Nonreciprocally Boosting Magnetoacoustic Coupling with Surface-Acoustic-Wave-induced Spin Transfer Torque

TL;DR

This paper demonstrates a novel method to enhance magnetoacoustic coupling in surface acoustic wave devices by using SAW-induced spin transfer torque, leading to nonreciprocal wave transport and potential on-chip applications.

Contribution

It introduces a nonreciprocal boosting technique for magnetoacoustic coupling via SAW-induced spin transfer torque in multilayer structures, with implications for device development.

Findings

Enhanced magnetoacoustic coupling by suppressing magnon dissipation.

Observation of nonreciprocal SAW transport under magnetic field.

Identification of Zhang-Li torque as the mechanism.

Abstract

Strengthening magnetoacoustic coupling is crucial to the improvement of the surface acoustic wave (SAW)-driven spintronics devices. A key challenge in enhancing magnetoacoustic coupling is minimizing the phonon and magnon dissipation of the device, which usually requires complicated techniques for generating shear-horizontal (SH) or standing waves to suppress the phonon dissipation. In this work, we significantly strengthened the magnetoacoustic coupling by suppressing the magnon dissipation via the SAW-induced spin-transfer-torque (STT) in Co/Cu/NiFe multilayer, which is facilitated by the non-parallel magnetization alignment between the two ferromagnetic layers. Also, this STT exhibits the form of Zhang-Li torque due to the SAW-induced spin wave, which gives rise to the unique nonreciprocal SAW transportation under external magnetic field. This finding opens new avenues for non-reciprocally boosting magnetoacoustic coupling, which pays the way for developing on-chip SAW-driven multifunctional devices.