DETERMINATION OF SURFACE-RESISTANCE AND MAGNETIC PENETRATION DEPTH OF SUPERCONDUCTING YBA2CU3O7-DELTA THIN-FILMS BY MICROWAVE-POWER TRANSMISSION MEASUREMENTS

A novel waveguide power transmission measurement technique has been developed to extract the complex conductivity (sigma* = sigma-1 - j-sigma-2) of superconducting thin films at microwave frequencies. We obtained the microwave conductivity of two laser-ablated YBa2Cu3O7-delta thin films on LaAlO3 with transition temperatures (T(c)) of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values we calculated the penetration depth (lambda) to be approximately 0.54 and 0.43-mu-m, and the surface resistance(R(s)) to be approximately 24 and 36 m-OMEGA at 36 GHz and 76 K for the two films under consideration. We further compared the R(s) values with those obtained from the change in the Q-factor of a 36 GHz TE011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. We found that this technique allows noninvasive characterization of high-T(c) superconducting thin films at microwave frequencies.