Grain alignment due to magnetic-field annealing in MnBi:Bi nanocomposites

Zhang, W. Y.; Kharel, Parashu; George, T. Adrian; Li, X. Z.; Mukherjee, Pinaki; Valloppilly, Shah R.; Sellmyer, David J.

doi:10.1088/0022-3727/49/45/455002

Cited by 14 publications

(9 citation statements)

References 25 publications

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“…The NCs rather get degraded lacking to design a large (BH) max beyond 7.3 MGOe or so [39,40]. Annealing in fields is realized a simple recipe to devise α-MnBi aligned in a high grade nanotexture [16,[39][40][41][42][43][44][45]. Though tuning field aligned FM NCs at anneals was proposed a long ago by Boothby et al in 1958 [46], yet the field annealed MnBi lacks either a high H c [41,45], or a duly large α-MnBi yield [16,42].…”

Section: Introductionmentioning

confidence: 99%

“…Annealing in fields is realized a simple recipe to devise α-MnBi aligned in a high grade nanotexture [16,[39][40][41][42][43][44][45]. Though tuning field aligned FM NCs at anneals was proposed a long ago by Boothby et al in 1958 [46], yet the field annealed MnBi lacks either a high H c [41,45], or a duly large α-MnBi yield [16,42]. A group of Hadjipanayis et al [39,40] studied the effects of field anneals on the α → β → α-MnBi transitions in Mn 50 Bi 48.5 Sb 1.5 , Mn 50 Bi 49 Sb 0.5 In 0.5 and Mn 50 Bi 46 Mg 3 Sb 0.5 In 0.5 melt-spun ribbons.…”

Section: Introductionmentioning

confidence: 99%

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A core–shell magnet Mn₇₀Bi₃₀ grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

2023

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The MnBi alloys is a model series of rare-earth free magnets for surge of technologies of small parts of automobiles, power generators, medical tools, memory systems, and many others. The magnetics stem primarily at unpaired Mn-3d5 spins (a 4.23 B moment) align parallel via an orbital moment 0.27 B of Bi-5d106s2p3 in a crystal lattice. Thus, using a surplus Mn (over Bi) in a Mn70Bi30 type alloy designs a spin-rich system of duly tailored properties useful for magnetics and other devices. In this view, we report here a strategy of a refined alloy powder Mn70Bi30 can grow into small crystals of hexagonal (h) plates at seeds as annealed in magnetic fields (in H2 gas). So, small h-plates (30 to 50 nm widths) are grown up at (002) facets, wherein the edges are turned down in a spiral ( 2.1 nm thicknesses) in a core-shell structure. The results are described with X-ray diffraction, lattice images and magnetic properties of a powder Mn70Bi30 (milled in glycine) is annealed at 573 K for different time periods, so to the Mn/Bi order at the permeable facets (seeds). Duly annealed samples exhibit an enhanced magnetization, Ms  70.8 emu/g, with duly promoted coercivity Hc  10.810 kOe (15.910 kOe at 350 K), energy–product 14.8 MGOe, and the crystal-field-anisotropy, K1  7.6x107 erg/cm3, reported at room temperature. Otherwise, Ms should decline at any surplus 3d5-Mn spins order antiparallel at the antisites. Enhanced Curie point 658.1 K (628 K at Mn50Bi50 alloy) anticipates that a surplus Mn does favor the Mn-Bi exchange interactions. Proposed spin models well describe the spin-dynamics and lattice relaxations (on anneals) over the lattice volume (with twins) and spin clusters.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A core–shell magnet Mn₇₀Bi₃₀ grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

2023

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“…In order to advance the field, it is necessary to develop rare-earth and expensive-metal-free permanent-magnet materials with good high-temperature properties. Some promising candidates of rare-earth-free, low-cost permanent magnets are MnBi, Mn 2 Ga, FeNi, (Fe, Co) 2 B, YCo 5, and HfCo 7 [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Among these low-cost magnets, MnBi has a special advantage where the magnetic anisotropy increases with the increasing temperature reaching a maximum value of about 22 Mergs cm −3 at 590 K [9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…Some promising candidates of rare-earth-free, low-cost permanent magnets are MnBi, Mn 2 Ga, FeNi, (Fe, Co) 2 B, YCo 5, and HfCo 7 [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Among these low-cost magnets, MnBi has a special advantage where the magnetic anisotropy increases with the increasing temperature reaching a maximum value of about 22 Mergs cm −3 at 590 K [9][10][11][12][13][14][15][16]. This makes MnBi magnets more stable against thermal demagnetization than Nd-Fe-B magnets above room temperature.…”

Section: Introductionmentioning

confidence: 99%

Modifying magnetic properties of MnBi with carbon: an experimental and theoretical study

Kharel¹,

Lama²,

Flesche³

et al. 2022

J. Phys. D: Appl. Phys.

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MnBi and MnBi-based materials have been investigated as prospective rare-earth-free permanent magnets with moderate energy product. One of the main issues with MnBi is the segregation of Bi during materials synthesis reducing net magnetization. We have found that MnBi synthesized in a carbon environment substantially reduces the amount of Bi segregation, improving its saturation magnetization. We have synthesized Mn55Bi45 and Mn55Bi45C samples using arc melting and high-vacuum annealing. The room temperature x-ray diffraction patterns indicate that both Mn55Bi45 and Mn55Bi45C crystallize in the hexagonal NiAs-type crystal structure. The Rietveld analysis of the x-ray patterns shows that the amount of Bi segregation reduces from 16 wt.% for Mn55Bi45 to 5 wt. % for Mn55Bi45C. The high-field (3T) magnetizations measured at room temperature are 61 emu/g and 66 emu/g for Mn55Bi45 and Mn55Bi45C, respectively. In addition, there is a slight increase in the value of the anisotropy constant, namely, 1.6 Merg/cm3 and 2.1 Merg/cm3 for Mn55Bi45 and Mn55Bi45C, respectively. To understand the role of C in enhancing the magnetization of MnBi, we carried out the first-principles calculations of both stoichiometric and nonstoichiometric MnBi alloys, which suggests that the increase of magnetization in Mn55Bi45C is due to the coating of MnBi grains with C.

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“…Consequently, the addition of secondary elements or materials, such as Ga (e.g., Mn 55 Bi 44 Ga) [ 12 ], Sn (e.g., MnBi 1- x Sn x ) [ 13 ], NaCl or C [ 14 ], and nanoparticles [ 15 ], to MnBi has been investigated in efforts to increase the H c . Furthermore, magnetic field annealing has been used to enhance the magnetic properties for permanent magnet applications [ 16 , 17 , 18 , 19 , 20 , 21 ].…”

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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Grain alignment due to magnetic-field annealing in MnBi:Bi nanocomposites

Cited by 14 publications

References 25 publications

A core–shell magnet Mn₇₀Bi₃₀ grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

A core–shell magnet Mn₇₀Bi₃₀ grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

Modifying magnetic properties of MnBi with carbon: an experimental and theoretical study

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

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Grain alignment due to magnetic-field annealing in MnBi:Bi nanocomposites

Cited by 14 publications

References 25 publications

A core–shell magnet Mn70Bi30 grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

A core–shell magnet Mn70Bi30 grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

Modifying magnetic properties of MnBi with carbon: an experimental and theoretical study

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

Contact Info

Product

Resources

About

A core–shell magnet Mn₇₀Bi₃₀ grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

A core–shell magnet Mn₇₀Bi₃₀ grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties