Ultrasonic attenuation in the heisenberg paramagnet. II. Antiferromagnets

Abstract

The propagation of sound waves in antiferromagnetic insulators is studied within the framework of two models which describe the interaction between the spin system and the lattice. In particular, expressions for the ultrasonic attenuation coefficient near the Néel point are obtained in terms of time-dependent correlation functions. The attenuation coefficient is found to be proportional to the square of the phonon frequency, to increase rapidly in the vicinity of the Néel point, and to be less singular than the attenuation coefficient for ferromagnetic insulators. © 1967 The American Physical Society.