Comparison between the ultrasonic and the low frequency Bordoni peaks in copper

A comparison between properties of the Bordoni peaks at low and high frequency is realised from experimental data of attenuation and velocity obtained at Hz and MHz frequencies. The measurements were obtained in crystalline samples, all of them cut from the same crystal lot. Significant differences on secondary properties are obtained for the low and the high frequency peaks. The high frequency relaxation is interpreted as produced by a single relaxation process due to kink pair formation with kink diffusion in dislocation lines, but the low frequency relaxation must be considered as a more complicated process.