FLUX PINNING AND CRITICAL CURRENTS IN MELT PROCESSED YBACUO SUPERCONDUCTORS

We report flux pinning behavior of melt processed YBaCuO containing Y2BaCuO5(211) inclusions. Although the size of the 211 inclusions is relatively large compared to the coherence length, they can work as pinning centers. We present the mechanism for pinning due to large normal precipitates. While large flux creep is observed in thin films exhibiting high J(c) values, flux creep rate is very small in melt processed YBaCuO having a magnitude lower J(c) values, which is understandable by considering that the pinning potential of large normal precipitates is much larger than that of small pinning centers and thereby the flux motion is less affected by thermal activation.