The ultrasonic logarithmic decrement and modulus defect in high-purity crystals were measured at 10, 30 and 50MHz, for temperatures of 5 to 373K. The samples were deformed by 3 to 20% at room temperature, along the <111> direction. The experimental data were fitted over the entire range of temperatures, by assuming that contributions arose from 2 kink mechanisms. These were relaxation via kink-pair formation, with diffusion in the dislocation line, and over-damped resonance of the kink chain; with a temperature-dependent number of kinks in the dislocation lines. In this way, both primary and secondary properties of the high-frequency Bordoni peak could be satisfactorily explained.

The Ultrasonic Bordoni Peak in Copper Crystals and the Kink Picture. A.O.Moreno-Gobbi, J.A.Eiras: Journal of Physics - Condensed Matter, 2000, 12[6], 859-70