ACTIVATION ENERGIES IN THE VORTEX LIQUID STATE OF BULK (Bi1.6Pb0.4)(Sr1.8Ba0.2)Ca2Cu3Oy SUPERCONDUCTOR

Magnetoresistivity measurements as a function of temperature, ρ(B, T) in applied magnetic field B up to 0.7 T have been carried out on a sample of the 110 K phase of the (Bi, Pb)-(Sr, Ba)-Ca-Cu-O system. The dρ/dT versus T curves in an applied magnetic field reveal the intra- and intergranular transitions. The behavior of these transitions as function of the magnetic field is presented. Thermally activated flux motion has been studied. The activation energy is proportional to (1−T/Tc)ln B, and suggests a 2D-state in which the dissipation is dominated by the cutting mechanism in an entangled flux liquid.