Anisotropic superconducting strip in an oblique magnetic field

TL;DR

This paper analyzes the critical state of a thin superconducting strip in an oblique magnetic field, revealing how magnetic profiles depend on the field orientation and how to extract the critical current density function from measurements.

Contribution

It provides a comprehensive analysis of the critical state in superconducting strips with non-uniform j_c(B), including methods to determine j_c(B) from magnetic profiles.

Findings

Magnetic profiles depend on in-plane field component and field application history.

Profiles can be used to extract j_c(B) without restrictions on its dependence.

The analysis applies to measurements via magneto-optical imaging or Hall sensors.

Abstract

The critical state of a thin superconducting strip in an oblique applied magnetic field H_a is analyzed without any restrictions on the dependence of the critical current density j_c on the local magnetic induction {\bf B}. In such a strip, j_c is not constant across the thickness of the sample and differs from J_c/d, where J_c is the critical sheet current. It is shown that in contrast to the case of {\bf B}-independent j_c, the profiles H_z(x) of the magnetic-field component perpendicular to the strip plane generally depend on the in-plane component H_{ax} of the applied magnetic field H_a, and on how H_a is switched on. On the basis of this analysis, we explain how and under what conditions one can extract j_c({\bf B}) from the magnetic-field profiles H_z(x) measured by magneto-optical imaging or by Hall-sensor arrays at the upper surface of the strip.