Microwave properties of YBa2Cu3O7−δ hightransitiontemperature superconducting thin films measured by the power transmission methodThe microwave properties of epitaxial YBa&u~O,-, thin films with critical temperatures T, up to 91.5 K and critical current densities J, up to 6 X lo6 A/cm2 at 77 K have been investigated between 5 and 20 GHz using coplanar transmission line resonators. Information about the surface resistance R, and the magnetic penetration depth AzL has been obtained from temperature-and power-dependent measurements of the quality factors and resonance frequencies of the resonators. The lowest surface resistance was 105 ,ufi at 77 K and 38 pa at 9 K measured at 6.2 GHz, respectively. The dependence of R, on the surface magnetic field Bti showed that with decreasing film quality the films exhibit a granular behavior. At high critical current densities J,> 4~ lo6 A/cm', the intrinsic properties of the material show up. The magnetic penetration depth was in the range between 160 and 270 nm. Both R, and AL. turned out to be sensitive to the film quality represented by the transition width AT, and the critical current density J, at 77 K. 1866

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