A Novel Method to Measure Microwave Critical Current Densities at Different Frequencies in HTS Thin Films

摘要

A novel method based on the odd modes of a single loaded micro-bridge resonator to measure the microwave critical current densities of high-temperature superconductor thin films at different frequencies is presented in this article. With the method, only a vector network analyzer and a resonator are needed. Therefore, the errors caused by complicated measurement platforms and the differences between samples which resonate at different frequencies are eliminated. A designed single loaded micro-bridge resonator was fabricated in a YBa2Cu3 O (7-x) (YBCO) thin film, and the zero-filed-cooled critical current densities at 3, 9, and 15 GHz, which are oscillation frequencies of the first three odd modes of this resonator, have been measured. The measurement results indicate that the microwave critical current density increases with frequency increasing. To explain the results, a model in terms of the translation process from superconducting state to normal state in transmission line is proposed.