Propagation of ultrasound near the phase transition in Ising systems

Abstract

The effects of order-parameter strain coupling on the critical (tricritical) soundattenuation and dispersion are studied above Tc in the elastically isotropic Ising model.Under free boundary conditions a cross-over in the behaviour of acoustic quantities to a‘strong-coupling’ regime is predicted. New scaling relations for the critical attenuation anddispersion are obtained and the corresponding scaling functions are calculated using an ε-expansion. Non-asymptotic effects are also discussed.