Atomistic simulations of <i>α</i>-<i>Fe</i>/Nd2Fe14B magnetic core/shell nanocomposites with enhanced energy product for high temperature permanent magnet applications

Westmoreland, S. C.; Skelland, C.; Shoji, Tetsuya; Yano, Masao; Kato, Akira; Ito, Masaaki; Hrkac, G.; Schrefl, T.; Evans, Richard F. L.; Chantrell, R.W.

doi:10.1063/1.5126327

Cited by 15 publications

(12 citation statements)

References 28 publications

(27 reference statements)

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“…The (BH) max values obtained for the considered compounds are found to be in comparison to the experimentally and theoretically obtained values of Nd 2 Fe 14 B [61,62] . The highest μ 0 H c that may be attained experimentally is determined by the μ 0 H a , and it has been demonstrated that the maximum μ 0 H c can be about one-quarter of the μ 0 H a value, and such discrepancy between experiment and theory maybe attributed to 'Brown paradox' [63].…”

Section: Resultssupporting

confidence: 60%

Large magnetic anisotropy in Co–Fe–Ni–N ordered structures: a first-principles study

Islam

2021

J. Phys.: Condens. Matter

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Material design of promising rare-earth free permanent magnet requires tailoring and controlling the intrinsic magnetic properties namely large saturation magnetization μ 0 M s, giant uniaxial magnetic anisotropy K u, and high Curie temperature T C. Based on first-principles electronic structure calculations, we present a detailed analysis for the intrinsic magnetic properties of Co x Fe1−x Ni and Co x Fe1−x NiN0.25 ordered structures. We predict an enhanced structural stability with improved K u ranging from 1.53–2.29 MJ m−3 for Co x Fe1−x NiN0.25 ordered structures, with the exception of CoNiN0.25 having planar anisotropy. Detailed analysis of the predicted large K u, based on perturbation theory and electronic structure calculations, is attributed to the cumulative effect of contribution from the increased tetragonal distortion and induced orbital distortion from the simultaneous Co substitution and interstitial N-doping. By tailoring the K u, we may create efficient and affordable PMs, bridging the gap between commonly used ferrite and high-performance Nd–Fe–B magnets.

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Section: Resultssupporting

confidence: 60%

Large magnetic anisotropy in Co–Fe–Ni–N ordered structures: a first-principles study

Islam

2021

J. Phys.: Condens. Matter

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“…The models are composed of soft and the hard mage exchange interactions among theses, respectively depicted in Fig. 21(a Westmoreland, et al [92] studied the effect of the soft magnet  -Fe by MC simulation and the SLLG equation using an atomistic Hamiltonian with thermal fluctuation. They used a simplified Hamiltonian that gives critical temperatures correctly, although the spin-reorientation transition is not realized.…”

Section: Effect Of Soft-magnet Grain Boundary On Coercivitymentioning

confidence: 99%

“…The Nd Fe B magnet consists of hard-magnet (Nd Fe B) grains, each of which is covered by a grain boundary material [ 24 , 51 , 54 , 90 ]. Thus, it is important to study how boundary phases affect the coercivity of the grains studied in the previous section.…”

Section: Effect Of Grain Boundarymentioning

confidence: 99%

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

Miyashita

Nishino

Toga

et al. 2021

Science and Technology of Advanced Materials

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For the practical use of magnets, particularly at high temperatures, the temperature dependence of magnetic properties is an important ingredient. To study the temperature dependence, methods of treating the thermal fluctuation causing the so-called activation phenomena must be established. To study finite-temperature properties quantitatively, we need atomistic energy information to calculate the canonical distribution. In the present review, we report our recent studies on the thermal properties of the Nd 2 Fe 14 B magnet and the methods of studying them. We first propose an atomistic Hamiltonian and show various thermodynamic properties, e.g., the temperature dependences of the magnetization showing a spin reorientation transition, the magnetic anisotropy energy, the domain wall profiles, the anisotropy of the exchange stiffness constant, and the spectrum of ferromagnetic resonance. The effects of the dipole-dipole interaction (DDI) in large grains are also presented. In addition to these equilibrium properties, we also study coercivity, which is the most important issue for magnets. The temperature dependence of the coercivity of a single grain was studied using the stochastic Landau-Lifshitz-Gilbert equation and also by the analysis of the free energy landscape, which was obtained by Monte Carlo simulation. It was found that the upper limit of coercivity at room temperature is about 3T, which is significantly lower than the so-called theoretical coercivity given by a simple coherent rotation model. The coercivity of a polycrystalline magnet, i.e., an ensemble of grains, is expected to be reduced further by the effects of the grain boundary phase, which is also studied. Surface nucleation is a key ingredient in the domain wall depinning process. Finally, we study the effect of DDI among grains and also discuss the distribution of properties of grains from the viewpoint of first order reversal curve.

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“…Micromagnetics continuum modellings for permanent magnets have been applied in analyses of magnetic properties of the Nd magnet [21]. However, to study the microscopic details, recently developed atomistic models are indispensable [16,[22][23][24][25][26][27][28][29][30][31][32][33][34]. Unlike the continuum modellings, the lattice structure (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…1) is introduced with * Electronic address: nishino.masamichi@nims.go.jp microscopic magnetic parameters and the temperature effect can be treated properly in the atomistic modellings. By using the atomistic models, quantitative properties of the Nd magnet have been intensively investigated [16,[22][23][24][25][26][27][28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Effect of the surface magnetic anisotropy of neodymium atoms on the coercivity in neodymium permanent magnets

2021

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The Nd permanent magnet (Nd2Fe14B) is an indispensable material used in modern energy conversion devices. The realization of high coercivity at finite temperatures is a burning issue. One of the important ingredients for controlling the coercive force is the surface property of magnetic grains. It has been reported by first-principles studies that the Nd atoms in the first (001) surface layer facing the vacuum have in-plane anisotropy perpendicular to the c axis, which may decrease the coercivity. Focusing on the surface anisotropy effect on the coercivity, we examine the coercivity at zero and finite temperatures by using an atomistic model reflecting the lattice structure of the Nd magnet with a stochastic Landau-Lifshitz-Gilbert equation method. We study general three cases, in which the Nd atoms in surface layers have (1) no anisotropy, (2) in-plane anisotropy, and (3) reinforced anisotropy for two types of surfaces, ( 001) and ( 100) surfaces. We find that in contrast to the zero-temperature case, due to the thermal fluctuation effect, the modification of only the first surface layer has little effect on the coercivity at finite temperatures. However, the modification of a few layers results in significant effects. We discuss the details of the dependence of the coercivity on temperature, type of surface, and modified layer depth, and also the features of domain growth in magnetization reversal.

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Atomistic simulations of α-Fe/Nd2Fe14B magnetic core/shell nanocomposites with enhanced energy product for high temperature permanent magnet applications

Abstract: This is a repository copy of Atomistic simulations of α-Fe /Nd2Fe14B magnetic core/shell nanocomposites with enhanced energy product for high temperature permanent magnet applications.

Cited by 15 publications

References 28 publications

Large magnetic anisotropy in Co–Fe–Ni–N ordered structures: a first-principles study

Large magnetic anisotropy in Co–Fe–Ni–N ordered structures: a first-principles study

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

Effect of the surface magnetic anisotropy of neodymium atoms on the coercivity in neodymium permanent magnets

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Atomistic simulations of α-Fe/Nd2Fe14B magnetic core/shell nanocomposites with enhanced energy product for high temperature permanent magnet applications

Abstract: This is a repository copy of Atomistic simulations of α-Fe /Nd2Fe14B magnetic core/shell nanocomposites with enhanced energy product for high temperature permanent magnet applications.

Cited by 15 publications

References 28 publications

Large magnetic anisotropy in Co–Fe–Ni–N ordered structures: a first-principles study

Large magnetic anisotropy in Co–Fe–Ni–N ordered structures: a first-principles study

Atomistic theory of thermally activated magnetization processes in Nd2Fe14B permanent magnet

Effect of the surface magnetic anisotropy of neodymium atoms on the coercivity in neodymium permanent magnets

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Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet