TEMPERATURE-DEPENDENT ROLES OF INTERGRAIN AND INTRAGRAIN CURRENT SYSTEMS ON THE CRITICAL-CURRENT AND MAGNETIZATION OF BSCCO-2223 AG TAPES/

In this study we examine the role of inter- and intragrain current sys tems on the temperature-dependent critical current and magnetization o f BSCCO-2223/Ag tapes. Experiments were done by measuring the sample m agnetization field with movable miniature Hall sensors. We found that both systems have their own irreversible characteristics. The overall level of the intergrain (transport) critical current density, J(c), wa s limited at both lower (<30 K) and higher temperatures (30-95 K) by i ntergranular nux pinning, which seemed to be related to the maximum Jo sephson current of the weak links. Furthermore, we found that the irre versible intragranular magnetization has an influence on the magnetic field dependence of the intergrain J(c): when the intragrain pinning i s strong (as at lower temperatures), the reduction of J(c) in magnetic fields is moderate, and, when it is weaker (at higher temperatures), the decrease of J(c) in fields is strong. This is a consequence of the field dependence of the maximum Josephson current density of the weak links, when the adjacent superconducting grains are in the mixed stat e.