Central peak position in magnetization loops of high-$T_c$ superconductors

TL;DR

The paper provides exact analytical expressions for the magnetization of superconducting thin strips with variable critical current density, showing the central peak at zero field and its shift due to granularity, aligning with experimental data.

Contribution

It introduces a precise analytical model for magnetization in superconducting strips and links peak shifts to granularity, advancing understanding of superconductor behavior.

Findings

Magnetization peak occurs at zero applied field in ideal samples.

Granularity shifts the peak to positive fields on the descending branch.

Model aligns well with experimental data for YBCO thin films.

Abstract

Exact analytical results are obtained for the magnetization of a superconducting thin strip with a general behavior J_c(B) of the critical current density. We show that within the critical-state model the magnetization as function of applied field, B_a, has an extremum located exactly at B_a=0. This result is in excellent agreement with presented experimental data for a YBCO thin film. After introducing granularity by patterning the film, the central peak becomes shifted to positive fields on the descending field branch of the loop. Our results show that a positive peak position is a definite signature of granularity in superconductors.