HIGHLY ANISOTROPIC MnBi MAGNETS

Authors

  • Nguyen Van Vuong Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi

DOI:

https://doi.org/10.15625/2525-2518/54/1A/11806

Keywords:

rare-earth-free MnBi magnets, anisotropy, anisotropic compaction.

Abstract

The rare-earth-free MnBi magnetic material is promising for high-temperature (150 200 oC) application of permanent magnets because of its large magnetocrystalline energy and especially the positive thermal coefficient of coercivity (dHc/dT > 0). Because of the moderate value of the spontaneous magnetization Ms 74 emu/g, the anisotropy of MnBi bulk magnets should be investigated to enhance the remanence Mr. With large ratio Mr/Ms and appropriate microstructure, the squareness of MnBi magnets should have high value leading the remanent coercivity bHc close to the intrinsic coercivity iHc, thus enhancing the energy product (BH)max. The paper presents an approach to loading and compacting of MnBi powders in the 18 kOe magnetic field oriented perpendicular to the pressing direction where MnBi grains can be freely rotated and oriented parallel to the field direction. Based on the energy minimization of the assembly of magnetized grains, the compacting pressure was chosen to optimize two parameters, the mass density and the coercivity iHc of magnets. The prepared MnBi bulk magnet had 8.4 g/cm3, Mr/Ms 0.92, 0.89 and (BH)max reached 8.4 MGOe.

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Published

2018-03-16

How to Cite

Vuong, N. V. (2018). HIGHLY ANISOTROPIC MnBi MAGNETS. Vietnam Journal of Science and Technology, 54(1A), 58. https://doi.org/10.15625/2525-2518/54/1A/11806

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Articles