Vol 68, No 3 (2023)

The use of X-ray synchrotron radiation makes it possible to observe the polarization, spectral, and angular dependences for diffraction reflections. Their theoretical study calls for application of a tensor approach to describe the interaction of X-rays with atoms of matter. Various representations of the tensor atomic scattering amplitude, results of experimental observations of the anisotropy of resonant X-ray scattering, and the relationship of the electric and magnetic multipole moments on atoms with the properties of forbidden resonant reflections are considered.

Many molecules and crystals are chiral, i.e., can exist as right- and left-handed mirror isomers. It is shown that the absolute configuration of monoatomic chiral crystals, including selenium, tellurium, and b-manganese, can be determined using multi-wavelength diffraction of circularly polarized X-ray radiation.

A successive consideration of the formation of X-ray diffraction phase contrast of weakly absorbing noncrystalline objects with statistically distributed small-scale density inhomogeneities has been performed. It was assumed that the incident X-ray beam has an arbitrary degree of spatial coherence, and the changes in the statistical characteristics of this radiation during Bragg diffraction reflection from the monochromator and analyzer were taken into account. The phenomena of the increase and/or decrease in the phase contrast from regions with randomly distributed microcalcifications, in dependence of their rms sizes, relative refractive index decrement, and the lengths of spatial coherence of radiation and phase correlation as a result of diffraction-enhanced diffuse scattering are explained.

A geometric approach to describing an electromagnetic field in a medium with sources as a single field object is proposed. The description is based on the coordinate-free covariant approach adopted in the present-day geometrized field theories. Maxwell’s equations in a medium with sources are presented in terms of differential 2-forms for electric and magnetic fields in a four-dimensional space-time continuum. The general
equations include special cases of propagation, scattering, and emission of an electromagnetic field in media with different properties.

The influence of the hydrogen and vacancies introduced into an alloy matrix as a result of electrolytic hydrogenation on the structural state of Pd–11.3 at % W alloy after fourfold hydrogenation has been studied. It is established that nonmonotonic changes in the sample defect structure are determined by the transformation of single vacancies into vacancy complexes (micropores and small dislocation loops), their decay during relaxation, and migration of vacancies from the matrix to the boundaries of coherent-scattering regions (CSRs) and backwards. The vacancy transformation rate into defect complexes depends on their concentration. Long-term relaxation of the alloy leads to almost complete transfer of vacancies from the matrix to the CSR boundaries. An interpretation of the obtained experimental data within the theory of development of hierarchical defect structures is proposed.

The structure, magnetic, magnetothermal, and magnetoelastic properties of Gd₅Si_2-xGe_2-xIn_2x (x = 0–0.1) intermetallic compounds have been studied in the region of magnetostructural phase transitions. It is shown that introduction of indium creates the effect of negative pressure, leading to a change in the critical temperature of the magnetic phase transition in the monoclinic phase of the compounds studied and to partial separation of the magnetic and structural phase transitions in them.

The paper presents the results of the synthesis, structural studies, and investigation of the magnetic and magnetostriction properties of new multicomponent alloys based on heavy rare-earth metals (R_1-xY_x)_0.8Sm_0.2Fe₂, where R = Tb, Gd, Dy, and Er, х = 0, 0.2, 0.4, 0.6, 0.8, and 1. It was found that alloys of these systems (except for the system with Tb) are single-phase and have the cubic С15 Laves structure. The lattice parameters for all systems were shown to change linearly with increasing х. The main magnetic characteristics of the alloys were determined. The following practically important phenomena were found: the magnetic compensation of the sublattice magnetization, the spin reorientation, and the sign inversion of magnetostriction constants.

A comprehensive study of phase composition, structural state, parameters of fine atomic structure, mechanical and tribological properties of molybdenum-carbon and tungsten-carbon-based coatings deposited by reactive magnetron sputtering in an acetylene-argon gas mixture has been carried out. It has been shown that the resulting coatings have a nanocomposite diamond-like carbon (DLC) structure based on the metal and the metal carbide phases with close sizes of coherently diffracting domains (CDD), approximately 3–7 nm, and on hydrogenated amorphous carbon. The coating nanohardness values were 13–15 and 20–23 GPa for the Mo-DLC and W-DLC coatings, respectively. The tribological tests have demonstrated that the Mo- and W-DLC coatings can reduce friction and effectively protect the steel surfaces hardened by them both under dry friction and under boundary lubrication conditions.

Iron-containing oxides form one of the most important classes of functional materials, which find a wide variety of applications. A promising approach is their use in biomedical technologies as components of systems for visualization, drug delivery, magnetic hyperthermia, etc. Nanocrystalline particles of Y3Fe5O12 garnet, obtained by glycine-nitrate combustion with subsequent thermal treatment, have been experimentally investigated. The results of studying the evolution of the crystal and magnetic structure of Y3Fe5O12 nanoparticles in dependence of the synthesis temperature are presented. A complex analysis using X-ray diffractometry, scanning electron microscopy, and Mössbauer spectroscopy has been performed. A relationship of the size and structural quality of Y3Fe5O12 nanoparticles with the observed magnetic characteristics is  evealed.

An essay on the 100-year history of the formation and development of the Department of X-ray Diffraction Analysis, subsequently transformed into the Department of Solid State Physics of the Faculty of Physics of Lomonosov Moscow State University, is presented.