Evolution of magnetic domain structures and coercivity in high-performance SmCo 2:17-type permanent magnets

Gutfleisch, Oliver; Müller, K.‐H.; Khlopkov, K.; Wolf, Manfred; Yan, Aru; Schäfer, Rudolf; Gemming, Thomas; Schultz, L.

doi:10.1016/j.actamat.2005.10.026

Cited by 210 publications

(67 citation statements)

References 36 publications

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“…In a bicontinuous structure, two phases interpenetrate one another and are each connected to itself throughout. Physically, these bicontinuous structures can form during phase-ordering in magnetic materials [42][43][44]46], spinodal decomposition in polymer mixtures [33,34,36], and in microemulsions [37,38]. Kwon et al confirmed that the bicontinuous structures simulated via conserved (spinodal decomposition) and nonconserved (phase-ordering) dynamics evolve selfsimilarly during coarsening [39,40].…”

Section: Introductionmentioning

confidence: 92%

“…Self-similar structures are ideally suited for developing theoretical understanding since they possess a single-modal distribution of features and the governing equation becomes time independent when scaled with the characteristic length scale. Two types of complex microstructures that evolve selfsimilarly are the bicontinuous structures that result from phase decomposition such as spinodal decomposition [33][34][35][36][37][38][39][40][41] and phase ordering [42][43][44][45][46]39,40]. In a bicontinuous structure, two phases interpenetrate one another and are each connected to itself throughout.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of interfacial curvatures of a bicontinuous structure generated via nonconserved dynamics

2015

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While coarsening of spherical particles has been well documented, our understanding of coarsening of complex microstructures is still limited. The first step in developing a theory of coarsening of microstructures with complex morphologies is to study coarsening of microstructures that evolve self-similarly. In this paper, we examine the morphological evolution of a self-similar two-phase bicontinuous structure generated via nonconserved dynamics (i.e., motion by mean curvature) to elucidate the complex dynamics of coarsening. We find that the evolution proceeds with some interfaces evolving toward topological singularities (pinching) while the majority of interfaces flatten. These two processes were also illustrated through the evolution equation for the mean curvature, which has a term that depends solely on the local curvatures, as well as a term that is proportional to the surface Laplacian of the mean curvature. The first term causes an increase in the magnitude of the mean curvature, while the second term causes smoothing of the mean curvature in a manner similar to diffusion of chemical species on a surface. The second term causes a large dispersion in the values of the time derivative of mean curvature at various locations in the structure, characterized neither by the mean curvature nor the Gaussian curvature.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Evolution of interfacial curvatures of a bicontinuous structure generated via nonconserved dynamics

2015

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“…Generally, the major driving force for research and development of rare-earth permanent magnets (RPMs) is the need for maximized energy densities at various operating temperatures. Most importantly, this includes less Dy-containing Nd 2 Fe 14 B-type magnets with much improved temperature stability for electromotor applications at around 450 K, [ 9 ] Pr 2 Fe 14 B-type magnets for applications at 77 K together with high Curie temperature ( T c ) superconductors, [ 10 ] and a new generation of SmCo 2:17-type magnets for applications at temperatures exceeding 670 K. [ 11,12 ] It also includes magnetic-power MEMS, [13][14][15][16] for example, a high-speed permanent magnetic generator, which require highly textured, thick RPM fi lms. [ 17 ] Nowadays, emphasis of research is on the control of microchemistry and structure of grain boundary phases and internal interfaces, which are crucial for the understanding of the relevant coercivity mechanisms and the related critical elementary magnetization reversal processes.…”

Section: Energy Consumption and The Need For High-effi Ciency Devicesmentioning

confidence: 99%

Magnetic Materials and Devices for the 21st Century: Stronger, Lighter, and More Energy Efficient

et al. 2010

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A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifically, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure-property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy efficiency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed.

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“…21) For instance, an optical microscope utilizing the Kerr effect is the most prevalent method, [22][23][24][25] and is still developing. [26][27][28] Magnetic-force microscopy (MFM) is also a commonly used technique for domain observation of NdFe-B materials. [29][30][31] Lorentz microscopy 32,33) and electron holography 34) have been utilized for thin-films.…”

Section: Introductionmentioning

confidence: 99%

Magnetic-Domain Structure Analysis of Nd-Fe-B Sintered Magnets Using XMCD-PEEM Technique

Yamamoto¹,

Yonemura²,

Wakita

et al. 2008

Mater. Trans.

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A combination of X-Ray Magnetic Circular Dichroism and PhotoEmission Electron Microscopy (XMCD-PEEM) was applied to the magnetic domain analysis of Nd-Fe-B sintered magnets. The XMCD-PEEM high-resolution images revealed both the magnetic domain structures and the microstructural morphologies. In the thermally demagnetized state, each grain in a polycrystalline sample exhibits a multidomain structure, which is magnetically coupled across grain boundaries. After the DC field-demagnetization, it changed to a single domain structure. The magnetization vector in each surface grain reversed to the negative direction during the field-demagnetization procedure because of the small coercivity in the surface region. In the present study, we observed this surface domain reversal for the first time by means of XMCD-PEEM imaging method, which is important in order to understand the surface phenomena of Nd-Fe-B magnets.

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Evolution of magnetic domain structures and coercivity in high-performance SmCo 2:17-type permanent magnets

Cited by 210 publications

References 36 publications

Evolution of interfacial curvatures of a bicontinuous structure generated via nonconserved dynamics

Evolution of interfacial curvatures of a bicontinuous structure generated via nonconserved dynamics

Magnetic Materials and Devices for the 21st Century: Stronger, Lighter, and More Energy Efficient

Magnetic-Domain Structure Analysis of Nd-Fe-B Sintered Magnets Using XMCD-PEEM Technique

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