RE-123-based oxide superconductors (REBa2Cu3O7-x: RE represents rare earth elements including Y) exhibit superconductivity at the temperature of liquid nitrogen and have low current losses and are thus extremely promising materials in a practical sense, and there is demand for RE-123-based oxide superconductors to be processed into wires and be used as conductors or electromagnetic coils for power supply and the like.
As an example of the structure of RE-123-based oxide superconducting wires, oxide superconducting wires obtained by using a base material made of a metal having a high mechanical strength, forming an intermediate layer having a favorable crystal orientation on the surface of the base material using an ion-beam-assisted deposition method (IBAD method), forming an oxide superconducting layer on the surface of the intermediate layer using a film-forming method, and forming a metal-stabilizing layer constituted of a highly conductive material such as Ag on the surface of the oxide superconducting layer are known.
When a magnetic field component, which varies in a direction perpendicular to the surface over time, is applied to an oxide superconducting wire, loop-like shielding currents flow in the surface of an oxide superconducting layer. The shielding currents cause magnetization losses that are discharged in a heat form. Therefore, when large shielding currents are generated, there has been a problem in that the energy efficiency of oxide superconducting wires decreases. In addition, when an oxide superconducting wire is processed into a coil shape and is supplied with currents so as to generate a magnetic field, the magnetic field is shielded due to shielding currents, and there has been a problem in that the magnetic field cannot be generated as designed.
In addition, shielding currents attenuate over time. Therefore, in a case in which an oxide superconducting wire is applied to a superconducting device generating a magnetostatic field which does not change over time, there has been a problem in that magnetic fields change over time due to the attenuation of shielding currents.
Shielding currents and the degrees of magnetization losses caused by the shielding currents depend on the width of the oxide superconducting layer. Therefore, when oxide superconducting wires are thinned, it is possible to reduce the shielding currents and the magnetization losses. In addition, in a case in which oxide superconducting wires are used in devices to which alternating-currents are applied such as motors or transformers, it is possible to reduce alternating-current losses caused by magnetic fields generated on the basis of flowing alternating-currents by thinning the oxide superconducting wires.
Patent Documents 1 and 2 disclose oxide superconducting wires thinned by dividing an oxide superconducting layer into a plurality of fragments.