Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

Klokkenburg, Mark; Erné, Ben H.; Wiedenmann, A.; Petukhov, Andrei V.; Philipse, Albert P.

doi:10.1103/physreve.75.051408

Cited by 84 publications

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“…Spontaneous chaining in zero field and coexistence of chains segments with hexagonal ordered domains has been observed when the magnetic field was increased [26]. Similar distorted hexagonal structures have been observed in Magnetite based ferrofluids by applying magnetic fields [43,45].…”

Section: Particle Correlations Induced By Magnetic Fieldssupporting

confidence: 57%

“…Two types of ferrofluids with nearly monodisperse nanoparticles have been investigated, namely concentrated Co-ferrofluid ("MFT3") [26,39,44] with a cobalt core of radius R c = 4.4 nm dispersed in a viscous synthetic hydrocarbon oil "Edwards L9" (monoalkylnaphthalene) and magnetite (Fe 3 O 4 ) particles of R c = 8.5 nm dispersed in decalin [43,45] both stabilised by a surfactant layer of a thickness D of about 2 nm. The maximal dipolar interaction energy E dd (max) for particles with saturation magnetisation M sat in head-to-tail conformation and closest contact = 2(R c + D) is given by…”

Section: Methodsmentioning

confidence: 99%

“…The Q range 0.2 nm −1 < Q < 1.2 nm −1 and resolution of the order of Q/Q < 0.3 allowed us to resolve properly the characteristic correlation peaks of the local hexagonal ordering that appear for the Co-FF samples at Q 1 = 0.4 nm −1 and Q 2 = 0.3 nm −1 [8,9] and for Fe 3 O 4 at Q 1 = 0.36 nm −1 and Q 2 = 0.34 nm −1 [45]. In order to analyse the full time dependence, intensities have been integrated in angle sectors over a width of 20 • at angles = 0 • , 30 • , 60 • , and 90 • .…”

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confidence: 99%

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Static and dynamic correlations in magnetic nanomaterials studied by small angle neutron scattering techniques

Wiedenmann

2010

Journées de la Neutronique

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Abstract. The performance of new techniques developed for Small Angle Neutron Scattering (SANS) is illustrated by investigations on magnetic colloids. Polarised neutrons ("SANSPOL") are introduced as a special type of contrast variation for magnetic systems. Examples of diluted magnetic systems are reviewed where low magnetic contrasts had to be analysed beside strong nuclear contributions or vice versa. In Ferrofluids magnetic core-shell composite particles and magnetic aggregates could be precisely evaluated beside non-magnetic micelles and free surfactants of similar sizes. In more concentrated Ferrofluids an external magnetic field induces a pseudo-crystalline ordering which coexists with chain like arrangements of particles. Ordering and relaxation processes of magnetic moments in nanoparticles have been monitored by time-resolved SANS. Slow relaxation of magnetic particle moments onto equilibrium has been studied after switch off a static field. In stroboscopic experiments, time-frame data acquisition has been synchronized with a periodic external magnetic field. When a continuous neutron flux was used in conventional SANS, the shortest accessible time range was limited to about 3 ms resulting from the wavelength spread. A breakthrough of time resolution into the micro-second range was achieved with the pulsed frame overlap TISANE technique, which allows us to exploit a dynamical range similar to that of X-ray photon-correlation spectroscopy. The analysis of time-dependent SANS data as a function of frequency, field and temperature allowed i) to determine the underlying statistics describing the particle moment orientation, ii) to extract the effect of field-induced inter-particle correlations, iii) to monitor the slowing down of the dynamics of moment rotation with decreasing temperature, iv) to study the effect of freezing of the solvent on the dynamics of the particle moments, and v) to work out the possible relaxation mechanisms (Néel and Brownian).

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Section: Particle Correlations Induced By Magnetic Fieldssupporting

confidence: 57%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Static and dynamic correlations in magnetic nanomaterials studied by small angle neutron scattering techniques

Wiedenmann

2010

Journées de la Neutronique

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“…Figure 9 (top) shows the ordering of magnetite nanoparticles on a surface under a ZFC and FC procedure; Figure 9 (bottom) shows the ordering of magnetite nanoparticles in bulk under ZFC and FC procedures [6].…”

Section: Structure Factorsmentioning

confidence: 99%

“…(Top) ordering of magnetite nanoparticles on a surface with a ZFC and FC procedure; (bottom) ordering of magnetite nanoparticles in bulk in ZFC and FC procedure (adapted from [6]). Under field, a well-defined hexagonal array forms.…”

Section: -P6mentioning

confidence: 99%

Neutron scattering on magnetic nano-objects

Ott

2014

Journées de la Neutronique

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MAGNETIC NANOSTRUCTURESDuring the last 20 years, the field of the magnetism of nanostructures has exploded. A huge number of new magnetic structures have appeared in which the nanometer scale plays a key role. It is possible to classify them into 3 categories: -In 3 dimensions, it is possible to identify a wide range of systems such as (i) nanoparticles in solutions forming ferrofluids, (ii) percolating phases as found in manganites for example, (iii) magnetic domains or domain walls in crystals, (iv) long range helical structures as found in MnSi or BiFeO 3 for example. These objects are ideally studied using Small Angle Neutron Scattering (SANS) which enable measuring either the shape of individual objects (form factor) or their long range organization (structure factor). -In 2 dimensions, nanometer size objects organized on surfaces. These objects can be either produced by lithography techniques or by self-organization processes. The scattering technique which can be used is either SANS or Grazing Incidence SANS. -In 1 dimension, thin films produced by physical means such as vacuum deposition (sputtering, evaporation, laser ablation ...): metal thin films, oxide thin films, magnetic semi-conductors. These systems are most ideally studied by polarized neutron reflectivity. This is the object of a dedicated chapter.In this chapter we describe in a first part the basics of SANS scattering applied to the study of magnetic nano-objects. This is illustrated by a few examples of recent studies on magnetic nanoparticles and phase separated materials. In a second part we discuss the GISANS technique and illustrate its use in the case of the study of self-organized magnetic domains. SMALL ANGLE NEUTRON SCATTERINGOne of the most mainstream technique used in neutron scattering is Small Angle Scattering. It is mostly used for polymer science and soft matter studies because of the contrast variation possibilities. It can also be used to perform studies on magnetic materials and take benefit of the strong magnetic scattering. This allows to probe nanometric properties of magnetic crystals.This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Unravelling Magnetic Nanochain Formation in Dispersion for In Vivo Applications

et al. 2021

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Self‐assembly of iron oxide nanoparticles (IONPs) into 1D chains is appealing, because of their biocompatibility and higher mobility compared to 2D/3D assemblies while traversing the circulatory passages and blood vessels for in vivo biomedical applications. In this work, parameters such as size, concentration, composition, and magnetic field, responsible for chain formation of IONPs in a dispersion as opposed to spatially confining substrates, are examined. In particular, the monodisperse 27 nm IONPs synthesized by an extended LaMer mechanism are shown to form chains at 4 mT, which are lengthened with applied field reaching 270 nm at 2.2 T. The chain lengths are completely reversible in field. Using a combination of scattering methods and reverse Monte Carlo simulations the formation of chains is directly visualized. The visualization of real‐space IONPs assemblies formed in dispersions presents a novel tool for biomedical researchers. This allows for rapid exploration of the behavior of IONPs in solution in a broad parameter space and unambiguous extraction of the parameters of the equilibrium structures. Additionally, it can be extended to study novel assemblies formed by more complex geometries of IONPs.

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Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

Cited by 84 publications

References 29 publications

Static and dynamic correlations in magnetic nanomaterials studied by small angle neutron scattering techniques

Static and dynamic correlations in magnetic nanomaterials studied by small angle neutron scattering techniques

Neutron scattering on magnetic nano-objects

Unravelling Magnetic Nanochain Formation in Dispersion for In Vivo Applications

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