RF electromagnetic investigation of an YBa/sub 2/Cu/sub 3/O/sub 7/ thin film by proximity coupling

摘要

Reports an investigation of the RF electromagnetic (EM) attenuation by a YBa/sub 2/Cu/sub 3/O/sub 7/ thin film at 1 GHz as a function of temperature. An increase in the attenuation was observed as the temperature was decreased below the superconducting transition temperature T/sub c/ approximately=84 K, followed by a rapid decrease at lower temperature ( approximately 25 K). A theoretical analysis of EM absorption due to M. Fibich (1965) is evoked to explain the experimental results. It is concluded that the absorption of 1-GHz electromagnetic waves in the present experimental arrangement is determined by the real part of the conductivity in the superconducting state. This implies that even for the high-temperature superconductors considered, the Em absorption is determined by the BCS (Bardeen-Cooper-Schrieffer) coherence factor II, appropriate for electromagnetic absorption and nuclear spin relaxation, as contrasted with the factor I with opposite sign, which is appropriate for sound absorption.