Amplitude- and Temperature-Dependent Pinning and Unpinning of Dislocations in bcc and hcpHe3

Abstract
Measurements of the temperature dependence of the longitudinal sound velocity and attenuation in solid He3 show a frequency-dependent anomaly due to interactions between the ultrasonic waves and dislocations. By application of high-amplitude sound pulses at temperatures below about 0.4 K, the attenuation can be greatly reduced and the velocity changed. Upon warming, the velocity and attenuation return to their initial values by a thermally activated process whose activation energy appears to be that of mobile vacancies.