Institute of Molecular Physics Polish Academy of Sciences ... - Poznań

Institute of Molecular Physics 

Polish Academy of Sciences 

Scientific Activity 2006-2009 

Selected Reports 

Poznań 2010

Foreword 

The Institute of Molecular Physics of the Polish Academy of Sciences is engaged in 

fundamental research in the field of condensed matter physics, studying materials with 

unique properties. In years 2006-2009, the scientific activity was developed in the three main 

directions: 

• Non-conventional dielectric materials 

• Advanced conducting materials for molecular electronics 

• New magnetic materials for advanced technology 

The Institute was organized into 14 divisions and employed about 120 people including about 

65 staff scientists. On an average, each year about 140 articles were published in international 

journals and about 200 contributions were presented on national and international 

conferences. The main fields of research can be characterized as follows: 

• Physics of magnetics: thin magnetic films and multilayers, magnetic alloys, 

amorphous magnetics, electronic structure 

• Physics of ferroics: dielectric relaxation in ferroelectrics, superionic conductors 

• Liquid crystals: dielectric, optical and electro-optical properties 

• Crystalline organic conductors and organic materials for photovoltaics 

• Molecular interactions in liquids: linear and nonlinear dielectric properties 

• Mesoscopic and nanoscopic systems 

• Spintronics and nanoelectronics 

• Low temperature physics 

• Solid state electron paramagnetic resonance (EPR): spin relaxation, phase transitions 

• Magnetic resonance imaging (MRI): porous materials, polymers 

• Computer simulations: granular systems, colloids, auxetics 

In this review, some most important achievements are shortly presented to give the reader a 

general knowledge about the Institute's activity in the years 2006-2009. 

Poznań, November 2010 

Vice-Director for Scientific Affairs 

Prof. Dr. Roman Świetlik

Electron Spin Echo Studies of Dynamics and Spin Relaxation of Free Radicals 

and Metal Ions in Diamagnetic Crystals 

Stanisław K. Hoffmann 

Solid State Radiospectroscopy Laboratory 

We use short (nanoseconds) microwave pulses for an excitation of spin systems and the 

system response deliver data on local electronic structure and dynamics of a paramagnetic 

center and its environment. 

Fig. 1. Modulated ESE decay and corresponding 

FT-spectra of ammonia radical in Tuttion salt crystal 

In fluorite type crystal BaF2 doped with 

Mn 2+ ions we have found by EPR and ESE 

measurements that MnF8-cub is distorted into 

two tetrahedra of Td-symmetry at about 45 K. 

Electron spin echo dephasing (phase 

relaxation) shows resonance type 

enhancement at about 10 K (Fig.2) due to 

jumps between the two tetrahedra. These 

jumps are visible as a local mode of 

vibrations in electron spin-lattice relaxation 

[2]. 

Modulated electron spin echo (ESE) decay of NH 3 

+ 

radical in Tutton salt (NH4)2Zn(SO4)2⋅6H2O crystal [1] 

and its Fourier transform spectrum (electron spin echo 

envelope modulation -ESEEM) allowed to observe NH4 

and H2O reorientations and its temperature behavior 

(Fig.1). It was found that an ordering and stabilization 

of the hydrogen bond network appears below 160 K and 

rigid lattice limit is reached practically below 50 K. 

Fig. 2 Enhancement of the phase relaxation rate 1/TM 

1/TM1/TM for Mn 2+ in BaF2.

Fig. 3. The ESE decay for Ti 2+ and Ti 2+ -Ti 2 pairs in SrF2 

and its Fourier transform spectra (insets) 

[1] S. K. Hoffmann, T. Radczyk, Mol. Phys. 104, 2423-2432 (2006) 

Complex motion of X-ray induced NH 3 

+ radicals in Tutton salt (NH4)2Zn(SO4)2⋅6H2O 

single crystal observed by EPR and ESEEM spectroscopy. 

[2] S. Lijewski, S. K. Hoffmann, J. Goslar, M. Wencka, V. A. Ulanov, 

J. Phys.:Condens. Matter 20, 385208 (2008). 

Dynamical properties and instability of local fluorite BaF2 structure around doped 

Mn 2+ ions - EPR and electron spin echo studies. 

[3] S. K. Hoffmann, S. Lijewski, J.Goslar, V.A. Ulanov, J. Magn. Res. 202, 14-23 (2009) . 

Electron spin-relaxation of exchange coupled pairs of transition metal ions in solids. 

Ti 2+ - Ti 2+ pairs and single Ti 2+ ions in SrF2 crystals. 

For Ti 2 (S=1) and Ti 2+ -Ti 2+ (S=2) pairs in 

SrF2 the temperature dependence of EPR 

spectra and spin relaxation was determined in 

temperature range 4.2–300 K. The results for 

dimers were analyzed in details. It was found 

that ions in dimers are ferromagnetically 

coupled with J=36 cm -1 and this singlet- 

triplet splitting governs the spin-lattice 

relaxation. The FT-spectrum of modulated 

ESE decay (Fig. 3) allowed to determine the 

off-center shift of Ti 2+ ions as 0.13 nm. [3]

Transport in Nanostructures: A Role of Electronic Correlations 

Bogdan Bułka 

Solid State Theory Division 

Electronic transport in nanostructures is one of the branch of research in the Solid State Theory 

Division. Our recent research is focused on electronic correlations in semiconducting nanostructures 

(quantum wires [1], quantum dots [2,3], magnetic devices [4]) as well as in molecular systems [5], 

and is performed within national and European scientific programs. The SPINTRA project was 

carried out within the EUROCORES Programmme “ Fundamentals of Nanonelectronics” of 

European Science Foundation in years 2006-2010. We studied, in cooperation with experimentalists 

from Institute of Physics, PAS, in Warsaw and theorists from University in Naples, ballistic 

transport in multi-terminal systems, in particular, a three terminal junction of ballistic wires. It was 

shown that opening a new conducting channel in the side electrode modifies the conductance [1]. 

Depending on scattering conditions the conductance shows singularities with different shapes 

(Fig.1). This is manifestation of the threshold effect in nanostructures. The effect have been well 

studied in the past in nuclear and atomic physics, and it is nicknamed Wigner cusp after E. P. 

Wigner, who predicted it in 1948. Moreover, we demonstrated the mode branching and bend 

resistance effects in this device. 

Fig.1 Conductance in the three terminal T-shaped 

device plotted vs. the gate voltage VG3 applied to the 

side electrode. The plots present different Wigner 

threshold singularities, for different couplings t03 

with the side electrode. The temperature smears the 

singularities (see blue and red curves). 

Fig.2 The map of the current cross-correlation 

function in the voltage space VtR, VbR for a 

system of two capacitively strongly coupled 

quantum dots. The maps shows that strong 

Coulomb interactions can lead to bunching of 

electrons transferred through the system [2].

In multiterminal devices currents can be correlated – transfer of electrons in one of the 

channel affects on transfer in the other channels. Because electrons are fermions, the crosscorrelation 

function of two scattered electrons is negative (scattered electrons are anti-bunched in 

contrast to scattered bosons, which are bunched). The studies were focused on dynamical 

correlations in the presence of Coulomb interactions and search for conditions for bunching of 

electrons [2] (see Fig.2, which presents the current cross-correlation function modified by Coulomb 

interactions). Charge fluctuations and the dynamical Coulomb blockade are also relevant for 

electronic transport through Quantum Point Contact. The studies [3] explained the 0.7 structure in 

the conductance characteristics and a shift of the position of the conductance plateau for a nonequilibrium 

situation. Our PhD students (also those from abroad) are involve in the research [also 

within Marie Curie Actions in Framework Programme: FP6 (2005-08) and FP7 (2010-14)] (see [3] 

as an example). 

Recently we have also shown that electron correlations inside a quantum dot placed between 

magnetic electrodes can switch direction of the spin polarization of the tunneling current [4]. 

Moreover, the tunneling magnetoresistance (TMR) can also change its sign. There are two types of 

TMR anomalies. One type, of a single particle origin, is the TMR sign change at the conductance 

resonances. The second type, caused by electron correlations, is the huge TMR enhancement taking 

place in-between Coulomb blockade peaks (see Fig. 3). Similar features have been observed 

experimentally in self-assembled InAs quantum dots coupled to nickel or cobalt leads. 

Fig. 3. TMR vs. gate voltage calculated for 

zero bias, leads polarizations PL=PR=0.5, 

temperature T=0.01U and various 

asymmetry parameters of the quantum dotleads 

coupling α. The curve for noninteracting 

dot is also shown [4].(U- 

Coulomb repulsion inside the dot). 

Selected publications: 

[1] B.R. Bułka and A. Tagliacozzo, Physical Review B 79, 075436 (2009); J. Wróbel, P. Zagrajek, 

M. Czapkiewicz, M. Bek, D. Sztenkiel, K. Fronc, R. Hey, K. H. Ploog, B. R. Bułka, Phys. Rev. 

B 81, 233306 (2010). 

[2] T. Kostyrko, B.R. Bułka, Physical Review B 79, 075310 (2009); G. Michałek, B. R. Bułka, 

Phys. Rev. B 80, 035320 (2009); G. Michałek, B.R. Bułka, J. Phys.: Cond. Matter 20, 275244, 

(2008). 

[3] B.R. Bułka, T. Kostyrko, M. Tolea, I.V. Dinu, J. Phys.: Cond. Matt. 19, 255211 (2007). 

[4] P. Stefański, Phys. Rev. B 79, 085312 (2009); P. Stefański, Phys. Rev. B 77, 125331 (2008). 

[5] T. Kostyrko, V. M. García-Suárez, C. J. Lambert, B. R. Bułka, Phys. Rev. B 81, 085308 (2010).

Computational Materials Science: First Principles Calculations 

Andrzej Szajek 

Solid State Theory Division 

Condensed matter physics and materials science are concerned fundamentally with 

understanding and exploiting the properties of systems of interacting electrons and atomic nuclei. 

Methods of band structure calculations are constantly improved and are now a tool for not only 

explaining observed properties but also for predicting with quite a good reliability properties of 

systems not yet experimentally established. An efficient and accurate scheme for solving the manyelectron 

problem of a crystal (with nuclei at fixed positions) is the local spin density approximation 

(LSDA) within the density functional theory (DFT). A calculation is said to be ab initio (or "from 

first principles") if it relies on basic and established laws of nature without additional assumptions 

or special models. 

The electronic structure plays a key role in determining transport, magnetic, optical, and 

bonding properties of solids. Our group tightly cooperates with experimental ones and performs 

calculations for real systems obtained in experimental laboratories. Calculations of the band 

structure are usually performed in the local spin density approximation. However in cases of 

important role played by electron correlations the LSD+U corrections are applied. Also full 

potential (FP) calculations instead of the atomic sphere approximation (ASA) are made, if needed. 

For systems with strong spin-orbit coupling fully relativistic (FR) formalisms are used. Orbital 

contributions to the magnetic moments can be also calculated including Brook’s orbital polarization 

(OP) term. In uranium compounds often non-colinear ordering of magnetic moments (NCMM) 

appears. It is possible to take into account chemical disorder, either by using large supercells or by 

the coherent potential approximation (CPA). In recent years the range of available computational 

codes was significantly broadened due to acquisitions. We can use: 

- WIEN2k (method of Linear Augmented Plane Waves: LSDA, FP, FR, LSD+U, OP) 

- VASP (methods using pseudopotentials: LSD+U, FP, FR, NCMM) 

- SPR KKR (method KKR – Green functions: ASA, FR, NCMM, OP, CPA) 

- FPLO (method Full-Potential Local-Orbital minimum-basis: FP, FR, CPA, LSD+U, OP) 

- LmtArt (method LMTO: FP, ASA, FR, LSDA, LSD+U). 

The studies of the Division are correlated with experimental and theoretical works in our 

institute as well as in Polish and foreign partners. The cooperation includes: 

- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 

Wrocław, Poland; 

- Faculty of Physics, A. Mickiewicz University, Poznań, Poland; 

- Institute of Physics, Silesian University, Katowice, Poland; 

- Institute of Physics, Polish Academy of Sciences, Warszawa, Poland; 

- Institute of Physics, Jagiellonian University, Kraków, Poland; 

- Institute of Materials Science and Engineering, Poznań University of Technology, Poland; 

- Institute of Solid State Research (IFF), Jülich, Germany. 

We focus our attention on very wide spectrum of materials: 

- strongly correlated electron systems, which are based on lanthanides (especially on cerium) 

and actinides with uranium in the main role. From among many interesting systems, one 

should notice newly discovered superconductors: the heavy fermion Ce2PdIn8 and the filledskutterudite 

ThPt4Ge12.

Fig.1 

Calculated Fermi surfaces of Ce2PdIn8 (Wien2k code; left side 

panel) and ThPt4Ge12 (FPLO code; lower panels) 

- Heusler type alloys, especially interested for their half-metallic transport properties and 

potential applications in spintronics; 

- semiconductors: ZnO, an II-VI oxide semiconductor, a promising material for various 

technological applications, especially for optoelectronic light-emitting devices in the visible and 

ultraviolet range of the electromagnetic spectrum; 

- TiNi, -LaNi5- and Mg2Ni-type phases are studied in relation to their exceptional 

hydrogenation properties, especially magnesium-based hydrogen storage alloys have been also 

considered to be possible candidates for electrodes in nickel-hydride (Ni-MH) batteries; 

- BiFeO3 bulk and thin film, heterostucture, nanostructure multiferoics, i.e. materials that 

show simultaneous ferroelectric, ferromagnetic and ferroelastic ordering, therefore they are very 

promising candidates for advanced sensors and new technologies. 


Fig. 2 

Calculations for ZnO semiconductor doped by 

Ag atoms: Spin density for (a) the relaxed 

geometry of isolated Ag, (b) for the nonrelaxed 

NN pair oriented in the (x, y) plane and (c) 

along the c axis, and (d) for the relaxed distant 

pair. Small (yellow), medium (magenta), and 

large (blue) balls represent O, Zn, and Ag 

atoms, respectively. (VASP results) 

1. D. Kaczorowski, A.P. Pikul, U. Burkhardt, M. Schmidt, A. Ślebarski, A. Szajek, M. Werwiński, 

and Yu. Grin, “Magnetic properties and electronic structures of intermediate valence 

systems CeRhSi2 and Ce2Rh3Si5”, J. Phys.:Condens. Matter 22 (2010) 215601. 

2. A.P. Pikul, D. Kaczorowski, Z. Gajek, A. Ślebarski, J. Stepień-Damm, A. Szajek, M. Werwiński 

“Complex magnetic behavior in CeRh3Si2”, Phys. Rev. B 81 (2010) 174408. 

3. V.H. Tran, D. Kaczorowski, W. Miiller, and A. Jezierski, “Two-band conduction in 

superconducting ThPt4Ge12”, Phys. Rev. B 79 (2009) 054520. 

4. V. H. Tran, B. Nowak, A. Jezierski, and D. Kaczorowski, „Electronic band structure, specific 

heat, and 195 Pt NMR studies of the filled skutterudite superconductor ThPt4Ge12” 

Phys. Rev. B 79 (2009) 144510. 

5. O. Volnianska, P. Boguslawski, J. Kaczkowski, P. Jakubas, A. Jezierski, and E. Kaminska 

“Theory of doping properties of Ag acceptors in ZnO”, Phys. Rev. B 80 (2009) 245212.

Giant Magnetoresistance and Ferromagnetic Shape Memory in Thin Films 

F. Stobiecki, J. Dubowik, B. Szymański, M. Urbaniak, P. Kuświk, K. Załęski 

Division of Thin Films 

Thin Films Laboratory specializes in the deposition and characterization of thin metallic magnetic 

films. The investigations are focused on sputter-deposited magnetic structures displaying giant 

magnetoresistance [1,2], Heusler type alloys exhibiting ferromagnetic shape memory effect [3], and 

recently on the influence of light ion bombardment on magnetic properties and magnetoresistance 

of multilayers with perpendicular magnetic anisotropy. In recent years we investigated 

comprehensively the [NiFe/Au/Co/Au]N multilayer system which is especially interesting due to the 

coexistence of magnetic NiFe layers with easy-plane magnetic anisotropy and the Co layers in 

which magnetization points perpendicularly to the plane. This leads to the magnetoresistance 

behavior which is promising from the application point of view and, on the other hand, to complex 

magnetostatic interactions between neighboring layers. These two issues were studied by 

complementary structural, magnetic, and transport techniques (X-Ray reflectivity, XMCD, PEEM, 

VSM, Mössbauer effect, magnetoreisitance). One of our most significant achievements was the 

direct experimental evidence of the influence of Co layers stripe domain structure on the 

magnetization reversal processes in NiFe layers [1]. It was shown (Fig.1) with element specific 

XRMS measurements that magnetization hysteresis of NiFe layers reveals the characteristic points 

of Co layers reversals (nucleation and annihilation of the stripe domain structure). 

Fig. 1 Within the hysteretic range of Co 

layers (panel d) the reversal of NiFe layers 

(panel f) is influenced by the stray fields 

originating from stripe domains present in 

Co layers displaying perpendicular 

anisotropy [1]. With the help of 

micromagnetic simulations we have also 

show [4] that the characteristic minima of 

resistance, seen in panel b, are caused by the 

same magnetostatic interactions 

Influence of the ion bombardment on magnetic and magnetoresistive properties of sputter deposited 

(Ni80Fe20/Au/Co/Au)10 multilayer was systematically investigated as part of our studies of materials 

potentially suitable for high density perpendicular recording. It is shown that variation of 

magnetoresistance with ion bombardment is mainly caused by anisotropy changes of Co layers. The 

demonstrated ability of tailoring the perpendicular anisotropy (see Fig. 2) results in a potentially 

better control of magnetic patterning via ion bombardment which can be utilized in the 

manufacturing of novel materials [5]. This was utilized for the manufacturing of artificial domain 

structures with the help of the so called nanosphere lithography (see Fig. 3). It was shown that the 

light ion bombardment through the hexagonally arranged polystyrene spheres leads to a domain

structure reflecting the periodicity of the mask [6] and at the same time introduces no topographical 

changes to the surface of the film. 

Fig. 2 The He + ion bombardment induces controllable changes in magnetic parameters of NiFe and 

Co layers. A strong decrease in HS Co with ion fuences, indicates the gradual weakening of the 

perpendicular anisotropy followed by a 

transition from the out-of-plane to the inplane. 

This property is especially important 

for magnetic patterning. 

Fig. 3 Hexagonally arranged, close-packed arrays of 

polystyrene nanospheres (diameter 470 nm) were 

deposited on the multilayer surfaces via a selfassembly 

process realized by dip coating. 

Subsequently, a thin 3 nm Au layer was deposited 

above the nanospheres in order to provide the charge 

transfer during ion bombardment. The ion 

bombardment through the mask consisting of 

nanospheres was performed using 10 keV He + -ions 

and with a dose D = 10 15 He + /cm 2 . Inset shows 

Fourier's transform of the image: the hexagonal 

symmetry of the domain distribution is also confirmed by the clear sixfold symmetry visible in the 

Fourier transform image. 


[1] F. Stobiecki, M. Urbaniak, B. Szymański, J. Dubowik, P. Kuświk, M. Schmidt, T. Weis, 

D. Engel, D. Lengemann, A. Ehresmann, I. Sveklo, A. Maziewski, Appl. Phys. Lett. 92, 012511 

(2008) 

[2] M. Urbaniak, F. Stobiecki, B. Szymański, A. Ehresmann, A. Maziewski, M. Tekielak, J. Appl. 

Phys. 101, 013905 (2007) 

[3] J. Dubowik, I. Gościańska, A. Szlaferek, and Y. V. Kudryavtsev, Materials Science-Poland 25, 

583 (2007) 

[4] M. Urbaniak, J. Appl. Phys. 104, 094909 (2008) 

[5] P. Kuświk, B. Szymański, M. Urbaniak, F. Stobiecki, I. Sveklo, J. Kisielewski, A. Maziewski, J. 

Jagielski, Act. Phys. Pol. A, 115, 352 (2009) 

[6] W. Glapka, P. Kuświk, I. Sveklo, M. Urbaniak, K. Jóźwiak, T. Weis, D. Engel, A. Ehresmann, 

M. Błaszyk, B. Szymański, A. Maziewski, F. Stobiecki, Act. Phys. Pol. A, 115, 348 (2009)

Multifunctional Dielectric Materials: 

Multiferroics, Ion Conductors and Their Composites with Polymers 

Czesław Pawlaczyk 

Ferroelectrics Laboratory 

Multiferroics: materials exhibiting simultaneously at least two types of long range order 

(ferroelectric, ferromagnetic, ferroelastic) 

⇓⇓⇓ 

coexistence of various order parameters 

spontaneous polarization P, magnetization M, deformation ηηηη 

Magnetoelectrics 

P & M 

Application: new generation of spintronic devices 

and magnetoresistive random access memories 

Studies: aimed at increase in magnetoelectric 

coupling of room-temperature magnetoelectrics via 

doping or combining with perovskites/spinels. 

Methods: dielectric and magnetic response, XPS, 

TEM, vibrational spectroscopy. 

Example: BiFeO3 nanopowders obtained by mechanosynthesis. 

Average structure: rhombohedrally 

distorted perovskite, grains of core-shell structure 

and mean size 20-25 nm. 

Annealing results in crystallization of the amorphous 

shell and increase in the mean grain size to 26-42 

nm. 

Local structure: Temperature dependence of the 

Raman bands of E(TO) & E(LO) symmetry shows 

anomaly at Néel temperature: 

ν [cm -1 ] 

520 

510 

500 

490 

480 

470 

References: 

MS 120 h Annealed 1h @773K 

T N 

0 100 200 300 400 

T [K] 

1. I.Szfraniak, M.Połomska, B.Hilczer, A.Pietraszko, 

L.Kępiński, Characterization of BiFeO3 nanopowders 

obtained by mechanochemical synthesis, J. Eur. Ceram. 

Soc., 27, 4399 (2007) 

2. I.Szafraniak-Wiza, W.Bednarski, S. Waplak, B.Hilczer, 

A.Pietraszko, L.Kępiński, Multiferroic Nanoparticles 

Studied by ESR, X-Ray Diffractionand Transmitssion 

Electron Microscopy, J. Nanosci. Nanotechnol., 9, 3246 

(2009) 

Ferroelectrics-ferroelastics 

P & ηηηη 

The Problem: phase transitions related to proton 

ordering in a hydrogen bond network. In 

MxHy(XO4)(x+y)/2 crystals (X=S, Se; y=1, 2, 3) a 

change in the proton order can result in ferroelastic 

and/or ferroelectric phases. 

Methods: dielectric and vibrational spectroscopy, 

DSC, XRD, optical imaging. 

Examples: (NH4)3H(SeO4)2 with isolated dimmers 

shows a sequence of ferroic phases and “ferroelastic 

domain structure memory”. 

bIV 

bIII 

aIII 

aIV 

ferroelast ferroelast superionic 

+ferroelectr 

CC (IV) C2/c(III) R3 (II) R-3m (I) 

181 275 300 332 

PHASE I, II 

(-3 1 0) 

I 

I 

T [K] 

PHASE III 

(3 1 0) 

⇐ 

⇓ ⇑ 

PHASE III 

(3 1 0) 

PHASE IV 

(3 -1 0) 

( 0 1 0 ) 

⇒ 

CsDSO4 crystal with protons ordered in infinite 

chains exhibits pretransitional effects: new ferroelastic 

domains and anomalies in ν(DSO) and ν4(SO4) 

Raman bands appear few degree below the transition 

to the paraelastic phase (420 K). 

Wavenumber [cm -1 Wavenumber [cm ] 

-1 ] 

840 

830 

820 

ν(SOD) νν 

(SOD) 

405 410 415 420 T [K] 425 

References: 

1. M.Połomska, A.Pietraszko, A.Pawłowski, J.Wolak, 

L.F.Kirpichnikova, Ferroelastic domain structure in 

some superprotonic conductors, Ferroelectrics, 376, 1- 

18 (2008) 

bIII

Ion conductors > solid electrolytes > proton conductors > 

anhydrous proton conductors 

(materials with proton conductivity without help of water molecules; 

potential application as membranes in hydrogen fuel cells) 

Crystalline hydrogen 

selenates and sulphates 

Acid salt electrolyte-based fuell cell offers some 

advantages over a polymeric one (no water 

management necessary, relaxed purity requirements 

on H fuel, increased catalyst activity, waste heat 

easier to manage) 

The crystals undergo structural, superprotonic 

phase transition at TS. Due to the change 

additional, structurally equivalent positions for 

protons appear in the structure. 

Methods: dielectric response, impedance 

spectroscopy, XRD, Raman spectroscopy, optical 

microscopy. 

Example: M3H(XO4)2 (M=NH4, Cs, Rb; X=S, Se) 

TTS: dynamically dis- 

ordered H-bond network 

This results in a stepwise increase in the proton 

conductivity: 

Reciprocal temperature dependence of the proton conductivity in 

the selenate crystals 

Our studies aim at understanding physical 

properties of the proton conductors: a mechanism 

of the proton conductivity and a role of ferroelastic 

properties in the transformation to the superprotonic 

phase. We also synthesize new crystals looking for 

materials with the best conductivity parameters. 

References: 

1. A. Pawłowski, Cz. Pawlaczyk, B. Hilczer, Electric 

conductivity in crystal group Me 3H(SeO4)2 (Me: NH4 + , 

Rb + , Cs + ), Solid State Ionics 44, 17 (1990) 

2. A. Pawłowski, M. Połomska, Fast proton conducting 

hydrogen sulfates and selenates: Impedance 

spectroscopy, Raman scattering and optical 

microscope study, Solid State Ionics 176, 2045 (2005) 

400 

-Z'' [kΩ] 

200 

Materials with 

heterocycle molecules 

5-membered heterpcycle molecules 

as e.g.: imidazole, C3H4N2 : 

triazole, methylimidazole and benzimidazole 

embedded in the crystalline or polymer structures 

can serve as proton solvents enhancing their proton 

conductivity. 

Materials studied: crystalline complexes of 

dicarboxylic acids and heterocyclic compounds, 

composites of biodegradable polymers and 

heterocycles (e.g. alginic acid and benzimidazole). 

Methods: X-ray diffraction (structure), impedance 

spectroscopy (conductivity), DSC and vibrational 

spectroscopy (molecular interactions). 

Examples: 

Imidazolium succinate: 

Joint pdfs maps for imidazole molecule (a) at 298K and (b) at 

330 K. 

2-methylimidazole glutarate (2-MIm GLU): 

800 

Z' [kΩ] 

400 

10 2 0 

10 4 

R 1 

10 6 

f [Hz] 

200 

-Z''[kΩ] 

10 2 0 

0 

0 200 400 

Z' [kΩ] 

600 800 

100 

10 4 

T=296 K 

R 2 

10 6 

f [Hz] 

An example of the impedance spectra for 2-MIm GLU at 296. 

References: 

1. K. Pogorzelec-Glaser, Cz. Pawlaczyk, A.Pietraszko 

and E. Markiewicz, Crystal structure and electrical 

conductivity of imidazolium succinate, Journal of 

Power Sources, 173, 800 (2007) 

2. P Ławniczak , K Pogorzelec-Glaser, Cz Pawlaczyk, 

A Pietraszko, L Szcześniak, New 2-methylimidazole- 

dicarboxylic acid molecular crystals: crystal structure 

and proton conductivity, J. Phys.: Condens. Matter 

21, 345403 (2009)

Liquid Crystals – Long History and Nowadays Everyday Applications 

Wojciech JeŜewski 

Molecular Interactions Laboratory 

Over a century, liquid crystals (LCs) continue to concentrate interest of both scientists and 

engineers. The answer to the question ‘why’ lies in amazing features of these materials, often 

called as ‘crystals that flow’. This expression seems to be paradoxical, but adequately 

characterizes LCs as substances that have an ability to flow, like conventional liquids, and 

that may exhibit long-range ordering, like solid crystals. Well-known examples of LCs are 

solutions of soap and various detergents, but also membranes of biological cells, some 

proteins, or the tobacco mosaic virus. When being stabilized in vessels, especially in thin 

cells, LCs can form various structures which, in contrast to structures of solid crystals, display 

only partial ordering with respect to positions or orientations of molecules. This is a 

consequence of strongly asymmetric shapes of molecules constituting LCs. Indeed, molecules 

that reveal a tendency to arrange in LC structures exhibit forms of long rods, boomerangs or 

bananas, ramified rod-like structures, flat disks, etc. More precisely, such molecules usually 

consist of a rigid part, being mainly 

responsible for aligning of molecules, and 

one or more flexible parts inducing, to a 

large extent, fluidity of a whole LC 

substance. A large variety of possible 

strongly asymmetric, directionally 

dependent (anisometric) shapes of 

molecules is reflected in their specific 

orientation and/or spatial orderings. As a 

result of the occurrence of anisotropic 

couplings between molecules on the one 

hand and the influence of walls of cells or 

vessels on the stabilization of structure of 

LC substances on the other hand, these 

substances form ordered regions or 

domains oriented in different directions. 

Such a complex multi-domain molecular 

arrangement of LC samples can easily be 

viewed under a microscope using polarized 

light. Then, the domains are revealed as 

contrasting areas organized into complex 

patterns. These patters, referred to as 

textures, are characteristic for particular 

substances, their molecular structures and 

orderings. Examples of different textures 

of LCs are illustrated by optical 

micrographs alongside the text. The 

assignment of a given type of texture to an 

appropriate kind of molecular order is an 

art requiring further investigations. 

However, the mere overall picture of the 

textures shows a very important property 

of LCs: the capability to create images of 

strong color saturation and high contrast. 

Another important optical property of LCs 

is a quick reorientation of molecules under 

an applied voltage and thereby a quick 

Examples of LC textures. Microphotographs 

were made in the Laboratory of Molecular 

Interactions of the Institute. 

change of the gray level or colors of images appearing in a consequence of lighting. This 

simple mechanism to control molecular orientation states and to generate high quality pictures 

plays a basic role in applications of LC materials in displays, visual screens, monitors, and TV

sets. Similar electro-optical mechanisms are used to develop other LC based display and nondisplay 

devices. Examples are ultra-fast integrated electronic electro-optic modulators 

necessary for ultra-fast optical switching (between orientation states of LCs) in 

telecommunication, computing, and navigation equipment. Other mechanisms of controlling 

states of LCs take advantage of effects of variations of molecular orientation in some liquid 

crystalline materials, and thereby a modification of their color, under changing temperature as 

well as under stretching or stressing. These effects are exploited, e.g., in thermometers and 

devices to measure stress distribution patterns. In a view of recent researches, potential 

applications of LCs are much wider. Very promising research fields that involve newly 

synthesized LC substances and/or new control methods are a programmable multi-frequency 

magnetic field approach to store large numbers of bits of information, the use of LCs on 

substrates with nanoimprinted topography in display devices of very low power consumption, 

or the employment of optical techniques of controlling distinct changes in orientation of 

molecules within interfacial (contacting) LC layers in sensors and noanostructure devices. 

The research program of the Laboratory of Molecular Interactions includes the elaboration 

and development of experimental methods to determine physical quantities describing 

dynamic and optical properties of LCs of various structures, research of different types of 

positional and orientational orders of molecules, especially in newly synthesized LC 

substances, studies of thermal and dynamic (induced by applied voltages) behaviors of LCs 

displaying complex, defected structures, investigations of electro-optic phenomena, studies of 

a methodological nature, etc. All these research fields have not only basic scientific character 

but are very important for developing modern LC technologies. The equipment of the 

Laboratory enables studies of both dielectric and electro-optic properties of LCs, registering, 

respectively, currents flow and light transmission 

through samples in the presence of alternating 

applied voltages. Recently, the laboratory has 

succeeded in developing a new method to 

register electro-optic response of LCs in a local 

manner, i.e., to measure variations of intensity of 

light passing small parts of thin samples being 

under an influence of alternating applied voltage. 

This has provided the opportunity to indicate that 

a contact of LCs with gas causes a relatively 

large-distance modification of electro-optical 

properties of LCs, and that this modification 

strongly depends on the shape of the LC-gas 

contact surface. The shape of the contact surface 

has been shown to be thermally controllable and 

to be conditioned by appropriate preparation of 

bounding surfaces of cells filled (in part) with a 

LC material. Micrographs presented on this page 

illustrate different configurations of the contact 

surface between a LC material and air. The 

application aspect of this research is that the use 

of LC cells containing even small amounts of gas 

in microdisplay devices can lead to reducing 

energy consumption of such devices. 

Microphotographs showing complex 

contact surfaces between a LC and air 

(visible as black areas) in thin cells.

Unconventional GMR Structures for Magnetoelectronics 

Tadeusz Luciński 

Surface Physics and Tunneling Spectroscopy Laboratory 

Conventional electronic devices work on the basis of electrical currents, i.e., they use 

the charge of the electron. Recently, researchers began investigating devices which 

functionality depends not only on electron charge but also on electron spin. Since spins are 

responsible for magnetic phenomena, it gives a potentially new dimension to future magnetic 

devices. In the foregoing decade a number of artificial layered structures have been designed 

to study the spin polarized transport or to exploit the specific response of the system for 

sensing a magnetic field in devices. 

Here we present the results of our investigations concerning the improvement of the 

magnetoresistive properties of layered magnetic thin films consisting of two or more 

ferromagnetic layers (F) separated by nonferromagnetic spacer layers (S). These systems, for 

metallic spacer layer, with thicknesses in the nm-range may exhibit the Giant Magneto 

Resistance (GMR) i.e., a property, which is important both for the basic understanding of 

spin-dependent magnetotransport as well as for their application in sensors and data storage 

technology. The main requirement to observe the GMR effect is the mutual rotation of the 

magnetizations in adjacent ferromagnetic layers from their noncolinear (usually antiparallel) 

to parallel configurations induced by magnetic field. There are several strategies to realize the 

GMR effect. The first and the oldest one is the utilization of the antiferromagnetic coupling 

between ferromagnetic layers which provides, for the certain spacer layer thickness, the 

antiparallel configuration of magnetization direction in adjacent ferromagnetic layers. In the 

second strategy one can use the ferromagnetic materials with different coercive fields 

(HC1≠HC2). Then the antiparallel magnetization configuration occurs for external magnetic 

fields HC1

a) 

b) 

Co2 

CuAgAu 

Co1 

Ni80Fe20 

CuAgAu 

Co 

CuAgAu 

Ni80Fe20 

*10 

-10 -5 0 

H (Oe) 

5 10 

Figure 1. The examples of GMR(H) characteristic of NiFe(3.5 nm)/Co1(2.5 nm)/CuAgAu(2.04 nm)/Co2(2.5 

nm) sandwich (a) and [NiFe(2 nm)/CuAgAu(2.5 nm)/Co(0.75 nm)]*10 multilayer (b) with highest GMR field 

sensitivities. 

between RKKY-like exchange coupling and the magnetostatic orange-peel coupling. We 

have shown that the values of the ferromagnetic coupling between Ni80Fe20/Co1 and Co2 for a 

constant CuAgAu spacer layer thickness can be either enhanced or reduced depending on the 

ratio between Co1, Co2 and Ni80Fe20 thicknesses. Therefore, the examined layered structures 

could be of interest for second generation of the GMR sensors since, their characteristics can 

be tailored by tuning the magnetic layer thickness. 

MnIr 

CoFe2 

NiFe 

Cu 

NiFe1 

Cu 

CoFe1 

MnIr 

GMR (%) 

4 

3 

2 

1 

0 

H (Oe) 

Figure 2. GMR(H) and magnetization M(H) characteristics of MnIr/CoFe1(1.6 nm)/Cu(3.3nnm)/Py1(1.4 

nm)/Cu(3.3 nm)/Py2(0.5 nm)/CoFe2(1.4 nm)/MnIr asymmetric dual spin-valve. Three different magnetization 

configurations are numbered and sweeping directions are indicated by gray arrows. 

In some applications of the GMR effect, the multilayer structures with special 

resistance characteristics on magnetic field R(H) are required. The most promising systems, 

which have already found a practical application, are spin-valve structures. We proposed a 

new layered system with two different ferromagnetic materials used as pinned layers in dual 

exchange biased structure (asymmetric dual spin-valve) 

GMR (%) 

GMR (%) 

6 

4 

2 

CoFe2/Py2 

Py1 

CoFe1 

3 

CoFe1 

8 

6 

4 

2 

0 

5.2 %/Oe 

-30 -20 -10 0 10 20 30 

2 

H (Oe) 

6.8%/Oe 

M(H) 

GMR(H) 

-1000 -750 -500 -250 0 250 

1 

Py1 

Py2/CoFe2 

M (a.u.)

MnIr/CoFe1/Cu/NiFe1/Cu/NiFe2/CoFe2/MnIr deposited onto thermally oxidized Si(100). 

Since in this structure the different ferromagnetic layers are exchange coupled to 

antiferromagnetic MnIr layer therefore we expected that there will be a different exchange 

coupling fields Hex between MnIr and CoFe1 and Py2/CoFe2 layers. We have shown that for 

properly chosen structure, with certain pinned layer thicknesses, of the dual spin-valves a 

novel three stages GMR(H) characteristic can be realized - three state logic system (Fig.2). 

The GMR effect can also be realized in layered structures with a use of an artificial 

antiferromagnet instead of antiferromagnetic layer. Since we have found that very strong 

antiferromagnetic coupling J=−1.93/m 2 accompanied by saturation field of 1.5T can be 

realized in Fe/Si multilayers therefore we applied this system as an artificial antiferromagnet 

in magnetoresistive (Fe/Si)15/Fe/Co1/Cu/Co2 pseudo-spin-valve (Fig. 3). We have used 

Co1/Cu/Co2 trilayer as the magnetoresistive structure with Co1(2) and Cu thicknesses of 

about 1.5 nm and 2.5 nm, respectively. The last Fe and the Co1 layers are in the intimate 

contact and therefore Fe/Co1 bilayer behaves as a first magnetoresistive layer in the 

examined structure. The field dependence of the sample resistance, shown in Fig. 3, reflects a 

typical GMR behavior. As can be seen, there are two switching fields: H1 related to the 

magnetization reversal of the top Co2 layer and H2 due to switching of the pinned Fe/Co1 

bilayer. Since Fe/Co1 bilayer is AF coupled to the rest of Fe/Si Ml structure it reverses at 

higher fields than the top Co2 layer and an antiparallel arrangement between magnetizations 

of the Fe/Co1 bilayer and the Co2 layer occurs between H1 and H2. 

Co2 

Cu 

Co1 

(Fe/Si)15+Fe 

artificial 

antiferromagnet 

-200 -100 0 100 200 

H (Oe) 

Figure 3. Magnetoresistance effect of (Fe/Si)15/Fe/Co1/Cu/Co2 pseudo-spin-valve structure with Fe/Si 

multilayer used as the artificial antiferromagnet. 

R (ΩΩ) 

1.180 

1.175 

1.170 

1.165 

H 2 

H 1

The Molecular Gels and Heterocyclic Proton–Conducting Materials 

RESEARCH PROFILE: 

Jadwiga Tritt-Goc 

Nuclear Magnetic Resonance Laboratory 

Research in the Nuclear Magnetic Resonance Laboratory in last years has mainly been 

focused on the study of new molecular gels and heterocyclic materials based on the imidazole 

molecules. The gels represent an important class of functional materials with potential applications in 

template materials, biomimetics, as viscosity modifiers in applications such as paint, coatings, oil 

recovery, in controlled drug release and in a variety of pharmaceutical and hygienic applications. The 

imidazole based compounds are interesting as alternatives to polymer membrain electrolyte fuel cells. 

In particular, we are interested in the self-assembly of organic gelators into aggregates, diffusion and 

relaxation phenomena, the liqiud-surface interactions and microstructure. 

ACHIEVEMENT: 

In our studies of the gels the interest is focused on the role of the solvent in gel formation. 

Such knowledge is very important in order to design gels with the desired structure and 

physicochemical properties. The nature of the interaction between the solvent and the gelator is one of 

the most interesting questions in the organogel studies. Polysaccharide-containing gelator, 1,2-O-(1ethylpropylidene)-α-D-glucofuranose 

(1) was the subject of our interest. It is one of the simplest, 

smallest and the most efficient gelators which possess excellent gelator properties over a broad 

spectrum of organic solvent. The solvent effect on organogel formation by 1 in nitrobenzene, 

chlorobenzene, benzene and toluene was studied by different methods. The FT-IR spectroscopy 

revealed that hydrogen bonding is the main driving force for gelator self-aggregation and gel 

formation. The gels are characterized by different hydrogen-bonding patterns, which are reflected in a 

different observed microstructure of the networks as observed by Optical polarization microscopy. 

The morphology of fibers of nitrobenzene organogel consists of straight, rod-like, and thinner fibers, 

in comparison to the elongated but generally not straight, and thicker fibers in the chlorobenzene 

organogel. The thermal stability of gels also differs and the ∆H is equal to 50.1 65.0, 72.2, and 50 

kJ/mol for nitrobenzene, chlorobenzene, toluene and benzene gels, respectively. The properties of the 

gels were correlated with different solvent parameters: the solubility parameter, δ, the solvent polarity 

parameter, ET(30), and the dielectric constant, ε. The Tgel value of the gel-material linearly decreases as 

δ and ET(30) increases but an exponential decrease of Tgel was observed as a function of the ε 

increase. We have shown that the polarity of the solvent influences the thermal stability of the gel, the 

hydrogen bonding network and finally the structure of gel network. 

The most important result concerns the study of the dynamics of toluene confined in the gel. 

Thanks to the 1 H field-cycling nuclear magnetic resonance relaxometry we were able to measure the 

spin-lattice relaxation time as a function of the magnetic field strength (expressed in the Larmor 

frequency scale) and temperature. The observed dispersion in the frequency range 10 kHz – 40 MHz 

gives strong evidence of the interaction between the toluene and the gelator aggregates. The data were 

interpreted in terms of the two-fraction fast-exchange (TFFE) model. Our results finally gave an 

answer to the until now not resolved question as to the interaction between the solvent and gelator in 

the gel system.

Gel formation and its microstructure 

Proton-spin lattice relaxation rates of toluene in 1,2-O-(1-ethylpropylidene)-α-D-glucofuranose gel (1 

– gel created with cooling rate 5 Kmin -1 , 2 – gel created with cooling rate 15 Kmin -1 ) measured as a 

function of the magnetic field strength at 223 K. The solid lines present the best fit of the two-fraction 

fast-exchange (TFFE) model to the experimental points. The dashed and dotted lines lines reflected 

the contribution from the bulk toluene, and the motionally-altered fraction of toluene (ring and CH3 

protons) in gel 1 and 2, respectively. 

SELECTED PUBLICATION: 

M. Bielejewski and J. Tritt-Goc, Evidence of solvent-gelator interactions in sugar-based organogel 

studied by Field-Cycling NMR relaxometry, Langmuir, 26, 17459- 17464(2010). 

M. Bielejewski, A. Łapiński, R. Luboradzki, J. Tritt-Goc, Solvent effect on 1,2-O-(1-ethylpropylidene)α-D-glucofuranose 

organogels properties, Langmuir, 25, 8274-8279 (2009). 

J. Kowalczuk, S. Jarosz and J. Tritt-Goc, Characterization of 4,6-O-(p-nitrobenzylidene)-α-Dglucopyranoside 

hydrogels and water diffusion in their networks, Tetrahedron 65, 9801–9806 (2009). 

J. Tritt-Goc, M. Bielejewski, R. Luboradzki, A. Łapiński, Thermal properties of the gel made by low 

molecular weight gelator 1,2–O-(1-ethylpropylidene)-α-D-glucofuranose with toluene and molecular 

dynamics of solvent, Langmuir, 24, 534-540 (2008). 

M. Bielejewski, A. Łapiński, J. Kaszyńska, R. Luboradzki, J. Tritt-Goc, 1,2-O-(1-Ethylpropylidene)-α- 

D-glucofuranose, a low molecular mass organogelator: benzene gel formation and their thermal 

stabilities, Tetrahedron Lett. 49, 6685-6689 (2008). 

A. Rachocki, K. Pogorzelec-Glaser, J. Tritt-Goc, 1 H NMR relaxation studies of protonconducting 

imidazolium salts, Appl. Magn. Reson. 34, 163-173 (2008). 

A. Rachocki, K. Pogorzelec-Glaser, A. Pietraszko, J. Tritt-Goc, The Structural Dynamics in the 

Proton–Conducting Imidazolium Oxalte, Journal of Physics: Condensed Matter 20, 505101 (2008).

Charge and Spin Transport in Carbon Nanostructures 

Stefan Krompiewski 

Laboratory "Theory of Nanostructures" 

The Theory of Nanostructures Laboratory specializes in spintronic oriented studies, aiming at 

making use of the spin degree of freedom for controlling an electronic transport. The research 

of the Laboratory is particularly focused on carbon nanostructures like nanotubes and 

graphene. The most important achievements in this field, in recent years, have been related to 

investigations of the effect of external magnetic field, doping, chirality, coupling with 

electrodes as well as electron correlations on electrical conductance and current-voltage 

characteristics of the carbon nanostructures. The electron correlation effects are revealed very 

pronouncedly in the Coulomb blockade transport regime (Fig. 1) and in the Kondo limit 

(Fig.2). 

Fig.1a Carbon nanotube conductance with two 

paramagnetic electrodes, as a function of bias 

and gate voltages, in the Coulomb blockade 

regime 

Rys. 2a Spin polarized conductance of the 

carbon nanotube quantum dot in the Kondo 

regime 

Rys. 1b Spin current flowing through a carbon 

nanotube, with one paramagnetic and one 

ferromagnetic electrode 

Rys. 2b Conductance of the nanotube quantum dot 

as a function of voltage and magnetic field, 

compared with an experiment (Inset) 

Especially intensive studies have been devoted to the so-called giant magnetoresistance 

(GMR) in both carbon nanotubes and graphene sandwiched between ferromagnetic 

electrodes. In particular, the GMR effect has been studied for different current directions in 

the honeycomb type lattice, and for various aspect ratios (width/length) of graphene ribbons. 

It has been also shown that the interface (Ni, Co)/graphene acts as an effective spin filter, 

leading to ca 100% spin-polatization of the current (even in the presence of disorder). This is 

illustrated in Fig. 3.

Number of atomic layers 

Fig. 3 Magnetoresistance of nickel-graphene-nickel junctions of the perfect system, as well as disordered ones: 

with imperfections (right hand side) and vacancies (bottom) 

Significant part of this research was carried out within the framework of the European project 

Carbon Devices at the Quantum Limit (CARDEQ) 

Selected publications 

1. S.Krompiewski, Semiconductor Science and Technology 21, S96-S102 (2006) 

2. V. M. Karpan, G. Giovannetti, P. A. Khomyakov, M. Talanana, A. A.Starikov, M. Zwierzycki, 

J. van den Brink, G. Brocks, and P. J. Kelly, Physical Review Letters 99, 176602 (2007) 

3. S. Krompiewski, V. K Dugaev, and J. Barnaś, Physical Review B 75, 195422 (2007). 

4. D. Krychowski, S. Lipiński, and S. Krompiewski, Journal of Alloys and Compounds 

442, 379 (2007) 

5. S. Krompiewski, Nanotechnology 18, 485708 (2007) 

6. S. Lipinski and D. Krychowski, J. Magn. Magn. 310, 2423 (2007) 

7. I. Weymann, J. Barnaś, and S. Krompiewski, Physical Review B 78, 035422 (2008) 

8. S. Krompiewski, Physical Review B 80, 075433 (2009)

Magnetism of Metastable Metallic Structures 

B. Idzikowski, B. Mielniczuk, Z. Śniadecki 

Magnetic Alloys Laboratory 

Some metallic glasses exhibit phase transitions involving complex magnetic ordering kinds 

(i.a. spero-, aspero-, sperimagnetism, spin glass state, mictomagnetism etc.). Due to their 

metastable crystalline structure it is interesting to investigate crystallization processes during 

their thermal activation and, for example, the electron transport mechanisms, characterized, 

i.a., by a negative value of the electric resistance temperature coefficient. At the Institute of 

Molecular Physics of the Polish Academy of Sciences (IFM PAN), one disposes of two 

technologies of producing amorphous alloys: rapid liquid quenching (melt spinning) in the 

form of ribbons and vacuum casting (suction casting) of multiple metallic alloys in the form 

of rods. Apparatus enabling one to perform measurements of calorimetric, structural, 

magnetic and electric transport properties are available. 

Lately, we have demonstrated that in the process of rapid liquid quenching it is 

possible to produce not only the stoichiometric inter-metallic compounds of metastable 

crystalline structure, but also multiple alloys of amorphous and mixed structure (amorphous 

plus crystalline phase/phases) [1-5]. 

The current subject of our investigations concerns the alloys R-TM-M of 

stoichiometry 1:6:6 containing rare earth ions (R = Dy, Y or La), transition metal 

(TM = Fe, Mn) and addition of other metal or metalloid (M = Al, Ge). The choice of elements 

shall conform to simple empirical rules (Fig. 1) which ensure the structural metastability for a 

given material. The alloy should contain at least three components; so, the multiple 

component alloys are preferred. With the increase in the number of components of various 

atomic sizes, a crystalline structure that could form in principle undergoes destabilization and 

an amorphous structure is formed. The diversity in atomic diameters should excess 12%. The 

last rule, introduced by A. Inoue, concerns the enthalpy of mixing of the main alloys 

components. The heat of mixing of the individual components should take negative values. 

The mechanism related to the repulsive interactions between some alloy components with 

positive enthalpy of mixing values are of some significance, as well [4, 5]. 

atomic radii 

differences 

( >12 %) 

multicomponent 

alloys 

( > 3) 

amorphous 

negative heat 

of mixing 

Fig. 1. Rules of choice of alloy components which favor the forming of the amorphous alloys 

(after A. Inoue, Acta Mater. 48 (2000) 279). 

The origin of the ordering of the spin glass type lies in a random distribution of 

magnitudes and signs of neighboring magnetic moments. It can follow a random distribution 

of magnetic ions, encountered in amorphous alloys, interacting with each other via RKKYtype 

coupling. Hence, in some cases they are coupled antiferromagnetically. This kind of 

ordering is characterized by a peak in the magnetic susceptibility as a function of temperature

at a freezing temperature Tf. This comes from a thermal blocking of the fluctuating magnetic 

moments. Yet another kind of magnetic ordering is related with the spin glass: 

mictomagnetism. The term cluster-spin-glass describes somewhat better the nature of the 

latter (see Fig. 2). 

Fig. 2. Mictomagnetic structure, schematically. 

The ions forming the alloy exhibit coupling within small clusters due to the direct 

dipolar coupling (Fig. 2). The clusters are coupled with each other by, e.g., RKKY-type 

interactions through a matrix with frustrated magnetic interactions. The resultant magnetic 

moments of the clusters are frozen, as in the case of spin glass, below a definite temperature 

at which the thermal energy becomes lower than that of the exchange interactions. In addition, 

due to the variations of the sizes of the clusters, in the magnetic susceptibility χ(T) as a 

function of temperature a spread out of the peak at the freezing temperature can be observed, 

which is not the case of spin glasses. 

Another characteristic of the mictomagnetics is a specific dependence of 

magnetization on the magnetic history of the sample. Cooling of the sample in a relatively 

weak magnetic field (of the order of 1 T) forces the freezing of magnetic moments of the 

clusters in the field direction when passing through Tf. It can be observed, i.a., when 

measuring M(H) as a shift (asymmetry) in the hysteresis loop on the axis of the applied field 

following the cooling of the sample below Tf in the presence of magnetic field (Fig. 3). 

M [µ B /f.u.] 

4 

2 

0 

-2 

-4 

-1.47 T 

1.12 T 

-9 -6 -3 0 3 6 9 

µ 0 H [T] 

shift of hysteresis 

loop approx. 0.17 T 

Fig. 3. Magnetization as a function of magnetic field for the DyMn3Ge3Fe3Al3 sample 

initially cooled in the field B = 1 T down to T = 2 K. Measurement performed at 2 K. 

The DyMn3Ge3Fe3Al3 sample was investigated at Le Mans, France (in collaboration 

with Dr J.-M. Greneche) by Mössbauer effect in an applied magnetic field. It was aimed at 

observing the magnetic fluctuations testifying for the existence of the mictomagnetic 

ordering. During the measurement at 77 K, the magnetic field of induction 0.04 T was applied 

perpendicularly to the γ-ray beam and in parallel to the surface of the sample. The anomalous 

values of the mean hyperfine field found confirm the formation of magnetic clusters.

elative transmission 

relative transmission 

1.00 

0.99 

0.98 

0.97 

1.00 

0.99 

0.98 

0.97 

without external magnetic field 

77 K 

77 K 

B = 0 T 

-3 0 

v [mm/s] 

3 

applied magnetic field 

B = 0.04 T 

-3 0 

v [mm/s] 

3 

a) 

b) 

Fig. 4. Mössbauer spectra of DyMn3Ge3Fe3Al3 sample measured at 77 K without (a) 

and with applied magnetic field (b) of induction B = 0.04 T. 

In the spectrum shown in Fig. 4 there are visible marked variations in relative 

intensities of the magnetic components (sextets – at both sides of the spectrum) and in the 

paramagnetic component (doublet – central peak). After applying a weak, constant magnetic 

field, the intensity of the sextets increases. The measurement at 77 K in the presence of 

magnetic field shows an increase in the share of the magnetic component from 36 to 45%. 

Such a behavior indicates a spin glass-type structure of magnetic moments on clusters 

(mictomagnetism) and not that of moments on single atoms. 

1. P. Kerschl, U.K. Röβler, T. Gemming, K.-H. Müller, Z. Śniadecki, B. Idzikowski, 

“Amorphous states of melt-spun alloys in the system Dy(Mn,Fe)6(Ge,Al)6“, Appl. Phys. 

Lett. 90 (2007) 031903 

2. Z. Śniadecki, B. Idzikowski, J.-M. Greneche, P. Kerschl, U.K. Röβler, L. Schultz, 

“Independence of magnetic behavior for different structural states in melt-spun DyMn6xGe6-xAlxFex 

(0≤x≤6)”, J. Phys.: Condens. Matter 20 (2008) 425212 

3. Z. Śniadecki, B. Idzikowski, “Calorimetric study and Kissinger analysis of melt-spun 

DyMn6-xGe6-xFexAlx (1≤x≤2.5) alloys”, 

J. Non-Cryst. Solids 354 (2008) 5159 

4. Z. Śniadecki, U.K. Röβler, B. Idzikowski, „Activation energies of crystallization in 

amorphous RMn4.5Ge4.5Fe1.5Al1.5 (R = La, Y, Dy) alloys” Acta Phys. Pol. A 115 (2009) 

409 

5. Z. Śniadecki, B. Mielniczuk, B. Idzikowski, J.-M. Greneche, and U. K. Rößler 

”Mechanism of amorphous state formation, crystalline structure, and hyperfine 

interactions in DyMn6−x Ge6Fex (0≤x≤6) alloys”, J. Appl. Phys. 108 (2010) 073516

Thermoelectric Power in Ce-based Compounds 

Tomasz Toliński 

Magnetic Alloys Laboratory 

The Seebeck effect (thermoelectric power - TEP) is a conversion of heat to the electricity. 

In a closed electrical circuit composed of different materials a thermoelectric power is 

induced if the contacts between the materials are in different temperatures. 

TEP is widely used in the production of the temperature sensors or high efficiency electrical 

cells, working as the electrical current generators or the cooling components. It implies 

applications in air-conditioning, cooling systems and thermostats. 

Our research concerns the thermoelectric properties of the Ce-based compounds, with a 

special emphasis on the studies of the basing mechanisms contributing to TEP. 

Thermoelectric power: CeNi4In, CeNi4Ga vs. CeCu4In, CeCu4Ga 

Thermoelectric power is connected with the density of states at the Fermi level Nd(EF) by the 

relation: 

The assumption that Nd(EF) is of the Lorentzian shape allowed us to interpret TEP of the Nibased 

compounds (Fig.1, right panel); however, it was necessary to consider two peaks near 

the Fermi level [1] and the classical linear term. It leads to the formula [2]:

In this way, the positions of the peaks of the density of states at EF were determined: Ef1 

=−1.8meV, Ef2 =1.35eV. 

In the compounds CeCu4In and CeCu4Ga (Fig.1) the Kondo effect is present (these 

compounds create the so called Kondo lattices). Additionally, the electric crystal field (CEF) 

influence can be important in these compositions. 

Usually, TEP in the Kondo lattices is described by the equation: 

neglecting the CEF effect and assuming Ef = TK (the so called Kondo temperature), Wf = 

πTK/Nf and Nf - degeneration 2J+1. 

In our analysis, we have successfully included CEF [1] assuming that it dominates the line 

width of the peak in the density of states, i.e. Wf = πTCEF/N, where TCEF is a measure of the 

splitting of the ground state by the crystal field. 

References: 

[1] T. Toliński, V. Zlatić, A. Kowalczyk, J. Alloys Compd. 490 (2010) 15. 

[2] M.D. Koterlyn, O. Babych, G.M. Koterlyn, J. Alloys Compd. 325 (2001) 6.

Toward Organic Solar Cell 

Andrzej Graja 

Division of Molecular Crystals 

Solar energy conversion is one of the most attractive topics for these years – it can contribute 

to solve energetic and environmental problems. Inorganic solar cells used at present are not 

ideal with respect to the cost, difficult technology as well as to problem of utilization. 

Fortunately, not long ago organic or molecular solar energy converters have been discovered. 

These new converters are exempted from all disadvantages of inorganic energy converters but 

have several important advantages such as easy accessibility and modification of structure or 

properties, environmental stability and harmless as well as cheapness. 

acceptor 

( C 60 ) 

e - hν 

Recent progress in organic synthesis allows us to manipulate and control processes 

important for solar energy conversion by linking adequate molecular donors and acceptors. 

Among wide variety of organic donor-acceptor complexes suitable for displaying 

photoinduced energy and electron transfer processes, the systems in which fullerene C60 

molecules are covalently linked to organic dyes working as electron-donor molecules have 

emerged as one of the most interesting and promising class of photoactive materials. 

The unique shape of the fullerene combined with its distinct physical properties make 

it a good candidate for preparation and functionalization of large supermolecular assemblies. 

Moreover, three-dimensional, conjugated system of fullerenes is able to transfer electrons 

very efficiently. On the other hand, organic dyes with their strong electronic absorption in the 

visible range, are some of the mostly used chromophores in photoactive molecular systems. 

Thus, detailed knowledge of the structure, electronic and molecular excitations as well as 

orientation of adequate transition moments are necessary for interpretation of energy or 

electron transfer processes. 

An important our attainment is collection and interpretation of unique data of several groups 

of organic photoactive systems containing the fullerene and various organic chromophores 

such as porphyrin-, thiophene -, and perylene-derived dyes. The overall value of these studies 

is an explanation of the spectral data for fullerene dyads and reference dye molecules, using 

infrared absorption and reflection–absorption methods, electronic and other unconventional 

spectral investigations, photocurrent measurements and wide use quantum chemical 

dye

investigations. Our studies of molecular organization and spatial orientation of the molecules 

in the thin films are particularly important. From conformational and spectral investigations, a 

strong correlation between the molecular structure of the investigated species and their 

electronic and vibrational spectra arises. The spectra of the dyads suggest a redistribution of 

charges on both fullerene and chromophore moieties. 

Choice of the best organic dyes as well as determination of the most favorable 

conditions are especially desirable for designing very efficient molecular solar energy 

converters and other photonic devices. 


1. D.Wróbel and A. Graja 

Modification of electronic structure in supramolecular fullerene-porphyrin systems studied by 

fluorescence, photoacoustic and photothermal spectroscopy. 

J. Photochem. Photobiol. A: Chemistry, 183, 79-88 (2006). 

2. K. Lewandowska, A. Bogucki, D. Wróbel and A. Graja 

IR reflection-absorption spectroscopic study of Langmuir-Blodgett films of selected porphyrins 

and their dyads to fullerene on gold substrates. 

J. Photochem. Photobiol. A: Chemistry, 188, 12-18 (2007). 

3. B. Laskowska, A. Łapiński, A. Graja and P. Hudhomme 

Spectral studies of new fullerens-tetrathiafulvalene based system. 

Chem. Phys., 332, 289-297 (2007). 

4. A. Graja, K. Lewandowska, B. Laskowska, A. Łapiński, D. Wróbel 

Vibrational properties of thin films and solid state of perylenediimide-fullerene dyads. 

Chem. Phys., 352, 339-344 (2008). 

5. B. Barszcz, B. Laskowska, A. Graja, E.Y. Park, T.-D. Kim, K.-S. Lee 

Vibrational spectroscopy as a tool for characterization of oligothiophene-fullerene linked dyads. 

Chem. Phys. Lett., 479, 224-228 (2009).

EPR and Conductivity Studies of Doped Protonic Conductors 

Stefan Waplak 

Division of Superconductivity and Phase Transition 

Solid acid compounds such as Me3H(XO4)2 family where Me = NH4, Tl, Cs, Rb, K; X = S, Se 

are studied for fuel cell application. These materials offer the advantages of the high value of 

protonic conductivity even at RT and can operate up to about 500K. Because the structural 

mechanism of conductivity is an intrinsic property of crystal lattice therefore the structural 

defects strongly influence on conductivity values. On the other hand the sample stability 

under temperature and humidity have to be correctly established for the results 

reproducibility. Our laboratory comes to original idea of fast proton conductors study. The 

idea resides essentially on studies of bulk (dielectric) and local parameters (EPR) versus an 

external conditions (humidity, electric field DC, AC) and paramagnetic defect types [1]. EPR 

spectroscopy allows to define the site position of paramagnetic defect, its coordination and 

concentrations. In addition EPR spectra are the best simple way to control a sample stability 

versus several cycles of heating/cooling and maximum temperature above of which the 

sample chemical/physical destruction is observed. This general idea is practically proved by 

ours last results on (NH4)3H(SO4)2 and Rb3H(SO4)2 doped with Mn 2+ paramagnetic ions. At 

first growing of conductivity by admixture has an original source generally. It is due to 

growing of vacancy number introduced by excess charge compensation of Mn 2+ ion which 

replaces monovalent NH4 or Rb, respectively. In (NH4)3H(SO4)2:Mn 2+ the concentration of 

4500 ppm increases the conductivity value over ten time. It is evoked by additional path for 

protons migrated along under DC field. The similar EPR and conductivity investigations in 

Rb3H(SO4)2:Mn 2+ have showed that the conductivity increasing due to divalent impurity has a 

general source of vacancy number growing in Me3H(XO4)2 crystal family [1,2].

EPR spectra anisotropy of the single-domain Rb3H(SO4)2:Mn 2 crystal recorded at 295 K: fresh 

sample (a) and after heating up to 500 K (b) An external magnetic field: B||a*. The (a) and 

(b) spectra comparison records the sample disproportion at the high temperature. 

[1] W. Bednarski, A. Ostrowski, S. Waplak Influence of Mn 2+ doping level on conductivity of 

(NH4)3H(SO4)2 superprotonic conductor. Solid State Ionic 179, 1974-1979 (2008) 

[2] A. Ostrowski, W. Bednarski, Proton dynamics in Rb3H(SO4)2 doped with Mn 2+ studied by 

EPR and impedance spectroscopy. Journal of Physics: Condensed Matter 21, 205401, (2009)

Molecular Spin Electronics 

Jan Martinek 


The field of molecular electronics emerged from the idea to use single molecule or group of 

such molecules as the active components of future electronic devices, which would operate 

analogical to key elements of today's microcircuits but would also provide some new 

functionality. We discuss a concept of molecular electronics exploiting carbon nanotubes and 

C60 molecules as molecular devices in the light of recent developments. One very interesting 

and promising group of such devices, which allow us to control and manipulate both a singleelectron 

and its spin, is ultra-small systems called quantum dots and single-electron transistors, 

where Coulomb interaction (Coulomb blockade) plays an important role. In quantum dots due 

to the control of a single electron charge, the possibility of manipulating of a single spin is 

opened up, which can be important for quantum computing. 

The manipulation of magnetization and spin is one of the fundamental processes in magnetoelectronics 

and spintronics, providing the possibility of writing information in a magnetic 

memory, and also because of the possibility of classical or quantum computation using spin. 

In most situations, this is realized by means of an externally applied nonlocal magnetic field, 

which is usually difficult to introduce into an integrated circuit. We propose to control the 

amplitude and sign of the spin-splitting of a quantum dot induced by the presence of 

ferromagnetic leads, using a gate voltage without further assistance of a magnetic field [1-3]. 

A conceivable realization of proposed system might be carbon nanotubes or other molecular 

systems in contact to ferromagnetic leads (ferromagnetic single-molecule transistor) [4]. New 

experimental results for a single carbon nanotube attached to nickel electrodes confirm the 

theoretical predictions [5]. 

1. J. Martinek, Y. Utsumi, H. Imamura, J. Barnas, S. Maekawa, J. König, and G. Schön, Phys. 

Rev. Lett. 91, 127203 (2003). 

2. J. Martinek, M. Sindel, L. Borda, R. Bulla, J. König, G. Schön, S. Maekawa, and J. von 

Delft, Phys. Rev. Lett. 91, 247202 (2003); Phys. Rev. B 72, 121302 (2005). 

3. M. Sindel, L. Borda, J. Martinek, R. Bulla, J. König, G. Schön, S. Maekawa, and J. von 

Delft, Phys. Rev. B 76, 045321 (2007). 

4. A. N. Pasupathy, R. C. Bialczak, J. Martinek, J. E. Grose, L. A. K. Donev, P. L. McEuen, 

and D. C. Ralph, Science 306, 86 (2004). 

5. J. R. Hauptmann, J. Paaske, and P.E. Lindelof, Nature Physics, (2008).

Local Superconducting Behavior of MgBx 

Z. Trybuła, W. Kempiński, Sz. Łoś, B. Strzelczyk, M. Trybuła, K. Kaszyńska, 

Division of Low Temperature Physics 

(in Odolanów) 

The activity of the Division of Low Temperature Physics concentrates on low temperature 

(down to 0.3K) studies: investigation of transport and physical properties of nanocarbon materials 

(nanotubes, fullerenes, carbon fibres) and superconductors, dielectric investigation of proton glass 

system, low temperatures properties of quantum paraelectric so-called incipient ferroelectric. 

One of our investigation are focused on superconductivity of MgB2, formation and evolution of 

superconducting regions [1-5]. Since the discovery of superconductivity in an intermetallic compound 

MgB2 [6] with transition temperature as high as 39 K, considerable progress has been made in the 

understanding of the properties of this material. One of our significant achievements was the 

experimental evidence of superconducting island of MgB2 far from the percolation threshold of the 

bulk superconducting MgB2 sample. 

A new attempt to synthesize MgB2 superconducting phase was used. Samples were prepared in 

order to define evolution of the superconducting phases after B ions implantation into the Mg substrate 

or vice versa followed by transient annealing using high intensity pulsed plasma beam or conventional 

heating. 

To get more information about the local composition of the superconducting island, and on the 

electronic properties of the surface and the layers right below, the magnetically modulated microwave 

absorption (MMMA), magnetization, four-probe electric conductivity measurements, low temperature 

scanning tunneling microscopy and spectroscopy (LT STM/STS) methods were used as well as the ex 

situ room temperature atomic force microscopy (AFM) and the X-ray photoelectron spectroscopy 

(XPS) investigations over the MgB2 obtained by the B + implantation into the Mg substrate. 

Fig. 1. The temperature dependence of the MMMA signals for the 

polycrystalline boron implanted by magnesium [1]. 

Fig. 2. Josephson hysteresis loop at T = 5 K for the polycrystalline boron 

implanted by magnesium [1]. 

Figure 1 shows 

MMMA signals versus 

temperature. Below 26 K the 

MMMA signal increases. The 

superconducting transition 

with onset of Tc below 25 K is 

well defined. The Josephson 

hysteresis loop (JHL) 

presented in Fig. 2 is the 

confirmation that the zero field 

MMMA line is related to the 

superconducting state. The 

resistivity (Fig. 3) drops 

sharply at a temperature which 

is in good agreement with Tc 

obtained in MMMA 

experiment. However, Rmin from Fig. 3 and Fig. 4 does not reach the zero value of resistance because 

the percolation limit was not achieved, and superconducting grain (islands) of MgB2 are realized.

Fig. 3 Temperature dependence of the normalized 

resistance for the polycrystalline boron implanted 

by magnesium [1]. 

The low temperature scanning tunneling microscopy and 

spectroscopy (LT STM/STS) measurements, using a 

commercial scanning tunneling microscope CryoSXM 

Omicron and the home made cryostat, filled with the liquid 

helium allows to cool down the microscope workplace 

down to 2K, confirm the presence of the local islands of 

Fig. 5 The scanning tunneling spectroscopy (STS) spectra 

of the MgBx surface sample: 

(a) sample in the normal state (room temperature); 

(b) sample in the superconducting state (9–13 K). 

Fig. 4 Resistance temperature dependences of 

the MgBx samples obtained by magnesium ion 

implantation into the bulk polycrystalline 

boron substrates.for three different annealing 

temperatures. 

superconducting structure MgB2 in MgBx materials. We get the information about the energy gap, 

∆=5meV, for MgB2, below the critical point (Tc=32 K) where the studied material is well defined as a 

superconducting one. 


[1] Z. Trybuła, W. Kempiński, B. Andrzejewski, 

L. Piekara-Sady, J. Kaszyński, M. Trybuła, 

J. Piekoszewski, J. Stanisławski, M. Barlak, and 

E. Richter, Acta Phys. Polon. A 109, 657 (2006). 

[2] B. Andrzejewski, W. Kempiński, Z. Trybuła, 

J. Kaszyński, J. Stankowski, Sz. Łoś, 

J. Piekoszewski, J. Stanisławski, M. Barlak, 

Z. Werner, P. Konarski, Cryogenics 47, 267 

(2007). 

[3] J. Piekoszewski, W. Kempiński, B. 

Andrzejewski, Z. Trybuła, J. Kaszyński, 

J. Stankowski, J. Stanisławski, M. Barlak, 

J. Jagielski, Z. Werner, R. Grötzschel, E. Richter, 

Surface & Coatings Technology 201, 8175 

(2007). 

[4] Sz. Łoś, W. Kempiński, J. Piekoszewski, 

L. Piekara-Sady, Z. Werner, M. Barlak, 

B. Andrzejewski, W. Jurga, K. Kaszyńska, Acta 

Physica Polonica A 114, 179 (2008). 

[5] Piekoszewski, W. Kempiński, M. Barlak, 

Z. Werner, Sz. Łoś, B. Andrzejewski, J. 

Stankowski, L. Piekara-Sady, E. Składnik- 

Sadowska, W. Szymczyk, A. Kolitsch, 

R. Grötzschel, W. Starosta, B. Sartowska, Surface 

and Coatings Technology 203, 2694 (2009). 

[6] J. Nagamatsu, N. Nakagawa, T. Muranaka, 

Y. Zenitani, J. Akimitsu, Nature 410, 63 (2001).

Auxetics and soft-matter systems 

A.C. Brańka, M. Kowalik, J. Narojczyk, K.V. Tretiakow, K.W. Wojciechowski 

Divison of Nonlinear Dynamics and Computer Simulations 

We develop and apply computer simulation methods for studies of condensed matter 

systems and investigate, so called, negative materials (like auxetics) as well as equilibrium 

and nonequilibrium (NE) properties and behaviour, like self-assembling, of soft matter (SA). 

For a long time it has been believed that materials with negative Poisson’s ratio, which 

decrease their transverse dimensions when longitudinally compressed – see fig. 1 – and 

increase them when stretched, do not exist in reality [1]. First mechanic [2] and 

thermodynamic [3] models of such systems, called at present auxetics, have been published in 

mid-eighties of the last century. That time the first auxetic materials have been also 

manufactured [4,5]. Recently, because of various potential applications, one can observe 

increasing interest in these materials [6]. 

Figure 1. Example of deformation 

at uniaxial compression of 

materials of various Poisson’s 

ratios: positive (rubber), zero 

(cork), and negative (auxetic). 

Searching for microscopic mechanisms of auxeticity is important from practical point 

of view and for understanding auxeticity. Thus, studies of influence various microscopic 

mechanism on Poisson’s ratio are important for basic research. Such studies, performed in our 

group, indicate that average Poisson’s ratio (which in anisotropic systems depends on 

longitudinal and transvers directions) increases with increasing disorder. Moreover, when 

disorder increases, the anisotropy of effective Poisson’s ratio (i.e. averaged over transverse 

directions) decreases – see fig. 2. 

Figure 2. Effective Poisson’s ratio 

dependence on the longitudinal 

direction in spherical coordinates 

for the hard dumbbell system with 

growing polydispersity of the 

spheres forming them. [7]. 

Recently, however, systems have been found in which increasing polidyspersity of 

particle sizes leads to decrease of the Poisson’s ratio in some directions, even to highly 

negative values [8]. The studies reveal a simple way to produce partially auxetic materials. 

Investigations concerning development of auxetic materials based on other microscopic 

mechanisms are in progress. The role of the symmetry in crystalline media is also studied in 

this context [9]. 

The soft sphere interaction is considered as a basic one for modelling simple fluids as 

well as important model of effective interactions of suspended colloidal or microgel particles. 

Comprehensive studies of structural, thermodynamic and dynamic properties of soft sphere 

systems have been made in both fluid and solid phases [10-13]. In particular, several new 

results were obtained for the inverse power fluids (IPF) in which the particle softness can be 

tuned by one parameter, n. For these systems, detailed calculations with the computer 

simulations were performed with the emphasis on very soft ones (n

phase diagram as particle softness increases. Furthermore, investigations of the solid phase indicated 

that the soft core in the interparticle interactions determine partially auxetic behaviour. 

Dynamic self-assembly (DySA) outside of thermodynamic equilibrium underlies 

many forms of adaptive and intelligent behaviours in both natural and artificial systems. At 

the same time, the fundamental principles governing DySA systems remain largely 

undeveloped. In this context, it is desirable to relate the forces mediating self-assembly to the 

non-equilibrium thermodynamics of the system – specifically, to the rate of energy 

dissipation. Numerical simulations were used [14] to calculate dissipation rates in a magnetohydrodynamic 

DySA system, and to relate these rates to dissipative forces acting between the 

system’s components. It was found that dissipative forces are directly proportional to the gradient 

of the dissipation rate with respect to a coordinate characterizing the steady-state assemblies, 

and the constant of proportionality linking these quantities is a characteristic time describing 

the response of the system to small, externally applied perturbations. This relationship 

complements and extends the applicability of Prigogine’s minimal-entropy-production 

formalism. It has been also shown [15] that excess dissipation rates in NESA systems are 

additive. This may prove useful in estimating the viscosities of colloidal suspensions. 

[1] L.D. Landau and E.M. Lifshits, Theory of elasticity, Pergamon Press, Oxford, 1993. 

[2] R. F. Almgren, An isotropic three dimensional structure with Poisson's ratio = - 1, 

Journal of Elasticity 15, 427 (1985). 

[3] K.W. Wojciechowski, Constant Thermodynamic Tension Monte Carlo Studies of Elastic 

Properties of a Two-Dimensional System of Hard Cyclic Hexamers, Molecular Physics 61, 

1247 (1987); K.W. Wojciechowski, A.C. Brańka, Negative Poisson ratio in a two-dimensional 

isotropic solid, Physical Review A40, 7222 (1989); K.W. Wojciechowski, Two-dimensional 

isotropic model with a negative Poisson ratio, Physics Letters A137, 60 (1989). 

[4] R.S. Lakes, Foam structures with a negative Poisson's ratio, Science 235, 1038 (1987). 

[5] K.E. Evans. Auxetic polymers – a new range of materials, Endeavour 15, 170 (1991). 

[6] C. Remillat, F. Scarpa, K. W. Wojciechowski, Preface, 2nd Conference and 5th Workshop 

on Auxetics and Other Unusual Systems Phys. Status Solidi B246, 2007 (2009); see also 

references there. 

[7] M. Kowalik, K.W. Wojciechowski, Poisson’s ratio of orientationally disordered hard 

dumbbell crystal in three dimensions. Journal of Non-Crystalline Solids 352, 4269 (2006). 

[8] J.W. Narojczyk, K.W. Wojciechowski, Elastic properties of degenerate f.c.c. crystal of 

polydisperse soft dimers at zero temperature , Journal of Non-Crystalline Solids 356, 2026 

(2010). 

[9] A.C. Brańka, D.M. Heyes, K.W. Wojciechowski, Auxeticity of cubic materials. Physica 

Status Solidi B246, 2063 (2009). 

[10] A.C. Brańka, D.M. Heyes, Thermodynamic properties of inverse power fluids, Physical 

Review E47, 031202, (2006). 

[11] D.M. Heyes, A.C. Brańka, Transport coefficients of soft repulsive particle fluids, Journal 

of Physics: Condensed Matter 20, 115102, (2008). 

[12] D.M. Heyes, A. C. Brańka, Interactions between microgel particles, Soft Matter 6, 2681, 

(2009). 

[13] D.M. Heyes, S.M. Clarke and A.C. Brańka, Soft-sphere soft glasses, Journal of Chemical 

Physics 131, 204506 (2009). 

[14] K.V. Tretiakov, K.J.M. Bishop, B.A. Grzybowski, Additivity of the excess energy 

dissipation rate in a dynamically self-assembled system, Journal of Physical Chemistry B113, 

7574, (2009). 

[15] K.V. Tretiakov, K.J.M. Bishop, B.A. Grzybowski, The dependence between forces and 

dissipation rates mediating dynamics self-assembly, Soft Matter 5, 1279, (2009).

Carbon Nanoparticles for Molecular Electronics 

W. Kempiński, M. Kempiński, D. Markowski 

Division of Low Temperature Physics (in Odolanów) 

Electronic properties of carbon nanostructures are one of the main research topics in the Division of 

Low Temperature Physics. Activated Carbon Fibers (ACF) show strong localization of spins within 

the nanoparticles building the fibers. Experimental results obtained with electron paramagnetic 

resonance (EPR) and direct measurements of the fibers’ resistance lead us to the conclusion that small 

carbon particles can be treated as quantum dots separated with potential barriers for hopping of charge 

carriers. Similarly to the granular metals, charge transport in ACF is described with the Coulomb-Gap 

Variable Range Hopping model [1], see Fig.1. 

Fig. 1 Resistance vs temperature for pure ACF. The 

insert presents the dependence of resistivity which is 

described with the following equation: 

1/ 

2 

0 

0 exp ) ( ⎟ ⎛ T ⎞ 

T = ρ ⎜ 

⎝ T ⎠ 

ρ , 

where T0, the activation energy for hopping, is of the 

order of few hundreds K. 

The spin localization, observed with EPR is affected by the adsorption of guest molecules within the 

porous structure of ACF [2,3], what is shown on Fig. 2. 

Fig. 2 EPR spectra of pure ACF (a) and ACF with 

adsorbed C6H5NO2 – nitrobenzene (b). Adsorption 

causes a strong increase of the spectrum amplitude 

and two additional, broader components appear in the 

spectrum. All the observed lines origin from 

nanoparticles building ACF, and the broader ones 

come from the nanoparticles closely interacting with 

adsorbed molecules. 

The localization of spins within the nanoparticles can be controlled by choosing specific guest 

molecules for adsorption. Dipolar H2O molecules cause six times more spins to be localized than nondipolar 

CCl4 [4]. If the localization depends on the type of adsorbed molecules, so do the transport 

properties. Fig. 3 presents the comparison of the results of resistance measurements acquired for ACF 

filled with different guest molecules: H2O, D2O and C6H5NO2.

Fig. 3 Temperature dependencies of 

resistance of pure ACF and ACF filled 

with different dipole molecules. The 

activation energy T0 increases with 

increasing dipole moment of the adsorbed 

molecules. Dipole moments of H2O, D2O 

and C6H5NO2 are as follows: 1.85 D, 

1.87 D and 3.98 D respectively. 

Another way to influence the spin localization and transport properties of matrices of carbon 

nanoparticles can be the external electric field. First results show that there is a significant effect of the 

electric field on the spin localization in ACF [5], see Fig. 4. 

Fig. 4 Temperature dependence of resistance 

of ACF filled with H2O molecules. There is a 

significant effect of switching on/off the 

external electric field. 

To determine the potential barriers for hopping of electrons in the systems of carbon nanoparticles, we 

shall try to examine the edge states of graphite (graphene) using the Low Temperature Scanning 

Tunneling Microscope (LT-STM). First image of the graphite edges, together with the determination 

of the number of visible graphene planes is presented on Fig. 5. 

Fig. 5 Surface of the 

Highly Oriented 

Pyrolytic Graphite 

(HOPG) observed with 

STM. 

References: 

[1] A. W. P. Fung, Z. H. Wang, M. S. Dresselhaus, G. Dresselhaus, R. W. Pekala, M. Endo, Phys. Rev. B 49 (1994) 17325 

[2] M. Kempiński, W. Kempiński, J. Kaszyński, M. Śliwińska-Bartkowiak, Appl. Phys. Lett. 88 (2006) 143103 

[3] S. Lijewski, M. Wencka, S. K. Hoffman, W. Kempiński, M. Kempiński, M. Śliwińska-Bartkowiak, Phys. Rev. B 77 

(2008) 014304 

[4] M. Kempiński, M. Śliwińska-Bartkowiak, W. Kempiński, Rev. Adv. Mater. Sci. 14 (2007)163 

[5] D. Markowski, W. Kempiński, M. Kempiński, Z. Trybuła, K. Kaszyńska, M. Śliwinska–Bartkowiak, Acta Phys. Pol . A 

118(3) (2010) 457

NEW EQUIPMENT 

Nuclear Magnetic Resonance Laboratory 

SPINMASTER FFC2000 (the fast Field Cycling NMR relaxometer) is a unique NMR instrument designed to 

measure the field dependence of NMR spin-lattice and spin-spin relaxation time T1 and T2 (Nuclear Magnetic 

Relaxation Dispersion profiles) from 10 kHz to 40 MHz ( 1 H Larmor frequency). 

The system consist of the following units: 1 Tesla wide-bore electromagnet, double circuit magnet/power 

supply cooling system; 3 NMR probes working in different frequency range; variable temperature controller 

system for sample temperature control with 0.1 °C precision in the range of - 120 to + 140 °C; local magnetic 

field compensation system for low Field Relaxometry and Personal NMR Console with Software package: 

AcqNMR32. 

The compact model of SPINMASTER FFC2000 with the electromagnet. The switching time between the 

polarization, relaxation and detection magnetic field can be 1 ms.

Division of Ferroelectrics 

Broadband Impedance/Dielectric 

Spectrometer 

Frequency range: 3 µHz ... 3 GHz 

Temperature control system: 

QUATRO Cryosystem: -160°C to +400°C 

Software package: 

WinDETA for automatic measurements 

WinPLOT for 2D and 3D data presentation 

WinTEMP for automatic temperature control 

WinFIT for analysis of measured data 

Novotherm-HT Temperature 

Control System 

Novotherm-HT 1200: 

20 .. 1200 °C

Surface Physics and Tunneling Spectroscopy Laboratory 

Main intruments 

Ultra-high vacuum MBE system (seven sources) equipped with X-ray 

Photoemission Spectrometer (XPS) scanning probe microscopy 

(STM, AFM, MFM) and RHEED 

Alternating Gradient Magnetometer (AGM) 

Equipment for magnetotransport measurements in electromagnet 

up to 25kOe and in Helmholtz coils up to 800 Oe.

Magnetic alloys laboratory 

Physical Property Measurement System Quantum Design 

PPMS – versatile system 

PPMS - vibrating sample magnetometer


BRUKER EPR Spectrometer ELEXSYS 500 

- S, X, Q-band CW-EPR 

- maximal external magnetic filed B = 1.7 T 

- X-band CW-ENDOR in the temperature range (4.2 – 300) K 

- measurements in the temperature range (4.2 – 500) K for X-band and (4.2 – 300) K for S, Q-band CW-EPR 

- measurements at an external electric fields and axial pressures 

- dual-mode cavity (parallel and perpendicular mode)

Division of Thin Films 

Sputter deposition system for the fabrication of multilayers 

Thin film deposition laboratory

Institute of Molecular Physics Polish Academy of Sciences ... - Poznań

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?