Magnetization curves and ac susceptibilites in type-II superconductors: geometry-independent similarity and effect of irreversibility mechanisms

TL;DR

This paper compares magnetic properties of different superconductor geometries, revealing a universal similarity in magnetization and susceptibility, and predicts a sign change in third harmonic due to different irreversibility mechanisms.

Contribution

It introduces a geometry-independent similarity in magnetization and susceptibility curves and predicts a sign reversal in the third harmonic of ac susceptibility related to irreversibility mechanisms.

Findings

Magnetization curves and susceptibilities are similar across geometries.

A sign reversal in the third harmonic of ac susceptibility is predicted.

The influence of edge barriers and bulk pinning on magnetic response is analyzed.

Abstract

The magnetic characteristics for superconducting samples of different geometries (plates and films of various widths) and orientation with respect to external field are compared. A similarity is established between the magnetization curves M(H) and the corresponding susceptibilities. A sign reversal is predicted for the 3rd harmonic of the ac susceptibillity when the irreversibility mechanism changes from bulk pinning to edge barrier. A mutual influence of the edge barrier and bulk pinning on the magnetization curves and field-dependent ac susceptibility is studied on the basis of an exactly solvable model (narrow plate in a parallel field and/or narrow film in a perpendicular magnetic field).