In order to study the vortex pinning determined by artificially introduced pinning centers in the small-vortex displacement regime, we measured the microwave surface impedance at 47.7 GHz in the mixed state of YBa2Cu3O7-δ; thin films, where submicrometric BaZrO3 particles have been incorporated. As a function of the BaZrO3content, we observed that the absolute losses slightly decrease up to a BaZrO3content of 5%, and then increase. We found that the magnetic-field-induced losses behave differently in that they are not monotonic with increasing BaZrO3concentration. At small concentration (2.5%) the field-induced losses increase, but large reduction in the losses themselves, by factors up to 3, is observed upon further increasing the BaZrO3concentration in the target up to 7%. Using measurements of both surface resistance and surface reactance, we estimate vortex pinning-related parameters. We found that BaZrO3inclusions introduce deep and steep pinning wells. In particular, the minimum height of the energy barrier for single vortices is raised. At larger BaZrO3content (5% and 7%) the phenomenon is at its maximum, but it is unclear whether it shows a saturation or not, leaving room for further improvements. © 2009 American Institute of Physics.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
Pompeo, N., Rogai, R., Augieri, A., Galluzzi, V., Celentano, G., & Silva, E. (2009). Reduction in the field-dependent microwave surface resistance in YBa. Journal of Applied Physics, 105(1), -. . https://doi.org/10.1063/1.3056179