History and recent progress of QMG™ and QMG bulk magnets

Abstract

The microstructure of QMG consists of a single crystal REBa2Cu3Ox phase and fine RE2BaCuO5 particles. Y-based QMG was first produced in 1988 by the Quench and Melt Growth method. A bulk magnet made from QMG was proposed in 1989. QMG bulk magnets were realized by enlargement technology using RE substitute seed crystals. Based on these technological innovations, the development of NMR and MDDS, which are product-based applications of bulk magnets, has recently been reported from the research institutes of applied development. The history of the initial development of these QMG materials and QMG bulk magnets was reviewed. In addition, as progress of the recent QMG bulk magnet development, a new reinforcement method for large ring bulk magnets that can trap 10 T class strong magnetic field magnetization has been reported. For high field magnetization, the reinforcement of bulk magnets is essential to prevent cracking due to large hoop force. Compared to the conventional reinforcement method using only the outer metal ring, the new reinforcement method has been developed using thin QMG rings and metal ring sheets as the composite material with the inner and outer metal rings. In the case of the QMG ring reinforced by the conventional method, cracking occurred at 10T magnetization. Whereas the QMG ring created by the new reinforcement method successfully trapped approximately 10 T.