Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic small-angle neutron scattering

Périgo, E.A.; Titov, Ivan; Weber, R.; Mettus, Denis; Peral, Inma; Vallcorba, Oriol; Honecker, Dirk; Feoktystov, Artem; Michels, Andreas

doi:10.1088/2053-1591/aab7aa

Cited by 5 publications

(5 citation statements)

References 50 publications

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“…[41][42][43][44] and references therein). Such cuboidal structures were, however, not directly observed in our samples by means of scanning and transmission electron microscopy 7,8,36 .…”

Section: Resultsmentioning

confidence: 55%

“…This method has previously been applied to study the structures of magnetic nanoparticles [12][13][14][15][16][17][18][19][20] , soft magnetic nanocomposites 21,22 , proton domains [23][24][25] , magnetic steels [26][27][28][29][30] , or Heusler-type alloys [31][32][33][34][35] . Regarding Nd-Fe-B, SANS investigations 8,36 have reported a peculiar cross-shaped angular anisotropy in the scattering cross section of the polycrystalline textured material. In the single-crystal study by Kreyssig et al 37 the crossshaped anisotropy was interpreted in terms of a fractallike magnetic domain structure.…”

Section: Introductionmentioning

confidence: 99%

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Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

Titov,

Honecker,

Mettus

et al. 2020

Preprint

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By means of temperature and wavelength-dependent small-angle neutron scattering (SANS) experiments on sintered isotropic and textured Nd-Fe-B magnets we provide evidence for the existence of an anisometric structure in the microstructure of the textured magnets. This conclusion is reached by observing a characteristic cross-shaped angular anisotropy in the total unpolarized SANS cross section at temperatures well above the Curie temperature. Comparison of the experimental SANS data to a microstructural model based on the superquadrics form factor allows us to estimate the shape and lower bounds for the size of the structure. Subtraction of the scattering cross section in the paramagnetic regime from data taken at room temperature provides the magnetic SANS cross section. Surprisingly, the anisotropy of the magnetic scattering is very similar to the nuclear SANS signal, suggesting that the nuclear structure is decorated by the magnetic moments via spin-orbit coupling. Based on the computation of the two-dimensional correlation function we estimate lower bounds for the longitudinal and transversal magnetic correlation lengths.

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“…[41][42][43][44] and references therein). Such cuboidal structures were, however, not directly observed in our samples by means of scanning and transmission electron microscopy 7,8,36 .…”

Section: Resultsmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

Titov,

Honecker,

Mettus

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…[41][42][43][44] and references therein). Such cuboidal structures were, however, not directly observed in our samples by means of scanning and transmission electron microscopy [7,8,36]. [46], and no Bragg diffraction from the Nd 2 Fe 14 B unit cell can occur for λ > 2d max ; in other words, the origin of the cross-shaped anisotropy in d /d is very likely related to the nuclear small-angle scattering arising from an anisotropic scatteringlength density distribution, not Bragg diffraction.…”

Section: Resultsmentioning

confidence: 57%

“…This method has previously been applied to study the structures of magnetic nanoparticles [12][13][14][15][16][17][18][19][20], soft magnetic nanocomposites [21,22], proton domains [23][24][25], magnetic steels [26][27][28][29][30], or Heuslertype alloys [31][32][33][34][35]. Regarding Nd-Fe-B, SANS investigations [8,36] have reported a peculiar cross-shaped angular anisotropy in the scattering cross section of the polycrystalline textured material. In the single-crystal study by Kreyssig et al [37] the cross-shaped anisotropy was interpreted in terms of a fractal-like magnetic domain structure.…”

Section: Introductionmentioning

confidence: 99%

Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

Titov

Honecker

Mettus

et al. 2020

Phys. Rev. Materials

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“…This suggests that the microstructural changes that are responsible for M(H 0 ) are not resolved by the SANS experiment (given the experimental q min and q max ), which probes a real-space structure between about 1 and 100 nm; however, this observation does not imply that SANS is not suitable for resolving displacement fields in magnetic BMG in the given q-range. In this context, we refer to a recent SANS study that investigates the effect of the annealing conditions (heating rate and temperature) on the magnetic microstructure of sintered Nd-Fe-B magnets [37]; while the temperature treatment has a strong effect on the coercivity (with a reduction of about 50% upon annealing), the associated changes in the microstructure surprisingly do not show up (or at best show up only very weakly) in the neutron-scattering signal.…”

Section: B (Nd 60 Fe 30 Al 10 ) 92 Nimentioning

confidence: 99%

Magnetic small-angle neutron scattering on bulk metallic glasses: A feasibility study for imaging displacement fields

Mettus

Deckarm

Leibner

et al. 2017

Phys. Rev. Materials

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Magnetic-field-dependent small-angle neutron scattering (SANS) has been utilized to study the magnetic microstructure of bulk metallic glasses (BMGs). In particular, the magnetic scattering from soft magnetic Fe 70 Mo 5 Ni 5 P 12.5 B 2.5 C 5 and hard magnetic (Nd 60 Fe 30 Al 10 ) 92 Ni 8 alloys in the as-prepared, aged, and mechanically deformed state is compared. While the soft magnetic BMGs exhibit a large field-dependent SANS response with perturbations originating predominantly from spatially varying magnetic anisotropy fields, the SANS cross sections of the hard magnetic BMGs are only weakly dependent on the field, and their angular anisotropy indicates the presence of scattering contributions due to spatially dependent saturation magnetization. Moreover, we observe an unusual increase in the magnetization of the rare-earth-based alloy after deformation. Analysis of the SANS cross sections in terms of the correlation function of the spin misalignment reveals the existence of field-dependent anisotropic long-wavelength magnetization fluctuations on a scale of a few tens of nanometers. We also give a detailed account of how the SANS technique relates to unraveling displacement fields on a mesoscopic length scale in disordered magnetic materials.

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Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic small-angle neutron scattering

Cited by 5 publications

References 50 publications

Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

Anisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets

Magnetic small-angle neutron scattering on bulk metallic glasses: A feasibility study for imaging displacement fields

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