Magnetic characterization of Ag-sheathed Bi(Pb)2223 tapes

Ag/BPSCCO (2223) tapes were characterized by SQUID magnetometry over a wide range of temperatures (4.2-95 K) and under a magnetic field H (up to 5 T) applied either parallel or perpendicular to the c axis of the tape. For the two different field orientations, taking into account (when required) the anisotropy of the currents and demagnetization effects, the values of the critical current density J(c) were evaluated as a function of the applied magnetic field H and temperature. The magnetization decay for H perpendicular to the c axis exhibited a non-linear dependence of the flux creep activation energy on the current J. From J(c)(T) behaviour and from the relaxation data M(t) some conclusions about dissipation mechanisms were drawn.