Internal friction peak in Csl single crystal at liquid helium temperatures

Acoustic relaxation in undeformed and plastically deformed CsI single cryst als is studied using the composite oscillator technique at frequencies (1-7 ) X 10(5) Hz in the temperature range 2-15 K. Plastic deformation leads to the emergence of an internal friction peak localized in the temperature ran ge 4-5 K, It is shown that the peak is shifted towards higher temperatures upon an increase of the vibrational frequency and corresponds to a thermall y activated relaxation process with very low values of activation energy U approximate to 1.9 X 10(-3) eV and the attack frequency nu(0) approximate t o 6.7 X 10(8) s(-1), The interaction of sound with dislocation kinks migrat ing in the second-order Peierls relief is considered as a possible mechanis m of peak formation. (C) 1998 American Institute of Physics. [S1063-777X(98 )01012-3].