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The interlayer exchange coupling in Fe/MgO(001) superlattices is found to increase exponentially with decreasing temperature. Around 150 K, the field-induced response changes from discrete switching-governed by field-driven domain propagation-to a collective rotation of the magnetic layers. This transition is accompanied by a change in the magnetic ground state from 180 degrees (antiferromagnetic) to 90 degrees alignment between adjacent Fe layers. These effects are argued to arise from quantum-well states, defined by the total thickness of the samples.

Legumin and vicilin, the main storage proteins from peas, are increasingly employed as functional ingredients for food. The purpose of this work was to better understand the interactions between these proteins and selected lipids, due to their potential consequences on interfacial functionality of protein preparations. Legumin and vicilin isolates were obtained after isoelectric precipitation followed by further purification using size exclusion chromatography. The interactions were studied using DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine): DOPE (1,2-dioleoyl-sn-glycero-3 phosphoethanolamine) as mixed supported lipid bilayers, using quartz crystal microbalance with dissipation monitoring (QCM-D) and complementary neutron reflectometry (NR) experiments. This approach, fundamental in nature, allowed to observe interactions at the molecular level in the presence of phospholipids interfaces. QCM-D data suggested that legumin did not show any significant affinity for the investigated lipid interface. On the contrary there were changes in the bilayer with vicilin injection. NR experiments also supported these observations, and modeling of the experimental data also suggested a structural reorganization of the bilayer after vicilin injection and rinsing. This unique fundamental study of legumin and vicilin leads to the hypothesis that vicilin forms complexes with phospholipids bilayers which can be dispersed and removed by rinsing. All together, this study adds to the current debate on the importance of endogenous and non-endogenous phospholipids presence in affecting surface functionality of pea protein isolates.

A comprehensive understanding of chemical interactions at the surface of hair represents an important area of research within the cosmetic industry and is essential to obtain new products that exhibit both performance and sustainability. This paper aims at contributing to this research by applying a combination of surface techniques (neutron reflectometry, quartz-crystal microbalance and atomic force microscopy) to study adsorption of surface active ingredients onto hair-mimetic surfaces. The surface of hair is not homogeneous due to chemical and physical damage, and this work focuses on partly damaged hair models, in which both hydrophobic and charged moieties are present. Examples of such mixed-surface models are rare in the literature, despite the interest in the topic. The studied actives were an anionic surfactant (sodium dodecyl sulphate, SDS) and a natural polysaccharide (chitosan) of two different molecular weights, to represent soluble polymer-surfactant associations of cosmetic interest in hair-care rinsing applications. The effect of the concentration of SDS, the molecular weight of chitosan, and the order in which SDS and chitosan are introduced are studied, and compared to totally hydrophobic and totally hydrophilic surfaces. Results show that SDS can interact with the hydrophobic portions of the mixed surface, and its adsorption increases if associated with chitosan. Interestingly, differences have been found in the adsorption behaviour of chitosan depending on its chain size. Both types can deposit onto the surface, but when SDS is added, the lower molecular weight chitosan keeps its extended conformation in a ca. 70 Å thick layer, while the higher molecular weight chitosan collapses to form a layer of about 30 Å. This knowledge opens the door to developing hair-care formulations with improved performance and sustainability.

Depth resolved characterization of structural and magnetic profiles of antiferromagnetic/ferromagnetic (AFM/FM) system upon annealing was performed in this work. We studied systems comprising of AFM IrMn₃ and FM (Co, Fe, Co₇₀Fe₃₀) bilayer structures using magnetometry, polarized neutron reflectometry, soft X-ray magnetic circular dichroism and secondary neutral spectrometry. Structural depth profiles obtained from neutron reflectometry indicate non-homogeneity of the AFM layer even before annealing, which is associated with the migration of manganese to the surface of the sample. Annealing of samples with CoFe and Co layers leads to a slight increase (∼ 5 %) in the migration of manganese, which, however, does not lead to significant degradation of the exchange coupling at the AFM/FM interface. A significantly different picture was observed in the Fe/IrMn₃ systems where a strong migration of iron into the AFM layer was observed upon annealing of the sample, leading to erosion of the magnetic profile, the formation of a non-magnetic alloy and degradation of the pinning strength. This study can be useful in the optimization of AFM/FM systems in different spintronics devices, including HDD read heads, where thermal annealing is applied at different stages of the device manufacturing process.

Artificial superlattices exhibit exceptional electronic, magnetic, optical, and mechanical properties which make them unique candidates for applications in a broad range of technologies. A common key feature of superlattices is the need for atomically abrupt interfaces. However, superlattices comprised of materials with different properties, such as melting points and diffusivities, pose large challenges for achieving high crystal quality of both constituents with abrupt interfaces. By employing ion-assisted magnetron sputter epitaxy, we present an innovative solution to this problem with utilizing a unique combination of thermal radiation and kinetic energy that enable sufficient adatom mobility for epitaxial growth of both materials. The research was implemented for the case of CrB₂/TiB₂ heteroepitaxial superlattices, as neutron interference mirrors, wherein the constituents’ melting points differ by 1100 K. Ion-induced intermixing was avoided by commencing growth of each TiB₂ and CrB₂ layer by up to 3 unit cells (uc) without ion assistance, forming a buffer to protect the interface during the ion-assisted growth of the remainder of each layer. Heteroepitaxial superlattice growth with interface widths σ_CrB2 ∼1 uc and σ_TiB2 ∼2 uc was confirmed for different modulation periods. More than 3000 uc (∼1 µm) thick superlattices with abrupt interfaces were demonstrated for neutron mirror applications.

This study further investigates the effects of ¹¹B₄C co-sputtering on the structural and optical properties of Fe/Si stacked multilayers, with a focus on neutron supermirror applications. X-ray and neutron reflectivity techniques confirm with greater clarity that ¹¹B₄C incorporation improves interface sharpness, reduces roughness, and enhances reflectivity for various multilayer periods, compared to earlier studies on a single period thickness. Neutron reflectivity measurements show reduced spin-flip intensities, while wafer-curvature measurements indicate a 50 % reduction in internal stress, allowing for higher mechanical stability of the multilayers. These improvements are attributed to the amorphization of Fe layers, which also suppress the formation of structural and magnetic domains responsible for stress and spin-flip scattering. In contrast, the pure Fe/Si sample exhibits a persistent half-order Bragg peak, indicating residual antiferromagnetic coupling. The results demonstrate that ¹¹B₄C enhances neutron optics by reducing spin-flip effects, increasing reflectivity and polarization, and alleviating stress, enabling the use of polarizers at reduced external fields compared to pure Fe/Si multilayers. These findings establish ¹¹B₄C as a transformative material for advancing neutron supermirror technology, paving the way for more efficient, stable, and high-performance polarizers in next-generation neutron optics.

The deposition process of the IrMn₃/Co₇₀Fe₃₀ bilayer of antiferromagnet/ferromagnet (AF/FM) type was modified by introducing a nitrogen additive in argon plasma during the magnetron sputtering of the Co₇₀Fe₃₀ layer. This slight modification significantly enhanced the exchange bias energy density and reduced coercivity of an AF/FM bilayer for the AF IrMn layer thickness ranging from 20 to 50 Å. Calculations indicate that the boost in exchange bias energy density and the reduction in coercivity can be attributed to the increased anisotropy energy of the AF layer, resulting in more effective pinning of the FM layer by AF grains. The increase in anisotropy is caused by the diffusion of nitrogen from the FM into the AF layer, as established by x-ray diffraction, neutron reflectometry, and x-ray magnetic circular dichroism. Our research allows us to improve magnetic characteristics of exchange-coupled FM/AF structures through minor modifications in the sputtering process and/or save up to 20% of the costly IrMn₃ target by reducing the thickness of the AF layer.

Hypothesis: Sponge phase (L3) lipid nanoparticles (L3-NPs) have been shown to have large potential for the encapsulation of biomolecules, such as enzymes, with applications in food and pharmaceutical science. In this study, we introduce new formulations of L3-NPs including the phospholipids dioleoylphosphatidylcholine (DOPC) and dioleoyltrimethylammonium propane (DOTAP). The interaction of these new L3-NPs with myoglobin is of interest for the development of iron supplements which can be incorporated during food processing. Experiments: We characterized the sample structure by small-angle X-ray scattering (SAXS) measurements with and without the addition of myoglobin. We also tested the myoglobin-lipid interaction in an experimental setup that mimicked the interface between the bilayer and water channels within the bicontinuous sponge structure. This included spreading the L3-NPs onto a hydrophilic surface to form supported lipid bilayers and characterizing their interaction with myoglobin by means of quartz crystal microbalance with dissipation monitoring and polarized neutron reflectometry. Findings: SAXS data indicate that the new formulations containing DOPC and DOTAP formed a sponge phase in the bulk. The data from the surface techniques showed that deposited bilayers containing DOPC were largely unaffected by the addition of myoglobin, whereas those without DOPC were destabilized and partially removed.

Single-crystal CrB₂/TiB₂ diboride superlattices with well-defined layers are promising candidates for neutron optics. However, excess B in sputter-deposited TiB_y using a single TiB₂ target deteriorates the structural quality of CrB_x/TiB_y (0001) superlattices. We study the influence of co-sputtering of TiB₂ + Ti on the stoichiometry and crystalline quality of 300-nm-thick TiB_y single layers and CrB_x/TiB_y (0001) superlattices on Al₂O₃(0001) substrates grown by DC magnetron sputter epitaxy at growth-temperatures T_S ranging from 600 to 900 °C. By controlling the relative applied powers to the TiB₂ and Ti magnetrons, y could be reduced from 3.3 to 0.9. TiB_2.3 grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films. Close-to-stoichiometry CrB_1.7/TiB_2.3 superlattices with modulation periods Λ = 6 nm grown at 750 °C showed the highest single crystal quality and best layer definition. TiB_2.3 layers display rough top interfaces indicating kinetically limited growth while CrB_1.7 forms flat and abrupt top interfaces indicating epitaxial growth with high adatom mobility.

The concept of scattering length density tuning for improved polarization is investigated for Fe/11B4⁢CTi multilayers and compared to the commonly used Fe/Si system in polarizing multilayer neutron optics. X-ray and neutron reflectivity, magnetization, and neutron polarization were measured on such multilayers, highlighting differences from conventional Fe/Si multilayers. The multilayer systems were deposited with 25 Å period thickness, a layer thickness ratio of 0.35, and 20 periods using ion-assisted dc magnetron sputtering. Replacing Si with 11B4⁢CTi for these multilayers showed an increase in reflectivity due to a reduction in interface width. Tuning the ratio between 11B4⁢C and Ti in the nonmagnetic layers enabled a wide range of scattering length density contrasting and matching for spin-down neutrons, which in turn led to an improved polarization. These findings demonstrate the potential of Fe/11B4⁢CTi multilayers as a promising option for polarizing neutron optics and highlight the concept of scattering length density tuning in a large range using 11B4⁢CTi.