Enhanced critical current properties in Ba0.6K0.4+xFe2As2 superconductor by over-doping of potassium

TL;DR

Over-doping potassium in Ba0.6K0.4Fe2As2 superconductors significantly enhances critical current density, especially in high magnetic fields, with minimal impact on the critical temperature, due to increased flux pinning from dislocations.

Contribution

This study demonstrates that slight potassium over-doping improves high-field critical current density in Ba0.6K0.4Fe2As2 superconductors by inducing dislocations that enhance flux pinning.

Findings

High-field Jc increased threefold with x=0.1 potassium over-doping.

Critical temperature decreased by less than 0.5 K with over-doping.

Dislocations from over-doping enhance flux pinning and intra-grain Jc.

Abstract

Phase-pure polycrystalline Ba0.6K0.4+xFe2As2 with were prepared using a one-step solid-state reaction method. We found that over-doping of potassium can improve critical current density (Jc). High-field Jc for samples with x = 0.1 is three times higher than that for samples with x = 0. Over-doping of K has minimal effect on the critical transition temperature (Tc). Less than 0.5 K degradations in Tc was measured for samples with x = 0.1. TEM revealed high concentration of dislocations in samples with x = 0.1, resulting in enhanced flux pining. Further analyses on magnetization loops for powder samples confirm that K over-doping can promote intra-grain Jc. Our results indicate that slight excess of K in Ba0.6K0.4Fe2As2 samples is beneficial to high-field applications.