Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet.
Atomistic theory of thermally activated magnetization processes in Nd(2)Fe(14)B permanent magnet.
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DOI：
10.1080/14686996.2021.1942197
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发表时间：
2021
影响因子：
5.5
通讯作者：
Sakuma A
中科院分区：
文献类型：
--
作者：
Miyashita S;Nishino M;Toga Y;Hinokihara T;Uysal IE;Miyake T;Akai H;Hirosawa S;Sakuma A
为了研究永磁体磁性能的温度依赖性，必须建立处理引起热活化现象的热波动的方法。为了定量地研究有限温度性质，我们需要原子能量信息来计算正则分布。本文综述了近年来钕铁硼磁体热性能的研究进展及其研究方法。我们首先提出了一个原子哈密顿量，并展示了各种热力学性质，例如，磁化的温度依赖性显示自旋重定向跃迁，磁各向异性能量，畴壁轮廓，交换刚度常数的各向异性，以及铁磁共振谱。讨论了大晶粒中偶极-偶极相互作用（DDI）的影响。除了这些平衡性质外，还利用随机Landau-Lifshitz-Gilbert方程和Monte Carlo模拟得到的自由能图分析，研究了单晶粒矫顽力与温度的关系。室温下的矫顽力上限约为3t。多晶磁体的矫顽力，即相互作用晶粒的集合，可望在晶界相的作用下进一步降低，并对此进行了研究。表面成核是畴壁脱屑过程中的关键因素。最后，我们研究了DDI对晶粒间的影响，并从一阶反转曲线的角度讨论了晶粒性质的分布。
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 Nd2Fe14B 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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影响因子：
3.2
作者：
GAUNT, P
通讯作者：
GAUNT, P
DOI：
10.1080/14686996.2021.1877092
发表时间：
2021-02-12
影响因子：
5.5
作者：
Gohda Y
通讯作者：
Gohda Y
影响因子：
3.2
作者：
Bance, S.;Seebacher, B.;Manabe, A.
通讯作者：
Manabe, A.
影响因子：
1.2
作者：
Fukada, Togo;Matsuura, Masashi;Sagawa, Masato
通讯作者：
Sagawa, Masato
影响因子：
3.7
作者：
Asselin, P.;Evans, R. F. L.;Nowak, U.
通讯作者：
Nowak, U.