Comparative study of type-II superconducting properties in polycrystalline NdFeAsO0.88F0.12 prepared by different methods

Abstract: Polycrystalline NdFeAsO0.88F0.12 superconductors prepared by high pressure (HP) and ambient pressure (AP) methods were comparatively studied by magnetization and transport measurements. Upper critical field H c2, irreversibility field H irr and the anisotropy parameter Γ were estimated from resistance transition curves. The broadening of transition width was observed, and was ascribed to both H c2 anisotropy and superconductivity inhomogeneity of samples. Magnetic hysteresis loops (MHLs) in low fields were measured to detect the trace of weak-link behavior. The reclosed hysteresis loops in low fields indicate that there are weak links in both samples. Magnetization critical current density J cm were derived from MHLs. Sample HP shows higher J cm than sample AP. Direct transport I–V measurements show that the transport critical current density J ct are very low but persist up to 9T, suggesting intrinsic strong-link existing in both samples. [ABSTRACT FROM AUTHOR]