Achievement of high coercivity in Sm(Fe0.8Co0.2)12 anisotropic magnetic thin film by boron doping

Sepehri-Amin, H.; Yukiya, Tamazawa; Kambayashi, M.; Saito, G.; Takahashi, Y. K.; Ogawa, Daisuke; Ohkubo, T.; Hirosawa, S.; Doi, M.; Shima, T.; Hono, K.

doi:10.1016/j.actamat.2020.05.026

Cited by 66 publications

(24 citation statements)

References 30 publications

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“…8(a) shows the in-plane and cross-sectional bright-field TEM images of the Sm(Fe 0.8 Co 0.2 ) 12 B 0.5 film. In the B-free Sm(Fe 0.8 Co 0.2 ) 12 sample, similar to what was shown in Fig.2(c), the columnar grains can be grown while they are in direct contact, as discussed in detail by Sepehri-Amin et al[50]. By the addition of B, a nanogranular structured Sm(Fe 0.8 Co 0.2 ) 12 grains with an average diameter of ~50 nm that is enveloped by a grain boundary phase can be observed[50].Fig.…”

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confidence: 78%

“…In the B-free Sm(Fe 0.8 Co 0.2 ) 12 sample, similar to what was shown in Fig.2(c), the columnar grains can be grown while they are in direct contact, as discussed in detail by Sepehri-Amin et al[50]. By the addition of B, a nanogranular structured Sm(Fe 0.8 Co 0.2 ) 12 grains with an average diameter of ~50 nm that is enveloped by a grain boundary phase can be observed[50].Fig. 8(b) and (c) show the high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images in the cross-section and in-plane directions.…”

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confidence: 78%

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Recent advances in SmFe₁₂-based permanent magnets

Takahashi

Sepehri-Amin

Ohkubo

2021

Science and Technology of Advanced Materials

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To realize a sustainable society, "green technology" with low (or even zero) CO 2 emissions, is required. A key material in such technology is a permanent magnet because it is utilized for electric-power conversion in several applications including electric vehicles (EVs), hybrid EVs (HEVs), and turbines for wind power generation. To realize highly efficient electric-power conversion, a stronger permanent magnet than Nd-Fe-B is necessary. One potential candidate is a Fe-rich SmFe 12 -based compound with a ThMn 12 structure. In this paper, the phase stability, structure, and intrinsic and extrinsic magnetic properties in both film and bulk forms are reviewed. Based on these results, a possible way to realize a strong SmFe 12 -based permanent magnet in bulk form is discussed.

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confidence: 78%

supporting

confidence: 78%

Recent advances in SmFe₁₂-based permanent magnets

Takahashi

Sepehri-Amin

Ohkubo

2021

Science and Technology of Advanced Materials

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“…As pointed out in Ref. 19 , this analytical spin model can be easily extended to Sm ions around the intergranular phases, which is crucially important in the coercivity mechanism 13,36,37 .…”

Section: Introductionmentioning

confidence: 88%

Statistical and analytical approaches to finite-temperature magnetic properties of the compound SmFe12

2020

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To investigate the magnetic properties of SmFe12, we construct an effective spin model, where magnetic moments, crystal field (CF) parameters, and exchange fields at 0 K are determined by first principles. Finite temperature magnetic properties are investigated by using this model. We further develop an analytical method with strong mixing of states with different quantum number of angular momentum J (J-mixing), which is caused by strong exchange field acting on spin component of 4f electrons. Comparing our analytical results with those calculated by Boltzmann statistics, we clarify that the previous analytical studies for Sm transition metal compounds overestimate the J-mixing effects. The present method enables us to make quantitative analysis of temperature dependence of magnetic anisotropy (MA) with high-reliability. The analytical method with model approximations reveals that the J-mixing caused by exchange field increases spin angular momentum, which enhances the absolute value of orbital angular momentum and MA constants via spin-orbit interaction. It is also clarified that these J-mixing effects remain even above room temperature. Magnetization of SmFe12 shows peculiar field dependence known as first-order magnetization process (FOMP), where the magnetization shows an abrupt change at certain magnetic field. The result of the analysis shows that the origin of FOMP is attributed to competitive MA constants between positive K1 and negative K2. The sign of K 1(2) appears due to an increase in CF potential denoted by the parameter A 0 2 r 2 (A 0 4 r 4) caused by hybridization between 3d-electrons of Fe on 8i (8j) site and 5d and 6p valence electrons on Sm site. It is verified that the requirement for the appearance of FOMP is given as −K2 < K1 < −6K2.

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“…Recently, anisotropic Sm(Fe 0.8 Co 0.2 ) 12 –B films composed of columnar grains (40 nm) textured with amorphous B intergranular boundary have been realized. The films exhibited a large room-temperature of 1.2 T, of 1.5 T, and very small temperature-dependent , promising excellent stability at T ≥ 150°C [ 110 ]. Unfortunately, they are metastable phases and, thus could not be realized in bulk for the fabrication of PMs.…”

Section: Synthesis Of Multielement R–t Mmpsmentioning

confidence: 99%

Synthesis of mesoscopic particles of multi-component rare earth permanent magnet compounds

Trinh

Kim

Sato

et al. 2021

Science and Technology of Advanced Materials

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Multielement rare earth (R)–transition metal (T) intermetallics are arguably the next generation of high-performance permanent magnetic materials for future applications in energy-saving and renewable energy technologies. Pseudobinary Sm 2 Fe 17 N 3 and (R,Zr)(Fe,Co,Ti) 12 (R = Nd, Sm) compounds have the highest potential to meet current demands for rare-earth-element-lean permanent magnets (PMs) with ultra-large energy product and operating temperatures up to 200°C. However, the synthesis of these materials, especially in the mesoscopic scale for maximizing the maximum energy product ( ), remains a great challenge. Nonequilibrium processes are apparently used to overcome the phase-stabilization challenge in preparing the R–T intermetallics but have limited control of the material’s microstructure. More radical bottom-up nanoparticle approaches based on chemical synthesis have also been explored, owing to their potential to achieve the desired composition, structure, size, and shape. While a great achievement has been made for the Sm 2 Fe 17 N 3 , progress in the synthesis of (R,Zr)(Fe,Co,Ti) 12 magnetic mesoscopic particles (MMPs) and R–T/T exchange-coupled nanocomposites (NCMs) with substantial coercivity ( ) and remanence ( , respectively, remains marginal.

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Achievement of high coercivity in Sm(Fe0.8Co0.2)12 anisotropic magnetic thin film by boron doping

Cited by 66 publications

References 30 publications

Recent advances in SmFe₁₂-based permanent magnets

Recent advances in SmFe₁₂-based permanent magnets

Statistical and analytical approaches to finite-temperature magnetic properties of the compound SmFe12

Synthesis of mesoscopic particles of multi-component rare earth permanent magnet compounds

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Achievement of high coercivity in Sm(Fe0.8Co0.2)12 anisotropic magnetic thin film by boron doping

Cited by 66 publications

References 30 publications

Recent advances in SmFe12-based permanent magnets

Recent advances in SmFe12-based permanent magnets

Statistical and analytical approaches to finite-temperature magnetic properties of the compound SmFe12

Synthesis of mesoscopic particles of multi-component rare earth permanent magnet compounds

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Product

Resources

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Recent advances in SmFe₁₂-based permanent magnets

Recent advances in SmFe₁₂-based permanent magnets