Influence of planar macrodefects on the anisotropy of magnetic-flux penetration in YBa2Cu3O7−δ

Abstract The magnetic flux penetration in a high-quality YBa 2 Cu 3 O 7−δ single crystal with an external field applied perpendicular to the crystalline c axis is directly visualized by means of the magneto-optical technique. The observations show that the field penetrates preferentially along the ab planes. Scanning acoustic microscopy reveals macrodefects along ab planes which strongly affect this anisotropy of the field penetration.