We report on the field dependence of the microwave complex resistivity data in YBa2Cu3O7-x/BaZrO3films grown by PLD at various BaZrO3content. The data, analyzed within a recently developed general framework for the mixed-state microwave response of superconductors, yield the field dependence of the fluxon parameters such as the vortex viscosity and the pinning constant. We find that pinning undergoes a change of regime when the BaZrO3content in the target increases from 2.5 mol.% to 5 mol.%. Simultaneously, the vortex viscosity becomes an increasing function of the applied magnetic field. We propose a scenario in which flux lines are pinned as bundles, and a crossover from dilute point pins to dense c-axis correlated defects takes place between 2.5 and 5 mol.% in the BZO concentration. Our data are inconsistent with vortices occupying mainly the BaZrO3sites at low fields, and suggest instead that vortices occupy both BaZrO3sites and interstitials in the YBa2Cu3O7-xmatrix, even at low fields. © 2010 IOP Publishing Ltd.
|Publication status||Published - 2010|
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)