Specific heat anomalies for in superconducting single crystal dopedBaFe2As2: comparison of different flux growth methods

Abstract

One way to address the nature of the superconductivity in the new iron pnictides is to measurethe low temperature specific heat in the superconducting state, where the temperature,field, and angular dependences of the specific heat each give important information. Wereport on an initial study of the specific heat down to 0.4 K in single crystals ofBa0.6K0.4Fe2As2,Tc = 32 K,prepared via Sn-flux and In-flux methods and compare to literature data for samples prepared usingthe self-flux method. We also report on the specific heat in zero and 1 T applied magnetic fields ofBa(Fe0.926Co0.074)2As2,Tc = 22 K, prepared via the In-flux method. All samples show upturns in the specific heat dividedby temperature below 2 K, with the upturn in the Sn-flux sample starting already at 4 K.These upturns, which are strongly dependent on the preparation method, impededetermination of the intrinsic properties.