Fabrication of YBa₂Cu₃O_y‐La_0.7Ca_0.3MnO_z‐YBa₂Cu₃O_y coplanar junctions and their anisotropic current‐voltage characteristics

Two types of YBa₂Cu₃O_y‐La_0.7Ca_0.3MnO_z‐YBa₂Cu₃O_y (YBCO‐LCMO‐YBCO) coplanar‐type junctions with a 0.2 μm gap were fabricated by electron‐beam lithography and Ar‐ion‐beam milling. One is a junction in which a current flows into the a‐b plane (ferromagnetic spin arrangement) of the LCMO and then passes through the channel along the c axis (antiferromagnetic arrangement), and the other is a junction in which the current only passes through the a‐b plane. In the former junction the current‐voltage characteristics show nonlinearity which suggests a superconductive linkage, while the latter has linear characteristics. This anisotropy of the proximity effect is attributed to anisotropy of the spin structure, because the LCMO film has a small anisotropy of the normal decay length in the a‐b plane and along the c axis.