Magnetization process in rapidly solidified neodymium-iron-boron permanent magnet materials

Initial magnetization and demagnetization data are reported for three forms of rapidly solidified Nd-Fe-B permanent magnet materials: melt-spun ribbons, hot-pressed magnets, and die upset magnets. In all three materials, the results are consistent with domain-wall pinning at Nd2Fe14B grain boundaries as the coercivity mechanism. Thermally demagnetized ribbons are comprised of single domain Nd2Fe14B grains, and both initial magnetization and demagnetization occur by depinning and wall motion. Domain walls move easily in die upset magnets until they become strongly pinned at grain edges. Complete magnetization requires an applied field greater than the coercive field. Hot-pressed magnets show a mixture of ribbon and die upset behavior.