Magnetization control by angular momentum transfer from surface acoustic wave to ferromagnetic spin moments

R Sasaki,Y Nii,Y Onose

doi:10.1038/s41467-021-22728-6

Abstract

Interconversion between electron spin and other forms of angular momentum is useful for spin-based information processing. Well-studied examples of this are the conversion of photon angular momentum and rotation into ferromagnetic moment. Recently, several theoretical studies have suggested that the circular vibration of atoms work as phonon angular momentum; however, conversion between phonon angular momentum and spin-moment has yet to be demonstrated. Here, we demonstrate that the phonon angular momentum of surface acoustic wave can control the magnetization of a ferromagnetic Ni film by means of the phononic-to-electronic conversion of angular momentum in a Ni/LiNbO3 hybrid device. The result clearly shows that the phonon angular momentum is useful for increasing the functionality of spintronic devices.

Highlights

Interconversion between electron spin and other forms of angular momentum is useful for spin-based information processing
This device is composed of a piezoelectric LiNbO3 substrate, two interdigital transducers (IDTs) and a ferromagnetic Ni film[19,20,21,22]
We have demonstrated magnetization control by the angular momentum transfer from a surface acoustic wave (SAW) to ferromagnetic spin moments

Summary

Introduction

Interconversion between electron spin and other forms of angular momentum is useful for spin-based information processing. Well-studied examples of this are the conversion of photon angular momentum and rotation into ferromagnetic moment. We demonstrate that the phonon angular momentum of surface acoustic wave can control the magnetization of a ferromagnetic Ni film by means of the phononic-to-electronic conversion of angular momentum in a Ni/LiNbO3 hybrid device. When a spinpolarized electrical current is injected into a microscale ferromagnet, the spin angular momentum of the conduction electrons is transferred to ferromagnetic localized moment (Fig. 1a). This mechanism is used to control magnetic storage in magnetoresistive random access memories[2]. A Rayleigh-type surface acoustic wave (SAW) has elliptically polarized displacement[17], which indicates that the phonon angular momentum is finite (Fig. 1c). We use the SAW current to demonstrate the conversion from phonon angular momentum to magnetization

Methods

Results

Conclusion