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Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet

To study the temperature dependence of magnetic properties of permanent magnets, methods of treating the thermal fluctuation causing the thermal activation phenomena must be established. To study finite-temperature properties quantitatively, we need atomistic energy information to calculate the cano...

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Autores principales: Miyashita, Seiji, Nishino, Masamichi, Toga, Yuta, Hinokihara, Taichi, Uysal, Ismail Enes, Miyake, Takashi, Akai, Hisazumi, Hirosawa, Satoshi, Sakuma, Akimasa
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Taylor & Francis 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8425694/
https://www.ncbi.nlm.nih.gov/pubmed/34512176
http://dx.doi.org/10.1080/14686996.2021.1942197
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author Miyashita, Seiji
Nishino, Masamichi
Toga, Yuta
Hinokihara, Taichi
Uysal, Ismail Enes
Miyake, Takashi
Akai, Hisazumi
Hirosawa, Satoshi
Sakuma, Akimasa
author_facet Miyashita, Seiji
Nishino, Masamichi
Toga, Yuta
Hinokihara, Taichi
Uysal, Ismail Enes
Miyake, Takashi
Akai, Hisazumi
Hirosawa, Satoshi
Sakuma, Akimasa
author_sort Miyashita, Seiji
collection PubMed
description To study the temperature dependence of magnetic properties of permanent magnets, methods of treating the thermal fluctuation causing the thermal 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, for example, 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, 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. The upper limit of coercivity at room temperature was found to be about 3 T at room temperature. The coercivity of a polycrystalline magnet, that is, an ensemble of interactinve 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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spelling pubmed-84256942021-09-09 Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet Miyashita, Seiji Nishino, Masamichi Toga, Yuta Hinokihara, Taichi Uysal, Ismail Enes Miyake, Takashi Akai, Hisazumi Hirosawa, Satoshi Sakuma, Akimasa Sci Technol Adv Mater Focus on Science and Technology of Element-Strategic Permanent Magnets To study the temperature dependence of magnetic properties of permanent magnets, methods of treating the thermal fluctuation causing the thermal 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, for example, 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, 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. The upper limit of coercivity at room temperature was found to be about 3 T at room temperature. The coercivity of a polycrystalline magnet, that is, an ensemble of interactinve 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. Taylor & Francis 2021-09-06 /pmc/articles/PMC8425694/ /pubmed/34512176 http://dx.doi.org/10.1080/14686996.2021.1942197 Text en © 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group. https://creativecommons.org/licenses/by/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Focus on Science and Technology of Element-Strategic Permanent Magnets
Miyashita, Seiji
Nishino, Masamichi
Toga, Yuta
Hinokihara, Taichi
Uysal, Ismail Enes
Miyake, Takashi
Akai, Hisazumi
Hirosawa, Satoshi
Sakuma, Akimasa
Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet
title Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet
title_full Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet
title_fullStr Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet
title_full_unstemmed Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet
title_short Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet
title_sort atomistic theory of thermally activated magnetization processes in nd(2)fe(14)b permanent magnet
topic Focus on Science and Technology of Element-Strategic Permanent Magnets
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8425694/
https://www.ncbi.nlm.nih.gov/pubmed/34512176
http://dx.doi.org/10.1080/14686996.2021.1942197
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