Flux creep in the Josephson mixed state of granular-orientedYBa sub 2 Cu sub 3 O sub 7 minus x thin thin films

A self-consistent critical current model in the Josephson mixed state is proposed for a series of {ital c}-oriented, polycrystalline and for a series of epitaxial triaxially oriented YBCO thin films. The flux pinning activation energies were experimentally determined from electrical transport measurements over a wide range of temperatures and were found to behave quite differently for the two types of granular film. With these activation energies applied to a superconductor-normal metal-superconductor weak-link system, thermally activated flux motion is shown to reproduce the experimentally measured critical current densities.