Mechanical investigation of flux dissipation in Hg system high-T-c superconductors

The mechanical dissipation and modulus in Hg system high-T-c superconductors were measured as functions of temperature, applied magnetic field and vibrating amplitude with the vibrating-reed technique. The depinning lines were obtained from the temperature where the dissipation peak occurred in different applied fields. It is found that the temperature of the maximum dissipation shifted towards lower temperature with increasing vibrating amplitude. Nonlinear thermally activated flux diffusion was used to explain the amplitude dependence of the flux dissipation. Another possible mechanism was also disscussed. Furthermore, the effect of Fe and Pb doping on the flux pinning of the samples was investigated.