Ultrasonic Attenuation near the Néel Temperature of Chromium

It has been known for several years that single crystals of chromium display a narrow peak in the ultrasonic attenuation at temperatures near the Neel temperature. There are presented detailed measurements of the attenuation of longitudinal waves which were made to ascertain whether the peak could be explained by a temperature‐dependent relaxation time. The attenuation was found to increase linearly with frequency for temperatures above the peak, and was not a simple function of frequency at lower temperatures. In either case, a simple relaxation mechanism appears not to operate, and a theory developed specifically for chromium seems necessary. The temperature dependence of the attenuation above the peak temperature follows a Gaussian falloff and is probably attributable to inhomogenieties, which smear out the local Neel temperatures.