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Magnetization processes in melt spun and sintered Nd-Fe-B-permanent magnets are significantly different because of their distinct grain size. We deduce from magnetization measurements on randomly oriented material that in melt spun Nd-FeB the homogeneous rotation of magnetization plays an important role in the whole field range, while for sintered magnets after thermal demagnetization an easy domain wall movement is the predominant process.

Al additions to sintered Nd-Fe-B magnets increase the coercivity by 140 % and decrease the anisotropy field, the remanence and the Curie temperature. Our results indicate that Al is located in the 2:14:1 phase and in an additional isotropic hard magnetic phase which enhances the coercivity. A microcrystalline model of magnetization reversal has been proposed