Recent developments toward understanding magnetization processes in Nd-Fe-B permanent magnet materials

The quick rise of an enormous market of high-coercivity grades of Nd-Fe-B sintered magnets for hybrid electric vehicles (HEV) has created a new concern about resources of certain elements such as Tb and Dy which is used in order to guarantee stability of magnetic flux at operating temperatures. Accordingly, improvements of coercivity in the Nd-Fe-B magnets at elevated temperatures without heavily using these scarece elements are required. For this goal, deeper understanding of the coercivity mechanism is neccesarry. In order to clearly study the relationship beween local microstructure and coercivity related to that microstructure, an approach using a model magnet composed of a thin sintered magnet and an Nd layer doposited on its surface is reported. Besides this micropscopic apporach, macroscopic approaches are also indespensable. Also described in this paper is investigation of successive recoil curves and their relation with magnetic domain structures in a system composed of submicron size grains of Nd2Fe14B that can be prepared by means of hydrogenation-disproportionation-dehydrogenation-decomposition process. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.