Manipulating superconductivity through the domain structure of a ferromagnet: experimental aspects and theoretical implications

TL;DR

This study experimentally demonstrates how the domain structure of a ferromagnet influences superconductivity in hybrid structures, showing multidomain states promote superconductivity while monodomain states suppress it, aligning with recent theories.

Contribution

It provides experimental evidence linking ferromagnetic domain structures to superconductivity behavior, supporting theoretical models of inhomogeneous exchange fields.

Findings

Multidomain ferromagnets promote superconductivity nucleation.

Monodomain ferromagnets suppress superconductivity.

Experimental results support theories of inhomogeneous exchange fields.

Abstract

In the present work we study experimentally the influence that the domain structure of a fer- romagnet (FM) has on the properties of a superconductor (SC) in bilayers and multilayers of La0.60Ca0.40MnO3/Nb and FePt/Nb proximity hybrids. Specific experimental protocols that were employed in the performed magnetization measurements enabled us to directly uncover a generic property of FM/SC hybrids: in the absence of an external magnetic field, the multidomain struc- ture of the FM promotes the nucleation of superconductivity, while its monodomain state strongly suppresses it. Our experimental findings support recent theoretical studies proposing that when an inhomogeneous exchange field is offered by the FM to the SC the superconducting pairs are not susceptible to pair-breaking.