Nonlinear microwave properties of YBa2Cu3O7-x block epitaxial films near the superconducting transition temperature

The structure and local properties of a nonlinear microwave response of YBa2Cu3O7-x block films, as well as microbridges of these films, are studied using low-temperature scanning microscopy. Correlation between the halfwidth of the temperature dependence of the third harmonic power WTH and the curve of the electron-beam induced voltage WEBIV is observed for the medium size of the block. A theoretical model is proposed, which demonstrates that the nonlinear microwave response for large blocks is determined by intrablock pinning of Abrikosov vortices; for blocks of smaller size, the response acquires an additional contribution associated with pinning of hypervortices on the Josephson network of the boundaries between the blocks