Critical Current Anisotropy and Flux Pinning in Ybcofool) and Ybco(Llo) Superconducting Thin Films Prepared by Krf Pulsed Laser Ablation

Direct transport critical current density (Jc) measurements were performed on laser ablated high quality YiBa2Cua07 superconducting thin films with Tco≥90 K, Jc a 5xl06 A/cm2 at 77 K, and intentionally controlled film orientations to investigate the Jc 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 JC(H) showed very different behaviors for different field orientations, indicating that the active pinning mechanisms may be different in two field directions. For the (HO)-oriented films with field applied normal to film surface, the pinning mechanism, as depicted from the scaling behavior of the global pinning force density, was found to follow the manifestation of surface-core pinning. At zero field, however, the temperature dependence of Jc revealed that, in all cases, the critical current was limited by flux creep with essentially the same creep kinetic factor expected for high-Tc cuprates. Detailed studies of the scaling behaviors of the pinning force density as functions of both field and temperatures for fields up to 7 Tesla will be presented and compared for different films and field orientations.