Study of higher-order harmonics of complex ac susceptibility in YBa2Cu3O7−δ thin films by the mutual inductive method

Abstract We have applied the mutual inductive method to study higher-order harmonics of complex ac susceptibility χ n = χ n ′ − i χ n ″ for YBa 2 Cu 3 O 7− δ thin films as function of the temperature and the applied magnetic field. The experimental results were compared with analytical and numerical results obtained from the Ishida–Mazaki model and the solution of the integral equation for the current density, respectively. Both models allow us to reproduce the main experimental features, however, as n increases the numerical model shows notable discrepancies. This failure can be attributed to the current–voltage characteristics. Also this investigation yields the activation energy U c and the critical current density J c both at T  = 0 for two samples.