Voltage-driven v.s. Current-driven Spin Torque in Anisotropic Tunneling Junctions

TL;DR

This paper theoretically investigates spin torque mechanisms in magnetic tunnel junctions with interfacial spin-orbit interaction, revealing voltage-driven and current-driven components with implications for magnetic device control.

Contribution

It introduces a theoretical model showing how interfacial spin-orbit interaction induces tunable spin torques in magnetic tunnel junctions, depending on barrier thickness.

Findings

Perpendicular torque $T_{\bot}$ can be electrically tuned by voltage.

In-plane torque $T_{||}$ emerges in thin barriers and is proportional to tunneling current.

Interfacial SOI generates spin torque without external spin polarizer.

Abstract

Non-equilibrium spin transport in a magnetic tunnel junction comprising a single magnetic layer in the presence of interfacial spin-orbit interaction (SOI) is studied theoretically. The interfacial SOI generates a spin torque of the form {\bf T}=T_{||}{\bf M}x({\bf z}x{\bf M})+T_{\bot}{\bf z}x{\bf M}, even in the absence of an external spin polarizer. For thick and large tunnel barriers, the torque reduces to the perpendicular component, $T_{\bot}$, which can be electrically tuned by applying a voltage across the insulator. In the limit of thin and low tunnel barriers, the in-plane torque $T_{||}$ emerges, proportional to the tunneling current density. Experimental implications on magnetic devices are discussed.