Acoustic relaxation in non-deformed and plastically deformed single crystals was studied by using a composite oscillator technique at 0.1 to 0.7MHz and 2 to 15K. It was found that plastic deformation led to the appearance of an internal friction peak which was localized between 4 and 5K. The peak shifted towards higher temperatures upon increasing the vibration frequency; corresponding to a thermally activated relaxation process with an activation energy of 0.0019eV and an attack frequency of 6.7 x 108/s. The interaction of sound waves with dislocation kinks migrating in the second-order Peierls relief was considered to be a possible cause of the peak.

Anomalies of Internal Friction in CsI Single Crystal at Liquid Helium Temperatures Caused by Plastic Deformation. V.D.Natsik, S.N.Smirnov, P.P.Pal-Val: Czechoslovak Journal of Physics, 1999, 49[7], 1091-6