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

We have applied the mutual inductive method to study higher-order harmonics of complex ac susceptibility χn=χn′−iχn″ for YBa2Cu3O7−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 Uc and the critical current density Jc both at T = 0 for two samples.