Magneto-optical characterization of YBa₂Cu₃O ₇ film uniformity

Using a magneto-optical technique, we have nondestructively imaged macroscopic variations in magnetic flux that penetrate laser-ablated, c-axis oriented, epitaxial YBa2Cu3O7 superconducting films deposited on crystalline (100)SrTiO3 substrates. Flux penetration into YBa2Cu3O7 films in an externally applied magnetic field is enhanced at crystalline substrate defect sites. A relationship between flux penetration and substrate defects is experimentally demonstrated with a YBa2Cu3O7 film deposited on an intentionally degraded crystalline SrTiO3 surface.