Magnetic structure factor of correlated moments in small-angle neutron scattering

Honecker, Dirk; Barquı́n, L. Fernández; Bender, Philipp

doi:10.1103/physrevb.101.134401

Cited by 13 publications

(14 citation statements)

References 75 publications

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“…Using the compressibility relation one can show that repulsive interparticle interactions result in S(q = 0) < 1, whereas attractive interactions give S(q = 0) > 1 [39]. Translated to our magnetic problem, the observed change in the slope of dΣ M /dΩ can be related to the increased strength of the dipolar interaction between the particles [40]. With increasing volume fraction x p the large-scale spin arrangement of the ensemble is, on the average, becoming more homogeneous due to the constraint of ∇ • M = 0 imposed by the poleavoidance principle.…”

Section: Introductionmentioning

confidence: 81%

Resolving complex spin textures in nanoparticles by magnetic neutron scattering

Vivas,

Yanes,

Berkov

et al. 2020

Preprint

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In the quest to image the three-dimensional magnetization structure we show that the technique of magnetic small-angle neutron scattering (SANS) is highly sensitive to the details of the internal spin structure of nanoparticles. By combining SANS with numerical micromagnetic computations we study the transition from single-domain to multi-domain behavior in nanoparticles and its implications for the ensuing magnetic SANS cross section. Above the critical single-domain size we find that the cross section and the related correlation function cannot be described anymore with the uniform particle model, resulting e.g. in deviations from the well-known Guinier law. We identify a clear signature for the occurrence of a vortex-like spin structure at remanence. The micromagnetic approach to magnetic SANS bears great potential for future investigations, since it provides fundamental insights into the mesoscale magnetization profile of nanoparticles.

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Section: Introductionmentioning

confidence: 81%

Resolving complex spin textures in nanoparticles by magnetic neutron scattering

Vivas,

Yanes,

Berkov

et al. 2020

Preprint

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“…182 The interparticle magnetic correlations of interacting particles' moments are reflected in the magnetic structure factor, which will deviate from the scattering of the structural arrangement. 190 Interestingly, the interparticle coupling can enhance the magnetic heating of nanoflower samples as shown by Sakellari et al 191 which illustrates the potential of dipolar interactions to (i) drive particle arrangement and to (ii) modify the static and dynamic magnetization behavior of MNP assemblies. In general, interparticle interactions can be an additional control parameter to produce collective magnetism, and which can be monitored by neutron scattering.…”

Section: Magnetic Interparticle Correlationsmentioning

confidence: 95%

Using small-angle scattering to guide functional magnetic nanoparticle design

Honecker,

Bersweiler,

Erokhin

et al. 2022

Preprint

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Magnetic nanoparticles offer unique potential for various technological, biomedical, or environmental applications thanks to the size-, shape-and material-dependent tunability of their magnetic properties. To optimize particles for a specific application, it is crucial to interrelate their performance with their structural and magnetic properties. This review presents the advantages of small-angle X-ray and neutron scattering techniques for achieving a detailed multiscale characterization of magnetic nanoparticles and their ensembles in a mesoscopic size range from 1 to a few hundred nanometers with nanometer resolution. Both X-rays and neutrons allow the ensemble-averaged determination of structural properties, such as particle morphology or particle arrangement in multilayers and 3D assemblies. Additionally, the magnetic scattering contributions enable retrieving the internal magnetization profile of the nanoparticles as well as the inter-particle moment correlations caused by interactions within dense assemblies. Most measurements are used to determine the time-averaged ensemble properties, in addition advanced small-angle scattering techniques exist that allow accessing particle and spin dynamics on various timescales. In this review, we focus on conventional small-angle X-ray and neutron scattering (SAXS and SANS), X-ray and neutron reflectometry, gracing-incidence SAXS and SANS, X-ray resonant magnetic scattering, and neutron spin-echo spectroscopy techniques. For each technique, we provide a general overview, present the latest scientific results, and discuss its strengths as well as sample requirements. Finally, we give our perspectives on how future small-angle scattering experiments, especially in combination with micromagnetic simulations, could help to optimize the performance of magnetic nanoparticles for specific applications.

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“…The POLARIS method has been successfully employed for studying the superparamagnetic response of concentrated ferrofluids (Wiedenmann, 2005), proton domains in deuterated solutions (van den Brandt et al, 2006;Aswal et al, 2008;Noda et al, 2016), the multiferroic properties of HoMn 3 single crystals (Ueland et al, 2010), the role of nanoscale heterogeneities for the magnetostriction of Fe-Ga alloys (Mudivarthi et al, 2010;Laver et al, 2010), local weak ferromagnetism in BiFeO 3 (Ramazanoglu et al, 2011), nanometre-sized magnetic domains and coherent magnetization reversal in an exchange-bias system (Dufour et al, 2011), precipitates in Heusler-based alloys (Benacchio et al, 2019), the magnetic microstructure of nanoscaled bulk magnets (Honecker et al, 2010;Michels et al, 2012), the internal spin structure of nanoparticles (Krycka et al, 2010(Krycka et al, , 2014Grutter et al, 2017;Orue et al, 2018;Bender, Fork et al, 2018;Oberdick et al, 2018;Ijiri et al, 2019;Bender et al, 2019;Honecker et al, 2020), and Invar alloys (Stewart et al, 2019). Polarization analysis further makes it possible to reveal the direction of the magnetic anisotropy in single-crystalline spin systems, e.g.…”

Section: Introductionmentioning

confidence: 99%

Uniaxial polarization analysis of bulk ferromagnets: theory and first experimental results

Malyeyev¹,

Titov²,

Dewhurst³

et al. 2022

J Appl Cryst

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On the basis of Brown's static equations of micromagnetics, the uniaxial polarization of the scattered neutron beam of a bulk magnetic material is computed. The approach considers a Hamiltonian that takes into account the isotropic exchange interaction, the antisymmetric Dzyaloshinskii–Moriya interaction, magnetic anisotropy, the dipole–dipole interaction and the effect of an applied magnetic field. In the high-field limit, the solutions for the magnetization Fourier components are used to obtain closed-form results for the spin-polarized small-angle neutron scattering (SANS) cross sections and the ensuing polarization. The theoretical expressions are compared with experimental data on a soft magnetic nanocrystalline alloy. The micromagnetic SANS theory provides a general framework for polarized real-space neutron methods, and it may open up a new avenue for magnetic neutron data analysis on magnetic microstructures.

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Magnetic structure factor of correlated moments in small-angle neutron scattering

Cited by 13 publications

References 75 publications

Resolving complex spin textures in nanoparticles by magnetic neutron scattering

Resolving complex spin textures in nanoparticles by magnetic neutron scattering

Using small-angle scattering to guide functional magnetic nanoparticle design

Uniaxial polarization analysis of bulk ferromagnets: theory and first experimental results

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