Large surface acoustic wave nonreciprocity in synthetic antiferromagnets

TL;DR

This study demonstrates significant nonreciprocal surface acoustic wave transmission in synthetic antiferromagnets, with potential applications in acoustic circulators and isolators, by tuning interlayer exchange coupling.

Contribution

It reveals how interlayer exchange coupling in ferromagnetic multilayers induces strong SAW nonreciprocity, a novel mechanism for acoustic device design.

Findings

SAW transmission depends on propagation direction in coupled ferromagnetic layers

Nonreciprocity increases with exchange coupling strength

Maximum nonreciprocity reaches 37 dB/mm with thin spacer layers

Abstract

We have studied the transmission of surface acoustic waves (SAWs) in ferromagnetic/non-magnetic/ferromagnetic tryilayers. The SAW scattering matrix is studied for devices with various non-magnetic spacer thickness, which defines the strength of the interlayer exchange coupling. We find the SAW transmission amplitude depends on their propagation direction when the two ferromagnetic layers are coupled antiferromagnetically. The degree of such SAW nonreciprocity increases with increasing exchange coupling strength and reaches 37 dB/mm for a device with the thinnest spacer layer. These results show the potential of interlayer exchange coupled synthetic antiferromagnets for viable acoustic nonreciprocal transmission devices, such as circulators and isolators.