References of "Michels, Andreas 50002669"
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See detailRole of higher-order effects in spin-misalignment small-angle neutron scattering of high-pressure torsion nickel
Oba, Yojiro; Bersweiler, Mathias UL; Titov, Ivan et al

in Physical Review Materials (2021), 5

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See detailRevealing defect-induced spin disorder in nanocrystalline Ni
Bersweiler, Mathias UL; Michels, Andreas UL; Sinaga, Evelyn Pratami UL et al

in Physical Review Materials (2021), 5(4), 044409

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See detailNeutron study of magnetic correlations in rare-earth-free Mn-Bi magnets
Malyeyev, Artem UL; Titov, Ivan; Bender, Philipp et al

in Physical Review Materials (2021), 5

We report the results of an unpolarized small-angle neutron scattering (SANS) study on Mn-Bi-based rare-earth-free permanent magnets. The magnetic SANS cross section is dominated by long-wavelength ... [more ▼]

We report the results of an unpolarized small-angle neutron scattering (SANS) study on Mn-Bi-based rare-earth-free permanent magnets. The magnetic SANS cross section is dominated by long-wavelength transversal magnetization fluctuations and has been analyzed in terms of the Guinier-Porod model and the distance distribution function. This provides the radius of gyration which, in the remanent state, ranges between about $220-240 \, \mathrm{nm}$ for the three different alloy compositions investigated. Moreover, computation of the distance distribution function in conjunction with results for the so-called $s$-parameter obtained from the Guinier-Porod model indicate that the magnetic scattering of a Mn$_{45}$Bi$_{55}$ sample has its origin in slightly shape-anisotropic structures. [less ▲]

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See detailUnraveling Nanostructured Spin Textures in Bulk Magnets
Bender, Philipp Florian UL; Leliaert, Jonathan; Bersweiler, Mathias UL et al

in Small Science (2021), 1(1), 2000003

One of the key challenges in magnetism remains the determination of the nanoscopic magnetization profile within the volume of thick samples, such as permanent ferromagnets. Thanks to the large penetration ... [more ▼]

One of the key challenges in magnetism remains the determination of the nanoscopic magnetization profile within the volume of thick samples, such as permanent ferromagnets. Thanks to the large penetration depth of neutrons, magnetic small-angle neutron scattering (SANS) is a powerful technique to characterize bulk samples. The major challenge regarding magnetic SANS is accessing the real-space magnetization vector field from the reciprocal scattering data. In this letter, a fast iterative algorithm is introduced that allows one to extract the underlying two-dimensional magnetic correlation functions from the scattering patterns. This approach is used here to analyze the magnetic microstructure of Nanoperm, a nanocrystalline alloy which is widely used in power electronics due to its extraordinary soft magnetic properties. It can be shown that the computed correlation functions clearly reflect the projection of the three-dimensional magnetization vector field onto the detector plane, which demonstrates that the used methodology can be applied to probe directly spin-textures within bulk samples with nanometer-resolution. This article is protected by copyright. All rights reserved. [less ▲]

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See detailMagnetic Small-Angle Neutron Scattering. A Probe for Mesoscale Magnetism Analysis
Michels, Andreas UL

Book published by Oxford University Press (2021)

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See detailChemical vapor deposition of CoFe2O4 micropillar arrays with enhanced magnetic properties
Aspe, B.; Malyeyev, Artem UL; Vakilinejad, A. et al

in Journal of Alloys and Compounds (2021), 890

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See detailLow-Temperature Growth of AlN Films on Magnetostrictive Foils for High-Magnetoelectric-Response Thin-Film Composites
Nguyen, T.; Fleming, Y.; Bender, P. et al

in ACS Applied Materials and Interfaces (2021), 13

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See detailToward Understanding Complex Spin Textures in Nanoparticles by Magnetic Neutron Scattering
G. Vivas, Laura; Yanes, Rocio; Berkov, Dmitry et al

in Physical Review Letters (2020), 125

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See detailMagnetic correlations in polycrystalline Tb0.15Co0.85
Bersweiler, Mathias UL; Bender, Philipp Florian UL; Peral Alonso, Inmaculada UL et al

in Journal of Physics: D Applied Physics (2020), 53

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See detailMagnetic Guinier law
Michels, Andreas UL; Malyeyev, Artem UL; Titov, Ivan UL et al

in IUCrJ (2020), 7

Small-angle scattering of x-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering ... [more ▼]

Small-angle scattering of x-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering curve from an assembly of particles. The Guinier law has originally been derived for nonmagnetic particle-matrix-type systems, and it is successfully employed for the estimation of particle sizes in various scientific domains (e.g., soft matter physics, biology, colloidal chemistry, materials science). An important prerequisite for it to apply is the presence of a discontinuous interface separating particles and matrix. Here, we introduce the Guinier law for the case of magnetic small-angle neutron scattering (SANS) and experimentally demonstrate its applicability for the example of nanocrystalline cobalt. It is well- known that the magnetic microstructure of nanocrystalline ferromagnets is highly nonuniform on the nanometer length scale and characterized by a spectrum of continuously varying long-wavelength magnetization fluctuations, i.e., these systems do not manifest sharp interfaces in their magnetization profile. The magnetic Guinier radius depends on the applied magnetic field, on the magnetic interactions (exchange, magnetostatics), and on the magnetic anisotropy-field radius, which characterizes the size over which the magnetic anisotropy field is coherently aligned into the same direction. In contrast to the nonmagnetic conventional Guinier law, the magnetic version can be applied to fully dense random-anisotropy-type ferromagnets. [less ▲]

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See detailThe benefits of a Bayesian analysis for the characterization of magnetic nanoparticles
Bersweiler, Mathias UL; Rubio, Helena Gavilan; Honecker, Dirk UL et al

in Nanotechnology (2020), 31(43), 435704

Magnetic nanoparticles offer a unique potential for various biomedical applications, but prior to commercial usage a standardized characterization of their structural and magnetic properties is required ... [more ▼]

Magnetic nanoparticles offer a unique potential for various biomedical applications, but prior to commercial usage a standardized characterization of their structural and magnetic properties is required. For a thorough characterization, the combination of conventional magnetometry and advanced scattering techniques has shown great potential. In the present work, we characterize a powder sample of high-quality iron oxide nanoparticles that are surrounded with a homogeneous thick silica shell by DC magnetometry and magnetic small-angle neutron scattering (SANS). To retrieve the particle parameters such as their size distribution and saturation magnetization from the data, we apply standard model fits of individual data sets as well as global fits of multiple curves, including a combination of the magnetometry and SANS measurements. We show that by combining a standard least-squares fit with a subsequent Bayesian approach for the data refinement, the probability distributions of the model parameters and their cross correlations can be readily extracted, which enables a direct visual feedback regarding the quality of the fit. This prevents an overfitting of data in case of highly correlated parameters and renders the Bayesian method as an ideal component for a standardized data analysis of magnetic nanoparticle samples. [less ▲]

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See detailAnisometric mesoscale nuclear and magnetic texture in sintered Nd-Fe-B magnets
Titov, Ivan UL; Honecker, Dirk UL; Mettus, Denis et al

in Physical Review Materials (2020), 4

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See detailDefect-induced Dzyaloshinskii–Moriya interaction in a nanocrystalline two-phase alloy
Quan, Yifan; Kohlbrecher, Joachim; Hautle, Patrick et al

in Journal of Physics: Condensed Matter (2020), 32

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See detailExperimental observation of third-order effect in magnetic small-angle neutron scattering
Metlov, Konstantin L.; Suzuki, Kiyonori; Honecker, Dirk UL et al

in Physical Review. B, Condensed Matter and Materials Physics (2020), 101

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See detailEffect of grain-boundary diffusion process on the geometry of the grain microstructure of Nd−Fe−B nanocrystalline magnets
Titov, Ivan UL; Barbieri, Massimiliano; Bender, Philipp Florian UL et al

in Physical Review Materials (2019), 3(084410),

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See detailMagnetic neutron scattering studies on Nd-Fe-B magnets (Keynote Lecture)
Michels, Andreas UL

Scientific Conference (2019, June 05)

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See detailMagnetic Guinier Law
Malyeyev, Artem UL; Michels, Andreas UL

Poster (2019, June)

We introduce the Guinier law for the case of magnetic SANS and provide an analysis of experimental data on a Nd-Fe-B-based nanocomposite and on a rare-earth-free MnBi permanent magnet. The robustness of ... [more ▼]

We introduce the Guinier law for the case of magnetic SANS and provide an analysis of experimental data on a Nd-Fe-B-based nanocomposite and on a rare-earth-free MnBi permanent magnet. The robustness of this novel approach is discussed and the quantities derived are analyzed in the framework of the existing research literature. [less ▲]

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See detailErratum: Third-order effect in magnetic small-angle neutron scattering by a spatially inhomogeneous medium [Phys. Rev. B 91, 054404 (2015)]
Metlov, K.L.; Michels, Andreas UL

in Physical Review. B, Condensed Matter and Materials Physics (2019), 99

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See detailEvidence for the formation of nanoprecipitates with magnetically disordered regions in bulk Ni50Mn45In5 Heusler alloys
Benacchio, G.; Titov, Ivan UL; Malyeyev, Artem UL et al

in Physical Review. B, Condensed Matter and Materials Physics (2019), 99

Detailed reference viewed: 189 (23 UL)