Critical current anisotropy and flux pinning in YBCO [001] and YBCO [110] superconducting thin films prepared by KrF pulsed laser ablation

Direct transport critical current density (J/sub c/) measurements were performed on laser-ablated high-quality Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ superconducting thin films with T/sub co/>or=90 K, J/sub c/ approximately=5*10/sup 6/ A/cm/sup 2/ at 77 K, and intentionally controlled film orientations to investigate the J/sub c/ anisotropy and predominant pinning mechanisms in these films. It was found that, for films with [001] oriented normal to the substrate, the field dependencies of the critical current densities J/sub c/(H) showed very different behavior for different field orientations, indicating that the active pinning mechanisms may be different in two field directions. For [110]-oriented films with field applied normal to the film surface, the pinning mechanism was found to follow the manifestation of surface-core pinning. At zero field, however, the temperature dependence of J/sub c/ revealed that, in all cases, the critical current was limited by flux creep with essentially the same creep kinetic factor expected for high-T/sub c/ cuprates. Detailed results on the scaling behaviors of the pinning force density as functions of both field and temperatures for fields up to 7 T are presented and compared for different films and field orientations.<
>