A new method for a local study of nonlinear microwave properties of superconductors

Abstract

We report a set of experimental data on local third-harmonic generation at microwave frequencies (0.5 GHz) in $YBa_2Cu_3O_7$ and Nb films. For local investigations of the nonlinear response a probe with inductive coupling was elaborated. The map of the nonlinear microwave response of a $YBa_2Cu_3O_7$ thin film is plotted below $T_c$ with high resolution. The third-harmonic power is measured as a function of temperature, input power and dc magnetic field at some areas of the film. The correlation between the depinning current density ${J_p}$ and the nonlinear microwave response is also demonstrated.