LOW-FIELD SCALING BEHAVIORS OF GLOBAL FLUX PINNING IN TL-BA-CA-CU-O THIN-FILMS

The scaling behaviors of global pinning force density (F(p) = J(c) X B) in dc sputtered TI-Ba-Ca-Cu-0 superconducting thin films as functions of both the reduced magnetic field and temperature were investigated by direct transport measurements for fields up to 4 kOe. It was found that, depending on the film granularities (originating from different deposition and annealing conditions and characterized by the temperature and magnetic-field dependencies of critical currents), vastly different scaling behaviors were manifested. For films with very high critical current densities, where the intragranular behaviors prevailed, the conventional surface core pinning by some high-density normal pinning centers combined with a significant flux creep appeared to be the predominant limiting mechanisms for the critical current densities, whereas in more granular films, suggestive collective-pinning effects arising from the weakly pinned fluxoids in the intergranular networks were observed.