Frustrated magnetism in face-centered-cubic (fcc) magnetic sublattices remains underexplored but holds considerable potential for exotic magnetic behavior. Here we report on the crystal structure and the magnetic and thermodynamic properties of the A-site-vacant hydroxide double perovskite MnSn(OH)6. Despite dominant antiferromagnetic interactions among Mn2+ moments, evidenced by a negative Curie-Weiss temperature, the lack of a sharp thermodynamic transition down to 350 mK implies the absence of long-range magnetic order. However, a broad hump in the specific heat at 1.6 K suggests short-range correlations. Neutron diffraction at low temperatures confirms the presence of three-dimensional antiferromagnetic correlations, manifested as diffuse magnetic scattering with a correlation length xi = 24.66 & Aring; and magnetic propagation vectors k = ( 1 1 2 ) and 1 2 2 (00.6250) at 20 mK.

The phase transformation in a mixture of hydrated NaBiO3 · nH2O and dehydrated NaBiO3 phase is studied during heating. The results indicate that generally the transformation occurs in two stages. At the first stage the hydrated NaBiO3 · nH2O phase converts to an anhydrous defective intermediate phase with the ilmenite-type structure similar to the initial dehydrated NaBiO3, but with increased lattice parameter c. According to nuclear magnetic resonance (NMR) the intermediate phase is associated with additional inequivalent Na. In terms of the Na–O interatomic distances the intermediate phase is closer to the hydrated phase, but in terms of the symmetry of Na coordination polyhedron it is already closer to the dehydrated one. The Na of the intermediate phase still remains in the sample after the complete dehydration and at the second stage there is a gradual recrystallization of the intermediate phase towards the initial NaBiO3 phase.

A study of samples of shielding materials which exploit plastic as the basis of neutron absorbing composite with 25%-37% weight boron-containing powder has been provided. Composite samples were prepared by fused filament fabrication (FFF). Acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG) plastics were used as the polymer matrix material, while boron nitride powder and amorphous boron powder were used as boron-containing fillers. According to measurements of the neutron transmission on the monochromatic beam of the IR-8 reactor (main monochromatic neutron beam line -2.4 & ANGS;), the use of boron as a filler in the plastic provides a decrease in the penetration depth of neutrons by 56%-78%: from 3.0 mm for a sample of plastic without filler to 0.65 mm for a sample with amorphous boron powder. Tensile and bending mechanical tests showed that the addition of boron-containing powder leads to development of brittleness of composite materials. The boron-containing samples experienced a 40%-55% of strength decrease and the failure of samples occurred without plastic deformation, while in ABS and PETG samples the plastic deformation takes up a significant portion of the test diagram.

Ferromagnetic inverse opal-like structures can be considered as ordered three-dimensional network of nanois-lands connected to each other by elongated links. These systems can serve as a playground for studying 3D nanomagnetism. At the same time the structure period (700 nm) and sample size are large enough to apply convenient integral and surface sensitive experimental techniques, but not small enough to use methods that are able to recover the full 3D magnetization distribution. In this regard, interpretation of experimental results should be carried out by means of simulations. We have studied the magnetic state of inverse opal -like structures by SQUID magnetometry and magnetic force microscopy in an external magnetic field. Results have been compared with micromagnetic simulations. We have found that the experimental data can be well interpreted in the frame of the spin-ice model suggested earlier. In particular the transversal magnetization predicted by this model has been found in fields applied along the [121] FCC axis. Its field dependence is in agreement with the results of the calculations.

The review is focused on the use of small-angle polarized-neutron diffraction to describe the orientation of local magnetization vector in spatially ordered magnetic metamaterials. The objects of study are direct and inverse opals; these materials are synthesized for diverse applications in magnetooptics, micro- and nanoelectronics, and photonics. The methodology of experiments and the theoretical base for processing experimental results are considered in detail. It is shown that the method of small-angle diffraction of polarized neutrons is unique in solving such problems; it is used at the limit of its possibilities when studying the magnetic structure under an applied field on the scale of ~400–800 nm. The questions of frustration of local magnetization vectors are discussed using the structural data on direct and inverse opals, obtained by ultra-small-angle diffraction of synchrotron radiation. The existing methods for synthesizing direct and inverse opals, which make it possible to obtain metamaterials with a three-dimensional ordered structure of nanoparticles, are also described.

Water embedded in the crystal structure of a solid hydrate may affect the functional properties of the material. A decisive step towards understanding the role of water in the restricted geometry is to unravel the arrangement and dynamics of water molecules. The paper attacks this issue using the example of NaBiO3–based material containing at ambient conditions a mixture of dehydrated NaBiO3 and hydrated NaBiO3⋅nH2O phase, with the latter being predominant. Inelastic neutron scattering and infrared spectroscopy are applied to explore the vibrations of water molecules for the hydrated phase in the initial state and during the release of water upon heating that eventually leads to a complete transformation to the dehydrated phase. The major peaks in the infrared spectra were assigned, particularly with the help of deuteration. Dynamic interaction of structurally equivalent water molecules was revealed from the analysis of water bending modes in infrared and Raman spectra. The change in the conformation of water molecules is discussed, as well as the deformation of matrix bonds during sample dehydration.

Mesocrystals are a class of nanostructured material, where a multiple-length-scale structure is a prerequisite of many interesting phenomena. Resolving the mesocrystal structure is quite challenging due to their structuration on different length scales. The combination of small- and wide-angle X-ray scattering (SAXS and WAXS) techniques offers the possibility of non-destructively probing mesocrystalline structures simultaneously, over multiple length scales to reveal their microscopic structure. This work describes how high dynamical range of modern detectors sheds light on the weak features of scattering, significantly increasing the information content. The detailed analysis of X-ray diffraction (XRD) from the magnetite mesocrystals with different particle sizes and shapes is described, in tandem with electron microscopy. The revealed features provide valuable input to the models of mesocrystal growth and the choice of structural motif; the impact on magnetic properties is discussed.

Arrays of ordered segmented nanowires are considered as a promising material for three-dimensional information storage systems. However, the presence of a large number of competing interactions significantly complicates the description of the magnetic behavior of such systems. In this work, the influence of the length of the nickel segment on the integral magnetic properties of the array is investigated. In particular, it is shown that the change in the direction of the easy axis of magnetization occurs when the segment length to diameter ratio is in the range from 10 to 20.

Mesocrystals are nanostructured materials consisting of individual nanocrystals having a preferred crystallographic orientation. On mesoscopic length scales, the properties of mesocrystals are strongly affected by structural heterogeneity. Here, we report the detailed structural characterization of a faceted mesocrystal grain self-assembled from 60 nm sized gold nanocubes. Using coherent X-ray diffraction imaging, we determined the structure of the mesocrystal with the resolution sufficient to resolve each gold nanoparticle. The reconstructed electron density of the gold mesocrystal reveals its intrinsic structural heterogeneity, including local deviations of lattice parameters, and the presence of internal defects. The strain distribution shows that the average superlattice obtained by angular X-ray cross-correlation analysis and the real, "multidomain" structure of a mesocrystal are very close to each other, with a deviation less than 10%. These results will provide an important impact to understanding the fundamental principles of structuring and self-assembly including ensuing properties of mesocrystals.

Correction for ‘Exploring the 3D structure and defects of a self-assembled gold mesocrystal by coherent X-ray diffraction imaging’ by Jerome Carnis et al., Nanoscale, 2021, DOI: 10.1039/D1NR01806J.

Mesocrystals are nanostructured materials consisting of individual nanocrystals having a preferred crystallographic orientation. On mesoscopic length scales, the properties of mesocrystals are strongly affected by structural heterogeneity. Here, we report the detailed structural characterization of a faceted mesocrystal grain self-assembled from 60 nm sized gold nanocubes. Using coherent X-ray diffraction imaging, we determined the structure of the mesocrystal with the resolution sufficient to resolve each gold nanoparticle. The reconstructed electron density of the gold mesocrystal reveals its intrinsic structural heterogeneity, including local deviations of lattice parameters, and the presence of internal defects. The strain distribution shows that the average superlattice obtained by angular X-ray cross-correlation analysis and the real, multidomain structure of a mesocrystal are very close to each other, with a deviation less than 10 percent. These results will provide an important impact to understanding of the fundamental principles of structuring and self-assembly including ensuing properties of mesocrystals.

Arrays of ordered segmented nanowires, which are ferromagnetic regions separated by non-magnetic inserts, are considered as a promising material for three-dimensional information storage systems. However, the presence of a large number of competing interactions significantly complicates the description of the magnetic behavior of such systems. In this paper, the effect of the segment length on the integral magnetic properties of Ni/Cu wires arrays is investigated. It is shown that the coercivity increases with an increase in the length of the magnetic segment for both the longitudinal and transverse directions of the long axis of the wires relative to the external magnetic field. A change in the direction of the easy magnetization axis was found with the ratio of the Ni segment length to the diameter in the range from 10 to 15.

The present study is focused on the investigation of the magnetic properties of hexagonally ordered iron nanowire arrays electrodeposited into anodic alumina templates. A series of 9 arrays of nanowires with a diameter of 52 nm, an interwire distance of 100 nm, and a length varying from 3.6 to 21.2 ?m is analyzed. Scanning electron microscopy, X-ray diffraction, SQUID magnetometry, and first-order reversal curves (FORC) analysis are used for the characterization of the nanowire arrays. The increase in coercivity with nanowire length is well described by a model of interacting wires, which are magnetized likely by a vortex domain wall mechanism. According to the width of distribution observed in the FORC diagrams, interaction fields decrease with increasing length, which supports the proposed model.

Arrays of ferromagnetic nanowires are promising for diverse areas of practical application ranging from data storage to drug delivery. This makes it essential to study their magnetic behavior and magnetization reversal mechanisms. Here, we report on the fabrication of ordered hexagonal arrays of iron nanowires by templated electrodeposition with the use of porous anodic alumina templates. This technique made it possible to obtain nanocomposites with aligned nanowires of pure α-Fe that are stable against oxidation. The arrangement of the nanowires is revealed by small-angle X-ray scattering and scanning electron microscopy. Magnetic properties of the nanowire arrays are studied using first-order reversal curves (FORC) analysis supported by micromagnetic calculations and analytical models. Differences in the magnetic behavior of the arrays of nanowires, whose length varies by two orders of magnitude, are discussed. Experimental evidence of the antiparallel magnetization of the long nanowires in the array in low fields is demonstrated.

Ordered ferromagnetic nanowire arrays are widely studied due to the diversity of possible applications. However, there is still no complete understanding of the relation between the array’s parameters and its magnetic behavior. The effect of vortex states on the magnetization reversal of large-diameter nanowires is of particular interest. Here, we compare analytical and micromagnetic models with experimental results for three arrays of iron nanowires with diameters of 33, 52 and 70 nm in order to find the balance between the number of approximations and resources used for the calculations. The influence of the vortex states and the effect of interwire interactions on the remagnetization curves are discussed. It has been found that 7 nanowires treated by a mean field model are able to reproduce well the reversal behavior of the whole array in the case of large diameter nanowires. Vortex states tend to decrease the influence of the structural inhomogeneities on reversal process and thus lead to the increased predictability of the system.

Geometrical frustration arised in spin ices leads to fascinating emergent physical properties. Nowadays there is a wide diversity of the artificial structures, mimicking spin ice at the nanoscale and demonstrating some new effects. Most of the nanoscaled spin ices are two dimensional. Ferromagnetic inverse opal-like structures (IOLS) are among inspiring examples of the three-dimensional system exhibiting spin ice behaviour. However, a detailed examination of its properties is not straightforward. An experimental technique which is able to unambiguously recover magnetization distribution in 3D mesoscaled structures is lacking. In this work, we used an approach based on complementary exploiting of small-angle neutron diffraction technique and micromagnetic simulations. An external magnetic field was applied along three main directions of the IOLS mesostructure. Comparison of the calculated and measured data allowed us to determine IOLS magnetic state. The results are in good agreement with the spin ice model. Moreover influence of the demagnetizing field and vortex states on the magnetizing process were revealed. Additionally, we speculate that this approach can be also applied to other 3D magnetic mesostructures.

Three-dimensional periodic tin structures were synthesized by filling pores in silicon opals with a sphere diameter of 194 nm (Sn190) and 310 nm (Sn300). The samples were examined by the ultra-small-angle x-ray diffraction method, energy dispersive x-ray microanalysis and scanning electron microscopy. It was found that the inverse opal structure consists of tin nanoparticles inscribed in octahedral and tetrahedral pores with diameters of 128 nm and 70 nm for the sample Sn300, and 80 nm and 42 nm for the sample Sn190. The study of the magnetic properties of the samples by SQUID magnetometry showed that magnetization reversal curves exhibit hysteretic behavior. The mechanisms of magnetic flux pinning in the samples depend on the size of the tin nanoparticles. Tin nanoparticles in Sn300 behave like a classical type-I superconductor. The hysteretic behavior of the magnetization reversal curves at low magnetic fields is due to the formation of a network of superconducting contours in Sn300. These superconducting contours effectively trap the magnetic flux. The octahedral tin nanoparticles in Sn190 remain type-I superconductors, but smaller tetrahedral particles behave like type-II superconductors. Type-I and II superconducting particles in Sn190 lead to the coexistence of different mechanisms of flux pinning These are flux trapping by superconducting contours at low magnetic fields and flux pinning by tetrahedral particles due to the surface barrier at high magnetic fields.