Superconductivity at 32 K and anisotropy in Tl_0.58Rb_0.42Fe_1.72Se₂ crystals

¹ Department of Physics, Zhejiang University - Hangzhou 310027, China
² Department of Physics, Hangzhou Normal University - Hangzhou 310036, China

^a mhfang@zju.edu.cn

Received: 27 January 2011
Accepted: 2 February 2011

Abstract

Tl_0.58Rb_0.42Fe_1.72Se₂ single crystals were successfully synthesized with the Bridgeman method. The physical properties are characterized by electrical resistivity, magnetization and Hall resistivity. Tl_0.58Rb_0.42Fe_1.72Se₂ undergoes a superconducting transition at T_c^onset=32 K and T_c^zero=31.4 K. Extrapolation of the upper critical field H_c2 at T_c to zero temperature gives a large value of H_c2(0) (H_c2(0)=221 T for H||ab and H_c2(0)=44.2 T for H||c). The Hall coefficient changes sign upon cooling down, indicating a possible multi-band behavior. The normal-state magnetic susceptibility decreases with decreasing temperature, suggesting strong antiferromagnetic (AFM) spin fluctuations, which might be related to the superconductivity (SC).