Anomalous Ultrasonic Attenuation above the Magnetic Critical Point

Abstract
The mode-mode coupling theory of Kadanoff and Swift is used to describe the rise in the ultrasonic attenuation as a material approaches its magnetic transition. Near the transition, dynamic fluctuations in the magnetic order cause increased absorption of the sound. Predictions are made of the increased attenuation in various models of magnetic systems. A comparison with experiment is carried out.