Measurement of microwave magnetic properties of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films

摘要

The magnetic property of high-T/sub c/ superconductors (HTS) at microwave frequency has been of increasing interest since their magnetic behavior is related to microwave vortex dynamics. Thus, we recently designed a cavity perturbation system (CPS) for simultaneous measurement of the resonant frequency (f/sub 0/) and the quality factor (Q). The magnetic susceptibilities (/spl chi/'-j /spl chi/") of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///MgO thin films at microwave frequencies were investigated and could be analyzed by cavity perturbation theory. We expected that the microwave magnetic susceptibility data as a function of temperature measured using the HTS thin film would explain the phenomenological superconducting dispersion relation. The transition temperature is 91 K and the temperature corresponding maximum imaginary part (/spl chi/") is 85 K. However, the transition temperature and surface resistance (R/sub s/) measured by a conventional transmission-line method were 86 K and 180 /spl mu//spl Omega/ at 40 K, respectively. We found absolute differences between the cavity perturbation method and the transmission line ones, and suggested the CPS is one of the most promising technique for measuring the magnetic susceptibility of HTS thin film with a 0.1/spl sim/1 /spl mu/m thickness.