Study of the propagation of an AC magnetic field through superconducting thick films

Studies of the propagation of an AC magnetic field through plasma sprayed superconducting Y₁Ba₂Cu₃O_7-x coatings have been carried out in the incident field frequency and intensity ranges 100 Hz to 100 kHz and 0.01 to 3.5 mT respectively. Results show that the shielding effectiveness increases exponentially with decreasing field intensity. Shielding effectiveness increases with coating thickness and its density. Coatings thinner than 100 mu m do not show any shielding. A non-linear dependence of critical magnetic field H* on both thickness and critical current density J_c of the specimen has been observed.