Samarium-cobalt magnet with grain growth inhibited SmCo.sub.5 crystals

摘要

Permanent magnets formed from rare earth cobalt compounds have high energy products. One rare earth cobalt composition, formulated by metallurgical sintering techniques, is a composition of a rare earth and cobalt such as samarium and cobalt containing about 37.2 weight per cent samarium which corresponds to 60 proportions of SmCo.sub.5 for each 40 proportions of Sm.sub.2 Co.sub.7. This composition is an excellent permanent magnet having an energy product at least as high as 15 × 10.sup.6 gauss-oersteds and up to 20 × 10.sup.6 gauss-oersteds or higher. SmCo.sub.5 contains roughly 33.8 weight per cent samarium, and Sm. sub.2 Co.sub.7 about 42.2 weight per cent samarium; I have found that samarium-cobalt materials containing samarium between about 36.5 weight per cent and about 38 weight per cent are preferred and can be developed into magnets of greatly improved properties. The samarium-cobalt magnet of this invention is basically comprised of crystals of SmCo.sub.5 and Sm. sub.2 Co.sub.7 wherein the SmCo.sub.5 crystals are surrounded by growth- inhibiting materials and are not larger than single domain size.