EXCESS CONDUCTIVITY AND THERMALLY ACTIVATED DISSIPATION STUDIES IN BI2SR2CA1CU2OX SINGLE-CRYSTALS

The resistivity of Bi2Sr2Ca1Cu2Ox single crystals has been measured in the ab-plane and along the c-axis. In all the directions the resistivity shows metallic behavior in the normal state. Room temperature resistivity along the c-direction is about 64 times higher than that in the ab-plane. Departure from the linear behavior occurs at 96 K and the zero resistance is obtained at 76 K. Excess conductivity analysis shows that the system is 2-dimensional in the temperature range 78.7-96 K and a 3-dimensional one below 78.7 K. Thus, a crossover from 2D to 3D is observed at 78.7 K in the Bi-2212 single crystal. This crossover was not detected in Bi 2212 or 2223 polycrystalline samples. The width of the transition (ΔT) varies with the application of magnetic field (H) as H0.85 in Bi 2212 single crystal. The pinning potential (U0) varies as H-α where α=0.3 for the Bi-2212 single crystal and 0.47 for polycrystalline sample. © 1990.