Superconducting spin valve effect in the Co/Pb/Co heterostructure with insulating interlayers

TL;DR

This study demonstrates a significant superconducting spin valve effect in Co/Pb/Co heterostructures with intentionally oxidized interfaces, challenging the assumption that perfect metallic contact is necessary for strong spin valve effects.

Contribution

It reveals that oxidized, intentionally deteriorated interfaces can still produce a substantial spin valve effect, providing an alternative approach to optimize superconducting spin valves.

Findings

Observed a 0.2 K shift in T_c with magnetization switching.

Confirmed earlier unverified results with oxidized interfaces.

Showed that interface deterioration does not eliminate the spin valve effect.

Abstract

We report the superconducting properties of the Co/Pb/Co heterostructures with thin insulating interlayers. The main specific feature of these structures is the intentional oxidation of both superconductor/ferromagnet (S/F) interfaces. We study variation of the critical temperature of our systems due to switching between parallel and antiparallel configurations of the magnetizations of the two magnetic layers. Common wisdom suggests that this spin valve effect, which is due to the S/F proximity effect, is most pronounced in the case of perfect metallic contact at the interfaces. Nevertheless, in our structures with intentionally deteriorated interfaces, we observed a significant full spin valve effect. A shift of the superconducting transition temperature $T_c$ by switching the mutual orientation of the magnetizations of the two ferromagnetic Co layers from antiparallel to parallel amounted to $\Delta T_c =0.2$ K at the optimal thickness of the superconducting Pb layer. Our finding verifies the so far unconfirmed earlier results by Deutscher and Meunier on an F1/S/F2 heterostructure with oxidized interlayers [https://doi.org/10.1103/PhysRevLett.22.395, G. Deutscher and F. Meunier, Phys. Rev. Lett. 22, 395 (1969)] and suggests an alternative route to optimize the performance of the superconducting spin valves.