Microstructure and magnetic properties of MnBi alloys with high coercivity and significant anisotropy prepared by surfactant assisted ball milling

Cao, Jun; Huang, Y.L.; Hou, Y.H.; Shi, Z.Q.; Yan, Xiaotong; Zhong, Zhenchen; Wang, G.P.

doi:10.1016/j.jmmm.2018.10.052

Cited by 35 publications

(20 citation statements)

References 28 publications

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“…The dependence i H c (D) was studied experimentally in [17][18][19][20], the results affirmed the above said tendency. By increasing the ball-milling times t m , the i H c of milled powders first increases, reaching a plateau and slightly drops when the grain size becomes smaller the domain size of ∼ 0.25 µm (see the inset of Fig.…”

Section: Critical Diamsupporting

confidence: 65%

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MnBi Magnetic Material: A Critical Review

Vuong

2019

Comm. in Phys.

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Manganese Bismuth (MnBi) - the ferromagnetic material attracting a great interest of the world magnetic society last years. The absence of rare-earth elements in compositions, the sizable magnetocrystalline anisotropy, the room-temperature moderate but high-temperature reasonable magnetization plus the positive temperature coefficient of coercivity and the moderate Curie temperature make MnBi bulk magnets very potential for high-temperature magnet application. This bright future is a little gray because the research results in the past were not as expected. The paper summarizes the results concerning the MnBi alloys, powders and bulk magnets investigated during past 67 years. The look on the difficulties inhibiting the development of this material is given and the proposals that might allow overcoming the difficulties and push again the efforts of research towards the goal of 12 MGOe for the energy product (BH)max of MnBi bulk magnets are discussed.

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Section: Critical Diamsupporting

confidence: 65%

“…The i H c (in kOe) vs D (in nm) adopted from[19] and ball-milling times (see the inset[20]). The binary phase diagram of Mn-Bi system adopted from Ref [21]…”

mentioning

confidence: 99%

MnBi Magnetic Material: A Critical Review

Vuong

2019

Comm. in Phys.

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“…The wheel speed was held constant in this experiment, however it may also play a role in affecting the ribbon and powder properties. The prolonged milling times of 7-10 hours typically lead to large decreases in magnetization, remanence, and kinks in the second quadrant demagnetization curves [15], however these features are not as severe in this experiment. This is largely due to the smaller radius of the ball milling jar and smaller milling media.…”

Section: Discussionmentioning

confidence: 61%

“…In practice this is usually achieved through ball milling. However, even low energy ball milling was found to be energetic enough for inducing the decomposition of the LTP-MnBi phase into Mn and Bi [11] [15] [20]. Cryomilling mitigates the decomposition issue to certain degree, but can't completely solve it [11] [21].…”

Section: Introductionmentioning

confidence: 99%

Optimizing Composition in MnBi Permanent Magnet Alloys

et al. 2019

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MnBi is an attractive rare-earth-free permanent magnetic material due to its low materials cost, high magnetocrystalline anisotropy (1.6 × 106 J m−3), and good magnetization (81 emu g−1) at room temperature. Although the theoretical maximum energy product (BH)max of 20 MGOe is lower than that of NdFeB-based magnets, the low temperature phase (LTP) of MnBi has a positive temperature coefficient of coercivity, up to 200 °C, which makes it a potential candidate for high temperature applications such as permanent magnet motors. However, the oxygen sensitivity of the MnBi compound and the peritectic reaction between Mn and Bi make it difficult to synthesize into a material with high purity. This challenge is partly offset by adding excess Mn to the alloy, with composition close to Mn55Bi45 resulting in the highest saturation magnetization after common processing techniques such as arc melting, casting, melt spinning, and ball milling. Here we report a systematic process which reduces the amount of excessive Mn, while simultaneously providing a large saturation magnetization (MS) of 79 emu g−1 at 300 K in the annealed Mn52Bi48 ribbons. We also report excellent magnetic properties in the ball powders, resulting in 0.5-5 µm particles with MS of 75.5 emu g−1, coercivity Hci of 10.8 kOe, and (BH)max of 13 MGOe using 9 T applied field at 300 K. A secondary annealing treatment on various ball milled powders increased Hci by up to 21%, and also resulted in an increase in MS up to 78.8 emu g−1.

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“…Rare-earth-free permanent magnets featuring high maximum energy products (( BH ) max ) between those of rare-earth and traditional rare-earth-free permanent magnets are in high demand for cost-effective, high-efficiency, and sustainable energy devices [ 1 , 2 ]. Among rare-earth-free permanent magnetic materials, MnBi exhibits the most promising magnetic properties, featuring high ( BH ) max values that exceed 9 MGOe for powder [ 3 , 4 , 5 , 6 , 7 ] and 7 MGOe for bulk [ 7 , 8 , 9 , 10 ]. Notably, the theoretical ( BH ) max of MnBi is 17.7 MGOe at 300 K [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of Mg and Sb Substitution on the Magnetic Properties of Magnetic Field Annealed MnBi Alloys

et al. 2020

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Rare-earth-free permanent magnets have attracted considerable attention due to their favorable properties and applicability for cost-effective, high-efficiency, and sustainable energy devices. However, the magnetic field annealing process, which enhances the performance of permanent magnets, needs to be optimized for different magnetic fields and phases. Therefore, we investigated the effect of composition on the crystallization of amorphous MnBi to the ferromagnetic low-temperature phase (LTP). The optimal compositions and conditions were applied to magnetic field annealing under 2.5 T for elemental Mg- and Sb/Mg pair-substituted MnBi. The optimum MnBi composition for the highest purity LTP was determined to be Mn56Bi44, and its maximum energy product, (BH)max, was 5.62 MGOe. The Mg-substituted MnBi exhibited enhanced squareness (Mr/Ms), coercivity (Hc), and (BH)max values up to 0.8, 9659 Oe, and 5.64 MGOe, respectively, whereas the same values for the Sb/Mg pair-substituted MnBi were 0.76, 7038 Oe, and 5.60 MGOe, respectively. The substitution effects were also investigated using first-principles calculations. The density of states and total magnetic moments of Mn16Bi15Mg and Mn16Bi15Sb were similar to those of pure Mn16Bi16. Conversely, the Sb-substituted MnBi resulted in a dramatic enhancement in the anisotropy constant (K) from a small negative value (−0.85 MJ/m3) to a large positive value (6.042 MJ/m3).

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Microstructure and magnetic properties of MnBi alloys with high coercivity and significant anisotropy prepared by surfactant assisted ball milling

Cited by 35 publications

References 28 publications

MnBi Magnetic Material: A Critical Review

MnBi Magnetic Material: A Critical Review

Optimizing Composition in MnBi Permanent Magnet Alloys

Effects of Mg and Sb Substitution on the Magnetic Properties of Magnetic Field Annealed MnBi Alloys

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