Critical current density and lower critical field in a superconducting Ca10(Pt4As8) (Fe2−x Ptx As2)5 single crystal

Abstract

We investigate the critical current density and the lower critical field in a superconducting single crystal. High quality single crystals were grown by the Bridgman method. A sample with a nominal composition of with x = 0.01 showed a of 32 K. A well-formed secondary peak in the specific temperature range was observed in the magnetic hysteresis for and , revealing the anisotropic nature of the flux pinning in the sample. The normalized volume pinning forces at various temperatures followed good fits with the scaling law ∝ ( with p = 1 and q = 2, which predicts the normal point-type pinning in the sample. The vortex phase diagram shows that the irreversibility field , the secondary peak field , and the onset field of the secondary peak follow a universal scaling law H(T) = H(0)(/. The temperature dependence of the superfluid density was fitted well by the two-gap BCS model in the full temperature range using two superconducting gaps, = 8.4 ± 0.5 meV and = 3.1 ± 0.5 meV.