Vortex States Induced by Proximity Effect in Hybrid Ferromagnet-Superconductor Systems

TL;DR

This paper investigates how proximity effects in ferromagnet-superconductor systems induce vortex states, affecting superconductivity nucleation and enabling state switching via exchange fields in mesoscopic structures.

Contribution

It introduces a mechanism for switching between vortex states driven by exchange fields, based on solving linearized Usadel equations for mesoscopic ferromagnet-superconductor systems.

Findings

Superconductivity nucleation is influenced by proximity to ferromagnets.

Exchange fields cause oscillatory behavior of Cooper pairs.

Switching between vortex states is possible due to exchange field effects.

Abstract

We consider superconductivity nucleation in multiply connected mesoscopic samples such as thin-walled cylinders or rings placed in electrical contact with a ferromagnet. The superconducting critical temperature and order parameter structure are studied on the basis of linearized Usadel equations. We suggest a mechanism of switching between the superconducting states with different vorticities caused by the exchange field and associated with the oscillatory behavior of the Cooper pair wave function in a ferromagnet.