Substrate of single crystal of oxide, device using said substrate and method of producing said superconductive device

A superconductive device, wherein said device comprises:

• a substrate of a single crystal composed of a strontium-neodymium-gallium based oxide of which composition includes a K.sub.2 NiF.sub.4 type crystal structure as represented by the following formula,
• Sr.sub.1-x Nd.sub.1-y Ga.sub.1-x O.sub.4-w
• (-0.1<x<0.1, -0.1<y<0.1, -0.1<z<0.1, -0.2<w<0.2),
• said single crystal comprising at least one element selected from the group consisting of calcium having a mol ratio relative to strontium within the range of 0.00001 to 0.1 mol, lanthanum having a mol ratio relative to neodymium within the range of 0.00001 to 0.1 mol, chromium having a mol ratio relative to gallium within the range of 0.00001 to 0.1 mol, and mixtures thereof, wherein said elements are added to said strontium-neodymium-gallium based oxide,
• and a superconductive thin film formed on said substrate, said thin film being composed of an oxide.

A method of producing a superconductive device, wherein said method comprises;

• a step of preparing a substrate of a single crystal composed of a strontium-neodymium-gallium based oxide of which composition includes a K.sub.2 NiF.sub.4 type crystal structure as represented by the following formula,
• Sr.sub.1-x Nd.sub.1-y Ga.sub.1-x O.sub.4-w
• (-0.1<x<0.1, -0.1<y<0.1, -0.1<z<0.1, -0.2<w<0.2),
• said single crystal comprising at least one element selected from the group consisting of calcium having a mol ratio relative to strontium within the range of 0.00001 to 0.1 mol, lanthanum having a mol ratio relative to neodymium within the range of 0.00001 to 0.1 mol, chromium having a mol ratio relative to gallium within the range of 0.00001 to 0.1 mol, and mixtures thereof, wherein said elements are added to said strontium-neodymium-gallium based oxide,
• and a step of forming on said single crystal substrate a superconductive thin film composed of an oxide of which lattice constants a and b each remain within the range of 3.76 to 3.92 angstroms or wherein said lattice constants a and b each remain within the range of 5.32 to 5.54 angstroms, said thin film growing in an epitaxial manner.