Global and local critical current density in superconducting SmFeAsO$_{1-x}$F$_x$ measured by two methods

TL;DR

This study compares global and local critical current densities in SmFeAsO$_{1-x}$F$_x$ superconductors using two measurement methods, revealing differences based on preparation techniques and magnetic field effects.

Contribution

It introduces a comparative analysis of critical current densities in polycrystalline SmFeAsO$_{1-x}$F$_x$ using remnant magnetic moment and Campbell's methods, highlighting the impact of preparation methods.

Findings

Global $J_c$ ~ 10^7 A/m^2 at 5 K, independent of preparation method.

Local $J_c$ ~ 10^{10} A/m^2, larger in PIT samples.

Local $J_c$ decreases slightly with increasing magnetic field.

Abstract

The critical current densities of polycrystalline bulk SmFeAsO$_{1-x}$F$_x$ prepared by the powder-in-tube (PIT) method and by a conventional solid-state reaction were investigated using the remnant magnetic moment method and Campbell's method. Two types of shielding current, corresponding to global and local critical current densities $J_{\rm c}$ were observed using both measurement methods. The global and local $J_{\rm c}$ were on the order of $10^7$ A/m$^2$ and $10^{10}$ A/m$^2$ at 5 K, respectively. The local $J_{\rm c}$ decreased slightly with increasing magnetic field. The global $J_{\rm c}$ was independent of the preparation method, while the local $J_{\rm c}$ was larger for samples prepared by PIT than for those prepared by solid-state reaction.