Intrinsic and extrinsic surface impedance of HTS: T- and H-dependencies

The application of HTS is obstructed by high surface impedances and their increases Z(T,f,H_rf) with rf field. To separate intrinsic from extrinsic and rf mode from HTS material properties well characterized films are required. Using TBCCO films and corrosion protected YBCO films well defined material and physical parameter dependencies have been found which for the first time allowed a unique separation of intrinsic surface resistances R_int(T,f,H_rf) from extrinsic residual losses R_res(T,f,H_rf) and shed light onto δZ∝H_rf² increases observed in TE₀₁₁ modes. The latter confirms that rf results of TE_01n-mode end-plate replacements are sensitive tools to study HTS thin film material properties before structuring. Aside from δR_s(H_rf)∝H_rfⁿ∝δX_s(H_rf), rf measurements in the frequency and time domain yield the ratio r=δ_s/δ_s which shows distinct T and f dependencies for various mechanisms and rf modes. r(T,f)≈1 indicates hysteresis losses of Josephson fluxons governed by the weakest links at the edges of the films, being weighted differently in TE_01n and strip-line modes.