Critical current versus field behaviour in Ag/BSCCO-2223 tapes with different critical currents

Abstract The dependence of J c upon applied magnetic field has been analysed in BSCCO-2223 tapes with different geometrical structures of the superconducting core. The samples, prepared by the PIT method, and rolled down to tapes of different thickness, were annealed up to three times with intermediate mechanical working. All measurements were carried out at 77 K, in magnetic field up to l T, applied both parallel and perpendicular with respect to the transport current. Several samples with the same J c and different I c and superconducting core thickness were measured and compared. All samples showed a qualitatively similar “memory effect”, with higher values of J c measured with decreasing magnetic field, but remarkable differences in the low fields regime, where thinner tapes (lower I c ) showed a faster decay of J c with B compared with the thicker ones. A simple semi-quantitative explanation, taking into account the self field of tapes, was well supported by tests carried out in a special experimental arrangement so designed as to allow to characterize the “true” zero self-field behaviour of the material.