Microwave response of cavity resonator with thin superconductor film depending on film temperature and orientation

The proposed version is given concerning the nature of previously found feature in the temperature dependence of microwave losses in the cavity resonator with a thin superconducting film placed perpendicular to the magnetic field of the resonator. An experiment with a film with its parallel orientation with respect to the field shows the absence of the feature. The appearance of the feature at T ≤ T_c region with a parallel orientation of the film is explained by a change in the field orientation and distribution in the film as the temperature changes. Comparison of the experimental data with the results of an analysis of the theoretical model that does not take into account the change in the field in the film shows that the model representation can be used for microwave impedance studies of films with a perpendicular orientation in the range from low temperatures to ∼ 2T_c / 3. We also obtained the relations for the effective surface impedance of superconducting films in the N state, which are necessary for constructing the dependence of the effective impedance on the temperature in the interval including T_c.