Role of Rare-Earth Elements in Permanent Magnet Materials.

Abstract

Synopsis Recent high-performance permanent magnets consist of rare-earth elements and transition metals. In this article, a role of rare-earth elements in permanent magnet materials is explained in terms of magnetocrystalline anisotropy in rare-earth intermetallics. A Coulomb interaction between aspherically distributed 4f-charge of trivalent rare-earth ions and neighboring localized charges has been shown to be a major source of such large magnetic anisotropy. A relation between the magnetic anisotropy and coercivity is briefly described by using a coherent rotation model of magnetic moment. High field magnetization curves in a series of Nd 2 Fe 14 B-type single crystal samples are introduced in order to explain why the Nd-Fe-B magnets show the highest energy product value. Finally, a concept of "anisotropy-magnetization specialization" has been given, which is useful to understand the high-performance mechanism in this system.. Review 2002 7 26 Dr., Sci.