The vortex phase diagram of Bi2Sr2CaCu2Oy investigated by the resistivity measurements

The mixed state of Bi2Sr2CaCu2Oy was investigated by the means of the resistivity measurements with the magnetic field applied parallel to the crystallographic c-axis direction. Under relatively low magnetic field, the resistivity showed an abrupt change with temperature at the vortex-lattice melting point, while smooth temperature dependence was observed at higher fields. Non-ohmic behavior of the resistivity was observed over a wide range of temperature and magnetic field, which apparently disappeared at high magnetic field. We discuss the observed behavior in the context of a possible vortex-glass transition.