Interaction of Ultrasonic Waves with Electron Spins

Abstract

We discuss the interaction between paramagnetic atoms and elastic waves at microwave frequencies by means of a total Hamiltonian comprising sound field, interaction, and spins. From this Hamiltonian and the Heisenberg commutation rules we obtain a set of coupled equations of motion. The condition of compatability leads in the usual way to a secular determinant, the solution of which is a dispersion relation exhibiting the familiar anomalous change in velocity and absorption of waves near resonance.