Observation of Uniform Supercurrent Flow in Polycrystalline K-doped Ba122 by Combined Magneto-optical Imaging and Finite-element Modeling

TL;DR

This study combines magneto-optical imaging and finite-element modeling to demonstrate uniform supercurrent flow in a polycrystalline K-doped Ba122 superconductor, emphasizing the importance of microstructural control.

Contribution

It provides the first combined experimental and modeling evidence of uniform supercurrent flow in polycrystalline iron-based superconductors.

Findings

Supercurrent circulates uniformly throughout the sample.

Good agreement between experimental data and finite element modeling.

Highlights microstructural control for improved flux pinning.

Abstract

Macroscopic current uniformity in a (Ba,K)Fe2As2 bulk sample produced by a process that demonstrated high trapped magnetic fields was evaluated through a comparative experimental and modeling approach. The bulk sample, with a well-defined square geometry, exhibited ideal roof-top patterns in magneto-optical (MO) images. Comparison of the magnetic moment, MO images, and finite element modeling results showed good agreement for the critical current density, suggesting that the supercurrent circulates uniformly throughout the sample on the order of MO resolution. These results highlight the importance of enhancing flux pinning strength and microstructural control at the submicron and grain boundary scale in iron-based superconducting polycrystalline materials.