Precise measurement of the microwave surface impedance of a YBa2Cu3O7-delta film on copper substrate

In measurement of the microwave surface resistance, R-s(T), of a high-T-c f ilm with a host-cavity method, in which the cavity material is usually copp er, the systematic error in R-s at low temperature can be significantly red uced through calibration with the data obtained by a niobium host cavity. U sing a cavity excited in the TE011 mode at 13.6 GHz, the procedure is illus trated for a c-axis oriented YBa2Cu3O7-delta film fabricated on 36 mm diame ter copper disk with yttria-stabilized-zirconia and chromium buffer layers. The temperature dependence in R-s(T) was consistent with that of the penet ration depth; both quantities behavior could be fit well by a modified two- fluid model, in which the fraction of the pairing normal carriers obeyed (T /T-c)(2) rather than (T/T-c)(4) with some 20% of the charge carriers remain ing normal. (C) 2000 American Institute of Physics. [S0021-8979(00)06108-9] .