Alternating Current-induced Interfacial Spin-transfer Torque

TL;DR

This paper studies how alternating current can resonantly enhance interfacial spin-transfer torque and introduces a method to estimate exchange interaction strength from domain wall motion, revealing new contributions to the torque.

Contribution

It demonstrates the resonance effect of AC on interfacial spin-transfer torque and identifies a novel contribution to the $eta$-term torque independent of spin relaxation.

Findings

Resonant enhancement of torques near exchange splitting energy

Direct estimation of exchange interaction strength from domain wall motion

Unconventional $eta$-term contribution proportional to current derivative

Abstract

We investigate an interfacial spin-transfer torque and $\beta$-term torque with alternating current (AC) parallel to a magnetic interface. We find that both torques are resonantly enhanced as the AC frequency approaches to the exchange splitting energy. We show that this resonance allows us to estimate directly the interfacial exchange interaction strength from the domain wall motion. We also find that the $\beta$-term includes an unconventional contribution which is proportional to the time derivative of the current and exists even in absence of any spin relaxation processes.