The propagation and attenuation of acoustic waves in ferromagnetic metals

Abstract The physics underlying the propagation and attenuation of acoustic waves in ferromagnetic metals is discussed. The propagating modes are considered as coupled acoustic phonon-magnon-photon modes and their dispersion relation is derived for both ferromagnetic insulators and metals by treating the modes as electromagnetic waves. The damping of the coupled modes is discussed in terms of the individual damping mechanisms for the acoustic phonons, magnons and photons and their relative content as a function of frequency. Data on the attenuation of high frequency (220 MHz) sound waves at low temperatures in ferromagnetic Ni is presented and discussed.