Acoustic gyromagnetic effect

Abstract

The gyromagnetic effect is one of the most significant discoveries in physics. It is associated with a mutual conversion of angular momentum between macroscopic mechanical rotation and microscopic electron spin. However, the gyromagnetic field generated by a feasible mechanical rotor is very small for practical applications. Surface acoustic waves are a promising candidate for improving the gyromagnetic effect because an elliptical oscillation of the lattice with a frequency of the GHz order can be realized. In this paper, experimental demonstrations of a gyromagnetic spin-wave excitation and its reciprocal effect, that is, a phase shift of the acoustic wave, are presented. Furthermore, we show that the gradient of the acoustic gyromagnetic field can produce an alternating spin current whose amplitude increases nonlinearly with the frequency.