The Bean-Livingston barrier at a superconductor/magnet interface

TL;DR

This paper investigates how the presence of a magnetic sheath influences the Bean-Livingston barrier at a superconductor/magnet interface, revealing significant modifications in flux penetration and critical current behavior.

Contribution

It introduces a classical London approach to analyze the barrier's dependence on geometry and magnetic permeability, highlighting the impact of magnetic sheaths on superconductor properties.

Findings

Magnetic sheath can significantly enhance the flux penetration field.

The average critical current density variation is suppressed by the magnetic sheath.

Theoretical predictions align with recent experimental observations.

Abstract

The Bean-Livingston barrier at the interface of type-II superconductor/soft-magnet heterostructures is studied on the basis of the classical London approach. This shows a characteristic dependence on the geometry of the particular structure and its interface as well as on the relative permeability of the involved magnetic constituent. The modification of the barrier by the presence of the magnet can be significant, as demonstrated for a cylindrical superconducting filament covered with a coaxial magnetic sheath. Using typical values of the relative permeability, the critical field of first penetration of magnetic flux is predicted to be strongly enhanced, whereas the variation of the average critical current density with the external field is strongly depressed, in accord with the observations of recent experiments.