Том 119, № 13 (2018)

The results of electronic structure calculations of imperfect crystals—nonstoichiometric metal oxides (TiO_2 – x, TiO_1 – x, Al₂O_3 – x) are reviewed. All calculations were performed within the density functional theory in the coherent potential approximation with vacancies randomly distributed in metal and oxygen sublattices. It is found that the deviations from stoichiometric composition are accompanied by appearance of vacancy induced electronic states inside the band gap of initial insulating oxides.

Using one of the methods of quantum nonequilibrium statistical physics we have investigated the spin transport transverse to the normal metal/ferromagnetic insulator interface in hybrid nanostructures. An approximation of the effective parameters, when each of the interacting subsystems (electron spin, magnon, and phonon) is characterized by its own effective temperature have been considered. We have constructed the macroscopic equations describing the spin-wave current caused by both the resonantly exciting spin subsystem of conduction electrons and an inhomogeneous temperature field in the ferromagnetic insulator. In addition, we have derived the generalized Bloch equations describing the spin-wave current propagation in the insulator and considering the resonant-diffusion nature of the propagation of magnons and their relaxation processes. We have shown that the spin-wave current excitation under combined resonance conditions bears a resonant nature. The formation of the two: injected and thermally excited, different in energies magnon subsystems and the influence of its interaction with phonon drag effect under spin Seebeck effect conditions in the magnetic insulator part of the metal/ferromagnetic insulator/metal structure is studied.

Various auxiliary-particle approaches to treat electron correlations in many-electron models are analyzed. Applications to copper-oxide layered systems are discussed. The ground-state magnetic phase diagrams are considered within the Hubbard and \(s\)–\(d\) exchange (Kondo) models for square and simple cubic lattices vs. band filling and interaction parameter. A generalized Hartree–Fock approximation is employed to treat commensurate ferro-, antiferromagnetic, and incommensurate (spiral) magnetic phases, and also magnetic phase separation. The correlations are taken into account within the Hubbard model by using the slave-boson approach. The main advantage of this approach is correct estimating the contribution of doubly occupied states number and therefore the paramagnetic phase energy.

In this ultrashort review we consider several ruthenates having layered structure with the Ru ions forming a honeycomb lattice (SrRu₂O₆, AgRuO₃, Li₂RuO₃, Na₂RuO₃, and α-RuCl₃). Depending on the number of d-electrons and Ru–Ru bond length these materials demonstrate very different physical properties.

The determination of trends in the emergence of magnetooptical properties and the influence of magnetic phase transitions on the optical properties of magnetic materials is a topical issue in various areas of physics and engineering. The present review is focused on the high-magnitude magnetooptical effects of magnetotransmission and magnetoreflection of unpolarized radiation in a wide spectral region discovered in manganites with colossal magnetoresistance (CMR). The physical mechanisms of these magnetooptical effects in manganites and the potential for their practical application are discussed. The questions requiring further study are formulated.

The main stages of the study of spin-polarized electron injection into InSb semiconductor are considered. The characteristics of electromagnetic absorption and radiation due to spin-polarized electron injection into an InSb are given. The fundamental parameters of spin-polarized electrons, such as the relaxation time and spin diffusion length, are determined. The spin polarization of the conduction electrons in InSb is measured by direct detection.

The microwave properties of magnetic metallic nanostructures with a giant magnetoresistance (GMR) effect are studied. It is shown that the microwave changes are caused by two physical reasons, namely, the radiofrequency GMR effect and ferromagnetic resonance.

This work is a brief review of investigations of the magnetic properties of binary and pseudobinary intermetallics containing non-Kramers praseodymium ions. Special attention is paid to the PrNi₅, PrCu₅, PrNi₂, and PrAl₂ compounds and substitutional solid solutions based on them.

The dependence of the transverse relaxation time T₂ on the liquid, flow velocity in a porous medium (for the water and water suspension of magnetic nanoparticles (MNPs)) is studied. The T₂ value allows measuring the filtration velocity of a liquid on the order of 0.05 mm/s. MNPs in a small concentration decrease T₂ but at the same time the dependence of T₂ on the liquid’s velocity becomes more pronounced.

A brief review of experimental and theoretical studies of half-metallic ferromagnets (HMF) and spin gapless semiconductors (SGS) is presented. An important role of non-quasiparticle states owing to electron-magnon scattering in transport properties is discussed. The problem of low-temperature resistivity in HMF is treated in terms of one-magnon and two-magnon scattering processes.

The behavior of a material upon deformation and subsequent heating is related to the stagewise development of the structure and is determined by the structure-forming processes developing under specific deformation conditions. The effect of the following relaxation processes on the thermal stability of the deformation structure in metals and alloys is analyzed: deformation-induced dislocation–disclination strengthening, deformation twinning, baric phase transformation, dynamic recovery, and dynamic recrystallization.

Electron-microscopic studies of the processes of self-organization and evolution of the microstructure of metals and intermetallic compounds under different strong external actions are carried out. Special attention is given to the study of processes controlling the formation of explosively welded joints. Welded joints such as copper–tantalum, copper–titanium, aluminum–tantalum, titanium–orthorhombic titanium aluminide, steel–steel, etc., are studied. It is shown that the main mechanisms of self-organization in metals, which lead to the formation of stable joints after a very strong and short-term explosive action, are the fragmentation of two types, i.e., the formation of cusps and splashes, the formation of quasi-wave and wave interfaces, and local melting. The self-organization processes are also studied under the action of another kind of strong external action—severe plastic deformation by high-pressure torsion (HPT). It is shown that the effect of the self-locking of dislocations in the intermetallic compounds disappears upon torsion.

The main results reflecting the relationship between the composition, structure, and mechanical properties of submicrocrystalline aluminum alloys produced by dynamic channel-angular pressing in the quasi-static \(\dot {\varepsilon }\) = (3.3–6.6) × 10³ s^–1 and dynamic \(\dot {\varepsilon }\) = (1–3) × 10⁵ s^–1 regimes of loading are presented.

The better characteristics of the long-term strength of the EP-450-ODS (oxide dispersion strengthened) steel are determined compared to the well-known oxygen-free reactor steels. Using the Mössbauer analysis of the deformed powder mixture ⁵⁶Fe₃O₄ + ⁵⁷Fe, the possibility of the deformation-induced dissolution of iron oxides in the steel matrix, which makes it possible to obtain high quality ODS steels in the process of subsequent high-temperature annealing (sintering), is shown. The enhanced strength characteristics are obtained in recrystallized samples of ODS iron (YS_0.2 ~ 570 MPa, UTS ~ 632 MPa) in the absence of any other alloying elements except for oxygen of air.