Irrelevance of magnetic proximity effect to spin-orbit torques in heavy metal/ferromagnet bilayers

TL;DR

This study investigates whether the magnetic proximity effect influences spin-orbit torques in heavy metal/ferromagnet bilayers and finds it has negligible impact compared to other interfacial effects.

Contribution

The paper demonstrates that the magnetic proximity effect does not significantly affect spin-orbit torques in HM/FM bilayers, challenging previous assumptions about its role.

Findings

MPE can be enhanced by thermal annealing.

MPE has no discernable influence on spin-orbit torques.

Other interfacial effects like spin memory loss are more significant.

Abstract

The magnetic proximity effect (MPE) is a well-established magnetic phenomenon that occurs at certain heavy metal (HM)/ferromagnet (FM) interfaces. However, there is still an active debate as to whether the presence of a MPE affects spin transport through such a HM/FM interface. Here we demonstrate that the MPE at Pt/Co and Au0.25Pt0.75/Co interfaces can be enhanced substantially by thermal annealing protocols. From this ability, we show that the MPE has no discernable influence on either the damping-like or the field-like spin-orbit torques exerted on the FM layer due to the spin Hall effect of the HM layer, indicating a minimal role of the MPE compared to other interfacial effects, e.g. spin memory loss and spin backflow.