Transmittance of YBa/sub 2/Cu/sub 3/O/sub 7/ thin films in the millimeter wave region

Temperature dependence of the transmittance of YBa/sub 2/Cu/sub 3/O/sub 7/ films on MgO substrates has been measured in the frequency range of 75-110 GHz. The transmittance was analyzed by taking account of the multiple reflection in the YBa/sub 2/Cu/sub 3/O/sub 7/ and MgO layers. Linear increase of the transmittance with temperature in the normal phase was explained by the Drude model, in which parameters (plasma frequency, relaxation time) obtained from the far-infrared measurements were used. The transmittance below T/sub c/ was analyzed by using the two-fluid model. Less steep increase of the transmittance above 50 K in the superconducting phase indicates that considerable amount of normal carriers exist even at temperatures sufficiently below T/sub c/.<
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