Magnetically Programmable Surface Acoustic Wave Filters: Device Concept and Predictive Modeling

TL;DR

This paper introduces a magnetically programmable SAW filter device that uses micromagnetic simulations to predict how magnetic states influence surface acoustic wave transmission, enabling frequency-specific control.

Contribution

It presents a novel device concept that programs internal magnetic states to control SAW attenuation, supported by an extended simulation model for arbitrary magnetization patterns.

Findings

Predicts 52.0 dB/mm change in SAW transmission at 3.8 GHz based on magnetic state.

Demonstrates the use of micromagnetic simulations for device modeling and design.

Extends energy conservation models for efficient simulation of magnetoelastic interactions.

Abstract

Filtering surface acoustic wave (SAW) signals of specified frequencies depending on the strength of an external magnetic field in a magnetostrictive material has garnered significant interest due to its potential scientific and industrial applications. Here, we propose a device that achieves selective SAW attenuation by instead programming its internal magnetic state. To this end, we perform micromagnetic simulations for the magnetoelastic interaction of the Rayleigh SAW mode with spin waves (SWs) in exchange-decoupled Co/Ni islets on a piezoelectric LiTaO$_3$ substrate. Due to the islets exhibiting perpendicular magnetic anisotropy, the stray-field interaction between them leads to a shift in the SW dispersion depending on the magnetic alignment of neighboring islets. This significantly changes the efficiency of the magnetoelastic interaction at specified frequencies. We predict changes in SAW transmission of 52.0 dB/mm at 3.8 GHz depending on the state of the device. For the efficient simulation of the device, we extend a prior energy conservation argument based on analytical solutions of the SW to finite-difference numerical calculations, enabling the modeling of arbitrary magnetization patterns like the proposed islet-based design.