Anisotropic superconducting properties of the aligned Sm_0.95La_0.05FeAsO_0.85F_0.15 microcrystalline powder

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

Corresponding author: hcku@phys.nthu.edu.tw

Received: 15 August 2008
Accepted: 18 November 2008

Abstract

The Sm_0.95La_0.05FeAsO_0.85F_0.15 compound is an anisotropic superconductor with a superconducting transition temperature T_c = 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 B_a and c-axis along the rotation axis. Anisotropic superconducting properties with anisotropic diamagnetic ratio ~ 2.4 was observed from low-field susceptibility and magnetization . The anisotropic low-field phase diagram with the variation of lower critical field gives a zero-temperature penetration depth = 521 nm and = 172 nm. The superconducting anisotropy parameter of 3.0 was obtained for this aligned microcrystalline powder.