High amplitude dislocation damping in superconducting Pb and In

The amplitude dependence of ultrasound absorption due to dislocations, 'alpha', has been studied for single crystals of pure lead and indium as well as for lead doped with Tl, Sn or Bi, both in the superconducting and normal state and for a wide range of ultrasound amplitudes, epsilon0. Pure and Tl-doped superconducting lead at large epsilon0 displayed a maximum on the α (epsilon0) dependence which became a plateau upon transition to the n-state. This is direct evidence for a change from static to dynamic dislocation hysteresis as a result of the increase in the electron drag constant. Limit values for the dislocation loop lengths have been estimated, viz. 2.4 x 10-4 cm < l/sub N/ < 10.4 x 10-4 cm. In other single crystals the dynamic hysteresis occurred both in the n- and s-state. In all the single crystals, α increased with the increase of epsilon0 above the maximum amplitude and onset of the plateau which was observed in both states. The effect is associated with non-linear phenomena arising at significant loop flexures. The amplitude dependence of the losses due to this effect has been analysed, the results of the analysis being in good agreement with the experimental data. (author)