Propagacja dźwięku w pobliżu przemiany fazowej

Abstract

The book deals with the theoretical studies of critical behaviour of ultrasonic wave attenuation and propagation velocity in magnets. The effect of spin-lattice relaxation on the ultrasonic attenuation and velocity is investigated on the basis of the stochastic model including the energy relaxation and the sound mode. A novel high frequency regime in the ultrasonic attenuation is predicted. The scaling functions are calculated in the one-loop approximation within the renormalisation group formalism. In the diffusive version of the model a detailed analysis of the connection between the heat conduction and sound propagation is studied. An overview of experimental and theoretical sound attenuation exponents is also given. The ultrasonic attenuation measurements in MnF2 are interpreted in terms of the theoretical model proposed.