Anisotropy and magnetic properties of Nd16Fe76B8 and Nd16Fe75.3B8Zr0.1 HDDR materials

The alloys with chemical compositions of Nd₁₆Fe_76-xB₈Zr_x (x=0, 0.1) have been HDDR processed, and the magnetic properties and anisotropy of the HDDR material have been characterised by means of VSM measurements using a magnetically aligned sample. Anisotropy of the HDDR powder material has been evaluated by comparing the remanence values of the aligned sample measured along the aligning direction and the direction perpendicular to it. It has been found that the intrinsic coercivity of the HDDR powder strongly depends on the particle size of the powder. As the particle size decreases, the intrinsic coercivity decreases radically, and this is explained in terms of structural damage induced in the particle during mechanical milling. It has also been found that the degree of alignment representing the anisotropy of the HDDR powder is enhanced with decreasing particle size. Some degree of alignment has also been observed in the HDDR material obtained from the Zr-free Nd-Fe-B-type alloy, and this may possibly be attributed to either incomplete disproportionation, excess grain growth of the recombined grains or the presence of very fine particles as: a result of milling