Variations caused in low-temperature dislocation internal friction in antimony by high-amplitude ultrasonic oscillations

We studied the changes caused in the dislocation internal friction of antimony single crystals by high-amplitude ultrasonic pulses at temperatures of 300, 78, 4.2, and 1.8°K. It was found that at 4.2 and 1.8 °K the high-amplitude pulses caused a decrease in the internal friction only in the amplitude-dependent region whereas at 78°K the internal friction increased over the entire range of amplitudes. The kinetics of the change in the internal friction under the effect of high-amplitude pulses was investigated. The fact that the maximum of the damped dislocation resonance shifted position when the temperature was lowered to 4.2°K is evidence of considerable changes in the dislocation structure of the specimens. The difference in the dislocation structures is responsible for the different character of the variations of the internal friction under the effect of high-amplitude pulses. The results are interpreted in terms of the concepts of the Granato-Liicke and Rogers theories of athermal dislocation unpinning.

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