Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O7-δ thin films by microwave power transmission measurements

A novel waveguide power transmission measurement technique has been developed to extract the complex conductivity (σ*=σ₁-jσ₂) of superconducting thin films at microwave frequencies. The microwave conductivity of two laser-ablated YBa₂Cu₃O_7-δ 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 was determined. From the conductivity values, the authors calculated the penetration depth (λ) to be approximately 0.54 and 0.43 μm and the surface resistance (R_s) to be approximately 24 and 36 mΩ at 36 GHz and 76 K for the two films under consideration. The R_s values were then compared to those obtained from the change in the Q-factor of a 36-GHz TE₀₁₁ -mode oxygen-free, high-conductivity (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. It was found that this technique allows noninvasive characterization of high-T _c superconducting thin films at microwave frequencies