Suppression of dissipative flux-motion in a high-Tc (Bi,Pb)-2212 superconductor by Dy-doping

The temperature and magnetic field dependences of the activation energy and flux-pinning properties of Dy-doped (Bi,Pb)-2212 superconductor are systematically measured for a broad doping range. The behaviour of vortex dynamics close to a vortex-liquid to glass transition [Uo(B,Tg)=kBTg] is analysed by the modified thermally activated flux-creep theory. The results show that the temperature and field dependence of Uo(B,T) is related to the strong thermal fluctuation at elevated temperatures and fields which can be suppressed by the introduction of the point defects due to Dy-doping. These point defects act as additional flux-pinning centers and the superconductor remains in the glassy-vortex-state.