Magnetization Process of High-Tc Superconductors due to Pulsed Field and Development of Superconducting Permanent Magnet

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The c-axis oriented REBa_2Cu_3O_<7*> quasi-single crystal grown by the melt-processing with the use of a seed crystal is known to capture magnetic fields of the order of 1 Tesla at 77 K and to enhance its capability by lowering the temperature. We believe that the trapping field ability of a superconducting permanent magnet can be further enhanced to the level more than 10 times as high as that of the ordinary Nd-Fe-B permanent magnet, if its microstructure is well controlled. The objective of the present work is to develop superconducting permanent magnetic materials generating 3-5 Tesla in the free space and to develop the pulsed field magnetization technique to magnetize the synthesized superconductor.In 1997, we synthesized the melt-processed bulk superconductors and analyzed the dynamical motion of the magnetic fluxes in the superconductor driven by the pulsed field. We observed the magnetization curve different from that obtained under the static field. When the pulsed field is l … More ow, the magnetic fluxes enter into the superconductor very slowly but begin to enter very rapidly once the intensity of the pulsed field exceeds 2-4 Tesla. We obtained crucial information about the viscous motion of the magnetic fluxes and pinning mechanism in the presence of the pulsed field. We could also successfully synthesized the Y-123, Sm-123 and Nd-123 quasi-single crystal by dispersing the 211 particles in the matrix uniformly.In 1998, We could enhance both superconducting and mechanical properties of the Sm-123 bulk superconductor by dispersing fine Ag particles in the matrix and could trap magnetic field of 1.7 Tesla at 77 K.The value could be increased to 9 Tesla at 25 K.All these data for the Sm-123 superconductors synthesized without any assistance of irradiation are the highest reported in the literature. This is 30 times as high as that of the Nd-Fe-B permanent magnet (reported in Chunichi-Shinbun, evening newspaper, March 27th, Heisei 10) . The research to magnetize this superconductor by the pulsed field has been also conducted. We have concluded that a magnetic field generator producing 3-5 Tesla in free space will be developed in very near future. Less