SUPERCONDUCTING TRANSPORT-PROPERTIES OF EPITAXIAL YBA2CU3O7-DELTA THIN-FILMS - A CONSISTENT DESCRIPTION BASED ON THERMALLY-ACTIVATED FLUX MOTION

The electrical-transport current properties of a series of epitaxial YBa2Cu3O7-delta thin films have been investigated using a range of techniques, including the activated electrical resistivity for fields B > B(irr), the irreversibility field; the I-V curves for both B > B(irr) and B < B(irr); and the resistive transitions in magnetic fields. The results are analyzed in the framework of a model for thermally-activated flux motion. The model utilizes a pinning barrier that is dependent on the current density J, temperature T, and applied magnetic field B, given by U0 is-proportional-to exp(-J/J(c0))(1 - t)n/B, with n approximately 1.8. The exponential J dependence agrees well with the behavior U is-proportional-to J(-mu) (mu approximately 0.8) of the collective-flux-creep model in the regime J < J(c0)), while properly describing the finite pinning potential observed in the activated-flux-flow regime as J --> 0. The resulting analysis using this form for U0 provides a quantitatively self-consistent interpretation of all sets of measurements.