Magneto‐optical investigation of flux penetration in Y1Ba2Cu3O7thin films

Abstract

Using the magneto‐optical Faraday effect the magnetic flux penetration into high T_c superconducting Y₁Ba₂Cu₃O₇ thin films is investigated. Epitaxially grown high quality films (T_c≳88 K, j_c≳10⁶ A/cm² at 77 K) show a flux penetration in three steps, the formation of a flux front if the acting magnetic field reaches H_c1 at the edge of the specimen, the movement of the flux front towards the center of the sample, and the increase of the flux density after the flux front reaches the center. The remanent state shows trapped magnetic flux in the film, indicating inhomogeneously distributed pinning centers.