Screening technique measurement of ac imaginary susceptibility and critical current density of YBa2Cu3O7-delta films

The screening technique was used to study systematically the ac susceptibil ity of superconducting YBa2Cu3O7-delta thin films in the temperature range of 32-83 K. We used the Fourier transform of the pick-up signal, coming fro m the secondary coil, to estimate the critical current density. From the ex perimental data we observed regularities in the imaginary part of ac suscep tibility, and confirmed that the flux creep mechanism is dominant. (C) 2000 American Institute of Physics. [S0021-8979(00)03105-4].