Anomaly in J(c)-B hysteresis for Bi-2212/Ag composite tape in high field

Transport J(c) is measured at 4.2 K in high magnetic fields up to 23 T for c-axis oriented Bi-2212/Ag composite tape prepared by using doctor blade cast tape and melt solidification techniques, and we find an anomaly in J(c)-B hysteresis around 19 T. The magnetic field is applied parallel to the tape surface (along the ab-plane). A typical J(c)-B hysteresis for polycrystalline oxide superconductor is observed below 18 T. Above 19 T, an inversion in J(c)-B hysteresis is observed. J(c)-B curves in field increasing and field decreasing sequence cross each other at a field around 19 T Between 18.7 T and 18.6 T in field decreasing sequence, J(c) increases 20% in value. At stable fields above 19 T after field increasing sequence, J(c) decreases with time.