Preparation and magnetic properties of MnBi

Yang, Yunbo; Chen, X. G.; Wu, Rongrong; Jian, Wei; Ma, Xiaobai; Han, Jiayu; Du, Honglin; Liu, S. Q.; Wang, C. S.; Yang, Youjian; Zhang, Y.; Yang, Jinbo

doi:10.1063/1.3672086

Cited by 49 publications

(27 citation statements)

References 14 publications

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“…The powder was aligned in a magnetic field of 18 kOe, hot-compacted at 300 o C for 10 min under pressure of 1500 psi. The prepared magnet had the high mass density = 8.4 g/cm 3 , high anisotropy M r /M s = 0.92, large squareness b H c / i H c = 0.89 and high energy product (BH) max = 8.4 MGOe. These results were obtained thanks to the technique of loading and rotating powder grains into the mold and the optimal compaction for maintaining the high anisotropy and balancing the remanence and coercivity of magnets.…”

Section: Resultsmentioning

confidence: 99%

“…3. Within the standard deviation of the error, the function (P) can be considered as linear, the mass density increased from 7.8 to 8.6 g/cm 3 by increasing P from 600 to 1800 psi. The influence of the annealing temperature T a on the magnet mass density is also observed.…”

Section: Preparation Of Highly Anisotropic Magnetsmentioning

confidence: 99%

“…This effect is abrupt when T a is over the melting temperature T m = 271 o C of Bi. Three magnets were prepared by using the same conditions except the value of T a , the density equals 7 and 7.5 g/cm 3 for T a = 220 and 260 o C, respectively and sharply increases to 8.4 g/cm 3 for T a = 300 o C.…”

Section: Preparation Of Highly Anisotropic Magnetsmentioning

confidence: 99%

“…The compaction of anisotropic magnets was also performed by optimizing the interaction between magnetized ferromagnetic particles to prepare dense magnets with a good balance between M r and b H c in order to improve (BH) max . The prepared MnBi magnet had 8.4 g/cm 3 , M r /M s 0.92, 0.89 and (BH) max reached the value of 8.4 MGOe.…”

Section: Introductionmentioning

confidence: 99%

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HIGHLY ANISOTROPIC MnBi MAGNETS

Vuong

2018

JST

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The rare-earth-free MnBi magnetic material is promising for high-temperature (150 200 o C) application of permanent magnets because of its large magnetocrystalline energy and especially the positive thermal coefficient of coercivity (dH c /dT > 0). Because of the moderate value of the spontaneous magnetization M s 74 emu/g, the anisotropy of MnBi bulk magnets should be investigated to enhance the remanence M r . With large ratio M r /M s and appropriate microstructure, the squareness of MnBi magnets should have high value leading the remanent coercivity b H c close to the intrinsic coercivity i H c , 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 i H c of magnets. The prepared MnBi bulk magnet had 8.4 g/cm 3 , M r /M s 0.92, 0.89 and (BH) max reached 8.4 MGOe.

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Section: Resultsmentioning

confidence: 99%

Section: Preparation Of Highly Anisotropic Magnetsmentioning

confidence: 99%

Section: Preparation Of Highly Anisotropic Magnetsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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HIGHLY ANISOTROPIC MnBi MAGNETS

Vuong

2018

JST

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“…Its room temperature saturation magnetization is about 75 emu/g or 8.4 kG with 5 T field. 6 The roadmap for developing a MnBi-based exchange-coupled magnet starts with preparing high purity MnBi compound in large quantity. Synthesizing MnBi is a challenge.…”

Section: Introductionmentioning

confidence: 99%

Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

Cui

Choi

et al. 2014

Journal of Applied Physics

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MnBi attracts great attention in recent years for its great potential as permanent magnetmaterials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μ B at 50 K and 300 K, respectively. MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 l B at 50 K and 300 K, respectively. V C 2014 AIP Publishing LLC.

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Hard Magnetic Properties of MnBi Low‐Temperature Phase

Yang

Zhao

et al. 2019

Materials Science and Technology

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MnBi low‐temperature phase (LTP) with NiAs‐type hexagonal crystal structure exhibits attractive magnetic and structural properties. In contrast to most of the ferromagnetic materials, coercivity of the LTP MnB increases with increasing temperature, which is above 20 kOe at 270 °C, making it a promising candidate as high‐temperature magnet. The high coercivity at high temperature is attributed to its large magnetocrystalline anisotropy and microstructure. In this work, the melt‐spinning MnBi ribbons, its powders, and bulk magnets were used to investigate the high‐temperature properties of MnBi compounds. It was found that the high‐temperature properties of the MnBi magnets show strong dependence on the initial composition and forms since there exists always a small amount of extra Bi and Mn/MnO phases in the magnetic powders as a result of the peritectic reaction and processing. It should be noted that the bulk magnets show better stability and magnetic properties compared to the ribbons. In addition, the mechanism of magnetization reversal for the bulk magnet changes with increasing temperature. At T = 300 and 350 K, the coercivity is mainly controlled by nucleation, while both inhomogeneous pinning and nucleation determine the magnetization reversal at temperatures higher than 400 K. The impurity phases of Bi and MnO at grain boundaries may act as a pinning center of the domain wall, thus reducing the exchange coupling and enhancing the coercivity at high temperatures.

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Preparation and magnetic properties of MnBi

Cited by 49 publications

References 14 publications

HIGHLY ANISOTROPIC MnBi MAGNETS

HIGHLY ANISOTROPIC MnBi MAGNETS

Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

Hard Magnetic Properties of MnBi Low‐Temperature Phase

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