Oriented composition fluctuation domains of a two-dimensionally confined critical Ising fluid.

A quasi-binary two-dimensional Ising critical system with the main components D2O and butyric acid confined by surfactant layers has been studied. The surfactant forms large planar layers and is the basis of the charge density waves with wave fronts aligned with the layers. To orient the domains in an external magnetic field, thulium ions were added to the system (replacing sodium in the surfactant with thulium and adding more TmCl3).

Mixed micellar solutions of an oleo-furan sulfonate surfactant with anionic and non-ionic surfactants.

Small angle neutron scattering (SANS) has been employed to examine the self-assembly behaviour of sodium 5-tetradecyl furan-2-sulfonate (STFS), an emerging anionic surfactant, in bulk dilute solutions. STFS was also studied in binary and ternary mixtures with a common non-ionic (hexaethylene glycol monododecyl ether, CE) and anionic (sodium dodecyl sulfate, SDS) surfactant to explore the shape, size and composition of the mixed systems in dilute solution. SANS confirmed that STFS alone formed prolate ellipsoidal micelles and transitioned to small polydisperse spherical core-shell micelles of 55 ± 5 Å diameter for mixed systems.

Association of Pluronics at silica surfaces and accompanying evolutions of inter particle interactions in conjugate nano-suspensions.

Phase behaviour and wetting properties of negatively charged silica nanosuspensions are influenced strongly by polyethylene oxide-polypropylene oxide-polyethylene oxide based non-ionic surfactants, known popularly as Pluronics. These triblock copolymers are adsorbed at silica nanoparticle surfaces and impart inter-particle attraction driven re-entrant liquid-liquid phase separations in silica nanosuspensions. The association characteristics of Pluronics at silica surfaces that lead to such behaviours are, however, not clearly understood yet.

Detector development for spin-echo SANS techniques using ZnS:Ag/LiF and Li glass scintillators.

Neutron spin-echo techniques exploit Larmor precession of the neutron spin to encode either the scattering angle or energy. These are powerful means to extend the measurable momentum transfer (Q) and energy (E) range in neutron scattering measurements. Standard small-angle neutron scattering (SANS) instruments are sensitive in a range of  10-200 nm, whereas these techniques allow the study of structures in materials on length scales of tens of nm up to tens of m.

Probing Interparticle Interaction and Ordering in Silica-Pluronic-Based Solutions and Emulsions by Small-Angle Scattering Techniques.

Introduction of non-DLVO forces by nonionic surfactants brings about fascinating changes in the phase behavior of silica nanosuspensions. We show here that alterations in the interaction and wetting properties of negatively charged silica nanoparticles (Ludox® LS) in the presence of polyethylene oxide-polypropylene oxide-polyethylene oxide-based triblock copolymers called Pluronics lead to the formation of stable o/w Pickering emulsions and interparticle attraction-induced thermoresponsive liquid-liquid phase separations. The results make interesting comparisons with those reported for Ludox® TM nanosuspensions comprising larger silica nanoparticles.

Exploring Anisotropy Contributions in Mn Co FeO Ferrite Nanoparticles for Biomedical Applications.

Designing well-defined magnetic nanomaterials is crucial for various applications, and it demands a comprehensive understanding of their magnetic properties at the microscopic level. In this study, we investigate the contributions to the total anisotropy of Mn/Co mixed spinel nanoparticles. By employing neutron measurements sensitive to the spatially resolved surface anisotropy with sub-Å space resolution, we reveal an additional contribution to the anisotropy constant arising from shape anisotropy and interparticle interactions.

Modulating shape transition in surfactant stabilized reverse microemulsions.

The formation of reverse microemulsions (RMs) of spherical shape in the oil/water/surfactant ternary mixture at high molar ratio of water to surfactant () is well established. Using dynamic light scattering, small-angle X-ray and neutron scattering, we elucidate the formation of non-spherical reverse microemulsions stabilised by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) at = 10 and volume fractions of the dispersed phase, , ranging from 0.005 to 0.

Investigation of Nanostructure and Interactions in Water-in-Xylene Microemulsions Using Small-Angle X-ray and Neutron Scattering.

The ability to modulate the size, the nanostructure, and the macroscopic properties of water-in-oil microemulsions is useful for a variety of technological scenarios. To date, diverse structures of water-in-alkane microemulsions stabilized by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) have been extensively studied. Even though the decisive parameter which dictates the phase behavior of micremulsions is the nature of the continuous phase, relatively very few reports are available on the structure and interactions in the microemulsions of aromatic oil.

Multiscale magnetization in cobalt-doped ferrite nanocubes.

The magnetization of cobalt ferrite nanocubes of similar size, but with varying Co/Fe ratio, is extensively characterized on atomistic and nanoscopic length scales. Combination of X-ray diffraction, Mössbauer spectroscopy, magnetization measurements and polarized small-angle neutron scattering (SANS) reveals that a lower amount of cobalt leads to an enhanced magnetization. At the same time, magnetic SANS confirms no or negligible near-surface spin disorder in these highly crystalline, homogeneously magnetized nanoparticles, resulting in an exceptionally hard magnetic material with high coercivity.

Using small-angle scattering to guide functional magnetic nanoparticle design.

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.

Magnetic nanoprecipitates and interfacial spin disorder in zero-field-annealed NiMnIn Heusler alloys as seen by magnetic small-angle neutron scattering.

Shell ferromagnetism is a new functional property of certain off-stoichiometric Ni-Mn-In Heusler alloys, with a potential application in non-volatile magnetic memories and recording media. One key challenge in this field remains the determination of the structural and magnetic properties of the nanoprecipitates that are the result of an annealing-induced segregation process. Thanks to its unique mesoscopic length scale sensitivity, magnetic small-angle neutron scattering appears to be a powerful technique to disclose the microstructure of such annealing-induced nanoprecipitates.

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

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.

Robust approaches for model-free small-angle scattering data analysis.

The small-angle neutron scattering data of nanostructured magnetic samples contain information regarding their chemical and magnetic properties. Often, the first step to access characteristic magnetic and structural length scales is a model-free investigation. However, due to measurement uncertainties and a restricted range, a direct Fourier transform usually fails and results in ambiguous distributions.

Clustering in ferronematics-The effect of magnetic collective ordering.

Clustering of magnetic nanoparticles can dramatically change their collective magnetic properties, and it consequently may influence their performance in biomedical and technological applications. Owing to tailored surface modification of magnetic particles such composites represent stable systems. Here, we report ferronematic mixtures that contain anisotropic clusters of mesogen-hybridized cobalt ferrite nanoparticles dispersed in liquid crystal host studied by different experimental methods-magnetization measurements, small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and capacitance measurements.

Toward Understanding Complex Spin Textures in Nanoparticles by Magnetic Neutron Scattering.

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 multidomain 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.

Unraveling Nanostructured Spin Textures in Bulk Magnets.

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.

Sub-millisecond time-resolved small-angle neutron scattering measurements at NIST.

Instrumentation for time-resolved small-angle neutron scattering measurements with sub-millisecond time resolution, based on Gähler's TISANE (time-involved small-angle neutron experiments) concept, is in operation at NIST's Center for Neutron Research. This implementation of the technique includes novel electronics for synchronizing the neutron pulses from high-speed counter-rotating choppers with a periodic stimulus applied to a sample. Instrumentation details are described along with measurements demonstrating the utility of the technique for elucidating the reorientation dynamics of anisometric magnetic particles.

The benefits of a Bayesian analysis for the characterization of magnetic nanoparticles.

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).

Probing the stability and magnetic properties of magnetosome chains in freeze-dried magnetotactic bacteria.

biosynthesize high-quality magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Here we perform magnetometry and polarized small-angle neutron scattering (SANS) experiments on a powder of freeze-dried and immobilized . We confirm that the individual magnetosomes are single-domain nanoparticles and that an alignment of the particle moments along the magnetic field direction occurs exclusively by an internal, coherent rotation.

Magnetic Guinier law.

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- 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 ( soft-matter physics, biology, colloidal chemistry, materials science).

Magnetic ordering of the martensite phase in Ni-Co-Mn-Sn-based ferromagnetic shape memory alloys.

The magnetic state of low temperature martensite phase in Co-substituted Ni-Mn-Sn-based ferromagnetic shape memory alloys (FSMAs) has been investigated, in view of numerous conflicting reports of occurrences of spin glass (SG), superparamagnetism (SPM) or long range anti-ferromagnetic (AF) ordering. Combination of DC magnetization, AC susceptibility and small angle neutron scattering (SANS) studies provide clear evidence for AF order in the martensitic phase of NiCoMnSn alloy and rule out SPM and SG orders. Identical studies on another alloy of close composition, NiCoMnSn, point to the presence of SG order in the martensitic phase and the absence of SPM behavior, contrary to earlier reports.

Using the singular value decomposition to extract 2D correlation functions from scattering patterns.

The truncated singular value decomposition (TSVD) is applied to extract the underlying 2D correlation functions from small-angle scattering patterns. The approach is tested by transforming the simulated data of ellipsoidal particles and it is shown that also in the case of anisotropic patterns (i.e.

Phase-Transfer and Stabilization of Highly Monodisperse Ferrite Nanoparticles into Polar Solvents by Ligand Exchange Synthesis.

Cobalt ferrite nanoparticles with controlled particle size are transferred from nonpolar into polar solvent by exchange of the as-synthesized oleic acid ligand shell with polyacrylic acid (PAA). The nanoparticles are highly monodisperse (σ < 6%), and the ligand exchange synthesis has no measurable effect on particle size, shape, or size distribution. The stability of the aqueous particle dispersion without significant interparticle correlations as observed using small-angle X-ray scattering confirms the successful phase-transfer.

Morphological and crystallographic orientation of hematite spindles in an applied magnetic field.

The magnetic response of spindle-shaped hematite (α-Fe2O3) nanoparticles was investigated by simultaneous small-angle and wide-angle X-ray scattering (SAXS/WAXS) experiments. The field-dependent magnetic and nematic order parameters of the magnetic single-domain nanospindles in a static magnetic field are fully described by SAXS simulations of an oriented ellipsoid with the implemented Langevin function. The experimental scattering intensities of the spindle-like particles can be modeled simply by using the geometrical (length, radius, size distribution) and magnetic parameters (strength of magnetic field, magnetic moment) obtained from isotropic SAXS and macroscopic magnetization measurements, respectively.