRu 2P 2 by a two-band gap model [3]. In<br />

c<strong>on</strong>sequence, the numerically calculated C(T) curve was well reproduced experimentally<br />

measured specific heat as a functi<strong>on</strong> of temperature when Δ 1/kTc 1 and Δ 2/kTc 2 were<br />

assumed to be 1.5 and 3.0, respectively.<br />

[1] T. Fujiwara et al., J. Phys.: C<strong>on</strong>f. Ser. 273, 012112 (2011). [2] J. Ying et al., Superc<strong>on</strong>d. Sci.<br />

Technol. 23, 115009 (2010). [3] H. Padamsee et al., J. Low. Temp. Phys. 12, 387 (1973).<br />

Proximity effect for asymmetrical three layered F/S structures in<br />

external magnetic field<br />

Maxim V. Avdeev, Sergey L. Tsarevskii and Yurii N. Proshin*<br />

Theoretical Physics Department, Kazan Federal University, Russia<br />

We study the critical temperature Tc of the three-layered ferromagnet/superc<strong>on</strong>ductor<br />

(F/S) structures at the external magnetic field H parallel to the film. For the F 1/S/F 2<br />

and F 1/F 2/S asymmetrical trilayers the triplet superc<strong>on</strong>ducting comp<strong>on</strong>ent is generated<br />

at n<strong>on</strong>collinear magnetizati<strong>on</strong>s of the F layers. Assuming that all S and F layers are<br />

dirty we solve boundary problem for the Usadel functi<strong>on</strong>. The results of numerical<br />

calculati<strong>on</strong>s for Tc as functi<strong>on</strong> thicknesses both F 1 and F 2 layers at various parameters<br />

F/S structure are resented. The applicati<strong>on</strong> to the spin-switch problem is discussed. We<br />

found that asymmetry can essentially change the spin-switch observati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>.<br />

Influence of proximity effect with Umklapp processes <strong>on</strong> the Josephs<strong>on</strong><br />

current in the SFS nanostructure<br />

Vadim Tumanov and Yurii N. Proshin*<br />

Theoretical Physics Department, Kazan Federal University, Russia<br />

We c<strong>on</strong>sider the Josephs<strong>on</strong> effect in symmetric superc<strong>on</strong>ductor-ferromagneticsuperc<strong>on</strong>ductor<br />

(SFS) system. The Josephs<strong>on</strong> current is calculated as a functi<strong>on</strong> of the<br />

ferromagnetic layer thickness d. The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairs<br />

in the F layer have a n<strong>on</strong>zero wave vector, and the transformati<strong>on</strong> the BCS pairs to the<br />

FFLO pairs (and vice versa) at passing through SF (FS) borders may be proceeded<br />

through the Umklapp processes [1]. To estimate the influence of proximity effect<br />

we use the expansi<strong>on</strong> of superc<strong>on</strong>ductor energy in the powers of an order parameter<br />

(near the critical temperature Tc). We take into account the dependence of the critical<br />

temperature Tc from the phase difference φ between the order parameter in the left and<br />

right S side of the SFS c<strong>on</strong>tact. Our results are compared with known data for the Nb/<br />

CuNi/Nb nanostructures [2] where the critical Josephs<strong>on</strong> current oscillati<strong>on</strong>s due to<br />

transiti<strong>on</strong>s between 0 and π phase state were observed. A good agreement is obtained<br />

by taking into account the Umklapp processes.<br />

1. Yu. A. Izyumov, Yu. N. Proshin, and M. G. Khusainov, Physics/Uspekhi 45, 109 (2002) 2. V.V.<br />

Ryazanov et al., Rev. Low Temp. Phys. 136, 385 (2004)<br />

July 8 - 13, 2012 Busan, Korea 215<br />

Poster Friday


Poster Friday<br />

SC27<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Superc<strong>on</strong>ducting characters under pressure in heavy fermi<strong>on</strong><br />

compounds CeIr(In 1-xCd x) 5 studied by In-NQR<br />

Mitsuharu Yashima<br />

Engineering Science, Osaka University, Japan<br />

The heavy fermi<strong>on</strong> compounds CeMIn 5 (M = Co, Rh, Ir) have provided to study the<br />

relati<strong>on</strong>ship between antiferromagnetism and superc<strong>on</strong>ductivity. CeCoIn 5 becomes<br />

superc<strong>on</strong>ducting with $T_c$ = 2.3 K at ambient pressure1. This value is the highest<br />

record in the Ce-based heavy fermi<strong>on</strong> superc<strong>on</strong>ductors. Since the existence of<br />

antiferromagnetic spin fluctuati<strong>on</strong>s is c<strong>on</strong>firmed, it is expected that superc<strong>on</strong>ductivity<br />

is induced by antiferromagnetic spin fluctuati<strong>on</strong>s in CeCoIn 5. CeRhIn 5 is an<br />

antiferromagnet with $T_N$ = 3.8 K at ambient pressure. Taking into account the<br />

lattice parameters of CeIrIn 5, it is speculated that an antiferromagnetic order is realized<br />

at ambient pressure, but it actually shows superc<strong>on</strong>ductivity with $T_c$ = 0.4 K.<br />

The value of $T_c$ is very low, as compared with the other CeMIn 5 compounds.<br />

$T_c$ increases with increasing pressure and reaches about 1 K around 3 GPa, but<br />

antiferromagnetic spin fluctuati<strong>on</strong>s are greatly suppressed with the applicati<strong>on</strong> of<br />

pressure. These results suggest that the superc<strong>on</strong>ducting mechanism of CeIrIn 5 may be<br />

quite different from that of the other CeMIn 5 compounds. In order to investigate the<br />

unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ducting characteristics in CeIrIn 5, the nuclear-quadrupoleres<strong>on</strong>ance<br />

(NQR) measurements were performed under pressure in pure and Cd-doped<br />

CeIrIn 5.<br />

SD01<br />

Giant and twofold oscillati<strong>on</strong>s of magnetoresistance in topological<br />

insulators Sb 2Te 3 and Bi 2Te 3 single crystals<br />

Zengji Yue, Xiaolin Wang* and Shixue Dou<br />

Spintr<strong>on</strong>ic and Electr<strong>on</strong>ic Materials Group, Institute for Superc<strong>on</strong>ducting &<br />

Electr<strong>on</strong>ic Materials, University of Woll<strong>on</strong>g<strong>on</strong>g NSW 2522,, Australia<br />

Topological insulators are quantum materials with an insulating bulk state and a topologically protected<br />

two dimensi<strong>on</strong>al metallic surface states.1,2 Unique electr<strong>on</strong>ic properties, such as the quantum spin Hall<br />

effect, magnetoelectric effects, magnetic m<strong>on</strong>opoles, and elusive Majorana states, are expected from<br />

topological insulators.3,4 Topological insulators have great potential applicati<strong>on</strong>s in spintr<strong>on</strong>ics and quantum<br />

informati<strong>on</strong> processing, as well as magnetoelectric devices with higher energy efficiency.5,6 To understand<br />

the macroscopic properties of the topological surface states and to investigate the possibility of their device<br />

applicati<strong>on</strong>s, transport and magnetic measurements of high-quality single crystals are indispensable.<br />

Anisotropic magneto-transport properties were studied in p-type Sb 2Te 3 and n-type Bi 2Te 3 topological<br />

insulators through angular dependent magnetoresistance (MR) measurements. Giant MR of up to 230% was<br />

observed, which exhibits linear at high fields without any trend towards saturati<strong>on</strong>. The giant MR displays<br />

a str<strong>on</strong>g anisotropy, up to 210%, and twofold symmetry at different temperatures and fields. The giant MR<br />

might be due to intravalley and intervalley scattering, and the str<strong>on</strong>g anisotropy might result from anisotropies<br />

of Fermi surface. The observed giant anisotropic MR of the Sb 2Te 3 and Bi 2Te 3 topological insulators could<br />

find applicati<strong>on</strong>s in magneto-electr<strong>on</strong>ic devices based <strong>on</strong> topological insulators, such as magnetic sensors.<br />

1. M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 4 (2010). 2. X. L. Qi and S. C. Zhang, Rev. Mod.<br />

Phys. 83, 1057 (2011). 3. B. A. Bernevig, T. L. Hughes, and S. C. Zhang, Science 314, 1757 (2006). 4. D.<br />

Hsieh, D. Qian, L. Wray, Y. Xia, Y. S. Hor, R. J. Cava, and M. Z. Hasan, Nature 452, 970 (2008). 5. J. E.<br />

Moore, Nature 464, 194 (2010) 6. X. L. Wang, S. X. Dou, and C. Zhang, NPG Asia Mater. 2, 31 (2010).<br />

SD02<br />

Engineering and manipulating topological qubits in 1D quantum wires<br />

Panagiotis Kotetes 1 , Alexander Shnirman 2 and Gerd Sch<strong>on</strong> 1<br />

1<br />

Institut fur Theoretische Festkorperphysik, Karlsruhe Institute of Technology,<br />

Germany<br />

2<br />

Institut fur Theorie der K<strong>on</strong>densierten Materie, Karlsruhe Institute of Technology,<br />

Germany<br />

UPGRADED<br />

216 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SD03<br />

Angle dependence of the Landau level spectrum in twisted bilayer<br />

graphene<br />

Min-young Choi, Young-hwan Hyun and Yo<strong>on</strong>bai Kim*<br />

Department of Physics, Sungkyunkwan University, Korea<br />

In the c<strong>on</strong>text of the low-energy effective theory, the exact Landau level spectrum<br />

of quasiparticles in twisted bilayer graphene with small twist angle is analytically<br />

obtained by spheroidal eigenvalues. We analyze the dependence of the Landau levels<br />

<strong>on</strong> the twist angle to find the points where the twofold degeneracy for twist angles<br />

is lifted in the n<strong>on</strong>zero modes and below (above) which massive (massless) fermi<strong>on</strong><br />

pictures become valid. In the perpendicular magnetic field of 10 tesla, the degeneracy<br />

is removed at approximately 3 degrees for a few low levels, specifically approximately<br />

2.56 degrees for the first pair of n<strong>on</strong>zero levels and approximately 3.50 degrees for<br />

the next pair. Massive quasiparticle appears at the angle less than 1.17 degrees in 10<br />

tesla, which matches perfectly with the recent experimental results. Since our analysis<br />

is applicable to the cases of arbitrary c<strong>on</strong>stant magnetic fields, we make predicti<strong>on</strong>s<br />

for the same experiment performed in arbitrary c<strong>on</strong>stant magnetic fields. For example,<br />

for 40 tesla we get the critical angle of 2.34 degrees and the sequence of angles<br />

5.11,7.01,8.42,... for the pairs of n<strong>on</strong>zero energy levels. The symmetry restorati<strong>on</strong><br />

mechanism behind the massive (massless) transiti<strong>on</strong> is c<strong>on</strong>jectured to be a tunneling<br />

(instant<strong>on</strong>) in momentum space.<br />

SD04<br />

Surface band structure study of Bismuth-based ternary topological<br />

insulators<br />

Madhab Neupane 1 , S.-y. Xu 1 , C. Liu 1 , L. A. Wray 2 , N. Alidoust 1 , A. Fedorov 3 , Y. S.<br />

Hor 4 , T.-r Chang 5 , H.-t. Jeng 6 , H. Lin 7 , B. Bansil 7 , R. J. Cava 4 and M. Z. Hasan 1<br />

1<br />

Physics, Princet<strong>on</strong> University, USA<br />

2<br />

Physics, Princet<strong>on</strong> University & ALS, Berkeley, USA<br />

3<br />

Physics, ALS, Berkeley, USA<br />

4<br />

Chemistry, Princet<strong>on</strong> University, USA<br />

5<br />

Physics, Nati<strong>on</strong>al Tsing Hua University,, China<br />

6<br />

Physics, Nati<strong>on</strong>al Tsing Hua University & Institute of Physics, Academia Sinica,,<br />

China<br />

7 Physics, Northeastern University, USA<br />

Utilizati<strong>on</strong> of topological surface states is expected to lead to new vistas in electr<strong>on</strong>ics<br />

and fundamental physics. However, most of the known topological insulators either do<br />

not feature necessary band structure c<strong>on</strong>diti<strong>on</strong>s (locati<strong>on</strong> of Dirac point with respect to<br />

the bulk band) or lack topological invariants essential for certain class of applicati<strong>on</strong>s.<br />

Using angle-resolved photoemissi<strong>on</strong> spectroscopy (ARPES), we reveal the electr<strong>on</strong>ic<br />

band structure topology of a family of ternary spin-orbit insulators some of which<br />

feature functi<strong>on</strong>al electr<strong>on</strong>ic structure with in-gap Dirac point while others feature<br />

novel topological invariants (weak Z 2 invariants) in crystalline form. These Bi-based<br />

ternary topological insulators provide a natural access to lattice matched magnetically<br />

ordered states to be utilized in future devices.<br />

SD05<br />

Topological aspects and transport properties of edge states in the<br />

multi-band superc<strong>on</strong>ductor Sr2RuO4 Yoshiki Imai 1 *, Katsunori Wakabayashi 2 and Manfred Sigrist 3<br />

1<br />

Department of Physics, Saitama University, Japan<br />

2<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Center for Materials Nanoarchitect<strong>on</strong>ics, Nati<strong>on</strong>al Institute for<br />

Materials Science, Japan<br />

3<br />

Theoretische Physik, Eidgenossische Technische Hochschule Zurich, Switzerland<br />

Motivated by the spin-triplet chiral p-wave superc<strong>on</strong>ductor Sr 2RuO 4, we investigate<br />

the edge state of multi-band superc<strong>on</strong>ductor by means of the three band tight-binding<br />

model including inter-orbital hybridizati<strong>on</strong> and spin-orbit coupling effects. These bands<br />

corresp<strong>on</strong>d to the alpha, beta and gamma bands of Sr 2RuO 4 where alpha and beta bands<br />

have hole- and electr<strong>on</strong>-like characters, respectively. In particular we focus <strong>on</strong> the<br />

topological aspects and transport properties in the chiral spin-triplet phase. Although<br />

a full quasiparticle excitati<strong>on</strong> gap in the bulk system, gapless edge states appear and<br />

affect both sp<strong>on</strong>taneous spin and charge currents which give rise to anomalous and<br />

spin Hall effect. In this c<strong>on</strong>text, we study the interplay between electr<strong>on</strong>- and hole-like<br />

particles and the effect of the genuinely two-dimensi<strong>on</strong>al gamma band in the formati<strong>on</strong><br />

of these edge states and edge currents. The topological aspects and correlati<strong>on</strong> effects<br />

<strong>on</strong> this system are also discussed.


SD06<br />

Influence of geometry <strong>on</strong> the edge states of Bi Nanoribb<strong>on</strong>s<br />

Hyun-jung Kim 1 , Gustav Bihlmayer 2 , Stefan Bluegel 2 and Jun-hyung Cho 1 *<br />

1<br />

Department of Physics and Research Institute for Natural Sciences, Hanyang<br />

University, Korea<br />

2<br />

Peter Gruenberg Institut and Institute for Advanced Simulati<strong>on</strong>, Forschungszentrum<br />

Juelich and JARA, Germany<br />

Two-dimensi<strong>on</strong>al (2D) topological insulators or 2D quantum spin Hall (QSH) systems<br />

provide an intriguing physical phenomena in c<strong>on</strong>densed matter physics. The 2D QSH<br />

phase is a band insulator but has gapless edge states. The salient feature of these edge<br />

states is that they are topologically protected. Here, using first-principles densityfuncti<strong>on</strong>al<br />

calculati<strong>on</strong>s, we investigate the effect of geometry <strong>on</strong> the edge states in zigzag<br />

Bi nanoribb<strong>on</strong> (ZBNR) reported as a 2D QSH system.[1] We c<strong>on</strong>sider various edge<br />

geometries involving the ideal terminati<strong>on</strong>, relaxati<strong>on</strong>, and reb<strong>on</strong>ded rec<strong>on</strong>structi<strong>on</strong>. We<br />

find that the reb<strong>on</strong>ded rec<strong>on</strong>structi<strong>on</strong> geometry is thermodynamically more stable than<br />

other geometries. Since the transiti<strong>on</strong> from the rec<strong>on</strong>structi<strong>on</strong> to the relaxati<strong>on</strong> geometry<br />

is kinetically feasible, the edge structure of ZBNR is expected to exhibit the orderdisorder<br />

transiti<strong>on</strong> as a functi<strong>on</strong> of temperature. We also find that the metallic feature<br />

of edge states is preserved with respect to the shear distorti<strong>on</strong> and b<strong>on</strong>d alternati<strong>on</strong>,<br />

but it is dramatically altered to produce a band-gap opening through the reb<strong>on</strong>ded<br />

rec<strong>on</strong>structi<strong>on</strong>. We discuss such an influence of geometry <strong>on</strong> the edge states of ZBNR in<br />

terms of the penetrati<strong>on</strong> depth of the edge states.<br />

[1] M. Wada, S. Murakami, F. Freimuth, and G. Bihlmayer, Phys. Rev. B 83, 121310(R) (2011).<br />

SD07<br />

Magnetotransport measurements in pulsed magnetic fields: a case for<br />

Fermiology studies in superc<strong>on</strong>ductors and topological insulators<br />

Frederik Wolff-fabris 1 *, Jun Sung Kim 2 , Erik Kampert 1 , Jo<strong>on</strong>bum Park 2 , Man Jim<br />

Eom 2 , Sergei Zherlitsyn 1 , Thomas Herrmannsdoerfer 1 and Jochen Wosnitza 1<br />

1 Dresden High Magnetic Field Laboratory (HLD), HZDR, Germany<br />

2 Department of Physic, Pohang University of Science and Technology, Korea<br />

Superc<strong>on</strong>ductors and Dirac materials, such as graphene and topological insulators, are intensively<br />

studied in high magnetic fields. In this work, we present the current status of magnetotransport<br />

measurements at the Dresden High Magnetic Field Laboratory (HLD) and discuss examples of<br />

phase-diagram and fermiology investigati<strong>on</strong>s in different compounds [1,2], as well as the new<br />

Dirac material [3] SrMnBi 2. Typical experiments in magnetic fields up to 85 T with 25 to 150 ms<br />

pulse durati<strong>on</strong> in samples spaces up to 16 mm are performed by discharging a 50 MJ capacitor<br />

bank. We use standard four-probe-technique measurements with AC currents up to 200 kHz and<br />

the l<strong>on</strong>gitudinal and transverse (Hall effect) voltages signals from the samples are digitized with a<br />

fast recording system. We observed quantum oscillati<strong>on</strong>s in magnetotransport measurements up<br />

to 63 T <strong>on</strong> crystals of SrMnBi 2 and, together with other techniques, this dem<strong>on</strong>strates that there<br />

is a Dirac dispersi<strong>on</strong> in the electr<strong>on</strong>ic structure of the double-sized Bi square net. However, in<br />

c<strong>on</strong>trast to graphene, the Dirac c<strong>on</strong>e in SrMnBi2 is highly anisotropic which suggests that the Bi<br />

square net can provide a new platform for highly anisotropic Dirac fermi<strong>on</strong>s. Aknowledgements<br />

Work at the HLD was supported by EuroMagNET II (No. 228043).<br />

[1] V. A. Gaparov, F. Wolff-Fabris, D. L. Sun et al. JETP 93, v.1, p. 29 (2010); [2] M. V. Kartsovnik, T. Helm, K. Putzke et al.<br />

New Journal of Physics 13, 015001 (2011); [3] J. Park, G. Lee, F. Wolff-Fabris et al. Physical Review Letters 107, 126402 (2011).<br />

SD08<br />

First-principles study of spin texture in the multilayer graphene <strong>on</strong><br />

Ni(111)<br />

Fumiyuki Ishii 1 *, Hiroki Kotaka 2 , Keisuke Sawada 3 and Mineo Saito 1<br />

1 Faculty of Mathematics and Physics, Kanazawa University, Japan<br />

2 Graduate School of Natural Science and Technology, Kanazawa University, Japan<br />

3 Graduate School of Natural Science and Technology,, Kanazawa University, Japan<br />

MOVED<br />

SD09<br />

SD10<br />

Magnetic properties of rare earth doped Bi 2Te 3<br />

Nahyun Jo, Youngha Choi, Kyujo<strong>on</strong> Lee and Myung-hwa Jung*<br />

Physics, Sogang University, Korea<br />

SD11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

A full quantum study <strong>on</strong> gapless modes and Axi<strong>on</strong> electrodynamics in<br />

topological insulator heterostructure systems<br />

Ken Shiozaki 1 *, Takahiro Fukui 2 and Satoshi Fujimoto 1<br />

1 Depertment of Physics, Kyoto University, Japan<br />

2 Depertment of Physics, Ibaraki University, Japan<br />

Three dimensi<strong>on</strong>al topological insulator heterostructure systems show the various novel phenomena<br />

such as gapless modes localized at defects or the Axi<strong>on</strong> resp<strong>on</strong>se in three dimensi<strong>on</strong>al topological<br />

insulator-magnetic insulator heterostructures. The origin of these phenomena is the n<strong>on</strong>trivial<br />

topology in both momentum and real spaces. Dealing with the spatial coordinates as the adiabatic<br />

parameter in the heterostructure systems, <strong>on</strong>e can introduce the semiclassical Hamilt<strong>on</strong>ian, which<br />

describes topological properties of the heterostructure system. On the other hand, in some cases,<br />

it also happens that semiclassical approaches fail to describe correctly topological features. In this<br />

study, we present full quantum treatment for three dimensi<strong>on</strong>al topological insulator heterostructure<br />

systems without the semiclassical approximati<strong>on</strong>. We, first, prove the index theorem for gapless<br />

modes in line defects of the topological insulator-magnetic insulator heterostructure systems.<br />

Sec<strong>on</strong>dly, we dem<strong>on</strong>strate a full quantum calculati<strong>on</strong> for the surface quantum anomalous Hall<br />

effect at the interface of the topological insulator-magnetic insulator heterostructure without using<br />

the Axi<strong>on</strong> effective acti<strong>on</strong>. We also show that gapless modes in line defects and the Axi<strong>on</strong> resp<strong>on</strong>se<br />

may be governed not <strong>on</strong>ly by helical Dirac fermi<strong>on</strong>s <strong>on</strong> the surfaces, but also by gapped bound<br />

states at the interface, the c<strong>on</strong>tributi<strong>on</strong> of which was missed in previous studies.<br />

Xiao-Liang Qi, Taylor L. Hughes, and Shou-Cheng Zhang, Phys. Rev. B 78, 195424 (2008). Jeffrey C.<br />

Y. Teo and C. L. Kane, Phys. Rev. B 82, 115120 (2010).<br />

Bi 2Te 3 is <strong>on</strong>e of 3-dimensi<strong>on</strong>al topological insulators together with Bi 2Se 3 and Bi 2Sb 3.<br />

[1] Recently, Binghai Yan et. al have theoretically reported that LaBiTe 3 is a str<strong>on</strong>g<br />

topological insulator. [2] We could c<strong>on</strong>jecture that rare-earth materials have fascinating<br />

magnetic properties, since it has filled outer shell ( 5s25p6 ) and simulataneously<br />

unfiled inner shell (4f n). [3] Therefore, we made both LaxBi 2-XTe 3 and CexBi 2-XTe 3,<br />

and measured transport and magnetic properties. LaxBi 2-XTe 3 is diamagnetic, while<br />

CexBi 2-XTe 3 is paramagnetic at low temperature. From the modified curie-wiess fit,<br />

we could obtain the effective magnetic moment of 2.56μB. This value dem<strong>on</strong>strates<br />

that the Ce i<strong>on</strong> is in trivalent state. However, the carrier density of CexBi 2-XTe 3 is<br />

observed to be <strong>on</strong> order smaller than that of Bi 2Te 3, giving rise to a str<strong>on</strong>g increase<br />

of carrier mobility. These results support a scenario of str<strong>on</strong>g topological insulator.<br />

Furthermore, a magnetoresistance ratio of CexBi 2-XTe 3 is 1600% at 70kOe, even<br />

though ferromagnetic FexBi 2-XTe 3 have 600% magnetoresistance ratio at 70kOe.<br />

[1] Y.L. Chen et. al., SCIENCE, 325, 178 (2005) . [2] Binghai et. al. PRB, 82, 161108(R) (2010). [3]<br />

Charles Kittel, Introducti<strong>on</strong> to Solid State Physic (John Wiley & S<strong>on</strong>s, Inc, New Jersey, 2005 ) .<br />

Ir<strong>on</strong> doping effect in topological insulator: Bi 2Te 3<br />

Nahyun Jo 1 , Youngha Choi 1 , Kyujo<strong>on</strong> Lee 1 , Jungw<strong>on</strong> Jang 2 , Jinhee Kim 2 , Akio<br />

Kimura 3 and Myung-hwa Jung 1 *<br />

1 Physics, Sogang University, Korea<br />

2 Korea Research of Standards and Science, Korea<br />

3 Physics, Hiroshima University, Japan<br />

Bi 2Te 3 is well-known topological insulator with anti-site defects which complicates<br />

the manipulati<strong>on</strong> of the Fermi level. It has also been reported that surface band of<br />

topological insulators is open when magnetic i<strong>on</strong>s are doped, because magnetic i<strong>on</strong>s<br />

are able to break the time reversal symmetry. In this report, we doped magnetic i<strong>on</strong>s<br />

of Fe into Bi 2Te 3 and studied the properties and the corresp<strong>on</strong>ding electr<strong>on</strong>ic structure.<br />

We found that a small amount of Fe i<strong>on</strong>s less than 0.4% do not open the surface gap,<br />

but reduce the anti-site defects. Thus, Fe-doped Bi 2Te 3 has linear magnetoresistance<br />

with high mobility (15,074cm2v-1s-1) which is three times higher than Bi 2Te 3 while<br />

Bi 2Te 3 has a deviati<strong>on</strong> from the linear dependence of magnetoresistance. The reducti<strong>on</strong><br />

of anti-site defects enhances the sample quality, so that we could observe quantum<br />

oscillati<strong>on</strong>s such as Shubnikov de Haas and de Haas van Alphen effect. In additi<strong>on</strong>,<br />

the spin-dependent ARPES data also dem<strong>on</strong>strate both clear surface state without gap<br />

opening and canted spin comp<strong>on</strong>ents in the c axis.<br />

July 8 - 13, 2012 Busan, Korea 217<br />

Poster Friday


Poster Friday<br />

SD12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magneto transport properties of topological insulator nanoribb<strong>on</strong>s of<br />

Bi2Te3 H<strong>on</strong>g-seok Kim 1 , Hosun Shin 2 , Eun-kyoung Je<strong>on</strong> 3 , Kung-w<strong>on</strong> Rhie 1 , Ju-jin Kim 4 ,<br />

Je<strong>on</strong>g-o Lee 3 , Jaey<strong>on</strong>g S<strong>on</strong>g 2 and Y<strong>on</strong>g-joo Doh 1 *<br />

1<br />

Dept. of Display and Semic<strong>on</strong>ductor Physics, Korea University Sej<strong>on</strong>g Campus,<br />

Korea<br />

2<br />

Korea Research Institute of Standards and Science, Korea<br />

3<br />

Korea Research Institute of Chemical Technology, Korea<br />

4<br />

Dept. of Physics, Ch<strong>on</strong>buk Nati<strong>on</strong>al University, Korea<br />

We report <strong>on</strong> the magneto transport properties of topological insulator nanoribb<strong>on</strong>s<br />

of Bi 2Te 3. The Bi 2Te 3 nanoribb<strong>on</strong>s were grown using the electrodepositi<strong>on</strong> processes<br />

and c<strong>on</strong>tacted with 100-nm-thick cobalt electrodes. At low temperature below T =<br />

10 K, the magnetoreistance increases with a magnetic field, B, which is attributed<br />

to a weak antilocalizati<strong>on</strong> effect. When the magnetic field (B) is applied parallel<br />

to the ferromagnetic electrodes <strong>on</strong> top of the nanoribb<strong>on</strong>, a switching behavior of<br />

the magnetoresistance is observed near B = 400 Oe. Temperature and gate voltage<br />

dependences of the spin valve effect is discussed as well.<br />

SD13<br />

Structural investigati<strong>on</strong>s of the topological insulators Bi 2Se 3-xTex<br />

Geetha Balakrishnan 1 *, Ravi Singh 1 , Devashibhai Adroja 2 , Kevin Knight 2 and<br />

Matthias Gutmann 2<br />

1 Department of Physics, University of Warwick, United Kingdom<br />

2 ISIS Facility, Rutherford Applet<strong>on</strong> Laboratory, United Kingdom<br />

The binary phases Bi 2Se 3 and Bi 2Te 3 have been discovered to exhibit three dimensi<strong>on</strong>al<br />

topological insulating behaviour. However, these compounds are not insulators when<br />

investigated in the bulk. Bi 2Se 3 is generally known to exhibit n-type c<strong>on</strong>ductivity<br />

and Bi 2Te 3 exhibits n or p-type c<strong>on</strong>ductivity depending <strong>on</strong> the synthesis c<strong>on</strong>diti<strong>on</strong>s.<br />

The bulk c<strong>on</strong>ductivity exhibited by these materials are seen as being detrimental<br />

to the investigati<strong>on</strong> of their surface c<strong>on</strong>ducting properties. We have examined the<br />

intermediate compositi<strong>on</strong>s Bi 2Se 3-xTex in order to study the role played by vacancies<br />

and anti-site defects in determining the bulk c<strong>on</strong>ducti<strong>on</strong> mechanisms. We report<br />

detailed structural refinements obtained by neutr<strong>on</strong> diffracti<strong>on</strong> experiments <strong>on</strong> several<br />

of the intermediary phases and draw correlati<strong>on</strong>s between the defect structures and<br />

their c<strong>on</strong>ducting / semic<strong>on</strong>ducting / insulating behaviour.<br />

SD14<br />

Josephs<strong>on</strong> effects in Bi 2Se 3 topological insulator nanoribb<strong>on</strong>s<br />

Hyunho Noh 1 , Lee-seul Park 2 , Eun-kyoung Je<strong>on</strong> 3 , H<strong>on</strong>g-seok Kim 4 , Je<strong>on</strong>g-o Lee 3 , Jin<br />

Seok Lee 2 , Jinhee Kim 1 and Y<strong>on</strong>g-joo Doh 4 *<br />

1 Korea Research Institute of Standards and Science, Korea<br />

2 Dept. of Chemistry, Sookmyung Women’s University, Korea<br />

3 Korea Research Institute of Chemical Technology, Korea<br />

4 Dept. of Display and Semic<strong>on</strong>ductor Physics, Korea University Sej<strong>on</strong>g Campus,<br />

Korea<br />

Topological insulators are exotic materials with bulk band gap and metallic edge<br />

states which are protected <strong>on</strong> their own boundary topologically. Here, we report <strong>on</strong><br />

the fabricati<strong>on</strong> and measurement results of the superc<strong>on</strong>ducting proximity juncti<strong>on</strong>s<br />

of topological insulator nanoribb<strong>on</strong>s of Bi 2Se 3. Single-crystalline Bi 2Se 3 nanoribb<strong>on</strong>s<br />

are synthesized using the vapor-liquid-solid method, while the superc<strong>on</strong>ducting Al<br />

electrodes are formed <strong>on</strong> top of the nanowire. When a magnetic field (H) is applied<br />

al<strong>on</strong>g the axial directi<strong>on</strong>, the magneto-resistance data exhibit quasi-periodic oscillati<strong>on</strong>s<br />

with an average periodicity of H* ~ 0.4 T, which is c<strong>on</strong>sistent with the Ahar<strong>on</strong>ov-<br />

Bohm oscillati<strong>on</strong>s. In the superc<strong>on</strong>ducting state, the supercurrent branch with a critical<br />

current of Ic ~ 90 nA is clearly observed in the current-voltage curve as a result of the<br />

superc<strong>on</strong>ducting proximity effect in Bi 2Se 3 nanoribb<strong>on</strong>. Quantized voltage steps of the<br />

Bi 2Se 3 nanoribb<strong>on</strong> Josephs<strong>on</strong> juncti<strong>on</strong> under the microwave irradiati<strong>on</strong> satisfy the ac<br />

Josephs<strong>on</strong> relati<strong>on</strong>.<br />

218 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SD15<br />

Electr<strong>on</strong>ic structure and transport properties of pt based heusler<br />

compounds with C1b structure for topological quantum phenomena<br />

Siham Ouardi 1 , Gerhard H. Fecher 1 , Shekhar Chandra 2 , Gloskovskii Andrei 3 and<br />

Felser Claudia 1<br />

1<br />

Johannes Gutenberg University and Max Planck Institute for Chemical Physics of<br />

Solids, Dresden, Germany<br />

2<br />

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany<br />

3<br />

Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University,<br />

Mainz, Germany<br />

Many of the Heusler compounds based <strong>on</strong> heavy elements with 1:1:1 compositi<strong>on</strong> and C1b structure are zero<br />

band gap insulators and exhibit partially an inverted band structure [1]. Based <strong>on</strong> a topologically protected<br />

electr<strong>on</strong>ic surface states, this class of materials is supposed to open up innovative directi<strong>on</strong>s for future<br />

technological applicati<strong>on</strong>s in spintr<strong>on</strong>ics, quantum computing and thermoelectrics. The density of states of Pt<br />

based Heusler compounds PtMZ (M = Y, Gd, Lu and Z= Sb, Bi) were investigated by bulk sensitive hard X-ray<br />

photoelectr<strong>on</strong> spectroscopy. The measured valence band spectra are clearly resolved and in well agreement with<br />

the first-principles calculati<strong>on</strong>s of the electr<strong>on</strong>ic structure of the compounds. Close to the Fermi energy, the linear<br />

behavior of the measured spectra at high excitati<strong>on</strong> energy where influences of the surface can be neglected<br />

improve bulk origin of the Dirac-c<strong>on</strong>e type density [2]. Furthermore, the temperature dependence of electrical<br />

c<strong>on</strong>ductivity, Hall mobility, Seebeck coefficient and thermal c<strong>on</strong>ductivity were investigated. The promising<br />

properties of those compounds open a high potential for new technological applicati<strong>on</strong>s.<br />

[1] S. Chadov, X. Qi, J. Kubler, G. H. Fecher, C. Felser, and S. Zhang, Nat Mater 9, 541 (2010). [2] S. Ouardi, C. Shekhar, G.<br />

H. Fecher, X. Kozina, G. Stryganyuk, C. Felser, S. Ueda, and K. Kobayashi, Appl. Phys. Lett. 98, 211901 (2011).<br />

SD16<br />

Gapless interface states in topological insulator/semic<strong>on</strong>ductor<br />

heterostructures<br />

Hugo Aramberri and Carmen Munoz*<br />

ICMM- C<strong>on</strong>sejo Superior de Investigaci<strong>on</strong>es Cientificas, Spain<br />

Based <strong>on</strong> first principles calculati<strong>on</strong>s we investigate the existence of topologicallyn<strong>on</strong>trivial<br />

states at the interface between a topological insulator (TI) and a<br />

semic<strong>on</strong>ductor (S) in TI/S heterostructures. We find that the emergence of gapless states<br />

depends <strong>on</strong> the symmetry of the juncti<strong>on</strong>, being protected by mirror symmetry. We<br />

discuss their characteristic dispersi<strong>on</strong> and spatial distributi<strong>on</strong> and analyze the quantum<br />

interference between helical states and its influence <strong>on</strong> the spin texture of the quasi<br />

two-dimensi<strong>on</strong>al states as a functi<strong>on</strong> of the semic<strong>on</strong>ductor thicknesses. From the firstprinciples<br />

calculati<strong>on</strong>s, we derive an effective Hamilt<strong>on</strong>ian, which captures the salient<br />

topological features. The effective model combined with a Green functi<strong>on</strong> matching<br />

method [1] allow us to investigate the evoluti<strong>on</strong> of the interacti<strong>on</strong> between interface<br />

helical Dirac fermi<strong>on</strong>s from finite heterostructures to actual seminfinite interfaces and<br />

therefore to analyze the novel behavior of the spin-charge coupling in two-dimensi<strong>on</strong>al<br />

layered systems with str<strong>on</strong>g spin-orbit coupling.<br />

[1] M. C. Munoz, V. R. Velasco and F. Garcia-Moliner, Phys. Rev. B. 39 (1989) 1786; M. C. Munoz<br />

and M. P. Lopez Sancho, Phys. Rev. B. 41 (1990) 8412.<br />

SD17<br />

Thermoelectric transport in topological insulators<br />

Oleg Tretiakov*<br />

Physics and Astr<strong>on</strong>omy, Texas A&M University, USA<br />

We study the thermoelectric properties of three-dimensi<strong>on</strong>al topological insulators<br />

with many holes (or pores) in the bulk. We show that at high density of these holes<br />

the thermoelectric figure of merit, ZT, can be large due to the c<strong>on</strong>tributi<strong>on</strong> of the<br />

c<strong>on</strong>ducting surfaces and the suppressed ph<strong>on</strong><strong>on</strong> thermal c<strong>on</strong>ductivity. The maximum<br />

efficiency can be tuned by an induced gap in the surface states dispersi<strong>on</strong> through<br />

tunneling, magnetic impurities, or external magnetic fields. The large values of ZT,<br />

much higher than unity for reas<strong>on</strong>able parameters, make this system a str<strong>on</strong>g candidate<br />

for applicati<strong>on</strong>s in heat management of nanodevices, especially at low temperatures.<br />

O. A. Tretiakov, Ar. Abanov, and Jairo Sinova, Applied Physics Letters, 99, 113110 (2011).


SD18<br />

Topological phase in a <strong>on</strong>e-dimensi<strong>on</strong>al interacting fermi<strong>on</strong> system<br />

Huaiming Guo<br />

Department of physics, Beihang University, China<br />

We study a <strong>on</strong>e-dimensi<strong>on</strong>al (1D) interacting topological model by means of the<br />

exact diag<strong>on</strong>alizati<strong>on</strong> method. The topological properties are first examined with the<br />

existence of the edge states at half-filling. We find that the topological phases are not<br />

<strong>on</strong>ly robust to small repulsive interacti<strong>on</strong>s, but also are stabilized by small attractive<br />

interacti<strong>on</strong>s, and also finite repulsive interacti<strong>on</strong> can drive a topological n<strong>on</strong>trivial<br />

phase into a trivial <strong>on</strong>e while the attractive interacti<strong>on</strong> can drive a trivial phase into a<br />

n<strong>on</strong>trivial <strong>on</strong>e. Next we calculate the Berry phase and parity of the bulk system and<br />

find that they are equivalent in characterizing the topological phases. With them we<br />

obtain the critical interacti<strong>on</strong> strengths and c<strong>on</strong>struct part of the phase diagram in the<br />

parameters’ space. Finally we discuss the effective Hamilt<strong>on</strong>ian at the large-U limit and<br />

provide an additi<strong>on</strong>al understanding of the numerical results. These results could be<br />

realized experimentally using cold atoms trapped in the 1D optical lattice.<br />

1: Xiao-Liang Qi and Shou-Cheng Zhang, Rev. Mod. Phys. 83, 1057 (2011). 2: J. E.<br />

Moore, Nature (L<strong>on</strong>d<strong>on</strong>) 464, 194 (2010). 3: M. Z. Hasan and C. L. Kane, Rev. Mod.<br />

Phys. 82, 304 (2011). 4: Huaiming Guo and Shun-Qing Shen, Phys. Rev.B 84, 195107<br />

(2011).<br />

SD19<br />

Robustness of 1D topological superc<strong>on</strong>ductors with Majorana edge<br />

states against lattice modulati<strong>on</strong><br />

Masaki Tezuka* and Norio Kawakami<br />

Department of Physics, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502,<br />

Japan<br />

SE01<br />

UPGRADED<br />

Temperature-pressure phase diagram of quadrupolar order in<br />

PrTr 2Al 20 (Tr=Ti,V)<br />

Toshiki Tanaka 1 , Kazuyuki Matsubayashi 2 *, Akihiko Hisada 2 , Akito Sakai 2 , Satoru<br />

Nakatsuji 2 , Yoshiya Uwatoko 2 and Yasunori Kubo 3<br />

1 Graduate School,Nih<strong>on</strong> Univ, Japan<br />

2 Institute for Solid State Physics, The University of Tokyo, Japan<br />

3 College of Humanities and Sciences,Nih<strong>on</strong> Univ, Japan<br />

PrTr 2Al 20 (Tr=Ti,V) crystallizes in a cubic CeCr 2Al 20 type structure with the space group Fd 3<br />

?m. According to neutr<strong>on</strong> experiment, crystal electric field (CEF) ground state of Pr i<strong>on</strong> is the<br />

n<strong>on</strong>-Kramers Γ 3 doublet [1]. Reflecting the n<strong>on</strong>-magnetic ground state, PrTi 2Al 20 and PrV 2Al 20<br />

exhibit quadrupolar ordering at TQ ~ 2.0 K and 0.6 K, respectively. It is notable that the low<br />

temperature electrical resistivity of PrV 2Al 20 shows √T dependence, suggesting the quadrupolar<br />

K<strong>on</strong>do effect[2]. In the present study, we have measured electrical resistivity under high<br />

pressure <strong>on</strong> PrTr 2Al 20 (Tr=Ti,V) single crystals in order to clarity the pressure dependence of TQ<br />

and K<strong>on</strong>do effect. Electrical resistivity of PrTi 2Al 20 shows the broad maximum centered at ~50<br />

K due to incoherent K<strong>on</strong>do-scattering processes <strong>on</strong> the ground state and the excited CEF level.<br />

With increasing pressure, the magnitude of this anomaly increases while the peak positi<strong>on</strong> is<br />

unchanged. At lower temperatures, it is found that a clear resistive drop at TQ ~ 2 K at ambient<br />

pressure. TQ first increases and shows the maximum under pressure. We will present the phase<br />

diagram of PrTi 2Al 20 together with that of PrV 2Al 20.<br />

[1]:T. J. Sato, S. Ibuka, A. Sakai and S. Nakatsuji: Meeting Abst. Phys. Soc. Jpn,Vol.65, Issue 2, Pt. 3,<br />

(2010) p. 584 [2]:A.Sakai, S.Nakatsuji : J. Phys. Soc Jpn. 80 (2011) 063701<br />

SE02<br />

SE03<br />

SE04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Soft point c<strong>on</strong>tact spectroscopy in the antiferromagnet Ce 2RhIn 8<br />

Eunsung Park 1 , Xin Lu 2 , Chung Jae W<strong>on</strong> 3 , Nam Jung Hur 3 , Eric D. Bauer 2 , Joe D.<br />

Thomps<strong>on</strong> 2 and Tus<strong>on</strong> Park 1 *<br />

1 Department of Physics, Sungkyunkwan University, Korea<br />

2 C<strong>on</strong>densed Matter & Magnet Science Group, Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

3 Department of Physics, Inha University, Korea<br />

We performed soft point c<strong>on</strong>tact spectroscopy <strong>on</strong> the Ce-based heavy fermi<strong>on</strong> systems<br />

(CeIn 3, CeCoIn 5, CeRhIn 5, CeIrIn 5, and Ce 2RhIn 8) with silver epoxy replacing a<br />

c<strong>on</strong>venti<strong>on</strong>al tip. Unlike CeIn 3 where the c<strong>on</strong>ductance dI/dV is enhanced below TN<br />

(=10K), the c<strong>on</strong>ductance of CeRhIn 5 at zero bias voltage is rapidly enhanced below<br />

8K, which is higher than TN of CeRhIn 5 (=3.8K). Heavy fermi<strong>on</strong> compounds with<br />

a magnetic order often show intermediate states that are characterized by a broad<br />

enhancement of c<strong>on</strong>ductance at temperatures higher than TN, while heavy fermi<strong>on</strong><br />

compounds without magnetic ordering reveal asymmetric c<strong>on</strong>ductance line-shape<br />

below characteristic temperature T*. The antiferromagnet Ce 2RhIn 8 is unique in that<br />

the intermediate state shows a V-shaped dip around zero biased voltage and is enhanced<br />

with decreasing temperature below 25K, which is much higher than T*=5K. Below<br />

TN=2.8K, a symmetric peak at zero bias voltage in the c<strong>on</strong>ductance spectra is enhanced<br />

within the V-shaped dip with decreasing temperature. We interpret the symmetric peak<br />

and V-shaped dip around zero bias as manifestati<strong>on</strong> of the antiferromagnetic (AFM)<br />

order and K<strong>on</strong>do dip in the K<strong>on</strong>do lattice system, respectively, indicating that Ce 2RhIn 8<br />

is at a boundary between AFM and K<strong>on</strong>do states.<br />

Evidence of a spin gap above the magnetic ordering temperature and<br />

crystal field excitati<strong>on</strong>s in CeOs2Al10 D T Adroja 1 *, P P Deen 2 , A D Hillier 1 , Y Muro 3 , J Kajino 4 , T Takabatake 4 , A M<br />

Strydom 5 , P Peratheepan 5 , F Demmel 1 , J R Stewart 1 and J Taylor 1<br />

1<br />

ISIS Facility, Rutherford Applet<strong>on</strong> Laboratory, Chilt<strong>on</strong>, OX11 0QX, United Kingdom<br />

2<br />

European Spallati<strong>on</strong> Source, St Algatan 4, Box 176 Lund 221 00, Sweden<br />

3<br />

Liberal Arts and Sciences, Toyama Prefectural University, Kurokawa 5180, Imizu 939-0398, Japan, Japan<br />

4<br />

Department of Quantum matter, ADSM, and IAMR, Hiroshima University, Higashi-Hiroshima, 739-8530,<br />

Japan, Japan<br />

5<br />

Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa, South<br />

Africa<br />

Recently, the opening of a spin gap has been reported in the intermetallic compounds CeT 2 Al 10 (T = Ru<br />

and Os) below TN = 27-29K through heat capacity and magnetic susceptibility measurements. Various<br />

theoretical models have been proposed to explain the spin gap formati<strong>on</strong>, for example a spin-Peierls and<br />

RVB models of Hanzawa for CeRu 2Al 10. To understand the nature of the spin gap formati<strong>on</strong> in CeOs 2Al 10,<br />

we have carried out low and high energies inelastic neutr<strong>on</strong> scattering (INS) measurements between 4.5 and<br />

65K. Our INS studies reveal a clear sign of a spin gap of 11meV at 4.5K and of 4meV at 35K, while above<br />

45K the observed resp<strong>on</strong>se transformed into a quasielastic line with linewdith of ~ 8 meV. The observati<strong>on</strong><br />

of a spin gap above TN suggests that its origin is not <strong>on</strong>ly due to the gapped spin wave, but also related to<br />

the hybridizati<strong>on</strong> between 4f- and c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong>s. Moreover the high energy INS study reveals two<br />

crystal field (CEF) excitati<strong>on</strong>s at 37 and 57meV. We have carried out an analysis of the INS data al<strong>on</strong>g with<br />

the single crystal susceptibility based <strong>on</strong> the CEF model, which gives good fit to both data sets.<br />

Role of quantum fluctuati<strong>on</strong>s in forming heavy-fermi<strong>on</strong>s for Ca2 xSrxRuO4 Naoya Arakawa and Masao Ogata<br />

Department of Physics, The University of Tokyo, Japan<br />

In order to understand a role of quantum fluctuati<strong>on</strong>s in forming heavy-fermi<strong>on</strong>s<br />

for Ca 2-xSrxRuO 4, we investigated the effect of quantum fluctuati<strong>on</strong>s <strong>on</strong> the massenhancement<br />

<strong>on</strong> the basis of the three-orbital Hubbard model for the Ru-t2g-orbitals.<br />

In this presentati<strong>on</strong>, I show the momentum-dependence of both the spin and charge<br />

susceptibilities for the tight-binding models at x = 2.0 and 0.5 within the random<br />

phase approximati<strong>on</strong> (RPA). I also present the variati<strong>on</strong> of γe, obtained by using the<br />

Hellmann-Feynman theorem and the RPA, between x=2.0 and 0.5 and address a role of<br />

both the spin and orbital fluctuati<strong>on</strong>s in enhancing γe for Ca 2-xSrxRuO 4.<br />

July 8 - 13, 2012 Busan, Korea 219<br />

Poster Friday


Poster Friday<br />

SE05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Specific heat of structure-disordered heavy-fermi<strong>on</strong> Ce xY 80-xMn 20<br />

alloys<br />

Yusuke Amakai 1 *, Shinya Tanaka 1 , Yasuhiro Shiojiri 1 , Naoki Mom<strong>on</strong>o 1 , Hideaki<br />

Takano 1 , Shigeyuki Murayama 1 , Yoshihisa Obi 2 and Koki Takanashi 2<br />

1 Graduate School of Engineering, Muroran Institute of Technology, Japan<br />

2 Institute for Material Research, Tohoku University, Japan<br />

Recently, we have reported physical properties of structure-disordered (a-)Ce xY 80-xMn 20<br />

alloys which show a heavy fermi<strong>on</strong> state in the n<strong>on</strong>-Bloch system without translati<strong>on</strong><br />

symmetry[1]. The specific heat Cp for present alloys follows γT + βT3 down to<br />

about 10 K. The T-linear coefficient γ shows a large value (~200 mJ/Ce-molK 2) and<br />

almost independent of the Ce-c<strong>on</strong>centrati<strong>on</strong>. However, the Cp/T vs. T2 plot of T <<br />

10 K deviates from the T-linear relati<strong>on</strong> with decreasing temperature. In this work, in<br />

order to clarify the factor of the deviati<strong>on</strong> of Cp/T for a-Ce xY 80-xMn 20 alloys, we have<br />

measured the low-temperature specific heat. We have estimated the temperature TA of<br />

the deviati<strong>on</strong> from the Cp/T vs. T 2 plot for present alloys. The TA is about 10 K, and<br />

almost independent of the Ce-c<strong>on</strong>centrati<strong>on</strong>. Therefore, the deviati<strong>on</strong> from the Cp/T<br />

for the present alloys would be c<strong>on</strong>sidered the crystalline-electric-field splitting of the<br />

six-fold degenerate level of the Ce 3+ i<strong>on</strong>. Detailed discussi<strong>on</strong>s will be presented at the<br />

c<strong>on</strong>ference.<br />

[1] Y. Amakai, et. al., Phys. Rev. B, 79(2009)245126.<br />

SE06<br />

Specific heat of structure-disordered heavy-fermi<strong>on</strong> CexY 80-xMn 20<br />

alloys<br />

Yusuke Amakai 1 *, Shinya Tanaka 1 , Yasuhiro Shiojiri 1 , Naoki Mom<strong>on</strong>o 1 , Hideaki<br />

Takano 1 , Shigeyuki Murayama 1 , Yoshihisa Obi 2 and Koki Takanashi 2<br />

1 Graduate School of Engineering, Muroran Institute of Technology, Japan<br />

2 Institute for Material Research, Tohoku University, Japan<br />

Recently, we have reported physical properties of structure-disordered (a-)CexY 80xMn<br />

20 alloys which show a heavy fermi<strong>on</strong> state in the n<strong>on</strong>-Bloch system without<br />

translati<strong>on</strong> symmetry[1]. The specific heat Cp for present alloys follows γT + βT3<br />

down to about 10 K. The T-linear coefficient γ shows a large value (~200 mJ/CemolK<br />

2) and almost independent of the Ce-c<strong>on</strong>centrati<strong>on</strong>. However, the Cp/T vs. T2<br />

plot of T < 10 K deviates from the T-linear relati<strong>on</strong> with decreasing temperature. In<br />

this work, in order to clarify the factor of the deviati<strong>on</strong> of Cp/T for a-CexY 80-xMn 20<br />

alloys, we have measured the low-temperature specific heat. We have estimated the<br />

temperature TA of the deviati<strong>on</strong> from the Cp/T vs. T 2 plot for present alloys. The TA is<br />

about 10 K, and almost independent of the Ce-c<strong>on</strong>centrati<strong>on</strong>. Therefore, the deviati<strong>on</strong><br />

from the Cp/T for the present alloys would be c<strong>on</strong>sidered the crystalline-electric-field<br />

splitting of the six-fold degenerate level of the Ce 3+ i<strong>on</strong>. Detailed discussi<strong>on</strong>s will be<br />

presented at the c<strong>on</strong>ference.<br />

[1] Y. Amakai, et. al., Phys. Rev. B, 79(2009)245126.<br />

SE07<br />

Synchrotr<strong>on</strong> X-ray diffracti<strong>on</strong> study <strong>on</strong> crystal structure of URu2Si2 Chihiro Tabata 1 *, Reiji Kumai 2 , Kensuke Kobayashi 2 , Hir<strong>on</strong>ori Nakao 2 , Yoichi<br />

Murakami 2 , Makoto Yokoyama 3 , Hiroyuki Hidaka 1 , Tatsuya Yanagisawa 1 and Hiroshi<br />

Amitsuka 1<br />

1<br />

Graduate School of Science, Hokkaido University, Japan<br />

2<br />

CMRC and PF, Institute of Materials Structure Science, High Energy Accelerator<br />

Research Organizati<strong>on</strong>, Japan<br />

3<br />

Faculty of Science, Ibaraki University, Japan<br />

URu 2Si 2 (the tetrag<strong>on</strong>al ThCr 2Si 2 type crystal structure; space group I4/mmm) has<br />

attracted much interest because of its peculiar phase transiti<strong>on</strong> at 17.5 K (≡To) [1-<br />

3]. Despite more than 25 years of intense research trying to identify the order<br />

parameter, the intrinsic nature of the phase transiti<strong>on</strong> has not been elucidated [4]. The<br />

ThCr 2Si 2 structure includes a free positi<strong>on</strong> parameter, z, of the Si 4(e) site. Since the<br />

Si i<strong>on</strong>s are located at the sec<strong>on</strong>d nearest-neighbor positi<strong>on</strong> of the U i<strong>on</strong>s, the precise<br />

determinati<strong>on</strong> of the z parameter might provide useful informati<strong>on</strong> for evaluati<strong>on</strong> of<br />

hybridizati<strong>on</strong> effects of 5f orbits with Si s, p states, calculati<strong>on</strong>s of a band structure,<br />

analyses for 29Si-NMR spectra, and so <strong>on</strong>. These pieces of knowledge might offer a<br />

clue to solving the issue of hidden order in URu2Si2. We will report our latest study<br />

of structural analyses of a single crystal of this material based <strong>on</strong> the X-ray diffracti<strong>on</strong><br />

measurements performed at BL-8A and B in the Phot<strong>on</strong> Factory KEK.<br />

[1] T.T.M. Palstra et al., Phys. Rev. Lett. 55, 2727 (1985). [2] M.B. Maple et al., Phys. Rev. Lett. 56, 185 (1986).<br />

[3] W. Schlabitz et al., Z. Phys. B 62, 171 (1986). [4] J.A. Mydosh and P.M. Oppeneer, arXiv:1107.0258v1 (2011).<br />

220 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SE08<br />

Spin-density wave order in the 2D heavy fermi<strong>on</strong> system CePt 2In 7<br />

Martin Manss<strong>on</strong> 1 *, Jun Sugiyama 2 , Yasmine Sassa 1 , Bastian M. Wojek 3 , Thomasz<br />

Durakiewicz 4 , Krunoslav Prsa 1 , Olof Gotberg 3 , Calin Rusu 5 , Daniel Andreica 5 ,<br />

Stephane P<strong>on</strong>s 6 , Marco Gri<strong>on</strong>i 6 , Oscar Tjernberg 3 and Eric D. Bauer 4<br />

1 Lab. for Solid State Physics, ETH Zurich, Switzerland<br />

2 Toyota Central Research and Development Labs. Inc., Japan<br />

3 Materials Physics, Royal Institute of Technology, KTH Stockholm, Sweden<br />

4 Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

5 Faculty of Physics, Babes-Bolyai University, Romania<br />

6 Institute of C<strong>on</strong>densed Matter Physics, EPF Lausanne, Switzerland<br />

The title compound is a recently discovered heavy fermi<strong>on</strong> material where the spacing between Ce-In<br />

planes is drastically increased. C<strong>on</strong>sequently, CePt 2In 7 inherit a truly 2D electr<strong>on</strong>ic structure. It was recently<br />

discovered that CePt 2In 7 is not <strong>on</strong>ly AF (TN=5.3 K) at ambient pressure but also becomes SC under<br />

pressure with a maximum transiti<strong>on</strong> temperature Tc=2.1 K at P=3.12 GPa. At lower pressures an intriguing<br />

coexistence of the AF order and SC phase is found, and that with increasing pressure Tc is increasing while<br />

TN decreases. The growth of the SC <strong>on</strong> the expense of the AF order suggests a crossover behavior of the Ce-<br />

4f electr<strong>on</strong>s from localized to itinerant, similar to what is c<strong>on</strong>sidered for the well-known CeRhIn 5 compound.<br />

In the presented work the low-temperature microscopic magnetic properties of the quasi-2D heavy fermi<strong>on</strong><br />

compound, CePt 2In 7 are investigated by using μSR. Clear evidence for the formati<strong>on</strong> of a SDW order is<br />

presented. The magnetic order parameter fit well to a modified BSC gap-energy functi<strong>on</strong> in a str<strong>on</strong>g-coupling<br />

scenario, possibly predicting the evoluti<strong>on</strong> of unc<strong>on</strong>venti<strong>on</strong>al pairing in the pressure induced superc<strong>on</strong>ducting<br />

phase of this compound. Finally, we also present recent pressure dependent μSR data.<br />

Funding Source: Swiss Nati<strong>on</strong>al Science Foundati<strong>on</strong> (Project 6, NCCR MaNEP), U.S. DOE Oce of<br />

Sciences, VR Sweden and Toyota CRDL.<br />

SE09<br />

Metal-n<strong>on</strong>metal transiti<strong>on</strong> in Cr partial substituted Ni 0.96S<br />

Masanori Matoba*, Yoichi Kamihara and Shuichiro Anzai<br />

Center for Applied Physics and Physico-Informatics, Keio University, Japan<br />

Hexag<strong>on</strong>al NiAs-type NiS exhibits a first-order metal-n<strong>on</strong>metal transiti<strong>on</strong> (MNT) at Tt=263K,<br />

resulting from the opening of narrow charge-transfer (CT) gap between the S 3p band and the<br />

upper Hubbard band [1,2]. The low temperature phase is the n<strong>on</strong>metallic antiferromagnetic<br />

state, while the high temperature phase shows metallic and Pauli-paramagnetic behavior<br />

[3,4]. The substituti<strong>on</strong> of vacancies for Ni atoms in NiS lowers Tt to be suppressed to be<br />

zero at d=0.035 in Ni 1-dS, so that metallic Ni 0.96S do not exhibit the MNT [5,6]. In this study,<br />

we synthesized Cr-partial substituted Ni 0.96S or (Ni 1-xCrx) 0.96S by a solid state reacti<strong>on</strong> in an<br />

evacuated silica tube to reveal the Cr-partial substituti<strong>on</strong> effect <strong>on</strong> the physical properties<br />

of metallic Ni 0.96S by the measurements of X-ray diffracti<strong>on</strong>, electrical resistivity, magnetic<br />

susceptibility, and thermopower. Surprisingly, (Ni 1-xCrx) 0.96S clearly exhibits the MNT, while<br />

metallic Ni 0.96S do not exhibit the MNT. The Tt increases with x sharply from x=0.025 (Tt=50<br />

K) to x=0.09 (Tt=260 K) by Cr-partial substituti<strong>on</strong> for Ni in Ni_{0.96}S. At the c<strong>on</strong>ference,<br />

electr<strong>on</strong>ic nature of Cr-partial substituted Ni 0.96S or (Ni 1-xCrx) 0.96S with ability for the opening of<br />

CT-gap will be discussed from the viewpoint of the str<strong>on</strong>gly correlated electr<strong>on</strong> systems.<br />

[1] A. Fujimori, H. Namatame, M. Matoba and S. Anzai, Phys. Rev. B 42, 620 (1990). [2] M. Imada, A. Fujimori, and Y.<br />

Tokura, Rev. Mod. Phys. 70, 1039 (1998). [3] J. T. Sparks and T. Komoto, Phys. Lett. A 25, 398 (1967). [4] S. Anzai<br />

and K. Ozawa, J. Phys. Soc. Jpn. 24, 271 (1968). [5] R. Brusetti, J. M. D. Coey, G. Czjzek, J. Fink, F. Gompf and H.<br />

Schmidt, J. Phys. F 10, 33 (1980). [6] M. Matoba and S. Anzai and A. Fujimori, J. Phys. Soc. Jpn. 60, 4230 (1991).<br />

SE10<br />

A study of ni-substituti<strong>on</strong> and pressure effects <strong>on</strong> the heavy-fermi<strong>on</strong><br />

Superc<strong>on</strong>ductor CeCu 2Si 2<br />

Yoichi Ikeda*, Yuzo Ito, Shingo Araki and Tatsuo C Kobayashi<br />

Graduate School of Natural Science and Technology, Okayama University, Japan<br />

The heavy-fermi<strong>on</strong> superc<strong>on</strong>ductor CeCu 2Si 2 shows an attractive enhancement of T_c<br />

around a critical pressure (~ 4.5 GPa), at which the T-linear variati<strong>on</strong> of resistivity, the<br />

enhancement of the residual resistivity, the rapid decrease of T 2 -coefficient and a sign of<br />

a valence crossover have been observed [1-3]. These characteristics have been believed<br />

to be signatures of the critical valence fluctuati<strong>on</strong>s associated with a valence transiti<strong>on</strong><br />

around its critical-end point [4, 5], while we have been requiring more signatures for<br />

clarificati<strong>on</strong> of the fascinating phenomena. Effects of the Ni substituti<strong>on</strong> <strong>on</strong> CeCu 2Si 2<br />

are investigated by means of specific heat and electrical resistivity measurements. A<br />

characteristic T-linear dependence of the resistivity is observed around x ~ 0.1 with a<br />

fracti<strong>on</strong>al resistivity drop due to filamentary superc<strong>on</strong>ductivity. In additi<strong>on</strong>, a variati<strong>on</strong><br />

of the power index n of a fit to ρ-ρ_0 = aT^n at low temperatures against T_1^max<br />

at which the resistivity shows a maximum is almost fully identical to the result of the<br />

high pressure experiment [1]. We would like to discuss for the similarities between Ni<br />

doping and pressure and the origin of the anomalous Fermi liquid state.<br />

[1] A. Holmes et al., PRB 69 (2004) 024508. [2] K. Fujiwara et al., submitted to J. Phys.: C<strong>on</strong>f. Ser.<br />

(SCES2011) Cambridge. [3] J. -P. Rueff et al., PRL 106 (2011) 186405. [4] K. Miyake, J. Phys.:<br />

C<strong>on</strong>dens. Matter 19 (2007) 125201. [5] G. Seyfarth et al., arXiv:1111.4873v1.


SE11<br />

Electrical resistivity measurement under pressure in the heavy fermi<strong>on</strong><br />

antiferromagnetic compound Ce2PtGa12 Ryo Sasaki 1 , Kazuyuki Matsubayashi 1 , Takuya Shiraishi 2 , Tetsuro Yamashita 2 , Shigeo<br />

Ohara 2 and Yoshiya Uwatoko 1<br />

1<br />

Institute for Solid State Physics, the University of Tokyo, Kashiwa, Chiba 277-8581,<br />

Japan<br />

2<br />

Department of Engineering Physics, Electr<strong>on</strong>ics and Mechanics, Graduate School of<br />

Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan<br />

Ce-based heavy-fermi<strong>on</strong> ternary compounds have been of interest because of<br />

their exotic physical properties under pressure, such as magnetic ordering and<br />

superc<strong>on</strong>ductivity.[1] In these systems, there is a competiti<strong>on</strong> between magnetic order<br />

of f-electr<strong>on</strong>s (RKKY effect) and the screening of magnetic moments (K<strong>on</strong>do effect)<br />

producing large effective electr<strong>on</strong> masses. Ce 2PtGa 12 orders antiferromagnetically at 7<br />

K, and specific heat measurements suggest that it is a moderate heavy-fermi<strong>on</strong> system<br />

with γ 191 mJ/mol K 2. For understand of competiti<strong>on</strong> between RKKY and K<strong>on</strong>do<br />

effect, We have measured the electrical resistivity under pressure <strong>on</strong> Ce 2PtGa 12 single<br />

crystal. In this paper, we will report the suppressi<strong>on</strong> of the antiferromagnetic order<br />

under higher pressure and discuss the electr<strong>on</strong>ic state in the vicinity of the critical<br />

pressure.<br />

[1] R. T. Macaluso et al., J. Solid State Chem. 178 (2005) 3547.<br />

SE12<br />

Anisotropy of URhGe<br />

Jack M Barraclough 1 *, Edward A Yelland 1 and Andrew D Huxley 2<br />

1<br />

School of Physics and Astr<strong>on</strong>omy, University of St Andrews and Scottish Universities<br />

Physics Alliance (SUPA), United Kingdom<br />

2<br />

School of Physics, University of Edinburgh and SUPA, United Kingdom<br />

The heavy fermi<strong>on</strong> material URhGe has garnered interest in recent years as an<br />

unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductor. It shows coexistence of ferromagnetism and p-wave<br />

superc<strong>on</strong>ductivity[1], and superc<strong>on</strong>ductivity which is re-entrant in magnetic field[2].<br />

We now believe the latter effect to be the result of proximity to a topological change<br />

in the Fermi-surface[3]. In this poster I report recent resistivity measurements <strong>on</strong><br />

samples of URhGe with well-defined current directi<strong>on</strong>. Most previous works do not<br />

c<strong>on</strong>sider this when reporting resistivity, however we find that some features can vary<br />

significantly as a functi<strong>on</strong> of current directi<strong>on</strong>. We discuss how these findings c<strong>on</strong>strain<br />

the anisotropy of the Fermi surface, and the possibility of a field dependent and/or<br />

anisotropic scattering rate. I also present data taken <strong>on</strong> high quality samples close to the<br />

quantum critical point. Interestingly, there is no enhancement of the superc<strong>on</strong>ducting<br />

Tc near the QCP compared to that observed with the field applied entirely al<strong>on</strong>g the<br />

crystalline b-axis, where a low temperature tricritical point is present.<br />

[1] F Hardy and A D Huxley, PRL 94 247006 (2005) [2] F Levy et al, Science 308 1343 (2005) [3]<br />

E A Yelland et al, Nature Physics 7, 890-894 (2011)<br />

SE13<br />

Study of spin wave and spin gap in single crystals of CeRu2Al10 using<br />

inelastic neutr<strong>on</strong> scattering measurements<br />

D T Adroja 1 *, E A Goremychkin 1 , A D Hillier 1 , Y Muro 2 , J Kajino 3 and T Takabatake 3<br />

1<br />

ISIS Facility, Rutherford Applet<strong>on</strong> Laboratory, Chilt<strong>on</strong>, OX11 0QX, United Kingdom<br />

2<br />

Liberal Arts and Sciences, Toyama Prefectural University, Kurokawa 5180, Imizu<br />

939-0398, Japan<br />

3<br />

Department of Quantum matter, ADSM, and IAMR, Hiroshima University, Higashi-<br />

Hiroshima, 739-8530, Japan<br />

We have carried out inelastic neutr<strong>on</strong> scattering (INS) investigati<strong>on</strong>s <strong>on</strong> single crystals<br />

of CeRu 2Al 10 using the high neutr<strong>on</strong> flux spectrometer MERLIN at ISIS facility. The<br />

crystals (total mass of 2.4g) were mounted in the b-c scattering plane. We carried out<br />

measurements using neutr<strong>on</strong> incident energy Ei=20 meV at 4.5 K for b // ki and c //<br />

ki. We have seen a clear dispersive spin wave type excitati<strong>on</strong>s coming out from the<br />

[1 0 0] and [0 2 0] antiferromagnetic z<strong>on</strong>e centres with a single i<strong>on</strong> anisotropic gap of<br />

~4.5 meV. On the other hand al<strong>on</strong>g [0 0 L] directi<strong>on</strong> the spin excitati<strong>on</strong>s exhibit weak<br />

dispersi<strong>on</strong> with almost Q-independent gap of 8 meV. The intensity of the peak al<strong>on</strong>g<br />

[0 0 L] is maximum at L = 0 and decreases with increasing L value, like Ce 3+ magnetic<br />

form factor. These results may suggest that excitati<strong>on</strong>s in the ab-plane can be explained<br />

by the gaped spin wave, but al<strong>on</strong>g [0 0 L] is dominated by the hybridizati<strong>on</strong> effect. We<br />

will present a detail analysis of the observed excitati<strong>on</strong>s.<br />

SE14<br />

SE15<br />

SE16<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Universal behavior in the n<strong>on</strong>linear magnetic resp<strong>on</strong>se of str<strong>on</strong>gly<br />

correlated metals<br />

B S Shivaram 1 , D G Hinks 2 , B Nartowt 3 and Pradeep Kumar 3<br />

1 Department of Physics, University of Virginia, USA<br />

2 Materials Science Divisi<strong>on</strong>, Arg<strong>on</strong>ne Nati<strong>on</strong>al Labs, USA<br />

3 Department of Physics, University of Florida, USA<br />

A diverse class of str<strong>on</strong>gly correlated electr<strong>on</strong>ic materials irrespective of whether<br />

they order magnetically or not, often exhibit a peak in the temperature dependence<br />

of the linear magnetic susceptibility, χ 1 . In n<strong>on</strong>-linear susceptibility measurements <strong>on</strong><br />

a number of heavy electr<strong>on</strong> materials including in single crystals of the prototypical<br />

str<strong>on</strong>gly correlated metal, UPt 3, we find that there exists a peak in the third order<br />

susceptibility, χ 3 as well. This peak in χ 3 occurs at a temperature T 3, which is roughly<br />

half the temperature T 1, at which the peak in χ 1 appears. This proporti<strong>on</strong>ality between<br />

T 3 and T 1 also reported previously in other heavy fermi<strong>on</strong> systems implies a universal<br />

behavior in the n<strong>on</strong>linear magnetic resp<strong>on</strong>se of correlated metals. The observed<br />

proporti<strong>on</strong>ality between T 3 and T 1 can is explained by a model which assumes a singlet<br />

ground state for the spins present in a crystalline electric field with a c<strong>on</strong>comitant<br />

doublet excited state, separated from the ground state by an energy Δ. This model also<br />

yields metamagnetic behavior at a magnetic field corresp<strong>on</strong>ding to Δ.<br />

X-ray absorpti<strong>on</strong> studies of the Ce2Rh1-xIrxIn8 intermetallic compounds<br />

Cris Adriano 1 , Nilmar Silva Camilo 2 , Leandro F Bufaical 3 , Leticie Med<strong>on</strong>ca Ferreira 4 ,<br />

Eduardo N Hering 5 , Pascoal G. Pagliuso 1 and Raimundo Lora-serrano 2 *<br />

1<br />

Instituto de Fisica 'Gleb Wataghin' UNICAMP, CP 6165, 13083-970 Campinas, SP, Brazil<br />

2<br />

Instituto de Fisica, Universidade Federal de Uberlandia, 38400-902 Uberlandia-MG, Brazil<br />

3<br />

Instituto de Fisica, Universidade federal de Goias, Goiania-GO, 74001-970, Brazil<br />

4<br />

Instituto de Fisica e Matematica, Universidade Federal de Pelotas (UFPel), CP 354, 96010-<br />

900 Pelotas, Brazil<br />

5<br />

Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de<br />

Janeiro, RJ, Brazil<br />

Within the series of heavy fermi<strong>on</strong>s Ce 2Rh 1-xIr xIn 8 compounds it has been recently observed the occurrence<br />

of two low-temperature superc<strong>on</strong>ducting (SC) phases as a functi<strong>on</strong> of temperature both at ambient pressure<br />

and under applied pressure for intermediate Ir-c<strong>on</strong>tent (x~0.25-0.7) with remarkable different behavior of<br />

both states as a functi<strong>on</strong> of pressure and x [1]. The details of the observed results seem to be reminiscent<br />

of the two SC phases found in the CeRh 1-xIr xIn 5 system, thus related to the higher dimensi<strong>on</strong>ality and<br />

structural disorder for the Ce2-1-8 systems. Here, we report the results of extended x-ray absorpti<strong>on</strong> fine<br />

structure measurements performed <strong>on</strong> Ce 2Rh 1-xIr xIn 8 (x = 0.0, 0.25, 0.75 and 1.0) at T = 10, 150 and 300<br />

K at the Rh K-edge and at the Ce and Ir-L 3 absorpti<strong>on</strong> edges in order to check the extent of the structural<br />

disorder at the Rh-Ir atomic sites and their relevance for the SC phases observed in the resistivity and<br />

specific heat measurements in these compounds. Our results point to the trivalent state of the Ce i<strong>on</strong>s, and<br />

that there is no evidence of phase separati<strong>on</strong> in the lowest measured temperature.<br />

[1] E. N. Hering, H. A. Borges et al. Phys. Rev. B 82 184517 (2010)<br />

Polarized neutr<strong>on</strong> diffracti<strong>on</strong> study <strong>on</strong> the magnetic ordering in<br />

UMn2Al20 Przemyslaw Swatek 1 *, Piotr Wisniewski 1 , Arsen Gukasov 2 and Dariusz Kaczorowski 1<br />

1<br />

Institute for Low Temperatures and Structure Research, Polish Academy of Sciences,<br />

Wroclaw, Poland<br />

2<br />

Laboratoire Le<strong>on</strong> Brillouin, CEA-CNRS, CE-Saclay, 91191 Gif sur Yvette, France<br />

The ternary intermetallic compounds UX 2Al 20 (X = Ti, V, Nb, Ta, and Cr), crystallizing with the cubic<br />

CeCr 2Al 20-type crystal structure, were characterized in the literature as weak Pauli paramagnets [1-3].<br />

In striking c<strong>on</strong>trast, the isostructural phase UMn 2Al 20 was reported to order ferromagnetically due to the<br />

presence of magnetic moments <strong>on</strong> the uranium atom sites [4]. In this c<strong>on</strong>tributi<strong>on</strong>, we present the results<br />

of our polarized neutr<strong>on</strong> diffracti<strong>on</strong> study <strong>on</strong> a high-quality single crystal of UMn 2Al 20, which was also<br />

carefully characterized by means of X-ray diffracti<strong>on</strong>, microprobe, magnetic, electrical transport and<br />

heat capacity measurements. The bulk properties were found very similar to those published in Ref. 4.<br />

In particular, the ferromagnetic transiti<strong>on</strong> at TC = 17 K was clearly revealed from the magnetic data,<br />

while the temperature-dependent specific heat and electrical resistivity were found nearly featureless. The<br />

magnetizati<strong>on</strong> density maps derived from the neutr<strong>on</strong> diffracti<strong>on</strong> data, showed that the ferromagnetism<br />

in UMn 2Al 20 arises due to the magnetic moments carried <strong>on</strong> the manganese atoms, while the uranium<br />

sublattice remains n<strong>on</strong>magnetic. This result appears perfectly c<strong>on</strong>sistent with the behavior of the UX 2Al 20 (X<br />

= Ti, V, Nb, Ta, and Cr) compounds, in which the U atoms do not exhibit any magnetic moments.<br />

[1] S. Niemann and W. Jeitschko, J. Solid State Chem., 114, 337 (1995). [2] K. Okuda et al. J. Phys. Soc. Jpn. 58, 4296 (1989).<br />

[3] P. Swatek and D. Kaczorowski, J. Solid State Chem., submitted. [4] C. H. Wang et al., Phys. Rev. B 82, 094406 (2010).<br />

July 8 - 13, 2012 Busan, Korea 221<br />

Poster Friday


Poster Friday<br />

SE17<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Antiferromagnetic ordering in single-crystalline Ce 2IrSi 3<br />

Maria Szlawska* and Dariusz Kaczorowski<br />

Institute of Low Temperature and Structure Research, Polish Academy of Sciences,<br />

Wrocław, Poland<br />

The novel cerium-based ternary silicide Ce 2IrSi 3, crystallizing with fully ordered<br />

derivative of the hexag<strong>on</strong>al AlB 2-type unit cell, has recently been characterized as a<br />

K<strong>on</strong>do lattice that orders antiferromagnetically at TN = 1.3 K [1]. An antiferromagnetic<br />

character of the ordering was inferred merely from the specific heat and electrical<br />

resistivity data, collected in applied magnetic fields. With the aim at verificati<strong>on</strong> of the<br />

presumed nature of the ground state, we have performed magnetic studies down to<br />

0.46 K and in external magnetic fields up to 7 T using a SQUID magnetometer. The<br />

results unambiguously corroborated the antiferromagnetic phase transiti<strong>on</strong> at 1.3 K,<br />

and additi<strong>on</strong>ally revealed pr<strong>on</strong>ounced magnetic anisotropy in the ordered state. The<br />

magnetizati<strong>on</strong> comp<strong>on</strong>ent measured within the hexag<strong>on</strong>al ab plane was found much<br />

larger than that taken al<strong>on</strong>g the c axis. This finding indicates that the magnetic moments<br />

in Ce 2IrSi 3 are c<strong>on</strong>fined to the basal plane. In a magnetic field of 0.5 T applied within<br />

the easy plane, the compound undergoes a metamagnetic-like phase transiti<strong>on</strong>. In turn,<br />

up<strong>on</strong> applying magnetic field al<strong>on</strong>g the hexag<strong>on</strong>al c axis some complex, yet more<br />

subtle changes in the magnetic structure seem to occur.<br />

[1] M. Szlawska and D. Kaczorowski, Phys. Rev. B 84 (2011) 094430<br />

SE18<br />

Berezinskii-kosterlitz-thouless transiti<strong>on</strong> in heavy fermi<strong>on</strong> superlattices<br />

Jian-huang She* and Alexander V Balatsky<br />

T-4, Los Alamos Nati<strong>on</strong>al Lab, USA<br />

Recently unc<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductivity has been observed in epitaxially grown<br />

heavy fermi<strong>on</strong> superlattices, where Cooper pairs are c<strong>on</strong>fined within two-dimensi<strong>on</strong>al<br />

K<strong>on</strong>do lattices (Nature Physics 7, 849(2011)). Here we propose to understand these<br />

experiments within the framework of Berezinskii-Kosterlitz-Thouless Transiti<strong>on</strong>.<br />

The observed behavior of the superc<strong>on</strong>ducting transiti<strong>on</strong> temperature can be<br />

understood in terms of phase fluctuati<strong>on</strong>s c<strong>on</strong>trolled by vortex-antivortex (un)binding.<br />

Reas<strong>on</strong>able agreement is found with the experiments. Furthermore, we predict a<br />

large renormalizati<strong>on</strong> of the penetrati<strong>on</strong> depth, which can be measured by future<br />

experiments. Evoluti<strong>on</strong> of the gap is explained by invoking effects of the interface.<br />

SE19<br />

Basic properties of the intermetallics APd 5Al 2 (An=Ce, Th, U, Np, Pu,<br />

Am)<br />

Jean-christophe Griveau*, Krzysztof Gofryk, Eric Colineau, Thomasz Klimczuk and<br />

Jean Rebizant<br />

ITU-JRC-EC, Germany<br />

WITHDRAWN<br />

222 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SE20<br />

Study of vibr<strong>on</strong> quasibound state in CeAg1-xCuxAl3, 0


SE23<br />

Electr<strong>on</strong>ic structure studies of UPt 3 using soft x-ray angle-resolved<br />

photoemissi<strong>on</strong> spectroscopy and band calculati<strong>on</strong><br />

Hiroshi Yamagami 1 , Ikuto Kawasaki 2 , Shin-ichi Fujimori 2 , Akira Yasui 2 , Tetsuo<br />

Okane 2 , Yukiharu Takeda 2 , Yuji Saitoh 2 , Yoshinori Haga 3 , Etsuji Yamamoto 3 and<br />

Yoshichika Onuki 4<br />

1 Department of Physics, Kyoto Sangyo University, Japan<br />

2 C<strong>on</strong>densed Matter Science Divisi<strong>on</strong>, Japan Atomic Energy Agency, Japan<br />

3 Advanced Science Research Center, Japan Atomic Energy Agency, Japan<br />

4 Graduate School of Science, Osaka University, Japan<br />

Electr<strong>on</strong>ic structure and Fermi surface of heavy fermi<strong>on</strong> superc<strong>on</strong>ductor UPt3 have<br />

been studied by de Haas-van Alphen experiments and various theories [1], and it is<br />

suggested that U5f itinerant band model is more comparable with the experiments. In<br />

order to observe the valence band structure of UPt3 directly, angle-angle photoemissi<strong>on</strong><br />

spectroscopy had been d<strong>on</strong>e using a discharge lamp [2]. However a 3-dimensi<strong>on</strong>al<br />

band structure of UPt3 has been not understood well. We have carried out soft x-ray<br />

angle-resolved photoemissi<strong>on</strong> spectroscopy experiment with the twin-helical undulator<br />

beamline BL23SU of SPring-8, and as a result the U5f itinerant bands of UPt3 can be<br />

detected together with the Pt 5d bands. In the paper we will discuss the band structure<br />

of UPt3 with a LDA band calculati<strong>on</strong>.<br />

[1] G. J. McMullan et al., New J. Phys. 10, 053029 (2008). [2] T. Ito et al., Phys. Rev. B 59, 8923<br />

(1999).<br />

SF01<br />

Field-dependent instability of the candidate quantum spin liquid in<br />

EtMe 3Sb[Pd(dmit) 2] 2 as revealed by NMR.<br />

Georgios Koutroulakis 1 *, T<strong>on</strong>g Zhou 2 , Stuart E. Brown 2 , Joe D. Thomps<strong>on</strong> 1 and Reizo<br />

Kato 3<br />

1 Los Alamos Nati<strong>on</strong>al Laboratory, USA<br />

2 UCLA, USA<br />

3 RIKEN, Japan<br />

SF02<br />

WITHDRAWN<br />

Magnetic states in quasi-2-D iridium oxides with large spin-orbit<br />

coupling<br />

Masaaki Isobe 1 *, Hirotaka Okabe1 and Jun Akimitsu 2<br />

1<br />

Str<strong>on</strong>gly Correlated Materials Group, Nati<strong>on</strong>al Institute for Materials Science<br />

(NIMS), Japan<br />

2<br />

Department of Physics and Mathematics, Aoyama Gakuin University, Japan<br />

The discovery of the novel Mott insulating state in Sr 2IrO 4 has developed a new research field<br />

<strong>on</strong> solid-state physics [1]. The str<strong>on</strong>g spin-orbit coupling with the moderate <strong>on</strong>-site Coulomb<br />

interacti<strong>on</strong> in the 5d electr<strong>on</strong> system yields the unc<strong>on</strong>venti<strong>on</strong>al Jeff = 1/2 Mott ground<br />

state. The 'spin-orbit Mott state' is similar to c<strong>on</strong>venti<strong>on</strong>al Mott states in 3d or 4d electr<strong>on</strong><br />

systems. However, the Jeff = 1/2 state is a c<strong>on</strong>siderably complex state hybridizing spin and<br />

orbital degrees of freedom. Therefore, investigati<strong>on</strong> of this state may give a new insight<br />

into d-electr<strong>on</strong> physics, and it may lead to possible unusual cooperative phenomena such as<br />

anisotropic superc<strong>on</strong>ductivity. In this presentati<strong>on</strong>, we review electr<strong>on</strong>ic and magnetic states<br />

in the novel K 2NiF 4-type iridate Ba 2IrO 4 [2]. We found that Ba 2IrO 4 is a quasi-2-D (square<br />

lattice) Heisenberg antiferromagnet (TN ~ 240 K) in which the magnetic moment (~0.34<br />

mB/Ir-atom) is significantly reduced by the low-dimensi<strong>on</strong>al quantum spin fluctuati<strong>on</strong> with<br />

a large magnetic correlati<strong>on</strong> |J|. Its electr<strong>on</strong>ic state undergoes an M-I transiti<strong>on</strong> from the Mott<br />

insulating state to a n<strong>on</strong>-Fermi-liquid state under high pressure (PC ~ 13.8 GPa) [3]. These<br />

behaviors are very similar to those in low-dimensi<strong>on</strong>al cuprates.<br />

[1] B.J. Kim et al., Phys. Rev. Lett. 101, 076402 (2008); Science 323, 1329 (2009). [2] H. Okabe et<br />

al., Phys. Rev. B 83, 155118 (2011). [3] H. Okabe et al., Phys. Rev. B 84, 115127 (2011).<br />

SF03<br />

SF04<br />

SF05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Quantum critical end point in ucoal proved by NMR measurements<br />

Hisashi Kotegawa 1 , Hiroki Nohara 1 , Hideki Tou 1 , Tatsuma D. Matsuda 2 , Etsuji<br />

Yamamoto 2 , Yoshinori Haga 2 , Zachary Fisk 3 , Yoshichika Onuki 4 , Valentin Taufour 5 ,<br />

Dai Aoki 5 , Georg Knebel 5 and Jacques Flouquet 5<br />

1 Kobe University, Japan<br />

2 JAEA, Japan<br />

3 University of California, USA<br />

4 Osaka University, Japan<br />

5 CEA-Grenoble, France<br />

Quantum critical end point (QCEP) emerges in a pressure - temperature - magnetic field phase diagram in<br />

ferromagnetic (FM) materials with tricriticality.[1-3] In UGe 2,[1,2] a first-order metamagnetic transiti<strong>on</strong>,<br />

which appears above a critical pressure of ~1.5 GPa, possesses a critical end point (CEP) at a finite T_<br />

CEP, above which the transiti<strong>on</strong> changes to crossover. The T_CEP decreases under pressure, and reaches<br />

0 K at the QCEP (P_QCEP ~ 3.6 GPa and H_QCEP ~ 18 T). In case of UCoAl, the QCEP is located at<br />

P_QCEP ~ 1.5 GPa and H_QCEP ~ 7 T.[3] Both systems exhibit the similar wing structures of the firstorder<br />

plane, but they are quantitatively different. It is an interesting issue what induces such difference<br />

and what kinds of quantum criticality is involved in the vicinity of QCEP with both instabilities of the<br />

magnetism and the Fermi surface. In this presentati<strong>on</strong>, we focus <strong>on</strong> 59Co-NMR measurements for<br />

UCoAl at ambient pressure [4] and under pressure. A c<strong>on</strong>trasting behavior between the nuclear spin<br />

relaxati<strong>on</strong> rates 1/T 1 and 1/T 2 dem<strong>on</strong>strate that str<strong>on</strong>g Ising-type magnetic fluctuati<strong>on</strong> develops at around<br />

CEP. The drastic pressure evoluti<strong>on</strong> of the fluctuati<strong>on</strong>s toward the QCEP is also reported.<br />

[1] V. Taufour et al., Phys. Rev. Lett. 105, 217201 (2010). [2] H. Kotegawa et al., J. Phys. Soc. Jpn. 80, 083703 (2011).<br />

[3] D. Aoki et al., J. Phys. Soc. Jpn. 80, 094711 (2011). [4] H. Nohara et al., J. Phys. Soc. Jpn. 80, 093707 (2011).<br />

The metal-insulator transiti<strong>on</strong> in ferromagnetic chromium hollandite<br />

Yutaka Ueda 1 *, Masahiko Isobe 1 , Tooru Yamauchi 1 , Akiko Nakao 2 , Hir<strong>on</strong>ori Nakao 2 ,<br />

Yukinori Ohta 3 and Takehisa K<strong>on</strong>ishi 3<br />

1 Institute for Solid State Physics, University of Tokyo, Japan<br />

2 C<strong>on</strong>densed Matter Research Center and Phot<strong>on</strong> Factory, IMSS, KEK, Japan<br />

3 Chiba University, Japan<br />

We discovered a metal to insulator transiti<strong>on</strong> (MIT), retaining ferromagnetic in the insulator phase, in<br />

ferromagnetic K 2Cr 8O 16 [1]. The MIT is accompanied by a structural change from a tetrag<strong>on</strong>al to a<br />

m<strong>on</strong>oclinic structures [2,3]. In the low temperature m<strong>on</strong>oclinic insulator phase, there is no evidence<br />

of charge separati<strong>on</strong>/order. Instead, the characteristic displacements of the Cr and O sites, resulting in<br />

Cr-O b<strong>on</strong>d alternati<strong>on</strong>s, are observed in the rectangular columns formed by the four chains (the fourchain<br />

columns). This indicates a lattice-dimerizati<strong>on</strong> with the formati<strong>on</strong> of Cr-tetramer in the four-chain<br />

columns. The observed structural characteristics and electr<strong>on</strong>ic structure calcualti<strong>on</strong>s lead us a model<br />

of MIT caused by the Peierls instability in the quasi-<strong>on</strong>e-dimensi<strong>on</strong>al four-chain column [2], namely<br />

the MIT is a “pure” Peierls transiti<strong>on</strong> of spinless fermi<strong>on</strong>s (fully spin polarized electr<strong>on</strong>s). On the other<br />

hand, isostructural RbxCr 8O 16 shows a ferromagnetic transiti<strong>on</strong> at Tc= 270 K but does not show any<br />

distinct MIT. Rb-deficiency could be a reas<strong>on</strong> for the absence of MIT. In a solid soluti<strong>on</strong> system, K2yRbyCr<br />

8O 16, the lattice parameters increase with increase of y. Tc also increases as Rb c<strong>on</strong>centrati<strong>on</strong><br />

increases. This is c<strong>on</strong>sistent with the decrease of Tc with increasing hydrostatic pressure in K 2Cr 8O 16.<br />

[1] K. Hasegawa et al., Phys. Rev. Lett. 103 (2009) 146403. [2] T. Toriyama et al., Phys. Rev. Lett.<br />

107 (2011) 266402 [3] A. Nakao et al., J. Phys. Soc. Jpn. to be published.<br />

Compositi<strong>on</strong> and transverse field-tuned quantum criticality in NbFe 2<br />

Sven Friedemann 1 , Max Hirschberger 1 , Yang Zou 1 , William J Duncan 2 , Andreas Neubauer 3 ,<br />

Thomas Bauer 4 , Louis Pedrero 5 , Manuel Brando 5 , Christian Pfleiderer 3 and F Malte Grosche 1<br />

1 Cavendish Laboratory, University of Cambridge, United Kingdom<br />

2 Department of Physics, Royal Holloway, University of L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

3 Physik Department E21, TU Munchen, Germany<br />

4 Max Planck Insitute for Chemical Physics, Dresden, Germany<br />

5 Max Planck Institute for Chemical Physics of Solids, Germany<br />

The low-temperature band magnet NbFe2 can be tuned by varying compositi<strong>on</strong>, magnetic field or pressure,<br />

providing an attractive candidate system for investigating quantum criticality in a transiti<strong>on</strong> metal compound.<br />

Near the compositi<strong>on</strong>-tuned quantum critical point, NbFe2 displays signatures of a logarithmic Fermi liquid<br />

breakdown: The electr<strong>on</strong>ic specific heat diverges logarithmically ΔC~T lnT and the resistivity exhibits<br />

n<strong>on</strong>-Fermi-liquid forms Δρ~T3/2 at low temperature T [1]. This quantum critical behavior is linked to<br />

the suppressi<strong>on</strong> of an antiferromagnetic phase in slightly Nb-rich samples which is stabilized towards Ferich<br />

samples. In additi<strong>on</strong>, NbFe2 with slight Fe excess features a ferromagnetic ground state underlying<br />

the antiferromagnetic phase. We find the ordered moment to point al<strong>on</strong>g the crystalline c-directi<strong>on</strong> in<br />

the ferromagnetic state. Importantly, the transiti<strong>on</strong> temperature of this ferromagnetic ground state can be<br />

suppressed in a magnetic field perpendicular to the directi<strong>on</strong> of the ordered moments, promoting NbFe2 as an<br />

interesting candidate to study transverse field tuning in an Ising-like metallic system. We report the significant<br />

suppressi<strong>on</strong> of Fermi liquid behavior close to the transverse-field induced quantum phase transiti<strong>on</strong>.<br />

Moreover, we utilize susceptibility measurements to study the nature of this quantum phase transiti<strong>on</strong>.<br />

[1] M. Brando, W. J. Duncan, D. Mor<strong>on</strong>i-Klementowicz, C. Albrecht, D. Gruener, R. Ballou, and F. M. Grosche, Phys. Rev. Lett. 101, 026401 (2008).<br />

July 8 - 13, 2012 Busan, Korea 223<br />

Poster Friday


Poster Friday<br />

SF06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Tuning ferromagnetism in Ce 1-xLaxAuGe: A specific heat and magnetic<br />

susceptibility study<br />

Buyisiwe M. S<strong>on</strong>dezi-mhlungu and Andre M. Strydom<br />

Physics, University of Johannesburg, South Africa<br />

SF07<br />

WITHDRAWN<br />

Anomalous hybridizati<strong>on</strong> effects in the cubic quadrupole systems<br />

PrTr 2Al 20 (Tr= Ti, V)<br />

Akito Sakai*, Eoin O’farrell and Satoru Nakatsuji<br />

ISSP, University of Tokyo, Japan<br />

The K<strong>on</strong>do effect, the screening process of magnetic dipole moments by c<strong>on</strong>ducti<strong>on</strong>(c) electr<strong>on</strong>s,<br />

is a well-known many-body phenomen<strong>on</strong> and recognized as a key mechanism which induces a<br />

lot of interesting phenomena. Interestingly, n<strong>on</strong>magnetic versi<strong>on</strong> of the K<strong>on</strong>do effect, so-called<br />

quadrupolar K<strong>on</strong>do effect, is theoretically predicted for the f 2 Γ 3 crystalline electric field ground<br />

doublet[1]. In this theory, the ground state is no l<strong>on</strong>ger Fermi liquid due to the overscreening of<br />

the quadrupole moment by c-electr<strong>on</strong>s. However, it is still uncertain what will happen in a real<br />

system with lattice periodicity. We have revealed that K<strong>on</strong>do effect is observed in cubic PrTr 2Al 20<br />

for the first time in materials which have n<strong>on</strong>magnetic Γ 3 ground doublet. Quadrupolar ordering is<br />

observed at TQ = 2.0 K (Ti) and 0.6 K (V) respectively, and in particular ferroquadrupolar ordering<br />

in PrTi 2Al 20[2, 3, 5, 6]. Interestingly, anomalous metallic behaviors were observed in PrV 2Al 20<br />

above TQ, most likely attributed to the quadrupolar K<strong>on</strong>do effect. In this presentati<strong>on</strong>, we will<br />

report the results of low temperature thermal and transport measurements of PrTr 2Al 20 and discuss<br />

the possibility of the quadrupolar K<strong>on</strong>do effect and quantum critical effect of quadrupolar ordering.<br />

[1] D. L. Cox, Phys. Rev. Lett. 59 (1987) 1240. [2] Akito Sakai and Satoru Nakatsuji, J. Phys. Soc. Jpn. 80<br />

(2011) 063701. [3] T. J. Sato, S. Ibuka, Y. Nambu, T. Yamazaki, A. Sakai and S. Nakatsuji, arXiv0301828.<br />

[4] M. Matsunami, M. Taguchi, A. Chainani, R. Eguchi, M.Oura, A. Sakai, S. Nakatsuji and S. Shin, Phys.<br />

Rev. B 84 (2011) 193101. [5] T U. Ito, W. Higemoto, K. Ninomiya, H. Luetkens, C.Baines, A. Sakai and S.<br />

Nakatsuji, J. Phys. Soc Jpn. 80 (2011) 113703. [6] M. Koseki et al., J. Phys. Soc. Jpn. 80 (2011) SA049.<br />

SF08<br />

N<strong>on</strong>-fermi-liquid properties of the n<strong>on</strong>-centrosymmetric heavyfermi<strong>on</strong><br />

compound CePtSi: a magnetic field study.<br />

Andre Strydom<br />

Physics, University of Johannesburg, South Africa<br />

The ternary intermetallic compound CePtSi and its n<strong>on</strong>magnetic equivalent LaPtSi<br />

form in the n<strong>on</strong>-centrosymmetric tetrag<strong>on</strong>al space group I41/md [1]. The structure is<br />

an ordered variant of the ThSi 2 type which provides dedicated atomic sites for each of<br />

the rare-earth atom, Pt, and Si. CePtSi is a heavy-fermi<strong>on</strong> compound with a very large<br />

electr<strong>on</strong>ic specific heat coefficient [2] and apparently with no sp<strong>on</strong>taneous magnetic<br />

ordering. N<strong>on</strong>-Fermi-liquid (nFL) behaviour found at low temperatures in a Pt-Si<br />

variati<strong>on</strong>al study of CePtSi has been reported [3], as well as aspects of nFL signatures<br />

at the verge of magnetic ordering in CePtSi doped with Ge [4]. In this work we focus<br />

<strong>on</strong> the low-temperature behaviour of magnetic susceptibility, electrical resistivity, and<br />

specific heat of CePtSi together with comparative properties in LaPtSi. The focus is <strong>on</strong><br />

the influence of applied magnetic fields and the stability of nFL scaling in CePtSi as a<br />

functi<strong>on</strong> of field.<br />

1. K. Klepp, and E. Parthe, Acta Cryst. B38 (1982) 1105. 2. W. H. Lee, and N. R. Shelt<strong>on</strong>, Phys. Rev.<br />

B 35 (1987) 5369. 3. T. Goetzfried et al, J. Low Temp. Phys. 127 (2002) 51. 4. F. Steglich et al, J.<br />

Low Temp. Phys. 95 (1994) 3.<br />

224 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SF09<br />

Vibr<strong>on</strong> quasi-bound state in the n<strong>on</strong>-centrosymmetric tetrag<strong>on</strong>al<br />

heavy-fermi<strong>on</strong> compound CeCuAl 3<br />

D T Adroja 1 *, A Del Moral 2 , C De La Fuente 2 , A Fraile 1 , E A Goremyhkin 1 , J Taylor 1 ,<br />

A Hillier 1 and F Fernandez-al<strong>on</strong>so 1<br />

1 ISIS Facility, Rutherford Applet<strong>on</strong> Laboratory, Chilt<strong>on</strong>, OX11 0QX, United Kingdom<br />

2 Laboratorio de <strong>Magnetism</strong>o, Depto Fisica Materia C<strong>on</strong>densada, Universidad de<br />

Zaragoza & ICMA, Spain<br />

We have investigated the n<strong>on</strong>-centrosymmetric tetrag<strong>on</strong>al heavy-fermi<strong>on</strong><br />

antiferromagnetic compound CeCuAl 3 (TN=2.5 K) using inelastic neutr<strong>on</strong> scattering<br />

(INS). Our INS results unequivocally reveal the presence of three magnetic excitati<strong>on</strong>s<br />

centred at 1.3, 9.8, and 20.5 meV. These spectral features cannot be explained within<br />

the framework of crystal-electric-field (CEF) models and recourse to Kramers’<br />

theorem for a 4f 1 Ce 3+ i<strong>on</strong>. To overcome these interpretati<strong>on</strong>al difficulties, we have<br />

extended the vibr<strong>on</strong> model for cubic CeAl 2 of Thalmeier and Fulde to tetrag<strong>on</strong>al pointgroup<br />

symmetry. This extensi<strong>on</strong> provides a satisfactory explanati<strong>on</strong> for the positi<strong>on</strong><br />

and intensity of the three observed magnetic excitati<strong>on</strong>s in CeCuAl3, as well as their<br />

dependence <strong>on</strong> momentum transfer and temperature. On the basis of our analysis, we<br />

attribute the observed series of magnetic excitati<strong>on</strong>s to the existence of a vibr<strong>on</strong> quasibound<br />

state.<br />

SF10<br />

Pressure-induced quantum criticality in the heavy-fermi<strong>on</strong> compound<br />

CeCoGe2.2Si0.8 J. Larrea J. 1 *, K.-a. Lorenzer 2 , M. Muller 1 , S. Paschen 1 , J. Teysser 3 and H. R<strong>on</strong>now 4<br />

1<br />

Institute of Solid State Physics, Vienna University of Technology, Wiedner Haupst. 8 - 10, 1040 Vien, Austria<br />

2<br />

Institute of Solid State Physics, Vienna University of Technology, Austria<br />

3<br />

de Physique de la Matiere C<strong>on</strong>densee, Universite de Geneve, Quai Ernest-Ansermet 24, 1211 Geneve,<br />

Switzerland<br />

4<br />

Laboratory for Quantum <strong>Magnetism</strong>, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland<br />

The pressure-tuned quantum critical point (QCP) of the antiferromagnetic heavy-fermi<strong>on</strong> compound<br />

CeCoGe 2.1Si 0.9 was claimed to be dominated by different effects <strong>on</strong> both sides of the QCP: <strong>on</strong> the magnetic<br />

side spin fluctuati<strong>on</strong>s govern the criticality, while <strong>on</strong> the n<strong>on</strong>-magnetic side the criticality is dominated by<br />

disorder that quenches the spin fluctuati<strong>on</strong>s [1]. Here we study high-quality CeCoGe 2.2Si 0.8 samples [2], with<br />

residual resistance ratios four times larger than those of the previously investigated CeCoGe 2.1Si 0.9 samples.<br />

Interestingly, while DC magnetic susceptibility measurements show that the Neel temperature of TN = 4K<br />

at zero pressure is <strong>on</strong>ly slightly reduced by pressure up to 3.0 kbar, a much str<strong>on</strong>ger decrease is observed for<br />

the specific heat anomaly. We will present electrical resistivity and specific heat measurements up to 15 kbar<br />

and down to 0.05 K, and establish the pressure - temperature phase diagram for CeCoGe 2.2Si 0.8. The critical<br />

behavior shall be compared to the <strong>on</strong>e observed for both CeCoGe 2.1Si 0.9 and the pure reference compound<br />

CeCoGe 3 [3]. We hope that this investigati<strong>on</strong> will elucidate the role of disorder. Acknowledgement: 'Financial<br />

support by the European Research Council (ERC Advanced Grant No 227378) is acknowledged.'<br />

[1] Alzamora M., F<strong>on</strong>tes M. B., Larrea J., Borges H. A., Baggio-Saitovitch E. M., Medeiros S. N. Phys. Rev. B 76 125106<br />

(2007). [2] J. Larrea J, J. Teyssier, H. R<strong>on</strong>now, M. Muller, S. Paschen. Submitted to J. Phys: C<strong>on</strong>f. Ser. [3] G. Knebel, D.<br />

Aoki, G. Lapertot, B. Salce, J. Flouquet, T. Kawai, H. Murunaka, R. Settai, Y. Onuki . J. Phys. Soc. Jpn. 78, 074714 (2009).<br />

SF11<br />

Anomalous thermoelectric effects in the heavy fermi<strong>on</strong> superc<strong>on</strong>ductor<br />

Ce 2PdIn 8<br />

Marcin Matusiak, Daniel Gnida and Dariusz Kaczorowski*<br />

Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Poland<br />

UPGRADED


SF12<br />

Unusual normal-state magnetotransport in the heavy-fermi<strong>on</strong><br />

superc<strong>on</strong>ductor Ce 2PdIn 8<br />

Daniel Gnida*, Marcin Matusiak and Dariusz Kaczorowski<br />

Institute of Low Temperature and Structure Research, Polish Academy of Sciences,<br />

Poland<br />

The normal-state behavior in the heavy-fermi<strong>on</strong> superc<strong>on</strong>ductor Ce 2PdIn 8 [1,2] has<br />

been probed by means of Hall coefficient (RH) and transverse magnetoresistivity (MR)<br />

measurements. Anomalous n<strong>on</strong>-Fermi-liquid-like features, observed below 8 K in<br />

both RH(T) and MR(T), are related to underlying quantum critical point, previously<br />

evidenced in the specific heat and the electrical resistivity data [1-5]. Intriguing<br />

magnetotransport properties observed in this compound exhibit close similarity to those<br />

reported before for CeCoIn 5 and can be explained in terms of the recently developed<br />

theory in which anisotropy of the Fermi surface and str<strong>on</strong>g backflow scattering of<br />

charge carriers <strong>on</strong> critical AF spin fluctuati<strong>on</strong>s are taken into account. What’s more,<br />

the magnetotransport in Ce 2PdIn 8 is shown to exhibit novel types of scaling that may<br />

appear universal for similar systems being at the verge of magnetic instability.<br />

[1] D.Kaczorowski, A.Pikul, D.Gnida, and V.H.Tran, Phys. Rev. Lett. 103 (2009) 027003; ibid<br />

104 (2010) 059702. [2] D.Kaczorowski, D.Gnida, A.Pikul, and V.H.Tran, Solid State Commun.<br />

150 (2010) 411. [3] J.K.D<strong>on</strong>g, H.Zhang, X.Qiu, B.Y.Pan, Y.F.Dai, T.Y.Guan, S.Y.Zhou, D.Gnida,<br />

D.Kaczorowski, and S.Y.Li, Phys. Rev. X 1 (2011) 011010. [4] Y.Tokiwa, P.Gegenwart, D.Gnida, and<br />

D.Kaczorowski, Phys. Rev. B 84 (2011) 140507(R). [5] V.H.Tran, D.Kaczorowski, R.T.Khan, and<br />

E.Bauer, Phys. Rev. B 83 (2011) 064504.<br />

SF13<br />

Specific heat and thermal c<strong>on</strong>ductivity studies of UCu4+xAl8-x compounds<br />

Farzana Nasreen 1 , Milt<strong>on</strong> Torikachvili 2 , Karunakar Kothapalli 3 , Yoshimitsu Kohama4,<br />

Vivien Zapf 5 and Heinrich Nakotte 6 *<br />

1<br />

Department of Physics & Astr<strong>on</strong>omy, University of Nevada, Las Vegas, NV 89154, USA<br />

2<br />

Department of Physics, San Diego State University, San Diego CA 92182, USA<br />

3<br />

Department of Material Science and Engineering, University of Maryland, College Park, MD, 20744, USA<br />

4<br />

The Institute for Solid State Physics, The University of Tokyo, Japan<br />

5<br />

MPA-Nati<strong>on</strong>al High Magnetic Field Laboratory, Los Alamos Nati<strong>on</strong>al Laboratory, Los Alamos, New<br />

Mexico 87545, USA<br />

6<br />

Department of Physics, New Mexico State University, Las Cruces, NM 88003, USA<br />

We report the thermal-c<strong>on</strong>ductivity and specific-heat measurements for eight UCu 4+xAl 8-x compounds (0 ≤ x<br />

≤ 2.0) as a functi<strong>on</strong> of temperature and magnetic field. Previous studies provided evidence of a transiti<strong>on</strong> from<br />

magnetic to a n<strong>on</strong>-magnetic heavy fermi<strong>on</strong> state at xcr = 1.15. Here we present complementary thermal-property<br />

studies as a functi<strong>on</strong> of temperature (55 mK - 300 K) and applied magnetic field (0 - 15 T). Specific heat data<br />

of n<strong>on</strong>-magnetic compound at xcr = 1.15 shows logarithmic divergence of low-temperature C/T and this n<strong>on</strong>-<br />

Fermi liquid (NFL) behavior can be attributed to the proximity of a quantum critical point. N<strong>on</strong>-magnetic<br />

compounds with higher Cu c<strong>on</strong>tent (x > xcr) exhibit unusual temperature scaling in the specific heat possibly due<br />

to an increase in disorder between Cu and Al. The complete study of magnetic field effect <strong>on</strong> NFL behavior was<br />

hampered by high c<strong>on</strong>tributi<strong>on</strong> from nuclear Schottky anomaly at low temperatures. The thermal c<strong>on</strong>ductivity<br />

data show stark c<strong>on</strong>trast between the magnetic (x = 0.5) and n<strong>on</strong>-magnetic compound (x = 1.75) - as evidenced<br />

in Lorentz numbers for example. Our results c<strong>on</strong>firm that a simple free-electr<strong>on</strong> picture is inadequate for the<br />

descripti<strong>on</strong> of the low-temperature thermal c<strong>on</strong>ductivity properties in n<strong>on</strong>-magnetic UCu 4+xAl 8-x compounds.<br />

SF14<br />

Dynamical cluster approximati<strong>on</strong> results of the two-orbital Hubbard<br />

model<br />

Hunpyo Lee 1 , Yu-zh<strong>on</strong>g Zhang 2 , Harald Jeschke 1 and Roser Valenti 1 *<br />

1 Institute for Theoretical Physics, University of Frankfurt, Germany<br />

2 Physics, T<strong>on</strong>gji University, China<br />

The orbital-selective phase transiti<strong>on</strong> (OSPT), which is induced by the interplay<br />

of a narrow band of localized electr<strong>on</strong>s and a wide band of itinerant electr<strong>on</strong>s, has<br />

been intensively explored in the multi-orbital systems. Using a dynamical cluster<br />

approximati<strong>on</strong> including the short-range correlati<strong>on</strong> as well as quantum fluctuati<strong>on</strong>s,<br />

we would like to analyze the behaviors of both degenerate two-orbital Hubbard<br />

model, where both orbitals have equal bandwidths and <strong>on</strong>e orbital is c<strong>on</strong>strained to be<br />

paramagnetic, while the sec<strong>on</strong>d <strong>on</strong>e is allowed to have an antiferromagnetic soluti<strong>on</strong><br />

and two-orbital Hubbard model with different bandwidth at half-filling. The OSPT,<br />

Fermi-liquid (FL), n<strong>on</strong>-FL, and insulator behaviors are observed in the both cases.<br />

Finally, we would discuss the implicati<strong>on</strong>s of the results in the c<strong>on</strong>text of the Fe-based<br />

superc<strong>on</strong>ductors.<br />

Phys. Rev. B 84, 020401(R) (2011). Ann. Phys. 523, No. 8-9, 689 (2011). Phys. Rev. Lett. 104,<br />

026402 (2010).<br />

SF15<br />

SG01<br />

SG02<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Renormalized parameters and c<strong>on</strong>vergence of energy scales <strong>on</strong> the<br />

approach to local quantum critical points<br />

D. J. G. Crow 1 *, Yunori Nishikawa 2 and Alex Hews<strong>on</strong> 1<br />

1 Department of Mathematics, Imperial College L<strong>on</strong>d<strong>on</strong>, United Kingdom<br />

2 Graduate School of Science, Osaka City University, Japan<br />

We c<strong>on</strong>sider a two impurity/dot Anders<strong>on</strong> model, where the impurities, hybridized<br />

with separate c<strong>on</strong>ducti<strong>on</strong> baths, are coupled by antiferromagnetic exchange interacti<strong>on</strong><br />

J and a direct interacti<strong>on</strong> U 12. The model has two types of quantum critical points<br />

associated, respectively, with a transiti<strong>on</strong> between K<strong>on</strong>do singlet to a local state, and<br />

a transiti<strong>on</strong> to a local charge ordered state. Using exact expressi<strong>on</strong>s for the spin and<br />

charge susceptibilities in terms of renormalized parameters we predict the values of<br />

the renormalized parameters <strong>on</strong> the approach to both types of critical point in terms<br />

of a single energy scale T*, such that at the critical point T*--> 0. From numerical<br />

renormalizati<strong>on</strong> group calculati<strong>on</strong>s we give complete phase diagram, and from an<br />

analysis of the low energy fixed point deduce the renormalized parameters. The results<br />

c<strong>on</strong>firm the predicti<strong>on</strong>s of the renormalized perturbati<strong>on</strong> theory and determine the<br />

value of T*. The emergence of a single energy scale which goes to zero at a quantum<br />

critical point may be a general feature which would lead to a natural explanati<strong>on</strong> of E/T<br />

scaling which has been observed at the quantum critical points of some heavy fermi<strong>on</strong><br />

compounds.<br />

NMR study of magnetic properties of Eu 1-xSrxMnO 3<br />

Kenji Shimizu 1 , Masanori Yamaguchi 1 , Shujuan Yuan 2 and Shixun Cao 2<br />

1 Physics, Faculty of Science, University of Toyama, Japan<br />

2 Physics, Shanghai University, China<br />

Perovskite-type manganite EuMnO 3 is known to be a compound with narrow eg-band<br />

width due to small Eu 3+ i<strong>on</strong>ic radius compared to La 3+ . The Eu 1-xSrxMnO 3 shows complex<br />

magnetic properties, depending <strong>on</strong> Sr c<strong>on</strong>centrati<strong>on</strong> x [1,2]. We have carried out 55Mn<br />

spin-echo NMR measurements <strong>on</strong> polycrystalline Eu 1-xSrxMnO 3 (0≤x≤0.5) samples<br />

at 4.2 or 1.4K, in order to clarify the microscopic local magnetic state of Mn i<strong>on</strong>s and<br />

the inhomogeneity in the compounds. Typical NMR spectra have been observed in the<br />

frequency range from 250MHz to 400MHz. For the A-type antiferromagnetic EuMnO 3,<br />

the res<strong>on</strong>ance frequency is about 260MHz, which is much lower than that observed for<br />

Mn 3+ in La 1-xSrxMnO 3. For 0.1 ≤ x ≤ 0.4, the res<strong>on</strong>ance lines, corresp<strong>on</strong>ding to Mn 4+ and<br />

Mn 3+ , have been observed around 310MHz and 390MHz, respectively. Furthermore,<br />

the spectra originated from Mn 2+ have been observed around 590MHz for 0.1≤x≤0.4.<br />

For Eu 0.5Sr 0.5MnO 3, the NMR spectrum spreads widely with several distinct peaks in the<br />

frequency range from 250MHz to 410MHz. In Eu 1-xSrxMnO 3, the spin-glass like behavior<br />

has been observed around x = 0.5[1,3]. The present NMR spectrum for Eu 0.5Sr 0.5MnO 3<br />

shows that the compound is in the inhomogeneous state due to competiti<strong>on</strong> between the<br />

antiferromagnetic and the ferromagnetic interacti<strong>on</strong>s.<br />

[1] Y. Tomioka et al., Phys. Rev. B 80 (2009) 174414. [2] Y. Tadokoro et al., Solid State I<strong>on</strong>ics 108<br />

(1998) 261. [3] A. Sundaresan et al., Phys. Rev. B 55 (1997) 5596.<br />

NMR study of successive magnetic transiti<strong>on</strong>s in A-site ordered<br />

perovskite LaMn 3Cr 4O 12<br />

Y. Kawasaki 1 , S. Takase 1 , Y. Kishimoto 1 , T. Ohno 1 , I. Yamada 2 , K Shiro 2 , R.<br />

Takahashi 2 , K. Ohgushi 3 , N. Nishiyama 4 , T. Inoue 4 and T. Irifune 4<br />

1 Institute of Technology and Science, The University of Tokushima, Japan<br />

2 Graduate School of Science and Engineering, Ehime University, Japan<br />

3 Institute for Solid State Physics, University of Tokyo, Japan<br />

4 Geodynamics Research Center, Ehime University, Japan<br />

In a simple ABO3 perovskite, when 75% of the A-site cati<strong>on</strong>s are substituted by another<br />

element, an A-site-ordered perovskite with a chemical formula of A'A 3B 4O 12 can be formed.<br />

These materials have attracted much attenti<strong>on</strong>, because they show a rich variety of physical<br />

phenomena, such as heavy-fermi<strong>on</strong> behavior in CaCu 3Ru 4O 12 and giant magnetoresistance<br />

in CaCu 3Mn 4O 12. These features may be related to the A-A and A-B exchange interacti<strong>on</strong>s in<br />

additi<strong>on</strong> to the usual B-B exchange interacti<strong>on</strong> seen in simple perovskite materials. Recently,<br />

new A-site ordered perovskite, LaMn 3Cr 4O 12, was prepared by using high pressure synthesis.<br />

The measurements of magnetic susceptibility and specific heat suggest two antiferromagnetic<br />

transiti<strong>on</strong>s at 150 K and 50 K in LaMn 3Cr4O 12. In this c<strong>on</strong>ference, we report microscopic<br />

investigati<strong>on</strong> <strong>on</strong> the magnetic properties of this material probed by La NMR. The res<strong>on</strong>ance<br />

line moderately broadens below 150 K and disappears below 50 K. These results are<br />

c<strong>on</strong>sistent with the two antiferromagnetic transiti<strong>on</strong>s. The temperature dependence of Knight<br />

shift indicates that the transiti<strong>on</strong> at 150 K is associated with the B-site Cr spin ordering and<br />

the other at 50 K is due to the A-site Mn spin ordering.<br />

July 8 - 13, 2012 Busan, Korea 225<br />

Poster Friday


Poster Friday<br />

SG03<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic properties of single crystalline U 2Fe 3Ge<br />

Margarida Henriques 1 *, Denis Gorbunov 2 , Ladislav Havela 3 , Alexander Andreev 2 and<br />

Ant<strong>on</strong>io G<strong>on</strong>calves 1<br />

1 UCQR, Technological and Nuclear Institute, Portugal<br />

2 Institute of Physics, Academy of Sciences of the Czech Republic, Czech Republic<br />

3 Department of C<strong>on</strong>densed Matter Physics, Faculty of Mathematics and Physics,<br />

Charles University, Czech Republic<br />

A number of Laves phases exist in intermetallic compounds based <strong>on</strong> uranium and<br />

transiti<strong>on</strong> metals. The compact structure of such phases, which leads to small U-U<br />

spacing and high U coordinati<strong>on</strong> numbers, gives rise to the 5f band and str<strong>on</strong>g<br />

hybridizati<strong>on</strong> with the n<strong>on</strong>-f states. U 2Fe 3Ge is a new ternary Laves phase [1],<br />

crystallizing in the Mg 2Cu 3Si-type structure, an ordered variant of the hexag<strong>on</strong>al<br />

MgZn 2-type (C14, P6 3/mmc). It exhibits very short U-U distances (below the Hill limit)<br />

al<strong>on</strong>g the c-axis (3.2 Å), still reaching a ferromagnetic order ( T C = 55 K). Surprisingly<br />

the Fe sub-lattice does not carry any significant ordered moment. A single crystal of<br />

U 2Fe 3Ge was prepared by the Czochralski method (a = 5.182(2) Å and c = 7.850(1) Å).<br />

Magnetizati<strong>on</strong> isotherms measured al<strong>on</strong>g the principal axes indicate that the magnetic<br />

moments lie in the basal plane of the hexag<strong>on</strong>al lattice, with the sp<strong>on</strong>taneous magnetic<br />

moment of 1 μ B/f.u. and no anisotropy within the basal plane. Magnetic moments<br />

are therefore perpendicular to the nearest U-U link, but the anisotropy values are<br />

anomalously low comparing e.g. to isostructural UNi 2.<br />

[1] M.S. Henriques et al., Solid State Commun. 148 (2008) 159.<br />

SG04<br />

Magnetic properties of a 5d transiti<strong>on</strong> metal oxide AOsO 4 (A = K, Rb,<br />

Cs)<br />

Junichi Yamaura, Kenya Ohgushi and Zenji Hiroi<br />

Institute for Solid State Physics, University of Tokyo, Japan<br />

We investigate the magnetic properties of AOsO 4 (A = K, Rb, Cs) which takes a 5d 1<br />

electr<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong> and would provide us with an interesting playground for spinorbit<br />

physics. The compound crystallizes in the scheelite structure comprising a<br />

distorted diam<strong>on</strong>d network of Os atoms. Magnetic susceptibility at high temperatures<br />

shows Curie-Weiss behavior with Weiss temperatures of -94, -29 and 12 K for the K,<br />

Rb and Cs compounds, respectively. For the K and Rb compounds, broad humps are<br />

observed at 55 and 35 K up<strong>on</strong> cooling and followed by antiferromagnetic transiti<strong>on</strong>s<br />

at 38 and 22 K, respectively. For the Cs compound, in c<strong>on</strong>trast, no antiferromagnetic<br />

transiti<strong>on</strong> is observed down to 2 K, but an anomaly appears at 151 K, below which<br />

the Weiss temperature is reduced to 3 K. Markedly, the magnetic effective moments<br />

estimated from the Curie c<strong>on</strong>stants are 0.85, 0.84, and 0.86 Bohr magnet<strong>on</strong> for the K,<br />

Rb, and Cs compounds, which are much smaller than the spin-<strong>on</strong>ly value of 1.73 Bohr<br />

magnet<strong>on</strong> for S = 1/2. Probably a large spin-orbit coupling must be taken into account.<br />

SG05<br />

Enhancement of curie temperature due to the coupling between fe<br />

itinerant electr<strong>on</strong>s and Dy localized electr<strong>on</strong>s in DyFe 2Zn 20<br />

Yosikazu Isikawa 1 , Toshio Mizushima 1 , Souta Miyamoto 1 , Keigou Kumagai 1 , Mako<br />

Nakahara 1 , Hiroaki Okuyama 1 , Takashi Tayama 1 , Tomohiko Kuwai 1 and Pascal Lejay 2<br />

1 Graduate School of Science and Engineering, University of Toyama, Japan<br />

2 Institute Neel, MCMF, CNRS, France<br />

The cubic RX2Zn20 has been recently insensitively examined, where R is rare<br />

earth atom and X is Fe, Co, Ru, etc. The exchange interacti<strong>on</strong> between R-R is weak<br />

because R atoms are diluted in this compound. In fact, for X = Co and Ru, Tc is less<br />

than 10 K for any R. In the case of Fe, however, Tc is significantly enhanced, and<br />

the origin of this high Tc is suspected to be involved the magnetism of Fe atoms. But<br />

the origin is not clear at present. We examined the magnetic properties and specific<br />

heat of DyFe2Zn20, and revealed experimentally unusual magnetic anisotropies, i.e.,<br />

large magneto-crystalline anisotropy at 2 K, which nature, however, disappears in the<br />

temperatures above 30 K below Tc. We analyzed these anomalous properties based <strong>on</strong><br />

the three assumpti<strong>on</strong>s: (1) crystalline electric field and exchange interacti<strong>on</strong> between<br />

R and R, (2) simplified Moriya theory for Fe, and (3) exchange interacti<strong>on</strong> between<br />

R and Fe. As a result, the enhancement of Tc, the str<strong>on</strong>g magnetic anisotropy at low<br />

temperatures, the disappearance of the magnetic anisotropy below Tc down to 30 K,<br />

and no anomaly of magnetic specific heat at Tc, etc. were well reproduced by this<br />

calculati<strong>on</strong>.<br />

226 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SG06<br />

Anomalous increase of TC in UGa 2 under pressure<br />

Ladislav Havela 1 , A. Kolomiets 2 , J. Prchal 1 and A. V. Andreev 3<br />

1 Department of C<strong>on</strong>densed Matter Physics, Charles University, Czech Republic<br />

2 Department of Physics, Lviv Polytechnic Nati<strong>on</strong>al University, Ukraine<br />

3 Institute of Physics, Academy of Sciences of the Czech Pepublic, Czech Republic<br />

SG07<br />

Phase transiti<strong>on</strong> between paramagnetic and spin polarized states in<br />

MnSi<br />

Sergey Demishev*, Vladimir Glushkov, Inna Lobanova, Vsevolod Ivanov, Nickolay<br />

Sluchanko and Alexey Semeno<br />

Low Temperatures and Cryogenic Engineering, General Physics Institute of RAS,<br />

Russia<br />

The of high-field regi<strong>on</strong> of the magnetic phase diagram of MnSi is probed by magnetizati<strong>on</strong>,<br />

resistivity and magnetoresistance measurements carried out in the temperature range 1.8-300 K<br />

for magnetic fields up to 8 T [1]. It is shown that the phase boundary between paramagnetic (PM)<br />

phase and spin-polarized (SP) phase is well-defined, has no positive slope as it was suggested<br />

previously, and appears to be practically vertical corresp<strong>on</strong>ding to transiti<strong>on</strong> temperature Tc~30 K.<br />

We argue that broad maxima of the resistivity and magnetizati<strong>on</strong> derivatives, which develops in<br />

the diapas<strong>on</strong> T >Tc, are not associated with a “diffuse” SP-PM transiti<strong>on</strong> and are a c<strong>on</strong>sequence<br />

of the specific form of functi<strong>on</strong>al dependences of these quantities in the paramagnetic phase. It<br />

is found that in the paramagnetic phase of MnSi a universal relati<strong>on</strong> between magnetoresistance<br />

and magnetizati<strong>on</strong>, Δρ/ρ= a0M 2 , holds in a wide range where magnetoresistance vary by<br />

more than two orders of magnitude. The analysis of the transport and magnetic res<strong>on</strong>ance data<br />

favors the explanati<strong>on</strong> of magnetic properties of MnSi by Heisenberg-type localized magnetic<br />

moments rather than by itinerant magnetism approach. A low temperature anomaly at T~15K<br />

corresp<strong>on</strong>ding to magnetoresistance and g factor changes is reported.<br />

1. S.V.Demishev et al., Phys. Rev.B 85, 045131 (2012)<br />

SG08<br />

ESR in mnsi: Heisenberg localized magnetic moments and spin<br />

polar<strong>on</strong>s<br />

Sergey Demishev*, Alexey Semeno, Vladimir Glushkov, Nickolay Sluchanko and<br />

Nickolay Samarin<br />

Low Temperatures and Cryogenic Engineering, General Physics Institute of RAS,<br />

Russia<br />

High frequency (60 GHz) electr<strong>on</strong> spin res<strong>on</strong>ance (ESR) has been studied in<br />

manganese m<strong>on</strong>osilicide, MnSi, single crystals [1]. The measurements performed<br />

within the 4.2-300 K temperatures range at the applied magnetic field up to 70<br />

kOe have dem<strong>on</strong>strated that the magnetic res<strong>on</strong>ance in MnSi is due to localized<br />

magnetic moments of the Heisenberg type with the g factor depending <strong>on</strong>ly slightly<br />

<strong>on</strong> temperature, g ~ 1.9-2. At the same time, it has been found that the ESR linewidth<br />

is determined by spin fluctuati<strong>on</strong>s and can be quantitatively described in the wide<br />

temperature range (4.2 K < T < 60 K) in the framework of the Moriya theory using<br />

the SL(T) functi<strong>on</strong>. The revealed deviati<strong>on</strong>s from the model of weak itinerant electr<strong>on</strong><br />

magnetism comm<strong>on</strong>ly used for the descripti<strong>on</strong> of the magnetic properties of MnSi<br />

indicate a possible spin-polar<strong>on</strong> nature of the unusual magnetic properties of this<br />

str<strong>on</strong>gly correlated metal.<br />

1. S.V.Demishev et al., JETP Letters, 93, 213 (2011)<br />

UPGRADED


SG09<br />

Magnetic susceptibility measurements at high pressures down to T=0.5<br />

K with SQUID magnetometer<br />

Yoshiaki Sato 1 *, Shun Makiyama 1 , Yasutaka Sakamoto 1 , Tadahiko Hasuo 1 , Yuji<br />

Inagaki 1 , Tetsuya Fujiwara 2 and Tatsuya Kawae 1<br />

1 Department of Applied Quantum Physics, Kyushu University, Japan<br />

2 Graduate School of Science and Engineering, Yamaguchi University, Japan<br />

We develop a 3He-insert attached to MPMS SQUID magnetometer and a pressure<br />

cell in order to measure magnetic susceptibility and magnetizati<strong>on</strong> precisely at high<br />

pressures down to T=0.5 K[1]. The 3He insert is made by stainless steel pipe with the<br />

inner diameter of 6.2mm and outer diameter of 6.5 mm. The liquid 3He is c<strong>on</strong>densed<br />

in the stainless pipe. The vacuum jacket made of a copper pipe with the outer diameter<br />

of 8.6 mm is soldered to the stainless pipe, which is also used for the heat exchange<br />

between 3He gas and 4He bath at T=1.7K. The temperature was measured by RuO 2<br />

thermometer mounted <strong>on</strong> the 3He c<strong>on</strong>tainer. A main body of pist<strong>on</strong>-cylinder pressure<br />

cell is made from Be-Cu. The outer diameter of the cell is 6 mm, while the inner<br />

diameter is 1.8mm which corresp<strong>on</strong>ds to the size of the tefl<strong>on</strong> cell.<br />

[1] Y. Sato, Y. Nakamura, H. Morodomi, T. Hasuo, Y.Inagaki, T. Kawae, H. S. Suzuki and T. Kitai:<br />

To be appeared in Journal of Physics: <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> Series.<br />

SG10<br />

Extincti<strong>on</strong> of photo-luminescence of Mn-doped ZnS nanocolloids in<br />

weak magnetic field<br />

H<strong>on</strong>g-van Bui 1 , Van-ben Pham 1 , Nam-nhat Hoang 2 * and Van-chau Dinh 2<br />

1<br />

Faculty of Physics, Vietnam Nati<strong>on</strong>al University, University of Natural Sciences, Viet<br />

Nam<br />

2<br />

Faculty of Technical Physics and Nanotechnology, Vietnam Nati<strong>on</strong>al University,<br />

University of Engineering and Technology, Viet Nam<br />

The extincti<strong>on</strong> of light passing through a nanocolloidal medium c<strong>on</strong>taining ferromagnetic oxide<br />

(such as Fe 3O 4) putting inside a cavity of weak magnetic field has been observed [1-3]. Here for<br />

the first time we report the extincti<strong>on</strong> of photo-luminescence of Mn-doped ZnS nanocolloid under<br />

the applied field of 270 Gauss. The Mn-doped ZnS nanopowders have been synthesized by using<br />

the hydrothermal method from zinc acetate and natri thiosulfat as the precursors (with SPAN-80<br />

as the surfactant). The particle size was determined to be within 10-20 nm; the lattice c<strong>on</strong>stant a<br />

= 5.41(2) A. The exitati<strong>on</strong> wavelength was 623.8 nm from a He-Ne laser. We have observed a<br />

systematic reducti<strong>on</strong> of photo-luminescence of a given liquid nanocolloid with time at applied field<br />

of 270 Gauss, despite of the field directi<strong>on</strong> and field development (upwards or downwards). The<br />

50% extincti<strong>on</strong> was achieved after 30 min and the saturati<strong>on</strong> extincti<strong>on</strong> after 1 hour. The memory<br />

effect was shown to preserve for more than 2 hours. We have measured the temperature of the<br />

sample during the experiment which was kept c<strong>on</strong>stant at 70 oC. We believe the PL extincti<strong>on</strong> was<br />

associated with the magnetic ordering but the ordering inside a liquid medium is a surprise.<br />

1. John Philip, J. M. Laskar and Baldev Raj. Appl. Phys. Lett. 92, 221911 (2008). 2. Rajesh Patel. Pure Appl. Opt. 11 (2009)<br />

125004 (5pp). 3. R.V. Mehta, Rajesh Patel, Rucha Desai, R.V. Upadhyay and Kinnari Parekh. Phys. Rev. Lett. 96,127402 (2006).<br />

SG11<br />

Electr<strong>on</strong>ic structure of A-site ordered perovskite CaCu3Ti4O12 studied<br />

by angle-resolved photoemissi<strong>on</strong> spectroscopy<br />

H. J. Im 1 *, M. Tsunekawa 2 , T. Sakurada 1 , K. Kawata 1 , T. Watanabe1, K. Takegahara 1 ,<br />

H. Miyazaki 3 and S. Kimura 4<br />

1<br />

Department of Advanced Physics, Hirosaki University, Japan<br />

2<br />

Faculty of Educati<strong>on</strong>, Shiga University, Japan<br />

3<br />

Department of Envir<strong>on</strong>mental and Materials Engineering, Nagoya Institute of<br />

Technology, Japan<br />

4<br />

UVSOR Facility, Institute for Molecular Science, Japan<br />

We present angle-resolved photoemissi<strong>on</strong> spectroscopy (ARPES) results of A-site<br />

ordered perovskite CaCu 3Ti 4O 12 (CCTO), which shows extremely high-dielectric<br />

c<strong>on</strong>stant over a wide range of temperature from 100 to 600 K and has an insulator<br />

phase in c<strong>on</strong>trast to a metal phase from the result of LDA band calculati<strong>on</strong>. We have<br />

observed the clear band dispersi<strong>on</strong>s, located in the higher binding energy than that<br />

expected in the LDA calculati<strong>on</strong>, and the negligible spectral weight at the Fermi level<br />

in agreement with the results of electrical resistivity measurements. From the ARPES<br />

results, we suggest that CCTO is Mott-insulator caused by the str<strong>on</strong>g correlati<strong>on</strong> effects<br />

of the electr<strong>on</strong>s in Cu 3d - O 2p hybridizati<strong>on</strong> bands.<br />

SG12<br />

SG13<br />

SG14<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Evidence of rattling transiti<strong>on</strong> in caged compounds LaRu 2Zn 20 and<br />

LaIr 2Zn 20: La-NMR studies<br />

Hideki Tou 1 *, Kenji Asaki 1 , Hisahi Kotegawa 1 , Takahiro Onimaru 2 , Keisuke T.<br />

Matsumoto 2 , Yukihiro F Inoue 2 and Toshiro Takabatake 2<br />

1 Department of Physics, Graduate School of Science, Kobe University, Japan<br />

2 ADSM, Hiroshima University, Japan<br />

Recently, RT 2Zn 20 (R = Pr, La; T = Ir, Ru) has attracted much attenti<strong>on</strong> because of the coexistence of<br />

superc<strong>on</strong>ductivity and a quadrupole ordered state observed in PrIr 2Zn 20[1,2] Superc<strong>on</strong>ductivity is also observed<br />

in LaRu 2Zn 20 (Tc=0.2 K) and LaIr2Zn20 (Tc=0.6 K), but not in PrRu 2Zn 20[1]. PrRu 2Zn 20 and LaRu 2Zn 20<br />

undergo first-order structural phase transiti<strong>on</strong> at Ts=138 and 150 K, respectively, whereas LaIr 2Zn 20 undergoes<br />

sec<strong>on</strong>d-order structural phase transiti<strong>on</strong> at Ts=200 K. To investigate the structural phase transiti<strong>on</strong> in RT 2Zn 20,<br />

139La(I=7/2) nuclear magnetic res<strong>on</strong>ance (NMR) measurements have been carried out for LaRu 2Zn 20 and<br />

LaIr 2Zn 20. For both compounds, quite narrow La-NMR line-widths less than 5 kHz without nuclear quadrupole<br />

splittings above Ts changes their spectral shape with broad tails distributed over the frequency range of 0.8 MHz,<br />

evidencing the lowering of the symmetry at La site[3]. Around Ts, the nuclear spin-lattice relaxati<strong>on</strong> rate (1/T1)<br />

show an unusual enhancement associated with the slowing down of the EFG fluctuati<strong>on</strong>s[3].To gain further<br />

insights, we have measured the nuclear spin-spin relaxati<strong>on</strong> rate (1/T2) for both compounds. We have found that<br />

the temperature dependence of 1/T2 has maximum around Ts associated with the structural phase transiti<strong>on</strong>. We<br />

will discuss low-energy spin dynamics in RT 2Zn 20 from microscopic points of view.<br />

[1] T. Onimaru, K. T. Matsumoto, Y. F. Inoue, K. Umeo, Y. Saiga, Y. Matsushita, R. Tamura, K. Nishimoto, I.<br />

Ishii, T. Suzuki, and T. Takabatake: J. Phys. Soc. Jpn. 79 (2010) 033704. [2] T. Onimaru, K. T. Matsumoto,<br />

Y. F. Inoue, K. Umeo, T. Sakakibara, Y. Karaki, M. Kubota, and T. Takabatake: Phys. Rev. Lett. 106 (2011)<br />

177001. [3] K. Asaki, H. Kotegawa, H. Tou, T. Onimaru, K. T. Matsumoto, Y. F. Inoue, T. Takabatake<br />

Unc<strong>on</strong>venti<strong>on</strong>al magnetic ordering in spin-orbit mott insulator with<br />

h<strong>on</strong>eycomb lattice<br />

Soham Manni 1 *, Yogesh Singh 2 and Phlipp Gegenwart 1<br />

1 I. Physikalisches Institut, Georg-August-Universitaet Goettingen, Germany<br />

2 IISER Mohali, India<br />

Iridates have recently attracted much attenti<strong>on</strong> due to a novel $S_{\rm eff}=1/2$ Mott insulating state,<br />

driven by the interplay of moderate electr<strong>on</strong>ic correlati<strong>on</strong>s with str<strong>on</strong>g spin-orbit coupling. We have<br />

synthesized A 2IrO 3 (A=Na,Li) which is a layered system with Ir moments sitting <strong>on</strong> a H<strong>on</strong>eycomb lattice.<br />

Theoretically, this system has been proposed as solid-state realizati<strong>on</strong> of the Heisenberg-Kitaev(HK)<br />

model, treating the superpositi<strong>on</strong> of isotropic antiferromagnetic exchange and highly anisotropic Kitaev<br />

type ferromagnetic nearest neighbor exchange. HK model predicts gapless spin-liquid ground state with<br />

Majorana fermi<strong>on</strong>ic excitati<strong>on</strong>s in Kitaev Limit[1]. Na 2IrO 3 shows a Mott insulating state of $S_{\rm<br />

eff}=1/2$ moments with predominant antiferromagnetic coupling, indicated by a Weiss temperature of<br />

$\Theta_W=-116$ K[2]. A bulk antiferromagnetic transiti<strong>on</strong> occurs at a much reduced temperature of<br />

$T_N = 15$ K, indicates substantial frustrati<strong>on</strong>. Res<strong>on</strong>ant X-ray magnetic scattering for the Na system<br />

indicates an unc<strong>on</strong>venti<strong>on</strong>al most-likely zig-zag magnetic structure[3]. For Mott insulating Li 2IrO 3 we<br />

observe a similar ordering temperature of 15 K, while the $\Theta_W$ is drastically reduced to $-33K$.<br />

These observati<strong>on</strong>s are compatible with an enhancement of the Kitaev c<strong>on</strong>tributi<strong>on</strong> compared to the<br />

Na-system, suggesting that Li 2IrO 3 is located closer to the Kitaev limit[4]. Work supported by Erasmus<br />

Mundus EURINDIA project and the AvH foundati<strong>on</strong>.<br />

[1] J. Chaloupka et al., Phys. Rev. Lett. 105, 027204 (2010). [2] Y. Singh and P. Gegenwart, Phys. Rev. B 82, 064412 (2010). [3] X.<br />

Liu et al., Y.Singh et al., Phys. Rev. B {\bf 83}, 220403(R) (2011). [4] Y. Singh, S. Manni, P. Gegenwart, arXiv:1106.0429<br />

YCr 6Ge 6: A kagome metal?<br />

Yui Ishii 1 *, Yoshihiko Okamoto 1 , Junichi Yamaura 1 , Hisatomo Harima 2 and Zenji<br />

Hiroi 1<br />

1 ISSP, Univ. Tokyo, Japan<br />

2 Dept. of Physics, Kobe Univ., Japan<br />

Itinerant electr<strong>on</strong>s <strong>on</strong> a kagome lattice are known to generate a flat band without<br />

dispersi<strong>on</strong>. It is expected that the flat band causes exotic phenomena induced by the<br />

kagome geometry such as a flat-band ferromagnetism. However, this has not been<br />

experimentally observed in real compounds, possibly because the flat band tends to<br />

be located far from the Fermi level. We have been looking for a candidate compound<br />

to realize “kagome metal” and recently focused <strong>on</strong> YCr 6Ge 6. It crystallizes in the<br />

HfFe 6Ge 6-type structure (space group P6/mmm) where Cr atoms form a kagome lattice.<br />

Band-structure calculati<strong>on</strong>s show that a flat band really exists slightly below EF<br />

near the Γ point toward the Κ and Μ points. This suggests that hole doping, such as<br />

the chemical substituti<strong>on</strong> of Ga for Ge, would make the flat band emerge at EF. We<br />

successfully synthesized single crystals of YCr 6Ge 6 and YCr 6Ge 6-xGax by the flux<br />

method. A Curie-Weiss like behavior is observed in magnetic susceptibility for both<br />

compounds. We will show the magnetic and transport properties and try to reveal the<br />

characteristics of the kagome metal.<br />

July 8 - 13, 2012 Busan, Korea 227<br />

Poster Friday


Poster Friday<br />

SG15<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Raman scattering spectra of PrRu 2Zn 20<br />

Norio Ogita 1 *, Takumi Hasegawa 1 , Masayuki Udagawa 1 , Keisuke Matsumoto 2 ,<br />

Takahiro Onimaru 2 and Toshiro Takabatake 2<br />

1 Graduate School of Arts and Sciences, Hiroshima Univ., Japan<br />

2 Graduate School of Advanced Sciences of Matter, Hiroshima Univ., Japan<br />

PrRu 2Zn 20 has the cubic structure with Fd-3m, where Pr-i<strong>on</strong> is encapsulated in<br />

the Frank-Kasper cage by 16 Zn atoms. In analogy of the filled skutterudites, this<br />

compound is expected to be observed an anharm<strong>on</strong>ic Pr vibrati<strong>on</strong> and exotic physical<br />

properties due to orbital degrees of freedom of the local f electr<strong>on</strong>s. shows structural<br />

transiti<strong>on</strong> at Ts=138K and remains a normal state in electr<strong>on</strong>ic c<strong>on</strong>ductivity down<br />

to 0.04K. On the other hand, isostructural PrIr 2Zn 20 shows an antiferro-quadrupolar<br />

ordering(Tq=0.11K) and a superc<strong>on</strong>ductivity(Tc=0.05K), without structural change<br />

above Tq. The difference of the low temperature properties between PrRu 2Zn 20 and<br />

PrIr 2Zn 20 might be originated from the structural transiti<strong>on</strong>, however, the origin of the<br />

structural transiti<strong>on</strong> and also the crystallographic structure below Ts are not clarified.<br />

Therefore, we have measured Raman scattering spectra of PrRu 2Zn 20. Am<strong>on</strong>g the<br />

Raman active ph<strong>on</strong><strong>on</strong>s; 3Ag +4 Eg +9 T2g, 2Ag +4 Eg +6 T2g peaks are observed at room<br />

temperature. With decreasing temperature, 4 peaks are newly observed below Ts in<br />

T2g spectra. This suggests the structural change around Ts. In comparis<strong>on</strong> with Eg<br />

spectra, the observati<strong>on</strong> of the similar energy peaks in both spectra suggests the crystal<br />

structure below Ts seems to be lower than cubic structure.<br />

SG16<br />

Superc<strong>on</strong>ducting state in KSn 2 with a MgZn 2-type (C14) Laves phase<br />

structure<br />

Shota Miyazaki, Kenji Kawashima, Tsukasa Ipp<strong>on</strong>jima, Michinori Fukuma and Jun<br />

Akimitsu<br />

Physics and Mathematics, Aoyama Gakuin University, Japan<br />

We have been searching for a new superc<strong>on</strong>ductor including alkali metal elements<br />

using high pressure / high temperture technique. High-pressure synthesis technique has<br />

been successfully employed in the search for new materials and new superc<strong>on</strong>ductors.<br />

To use a closed system for high pressure synthesis is effective not <strong>on</strong>ly to stabilize a<br />

compositi<strong>on</strong> but also to expand a solid-soluti<strong>on</strong> range. We successfully synthesized<br />

the polycrystalline sample of KSn 2 as a main phase and discovered that KSn 2 was a<br />

superc<strong>on</strong>ductor with T c = 3.2 K. KSn 2 has a hexag<strong>on</strong>al MgZn 2-type (C14) structure<br />

(space group P6 3/mmc, No.194) called Laves phase. The magnetizati<strong>on</strong> versus<br />

magnetic field curve shows a typical type-ll superc<strong>on</strong>ducting behavior. We determined<br />

the lower critical field and penetrati<strong>on</strong> depth, to be about H c1(0) = 150 Oe and λ GL(0) =<br />

210 nm, respectively, using the Ginzburg-Landau equati<strong>on</strong>s. From the density of state<br />

calculati<strong>on</strong>s, we found that Sn p-orbital mainly c<strong>on</strong>tributes near the N(E F) level and<br />

plays an important role for the superc<strong>on</strong>ducting state in KSn 2.<br />

SG17<br />

Layered nanosized structures <strong>on</strong> basis of diluted magnetic<br />

semic<strong>on</strong>ductors and heusler alloys<br />

Evgeny Sergeevich Demidov*, Ekaterina Pavlova, Aleksandr Bobrov, Vitaliy<br />

Podolskii, Valeriy Lesnikov, Sergey Gusev and Ant<strong>on</strong> Tr<strong>on</strong>ov<br />

Solid State Electr<strong>on</strong>ics Chair, Nizhny Novgorod State University, Russia<br />

The laser and RF magnetr<strong>on</strong> synthesis of nanosized layers of the diluted magnetic semic<strong>on</strong>ductors<br />

(DMS) <strong>on</strong> the basis of compounds III-V and elementary semic<strong>on</strong>ductors Ge or Si with Mn or<br />

Fe impurities and Co 2MnSi Heusler alloys (HA) <strong>on</strong> single crystal substrates GaAs, Si or Al 2O 3<br />

with ferromagnetism till 500K was earlier dem<strong>on</strong>strated [1-3]. In this report our new researches<br />

of properties of DMS Si:Mn and magnetic tunnel juncti<strong>on</strong>s (MTJ) with ferromagnetic HA<br />

plates and dielectric interlayer are presented. The features of FMR of MTJ with ferromagnetic<br />

exchange interacti<strong>on</strong>, anisotropic negative magnetoresistance, I-V n<strong>on</strong>linearity and hysteresis<br />

of MTJ and single DMS and HA layers at small current density were observed at 77-300К.<br />

The high-resoluti<strong>on</strong> transmissi<strong>on</strong> electr<strong>on</strong> microscopy (HRTEM) and selected area electr<strong>on</strong><br />

diffracti<strong>on</strong> (SAED), made <strong>on</strong> JEM-2100F of JEOL, show that the laser synthesis of epitaxial<br />

layers of DMS Si:15%Mn/GaAs with Curie point 500K, perfect diam<strong>on</strong>d like crystal structure<br />

and self-organized superlattice is possible. Supported by RFBR (08-02-01222-a, 11-02-00855a),<br />

the Ministry of Educati<strong>on</strong> of Russian Federati<strong>on</strong> (projects 2.1.1/2833 and 2.1.1/12029) and<br />

the State c<strong>on</strong>tract № 02.740.11.0672 of the Federal purpose program 2009-2013 is acknowledged.<br />

[1] E.S. Demidov, V.V. Podolskii, V.P. Lesnikov et al, JETP, 106, 110 (2008). [2] E.S. Demidov, B.A. Ar<strong>on</strong>z<strong>on</strong>, S.N. Gusev et<br />

al, JMMM, 321 (2009) 690. [3] E.S. Demidov, b, V.V. Podolskii, B.A. Ar<strong>on</strong>z<strong>on</strong> et al, Bull. RAS: Physics, 74 (2010) 1389.<br />

228 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SG18<br />

Metal-insulator and spin-state transiti<strong>on</strong> in polycrystalline (Pr 1-yREy) 1xCaxCoO<br />

3 (RE=rare earth elements) in magnetic fields<br />

Tomoyuki Naito 1 *, Hiroko Sasaki 1 , Motoharu Kato 1 , Satoru Ogawa 1 , Hiroyuki<br />

Fujishiro 1 , Terukazu Nishizaki 2 and Norio Kobayashi 2<br />

1 Iwate University, Japan<br />

2 Institute for Materials Research, Tohoku University, Japan<br />

We have measured the temperature dependences of the resistivity and the<br />

magnetic susceptibility in various magnetic fields up to 17 T and 5 T, respectively,<br />

for polycrystalline (Pr 1-yREy) 1-xCaxCoO 3 (RE=rare earth elements). For<br />

(Pr 0.8Sm 0.2) 0.7Ca 0.3CoO 3 sample, a metal-insulator transiti<strong>on</strong> (MIT) and spin-state<br />

transiti<strong>on</strong> (SST) between the intermediate (IS) and the low spin (LS) states almost<br />

simultaneously took place around 40 K at 0 T. The MI-SST temperature decreased<br />

with increasing magnetic field, and the MI-SST was suddenly suppressed above 10 T.<br />

The MI-SST temperatures were about 38 K at 5 T and 29 K at 9 T. In the samples with<br />

higher y, in which the MI-SST temperature at 0 T was higher, the reducti<strong>on</strong> of the MI-<br />

SST temperature became small and the MI-SST survived up to the highest magnetic<br />

field in this study. The similar behavior was observed in other RE substituted samples.<br />

The obtained results suggest that the magnetic field stabilizes the IS state, which<br />

c<strong>on</strong>trasts with the fact that the applicati<strong>on</strong> of the external pressure induces the LS state.<br />

We discuss the origin of the magnetic field effect <strong>on</strong> the MI-SST.<br />

SG19<br />

Magnetic field-induced lattice effects in a quasi-2D organic c<strong>on</strong>ductor<br />

close to the Mott metal-insulator transiti<strong>on</strong><br />

Mariano De Souza 1 *, Andreas Bruel 2 , Christian Strack 2 , Dieter Schweitzer 3 and<br />

Michael Lang 2<br />

1 Physics, Universidade Estadual Paulista - Unesp (Sao Paulo State University), Brazil<br />

2 Physics, Goethe-Universitat Frankfurt, Germany<br />

3 Physics, Stuttgart Universitat, Germany<br />

Organic charge-transfer salts of the κ-phase (BEDT-TTF)$_2$X family have been recognized as prototypes for<br />

studying electr<strong>on</strong>ic correlati<strong>on</strong> phenomena [1]. Their ground states can be tuned either by varying the counter<br />

ani<strong>on</strong> X or by applying external pressure. For the X = Cu[N(CN) 2]Cl salt, for example, the ground state is an<br />

antiferromagnetic-Mott insulator, whereas for X = Cu[N(CN) 2]Br, it is a superc<strong>on</strong>ductor. Fully deuterated single<br />

crystals of the latter substance are located <strong>on</strong> the verge of the Mott metal-insulator (MI) transiti<strong>on</strong> and, for this<br />

reas<strong>on</strong>, c<strong>on</strong>stitute a material of particular interest for exploring the critical behavior of the π-electr<strong>on</strong> system<br />

around the Mott transiti<strong>on</strong> [2,3]. Here we present ultra-high-resoluti<strong>on</strong> dilatometry studies at varying magnetic<br />

fields <strong>on</strong> a fully deuterated X = Cu[N(CN) 2]Br salt. Our thermal expansi<strong>on</strong> data reveal two remarkable features:<br />

(i) the Mott MI transiti<strong>on</strong> temperature T$_{MI}$ = (13.6 ± 0.6)K is insensitive to fields up to 10 T, (ii) for<br />

fields al<strong>on</strong>g the interlayer b-axis, a B-induced first-order transiti<strong>on</strong> at T$_{SF}$ = (9.5 ± 0.5)K is observed.<br />

This transiti<strong>on</strong> manifests itself in a sharp negative spike in the expansivity, whose positi<strong>on</strong> is found to be field<br />

insensitive. Possible scenarios to describe this field-induced phase transiti<strong>on</strong> will be discussed.<br />

[1] N. Toyota, M. Lang, J. Muller, Low-Dimensi<strong>on</strong>al Molecular Metals 2007, Springer, Germany<br />

[2] M. de Souza, A. Bruehl, Ch. Strack, B. Wolf, D. Schweitzer, M. Lang, Phys. Rev. Lett. 99, 037003<br />

(2007) [3] L. Bartosch, M. de Souza, M. Lang, Phys. Rev. Lett. 104, 245701 (2010)<br />

SG20<br />

Metallic transiti<strong>on</strong> of the colossal magnetoresistance material FexMn1 xS (x=0.18) under high pressure<br />

Yoshimi Mita 1 *, Tomoko Kagayama 2 , G. M. Abramova 3 , G. A. Petrakovskii 3 and V. V.<br />

Sokolov 4<br />

1<br />

Materials Physics, Engineering Science, Osaka University, Japan<br />

2<br />

Center of Quantum Science and Technology under Extreme C<strong>on</strong>diti<strong>on</strong>s, Osaka<br />

University, Japan<br />

3<br />

L.V.Kirensky Institute of Physics, Russia<br />

4<br />

A.V.Nikolaev Institute of Inorganic Chemistry, Russia<br />

The discovery of the colossal magnetoresistance in FexMn 1-xS solid soluti<strong>on</strong>s [1] aroused<br />

many researcher’s interests in studying the physical properties of this system. We studied<br />

the pressure induced phase transiti<strong>on</strong> of FexMn 1-xS (x=0.18) by infrared (IR) reflecti<strong>on</strong> and<br />

X-ray analysis up to 40 GPa at room temperature. It is shown by X-ray analysis that the<br />

structure of this sample is NaCl type at ambient pressure and a structural change starts around<br />

17 GPa and the mixed phase between the NaCl type low pressure phase and the structure<br />

unknown high pressure phase c<strong>on</strong>tinues up to around 25 GPa. On the other hand, the IR<br />

reflectivity increases from 15 GPa and becomes highly remarkable around 20 GPa. The<br />

spectra do not show any changes from 30 GPa. These results suggest that the phase transiti<strong>on</strong><br />

of FexMn 1-xS (x=0.18) at room temperature starts around 15 GPa and completes around 30<br />

GPa and the high pressure phase is not a band overlapping semimetal but a true metallic.<br />

G.A. Petrakovskii, L.I. Ryabinkina, N.I. Kiselev, D.A. Velikanov, A.F. Bovina, G.M. Abramova, JETP<br />

Lett. 69 (1999) 949.


SG21<br />

Optimal design of IPMSM having double barrier for minimizing<br />

cogging torque and torque ripple<br />

Hyoung Uk Nam 1 , Hyun Rok Cha 1 , Kwang He<strong>on</strong> Kim 2 , Dae Young Lym 1 and Tae<br />

W<strong>on</strong> Je<strong>on</strong>g 1<br />

1 Automotive R&D, Korea Institute of Industrial Technology, Korea<br />

2 Department of Electrical Engineering, University of the Ch<strong>on</strong>nam, Korea<br />

In this paper, a design method for shape optimizati<strong>on</strong> of stator and rotor of a double barrier in<br />

the form of IPMSM for NEV(Neighborhood Electric Vehicle) is proposed. IPMSM has two big<br />

problems which are high cogging torque and high torque ripple that causes performance degradati<strong>on</strong><br />

of the motor and noise, and vibrati<strong>on</strong> during the motor rotati<strong>on</strong>. To solve the problem, ways of<br />

reducing the cogging torque and torque ripple as a method for forming the shape of the motor stator<br />

and rotor factors were searched. Especially, the factors which greatly affected cogging torque and<br />

torque ripple were studied and verified their mutual c<strong>on</strong>necti<strong>on</strong>. Moreover it was found that the<br />

most influential factors was the slot open and the slot teeth angle. The results of the experiment<br />

which reduced cogging torque and torque ripple verified, while the optimizati<strong>on</strong> proceeded <strong>on</strong> the<br />

basis of the factors that were searched. So the prototype of the optimized IPMSM was designed, its<br />

performance was evaluated. The optimizati<strong>on</strong> was verified by the performance evaluati<strong>on</strong>.<br />

[1] Y.D. Yao, D.R. Huang, J.C. Wang, S.H. Liou, S.J. Wang, 1997, IEEE Tran. Magn. 33 1997: 4095. [2] N. Bianchi, S.<br />

Bolognani, 2008, IEEE Trans. Ind. Appl. 38 (5) 2002 : 1259. [3] T. Ishikawa, M. Matsuda, M. Matsunami, 1998, IEEE Trans.<br />

Magn. 34 (5) 1998 : 3503. [4] Z.Q. Zhu, D. Howe, E. Bolte, B. Ackermann, 1993, IEEE Trans. Magn. 29 1993:124. [5] H<strong>on</strong>g<br />

E, Ben-Ahmed AH, Lucidame J. 1997, Switching flux permanent magnet polyphased synchr<strong>on</strong>ous machine. In: Proceedings<br />

of the 7th European c<strong>on</strong>ference <strong>on</strong> power electr<strong>on</strong>ics and applicati<strong>on</strong>s, Tr<strong>on</strong>dheim, Norwegen, 1997: p. 903-908.<br />

SG22<br />

Implementati<strong>on</strong> of first-principle calculati<strong>on</strong> in combinati<strong>on</strong> with a<br />

dynamical cluster approximati<strong>on</strong><br />

Hunpyo Lee 1 , Kateryna Foyevtsova 1 , Johannes Ferber 1 , Markus Aichhorn 2 , Harald<br />

Jeschke 1 and Roser Valenti 1 *<br />

1 Institute for Theoretical Physics, University of Frankfurt, Germany<br />

2 Institute for Theoretical and computati<strong>on</strong>al Physics, TU Graz, Austria<br />

While the combinati<strong>on</strong> of the local density approximati<strong>on</strong> (LDA) with dynamical<br />

mean field theory (DMFT) opened the door to a realistic descripti<strong>on</strong> of correlated<br />

compounds, the improvement of the method is <strong>on</strong>going. In this work, we present a<br />

combinati<strong>on</strong> of LDA with the dynamical cluster approximati<strong>on</strong> (LDA+DCA) in the<br />

framework of the full-potential linear augmented plane-wave method, and compare our<br />

results to LDA+DMFT calculati<strong>on</strong>s as well as experimental observati<strong>on</strong>s <strong>on</strong> SrVO 3.<br />

We find a qualitative agreement of the momentum resolved spectral functi<strong>on</strong> with<br />

angle-resolved photoemissi<strong>on</strong> spectra (ARPES) and former LDA+DMFT results. As<br />

a correcti<strong>on</strong> to LDA+DMFT, we observe more pr<strong>on</strong>ounced coherent peaks below the<br />

Fermi level, as indicated by ARPES experiments. In additi<strong>on</strong>, we resolve the spectral<br />

functi<strong>on</strong>s in the ${\bf K}_{0}=(0,0,0)$ and ${\bf K}_{1}=(\pi,\pi,\pi)$ sectors of<br />

DCA, where band insulating and metallic phases coexist. Our approach can be applied<br />

to correlated compounds where not <strong>on</strong>ly local quantum fluctuati<strong>on</strong>s but also spatial<br />

fluctuati<strong>on</strong>s are important.<br />

arXiv:1111.0890<br />

SH01<br />

Oscillatory transformative domain wall inner structure of depinning<br />

domain wall around notched ferromagnetic wire<br />

Dede Djuhana 1 *, Bambang Soegij<strong>on</strong>o 1 , H<strong>on</strong>g-guang Piao 2 , Suhk Kun Oh 3 , Se<strong>on</strong>g-cho<br />

Yu 3 and D<strong>on</strong>g-hyun Kim 3<br />

1 Physics, Department of Physics, university of Ind<strong>on</strong>esia, Ind<strong>on</strong>esia<br />

2 Materials Science and Engineering, Department of Materials Science and<br />

Engineering, Tsinghua University, Beijing, China, China<br />

3 Physics, Chungbuk Nati<strong>on</strong>al University, Che<strong>on</strong>gju 361-763, South Korea, Korea<br />

We have investigated domain wall (DW) depinning behavior around a geometric notch in ferromagnetic<br />

nanowires by means of micromagnetic simulati<strong>on</strong> [1]. Nanowires with different notch geometries by<br />

changing a depth (d) and a half-width of the notch (s) have been c<strong>on</strong>sidered. A domain wall with a transverse<br />

wall structure is initially prepared to be positi<strong>on</strong>ed at the notch. Depinning field pulse of 1 ns durati<strong>on</strong> is<br />

applied to trigger DW depinning behavior with a systematic variati<strong>on</strong> of depinning field strengths. With<br />

increase of s, the domain wall depinning field tends to decrease. Change of an aspect ratio is also c<strong>on</strong>sidered,<br />

where a relatively insensitive variati<strong>on</strong> of depinning field is observed with respect to the aspect ratio d/<br />

s greater than 2. With variati<strong>on</strong> of depinning field strength, we have found that DW internal structure<br />

changes during the depinning process. At lower depinning field (< 4 mT), DW keeps the initial tranverse<br />

wall structure during the depinning process, whereas higher depinning field (> 4 mT), DW is depinned<br />

with a transformati<strong>on</strong> of the inner structure with antivortex so<strong>on</strong> after DW has escaped from the notch. The<br />

transformati<strong>on</strong> of the DW inner structure is obviously related to the Walker breakdown phenomen<strong>on</strong>.<br />

[1] M. J. D<strong>on</strong>ahue and D. G. Porter, OOMMF User’s Guide, http://math.nist.gov/oommf (2002).<br />

SH02<br />

SH03<br />

SH04<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Unidirecti<strong>on</strong>al thermal effects in current-induced domain wall moti<strong>on</strong><br />

Jacob Torrej<strong>on</strong> 1 , Gregory Malinowski 1 , Javier Curiale 1 , Andre Thiaville 1 *, Daniel<br />

Lacour 2 , Francois M<strong>on</strong>taigne 2 and Michel Hehn 2<br />

1<br />

Laboratoire de Physique des Solides, Universite Paris-Sud, CNRS , 91405 Orsay,<br />

France., France<br />

2<br />

Institut Jean Lamour, Universite Nancy I, 54506 Vandoeuvre-les-Nancy, France.,<br />

France<br />

We show unidirecti<strong>on</strong>al moti<strong>on</strong> of a domain wall (DW) due to thermal effects in<br />

permalloy nanostrips using magnetic force microscopy <strong>on</strong> a RF-c<strong>on</strong>tacted sample. A<br />

deterministic thermal driven moti<strong>on</strong> has been found for current excitati<strong>on</strong> in the range<br />

of few nanosec<strong>on</strong>ds. The cooperati<strong>on</strong> between thermal effect and spin transfer torque<br />

induces larger and more effective displacements towards the center of nanostrip, the<br />

hotter part. The thermal effects are generated by Joule heating, and amplified by poor<br />

heat diffusi<strong>on</strong> through thick SiO 2 (100 nm). An important issue in thermal transport<br />

is the temperature gradient related to the positi<strong>on</strong>s of sinks (thick Au electrodes),<br />

resp<strong>on</strong>sible (partly at least) for the unidirecti<strong>on</strong>al DW moti<strong>on</strong> towards hotter part. Such<br />

behaviour has been recently predicted by magn<strong>on</strong>s spin transfer [1]. On the other hand,<br />

the propagati<strong>on</strong> of DW could be affected by other thermoelectric effects. However, we<br />

anticipate the spin currents created by Spin Seebeck effect [2] or anomalous Nernst<br />

effect [3] to be small compared to the critical current density for DW moti<strong>on</strong>.<br />

[1] D. Hinzke et al; PRL 107, 027205 (2011). [2] K. Uchida et al; Nature 455, 778 (2008). [3] S. Y.<br />

Huang et al ; PRL 107, 216604 (2011).<br />

Effect of the oersted field <strong>on</strong> current-induced domain wall moti<strong>on</strong> and<br />

domain wall chirality in multilayer nanostripes<br />

Stefania Pizzini 1 *, Zahid Ishaque 1 , Jan Vogel 1 , Vojtech Uhlir 1 , Nicolas Rougemaille 1 ,<br />

Olivier Fruchart 1 , Jean-christophe Toussaint 1 , Julio Camarero 2 , Julio C. Cezar 3 and<br />

Fausto Sirotti 4<br />

1<br />

Institut Neel, Centre Nati<strong>on</strong>al de la Recherche Scientifique, Grenoble, France<br />

2<br />

Universidad Aut<strong>on</strong>oma de Madrid, Spain<br />

3<br />

European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility (ESRF), Grenoble, France<br />

4<br />

Synchrotr<strong>on</strong> SOLEIL, Gif sur Yvette, France<br />

Current-induced domain wall moti<strong>on</strong> is more efficient in Permalloy(Py)/Cu/Co trilayer nanostripes than<br />

in single Py nanostripes. We used time-resolved photoemissi<strong>on</strong> electr<strong>on</strong> microscopy combined with x-ray<br />

magnetic circular dichroism (XMCD-PEEM) to image the magnetic c<strong>on</strong>figurati<strong>on</strong> in the Py layer of<br />

these nanostripes, during the current pulses, with 50ps time resoluti<strong>on</strong>. During the current pulses the Py<br />

magnetizati<strong>on</strong> tilts towards the transverse directi<strong>on</strong>. The large tilt angles (up to 70°) can be reproduced by<br />

micromagnetic simulati<strong>on</strong>s <strong>on</strong>ly when both the Oersted field and the magnetostatic interacti<strong>on</strong>s between Py<br />

and Co are taken into account. Magnetic Force Microscopy (MFM) measurements were performed <strong>on</strong> Py/<br />

Metal bilayer nanostripes, with different metal thicknesses, varying the transverse field for a given current<br />

density. We show that the Oersted field stabilizes transverse domain walls with a transverse comp<strong>on</strong>ent parallel<br />

to the Oersted field, even for widths and thicknesses of the Py layer for which vortex walls are more stable.<br />

Once the chirality of the wall is compatible with the Oersted field, the domain wall moves with current pulses<br />

without changing c<strong>on</strong>figurati<strong>on</strong>, indicating that the Walker breakdown is suppressed. This phenomen<strong>on</strong> could<br />

therefore explain the large domain wall velocities that we have observed in Py/Cu/Co nanostripes.<br />

Domain-wall moti<strong>on</strong> in permalloy nanowires with magnetic soft spots<br />

Andreas Vogel 1 *, Sebastian Wintz 2 , Theo Gerhardt 1 , Lars Bocklage 1 , Thomas Strache 2 ,<br />

Mi-young Im 3 , Peter Fischer 3 , Juergen Fassbender 2 , Jeffrey Mccord 4 and Guido Meier 1<br />

1 Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Germany<br />

2 Institut fuer I<strong>on</strong>enstrahlphysik und Materialforschung, Helmholtz-Zentrum Dresden-Rossendorf, Germany<br />

3 Center for X-ray Optics, Lawrence Berkeley Nati<strong>on</strong>al Laboratory, USA<br />

4 Institut fuer Materialwissenschaften, Christian-Albrechts-Universitaet zu Kiel, Germany<br />

Recent c<strong>on</strong>cepts of n<strong>on</strong>volatile data-storage devices involve the c<strong>on</strong>trolled moti<strong>on</strong> of magnetic domain walls<br />

(DWs) in nanowires [1]. To realize such a device, a manageable fabricati<strong>on</strong> process of reproducible and reliable<br />

pinning sites for individual DWs is required. We use irradiati<strong>on</strong> with chromium i<strong>on</strong>s to create local c<strong>on</strong>fining<br />

potentials via an effective reducti<strong>on</strong> of the saturati<strong>on</strong> magnetizati<strong>on</strong> in lithographically predefined regi<strong>on</strong>s. Fielddriven<br />

pinning and depinning at the so-called magnetic soft spots is directly observed using x-ray microscopy<br />

[2]. The shape of the potential is characterized via micromagnetic simulati<strong>on</strong>s and electrical measurements of<br />

the anisotropic magnetoresistance. Moreover, we dem<strong>on</strong>strate reliable DW depinning by single current pulses<br />

in a permalloy nanowire c<strong>on</strong>taining a square-shaped magnetic soft spot [3]. A DW can be moved back and forth<br />

between different soft spots al<strong>on</strong>g a wire. Lower requirements <strong>on</strong> the resoluti<strong>on</strong> of the lithography equipment<br />

in comparis<strong>on</strong> to geometric c<strong>on</strong>stricti<strong>on</strong>s <strong>on</strong> the nanoscale, a small distributi<strong>on</strong> of properties due to parallel<br />

processing of many pinning sites during implantati<strong>on</strong>, and fine tunability of the strength of the pinning potential<br />

via the chromium i<strong>on</strong> fluence make the magnetic soft spots a promising candidate for applicati<strong>on</strong>s.<br />

[1] D. A. Allwood, Gang Xi<strong>on</strong>g, M. D. Cooke, C. C. Faulkner, D. Atkins<strong>on</strong>, N. Vernier, R. P. Cowburn, Science 296, 2003 (2002);<br />

S. S. P. Parkin, U. S. Patent No. US 683 400 5 (2004). [2] A. Vogel, S. Wintz, J. Kimling, M. Bolte, T. Strache, M. Fritzsche,<br />

M.-Y. Im, P. Fischer, G. Meier, and J. Fassbender, IEEE Trans. Magn. 46, 1708 (2010). [3] A. Vogel, S. Wintz, T. Gerhardt, L.<br />

Bocklage, T. Strache, M.-Y. Im, P. Fischer, J. Fassbender, J. McCord, and G. Meier, Appl. Phys. Lett. 98, 202501 (2011).<br />

July 8 - 13, 2012 Busan, Korea 229<br />

Poster Friday


Poster Friday<br />

SH05<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Direct observati<strong>on</strong> of nearly mass-less domain walls in nanostripes<br />

with perpendicular magnetic anisotropy<br />

Stefania Pizzini 1 *, Jan Vogel 1 , Marlio B<strong>on</strong>fim 2 , Olivier Boulle 3 , Emilie Jue 3 , Nicolas<br />

Rougemaille 1 , Mihai Mir<strong>on</strong> 3 , Ales Hrabec 1 , Gilles Gaudin 3 , Julio C. Cezar 4 and Fausto<br />

Sirotti 5<br />

1 Institut Neel, Centre Nati<strong>on</strong>al de la Recherche Scientifique, Grenoble, France<br />

2 Departamento de Engenharia Eletrica, Universidade do Parana, Curitiba, Brazil<br />

3 Spintec, CEA/CNRS/UJF/GINP, INAC, Grenoble, France<br />

4 European Synchrotr<strong>on</strong> Radiati<strong>on</strong> Facility (ESRF), Grenoble, France<br />

5 Synchrotr<strong>on</strong> SOLEIL, Gif-sur-Yvette, France<br />

Important inertial effects have been recently shown for domain walls in permalloy nanostripes. These<br />

transient effects, giving rise to an effective domain wall (DW) mass, are caused by deformati<strong>on</strong>s of<br />

the DW internal structure when a current pulse is applied. We have used time-resolved photoemissi<strong>on</strong><br />

electr<strong>on</strong> microscopy combined with x-ray magnetic circular dichroism to study current-induced DW<br />

moti<strong>on</strong> in Pt/Co/AlOx nanostripes with perpendicular anisotropy and Rashba spin-orbit coupling. We<br />

show that in these nanostripes the DWs move at c<strong>on</strong>stant speed during the current pulse and inertial<br />

effects are much smaller than in permalloy nanostripes, i.e. the delay of the linear moti<strong>on</strong> with respect<br />

to the pulse is less than 1 ns and the transient moti<strong>on</strong> is smaller than 30 nm. The transient displacement<br />

δq depends of the change of generalized DW angle φ : δq = -Δ/α δφ where Δ the domain wall width at<br />

rest and α the damping parameter. The negligible inertia in our system is accounted for by the narrow<br />

DW width and the small DW angle due to the presence of a transverse magnetic field of Rashba origin.<br />

Such small inertial effects could be efficiently exploited in devices based <strong>on</strong> manipulati<strong>on</strong> of DWs.<br />

SH06<br />

Modified phase diagram of domain walls in FeNi/Cu/Co nanostripes<br />

Nicolas Rougemaille 1 *, Vojtech Uhlir 1 , Olivier Fruchart 1 , Zahid Ishaque 1 , Jan Vogel1,<br />

Stefania Pizzini 1 , Zoukaa Kassir-bod<strong>on</strong> 1 , Aurelien Massboeuf 2 , Andrea Locatelli 3 ,<br />

Onur Mentes 3 , Michal Urbanek 4 and Jean-christophe Toussaint 1<br />

1<br />

Institut Neel, Centre Nati<strong>on</strong>al de la Recherche Scientifique, Grenoble, France<br />

2<br />

Laboratoire d'Etude des Materiaux par Microscopie Avancee, INAC/CEA, Grenoble,<br />

France<br />

3<br />

Sincrotr<strong>on</strong>e ELETTRA, Trieste, Italy<br />

4<br />

Institute of Physical Engineering, Brno University of Technology, Brno, Czech<br />

Republic<br />

Magnetic domain walls (DWs) c<strong>on</strong>fined in nanostructured magnetic materials display a wealth of specific<br />

static and dynamic physical properties. For magnetic nanostripes with sub-micr<strong>on</strong> widths and in-plane<br />

magnetizati<strong>on</strong>, head-to-head DWs are either of transverse (TW) or vortex (VW) type and are characterized<br />

by a chirality, asymmetry and/or polarity. Due to their small size and fast dynamics, magnetic domain walls<br />

are promising candidates in the area of informati<strong>on</strong> processing and storage. The dynamic properties of<br />

these DW under applicati<strong>on</strong> of current pulses through the spin transfer torque (STT) is <strong>on</strong>e of the exciting<br />

subjects of spintr<strong>on</strong>ics. We used numerical simulati<strong>on</strong>s and analytical modelling to predict the phase<br />

diagram of transverse versus vortex walls in Py/Cu/Co trilayer nanostripes, in which high current-induced<br />

DW velocities have been observed. The DW is located in the Py layer while the Co layer is initialized as<br />

single domain. We have found that due to magnetostatic interacti<strong>on</strong>s between Py and Co magnetizati<strong>on</strong>s,<br />

the TWs are energetically significantly more favourable in the Py layer of the trilayer nanostripes than in<br />

single Py nanostripes. We have experimentally verified part of this modified phase diagram with different<br />

microscopy techniques, including Magnetic Force Microscopy and Photoelectr<strong>on</strong> Emissi<strong>on</strong> Microscopy.<br />

SH07<br />

Effect of current <strong>on</strong> a threshold width for a dimensi<strong>on</strong>al transiti<strong>on</strong> of<br />

domain wall dynamics in Co/Ni<br />

Kab-jin Kim 1 *, D. Chiba 1 , K. Kobayashi 1 , S. Fukami 2 , M. Yamanouchi 2 , H. Ohno 2<br />

and T. Ono 1<br />

1 Institute for Chemical Research, Kyoto University, Uji, Kyoto, Japan<br />

2 Center for Spintr<strong>on</strong>ics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-<br />

ku, Sendai 980-8577, Japan<br />

The effect of current <strong>on</strong> the dimensi<strong>on</strong>al transiti<strong>on</strong> of domain wall (DW) moti<strong>on</strong> is<br />

investigated in Co/Ni nanowires by accompanying magnetoresistance measurement. As<br />

reducing the nanowire width, we found that the domain wall (DW) moti<strong>on</strong> is changed<br />

from stripe pattern expansi<strong>on</strong> to purely wall moti<strong>on</strong>, implying that the dimensi<strong>on</strong>al<br />

transiti<strong>on</strong> from 2D to 1D. The threshold width for this transiti<strong>on</strong> is found to str<strong>on</strong>gly<br />

depend <strong>on</strong> the relative directi<strong>on</strong> of magnetic field and current <strong>on</strong> DW: parallel<br />

(antiparallel) directi<strong>on</strong> has much smaller (larger) transiti<strong>on</strong> width, which is mainly<br />

because of different forces mechanism by magnetic field and current. The present work<br />

provides the upper boundary for domain-wall-moti<strong>on</strong> based devices applicati<strong>on</strong>s.<br />

(Acknowledgement) This work was partly supported by a Grant-in-Aid for Scientific Research and<br />

FIRST Program from JSPS.<br />

230 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SH08<br />

Simulati<strong>on</strong>s of field driven domain wall moti<strong>on</strong> in permalloy nanowires<br />

with difference dimensi<strong>on</strong><br />

Chia-chi Chang 1 , Chao-hsien Huang 2 , Tian-chiuan Wu 3 , J<strong>on</strong>g-ching Wu 2 and Lance<br />

Horng 2<br />

1<br />

Department of Physics, Nati<strong>on</strong>al Changhua University of Educati<strong>on</strong>, Taiwan<br />

2<br />

Department of Physics, Taiwan SPIN Research Center, Nati<strong>on</strong>al Changhua<br />

University of Educati<strong>on</strong>, Taiwan<br />

3<br />

Department of Electr<strong>on</strong>ic Engineering, Nati<strong>on</strong>al Formosa University, Taiwan<br />

In recent years, the domain wall moti<strong>on</strong> in permalloy nanowire has been intensively<br />

investigated because it could give promise of a new type memory with many<br />

advantages. In our researches, the domain wall moti<strong>on</strong> in permalloy nanowires driven<br />

by external magnetic field have been simulated by a commercial software LLG<br />

simulati<strong>on</strong>. The simulated results presented that the velocity of DW moti<strong>on</strong> increases<br />

below a critical field value which is called Walker breakdown field; above that field the<br />

velocity of domain wall obviously decrease. The velocity of the domain wall and the<br />

critical field is dependent <strong>on</strong> the dimensi<strong>on</strong> of the nanowire. The domain wall velocity<br />

increases as the wire width increases, and the critical field decreases as wire width<br />

increases with n<strong>on</strong>-linear relati<strong>on</strong>.<br />

1. GEOFFREY S. D. BEACH*, CORNELIU NISTOR, CARL KNUTSON, MAXIM TSOI AND<br />

JAMES L. ERSKINE, nature materials VOL 4 OCTOBER 2005 2. Andrew Kunz, IEEE Trans.<br />

Mag. VOL. 42, NO. 10, OCTOBER 2006 3. Stuart S. P. Parkin,* Masamitsu Hayashi, Luc Thomas,<br />

Science 320, 190 2008<br />

SH09<br />

Voltage c<strong>on</strong>trol of magnetisati<strong>on</strong> and magnetic domain c<strong>on</strong>figurati<strong>on</strong>s<br />

in magnetostrictive epitaxial Fe 1-xGa x thin films<br />

Duncan E Parkes 1 , Stuart A Cavill 2 , Aidan T Hindmarch 3 , Peter Wadley 1 , Fintan Mcgee 1 ,<br />

Kevin W Edm<strong>on</strong>ds 1 , Richard P Campi<strong>on</strong> 1 , Andrew W Rushforth 1 * and Bryan L Gallagher 1<br />

1 School of Physics and Astr<strong>on</strong>omy, University of Nottingham, Nottingham NG7 2RD, United Kingdom<br />

2 Beamline I06, Diam<strong>on</strong>d Light Source Chilt<strong>on</strong>, Didcot, Oxfordshire OX11 0DE, United Kingdom<br />

3 Centre for Materials Physics, Durham University, South Road, Durham, DH1 3LE, United Kingdom<br />

The c<strong>on</strong>trol of ferromagnetic domains and domain walls by electrical means is a desirable objective for<br />

applicati<strong>on</strong>s in many existing and proposed informati<strong>on</strong> storage[1,2] and logical processing[3] devices. One<br />

route to achieve this goal is via hybrid ferromagnet/piezoelectric transducer devices [4-6] in which a voltage<br />

applied to the transducer induces mechanical strain in the ferromagnet affecting the magnetic anisotropy through<br />

the inverse magnetostricti<strong>on</strong> effect. We have implemented epitaxially grown thin films of Fe81Ga19 in such a<br />

device. Through a combinati<strong>on</strong> of magnetotransport measurements, magneto-optical Kerr effect (MOKE) and<br />

high resoluti<strong>on</strong> photoemissi<strong>on</strong> electr<strong>on</strong> microscopy (PEEM) we dem<strong>on</strong>strate that our epitaxial films possess an<br />

excepti<strong>on</strong>ally large magnetostricti<strong>on</strong> (enhanced over that previously observed in bulk samples[7]) and a str<strong>on</strong>g<br />

cubic magnetocrystalline anisotropy. We exploit these properties to achieve voltage c<strong>on</strong>trol of the magnetisati<strong>on</strong><br />

and magnetic domain walls, including the rec<strong>on</strong>figurati<strong>on</strong> of ordered domain patterns in structured geometries,<br />

and n<strong>on</strong>-volatile switching of the magnetisati<strong>on</strong> in the absence of external magnetic fields. Such functi<strong>on</strong>alities<br />

will be directly applicable to informati<strong>on</strong> storage and processing technologies.<br />

[1] W.J. Gallagher and S.S.P. Parkin, IBM J. Res. & Dev. 1, 5 (2006). [2] S.S.P. Parkin, M. Hayashi, and<br />

L. Thomas, Science 320, 190 (2008). [3] D.A. Allwood, et al. Science 309, 1688 (2005). [4] Sang-Koog<br />

Kim et al., J. Mag. Mat. Res. 267, 127 (2003), [5] J-W Lee et al., Appl. Phys. Lett. 82, 2458 (2003). [6] A.W.<br />

Rushforth et al., Phys. Rev. B. 78, 085314 (2008). [7] A.E. Clark, et al. J. Appl. Phys. 93, 8621 (2003).<br />

SH10<br />

Restricted oscillati<strong>on</strong> period effect in the domain wall propagati<strong>on</strong><br />

after walker breakdown<br />

Xiao-ping Ma 1 , Zhe Fan 1 , Je-ho Shim 2 , Sang-hyuk Lee 2 , Djati Handoko 2 , H<strong>on</strong>g-guang<br />

Piao 3 * and D<strong>on</strong>g-hyun Kim 2<br />

1 Science of College, Huaihai Institute of Technology, China<br />

2 Department of Physics, Chungbuk Nati<strong>on</strong>al University, Korea<br />

3 Materials Science and Engineering, Tsinghua University, China<br />

Understanding and c<strong>on</strong>trol of dynamic behaviors for magnetic domain wall (DW) in<br />

ferromagnetic nanowire has become <strong>on</strong>e of important issues in realizati<strong>on</strong> of potential<br />

spintr<strong>on</strong>ic applicati<strong>on</strong>s such as DW logic and memory devices. In this work, we have<br />

intensively explored antivortex DW dynamic behaviors in ferromagnetic nanowires after<br />

Walker breakdown by means of the mircomagnetic simulati<strong>on</strong> [1]. The nanowire has 2000nm<br />

length. The wire width w varied from 25 to 100 nm, and the wire thickness t varied<br />

from 0.5 to 12 nm. In all simulati<strong>on</strong>, the material parameter of Permalloy is used. The unit<br />

cell dimensi<strong>on</strong> is 2.5×2.5×t nm3 and the Gilbert damping c<strong>on</strong>stant α = 0.01.We have found<br />

that the DW dynamic behavior in the ferromagnetic nanowire significantly depend <strong>on</strong> the<br />

wire thickness and width. Interestingly, the oscillati<strong>on</strong> period of the DW propagati<strong>on</strong> is not<br />

significantly change with variati<strong>on</strong> of the wire thickness is <strong>on</strong>ly dependent the wire width. By<br />

detailed analysis, we propose that there could be a new mechanism to restrict the oscillati<strong>on</strong><br />

period of the DW propagati<strong>on</strong> in the ferromagnetic nanowire after the Walker breakdown.<br />

[1] M. J. D<strong>on</strong>ahue and D. G. Porter, OOMMF User's Guide, from http://math.nist.gov/oommf (2002).


SH11<br />

Domain wall moti<strong>on</strong> by thermal gradients in Fe/W(110)<br />

J<strong>on</strong>athan Philippe Chico Carpio 1 *, Anders Bergman 1 , Lars Bergqvist 2 and Olle<br />

Erikss<strong>on</strong> 1<br />

1 Physics and Astr<strong>on</strong>omy (Materials Theory Divisi<strong>on</strong>), Uppsala University, Sweden<br />

2 Dept. of Materials Science and Engineering, Royal Institute of Tech<strong>on</strong>olgy (KTH), Sweden<br />

The Spin Seebeck effect recently observed [1] has opened new areas of research in magnetic materials.<br />

One c<strong>on</strong>sequence of the Spin Seebeck effect is the movement of domain walls in magnetic materials [2].<br />

In our current research we have studied the behavior of a domain wall in the presence of a thermal gradient<br />

in a 2D system by using the atomistic spin dynamics approach present in the UppASD code [3, 5]. This is<br />

based in the Landau-Lifshitz-Gilbert equati<strong>on</strong>, where the atomistic spins are described using a Heisenberg<br />

Hamilt<strong>on</strong>ian c<strong>on</strong>structed from parameters obtained from first principles calculati<strong>on</strong>s. Temperature effects<br />

are taken into account by Langevin dynamics [3-4]. The system chosen is a m<strong>on</strong>olayer of Fe <strong>on</strong> W (110)<br />

which exhibits a large anisotropy while having a soft exchange [5], resulting in domain wall thickness of<br />

the order of~ 1 - 2 nanometers. By subjecting this material to a thermal gradient we are able to observe<br />

a temperature dependent movement of the domain wall as well as changes of the spatial magnetizati<strong>on</strong><br />

profile of the system. We compare this temperature gradient driven moti<strong>on</strong> with the spin transfer torque<br />

driven domain wall moti<strong>on</strong> observed for the system when subjected to a current.<br />

[1] K. Uchida, et al. Observati<strong>on</strong> of the spin Seebeck effect. Nature, 455:778, 2008. [2] D. Hinzke, and U. Nowak. Domain Wall<br />

Moti<strong>on</strong> by the Magn<strong>on</strong>ic Spin Seebeck Effect. Phys. Rev. Letters, 107:027205, 2011. [3] B. Skubic et al.. A method for atomistic<br />

spin dynamics simulati<strong>on</strong>s: implementati<strong>on</strong>s and examples. J. Phys.: C<strong>on</strong>dens. Matter, 20:315203, 2008. [4] V. P. Antropov et<br />

al. Spin dynamics in magnets: Equati<strong>on</strong> of moti<strong>on</strong> and finite temperature effects. Phys. Rev. B, 54:1019, 1996. [5] A. Bergman,<br />

et al. Magn<strong>on</strong> softening in a ferromagnetic m<strong>on</strong>olayer: A first-principles spin dynamics study. Phys. Rev. B, 81:144416, 2010.<br />

SH12<br />

Transverse domain wall moti<strong>on</strong> in notched ferromagnetic nanowire by<br />

spin transfer torque<br />

Arnab Ganguly, Anjan Barman and Saswati Barman*<br />

C<strong>on</strong>densed Matter Physics and Material Sciences, S. N. Bose Nati<strong>on</strong>al Centre for<br />

Basic Sciences, Saltlake, Kolkata, India, India<br />

We have investigated domain wall moti<strong>on</strong> in notched permalloy nanowires driven by<br />

spin polarized current. We solve modified Landau-Lifshitz Gilbert equati<strong>on</strong> including<br />

the effect of spin-transfer torque by micromagnetic simulati<strong>on</strong>. The ferromagnetic<br />

ground states for the studied geometries show transverse domain walls located at<br />

different regi<strong>on</strong>s depending up<strong>on</strong> the positi<strong>on</strong>, shape, dimensi<strong>on</strong> and symmetry of the<br />

notch in the nanowire. We have studied the effect of the spin torque <strong>on</strong> domain-wall<br />

displacement and domain-wall velocity. We find that the domain wall velocity is higher<br />

for single notched nanowire as compared to multiple notches. For rectangular notches<br />

of dimensi<strong>on</strong> 10 nm x 5 nm, transverse domain wall is pinned at <strong>on</strong>e edge of the notch<br />

but it gets depinned for current density ~ 10 8 A/m 2 . We observe the current induced<br />

domain wall oscillati<strong>on</strong> followed by a damped periodic translati<strong>on</strong>al moti<strong>on</strong> of the<br />

transverse wall al<strong>on</strong>g with a switching of transverse domain wall from ‘?’ to ‘V’ like<br />

c<strong>on</strong>figurati<strong>on</strong> and vice versa via head to head or tail to tail domain wall formati<strong>on</strong>.<br />

1. Z. Li and S. Zhang, Phys.Rev. B, 70, 024417 (2004) . 2. A. Thiaville, Y. Nakatani, J. Miltat, and N.<br />

Vernier, J. Appl. Phys. 95, 7049 (2004) . 3. M. Hayashi, L. Thomas, C. Rettner, R. Moriya, X. Jiang,<br />

and S. S. P. Parkin, Phys. Rev. Lett. 97, 207205, (2006). 4. P. Chureemart, R. F. L. Evans and R. W.<br />

Chantrell, , Phys.Rev. B 83, 184416 (2011).<br />

SH13<br />

Domain wall c<strong>on</strong>figurati<strong>on</strong> and magneto-transport properties in dual<br />

spin-valve with<br />

By<strong>on</strong>g Sun Chun 1 *, Chany<strong>on</strong>g Hwang 1 , Han-chun Wu 2 , Mohamed Abid 3 , Su Jung<br />

Noh 4 and Young Keun Kim 4<br />

1 Korea Research Institute of Standards and Science, Korea<br />

2 CRANN, School of Physics, Trinity College Dublin, Ireland<br />

3 Ecole Polytechnique Federale de Lausanne, Switzerland<br />

4 Department of Materials Science and Engineering, Korea University, Korea<br />

The effect of the directi<strong>on</strong> of the applied magnetic field <strong>on</strong> the magneto-transport properties<br />

including domain wall (DW) c<strong>on</strong>figurati<strong>on</strong> and magnetizati<strong>on</strong> reversal process has been<br />

studied with a synthetic antiferromagnet-based dual spin-valve (SAF-DSV) structure (i.e.<br />

the SV structure is doubled symmetrically with respect to the FM). We can tune the DW<br />

c<strong>on</strong>figurati<strong>on</strong> and its reversal process from a vortex to a transverse type by changing the<br />

directi<strong>on</strong> of applied magnetic field respect to the nano-scale c<strong>on</strong>stricted SAF-DSV. When<br />

the field is applied al<strong>on</strong>g the perpendicular directi<strong>on</strong> to the nano-scale c<strong>on</strong>stricted SAF-DSV,<br />

the perpendicular magnetic moments are developed due to the transverse magnetizati<strong>on</strong><br />

reversal process. This multi step switching process reflects the pinning and depinning of a<br />

DW at the nano-scale c<strong>on</strong>stricti<strong>on</strong>. Our results also show an asymmetric depinning field.<br />

We dem<strong>on</strong>strate, if nano-scale c<strong>on</strong>stricti<strong>on</strong> is asymmetric al<strong>on</strong>g its length, i.e. expansi<strong>on</strong>s<br />

from both sides of the neck into the two nanowires are not identical, and then an asymmetric<br />

energy barrier to domain wall propagati<strong>on</strong> is formed. This is due to the difference in DW<br />

width, which leads to an asymmetry in the domain wall depinning forces.<br />

SH14<br />

SH15<br />

SH16<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Dynamics of domain-wall oscillati<strong>on</strong>s in magnetic nanorings driven by<br />

circularly rotating fields<br />

Youn-seok Choi, Young-sang Yu, D<strong>on</strong>g-soo Han, Hyunsung Jung, Ki-suk Lee and<br />

Sang-koog Kim*<br />

Nati<strong>on</strong>al Creative Research Initiative Center for Spin Dynamics & Spin-Wave Devices<br />

& Nanospinics Lab, Research Institute of Adv. Materials, Dep. of Materials Sci. &<br />

Eng., Seoul Nat'l Univ., Seoul, Korea<br />

The manipulati<strong>on</strong> of magnetic domain walls in geometrical c<strong>on</strong>finements such as nanostrips and nanorings<br />

has become essential in informati<strong>on</strong> device technologies [1]. In particular, ring structures have attracted much<br />

attenti<strong>on</strong> because domain walls can be easily positi<strong>on</strong>ed and manipulated by the applicati<strong>on</strong> of magnetic fields<br />

or currents [2-4]. In the present work, we studied possible transverse domain-wall (TW) oscillati<strong>on</strong>s with certain<br />

frequency ranges in magnetic nanorings driven by circularly rotating fields <strong>on</strong> the nanoring plane. We used<br />

a permalloy nanoring with an <strong>on</strong>i<strong>on</strong> state that has a tail-to-tail and a head-to-head transverse wall. From the<br />

micromagnetic simulati<strong>on</strong>s, it was found that the frequency of the TW oscillati<strong>on</strong>s varies with the frequency and<br />

amplitude of the applied rotating field. Moreover, the frequency range of the persistent TW oscillati<strong>on</strong>s become<br />

wider for a str<strong>on</strong>ger field amplitude, as far as the frequency range is below a certain critical frequency value. We<br />

also found a phase diagram of the characteristic TW oscillati<strong>on</strong> dynamics <strong>on</strong> the plane of the field strength and<br />

frequency. We will present our interpretati<strong>on</strong>s of those simulati<strong>on</strong> results based <strong>on</strong> analytical calculati<strong>on</strong>s.<br />

*Corresp<strong>on</strong>ding author: sangkoog@snu.ac.kr [1] S. S. P. Parkin et al., Science 320, 190 (2008). [2] J. Rothman et al.,<br />

Phys. Rev. Lett. 86, 1098-1101 (2001). [3] M. Klaui et al., Phys. Rev. B 68, 134426 (2003). [4] Y. Hou et al., Appl. Phys. Lett<br />

98, 042510 (2011). [5] This work was supported by the Basic Science Research Program through the Nati<strong>on</strong>al Research<br />

Foundati<strong>on</strong> of Korea (NRF) funded by the Ministry of Educati<strong>on</strong>, Science and Technology (Grant No. 20110000441).<br />

Modeling field-induced transformati<strong>on</strong>s of domain walls in magnetic<br />

stripes<br />

Andrzej Janutka<br />

Institute of Physics, Wroclaw University of Technology, Poland<br />

WITHDRAWN<br />

Interacti<strong>on</strong> between propagating spin-waves and domain walls <strong>on</strong> a<br />

ferromagnetic nanowire<br />

June Seo Kim 1 , Martin Staerk 2 , Jungbum Yo<strong>on</strong> 3 , Chun Yeol You 3 , Luis Lopez-diaz 4 ,<br />

Eduardo Martinez 4 and Mathias Klaeui 1 *<br />

1 Institut fuer Physik, Johanes Gutenberg-Universitaet Mainz, Germany<br />

2 Fachbereich Physik, Universitaet K<strong>on</strong>stanz, Germany<br />

3 Department of Physics, Inha University, Korea<br />

4 Department of Physics, Universidad de Salamanca, Spain<br />

The recent discovery that propagating spin waves (SWs) move a domain wall has<br />

created a new possibility to manipulate magnetizati<strong>on</strong> [D<strong>on</strong>g-Soo, Han et al., Appl.<br />

Phys. Lett. 94, (2009) 112502]. Here, we numerically investigate the interacti<strong>on</strong><br />

between propagating spin waves and a transverse domain wall in a nanowire by<br />

using micromagnetic simulati<strong>on</strong>s. In order to understand the mechanisms that lead to<br />

domain wall moti<strong>on</strong>s, we calculate to domain wall velocity and the depinning fields<br />

for a pinned domain wall that is depinned in and against the directi<strong>on</strong> of the spin wave<br />

propagati<strong>on</strong>. We find that the physical origin of the spin wave induced domain wall<br />

moti<strong>on</strong> str<strong>on</strong>gly depends <strong>on</strong> the propagating spin wave frequency. At certain spin wave<br />

frequencies, transverse domain wall oscillati<strong>on</strong>s lead to transverse wall displacement<br />

by the spin waves, while at other frequencies, large reflecti<strong>on</strong> and effective momentum<br />

transfer are the main drivers of the spin wave induced domain wall moti<strong>on</strong>.<br />

July 8 - 13, 2012 Busan, Korea 231<br />

Poster Friday


Poster Friday<br />

SI01<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Spin oscillati<strong>on</strong>s in a free molecular magnet<br />

Gwang-hee Kim<br />

Physics, Sej<strong>on</strong>g University, Korea<br />

Applying an external acoustic wave, we study spin oscillati<strong>on</strong>s in a magnetic<br />

nanoparticle that is free to rotate about its anisotropy axis. Using Hamilt<strong>on</strong>ian of a<br />

rotated two-state spin system, we have shown that superpositi<strong>on</strong> of spin and rotati<strong>on</strong>al<br />

states makes a crucial effect <strong>on</strong> spin oscillati<strong>on</strong>s which exhibit quantum beats of the<br />

magnetizati<strong>on</strong>. In order to study such a beat structure, we compute dynamics of the<br />

magnetizati<strong>on</strong> by employing a perturbative approach, and discuss c<strong>on</strong>diti<strong>on</strong>s under<br />

which this novel quantum effect can be generated. The results are expected to be tested<br />

in existing experimental techniques.<br />

SI02<br />

Effects of n<strong>on</strong>linear spin dynamics <strong>on</strong> spin pumping<br />

Sankha Subhra Mukherjee, Praveen Deorani, Siddharth Rao, Jae Hyun Kw<strong>on</strong> and<br />

Hyunsoo Yang*<br />

ECE, Nati<strong>on</strong>al University of Singapore, Singapore<br />

Spin pumping has garnered significant interest in recent times. Most of the studies of<br />

spin pumping have been <strong>on</strong> systems in which the magnetizati<strong>on</strong> dynamics was linear.<br />

In n<strong>on</strong>linear dynamics, however, large-angle, n<strong>on</strong>linear, chaotic dynamics are regularly<br />

produced. We explore the nature of spin pumping signals resulting from n<strong>on</strong>linear<br />

magnetizati<strong>on</strong> dynamical phenomen<strong>on</strong>. The device geometry comprises of a permalloy<br />

(Py) layer in c<strong>on</strong>tact with a n<strong>on</strong>magnetic Pt layer. Magnetizati<strong>on</strong> dynamics is produced<br />

in the system by an rf signal applied to a coplanar waveguide patterned <strong>on</strong> top. Spin<br />

injected into the Pt is c<strong>on</strong>verted, due to the inverse spin Hall effect (ISHE), to a charge<br />

current and has been measured across the Pt layer. We will show that the system under<br />

study shown some high peaks at certain frequencies. The frequencies at which the<br />

peaks occur have been shown to be n<strong>on</strong>-stochastic, even though <strong>on</strong>e would expect<br />

them to be stochastic. Also, a frequency shift in the precessi<strong>on</strong>al res<strong>on</strong>ant frequency has<br />

been observed as a functi<strong>on</strong> of the applied power. A similar shift had been previously<br />

observed in spin wave n<strong>on</strong>linear dynamics in a different c<strong>on</strong>figurati<strong>on</strong>. The origin of<br />

the peaks and frequency shifts are discussed.<br />

SI03<br />

Sharp spectral linewidth in spin torque oscillator with perpendicular<br />

magnetized Co/Pd free layer<br />

Yuki Kawada*, Hiroshi Naganuma, Mikihiko Oogane and Yasuo Ando<br />

Applied Physics, Tohoku university, Japan<br />

There has been some scientific and practical interest in spin torque oscillator (STO) using<br />

perpendicular materials [1]. For applicati<strong>on</strong> of STO to informati<strong>on</strong>-communicati<strong>on</strong> nano<br />

RF devices, it is important to investigate linewidth properties, although comprehensive<br />

understanding of linewidth properties in STO using perpendicular materials is still lacking.<br />

In this study, we have measured spin torque oscillati<strong>on</strong> in giant magnetoresistance devices<br />

having a Co/Pd extended free layer and a NiFe/CoFe nanomagnet fixed bilayer. The total<br />

thickness of Co/Pd is 2.4 nm, and it was c<strong>on</strong>firmed that Co/Pd has perpendicular magnetic<br />

anisotropy by vibrating sample magnetometer. Spin torque oscillati<strong>on</strong> was measured<br />

under the low in-plane magnetic field using spectral analyzer. Microwave signal induced<br />

by spin transfer torque was clearly observed with oscillating frequency at 3.3 GHz. This<br />

frequency increased with increasing applied current i.e. positive n<strong>on</strong>linear frequency shift.<br />

Obtained minimum spectral linewidth was 13 MHz, which is very small, compared with<br />

that of previous work <strong>on</strong> perpendicular materials [2]. Our results suggest that applying the<br />

low magnetic field to the Co/Pd film plane is efficient to obtain sharp spectral linewidth.<br />

This work was partly supported by Strategic Japanese-German cooperative program<br />

(ASPIMATT) from JST and by Japan Society for Promoti<strong>on</strong> of Science.<br />

[1] S. M. Mohseni et al., Phys. Status Solidi RRL 5, 432 (2011). [2] C. H. Sim et al., J. Appl. Phys. 109, 07C905 (2011).<br />

232 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SI04<br />

Clocking schemes for solit<strong>on</strong> propagati<strong>on</strong> in a ferromagneticallycoupled<br />

quantum-dot chain<br />

Kye<strong>on</strong>g-d<strong>on</strong>g Lee 1 *, Hy<strong>on</strong>-seok S<strong>on</strong>g 1 , Chun-yeol You 2 and Sung-chul Shin 3<br />

1<br />

Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST,<br />

Korea<br />

2<br />

Department of Physics, Inha University, Korea<br />

3<br />

Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST,<br />

and Department of Emerging Materials Science, DGIST, Korea<br />

Transmissi<strong>on</strong> of magnetic signals al<strong>on</strong>g the ferromagnetically-coupled quantum-dot<br />

chain is an essential property to realize the magnetic quantum cellular automata. In<br />

the dot chain, a magnetic signal is represented by a topological solit<strong>on</strong> with a head-tohead<br />

or tail-to-tail state. The solit<strong>on</strong> is excepti<strong>on</strong>ally stable coming from the topology<br />

of the system potential-energy surface, and could be driven by an external magnetic<br />

field. In additi<strong>on</strong> to the external field, a global clocking field is used to further c<strong>on</strong>trol<br />

propagati<strong>on</strong> speed. We investigate the effect of the clocking field al<strong>on</strong>g the hard axis to<br />

vary the propagati<strong>on</strong> speed, together with the local trigger field al<strong>on</strong>g the easy axis to<br />

initialize the solit<strong>on</strong> propagati<strong>on</strong> by utilizing micromagnetic simulati<strong>on</strong>. Interestingly,<br />

it is found that the required static field to initiate the solit<strong>on</strong> moti<strong>on</strong> is a little larger<br />

than the minimum field to maintain the solit<strong>on</strong> moti<strong>on</strong>, and <strong>on</strong>ly local trigger field<br />

is required to initiate the solit<strong>on</strong> propagati<strong>on</strong>. Furthermore, we reveal the role of the<br />

global clocking field in the propagati<strong>on</strong> speed, unexpectedly, the clocking field impedes<br />

the solit<strong>on</strong> moti<strong>on</strong>.<br />

SI05<br />

Spin wave propagati<strong>on</strong> in single crystal Au(001)/Fe(001)/MgO(001)<br />

waveguides<br />

Yoichi Shiota, Shinji Miwa, Norikaze Mizuochi, Teruya Shinjo and Yoshishige<br />

Suzuki*<br />

Graduate School of Engineering Science, Osaka University, Japan<br />

The needs for the development of future computing and informati<strong>on</strong> storage devices have<br />

led the emerging field of spintr<strong>on</strong>ics. Since spin waves can propagate macroscopic distance<br />

in ferromagnetic material, they can be used as informati<strong>on</strong> carrier. Typically spin wave<br />

propagati<strong>on</strong>s were investigated using garnet films or permalloy films, both of which have small<br />

crystallographic anisotropy. Here we investigated spin wave propagati<strong>on</strong>s using spin wave<br />

spectroscopy technique [1] in single crystal Fe waveguides with cubic and uniaxial surface<br />

anisotropies. The sample, Au(001)-50nm/ Fe(001) / MgO(001)-10nm, were fabricated <strong>on</strong><br />

MgO(001) substrate using MBE system. We varied thickness of Fe (0.5-20 nm), waveguide<br />

width (1-100 µm), and distance of two antennae (0-40 µm). The static in-plane magnetic<br />

field was applied perpendicular to waveguide. In this way, magneto-static surface waves<br />

were propagated al<strong>on</strong>g the ferromagnetic waveguides. The group velocity of spin wave was<br />

estimated from the oscillati<strong>on</strong> period in transmissi<strong>on</strong> spectra. It was about 8.5 µm/ns in 20<br />

nm thick waveguide under 500 Oe external magnetic field. We found that this value linearly<br />

decreases as decreasing the thickness. The c<strong>on</strong>tributi<strong>on</strong> of magnetic anisotropies as functi<strong>on</strong>s of<br />

thickness and width of ferromagnetic layer to the spin waves was also investigated.<br />

[1] V. Vlaminck, et al., Science 322, 410 (2008)<br />

SI06<br />

Microscopic theory <strong>on</strong> the spin relaxati<strong>on</strong> in an inhomogeneous spin<br />

dynamics<br />

Nobuyuki Umetsu, Daisuke Miura and Akimasa Sakuma<br />

Tohoku University, Japan<br />

The mechanisms of Gilbert damping in materials with inhomogeneous spin dynamics<br />

are more complicate than that with homogeneous spin dynamics (Kittel mode). It is<br />

well known that the magnetic impurities c<strong>on</strong>tribute to Gilbert damping with Kittel<br />

mode, <strong>on</strong> the other hand, the n<strong>on</strong>magnetic impurities d<strong>on</strong>’t affect that. Recently, it<br />

has become clear that in the presence of spin waves (inhomogeneous dynamics), the<br />

n<strong>on</strong>magnetic impurities c<strong>on</strong>tribute to Gilbert damping c<strong>on</strong>stant, α [1]. In this case, α<br />

is proporti<strong>on</strong>al to square of wave vector q in the limit q→0. The aim of our study is to<br />

clarify the q-dependence of α in the entire q range from microscopic theory. Our model<br />

is described by s-d model which c<strong>on</strong>sists of localized spins, and c<strong>on</strong>ducting electr<strong>on</strong>s.<br />

In additi<strong>on</strong> to this, we c<strong>on</strong>sider the n<strong>on</strong>magnetic and magnetic impurities scattering.<br />

We obtain the precise expressi<strong>on</strong> of α from the linear resp<strong>on</strong>se theory. C<strong>on</strong>sequently,<br />

we find that α is proporti<strong>on</strong>al to 1/q in k↑-k↓


SI07<br />

Ultrafast transfer of spin in a n<strong>on</strong>-collinearly magnetized multilayer<br />

Koen Kuiper*, Sjors Schellekens and Bert Koopmans<br />

Eindhoven University of Technology, Netherlands<br />

Femtosec<strong>on</strong>d laser pulses can trigger intriguing dynamic phenomena in magnetic<br />

systems such as quenching of magnetizati<strong>on</strong> within 100 fs. An effect hardly explored<br />

is that due to the laser heating high densities of hot electr<strong>on</strong>s are generated, which<br />

can lead to transfer of spin angular momentum across different nano-layers at a<br />

femtosec<strong>on</strong>d timescale. By c<strong>on</strong>trolling these spin currents, we effectively combine<br />

the field of spin-caloritr<strong>on</strong>ics with ultrafast magnetizati<strong>on</strong> dynamics, providing<br />

access to spin-caloritr<strong>on</strong>ics at ultimate timescales and a unique opportunity for the<br />

development of new spintr<strong>on</strong>ic devices. Malinowski et al. [1] showed in a timeresolved<br />

MO-Kerr effect experiment that spin-dependent transfer of hot electr<strong>on</strong>s<br />

can speed up the demagnetizati<strong>on</strong> process. Here, in order to maximize the torque<br />

applied by these electr<strong>on</strong>s, we explore laser induced dynamics in a SiOx/Pt/Co/Al(~1<br />

nm)/Co/Al sample with a n<strong>on</strong>-collinear orientati<strong>on</strong> of the magnetizati<strong>on</strong>, i.e. an inplane<br />

magnetized top Co- and an out-of-plane bottom Co-layer. We provide a proofof-principle<br />

dem<strong>on</strong>strati<strong>on</strong> of laser-induced spin transfer across the Al spacer layer.<br />

The absorbed spin transfer and torque <strong>on</strong> the magnetizati<strong>on</strong> of the receiving layer<br />

cause an ultrafast canting of its magnetizati<strong>on</strong>, which is experimentally observed as a<br />

successively induced GHz-precessi<strong>on</strong> of the in-plane magnetized Co layer.<br />

[1] G. Malinowski, F. Dalla L<strong>on</strong>ga, J.H.H. Rietjens, P.V. Paluskar, R. Huijink, H.J.M. Swagten, and B.<br />

Koopmans, Nature Phys. 4, 855-858 (2008).<br />

SI08<br />

Investigati<strong>on</strong> of spin wave interference circuit with metallic thin film<br />

Nana Sato 1 , Koji Sekiguchi 2 * and Yukio Nozaki 3<br />

1 Department of Physics, Keio University, Japan<br />

2 Department of Physics, Keio University, PRESTO, JST, Japan<br />

3 Department of Physics, Keio University, CRESTO, JST, Japan<br />

Spin waves are promising phenomen<strong>on</strong> for the future spintr<strong>on</strong>ic devices with low power<br />

c<strong>on</strong>sumpti<strong>on</strong>. For the realizati<strong>on</strong> of the spin wave device, we focused <strong>on</strong> the interference<br />

effect of spin waves[1]. Magnetostatic surface wave (MSSW) was excited in a NiFe thin<br />

film by applying a c<strong>on</strong>tinuous RF field. In order to excite and detect MSSW, a pair of<br />

asymmetric coplanar wave guides (ACPWs) was fabricated <strong>on</strong> the NiFe thin film. The<br />

MSSW was excited by <strong>on</strong>e ACPW, and its signal was detected by the other ACPW as an<br />

induced voltage in a real-time oscilloscope. The advantage of c<strong>on</strong>tinuous excitati<strong>on</strong> lies<br />

in that the MSSW signal becomes stable in time and space, enabling us to sensitively<br />

detect the spin wave interference. For the observati<strong>on</strong> of spin wave interference, another<br />

strip line was inserted in the middle positi<strong>on</strong> between the ACPWs. From ACPWs in both<br />

sides of the inserted strip line two different MSSWs having opposite wave vectors were<br />

excited. By changing the phase of RF fields, the phase difference between two MSSWs<br />

was c<strong>on</strong>trolled. Induced voltage signal at the inserted strip line was changed according<br />

to the phase difference, indicating that we can observe the interference of MSSWs.<br />

[1] M. P. Kostylev et al., Appl. Phys. Lett. 87, 153501 (2005)<br />

SI09<br />

Current-induced magnetizati<strong>on</strong> dynamics of synthetic antiferromagnetic<br />

free layers<br />

Seo-w<strong>on</strong> Lee 1 , Daria Gusakova 2 , Liliana Buda-prejbeanu 2 , Ursula Ebels 2 , Bernard<br />

Dieny 2 and Kyung-jin Lee 1 *<br />

1 Department of Material Science and Engineering, Korea University, Korea<br />

2 SPINTEC, UMR CEA/CNRS/UJF & G-INP, INAC, France<br />

The spin polarized current-induced magnetizati<strong>on</strong> dynamics is studied theoretically in the frame of the driftdiffusi<strong>on</strong><br />

model [1-3] for two different spin-valve (SV) structures: (i) single free layer (SSV) Pol/Cu/FM and<br />

(ii) synthetic anti-ferromagnetic free layer (SyAF-SV) Pol/Cu/FM/Ru/FM. In a first step we have analyzed<br />

the effect of the angular dependence of the spin transfer torque (STT) <strong>on</strong> the magnetizati<strong>on</strong> dynamics for<br />

SSVs. For this four SSVs were c<strong>on</strong>sidered: SSV1 (Co(3.5)/Cu(3)/Co(3)), SSV2 (Co(3.5)/Ru(3)/Co(3)),<br />

SSV3 (Co(3.5)/Cu(3)/Py(3)), and SSV4 (Co(3.5)/Ru(3)/Py(3)). The polarizing layer, Co(3.5), is fixed. We<br />

found that these four different structures have different magnitudes and angular dependences of STT leading<br />

to different current - magnetic field phase diagrams with different critical values and ranges for dynamics.<br />

In the case of SyAF-SVs the drift-diffusi<strong>on</strong> model allows us to take account of not <strong>on</strong>ly STT at Cu/FM but<br />

also STTs at FM/Ru and Ru/FM interfaces. The corresp<strong>on</strong>ding phase diagram is distinct from the <strong>on</strong>e where<br />

STT across Ru has not been c<strong>on</strong>sidered. Hence, this reveals that the STT through Ru c<strong>on</strong>siderably affects<br />

the dynamics of a synthetic free layer. We discuss the results as a functi<strong>on</strong> the strength of the Ruderman-<br />

Kittel-Kasuya-Yosida (RKKY)-type exchange interacti<strong>on</strong>s through Ru.<br />

[1] A. Brataas, Y. V. Nazarov, and G. E. W. Bauer, Phys. Rev. Lett. 84, 2481 (2000); A. Brataas, Y. V. Nazarov,<br />

and G. E. W. Bauer, Eur. Phys. J. B 22, 99 (2001). [2] J. Barnas, A. Fert, M. Gmitra, I. Weymann, and V. K.<br />

Dugaev, Phys. Rev. B 72, 024426 (2005). [3] S. W. Lee and K. J. Lee, J. Kor. Phys. Soc. 55, 1501 (2009).<br />

SI10<br />

SI11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magn<strong>on</strong> excitati<strong>on</strong> studies in str<strong>on</strong>gly correlated electr<strong>on</strong> systems<br />

Cecilia I. Ventura 1 *, Marcello Acquar<strong>on</strong>e 2 and Iv<strong>on</strong> R. Buitrago 3<br />

1 Teoria de Solidos, Centro Atomico Bariloche, and Univ. Nac. Rio Negro,, Argentina<br />

2 IMEM-CNR, Dip. di Fisica, Universita di Parma, Italy<br />

3 Teoria de Solidos, Centro Atomico Bariloche, and Inst. Balseiro, Argentina<br />

WITHDRAWN<br />

Magnetoplasm<strong>on</strong>ic hybrid nanoparticles<br />

Francesco Pineider 1 *, Giulio Campo 2 , Cesar De Julian Fernandez 1 and Claudio<br />

Sangregorio 1<br />

1 Department of Chemistry, University of Florence, CNR-ISTM, Italy<br />

2 Department of Chemistry, University of Florence, Italy<br />

Magnetoplasm<strong>on</strong>ics is a very promising branch of active plasm<strong>on</strong>ics that uses a magnetic field<br />

to modulate plasm<strong>on</strong> res<strong>on</strong>ance: [1] the field-mediated modulati<strong>on</strong> of the plasm<strong>on</strong>ic resp<strong>on</strong>se of<br />

nanoparticles is expected to have str<strong>on</strong>g implicati<strong>on</strong>s in light guiding applicati<strong>on</strong>s <strong>on</strong> plasm<strong>on</strong><br />

res<strong>on</strong>ance-based sensing. [2,3] In this paper we show how ordinary gold nanoparticles' optical<br />

properties are modified by the magnetic field and describe the origin of such magnetoplasm<strong>on</strong>ic<br />

behaviour. Then, using a combined approach with the aid of magneto-optics, magnetometry<br />

and x-ray spectroscopy we investigate several routes to increase the resp<strong>on</strong>se to the magnetic<br />

field by adding a magnetic moiety to the gold nanoparticle. We found that when a transiti<strong>on</strong><br />

metal oxide is added to the gold core in core@shell and heterodimer geometries, the two<br />

materials (magnetic and plasm<strong>on</strong>ic) behave independently, thus giving rise to bifuncti<strong>on</strong>al<br />

magnetic-plasm<strong>on</strong>ic nanoparticle hybrids. True magnetoplasm<strong>on</strong>ic behaviour is instead<br />

found when a higher degree of hybridisati<strong>on</strong> exists between the two moieties, as in the case<br />

when metallic magnetic metals are added to the gold moiety, thus achieving an enhancement<br />

of the magnetic resp<strong>on</strong>se of the optical properties and giving rise to a synergic, n<strong>on</strong>-additive<br />

spectroscopic signature in the magneto-optical spectrum.<br />

1. V. Temnov et al., Nature Phot<strong>on</strong>., 2010, 4, 107. 2. Anker, J. N. et al. Nature Mater.2008 7, 442. 3.<br />

Mayer, K. M., Hafner, J. H. Chem. Rev. 2011, 111, 3828.<br />

SI12<br />

Inhomogeneous standing spin wave excited by the patterned periodic<br />

electrode<br />

Kohei Kiseki 1 , Satoshi Yakata 1 and Takashi Kimura 2 *<br />

1 Kyushu University, Japan<br />

2 Kyushu Univsersity, Japan<br />

There has been a great deal of attenti<strong>on</strong> in the spin waves excited in ferromagnetic films<br />

because of their various potential applicati<strong>on</strong>s such as spin-wave-based logic circuit<br />

and the interc<strong>on</strong>necti<strong>on</strong> device between the electric and spintr<strong>on</strong>ic devices. Efficient<br />

excitati<strong>on</strong> and manipulati<strong>on</strong> of the spin wave are important issues for the realizati<strong>on</strong>s<br />

of practical device applicati<strong>on</strong>s. Spin wave interference in three dimensi<strong>on</strong>al spin<br />

structures may enhance the amplitude of the spin oscillati<strong>on</strong>. For this purpose, we here<br />

systematically investigated the thickness dependence of res<strong>on</strong>ant frequency of the<br />

standing spin wave. We prepared Permalloy films with various thicknesses and excite<br />

the standing spin wave by using a periodic n<strong>on</strong>magnetic Cu electrode. The res<strong>on</strong>ant<br />

frequency of the spin wave was found to increase with the Permalloy thickness. This<br />

can be understood by the increase of the n<strong>on</strong>-excited layer around the bottom of<br />

Permalloy layer, which induces the effective magnetic field to the excited layer via<br />

the exchange interacti<strong>on</strong>. We also perform similar studies of the standing spin wave<br />

in the other ferromagnetic structures exchange biased and ferromagnetic/n<strong>on</strong>magnetic<br />

multi-layered film and present the optimized structure for increasing the output signal<br />

induced by the spin wave excitati<strong>on</strong>.<br />

July 8 - 13, 2012 Busan, Korea 233<br />

Poster Friday


Poster Friday<br />

SI13<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Observati<strong>on</strong> of spin-waves by time-resolved magneto-optic kerr effect<br />

microscope<br />

Sang-jun Yun 1 , Jae-chul Lee 2 , Kyung-ho Shin 2 and Sug-b<strong>on</strong>g Choe 1 *<br />

1 Department of Physics and Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Korea<br />

2 Spin Device Research Center, Korea Institute of Science and Technology, Korea<br />

Spin-wave is an ordering of the magnetizati<strong>on</strong> when the magnetizati<strong>on</strong> of a<br />

ferromagnet is tilted away from its equilibrium state. The spin-waves in metallic thin<br />

films have been recently studied as an emerging field of magnetism for magnetic<br />

recording and spintr<strong>on</strong>ics devices. The spin-waves can be detected by either electrical<br />

or optical method for either frequency or time domain, respectively. In the frequency<br />

domain the ferromagnetic res<strong>on</strong>ance has been comm<strong>on</strong>ly employed to detect the<br />

spin-waves, whereas in the time domain, it is typical to detect damped oscillati<strong>on</strong> of<br />

magnetizati<strong>on</strong> excited by a short magnetic pulse via an inductive or optical apparatus.<br />

Here we report the experimental results <strong>on</strong> the spin-waves by use of all optical pumpprobe<br />

method. 20-nm-thick Co thin films are prepared <strong>on</strong> a GaAs substrate by dc<br />

magnetr<strong>on</strong> sputtering. The pump beam is focused <strong>on</strong>to a spot with a diameter 1 μm of<br />

a sample under an applied magnetic field 2 kOe at normal directi<strong>on</strong> of the film surface.<br />

The spin-waves are then observed by c<strong>on</strong>trolling the tilt angle of the probe beam with<br />

a fixed pump beam. Using this method, a propagating spin-wave can be measured<br />

directly and further analysis will be discussed.<br />

SI14<br />

Nuclear magnetic res<strong>on</strong>ance study of prot<strong>on</strong> dynamics in ZnO<br />

Jun Kue Park, Kyu W<strong>on</strong> Lee and Cheol Eui Lee*<br />

Department of Physics, Department of Physics and Institute for Nano Science, Korea<br />

University, Seoul 136-713, Korea, Korea<br />

Hydrogen acting as a dopant is widely known in compound semic<strong>on</strong>ductors including<br />

many oxides. However, in order for such doping to be technologically relevant, the<br />

thermal stability of the H-d<strong>on</strong>or must be enough to avoid degradati<strong>on</strong> during device<br />

operati<strong>on</strong> at and above room temperature. Here, we have carried out 1H NMR<br />

measurements in order to understand prot<strong>on</strong> moti<strong>on</strong>s in the ZnO lattice at temperatures<br />

between 200 K and 400 K. In our post-annealed ZnO, there are two prot<strong>on</strong> species, <strong>on</strong>e<br />

of which can be assigned to prot<strong>on</strong>s at interstitial sites (Hi + ) in ZnO. The other species<br />

shows no appreciable moti<strong>on</strong> in the temperature range. The distinct activati<strong>on</strong> energies<br />

obtained for the Hi + moti<strong>on</strong>, 0.27 eV and 0.42 eV, are associated with the reorientati<strong>on</strong><br />

around the b<strong>on</strong>ding oxygen atom and hopping between neighboring oxygen atoms,<br />

respectively. These activati<strong>on</strong> energies for diffusi<strong>on</strong>, obtained from the spin-spin<br />

relaxati<strong>on</strong> measurements, are in close agreement with those obtained from ab initio<br />

calculati<strong>on</strong>s.<br />

[1] J. K. Park, K. W. Lee, W. Lee, C. E. Lee, D.-J. Kim, and W. Park, Solid State Commun. 152, 116<br />

(2012). [2] M. G. Wardle, J. P. Goss, and P. R. Bridd<strong>on</strong>, Phys. Rev. Lett. 96, 205504 (2006). [3] L.<br />

-Q. Wang, X. -D. Zhou, G. J. Exarhos, L. R. Peders<strong>on</strong>, C. Wang, C. F. Windisch, and C. Yao, Appl.<br />

Phys. Lett. 91, 173107 (2007).<br />

SI15<br />

Micromagnetic study of magn<strong>on</strong>ic band gaps in waveguides with a<br />

periodic variati<strong>on</strong> of the saturati<strong>on</strong> magnetizati<strong>on</strong><br />

Florin Ciubotaru*, Andrii V. Chumak, Bjoern Obry, Alexander A. Serga and Burkard<br />

Hillebrands<br />

Faculty of Physics, University of Technology, Kaiserslautern, Germany<br />

Spin wave propagati<strong>on</strong> in micro-sized magn<strong>on</strong>ic crystals (MCs) is intensively studied<br />

due to their potential technological applicati<strong>on</strong> for signal processing in spintr<strong>on</strong>ic<br />

devices. Here we report <strong>on</strong> micromagnetic simulati<strong>on</strong>s [1] of the spin wave propagati<strong>on</strong><br />

in a MC realized as a permalloy (Ni 80Fe 20) waveguide with a periodical variati<strong>on</strong> of<br />

its saturati<strong>on</strong> magnetizati<strong>on</strong>. In real structures the variati<strong>on</strong> of magnetizati<strong>on</strong> can be<br />

achieved by using an i<strong>on</strong> implantati<strong>on</strong> technique. The 2 μm-wide waveguide of 40 nm<br />

thickness is magnetized transversal to its l<strong>on</strong>g axis. The MC lattice c<strong>on</strong>stant is equal<br />

to 1 μm. The spin-wave transmissi<strong>on</strong> characteristics have been studied as a functi<strong>on</strong><br />

of the width of the implanted areas and of the level of the magnetizati<strong>on</strong> variati<strong>on</strong> M/<br />

M0. Frequency band gaps were clearly observed in the spin-wave transmissi<strong>on</strong> spectra.<br />

The dependences of the depth, width and the positi<strong>on</strong> in frequency and space of the<br />

rejecti<strong>on</strong> band gaps <strong>on</strong> the above parameters are referred in our studies. The role of<br />

the higher order spin-wave width modes <strong>on</strong> the MC properties is discussed as well.<br />

Support from DFG (grant SE-1771/1-2) is gratefully acknowledged.<br />

[1] OOMMF open code, M. J. D<strong>on</strong>ahue, and D. G. Porter, Report NISTIR 6376, NIST,<br />

Gaithersburg, MD (1999).<br />

234 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SI16<br />

Spin-transfer induced spin waves of a magnetic point c<strong>on</strong>tact with a<br />

c<strong>on</strong>fined domain wall<br />

Hiroko Arai, Hiroshi Tsukahara and Hiroshi Imamura*<br />

Advanced industrial science and technology (AIST), Japan<br />

Spin-transfer induced microwave oscillati<strong>on</strong> will be a powerful candidate for<br />

applicati<strong>on</strong>s in future wireless telecommunicati<strong>on</strong> technologies. According to Ref.<br />

[1], the oscillati<strong>on</strong> of a domain wall between the Bloch- and Neel-type magnetic<br />

c<strong>on</strong>figurati<strong>on</strong>s is induced by a direct current and the corresp<strong>on</strong>ding oscillati<strong>on</strong><br />

frequency is proporti<strong>on</strong>al to the current density. It is also known that the current<br />

injected through a point c<strong>on</strong>tact can excite a variety of spin wave modes [2-4]. It is<br />

intriguing to ask if such spin wave modes can be excited in a thin magnetic layer<br />

c<strong>on</strong>nected to a magnetic point c<strong>on</strong>tact c<strong>on</strong>taining a domain wall. From our calculati<strong>on</strong><br />

we found that three different kinds of spin wave modes can be excited in the thin<br />

film depending <strong>on</strong> the bias current density. The low frequency mode just above the<br />

threshold is the propagating spin wave mode. Then the oscillati<strong>on</strong> frequency increases<br />

drastically with increasing the current density and reaches more than 100 GHz. At high<br />

current density the excited spin wave mode is a propagating mode with a large angle<br />

precessi<strong>on</strong>. We also found that applied field independence of the frequency for the<br />

sec<strong>on</strong>d mode. We shall discuss the physics behind the excitati<strong>on</strong> of spin wave modes.<br />

[1] M. Franchin, T. Fischbacher, G. Bordign<strong>on</strong>, P. de Groot, H. Fangohr, Phys. Rev. B 78, 054447 (2008).<br />

[2] J. C. Sl<strong>on</strong>czewski, J. Magn. Magn. Mater. 195, L261 (1999). [3] A. Slavin and V. Tiberkevich, Phys.<br />

Rev. Lett. 95, 237201 (2005). [4] D. V. Berkov and N. L. Gorn, Phys. Rev. B. 80, 064409 (2005).<br />

SI17<br />

Spin-torque-nano-oscillator using the perpendicular magnetized<br />

CoFeB/MgO/CoFeB magnetic tunnel juncti<strong>on</strong>s<br />

Hiroshi Naganuma 1 *, Nobuhito Inami 1 , Yuki Kawada 1 , Mikihiko Oogane 1 , Yasuo<br />

Ando 1 , Kotaro Mizunuma 2 , Hideo Sato 3 , Michihiko Yamanouchi 3 , Shoji Ikeda 4 and<br />

Hideo Ohno 4<br />

1 Department of Applied Physics, Tohoku University, Japan<br />

2 RIEC, Tohoku University, Japan<br />

3 CSIS, Tohoku University, Japan<br />

4 CSIS, RIEC, Tohoku University, Japan<br />

Perpendicular magnetized free layer in the magnetic tunnel juncti<strong>on</strong>s (p-MTJs) has advantages for spintorque-nano-oscillator<br />

because coherent precessi<strong>on</strong>, high output power, and increasing precessi<strong>on</strong> frequency<br />

due to high magnetocrystalline anisotropy, can be expected. In this study, the microwave transmissi<strong>on</strong><br />

properties were investigated for the p-MTJs using thin CoFeB. The multilayer was prepared by UHV<br />

sputtering system and patterned it into 40-nm-sized juncti<strong>on</strong>s with coplanar waveguide electrode. The<br />

microwave properties were measured under the in-plane magnetic field of 3 kOe to tilt the free layer. The<br />

tunnel magnetoresistance ratio was 70% and 0.9% for the out-of-plane and in-plane directi<strong>on</strong>, respectively.<br />

Below -0.24 mA, the spin torque noise was observed with broad signal. The STO signal was clearly observed<br />

above -0.30 mA at 6 GHz, and the sec<strong>on</strong>d harm<strong>on</strong>ic signal was not observed due to the single-precessi<strong>on</strong>mode<br />

by small juncti<strong>on</strong> size. The linewidth and output power was 650 MHz and 1.1 nW, respectively. Power<br />

has a potential to be more enhanced by stabilizing the pinned layer to increase the relative angle between<br />

free and pinned layer. This study was partly supported by ASPIMATT (JST), by Grant-in-Aid for Young<br />

Scientists A (No. 22686001), by FIRST program (JSPS), and by Maekawa-Hou<strong>on</strong>kai foundati<strong>on</strong>.<br />

SI18<br />

Planar approximati<strong>on</strong> for spin-transfer devices with tilted polarizer<br />

Ya. B. Bazaliy*<br />

Department of Physics and Astr<strong>on</strong>omy, University of South Carolina, Columbia SC,<br />

USA and Institute of <strong>Magnetism</strong> of NASU, Ukraine<br />

Planar spin-transfer devices with dominating easy-plane anisotropy can be described<br />

by an effective <strong>on</strong>e-dimensi<strong>on</strong>al equati<strong>on</strong> for the in-plane azimuthal angle [1-3]. Such<br />

a descripti<strong>on</strong> maps the Landau-Lifshitz-Gilbert equati<strong>on</strong> <strong>on</strong> the Newt<strong>on</strong> equati<strong>on</strong> for<br />

the moti<strong>on</strong> of classical particle in a <strong>on</strong>e-dimensi<strong>on</strong>al potential and thus provides an<br />

intuitive understanding of the magnetic dynamics, allowing <strong>on</strong>e to obtain qualitative<br />

results without performing detailed calculati<strong>on</strong>s. We apply the effective planar equati<strong>on</strong><br />

to describe magnetic switching and precessi<strong>on</strong> states in spin transfer devices with tilted<br />

polarizer [4]. The approach allows <strong>on</strong>e to list the possible dynamic regimes, including<br />

the precessi<strong>on</strong> cycles, and sketch the switching diagram of the device.<br />

[1] Ya. B. Bazaliy, Appl. Phys. Lett. 91, 262510 (2007). [2] Ya. B. Bazaliy, Phys. Rev. B 76,<br />

140402(R) (2007). [3] Ya. B. Bazaliy and F. Arammash, Phys. Rev. B 84, 132404 (2011). [4] Ya. B.<br />

Bazaliy, Phys. Rev. B 85, 014431 (2012).


SJ01<br />

Fast SpinRAM simulati<strong>on</strong> by GPU<br />

Kiyoaki Oomaru* and Yoshinobu Nakatani<br />

The University of Electro-Communicati<strong>on</strong>s, Japan<br />

Spin transfer torque driven magnetoresistive random access memory (SpinRAM) is<br />

<strong>on</strong>e of the candidates of the next generati<strong>on</strong> n<strong>on</strong> volatile memory, and it is studied<br />

intensively. Micromagnetic simulati<strong>on</strong> is <strong>on</strong>e of the methods to study it. In the<br />

SpinRAM simulati<strong>on</strong>, because the size of the MTJ element is small, the number<br />

of the calculati<strong>on</strong> cells is small, and the calculati<strong>on</strong> for <strong>on</strong>e simulati<strong>on</strong> takes <strong>on</strong>ly a<br />

few minutes. However in the real analysis, more than milli<strong>on</strong>s of simulati<strong>on</strong>s are<br />

repeated with different c<strong>on</strong>diti<strong>on</strong>s, the total simulati<strong>on</strong> time becomes huge. Speed up<br />

of the simulati<strong>on</strong> is important. Recently, a Graphic Processing Unit (GPU) is used to<br />

accelerate the micromagnetic simulati<strong>on</strong>. The accelerati<strong>on</strong> rate str<strong>on</strong>gly depends <strong>on</strong> the<br />

number of the calculati<strong>on</strong> cells, and a huge number of the calculati<strong>on</strong> cells is required<br />

to achieve high speed up ratio. Speed up can not be expected in SpinRAM simulati<strong>on</strong><br />

by GPU. In this paper, we propose the simulati<strong>on</strong> method to calculate a number of<br />

the MTJ elements in parallel by GPU, and achieve 75 times of the speed up ratio<br />

in maximum. This study was supported by New Energy and Industrial Technology<br />

Development organizati<strong>on</strong> (NEDO) partly.<br />

SJ02<br />

Micromagnetic simulati<strong>on</strong>s for the spin dynamics and Gilbert damping<br />

c<strong>on</strong>stants in nano-dot with perpendicular magnetic anisotropy<br />

Jungbum Yo<strong>on</strong> 1 , Chun-yeol You 1 * and Myung-hwa Jung 2<br />

1 Department of Physics, Inha Universirty, Korea<br />

2 Department of Physics, Sogang Universirty, Korea<br />

Spin dynamics and the magnetic damping of a nano-dot ellipse with perpendicular<br />

magnetic anisotropy (PMA) are presented by the micromagnetic simulati<strong>on</strong>s. While the<br />

in-plane static magnetic field is applied to the l<strong>on</strong>g axis of the ellipse, the small in-plane<br />

RF magnetic field is applied to the short axis of the ellipse to mimic the ferromagnetic<br />

res<strong>on</strong>ance (FMR) technique. The susceptibility can be obtained by the power spectra<br />

of fast Fourier transform (FFT) from magnetizati<strong>on</strong>s dynamics. There are two regi<strong>on</strong>s<br />

in the external static field dependence res<strong>on</strong>ance frequencies for typical PMA system.<br />

(I) With small external field, the magnetizati<strong>on</strong> is tilted to the static field directi<strong>on</strong><br />

with the finite angle from the film normal. (II) If the static field is str<strong>on</strong>g enough, the<br />

magnetizati<strong>on</strong> is aligned to the static field, where the Zeeman energy overcomes the<br />

PMA energy. In this simulati<strong>on</strong>, the extract Gilbert damping c<strong>on</strong>stants from the line<br />

widths of the res<strong>on</strong>ance peaks from two different regi<strong>on</strong>s. Surprisingly enough, the<br />

obtained values (α_I = 0.0165 and α_II = 0.0194) are different from the input value (α<br />

= 0.027). It implies that the experimentally obtained α can be different from the real<br />

values.<br />

SJ03<br />

Micromagnetic study <strong>on</strong> micro-structured ferromagnetic thin film for<br />

high frequency device applicati<strong>on</strong>s<br />

Keigo Ito, Teppei Takashima, Terumitsu Tanaka* and Kimihide Matsuyama<br />

ISEE, Kyushu University, Japan<br />

The ferromagnetic metallic thin films of Fe has been c<strong>on</strong>sidered as promising materials<br />

for <strong>on</strong>-chip microwave devices, owing to the much higher saturati<strong>on</strong> magnetizati<strong>on</strong> Ms<br />

compared with a c<strong>on</strong>venti<strong>on</strong>al material of yttrium ir<strong>on</strong> garnet (YIG). Understanding<br />

of demagnetizing effects, related to Ms, is important for the design of micro-structured<br />

devices with the high Ms material[1]. In the present study, geometrical effects of microstructured<br />

magnetic thin films <strong>on</strong> high frequency magnetic properties are numerically<br />

investigated with micromagnetic simulati<strong>on</strong>s. The standard material parameters of Fe<br />

with cubic anisotropy are assumed in the simulati<strong>on</strong>. The values of μ’ (@ 1 GHz) and<br />

the res<strong>on</strong>ance frequency fFMR for various aspect ratios w/t are compared. The increase<br />

of μ’ with the decrease of w/t is attributable to the size effect in fFMR, related to the<br />

demagnetizing coefficient al<strong>on</strong>g the film normal directi<strong>on</strong>. It should be noticed that<br />

the μ’ for the same w/t with different w and t is identical. The results suggest that the<br />

demagnetizing effect <strong>on</strong> the high frequency magnetic properties becomes prominent<br />

for the w/t smaller than 400 in the structured Fe thin film.<br />

[1] N. Cramer et al., J. Appl. Phys., 87, 6911 (2000)<br />

SJ04<br />

SJ05<br />

SJ06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Atomistic modelling of magnetizati<strong>on</strong> dynamics with spin torque<br />

Phanwadee Chureemart, Richard F. L. Evans, Irene D'amico and Roy W. Chantrell<br />

Physics, University of York, United Kingdom<br />

The dynamics of the magnetizati<strong>on</strong> following the introducti<strong>on</strong> of a spin current is<br />

studied by using an atomistic model coupled with spin accumulati<strong>on</strong>. The evoluti<strong>on</strong><br />

of the magnetizati<strong>on</strong> and spin accumulati<strong>on</strong> in a trilayer system are calculated selfc<strong>on</strong>sistently,<br />

the interacti<strong>on</strong> between magnetisati<strong>on</strong> and spin current provided by an<br />

s-d exchange term. A spin-polarised current is introduced into the system c<strong>on</strong>taining<br />

a domain wall whose width is varied by changing the anisotropy c<strong>on</strong>stant. The<br />

magnetisati<strong>on</strong> is calculated using an atomistic model based <strong>on</strong> the Heisenberg<br />

exchange energy and spin dynamics introduced via the Landau-Lifshitz-Gilbert<br />

equati<strong>on</strong>. The net spin torque c<strong>on</strong>tributes two important comp<strong>on</strong>ents: the adiabatic<br />

(AST) and n<strong>on</strong>adiabatic torques (NAST). We show that both arise naturally when<br />

calculated directly from the spin accumulati<strong>on</strong>. The maximum value of the AST and<br />

NAST are c<strong>on</strong>sidered for each thickness of domain wall. Both torques decrease as the<br />

domain wall thickness increases. The n<strong>on</strong>adiabaticity factor, defined as the ratio of the<br />

NAST and AST is also shown. Increasing the domain wall thickness gives rise to a<br />

small angle between magnetisati<strong>on</strong> in domain wall. Interestingly the degree of NAST<br />

tends to decay to zero as the thickness of DW increases relative to the spin diffusi<strong>on</strong><br />

length.<br />

Highly parallelized micromagnetic simulator using fast multipole<br />

method<br />

Sung-hyun Lee 1 , Chun-yeol You+ and Sung-chul Shin 3 *<br />

1 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST, Daeje<strong>on</strong> 305-701, Korea<br />

2 Department of Physics, Inha University, Inche<strong>on</strong> 402-751, Korea<br />

3 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST, Daeje<strong>on</strong> 305-701, Korea,<br />

Department of Emerging Material Science, DGIST, Daegu 711-873, Korea<br />

We have developed an alternative method for computing the magnetostatic field of arbitrary-shaped<br />

ferromagnetic systems instead of fast Fourier transform (FFT). The method is based <strong>on</strong> the Taylor<br />

expansi<strong>on</strong> of the potential, as is required by the fast multipole method (FMM)[1][2], the most efficient<br />

method known for calculating mangnetostatic fields in very large systems. The FMM scales as O(N) in<br />

both time and space complexity compared to the direct method with O(N 2 ), or FFT with O(N logN)[3]<br />

and even easier to be parallelized, which is a more valuable soluti<strong>on</strong> for larger ferromagnetic systems.<br />

Graphical processing units (GPU) are now increasingly viewed as data parallel compute coprocessors that<br />

can provide significant computati<strong>on</strong>al performance at low price[4]. We have developed a micromagnetic<br />

simulator using the parallelized method with GPU and have tested in various c<strong>on</strong>figurati<strong>on</strong>s. In that case<br />

speedups of over a factor 100X can easily be obtained compared to the CPU-based OOMMF[5] program<br />

developed at NIST. The tests are carried out with μMag Standard Problem[6] #1,#2,#3,#4.<br />

[1] L. Greengard and V. Rokhlin, J. Comp. Phys. 73, 325-348 (1987). [2] P. B. Visscher and D. M. Apalkov, 'Simple<br />

recursive Cartesian implementati<strong>on</strong> of fast multipole algorithm', [3] R. Ferre, 'Large scale micromagnetic calculati<strong>on</strong>s for<br />

finite and infinite 3D ferromagnetic systems using FFT', Comp. Phys. Commun., 105, 169-186 (1997). [4] CUDA, http://<br />

www.nvidia.com [5] OOMMF, http://math.nist.gov/oommf [6] μMag, http://www.ctcms.nist.gov/~rdm/mumag.org.html<br />

Effect of calculati<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>s <strong>on</strong> the numerical simulati<strong>on</strong> of<br />

magnetic materials with random magnetic anisotropy<br />

S. J. Lee 1 , Suguru Sato 1 , Hideto Yanagihara 1 , Eiji Kita 1 * and Chiharu Mitsumata 2<br />

1 Institute of Applied Physics, University of Tsukuba, Japan<br />

2 Graduate School of Engineering, Tohoku University, Japan<br />

Numerical simulati<strong>on</strong> was performed <strong>on</strong> magnetic materials with random anisotropy.<br />

An assembly of magnetically interacting grains with randomly oriented uniaxial<br />

anisotropy was provided and magnetizati<strong>on</strong> was calculated using the Landau-Lifshitz-<br />

Gilbert equati<strong>on</strong>. The magnetizati<strong>on</strong> in a particular grain is assumed to align in the<br />

same directi<strong>on</strong> (single spin model).[1] Calculati<strong>on</strong>s were carried out for N × N × N<br />

three dimensi<strong>on</strong>al cells changing cell sizes from 5 to 40 nm. The interacti<strong>on</strong> at the<br />

interface between grains was taken into account by the interacti<strong>on</strong> energy between the<br />

unit vectors representing grain magnetizati<strong>on</strong> directi<strong>on</strong>s. N was changed from 10 to 64.<br />

In the case of N = 10, the relati<strong>on</strong> between coercive forces and grain sizes was obtained<br />

to be δ = 5.7 in Hc ~ D^δ, and fits to the primitive theory of random anisotropy model<br />

(RAM) δ = 6. As the N increased, the δ tends to decrease slightly from 5.7 to 4.2.<br />

The grain sizes where the coercive force becomes less dependent <strong>on</strong> the grain size,<br />

suggesting the natural exchange length, did not changed much.<br />

[1] S.-J. Lee, S. Sato, H. Yanagihara, E. Kita, and C. Mitsumata, J. Magn. Magn. Mater. 323 (2011)<br />

28.<br />

July 8 - 13, 2012 Busan, Korea 235<br />

Poster Friday


Poster Friday<br />

SJ07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Vortex and antivortex formati<strong>on</strong> in magnetic rolled-up nanotubes<br />

Jehyun Lee 1 , Denys Makarov 2 , Robert Streubel 2 , Carlos Cesar Bof Buf<strong>on</strong> 2 , Celine<br />

Vervacke 2 , Dieter Suess 3 , Josef Fidler 3 , Oliver G Schmidt 2 and Sang-koog Kim 1 *<br />

1 Nati<strong>on</strong>al Creative Research Center for Spin Dynamics & Spin-Wave Devices and Nanospinics<br />

Lab., Research Institute of Adv. Materials, Dep. of Materials Sci. & Eng., Seoul Nat'l Univ., Korea<br />

2 Institute for Integrative Nanosciences, IFW Dresden, Germany<br />

3 Institute of Solid State Physics, Vienna University of Technology, Austria<br />

Magnetic nanotubes have attracted c<strong>on</strong>siderable attenti<strong>on</strong> owing to both fundamental and technological<br />

interest1-2. Using a rolling-up fabricati<strong>on</strong> technology3, patterned multilayer tubes can be prepared that exhibit<br />

significant modificati<strong>on</strong>s of magnetic behaviors compared to those of thin-film structures4-5. In order to elucidate<br />

the underlying physics, we c<strong>on</strong>ducted micromagnetic simulati<strong>on</strong>s of possible spin c<strong>on</strong>figurati<strong>on</strong>s in rolled-up<br />

nanotubes. When a permalloy platelet of dimensi<strong>on</strong>s 400 x 400 x 5 nm3 is rolled up, various spin c<strong>on</strong>figurati<strong>on</strong>s<br />

are found to be either C-state, vortex(V) state or anti-vortex(AV) state in the plane of thin films with more spins<br />

being forced to be aligned al<strong>on</strong>g the tube axis. Therefore, the regi<strong>on</strong> whose spins are aligned transversely to the<br />

tube axis is compressed. The modified spin alignment is supposed to increase the anisotropy magnetoresistance<br />

ratio. Although the reorientati<strong>on</strong> of local magnetizati<strong>on</strong>s in the rolled-up tubes results in increases of the exchange<br />

energy, it reduces much more the magnetostatic energy, particularly for AV state. C<strong>on</strong>sequently, the total energies<br />

of various spin c<strong>on</strong>figurati<strong>on</strong>s are similar. The cores in the V and AV states of the rolled-up tubes show another<br />

interesting feature: the stray fields inside the tubes are cancelled out at the positi<strong>on</strong>s.<br />

This work was supported by Basic Science Research Program through the Nati<strong>on</strong>al Research Foundati<strong>on</strong> of Korea (NRF) funded<br />

by the Ministry of Educati<strong>on</strong>, Science and Technology (No. 20110000441). 1. S. Allende, J. Escrig, D. Altbir, E. Salcedo, M. Bahiana,<br />

The Eur. Phy. J. B 66, 37 (2008). 2. E. J. Smith et al., Nano Letters 11, 4037 (2011/10/12, 2010). 3. O. G. Schmidt, K. Eberl, Nature<br />

410, 168 (2001). 4. C. Muller et al., Appl Phys Lett 100, 022409 (2012). 5. C. Muller et al., Appl Phys Lett 94, 102510 (2009).<br />

SJ08<br />

Magneto resistance study using micro magnetic simulati<strong>on</strong>s in<br />

permalloy nano ladder<br />

Venkateswarlu Dasari*, Vineeth Mohanan Parakkat and Anil P. S. Kumar<br />

Physics, Indian Institute of Science, India<br />

Micromagnetic simulati<strong>on</strong> is <strong>on</strong>e of the tools to investigate magnetizati<strong>on</strong> reversal mechanism<br />

in nano-wires and nano structures. In the open source simulators like OOMMF[1], magneto<br />

transport studies viz., Anisotropic Magnetoresistance (AMR) is not available and is n<strong>on</strong>trivial<br />

since it involves solving the generalized Laplacian equati<strong>on</strong> for getting the spatial<br />

distributi<strong>on</strong> of current density[2]. In the case of nano wires, the current density is c<strong>on</strong>sidered<br />

to be uniform[3]; in this quasi uniform state <strong>on</strong>e can apply phenomenological expressi<strong>on</strong> in<br />

deriving the AMR. We apply this c<strong>on</strong>diti<strong>on</strong> in OOMMF-simulati<strong>on</strong>s and is compared with<br />

the commercial software “LLG-simulator”[4]. For this purpose, we c<strong>on</strong>sidered single wire of<br />

length(L) 1000nm, width(W) 100nm and thickness(t) 5nm. Both the simulators agree with<br />

each other within a maximum error of 5%. Further, we studied a ladder structure formed<br />

by joining these two wires, with interc<strong>on</strong>nects of L=100nm, W=20nm and t=5nm. In this<br />

ladder structure, we varied number of steps by keeping the periodic separati<strong>on</strong> as 50nm. It<br />

was found that the coercivity falls n<strong>on</strong>-linearly from 312 to 255G when the number of steps<br />

increased from 1 to 13. The resistance measured at remanence states drops linearly, which<br />

indicates the decrease in remanence due to the local nucleati<strong>on</strong> centers.<br />

1. M. J. D<strong>on</strong>ahue and D.G. Porter, http://math.nist.gov/oommf 2. S. Manik<strong>on</strong>da, M. Berz and K. Makino,<br />

IEEE Trans. Comp., 4, 1604 (2005) 3. C. Hassel, F. M. Romer, R. Meckenstock, G. Dumpich, and J.<br />

Lindner, Phys. Rev. B, 77, 224439 (2008) 4. M. R. Scheinfein, http://llgmicro.home.mindspring.com/<br />

SJ09<br />

Soft layer driven switching of microwave-assisted magnetic recording<br />

<strong>on</strong> segmented perpendicular media<br />

Jing Qiang Goh 1 *, Zhi-min Yuan 2 , Lei Shen 2 , Tiejun Zhou 2 and Yuan Ping Feng 1<br />

1 Department of Physics, Nati<strong>on</strong>al University of Singapore, Singapore<br />

2 Data Storage Institute, Agency for Science, Technology and Research, Singapore<br />

In this work, we use micromagnetic modeling to investigate microwave-assisted<br />

magnetic recording <strong>on</strong> segmented perpendicular media. Two types of microwave<br />

fields, sinusoidal and finite bandwidth square microwaves, have been chosen for<br />

our study. We show that microwave fields, when applied to the soft segment, can<br />

assist the magnetizati<strong>on</strong> reversal of the hard segment. The calculated assisted<br />

frequencies are insensitive to the variati<strong>on</strong> of inter-segment exchange coupling of<br />

segmented perpendicular media. Our results suggest that sinusoidal microwave fields<br />

are practically more feasible than square microwave fields for the soft layer driven<br />

switching mechanism of segmented perpendicular media.<br />

1) C.-K. Goh, Z. min Yuan, T. Zhou, L. Wang, and B. Liu, J. Appl. Phys. 105, 07B908 (2009). 2) C.-K.<br />

Goh, Z. min Yuan, and B. Liu, Appl. Phys. Lett. 94,152510 (2009). 3) J.-G. Zhu and Y. Wang, IEEE<br />

Trans. Magn. 47, 4066 (2011).<br />

236 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SK01<br />

Top composite free layer n<strong>on</strong>-collinear spin valve for hysteresis-free<br />

GMR sensors<br />

Vladimir V. Ustinov*, Michael A. Milyaev, Larisa I. Naumova, Tatiana P. Krinitsina<br />

and Vladimir V. Proglyado<br />

Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, Russia<br />

Top spin valves Ta/[FeNi/CoFe]/Cu/CoFe/FeMn/Ta based <strong>on</strong> FeMn antiferromagnet<br />

with varying [Fe 20Ni 80/Co 90Fe 10] composite free layer parameters and Cu interlayer<br />

thickness were prepared by DC magnetr<strong>on</strong> sputtering. GMR characteristics of spin<br />

valves (SV) were investigated under the c<strong>on</strong>diti<strong>on</strong>s of n<strong>on</strong>-collinear SV geometry<br />

when the applied magnetic field and pinning directi<strong>on</strong> for bottom magnetic layer<br />

are not collinear. It was shown that the value of low field hysteresis caused by free<br />

layer magnetizati<strong>on</strong> reversal can be reduced down to 0.1 Oe keeping the GMR ratio<br />

about 10 % by using both layers thicknesses and n<strong>on</strong>-collinearity angle variati<strong>on</strong>.<br />

The magnetoresistive sensitivity of n<strong>on</strong>-collinear is about 1 %/Oe. Low-hysteresis<br />

free layer magnetizati<strong>on</strong> reversal is mainly due to coherent rotati<strong>on</strong> of magnetizati<strong>on</strong>.<br />

The dependences of low field hysteresis value and GMR ratio <strong>on</strong> the Cu spacer layer<br />

thickness and the angle between applied magnetic field and pinning directi<strong>on</strong> are<br />

presented.<br />

SK02<br />

Str<strong>on</strong>g texture and low hysteresis in MnIr-based top spin valve<br />

Mikhail Milyaev, Larisa Naumova, Vyacheslav Proglyado, Tatiana Krinitsina,<br />

Nataliya Bannikova and Vladimir Ustinov<br />

Institute of Metal Physics UB RAS, Russia<br />

“Spin valve” nanostructures with GMR and TMR are widely used in spintr<strong>on</strong>ics. In<br />

some devices the hysteresis of magnetoresistance must be negligible. The hysteresis is<br />

weak in the spin valves with axial texture. In this work we study the dependence<br />

of the free layer hysteresis loop width <strong>on</strong> the texture strength that is characterized by the<br />

FWHM of rocking curve. The top spin valves [Ta, (Ni 80Fe 20) 60Cr 40)]/Ni 80Fe 20/Co 90Fe 10/<br />

Cu/Co 90Fe 10/Mn 75Ir 25/Ta with various thickness of the magnetic and n<strong>on</strong>magnetic layers<br />

are investigated. On the base of magnetic, magnetoresistance and XRD data the n<strong>on</strong>linear<br />

dependence between FWHM of rocking curves measured at the integrated (111) Bragg<br />

peak of Ni 80Fe 20, Co 90Fe 10 and Cu layers and free layer coercivity is established. A<br />

correlati<strong>on</strong> between GMR ratio and FWHM is not revealed. It is shown that in the spin<br />

valve Ta(50A)/NiFe(30A)/CoFe(20A)/Cu(22A)/CoFe(25A)/MnIr(50A)/Ta(20A) with<br />

sharp texture, GMR ratio of 10.6 % and minimal coercivity of 8.7 Oe, the free<br />

layer hysteresis can be effectively reduced down to few tenth of Oersted [1]. This study is<br />

supported by RFBR, project No. 10-02-00590, by the Program of Presidium RAS, project<br />

No. 12-P-2-1051, and OFI-UB RAS, project No. 11-2-23-NPO.<br />

[1] V.V. Ustinov et al. Phys. Met. Metallogr. in press.<br />

SK03<br />

Low temperature crystallizati<strong>on</strong> process in Co 2FeSi Heusler alloy thin<br />

films<br />

Luke Fleet 1 , M. J. Walsh 1 , J. Sagar 1 , T. Nakayama 2 and A. Hirohata 1 *<br />

1 The University of York, United Kingdom<br />

2 Nagaoka University of Technology, Japan<br />

One of the major challenges for Heusler alloys is to achieve a high L 21 ordering at<br />

low annealing temperatures in order to limit interdiffusi<strong>on</strong> in multilayer devices.<br />

We report a low temperature crystallizati<strong>on</strong> process of polycrystalline Co 2FeSi films<br />

using in-situ imaging techniques. 20nm thick Co 2FeSi films were annealed in-situ up<br />

to 600°C with both TEM and diffracti<strong>on</strong> patterns recorded. We show that the grain<br />

crystallizati<strong>on</strong> starts to occur at 230°C with no additi<strong>on</strong>al nucleati<strong>on</strong> occurring after<br />

30 minutes but further annealing does improve the grain ordering. By varying the<br />

growth c<strong>on</strong>diti<strong>on</strong>s it is possible to change the number of nucleati<strong>on</strong> sites and also the<br />

median grain size. Through varying the initial film morphology it is possible to change<br />

the number of nucleati<strong>on</strong> sites and also the median grain size from 20 to 250nm.<br />

Magnetic measurements show that the magnetic moment is over 80% of the theoretical<br />

value predicted [1]. This shows that a high degree of ordering can be created for<br />

polycrystalline films after a low temperature anneal of less than 300°C.<br />

[1] A. Hirohata, and Y. Otani, Epitaxial Ferromagnetic Films And Spintr<strong>on</strong>ic Applicati<strong>on</strong>s<br />

(Transworld Research Network, 2009).


SK04<br />

Spin-polarized itinerant electr<strong>on</strong>s in Co2MnAl and Co2MnSi studied<br />

by magnetic Compt<strong>on</strong> scattering<br />

Soichiro Mizusaki 1 , Tomohiro Ohnish 1 , Masayoshi Itou 2 , Yoshiharu Sakurai 2 , Tadashi C Ozawa 3 , Hiroaki<br />

Samata 4 , Yoshihiko Noro 5 and Yujiro Nagata 1<br />

1<br />

Aoyama Gakuin University, Japan<br />

2<br />

Japan Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research institute (JASRI/SPring-8), Japan<br />

3<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Center for Materials Nanoarchitect<strong>on</strong>ics, Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

4 Kobe University, Japan<br />

5 Kawazoe Fr<strong>on</strong>tier Technologies, Co. Ltd., Japan<br />

Investigating the spin-polarized itinerant electr<strong>on</strong> states in the intermetallic alloys and compounds<br />

is indispensable for the development of potential spintr<strong>on</strong>ic materials. In this work, we have studied<br />

the relati<strong>on</strong>ship between the number of sp itinerant electr<strong>on</strong>s and the spin moment in the compounds<br />

Co 2MnZ (Z=Al or Si), using synchrotr<strong>on</strong>-based Magnetic Compt<strong>on</strong> scattering (MCS)[1], which<br />

provide the bulk spin-polarized electr<strong>on</strong> momentum distributi<strong>on</strong>s, ie. magnetic Compt<strong>on</strong> profiles<br />

(MCPs). The shape of MCPs depends <strong>on</strong> the number of spin-polarized electr<strong>on</strong>s of occupied orbitals,<br />

and the area of MCP corresp<strong>on</strong>ds to the spin moment. Co 2MnZ (Z=Al or Si) is a good system to<br />

investigate the spin-polarized itinerant electr<strong>on</strong> states since the number of sp itinerant electr<strong>on</strong>s can<br />

be changed without affecting the number of 3d electr<strong>on</strong>s. The following results were obtained . 1. The<br />

total spin moment increases by 1 μ B/f.u. from Co 2MnAl (4μ B/f.u.) to Co2MnSi (5μ B/f.u.), with <strong>on</strong>e sp<br />

electr<strong>on</strong> difference. 2: The proporti<strong>on</strong> of the partial spin moment carried by sp itinerant electr<strong>on</strong>s is<br />

same for Co 2MnAl and Co 2MnSi. From these findings, additi<strong>on</strong>al sp electr<strong>on</strong>s occupy the 3d electr<strong>on</strong><br />

states and increases the localized spin moment. This enhances the spin polarizati<strong>on</strong> of itinerant<br />

electr<strong>on</strong>s through the indirect magnetic exchange interacti<strong>on</strong>.<br />

[1] M. J. Cooper, P. E. Mijnarends, N. Shiotani, N. Sakai, and A. Bansil, in X-ray Compt<strong>on</strong> scattering, Oxford<br />

University Press, Oxford, 2004.<br />

SK05<br />

Evidence of inelastic tunneling in magnetic tunnel juncti<strong>on</strong>s via<br />

capacitance-voltage characteristics<br />

Ajeesh M Sahadevan 1 *, Gopinadhan Kal<strong>on</strong> 2 , Charanjit S Bhatia 1 and Hyunsoo Yang 2<br />

1<br />

Department of Electrical & Computer engineering, Nati<strong>on</strong>al University of<br />

Singapore, Singapore<br />

2<br />

Department of Electrical & Computer engineering, NUSNNI-Nanocore, Nati<strong>on</strong>al<br />

University of Singapore, Singapore<br />

Magnetic tunnel juncti<strong>on</strong>s (MTJ) have played a key role in the development of HDDs as well as next<br />

generati<strong>on</strong> n<strong>on</strong>-volatile memories. For high speed applicati<strong>on</strong>s, capacitance and RC time c<strong>on</strong>stant analysis of<br />

MTJs becomes very important. Also for metal-insulator-metal structures with extremely thin tunnel barriers as<br />

in MTJs, the capacitance is mainly determined by the interface properties of the structure as the electric field<br />

penetrati<strong>on</strong> becomes significant. Since in MTJs the interfaces are very critical in determining the tunneling<br />

magnetoresistance (TMR), study of capacitance becomes very relevant for better understanding of these<br />

devices. We report the temperature dependence of C-V characteristics in MTJs. All our MTJs show a negative<br />

tunneling magnetocapacitance (TMC) with a magnitude lower than the TMR [1]. At temperatures lower than<br />

100 K, a zero-bias anomaly appears in the C-V profile. The behavior is similar to inelastic tunneling or zerobias<br />

anomaly in MTJs. Zero-bias anomaly in the R-V characteristics of MTJs has been attributed to magn<strong>on</strong><br />

and ph<strong>on</strong><strong>on</strong> assisted tunneling or thorough impurities inside the barrier. But since the capacitance is mainly<br />

c<strong>on</strong>tributed from the interfaces, the origin of these effects is from the interfaces rather than the bulk.<br />

[1] P. Padhan et al., Appl. Phys. Lett. 90, 142105 (2007).<br />

SK06<br />

Spin-polarizati<strong>on</strong> measurements for Co 2MnSi using Co 2MnSi/MgO/<br />

NbN epitaxial tunnel juncti<strong>on</strong>s<br />

Ken-ichi Matsuda, Takaho Shinoki, Tomoyuki Taira, Tetsuya Uemura and Masafumi<br />

Yamamoto<br />

Div. of Electr<strong>on</strong>ics for Informatics, Hokkaido University, Japan<br />

Spin-polarizati<strong>on</strong> measurements were carried out for the Co-based Heusler alloy, Co 2MnSi (CMS,<br />

for short), using CMS/MgO/NbN epitaxial tunnel juncti<strong>on</strong>s. The layer structure was as follows:<br />

(from the substrate side) MgO buffer (10 nm) /NbN (10 nm)/MgO barrier (1.4-3.2 nm)/CMS (3<br />

nm)/Co 50Fe 50 (1nm)/IrMn (10nm)/Ru cap (5 nm). All the samples were successively deposited<br />

<strong>on</strong> MgO(001) single-crystal substrates in an ultrahigh vacuum chamber. Spin-polarizati<strong>on</strong><br />

measurements were carried out at 1.5 K using the c<strong>on</strong>venti<strong>on</strong>al lock-in technique. The spin<br />

polarizati<strong>on</strong>s (P) were evaluated for three different film compositi<strong>on</strong>s of CMS: Co 2Mn 0.72Si 0.81,<br />

Co 2Mn 1.00Si 0.81, and Co 2Mn 1.40Si 0.81. At H = 0 T, typical differential c<strong>on</strong>ductance curves were clearly<br />

observed, and were well-fitted by the modified-BTK theory [1]. The superc<strong>on</strong>ducting energy gap<br />

extracted from the analysis was about 2.5 meV [2]. The P values evaluated at H = 8 T were 0.41,<br />

0.50, and 0.54 for respective CMS films. Thus, the P increased with increasing Mn-compositi<strong>on</strong> in<br />

CMS films. This result is c<strong>on</strong>sistent with the increase of the TMR ratios for CMS/MgO/CMS fullyepitaxial<br />

magnetic tunnel juncti<strong>on</strong>s, and can be qualitatively understood from the view point of the<br />

suppressi<strong>on</strong> of minority-spin in-gap states that resulted from the reducti<strong>on</strong> of CoMn anti-sites [3].<br />

[1] G. J. Strijkers, Y. Ji, F. Y. Yang, C. L. Chien, and J. M. Byers, Phys. Rev. B, 63 (2001) 104510. [2] H.<br />

Yang, S.-H. Yang, C. Kaiser, and S. Parkin, Appl. Phys. Lett., 88 (2006) 182501. [3] M. Yamamoto, T.<br />

Ishikawa, T. Taira, G.-f. Li, K.-i. Matsuda, and T. Uemura, J. Phys.: C<strong>on</strong>d. Matt., 22 (2010) 164212.<br />

SK07<br />

SK08<br />

SK09<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Variati<strong>on</strong> of point-c<strong>on</strong>tact andreev reflecti<strong>on</strong> spectra of<br />

ferromagnetically ordered metals<br />

Elina Tuuli* and Kurt Gloos<br />

Department of Physics and Astr<strong>on</strong>omy, University of Turku, Finland<br />

Point-c<strong>on</strong>tact Andreev reflecti<strong>on</strong> (AR) spectra of ferromagnets are usually fitted with<br />

modified BTK models that take into account the spin polarizati<strong>on</strong>. On the other hand,<br />

AR spectra of n<strong>on</strong>-magnetic metals are often described by a BTK model that includes<br />

Dynes' lifetime parameter. The two models yield rather similar spectra and can in fact<br />

be used to fit the spectra of both magnets and n<strong>on</strong>-magnets. The differences between<br />

them are most pr<strong>on</strong>ounced at low temperatures but str<strong>on</strong>gly suppressed by thermal<br />

smearing. We have applied the two models to point c<strong>on</strong>tacts between the classical<br />

band ferromagnets Co, Fe, and Ni and the c<strong>on</strong>venti<strong>on</strong>al superc<strong>on</strong>ductors Nb, Ta, and<br />

Al as functi<strong>on</strong> of temperature. The spectra varied between an absent superc<strong>on</strong>ducting<br />

signal and an occasi<strong>on</strong>al Josephs<strong>on</strong>-like anomaly with a large resistance drop at<br />

zero bias, while many spectra had the typical Andreev reflecti<strong>on</strong> double-minimum<br />

structure. However, we could reproduce the expected c<strong>on</strong>stant polarizati<strong>on</strong> of the<br />

ferromagnet and a BCS-type dependence of the superc<strong>on</strong>ducting gap <strong>on</strong>ly in a few<br />

cases. This unexpected variati<strong>on</strong> could be related to the interplay of ferromagnetism<br />

and superc<strong>on</strong>ductivity at the interfaces.<br />

Fabricati<strong>on</strong> of Highly Sensitive Magnetic Tunnel Juncti<strong>on</strong>s for Biomagnetic<br />

Field Sensor Applicati<strong>on</strong><br />

Kosuke Fujiwara 1 *, Mikihiko Oogane 1 , Takuo Nishikawa 2 , Saeko Yokota 1 , Hiroshi<br />

Naganuma 1 and Yasuo Ando 1<br />

1 Department of Applyed Physics, Tohoku University, Japan<br />

2 LC Business Department, K<strong>on</strong>icaminolta Opto,Inc., Japan<br />

The discovery of large tunnel magneto-resistance (TMR) effect of over 200% in MgO based<br />

magnetic tunnel juncti<strong>on</strong>s (MTJs)[1,2] enabled us to design highly sensitive magnetic field<br />

sensors[3,4], such as a bio-magnetic field sensor. For this purpose, we need MTJs with a high<br />

sensitivity and hysteresis-free resp<strong>on</strong>ses. In this study, we fabricated MTJs with a NiFe 70/<br />

Ru 0.9/ CoFeB 3 (in nm) bottom synthetic ferri-coupled free layer and an MgO barrier layer.<br />

This thick NiFe layer serves low magnetic anisotropy[5]. The MTJs were annealed at 325°C<br />

by applying a magnetic field. After the first annealing, we rotated directi<strong>on</strong> of the magnetic<br />

field to 90 degree and annealed at 300°C. This sec<strong>on</strong>d annealing redirects easy axis of pinned<br />

layer. The TMR properties were measured using DC four probes with an applied magnetic<br />

field al<strong>on</strong>g the hard axis of the free layer, and we have successfully observed the very high<br />

sensitivity of 25.3%/Oe and hysteresis free resp<strong>on</strong>se. Developed MTJs are promising for<br />

bio-magnetic sensor applicati<strong>on</strong>. This work was partly supported by S-Innovati<strong>on</strong> program,<br />

Japan Science and Technology Agency (JST).<br />

[1] S. Yuasa et al, Nat. Mater., 3 (2004) 868. [2] S. S. P. Parkin et al, Nat. Mater., 3 (2004) 862 [3] D.<br />

Mazumdar et al, J. Appl. Phys., 103 (2008) 113911. [4] J. M. Almeida et al, J. Appl. Phys., 105 (2009)<br />

07E722. [5] K. Fujiwara et al, Jpn. J. Appl. Phys., 50 (2011) 013001<br />

Oscillatory exchange coupling and str<strong>on</strong>g magnetoresistance effect in<br />

Fe/AgX/Fe (001) heterostructures with X=Cl and Br<br />

Petru Vlaic 1 * and Emil Burzo 2<br />

1<br />

Biophysics Department, University of Medicine and Pharmacy 'Iuliu Hatieganu'<br />

400023 Cluj-Napoca, Romania<br />

2<br />

Faculty of Physics, Babes-Bolyai University RO-400084 Cluj-Napoca, Romania<br />

AgCl and AgBr silver halides crystallize under ambient c<strong>on</strong>diti<strong>on</strong>s in rock salt geometry having<br />

lattice parameters epitaxially compatible with Fe structure. AgCl and AgBr compounds are wide<br />

bang gap semic<strong>on</strong>ductors with indirect band gaps of 3.2 eV and 2.69 eV, respectively. Thus<br />

Fe/AgX/Fe (001) magnetic tunnel juncti<strong>on</strong>s (MTJs) with X=Cl and Br may represent feasible<br />

heterostructures for comparative studies with sp based Fe/MgO/Fe and Fe/NaCl/Fe juncti<strong>on</strong>s<br />

as well as for spintr<strong>on</strong>ic applicati<strong>on</strong>s. In present c<strong>on</strong>tributi<strong>on</strong> structural, electr<strong>on</strong>ic and magnetic<br />

properties of Fe/AgX/Fe (001) MTJs are theoretically investigated by means of a self-c<strong>on</strong>sistent<br />

Green’s functi<strong>on</strong> technique for surface and interfaces implemented within tight-binding linear<br />

muffin-tin orbital (TB-LMTO) method. The spin-dependent transport properties are determined<br />

by means of Kubo approach implemented within TB-LMTO formalism. Formati<strong>on</strong> of sharp<br />

Fe/AgCl(AgBr) interfaces and enhancement of interfacial Fe magnetic moments are predicted.<br />

Metal induced gap states <strong>on</strong> both ani<strong>on</strong> and cati<strong>on</strong> sites are observed. Oscillatory exchange<br />

couplings between ferro- and antiferromagnetic states with decreasing amplitude are evidenced.<br />

Spin-dependent transport properties are determined by the complex band structures of AgCl and<br />

AgBr barriers. Tunneling magnetoresistance ratios as high as 3500 % are predicted for Fe/AgCl/<br />

Fe MTJs in asymptotic regime and even higher values for Fe/AgBr/Fe juncti<strong>on</strong>s.<br />

July 8 - 13, 2012 Busan, Korea 237<br />

Poster Friday


Poster Friday<br />

SK10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Transport properties in double MgO barrier magnetic tunnel juncti<strong>on</strong>s<br />

with Fe nano-particles<br />

Pham Van Thach, Do Bang, Shinji Miwa, Takayuki Nozaki, Eiichi Tamura, Norikazu<br />

Mizuochi, Teruya Shinjo and Yoshishige Suzuki*<br />

Graduate School of Engineering Science, Osaka University, Toy<strong>on</strong>aka, Osaka 560-<br />

8531, Japan<br />

Interplay between spin dependent electr<strong>on</strong> tunneling and Coulomb blockade effect [1,2] is <strong>on</strong>e of the<br />

most attractive subjects in spintr<strong>on</strong>ics field because it is expected to give rise to remarkable tunnel<br />

magnetoresistance (TMR) effect as well as exhibit fascinating phenomena such as K<strong>on</strong>do effect[3]. And<br />

in order to realize this interplay, double barrier magnetic tunnel juncti<strong>on</strong>s (MTJs) with ferromagnetic<br />

nano-paricles are good candidates. In this research, double barrier MTJs with structure of MgO(001)<br />

substrate/MgO/Cr/Fe/MgO/Fe particles(t = 0.12 - 1.37)/MgO/Fe/Au (unit in nanometer) are fabricated.<br />

An average diameter of the Fe nano-particles estimated by Langevin functi<strong>on</strong> fitting reveals an almost<br />

linear relati<strong>on</strong> with t for t ≤ 1.02 nm. Coulomb blockade effect was observed for t ≤ 1.02 nm, and the<br />

t dependence of the Coulomb energy of the Fe nano-particles was explained c<strong>on</strong>sistently by a simple<br />

capacitance model. Interestingly, electr<strong>on</strong> tunneling spectra (dI/dV) and TMR show a dip around zero<br />

bias at low temperatures. A suppressi<strong>on</strong> of the TMR around zero bias implies a phenomen<strong>on</strong> like K<strong>on</strong>do<br />

physics. The transport properties in the double barrier MTJs having Fe nano-particles were also compared<br />

with those in a double barrier MTJ with the c<strong>on</strong>tinuous middle Fe layer and a single barrier MTJ.<br />

Acknow ledgements: This work is supported by Grant-in-Aid for Scientific Research (S), MEXT,<br />

Japan. (No. 23226001). [1]. S. Mitani et al. Phys. Rev. Lett. 81, 2799 (1998). [2]. H. Sukegawa et<br />

al. Phys. Rev. Lett 94, 068304 (2005). [3]. K. I. Lee et al., Phys. Rev. Lett. 98, 107202 (2007).<br />

SK11<br />

Characterisati<strong>on</strong> of Epitaxial and Polycrystalline Co2FeSi thin films<br />

James Sagar 1 , Hiroaki Sukegawa 2 , Le<strong>on</strong>ardo Lari 3 , Vlado K Lazarov 3 , Seiji Mitani 4<br />

and Atsufumi Hirohata 5 *<br />

1<br />

Department of Physics, University of York, United Kingdom<br />

2<br />

Magnetic Materials Centre, Nati<strong>on</strong>al Institute for Materials Science (NIMS), 1-2-1<br />

Sengen, Tsukuba 305-0047, Japan<br />

3<br />

Department of Physics, University of York, York, YO10 5DD, United Kingdom<br />

4<br />

Magnetic Materials Centre, Nati<strong>on</strong>al Institute for Materials Science (NIMS), 1-2-1<br />

Sengen, Tsukuba, Japan<br />

5<br />

Department of Electr<strong>on</strong>ics, University of York, York, YO10 5DD, United Kingdom<br />

We have grown and characterised both epitaxial and polycrystalline Co 2FeSi thin films using<br />

UHV magnetr<strong>on</strong> and HiTUS sputtering. The structure of the films has been studied using XRD,<br />

TEM and STEM. The combinati<strong>on</strong> of these techniques allows analysis of the structure and defects<br />

within the films. Magnetic characterisati<strong>on</strong> has been carried out using AGFM and VSM. UHV<br />

magnetr<strong>on</strong> sputtered films have been found to become increasingly L 21 ordered after annealing<br />

above 500°C. HiTUS deposited samples form a polycrystalline film from and amorphous Co, Fe<br />

and Si matrix after annealing at 500°C for 3, 6 and 9 hours with large (50nm-250nm) L 21 and B 2<br />

ordered grains. This growth process results in films with large Hc (>500Oe) these values are two<br />

orders of magnitude greater than those found for epitaxial films [1]. The magnetic resp<strong>on</strong>se of these<br />

polycrystalline films has been found to improve with the use of a 6nm Cr or Ag buffer layer. This is<br />

shown by a decrease is Hc and an increase in Ms to greater than 85% of the theoretical value.<br />

[1] J.Sagar, et al, IEEE. Trans. Mag, 47, 2440 (2011)<br />

SK12<br />

Inverse spin polarizati<strong>on</strong> at benzene/ir<strong>on</strong> interface<br />

Souraya Goumri-said*, Mohammed Benali Kanoun, Udo Schwingenschlogl and<br />

Aurelien Manch<strong>on</strong><br />

Physical Sciences and Engineering Divisi<strong>on</strong>, King Abdullah University of Science and<br />

Technology (KAUST), Saudi Arabia<br />

Organic spin-valves involving an organic spacer inserted between two magnetic electrodes have<br />

been successfully realized and led to sizable magnetoresistance ratios [1-3]. The accurate design of<br />

the interfacial electr<strong>on</strong>ic structure c<strong>on</strong>trolling the spin injecti<strong>on</strong> is critical to obtain high performance<br />

devices. Intriguingly, recent reports claimed that interfacial spin polarizati<strong>on</strong> may be reversed in some<br />

cases [4, 5]. We address the nature of the spin polarizati<strong>on</strong> Benzene/ Fe (100) interface using ab-initio<br />

approach. The surface is modeled by 6 layers of Fe (100) and the positi<strong>on</strong> of the Benzene molecule<br />

<strong>on</strong> Fe (100) surface is determined by a combinati<strong>on</strong> of the chemisorpti<strong>on</strong> of the π-molecule <strong>on</strong> the<br />

reactive surface and the str<strong>on</strong>g interacti<strong>on</strong> of the d-metal orbital with π-molecule orbitals. We find that<br />

the presence of the Benzene molecule dramatically modifies the electr<strong>on</strong>ic structure of the interface and<br />

can lead to drastic change in the interfacial spin polarizati<strong>on</strong>. While the Benzene molecule becomes<br />

slightly magnetic (0.032 μ B by C atom), it is found that the polarizati<strong>on</strong> of the interfacial Fermi electr<strong>on</strong>s<br />

is reversed from 0.59 (pure Fe surface) to -0.70 (Fe/Benzene interface). This polarizati<strong>on</strong> reversal is<br />

analyzed in terms of orbital overlaps between the Benzene p-orbitals and Fe-d orbitals .<br />

[1] V. Dediu, M. Murgia, F. C. Matacotta, C. Taliani, and S. Barbanera, Solid State Commun. 122, 181 (2002).<br />

[2] Z. H. Xi<strong>on</strong>g, D. Wu, Z. Valy Vardeny, and J. Shi, Nature 427, 821 (2004); Yoo et al., Nature Materials<br />

9, 638 (2010) [3] C. Barraud, et al. Nature Physics 6, 615 (2010) [4] Atodiresei et al, Phys. Rev. Lett. 105,<br />

066601 (2010) [5] M. Saeys, M. Reyniers, and G. B. Marin, J. Phys. Chem. B 106, 7489 (2002).<br />

238 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SK13<br />

Local atomic structure analysis of ferromagnetic semic<strong>on</strong>ductor<br />

GeMnTe by atomic resoluti<strong>on</strong> holography<br />

Naohisa Happo 1 *, Yuki Takehara 1 , Makoto Fujiwara 1 , Koichi Tanaka 1 , Fumihiko<br />

Matsui 2 , Hiroshi Daim<strong>on</strong> 2 , Tomohiro Matsushita 3 , Kyoko Okada 3 , Shinya Senba 4 ,<br />

Shinya Hosokawa 5 , Kouichi Hayashi 6 and Hir<strong>on</strong>ori Asada 7<br />

1<br />

Graduate School of Informati<strong>on</strong> Sciences, Hiroshima City University, Japan<br />

2<br />

NAIST, Japan<br />

3<br />

SPring-8/JASRI, Japan<br />

4<br />

Ube Nati<strong>on</strong>al College of Technology, Japan<br />

5<br />

Hiroshima Institute of Technology, Japan<br />

6<br />

IMR, Tohoku University, Japan<br />

7<br />

Yamaguchi University, Japan<br />

The IV-VI diluted magnetic semic<strong>on</strong>ductor GeMnTe is expected as a spintr<strong>on</strong>ics material, because it shows a<br />

ferromagnetic order below 190 K at x = 0.08 [1]. It is believed that its ferromagnetism is a carrier induced type.<br />

However, another possibility is a cluster formati<strong>on</strong> of a ferromagnetic MnGe binary alloy. The soluti<strong>on</strong> can be<br />

obtained by an investigati<strong>on</strong> of the crystal structure around the each element. Recently, we have investigated<br />

the atomic arrangement around the Ge and Mn atoms in the GeMnTe by an X-ray fluorescence holography<br />

(XFH) [2, 3]. The obtained atomic images from the XFH suggest that the Mn atoms replace with the Ge<br />

atoms in the host GeTe, the Mn positi<strong>on</strong> is stable in the exact positi<strong>on</strong>s of the ani<strong>on</strong> fcc sub lattice [2], and the<br />

Ge positi<strong>on</strong> is fluctuated [3]. We have also performed the Te 4d photoelectr<strong>on</strong> holography (PEH) in order to<br />

investigate the local structure around the Te atoms in the GeMnTe thin film single crystal. The obtained atomic<br />

image from the PEH suggests that the Te atoms are not located at the exact positi<strong>on</strong>s of the fcc ani<strong>on</strong> sublattice.<br />

[1] Y. Fukuma, et al., Appl. Phys. Lett. 93 (2008) 252502. [2] N. Happo, et al., Jpn. J. Appl. Phys.<br />

50 (2011) 05FC11. [3] N. Happo, et al., e-Journal of Surface and Nano Technology 9 (2011) 247.<br />

SK14<br />

Dependence of the tunneling magnetoresistance <strong>on</strong> the inserted<br />

n<strong>on</strong>magnetic layer<br />

Changsik Choi and Byung Chan Lee*<br />

Department of Phyics, Inha University, Korea<br />

When a crystalline n<strong>on</strong>magnetic (NM) layer was inserted between the tunnel barrier<br />

and a magnetic layer in magnetic tunnel juncti<strong>on</strong>s (MTJs), it was observed that the<br />

tunneling magnetoresistance (TMR) decayed and oscillated as a functi<strong>on</strong> of the<br />

thickness of the n<strong>on</strong>magnetic layer. In this paper, the TMR dependence <strong>on</strong> the NM<br />

layer is investigated theoretically. The c<strong>on</strong>ductance was calculated with the Landauer-<br />

Buttiker formalism, and the c<strong>on</strong>ductance difference between the parallel and antiparallel<br />

magnetizati<strong>on</strong>s was given in an analytical form with the spin-dependent<br />

reflecti<strong>on</strong> amplitudes. In order to check the validity of our model, numerical<br />

calculati<strong>on</strong>s were carried out. An effective mass theory was adopted for the electr<strong>on</strong>ic<br />

structure of each material, and several cases were c<strong>on</strong>sidered. It was shown that our<br />

simple model agreed well with the results of the numerical calculati<strong>on</strong>s. Our model<br />

can be applied also to more realistic cases with the full-band structures. The oscillati<strong>on</strong><br />

period was determined from the extremal vectors of the Fermi surface of the NM<br />

material, and the selecti<strong>on</strong> rules for the oscillati<strong>on</strong> period were obtained. Comparis<strong>on</strong>s<br />

with the experimental data and the previous theoretical results will be presented.<br />

SK15<br />

The bulk Fe-Mo double perovskite analyzed from a small clusters<br />

perspective<br />

Eliel Carvajal Quiroz 1 *, Raul Oviedo Roa 2 , Miguel Cruz Iriss<strong>on</strong> 1 and Oracio Navarro 3<br />

1 Instituto Politecnico Naci<strong>on</strong>al, ESIME-Culhuacan, Mexico<br />

2 Programa de Investigaci<strong>on</strong> en Ingenieria Molecular, Instituto Mexicano del Petroleo, Mexico<br />

3 Instituto de Investigaci<strong>on</strong>es en Materiales, Universidad Naci<strong>on</strong>al Aut<strong>on</strong>oma de Mexico,<br />

Mexico<br />

Being the Sr 2FeMoO 6 double perovskite am<strong>on</strong>g the promising materials for spintr<strong>on</strong>ic<br />

applicati<strong>on</strong>s, the bulk case was studied in this work; but attenti<strong>on</strong> was focused, also, <strong>on</strong> the<br />

octahedral arrangements FeO 6 and MoO 6 as well as <strong>on</strong> FeO 4 and FeMoO 11 clusters. Calculati<strong>on</strong>s<br />

were made using Density Functi<strong>on</strong>al Theory (DFT) and the Perdew-Burke-Ernzerhof (PBE)<br />

functi<strong>on</strong>al within the Generalized Gradient Approximati<strong>on</strong> (GGA) scheme. In order to<br />

understand the differences in the behavior am<strong>on</strong>g up- and down-spin electr<strong>on</strong>s observed in the<br />

half-metallic Sr 2FeMoO 6 double perovskite, the orbitals and density of states were analyzed. Our<br />

results reveal that the half-metallic character is present ever since the isolated (FeO 6)4- cluster<br />

and is a c<strong>on</strong>sequence of the n<strong>on</strong>-zero spin at Fe atom coming from t2g orbitals. The (MoO 6)6-<br />

octahedra does not inhibit the perovskite half-metallic character because this Mo-c<strong>on</strong>taining<br />

cluster has a zero total spin. In additi<strong>on</strong>, Sr atoms were aggregated to the studied cluster, not<br />

just because of the searched relati<strong>on</strong> between the bulk material and the cluster units properties,<br />

because they give the impressi<strong>on</strong> that play a relevant role to become stable the charge even<br />

though the energy deepest of the states c<strong>on</strong>tributed by them. Acknowledgments: Work supported<br />

by Multidisciplinary Project SIP-IPN: 2012-1439, PAPIIT-IN108710 UNAM.


SK16<br />

Tunneling magnetoresistance effect in magnetic tunneling juncti<strong>on</strong>s<br />

with a high resistance ferromagnetic oxide Fe 2.5M 0.5O 4(M = Mn, Zn)<br />

electrode<br />

Eiji Shikoh 1 *, Teruo Kanki 2 , Hidekazu Tanaka 2 , Teruya Shinjo 1 and Masashi Shiraishi 1<br />

1 Eng. & Sci., Osaka University, Japan<br />

2 ISIR, Osaka University, Japan<br />

Recently, molecular spintr<strong>on</strong>ics has attracted much attenti<strong>on</strong>. To improve the spin injecti<strong>on</strong><br />

efficiency from ferromagnetic electrodes into molecular materials, by avoiding an impedance<br />

mismatch problem, the use of high resistance ferromagnetic electrodes is more accessible than other<br />

methods. In this study, a high resistance ferromagnetic oxide Fe 2.5M 0.5O 4(FMO: M = Mn, Zn) was<br />

focused and observati<strong>on</strong> of a tunneling magnetoresistance (TMR) effect in magnetic tunneling<br />

juncti<strong>on</strong>s (MTJs) with an FMO electrode was implemented. MTJs composed of MgO(100)-sub.<br />

/ FMO(thickness, 25-30 nm) / Al-O(1.5-2) / Ni 80Fe 20(20) were fabricated by using pulsed laser<br />

depositi<strong>on</strong>, EB depositi<strong>on</strong>, photolithography, Ar i<strong>on</strong> milling, and sputtering. Magnetic properties<br />

were investigated with magnetic Kerr effect measurements. Magnetoresistance properties were<br />

measured with a 4-terminal-method. A TMR effect reflecting the magnetizati<strong>on</strong> processes of the both<br />

ferromagnetic electrodes in the MTJs with M = Mn was successfully observed, and the TMR ratio<br />

was approximately 0.85% at room temperature (RT) [1]. The spin-polarizati<strong>on</strong> of FMO with M =<br />

Mn at RT was estimated to be at least 0.94%[1]. Higher spin-polarizati<strong>on</strong> is expected by improving<br />

the interface and the barrier qualities between the ferromagnetic electrodes.<br />

[1] E. Shikoh, et al., Solid State Commun. 151, 1296 (2011).<br />

SK17<br />

M<strong>on</strong>itoring of gamma radiati<strong>on</strong> interacti<strong>on</strong> in PHR sensor<br />

D.g. Park and Ho<strong>on</strong> S<strong>on</strong>g<br />

korea atomic energy research institute, Korea<br />

The Planar Hall Resistance (PHR) sensors have been found to be capable of magnetic<br />

micro and nano bead detecti<strong>on</strong> as the signal to noise ratio in these PHR sensors<br />

are higher by several orders compared to others magnetoresistive biosensors. In<br />

additi<strong>on</strong>, the spin valve multilayer are c<strong>on</strong>sidered as novel structures for a high<br />

sensitivity and uniform magnetizati<strong>on</strong> rotati<strong>on</strong> compared to exchange biased bilayer<br />

structure for planar Hall resistance sensors.(1). In this work, we discussed a method<br />

for immobilizati<strong>on</strong> of magnetic labels <strong>on</strong> the PHR sensor for sensitive detecti<strong>on</strong> of<br />

magnetic labels. We used photolithography to generate the functi<strong>on</strong>alized sensor<br />

surface to dem<strong>on</strong>strate the capacity of m<strong>on</strong>itoring the immobilizati<strong>on</strong> of biomolecule.<br />

The PHR sensor was irradiated by Co source up to 80 Gy and the sensor characteristic<br />

was compared with n<strong>on</strong> irradiated <strong>on</strong>e. The field sensitivity obtained by the slope (ΔV/<br />

ΔH) of the field-voltage curve was not changed by high dose irradiati<strong>on</strong> up to 80 Gy.<br />

The sensitivity of the PHR sensor was identified detecting the different c<strong>on</strong>centrati<strong>on</strong> of<br />

magnetic beads. We have successfully dem<strong>on</strong>strated the immobilizati<strong>on</strong> of streptavidin<br />

coated magnetic bead to the single stranded olig<strong>on</strong>ucleotide <strong>on</strong> the Au coated PHR<br />

sensor surface for the detecti<strong>on</strong> of magnetic labels.<br />

[1] P. E. Sheehan and L. J. Whitman, Nano lett. 5, 803 (2005).<br />

SK18<br />

Reactively sputtered MgAl2O4 barrier layers for Heusler tunnel<br />

juncti<strong>on</strong>s<br />

Keima Inagaki*, Naoto Fukatani, Kenichiro Mari, Hirohito Fujita, Tetsuya Miyawaki,<br />

Kenji Ueda and Hidehumi Asano<br />

Crystalline Materials Science, Nagoya University, Japan<br />

Magnetic tunnel juncti<strong>on</strong>s (MTJs) using epitaxial MgO barriers have attracted great interest<br />

because they exhibit large tunnel magnetoresistance (TMR) ratios. However, the large lattice<br />

mismatch (about 4%) between MgO and half-metallic Heusler alloy induces misfit dislocati<strong>on</strong>s<br />

and antisite disorder at the surface of ferromagnetic electrode[1]. Thus, coherent growth of MTJ is<br />

important for further improvement of device performance. This study focuses <strong>on</strong> spinel MgAl 2O 4<br />

as a tunnel barrier lattice-matched with half-metallic Heusler alloy. We fabricate a Fe 2CrSi/<br />

MgAl 2O 4 juncti<strong>on</strong> by reactive sputtering, which can c<strong>on</strong>trol the crystallinity and degree of<br />

oxidati<strong>on</strong> of the films strictly, and investigate its crystal structure and electrical transport properties.<br />

MgAl 2O 4 films were deposited from a MgAl 2 target in Ar + O 2 atmosphere. Epitaxial Fe 2CrSi /<br />

MgAl 2O 4 juncti<strong>on</strong>s were obtained by inserting an ultrathin MgAl 2 interlayer, which worked as a<br />

protecti<strong>on</strong> layer for oxidizati<strong>on</strong> at the surface of Fe 2CrSi. The rocking width of MgAl 2O 4 (004)<br />

was around 1º, which is small value compared to that of the electr<strong>on</strong>-beam evaporated MgO[2].<br />

Current-voltage curve was fitted by Simm<strong>on</strong>s’ tunneling theory, and we obtained barrier hight φ =<br />

0.86-0.95 eV for the Fe 2CrSi/MgAl 2O 4/CoFe MTJ. Present epitaxial MgAl 2O 4 barrier deposited<br />

by reactive sputtering is expected to realize high performance spintr<strong>on</strong>ic devices.<br />

[1]T. Miyajima, M. Oogane, Y. Kotaka, T. Yamazaki, M. Tsukada, Y. Kataoka, H. Naganuma, and Y. Ando: Appl. Phys. Express 2<br />

(2009) 093001. [2]G. X. Miao, Y. J. Park, and J. S. Moodera: Phys. Rev. Lett., 100 (2008) 246803.<br />

SK19<br />

SK20<br />

SK21<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Half-metallic properties of (001) surfaces of the Cr substituted rocksalt<br />

GeTe-based compounds<br />

Kalpana Kamalkishor Landge, Beata Bialek and Jae Il Lee*<br />

Physics, Inha university, Korea<br />

Much effort has been devoted to the development of new magnetic materials for the<br />

spintr<strong>on</strong>ic applicati<strong>on</strong>s. Recently, new half-metallic ferromagnets based <strong>on</strong> the rock-salt<br />

semic<strong>on</strong>ductor GeTe were found [1]. In the bulk structure, GeTe becomes half-metal<br />

when some of Ge atoms are substituted by Cr or V. We report the properties of (001)<br />

surfaces of Cubic CrGe 3Te 4 and tetrag<strong>on</strong>al CrGeTe 2 with two different terminati<strong>on</strong>s,<br />

i.e. GeTe and CrTe terminati<strong>on</strong>s, as obtained by using the FLAPW [2] within GGA.<br />

We found that both CrTe- and GeTe-terminated CrGe 3Te 4 and CrGeTe 2 (001) surfaces<br />

c<strong>on</strong>serve the half-metallic properties of their bulk structures by analyzing the DOS and<br />

c<strong>on</strong>firmed from the integer value of total magnetic moment (MM) per unit cell. The<br />

center layer energy gap is much larger as compared to its bulk. The energy gap and half<br />

metallic gap became wider with the larger substituti<strong>on</strong> of Ge atom by Cr atoms. In the<br />

CrTe-terminated surface the MM of the Cr atom at the surface layer has been enhanced<br />

as compared to the center layer Cr atoms by the surface effect. The calculated value of<br />

MM <strong>on</strong> Cr at the top layer of the surfaces is 3.7 μ B in the both system.<br />

[1] Y. H. Zhao, W. H. Xie, L.F. Zhu, and B. G. Liu, J. Phys.: C<strong>on</strong>dens. Matter 18, 10259 (2006). [2] E.<br />

Wimmer, H. Krakauer, M. Weinert, and A. J. Freeman, Phys. Rev. B 24, 6864 (1981), and references<br />

therein ; M. Weinert, E. Wimmer, and A. J. Freeman, Phys. Rev. B 26, 4571 (1982).<br />

Electr<strong>on</strong>ic structure and spin polarizati<strong>on</strong> of Co 2-xFe 1+xSi Heusler alloy<br />

Hiroyoshi Itoh 1 * and Syuta H<strong>on</strong>da 2<br />

1 Department of Pure and Applied Physics, Kansai University, Japan<br />

2 Faculty of Pure and Applied Science, University of Tsukuba, Japan<br />

We study the electr<strong>on</strong>ic structure and spin polarizati<strong>on</strong> for Co-based Heusler alloys<br />

of Co 2-xFe 1+xSi using the first principles calculati<strong>on</strong>s to discuss the spin injecti<strong>on</strong><br />

into semic<strong>on</strong>ductors and paramagnetic metals. Half-metallic Heusler alloys such<br />

as Co 2MnSi, Co 2FeSi, and Fe 2MnSi are promising materials for spin generator,<br />

injector, and detector. Recently, epitaxial films of Fe 2MnSi [1] and Co 2FeSi [2] have<br />

been successfully fabricated <strong>on</strong> Ge or Si substrates and the spin-dependent transport<br />

properties have been measured. Obtained results seem sensitive to the degree of<br />

disorder and the compositi<strong>on</strong> of the alloy. In this c<strong>on</strong>tributi<strong>on</strong>, we examine compositi<strong>on</strong><br />

dependence of the electr<strong>on</strong>ic structure for Co 2-xFe 1+xSi by performing band calculati<strong>on</strong>s<br />

based <strong>on</strong> the density-functi<strong>on</strong>al theory (DFT) in the generalized gradient approximati<strong>on</strong><br />

(GGA) using the projector-augmented wave (PAW) method. It is shown that the spin<br />

polarizati<strong>on</strong> defined by the total DOS decreases from +100% at x=0 and changes the<br />

sign with increasing Fe compositi<strong>on</strong> x because the half-metallicity is lost. However,<br />

the spin polarizati<strong>on</strong> defined by the s-comp<strong>on</strong>ent of DOS (partial DOS) keeps positive<br />

although it decreases with increasing x from x=0 to x=2.<br />

[1] K. Hamaya et al.: Phys. Rev. Lett. 102 (2009) 137204. [2] A. Yamada et al.: Appl. Phys. Lett. 96<br />

(2010) 082511.<br />

Large enhancement of Kerr rotati<strong>on</strong> of GMR periodic patterns using<br />

Pt / Co free layer<br />

Kakeru Wada 1 , Tsukasa Kobayashi 1 , Yuuki Oshino 1 , Hiroshi Ono 2 , Tatsutoshi Shioda 2 , Kenji<br />

Machida 3 , Ken-ichi Aoshima 3 , Kiyoshi Kuga 3 , Hiroshi Kikuchi 3 , Naoki Shimidzu 3 , Akira<br />

Emoto 4 and Takayuki Ishibashi 1 *<br />

1 Department of Materials Science Technology, Nagaoka University of Technology, Japan<br />

2 Department of Electrical Engineering, Nagaoka University of Technology, Japan<br />

3 Science and Technical Research Laboratories, Japan Broadcasting Corp, Japan<br />

4 Nati<strong>on</strong>al Institute of Advanced Industrial Science and Technology, Japan<br />

Magneto-optical spatial light modulator (MO-SLM) driven by spin transfer switching is a promising device<br />

for holographic 3D display. However, a small Kerr rotati<strong>on</strong> angle is an issue to be solved to realize the MO-<br />

SLM. In this paper, we report an enhancement of Diffracti<strong>on</strong> Magneto-Optic Kerr Effect (DMOKE) obtained<br />

for periodic GMR patterns. A GMR structures with Pt/Co free layer were used in this experiment. The samples<br />

were patterned into periodic structures with sizes of 5-50 μm and pitches of 10-100 μm. SiO 2 was deposited<br />

<strong>on</strong> the etched area after the patterning to obtain flat surfaces. DMOKE of the GMR patterns were measured by<br />

using a He-Ne laser with a wavelength of 632.8 nm and an incidence of 30°. DMOKE hysteresis loops were<br />

clearly observed, corresp<strong>on</strong>ding to the magnetizati<strong>on</strong> reversal of the free layers, and Kerr rotati<strong>on</strong> angles of (1,0)<br />

and (1,1) diffracti<strong>on</strong> spots were measured to be 0.5°, which is six times larger than a polar Kerr rotati<strong>on</strong> angle<br />

measured before the patterning. We c<strong>on</strong>sider that the large enhancement of DMOKE is due to an interference<br />

effect occurred in the periodic GMR structures embedded in SiO2. This work was supported by the NICT.<br />

K. Aoshima et al, Appl Phys Let, 44, 052507 (2007)<br />

July 8 - 13, 2012 Busan, Korea 239<br />

Poster Friday


Poster Friday<br />

SK22<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Ab-initio and tight-binding calculati<strong>on</strong>s of magnetic anisotropy<br />

phenomena in CoPt<br />

Jan Zemen 1 , Jan Masek 2 and Tomas Jungwirth 3<br />

1 School of Physics and Astr<strong>on</strong>omy, University of Nottingham, Nottingham NG7 2RD, United Kingdom<br />

2 Institute of Physics ASCR v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic<br />

3 Institute of Physics ASCR v.v.i., Czech Republic & University of Nottingham, United Kingdom<br />

Ordered CoPt alloys hold potential for applicati<strong>on</strong>s in high density magnetic recording due to the combinati<strong>on</strong> of<br />

exchange and spin-orbit interacti<strong>on</strong>s giving rise to large magnetic anisotropies. Tunneling Magnetoresistance [1] and<br />

Tunneling Anisotropic Magnetoresistance [2] have been dem<strong>on</strong>strated in tunneling devices with CoPt electrodes.<br />

C<strong>on</strong>trolling the spin-orbit coupling (SOC) phenomena is essential as the same anisotropy that ensures thermal<br />

stability of a memory element makes the writing by external magnetic fields or electric currents challenging. An<br />

alternative to the spin transfer torque (STT) effect in multi-domain systems is based <strong>on</strong> current induced polarizati<strong>on</strong><br />

of the c<strong>on</strong>ducti<strong>on</strong> electr<strong>on</strong> spins in structures possessing SOC and lacking inversi<strong>on</strong> symmetry. Switching of a<br />

ferromagnetic layer induced by in-plane current has been shown recently in a Co-Pt bilayer [3]. Another promising<br />

way of c<strong>on</strong>trolling the magnetic anisotropy via SOC utilizes lattice strains induced by piezo stressors. We study<br />

SOC effects in strained CoPt multilayer structures using a relativistic full-potential linearized augmented plane-wave<br />

method. We compare the variati<strong>on</strong>s of anisotropies of magnetic total energies (MAE) and density of states (ADOS)<br />

also to our tight-binding calculati<strong>on</strong>s using a realistic Slater-Koster parametrizati<strong>on</strong> which provide more practical<br />

basis for further research of magnetotransport anisotropies in CoPt based nanostructures.<br />

[1] Gukche<strong>on</strong> Kim, Yuya Sakuraba, Mikihiko Oogane, Yasuo Ando, and Terunobu Miyazaki, Appl. Phys. Lett. 92, 172502 (2008). [2] B. G. Park, J. Wunderlich, D. A. Williams,<br />

S. J. Joo, K.Y. Jung, K. H. Shin, K. Olejnik, A. B. Shick, and T. Jungwirth, PRL 100, 087204 (2008). [3] Ioan Mihai Mir<strong>on</strong>, Kevin Garello, Gilles Gaudin, Pierre-Jean Zermatten,<br />

Marius V. Costache, Stephane Auffret, Sebastien Bandiera, Bernard Rodmacq, Alain Schuhl, and Pietro Gambardella, Nature 476, 189-193 (2011).<br />

SK23<br />

Spin polarizati<strong>on</strong> of half-metallic Heusler alloy Co 2MnSi by Andreev<br />

reflecti<strong>on</strong> measurements<br />

Iduru Shigeta 1 *, Yuya Nishisako 1 , Kohei Harumori 1 , Akinari Okubo 2 , Rie Y. Umetsu 3 ,<br />

Masakazu Ito 1 , Keiichi Koyama 1 , Ryosuke Kainuma 2 and Masahiko Hiroi 1<br />

1 Department of Physics and Astr<strong>on</strong>omy, Kaghosima University, Japan<br />

2 Department of Materials Science, Tohoku University, Japan<br />

3 Institute for Materials Research, Tohoku University, Japan<br />

We report spin polarizati<strong>on</strong> measurements of half-metallic Heusler alloy Co 2MnSi. Heusler<br />

alloys are regarded as the most promising half-metallic materials for spintr<strong>on</strong>ics applicati<strong>on</strong>s<br />

because of their high Curie temperature and low coercivity. Recently, large tunneling<br />

magnetoresistance (TMR) value was experimentally reported from a Co 2MnSi/Al-O/Co 2MnSi<br />

magnetic tunnel juncti<strong>on</strong> (MTJ), which was attributed to the half-metallicity of Co 2MnSi.<br />

Therefore, we have determined the spin polarizati<strong>on</strong> of Co 2MnSi by the Andreev reflecti<strong>on</strong><br />

technique. Polycrystalline Co 2MnSi samples were fabricated by using a high-frequency<br />

inducti<strong>on</strong> furnace. We have made planar-type juncti<strong>on</strong>s by depositing Pb <strong>on</strong> the polished<br />

surface of the polycrystalline Co 2MnSi samples. The differential c<strong>on</strong>ductance of Co 2MnSi/Pb<br />

planar-type juncti<strong>on</strong>s was measured between 1.5 K and 10K by the lock-in amplifier technique.<br />

The obtained differential c<strong>on</strong>ductance was able to be fitted very well by the modified Bl<strong>on</strong>der-<br />

Tinkham-Klapwijk (BTK) model. We have found the spin polarizati<strong>on</strong> of approximately 50%<br />

from the analysis of Andreev reflecti<strong>on</strong> measurements of half-metallic Heusler alloy Co 2MnSi.<br />

SK24<br />

Electr<strong>on</strong>ic properties of Co2FexMn1-xSi Heusler alloys studied by hard<br />

X-ray photoelectr<strong>on</strong> spectroscopy<br />

A. Gloskovskii 1 , S. Ouardi 1 , G. H. Fecher 2 , S. Thiess 3 , W. Drube 3 , B. Detlefs 4 , T. Kubota 5 , Y. Ando 5<br />

and C. Felser 2<br />

1<br />

Johannes Gutenberg University, Mainz, Germany<br />

2<br />

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany<br />

3<br />

Deutsches Elektr<strong>on</strong>en-Synchrotr<strong>on</strong> DESY, Hamburg, Germany<br />

4<br />

ESRF, Grenoble, France<br />

5<br />

Department of Applied Physics, Graduate School of Engineering, Tohoku University, Japan<br />

One major research area where Co 2 based Heusler compounds are investigated is <strong>on</strong> TMR juncti<strong>on</strong>s.<br />

Fully epitaxial magnetic tunnel juncti<strong>on</strong>s (MTJs) with a Co 2YZ thin film as a base electrode and a<br />

MgO tunnel barrier exhibit high TMR ratios. Quaternary Co2Fe xMn 1-xSi (CFMS) Heusler alloys are<br />

even more promising because the substituti<strong>on</strong> of Mn by Fe increases the number of valence electr<strong>on</strong>s<br />

and therefore leads to higher Curie temperatures above 1000 K. Kubota et al. found a maximum<br />

TMR ratio for Co2Fe xMn 1-xSi (x = 0…1)-CoFe MTJs [1] for Fe fracti<strong>on</strong>s of between x=0.4 and 0.6.<br />

The halfmetallic character disappeared for samples with x≥0.8. The reas<strong>on</strong> of this behaviour is still<br />

unknown. A B 2 and L 21 site ordered stack of MgO substrate/ Cr [40 nm] buffer layer/ Co2Fe xMn 1-xSi<br />

[30 nm]/ MgO [2 nm]/ AlO x [1.3 nm] (x = 0, 0.2…1.0) films was studied at beamline P09 at PETRA<br />

III and beamline ID32 at the ESRF. The hard X-Ray photoelectr<strong>on</strong> spectroscopy studies were<br />

performed with an excitati<strong>on</strong> energy of 6 keV. It was found that the positi<strong>on</strong> of Co 2p core levels and<br />

the density of states in the valence band regi<strong>on</strong> str<strong>on</strong>gly depend <strong>on</strong> the Fe/Mn ratio.<br />

[1] Takahide Kubota, Sumito Tsunegi, Mikihiko Oogane, Shigemi Mizukami, Terunobu Miyazaki, Hiroshi<br />

Naganuma, and Yasuo Ando APL 94 (2009) 122504<br />

240 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SK25<br />

Ab-initio calculati<strong>on</strong> of the magnetic properties of bn nanoribb<strong>on</strong><br />

Jeffrey Rufinus<br />

Science Divisi<strong>on</strong>, Widener University, USA<br />

The emerging field of spin electr<strong>on</strong>ics (spintr<strong>on</strong>ics) has been c<strong>on</strong>tinuously attracting<br />

researchers. Substantial theoretical and experimental efforts have been made in the<br />

quest to find the candidates for future spintr<strong>on</strong>ics devices. Recently, the search for<br />

new spintr<strong>on</strong>ics materials has also included graphene-based materials due to the<br />

theoretical predicti<strong>on</strong> that this type of material may show the half-metallic property.<br />

Here, we present the results of a density functi<strong>on</strong>al theory within a generalized gradient<br />

approximati<strong>on</strong> study of Bor<strong>on</strong> Nitride (BN) nanoribb<strong>on</strong>. The objective of this study is<br />

to determine whether this type of material will be ferromagnetic or antiferromagnetic<br />

if the width is varied. Our results show that the narrow zigzag shaped BN nanoribb<strong>on</strong><br />

prefers ferromagnetic or antiferromagnetic state depending <strong>on</strong> the width. Thus, by<br />

c<strong>on</strong>trolling the width (and growth directi<strong>on</strong>) it is possible to manipulate the magnetic<br />

property of this material. These results are of the scientific interest in exploring the<br />

magnetic properties of BN-based nanoribb<strong>on</strong> for future spintr<strong>on</strong>ics.<br />

SK26<br />

Synthesis and functi<strong>on</strong>al properties of polycrystalline Fe3Si-based magnetic tunnel juncti<strong>on</strong>s<br />

Alexander Goikhman 1 *, Galina Kupriyanova 1 , Roberto Mantovan 2 , Andrei<br />

Zenkevich 3 and Ksenia Maksimova 1<br />

1<br />

REC 'Functi<strong>on</strong>al Nanomaterials', Imanuel Kant Baltic Federal University, Russia<br />

2<br />

Laboratorio MDM IMM-CNR, Italy<br />

3<br />

NRNU 'Moscow Engineering Physics Institute', Russia<br />

Magnetic tunnel juncti<strong>on</strong>s (MTJs), c<strong>on</strong>sisting of two ferromagnetic (FM) layers separated by ultrathin<br />

tunnel barrier are key elements in a wide range of spintr<strong>on</strong>ic devices, particularly, as bit elements in magnetic<br />

memories and as reading heads in racetrack memory c<strong>on</strong>cept. The improvement of the MTJs tunnel<br />

magnetoresistance (TMR) might be attained by the selecti<strong>on</strong> of the materials with high spin-polarizati<strong>on</strong><br />

and the appropriate combinati<strong>on</strong> of FM electrodes and tunnel barrier [1]. In this work, we discuss the<br />

applicability of a half-metal Heusler alloy Fe 3Si as an top and bottom electrodes in MTJ, the material which<br />

has been poorly adopted so far [2,3]. MTJs based <strong>on</strong> polycrystalline Fe 3Si ferromagnetic (FM) electrodes<br />

and both SiO 2 and MgO tunnel (~1~3 nm) insulators (TI) have been grown by the combinati<strong>on</strong> of pulsed<br />

laser depositi<strong>on</strong> (using two-laser co-depositi<strong>on</strong> approach) and i<strong>on</strong> beam assisted depositi<strong>on</strong> techniques. The<br />

morphology, phase compositi<strong>on</strong> and structural properties of individual layers as well as the intermixing and<br />

chemical reacti<strong>on</strong>s at the FM/TI interface have been investigated. The magnetic properties of the trilayers<br />

and preliminary TMR measurements <strong>on</strong> Fe 3Si-based MTJs obtained at wide range of temperatures (2-400 K)<br />

will be presented, aiming at the evaluati<strong>on</strong> of potential of Fe 3Si-based MTJs for spintr<strong>on</strong>ics.<br />

1. S.D. Bader, S.S.P. Parkin, Annu. Rev. C<strong>on</strong>dens. Matter Phys. 2010, 1:71-88 2. Y. Ando, K. Hamaya et al.,<br />

Appl. Phys. Lett. 2009, 94 182105 3. K. Harada, K.S. Makabe et al., J. of Phys.: C<strong>on</strong>f. Ser. 2011, 266 012088<br />

SK27<br />

Half-metallic properties of the (001) surfaces of the half-heusler<br />

compounds GeKCa and SnKCa<br />

Lee-hyun Cho 1 , Beata Bialek 1 , Jae Il Lee 1 * and Miyoung Kim 2<br />

1 Physics, Inha University, Korea<br />

2 Divisi<strong>on</strong> of Energy System Research, Ajou University, Korea<br />

The sp or d0 half-metallic materials have been attracted more and more increasing<br />

attenti<strong>on</strong>. A recent first-principles calculati<strong>on</strong> found that the half-Heusler compounds,<br />

GeKCa and SnKCa, are half-mtallic [1]. We investigated the magnetic and halfmetallic<br />

properties of the (001) surfaces of the GeKCa and the SnKCa by using the all<br />

electr<strong>on</strong> full-potential linearized augmented plane wave method [2] within generalized<br />

gradient approximati<strong>on</strong>. We c<strong>on</strong>sidered two different terminati<strong>on</strong>s for each compound,<br />

i. e. Ge (or Sn) and KCa terminati<strong>on</strong>s. From the calculated density of states, we<br />

found that the Ge or the Sn terminati<strong>on</strong> reserves the half-metallicity, while the KCa<br />

terminati<strong>on</strong> for both compounds is not half-metallic. The magnetic moments for the<br />

surface Ge and Sn atoms are much enhanced compared to the bulk values, but the KCa<br />

surface for both compounds is almost magnetically dead.<br />

[1] J. Chen, G. Y. Guo, K. L. Yao, and M. H. S<strong>on</strong>g, J. Alloy. Compd. 509, 10172 (2011). [2] E.<br />

Wimmer, H. Krakauer, M. Weinert, and A. J. Freeman, Phys. Rev. B 24, 864 (1981), and references<br />

therein ; M. Weinert, E. Wimmer, and A. J. Freeman, Phys. Rev. B 26, 4571 (1982).


SK28<br />

Half-metallicity in hydrogenated carb<strong>on</strong> nanotubes<br />

Kyu W<strong>on</strong> Lee, Gi-wan Je<strong>on</strong> and Cheol Eui Lee*<br />

Physics, Korea University, Korea<br />

Zigzag-edge graphene nanoribb<strong>on</strong>s (ZGNRs) show half-metallicity arising from edgelocalized<br />

electr<strong>on</strong> states under an electric field, enabling fully spin-polarized electrical<br />

current and thus providing a basis for spintr<strong>on</strong>ics. While carb<strong>on</strong> nanotubes (CNTs),<br />

obtained by rolling up the ZGNRs, have themselves no edges, edge states have been<br />

identified in hydrogenated CNTs. Thus, whether or not the CNTs can be half-metallic<br />

under an electric field becomes an issue of great interest. Here, our density functi<strong>on</strong>al<br />

theory (DFT) calculati<strong>on</strong>s show that the edge states in the CNTs are unstable under an<br />

electric field due to the spin-c<strong>on</strong>serving electr<strong>on</strong> transfer between the edges, but a large<br />

enough transfer barrier between the edge states, obtained by c<strong>on</strong>trolling the adsorpti<strong>on</strong><br />

patterns, can render the CNTs half-metallic. Our results can be extended to most carb<strong>on</strong><br />

systems thus opening a new route to materials engineering and providing a deeper<br />

understanding of the electr<strong>on</strong>ic properties of π-b<strong>on</strong>d network edges.<br />

1. Y-W. S<strong>on</strong>, M. L. Cohen, S. G. Louie, Nature 444, 347 (2006 ). 2. Z. Sljivancanin, Phys. Rev. B 84,<br />

085421 (2011).<br />

SK29<br />

Enhanced perpendicular magnetic anisotropy in Fe/(MgAl 2)OX<br />

bilayer structures with interface optimizati<strong>on</strong> processes<br />

J.w Koo 1 , S Mitani 2 , H Sukegawa 2 , Z.c Wen 2 , T Niizeki 2 , S Kasai 2 and K Inomata 2<br />

1 University of Tsukuba, Tsukuba Nati<strong>on</strong>al Institute for Material Science, Japan<br />

2 Nati<strong>on</strong>al Institute for Materials Science, Tsukuba, Japan<br />

Ferromagnetic metals (FM) electrodes with large perpendicular magnetic anisotropy<br />

(PMA) are actively being investigated. Recently PMA arising at the interface between a<br />

FM and an oxide layer such as CoFeB/MgO [1] and Co 2FeAl/MgO [2] were reported.<br />

The PMA at which between FMs and oxide barrier materials has attracted much<br />

attenti<strong>on</strong> not <strong>on</strong>ly for the STT-MRAM applicati<strong>on</strong>s but also for spintr<strong>on</strong>ic devices<br />

with electric field c<strong>on</strong>trol of magnetizati<strong>on</strong>. The detailed mechanism of the interface<br />

PMA is still an open questi<strong>on</strong> since the experimental reports, in particular the materials<br />

examined, are much limited. Here, we report the enhanced PMA in Fe/MgAl 2O X<br />

structures with the effective perpendicular magnetic anisotropy energy density (Keff)<br />

~ 3 erg/cm 3 . In the case of an Fe layer with a crystalline (MgAl 2)O X layer, it exhibited<br />

perpendicular magnetizati<strong>on</strong> characteristics, and the value of Keff was increased from<br />

~ 0 to ~3 erg/cm 3 with increasing annealing temperature. Furthermore, even in the Fe<br />

layer with amorphous (MgAl 2)O X, a large interface magnetic anisotropy was obtained.<br />

[1] S. Ikeda et al., Nature Mater. 9, 721 (2010) [2] Z. C. Wen et al., Appl. Phys. Lett. 98, 242507<br />

(2011).<br />

SK30<br />

Graphene nano-ribb<strong>on</strong> and the ripple effect<br />

Hsin-han Lee, Kuo-chin Chen and Ching-ray Chang*<br />

Physics, Nati<strong>on</strong>al Taiwan University, Taiwan<br />

Graphene is a possible nano-device in the future. There are several experiment and<br />

theory exhibit that the graphene would generate the ripple in some c<strong>on</strong>diti<strong>on</strong>s[1-3], and<br />

there is a “geometrical effect” <strong>on</strong> the curved surface with Rashba spin-orbit effect[4].<br />

We investigate the transport property and the spin density accumulati<strong>on</strong> <strong>on</strong> the<br />

graphene nano-ribb<strong>on</strong> with the ripple. This research used the n<strong>on</strong>-equilibrium Green<br />

functi<strong>on</strong>(NEGF) of the Landauer formula[5.6] to compute the numerical results for the<br />

system.<br />

[1] C. H. Lui, Li Liu, K. F. Mak, George W. Flynn and T<strong>on</strong>y F. Heinz, Nature 462, 339-341 (2009)<br />

[2] Daniel Huertas-Hernando, F. Guinea, and Arne Brataas, Phys. Rev. B 74, 155426 (2006) [3]<br />

Z. Wang and M. Devel, Phys. Rev. B 83, 125422 (2011) [4] T.-C. Cheng, J.-Y. Chen and C.-R.<br />

Chang , Phys Rev B. 84. 214423 (2011) [5] S. Datta. .Electr<strong>on</strong>ic transport in mesoscopic systems'.<br />

Cambridge University Press, Cambridge (1995) [6] S. Datta. .Quantum Transport: Atom to<br />

Transistor'. Cambridge University Press, Cambridge (2005).<br />

SK31<br />

SK32<br />

SK33<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Enhancement of spin signal in all-metallic lateral spin valves with halfmetallic<br />

heusler alloy<br />

Shinya Kasai, Yukiko Takahashi, Shigeyuki Hirayama, Seiji Mitani and Kazuhiro<br />

H<strong>on</strong>o<br />

Nati<strong>on</strong>al Institute for Materials Science, Japan<br />

A lateral spin valve (LSV), c<strong>on</strong>sisting of two ferromagnetic wires c<strong>on</strong>nected with<br />

<strong>on</strong>e n<strong>on</strong>-magnetic wire, is <strong>on</strong>e of the promising devices to c<strong>on</strong>vert charge currents to<br />

pure spin currents, and vice versa. The c<strong>on</strong>versi<strong>on</strong> ratio is, however, still too small,<br />

because of the large spin absorpti<strong>on</strong> in ferromagnetic wires. Recently, Fukuma et al.<br />

have dem<strong>on</strong>strated that inserting the MgO barrier between ferromagnetic and n<strong>on</strong>magnetic<br />

wires suppresses the spin absorpti<strong>on</strong>, resulting in the enhancement of the<br />

spin signal[1]. Here, we dem<strong>on</strong>strate another way, using the half-metallic Heusler<br />

alloy as ferromagnetic electodes. The devices were fabricated from a film stack of<br />

SiO 2(2)/Cu(10)/Co 2FeGa 0.5Ge 0.5(25)/Ag(10)/Cr(1) <strong>on</strong> MgO substrate (unit in nm).<br />

The n<strong>on</strong>-magnetic wire was made of 100 nm-thick Cu. The typical wire width was<br />

150 nm, while the distance between two ferromagnetic wires was 350 nm. The n<strong>on</strong>local<br />

resistance observed is 12.8 mΩ at room temperature that increases up to 44.8<br />

mΩ below 10 K[2]. These values are much larger than those in typical LSVs made of<br />

Permalloy and Cu in previous reports, indicating the advantage of the half-metallic<br />

Heusler alloys as ferromagnetic electrodes in LSV.<br />

[1]Y. Fukuma, L. Wang, H. Idzuchi, S. Takahashi, S. Maekawa, and Y. Otani, Nature Mater. 10, 527 (2011). [2]Y.<br />

K. Takahashi, S. Kasai, S. Hirayama, S. Mitani, and K. H<strong>on</strong>o, Appl. Phys. Lett. 100, 052405 (2012).<br />

Effect of electr<strong>on</strong> beam rapid thermal annealing <strong>on</strong> the TMR of<br />

CoFeB/MgO/CoFeB magnetic tunnel juncti<strong>on</strong>s<br />

Ganesh K Rajan 1 , Shivaraman Ramaswamy 2 *, C Gopalakrishnan 2 and John<br />

Thiruvadigal 3<br />

1<br />

Nanotechnology Research Center, SRM University, India<br />

2<br />

SRM University, India<br />

3<br />

Department of Physics and Nanotechnology, SRM University, India<br />

In this paper, we present our studies <strong>on</strong> the effect of Electr<strong>on</strong> Beam Rapid Thermal<br />

Annealing (ERTA) <strong>on</strong> the structural evoluti<strong>on</strong> and related transport properties of<br />

CoFeB/MgO/NiFe MTJ. The MgO based tunneling juncti<strong>on</strong>s were fabricated in a DC-<br />

RF magnetr<strong>on</strong> sputtering system with a base pressure 2 X 10 -7 mBar. An e-beam gun<br />

with a 3kV power supply was used to facilitate electr<strong>on</strong> bombardment <strong>on</strong> the MTJ for<br />

the purpose of rapid annealing .We observed the evoluti<strong>on</strong> of TMR in CoFeB/MgO/<br />

NiFe MTJ when subjected to ERTA. The main factor that distinguishes this study from<br />

other rapid annealing based studies is that the evoluti<strong>on</strong> of TMR happened within a<br />

very short annealing time (20 sec<strong>on</strong>ds). We observed an ultrafast crystallizati<strong>on</strong> of the<br />

FM layers of the MTJ which resulted in the evoluti<strong>on</strong> of TMR.<br />

1. S. Yuasa, T. Nagahama, A. Fukushima, Y. Suzuki and K. Ando, Nature Mater., vol. 3, pp. 868 - 871, Dec.<br />

2004. 2. S. S. P. Parkin, C. Kaiser, A. Panchula, P. M. Rice, B. Hughes, M. Samant and S. H. Yang, Nature<br />

Mater., vol. 3, pp. 862 - 867, Dec. 2004. 3. R. Cao, T. Moriyama, W. G. Wang, X. Fan, J. Kolodzey, S. H.<br />

Chen, C. R. Chang, Y. Tserkovnyak, B. K. Nikolic and J. Q. Xiao, IEEE Trans. Mag., vol. 45, pp. 3434 -<br />

3440, Oct. 2009.<br />

Preparati<strong>on</strong> of Ti-N films for a capping layer of a CoFeB/MgOmagnetic<br />

tunnel juncti<strong>on</strong><br />

Atsushi Sugihara*, Soichiro Osaki and Ryoichi Nakatani<br />

Osaka University, Japan<br />

CoFeB/MgO-MTJ is the most promising system for Spin-RAM because of its high<br />

tunnel magneto-resistance (TMR) [1]. Recently, perpendicular magnetic anisotropy<br />

(PMA) which was expected to reduce current density for magnetic switching by spintransfer<br />

torque (Jc0) down to applicable value (


Poster Friday<br />

SK34<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Half-Metallic Molecular Wire <strong>on</strong> Silic<strong>on</strong> Surface<br />

Yunhao Lu 1 , Yuan Ping Feng 2 * and Shuo-wang Yang 3<br />

1 Nati<strong>on</strong>al University of Singapore, Zhejiang University of China, Singapore<br />

2 Nati<strong>on</strong>al University of Singapore, Singapore<br />

3 Institute of High Performance Computing, Singapore<br />

Based <strong>on</strong> DFT calculati<strong>on</strong>s including the molecular dynamic simulati<strong>on</strong>s, at first time,<br />

we describe a feasible reacti<strong>on</strong> path to make a robust half metallic Mo-borine sandwich<br />

molecular wire <strong>on</strong> hydrogen-terminated Si(001) surface al<strong>on</strong>g [100] directi<strong>on</strong>. The<br />

wire is chemically b<strong>on</strong>ded to the surface, therefore, it is solid enough against thermoperturbati<strong>on</strong>,<br />

at least up to room temperature. Meanwhile, the electr<strong>on</strong>ic and magnetic<br />

properties of this molecular wire are tunable via an external electric field (EEF), and<br />

the wire exhibits multifuncti<strong>on</strong>al electr<strong>on</strong>ic and magnetic states, which allows it to<br />

work as a multistep molecular switch or/and multistep informati<strong>on</strong> storage comp<strong>on</strong>ent.<br />

Fantastically, this surface wire seems independent from the underplayed silic<strong>on</strong> bulk<br />

even under EEF situati<strong>on</strong>s since bulk properties have not been affected. This is because<br />

the charge transfers are c<strong>on</strong>strained within the wire and the upmost layer Si atoms <strong>on</strong>ly.<br />

All of these features should be meaningful in the applicati<strong>on</strong>s of molecular electr<strong>on</strong>ics<br />

or spintr<strong>on</strong>ics in near future.<br />

SL01<br />

Structural and magnetic studies of sol-gel prepared hexag<strong>on</strong>al<br />

BaFe12O19 Yat Choy W<strong>on</strong>g 1 *, Geok Bee Teh 2 , Sun Yung Kim 1 and James Wang 1<br />

1<br />

Faculty of Engineering and Industrial Sciences, Swinburne University of Technology,<br />

Australia<br />

2<br />

Divisi<strong>on</strong> of Chemistry and Biology, School of Arts and Science, Tunku Abdul<br />

Rahman College, Malaysia<br />

Barium hexaferrite particles prepared by sol-gel method was characterised<br />

using X-ray diffracti<strong>on</strong> spectroscopy (XRD), Field emissi<strong>on</strong> scanning electr<strong>on</strong><br />

microscopy (FeSEM), Superc<strong>on</strong>ducting Quantum Interference Device (SQUID) and<br />

Thermogravimetric analysis (TGA). Nano-sized particles BaFe 12O 19 and Fe 2O 3 were<br />

obtained after calcinati<strong>on</strong> at 8000C. The BaFe 12O 19 microstructure showed an average<br />

grain size of 200nm and recorded a saturati<strong>on</strong> and remanent magnetisati<strong>on</strong> of 60 and<br />

35 emu/g, respectively. In additi<strong>on</strong>, a commercially available BaFe 12O 19 was also<br />

studied. The feature observed was quite distinctive and was mostly in platelets form<br />

and much larger in size. It has a saturati<strong>on</strong> and remanent magnetisati<strong>on</strong> of 70 and 5<br />

emu/g, respectively. The poor remanent magnetism of this commercially available<br />

BaFe 12O 19 was due to large particle size and accompanied by an increased in surface<br />

area. TGA performed at 1000°C recorded about 1.8% wt loss in the sol-gel prepared<br />

barium hexaferrite compared with 0.2% as observed in the commercial product.<br />

SL02<br />

Magnetizati<strong>on</strong> reversal process in antiferromagnetically coupled (Co/<br />

Pd)/Ru/(Co/Pd) multilayer dot pattern<br />

Shunji Ishio 1 *, Yuta Kobayashi 1 , Takashi Hasegawa 1 , Akira Arakawa 1 , Hiromi Sasaki 1 ,<br />

Zh<strong>on</strong>gjie Yan 2 and Xi Liu 2<br />

1 Department of Materials Science and Engineering, Akita University, Japan<br />

2 Venture Business Laboratory, Akita University, Japan<br />

Magnetizati<strong>on</strong> reversal process, exchange interacti<strong>on</strong> Hex between layers and<br />

coercivity in the antiferromagnetically coupled (Co/Pd)/Ru/(Co/Pd) dot patterns were<br />

studied as a functi<strong>on</strong> of dot size. Pd 10.5/[Pd 0.7/Co 0.4] 4/Ru 0.4/[Co 0.4/Pd(1.5 nm)]6 were<br />

sputtered <strong>on</strong>to pre-patterned Si substrates. Dot shape was designed to be 100 - 3000<br />

nm square. Magnetizati<strong>on</strong> measurements revealed that top and bottom layers have<br />

a perpendicular magnetic anisotropy and couple each other antiferromagnetically at<br />

remanent state. MFM measurement indicated that the magnetic state of each layer<br />

becomes single domain below side length d=200 nm. Complicated magnetizati<strong>on</strong><br />

reversal process was observed. The magnetizati<strong>on</strong> reversal starts from a nucleati<strong>on</strong><br />

of reverse domain at dot edge in the reversal from the↑/↓ (↓/↑) state to the ↑/↑ (↓/↓)<br />

state, while the coherent rotati<strong>on</strong> type behaviour was found in the ↑/↑ (↓/↓) to ↑/↓<br />

(↓/↑) reversal. Hex was about 2.2 kOe in the film and decreases to less than 1 kOe at<br />

d=100 nm. Coercivity is about 1 kOe for the film and is almost c<strong>on</strong>stant independently<br />

<strong>on</strong> the dot size. The magnetizati<strong>on</strong> reversal process and the dependence of Hex and<br />

coercivity <strong>on</strong> dot size are discussed in terms of the structural and magnetic property of<br />

intermediate Ru layer in patterned dots.<br />

242 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SL03<br />

Magnetic properties of mechanically alloyed Fe-Cu particles<br />

Osamu Kohmoto, Masakazu Uchida and Yasushi Matsushima<br />

Okayama University, Japan<br />

Mechanically alloyed powders have metastable structure. In the Fe-Cu phase<br />

diagram, both the Fe and Cu are known to have quite small solubility in to Cu and<br />

Fe, respectively, at room temperature. We have prepared x at% Cu-Fe particles by<br />

mechanical alloying. The starting materials were pure Fe and Cu powers. The crystallite<br />

sizes of Fe with 700 A for bcc(110) and Cu with 45 nm for fcc(111) decreases below 20<br />

nm at milling time of 500 h. The 500-h-milled alloys with x=0-30 % Cu show a single<br />

bcc phase, and the alloys with x=35-100 % Cu show a single fcc phase. Co-existence<br />

of fcc and bcc phases is not observed at x=30 and 35 %Cu. However, at x=30 at %,<br />

a slight increase in the mass density deduced by lattice parameter is observed and the<br />

density jumps by 0.85 g/cm3 at 35 at%. The magnetizati<strong>on</strong> at 16 kOe decreases from<br />

200 emu/g with increasing Cu c<strong>on</strong>tent, however, it has a sudden decrease at 35at% Cu<br />

of the phase boundary. The magnetizati<strong>on</strong> reaches zero at x=90 % Cu. Coercive force<br />

increases initially with the Cu c<strong>on</strong>tent, however, it has a sudden jump at the phase<br />

boundary.<br />

SL04<br />

Temperature dependence of the coercive force of ferromagnetic TM-<br />

Al-O (TM=Fe, Co) granular films<br />

Shintaro Nakamura 1 *, Akira Yoshihara 2 , Shigehiro Ohnuma 3 and Tsutomu Nojima 1<br />

1<br />

Institute for Materials Research, Tohoku University, Japan<br />

2<br />

Ishinomaki Senshu University, Japan<br />

3<br />

Research Institute for Electromagnetic Materials, Japan<br />

Temperature development of the coercive force (Hc) of ferromagnetic TM-Al-O<br />

granular films has been investigated in a temperature range from 290 K down to 5 K.<br />

Each film is prepared using the magnetr<strong>on</strong> sputtering method. During the depositing<br />

process, a dc magnetic field was applied parallel to the film surface to induce in-plane<br />

uniaxial anisotropy. An Fe-Al-O granular film shows no clear in-plane anisotropy<br />

at 290 K. On the other hand, Co-Al-O films show clear in-plane anisotropy at 290<br />

K. The Hc of the Fe-Al-O film is found to be almost independent of temperature.<br />

In c<strong>on</strong>trast that of Co-Al-O films str<strong>on</strong>gly depends <strong>on</strong> temperature. The Hc of Co-<br />

Al-O films al<strong>on</strong>g the easy axis increases rapidly with decreasing temperature. This<br />

behavior in the Hc also depends <strong>on</strong> the Co-c<strong>on</strong>centrati<strong>on</strong>. For films with lower Coc<strong>on</strong>centrati<strong>on</strong><br />

and larger electrical resistivity, enhancement of the Hc becomes larger at<br />

the lowest temperature. The Hc of Co-Al-O films shows characteristic behavior at low<br />

temperatures. It increases with decreasing temperature, following a logarithmic law<br />

below about 50 K.<br />

SL05<br />

Microscopic dipole-exchange theory for magn<strong>on</strong>ic crystal arrays of<br />

interacting ferromagnetic nanorings<br />

Jan Borchmann, Hoa Nguyen and Michael Cottam<br />

Department of Physics and Astr<strong>on</strong>omy, University of Western Ontario, Canada<br />

A microscopic theory is employed to study magn<strong>on</strong>ic crystals represented by <strong>on</strong>edimensi<strong>on</strong>al<br />

arrays of ferromagnetic nanorings. The Hamilt<strong>on</strong>ian-based formalism<br />

includes exchange and dipole-dipole coupling within each ring, the l<strong>on</strong>g-range dipolar<br />

coupling between rings, and an external applied magnetic field. Depending <strong>on</strong> the<br />

applied field, as well as the size of the rings and the inter-ring spacing, the array<br />

elements may be in a vortex, <strong>on</strong>i<strong>on</strong> (bidomain), or other inhomogeneous magnetizati<strong>on</strong><br />

state. Numerical results are reported for the magn<strong>on</strong>ic bands and gaps in Permalloy<br />

nanorings with outer diameter typically 80 to 120 nm, thickness typically 15 to 30 nm,<br />

and spacing varied between 10 and 100 nm. For low values of the field (e.g., 0.02 T)<br />

al<strong>on</strong>g the length of the array, the vortex state is favored energetically and it is found<br />

that the magn<strong>on</strong>ic bands are fairly broad and the gaps are relatively small, particularly<br />

when the spacing is reduced. C<strong>on</strong>versely, at larger fields (e.g., 0.2 T) favoring the<br />

<strong>on</strong>i<strong>on</strong> state, the magn<strong>on</strong>ic bands are narrower and the gaps larger. Varying the inner<br />

diameter of the rings, as well as the spacing, can c<strong>on</strong>trol the transiti<strong>on</strong> fields between<br />

the different states, which may be advantageous for device applicati<strong>on</strong>s.


SL06<br />

Synthesis and magnetic properties of zinc ferrite nanocrystals and<br />

their applicati<strong>on</strong>s<br />

Yang Yang, Xiaoli Liu, Chin Shen Ong and Jun Ding*<br />

Materials Science and Engineering, Nati<strong>on</strong>al University of Singapore, Singapore<br />

We studied magnetic properties of zinc ferrite nanoparticles via thermal decompositi<strong>on</strong>,<br />

whereas zinc i<strong>on</strong>s partially replace ir<strong>on</strong> i<strong>on</strong>s at A sites with a nominal compositi<strong>on</strong> of<br />

(Zn 0.5Fe 0.5)Fe 2O 4. Our first-principle calculati<strong>on</strong> has shown that Zn i<strong>on</strong> has significantly<br />

lower formati<strong>on</strong> energy at A-site compared to the substituti<strong>on</strong> of B-site and an<br />

enhancement of saturati<strong>on</strong> magnetizati<strong>on</strong> of 10-20% is obtained due to the reducti<strong>on</strong><br />

of the total magnetic moment of A-site which is antiferromagnetically coupled with<br />

B-site. The ir<strong>on</strong> and zinc precursors [Fe(acac)3, Zn(acac)2.xH 2O] were used in the<br />

synthesis of zinc ferrite particles. We have found that a molar ratio of zinc precursor<br />

to ir<strong>on</strong> precursor of 1:2 is required for the end product of (Zn 0.5Fe 0.5)Fe 2O 4. It has been<br />

found that magnetizati<strong>on</strong> measured at room temperature is dependent sensitively<br />

<strong>on</strong> particles. Room temperature magnetizati<strong>on</strong> reaches 100.9 emu/g for zinc ferrite<br />

nanoparticles with an average particle size of 85 nm. The value is significantly larger<br />

than that of bulk Fe 3O 4 (80-90 emu/g). The as-synthesized zinc ferrite particles with<br />

an average particle size of 26 nm were selected for magnetic fluid hyperthermia. After<br />

mPEG surface coating, the particles could be well dispersed in water. A comparative<br />

high SAR value of 630 W/g was obtained.<br />

SL07<br />

Nanocrystallite size-induced changes in the magnetic and transport<br />

properties of La 1-xCa xMnO 3 (x = 1/8, 3/8, 5/8) manganite<br />

Yugandhar Bitla and S. N. Kaul*<br />

School of Physics, University of Hyderabad, Central University P.O., Hyderabad -<br />

500 046, India<br />

Magnetizati<strong>on</strong>, magnetic hysteresis loops/isotherms, linear and n<strong>on</strong>-linear ac<br />

susceptibility, electrical resistivity and magnetoresistance measurements have been<br />

performed <strong>on</strong> 40 nm nanocrystalline La 1-xCa xMnO 3 (x = 1/8, 3/8, 5/8). Compared to the<br />

bulk, reducing the crystallite size down to 40 nm results in the following changes. For x =<br />

1/8 [1], lowers paramagnetic insulating (PMI)- ferromagnetic insulating (FMI) transiti<strong>on</strong><br />

temperature T_(c) to 143 K, induces the metal-insulator (MI) transiti<strong>on</strong> at T_(MI) = 77<br />

K and charge ordering (CO)/orbital ordering (OO) transiti<strong>on</strong> at T_(CO/OO) = 35 K but<br />

leaves the insulating cluster spin glass transiti<strong>on</strong> temperature T_(g), the temperature T_<br />

(JT) below which short-range antiferromagnetic (AF) order coexists with OO and the<br />

spin-wave stiffness at 0 K, D(0) = 35(2) meVA 2 , essentially unaltered. For x = 3/8, lowers<br />

T_(MI) to 234 K, a sec<strong>on</strong>d-order (first-order) PMI-FMI phase transiti<strong>on</strong> occurs at T_<br />

(c) = 273.5 K when the applied magnetic field, H = 0 (H ≠ 0), D(0) retains its bulk value<br />

[2] 145(5) meVA 2 and T_(CO) reduces to 30 K. For x = 5/8, FM and CO ordering in the<br />

insulating state sets in at T_(c) = T_(CO) = 270 K and transiti<strong>on</strong> to the AF/OO phase<br />

occurs at T_(AF) = 50 K.<br />

[1] Y. Bitla and S. N. Kaul, J. Appl. Phys. 111, xxxx (2012) at press. [2] J. J. Rhyne et al., J. Magn.<br />

Magn. Mater. 226-230, 775 (2001).<br />

SL08<br />

Magnetic and magneto-optical properties of bilayered Co/Ni anti-dot<br />

arrays<br />

N. G. Deshpande 1 , H. Y. Zheng 1 , J. S. Hwang 1 , S. J. Lee 1 , Y. P. Lee 1 *, J. Y. Rhee 2 and K.<br />

W. Kim 3<br />

1<br />

Physics, Hanyang University, Korea<br />

2<br />

Physics, Sungkyunkwan University, Korea<br />

3<br />

Informati<strong>on</strong> Display, SUN MOON University, Korea<br />

In this study, we have successfully fabricated bilayered Co/Ni anti-dot arrays using<br />

photolithography and c<strong>on</strong>trolled wet-etching processes. Such a ferromagnetic structure was<br />

made by sequentially depositing Co (40 nm)/Ni (5 nm) bilayer <strong>on</strong> a Si substrate. The anti-dot<br />

patterning with a hole diameter of 1 -m was d<strong>on</strong>e <strong>on</strong>ly <strong>on</strong> the upper Co layer, while the Ni<br />

underlayer was kept uniform. The magnetic properties of anti-dot arrays were investigated by<br />

using a superc<strong>on</strong>ducting-quantum-interference-device magnetometer and by magnetic-force<br />

microscopy (MFM). The l<strong>on</strong>gitudinal Kerr rotati<strong>on</strong> (LKR) of the zeroth- and the first-order<br />

diffracted beams were measured at an incidence angle of 30°. Significantly, it was observed<br />

that the LKR of the first-order diffracted beam is nearly 4 times larger than that of the zerothorder<br />

beam. The simulated results for the hysteresis loops matched qualitatively well with<br />

the experimentally obtained <strong>on</strong>es. The MFM images revealed well-defined periodic domain<br />

structures which can be ascribed to the anisotropies such as magnetic uniaxial anisotropy,<br />

c<strong>on</strong>figurati<strong>on</strong>al anisotropy, etc. We observed that the magnetizati<strong>on</strong> reversal of such a system<br />

proceeds through the formati<strong>on</strong> and the annihilati<strong>on</strong> of domains. The observed changes in the<br />

magnetic properties are closely related to the patterning that hinders the domain-wall moti<strong>on</strong>.<br />

SL09<br />

SL10<br />

SL11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Diffracted magneto-optical Kerr effect of Co anti-dot structure in<br />

different arrangements<br />

H. Y. Zheng 1 , N. G. Deshpande 1 , X. R. Jin 1 , J. Y. Rhee 2 , K. W. Kim 3 and Y. P. Lee 1 *<br />

1 Physics, Hanyang University, Korea<br />

2 Physics, Sungkyunkwan University, Korea<br />

3 Informati<strong>on</strong> Display, SUN MOON University, Korea<br />

To fullfill the increasing requirement for the miniaturizati<strong>on</strong> of magnetic materials, the<br />

effective extracti<strong>on</strong> of informati<strong>on</strong> from the nano-scale structures becomes hot issue. Some<br />

of techniques, such as diffracted magneto-optical Kerr effect (DMOKE), magnetic-force<br />

microscopy and Lorentz scanning transmissi<strong>on</strong> electr<strong>on</strong> microscopy, have been utilized to<br />

read the magnetic informati<strong>on</strong>. As a derivative technique of MOKE, which can be applied in<br />

describing the magnetic hysteresis loops, the DMOKE provides us more unique performance,<br />

since the diffracted light is more sensitive to the change of the magnetizati<strong>on</strong> distributi<strong>on</strong> in<br />

magnetic material. Micromagnetic simulati<strong>on</strong> is also a useful method to study the process of<br />

magnetizati<strong>on</strong> reversal. In order to get the distributi<strong>on</strong> of magnetizati<strong>on</strong>, the Object Oriented<br />

Micromagnetic Framework (OOMMF) program with periodic boundary c<strong>on</strong>diti<strong>on</strong> was<br />

employed. By combining DMOKE and the micromagnetic simulati<strong>on</strong>, we can theoretically<br />

and experimentally get more exact magnetic informati<strong>on</strong>. We investigated the transverse<br />

DMOKE and the magnetizati<strong>on</strong>-reversal process in rhombic and square lattice arrangements<br />

of Co anti-dot structures. The hysteresis loops of the diffracted beams are described by the<br />

magnetic form factor. The shape of hysteresis loops of the diffracti<strong>on</strong>s, especially, at the points<br />

of inflecti<strong>on</strong> of the loop, is expected to indicate a special distributi<strong>on</strong> of magnetizati<strong>on</strong>.<br />

M<strong>on</strong>odisperse magnetic nanoparticles: effects of surfactant<br />

c<strong>on</strong>centrati<strong>on</strong> <strong>on</strong> the reacti<strong>on</strong> between Fe(acac)3 and Pt(acac)2<br />

Komkrich Chokprasombat 1 *, Phimphaka Harding 1 , Chitnar<strong>on</strong>g Sirisathitkul 1 , P<strong>on</strong>gsakorn<br />

Jantaratana 2 , Sujittra Chandarak 3 and Rattikorn Yimnirun 4<br />

1<br />

School of Science, Walailak University, Thailand<br />

2<br />

Department of Physics, Kasetsart University, Thailand<br />

3<br />

School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology,<br />

Thailand<br />

4<br />

School of Physics, Institute of Science, Suranaree University of Technology, Thailand<br />

Magnetic properties of m<strong>on</strong>odisperse nanoparticles for ultrahigh density recording and biomedical<br />

applicati<strong>on</strong>s are sensitive to their shape and size distributi<strong>on</strong>s. These attributes are, in turns, dictated<br />

by several parameters during the synthesis and heat treatments. In this work, m<strong>on</strong>odisperse<br />

magnetic nanoparticles with size of around 4-5 nm were synthesized by the modified polyol<br />

process with 1.0 mmol Fe(acac)3 and 0.5 mmol Pt(acac)2 as starting materials. The as-synthesized<br />

nanoparticles were transformed from their superparamagnetic phase to the ferromagnetic state by<br />

annealing in arg<strong>on</strong> atmosphere at 570 C for 1 hour. Without any reducing agents, c<strong>on</strong>centrati<strong>on</strong><br />

of surfactants (oleic acid and oleylamine) of 1.5 - 4.5 mmol affected morphology and magnetic<br />

properties of the nanoparticles. When 2.5 mmol of each surfactant was used, the as-synthesized<br />

nanoparticles have the smallest variati<strong>on</strong>s in size and shape. However, the higher c<strong>on</strong>centrati<strong>on</strong> of<br />

oleic acid and oleylamine led to a higher coercivity in annealed nanoparticles which are related to<br />

the size distributi<strong>on</strong>. These results indicated that the appropriate amount of surfactants must be used<br />

in order to optimize the size distributi<strong>on</strong> and magnetic hysteresis of nanoparticles.<br />

Hollow MnCO3 and MnSiO3 nanosphares<br />

Zv<strong>on</strong>ko Jaglicic 1 , Jin Bae Lee 2 , Hae Jin Kim 2 and Janez Dolinsek 3<br />

1<br />

Dept. of Physics, Institute of Mathematics, Physics and Mechanics & University of<br />

Ljubljana, FGG, Slovenia<br />

2<br />

Divisi<strong>on</strong> of Materials Science, Korea Basic Science Institute, Daeje<strong>on</strong> 305-333,<br />

Korea<br />

3<br />

C<strong>on</strong>densed Matter Physics, J Stefan Institute, University of Ljubljana, Jamova 39,<br />

SI-1000 Ljubljana, Slovenia<br />

Magnetic nanoparticles can be used in many different applicati<strong>on</strong>s ranging from medicine,<br />

electromagnetic wave detectors to digital informati<strong>on</strong> storage. Hollow nanosphares offers<br />

additi<strong>on</strong>al functi<strong>on</strong>ality. For example they show improved electrochemical performance<br />

for batteries or can be used for drug delivery. We synthesised MnCO 3 and MnSiO 3<br />

hollow nanospheres with a diameter of few nanometers and thickness of <strong>on</strong>ly few atomic<br />

layers. In the MnSiO 3 hollow nanospheres a small c<strong>on</strong>centrati<strong>on</strong> of Mn 3O 4 was detected<br />

from magnetic measurements. Its str<strong>on</strong>g ferrimagnetic signal at TN = 42 K suppressed<br />

the signal of intrinsic magnetic properties of MnSiO 3 nanospheres. On the other hand in<br />

the MnCO 3 nanospheres no Mn 3O 4 was detected which enable us to study their dc and<br />

ac magnetic properties. The Neel temperature at around 33.5 K is between the reported<br />

values for MnCO 3 single crystal (34.3 K) and powder sample (31.0 K)[1]. A coercive<br />

field and remanent magnetizati<strong>on</strong> of MnCO 3 nanospheres measured at 5 K are decreased<br />

in comparis<strong>on</strong> to the bulk system.<br />

[1] A. Kosterov, T. Frederichs, T. v<strong>on</strong> Dobeneck, Physics of the Earth and Planetary Interiors 154 (2006) 234-242.<br />

July 8 - 13, 2012 Busan, Korea 243<br />

Poster Friday


Poster Friday<br />

SL12<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Shape-c<strong>on</strong>trolled synthesis and magnetic properties of FePt nanocubes<br />

Mingge Zhou 1 *, Wei Li 2 , Minggang Zhu 2 , D<strong>on</strong>g Zhou 2 and Yangl<strong>on</strong>g Hou 3<br />

1 Divisi<strong>on</strong> of Functi<strong>on</strong>al Materials, Central Ir<strong>on</strong> and Steel Research Institute, China<br />

2 Central Ir<strong>on</strong> and Steel Research Institute, China<br />

3 Department of Advanced Materials and Nanotechnology, College of Engineering,<br />

Peking University, China<br />

In this article, synthesis of m<strong>on</strong>odisperse ir<strong>on</strong>-platinum (FePt) nanoparticles by<br />

reducti<strong>on</strong> of platinum acetylacet<strong>on</strong>ate followed by thermal decompositi<strong>on</strong> of ir<strong>on</strong><br />

pentacarb<strong>on</strong>yl in the presence of oleic acid and oleylamine stabilizers is reported,<br />

Particle shape is c<strong>on</strong>trolled by the additi<strong>on</strong> of Mo(CO)6, our synthesis yields particles<br />

with shapes that are close to cubic and their size can be c<strong>on</strong>trolled from 7 to 10 nm, In<br />

order to form FePt film, Then the self-assembly FePt nanocubes were annealed at 700<br />

°C for an hour did the FePt nanoparticle transform to the fct phase.The phase analysis,<br />

structure, and magnetic properties were determined by X-ray diffracti<strong>on</strong> (XRD), High<br />

resoluti<strong>on</strong> transmissi<strong>on</strong> electr<strong>on</strong> microscope (HRTEM), Scanning electr<strong>on</strong> microscope<br />

and vibrating sample magnetometer (VSM) techniques.<br />

SL13<br />

Magnetic properties of NiO/Ni(OH)2 core-shell nanostructures<br />

Mangesh B. Mahajan and P. A. Joy*<br />

Physical and Materials Chemistry, Nati<strong>on</strong>al Chemical Laboratory, Pune, India<br />

Antiferromagnetic materials show interesting and anomalous properties when their size<br />

is reduced to nanodimensi<strong>on</strong>s. The magnetic susceptibility is increased with decreasing<br />

particle size(1). Bulk NiO is antiferromagnetic and recent studies showed that NiO<br />

nanoparticles exhibit aging and memory effects similar to that of spin glasses(2). The<br />

finite size and surface effects play major role in determining the magnetic behaviour of<br />

these nanoparticles(3). We have synthesized NiO nanoparticles by a simple chemical<br />

route followed by calcinati<strong>on</strong>. The freshly prepared sample was dispersed in water,<br />

then filtered and dried in air to get NiO/Ni(OH) 2 core-shell type nanostructures.<br />

These nanostructures were characterized by using different techniques and magnetic<br />

properties using SQUID-VSM. Magnetic properties of nanoparticles of NiO, Ni(OH) 2,<br />

and NiO/Ni(OH) 2 have been compared to study the effect of Ni(OH) 2 layer <strong>on</strong> NiO.<br />

Low temperature M-H curves showed c<strong>on</strong>siderable difference in the coercivities<br />

and saturati<strong>on</strong> magnetizati<strong>on</strong> values of the core-shell structure. From ZFC and FC<br />

measurements it is observed that magnetic behaviour of the NiO/Ni(OH) 2 core-shell<br />

nanoparticles differs substantially from that of bare NiO and Ni(OH) 2 nanoparticles.<br />

The observed changes are explained in terms of lower size of NiO core and the effect<br />

of different inter-particle interacti<strong>on</strong>s with and without the hydroxide layer.<br />

1. J. T. Richards<strong>on</strong> and W. O. Milligan, Phys. Rev. 102, 1289 (1956). 2. S. D. Tiwari and K. P. Rajeev, Phys. Rev. B,<br />

72, 104433 (2005). 3. R. H. Kodama, Salah A. Makhlouf and A. E. Berkowitz, Phys. Rev. Lett. 79, 1393 (1997).<br />

SL14<br />

Structual and magnetic properties of MFe2O4 (M=Ni, Mg) nano hollow<br />

spheres<br />

K. K<strong>on</strong>ishi 1 *, T. Sakurai 1 , Y. Nagano 2 , N. Manabe 2 and Y. Morimoto 2<br />

1<br />

Department og Physics, Graduate School of Science and Engineering, Ehime<br />

University, Japan<br />

2<br />

Department og Physics, Faculty of Science, Ehime University, Japan<br />

Hollow sphere structures have recently received c<strong>on</strong>siderable attenti<strong>on</strong> because of<br />

their novel interior geometry and surface functi<strong>on</strong>ality. In this report, sub-micrometersized<br />

hollow spheres assembled from ferrite nanoparticles have been prepared by a wet<br />

chemial process. Measurements of dc-susceptibility and magnetizati<strong>on</strong> were carried<br />

out <strong>on</strong> samples of MFe 2O 4 (M= Ni, Mg) nanoparticles with average diameter 4-5<br />

nm, and hollow spheres (500 nm in diameter) with about 12-17nm thickness shell. A<br />

superparamagnetic-type blocking process is observed in the ZFC and FC magnetizati<strong>on</strong><br />

and magnentic susceptibility for all samples. Furthermore, a behavior due to surface<br />

spin freezing of nanoparticles is found in Ni-ferrite. The surface spin freezing<br />

temperatures Tf are quite lower than the blocking temperature, and the magnetic field<br />

dependence is different between nanoparticle and hollow sphere. The spin-glass nature<br />

of Ni-ferrite nanoparticle is dem<strong>on</strong>strated by the magnetice field dependence of Tf<br />

following the well known Almeida-Thouless line. In c<strong>on</strong>trast, Tf (H) of Ni-ferrite<br />

hollow sphere hints at failure of Gabay-Toulouse theory as well as the AT type.<br />

244 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SL15<br />

Magnetizati<strong>on</strong> reversal in patterned arrays of (001)Fe particles<br />

Maj Hans<strong>on</strong> 1 *, Rimantas Brucas 2 and Erik Wahlstrom 3<br />

1 Department of Applied physics, Chalmers university of technology, Sweden<br />

2 Department of Engineering Science, Solid State Physics,, Uppsala University,<br />

Sweden<br />

3 Institutt for fysikk, NTNU, Norway<br />

Arrays of elliptical Fe particles prepared by patterning [1] of epitaxial (001)Fe films<br />

may serve as model systems for studies of the processes of magnetizati<strong>on</strong> reversal in<br />

sub-micr<strong>on</strong> size particles. In this work we studied such systems with film thicknesses<br />

in the range between 10 nm and 50 nm. Ellipses with aspect ratio 1:3 were prepared<br />

with their short axes being 50, 100 and 150 nm and varying inter-particle distances.<br />

The magnetic domain state and the magnetizati<strong>on</strong> reversal of individual particles were<br />

investigated by magnetic force microscopy (MFM) and micromagnetic calculati<strong>on</strong>s.<br />

Magnetizati<strong>on</strong> curves of the arrays, comprising about 106 particles, were measured<br />

with an alternating gradient force magnetometer (AGM). Within the range of actual<br />

sizes we find that the largest particles may be left in a multi- or bidomain (MD) state<br />

after demagnetizati<strong>on</strong> whereas the smallest show single-domain (SD) properties. In<br />

particular we analyze the influence of interacti<strong>on</strong>s and the transiti<strong>on</strong> from MD to SD<br />

behaviour as displayed in the shape of the hysteresis curves and in the MFM images<br />

taken after remanent demagnetizati<strong>on</strong>. The single particle properties are compared with<br />

results from micromagnetic calculati<strong>on</strong>s.<br />

1. M. Hans<strong>on</strong> et al. JAP 85 (1999) 2793<br />

SL16<br />

C<strong>on</strong>trollable structure and magnetic properties of cobalt nanowires by<br />

tuning depositi<strong>on</strong> voltage<br />

Xiu Xiu Fan 1 , Hai Ning Hu 2 and Zh<strong>on</strong>g Shi 3 *<br />

1<br />

Surface Physics State Laboratory and Department of Physics, Fudan University,<br />

China<br />

2<br />

School of Mathematics and Physics, Shanghai University of Electric Power, China<br />

3<br />

Department of Physics, T<strong>on</strong>gji University, China<br />

Magnetic properties of Co nanowires have been shown to be c<strong>on</strong>trolled by various growth parameters. The<br />

depositi<strong>on</strong> voltage shows great c<strong>on</strong>venience in c<strong>on</strong>trolling microstructure. Reported results were mostly<br />

focused <strong>on</strong> low voltages[1-4]. In this work, Co nanowires were fabricated into ordered AAO templates by dc<br />

electrodepositi<strong>on</strong> in a wide range of depositi<strong>on</strong> voltage at 20°C. With depositi<strong>on</strong> voltages of 2.0 and 4.5 V, Co<br />

nanowires are of hcp(100) and fcc(220) al<strong>on</strong>g the nanowire-axis, respectively. Two structures coexist for medium<br />

voltages. For all samples, the easy axes of magnetocrystalline (Kmc) and shape (Ksh) anisotropy make angles to<br />

each other. For low voltages, Kmc and Ksh are close to each other, resulting in small coercivity Hc(||) and Hc(┴)<br />

for H parallel and perpendicular to nanowire-axis. Since Kmc is <strong>on</strong>e order smaller than Ksh and thus the easyaxis<br />

lies al<strong>on</strong>g the nanowire-axis for high voltages, large Hc(||) is obtained at room temperature. For low and high<br />

voltages, Hc(||) first decreases and then increases with a minimum at 200 K, and increases m<strong>on</strong>ot<strong>on</strong>ically with T<br />

increasing from 50 to 390 K[5], respectively. The angular dependence of Hc shows a combined magnetic reversal<br />

process which can be described by curling and/or transverse domain wall modes[6].<br />

1. H. Zeng, R. Skomski, and et al., Phys. Rev. B 65, 134426 (2002). 2. H. Zeng, M. Zheng, and et al., J. Appl. Phys. 87, 4718 (2000). 3. H. Pan, B. Liu,<br />

and et al., J. Phys. Chem. B 109, 3094 (2005). 4. X. H. Han, Q. F. Liu, and et al., J. Phys. D: Appl. Phys. 42, 095005 (2009). 5. J. Sanchez-Barriga, M.<br />

Lucas, and et al., Phys. Rev. B 80, 184424 (2009). 6. M. Vazquez and L. G. Vivas, physica status solidi (b) 248, 2368 (2011).<br />

SL17<br />

Magnetotransmissi<strong>on</strong> effect in Nd 0.5Sr 0.5MnO 3 nano-composites<br />

Elena Mostovshchikova, Natalya Loshkareva, Andrey Telegin*, Nikolay Solin,<br />

Sergey Naumov and Sergey Telegin<br />

Institute of Metal Physics UD of RAS, Russia<br />

Magnetic and optical properties of composites <strong>on</strong> the base of Nd 0.5Sr 0.5MnO 3 powders diluted in dielectric<br />

matrix have been studied. Nd 0.5Sr 0.5MnO 3 manganite is interesting due to existence of two different type<br />

of phase transiti<strong>on</strong>s: the first <strong>on</strong>e is from paramagnetic semic<strong>on</strong>ductor to the FM metallic state near TC-<br />

250 K, the sec<strong>on</strong>d <strong>on</strong>e is from the FM metallic state to CE-type AFM insulating state with charge ordering<br />

near TCO-160 K [1]. The giant negative magnetotransmissi<strong>on</strong> effect (relative change of natural light<br />

transmissi<strong>on</strong> under the magnetic field) up to 14% in the field H = 0.8 T was revealed for Nd 0.5Sr 0.5MnO 3<br />

composites near TC in the infrared range. The charge ordering and AFM state may by destroyed by<br />

decreasing of grains to nanoscale size [2] resulting in appearing of new effects. The remarkable feature<br />

of Nd 0.5Sr 0.5MnO 3 nano-composite with average grain size about 100 nm is an existence of significant<br />

magnetotransmissi<strong>on</strong> about 7% in the wide temperature range near and far below TC. It was explained<br />

by the significant c<strong>on</strong>tributi<strong>on</strong> of nano-particle shells with disordered spins to the magnetic properties of<br />

nano-composite. Finally, such a composite material is a promising candidate for future magneto-optical<br />

applicati<strong>on</strong>s [3].<br />

[1] H. Kawano, R. Kajimoto, H. Yoshizawa, Y. Tomioka, H. Kuwahara, and Y. Tokura. Phys. Rev. Lett. 78, 4253 (1997)<br />

[2] R.H. Kodama. JMMM 200, 359 (1999); R.H. Kodama and A.E. Berkowitz. Phys. Rev. B 59, 6321 (1999) [3] A.B.<br />

Granovskii, Yu.P. Sukhorukov, A.V. Telegin et al, J. of Experimental and Theoretical Physics, 112, No1, 77 (2011)<br />

Supported by the program of DPS RAS “Physics of new materials and structures”, grant MK-1048.2012.2 and RFBR<br />

grants No 10-02-00038, 11-02-00252, 12-02-00208


SL18<br />

Influence of asymmetric permalloy ring <strong>on</strong> magnetizati<strong>on</strong><br />

c<strong>on</strong>figurati<strong>on</strong> and switching behavior<br />

Chao-hsien Huang 1 *, Lance Horng 1 , Nian-jia Cheng 2 , Tian-chiuan Wu 3 and J<strong>on</strong>g-ching Wu 1<br />

1 Department of Physics, Nati<strong>on</strong>al Changhua University of Educati<strong>on</strong>, Taiwan<br />

2 Institute of phot<strong>on</strong>ics, Nati<strong>on</strong>al Changhua University of Educati<strong>on</strong>, Taiwan<br />

3 Department of Electr<strong>on</strong>ic Engineering, Nati<strong>on</strong>al Formosa University, Taiwan<br />

By introducing an inner circle shifted al<strong>on</strong>g the diameter of outer circle, an asymmetric ring and the<br />

asymmetric ratio (R) are defined to c<strong>on</strong>trol over the vortex state (flux-closure state) nucleati<strong>on</strong> and<br />

annihilati<strong>on</strong> field in asymmetric Permalloy (Py) rings. Series of asymmetric Permalloy rings with<br />

different diameter and asymmetric ratio were prepared to observe the magnetic switching behavior<br />

and the magnetizati<strong>on</strong> c<strong>on</strong>figurati<strong>on</strong>. The asymmetry of Py rings with thickness of 20 nm, outer<br />

diameter (Do) of 300, 500, 800 nm, inner diameter (d) of 100, 150, 200, 250, 300 nm, and shift<br />

length (S) of 30, 50, 70, 100, 120, 150 nm. Numerical micromagnetic simulati<strong>on</strong>s are carried out<br />

using the object-oriented micromagnetic framework (OOMMF) software. With applied field from<br />

the positive to negative magnetic field, the magnetic field at which the vortex nucleate in the Py ring<br />

is defined as the nucleati<strong>on</strong> field (Hn). The annihilati<strong>on</strong> field (Han) is the magnetic field where the<br />

vortex annihilate. Linear relati<strong>on</strong>s of vortex state nucleati<strong>on</strong> and annihilati<strong>on</strong> fields to asymmetric<br />

ratio were found, and are useful mainly for c<strong>on</strong>trolling the nucleati<strong>on</strong> and annihilati<strong>on</strong> fields.<br />

1. P. Vavassori, R. Bovolenta, V. Metlushko and B. Ilic, J. Appl. Phys. 99, 053902 (2006) 2. E. Saitoh, M. Kawabata, K.<br />

Harii, H. Miyajima and T. Yamaoka, J. Appl. Phys. 95, 1986 (2004) 3. X. H. Wang, W. K. Peng, and W. S. Lew, J. Appl.<br />

Phys. 106, 043905 (2009) 4. A. Subramani, D. Geerpuram, V. Baskaran, J. Friedlund, and V. Metlushko, Physica C 437-<br />

438, 293 (2006) 5. F. Giesen, J. Podbielski, B. Botters, and D. Grundler, Phys. Rev. B 75, 184428 (2007)<br />

SL19<br />

Fabricati<strong>on</strong> of high aspect ratio nanoscale magnetic tunnel juncti<strong>on</strong><br />

etch mask by oxygen plasma assisted resist trimming<br />

B<strong>on</strong>gho Kim 1 , Daeh<strong>on</strong>g Kim 1 , Sungwoo Chun 1 , Hyungyu Lee 1 , Se<strong>on</strong>jun Choi 1 and<br />

Seung-beck Lee 2 *<br />

1 Department of Electr<strong>on</strong>ic Engineering, Hanyang University, Seoul, Korea<br />

2 Department of Nanoscale Semic<strong>on</strong>ductor Engineering, Hanyang University, Seoul,<br />

Korea<br />

The development of large-area, nanostructure patterning with high aspect ratios is a challenging<br />

problem that must be addressed for potential applicati<strong>on</strong>s in high performance nanoscale devices[1].<br />

When negative resist pillar patterns are formed using electr<strong>on</strong> beam lithography,the forward and<br />

backward scattering of the electr<strong>on</strong>s limit the resoluti<strong>on</strong> therefore, the resist layer should be thinner.<br />

When the patterned resist pillars were used as dry etching masks, the resist polymer during the<br />

process requires the pillars to have high aspect ratio. Also,due to chemical processing, high aspect<br />

ratio resist pillars have a high probability of falling over due to capillary forces <strong>on</strong> the pillars[2].<br />

We report <strong>on</strong> a simple method to overcome the low aspect ratio and the collapse of resist by using<br />

oxygen plasma assisted resist trimming.Firstly,We used 170 nm thick negative electr<strong>on</strong> beam resist<br />

and patterned 55 nm dot arrays using 80 kV electr<strong>on</strong>-beam.Next, resist trimming process was d<strong>on</strong>e<br />

using oxygen plasma ashing at 50 W and 0.1 Torr for 70 sec<strong>on</strong>ds.This process resulted in 5 nm<br />

trimming in all directi<strong>on</strong>. Therefore the 70 s ashing resulted in a 30 nm diameter and 145 nm tall<br />

resist pillar increasing the aspect ratio from 3 to 5, which is about 70 % increase.<br />

[1] Hwan-Jin Je<strong>on</strong>, Kyoung Hwan Kim,. Nano Lett. 2010, 10, 3604-3610 [2] Toshihiko<br />

TANAKA,Mitsuaki MORIGAMI,Nobufumi ATODA,. Jpn. J. Appl. Phys. Vol. 32 (1993) PP.6059-6064<br />

SL20<br />

Magnetic properties of ir<strong>on</strong>(III) oxide nanostructures by hydrothermal<br />

synthesis<br />

Raquel A Ribeiro*, Allan M Xavier and Flavio L Souza<br />

Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC - UFABC,<br />

Brazil<br />

The hydrothermal synthesis of nanoparticles enables functi<strong>on</strong>al c<strong>on</strong>trol <strong>on</strong> the<br />

distributi<strong>on</strong> of particle size, morphology and crystallinity by c<strong>on</strong>trolling the synthesis<br />

parameters. The synthesis of nanoparticles of ir<strong>on</strong> oxide by this method was performed<br />

by raising the temperature of a autoclavable bottle c<strong>on</strong>taining a soluti<strong>on</strong> of ir<strong>on</strong>(III)<br />

chloride, sodium nitrate and hydrochloric acid in appropriate quantities. Ir<strong>on</strong> oxide<br />

powders synthesized under c<strong>on</strong>diti<strong>on</strong>s previously published in the literature were<br />

treated in a box furnace at temperatures of 390, 450, 550 and 800 °C. For these samples<br />

we performed structural, morphological and magnetical characterizati<strong>on</strong>. The images<br />

of transmissi<strong>on</strong> electr<strong>on</strong> microscopy provide evidence that the 1D nanostructures<br />

of ir<strong>on</strong>(III) oxide, are joined by surfaces with n<strong>on</strong>-oriented crystallographic planes,<br />

suggesting that the growth of these particles occurs by oriented coalescence. After<br />

heat treatment a phase transiti<strong>on</strong> occurs from akaganeite to hematite. Magnetizati<strong>on</strong><br />

measurements show that akaganeite presents weak magnetic behavior, whereas the<br />

hematite phase presents a larger remnant magnetizati<strong>on</strong> and coercive field. We thank<br />

the support of Brazilian agencies FAPESP and CNPq.<br />

SL21<br />

SL22<br />

SL23<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic dot-antidot lattice for c<strong>on</strong>trol of magnetic anisotropy<br />

Sadashivaiah Sakshath*, Kalappattil Vijaysankar, Karki S Bhagyashree, Subray V<br />

Bhat and P. S. Anil Kumar<br />

Department of Physics, Indian Institute of Science, Bangalore, India<br />

The magnetic anisotropy of epitaxial Fe/GaAs(100) films varies with thickness of<br />

the film.[1, 2] We have prepared rectangular lattices of antidots using epitaxial 35<br />

m<strong>on</strong>olayer (ML) Fe/GaAs(100) films deposited by Pulsed laser depositi<strong>on</strong> in an<br />

ultrahigh vacuum chamber whose base pressure was less than 2exp(-10) Torr. 10ML<br />

MgO/35ML Fe/GaAs(100) film was c<strong>on</strong>trollably etched to reduce the thickness of<br />

lithographically defined regi<strong>on</strong>s of the Fe film to 19ML and capped with MgO before<br />

liftoff. Thus square antidot regi<strong>on</strong>s of size 200nm c<strong>on</strong>taining Fe of thickness lower<br />

than the surrounding matrix were created. Thus we have created a 2 dimensi<strong>on</strong>al<br />

magnetic system having a uniform material compositi<strong>on</strong> but c<strong>on</strong>trolled lateral variati<strong>on</strong><br />

of local magnetic anisotropy. The spacing between the antidot regi<strong>on</strong>s is varied from<br />

~ 200nm to 400nm. Investigati<strong>on</strong>s of magnetic anisotropy <strong>on</strong> the dot-antidot bilayer<br />

were performed using Magneto-Optical Kerr effect in l<strong>on</strong>gitudinal c<strong>on</strong>figurati<strong>on</strong> and<br />

Ferromagnetic Res<strong>on</strong>ance. Anisotropy c<strong>on</strong>stants are evaluated and it shows that the<br />

ratio of the magnitude of the uniaxial anisotropy to the magnitude of the four fold<br />

anisotropy is much higher (0.96) in the dot-antidot bilayer even with a square lattice.<br />

This is discussed in terms of exchange coupling between the antidot regi<strong>on</strong> and the<br />

surrounding matrix.<br />

[1] G. Wastlbauer and J. A. C. Bland, Adv. Phys. 54, 137 (2005) [2] S. Sakshath et al, J. Appl. Phys. 109, 07C114 (2011)<br />

Effect of diameter of the wires <strong>on</strong> magnetic properties of<br />

electrodeposited CoNiP hard magnetic nanowires<br />

Tuan Tu Le 1 *, Pham H<strong>on</strong>g Quang 1 , Luu Van Thiem 2 , T.s. Ramulu 3 and Cheolgi Kim 3<br />

1<br />

Faculty of physics, University of Science, Vietnam Nati<strong>on</strong>al University, 334 Nguyen Trai, Thanh<br />

Xuan, Hanoi, Vietnam, Viet Nam<br />

2<br />

Faculty of Engineering Physics and Nanotechnology, College of Technology, Vietnam Nati<strong>on</strong>al<br />

University,144 Xuan Thuy, Caugiay, Hanoi, Vietnam, Viet Nam<br />

3<br />

Deparment of Materials Science and Engineering, Chungnam Nati<strong>on</strong>al University, Daeje<strong>on</strong> 305-<br />

764, South Korea, Korea<br />

The magnetic properties in CoNiP nanowires arrays with diameter of nanowires in range of 50-800nm<br />

were investigated. All the samples were prepared by electrodepositi<strong>on</strong> method with pH of 3.1 and room<br />

temperature. The electrochemical potential of CoNiP were determined by cycle voltammetary. The crystalline<br />

structure and morphology of the samples were characterized by X-ray diffracti<strong>on</strong> (XRD) and Scanning<br />

Electr<strong>on</strong> Miroscopy (SEM), respectively. The hysteresis loops were measured at room temperature using<br />

vibrating sample magnetometry (VSM) and alternating gradient magnetometry (AGM) with magnetic field<br />

applied perpendicular and parallel to the wire axis. The mixture of fcc and hcp polycrystalline phases of the<br />

CoNiP based nanowires has been indicated by the XRD pattern. The obtained results show that with 800 nm<br />

of diameter of the nanowires we can obtain maximum coercivity value (2070 Oe). The uniaxial anisotropy<br />

values dependent <strong>on</strong> diameter of the wires are calculated. The anisotropy of the samples are quasi-<strong>on</strong>edimensi<strong>on</strong>al<br />

anisotropic is also found when diameter of the wires are less than 500 nm.<br />

[1] A. Fert, L. Piraux, Journal of <strong>Magnetism</strong> and Magnetic Materials 200 (1999) 338 [2] Shan Guan and Bradley J. Nels<strong>on</strong>, Journal of The Electrochemical Society, 152 (4)<br />

(2005) C190 [3]R.N. Emers<strong>on</strong>, C. Joseph Kennady, S. Ganesan, Thin Solid Films 515 (2007) 3391 [4] P. Cojocaru, L. Magagnin, E. Gomez, E. Valles, Journal of Alloys and<br />

Compounds 503 (2010) 454 [5] Takanari Ouchi, Naofumi Shimano, Takayuki Homma, Electrochimica Acta 56 (2011) 9575<br />

Switching behavior of lithographically defined grid of permalloy<br />

nanowires studied with magnetoresistance<br />

Venkateswarlu Dasari, Vineeth Mohanan Parakkat and Anil P. S. Kumar<br />

Physics, Indian Institute of Science, India<br />

We report the switching behavior of a grid [1] of permalloy nanowires fabricated using<br />

e-beam lithography and DC-magnetr<strong>on</strong> sputtering followed by lift-off process. The<br />

wires are of 20 nm thickness and about 120 nm wide. The periodicity between the<br />

wires is maintained at <strong>on</strong>e micr<strong>on</strong> throughout the grid. The grid is made as a Hall bar<br />

geometry which c<strong>on</strong>sists of few hundreds of juncti<strong>on</strong> regi<strong>on</strong>s. The magnetoresistance<br />

study indicate that the node regi<strong>on</strong>s in the grid acts as defects in the horiz<strong>on</strong>tal wires<br />

in l<strong>on</strong>gitudinal magnetic field, which in turn leads to the nucleati<strong>on</strong> of domains. Thus,<br />

the switching process in the horiz<strong>on</strong>tal wires is governed by these defect centers<br />

[2]. The switching field varies from 80 Oe to 140 Oe for transverse to l<strong>on</strong>gitudinal<br />

magnetoresistance. The n<strong>on</strong> zero coercivity (80 Oe ) in transverse magnetoresistance is<br />

due to the presence of nodes. These nodes possess four-fold anisotropy with easy axes<br />

al<strong>on</strong>g the diag<strong>on</strong>al directi<strong>on</strong>s. Further, the micro-magnetic simulati<strong>on</strong>s using Object<br />

Oriented Micro Magnetic Framework (OOMMF) with the two dimensi<strong>on</strong>al periodic<br />

boundary c<strong>on</strong>diti<strong>on</strong>, gives the informati<strong>on</strong> about the domain c<strong>on</strong>figurati<strong>on</strong> which<br />

supports our experimental findings.<br />

1. S. P. Li, A. Lebib, D. Peyrade, M. Natali, Y. CheN, W. S. Lew and J. A. C. Bland J. Appl. Phys. 90,<br />

521 (2001) 2. A. O. Adeyeye and M. E. Welland, J. Appl. Phys. 92, 3896 (2002)<br />

July 8 - 13, 2012 Busan, Korea 245<br />

Poster Friday


Poster Friday<br />

SL24<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetizati<strong>on</strong> reversal modes in narrow FePt nanowires with high<br />

perpendicular anisotropy<br />

Van Dai Nguyen 1 , Laurent Vila 1 , Matthieu Tissier 2 , Alain Marty 1 , Murat Cubukcu 1 , Piotr<br />

Laczkowski 1 , Williams Savero-torres 1 , Juan-carlos Rojas Sanchez 1 and Jean-philippe Attane 1<br />

1 Universite Joseph Fourier, BP 53, 38041, Grenoble and INAC/ CEA Grenoble, France<br />

2 LPTMC, CNRS-UMR 7600, Universite Pierre et Marie Curie, boite 121, 4 Pl. Jussieu, 75252<br />

Paris Cedex, France<br />

In this c<strong>on</strong>tributi<strong>on</strong>, we present the dependence of magnetizati<strong>on</strong> reversal modes in FePt nanowires with<br />

the width ranging from 2000 nm to 30nm using magneto-transport and magnetic force microscopy (MFM)<br />

measurements. Magneto-transport measurements showed an enhancement of magnetic coercivity when<br />

reducing the width. Theoretical calculati<strong>on</strong>s suggest that this coercivity increase is not <strong>on</strong>ly due to the<br />

suppressi<strong>on</strong> of available propagati<strong>on</strong> paths but also to the c<strong>on</strong>tributi<strong>on</strong> of the roughness. Further study<br />

of the magnetizati<strong>on</strong> reversal process using MFM shows that three different reversal modes can appear.<br />

Indeed, for widths above 500 nm, the structure of the reversed magnetic domains appears to be similar to<br />

those of the c<strong>on</strong>tinuous FePt film: the reversed magnetic domain grows and expands within a dendritic<br />

structure. For widths below the characteristic dendrite width (~300 nm), the reversal takes place by<br />

propagati<strong>on</strong> of a single DW that reverse the whole wire. Finally, we show that another behavior appears<br />

at very low widths: when reducing the widths below 50 nm, the propagati<strong>on</strong> field becomes larger than<br />

the nucleati<strong>on</strong> field. Nucleati<strong>on</strong> thus occurs randomly, the reversal c<strong>on</strong>sisting in a mix of nucleati<strong>on</strong> and<br />

propagati<strong>on</strong>. Such behavior could prevent the use of ultra-narrow wires for DW-based spintr<strong>on</strong>ic devices.<br />

J. P. Attane et al., Phys. Rev. B, 84, 144418 (2011) J. P. Attane et al., Phys. Rev. B, 82, 024408 (2010)<br />

SL25<br />

Structural and magnetic behaviour of nanocrystalline CaFe 2O 4<br />

S. N. Dolia*, Arvind Samariya, Arun S. Prasad, P. K. Sharma, M. S. Dhawan and S. P.<br />

Pareek<br />

Department of Physics, University of Rajasthan, Jaipur, India, India<br />

Abstract. Study of the structural and magnetic properties of the nanoparticles of large<br />

cati<strong>on</strong> substituted ferrite, CaFe 2O 4 have been reported here. The cubic spinel phase of<br />

CaFe 2O 4 could be synthesized effectively in nanocrystalline form of size 5.9 nm using<br />

advanced sol-gel method. The sample was then heated at 1000 °C leading to bulk<br />

size of orthorhombic structure. Very interestingly, the nanoparticles of CaFe 2O 4 get<br />

transformed from cubic spinel structure to its characteristic orthorhombic structure <strong>on</strong><br />

annealing at 1000 0C. Rietveld profile refinement of the XRD patterns was performed<br />

to study the nature of crystal structure. The SQUID magnetizati<strong>on</strong> measurements<br />

divulged that the nanocrystalline sample is superparamagnetic above the blocking<br />

temperature of 150 K whereas the bulk sample is ferromagnetic even at room<br />

temperature. The reducti<strong>on</strong> in saturati<strong>on</strong> magnetizati<strong>on</strong> in the case of nanoparticles<br />

as compared to its bulk counterpart has been explained <strong>on</strong> the basis that the magnetic<br />

moments in the surface layers of a nanoparticle are in a state of frozen disorder. The<br />

departure of the field cooled curve from the zero field cooled curves in the momentversus-temperature<br />

plot, further c<strong>on</strong>firmed the room temperature superparamagnetic<br />

behavior of the nanocrystalline CaFe 2O 4.<br />

SL26<br />

Magnetoresistance of helimagnetic ordering in single crystal FeGe<br />

nanowires<br />

Tae-e<strong>on</strong> Park 1 , Byoung-chul Min 1 , D<strong>on</strong>g-jea Seo 2 , Younho Park 1 , He<strong>on</strong>-jin Choi 2 and<br />

Jo<strong>on</strong>ye<strong>on</strong> Chang 1 *<br />

1 Spin Device Research Center, KIST, Korea<br />

2 Deparment of Materials Science and Engineering, Y<strong>on</strong>sei University, Korea<br />

We report <strong>on</strong> the synthesis, structural characterizati<strong>on</strong>, and magneto-transport of single<br />

crystalline FeGe NWs. Transiti<strong>on</strong> metal silicides and germanides have attracted a lot of<br />

attenti<strong>on</strong> because of their chiral cubic helimagnetism as a c<strong>on</strong>sequence of the Dzyaloshinskii-<br />

Moriya interacti<strong>on</strong>. FeGe is known to have a high Neel temperature and helical spin order<br />

with a relatively l<strong>on</strong>g period. In additi<strong>on</strong>, <strong>on</strong>e dimensi<strong>on</strong>al-c<strong>on</strong>finement of the spin structure<br />

might enhance the helical magnetic ordering of FeGe NWs as the nano-c<strong>on</strong>finement often<br />

alter or improve the properties. We have synthesized single crystalline FeGe NWs by CVD<br />

process without any catalyst. We have investigated the helimagnetic ordering in FeGe NWs by<br />

using electrical and magneto-transport measurements. When the magnetic field was applied<br />

l<strong>on</strong>gitudinal to the NW axis, the signature of the helimagnetism in the FeGe NWs was observed<br />

up to near room temperature. The magneto-transport measurements reveal three magnetic states<br />

of the FeGe NWs: the helimagnetic state, c<strong>on</strong>ical helimagnetic state, and ferromagnetic state.<br />

The magnetic transiti<strong>on</strong>s from the c<strong>on</strong>ical helimagnetic state to ferromagnetic state in FeGe<br />

NWs was clearly observed and occurred at much higher field those observed in the bulk FeGe.<br />

The relati<strong>on</strong>ship between nano-sized c<strong>on</strong>finement and the c<strong>on</strong>ical helimagnetic state will be<br />

discussed in detail.<br />

246 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SL27<br />

Arrays of interacting ferromagnetic nanofilaments: small-angle<br />

neutr<strong>on</strong> diffracti<strong>on</strong> study<br />

Natalia Grigoryeva 1 *, Sergey Grigoriev 2 , Arseniy Syromyatnikov 2 , Andrey<br />

Chumakov 2 , Helmut Eckerlebe 3 , Kirill Napolskiy 4 , Ilya Roslyakov 4 and Andrey<br />

Eliseev 4<br />

1 Faculty of Physics, Saint Petersburg State University, Russia<br />

2 K<strong>on</strong>stantinov Petersburg Nuclear Physics Institute, Russia<br />

3 Helmholtz Zentrum Geesthacht, Germany<br />

4 Moscow State University, Russia<br />

Magnetic properties of spatially ordered arrays of interacting nanofilaments have been studied<br />

by means of small-angle diffracti<strong>on</strong> of polarized neutr<strong>on</strong>s. Several diffracti<strong>on</strong> maxima or rings<br />

that corresp<strong>on</strong>d to the scattering of the highly ordered structure of pores/filaments with hexag<strong>on</strong>al<br />

packing have been observed in neutr<strong>on</strong> scattering intensity maps. The interference (nuclear-magnetic)<br />

and pure magnetic c<strong>on</strong>tributi<strong>on</strong>s to the scattering have been analyzed during the magnetic reversal<br />

of the nanofilament array in a field applied perpendicular to the nanofilament axis. The average<br />

magnetizati<strong>on</strong> and the interference c<strong>on</strong>tributi<strong>on</strong> proporti<strong>on</strong>al to it increase with the field and are<br />

saturated at H = Hs. The magnetic reversal process occurs almost without hysteresis. The intensity<br />

of the magnetic c<strong>on</strong>tributi<strong>on</strong> has hysteresis behavior in the magnetic reversal process for both the<br />

positive and negative fields that form the field dependence of the intensity in a butterfly shape. It has<br />

been shown that this dependence is due to the magnetostatic interacti<strong>on</strong> between the filaments in<br />

the field range of H ≤ Hs. A theory for describing the magnetic properties of the arrays of interacting<br />

ferromagnetic nanofilaments in the magnetic field has been proposed.<br />

SL28<br />

Magnetic properties of nanometer scale FeCr antidot array system<br />

Shivaraman Ramaswamy and Geo George Philip<br />

Nanotechnology Research Center, SRM University, India<br />

In this work, we have fabricated periodic nanometer scale antidot array of FeCr. The depositi<strong>on</strong> was<br />

d<strong>on</strong>e using electr<strong>on</strong> beam evaporati<strong>on</strong>. The substrate was first coated with 100nm of a suitable resist<br />

(ZEP-520A) using spin coating. Then, the mask was patterned <strong>on</strong> the substrate using an electr<strong>on</strong><br />

beam attached to field emissi<strong>on</strong> scanning electr<strong>on</strong> microscope to generate the necessary pattern.<br />

After the development, the FeCr (40nm) was coated <strong>on</strong>to the resist at 0.1A/s using electr<strong>on</strong> beam<br />

evaporati<strong>on</strong>. The antidot pitch was maintained at 400nm and the antidot diameter was found to be<br />

300nm. The magnetic nature of the sample was characterized using vibrating sample magnetometer<br />

and the in-plane magnetic anisotropy of the system was investigated using torque magnetometer.<br />

Further, the magnetoresistance measurements were taken using an inline four point probe. The results<br />

indicate that the antidot array system has a predominant ferromagnetic nature, has an n-fold rotati<strong>on</strong>al<br />

symmetry with relati<strong>on</strong> to the magnetic anisotropy. The easy axis, the hard axis of magnetizati<strong>on</strong><br />

al<strong>on</strong>g with the net anisotropic energy has also been determined. All data have been appropriate<br />

discussed in the work. The use of antidot array systems for various applicati<strong>on</strong>s is an intriguing new<br />

area of research.<br />

E.R. Spada, G.M.C. Pereira, E.F. Jasinski, A.S. da Rocha, O.F. Schilling, M.L. Sartorelli. Anisotropic magnetoresistance<br />

in electrodeposited cobalt antidot arrays. Journal of <strong>Magnetism</strong> and Magnetic Materials 320 (2008) 253-256. L.J.<br />

Heyderman, S. Czekaj, F. Nolting, D.H. Kim, P. Fischer. Cobalt antidot arrays <strong>on</strong> membranes: Fabricati<strong>on</strong> and<br />

investigati<strong>on</strong> with transmissi<strong>on</strong> X-ray microscopy. Journal of <strong>Magnetism</strong> and Magnetic Materials 316 (2007) 99-102. M.<br />

Tanaka, K. Itoha, H. Iwamotoa, A. Yamaguchia, H. Miyajimaa, T. Yamaokab Magnetic properties of nanometer-scale FeNi<br />

antidot array system. (2006).<br />

SL29<br />

Fabricati<strong>on</strong> of Al-Ni core-shell structured particles via electroless ni<br />

plating<br />

Youn-kyoung Baek*, Jung-goo Lee, Sangsun Yang and Chul-jin Choi<br />

Powder & Ceramic Research Divisi<strong>on</strong>, Korea Institute of Materials Science, Korea<br />

Al alloy powders have been of much interest in recent years due to their various<br />

applicati<strong>on</strong>s such as metallurgical, chemical, paint & pigment industries, aerospace<br />

applicati<strong>on</strong>s due to their lightness in weight and processability. Major research efforts<br />

have been made for improving their functi<strong>on</strong>alities by additi<strong>on</strong> or depositi<strong>on</strong> of<br />

alloying elements such as Ni and by c<strong>on</strong>trolling the structure. However, it is difficult<br />

to fabricate these alloy powders by traditi<strong>on</strong>al metallurgical process and it is necessary<br />

to evolve new methods. Core-shell structured particles are attracting c<strong>on</strong>siderable<br />

attenti<strong>on</strong> as a c<strong>on</strong>sequence of their potential applicati<strong>on</strong> in different areas of science<br />

and technology. Functi<strong>on</strong>alizing the Al core with suitable shell materials indeed opens<br />

the door to specific physical, chemical and optical performances of Al. However, due<br />

to the oxide layer present <strong>on</strong> Al surface, it is difficult to plate Al with any metal or<br />

metallic base surface coating by post wet depositi<strong>on</strong> techniques. Thus, we fabricated<br />

Al-Ni core-shell structured powders using electroless Ni plating. The pre-treatment<br />

was c<strong>on</strong>ducted for the formati<strong>on</strong> of Ni shell as well as removal of the oxide layer.<br />

The formati<strong>on</strong> of Ni shell <strong>on</strong> Al core powder was c<strong>on</strong>firmed by SEM, XRD and VSM<br />

results.


SM01<br />

Breakdown of barkhausen critical scaling behavior with increasing<br />

domain wall pinning in fe thin films<br />

Hun-sung Lee 1 , Kwang-su Ryu 2 , Chun-yeol You 3 , Kun-rok Je<strong>on</strong> 1 , Stuart S. P. Parkin 2<br />

and Sung-chul Shin 1 *<br />

1<br />

Korea Advanced Institute of Science and Technology (KAIST), Daeje<strong>on</strong> 305-701,<br />

Korea<br />

2<br />

IBM Research Divisi<strong>on</strong>, Almaden Research Center, San Jose, CA 95120, USA<br />

3<br />

Department of Physics, Inha University, Inche<strong>on</strong> 402-751, Korea<br />

We report a breakdown of Barkhausen critical scaling behavior in Fe films with<br />

increasing domain wall pinning by means of a Kerr microscope, capable of direct<br />

domain observati<strong>on</strong>. From the the domain reversal patterns in the films, we find that the<br />

Barkhausen jump size generally decreases with increasing Fe thickness, showing the<br />

increased domain wall pinning density. Surprisingly, the power-law scaling behavior of<br />

Barkhausen jump size distributi<strong>on</strong> gradually disappears as pinning of domain walls in<br />

the Fe layer increases. This is due to the fact that magnetizati<strong>on</strong> reversal mechanism is<br />

changed from a random Barkhausen avalanche dominant mode to thermally activated<br />

domain wall creep dominant mode.<br />

SM02<br />

Enhanced critical fields in MnSi thin films<br />

Dirk Menzel*, Josefin Engelke, Tommy Reimann and Stefan Suellow<br />

Institute for C<strong>on</strong>densed Matter Physics, Technische Universitaet Braunschweig,<br />

Germany<br />

The magnetic properties of the cubic helimagnet MnSi are governed by the<br />

Dzyaloshinskii- Moriya interacti<strong>on</strong> which in the bulk stabilizes a helical ground state<br />

below 29 K with a spin-helix wavelength of 18 nm and a propagati<strong>on</strong> vector al<strong>on</strong>g<br />

the [111] directi<strong>on</strong>. Recently, MnSi has attracted a lot of attenti<strong>on</strong> after a skyrmi<strong>on</strong><br />

lattice had been discovered in the so called A-phase. We have prepared thin MnSi<br />

films <strong>on</strong> Si(111) substrate by alloying a single Mn layer into the substrate as well as by<br />

codepositi<strong>on</strong> of Mn and Si. RHEED analysis in combinati<strong>on</strong> with TEM investigati<strong>on</strong><br />

reveals that codepositi<strong>on</strong> leads to smooth films whereas the alloying process generates<br />

rather three dimensi<strong>on</strong>al MnSi islands. In comparis<strong>on</strong> to bulk material, the films show<br />

an enhanced magnetic ordering temperature of 45 K, which has been determined using<br />

SQUID magnetometry. Magnetizati<strong>on</strong>, resistivity, magnetoresistance, and Hall effect<br />

measurements have been performed <strong>on</strong> the films. They show that the critical fields<br />

describing the transiti<strong>on</strong> from the helical to a c<strong>on</strong>ical spin phase and from the c<strong>on</strong>ical<br />

phase to a parallel spin alignment are dependent <strong>on</strong> the film thickness and enhanced in<br />

comparis<strong>on</strong> to single crystalline MnSi.<br />

SM03<br />

<strong>Magnetism</strong> and Cr 2O 3-Fe 2O 3 structure of CoFe/Cr-NOL surface<br />

Naoki Shimomura 1 *, Kazuya Sawada 2 , Tomohiro Nozaki 1 , Masaaki Doi 3 and Masashi<br />

Sahashi 1<br />

1 Department of Electr<strong>on</strong>ic Engineering, Graduate School of Engineering, Tohoku<br />

University, Japan<br />

2 Toshiba Corporati<strong>on</strong>, Japan<br />

3 Tohoku Gakuin University, Japan<br />

Magnetoelectric (ME) effect has been investigated for realizing electric c<strong>on</strong>trolled spintr<strong>on</strong>ic<br />

device, such as MERAM. Cr 2O 3 is the most promising material for the applicati<strong>on</strong> due to high<br />

Neel temperature (TN : ~307K). Switching exchange bias field by applying electric field using<br />

bulk Cr 2O 3 (0.6mm) has been reported [1]. Recently, we have observed high blocking temperature<br />

(TB : ~250K) of CoFe/Cr-NOL (Nano-Oxide-Layer) c<strong>on</strong>taining Cr 2O 3 and Fe 2O 3 (TN ~ 950K)<br />

in its surface, in spite of the ultrathin thickness (less than 1nm). The NOL is prepared by Natural<br />

Oxidati<strong>on</strong> (N.O.) of CoFe and ultrathin (1ML) Cr layer [2]. To clarify the reas<strong>on</strong> of high TB<br />

of the NOL is important for achieving thin Cr 2O 3 film that shows ME effect higher than room<br />

temperature. In this study, we have investigated the structure and magnetic property of CoFe/Cr-<br />

NOL by varying c<strong>on</strong>stituti<strong>on</strong> c<strong>on</strong>diti<strong>on</strong>, such as depositi<strong>on</strong> system and N.O. intensity. It was found<br />

that mixing of Cr into CoFe layer before N.O. and high N.O. intensity cause the formati<strong>on</strong> of<br />

Cr 2O 3-Fe 2O 3 solid soluti<strong>on</strong> in NOL surface, which lower the TB. It is indicated that the presence of<br />

not Cr 2O 3-Fe 2O 3 solid soluti<strong>on</strong> but the existence of both Cr 2O 3 and Fe 2O 3 is needed for high TB.<br />

[1] Xi He, Yi Wang, Ning Wu, Anth<strong>on</strong>y N. Caruso, Elio Vescovo, Kirill D. Belashchenko Peter A. Dowben, and Christian Binek,<br />

Nature Mater. 9, 579 (2010). [2] K. Sawada, N. Shimomura, M. Doi, and M. Sahashi, J. Appl. Phys 107, 09D713 (2010).<br />

SM04<br />

SM05<br />

SM06<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic phase diagram for n<strong>on</strong>-epitaxial Cr/Gd/Cr-multilayers<br />

Andres Rosales Rivera 1 *, Juan Fernando Jaramillo 1 , Nicolas Ant<strong>on</strong>io Salazar 1 , Olatz<br />

Idigoras 2 and Andreas Berger 2<br />

1 Laboratorio de <strong>Magnetism</strong>o y Materiales Avanzados, Universidad Naci<strong>on</strong>al de<br />

Colombia, Sede Manizales, Colombia, Colombia<br />

2 CIC nanoGUNE C<strong>on</strong>solider, Tolosa Hiribidea 76, E-20018 D<strong>on</strong>ostia-San Sebastian,<br />

Spain<br />

In this work, the low-temperature phase and critical behavior at high temperature of<br />

inhomogeneous gadolinium-chromium samples were investigated using DC magnetizati<strong>on</strong><br />

measurements. The samples were prepared as Cr(50nm)/Gd(100nm)/Cr(50nm) multilayers<br />

grown <strong>on</strong>to Si(110) single crystal substrates by means of sputter depositi<strong>on</strong>. The samples’<br />

inhomogeneity was c<strong>on</strong>trolled by annealing at different temperatures Tan = 200, 400, and<br />

500°C during 10 minutes, and their magnetizati<strong>on</strong> was measured using zero field cooling (ZFC)<br />

and field cooling (FC) procedures at several applied fields. In the vicinity of room temperature,<br />

the magnetic behavior of the samples is compatible with a ferromagnetic ground state,<br />

which undergoes a rounded ferromagnetic (F)-paramagnetic (P) phase transiti<strong>on</strong> at a critical<br />

temperature, Tc. At temperatures below Tc, however, differences between the magnetizati<strong>on</strong><br />

measured in the zero field cooling (Mzfc) and field cooling (Mfc) procedures are observed.<br />

Mfc decreases with increasing temperature. Mzfc increases with increasing temperature and,<br />

in additi<strong>on</strong> to the F-P phase transiti<strong>on</strong> at Tc, shows a peak at a certain temperature Tg < Tc. It<br />

was also found that Mzfc is time dependent at low field and irreversible below an irreversible<br />

temperature Ti(H). A (H,T) phase diagram that c<strong>on</strong>tains Tc, Ti(H) and Tg(H) is presented for<br />

each of the samples.<br />

Revealing the volume magnetic anisotropy of Fe films epitaxied <strong>on</strong><br />

GaAs(001) surface<br />

G. Chen 1 , J. Zhu 1 , J. Li 2 and Yizheng Wu 3<br />

1 physics department, Fudan university, China<br />

2 Physics department, Fudan university, China<br />

3 phyiscs department, Fudan university, China<br />

Fe film grown <strong>on</strong> GaAs(001) is a model system for studying the spin injecti<strong>on</strong> from<br />

a ferromagnetic layer into the semic<strong>on</strong>ductor substrate. The Fe/GaAs(001) system<br />

exhibits a remarkable in-plane uniaxial magnetic anisotropy (UMA) with an easy<br />

axis (EA) parallel to the GaAs[110] directi<strong>on</strong>, and such UMA is usually believed<br />

to originate entirely from the Fe/GaAs interface. In this c<strong>on</strong>tributi<strong>on</strong>, we will show<br />

our quantitative studies <strong>on</strong> the thickness dependent magnetic anisotropy in Au/Fe/<br />

GaAs(001) system using the magneto-optic Kerr effect with a rotating magnetic field.<br />

Through a clear 1/dFe relati<strong>on</strong> of the UMA, we found a UMA comp<strong>on</strong>ent with the EA<br />

parallel to the GaAs directi<strong>on</strong> which originates from the volume c<strong>on</strong>tributi<strong>on</strong>. Such<br />

volume UMA is sensitive to the growth temperature and also str<strong>on</strong>gly correlate with<br />

the interface anisotropy. We can c<strong>on</strong>clude that both the volume anisotropy and the<br />

interfacial anisotropy are related to the ordered atomic structure at Fe/GaAs interface.<br />

Our results may introduce a new aspect for further understanding the origin of UMA in<br />

Fe/GaAs(001) system.<br />

1) G. Chen, J. Zhu, J. Li, F. Z. Liu, and Y. Z. Wu, Appl. Phys. Lett. 98, 132505(2011)<br />

Structures and magnetic properties of ultrathin Ni/Cu(100) in<br />

hydrochloric acid<br />

Jyh-shen Tsay*, Chun-liang Lin, An-wei Wu, Ying-chieh Wang and Yu-chieh Tseng<br />

Nati<strong>on</strong>al Taiwan Normal University, Taiwan<br />

Microstructure and magnetic properties of ultrathin Ni/Cu(100) prepared by way of<br />

electrochemical approaches are investigated. In a pure supporting electrolyte, the STM<br />

image of the chloride covered Cu(100) surfaces show the formati<strong>on</strong> of 90-degree step<br />

edges of the terraces as a result of the electrochemical annealing [1]. After adding<br />

NiCl 2, the hydrogen evoluti<strong>on</strong> reacti<strong>on</strong> is advanced to a more positive potential. Nickel<br />

atoms attach <strong>on</strong>to the steps and the surface shows single atomic steps corresp<strong>on</strong>ding to<br />

a layer-by-layer growth. As the coverage of Ni increases, large amount of clusters form<br />

<strong>on</strong> the surface. The adsorpti<strong>on</strong> of chloride ani<strong>on</strong>s occurs <strong>on</strong> the top of the films [2]. For<br />

thin Ni layers, no magnetic hystsresis is observed due to the lowered Curie temperature<br />

for ultrathin overlayers. As the Ni coverage increases, hystsresis loop is observed with<br />

in-plane anisotropy of the films. For thicker films spin reorientati<strong>on</strong> transiti<strong>on</strong> occurs<br />

that may be due to the strain relaxati<strong>on</strong> in the Ni overlayer. The high squareness of the<br />

magnetic hysteresis loops c<strong>on</strong>firms the smooth interfaces of the Ni films.<br />

[1] S.L. Tsay, et al, Phys. Chem. Chem. Phys. 12, 14950 (2010); [2] P.Y. Yen, et al, J. Phys. Chem. C<br />

115 (2011) 23802.<br />

July 8 - 13, 2012 Busan, Korea 247<br />

Poster Friday


Poster Friday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

SM07<br />

Improvement in structural and magnetic properties of laser ablated<br />

Ni-Zn Ferrite thin films<br />

Raghavender A T 1 *, Nguyen Hoa H<strong>on</strong>g 1 , Ekaterina Chikoidze 2 , Yves Dum<strong>on</strong>t 2 and<br />

Kurisu Makio 3<br />

1 Department of Physics and Astr<strong>on</strong>omy, Seoul Nati<strong>on</strong>al University, Korea<br />

2 Laboratoire GeMAC, Universite de Versailles, France<br />

3 Department of Physics, Ehime University, Japan<br />

Zinc, as known as n<strong>on</strong>-magnetic element, has been doped into Nickel-Ferrites under<br />

thin film form, with a hope to modify its structural and magnetic properties, in order to<br />

have the appropriate requirements for high frequency applicati<strong>on</strong>s. Laser ablated Ni 1xZn<br />

xFe 2O 4 (0 ≤ x ≤1) thin films grown <strong>on</strong> R-cut Al 2O 3 (0001) substrates using pulsed<br />

laser depositi<strong>on</strong> (PLD) technique are single phase with (l l l) orientati<strong>on</strong>, and they<br />

are room temperature str<strong>on</strong>gly ferromagnetic, while others’ similar works reported<br />

ferromagnetism <strong>on</strong>ly at low temperatures. Additi<strong>on</strong>ally, the higher HC value in our<br />

films compared to what others reported indicates that somehow we have found an<br />

appropriate way to make Ni-Zn ferrites become potential candidates for modern<br />

miniaturizati<strong>on</strong> of electr<strong>on</strong>ic devices. The zero field cooled ? field cooled (ZFC-FC)<br />

magnetizati<strong>on</strong> curves for all the films shows the blocking temperature (TB) suggesting<br />

a str<strong>on</strong>g anisotropy. Research <strong>on</strong> Ni 1-xZn xFe 2O 4 (0 ≤ x ≤1) thin films would be very<br />

promising for device market.<br />

SM08<br />

A basic study of magnetic anisotropy strength c<strong>on</strong>trol using FeSiB<br />

magnetostrictive thin film<br />

Jaew<strong>on</strong> Shin*, Sung Ho<strong>on</strong> Kim, Genki Kitazawa, Shuichiro Hashi and Kazushi Ishiyama<br />

Research Institute of Electrical Communicati<strong>on</strong>, Tohoku University, Japan<br />

The Magneto-Impedance (MI) sensors are used for various applicati<strong>on</strong>s [1, 2]. A magnetic anisotropy<br />

c<strong>on</strong>trolling is important to improve sensitivity of MI sensor. Therefore, our research group proposed a new<br />

and simpler method to c<strong>on</strong>trol magnetic anisotropy using inverse-magnetosricti<strong>on</strong> and difference of thermal<br />

expansi<strong>on</strong> coefficient in bimetal thin film[3]. To exploit the proposed method, investigati<strong>on</strong> of a fabricati<strong>on</strong> ratio<br />

between two layers (thickness and length) requires due to the sensitivity of proposed MI sensor is determined by<br />

changes in fabricati<strong>on</strong> ratio. In this paper, we introduce the changes of magnetic anisotropy field (Hk) strength<br />

to develop high and adjustable sensitive MI sensor according to changes in geometrical properties of layers. The<br />

thin films were deposited by RF magnetr<strong>on</strong> sputter. Fe 72Si 14B 14 and Molybdenum were used for the magnetic<br />

and c<strong>on</strong>ductive layer, respectively. The fabricated thin films annealed to release the local stress. We carried<br />

out magnetic domain observati<strong>on</strong> by Kerr-microscope. Moreover, Hk value was obtained by VSM. Based<br />

<strong>on</strong> the experiments, we could c<strong>on</strong>firm that Hk value was c<strong>on</strong>trolled by the geometrical properties because the<br />

geometrical properties can determine the generated stress in the magnetostrictive magnetic layer. This research<br />

provides the fabricati<strong>on</strong> range and expectati<strong>on</strong> of the sensitivity of MI sensor.<br />

[1]Y. Murayama, T. Ozawa, S. Yabukami, K. Ishiyama, and K.I. Arai, “High-Frequency Carrier-Type Magnetic Field Sensor with a Sub-pT<br />

Resoluti<strong>on</strong> Using a Magnetic Film and a Transmissi<strong>on</strong> Line,” J. Magn. Soc. Jpn, 31, 17-22, 2007. [2]T. Morikawa, Y. Nishibe, H. Yamadera,<br />

Y. N<strong>on</strong>omura, M. Takeuchi, and Y. Taga, “Giant Magneto-Impedance Effect in Layered Thin Films,” IEEE Trans. Magn., 33, 4367-4372,<br />

1997. [3] Jaew<strong>on</strong> Shin, Sung Ho<strong>on</strong> Kim, Yasuaki Suwa, Shuichiro Hashi, Kazushi Ishiyama, “C<strong>on</strong>trol of In-plane Uniaxal Anisotropy of<br />

Fe72Si14B14 Magnetostrictive Thin Film Using a Thermal Expansi<strong>on</strong> Coefficient,” J. Appl. Phys (will be published in April)<br />

SM09<br />

Magnetic properties of co thin films <strong>on</strong> polyethylene naphthalate<br />

organic substrates<br />

Hideo Kaiju*, Taro Abe, Kenji K<strong>on</strong>do and Akira Ishibashi<br />

Research Institute for Electr<strong>on</strong>ic Science, Hokkaido Univerisity, Japan<br />

Recently we have proposed spin quantum cross (SQC) devices, in which molecules<br />

are sandwiched between two edges of magnetic thin films deposited <strong>on</strong> organic<br />

substrates with their edges crossed. According to our recent calculati<strong>on</strong>, SQC devices<br />

exhibit large magnetoresistance effect at room temperature. In this study, towards the<br />

fabricati<strong>on</strong> of SQC devices, we have investigated magnetic properties and surface<br />

morphologies of Co thin films <strong>on</strong> polyethylene naphthalate (PEN) organic substrates.<br />

Co thin films were thermally evaporated <strong>on</strong> PEN substrates under a magnetic field in a<br />

high vacuum chamber. The magnetizati<strong>on</strong> curves were measured by focused magnetooptic<br />

Kerr effect techniques at room temperature. The surface morphologies were<br />

analyzed by atomic force microscope. As a result, the surface roughness decreases<br />

from 1.3 to 0.55 nm with increasing the Co thickness up to 55 nm, where a two-step<br />

smoothing phenomen<strong>on</strong> can be seen. As for magnetic properties, the coercive force<br />

and the squareness of the hysteresis loop show the maximum values at a Co thickness<br />

of 5.3 nm. This peak is due to the rotati<strong>on</strong> of the uniaxial magnetic anisotropy formed<br />

from both the induced magnetic anisotropy and the shape magnetic anisotropy affected<br />

by the surface morphologies of Co/PEN and PEN substrates.<br />

248 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SM10<br />

Effects of dimensi<strong>on</strong>ality <strong>on</strong> magnetizati<strong>on</strong> of Ho and Sm-doped<br />

BiFeO 3 thin films<br />

Tae-young Kim 1 *, Anupati Telugu Raghavender 2 , Sugawara Takashi 3 , Makio Kurisu 3 and<br />

Nguyen Hoa H<strong>on</strong>g 4<br />

1 Physics, Seoul Nati<strong>on</strong>al University, Korea<br />

2 Physics, Seoul Nati<strong>on</strong>al University, India<br />

3 Physics, Ehime university, Japan<br />

4 Physics, Seoul Nati<strong>on</strong>al University, France<br />

BiFeO3 is promising multiferroic material due to high ferroelectric (1100 K) and antiferromagnetic (650<br />

K) ordering temperatures. Reports of other groups have suggested that by reducing the dimensi<strong>on</strong>ality, the<br />

spiral magnetic ordering could be suppressed [1]. Thus, multiferroics in thin films and nanocrystalline forms<br />

could enhance the magnetic properties [2]. In BiFeO 3, if Bi is substituted by a small amount of divalent or<br />

trivalent metal i<strong>on</strong>s, or Fe is substituted by transiti<strong>on</strong> metal i<strong>on</strong>, a significant enhancement in magnetizati<strong>on</strong><br />

can be achieved. We have prepared the nanocrystalline RE-BiFeO 3 (RE = Sm and Ho) by using sol-gel<br />

method to be target materials for thin films fabricati<strong>on</strong>. RE-BiFeO 3 films were grown <strong>on</strong> LaAlO 3 substrates<br />

using pulsed laser depositi<strong>on</strong> technique. All the films show a single phase of rhombohedral structure with<br />

space group R3c. Significant changes in the structural properties were observed as the thickness of the films<br />

increases. The magnetizati<strong>on</strong> observed in the case of Ho is much higher than those reported in literature<br />

and also Sm-doping shows better magnetizati<strong>on</strong> values. The magnetizati<strong>on</strong> increases as the film becomes<br />

thinner. This is a str<strong>on</strong>g evidence for the origin of surface magnetism that exist in the films.<br />

[1] P. Thakuria and P. A. Joy, J. Appl. Phys. 97 (2010) 162504. [2] J. Wang, J. B. Neat<strong>on</strong>, H. Zheng, V. Nagarajan, S. B. Ogale, B. Liu, D. Viehland, V.<br />

Vaithyanathan, D. G. Schlom, U. V. Waghmare, N. A. Splandin, K. M. Rabe, M. Mutting and R. Ramesh, Science, 299 (2003) 1717 .<br />

SM11<br />

Substrate-dependent electr<strong>on</strong>ic anisotropy of epitaxial multiferroic<br />

DyMnO 3 and Dy 0.8Ca 0.2MnO 3thin films<br />

Kueih-tzu Lu, S. C. Haw, T. L. Chou, J. M. Lee, S. A. Chen and J. M. Chen<br />

Nati<strong>on</strong>al Synchrotr<strong>on</strong> Radiati<strong>on</strong> Research Center, Taiwan<br />

We investigated the substrate-dependent electr<strong>on</strong>ic structure and anisotropic b<strong>on</strong>ding<br />

of the Mn 3d states in DyMnO 3 and Dy 0.8Ca 0.2MnO 3 thin films <strong>on</strong> SrTiO 3(001) and<br />

LaAlO 3(110) substrates using polarizati<strong>on</strong>-dependent x-ray absorpti<strong>on</strong> spectroscopy<br />

(XAS) at O K-, Mn L- and Mn K-edges for three polarizati<strong>on</strong>s, E || a, E || b and<br />

E || c. Polarizati<strong>on</strong>-dependent x-ray absorpti<strong>on</strong> spectra at O K-, Mn L23- and Mn<br />

K-edges of orthorhombic DyMnO 3/LaAlO 3(110) thin films show a str<strong>on</strong>g polarizati<strong>on</strong><br />

dependence, whereas orthorhombic DyMnO 3 /SrTiO 3(001) thin films show nearly<br />

isotropic spectral structure. The main peak in polarized Mn L2,3-edge XAS spectra<br />

of DyMnO 3/LaAlO 3(110) thin films for the E || b polarizati<strong>on</strong> lies at a lower energy<br />

than for polarizati<strong>on</strong>s E || a and E || c. This indicates a great anisotropy in Mn 3d-O<br />

2p hybridizati<strong>on</strong>, reflecting an orbital ordering and a highly anisotropic coplanar<br />

Mn-O b<strong>on</strong>ding in DyMnO 3/LaAlO 3(110) thin films. Orbital ordering of eg-orbital<br />

and the highly anisotropic in-plane Mn-O b<strong>on</strong>ding is an indispensable factor to the<br />

formati<strong>on</strong> of complicated incommensurate modulated magnetic structures observed<br />

in orthorhombic DyMnO 3. The present results provide important implicati<strong>on</strong>s for the<br />

microscopic understanding of the multiferroic DyMnO 3.<br />

SM12<br />

Enhanced magnetizati<strong>on</strong> by substituti<strong>on</strong> of Zn 2+ in Fe 3O 4 films<br />

Chang-yup Park 1 , J<strong>on</strong>g-hyun S<strong>on</strong>g 2 , Chun-yeol You 3 and Sung-chul Shin 4 *<br />

1 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, Korea<br />

Advanced Institute of Science and Technology, Daeje<strong>on</strong> 305-701, Korea<br />

2 Department of Physics, Chungnam Nati<strong>on</strong>al University, Daeje<strong>on</strong> 305-764, Korea<br />

3 Department of Physics, Inha University, Inche<strong>on</strong> 402-751, Korea<br />

4 Department of Physics and Center for Nanospinics of Spintr<strong>on</strong>ic Materials, KAIST,<br />

Daeje<strong>on</strong>, Department of Emerging Materials Science, DGIST, Daegu, Korea<br />

Fe 3O 4 is <strong>on</strong>e of the key materials as efficient spin injector for spintr<strong>on</strong>ic device. Thereby<br />

c<strong>on</strong>siderable researches have been carried out to obtain high magneto resistance ratio<br />

(MR), however no report show enough MR because of interface c<strong>on</strong>cerned problems<br />

and uncertainty of half metallic identity itself. Hence we choose Fe 3O 4 to investigate<br />

its nature and enhancement of magnetic and electric properties by substituti<strong>on</strong> of Zn 2+<br />

i<strong>on</strong>. Firstly we carried out magnetizati<strong>on</strong> hysteresis loop measurement by means of<br />

alternating gradient magnetometer. To find out a role of Zn substituti<strong>on</strong>, we fabricated<br />

Fe 1.8Zn 1.2O 4 film and the saturati<strong>on</strong> magnetizati<strong>on</strong> strikingly enhanced to 283 emu/cc<br />

from 79 emu/cc of the epitaxial Fe 3O 4 film. We believe that the 3.6 times enhancement<br />

is ascribed to the substituti<strong>on</strong> of Zn 2+ i<strong>on</strong> instead of Fe i<strong>on</strong> at tetrahedral A site which<br />

spin is antiparallel to that of Fe i<strong>on</strong> at octahedral B site in inverse spinel structure of<br />

Fe 3O 4.


SM13<br />

Growth temperature dependence of crystal orientati<strong>on</strong> and magnetic<br />

properties of CoMn2O4 thin films<br />

Taeyoung Koo 1 , Jaeyoung Kim 1 , Sunhee Kang 2 , Illw<strong>on</strong> Kim 2 , Yo<strong>on</strong>hee Je<strong>on</strong>g 3 , Myunghwa<br />

Jung 4 and J<strong>on</strong>ghyun S<strong>on</strong>g 5 *<br />

1<br />

Pohang Accelerator Laboratory, Korea<br />

2<br />

Physics, Ulsan University, Korea<br />

3<br />

Physics, Pohang University of Science and Technology, Korea<br />

4<br />

Physics, Sogang University, Korea<br />

5<br />

Physics, Chungnam Nati<strong>on</strong>al University, Korea<br />

Co xMn 3-xO 4(0≤x≤3), which crystallize in the spinel structure, are str<strong>on</strong>g candidates of multiferoics which can be<br />

used in various technical applicati<strong>on</strong>s due to their thermal, electrical and magnetic properties. In the present work,<br />

we report <strong>on</strong> the growth of epitaxial CoMn 2O 4 thin films <strong>on</strong> Nb-doped SrTiO 3(001) substrate using Pulsed Laser<br />

Depositi<strong>on</strong> and their magnetic properties. With all other growth parameters fixed, the growth temperature (Tg) was<br />

changed from 720oC to 920oC. The sample with Tg =720oC shows a str<strong>on</strong>gly tensile strained epitaxial crystal<br />

structure with the orientati<strong>on</strong> of (400). The M-H loops shows a ferrimagnetic behavior with the coercive field of<br />

~1.7 T. However, with increasing Tg up to 870oC, the tensile strained crystal domain becomes weaker whereas<br />

the domain of mixed orientati<strong>on</strong>s of relaxed (400) and (004) appear and has gained predominance. The M-H loops<br />

shows a weakened ferrimagnetism compared to the sample with Tg =720oC. With further increasing Tg to 920oC,<br />

interestingly, the crystal structure turns to be oriented (004) and the magnetic properties exhibit enhanced saturated<br />

magnetizati<strong>on</strong> with negligible coercive field. These observati<strong>on</strong>s indicate that the growth temperature plays a<br />

crucial role in determining the crystal structure and magnetic properties of CoMn 2O 4 thin film.<br />

[1]. V. Eladio, M. R. Rosa, L. M. V. Jose, and G. M. Oscar, Chem. Mater. 8, 1078 (1996). [2]. H. T. Zhang and X. H. Chen, Nanotechnology 17, 1384 (2006).<br />

SM14<br />

Structure and magnetic properties of Fe 3O 4 thin films <strong>on</strong> different<br />

substrates by Pulsed Laser Depositi<strong>on</strong><br />

Xuelian Huang, Yang Yang and Jun Ding*<br />

Materials Science and Engineering, Nati<strong>on</strong>al University of Singapore, Singapore<br />

Magnetite is an attractive magnetic oxide to be used in magneto-transport applicati<strong>on</strong>s.[1]Many<br />

researchers have studied how to optimize the depositi<strong>on</strong> c<strong>on</strong>diti<strong>on</strong> for high quality magnetite thin<br />

films.[2]In this work,magnetite thin films were deposited <strong>on</strong> different substrates at temperatures<br />

varying from 100°C to 450°C,and their structure,magnetic and magneto-transport properties have<br />

been studied. XPS and Raman spectra reveal single phase of Fe 3O 4 <strong>on</strong> all the substrates.When film<br />

thickness is small and temperature is relatively high(>300°C),magnetite thin films <strong>on</strong> single crystal<br />

SiO 2,Si and amorphous glass exhibit str<strong>on</strong>g (111) texture,no matter they have either a huge lattice<br />

mismatch or n<strong>on</strong>e matching with Fe 3O 4.The (111)texture can be formed at lower temperature(100°C)<br />

<strong>on</strong> (002)-ZnO due to the minimizati<strong>on</strong> of both surface and interfacial energy.The films <strong>on</strong> (0001)-<br />

Al 2O 3 show (111)-epitaxial structure in a large temperature range(100-450°C). The saturated<br />

magnetizati<strong>on</strong> for all the (111)oriented magnetite films are in the reported thin-film range.Magneto<br />

resistance up to 4% has been obtained.The out-of-plane MR exhibit quadratic behavior up to 6000<br />

Oe,whereas the in-plane MR is linear in this regime,which suggests the presence of anti-phase<br />

boundaries.[3]Large substrate-induced strain was found in the films grown <strong>on</strong> Al 2O 3 due to the lattice<br />

mismatch (8%),which significantly affected the magnetic anisotropy of the thin film.<br />

[1] H. Liu, E.Y. Jiang, H.L. Bai, R.K. Zheng, H.L. Wei, X.X. Zhang, Appl. Phys. Lett. 83 (2003) 3531. [2] S. Kale, S.M. Bhagat, S.E. Lofland,<br />

T. Scabarozi, S.B. Ogale, A. Orozco,S.R. Shinde, T. Venkatesan, B. Hannoyer, B. Mercey, W. Prellier, Phys.Rev. B 64 (2001) 205413. [3] W.<br />

Eerenstein, T. T. M. Palstra, S. S. Saxena, and T. Hibma Phys. Rev. L 88 (2002) 247204.<br />

SM15<br />

Influence of crystallographic orientati<strong>on</strong> <strong>on</strong> the magnetic properties of<br />

NiFe, Ni, and Co epitaxial fcc films grown <strong>on</strong> single-crystal substrates<br />

Taiki Ohtani*, Tetsuroh Kawai, Mitsuru Ohtake and Masaaki Futamoto<br />

Chuo Univercity, Japan<br />

NiFe, Ni, and Co crystals with fcc structure are soft magnetic materials and have been used in magnetic<br />

thin film devices like magnetic heads and sensors. Magnetic property varies depending <strong>on</strong> the film texture<br />

[1,2]. In the present study, Ni 80Fe 20 (at. %), Ni, and Co films with fcc (100) and (111) orientati<strong>on</strong>s were<br />

prepared by hetero-epitaxial growth <strong>on</strong> single-crystal substrates of GaAs(100) and Al 2O 3(0001). The<br />

magnetic anisotropy, the magnetizati<strong>on</strong> structure, and the magnetostricti<strong>on</strong> were investigated by employing<br />

RHEED, XRD, Bitter, and magnetostricti<strong>on</strong> measurements. NiFe, Ni, and Co films of fcc(100) orientati<strong>on</strong><br />

showed four-fold symmetries in-plane magnetic anisotropy. The easy magnetizati<strong>on</strong> axes were parallel to<br />

[011] and [01-1] directi<strong>on</strong>s. 90° magnetic domain walls were observed for the epitaxial films. The in-plane<br />

magnetizati<strong>on</strong> properties were reflecting the magnetocrystalline anisotropies of respective bulk fcc crystals.<br />

On the c<strong>on</strong>trary, the in-plane magnetizati<strong>on</strong> properties were isotropic for NiFe, Ni, and Co films with<br />

fcc(111) orientati<strong>on</strong>. In magnetostricti<strong>on</strong> measurement, the magnetostricti<strong>on</strong> behavior of epitaxial magnetic<br />

thin film depended delicately <strong>on</strong> the magnetic domain structure and the domain wall moti<strong>on</strong> under an<br />

influence of magnetic field. At the c<strong>on</strong>ference, the inter-relati<strong>on</strong>ships of magnetic anisotropy, magnetizati<strong>on</strong><br />

structure, and magnetostricti<strong>on</strong> will be discussed for these epitaxial thin films.<br />

[1] Y. Nukaga, M. Ohtake, M. Futamoto, F. Kirino, N. Fujita, N. Inaba.: IEEE Trans. Magn., vol. 45, pp.<br />

2519-2522, 2009. [2] M. Ohtake, T. Tanaka, K. Matsubara, F. Kirino, M. Futamoto.: J. Phys.: C<strong>on</strong>f. Ser., vol.<br />

303, pp. 012015_1-6, 2011.<br />

SM16<br />

SM17<br />

SM18<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Magnetic coupling in manganite-based thin film heterostructures<br />

studied by Electr<strong>on</strong> Holography<br />

Luis Alfredo Rodriguez 1 , Lorena Marin 2 , Cesar Magen 3 *, Irene Lucas 4 , Pedro Ant<strong>on</strong>io Algarabel 4 ,<br />

Luis Morell<strong>on</strong> 2 , Jose Maria De Teresa 4 and Manuel Ricardo Ibarra 1<br />

1 LMA-INA, Universidad de Zaragoza, 50018, Zaragoza, Spain<br />

2 INA, Universidad de Zaragoza, 50018, Zaragoza, Spain<br />

3 LMA-INA and ARAID, Universidad de Zaragoza, 50018, Zaragoza, Spain<br />

4 ICMA, Universidad de Zaragoza-CSIC, 50009, Zaragoza, Spain<br />

Advances in nanofabricati<strong>on</strong> of magnetic nanomaterials leads to search for new tools to measure physical<br />

properties at the nanoscale, such as magnetizati<strong>on</strong>. Accurate characterizati<strong>on</strong> of the magnetizati<strong>on</strong> states in<br />

nanostructures is of the utmost importance in the development new devices such as magnetic tunnel juncti<strong>on</strong>s<br />

(MTJs) [1]. Transmissi<strong>on</strong> electr<strong>on</strong> microscopy (TEM) techniques such as Electr<strong>on</strong> Holography (EH) allows the<br />

quantitative imaging of the magnetizati<strong>on</strong> states of ferromagnetic materials with unprecedented spatial resoluti<strong>on</strong><br />

at the nanometer level [2]. Furthermore, EH can be combined with the in situ variati<strong>on</strong> of external parameters such<br />

as magnetic and electric fields, temperature, etc. In particular, we use a TEM cryo-holder to image magnetizati<strong>on</strong><br />

states of ferromagnets with low TC (down to 100 K) while varying in situ the magnetic field applied by the<br />

objective lens of the TEM. In this work, we present the EH study of the magnetizati<strong>on</strong> switching of La-Sr and La-<br />

Ca manganite thin films (TC = 180 and 300 K, respectively) and manganite-based MTJs [3]. The (de)coupling of<br />

magnetic electrodes in MTJs is analyzed by performing hysteresis loops at 100 K to determine the switching fields<br />

from the direct observati<strong>on</strong> of the magnetizati<strong>on</strong> orientati<strong>on</strong> of the electrodes up<strong>on</strong> magnetic field [4].<br />

[1] S Yuasa et al., Nat. Mat. 3 (12): 868-871 (2004); S. S. P. Parkin et al. Nat. Mat. 3 (12): 862-867 (2004). [2] R. E. Dunin-Borkowski, M. R. McCartney, D. J. Smith, Electr<strong>on</strong><br />

Holography of Nanostructured Materials. In Encyclopaedia of Nanoscience and Nanotechnology; Nalwa, H. S., Ed.; American Scientific Publishers: Stevens<strong>on</strong> Ranch,<br />

California, 2004; Vol. 3, pp 41-100. [3] M. Bowen et al., Appl. Phys. Lett. 82, 233 (2003). [4] E. Jav<strong>on</strong>, A. Masseboeuf, C. Gatel and E. Snoeck, J. Appl. Phys. 107, 09D310 (2010)<br />

Properties of hybrid superc<strong>on</strong>ductor/ferromagnet (SC/FM) multilayers<br />

U. D. Chac<strong>on</strong> Hernandez 1 , Y. T. Xing 2 , William E. Alayo 1 , Magda B. F<strong>on</strong>tes 1 , Jorge L. G<strong>on</strong>zalez 3 , Liying<br />

Liu 4 , G. Solorzano 4 and E. Baggio-saitovitch 1<br />

1 Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil, Brazil<br />

2 Universidade Federal Fluminense Niteroi, Brazil, Brazil<br />

3 Universidade Federal do Espirito Santo, Vitoria, Brazil, Brazil<br />

4 PUC-Rio de Janeiro, Brazil<br />

Recent research <strong>on</strong> systems that c<strong>on</strong>tain two types of materials (hybrid systems) shows that new phenomena can<br />

be observed. One of such hybrid systems is superc<strong>on</strong>ductor/ferromagnet (SC/FM) nanocomposites, which shows<br />

coexistence of superc<strong>on</strong>ductivity and ferromagnetism with unusual properties. We use niobium (Nb) as the<br />

superc<strong>on</strong>ducting layers with fixed thickness (50 nm) and cobalt or permalloy (NiFe) as the ferromagnetic layers<br />

with different thickness (5, 10 and 20 nm). The films prepared by magnetr<strong>on</strong> sputtering depositi<strong>on</strong> technique,<br />

have been characterized by x-rays diffracti<strong>on</strong> and in some cases the cross secti<strong>on</strong> at interface were studied by<br />

TEM. Characterizati<strong>on</strong> of SC and FM transiti<strong>on</strong>s was d<strong>on</strong>e by resistivity and magnetizati<strong>on</strong> measurements. The<br />

properties of superc<strong>on</strong>ductor changed at the SC/metal interface because of the proximity effect, for example,<br />

decrease of Tc. Moreover, the magnetic layers between superc<strong>on</strong>ducting layers will give have more influence <strong>on</strong><br />

the superc<strong>on</strong>ductivity due to its stray field. Our results show that when the external magnetic field is close to the<br />

upper critical field Hc2, the SC/FM multilayers can have a vortex solid to a liquid phase transiti<strong>on</strong>. We believe<br />

that the stray field of the magnetic layers c<strong>on</strong>tributes to the melting of the vortex solid state.<br />

[1] A. I. Buzdin. Rev. Mod. Phys., 77(3):935, 2005. [2] Y. T. Xing, H. Micklitz, T. G. Rappoport, M. V. Milo sevi c, I. G. Sol orzano-Naranjo, and E. Baggio-<br />

Saitovitch. Phys. Rev. B, 78(22):224524, 2008. [3] Y. T. Xing, H. Micklitz, W. T. Herrera, T. G. Rappoport, and E. Baggio-Saitovitch. The European Physical Journal<br />

B - C<strong>on</strong>densed Matter and Complex Systems, 76:353{357, 2010. [4] E. A. Demler, G. B. Arnold, and M. R. Beasley. Phys. Rev. B, 55(22):15174{15182, Jun 1997. [5]<br />

I. A. Garifullin. Journal of <strong>Magnetism</strong> and Magnetic Materials, 240(1-3):571 - 576, 2002. 4th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> Symposium <strong>on</strong> Metallic Multilayers.<br />

Effect of substrate <strong>on</strong> the anisotropic magnetotransport in<br />

Sm 0.45Nd 0.10Sr 0.45MnO 3 thin films<br />

Pawan Kumar 1 , M. K. Srivastava 1 , G. D. Verma 2 , R. K. Dwivedi 3 and H. K Singh 1<br />

1 Quantum Phenomena and Applicati<strong>on</strong>s, Nati<strong>on</strong>al Physical Laboratory (CSIR), India<br />

2 Department of Physics, IIT Roorkee, India<br />

3 Department of Physics & Materials Science and Engineering, Jaypee Institute of<br />

Informati<strong>on</strong> Technology (Deemed University), India<br />

Sm 0.45Nd 0.10Sr 0.45MnO 3 thin films <strong>on</strong> single crystal LAO and STO substrates were<br />

prepared by ultras<strong>on</strong>ic nebulized spray pyrolysis. The PM-FM transiti<strong>on</strong> was observed<br />

at TC - 153 K and 150 K in film <strong>on</strong> LAO and STO, respectively. The magnetic moment<br />

was found to be smaller in film <strong>on</strong> STO and it showed str<strong>on</strong>ger bifurcati<strong>on</strong> between the<br />

ZFC-FC magnetizati<strong>on</strong>. The isothermal M-H loops measured with H applied parallel<br />

and normal to the film surface showed that the easy axis was in the film plane, while<br />

the hard axis was al<strong>on</strong>g the normal. The dominance of the shape anisotropy explains<br />

the in-plane magnetic easy axis. Large low field magnetoresistance (MR) is observed in<br />

both films. The occurrence of significantly smaller peak anisotropic magnetoresistance<br />

(AMR) at a temperature lower than the TIM and the broadening of the AMR-T curve<br />

suggest that films <strong>on</strong> STO have higher fracti<strong>on</strong> of the AFM-COI phase. The difference<br />

in the magnetotransport anisotropy in the set of films has been explained in terms of<br />

substrate induced strain, e.g., STO provides tensile strain, which is known to favor the<br />

AFM-SE and CO-OO phases.<br />

July 8 - 13, 2012 Busan, Korea 249<br />

Poster Friday


Poster Friday<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

SM19<br />

<strong>Magnetism</strong> of multilayer (CoNiPsoft/CoPhard)n films<br />

Gennady Patrin 1 , Marina Pal'chik 2 , Dmitry Balaev 2 , Semi<strong>on</strong> Kiparisov 2 and<br />

K<strong>on</strong>stantin Patrin 2<br />

1 Siberian Federal University, Russia<br />

2 Institute of Physics of Siberian Branch of Russian Academy of Sciences, Russia<br />

The (CoNiPsoft/CoPhard)n films were prepared by chemical depositi<strong>on</strong> method.<br />

The c<strong>on</strong>tent of phosphorus was 8 % at. in each layer. In hard magnetic layer the CoP<br />

was in hexag<strong>on</strong>al state and in soft magnetic layer the CoNiP was in amorphous state.<br />

The thickness of each layer was t = 4 nm. Magnetic measurements were made with<br />

vibrating-coil magnetometer in temperature range T = 77 ÷ 400 K and in magnetic<br />

fields H < 10 kOe. We investigated changes of magnetic parameters in dependence<br />

<strong>on</strong> number of layers in multilayer structure. In our experiments number of layer pairs<br />

was n ≤ 15. Earlier [1] it was established that the coercive force (HC) of CoP layers<br />

depends <strong>on</strong> layer thickness and HC rises when layer thickness increases. In given case<br />

at nitrogenous temperatures the coercive forces of soft magnetic and hard magnetic<br />

layers were ~ 20 Oe and ~ 1000 Oe, respectively. The combinati<strong>on</strong> of these layers into<br />

structure leads to substantial change of magnetic behavior of structure in whole [2]. It<br />

attracts attenti<strong>on</strong> that the soft magnetic layer determines the behavior of magnetizati<strong>on</strong><br />

of film structure decreasing the coercive force of system.<br />

[1] A.V. Chzhan, G.S. Patrin, et al., Phys. Met. Metalloved., 109 (2010) 1. [2] A.V. Chzhan, G.S.<br />

Patrin, et al., Bull. Russ. Acad. Sci. Phys., 76, (2012) 180<br />

SM20<br />

Significant change in the antiferromagnetic-to-ferromagnetic phase<br />

transiti<strong>on</strong> temperature of epitaxial FeRh thin films by Ga substituti<strong>on</strong><br />

Ippei Suzuki 1 *, Mitsuru Itoh 1 , Tetsuya Sato 2 and Tomoyasu Taniyama 1<br />

1 Materials and Structures Laboratory, Tokyo Institute of Technology, Japan<br />

2 Department of Applied Physics and Physico-Informatics, Keio University, Japan<br />

B 2 ordered FeRh alloys exhibit fascinating magnetic properties such as the firstorder<br />

magnetic phase transiti<strong>on</strong> from the antiferromagnetic (AF) to ferromagnetic<br />

(FM) states at around 400 K. For a step toward the incorporati<strong>on</strong> of this material into<br />

devices, the c<strong>on</strong>trol of the transiti<strong>on</strong> temperature in a thin film form is <strong>on</strong>e of the most<br />

critical issues. In this study, we find that Ga substituti<strong>on</strong> in FeRh efficiently reduces<br />

the transiti<strong>on</strong> temperature down to room temperature, making the use of this material<br />

a reality. A 30-nm-thick FeRh thin film and a Ga-substituted FeRh(Ga-FeRh) were<br />

epitaxially grown <strong>on</strong> MgO(001) substrates by molecular beam epitaxy. The temperature<br />

dependent magnetizati<strong>on</strong> of the epitaxial films clearly dem<strong>on</strong>strates the reducti<strong>on</strong> of<br />

the transiti<strong>on</strong> temperature down to room temperature. The change in the transiti<strong>on</strong><br />

temperature can be understood in terms of a possible change in the electr<strong>on</strong>ic states<br />

near the Fermi level due to the lattice expansi<strong>on</strong>, leading to a more stable FM state in<br />

Ga-FeRh. In fact, the out-of-plane lattice parameters calculated from the XRD patterns<br />

are found to expand from 2.990 to 3.003 Å by the Ga substituti<strong>on</strong>. Work supported in<br />

part by Industrial Technology Research Grant Program in 2009 from NEDO, Japan.<br />

SN01<br />

Structural and magnetic properties of Sm 2Co 17 nanoflakes prepared by<br />

surfactant-assisted ball milling<br />

Ming Yue, Rui Pan, Xiaofei Yin, D<strong>on</strong>gtao Zhang, Weiqiang Liu and Jiuxing Zhang<br />

College of Materials Science and Engineering, Beijing University of Technology,<br />

China<br />

Microstructure, crystal structure and magnetic properties were studied for Sm 2Co 17<br />

nanoflakes prepared by surfactant-assisted high energy ball milling with heptane and<br />

oleic acid as the milling medium. Effect of ball milling time <strong>on</strong> the crystallographic<br />

alignment evoluti<strong>on</strong> and coercivity of the nanoflakes were systematically investigated.<br />

Microstructure observati<strong>on</strong> shows that the Sm 2Co 17 nanoflakes have an average<br />

thickness of less than 100 nanometers with an aspect ratio as high as 100. For the 2<br />

hours ball milled nanoflakes, the intensity ratio between (004) and (302) reflecti<strong>on</strong><br />

peaks, which indicates the degree of c-axis crystal texture of the Sm 2Co 17 phase,<br />

reaches the maximum value am<strong>on</strong>g all the samples, revealing that the str<strong>on</strong>gest c-axis<br />

crystal texture was obtained in this nanoflakes. As the ball milling time increases, the<br />

intensity ratio drops gradually indicating that the l<strong>on</strong>g time milling process undermines<br />

the c-axis crystallographic alignment of Sm 2Co 17 phase in the nanoflakes. On the other<br />

hand, it is found that as the ball milling time increases from 2h to 10h, the coercivity<br />

of the nanoflakes firstly increases, peaks at 2.8kOe for 8h, and then decreases again.<br />

Further investigati<strong>on</strong> indicates that the microstructure evoluti<strong>on</strong> plays an important role<br />

in the coercivity variance of the Sm 2Co 17 nanoflakes.<br />

250 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SN02<br />

Rotor structure optimizati<strong>on</strong> of interior permanent magnet by using<br />

resp<strong>on</strong>se surface method<br />

Jung-ho Han, Ik-sang Jang, Mi-jung Kim, Ki-doek Lee and Ju Lee*<br />

Electrical Engineering, Hanyang University, Korea<br />

Due to limited energy sources and envir<strong>on</strong>mental polluti<strong>on</strong> issues recently, the needs<br />

of high efficiency electricity equipments are steadily increasing. Am<strong>on</strong>g them, an IPM<br />

is being developed for the applicati<strong>on</strong> of eco-friendly vehicle. An Interior Permanent<br />

Magnet has a structure of inserted permanent magnet in the inner rotor. These motor<br />

requires high torque and low torque ripple. It was designed with 8 pole 36 slot of<br />

stator and rotor, alternating N pole and S pole of permanent magnet and triangle<br />

type permanent magnet. In order to find the optimized c<strong>on</strong>diti<strong>on</strong>, Central Composite<br />

Designs method and Box-Behnken method of Resp<strong>on</strong>se Surface Method were used for<br />

finding design variable and minimizing variati<strong>on</strong> of design variable. Comparing two<br />

Surface Reacti<strong>on</strong> Methods, electromagnetic finite element method analysis based <strong>on</strong><br />

inserting variati<strong>on</strong> of design variables, torque, torque ripple, harm<strong>on</strong>ics were obtained<br />

and optimized final value was obtained by safety factor through mechanical stiffness<br />

analysis.<br />

[1] Ian P. Brown, Robert D. Lorenz, “Resp<strong>on</strong>se Surface Methodlogies for the Design of Inducti<strong>on</strong> Machine Self-Sensing Rotor<br />

Positi<strong>on</strong> Saliencies”, Proceeding of <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Electrical Machines and Systems, p1354-1359, 2007 [2] I. P.<br />

Brown and R. D. Lorenz, 'Resp<strong>on</strong>se surface methodologies for the design of inducti<strong>on</strong> machine self-sensing rotor positi<strong>on</strong> saliencies,'<br />

ICEMS, 2007. [3] K. Ide, I. Murokita, S. Mitsujiro, O. Motomichi, N. Yukio, J. I. Ha, and S. K. Sul, 'Finite element analysis of<br />

sensorless inducti<strong>on</strong> machine by high frequency injecti<strong>on</strong>,' Proc. of the IPEC, Tokyo, Japan, 2000.<br />

SN03<br />

Magnetizati<strong>on</strong> reversal behavior of FePt/MgO/FePt thin film<br />

Hiroki Iwama, Shinji Matsumoto, Katsuya Sugawara, Kotaro Sato, Masaaki Doi and<br />

Toshiyuki Shima<br />

Tohoku Gakuin University, Japan<br />

L10 ordered FePt alloy has attracted much attenti<strong>on</strong>, since they are believed to be good<br />

candidates for future magnetic devises. It is also thought to overcome the problem<br />

of thermal fluctuati<strong>on</strong> in nano-meters scale. A lot of studies such as thin films and<br />

self-assembled nano particles have been investigated [1-3]. However, the magnetic<br />

properties of the multilayered FePt alloy have not been completely clarified. In order<br />

to understand the magnetizati<strong>on</strong> reversal, FePt/MgO/FePt trilayer films have been<br />

fabricated and detailed magnetic domain observati<strong>on</strong> have been investigated. FePt<br />

bottom layer was co-deposited with Fe and Pt <strong>on</strong> Au buffer layer by using an UHVcompatible<br />

magnetr<strong>on</strong> sputtering system. Then, the intermediate MgO layer and<br />

FePt top layer were deposited. Finally, the samples were annealed at Ta of 600 ºC.<br />

The magnetic domain structure was observed by magnetic force microscope (MFM)<br />

in applied fields up to ±6 kOe. Remarkable steps of the magnetizati<strong>on</strong> in the sec<strong>on</strong>d<br />

quadrant were observed for all the samples. This is thought to arise from the difference<br />

in the chemical ordering of top and bottom FePt layers. Independent magnetizati<strong>on</strong><br />

reversal of the top and bottom FePt layers was clearly observed at the FePt/MgO/FePt<br />

circular dots by the MFM measurements.<br />

[1] T. Shima et al., Appl. Phys. Lett. 99. 033516 (2006). [2] T. Shima et al., Appl. Phys. Lett. 81.<br />

1050 (2002). [3] S. Matsumoto et al., J. Phys.: C<strong>on</strong>f. Ser. 266. 012038 (2011).<br />

SN04<br />

Efficiency and torque density improvement of interor permanant<br />

magnet synchr<strong>on</strong>ous motor<br />

Mi Jung Kim, Ki Doek Lee, Jae-jun Lee, Je<strong>on</strong>g-ho Han, Tae-chul Je<strong>on</strong>g, Wo<strong>on</strong>g-chan<br />

Chae and Ju Lee*<br />

Hanyang University, Korea<br />

The motor should be designed with a minimum of because motor weight has quite large<br />

porti<strong>on</strong> in totality mass; because there is no generator as electrical vehicle, the high<br />

efficiency is demanded in order to increase the 1 charging distance. In this paper, the<br />

technique is presented for progressi<strong>on</strong> of the torque density and the efficiency through the<br />

relative electric loading and the shape of rotor magnet. In case of the established model,<br />

the required torque satisfied at the rated speed and maximum speed, however, the torque<br />

density is low. When the mass of occupied by the motor is going to be bulky, 1 charging<br />

distance is decrease due to the increase in the driving load. The current density was<br />

increased to boost the torque density. The motor size could be decreased owing to change<br />

the current density, but there is a weakness at efficiency. The copper loss is enlarging with<br />

the current density. To increasing both of them efficiency and power density, the relative<br />

magnetic loading also should increase according to increase the relative electric loading.<br />

To increase the relative magnetic loading, redesign the PM shape of rotor.<br />

[1] Yukio H<strong>on</strong>da, Tomokazu Nakamura, Toshiro Higaki, Yoji Takeda, 'Motor design c<strong>on</strong>sideratioin and test results of an<br />

interior permanent magnet synchr<strong>on</strong>ous motor for electric vehicles', IEEE Industry Applicati<strong>on</strong>s Society, Annual Meeting,<br />

pp. 75~82, 1997 [2] Sung-Il Kim,etc., “Optimizati<strong>on</strong> for reducti<strong>on</strong> of torque ripple in interior permanent magnet motor by<br />

using the taguchi method”, IEEE Trans. <strong>on</strong> magnetics, vol. 41, no.5, pp. 1796~1799, 2005


SN05<br />

An effective skew method for torque ripple reducti<strong>on</strong> in surfacemounted<br />

permanent magnet motor<br />

Taewoo Kim and Junghwan Chang*<br />

Electrical Engineering, D<strong>on</strong>g-A University, Busan, 604-714, Korea, Korea<br />

This paper deals with an effective skew method for surface-mounted permanent<br />

magnet motor (SPMSM). Skew is a comm<strong>on</strong> method to reduce cogging torque and<br />

torque ripple as well, and it can be d<strong>on</strong>e by c<strong>on</strong>tinuous way in small machines or multistepwise<br />

method in big machines [1-2]. Generally, these c<strong>on</strong>venti<strong>on</strong>al ways assume that<br />

the magnetic flux density distributi<strong>on</strong>s are same in axial directi<strong>on</strong> and the c<strong>on</strong>tributi<strong>on</strong><br />

of the rotor <strong>on</strong> the generated torque is also same in all axial directi<strong>on</strong>. However, the<br />

air-gap flux density is not uniform in axial directi<strong>on</strong>, and it is rapidly reduced at both<br />

ends of the motor. Especially, in the pancake type motor, the influence of end sides is<br />

significant. Thus, for skew to be effective, n<strong>on</strong>-uniform air gap flux density distributi<strong>on</strong><br />

in axial directi<strong>on</strong> should be c<strong>on</strong>sidered. In this paper, <strong>on</strong>e method for an effective skew<br />

is suggested by c<strong>on</strong>sidering flux density distributi<strong>on</strong> in axial directi<strong>on</strong>, and the results<br />

will be c<strong>on</strong>firmed by 3D finite element analysis.<br />

[1] R. Islam, I. Husain, A. Fardoun, and K. McLaughlin, 'Permanent Magnet Synchr<strong>on</strong>ous Motor<br />

Magnet Designs with Skewing for Torque Ripple and Cogging Torque Reducti<strong>on</strong>,' IEEE Trans. Ind.<br />

Appl., vol.45, no.1, pp.152-160, 2009. [2] Y. D<strong>on</strong>mezer, L.T. Ergene, 'Skewing effect <strong>on</strong> interior type<br />

BLDC motors,' ICEM XIX <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g>, pp.1-5, 2010<br />

SN06<br />

Effect of carb<strong>on</strong> additive <strong>on</strong> the TbCu 7-type melt spun Sm(Co, M)7<br />

(M=Ti, Zr, Hf, V, Nb and Ge) ribb<strong>on</strong>s<br />

C.c. Hsieh 1 , H.w. Chang 2 , C.w. Shih 1 , W.c. Chang 1 * and C.c. Shaw 3<br />

1 Nati<strong>on</strong>al Chung Cheng University, Taiwan<br />

2 Tunghai University, Taiwan<br />

3 Superrite Electr<strong>on</strong>ics Co. Ltd, Taiwan<br />

Recently, Sm-Co compounds with TbCu 7-type structure have received intensive<br />

attenti<strong>on</strong> due to their excellent intrinsic magnetic properties, which have potential<br />

to be used as the starting materials for making b<strong>on</strong>ded magnets for above 150 oC<br />

applicati<strong>on</strong>s. Our previous studies indicated that pure TbCu 7-type structure could<br />

be obtained easily in melt spun Sm(Co,M)7 (M=Ti, Zr, Hf, V, Nb and Ge) ribb<strong>on</strong>s.<br />

Based <strong>on</strong> the purpose of developing Sm(Co,M)7 alloys with TbCu 7-type structure<br />

for practical usage, effect of carb<strong>on</strong> <strong>on</strong> the microstructure and magnetic properties<br />

of melt spun SmCo 7-xM xC0.1 (M=Ti, Zr, Hf, V, Nb and Ge; x=0-0.3) ribb<strong>on</strong>s were<br />

studied. Based <strong>on</strong> the XRD and TEM analysis, a pure 1:7 phase could be kept for the<br />

ribb<strong>on</strong>s with M= Nb, and Ge, but carbide phases, eg. TiC for M=Ti, ZrC for M=Zr,<br />

Sm 2C 3 for M=Hf, and SmCoC 2 for M=V, respectively, were found for other ribb<strong>on</strong>s.<br />

Nevertheless, a slight C additi<strong>on</strong> may effectively refine the microstructure and improve<br />

both the intrinsic coercvity and the magnetic energy product in all the studied ribb<strong>on</strong>s.<br />

Am<strong>on</strong>g them, the SmCo 6.9V 0.1C 0.1 ribb<strong>on</strong>s with σr=58.7 emu/g, iHc=13.5 kOe and (BH)<br />

max=9.3 MGOe, and SmCo 6.9Hf 0.1C 0.1 ribb<strong>on</strong>s with σr=61.6 emu/g, iHc=11.8 kOe and<br />

(BH)max=10.3 MGOe are suitable for the b<strong>on</strong>ded magnet applicati<strong>on</strong>s.<br />

SN07<br />

Study of designed inducti<strong>on</strong> motor <strong>on</strong> cryogenic LNG pump system<br />

Jinsung Kim and Gwansoo Park*<br />

Pusan Nati<strong>on</strong>al University, Korea<br />

In this Paper, I designed LNGs main cargo pump's motor using LNGs ship. LNGs<br />

ship has made a high value product and w<strong>on</strong> steady demand order in every year.<br />

However, in Korea, when we make a LNGs ship, we import the key products from<br />

other countries(It's almost 60% of order price). So, we need to develop original skill<br />

about key product. LNGs main cargo pump's motor is submerged, and inducti<strong>on</strong><br />

motor type. In this paper, first of all, design the inducti<strong>on</strong> motor using c<strong>on</strong>stants at<br />

room temperature. And then, we re-design the motor c<strong>on</strong>sidering an extremely low<br />

temperature. This motor's working operati<strong>on</strong> temperature is -163°C. Because of that, it<br />

can make a special design. In other words, we d<strong>on</strong>'t need to think about heat loss as like<br />

as room temperature. In this reas<strong>on</strong>, we c<strong>on</strong>sider about losses by current density and<br />

flux density. First, coil loss is generated a heat. So, it can be cooling the coil heat loss<br />

immediately. On the other hands, magnetic saturati<strong>on</strong> has effect <strong>on</strong> characteristics of<br />

material (specially, B-H curve). So, we think about magnetic saturati<strong>on</strong>, even it works<br />

at low temperature.<br />

L.Dlufiewicz, J. Kolowrotkierwicz, W. Szelag, M. Barancki, and R. Neumann, Electrical Motor<br />

for Liquid Gas Pump, SPEEDAM, pp.311-316 (2006). Shiyley R, Miller H, Development of a<br />

Submerged Winding Inducti<strong>on</strong> Generator for Cryogenic Applicati<strong>on</strong>, C<strong>on</strong>f. of IEEE Symp. <strong>on</strong><br />

Electrical Insulati<strong>on</strong>, pp.243-246 (2000). Rush, S, Submerged Motor LNG Pumps in Send-out<br />

System Service, Pumps&System, pp.32-37, (2004). Stephen J. Chapman, Electric Machinery<br />

Fundamentals, pp.380-425, (2003).<br />

SN08<br />

SN09<br />

SN10<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Structural and magnetic properties of nanocrystalline BaFe 12O 19<br />

synthesized by microwave-hydrothermal method<br />

K Sadhana and K Praveena<br />

Materials Research Centre, Indian Institute of Science, Banglore-560012, India, India<br />

The nanocrystalline BaFe 12O 19 powders were prepared by Microwave-Hydrothermal<br />

(M-H) method at 200°C/45 min. The as synthesized powders were characterized by<br />

using X-ray diffracti<strong>on</strong> (XRD). The present were densified at different temperatures i.e.,<br />

750°C, 850°C, 900°C and 950°C for 1h using microwave sintering method. The phase<br />

formati<strong>on</strong> and morphology studies were carried out using XRD and field emissi<strong>on</strong><br />

scanning electr<strong>on</strong> microscopy (FE-SEM). The average grain sizes of the sintered<br />

samples were found to be in the range of 185 to 490 nm. The magnetic properties such<br />

as saturati<strong>on</strong> magnetizati<strong>on</strong> and coercive field of sintered samples were calculated<br />

based <strong>on</strong> magnetizati<strong>on</strong> curves. A possible relati<strong>on</strong> between the magnetic hysteresis<br />

curves and the microstructure of the sintered samples was investigated.<br />

Research magnetic properties of Fe-O alloys with different texture<br />

degrees and ratios of phases using simulating<br />

Alexey Lileev*, Ivan Pelevin and Anna Starikova<br />

Nati<strong>on</strong>al University of Science and Technology 'MISIS', Russia<br />

The present article is c<strong>on</strong>cerned with investigati<strong>on</strong> of magnetic properties of Fe-O<br />

alloys, simulating their magnetic behaviour and causati<strong>on</strong> of the high-coercivity<br />

state of these alloys. Initial materials were powder so-called “Blue dust” and mixture<br />

of this powder with Fe powder with different rati<strong>on</strong>s of these phases. “Blue dust”<br />

is a powder of Fe 2O 3, it’s a natural Indian raw. Reserves of this material sufficient<br />

large, so a producti<strong>on</strong> material with high magnetic properties from it is an urgent<br />

problem. Initial samples were powdered in high-energy ball mill for different time<br />

periods. This treatment leads to phase transformati<strong>on</strong>. The phase compositi<strong>on</strong>s were<br />

investigated by X-ray analysis. The impact of time of milling and initial compositi<strong>on</strong><br />

<strong>on</strong> magnetic properties was explored. Milled nanocrystalline powders were subjected<br />

to a low-temperature crystallizati<strong>on</strong> annealing in magnetic field. It leaded to phase<br />

transformati<strong>on</strong>. Powder was pressed into cubic shape samples. The dependence<br />

of magnetic properties <strong>on</strong> compositi<strong>on</strong> after annealing was also investigated. The<br />

computer simulating was used to understand which phase is cause og forming the highcoercitive<br />

state of material. Initial parameters were set so that result corresp<strong>on</strong>ds to<br />

experimental data. The parameter changing showed quite how each of them influence<br />

<strong>on</strong> magnetic properties.<br />

Study <strong>on</strong> FePt/Fe exchange coupling nanocomposite thin films<br />

Wenli Pei<br />

ATM, Northeastern University, China<br />

Granular FePt films with island microstructures have been deposited by DC magnetr<strong>on</strong><br />

sputtering. The FePt grain size and distance am<strong>on</strong>g FePt grains could be c<strong>on</strong>trolled by<br />

tuning sputtering c<strong>on</strong>diti<strong>on</strong>. An ir<strong>on</strong> layer was deposited <strong>on</strong> the c<strong>on</strong>trollable island FePt<br />

film to produce FePt/Fe nanocomposite thin film. The composite films show a hard/soft<br />

magnetic exchange coupling after annealing, because the FePt grains in the composite<br />

film became L10 structure with good hard magnetic properties after annealing. The<br />

exchange coupling could be modified by tuning granular FePt structure and thickness<br />

of Fe layer, which means it’s promising to produce FePt/Fe nanocomposite magnet<br />

with good magnetic properties by this method.<br />

1. Kneller E F, Hawig R. The exchange-spring magnet: a new material principl for permanent<br />

magnets. Magnetics [J], IEEE Transacti<strong>on</strong>s <strong>on</strong> Magnetics, 1991. 27(4): 3588- 3560. 2. Zhou J,<br />

Skomski R, Li X, et al. Permanent-magnet properties of thermally processed FePt and FePt-Fe<br />

multilayer films [J], IEEE Transacti<strong>on</strong>s <strong>on</strong> Magnetics, 2002, 38(5Part 1): 2802-2804.<br />

July 8 - 13, 2012 Busan, Korea 251<br />

Poster Friday


Poster Friday<br />

SN11<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Effects of Sm c<strong>on</strong>tent <strong>on</strong> thermal stability of sintered Sm2Co 17 magnets<br />

Minggang Zhu, Haibo Feng, Wei Li, Yikun Fang, Wenchen Zhang and Wei Pan<br />

China Ir<strong>on</strong> & Steel Research Institute Group, China<br />

Investigati<strong>on</strong>s <strong>on</strong> envir<strong>on</strong>ment stability of the Sm 2Co 17 type magnets have been <strong>on</strong>e<br />

of hot pots <strong>on</strong> applicati<strong>on</strong>s of Sm-Co based magnets. Effects of heavy rare-earth<br />

elements substitute Sm <strong>on</strong> temperature coefficient of remanence (?) of the magnets<br />

have been investigated systematically [1]. Sm 2Co 17 magnet with high coercivity has<br />

the best thermal stability am<strong>on</strong>g all permanent magnets [2]. The reversible temperature<br />

coefficient ? was zero in the (Sm 1-xGd x)(CoFeCuZr)z magnet when x=0.55[3]. In this<br />

paper, the dependence of Sm c<strong>on</strong>tent <strong>on</strong> temperature coefficient of 2:17 type Sm-Co<br />

magnets at different temperature were investigated. As shown in Fig.1, the temperature<br />

coefficient increased with temperature when z value of the magnets is the same. While,<br />

the temperature coefficients of remanence firstly decreased and then increased with<br />

z value at the same temperature. When z=7.87, magnet with the best temperature<br />

stability, the highest coercivity and the lowest temperature coefficient of remanence<br />

were obtained.<br />

[1]Chen Christina, G<strong>on</strong>g Wei, Michael Walmer H. Journal Applied Physics, 2002, 91(10): 8483.<br />

[2]Li D, Misdrum H F, and Strnat K J. Journal Applied Physics, 1988, 63(8): 3984. [3]Liu Jinfang,<br />

Payal Vora and Michael Walmer. Journal of Ir<strong>on</strong> Steel Research <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g>, 2006, 13: 319.<br />

SN12<br />

Simulati<strong>on</strong> of die-upsetting process of hot-deformed magnets<br />

Bin Lai*, Huijie Wang, Minggang Zhu and Wei Li<br />

Divisi<strong>on</strong> of Functi<strong>on</strong>al Materials, Central Ir<strong>on</strong> & Steel Research Institute, China<br />

A plastic deformati<strong>on</strong> simulati<strong>on</strong> was performed by using a three dimensi<strong>on</strong>al finite element<br />

method based deformati<strong>on</strong> modeling software in order to clearly understand the die-upsetting<br />

process in detail. It was found by the plastic deformati<strong>on</strong> simulati<strong>on</strong> that the effective strains of<br />

Nd-Fe-B die-upset magnets reduced from the middle to the ends of magnetic specimens al<strong>on</strong>g<br />

the c-axis, or the press directi<strong>on</strong>, so the crystallographic orientati<strong>on</strong> deteriorated for the grains<br />

approached to both ends of die-upset magnets. The magnetic properties were improved with<br />

increase of effective strains of die-upset magnets.The remanence Br and maximum energy<br />

product (BH) m were high for the specimens, machined from the central regi<strong>on</strong> of magnets,<br />

because the microstructure of die-upset magnets was homogeneous and grains were aligned<br />

well in the central regi<strong>on</strong> of deformed magnets according to the simulati<strong>on</strong>. Experimentally,<br />

the magnetic properties, X-ray diffracti<strong>on</strong> patterns and microstructure of hot-deformed Nd-<br />

Fe-B magnets were studied. The magnetic properties were improved with decreased height of<br />

magnet specimens which were obtained by symmetrically removing both ends of die-upset<br />

magnets. The grain misalignment was as enhanced from the middle to both ends of die-upset<br />

magnets al<strong>on</strong>g c-axis.The microstructural characterizati<strong>on</strong> was verified by experiment.<br />

[1] Yutaka, Matsuura, J. Magn. Magn. Mater. 303 (2006) 344 [2] N. Yoshikawa, T. Iriyama, and H. Yamada. IEEE Trans. Magn., 35 (1999)<br />

3268 [3] T. Harada, M. Fujita, T. Kuji, Journal of Alloys and Compounds, 243 (1996) 139 [4] T. Saito, M. Fujita, T.kuji, et al., J. Appl. Phys.,<br />

83 (1998) 6390 [5] Y. Yoshida, Y. Kasai, T. Watanabe, et al., J. Appl. Phys. 69 (1991) 5841 [6] D. N. Brown, B. Smith, B.M.Ma, et al., IEEE<br />

Trans. Magn., 40 (2004) 2895 [7] M. Le<strong>on</strong>owicz, D. Derewnicka, M. Wozniak, et al., 153/154 (2004) 860<br />

SN13<br />

Synthesis of high magnetic moment nanowires for encoding and<br />

decoding of barcode segments for multiplexing bio- applicati<strong>on</strong>s<br />

Torati Sri Ramulu 1 , Reddy Venu 1 , Brajalal Sinha 1 , Xinghao Hu 1 , Sook Soo Yo<strong>on</strong> 2 and<br />

Cheol Gi Kim 1 *<br />

1 Material science and engineering, Chungnam nati<strong>on</strong>al university, Korea<br />

2 Material science and engineering, And<strong>on</strong>g nati<strong>on</strong>al university, Korea<br />

Abstract: Sequential template electrochemical synthesis of multisegment nanowires with<br />

magnetic and n<strong>on</strong>-magnetic segments have been extremely significant for barcoding,<br />

multiplexing and biosensing applicati<strong>on</strong>s [1,2]. Especially, Hard magnetic segment with high<br />

saturati<strong>on</strong> magnetizati<strong>on</strong> and remenance materials are more c<strong>on</strong>venient for multiplexing<br />

biological applicati<strong>on</strong>s. In the present article we have synthesized three different types of<br />

magnetic nanowires ( CoNiP, CoPtP and CoFeP) for a magnetic segment of barcode nanowires<br />

by electrochemical depositi<strong>on</strong> technique using a polycarb<strong>on</strong>ate membrane with a diameter of<br />

50 nm. The length of the nanowires was found to be around 6 μm. We compared the magnetic<br />

properties of all the synthesized materials and found to be the CoPtP magnetic nanowires have<br />

higher saturati<strong>on</strong> and remenence. In order to dem<strong>on</strong>strate the decoding of barcode nanowires<br />

using the magnetoresistance sensor in flow cytometry, we calculated the spatial distributi<strong>on</strong> of<br />

the stray magnetic field produced by the barcode nanowire by means of finite element method<br />

(FEM) using the commercial Maxwell software. The CoPtP shows most higher spatial variati<strong>on</strong><br />

compared to the CoFeP and CoNiP, which means CoPrP is most advantageous compositi<strong>on</strong> for<br />

the hard magnetic segment.<br />

[1] K. B. Lee, S. Park, and C. A. Mirkin, 2004, Angew. Chem. Int. Ed., 43, 3048 [2] A. K. Salem, P. C. Sears<strong>on</strong> And K. W. Le<strong>on</strong>g, Nat.Mat., 2003, 2, 668.<br />

252 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SN14<br />

A new mechanism of electromagnetic linear-actuator using a magnetic<br />

silic<strong>on</strong>e rubber<br />

Takanori Fukushi, Sung Ho<strong>on</strong> Kim*, Shuichiro Hashi and Kazushi Ishiyama<br />

Research Institute of Electrical Communicati<strong>on</strong>, Tohoku University, Japan<br />

We propose a new mechanism of electromagnetic linear-actuator for biomedical applicati<strong>on</strong>s such<br />

as an artificial muscle and medical micro-robots [1-3]. The proposed mechanism requires two<br />

armatures and magnetic rubber in the DC-solenoid. The proposed structure is series c<strong>on</strong>necti<strong>on</strong>:<br />

armature_1, magnetic rubber, and armarture_2. Therefore, D.C magnetic field produces attractive<br />

force between the two armatures. At that time, the magnetic rubber causes increase of attractive<br />

force because the magnetic rubber was fabricated by ir<strong>on</strong> powders with silic<strong>on</strong>e elastormer (36 : 64<br />

wt %), as a cylindrical shape (diameter:12 mm and height: up to 8.9 mm). Its magnetic properties<br />

were measured by VSM; magnetizati<strong>on</strong> and coercive force are 50 emu/g and 40 Oe, respectively.<br />

We compared magnetic force between the two armatures with the magnetic rubber and with a n<strong>on</strong>magnetic<br />

rubber in magnetic field of 600 Oe. We found the magnetic rubber made the attractive force<br />

1.7 times larger. This also means the use of magnetic rubber makes the low power c<strong>on</strong>sumpti<strong>on</strong>. The<br />

largest advantages of this magnetic rubber are the increase of attractive force, generati<strong>on</strong> of reacti<strong>on</strong><br />

force, and the flexibility as soft elastmer, so it can be used for various biomedical applicati<strong>on</strong>s. The<br />

details will be introduced in the c<strong>on</strong>ference.<br />

[1] B.Kim, M.G.Lee, Y.P.Lee, Y.Kim, and G.Lee, “An earthworm-like micro robot using shape memory alloy actuator,” Sens. Actuators A.,<br />

125, 429-437, 2006. [2] H.Lu, J.Zhu, Z.Lin, and Y.Guo, “An inchworm mobile robot using electromagnetic linear actuator,” Mechatr<strong>on</strong>ics,<br />

1-10, 2009. [3] T.Niino, S.Egawa, H.Kimura, and T.Higuchi, “Electrostatic Artificial Muscle: Compact, High-Power Linear Actuators with<br />

Multiple-Layer Structures,” Proc. IEEE Micro Electro Mechanical Systems Workshop, 94, 130-135, 1994<br />

SN15<br />

Novel microcrystalline Co-Zr-B RE-free hard magnetic alloys<br />

Sofoklis Makridis and Evagelos Gkanas<br />

Department of Mechanical Engineering, University of Western Maced<strong>on</strong>ia, Greece<br />

The investigati<strong>on</strong> of rapidly solidified alloys is important both for the basic informati<strong>on</strong><br />

it gives about the structural and compositi<strong>on</strong>al limits of magnetism and for the<br />

technical potential of new alloys. Co-based amorphous alloys have the advantage of<br />

relatively high saturati<strong>on</strong> flux density and low magnetostricti<strong>on</strong>. The glass formability<br />

and technical magnetic properties of rapidly solidified Co(rich)-Zr-B alloys were<br />

investigated in the compositi<strong>on</strong> range Co 82Zr xB 20-x. in order to determine the glass<br />

forming range and explore the magnetic characteristics as a functi<strong>on</strong> of compositi<strong>on</strong><br />

and quenching rate. The alloys were found to be completely glassy for low x whereas<br />

all the other compositi<strong>on</strong>s studied were completely or partially crystalline. The typical<br />

glassy alloys showed good soft magnetic properties. The crystalline alloys with Zr<br />

c<strong>on</strong>tent higher than 80 % in Bor<strong>on</strong> were characterized by a coercive force in excess of<br />

4 kOe. Slow-cooled samples of the same compositi<strong>on</strong> showed coercivity in the order<br />

of 120 Oe.<br />

SO01<br />

First-principles study <strong>on</strong> the half-metallicity of full-Heusler alloy<br />

Co 2VGa (111) surface<br />

H<strong>on</strong>gpei H<strong>on</strong>g, Kailun Yao* and Guoying Gao<br />

physics, Huazh<strong>on</strong>g university of science and technology, China<br />

A recent experimental study indicates that full-Heusler alloy Co 2VGa exhibits halfmetallic<br />

ferromagnetism and the magnetic moment measured at 5 K is independent<br />

of high pressure up to 12.1 kbar (T. Kanomata et al Phys. Rev. B 82, 144415 (2010)).<br />

Using the full potential linearized augmented plane-wave method, we here further<br />

investigate the structural, electr<strong>on</strong>ic and magnetic properties of all possible (111)<br />

surfaces of Co 2VGa. Both structural relaxati<strong>on</strong> and calculated surface energy reveal<br />

that Ga-terminated surface is more stable than other terminati<strong>on</strong>s. From the analysis of<br />

the spin-polarized density of states, we find that the half-metallicity c<strong>on</strong>firmed in bulk<br />

Co 2VGa is lost at Co-terminated surfaces but still maintained at V-terminated and Gaterminated<br />

surfaces. Moreover, the obtained magnetic moments show that the atomic<br />

magnetic moments of the (111) surfaces are greatly different from the bulk values.


SO02<br />

Magnetic and res<strong>on</strong>ance properties of Bi 24(CoBi)O 40<br />

Sergey Stepanovich Aplesnin 1 , Maksim Nicolaevich Sitnikov 1 , Lubov Victorovna<br />

Udod 2 and Dmitrii Anotol'evich Velicanov 2<br />

1 M.F. Reshetnev Siberian State Aerospace University, Russia<br />

2 L.V. Kirensky Institute of Physics, Russia<br />

The cubic bismuth oxide is characterized by charge ordering of bismuth i<strong>on</strong>s. A study<br />

of magnetic moment of cobalt i<strong>on</strong>s is used to establish the valence state of bismuth<br />

i<strong>on</strong>s. The aim of study is to establish the interrelati<strong>on</strong> between spin and elastic<br />

subsystems. Measurements of the magnetizati<strong>on</strong> was carried out over the temperature<br />

range 4K-300 K in the field H=50 kOe and the magnetizati<strong>on</strong> curve M(H) was<br />

determined at the temperatures T=5 K and T=300 K. The temperature dependence<br />

of magnetic susceptibility is well fitted to the Curie-Weiss law with the Curie-Weiss<br />

temperature θ=- 12.3 К and the effective magnetic moment is μ=5.08μB . The bismuth<br />

cobaltit is paramagnetic at T >4 K. The electr<strong>on</strong> paramagnetic res<strong>on</strong>ance (EPR)<br />

spectra were recorded from 77 K to 300 K at 9.3 GHz. The g- factor increases versus<br />

temperature that can be qualitatively explained by local deformati<strong>on</strong> of structure at<br />

variati<strong>on</strong> of bismuth i<strong>on</strong> valence. As a result, the magnetic anisotropy field is enhanced<br />

at the heating. EPR linewidth varies linearly with temperature that is explained by spinph<strong>on</strong><strong>on</strong><br />

interacti<strong>on</strong>. Relaxati<strong>on</strong> of magnetic moment is due to str<strong>on</strong>g interacti<strong>on</strong> with<br />

the elastic lattice.<br />

SO03<br />

Field induced phase transiti<strong>on</strong>s and magnetocaloric properties in Er 1xLu<br />

xFe 2O 4 compound<br />

Peng Zhang 1 , Ying-de Zhang 1 , Young-yeal S<strong>on</strong>g 1 , Jae-ye<strong>on</strong>g Kim 2 , Bo-wha Lee 2 and<br />

Se<strong>on</strong>g-cho Yu 1 *<br />

1 Physics, Chungbuk Nati<strong>on</strong>al University, Korea<br />

2 Physics, Hankuk University of Foreign Studies, Korea<br />

Rare earth (RE)-ferrites have attracted attenti<strong>on</strong> in recent years due to their various<br />

phase transiti<strong>on</strong>s (PTs) near room temperature. Their magnetic phase is determined by<br />

competiti<strong>on</strong> between antiferromagnetic and ferrimagnetic coupling of the localized<br />

Fe i<strong>on</strong>s. Magnetocaloric effect (MCE) reaches the maximum near the magnetic PT<br />

temperature. Despite of many works of the PT, however, there are very limited works<br />

<strong>on</strong> MCE in the RE-ferrites with two RE elements. In this work <strong>on</strong>e has investigated<br />

field induced magnetic PT properties and MCE in the vicinity of the PT point.<br />

Stoichiometric polycrystalline samples of Er 1-xLu xFe 2O 4 (0.1 ≤ x ≤ 0.8) were prepared<br />

by solid-state reacti<strong>on</strong> method. Magnetic measurements were performed using a<br />

SQUID magnetometer. Fig.1 gives isothermal M-H curves of Er 0.9Lu 0.1Fe 2O 4, from<br />

which the field induced PT can be seen clearly from the magnetizati<strong>on</strong> curves in the<br />

range of 208 K-240 K indicating a first order structural type PT[1]. Fig. 2 shows<br />

magnetic entropy change (ΔSM) curves. With a maximum field of 1 T and 3 T, the<br />

maximum value of ΔSM are 0.49 J•kg-1K-1and 1.04 J•kg-1K-1 at 249 K, respectively.<br />

The maximum ΔSM were appeared near the transiti<strong>on</strong> temperature and their MCE will<br />

be explained in terms of PTs.<br />

SO04<br />

Magnetic properties of heusler-type Ni-Mn-Ga glass-coated microwires<br />

Valeria Rodi<strong>on</strong>ova 1 , Maxim Ilyn 2 , Valentina Zhukova 2 *, Alexander Granovsky 3 , Alexander<br />

Ar<strong>on</strong>in 4 , Galina Abrosimova 4 and Arcady Zhukov 5<br />

1 Dpto. de Fisica de Materiales and Faculty of Physics, UPV/EHU San Sebastian, Lom<strong>on</strong>osov<br />

Moscow State University and Immanuel Kant Baltic Federal University, Russia<br />

2 Dpto. de Fisica de Materiales, UPV/EHU, Spain<br />

3 Dpto. de Fisica de Materiales and Faculty of Physics, UPV/EHU, San Sebastian, Spain and<br />

Lom<strong>on</strong>osov Moscow State University, Moscow, Russia<br />

4 Insitute of solid State Physics, RAS, Chernogolovka, 142432, Moscow Regi<strong>on</strong>, Russia<br />

5 Dpto. de Fis. Mater., UPV/EHU San Sebastian and IKERBASQUE, Basque Foundati<strong>on</strong> for<br />

Science, Bilbao, Spain<br />

Studies of magnetic shape-memory alloys (MSMAs) attracted growing attenti<strong>on</strong> within last few years owing<br />

to significant magnetic-field-induced strain (MFIS) useful for applicati<strong>on</strong>s in actuators, sensors and for energy<br />

harvesting. From point of view of applicati<strong>on</strong>s, miniaturizing of MSMA-based devices based <strong>on</strong> small-size MSMA<br />

materials is quite important. Main advantage of Ni-Mn-Ga Heusler-type microwires is related with composite<br />

character, allowing producti<strong>on</strong> of l<strong>on</strong>g microwire from brittle Ni-Mn-Ga alloy. C<strong>on</strong>sequently the aim of this paper<br />

is to present results <strong>on</strong> Heusler-type Ni 49.5Mn 25.4Ga 25.1 glass-coated microwires. We fabricated few metres l<strong>on</strong>g<br />

microwire and measured magnetizati<strong>on</strong>, M, versus magnetic field, H, curves in as-prepared and annealed up to 790<br />

K microwires. After annealing M(H) curves drastically changed: in as-prepared microwires magnetic transformati<strong>on</strong><br />

appears around 175 K. The sample seems c<strong>on</strong>tain the sec<strong>on</strong>d magnetic phase which orders at low temperature<br />

giving rise to fast increase of the magnetizati<strong>on</strong> below 30 K. Meanwhile comm<strong>on</strong> ferromagnetic behaviour was<br />

observed at around 325 K for the annealed sample without any evidence of existence of sec<strong>on</strong>d magnetic phase.<br />

X-ray diffracti<strong>on</strong> allows to detect significant structural changes after annealing. Obtained results are discussed taking<br />

into account str<strong>on</strong>g internal stresses induced by fabricati<strong>on</strong> of composite microwires and high quenching rate.<br />

SO05<br />

SO06<br />

SO07<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Compensated magnetism in double perovskites A 2CrFeO 6 (A=La,Sr)<br />

Kyo-ho<strong>on</strong> Ahn 1 and Kwan-woo Lee 2 *<br />

1 Department of Applied Physics, Graduate School, Korea University, Sej<strong>on</strong>g, Korea<br />

2 Department of Display and Semic<strong>on</strong>ductor Physics, Korea University, Sej<strong>on</strong>g, Korea<br />

Precise compensati<strong>on</strong> of magnetic moment in solid state compounds is very rare. An<br />

example is the so-called half-metallic antiferromagnet (HMAFM), which has <strong>on</strong>e<br />

metallic spin channel and the other insulating spin channel with the zero net moment.<br />

Double perovskite compounds of A 2BB’O 6 have been theoretically investigated<br />

as the most promising candidates for the last 15 years. Very recently, nearly wellordered<br />

epitaxial La 2CrFeO 6 films, theoretically predicted to be a HMAFM, were<br />

synthesized using pulsed laser depositi<strong>on</strong>. This sample shows the saturated moment of<br />

~2 μB, implying the ferrimagnetically ordered S=3/2 Cr 3+ and S=5/2 Fe 3+ . This results<br />

are c<strong>on</strong>troversial to the previous experimental results <strong>on</strong> artificial LaCrO 3/LaFeO 3<br />

superlattices, which proposed a ferromagnetic order, as well as the existing theoretical<br />

predicti<strong>on</strong>s. In this presentati<strong>on</strong>, we will revisit this system with first principles<br />

calculati<strong>on</strong>s using LDA+U, the modified Becker-Johns<strong>on</strong> functi<strong>on</strong>al, and fixed spin<br />

moment. Our results are c<strong>on</strong>sistent with the recent experimental results, showing a<br />

ferrimagnetic insulating La 2CrFeO 6. Furthermore, we have investigated the Sr-analog<br />

Sr 2CrFeO 6, which is as yet unsynthesized. C<strong>on</strong>trary to La 2CrFeO 6, this system has the<br />

tetravalent Cr and Fe i<strong>on</strong>s with antialigned S=1 moments, resulting in zero net moment.<br />

Our findings suggest a precise HMAFM Sr 2CrFeO 6.<br />

Possible half-metal antiferromangetism in double perovskites<br />

A 2VMnO 6 (A=La,Sr)<br />

Myung-chul Jung 1 , Young-jo<strong>on</strong> S<strong>on</strong>g 1 and Kwan-woo Lee 2 *<br />

1 Department of Applied Physics, Graduate School,, Korea University, Sej<strong>on</strong>g,, Korea<br />

2 Department of Display and Semic<strong>on</strong>ductor Physics, Korea University, Sej<strong>on</strong>g,,<br />

Korea<br />

A half-metallic antiferromagnet (HMAFM) is half-metallic without macroscopic<br />

magnetic moment. HMAFM has been c<strong>on</strong>sidered a promising candidate of a spin<br />

injector in spintr<strong>on</strong>ics, though no true HMAFM has been established yet. Very recently,<br />

A well-ordered double perovskite La 2VMnO 6, which was theoretically predicted to<br />

be HMAFM 15 years ago, has been synthesized by pulsed-laser depositi<strong>on</strong>. C<strong>on</strong>trary<br />

to the theoretical predicti<strong>on</strong>s, the saturated magnetic moment of 2 μB/f.u. implies<br />

an ferrimagnetically ordered S=1 V 3+ and S=2 Mn 3+ i<strong>on</strong>ic state, below TN=20 K.<br />

Besides, the synchrotr<strong>on</strong> radiati<strong>on</strong> photoemissi<strong>on</strong> measurement indicates an insulating<br />

La 2VMnO 6 with a gap of 0.9 eV, instead of being half-metallic. In this presentati<strong>on</strong>,<br />

we will revisit this system using various first principles calculati<strong>on</strong>s to unravel these<br />

discrepancies between the previous theoretical suggesti<strong>on</strong>s and the experimental<br />

results. Furthermore, our calculati<strong>on</strong>s suggest that the Sr-analog Sr2VMnO6 is a<br />

ferrimagnetic half-metal, c<strong>on</strong>trary to the ferrimagnetic insulator La 2VMnO 6.<br />

Focused magneto-optic kerr effect spectroscopy in Ni 75Fe 25 and Fe<br />

ferromagnetic thin films <strong>on</strong> organic substrates<br />

Kenji K<strong>on</strong>do*, Hideo Kaiju and Akira Ishibashi<br />

Laboratory of Quantum Electr<strong>on</strong>ics, Research Institute for Electr<strong>on</strong>ic Science, Japan<br />

We have developed the theory of focused magneto-optic Kerr effect (MOKE) for<br />

multilayer thin films and applied it to the surface magnetic properties, which have been<br />

observed by focused MOKE, for Ni 75Fe 25 and Fe thin films evaporated <strong>on</strong> polyethylene<br />

naphthalate (PEN) organic substrates. We have experimentally obtained the Ni 75Fe 25<br />

thickness dependence of Kerr rotati<strong>on</strong>s for as-deposited thin films and exposed thin<br />

films at an atmosphere for 1-year, respectively. The theoretical thickness dependences<br />

of Kerr rotati<strong>on</strong>s have been calculated using magneto-optic c<strong>on</strong>stants Q’s of 0.01*exp<br />

(- i 48π/180) and 0.025*exp (- i 57π/180), respectively. The calculated results are in<br />

good agreement with the experimental data. Also, the Ni 75Fe 25 thin films exposed for<br />

1-year show larger magnetizati<strong>on</strong> than the as-deposited Ni 75Fe 25 thin films in the range<br />

of 1-20 nm. We c<strong>on</strong>sider that the reas<strong>on</strong> is that the surface of Ni 75Fe 25 has transformed<br />

to locally Fe-rich surface because of the segregati<strong>on</strong> of Fe. We have also measured the<br />

Kerr rotati<strong>on</strong>s of Fe deposited <strong>on</strong> PEN. The Q of Fe/PEN was 0.025*exp (- i 47π/180).<br />

To our knowledge, the magneto-optic c<strong>on</strong>stants have been estimated for ferromagnetic<br />

thin films <strong>on</strong> PEN for the first time.<br />

July 8 - 13, 2012 Busan, Korea 253<br />

Poster Friday


Poster Friday<br />

SO08<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

The structural and magnetic properties of the magneto-caloric<br />

compounds Mn0.66Fe1.29P1-xSix (x = 0.34, 0.37 and 0.42)<br />

Zhiqiang Ou 1 *, L. Zhang 1 , N.h. Dung 1 , L. Van Eijck 2 , M. Avdeev 3 , A.m. Mulders 4 and E. Bruck 1<br />

1<br />

FAME Secti<strong>on</strong>, R3, Faculty of Applied Sciences, Delft University of Technology, Netherlands<br />

2<br />

NPM2 Secti<strong>on</strong>, R3, Faculty of Applied Sciences, Delft University of Technology, Netherlands<br />

3<br />

Australian Nuclear Science and Technology Organisati<strong>on</strong>,Locked Bag 2001, Kirrawee DC NSW 2232,<br />

Australia<br />

4<br />

School of Physical, Envir<strong>on</strong>mental and Mathematical Sciences, UNSW in Canberra, ACT 2610, Australia<br />

The magneto-caloric effect (MCE) is the thermal resp<strong>on</strong>se of a magnetic material to an applied magnetic<br />

field, results in a change of temperature.[1,2] (Mn,Fe)2(P,Si) compounds are known for their potential for<br />

room-temperature magnetic refrigerati<strong>on</strong>, due to large MCE and tunable working temperatures, cheap<br />

and abundant raw materials.[3] In this study, the single phase compounds Mn 0.66Fe 1.29P 1-xSi x (x = 0.34,<br />

0.37 and 0.42) have been synthesized. The crystal and magnetic structure have been investigated by<br />

means of neutr<strong>on</strong> and X-ray powder diffracti<strong>on</strong>. The refinement shows the compounds crystallize in the<br />

hexag<strong>on</strong>al Fe 2P-type structure (P-62m). The 3f site is nearly completely occupied by Fe atoms, the 3g site<br />

is occupied by Mn atoms and the excess Fe atoms, while the P and Si are randomly mixed. It is shown<br />

that the average magnetic moment in the 3g site is larger than that in the 3f site, 2.64 versus 1.81 μB for<br />

the compound with x = 0.34 at 10 K. The alignment of the magnetic moment has changed from almost<br />

c-directi<strong>on</strong> to a-b plane with increasing Si c<strong>on</strong>tent from x = 0.34 to x = 0.42. The compounds show a<br />

str<strong>on</strong>g magnetic field induced transiti<strong>on</strong>, small magnetic hysteresis and large magnetic entropy changes.<br />

[1] V.K. Pecharsky and K.A. Gschneidner, Phys. Rev. Lett. 78, 4494 (1997). [2] E. Bruck, J. Phys D: Appl. Phys. 38, p. R381-R391 (2005). [3] D. T.<br />

Cam Thanh, E. Bruck, N. T. Trung, J. C. P. Klaasse, K. H. J. Buschow, Z.Q. Ou, O. Tegus and L. Car<strong>on</strong>, J. Appl. Phys. 103, 07B318 (2008)<br />

SO09<br />

Faraday rotati<strong>on</strong> characteristics in wide-gap magnetic semic<strong>on</strong>ductor<br />

ZnMnTe and ZnMnSe films<br />

Masaaki Imamura*<br />

Electrical Engineering, Fukuoka Institute of Technology, Japan<br />

II-VI based magnetic semic<strong>on</strong>ductors with a wide optical band gap are expected to<br />

show high potential for optical applicati<strong>on</strong>s utilizing short wavelength laser diodes,<br />

such as 532-nm green and 475-nm blue LDs [1]. ZnMnTe and ZnMnSe exhibit their<br />

absorpti<strong>on</strong> edges at 428-544 and 428-458 nm, respectively [2]. The edge is not so<br />

influenced by the Mn c<strong>on</strong>centrati<strong>on</strong>, as is typically observed in CdMnTe. We have<br />

c<strong>on</strong>firmed that the Faraday rotati<strong>on</strong> in the ZnMnTe films deposited <strong>on</strong> quartz glass<br />

substrates is large near the absorpti<strong>on</strong> edge. Crystallinity was evaluated using an x-ray<br />

diffractometer. The preferred (111) growth reported previously for CdMnTe films <strong>on</strong><br />

QG substrates was also observed in the ZnMnTe and ZnMnSe films with weaker peak<br />

intensities.This paper reports the Faraday rotati<strong>on</strong> angle of those films synthesised <strong>on</strong><br />

QG substrates by using molecular beam epitaxy with a thickness of 2 μm. A Faradayeffect<br />

signal observed for the ZnMnTe film using a 532-nm green LD has shown that<br />

ZnMnTe films are useful for green lights.We developed equipment for observing the<br />

Faraday effect directly under ac magnetic fields generated by a ring magnet. The results<br />

of a direct Faraday rotati<strong>on</strong> observati<strong>on</strong> sucessfully made for the ZnMnTe films under<br />

ac fields are shown.<br />

[1] M. Imamura et al., IEEE Trans. Magn. 42, 3078 (2006). [2] M. Imamura et al., J.Appl.Phys. 99,<br />

08M706 (2006).<br />

SO10<br />

<strong>Magnetism</strong> and multiplets in Fe-phthalocyanine molecules<br />

Yukie Kitaoka 1 *, Kohji Nakamura 1 , Toru Akiyama 1 , Tom<strong>on</strong>ori Ito 1 , Michael Weinert 2<br />

and Arthur J. Freeman 3<br />

1 Mie University, Japan<br />

2 University of Wisc<strong>on</strong>sin-Milwaukee, USA<br />

3 Northwestern University, USA<br />

A challenge to miniaturize devices for novel magnetic applicati<strong>on</strong> now extends to treating the<br />

extreme limit of a single atom or molecule. Moreover, for molecules with transiti<strong>on</strong>-metals,<br />

multiplets are essential aspects of their electr<strong>on</strong>ic structure. It is often difficult, however, to<br />

evaluate such multiplets within a given ligand (or crystal) symmetry. Here, we carry out firstprinciples<br />

calculati<strong>on</strong>s with the FLAPW method[1] for Fe-phthalocyanine (FePc), in which<br />

the multiplets are treated by imposing a density matrix c<strong>on</strong>straint <strong>on</strong> the d-orbital occupati<strong>on</strong><br />

numbers. Results predict that there are three stati<strong>on</strong>ary multiplets - ³Eg (d²xy, d²z2, d³xz+yz),<br />

³B2g (dxy, dz2, d 4 xz+yz), and ³A2g (d²xy, d²z2, d²xz+yz) - in a single FePc molecule, and total<br />

energy calculati<strong>on</strong>s dem<strong>on</strong>strate that the ground state is the ³A2g. Furthermore, a columnar<br />

stacking of the FePc molecules (as seen in α-FePc) changes the ground state to ³Eg due to<br />

hybridizati<strong>on</strong> between adjacent molecules. In qualitative agreement with recent XMCD<br />

experiments[2], the magnetic anisotropy energy for the columnar stacking structure has a large<br />

negative value of 0.6 meV/molecule, indicating that the magnetizati<strong>on</strong> favors pointing in the<br />

planar directi<strong>on</strong>, and a large orbital moment of 0.14 μB is induced.<br />

[1] Wimmer, Krakauer, Weinert, Freeman, PRB 24, 864 (1981); Weinert, Wimmer, Freeman, PRB 26, 4571 (1982). [2]<br />

Bartolome, Garcia, Filoti, Gredig, Colesniuc, Schuller, Cezar, Phys. Rev. B 81, 195405 (2010).<br />

254 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SO11<br />

Elastic anisotropy in ferromagnetic shape memory alloy of n<strong>on</strong>stoichiometric<br />

Ni 2MnGa 1-xIn x<br />

Fumiya Kitanishi*, Kohji Nakamura, Toru Akiyama and Tom<strong>on</strong>ori Ito<br />

Mie University, Japan<br />

In magnetic shape memory (MSM) effect, the elastic and magnetocrystalline anisotropies<br />

play an important role. Moreover, experiments reported an enhancement of the MSE<br />

effect in a n<strong>on</strong>-stoichiometric metallic compounds.[1] Here, in order to discuss a role<br />

of the n<strong>on</strong>-stoichiometry, we developed a method for determining elastic property of<br />

n<strong>on</strong>-stoichiometric compounds from first principles calculati<strong>on</strong>s and cluster expansi<strong>on</strong><br />

method,[2] and applied to n<strong>on</strong>-stoichiometric Ni 2MnGa 1-xIn x. For calculati<strong>on</strong>s, first,<br />

the formati<strong>on</strong> energies of ordered structures as functi<strong>on</strong>s of volume V and c/a, ΔE_<br />

o(V,c/a), were calculated by using the FLAPW method.[3] Then, by using the cluster<br />

expansi<strong>on</strong> method, the formati<strong>on</strong> energy of a disordered state with n<strong>on</strong>-stoichiometric<br />

compositi<strong>on</strong>s, ΔE_o(V,c/a), were obtained in terms of many-body correlati<strong>on</strong> functi<strong>on</strong>s.<br />

Elastic properties of the bulk modulus, B, and the elastic tetrag<strong>on</strong>al anisotropy,<br />

C’=(C_11-C_12)/2, were numerically obtained from the ΔE_d(V,c/a) of the disordered<br />

state. Results indicate that the B has an almost linear relati<strong>on</strong> with respect to x. However,<br />

a deviati<strong>on</strong> from stoichiometric compositi<strong>on</strong> is found to enhance the elastic tetrag<strong>on</strong>al<br />

anisotropy; e.g., for a n<strong>on</strong>-stoichiometric compositi<strong>on</strong> of x=0.125, the C’ decreases by 0.4<br />

GPa compared to that in x=0, and the C’ increases when the x increases over about 0.125.<br />

[1] R. Kainuma et al., Nature 439, 957 (2006). [2] J. W. D. C<strong>on</strong>nolly and A. R. Williams, Phys. Rev.<br />

B 59, R2486 (1998). [3] K. Nakamura, et al., Phys. Rev. B 67, 14405 (2003).<br />

SO12<br />

Structure and properties of double perovskite system La 2Co 1-xFe xMnO 6<br />

(x=0, 0.1, 0.2, 0.3)<br />

The-tan Pham, Huyen-yen Pham and Nam-nhat Hoang*<br />

Faculty of Technical Physics and Nanotechnology, Vietnam Nati<strong>on</strong>al University,<br />

University of Engineering and Technology, Viet Nam<br />

Insulating ferromagnets of type RE 2AMnO 6 where A is transiti<strong>on</strong> metal and RE rare<br />

earth have received a renewed interest. Although the bulk La 2CoMnO 6 has been<br />

extensively studied, its Fe-doped possed several questi<strong>on</strong>s that should be addressed.<br />

The substituti<strong>on</strong> of Fe into the B site induced the increase in ferromagnetism at the<br />

cost of TC. It was also accompanied by a structure transiti<strong>on</strong> from orthorhombic to<br />

m<strong>on</strong>oclinic. The m<strong>on</strong>oclinic crystal symmetry occurred in the space group P21/n,<br />

with cell parameters a = 5.532 A, b=5.492 A, c=7.784 A, beta = 89.92°. The magnetic<br />

measurement showed that the magnetizati<strong>on</strong> reached maximum value of 4.7uB/ u.c.<br />

This value agrees well with the theoretically expected value.<br />

SO13<br />

Density-functi<strong>on</strong>al study <strong>on</strong> spin-crossover in several Fe-based<br />

molecules<br />

Tuan Anh Nguyen* and Thanh Van Nguyen<br />

Faculty of Physics, Hanoi University of Science, Viet Nam<br />

Spin crossover (SCO) complexes are now very potential candidates for applicati<strong>on</strong>s<br />

such as molecular switches, display and memory devices [1]. The SCO phenomen<strong>on</strong><br />

can be qualitatively explained by the ligand field model, however, designing transiti<strong>on</strong><br />

metal complexes with expected SCO behavior is still a big challenge in the field of<br />

materials science. In this paper, in order to explore more about the way to c<strong>on</strong>trol<br />

SCO behavior of transiti<strong>on</strong> metal complexes, we present a density functi<strong>on</strong>al study<br />

<strong>on</strong> the geometric structure, electr<strong>on</strong>ic structure and SCO of a series of eight Fe-based<br />

molecules [2-7]. Our calculated results show that SCO in these Fe-based molecules<br />

is accompanied with charge transfer between the Fe atom and ligands. This causes<br />

change in the electrostatic energy (ΔU) as well as the total electr<strong>on</strong>ic energy of these<br />

molecules. Moreover, our calculated results dem<strong>on</strong>strate an important c<strong>on</strong>tributi<strong>on</strong> of<br />

the interi<strong>on</strong>ic interacti<strong>on</strong>s to ΔU, and there is the relati<strong>on</strong> between ΔU and the thermal<br />

hysteresis behavior of SCO in these molecules. These results should be helpful for<br />

developing new SCO molecules.<br />

[1]. H. A. Goodwin, et.al., Top. Curr. Chem. 233, 1 (2004). [2]. Nicolas Moliner, et.al., Inorganica Chimica<br />

Acta, 291, 279 (1999). [3]. B. Weber, W. Bauer, J. Obel, Angew. Chem. Int. Ed. 47, 10098 (2008). [4]. Gaelle<br />

Dupouy, et.al., Inorg. Chem., 47, 8921 (2008). [5]. B. Weber, et.al., Inorg. Chem. 47, 487 (2008). [6]. B. Weber,<br />

et.al., Eur. J. Inorg. Chem. 4891 (2008). [7]. B. Weber, et.al., Eur. J. Inorg. Chem. 5527 (2009).


SO14<br />

Magnetic properties of Cu 70.9Al 18.1Mn 11 ferromagnetic shape memory<br />

alloy<br />

S Chatterjee 1 , S Giri 2 and S Majumdar 2 *<br />

1 UGC-DAE C<strong>on</strong>sortium for Scientific Research, Kolkata Centre, India<br />

2 Department of Solid State Physics, Indian Associati<strong>on</strong> for the Cultivati<strong>on</strong> of Science,<br />

India<br />

The ferromagnetic shape memory alloy (FSMA) of nominal compositi<strong>on</strong><br />

Cu 70.9Mn 11Al 18.1 has been studied through electr<strong>on</strong>ic transport, dc magnetizati<strong>on</strong> and<br />

ac susceptibility measurements. Unlike other Cu c<strong>on</strong>taining shape memory alloys,<br />

Cu-Mn-Al systems of alloys show interesting magnetic behaviour. Ferromagnetism<br />

in Cu-Mn-Al alloys come from the Rudermann-Kittel-Kasuya-Yosida (RKKY) type<br />

ferromagnetic exchange interacti<strong>on</strong> between Mn atoms. The studied alloy undergoes<br />

ferromagnetic to glassy transiti<strong>on</strong> below martensitic transiti<strong>on</strong> (MT). Clear frequency<br />

shift in ac susceptibility measurement is observed near the step like anomaly present in<br />

the zero field cooled dc magnetizati<strong>on</strong> data, which actually indicates the <strong>on</strong>set of spin<br />

glass freezing in the sample. Isothermal magnetizati<strong>on</strong> (M) measurement as a functi<strong>on</strong><br />

of magnetic field (H) at 5K with field cooled c<strong>on</strong>diti<strong>on</strong> (sample cooled in presence of<br />

different magnetic field) has been performed but no shift in M(H) loop is observed. It<br />

indicates that no exchange pinning is originated in the sample due to field cooling.<br />

SO15<br />

Magnetic properties of dioxygen molecules c<strong>on</strong>fined in single-walled<br />

carb<strong>on</strong> nanotubes<br />

Yusuke Nakai 1 *, Shin Tadera 1 , Haruka Kyakuno 1 , Keitaro Harada 1 , Kazuyuki<br />

Matsuda 2 , Kazuhiro Yanagi 1 and Yutaka Maniwa 1<br />

1<br />

Department of Physics, Graduate School of Science, Tokyo Metropolitan University,<br />

Japan<br />

2<br />

Faculty of Engineering, Kanagawa University, Japan<br />

Materials c<strong>on</strong>fined in quasi-1D single-walled carb<strong>on</strong> nanotubes (SWCNTs) exhibits unique<br />

properties that differ from the bulk counterparts [1]. Am<strong>on</strong>g many kinds of intercalates, a<br />

dioxygen molecule (O 2), which has a spin S = 1 in the ground state, c<strong>on</strong>fined in SWCNTs<br />

may offer well-defined envir<strong>on</strong>ment to investigate the physics of a quasi-1D spin-1 magnet.<br />

We present magnetic susceptibility and x-ray diffracti<strong>on</strong> measurements as well as theoretical<br />

simulati<strong>on</strong>s <strong>on</strong> the dioxygen molecules c<strong>on</strong>fined in SWCNTs. Our XRD measurements<br />

c<strong>on</strong>firmed that the O 2 molecules are absorbed inside the SWCNTs at low temperatures. Our<br />

magnetic susceptibility data shows the signature of the opening of a gap in spin excitati<strong>on</strong>s at<br />

low temperatures, which differs from bulk O 2 molecules. We interpret this result in terms of 1D<br />

antiferromagnets with S = 1, which is supported by our first-principles calculati<strong>on</strong> suggesting<br />

that an isolated O 2 molecule inside a SWCNT of over 0.8 nm in diameter possess a spin S = 1.<br />

We will also discuss the c<strong>on</strong>densed structure of O 2 inside SWCNTs <strong>on</strong> the basis of our XRD<br />

data and molecular dynamics simulati<strong>on</strong>s [2].<br />

[1] Y. Maniwa et al., Chem. Phys. Lett. 401 (2005) 534. [2] K. Hanami et al., J. Phys. Soc. Jpn. 79<br />

(2010) 023601.<br />

SO16<br />

Magneto-elastic coupling and magnetocaloric effect in Fe 2P-based Mn-<br />

Fe-P-Si compounds<br />

N. H. Dung 1 *, L. Zhang2, Z. Q. Ou 1 and E. Bruck 1<br />

1 Delft University of Technology, Netherlands<br />

2 BASF Netherlands B.V & Delft University of Technology, Netherlands<br />

Structural, magnetic and magnetocaloric properties of Fe 2P-based Mn-Fe-P-Si<br />

compounds were investigated. The study reveals a str<strong>on</strong>g magneto-elastic coupling that<br />

starts to develop in the paramagnetic state and grows when the ferromagnetic transiti<strong>on</strong><br />

temperature is approached. This magneto-elastic coupling over a large temperature<br />

range around the transiti<strong>on</strong> temperature results in a first-order phase transiti<strong>on</strong> with<br />

abrupt changes in lattice parameters. Moreover, a correlati<strong>on</strong> is observed between the<br />

hysteresis and the disc<strong>on</strong>tinuous changes in lattice parameters at the transiti<strong>on</strong>. The<br />

gradual development of the magneto-elastic coupling near the transiti<strong>on</strong> temperature,<br />

which is attributed to competiti<strong>on</strong> between moment formati<strong>on</strong> and b<strong>on</strong>ding [1],<br />

c<strong>on</strong>tributes to a reduced hysteresis. We also show the thermal evoluti<strong>on</strong> of the magnetic<br />

moments. Interestingly, the magnetic moments <strong>on</strong> the 3f site are formed and gradually<br />

increase in the paramagnetic state, and suddenly jump to a larger value when magnetic<br />

order is established.<br />

[1] N. H. Dung, Z. Q. Ou, L. Car<strong>on</strong>, L. Zhang, D. T. Cam Thanh, G. A. de Wijs, R. A. de Groot, K. H.<br />

J. Buschow, E. Bruck, Adv. Energy Mater. 1, 1215 (2011).<br />

SO17<br />

Magnetorefractive effect in manganites<br />

Andrey Telegin*, Yurii Sukhorukov and Vladimir Bess<strong>on</strong>ov<br />

Institute of Metal Physics UD of RAS, Russia<br />

SO18<br />

SO19<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

We studied a magnetic-field-induced change in reflectivity (magnetoreflecti<strong>on</strong>) and transmissi<strong>on</strong><br />

(magnetotransmissi<strong>on</strong>) of natural light in La 1-xA xMnO 3 (A=Ca,Sr,K,Ag) manganites possessed the colossal<br />

magnetoresistance effect (CMR)[1-3]. It was showed the magnetoreflecti<strong>on</strong> and magnetotransmissi<strong>on</strong><br />

effects in manganites are an optical resp<strong>on</strong>se to the CMR in the IR-regi<strong>on</strong>. Effects can reach tens of<br />

percents in the field of 0.3-1 T near the magnetic phase transiti<strong>on</strong> temperature. The observed phenomena<br />

are c<strong>on</strong>nected with the change of ratio between the localized and delocalized charge carriers under the<br />

magnetic field applied [2]. At the same time, there is no strict correlati<strong>on</strong> between these effects and CMR<br />

in the visible range. The observed phenomena are c<strong>on</strong>nected with the alterati<strong>on</strong> of the optical density<br />

under the magnetic field in the range of interband transiti<strong>on</strong>s [3]. Magnitude of effects is <strong>on</strong>e order as less<br />

as that in the IR-regi<strong>on</strong>. The nature of observed effects in manganites can be satisfactory explained within<br />

the framework of the theory of magnetorefractive effect [4]. The results of study of magnetoreflecti<strong>on</strong> and<br />

magnetotransmissi<strong>on</strong> in manganites may be proposed for creati<strong>on</strong> of different magnetic and electr<strong>on</strong>ic<br />

sensors and light modulators.<br />

[1] Yu.P. Sukhorukov, A.V. Telegin, A.B. Granovsky et al., J. of Experimental and Theoretical Physics, 138, No 3, 402 (2010). [2] A.B.<br />

Granovskii, Yu.P. Sukhorukov, A.V. Telegin et al, J. of Experimental and Theoretical Physics, 112, No1, 77 (2011) [3] Yu.P. Sukhorukov, A.V.<br />

Telegin, A.B. Granovsky et al, J. of Experimental and Theoretical Physics, 141, No1, 160 (2012) [4] Yurasov A.N., Bakhvalova T.N., Telegin A.V.<br />

et al, Abstracts of the 20th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Soft magnetic materials SMM-2011, Greece, 18-22 September, p.244<br />

Supported by the program of DPS RAS “Physics of new materials and structures”, grant MK-1048.2012.2 and RFBR grants No<br />

10-02-00038, 11-02-00252, 12-02-00208<br />

Electroresistance and joule heating effects in manganite thin films<br />

Luis Pena, Regina Galceran, Zorica K<strong>on</strong>stantinovic, Alberto Pomar, Bernat Bozzo,<br />

Lluis Balcells, Felip Sandiumenge and Benjamin Martinez*<br />

Magnetic Materials and Functi<strong>on</strong>al Oxides, ICMAB - CSIC, Spain<br />

Electroresistance (ER), i.e. electric field- and/or current-induced resistance switching,<br />

has attracted much attenti<strong>on</strong> recently because of the possibility of using it for the<br />

implementati<strong>on</strong> of resistance random access memories (ReRAM). Although ER is<br />

a quite comm<strong>on</strong> phenomen<strong>on</strong> in transiti<strong>on</strong> metal oxides, that has been extensively<br />

studied both theoretically and experimentally, the precise mechanism involved is not<br />

clear yet. In this work we report <strong>on</strong> the ER measurements in patterned La 2/3Sr 2/3MnO 3<br />

(LSMO) thin films prepared by sputtering. In order to analyze Joule heating effects<br />

we have evaporated a Pt layer <strong>on</strong> top of the LSMO path to have access to the<br />

actual temperature of the sample while measuring resistance of LSMO path or I(V)<br />

characteristic curves. I(V) curves have been measured at different temperatures and the<br />

corresp<strong>on</strong>ding resistance values are compared with that of the R(T) curve taking into<br />

account the actual temperature of the sample in order to clarify the role of Joule heating<br />

in the observed change of the resistance.<br />

Magnetocaloric effect and other properties of cold rolled Gd ribb<strong>on</strong>s<br />

Sergey V. Taskaev 1 , Vasiliy D. Buchelnikov 1 , Igor V. Bychkov 1 , Anatoliy P. Pelennen 2 , Oliver Gutfleisch 3 ,<br />

K<strong>on</strong>stantin P. Skokov 4 , Vladimir V. Khovaylo 5 , Victor V. Koledov 6 and Vladimir G. Shavrov 6<br />

1<br />

Physics department, Chelyabinsk State University, Chelyabinsk, Russia<br />

2<br />

South-Ural State University, Chelyabinsk, Russia<br />

3<br />

Technische Universitat Darmstadt, Darmstadt, Germany<br />

4 IFW, Dresden, Germany<br />

5 MISIS, Moscow, Russia<br />

6 IRE RAS, Moscow, Russia<br />

The number of papers devoted to magnetic refrigerati<strong>on</strong>, magnetocaloric materials and high-field magnetic<br />

systems has grown at an exp<strong>on</strong>ential rate in the past 10 years (K.A. Gschneidner et al., 2008) [1]. Since First<br />

<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> Magnetic Refrigerati<strong>on</strong> at Room Temperature many researches in different countries<br />

mobilize their efforts in the field of c<strong>on</strong>structing commercial magnetic refrigerator. There are numerous different<br />

magnetocaloric alloys such as La-Fe-Si, Gd-Si-Ge, Ni-Mn-X (X = Ga, In, Sn, Sb) [2-3]. Usually the magnetic<br />

refrigerant materials are either packed in a magnetocaloric bed as small spheres attached around a disk as a ribb<strong>on</strong><br />

or separated in a pile of thin, equally spaced sheets. Thus <strong>on</strong>e the ways of engineering MCE materials is tightly<br />

c<strong>on</strong>nected with preparing very thin (a few micr<strong>on</strong>s) ribb<strong>on</strong>s of high value MCE alloys with good mechanical<br />

properties. At present rapid solidificati<strong>on</strong> is the main technique for producing this kind of materials [4]. In our<br />

work we investigate magnetocaloric effect, magnetic and mechanical properties of Gd cold rolled samples of<br />

different thickness. Both theoretical and experimental aspects of the investigati<strong>on</strong> are discussed.<br />

1. Gschneidner K.A. Jr. et al. Thirty years of near room temperature magnetic cooling: Where we are today and future prospects, Int. J. Refrig, 31, 945 (2008).<br />

2. A. Planes, L. Manosa, and M. Acet, J. Phys.: C<strong>on</strong>dens. Matter 21, 233201 (2009). 3. X. Moya, L. Manosa, A. Planes, S. Aksoy, M. Acet, E. Wassermann, and<br />

T. Krenke, Phys. Rev. B. 75, 184412 (2007). 4. P. M. Shan et al. Magnetic behavior of melt-spun gadolinium, Phys. Rev. B. 77, 184415 (2008).<br />

July 8 - 13, 2012 Busan, Korea 255<br />

Poster Friday


Poster Friday<br />

SO20<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Fabricati<strong>on</strong> and properties of double perovskite SrLaVRuO 6<br />

Ryosuke Zenzai*, Tetsuya Miyawaki, Kenji Ueda and Hidefumi Asano<br />

Crystalline Materials Science, Nagoya University, Japan<br />

Half-metallic antiferromagnets (HMAF) exhibiting both fully spin-polarized charge<br />

transport and zero net magnetic moment are expected to provide not <strong>on</strong>ly a fertile<br />

playground for fundamental research but also new spintr<strong>on</strong>ic devices. Although the<br />

theoretical calculati<strong>on</strong>s predicted candidates for HMAFs, experimental searches for<br />

HMAFs have so far been unsuccessful. This paper reports <strong>on</strong> the fabricati<strong>on</strong> and<br />

properties of SrLaVRuO 6 polycrystalline bulks and epitaxial films. SrLaVRuO 6 bulks<br />

were synthesized by a solid-state reacti<strong>on</strong> at 1100~1350 °C in Ar + (0~3) % H 2 gas.<br />

Structural characterizati<strong>on</strong> revealed that the main phase of the bulk samples was of<br />

a double perovskite crystal structure with lattice parameters of 0.7888~0.7905 nm.<br />

However, all the bulks c<strong>on</strong>tained the impurity phase (Sr 3V 2O 8), which is a n<strong>on</strong>magnetic<br />

semic<strong>on</strong>ductor. The bulks exhibited magnetizati<strong>on</strong> values of 10-3 μB per formula unit<br />

at 77 K, negative paramagnetic Curie temperature values and metallic temperature<br />

dependence of the resistivity. These properties are assumed to be intrinsic to double<br />

perovskite SrLaVRuO 6 by c<strong>on</strong>sidering the n<strong>on</strong>magnetic semic<strong>on</strong>ducting nature of<br />

Sr 3V 2O 8. Moreover, SrLaVRuO 6 thin films were prepared <strong>on</strong> LaAlO 3, SrTiO 3 (001)<br />

substrates by magnetr<strong>on</strong> sputtering. Structural characterizati<strong>on</strong> revealed that these thin<br />

films were grown epitaxially <strong>on</strong> these substrates, and phase pure double perovskite.<br />

J. H. Park, S. K. Kw<strong>on</strong>, and B. I. Min, Phys. Rev. B 65 (2002) 174401.<br />

SO21<br />

Giant magnetoresistive effect in n<strong>on</strong>-magnetic silic<strong>on</strong><br />

Tae Ho Lee 1 , H<strong>on</strong>g-seok Kim 1 , Woo Lee 2 and Y<strong>on</strong>g-joo Doh 1 *<br />

1<br />

Dept. of Display and Semic<strong>on</strong>ductor Physics, Korea University Sej<strong>on</strong>g Campus,<br />

Korea<br />

2<br />

Korea Research Institute of Standards and Science, Korea<br />

Recently magnetoresistive effects in n<strong>on</strong>-magnetic semic<strong>on</strong>ductors, particularly<br />

silic<strong>on</strong>, have gained c<strong>on</strong>siderable attenti<strong>on</strong> owing to the large magnitude of the effect,<br />

which is comparable, or even larger than, that of the performance of commercial<br />

giant-magnetoresistance devices. The underlying mechanism resp<strong>on</strong>sible for the giant<br />

magnetoresistance in silic<strong>on</strong>, however, has not yet been fully explored. Here we report<br />

that a simple device, based <strong>on</strong> a lightly doped silic<strong>on</strong> substrate c<strong>on</strong>tacted with two<br />

indium c<strong>on</strong>tacts, shows a positive magnetoresistance over 10,000 per cent for magnetic<br />

fields between 0 and 1 T at low temperature of 3 K. Current-voltage characteristics<br />

exhibit a n<strong>on</strong>linear behavior, which is highly sensitive to temperature and magnetic<br />

field. We have extensively studied magnetoresistive effect in silic<strong>on</strong> with varying bias<br />

voltage, temperature, electrode spacing, and the relative angle between the substrate<br />

and the applied magnetic field. Since our device is based <strong>on</strong> a c<strong>on</strong>venti<strong>on</strong>al silic<strong>on</strong><br />

platform and is highly sensitive to low magnetic field, it could be used to develop new<br />

devices of silic<strong>on</strong>-based magnetoelectr<strong>on</strong>ics.<br />

SO22<br />

Effect of Fe substituti<strong>on</strong> <strong>on</strong> Ni-Mn-In shape memory alloys: Magnetic<br />

and magneto-structural properties<br />

Radha S 1 , Ashwin Mohan 2 and A. K. Nigam 2 *<br />

1 Department of Physics, University of Mumbai, India<br />

2 Department of C<strong>on</strong>densed Matter Physics and Materials Science, Tata Institute of<br />

Fundamental Research, India<br />

The Ni-Mn based ferromagnetic shape memory alloys have been extensively investigated for their<br />

multifuncti<strong>on</strong>al properties emerging by suitable chemical substituti<strong>on</strong>s. The off-stoichiometric Ni 50Mn 25+xIn 25-x<br />

exhibit martensitic transiti<strong>on</strong> for In c<strong>on</strong>centrati<strong>on</strong> in the range 13-16 at%. In the Ni 50Mn 35In 15 alloy, the<br />

ferromagnetic transiti<strong>on</strong> occurs at Curie temperature TC = 305 K with a c<strong>on</strong>commitant austenite to martensitic<br />

transiti<strong>on</strong>. A large inverse magnetocaloric effect and anomalous magnetic behavior have earlier been reported<br />

for this alloy [1]. The present work reports the effect of Fe-substituti<strong>on</strong> (0.5 to 2 at%) <strong>on</strong> the magneto-structural<br />

transiti<strong>on</strong> and magnetic behavior of the Ni 50Mn 35In 15 alloy. The martensitic transiti<strong>on</strong> goes down to 255 K for<br />

1at% Fe alloy with str<strong>on</strong>g hysteresis between zero field-cooled (ZFC) and field-cooled (FC) data while it nearly<br />

disappears for the 2at% Fe alloy. The 0.5 at% Fe substituted alloy shows a temperature dependent field-induced<br />

metamagnetic transiti<strong>on</strong> between 250-220K while this transiti<strong>on</strong> is not observed up to fields of 6T in 1at% Fe<br />

substituted alloy. A thermal hysteresis in the temperature dependence of resistance is observed between heating<br />

and cooling cycles due to austenitic-martensitic transiti<strong>on</strong>s up to 1 at% Fe substituti<strong>on</strong>. The substituti<strong>on</strong> of 2 at%<br />

Fe suppresses the martensitic transiti<strong>on</strong> without affecting the ferromagnetic transiti<strong>on</strong>.<br />

[1] P.A. Bhobe, K.R. Priolkar and A.K. Nigam, Appl. Phys. Lett. 91 (2007) 242503<br />

256 The 19 th <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Magnetism</strong><br />

SO23<br />

Magnetic properties and magnetocaloric effect in shape memory alloys<br />

Ni-Mn-Ga<br />

Rafael Fayzullin, Vasiliy Buchelnikov, Sergey Taskaev and Mikhail Drobosyuk<br />

Chelyabinsk State University, Russia<br />

The magnetocaloric effect (MCE) is the ability of magnetic materials to heat up or<br />

cool down when placed in or removed from an external magnetic field. The magnetic<br />

materials with large values of MCE can be applied in the magnetic refrigerati<strong>on</strong><br />

technique [1]. Recent experimental studies have shown that Ni-Mn-Ga Heusler alloys are<br />

also attractive for the applicati<strong>on</strong> in magnetic refrigerati<strong>on</strong> [2]. In this work the magnetic<br />

and magnetocaloric properties of the ferromagnetic shape memory alloys Ni 2+xMn 1xGa<br />

(x=0.07; 0.08; 0.09) were experimentally studied. The MCE measurements were<br />

performed by the setup produced by AMT&C [3]. In this setup, the adiabatic temperature<br />

change ΔTad was measured by a direct method with help of a thermocouple. Magnetic<br />

field up to 2 T was created by Halbach permanent magnet. The magnetic field strength<br />

was measured by Hall probe. Signals from the thermocouple and Hall probe were<br />

recorded simultaneously what allowed us to measure ΔTad as a functi<strong>on</strong> of magnetic field<br />

H. All alloys exhibit the positive MCE typical near the sec<strong>on</strong>d-order phase. Our MCE<br />

measurements of Ni 2+xMn 1-xGa have shown that the maximal MCE is observed near the<br />

Curie point. The maximal values of MCE are 1.2 - 1.6 K near the room temperature.<br />

[1] K. Gschneidner, Jr. and V.K. Pecharsky, Int. J. Refrig., 31 (2008) 945. [2] A. Planes, L. Manosa,<br />

and M. Acet, J. Phys.: C<strong>on</strong>dens. Matter. 21 (2009) 233201. [3] Y.I. Spichkin, et al, Proc. 3rd IIF-IIR<br />

Intern. C<strong>on</strong>f. Magnetic Refrigerati<strong>on</strong> at Room Temperature, IIF/IIR (2009) 173.<br />

SO24<br />

Magnetic susceptibility avalanches in thermally-induced first-order<br />

phase transiti<strong>on</strong> of La(Fe 0.88Si 0.12) 13 magnetocaloric compound<br />

Asaya Fujita* and Hitomi Yako<br />

Department of Materials Science, Tohoku University, Japan<br />

Magnetic materials with large magnetocaloric effects due to the first-order phase transiti<strong>on</strong><br />

attract attenti<strong>on</strong> as candidates for room temperature magnetic refrigerants. NaZn 13type<br />

La(Fe xSi 1-x) 13 compounds exhibit thermally-induced first-order ferromagnetic (F) -<br />

paramagnetic (P) transiti<strong>on</strong> at the Curie temperature Tc and the itinerant-electr<strong>on</strong> metamagnetic<br />

transiti<strong>on</strong> takes place above Tc [1]. Evoluti<strong>on</strong> of the transiti<strong>on</strong> determines the operating speed<br />

of magnetic refrigerati<strong>on</strong>, therefore, a detailed observati<strong>on</strong> is necessary. In the present study,<br />

appearance of the avalanche behavior [2] in the progress of thermally-induced transiti<strong>on</strong> has<br />

been examined by measuring the magnetic susceptibility χ. The value of χ up<strong>on</strong> cooling at<br />

0.4 K / min. exhibits a smooth variati<strong>on</strong> across the transiti<strong>on</strong> and its first derivative, dχ/dT,<br />

shows no jerky change. Meanwhile, the avalanche-like behavior is observed in dχ/dT around<br />

Tc up<strong>on</strong> heating. Furthermore, the number and height of avalanches are dramatically changed<br />

by external magnetic fields. Generally, the avalanche behavior is induced by the quenched<br />

disorders, however, such a mechanism can not explain the influence of magnetic field.<br />

C<strong>on</strong>sidering the fact that the kinetics of the transiti<strong>on</strong> is influenced by the demagnetizati<strong>on</strong><br />

effect [3], these results indicate that the nucleati<strong>on</strong>- growth behavior is affected by the magnetic<br />

dipole interacti<strong>on</strong>.<br />

[1] A. Fujita, S. Fujieda, Y. Hasegawa, K. Fukamichi: Phys. Rev. B 67 (2003), 104416. [2] E. Vives, J. Ortin, L. Manosa, I. Rafols, R. Perez-Magrane, A.<br />

Planes: Phys. Rev. Lett. 72 (1994), 1694. [3] H. Yako, S. Fujieda, A. Fujita, K. Fukamichi: IEEE Trans. Magn. 47 (2011), 2482.<br />

SO25<br />

Phase coexistence and magnetocaloric effect <strong>on</strong> martensitic transiti<strong>on</strong><br />

in Ni-Co-Mn-Sn metamagnetic shape memory alloy<br />

Bo Gao 1 *, Wen Guan 1 , Yu Wang 1 , Sen Yang 1 , Xiaoping S<strong>on</strong>g 1 , Fengxia Hu 2 , Jir<strong>on</strong>g Sun 2 and<br />

Baogen Shen 2<br />

1<br />

MOE Key Laboratory for N<strong>on</strong>equilibrium Synthesis and Modulati<strong>on</strong> of C<strong>on</strong>densed Matter, Xi'an<br />

Jiaot<strong>on</strong>g University, China<br />

2<br />

State Key Laboratory of <strong>Magnetism</strong>, Institute of Physics, Chinese Academy of Sciences, China<br />

Since the discovery of the metamagnetic shape memory effect in Ni 45Co 5Mn 36.7In 13.3 Heusler alloys [1], a member<br />

of studies <strong>on</strong> magnetocaloric effect (MCE) have been made in metamagnetic shape memory alloys. It is found<br />

that metamagnetic shape memory alloys exhibit large MCE in the vicinity of martensitic transformati<strong>on</strong>. But for<br />

the first-order transiti<strong>on</strong>, whether and to what extent the Maxwell relati<strong>on</strong> is applicable are problems requiring<br />

further study [2]. In this paper, we will discuss the appropriate approach to evaluate the MCE in Ni-Co-Mn-<br />

Sn alloys. The energy dispersive spectrometer shows that the sample compositi<strong>on</strong> is Ni 43.2Co 3.1Mn 41.8Sn 11.9. The<br />

thermo-magnetic curves indicate the martensitic transformati<strong>on</strong> can be driven by the magnetic field. It is observed<br />

that metamagnetic transiti<strong>on</strong> takes place in a wide temperature range from the magnetizati<strong>on</strong> isotherms. The<br />

entropy change calculated by Maxwell relati<strong>on</strong> is up to 30J/kgK under a field change of 0-5T. Meanwhile, we<br />

calculated the entropy change based <strong>on</strong> heat capacity measured under 0 and 5T, and an entropy change of ~3J/<br />

kgK is obtained for a field change of 0-5T. According to the different results from magnetic and calorimetric<br />

measurements, we find that the Maxwell relati<strong>on</strong> should be used with cauti<strong>on</strong> <strong>on</strong> martensitic transformati<strong>on</strong><br />

including phase coexistence.<br />

[1] R. Kainuma, Y. Imano, W. Ito, Y. Sutou, H. Morito, S. Okamoto, O. Kitakami, K. Oikawa, A. Fujita, T. Kanomata, and K. Ishida, Nature 439, 957 (2006)<br />

[2] G. J. Liu, J. R. Sun, J. Shen, B. Gao, H. W. Zhang, F. X. Hu, and B. G. Shen, Appl. Phys. Lett. 90, 032507 (2007)


SO26<br />

Balance between the growth rate of ferromagnetic phase and<br />

demagnetizing fields in itinerant electr<strong>on</strong> metamagnetic transiti<strong>on</strong> of<br />

La(Fe 0.88Si 0.12) 13<br />

Hitomi Yako* and Asaya Fujita<br />

Tohoku university, Japan<br />

Str<strong>on</strong>g interplay between an itinerant electr<strong>on</strong> metamagnetic (IEM) transiti<strong>on</strong> and<br />

magnetocaloric effects in NaZn 13-type La(FexSi1-x)13 has been investigated.[1-3] Recently,<br />

we have dem<strong>on</strong>strated that progress of the IEM transiti<strong>on</strong> is influenced by the demagnetizati<strong>on</strong><br />

effect in La(Fe 0.88Si 0.12) 13.[4] Especially, the progress is arrested in midstream even under the<br />

magnetic fields, μH larger than the critical value, μHc by setting l<strong>on</strong>gitudinal directi<strong>on</strong> of the<br />

sample perpendicular to the field directi<strong>on</strong> ( θ = 90 degrees ). In the present study, the angular<br />

dependence of the transiti<strong>on</strong> progress is examined and the influence of demagnetizati<strong>on</strong> effect<br />

<strong>on</strong> the IEM transiti<strong>on</strong> is discussed. The time-dependent magnetizati<strong>on</strong> measurements were<br />

carried out at 200 K under the c<strong>on</strong>stant value of μH by changing θ from 0 to 90 degrees. The<br />

transiti<strong>on</strong> starts to proceed under the magnetic field larger than μHs. However, the transiti<strong>on</strong><br />

is arrested in midstream, and the completi<strong>on</strong> of transiti<strong>on</strong> emerges <strong>on</strong>ly after μHc exceeds the<br />

threshold value, μHt. The values of μHs and μHt are evaluated to be 0.60 and 0.75 T for θ =<br />

30 degrees and 0.70 and 1.00 T for 90 degrees, respectively. The growth rate of ferromagnetic<br />

phase is dominated by keeping the balance with demagnetizing fields.<br />

[1] A. Fujita et al., J. Appl. Phys., 85, 4756-4758, ( 1999 ). [2] F. X. Hu et al., Appl. Phys. Lett., 78, 3675-3677, ( 2001 ). [3] O.<br />

Gutfleisch et al., J. Appl. Phys., 97, 10M305:1-10M305:3, ( 2005 ). [4] H. Yako et al., IEEE Trans, Mag., 47, 2482-2485, ( 2011 ).<br />

SO27<br />

Temperature dependent structural and magnetic properties of Ni-Mn-<br />

In Heusler alloy glass-coated microwires<br />

Valeria Rodi<strong>on</strong>ova 1 *, Mikhail Ipatov 2 , Maxim Ilyn 3 , Valentina Zhukova 4 , Alexander Granovsky 5 and Arcady Zhukov 6<br />

1<br />

I. Kant Baltic Federal University, UPV/EHU, Lom<strong>on</strong>osov Moscow State University, Russia<br />

2<br />

UPV/EHU, Spain<br />

3<br />

Centro de Fisica de Materiales, CSIC/UPV, Spain<br />

4<br />

Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, Spain<br />

5<br />

Lom<strong>on</strong>osov Moscow State University, IKERBASQUE, Basque Foundati<strong>on</strong> for Science, Russia<br />

6<br />

Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU,IKERBASQUE, Basque Foundati<strong>on</strong> for Science, Spain<br />

Magnetic shape-memory alloys (MSMAs) attracted growing attenti<strong>on</strong> owing to shape memory effect, originated from the<br />

coupling between magnetic and structural ordering. From point of view of technological applicati<strong>on</strong>s, miniaturizing of MSMAbased<br />

devices using MSMA particles, wires, ribb<strong>on</strong>s, films, bi- and multilayers, pillars is quite important. Here we report <strong>on</strong><br />

studies of magnetic properties of n<strong>on</strong>-stoichiometric Heusler-type Ni 50Mn 34.5In1 5.5, Ni 48Co 2Mn 35In 15 and Ni 49.5Mn 25.4Ga 25.1 glasscoated<br />

microwires prepared using Taylor-Ulitovsky technique. The principle interest in glass-coated microwires is related<br />

with their composite character allowing to c<strong>on</strong>trol the strength of internal stresses. We measured magnetizati<strong>on</strong> curves at<br />

different temperatures. As-prepared microwires did not show ferromagnetic ordering at room temperature. From temperature<br />

dependence of magnetizati<strong>on</strong> we found that annealed microwires showed Curie temperature about 270 K (Ni 50Mn 34.5In 15.5<br />

microwires), between 225K and 240 K (Ni 48Co 2Mn 35In 15 microwires with different metallic nucleus diameters) and 315 K for<br />

Ni 49.5Mn 25.4Ga 25.1. Microwires Ni 50Mn 34.5In 15.5, Ni 48Co 2Mn 35In 15 and Ni 49.5Mn 25.4Ga 25.1 exhibited phase transiti<strong>on</strong> at 240 K, 115<br />

K and 300 K respectively. From point of view of applicati<strong>on</strong>s the most promising properties exhibit thinnest Ni 49.5Mn 25.4Ga 25.1<br />

microwire (with metallic nucleus diameter 10,4 mkm and total diameter of 16 mkm) showing the phase transiti<strong>on</strong> near Curie<br />

temperature.<br />

SO28<br />

Magnetooptical Kerr effect enhancement in Co/TiO 2 layered films<br />

Victor Polyakov 1 , K<strong>on</strong>stantin Patrin 1 , Klaudia Polyakova 1 *, Vitaly Seredkin 1 and<br />

Gennady Patrin 2<br />

1 L.V. Kirensky Institute of Physics, SB RAS, Russia<br />

2 Siberian Federal University, Russia<br />

As is known, the magneto-optical properties of the composite metal-dielectric systems<br />

are determined by the volume of a magnetic phase and the properties of a dielectric<br />

matrix or dielectric layers. Of special interest are the magneto-optical properties of the<br />

composite films c<strong>on</strong>taining TiO 2 whose permittivity is higher as compared to SiO 2 and<br />

Al 2O 3. Here, we report the results of the magneto-optical study of Co/TiO 2 multilayers.<br />

Particularly we studied spectral dependence of the polar Kerr effect of Co / TiO 2<br />

layered structure of with various number of layers. The composite Co/TiO 2 periodic<br />

structures c<strong>on</strong>sisting of 2--12 pairs of layers (n) were prepared by sequential depositi<strong>on</strong><br />

of Co and titanium oxide by i<strong>on</strong>-plasma sputtering and reactive i<strong>on</strong>-plasma sputtering,<br />

respectively, <strong>on</strong>to glass substrates. The respective thicknesses of magnetic and titanium<br />

oxide layers were 5 and 17 nm. Study of spectral dependence of polar Kerr effect<br />

showed that the spectra of the Co/TiO 2 layered structures are res<strong>on</strong>ance, with the large<br />

growth of the angle of rotati<strong>on</strong> near the res<strong>on</strong>ance. The maximum angle of rotati<strong>on</strong><br />

n<strong>on</strong>m<strong>on</strong>ot<strong>on</strong>ically depends <strong>on</strong> the number of layers. The maximum Kerr rotati<strong>on</strong> angle<br />

(2θk=7.3 deg) observed at a wavelength of 540 nm corresp<strong>on</strong>ds to n = 8.<br />

SO29<br />

SO30<br />

Disorder effects in giant magnetocaloric materials<br />

Joao S Amaral*, Soma Das and Vitor S Amaral<br />

CICECO and Dept. of Physics, Universidade de Aveiro, Portugal<br />

SO31<br />

<str<strong>on</strong>g>POSTER</str<strong>on</strong>g><br />

Electr<strong>on</strong>ic structure calculati<strong>on</strong>s and the magnetic properties of<br />

Ru 2FeZ (Z = Al and Ga)<br />

Ramesh Kumar K and Thamizhavel A*<br />

Department of C<strong>on</strong>densed Matter Physics and Materials Science, Tata Institute of<br />

Fundamental Research Mumbai 400005, India<br />

After the discovery of half-metallic character in NiMnSb by de Groot et al. Heusler<br />

alloys have drawn much attenti<strong>on</strong> due to the possible applicati<strong>on</strong> in magneto-electr<strong>on</strong>ic<br />

devices [1,2]. In the quest of finding half-metallic character in 4d transiti<strong>on</strong> element<br />

based Heusler alloy we present the electr<strong>on</strong>ic structure and magnetic properties<br />

of Ru 2FeGa/Al. The band structure calculati<strong>on</strong>s were d<strong>on</strong>e using the state-of-theart<br />

density functi<strong>on</strong>al technique with the PWSCF code [3]. The equilibrium lattice<br />

parameter was found by fitting energy vs volume data to the Murghnan equati<strong>on</strong> of<br />

state. At the equilibrium lattice parameter the total energy difference between the n<strong>on</strong>magnetic<br />

state and ferromagnetic state was observed to be of the order of 5 meV which<br />

suggest that these systems are having stable magnetic ground state. In ferromagnetic<br />

ground state the lattice parameter was observed to be 5.988 A for Ru 2FeGa and 5.982<br />

A for Ru 2FeAl. From the DOS Vs Energy diagram it is found that the systems are not<br />

half-metallic in nature. However, the calculati<strong>on</strong> showed very high spin polarizati<strong>on</strong> at<br />

the Fermi level. The spin polarizati<strong>on</strong> (P) value was found to be 83 % in both the cases.<br />

1. R. A. de Groot, F. M. Mueller, P. G. van Engen and K.H. J. Buschow , Phys. Rev. Lett. 50 2024<br />

(1983). 2. C. Felser, G. H. Fecher, and B. Balke Angew. Chem. Int. Ed., 46 688 (2007). 3. S. Bar<strong>on</strong>i<br />

et al http://www.pwscf.org/<br />

In striving for mass producti<strong>on</strong> of magnetocaloric materials for refrigerati<strong>on</strong> applicati<strong>on</strong>s, <strong>on</strong>e<br />

has to face the fact that these will not be laboratory-grade materials, and will necessarily present<br />

compositi<strong>on</strong> gradients due to lower quality reagents. Some c<strong>on</strong>sequences are expected: the<br />

maximum value of magnetic entropy change (ΔSM) should decrease compared to a “pure”<br />

material, and broadening of the ΔSM(T) curves, as observed in elementary ferromagnets [1].<br />

Some theoretical work has focused <strong>on</strong> this topic, for sec<strong>on</strong>d-order phase transiti<strong>on</strong> systems [2-<br />

5]. Still, these theoretical c<strong>on</strong>siderati<strong>on</strong>s do not directly apply to giant magnetocaloric materials.<br />

We present a study <strong>on</strong> the effect of disorder <strong>on</strong> the magnetic and magnetocaloric properties<br />

of first-order phase transiti<strong>on</strong> systems, via the use of the Bean-Rodbell [6] model. Disorder is<br />

shown to “smooth” the disc<strong>on</strong>tinuities <strong>on</strong> magnetizati<strong>on</strong> and ΔSM, and also affect magnetic<br />

hysteresis. For sufficiently large disorder, the ΔSM(T) curves resemble the distributi<strong>on</strong> functi<strong>on</strong>.<br />

We discuss how the magnetic field dependence of ΔSM is affected by disorder, in light of a<br />

“sec<strong>on</strong>d-order like” dependence of ΔSM <strong>on</strong> applied magnetic field, for disordered LaFeSi<br />

samples [5]. Aging effects <strong>on</strong> hydrogenated LaFeSi samples, that degrade even in storage [7],<br />

are discussed taking into account our theoretical simulati<strong>on</strong>s.<br />

[1] Gschneidner Jr. K. A., Pecharsky V. K., Tsokol A. O., 2005, Rep. Prog. Phys. 58 1479. [2] Romanov A. Y., V. P.<br />

Silin V. P., 1997, Phys. Met. Metallogr. 83, 111. [3] Amaral J. S. et al., 2008, J. N<strong>on</strong>-Cryst. Solids 354, 5301. [4]<br />

Bahl C. R. H., et al., 2011, J. Magn. Magn. Mat. 324 564. [5] Lyubina J. et al., 2011 Phys. Rev. B. 83 012403. [6]<br />

Bean C. P., Rodbell D. S., 1962, Phys. Rev. 126 104. [7] Barcza, A. et al., 2011, IEEE Trans. Magn. 47 3391.<br />

On the Curie temperature dependency of the Magnetocaloric effect<br />

Joao H Belo 1 , Joao S Amaral 2 *, Andre M Pereira 1 , Soma Das 2 , Vitor S Amaral 2 and<br />

Joao P Araujo 1<br />

1 IFIMUP and IN, Dept. de Fisica e Astr<strong>on</strong>omia, FCUP, 4169-007 Porto, Portugal<br />

2 CICECO and Dept. of Physics, Universidade de Aveiro, Portugal<br />

A theoretical study of the magnetcaloric effect dependency <strong>on</strong> simple ferromagnetic<br />

microscopic parameters is here presented. C<strong>on</strong>sidering the Bean-Rodbell model [1] of<br />

magnetovolume coupling within the Weiss mean field theory, the magnetic entropy change<br />

of systems undergoing first and sec<strong>on</strong>d order magnetic phase transiti<strong>on</strong> was numerically<br />

simulated. Through these simulati<strong>on</strong>s, the magnetic entropy change behavior was studied as<br />

a functi<strong>on</strong> of: Tc , spin value, applied field changes and the nature of the transiti<strong>on</strong> c<strong>on</strong>sidered.<br />

The main result found for both first and sec<strong>on</strong>d order magnetic transiti<strong>on</strong>s systems is the linear<br />

dependency of the ΔSM(T) maximum value <strong>on</strong> Tc 2/3 . By starting from the magnetizati<strong>on</strong> mean<br />

field state equati<strong>on</strong> an approximated expressi<strong>on</strong> for the magnetic entropy change as a functi<strong>on</strong><br />

of microscopic magnetic parameters was reached, c<strong>on</strong>firming the Tc 2/3 dependency. We have<br />

found that many ferromagnetic systems, both undergoing sec<strong>on</strong>d (GdTbCo [2], RR’Al [3] (R =<br />

rare earth), RCoMn [4]) and first-order (MnFePAs [5], GdSiGe [7], RCo [7]) phase transiti<strong>on</strong>s,<br />

obey this relati<strong>on</strong> between the magnetocaloric effect and Tc.<br />

[1] Bean C. P., Rodbell D. S., 1962, Phys. Rev. 126 104. [2] K. Zhou et al. Solid State Commun. 137,<br />

275 (2006). [3] N. Duc, D. Anh, and P. Brommer, Physica B - C<strong>on</strong>d. Matter 319, 1 (2002). [4] A. K.<br />

Pathak et al., J. Magn. Magn. Mater. 323, 2436 (2011). [5] O. Tegus et al., Physica B - C<strong>on</strong>d. Matter<br />

319, 174 (2002). [6] K. A. Gschneidner, V. K. Pecharsky, and A. O. Tsokol, Rep. Prog. Phys. 68, 1479<br />

(2005). [7] N. Duc, D. Anh, and P. Brommer, Physica B - C<strong>on</strong>d. Matter 319, 1 (2002).<br />

July 8 - 13, 2012 Busan, Korea 257<br />

Poster Friday

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