FLUX CREEP AND THE NATURE OF A FLUX BUNDLE IN HIGH-TC THIN-FILMS

We describe measurements of the temperature and magnetic-field dependence of the resistance and critical current in laser-deposited thin films of the high-temperature superconductor YBa2Cu3O7-x. We identify two regimes: At low current densities and magnetic fields the sample is Ohmic. We attribute dissipation in this regime to activated flux motion of individual flux quanta in a vortex glass. In the high current and magnetic-field regime we show that collective vortex motion is occurring, and we propose a model for the structure of a flux bundle. © 1990 The American Physical Society.