Anomalies of internal friction in CsI single crystal at liquid helium temperatures caused by plastic deformation

摘要

Acoustic relaxation in undeformed and plastically deformed CsI single crystal has been studied using the composite oscillator technique at frequencies(1-7)×10~5 Hz in the tem- perature range 2-15 K. Plastic deformation leads to appearance of an internal friction peak localized in the temperature interval 4-5 K. It is shown that the shifts towards higher temperatures when increasing the vibration frequency and corresponds to a thermally ac- tivated relaxation process with very low values of the activation energy U≈109×10~-3eV and the attack frequency v_06.7≈10~8×s~-1. Interaction of sound with dislocation kinks migrating in the second order Peierls relief is considered as a possible mechanism of the peak.