The evolution of phase constitution and microstructure in iron-rich 2:17-type Sm-Co magnets with high magnetic performance

Zhang, Chaoyue; Liu, Zhuang; Li, Ming; Liu, Lei; Li, Tianyi; Chen, Renjie; Lee, Don; Yan, Aru

doi:10.1038/s41598-018-27487-x

Cited by 55 publications

(13 citation statements)

References 32 publications

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“…It indicated that the 1:5H cell boundary precipitates, which play an essential role on the coercivity, had a very small fraction at the solution-treated state or after aging for 0.5 h. Figure 2 shows the powder XRD patterns of the magnets. The fundamental reflections of all the samples could be contributed from the phases reported in the 2:17-type Sm-Co magnets including 1:5H, 1:7H, 2:17H, 2:17R, 2:17R', and Sm n+1 Co 5n−1 phases [25,[31][32][33][34][35][36]. In Figure 2a, a very weak peak of {023} was present at 2θ of~40.3 • for the solution-treated sample, which is the characteristic peak of 2:17H [35].…”

Section: Resultsmentioning

confidence: 98%

“…Figure 2 shows the powder XRD patterns of the magnets. The fundamental reflections of all the samples could be contributed from the phases reported in the 2:17-type Sm-Co magnets including 1:5H, 1:7H, 2:17H, 2:17R, 2:17R’, and Sm n+1 Co 5n−1 phases [ 25 , 31 , 32 , 33 , 34 , 35 , 36 ]. In Figure 2 a, a very weak peak of {023} was present at 2 θ of ~40.3° for the solution-treated sample, which is the characteristic peak of 2:17H [ 35 ].…”

Section: Resultsmentioning

confidence: 99%

“…Prior to presenting the TEM characterization results, it should be noted that the 2:17R phase exhibits a nanotwin structure in 2:17-type Sm-Co-Fe-Cu-Zr magnets [ 37 , 38 ]. The 1:5H precipitates usually occupy the {011} 2:17R pyramidal cell boundaries and the 1:3R lamellar precipitates usually occupy the {001} basal planes across the cells and cell boundaries [ 32 , 33 , 35 ]. Recent work has revealed that there is also a 2:17R’ phase, the intermediate phase of 2:17R, having one faulted basal layer in the 2:17R lattice, which is usually observed at the cell edges [ 20 ].…”

Section: Resultsmentioning

confidence: 99%

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Grain Boundary Evolution of Cellular Nanostructured Sm-Co Permanent Magnets

et al. 2021

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Grain boundaries are thought to be the primary demagnetization sites of precipitate-hardening 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets with a unique cellular nanostructure, leading to a poor squareness factor as well as a much lower than ideal energy product. In this work, we investigated the grain boundary microstructure evolution of a model magnet Sm25Co46.9Fe19.5Cu5.6Zr3.0 (wt. %) during the aging process. The transmission electron microscopy (TEM) investigations showed that the grain boundary region contains undecomposed 2:17H, partially ordered 2:17R, 1:5H nano-precipitates, and a Smn+1Co5n-1 (n = 2, 1:3R; n = 3, 2:7R; n = 4, 5:19R) phase mixture at the solution-treated state. After short-term aging, further decomposition of 2:17H occurs, characterized by the gradual ordering of 2:17R, the precipitation of the 1:5H phase, and the gradual growth of Smn+1Co5n−1 compounds. Due to the lack of a defect-aggregated cell boundary near the grain boundary, the 1:5H precipitates are constrained between the 2:17R and the Smn+1Co5n-1 nano-sheets. When further aging the magnet, the grain boundary 1:5H precipitates transform into Smn+1Co5n-1 compounds. As the Smn+1Co5n-1 compounds are magnetically softer than the 1:5H precipitates, the grain boundaries then act as the primary demagnetization sites. Our work adds important insights toward the understanding of the grain boundary effect of 2:17-type Sm-Co-Fe-Cu-Zr magnets.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Grain Boundary Evolution of Cellular Nanostructured Sm-Co Permanent Magnets

et al. 2021

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“…Especially important is the enhancement of coercivity due to domain-wall (DW) pinning, which arises from the difference in the DW energy between the cells and the cell walls because of their different magnetocrystalline anisotropy [10][11][12][13][14][15][16][17] . This has been well-documented experimentally by Lorentz transmission electron microscopy (LTEM), magnetic force microscopy and Kerr microscopy [18][19][20][21][22][23][24] .…”

Section: Introductionmentioning

confidence: 95%

Temperature dependence of magnetization processes in Sm(Co, Fe, Cu, Zr)z magnets with different nanoscale microstructures

Pierobon

Schäublin

Kovács

et al. 2021

Journal of Applied Physics

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The characteristic microstructure of Sm(Co,Fe,Cu,Zr) z alloys with SmCo 5 cell walls in Sm 2 Co 17 cells, all intersected by Zr-rich platelets, makes them some of the best performing high-temperature permanent magnets. Plentiful research has been performed to tailor the microstructure at the nanoscale, but due to its complexity many questions remain unanswered about the effect of the individual phases on the magnetic performance at different temperatures. Here, we explore this mechanism effect for three different Sm(Co,Fe,Cu,Zr) z alloys by deploying high-resolution magnetic imaging via in-situ transmission electron microscopy and three-dimensional chemical analysis using atom probe tomography. We show that their microstructures differ in terms of SmCo 5 cell-wall and Z-phase size and density, as well as the Cu concentration in the cell walls, and demonstrate how these features influence the magnetic domain size and density and thus form different magnetic textures. Moreover, we illustrate that the dominant coercivity mechanism at room temperature is domain-wall pinning and show that magnets with a denser cell-wall network, a steeper Cu gradient across the cell-wall boundary, and thinner Z-phase platelets have a higher coercivity. We also show that the coercivity mechanism at high temperatures is domain-wall nucleation at the cell walls. Increasing the Cu concentration inside the cell walls decreases the transition temperature between pinning and nucleation, significantly decreasing the coercivity with increasing temperature. We therefore provide a detailed explanation of how the microstructure on the atomic to nanoscale directly affects the magnetic performance and provide detailed guidelines for an improved design of Sm(Co,Fe,Cu,Zr) z magnets.

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“…The enhanced coercivity in these cellular Sm-Co magnets emerges from the difference between the magnetocrystalline anisotropy of the two phases and consequently the difference in domainwall energy [9]. While conventional wisdom states that this microstructure constitutes a pinning system for domain walls, the exact magnetization processes remain elusive despite the intense activities that have been performed to understand the interaction of domain walls with the SmCo 5 cells [13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Unconventional magnetization textures and domain-wall pinning in Sm–Co magnets

Pierobon

Kovács

Schäublin

et al. 2020

Sci Rep

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Some of the best-performing high-temperature magnets are Sm–Co-based alloys with a microstructure that comprises an $$\hbox {Sm}_2\hbox {Co}_{17}$$ Sm 2 Co 17 matrix and magnetically hard $$\hbox {SmCo}_5$$ SmCo 5 cell walls. This generates a dense domain-wall-pinning network that endows the material with remarkable magnetic hardness. A precise understanding of the coupling between magnetism and microstructure is essential for enhancing the performance of Sm–Co magnets, but experiments and theory have not yet converged to a unified model. Here, transmission electron microscopy, atom probe tomography, and nanometer-resolution off-axis electron holography have been combined with micromagnetic simulations to reveal that the magnetization state in Sm–Co magnets results from curling instabilities and domain-wall pinning effects at the intersections of phases with different magnetic hardness. Additionally, this study has found that topologically non-trivial magnetic domains separated by a complex network of domain walls play a key role in the magnetic state by acting as nucleation sites for magnetization reversal. These findings reveal previously hidden aspects of magnetism in Sm–Co magnets and, by identifying weak points in the microstructure, provide guidelines for improving these high-performance magnetic materials.

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The evolution of phase constitution and microstructure in iron-rich 2:17-type Sm-Co magnets with high magnetic performance

Cited by 55 publications

References 32 publications

Grain Boundary Evolution of Cellular Nanostructured Sm-Co Permanent Magnets

Grain Boundary Evolution of Cellular Nanostructured Sm-Co Permanent Magnets

Temperature dependence of magnetization processes in Sm(Co, Fe, Cu, Zr)z magnets with different nanoscale microstructures

Unconventional magnetization textures and domain-wall pinning in Sm–Co magnets

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