PROBLEM TO BE SOLVED: To make use of a low-temperature resistance magnet by using wire rods, tape or plate of Y base or Bi base high-temperature superconductor under flux low-resistance conditions.
SOLUTION: Y Ba2Cu3O (Y-123) has an advantage as Y base high-temperature superconductor and Bi2Sr2CaCu2O8 (Bi-2212), Bi2Sr2Ca2Cu3O10 (Bi-2223) or the like has an advantage as Bi base high-temperature superconductor. Since the flux flow resistance state is near the area determined by a definition of critical current density, its resistivity is about 10-10 Ωcm. Since the high-strength material exhibits about 80% of that of copper at a room temperature, its resistivity is only 10-5 Ωcm and becomes only 10-6 Ωcm even it is cooled to 4.2 K. In a state of flux flow of a high-temperature superconductor, the resistance at a low temperature can be reduced to 1/100 of copper and to 1/10000 of a high- strength material. Accordingly, even if it is difficult to create an ideal state of superconductivity with zero resistance, incommensurable low resistance can be constantly obtained.