An overstoichiometric Nd-Fe-B hard magnetic material

Abstract

A commercial Nd-rich Nd-Fe-B-based hard magnetic material was studied. The obtained results were compared before and after recording of the thermomagnetic curve up to 800?C. The curve itself showed clearly besides Curie points of the Nd2Fe14B phase and ?-Fe also another critical temperature. M?ssbauer spectroscopic (MS) phase analysis and X-Ray diffraction analysis (XRD) showed in addition to the commonly known phases Nd2Fe14B and NdFe4B4 also some paramagnetic and ferromagnetic iron atoms (MS) and Fe17Nd2 intermetallics (XRD). During the exerted thermal treatment, the content of the Nd2Fe14B and NdFe4B4 phases remained almost unchanged, while iron atoms from remnant minor phases built a separate ?-Fe phase. The XRD pattern also showed the presence of some minor Nd phase. The results of SQUID magnetic measurements suggest a nanocrystalline decoupled structure of the Nd-rich alloy in the optimized magnetic state. Measurement of the magnetization loop showed, in spite of small changes in the phase composition, that magnetic properties of the quality material deteriorated during the thermal treatment.