Anomalies of sound propagation near orientational phase transitions in antiferromagnets

Abstract

AbstractThe sound velocity and attenuation anomalies, connected with the orientational phase transitions (OPT) of first and second order, are investigated for antiferromagnets and ferromagnets. For the first order OPT the anomalies are determined by the motion of the domain walls of the transitional domain structure, while for the second order one they are determined by the interaction of the sound wave and nonequilibrium deviations of the magnetization. The consideration of the influence of the magnetic subsystem on the sound propagation is reduced to the renormalization of the elastic constants. The wave equation and general expressions for the renormalization of the elastic constants, sound velocity, and attenuation are received, taking the magnetostriction and piezomagnetism into account. The comparison of the results received and available experimental data reveals the agreement of the theory and experiments.