Critical current density and lower critical field in a superconducting Ca-10(Pt4As8) (Fe2-x PtxAs2)(5) single crystal

Abstract

We investigate the critical current density Jc and the lower critical field Hc1 in a superconducting Ca10(Pt4As 8)(Fe2-xPtxAs2) 5 single crystal. High quality single crystals were grown by the Bridgman method. A sample with a nominal composition of Ca10(Pt4As8)(Fe 2-xPtxAs2)5 with x = 0.01 showed a Tc of 32 K. A well-formed secondary peak in the specific temperature range was observed in the magnetic hysteresis for H∥c and H∥ab, revealing the anisotropic nature of the flux pinning in the sample. The normalized volume pinning forces fp at various temperatures followed good fits with the scaling law fp ∝ hp(1 - h) q 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 Hirr , the secondary peak field Hsp, and the onset field of the secondary peak Hmin follow a universal scaling law H(T) = H(0)(1 - T /Tc)n. The temperature dependence of the superfluid density ρ̃(T) was fitted well by the two-gap BCS model in the full temperature range using two superconducting gaps, Δ1 = 8.4 ± 0.5 meV and Δ2 = 3.1 ± 0.5 meV. © 2014 IOP Publishing Ltd Printed in the UK.