Volume 84, Number 6, December 2008
Article Number 67014
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 12 January 2009
EPL, 84 (2008) 67014
DOI: 10.1209/0295-5075/84/67014

Anisotropic superconducting properties of the aligned Sm0.95La0.05FeAsO0.85F0.15 microcrystalline powder

B. C. Chang1, C. H. Hsu1, Y. Y. Hsu2, Z. Wei3, K. Q. Ruan3, X. G. Li3 and H. C. Ku1

1   Department of Physics, National Tsing Hua University - Hsinchu 30013, Taiwan
2   Department of Physics, National Taiwan Normal University - Taipei 11677, Taiwan
3   Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China - Hefei 230026, China

received 15 August 2008; accepted in final form 18 November 2008; published December 2008
published online 12 January 2009

The Sm0.95La0.05FeAsO0.85F0.15 compound is an anisotropic superconductor with a superconducting transition temperature Tc = 52 K. Due to the Fe spin-orbital related anisotropic exchange coupling, the tetragonal microcrystalline powder can be aligned at room temperature using the field-rotation method where the tetragonal ab-plane is parallel to the aligned magnetic field Ba and c-axis along the rotation axis. Anisotropic superconducting properties with anisotropic diamagnetic ratio $\chi _{c}/\chi _{ab}$ ~ 2.4 was observed from low-field susceptibility $\chi (T)$ and magnetization M(Ba). The anisotropic low-field phase diagram with the variation of lower critical field gives a zero-temperature penetration depth $\lambda _{c}(0)$ = 521 nm and $\lambda _{ab}(0)$ = 172 nm. The superconducting anisotropy parameter $\gamma =\lambda _{c}/\lambda _{ab}$ of 3.0 was obtained for this aligned microcrystalline powder.

74.70.-b - Superconducting materials.
75.30.Fv - Spin-density waves.
75.30.Gw - Magnetic anisotropy.

© EPLA 2008