•A Cu/Ti neutron supermirror was developed and optimized for high overall and low spin-dependent neutron reflectivities.•Control of the roughness growth allowed to achieve 90% reflectivity at the reflection edge (polarized and non-polarized).•The magnetization of this coating was reduced to a level between 30 and 50 times below that of NiMo/Ti supermirrors.•The spin-flip reflectivity of < 1.8 × 10−5 makes these neutron mirrors suitable for extremely low-spin-flip applications [56].

Correction for 'Structural insights into fusion mechanisms of small extracellular vesicles with model plasma membranes' by Fabio Perissinotto et al., Nanoscale, 2021, 13, 5224-5233, DOI: .

Extracellular vesicles (EVs) are a potent intercellular communication system. Such small vesicles transport biomolecules between cells and throughout the body, strongly influencing the fate of recipient cells. Due to their specific biological functions they have been proposed as biomarkers for various diseases and as optimal candidates for therapeutic applications. Despite their extreme biological relevance, their mechanisms of interaction with the membranes of recipient cells are still hotly debated. Here, we propose a multiscale investigation based on atomic force microscopy, small angle X-ray scattering, small angle neutron scattering and neutron reflectometry to reveal structure-function correlations of purified EVs in interaction with model membrane systems of variable complex compositions and to spot the role of different membrane phases on the vesicle internalization routes. Our analysis reveals strong interactions of EVs with the model membranes and preferentially with the borders of protruding phase domains. Moreover, we found that upon vesicle breaking on the model membrane surface, the biomolecules carried by/on EVs diffuse with different kinetics rates, in a process distinct from simple fusion. The biophysical platform proposed here has clear implications on the modulation of EV internalization routes by targeting specific domains at the plasma cell membrane and, as a consequence, on EV-based therapies.

Time-of-flight in situ neutron reflectometry (i-NR) on Si/[57Fe(x nm)/natFe(x nm)]4/Pt with x = 4 and 8 nm multilayers during consecutive heat treatments at 423, 448, 473 and 498 K reveal an unexpected rearrangement of free volumes and an interface smoothening in the isotopic Fe multilayer below 473 K, before the regime of regular Bragg intensity decay starts. The bilayer period dependence of the diffusivities at around 500 K, however, does not follow predictions of Harrison’s theory for the C-type regime representing grain boundary diffusion.

Structuring of aqueous suspensions of colloidal silica nanoparticles near an isolated planar silica-water interface is studied by specular neutron reflectivity. The reflectivity data clearly show that the suspensions develop a damped, oscillatory concentration profile in the normal direction to the interface. The wavelengths of these oscillations agree well with those independently determined by direct force measurements in the slit-geometry. The reflectivity data further demonstrate that the oscillatory structure persists over several layers and that the first particle layer is separated from the interface by a particle-free region.

Alpha-Synuclein (AS) is the protein playing the major role in Parkinson's disease (PD), a neurological disorder characterized by the degeneration of dopaminergic neurons and the accumulation of AS into amyloid plaques. The aggregation of AS into intermediate aggregates, called oligomers, and their pathological relation with biological membranes are considered key steps in the development and progression of the disease. Here we propose a multi-technique approach to study the effects of AS in its monomeric and oligomeric forms on artificial lipid membranes containing GM1 ganglioside. GM1 is a component of functional membrane micro-domains, called lipid rafts, and has been demonstrated to bind AS in neurons. With the aim to understand the relation between gangliosides and AS, here we exploit the complementarity of microscopy (Atomic Force Microscopy) and neutron scattering (Small Angle Neutron Scattering and Neutron Reflectometry) techniques to analyze the structural changes of two different membranes (Phosphatidylcholine and Phosphatidylcholine/GM1) upon binding with AS. We observe the monomer- and oligomer-interactions are both limited to the external membrane leaflet and that the presence of ganglioside leads to a stronger interaction of the membranes and AS in its monomeric and oligomeric forms with a stronger aggressiveness in the latter. These results support the hypothesis of the critical role of lipid rafts not only in the biofunctioning of the protein, but even in the development and the progression of the Parkinson's disease.

A neutron polarizer using four successive reflections on m = 2.5 supermirrors was built and installed at the GINA neutron reflectometer at the Budapest Neutron Centre. This simple setup exhibits 99.6% polarizing efficiency with 80% transmitted intensity of the selected polarization state. Due to the geometry, the higher harmonics in the incident beam are filtered out, while the optical axis of the beam remains intact for easy mounting and dismounting the device in an existing experimental setup.

The Fe-on-Ti and Ti-on-Fe interfaces were studied experimentally by Mössbauer spectroscopy (MS), transmission electron microscopy (TEM) and x-ray reflectometry (XRR) on Ti/Fe/Ti trilayers grown on Si(1 1 1) substrates by vacuum evaporation. The nanoscale structure and composition were explored in cross sections using TEM, the layer structure and the interface widths by specular x-ray reflectometry. MS was applied to identify the interface alloy phases and to determine the pure and alloyed Fe layer fractions. The experimental results were compared with molecular dynamics (MD) simulations of layer growth on Fe or Ti underlayers of different orientations. The concentration distributions provided by MD simulations show an asymmetry at the interfaces in the layer growth direction. The transition is atomically sharp at the Ti-on-Fe interface for the (0 0 1) and (1 1 0) crystallographic orientations of the Fe underlayer, while it spreads over a few atomic layers for Fe(1 1 1) underlayer and for all studied Ti underlayer orientations at the Fe-on-Ti interface. MS and XRR data on Ti/Fe/Ti trilayers confirm the asymmetry between the bottom and top Fe interface, but the inferred interface widths considerable exceed those deduced from the MD simulations.

Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

Neutron supermirrors (SMs), the major components of neutron optical devices, are depth-graded d -spacing multilayers of several hundreds to several thousands of bilayers. The interface roughness is a major factor in the reflectivity of multilayers. This influence is especially significant if the number of bilayers is large. In this work, the interface roughness and its correlations were studied in DC-sputtered Ni–Ti neutron supermirrors. Detector scans were carried out to observe off-specular neutron scattering in selected regions of the q space from (increasing bilayer thickness) normal- and (decreasing bilayer thickness) reverse-layer-sequence SMs. In-plane and out-of-plane roughness correlations are manifested in diffuse scatter plateaus and peaks which are interpreted in terms of resonant diffuse scattering. Distorted wave Born approximation simulations quantitatively reproduce the characteristic features of the measured detector scans with reasonable roughness correlation parameters, i.e. in-plane and out-of-plane correlation lengths, common interface roughness, and Hurst parameters. The different character of resonant diffuse scattering from normal- and reverse-layer-sequence SMs is qualitatively explained and systematized using quasi-kinematical considerations in terms of material and SM parameters. The total off-specular intensity of the supermirrors was found to be non-monotonic with respect to the specular reflectivity at the corresponding angle of incidence.

We use argon ion-bombardment during Fe layer deposition as a way to tailor the structural and magnetic properties of bilayer and multilayer systems containing Fe/FeV components. We present structural and magnetic results on Fe/FeV bilayer and Fe/Fe-oxide/Fe/FeV multilayer systems. Magnetization measurements were taken over a range of temperatures and show the expected ferromagnetic behavior for the Fe/FeV bilayer. The Fe/Fe-oxide/Fe/FeV multilayer demonstrates an enhanced coercivity and exchange bias at low temperatures, both due to the presence of the antiferromagnetic Fe-oxide layer. Polarized neutron reflectometry results (scattering length density depth profile and neutron spin asymmetry) were used to identify mixed interfacial layers resulting from ion-bombardment. These demonstrated a lower magnetic moment than bulk Fe layers and may undergo a reversal process that differs from non-mixed layers within the sample.

The instrumental concept of HERITAGE - a reflectometer with a horizontal sample geometry - fitted to the long pulse structure of a neutron source is presented. It is dedicated on creating a new class of reflectometers achieving the unprecedentedly high flux for classical specular reflectometry combined with off-specular reflectometry and grazing incidence small-angle scattering (GISANS), thus resulting in a complete 3-d exploration for lateral structures in thin films. This is achieved by specially designed neutron guides: in the horizontal direction (perpendicular to the scattering plane) it has an elliptic shape and focusses neutrons onto the sample. In the vertical direction it has a multichannel geometry providing a smooth divergence distribution at the sample while accepting the whole beam from a compact high-brilliance flat moderator. The modular collimation setup of HERITAGE provides an extremely high flexibility in respect to sample geometries and environments, including the possibility to study all types of solid and liquid interfaces statically or kinetically. Moreover, the use of multiple beam illumination allows for reflectivity and GISANS measurements at liquid interfaces both from above and below without any movement of the sample. This concept assures that reflectivity and GISANS measurements can be performed in its best way as the maximum possible and usable flux is delivered to the sample, outperforming all present-day or already planned for the ESS reflectometers and GISANS setups in flux and in measuring time for standard samples.

The chemical mixing at the Fe-on-Ti and Ti-on-Fe, i.e. the bottom and top interfaces of Fe in atomically deposited layers, were studied experimentally and by molecular dynamics simulations of the layer growth. The basic structure and chemical composition of the layers were explored in cross-sections using transmission electron microscopy. The calculations show a concentration distribution along the layer growth direction which is atomically sharp at the Ti-on-Fe interface for the (001) and (110) crystallographic orientations of the Fe layer, while it varies over a few atomic layers for Fe(111) substrate and at the Fe-on-Ti interface for all studied substrate orientations. Conversion electron Mössbauer spectroscopy and X-ray reflectometry measurements indicate an even larger asymmetry of the bottom and top Fe interface in Ti/Fe/Ti trilayers grown over Si(111) substrate by vacuum evaporation.

Changes in the relative 56Fe/57Fe isotope fractions due to Fe self-diffusion, that is active at the grain boundaries of different dimensions, can be monitored by neutron reflectometry with atomic length scale precision.

The effect of selfabsorption in Mössbauer sources is studied in detail. Spectra were measured using an old 57 C o/R h source of 74M B q activity with an original activity of ca. 3.7G B q and a 0.15G B q 57 C o/α − F e source magnetized by an in-plane magnetic field of 0.2 T. The 57 C o/α − F e source of a thickness of 25 μ was used both from the active and the inactive side giving cause to very different selfabsorption effects. The absorber was a single crystal of ferrous ammonium sulphate hexahydrate (FAS). Its absorption properties were taken over from a detailed study (Bull et al., Hyperfine Interact. 94(1–3), 1; Spiering et al. 2). FAS (space group P21/c) crystallizes as flat plates containing the (\(\overline {2}\)01) plane. The γ-direction was orthogonal to the crystal plate. The 57 C o atoms of the 57 C o/R h source were assumed to be homogeneously distributed over a 6μ thick Rh foil and to follow a one dimensional diffusion profile in the 25 μ Fe-foil. The diffusion length was fitted to 10 μ. The theory follows the Blume-Kistner equations for forward scattering (Blume and Kistner, Phys. Rev. 171, 417, 3) by integrating over the source sampled up to 128 layers.

Agglomeration or dewetting is technologically important in the microelectronics industry as it is one of the methods of producing arrays of nanosized metal clusters. This report investigates the grain morphology evolution due to low-temperature annealing (473 K) in Fe layers with Pt overlayers. X-ray diffuse scattering and grazing-incidence small-angle X-ray scattering (GISAXS) have been used to access different correlation lengths and correlate them with grain sizes from transmission electron microscopy. Overall, the GISAXS data indicate that the nanoparticles or nanoclusters in the samples appear as bimodal distributions. It is shown that, for an Fe layer with vertical grain sizes of 5 and 11 nm, irrespective of cluster size, there is no signature of agglomeration between the Fe and Pt layers even with very long annealing times (3000 min). The vertical grain sizes are mediated by the film thickness. Furthermore, an alternating variation with grain sizes of 4 and 7 nm is achieved by Al doping, but without a restriction on the Fe layer thickness. Even in this case, the agglomeration process is seen to remain unaffected by annealing for the same time durations, but only for the larger sized nanoclusters. The smaller ones are seen to grow in size, with increased correlation lengths for the maximum annealing time owing to higher surface energy.

An increase of the magnetic moment in superconductor/ferromagnet (S/F) bilayers V(40nm)/F [F=Fe(1,3nm), Co(3nm), Ni(3nm)] was observed using SQUID magnetometry upon cooling below the superconducting transition temperature Tc in magnetic fields of 10 Oe to 50 Oe applied parallel to the sample surface. A similar increase, often called the paramagnetic Meissner effect (PME), was observed before in various superconductors and superconductor/ferromagnet systems. To explain the PME effect in the presented S/F bilayers a model based on a row of vortices located at the S/F interface is proposed. According to the model the magnetic moment induced below Tc consists of the paramagnetic contribution of the vortex cores and the diamagnetic contribution of the vortex-free region of the S layer. Since the thickness of the S layer is found to be 3-4 times less than the magnetic field penetration depth, this latter diamagnetic contribution is negligible. The model correctly accounts for the sign, the approximate magnitude and the field dependence of the paramagnetic and the Meissner contributions of the induced magnetic moment upon passing the superconducting transition of a ferromagnet/superconductor bilayer.