BEHAVIOR OF CRITICAL CURRENTS IN BI-PB-SR-CA-CU-O/AG TAPES FROM TRANSPORT AND MAGNETIZATION MEASUREMENTS - DEPENDENCE UPON TEMPERATURE, MAGNETIC-FIELD, AND FIELD ORIENTATION

We have measured the dependence of the transport critical-current density on magnetic field and temperature of a high-J(c) Bi-Sr-Ca-Cu-O/Ag tape sample. At low temperature, J(c) > 10(4) A/cm2 extends to high fields as previously reported by several groups. For T > 20 K and with the applied field parallel to the c axis, J(c) declines precipitously with increasing field and temperature, reflecting the properties of intragranular pinning. The variation of J(c) with the angle between B and the tape normal is consistent with a two-dimensional model of the vortex lattice. Independent determination of J(c) by magnetic hysteresis measurement shows rough agreement with transport J(c)'s at low fields but falls below by a factor that increases with increasing field and temperature. This can be accounted for by a model for thermally activated flux motion.