Effect of the sample geometry on the second magnetization peak in single crystalline Ba$_{0.63}$K$_{0.37}$BiO$_3$ thick film

TL;DR

This study investigates how the geometry of a single crystalline Ba$_{0.63}$K$_{0.37}$BiO$_3$ superconducting film affects the second magnetization peak, revealing that the SMP diminishes with decreasing sample size and is influenced by thermomagnetic effects.

Contribution

It demonstrates that the second magnetization peak's dependence on sample geometry cannot be explained by vortex pinning models, highlighting the roles of thermomagnetic instability and current distribution.

Findings

SMP vanishes as film dimensions decrease

Sample geometry influences the SMP presence

Thermomagnetic effects explain SMP behavior

Abstract

Magnetization hysteresis loop $M(H)$ measurements performed on a single crystalline Ba$_{0.63}$K$_{0.37}$BiO$_3$ superconducting thick film reveal pronounced sample geometry dependence of the "second magnetization peak" (SMP), i.e. a maximum in the width of $M(H)$ occurring at the field $H_{\rm SMP}(T)$. In particular, it is found that the SMP vanishes decreasing the film dimension. We argue that the observed sample geometry dependence of the SMP cannot be accounted for by models which assume a vortex pinning enhancement as the origin of the SMP. Our results can be understood considering the thermomagnetic instability effect and/or non-uniform current distribution at $H < H_{\rm SMP}$ in large enough samples.