Magnetization processes in two different types of anisotropic, fully denseNdFeB hydrogenation, disproportionation, desorption, and recombination magnets

Two types of textured, fully dense NdFeB hydrogenation, disproportionation, desorption, and recombination (HDDR) magnets were produced. The first type was produced by hot pressing isotropic HDDR powder followed by die upsetti ng; the second, by hot pressing prealigned, anisotropic HDDR powder (MQA-T) . Studies of the magnetization processes revealed that for isotropic HDDR p owder and its hot pressed and die-upset magnets a much larger initial susce ptibility is found after thermal demagnetization than after reverse dc-fiel d demagnetization. Prealigned, hot pressed magnets made from MQA-T material showed a different virgin magnetization curve, indicating a unique coerciv ity mechanism. Interaction domains larger than the average grain size can b e observed in both cases by Kerr microscopy, with the MQA-T type showing si gnificantly broader interaction domains. (C) 2000 American Institute of Phy sics. [S0021-8979(00)51508-4].