Comparing powder magnetization and transport critical current of Bi,Pb(2223) tapes

The magnetic field dependence of the critical current in (Bi, Pb)(2)Sr2Ca2Cu3O10+x tapes is compared with the magnetization response of isolated grains extracted from the tapes. Special attention is paid to the low-field behavior. The goal of the experiment is to test the widely-used hypothesis that current paths in these tapes contain both weak- and strong- linked branches, which in low field act in parallel. The data, agree with this hypothesis; at temperatures above 50 K the powder magnetization drops off exponentially from the self-field to the irreversibility field, while the transport and magnetization currents in the intact tapes show. an extra low-field component. Below 50 K the powder behavior becomes less straightforward, hut the parallel-path picture in the tapes still holds.