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Name (Title):
Shen V. CHONG (JSPS Postdoctoral Fellow)
Affiliation:
Institute of Materials Science, University of Tsukuba
Address:
1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573
Poster Session PS-17
Email: s_chong@ims.tsukuba.ac.jp
Home Page: n/a
Presentation Title:
Superconductivity and Magnetic Ordering Induced by Yttrium-doping in AFe2As2 (A = Sr, Ca)
Abstract:
Spurred on by the report of higher transition temperatures (Tc) in iron oxypnictide,
LaFeAsO1-xFx, by Kamihara et al., 1 a series of iron-pnictides and iron-chalcogenides has since
been discovered to be superconducting some with even higher Tc compared to the original report.
The so-called 122 FeAs compounds (AFe2As2, where A = Ba, Sr, Ca, Eu) are the second series in
the iron-pnictide family to be synthesized with Tc reaching up to 38 K. 2 The appealing factor of
these ternary iron-arsenides is that all the constituents are metal or semi-metal, which promotes a
lower preparation temperature, and their synthesis are more straightforward. Superconductivity in
these 122 FeAs can be achieved either through doping with monovalent cations on the alkaline
earth metal sites (interlayer hole-doping) or substituting some of the iron with cobalt (intralayer
electron doping). This report focuses on work which has been carried out on Sr- and Ca-Fe2As2 in
an attempt to probe whether interlayer electron-doping is possible in these 122 FeAs, with
yttrium as the dopant (which ionic radius is in close proximate size to Sr 2+ and Ca 2+ ).
Superconductivity was indeed observed in Sr1-xYxFe2As2 within a narrow range of x = 0.3 to 0.5
(Fig. 1a). Hall effect measurements confirm the electron doping nature of this new
superconductor. In Ca1-xYxFe2As2 despite noticeable diamagnetic signals in the magnetization
curves (Fig 1b), superconductivity was not observed in transport measurements, which can only
suggest the presence of some interesting magnetic ordering induced by Y-doping, or minute
superconducting phases might be included in a large non-superconducting matrix.
��(m�-cm)
0.6
0.5
0.4
0.3
0.2
0.1
onset T c ~26.4 K
��(m�-cm)
0.0
T (K)
0 10 20 30 40 50 60 70
T (K)
0.07
0.06
0.05
0.04 Y = 0.6
0.03 Y = 0.2
0.02
0.01
Y = 0.4
Y = 0.3
Y = 0.5
0.00
0 10 20 30 40 50
M (emu/g)
FC 2Oe
-0.0005
-0.0010
FC 1Oe
-0.0015
-0.0020
References :
[1] Y. Kamihara et al., J. Am. Chem. Soc. Vol. 130 (2008) 3296.
[2] K. Sasmal et al., Phys. Rev. Lett. 101 (2008) 107007; M. Rotter et al., Vol. 101 (2008)
107006; G.F. Chen et al., Chin. Phys. Lett. Vol. 25 (2008) 3403.
0.0000
-0.0025
0
ZFC 1
& 2Oe
20 40 60
T (K)
T (K)
80 100
�(m�-cm)
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0 50 100 150 200 250 300
Fig. 1 R-T of Sr1-xY xFe2As2 (a) and M-T of Ca0.7Y 0.3Fe2As2 displaying
superconducting- like magnetic transition at 84 and 37 K (b).
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