鉄ニクタイド系高温超伝導多結晶バルク磁石の開発

抄録

This article reviews the recent development of bulk trapped field magnet made with iron-based superconductor (IBSC). A trapped field of over 1 T at 5 K and 0.5 T at 20 K has been measured between a stack of magnetized cylinders of bulk polycrystalline Ba_0.6K_0.4Fe₂As₂ superconductors 10 mm in diameter. Magneto-optical imaging revealed a trapped field distribution corresponding to uniform macroscopic current loops circulating through the sample. A standard numerical modelling technique using the measured J_c(B, T) characteristics of a small specimen reproduced the experimentally measured trapped fields well, again indicating the homogeneous current loops in the polycrystalline bulk. Given the untextured polycrystalline nature of the cylinders and their large irreversibility field, it is expected that larger IBSC bulks could trap much higher field.