The c-axis dissipation and vortex phases in Bi2Sr2CaCu2O8+x crystals

We report on measurements of the resistivities of Bi2Sr2CaCu2O8+x crystals along the c axis (rho(c)) as well as in the ab plane (rho(ab)) in magnetic fields applied parallel to the c-axis (H parallel to c) from 10 Oe to 60 kOe. From the temperature dependence of the resistivity ratio rho(ab)/rho(c) in relatively low magnetic field below 1 kOe, we identified the vortex-solid, pancake-vortex and possible line-vortex phases. This suggests that a vortex solid in highly anisotropic high-T-c superconductors like Bi2Sr2CaCu2O8+x crystals, at least in this nonequilibrium situation, exhibits a two-stage transition into a vortex gas via a vortex liquid. (C) 1997 Elsevier Science Ltd.X112sciescopu