Nonreciprocal Properties of the Backward Spin Waves

Abstract

The nonreciprocal properties of the modes of a backward spin wave in a tangentially magnetized ferrite plate have been investigated. It has been established that ratio R between the normalized amplitudes of the magnetic potential for two waves with the oppositely directed wave vectors oriented at angles φ and φ – π relative to the external magnetic field on the plate surface significantly depends on the φ value. The fR value divides the range of existence of the backward spin waves into two frequency bands: at frequencies below fR, the R(φ) dependence is monotonic (parameter R takes the minimum and maximum values at angles similar to the wave vector cutoff angles) and, at frequencies above fR, there are extreme points (maximum and minimum) at φ values equal the maximum cutoff angles of the surface spin wave. A formula has been derived for the wave vector orientation at which the m-th extreme point lying on one of the plate surfaces arises in the distribution of the amplitude of the magnetic potential of the mth wave mode in the ferrite plate cross section.