Vortex pinning and dynamics in high performance Sr0.6K0.4Fe2As2 superconductor

TL;DR

This study investigates vortex pinning mechanisms and dynamics in a high-performance Sr0.6K0.4Fe2As2 superconductor, revealing dominant grain boundary pinning, effective dislocation centers, and a vortex phase diagram with elastic to plastic creep crossover.

Contribution

It provides new insights into vortex pinning mechanisms and dynamic behavior in Sr0.6K0.4Fe2As2 superconductors, including the role of grain boundaries and dislocations.

Findings

Grain boundary pinning is dominant.

Dislocations serve as effective pinning centers.

A vortex phase diagram with elastic to plastic creep crossover.

Abstract

We have studied vortex pinning and dynamics in a Sr0.6K0.4Fe2As2 superconducting tape with critical current density Jc~0.1 MA/cm2 at 4.2 K and 10 T. It is found that grain boundary pinning is dominant in the vortex pinning mechanism. Furthermore, we observe large density of dislocations which can also serve as effective pinning centers. We find that the temperature dependence of critical current density is in agreement with the model of vortices pinned via spatial fluctuation of charge carrier mean free path. Magnetic relaxation measurement indicates that the magnetization depends on time in a logarithmic way. The relaxation rate in the low and intermediate temperature region is small, and it exhibits a weak temperature and field dependence. A crossover from elastic creep to plastic creep regime is observed. Finally, we conclude a vortex phase diagram for the high performance Sr0.6K0.4Fe2As2 superconducting tape.