Structure and phases of low-neodymium NdFeB permanent magnets

Structures and phase compositions of two low-neodymium magnetically hard materials, differing by the way of preparation — centrifugal atomization and melt spinning — were compared using Mössbauer spectroscopy, X-ray diffraction and measurements of thermomagnetic curves. Better hard magnetic characteristics of the melt-spun material are explained on the basis of the differences in the content of surface and/or interface Fe(Nd,B) phases. Their remarkable presence in the centrifugally atomized material lowers the content of Fe₃B, Fe₂B, α-Fe, and Nd₂Fe₁₄B phases that are responsible for the magnetic quality of the material. There are only subtle differences in the phase compositions of both materials after thermomagnetic measurement, where the α-Fe phase prevails as a product of the thermal decomposition.