Power law analysis for temperature dependence of magnetocrystalline anisotropy constants of Nd2Fe14B magnets

Miura, Daisuke; Sakuma, Atsushi

doi:10.1063/1.5021969

Cited by 15 publications

(21 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most recently, the above-mentioned numerical methods have been applied to a realistic model for rare-earth intermetallics, and quantitative results comparable to the experimental results were obtained by first-principles calculations [10][11][12][13][14][15] and by Monte Carlo methods [16][17][18][19][20]. On the other hand, to date, simpler analyses have also been conducted on the basis of phenomenological theory [21][22][23][24] or mean field theory (MFT) [3,14,[25][26][27] to understand the mechanism of the coercive forces of rare-earth permanent magnets and to identify the factors dominating these mechanisms.…”

Section: Introductionmentioning

confidence: 93%

“…In our previous studies on the MA of Nd 2 Fe 14 B magnets [24][25][26], the total magnetization was assumed to be collinear to the Fe magnetization. However, this assumption raises a serious error in evaluations for the MA of the R 2 Fe 14 B magnet, the R magnetization of which is highly non-collinear to its Fe magnetization.…”

Section: Introductionmentioning

confidence: 99%

“…This view of the power law enables us to immediately establish that a narrow plateau appears in the low-temperature range and that higher-order MACs rapidly decay with increasing temperature compared with lower-order ones. These features describe the general behavior of on-site MA in homogeneous local moment systems [21,24,27,44].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Non-collinearity Effects on Magnetocrystalline Anisotropy for R₂Fe₁₄B Magnets

Miura

Sakuma

2019

J. Phys. Soc. Jpn.

Self Cite

View full text Add to dashboard Cite

We present a theoretical investigation of the magnetocrystalline anisotropy (MA) in R 2 Fe 14 B (R is a rare-earth element) magnets in consideration of the non-collinearity effect (NCE) between the R and Fe magnetization directions. In particular, the temperature dependence of the MA of Dy 2 Fe 14 B magnets is detailed in terms of the nth-order MA constant (MAC) K n (T ) at a temperature T . The features of this constant are as follows: K 1 (T ) has a broad plateau in the low-temperature range and K 2 (T ) persistently survives in the high-temperature range. The present theory explains these features in terms of the NCE on the MA by using numerical calculations for the entire temperature range, and further, by using a high-temperature expansion. The high-temperature expansion for K n (T ) is expressed in the form of K n (T ) = κ 1 (T ) [1 + δ(T )] [−δ(T )] n−1 , where κ 1 (T ) is the part without the NCE and δ(T ) is a correction factor for the NCE introduced in this study. We also provide a convenient expression to evaluate K n (T ), which can be determined only by a second-order crystalline electric field coefficient and an effective exchange field. * dmiura@solid.apph.tohoku.ac.jp 1 arXiv:1812.03611v2 [cond-mat.mtrl-sci]

show abstract

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Non-collinearity Effects on Magnetocrystalline Anisotropy for R₂Fe₁₄B Magnets

Miura

Sakuma

2019

J. Phys. Soc. Jpn.

Self Cite

View full text Add to dashboard Cite

show abstract

“…and J = 9/2, g = 8/11, H Nd = 350K, 35) T C = 586K; 36,37) for detail, see Ref. 11. Each fitting parameter K EPL (0) is determined as K EPL 1 (0) = −6.28MJ/m 3 , K EPL 2 (0) = 21.27MJ/m 3 , and K EPL 3 (0) = −8.48MJ/m 3 by fitting Eqs.…”

Section: Brief Notementioning

confidence: 99%

“…1. To estimate the values of the MACs over the entire temperature range, we can use the EPL as 11) K EPL 1 (T ) = K EPL 1 (0)µ Nd (T ) 3…”

mentioning

confidence: 99%

Analytic expression for magnetic activation energy

Miura¹,

Sakuma²

2019

Jpn. J. Appl. Phys.

Self Cite

View full text Add to dashboard Cite

We theoretically investigate the magnetic activation energy of permanent magnets. Practically, it is widely used in a phenomenological form as F B (H ext is the activation energy in the absence of an external magnetic field H ext , n is a real parameter, and H 0 is defined by the equationWe derive the general and direct expressions for these phenomenological parameters under the restriction of uniform rotation of magnetization and on the basis of the perturbative theory with respect to H ext . Further, we apply our results to Nd 2 Fe 14 B magnets and confirm the validity of the proposed method by comparing with the Monte Carlo calculations.Elucidating the dominant factors in the coercive force of permanent magnets is a central issue in the fields of magnetics and material science. Magnetocrystalline anisotropy (MA) is one of the dominant factors governing the coercive force in rare-earth (RE) magnets such a Nd-Fe-B magnet, 1, 2) whose temperature dependence has been investigated by many authors. 3-6) From the theoretical viewpoint, the MA of a ferromagnet is specified by its free energy density as a function of the magnetization angle, and practically, its temperature dependence is expressed in terms of th-order MA constants (MACs), K (T ), at a temperature T .Especially, in RE magnets, it is often found that those have higher order MACs and strongly depends on temperature. Fortunately, these complex features can be understood within mean field theories (MFTs). 7-12) Most recently, 11) we described the temperature-dependent MA in local moment systems by using Zener's phenomenological theory 13) and derived it in an extended form of the Akulov-Zener-Callen-Callen power law, [13][14][15] which is used to obtain a temperature dependence curve of K (T ) later in this study; there, it is referred to as the "extended power law (EPL) ." On the other hand, it was reported that inhomogeneity in magnetic structures seriously affects the coercive forces, 16) and thus numerical analyses have been continued to date. [17][18][19][20][21][22] As mentioned above, the temperature dependence of MA in RE magnets has been understood well. However, the role of MA in the coercive force mechanism is not clear at this

show abstract

Recent advances in mechanical properties of sintered NdFeB magnets

Liang,

Shao,

Que

et al. 2024

Journal of Alloys and Compounds

View full text Add to dashboard Cite

Power law analysis for temperature dependence of magnetocrystalline anisotropy constants of Nd2Fe14B magnets

Cited by 15 publications

References 50 publications

Non-collinearity Effects on Magnetocrystalline Anisotropy for R₂Fe₁₄B Magnets

Non-collinearity Effects on Magnetocrystalline Anisotropy for R₂Fe₁₄B Magnets

Analytic expression for magnetic activation energy

Recent advances in mechanical properties of sintered NdFeB magnets

Contact Info

Product

Resources

About

Power law analysis for temperature dependence of magnetocrystalline anisotropy constants of Nd2Fe14B magnets

Cited by 15 publications

References 50 publications

Non-collinearity Effects on Magnetocrystalline Anisotropy for R2Fe14B Magnets

Non-collinearity Effects on Magnetocrystalline Anisotropy for R2Fe14B Magnets

Analytic expression for magnetic activation energy

Recent advances in mechanical properties of sintered NdFeB magnets

Contact Info

Product

Resources

About

Non-collinearity Effects on Magnetocrystalline Anisotropy for R₂Fe₁₄B Magnets

Non-collinearity Effects on Magnetocrystalline Anisotropy for R₂Fe₁₄B Magnets