Nonlinear Acoustic Spin Pumping Caused by Temperature-Dependent Frequency Shifts of Surface Acoustic Waves

The resonant frequencies of surface acoustic wave (SAW) peaks are known to shift with temperature due to the change in sound velocity of a piezoelectric substrate. Here, we demonstrate that the previously observed nonlinear power dependence of spin current generated by SAWs is a consequence of frequency shifts of SAW peaks due to heating generated at the interdigital transducers. Furthermore, we have observed the emergence of higher-frequency peaks and changes in peak shapes, specifically at high input power. These phenomena are exclusively apparent when utilizing an acoustic cavity constructed with acoustic Bragg reflector gratings. Our systematic study aims at assisting in a deeper understanding of SAW devices in spintronics, particularly, when using acoustic cavities.

Automated summary

We find that the temperature-induced changes in sound velocity of a piezoelectric substrate lead to shifts in the resonant frequencies of surface acoustic wave (SAW) peaks. The previously observed nonlinear power dependence of spin current generated by SAWs is a result of frequency shifts of SAW peaks caused by heating at the interdigital transducers. Additionally, the utilization of an acoustic cavity constructed with acoustic Bragg reflector gratings leads to the emergence of higher-frequency peaks and changes in peak shapes, particularly at high input power.