Spin-orbit torques in heavy metal/ferromagnet bilayers with varying strength of interfacial spin-orbit coupling

TL;DR

This study provides experimental evidence that interfacial spin-orbit coupling significantly influences spin transport and spin-orbit torques in heavy metal/ferromagnet bilayers, affecting device efficiency.

Contribution

It demonstrates that interfacial spin-orbit coupling is the main factor behind spin memory loss and impacts spin-orbit torques, highlighting the need to minimize ISOC for better SOT devices.

Findings

Increased ISOC reduces dampinglike SOT linearly.

ISOC degrades spin transparency at the interface.

Fieldlike SOT is mainly influenced by the spin Hall effect.

Abstract

Despite intense efforts it has remained unresolved whether and how interfacial spin-orbit coupling (ISOC) affects spin transport across heavy metal (HM)/ferromagnet (FM) interfaces. Here we report conclusive experiment evidence that the ISOC at HM/FM interfaces is the dominant mechanism for "spin memory loss". An increase in ISOC significantly reduces, in a linear manner, the dampinglike spin-orbit torque (SOT) exerted on the FM layer via degradation of the spin transparency of the interface for spin currents generated in the HM. In addition, the fieldlike SOT is also dominated by the spin Hall contribution of the HM and decreases with increasing ISOC. This work reveals that ISOC at HM/FM interfaces should be minimized to advance efficient SOT devices through atomic layer passivation of the HM/FM interface or other means.