MAGNETOFINGERPRINTS OF SUPERCONDUCTING FILMS - VORTEX DYNAMICS AND MESOSCOPIC-SCALE DISORDER

The variations of voltage and voltage noise with magnetic field in c-a xis-oriented DyBa2Cu3O7-8 thin films exhibit reproducible, microstruct ure-dependent ''magnetofingerprints'' (MFs). The MF's can be scrambled with the reversal of the direction of the Lorentz force on field-indu ced vortices. Analysis of the noise suggests a strong dependence of th e local free-energy landscape on vortex density similar to global frus tration effects found in periodic superconducting networks. Above fiel ds which roughly match vortex separation with mesoscopic-scale disorde r in the films the noise and the fine structure of the MFs are suppres sed, suggesting a crossover to a more weakly pinned vortex-liquid regi me.