ANISOTROPIC JOSEPHSON-JUNCTIONS OF Y-BA-CU-O/AU/NB FILM SANDWICHES

Superconductor-normal metal-superconductor (SNS) Josephson junctions consisting of Y-Ba-Cu-O/Au/Nb film-layered structure have been fabricated using epitaxial Y-Ba-Cu-O films. SNS junctions with a-b plane orientated Y-Ba-Cu-O films exhibit the Josephson effect, while the junctions with c-axis orientated Y-Ba-Cu-O films have no Josephson current. Moreover, a-b plane orientated junctions show anisotropic Fraunhofer patterns in the magnetic field dependence of the critical current according to the direction of film orientations. These anisotropic behaviors reveal that the proximity effect is strongly affected by the anisotropic coherence length and the magnetic penetration depth of Y-Ba-Cu-O films.