Tunable Surface Acoustic Wave Resonator Based on Magneto-Acoustic Waveguide

Abstract

Magnetic field tunable surface acoustic wave (SAW) devices are promising candidates for frequency tunable applications such as tunable acoustic filters, magnetic field sensors, and quantum acoustic devices. However, achieving practical levels of tunability remains a significant challenge. We enhance the tunability by introducing a magneto-acoustic waveguide design that concentrates acoustic energy within a magnetostrictive layer with low acoustic velocity, thereby amplifying the delta-E effect and enhancing its impact on SAW propagation. Using a 128°Y-X cut LiNbO3/SiO2/Fe $_{{70}.{4}}$ Ga $_{{17}.{6}}$ B12 (FeGaB) structure, we demonstrate that the tunability correlates with the thickness of FeGaB, consistent with our simulation results. The device with a 670 nm thick FeGaB magneto-acoustic waveguide achieves a maximum frequency shift of 5.134 MHz, corresponding to a tunability of 1.23%. These results underscore the efficacy of the magneto-acoustic waveguide approach in significantly enhancing the tunability of magnetic SAW devices, offering a viable path toward more practical tunable microwave components.