Inhomogeneous vortex-state-driven enhancement of superconductivity in nanoengineered ferromagnet-superconductor heterostructures

TL;DR

This study demonstrates that inhomogeneous magnetic domains in nanoengineered ferromagnet-superconductor heterostructures can enhance superconductivity through magnetic flux mobility, challenging traditional views of antagonism between ferromagnetism and superconductivity.

Contribution

It introduces a novel explanation for magnetic field induced superconductivity based on flux mobility differences in inhomogeneous FM-SC systems.

Findings

Magnetic flux mobility varies with inhomogeneous magnetic domains.

FIS can be explained by flux dynamics rather than antagonism.

Nanoengineered heterostructures show enhanced superconductivity due to inhomogeneity.

Abstract

Thin film heterostructures provide a powerful means to study the antagonism between superconductivity (SC) and ferromagnetism (FM). One interesting issue in FM-SC hybrids which defies the notion of antagonistic orders is the observation of magnetic field induced superconductivity (FIS). Here we show that in systems where the FM domains/islands produce spatial inhomogeneities of the SC order parameter, the FIS can derive significant contribution from different mobilities of the magnetic flux identified by two distinct critical states in the inhomogeneous superconductor. Our experiments on nanoengineered bilayers of ferromagnetic CoPt and superconducting NbN where CoPt/NbN islands are separated by a granular NbN, lend support to this alternative explanation of FIS in certain class of FM-SC hybrids.