Fabrication of YBa2Cu3Oy-La0.7Ca0.3MnOz-YBa2Cu3Oy coplanar junctions and their anisotropic current-voltage characteristics

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Abstract
Two types of YBa2Cu3Oy‐La0.7Ca0.3MnOz‐YBa2Cu3Oy (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.