TEMPERATURE DEPENDENCE OF DISLOCATION RESONANCE DAMPING

Abstract
We have simultaneously measured the frequency dependence (10 to 90 MHz) of the ultrasonic attenuation α and sound velocity v on high purity Cu as function of temperature (4.2 ≤ T ≤ 300K). Irradiation pinning was used to separate the dislocation resonance (DR) contributions α_D and Ɗv_D/v_o. The evaluation of data is considerably improved by the use of the frequency dependence of Ɗv_D/v_o, specially at T < 50K where α_D becomes masked by the phonon-electron attenuation. The observed DR-effects have been analyzed in terms of the Granato-Lücke DR-theory. From the derived temperature dependences of ΛL², B/Λ and L²B (Λ dislocation density, L dislocation mean free loop length between pinning points, B dislocation drag coefficient) we find (i) B(T) in agreement with current theories and B(273K) = (4 ± 2 ). 10^-5Ns/m² including the electron drag coefficient B^e = (4 ± 2).10^-6Ns/m² ; (ii) L to be independent of T but Λ to decrease with T down to the lowest T. This Λ(T) behaviour is discussed.