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When the neutron scattering technique, Spin Echo Resolved Grazing Incidence Scattering (SERGIS) concept, was originally put forward by Rekveldt [Physica B 1135, 234–236 (1997)] and Felcher et al. [Proc. SPIE 4785, 164 (2002)], they recognized that the specular scattering and the off-specular scattering could be spatially separated due to the tight neutron beam collimation in the scattering plane, a necessity for any reflectometry experiment. In this Letter, we show that it is possible to make large area measurements of periodic grating structures using SERGIS in a number of interesting scenarios. The SERGIS data can be analyzed using a dynamical theory, which makes it possible to effectively retrieve the lateral profile of a commercial periodic diffraction grating. Interestingly, this is still the case even when that grating is buried beneath a highly deuterated poly(methyl methacrylate-D8) polymer layer. We also clearly demonstrate that the maximum sensitivity to lateral structures is achieved when the specular reflection from the grating is excluded from the data analysis, demonstrating a feature of SERGIS that was proposed over two decades ago. [ABSTRACT FROM AUTHOR]

Abstract: The development and testing of the Off Specular MicrOstrip Neutron Detector (OSMOND) is described. Based on a microstrip gas chamber the aim of the project was to produce a high counting rate detector capable of replacing the existing rate limited scintillator detectors currently in use on the CRISP reflectometer for off specular reflectometry experiments. The detector system is described together with results of neutron beam tests carried out at the ISIS spallation neutron source. [Copyright &y& Elsevier]

The reflection of neutrons from a helium surface is observed for the first time. The 4He surface is smoother in the superfluid state at 1.54 K than in the case of the normal liquid at 2.3 K. In the superfluid state we also observe a surface layer ∼200 Å thick which has a subtly different neutron scattering cross section, which may be explained by an enhanced Bose-Einstein condensate fraction close to the helium surface. The application of neutron reflectometry described in this paper creates new and exciting opportunities for the surface and interfacial study of quantum fluids. [ABSTRACT FROM AUTHOR]

[Display omitted] Cationic surfactants have a wide range of applications, often associated with their affinity for a range of solid surfaces and their anti-microbial properties. Manipulating their adsorption and self-assembly properties is key to most applications, and this is commonly achieved through surfactant mixtures or manipulating their headgroup or alkyl chain structure. Achieving this through adjustments to their headgroup structure is less common in cationic surfactants than in anionic surfactants. Ethoxylation provides the ability to adjust the hydrophilic / hydrophobic balance, as extensively demonstrated in a range of anionic surfactants. This same approach has been applied here to a range of ethoxylated cationic surfactants in the form of the quaternary ammonium salts, and their tertiary nonionic equivalents before quaternisation. Their adsorption and self-assembly properties are investigated using predominantly the neutron scattering techniques of neutron reflectivity, NR, and small angle neutron scattering, SANS. The trends in the adsorption at the air–water interface and the self-assembly in aqueous solution demonstrate how the hydrophilic / hydrophobic balance can be adjusted by varying the degree of ethoxylation and the alkyl chain length, and illustrate the degree of interdependence of the different structural changes. The variation in the adsorption and the micelle structure shows how the surfactant conformation / packing changes as the degree of ethoxylation and alkyl chain length increases and how the introduction of charge induces further changes. [ABSTRACT FROM AUTHOR]

Presents information on a comparison between the experimental results and the polarization behavior predicted for quasi-isotropic single-frequency YAG laser. Information on the calculations which are done; Findings of the calculations.

Presents information on model for the polarization states of a single-frequency Nd...YAG laser. Details on the laser; Assumption that the laser cavity is linear and quasi-isotropic.

The long-range magnetic structure in Co/Pt multilayers magnetically patterned by ion irradiation is observed by off-specular polarized neutron reflectivity. While both specular and off-specular measurements indicate the formation of an artificial domain structure when the sample is in its remanent state, resonant peaks seen in the diffuse scatter reveal long-range magnetic ordering with periodicity in agreement with the design value. These peaks are completely suppressed when the sample is saturated in plane, confirming their origin in the magnetic patterning of the multilayer. [ABSTRACT FROM AUTHOR]

Neutron spin echo resolved grazing incidence scattering (SERGIS) was used to probe crystallites of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) produced by extensive thermal annealing of a poly(3-hexylthiophene-2,5-diyl)(P3HT):PCBM organic photovoltaic layer. After annealing a thin film of P3HT:PCBM, PCBM crystallites appear on the sample surface, and a strong SERGIS signal is observed superimposed on the specular reflection. Features in the data can be readily correlated with length scales of the crystallites determined using atomic force microscopy and indicate that in such cases the SERGIS signal may be interpreted as a form of small angle neutron scattering. [ABSTRACT FROM AUTHOR]

Neutron reflection was used to measure the build-up of layers at the air surface as the smectic phase was approached from higher temperatures in a nematic liquid crystal. The liquid crystal was 4-octyl-4'-cyanobiphenyl with a deuterated core and hydrogenous tails. The development of surface smectic layers in the nematic phase was followed by measuring specular reflectivity and monitoring the pseudo-Bragg peak from the layers. The pseudo-Bragg peak therefore corresponded to the formation of long-range smectic layers at the surface as the transition temperature is approached. The results were consistent with the continuous growth of smectic layers at the surface and the amplitude of the smectic density wave decayed with increasing distance from the surface. The depth over which the smectic layering occurred at the interface was found to be ∼450 Å at a quarter of a degree above the nematic to smectic A bulk transition. The smectic order parameter at the surface was ∼0.1 which is much less that found for typical homeotropic alignment agents. [ABSTRACT FROM AUTHOR]

We demonstrate, using spin polarized neutron reflectivity measurements, that one can form a large stack of magnetically decoupled spin-membranes of Gadolinium ions and reduce the effect of the substrate substantially to study short-range two-dimensional (2D) ferromagnetic ordering. No spontaneous magnetization was observed in these membranes as the magnetic field was applied along an in-plane direction. The results are consistent with theoretical predictions of 2D in-plane spin systems having strong interplay of exchange, magneto-crystalline anisotropy and dipolar interactions. These metal–organic multilayer films will enable us to verify various theoretical predictions regarding spin-fluctuations in 2D systems using conventional magnetic measurements and neutron scattering studies. [ABSTRACT FROM AUTHOR]

Interphase precipitation occurring during solid-state phase transformations in micro-alloyed steels is generally studied through transmission electron microscopy, atom probe tomography, and ex situ measurements of Small-Angle Neutron Scattering (SANS). The advantage of SANS over the other two characterization techniques is that SANS allows for the quantitative determination of size distribution, volume fraction, and number density of a statistically significant number of precipitates within the resulting matrix at room temperature. However, the performance of ex situ SANS measurements alone does not provide information regarding the probable correlation between interphase precipitation and phase transformations. This limitation makes it necessary to perform in situ and simultaneous studies on precipitation and phase transformations in order to gain an in-depth understanding of the nucleation and growth of precipitates in relation to the evolution of austenite decomposition at high temperatures. A furnace is, thus, designed and developed for such in situ studies in which SANS measurements can be simultaneously performed with neutron diffraction measurements during the application of high-temperature thermal treatments. The furnace is capable of carrying out thermal treatments involving fast heating and cooling as well as high operation temperatures (up to 1200 °C) for a long period of time with accurate temperature control in a protective atmosphere and in a magnetic field of up to 1.5 T. The characteristics of this furnace give the possibility of developing new research studies for better insight of the relationship between phase transformations and precipitation kinetics in steels and also in other types of materials containing nano-scale microstructural features. [ABSTRACT FROM AUTHOR]

A time-of-flight modulation of intensity by zero effort spectrometer mode has been developed for the Larmor instrument at the ISIS pulsed neutron source. The instrument utilizes resonant spin flippers that employ electromagnets with pole shoes, allowing the flippers to operate at frequencies up to 3 MHz. Tests were conducted at modulation frequencies of 103 kHz, 413 kHz, 826 kHz, and 1.03 MHz, resulting in a Fourier time range of ∼0.1 ns to 30 ns using a wavelength band of 4 Å–11 Å. [ABSTRACT FROM AUTHOR]

Neutron spin-echo resolved grazing incidence scattering (SERGIS) measurements performed on a silicon diffraction grating with a rectangular profile were shown in our previous publications to be well explained by dynamical theory calculations. The theory is based on a Bloch wave expansion of the neutron wavefunction in the periodic layer of the grating, which includes all multiple scattering within that layer. Calculations show that the spin-echo polarization should be very sensitive to the scattering geometry (i.e., incident angle, sample alignment and beam divergence) and the sample specifications (i.e., grating period, groove depth). To test these predictions, SERGIS measurements have been performed on a set of gratings with different specifications in various scattering geometries. In all cases, simulations based on the dynamical theory, with all the parameters set to their known values, are in good agreement with the collected data. [ABSTRACT FROM AUTHOR]

We report results on the effect of the AlOx barrier layer on the magnetic moment of Fe using polarized neutron reflection. The sample has nominal composition 25 nm Au/5 nm Fe/ 1.3 nm AlOx /GaAs(001). The metal deposition was done in ultrahigh vacuum and the Al oxidation was performed in two steps. From the fit to the neutron data we obtain for the magnetic moment of Fe the value (2.164±0.026)μB, very close to the bulk value (2.185μB at room temperature). We conclude that there is no dead layer at the AlOx interface. [ABSTRACT FROM AUTHOR]

Electron scattering mechanisms within metallic multilayers are affected by both structural and magnetic disorders. Off-specular x-ray scattering has long been used to probe the structural interfaces, and it is only recently that it has been applied to the study of magnetic disorder. We compare the resonant magnetic x-ray scattering with off-specular neutron studies from magnetron-sputtered Co/Cu and Co/Ru multilayers grown at the second antiferromagnetic coupling peak. Both techniques yield similar results for the Cu system, and a simple domain model can be applied to extract the magnetic interface morphological parameters. For the Cu system, the in-plane correlation length is field dependent and is 880 ± 20 Å after saturation along the hard axis, but increases to 7000 ± 100 Å after saturation along the orthogonal easy axis. Both systems show strong out-of-plane correlations in both the structural and magnetic disorders. In all cases, the out-of-plane correlation length for the structural interfaces is 200-250 Å, but the ratio of the magnetic to structural correlations length is dependent on the magnitude of the exchange coupling and ranges from 0.4 to 1.4. [ABSTRACT FROM AUTHOR]

We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities. [ABSTRACT FROM AUTHOR]

In this article we present a detailed investigation of the structural and magnetic properties of exchange biased NiFe (ferromagnet)/FeMn (antiferromagnet) thin films. The influence of the shape anisotropy on exchange bias and the magnetization reversal mechanism in a sample with patterned lines is compared with a continuous two-dimensional reference sample. Polarized neutron reflectivity (PNR) is employed to study the magnetization reversal by analyzing the spin-flip and non-spin-flip reflectivities. PNR measurements show that the magnetization reversal in the reference two-dimensional film and patterned lines is by domain wall motion rather than coherent rotation of magnetization. [ABSTRACT FROM AUTHOR]

We have studied how the magnetic properties of oxygen-deficient EuO sputtered thin films vary as a function of thickness. The magnetic moment, measured by polarized neutron reflectometry, and the Curie temperature are found to decrease with reducing thickness. Our results indicate that these surface-induced effects are caused by the reduced number of nearest neighbors, band bending, and the partial depopulation of the 4f states of Eu. [ABSTRACT FROM AUTHOR]

Abstract: Neutron radiation offers significant advantages for the study of biological molecular structure and dynamics. A broad and significant effort towards instrumental and methodological development to facilitate biology experiments at neutron sources worldwide is reviewed. [Copyright &y& Elsevier]

Carefully controlled interfaces between two materials can give rise to novel physical phenomena and functionalities not exhibited by either of the constituent materials alone. Modern synthesis methods have yielded high-quality heterostructures of oxide materials with competing order parameters. Although magnetic correlations at the interface are expected to be important in determining the macroscopic properties of such systems, a quantitative determination of the interfacial magnetization profile has thus far not been reported. Here we examine superlattices composed of the half-metallic ferromagnet La2/3Ca1/3MnO3 and the high-temperature superconductor YBa2Cu3O7 by absorption spectroscopy with circularly polarized X-rays and by off-specular neutron reflectometry. The resulting data yield microscopic insight into the interplay of spin and orbital degrees of freedom at the interface. The experiments also reveal an extensive rearrangement of the magnetic domain structure at the superconducting transition temperature. This methodology establishes an incisive probe of the interplay between competing electronic order parameters in oxide heterostructures. [ABSTRACT FROM AUTHOR]

The effect of MgO tunnel barriers on the magnetic moment of ultrathin magnetic Fe and Co layers is studied by polarized neutron reflectivity. The MgO barriers were grown by molecular beam epitaxy using either direct evaporation from a source crystal or evaporation of Mg in an oxygen background atmosphere. A decrease of the magnetic moment is observed for both Fe and Co, and atomic intermixing of 1.5–3.5 ML at interfaces between the Fe, Co, and MgO is determined. Evaporation from a MgO source crystal yields a tunnel layer which displays better stoichiometry and epitaxy than is obtained using the other growth method. [ABSTRACT FROM AUTHOR]

Abstract: The atomic structure and magnetic properties of Fe/Mn superlattices are presented. X-ray diffraction and modelling have been performed, and the Fe/Mn superlattices are found to have atomically flat interfaces, with the Mn stabilised in the body-centred tetragonal structure. We have studied the ordering of the ferromagnetic Fe blocks. Either an antiferromagnetic, ferromagnetic or non-colinear magnetic structure is found, depending on Mn thickness. The antiferromagnetic ordering of the Mn has been studied by neutron diffraction in a superlattice of composition . A totally unexpected magnetic structure is obtained, with Mn moments perpendicular to those of Fe. On the basis of these results, the simple antiferromagnetic ordering assumed for other exchange-biased systems should, therefore, be reconsidered. [Copyright &y& Elsevier]

We present magnetometry data for a range of Fe thicknesses grown on GaAs and InAs substrates in order to determine the factors governing the evolution of the magnetic moment of epitaxial Fe grown on a zinc-blende semiconductor. Fe films grown at room temperature by molecular beam epitaxy were characterized structurally and magnetically. The estimated roughness amplitudes were 0.3 ± 0.2 nm for the Fe/GaAs interface and 0.6 ± 0.2 nm for Fe/InAs. We observe a greater reduction of the Fe magnetic moment for films grown on InAs as compared to GaAs, as the Fe films reach a bulk-like moment (within 10% deviation) at a thickness of ∼5.2 nm and ∼2.2 mn, respectively. We conclude that the growth conditions, in particular interface and interdiffusion effects, are the dominant mechanisms influencing the value of the magnetic moment for ultrathin Fe films on GaAs and InAs. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are nanosized topologically protected spin textures with particlelike properties. They can form lattices perpendicular to the magnetic field, and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small-angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu2 OSeO3 and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history of the sample, which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Furthermore, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field. [ABSTRACT FROM AUTHOR]

The reference chiral helimagnet MnSi is the first system where Skyrmion lattice correlations have been reported. At a zero magnetic field the transition at TC to the helimagnetic state is of first order. Above TC, in a region dominated by precursor phenomena, neutron scattering shows the buildup of strong chiral fluctuating correlations over the surface of a sphere with radius 2π/ℓ, where ℓ is the pitch of the helix. It has been suggested that these fluctuating correlations drive the helical transition to first order following a scenario proposed by Brazovskii for liquid crystals. We present a comprehensive neutron scattering study under magnetic fields, which provides evidence that this is not the case. The sharp first order transition persists for magnetic fields up to 0.4 T whereas the fluctuating correlations weaken and start to concentrate along the field direction already above 0.2 T. Our results thus disconnect the first order nature of the transition from the precursor fluctuating correlations. They also show no indication for a tricritical point, where the first order transition crosses over to second order with increasing magnetic field. In this light, the nature of the first order helical transition and the precursor phenomena above TC, both of general relevance to chiral magnetism, remain an open question. [ABSTRACT FROM AUTHOR]

We present a comprehensive small angle neutron scattering and neutron spin echo spectroscopy study of the structural and dynamical aspects of the helimagnetic transition in Fe1-xCoxSi with x=0.30. In contrast to the sharp transition observed in the archetype chiral magnet MnSi, the transition in Fe1-xCoxSi is gradual, and long-range helimagnetic ordering coexists with short-range correlations over a wide temperature range. The dynamics are more complex than in MnSi and involve long relaxation times with a stretched exponential relaxation which persists even under magnetic field. These results in conjunction with an analysis of the hierarchy of the relevant length scales show that the helimagnetic transition in Fe1-xCoxSi differs substantially from the transition in MnSi and question the validity of a universal approach to the helimagnetic transition in chiral magnets. [ABSTRACT FROM AUTHOR]