Vol 88, No 7 (2024)

The Ornstein-Zernike integral equations for thermodynamically equilibrium liquids are considered, considering irreducible diagrams. An algorithm for calculating the first irreducible diagram is formulated for a spatially homogeneous fluid. For liquids bordering a solid surface, an equation is obtained that implicitly considers all irreducible diagrams.

The results of an analysis of the structural and luminescent properties of Ce, Gd codoped aluminoborosilicate glasses are presented. It is shown that the luminescence intensity of oxygen-deficient centers increases with the simultaneous embedding of Ce, Gd ions and changes non-linearly with their concentration. This phenomenon correlates with the process of non-linear change of the glass polymerization and the number of highly symmetrical positions of Gd³⁺-ions. The codoping effect is explained by the coexistence of different structural positions of codopant ions in the aluminoborosilicate glass matrix and their interaction with intrinsic defects of the glass matrix.

For the first time we studied the single-color centers in sodium fluoride crystals. The quantum intensity trajectories of three types of luminescence centers emitting in the visible region of the spectrum were observed; one of which is the F₃⁺-center. The blinking of quantum trajectories is caused by transitions of the centers from the excited singlet state to the triplet state and, further, to the main singlet state. The average lifetime of the main triplet state for F₃⁺-centers measured from observations of quantum trajectories of luminescence of single centers is 1.9 s, which coincides with the results of past measurements on the decay kinetics of triplet luminescence of ensemble of F₃⁺-centers.

Spectral and kinetic characteristics of photoluminescence of BaF₂ and SrF₂ crystals implanted with high-energy (~ 100 keV) Ag ions have been studied. The photoluminescence spectra of both crystals have a similar structure, three components are observed with maxima in the wavelength ranges 500—550, 600—670 and 760—770 nm. Positions of the maxima depend on the matrix material and excitation wavelength. Study of the kinetic curves of luminescence decay allowed to distinguish three components with characteristic decay times of ≤ 1ns, about 4 ns and 13—15 ns.

Systematic studies of the proximity effect of superconductor/normal metal, superconductor/antiferromagnet and superconductor/ferromagnet in structures with varying thickness of the superconducting lead layer have been carried out. It has been shown that in these systems the behavior of the superconducting transition temperature T_c with decreasing thickness of the superconducting layer is different. For superconductor/antiferromagnet structures, within the limits of the studied lead layer thicknesses, changes in T_c are insignificant. As the lead layer thickness decreases, the electrical resistance ratio RRR (R_300K/R_10K) decreases significantly, which may indicate an increase in the contribution of surface defects. The width of superconducting transitions increases with decreasing thickness of the lead layer, which indicates the manifestation of size effects.

We presented the results of experimental studies of static magnetic properties and modeling of magnetization reversal in an epitaxial thin film of the L1₀-phase of the PdFe compound and the PdFe/W/PdFe heterostructure on MgO (001) substrates. It is shown that the PdFe/W/PdFe heteroepitaxial structure with the α-W layer thickness of ~ 0.7 nm represents an artificial antiferromagnet with perpendicular magnetic anisotropy and an exchange integral value of $\text{J}\simeq \text{1.7}\cdot {\text{10}}^{-3}Дж/{м}^2$. Micromagnetic modeling of the equilibrium domain structure and its evolution in an external magnetic field made it possible to satisfactorily describe the magnetization reversal curve of the studied thin-film heterostructure.

We presented the results of studies of the magnetostatic and magnetic resonance properties of a Fe₃Al/Pt thin-film bilayer structure synthesized by the molecular beam epitaxy method. Magnetometry and ferromagnetic resonance data indicate four-fold in-plane magnetocrystalline anisotropy of the Fe₃Al layer. Under spin pumping conditions, the magnetic field dependence of the voltage signal arising due to the inverse spin Hall effect was measured, and the quantitative characteristic of the spin-charge transformation, the spin-Hall angle, in platinum was assessed as θ_SH = 0.030 ± 0.005.

We studied the possibility of modifying the near-surface silicon layer before and after ion implantation, followed by pulsed light annealing, in order to structure the surface of the substrates in order to increase the efficiency of their use in solar energy. The results were compared with the data obtained on monocrystalline and implanted germanium.

The effect of the PMN-PT piezoelectric substrate ([Pb(Mg_1/3Nb_2/3) O₃]_0.7 — [PbTiO₃]_0.3) on the superconducting properties of the PMN-PT/Co1/Cu/Co2/Cu/Pb thin-film heterostructure was studied. The change in superconducting transition temperature (T_c) was recorded when an electric field was applied to the PMN-PT substrate and in an external magnetic field. The maximum difference in T_c was 15 mK when an electric field of 1 kV/cm was applied. In an external magnetic field, the maximum difference in T_c was more than 80 mK when the mutual direction of the magnetizations of the ferromagnetic layers changed from parallel/antiparallel to perpendicular.

The crystal formation of Fe-Ga oxides and Fe-Ga-Cu borates was studied in multicomponent flux system based on Bi₂Mo₃O₁₂-Na₂B₄O₇. Thermal dependence of magnetization of electron spin resonance of obtained Fe_1.1Ga_0.9O₃ single crystal was studied, the Curie — Weiss temperature (θ_CW = 289 K) and ferrimagnet-paramagnet phase transition temperature T_C = 288 K have been defined. The spin-wave resonance lines are observed in the spectrum of magnetic resonance in the ordered phase.

New heptanuclear mixed-valence iron complexes with pentadentate ligands have been synthesized, and their magnetic properties have been studied. It has been found that the presence of thiocyanate anions leads to the emergence of spin-crossover properties by magnetometry and EPR methods. The insertion of long alkoxy chains into the molecule leads to thermotropic liquid crystalline properties and enhanced cooperative magnetic properties.

The properties of the superconducting spin valve Fe1/Cu/Fe2/Cu/Pb on a piezoelectric substrate PMN-PT ([Pb(Mg_1/3Nb_2/3) O₃]_0.7 — [PbTiO₃]_0.3) in external magnetic and electric fields are studied. The magnitude of the shift of the superconducting transition temperature more than 200 mK was found when the mutual orientation of the magnetizations of the ferromagnetic layers changes from antiparallel to perpendicular in the magnetic field H₀ = 1 kOe. In this case, an anomalous behavior of the dependence of superconducting transition temperature on the angle between the magnetizations of the ferromagnetic layers was detected, which manifested itself in the maximum values of superconducting transition temperature at an orthogonal orientation of the magnetizations of the ferromagnetic layers. The full effect of the superconducting spin valve was observed. It has been established that with an increase in the applied electric field to the PMN-PT piezoelectric substrate, the shift of the superconducting transition temperature increases. The maximum shift was 10 mK at an electric field strength of 1 kV/cm.