Magnetization reversal of a Nd-Cu-infiltrated Nd-Fe-B nanocrystalline magnet observed with small-angle neutron scattering

Saito, Kotaro; Ueno, Tetsuro; Yano, Masao; Harada, Masashi; Shoji, Tetsuya; Sakuma, Noritsugu; Manabe, Akira; Kato, Akira; Keiderling, U.; Ono, Kanta

doi:10.1063/1.4908026

Cited by 9 publications

(11 citation statements)

References 16 publications

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“…It was Takeda et al, 2012 who continued with SANS research on sintered Nd−Fe−B magnets by analyzing the temperature dependence of SANS patterns, with special attention to the correlation between the average structure and the coercivity. The effect of the grain-boundary diffusion process on the magnetizationreversal of isotropic sintered (Périgo et al, 2016) and hotdeformed (textured) nanocrystalline (Saito et al, 2015;Yano et al, 2014Yano et al, , 2012) Nd−Fe−B magnets has been investigated.…”

Section: B Selected Results On Nd−fe−b Magnetsmentioning

confidence: 99%

Magnetic small-angle neutron scattering

et al. 2019

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Small-angle neutron scattering (SANS) is one of the most important techniques for microstructure determination, being utilized in a wide range of scientific disciplines, such as materials science, physics, chemistry, and biology. The reason for its great significance is that conventional SANS is probably the only method capable of probing structural inhomogeneities in the bulk of materials on a mesoscopic real-space length scale, from roughly 1 − 300 nm. Moreover, the exploitation of the spin degree of freedom of the neutron provides SANS with a unique sensitivity to study magnetism and magnetic materials at the nanoscale. As such, magnetic SANS ideally complements more real-space and surface-sensitive magnetic imaging techniques, e.g., Lorentz transmission electron microscopy, electron holography, magnetic force microscopy, Kerr microscopy, or spinpolarized scanning tunneling microscopy. In this review article we summarize the recent applications of the SANS method to study magnetism and magnetic materials. This includes a wide range of materials classes, from nanomagnetic systems such as soft magnetic Fe-based nanocomposites, hard magnetic Nd−Fe−B-based permanent magnets, magnetic steels, ferrofluids, nanoparticles, and magnetic oxides, to more fundamental open issues in contemporary condensed matter physics such as skyrmion crystals, noncollinar magnetic structures in noncentrosymmetric compounds, magnetic/electronic phase separation, and vortex lattices in type-II superconductors. Special attention is paid not only to the vast variety of magnetic materials and problems where SANS has provided direct insight, but also to the enormous progress made regarding the micromagnetic simulation of magnetic neutron scattering.

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Section: B Selected Results On Nd−fe−b Magnetsmentioning

confidence: 99%

Magnetic small-angle neutron scattering

et al. 2019

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“…Experimental data for the correlation function of the spinmisalignment SANS cross section of nanocrystalline Co and Ni have been successfully analyzed using the here presented theoretical expressions. It would also be of interest to employ the present approach for studying long-range magnetic correlations, as accessible on a USANS instrument (Jericha et al, 2013), or the magnetic microstructure of state-of-the-art nanocrystalline NdFeB-based permanent magnets (Bick et al, 2013;Yano et al, 2014;Pé rigo et al, 2015;Saito et al, 2015).…”

Section: Figure 14mentioning

confidence: 99%

Small-angle neutron scattering correlation functions of bulk magnetic materials

Mettus

Michels

2015

J Appl Crystallogr

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On the basis of the continuum theory of micromagnetics, the correlation function of the spin-misalignment small-angle neutron scattering cross section of bulk ferromagnets (e.g. elemental polycrystalline ferromagnets, soft and hard magnetic nanocomposites, nanoporous ferromagnets, or magnetic steels) is computed. For such materials, the spin disorder which is related to spatial variations in the saturation magnetization and magnetic anisotropy field results in strong spin-misalignment scattering dAE M /d along the forward direction. When the applied magnetic field is perpendicular to the incoming neutron beam, the characteristics of dAE M /d (e.g. the angular anisotropy on a two-dimensional detector or the asymptotic power-law exponent) are determined by the ratio of magnetic anisotropy field strength H p to the jump ÁM in the saturation magnetization at internal interfaces. Here, the corresponding one-and twodimensional real-space correlations are analyzed as a function of applied magnetic field, the ratio H p /ÁM, the single-particle form factor and the particle volume fraction. Finally, the theoretical results for the correlation function are compared with experimental data on nanocrystalline cobalt and nickel.

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“…[14] for a review) provides information about the variations of both the magnitude and orientation of the magnetization vector field in the bulk and on a nanometer length scale (approximately 1-300 nm). SANS is extremely sensitive to longwavelength magnetization fluctuations, and it has only recently been employed for characterizing Nd-Fe-B-based permanent magnets: for example, the field dependence of characteristic magnetic length scales during the magnetization-reversal process in isotropic Nd-Fe-B-based nanocomposites [15] and in isotropic sintered Nd-Fe-B [16] was studied, the exchange-stiffness constant has been determined [17], the observation of the so-called spike anisotropy in the magnetic SANS cross section has been explained with the formation of flux-closure patterns [18], magnetic multiple scattering has been detected [19], textured Nd-Fe-B has been investigated [20], and the effect of grain-boundary diffusion on the magnetization-reversal process of isotropic [21] and hot-deformed textured [22][23][24] nanocrystalline Nd-Fe-B magnets has been studied. In this paper, exchange-coupled model magnets are investigated by SANS in order to quantitatively evaluate the spin disorder and to clarify the possible anisotropy of magnetic interactions.…”

Section: Introductionmentioning

confidence: 99%

Spin Structures of Textured and Isotropic Nd-Fe-B-Based Nanocomposites: Evidence for Correlated Crystallographic and Spin Textures

et al. 2017

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We report the results of a comparative study of the magnetic microstructure of textured and isotropic Nd 2 Fe 14 B=α-Fe nanocomposites using magnetometry, transmission electron microscopy, synchrotron x-ray diffraction, and, in particular, magnetic small-angle neutron scattering (SANS). Analysis of the magnetic neutron data of the textured specimen and computation of the correlation function of the spinmisalignment SANS cross section suggests the existence of inhomogeneously magnetized regions on an intraparticle nanometer length scale, about 40-50 nm in the remanent state. Possible origins for this spin disorder are discussed: it may originate in thin-grain-boundary layers (where the material parameters are different than in the Nd 2 Fe 14 B grains), or it may reflect the presence of crystal defects (introduced via hot pressing), or the dispersion in the orientation distribution of the magnetocrystalline anisotropy axes of the Nd 2 Fe 14 B grains. X-ray powder diffraction data reveal a crystallographic texture in the direction perpendicular to the pressing direction-a finding which might be related to the presence of a texture in the magnetization distribution, as inferred from the magnetic SANS data.

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Magnetization reversal of a Nd-Cu-infiltrated Nd-Fe-B nanocrystalline magnet observed with small-angle neutron scattering

Cited by 9 publications

References 16 publications

Magnetic small-angle neutron scattering

Magnetic small-angle neutron scattering

Small-angle neutron scattering correlation functions of bulk magnetic materials

Spin Structures of Textured and Isotropic Nd-Fe-B-Based Nanocomposites: Evidence for Correlated Crystallographic and Spin Textures

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