Krupka, J., Wosik, J., Jastrzebski, C., Ciuk, T., Mazierska, J., and Zdrojek, M. (2013) Complex conductivity of YBCO films in normal and superconducting states probed by microwave measurements. IEEE Transactions on Applied Superconductivity, 23 (2). 1501011. pp. 1-11.

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Abstract

We report on microwave frequency characterization of yttrium barium copper oxide (YBCO) thin films in both normal and in superconducting state. A microwave single-post dielectric resonator technique using two different resonators was used for the complex conductivity determination of YBCO samples on dielectric substrates. The intrinsic complex conductivity of YBCO films was determined from the measured resonator quality factor Q and resonant frequency values employing rigorous electromagnetic modelling of the resonant structures with the mode-matching and Rayleigh-Ritz techniques. Such approach allowed us to determine the intrinsic properties of the films (conductivity, permittivity, and penetration depth) without any simplifications or errors associated with appropriate modelling employing perturbation theory. We describe the superconducting material only through its intrinsic properties, such as complex conductivity, which does not depend on the thickness of the sample and other parameters. Fro both simulations and experimental results we show that the proposed method of intrinsic complex conductivity determination is particularly useful for the characterisation of very thin YBCO films. To support the novelty of our approach it is shown that significant differences appear between the rigorous and perturbation computations for thin films (below 50nm).

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