A US and Japanese international collaboration team is the first to use an iron-based high temperature superconductor as a strong magnet.
Powerful superconducting magnets that are used for high-tech medical and energy applications, require cooling to low temperature, which is typically done with scarce and expensive liquid helium. Ferromagnetic permanent magnets, such as neodymium-iron-boron magnets, require rare earth elements, which are strategic materials. Therefore, developing high-temperature superconductors that can be used above liquid helium temperature without using rare earth elements has been undertaken. However a technology enabling iron-based high temperature superconductor to be used as magnets had not been demonstrated before.
Tokyo Univ. of Agriculture and Technology, Japan and The National High Magnetic Field Laboratory, US, demonstrated that a 1 cm diameter bulk iron-based superconductor could trap a magnetic field exceeding 1 Tesla. The iron-based superconducting polycrystalline bulk, which was made up of nano-scale (~100 nm) grains, exhibited uniform magnetic field distribution and high mechanical strength, both of which are essential for high field magnets.
The iron-based superconductors have several important advantages: the raw materials do not contain rare earth elements, the fabrication process is simple and inexpensive, and it is possible to cool them with a compact cryocooler. These advantages are expected to facilitate realizing powerful superconducting magnets that are compact, portable, and ubiquitous because standard ceramic fabrication processes can be applied, it is possible that similar strong magnets can be made with other high temperature materials. Thus superconducting nano polycrystalline bulk materials are expected to be the new standard for developing novel strong magnets.
Research Area “New Materials Science and Element Strategy”
Research Theme “Development of Ubiquitous Superconducting Magnet by Grain Boundary Engineering”
J. D. Weiss, A. Yamamoto, A. A. Polyanskii, R. B. Richardson, D. C. Larbalestier, and E. E. Hellstrom. “Demonstration of an iron-pnictide bulk superconducting magnet capable of trapping over 1 T”. Superconductor Science & Technology – Fast Track Communication, Published online 30 September 2015, doi: 10.1088/0953-2048/28/11/112001.
Akiyasu Yamamoto, Ph.D.
Associate Professor, Department of Applied Physics, Tokyo University of Agriculture and Technology
Sofia Saori Suzuki
Green Innovation Group, Department of Innovation Research, JST