Flux creep characteristics in the presence of a pinning distribution for Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconducting thin films

Nonlinear current-voltage I-V characteristics in Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films have been studied for flux creep taking into account the inhomogeneous pinning strength. By measuring the frequency dependence of the I-V characteristics, we separated the flux creep and flux flow properties. I-V curves split in the low electric-field region depending on the measurement frequency. From the frequency dependant I-V curves, we obtained the maximum creep field, at which flux creep crossed over to flux flow. By use of the Weibull function, which describes the depinning probability of flux lines in pinning sites, we determined the pinning distribution from the flow nonlinearity obtained from AC measurements. The flux creep electric-field was calculated by integrating the Arrhenius equation according to the pinning distribution. The obtained expressions agreed will with the measurement over more than six decades of electric field.<
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