Transport Properties of the Iron-based Superconductor SrFe2(As,P)2 in High Magnetic Fields

Abstract

We have investigated the resistive upper critical field (μ 0 H c2) of the iron-based superconductor SrFe2(As1−x P x )2 (x=0.35, T c∼29 K) in pulsed high magnetic fields of up to 52 T. For H∥ab, $\mu_{0}H_{\mathrm{c}2}^{ab}(T)$ exhibits the Werthamer-Helfand-Hohenberg (WHH) like behavior. While, for H∥c, $\mu_{0}H_{\mathrm {c}2}^{c}(T)$ is almost linear against T and exhibits a slightly upward curvature near T c. The anisotropy of μ 0 H c2 decreases from 2.5 near T c to ∼1.2 at T=0 K monotonically. Similar isotropic behavior of μ 0 H c2 at low temperatures has also been observed in the Fe1+δ (Te,Se). We demonstrate the results of the two-band analysis for μ 0 H c2(T) on the present sample and discuss the anisotropy of μ 0 H c2 by comparing with those in some kinds of iron-based superconductors.