Peculiarities of performance of the spin valve for the superconducting current

TL;DR

This study investigates the spin valve effect in a superconductor/ferromagnet multilayer, revealing how the superconducting transition temperature difference depends on ferromagnetic layer thickness and demonstrating near-complete switching behavior.

Contribution

It provides experimental insights into the dependence of the spin valve effect on ferromagnetic layer thickness, highlighting conditions for maximum effect and full switching in superconducting states.

Findings

Maximum spin valve effect at d_{Fe1} ~ d_{Fe2}

Significant increase in ΔT_c compared to previous models

Near-complete switching from normal to superconducting state

Abstract

The spin valve effect for the superconducting current based on the superconductor/ferromagnet proximity effect has been studied for a CoO_x/Fe1/Cu/Fe2/Cu/Pb multilayer. The magnitude of the effect $\Delta T_c$ = T_c^{AP} - T_c^{P}, where T_c^{P} and T_c^{AP} are the superconducting transition temperatures for the parallel (P) and antiparallel (AP) orientation of magnetizations, respectively, has been measured for different thicknesses of the Fe1 layer d_{Fe1}. The obtained dependence of the effect on d_{Fe1} reveals that $\Delta T_c$ can be increased in comparison with the case of a half-infinite Fe1 layer considered by the previous theory. A maximum of the spin valve effect occurs at d_{Fe1} ~ d_{Fe2}. At the optimal value of d_{Fe1}, almost full switching from the normal to the superconducting state when changing the mutual orientation of magnetizations of the iron layers Fe1 and Fe2 from P to AP is demonstrated.