Comparative study of transport and magnetic Jc in the polycrystalline iron-based superconductor NdFeAsO{0.88}F{0.12}

TL;DR

This study compares the transport and magnetic critical current densities in NdFeAsO0.88F0.12 superconductors prepared by different methods, revealing weak-link behavior and differences in magnetic and transport properties.

Contribution

It provides a comparative analysis of high-pressure and ambient-pressure synthesized samples, highlighting the impact on critical current densities and weak-link phenomena.

Findings

High-pressure samples have higher magnetic critical current density Jcm.

Transport critical current density Jct is very low and similar in both samples.

Weak-links are present in both samples, affecting current transport.

Abstract

Polycrystalline NdFeAsO0.88F0.12 superconductors prepared by high pressure (HP) and ambient pressure (AP) method were comparatively studied by magnetization and transport measurements. Upper critical field (Hc2), irreversibility field (Hirr) and the anisotropy parameter were estimated from resistance transition curves. The broadening of transition width was observed, and ascribed to both Hc2 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 manifest that there are weak-links in both samples. Magnetization critical current density Jcm were derived from MHLs. High-pressure synthesized sample shows higher Jcm. However, by means of direct transport I-V measurements, transport critical current density Jct was very low. The Jct values for two samples are comparable. Large discrepancies between Jcm and Jct also indicate that there are weak-links in both samples. The relative mechanism is discussed in detail.