IMPEDANCE PROPERTIES AND MICROWAVE MAGNETIC-FIELD DEPENDENCE OF SURFACE-RESISTANCE OF YBACUO

The microwave magnetic field H-omega dependence of the surface resista nce R(S) for a YBa2Cu3O7-delta ceramic and thin film has been studied in 8 mm wave band. It is shown that for the film one of mechanisms con sistent with the obtained dependence R(S)(H-omega) may be microwave-in duced flux motion. For the ceramic specimen, the above dependence is i n agreement with the model of Sridhar for the nonlinear high-frequency response of a planer superconductor in a current-induced critical sta te and with Gurevich's theory of the nonlinear dynamics of vortices in high-J(C) overdamped Josephson contacts. An approach was applied whic h allows us to perform measurements without preliminary patterning of the samples.