Vol 126, No 4 (2025)

The review provides a theoretical description of the structures of currently known three-dimensional magnetic vortices in magnets with and without an inversion center. For the case of an isotropic and uniaxial ferromagnet, the following cnoidal and spiral “hedgehogs”, vortex structures of the “inclusion” type, a vortex filament with various two-dimensional topological charges, a vortex circular filament, and a vortex ring domain wall are considered. The structure of magnetic vortices in various nanostructures is described. It is shown how a spin-transfer nanooscillator can be used to create a dissipative magnetic droplet soliton. For magnets without an inversion center, the structure of vortex objects of the following type is considered: a stack of spin spirals, magnetic skyrmion braids and magnetic skyrmion beams. It is shown that the three-dimensional structure of the vortex is the cause of a nontrivial interaction of skyrmions. An experimentally discovered new type of particle-like state in chiral magnets, the chiral bobber, is described and a concept of magnetic solid-state memory is proposed on its basis.

Magnetic properties and superconducting characteristics of borides RERh_3.8Ru_0.2B₄ with LuRu₄B₄ type structure (RE = Y, Er, Ho, Dy), as well as compounds GdRh_3.8Ru_0.2B₄ have been investigated in order to establish formation patterns of superconducting and magnetic subsystems in presented compounds, and their mutual influence. The analysis showed that there is no direct relationship between the critical temperature (T_c) of RERh_3.8Ru_0.2B₄ compounds and their magnetic subsystem. However, a monotonic decrease in the RERh_3.8Ru_0.2B₄ borides critical temperature at successive replacement of RE with Y by Er, Ho, Dy has been established. In this case, the T_c depends linearly on S(S+1), where S is the spin quantum number of the RE⁺³ ion. Such critical temperature behavior can be associated with the exchange interaction of the conduction electrons spins with the magnetic moments of the RE⁺³ ions, which increases as the spin quantum number S of the ion increases. The absence of superconductivity in the GdRh_3.8Ru_0.2B₄ compound is also within the established pattern.

In the temperature range from 78 to 293 K, the temperature dependences of the electrical resistivity of Co_2−xMn_1+xAl (x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys as well as their optical properties in the range of (0.155–5) eV at room temperature. It is shown that the electrical resistivity of all alloys exceeds 250 µOhm×cm and grows with increasing manganese content to values exceeding 380 µOhm×cm, and the type of temperature dependence of electrical resistivity changes from “metallic” for Co₂MnAl to “semiconductor-like” for Mn₂CoAl with transition through the invar Co_1.75Mn_1.25Al. It is demonstrated that interband transitions play a crucial role in the formation of the optical properties of the studied alloys. It is found that at room temperature, the electrical conductivity and optical conductivity at 0.38 eV decrease with increasing manganese concentration at x = 0.5 and 0.75, respectively, and then change slightly with increasing x. It is suggested that this behavior is related to changes in the band spectrum of alloys, which are most strongly manifested in the Mn₂CoAl alloy.

The structural and magnetic nonequivalence of Ni²⁺ nickel ions in single crystals of lithium-gallium spinel has been studied by Electron Paramagnetic Resonance (EPR). The distribution of ions over sublattices and structurally unequal positions in the unit cell of the crystal lattice of a lithium-gallium spinel single crystal Li_0.5Ga_2.5O₄ is shown. The parameters and properties of materials are determined by this distribution of ions. Two types of centers are formed in a single crystal. Nickel Ni²⁺ ions are replaced in structurally unequal positions by gallium ions located in a tetrahedral environment and lithium ions located in an octahedral environment. The research can be used to analyze the properties of spinel ferrites and non-monocrystalline materials. The perspective of the work lies in the fact that currently powder materials are usually used in practice. But their properties vary depending on the production technology. Using the example of single crystals, it is shown how the introduced impurity ions are distributed. This distribution occurs uniformly over structurally unequal positions. It should be taken into account that in the case of rapid cooling during the growth of single crystals and films, the ion distribution may be different.

Mechanical tests of ring samples cut from the lower, central and upper sections of two fuel rods irradiated in the BN-600 reactor were carried out. Using the analysis of the stress-strain state, the values of the destructive stress and the degree of shear deformation accumulated before fracture were obtained, and a quantitative assessment of the damage to the fuel element shell material was performed. The microstructure was additionally investigated. It is shown that with the forged structure and sufficient plasticity reserve, the damage of the irradiated fuel element shell material is at a satisfactory level.

The process of precipitation of primary and secondary particles in the Al–0.27Zr–0.17Si–0.30Er alloy (in wt %) produced by casting with induction heating and stirring is studied. The homogeneity of the distribution of the specific electrical resistance (SER, ρ) and microhardness (HV) over the cross section of the ingot is studied, the optimal mode of alloy aging is determined. The values of the yield strength, tensile strength and relative elongation before failure of the coarse-grained alloy samples are determined. The dependences of HV and SER on the annealing temperature and time are plotted and the parameters of the Johnson–Mehl–Avrami–Kolmogorov equation describing the intensity of solid solution decomposition during annealing are determined. Thin (Ø 0.3 mm) wires of the Al–0.27Zr–0.17Si–0.30Er alloy are produced by cold drawing; The strength, SER and hardness of the wires in the initial state and after heat resistance tests in accordance with GOST R 62004–2014 were investigated.