Increasing the performance of the superconducting spin valve using a Heusler alloy

TL;DR

This study demonstrates that using a Heusler alloy as the F2 layer in superconducting spin-valve heterostructures significantly enhances the switching effect of superconductivity, nearly doubling the effect compared to traditional ferromagnetic layers.

Contribution

The paper introduces a novel heterostructure with a Heusler alloy F2 layer that markedly improves the superconducting spin-valve performance over previous designs.

Findings

Superconducting spin-valve effect is significantly enhanced with Heusler alloy F2 layer.

The effect magnitude doubles compared to Fe-based multilayers.

Theoretical analysis attributes enhancement to a smaller exchange field in the Heusler alloy.

Abstract

We have studied superconducting properties of the spin-valve thin layer heterostructures CoO$_x$/F1/Cu/F2/Cu/Pb where the ferromagnetic F1 layer was standardly made of Permalloy whereas for the F2 layer we have taken a specially prepared film of the Heusler alloy Co$_2$Cr$_{1-x}$Fe$_x$Al with a small degree of spin polarization of the conduction band. The heterostructures demonstrate a significant superconducting spin-valve effect, i.e. a complete switching on and off of the superconducting current flowing through the system by manipulating the mutual orientations of the magnetization of the F1 and F2 layers. The magnitude of the effect is doubled in comparison with the previously studied analogous multilayers with the F2 layer made of the strong ferromagnet Fe. Theoretical analysis shows that a drastic enhancement of the switching effect is due to a smaller exchange field in the heterostructure coming from the Heusler film as compared to Fe. This enables to approach almost ideal theoretical magnitude of the switching in the Heusler-based multilayer with the F2 layer thickness of $\sim 1$\,nm.