Temperature dependent magnetization reversal process of a Ga-doped Nd-Fe-B sintered magnet based on first-order reversal curve analysis

Okamoto, Satoshi; Miyazawa, Kazunori; Yomogita, Takahiro; Kikuchi, Nobuaki; Kitakami, Osamu; Toyoki, Kentaro; Billington, David P.; Kotani, Yoshinori; Nakamura, Tetsuya; Sasaki, Taisuke; Ohkubo, T.; Hara, Kazuhiro; Takada, Yoko; Sato, T.; Kaneko, Yuji; Kato, Akira

doi:10.1016/j.actamat.2019.08.004

Cited by 30 publications

(4 citation statements)

References 37 publications

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“…解析などの巨視的な解析手法に加え [20][21][22] ，最近では磁気トモグラフィー測定による微視的な解析手法も整備されつつある [23][24][25] ．また，Micromagnetic (MM) シミュレーションも大きな進展を見せており [26][27][28][29][30][31] ，計算機や計算アルゴリズムの進化に加えて機械学習を導入した高速化，大規模化 [32][33][34] や電子顕微鏡で得た実際の微細組織構造をモデリングする手法の開発 [35][36][37] なども進められている． ÁEðM; HÞ ¼ EðM [20][21][22]62)…”

Section: はじめにunclassified

Recent Unrevealing on Magnetic Hysteresis of Permanent Magnets

Okamoto

2023

J. Japan Inst. Metals and Materials

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Magnetic hysteresis and coercivity mechanism of a permanent magnet have been long discussed, and their understandings have been significantly deepened during the last decade. Magnetization reversal in a permanent magnet proceeds with thermally activated nucleation and domain wall depinning processes followed by magnetic domain expansions. To treat theoretically the thermally activated magnetization reversal process, atomistic spin model and continuum calculations have been performed. Through these multi-scale calculations, the physical meanings of fluctuation field and activation volume which have been used phenomenologically become very clear. Experimental approaches for both microscopic and macroscopic thermally activated magnetization reversal processes and magnetic domain growths have been also performed. It is expected that these theoretical and experimental multi-scale studies will be integrated to fully understand the magnetic hysteresis and coercivity mechanism with the aid of data science technologies in the future.

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Section: はじめにunclassified

Recent Unrevealing on Magnetic Hysteresis of Permanent Magnets

Okamoto

2023

J. Japan Inst. Metals and Materials

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“…[5][6][7][8][9] Studies have shown that optimizing the microstructure of magnets is a common approach to improving magnetic properties. [10][11][12][13][14] Corrosion resistance during practical application is another important indicator for evaluating NdFeB magnets. [15,16] Conventional corrosion processes preferentially dissolve several low-potential grain boundary phases such as Nd-rich and B-rich ones.…”

Section: Introductionmentioning

confidence: 99%

“…It has been demonstrated that the addition of nonmagnetic alloy additives, such as Nd-rich and Pr-rich alloys, can optimize the microstructure to enhance magnetic properties and corrosion resistance. [10][11][12][13][14]21,22] Furthermore, enhancing both magnetic properties and corrosion resistance is a challenge, and one of the properties may deteriorate. [18,20,23] Currently, the addition of microelements during the melting process has been widely used to optimize magnetic properties.…”

Section: Introductionmentioning

confidence: 99%

Effect of In doping on the evolution of microstructure, magnetic properties and corrosion resistance of NdFeB magnets

Li 李,

Fan 范,

Jia 贾

et al. 2024

Chinese Phys. B

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The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets. In this work, a small amount of Indium (In) was added to the NdFeB magnet by induction melting to systematically investigate its effect on the evolution of the microstructure, magnetic properties, and corrosion resistance of the NdFeB magnet. The microstructural analysis illustrated that minor In-addition generated more grain boundary phases and an abundant amorphous phase at the triple junction grain boundary. While the addition of In element failed to enhance the magnetic isolation effect between adjacent matrix grains, fortuitously, its incorporation elevated the electrochemical potential of the In-containing magnets. Besides, during corrosion, an In-rich precipitate phase formed, hindering the ingress of the corrosive medium into the magnet. Consequently, this significantly bolstered the corrosion resistance of sintered NdFeB magnets. The phase formation, magnetic properties, and corrosion resistance of In-doped NdFeB magnets are detailed in this work, which provides a new prospect for the preparation of high-performance sintered NdFeB magnets.

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“…More generally, changing the temperature can trigger transitions between different magnetic phases, possibly accompanied by structural changes [9]. Other examples of temperature-dependent magnetic phenomena include the loss of coercivity with heating [10], zero thermal-expansion (invar) behaviour [11], and magnetization switching in compensated ferrimagnets [12].…”

Section: Introductionmentioning

confidence: 99%

MARMOT: magnetism, anisotropy, and more, using the relativistic disordered local moment picture at finite temperature

Patrick¹,

Staunton²

2022

Electron. Struct.

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We present MARMOT, a hybrid Python/FORTRAN implementation of the disordered local moment picture within multiple scattering density-functional theory. MARMOT takes atom-centred, scalar-relativistic potentials and constructs an effective medium (within the coherent potential approximation) to describe the disordered magnetic moment orientations at finite temperature. By solving the single-site scattering problem fully relativistically, spin–orbit effects are included, allowing the magnetocrystalline anisotropy to be calculated. Magnetic transition temperatures, spin and orbital moments, the density-of-states, and analytical parameterizations of the magnetic potential energy surface can also be calculated. Here, we describe the theory and practical implementation of MARMOT, and demonstrate its use by calculating Curie temperatures, magnetizations and anisotropies of bcc Fe, GdFe2 and YCo5.

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Temperature dependent magnetization reversal process of a Ga-doped Nd-Fe-B sintered magnet based on first-order reversal curve analysis

Cited by 30 publications

References 37 publications

Recent Unrevealing on Magnetic Hysteresis of Permanent Magnets

Recent Unrevealing on Magnetic Hysteresis of Permanent Magnets

Effect of In doping on the evolution of microstructure, magnetic properties and corrosion resistance of NdFeB magnets

MARMOT: magnetism, anisotropy, and more, using the relativistic disordered local moment picture at finite temperature

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