Flux creep in the Josephson mixed state of granular‐oriented YBa2Cu3O7−xthin thin films

A self‐consistent critical current model in the Josephson mixed state is proposed for a series of 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.