Enhancing Energy Product and Thermal Stability of 
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 by Interstitial Doping

Odkhuu, Dorj; Ochirkhuyag, Tumentsereg; Hong, Soon Cheol

doi:10.1103/physrevapplied.13.054076

Cited by 23 publications

(7 citation statements)

References 38 publications

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“…The lattice constants of ThMn 12 -type RFe 12 and R 2 Fe 17 reported in Refs. [43,44,[63][64][65] obtained via different DFT codes are also underestimated to some extent, which are consistent with our results. The exception for cerium occurs presumably because Ce in the rhombohedral Ce 2 Fe 17 adopts a valency of 4+ instead of 3+ [44], which is quite distinct from the other RE elements.…”

Section: Resultssupporting

confidence: 92%

Lattice dynamics effects on finite-temperature stability of $R_{1-x}$Fe$_{x}$ ($R$ = Y, Ce, Nd, Sm, and Dy) alloys from first principles

Xing,

Ishikawa,

Miura

et al. 2021

Preprint

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We report the effects of lattice dynamics on thermodynamic stability of binary R1−xFex (0 < x < 1) compounds (R: rare-earth elements, Y, Ce, Nd, Sm, and Dy) at finite temperature predicted by first-principles calculation based on density functional theory (DFT). We first demonstrate that the thermodynamic stability of R1−xFex (0 < x < 1) alloys cannot be predicted accurately by the conventional approach, where only the static DFT energy at T = 0 K is used. This issue can be overcome by considering the entropy contribution, including electronic and vibrational free energies, and we obtained convex hull plots at finite temperatures that successfully explain the thermodynamic stability of various known compounds. Our systematic calculation indicates that vibrational entropy helps stabilize various R1−xFex compounds with increasing temperature. In particular, experimentally reported R2Fe17 compounds are predicted to become thermodynamically stable above ∼800 K. We also show that thermodynamic stability is rare-earth dependent and discuss its origin. Besides the experimentally reported structures, the stability of two new monoclinic RFe12 structures found by Ishikawa et al. [Phys. Rev. Mater. 4, 104408 (2020)] based on a genetic algorithm are investigated. These monoclinic phases are found to be dynamically stable and have larger magnetization than the ThMn12-type RFe12. Although they are thermodynamically unstable, the formation energies decrease significantly with increasing temperature, indicating the possibility of synthesizing these compounds at high temperatures.

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Section: Resultssupporting

confidence: 92%

Lattice dynamics effects on finite-temperature stability of $R_{1-x}$Fe$_{x}$ ($R$ = Y, Ce, Nd, Sm, and Dy) alloys from first principles

Xing,

Ishikawa,

Miura

et al. 2021

Preprint

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“…Nevertheless, to check the influence of Co substitution on lattice structure, we optimize the lattice constant and the volume for all x values. Following our expectation, the results show only a marginal decrease in lattice parameter and volume (with a maximum deviation of 1%) upon increasing Co content, in line with the findings by Odkhuu et al [18] for 1:12 compounds, and the experimental findings by Xu and Shaheen on 2:17 compounds. [19] This minimal change is found to have no appreciable effect on magnetic properties, as explicitly checked on representative compounds with x = 1, 4 and 7.…”

Section: Dft Calculated Properties Of Predicted Compounds Crystal Str...supporting

confidence: 92%

“…The Co:Fe ratio is thus restricted within 0.4. (b) Co substitution in place of Fe has been reported [17,18] to be efficient in simultaneous enhancements of K u as well as T c in several TM magnets. This is in sharp contrast to other TM substitutes, such as Ti, Mo, Cr, and V, where magnetic anisotropy as well as T c are generally suppressed.…”

Section: Introductionmentioning

confidence: 99%

Prediction on Properties of Rare-earth 2-17-X Magnets Ce2Fe17-xCoxCN : A Combined Machine-learning and Ab-initio Study

Halder,

Rom,

Ghosh

et al. 2020

Preprint

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We employ a combination of machine learning and first-principles calculations to predict magnetic properties of rare-earth lean magnets. For this purpose, based on training set constructed out of experimental data, the machine is trained to make predictions on magnetic transition temperature (Tc), largeness of saturation magnetization (µ0Ms), and nature of the magnetocrystalline anisotropy (Ku). Subsequently, the quantitative values of µ0Ms and Ku of the yet-to-be synthesized compounds, screened by machine learning, are calculated by firstprinciples density functional theory. The applicability of the proposed technique of combined machine learning and first-principles calculations is demonstrated on 2-17-X magnets, Ce2Fe17−xCoxCN. Further to this study, we explore stability of the proposed compounds by calculating vacancy formation energy of small atom interstitials (N/C). Our study indicates a number of compounds in the proposed family, offers the possibility to become solution of cheap, and efficient permanent magnet.

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“…A strong reduction of the Curie temperature with increase of c/a was obtained by Jakobsson et al by mapping the DFT results onto the classical Heisenberg model [30]. In addition, the effect of interstitial doping on magnetic anisotropy and structural stability of tetragonal Fe-Co was studied [17][18][19][20]28].…”

Section: Introductionmentioning

confidence: 89%

“…Another approach to stabilize the tetragonal distortion in Fe-Co is to use interstitial doping with light elements such as C [17], N [18], or B [19,20]. There was also an attempt by Gao et al to incorporate tungsten with large spin-orbit coupling in Fe-Co films, that resulted in large magnetization and enhanced perpendicular coercive fields of 2-3 kOe at low W concentration [21].…”

Section: Introductionmentioning

confidence: 99%

Coulomb correlations and magnetic properties of L1$_0$ FeCo: a DFT+DMFT study

Belozerov,

Katanin,

Anisimov

2022

Preprint

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We consider electronic correlation effects and their impact on magnetic properties of tetragonally distorted chemically ordered FeCo alloy (L1 0 structure) being a promising candidate to rare-earthfree permanent magnets. We employ a state-of-the-art method combining the density functional (DFT) and dynamical mean-field theory (DMFT). According to our results, the predicted Curie temperature reduces with increase of lattice parameters ratio c/a and reaches nearly 850 K at c/a = 1.22. For all considered c/a from 1 to √ 2 we find well-localized magnetic moments on Fe sites, which are formed due to strong correlations originating from Hund's coupling. At the same time, magnetism of Co sites is more itinerant with a much less lifetime of local magnetic moments. However, these short-lived local moments are also formed due to Hund's exchange.Electronic states at Fe sites are characterized by non-quasiparticle form of self-energies, while the ones for Co sites are found to have a Fermi-liquid-like shape with quasiparticle mass enhancement factor m * /m ∼ 1.4, corresponding to moderately correlated metal. The strong electron correlations on Fe sites leading to Hund's metal behaviour can be explained by peculiarities of density of states, which has pronounced peaks near the Fermi level, while weaker many-body effects on Co sites can be caused by stronger deviation from half-filling of their 3d states. The obtained momentum dependence of magnetic susceptibility suggests that the ferromagnetic ordering is the most favourable one except for the near vicinity of the fcc structure and the magnetic exchange is expected to be of RKKY-type.

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Enhancing Energy Product and Thermal Stability of SmFe12 by Interstitial Doping

Cited by 23 publications

References 38 publications

Lattice dynamics effects on finite-temperature stability of $R_{1-x}$Fe$_{x}$ ($R$ = Y, Ce, Nd, Sm, and Dy) alloys from first principles

Lattice dynamics effects on finite-temperature stability of $R_{1-x}$Fe$_{x}$ ($R$ = Y, Ce, Nd, Sm, and Dy) alloys from first principles

Prediction on Properties of Rare-earth 2-17-X Magnets Ce2Fe17-xCoxCN : A Combined Machine-learning and Ab-initio Study

Coulomb correlations and magnetic properties of L1$_0$ FeCo: a DFT+DMFT study

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