Density effect on critical current density and flux pinning properties of polycrystalline SmFeAsO1-xFx superconductor

TL;DR

This study systematically examines how sample density affects flux pinning and critical current density in polycrystalline SmFeAsO1-xFx superconductors, revealing density-dependent variations in superconducting properties and pinning mechanisms.

Contribution

It provides new insights into the relationship between sample density and flux pinning properties, highlighting the impact of density control on superconductor performance.

Findings

Superconducting volume fraction decreases with lower sample density.

High-density samples exhibit multiple peaks in flux pinning force density.

Main intragranular pinning is identified as normal point pinning.

Abstract

A series of polycrystalline SmFeAs1-xOx bulks was prepared to systematically investigate the influence of sample density on flux pinning properties. Different sample densities were achieved by controlling the pelletizing pressure. The superconducting volume fraction, the critical current densities Jcm and the flux pinning force densities Fp were estimated from the magnetization measurements. Experimental results manifest that: (1) the superconducting volume fraction decreases with the decreasing of sample density. (2) The Jcm values have the similar trend except for the sample with very high density may due to different connectivity and pinning mechanism. Moreover, The Jcm(B) curve develops a peak effect at approximately the same field at which the high-density sample shows a kink. (3) The Fp(B) curve of the high-density sample shows a low-field peak and a high-field peak at several temperatures, which can be explained by improved intergranular current, while only one peak can be observed in Fp(B) of the low-density samples. Based on the scaling behaviour of flux pinning force densities, the main intragranular pinning is normal point pinning.