Tunable pinning of a superconducting vortex a by a magnetic vortex

TL;DR

This paper theoretically investigates how a magnetic nanodisk in a vortex state can be used to tune the pinning of a superconducting vortex line through magnetic interactions influenced by an external field.

Contribution

It introduces a model for tunable vortex pinning using magnetic nanodisks, combining London and Landau-Lifshitz theories with the rigid vortex approximation.

Findings

Pinning is mainly due to magnetization changes induced by the vortex line.

External magnetic field can tune the pinning potential.

Magnetization curve of the nanodisk is affected by the vortex line.

Abstract

The interaction between a straight vortex line in a superconducting film and a soft magnetic nanodisk in the magnetic vortex state in the presence of a magnetic field applied parallel to the film surfaces is studied theoretically. The superconductor is described by London theory and the nanodisk by the Landau-Lifshitz continuum theory of magnetism, using the approximation known as the rigid vortex model. Pinning of the vortex line by the nanodisk is found to result, predominantly, from the interaction between the vortex line and the changes in the nanodisk magnetization induced by the magnetic field of the vortex line and applied field. In the context of the rigid vortex model, these changes result from the displacement of the magnetic vortex. This displacement is calculated analytically by minimizing the energy, and the pinning potential is obtained. The applied field can tune the pinning potential by controlling the displacement of the magnetic vortex. The nanodisk magnetization curve is predicted to change in the presence of the vortex line