Critical current density and lower critical field in a superconducting Ca₁₀(Pt₄As₈) (Fe_2-xPt _xAs₂)₅ single crystal

We investigate the critical current density Jc and the lower critical field H_c1 in a superconducting Ca₁₀(Pt₄As ₈)(Fe_2-xPt_xAs₂) 5 single crystal. High quality single crystals were grown by the Bridgman method. A sample with a nominal composition of Ca₁₀(Pt₄As₈)(Fe _2-xPt_xAs₂)₅ with x = 0.01 showed a T_c 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 f_p at various temperatures followed good fits with the scaling law f_p ∝ h^p(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 H_irr , the secondary peak field H_sp, and the onset field of the secondary peak H_min follow a universal scaling law H(T) = H(0)(1 - T /T_c)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.