Transport Properties of the Iron-Oxypnictide Superconductor PrFeAsO1−y in High Magnetic Fields

Abstract

We report the resistively determined upper critical field μ0Hc2 of the iron-oxypnictide superconductor PrFeAsO1−y (y ∼ 0.15), which exhibits superconductivity at Tc = 44 K The resistivity ρ(H,T) was measured with a typical four-probe method in static magnetic fields of up to 14 T and in pulsed high magnetic fields of up to 52 T With increasing magnetic fields, the superconducting transition width of the ρ(T) curve for H ‖ c becomes broader than that for H ‖ ab. This behavior is likely to be due to dissipation associated with thermally activated vortex motion. The μ0Hc2(T) curves for both H ‖ ab and H ‖ c exhibit a pronounced upward curvature below Tc and are very different from the conventional one-band Werthamer-Helfand-Hohenberg behavior. This result suggests that the iron-oxypnictide superconductor is a multiband system. We demonstrate the results of the two-band analysis for μ0Hc2(T) and discuss the anisotropy of μ0Hc2 on some kinds of iron-based superconductors.