Synchrotron X-ray absorption near-edge structure (XANES) spectra are used to complement X-ray diffractometry (XRD) in the phase identification of pressed manganese–bismuth (MnBi) pellets. The heat treatment at 1000°C for 10 min after the synthesis improves the ferromagnetic properties. The magnetisation and coercive field are further enhanced when the Mn:Bi ratio is raised to 2:1. The obtained magnetic properties are related to the MnBi peaks in XRD patterns as well as the Mn-edge XANES spectra. Although the spectra in the case of Mn:Bi ratio of 2:1 and 3:1 resemble that of MnO reference, the pre-edge is shifted by the contribution of zero valent Mn and the peak intensity is reduced. A variety of phases in MnBi alloys dictate their magnetic properties required for permanent magnets and desirable ferromagnetic properties are governed by the increase of MnBi phase at the expense of MnO.

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Effects of composition and heat treatment on manganese–bismuth magnets

References

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