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摘要
YBa2Cu3O7-x epitaxial films have been studied by near-field nonlinear microwave and low-temperature scanning microscopies. A correlation between the half-widths of peaks in the temperature dependences of third-harmonic power, electron-beam-induced voltage, and the size of the x-ray coherent region (average grain size) was revealed. According to a two-phase model, the nonlinear microwave response is determined by intragrain vortex pinning at large grain sizes and by pinning at intergrain boundaries at small grain sizes. The results of model calculations suggest that a threefold increase in the average grain size can result in a 100-fold decrease in the nonlinear coefficient of YBa2Cu3O7-x films.
- 出版日期2007-8
