Electromagnetic radiation of the travelling spin wave propagating in an antiferromagnetic plate. Exact solution

Abstract

The exact solution of radiation problem of a spin wave travelling in an antiferromagnetic (AFM) plate was found. The spin wave with in-plane oscillations of antiferromagnetism vector was considered. In this case the magnetization vector is oscillating being perpendicular to the AFM plate and depends on time and plane coordinates as travelling wave does. This model allows to obtain exact analytical expression for Hertzian vector and, consequently, the retarded potentials and field strengths as well. It is shown that expressions obtained describe Cherenkov radiation caused by the travelling wave. The radiated electromagnetic wave is the TEM type if a phase velocity exceeds the speed of light. Otherwise electric and magnetic field values exponentially decrease in the direction normal to the plate. The energy losses were evaluated also.