Новые публикации

https://doi.org/10.1021/acs.inorgchem.4c00555

A luminescent zero-dimensional organic–inorganic hybrid indium halide (TUH)₆[In_1–xSb_xBr₆]Br₃ (TU = thiourea, 0 ≤ x ≤ 0.0998) was synthesized via the solvothermal method. In structures, resolved by single-crystal X-ray diffraction, isolated distorted [InBr₆]^3– and [SbBr₆]^3– octahedra are linked to organic TUH⁺ cations by intermolecular N–H···Br and N–H···S hydrogen bonds. The crystals were characterized by elemental analysis, TG-DSC, powder X-ray diffraction, FTIR analysis, and steady-state absorption and photoluminescence spectroscopy. (TUH)₆[In_1–xSb_xBr₆]Br₃ exhibits a broadband yellow-orange emission centered at 595–602 nm with a half-width of 141–149 nm (0.48–0.52 eV) and a large Stokes shift of 232–238 nm (1.33–1.35 eV). This emission can be attributed to the self-trapped exciton emission of triplet states of the octahedral anion [SbBr₆]^3– or [InBr₆]^3–. Two possible emission mechanisms were discussed. Doping with Sb³⁺ leads to a significant increase in photoluminescence quantum yield from 25.7 at x = 0 to 48.4% at x = 0.0065, when excited at 365 nm, indicating the potential use of (TUH)₆[In_1–xSb_xBr₆]Br₃ compounds in the field of photonics.

https://doi.org/10.1134/S2517751624020033

A procedure has been proposed for producing ceramic substrates for filtration membranes based on a narrow fraction of fine fly ash microspheres using cold uniaxial pressing followed by high-temperature firing. It has been shown that increasing the sintering temperature from 1000 to 1150°C leads to a decrease in open porosity from 40 to 24%, a decrease in the average pore size from 1.60 to 0.34 μm, and an increase in the compressive strength from 9.5 to 159 MPa. The resulting substrates are characterized by water permeability values of 1210, 310, 240, 170 L m⁻² h⁻¹ bar⁻¹ at sintering temperatures of 1000, 1050, 1100 and 1150°C, respectively. Experiments on filtration of aqueous suspensions of fine microspheres (d_av = 2.5 µm) and microsilica (d_av = 1.9 μm) through a substrate produced at a sintering temperature of 1150°C have shown the rejection close to 100%. The proposed methodology for using ash waste in the production of membrane materials promotes the development of technologies for the integrated processing of thermal energy waste.

https://doi.org/10.1103/PhysRevE.109.054703

A photonic crystal microcavity with the liquid crystal resonant layer tunable by heating has been implemented. The multiple vanishing resonant lines corresponding to optical bound states in the continuum are observed. The abrupt change in the resonant linewidth near the vanishing point can be used for temperature sensing.

Современные проблемы дистанционного зондирования Земли из космоса. 2024. Т. 21. № 2. С. 51-60

Представлены результаты серии измерений амплитудно-временной зависимости интерференционного поля сигналов глобальных навигационных спутниковых систем (ГНСС) диапазона L1 (λ ≈ 0,19 м) при отражении от слоистых сред: снежно-ледового покрова пресноводного озера в зимне-весенний период и вблизи лесного массива. По результатам измерений выполнены: первичная выборка данных измерений с использованием облачного сервиса, последующая обработка данных путём быстрого фурье-преобразования (БФП) и дальнейший анализ результатов с помощью методик, применяемых в многолучевой ГНСС-рефлектометрии. Для анализа полученных рефлектограмм использована модель многолучевой интерференции в слоистых средах, для чего привлечена схема геометрической оптики. Это позволило, используя коэффициенты пропускания и отражения Френеля, рассчитать амплитуду и фазу волн, пришедших наряду с прямым сигналом на приёмную антенну. В дополнение к экспериментальным данным в работе представлены результаты вычислительного моделирования динамики снежно-ледового покрова, что позволило определить его температурный режим, состояние, другие термодинамические характеристики. Моделирование проведено на основе численного решения задачи Стефана в обобщённой постановке с учётом локальных климатических данных. Это позволило не только оценить текущее состояние слоёв, но и спрогнозировать их динамическое развитие с использованием метеорологических прогнозов. Результаты исследования могут применяться для мониторинга состояния ледового покрова от становления до таяния, а также лесных массивов с целью анализа их влажности, пожароопасности и густоты посадки.

https://doi.org/10.1016/j.jcrysgro.2024.127716

The phase formation of terbium chromoborate TbCr₃(BO₃)₄ in the bismuth trimolybdate and lithium tungstate melt–solutions has been studied. The absence of the terbium chromoborate trigonal phase in the bismuth trimolybdate-based system at all component ratios has been shown. The component ratio in the lithium tungstate-based system has been found at which the TbCr₃(BO₃)₄ trigonal crystals are formed at temperatures above 1100 °C; below this temperature, the monoclinic phase dominates. The structural and magnetic properties of the grown crystals have been studied. It has been established that the trigonal and monoclinic TbCr₃(BO₃)₄ crystals synthesized from the lithium tungstate-based solvent exhibit identical magnetic properties. At the same time, a significant difference of the magnetic properties of the single crystals synthesized from the bismuth molybdate melt–solution has been observed. This difference has been attributed to the effect of Bi³⁺ ions that partially replace Tb³⁺ ions.

https://doi.org/10.1016/j.inoche.2024.112449

The structure and properties of three layered heterometallic quaternary sulfides SrLaCuS₃, SrNdCuS₃ and SrTmCuS₃ were studied for the first time using first-principles calculations in the stoichiometric and nonstoichiometric approximations. The applied DFT-based computations were performed using a hybrid functional with the contribution of nonlocal exchange in the Hartree-Fock formalism. It was revealed that the nonstoichiometry of SrLaCuS₃ and SrNdCuS₃ must be considered for modeling phonon spectra, elastic properties and band gaps. The wavenumbers and types of the Raman and “silent” modes at the Г-point were determined. From the analysis of displacement vectors, the degree of participation of ions in each mode was determined. The elastic constants and elastic moduli of the reported sulfides were calculated.

https://doi.org/10.1016/j.matchemphys.2024.129400

Huntite-like borates are versatile and promising materials with wide range of applications in frequency conversion, UV light generation, lighting, displays, quantum information storage, and more, demonstrated by their various properties and uses in scientific research. In this work, EuAl₃(BO₃)₄ powder was prepared through multi-stage solid-state reaction method using high-purity starting reagents: Eu₂O₃, Al₂O₃ and H₃BO₃, considering a 20 wt% excess of H₃BO₃ to compensate for B₂O₃ volatilization. Obtained samples undergo several treatments at varying temperatures and their phase purity is subsequently verified through powder X-ray diffraction analysis. The scanning electron microscopy reveals that resulting EuAl₃(BO₃)₄ powder consists of granules exhibiting irregular morphologies with dimensions of 0.5–8 μm. The electronic band structure of EuAl₃(BO₃)₄, calculated using the GGA PBE method, reveals f-states of Eu near 4 eV. These states do not produce emphasized peaks on simulated absorbance spectra. Using of DFT + U for the f-states of Eu pushed up f-bands above 6 eV and the charge transfer from p-O to d-Eu was obtained (E_g^direct = 5.63 eV, E_g^indirect = 5.37 eV using U_eff = 4 eV). The variation of U_eff has a weak influence on the position of the bottom of the conduction band. The experimental bandgaps of EuAl₃(BO₃)₄ crystalline powder, both direct and indirect, are found to be 3.96 and 3.67 eV, correspondingly. These values are lower than theoretical values what is associated with limitations of DFT calculations involving f electrons. The Raman spectrum of EuAl₃(BO₃)₄ powder is discussed, detailing the contributions of different ions to specific spectral bands. Investigation of high-resolution luminescence spectra shows the possibility to estimate the content of defects by the testing the violation of the prohibition of ultranarrow ⁵D₀ → ⁷F₀ line that is forbidden in the ideal crystalline structure of trigonal EuAl₃(BO₃)₄.

https://doi.org/10.1016/j.jallcom.2024.174683

Single crystals of LaCr₃(BO₃)₄ were synthesized through spontaneous nucleation from a K₂Mo₃O₁₀ flux melt. The crystal structure was determined using single-crystal X-ray diffraction (XRD) at temperatures of 293 K and 85 K. LaCr-borate crystallizes in the monoclinic C2/c space group with unit cell parameters a = 7.47980(5) Å, b = 9.55180(7) Å, c = 11.48330(8) Å, β= 104.0060(6)°, V = 796.04(1) ų (for C1, T = 293 K), and a = 7.47380(5) Å, b = 9.55520(7) Å, c = 11.47100(8) Å, β = 103.9330(6)°, V = 795.08(1) ų (for C2, T = 85 K), each with Z = 4. The temperature dependence of the unit cell parameters, including the monoclinic angle (β) and the unit cell volume (V), was investigated over the range of 85–293 K. No structural phase transitions were observed in the low-temperature region down to 85 K. Differential scanning calorimetry (DSC) measurements revealed no high-temperature phase transitions between 50 and 1350°C. Infrared (IR) spectroscopy confirmed the monoclinic structure of LaCr₃(BO₃)₄ crystals, revealing characteristic absorption bands, including the lowest frequency mode associated with the translational vibrations of the La³⁺ ion.

https://doi.org/10.1134/S106287382370627X

Ferrihydrite nanoparticles are synthesized and characterized. The dependences of heating of powders are studied upon pumping by a high-frequency electromagnetic field on a dc magnetic field. It is shown that the experimental dependence of the temperature of particles on a dc magnetic field is consistent with the theory of ferromagnetic resonance for an isotropic superparamagnet.

https://doi.org/10.1134/S1062873823706244

Results are presented from investigating the ferromagnetic resonance spectra of arrays of Co‒Ni and Co‒Fe‒Ni wires with different composition gradients, deposited into polycarbonate track-etched membranes. The effect interfaces and concentration gradients have on the effective fields of the investigated wires is examined. An anomalous angular dependence of the fields of ferromagnetic resonance is observed for the wire arrays at a pore density of ~18% in the membrane.

 https://doi.org/10.3390/polym13101553

The study reports results of using a CO₂-laser in continuous wave (3 W; 2 m/s) and quasi-pulsed (13.5 W; 1 m/s) modes to treat films prepared by solvent casting technique from four types of polyhydroxyalkanoates (PHAs), namely poly-3-hydroxybutyrate and three copolymers of 3-hydroxybutyrate: with 4-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate (each second monomer constituting about 30 mol.%). The PHAs differed in their thermal and molecular weight properties and degree of crystallinity. Pristine films differed in porosity, hydrophilicity, and roughness parameters. The two modes of laser treatment altered these parameters and biocompatibility in diverse ways. Films of P(3HB) had water contact angle and surface energy of 92° and 30.8 mN/m, respectively, and average roughness of 144 nm. The water contact angle of copolymer films decreased to 80–56° and surface energy and roughness increased to 41–57 mN/m and 172–290 nm, respectively. Treatment in either mode resulted in different modifications of the films, depending on their composition and irradiation mode. Laser-treated P(3HB) films exhibited a decrease in water contact angle, which was more considerable after the treatment in the quasi-pulsed mode. Roughness parameters were changed by the treatment in both modes. Continuous wave line-by-line irradiation caused formation of sintered grooves on the film surface, which exhibited some change in water contact angle (76–80°) and reduced roughness parameters (to 40–45 mN/m) for most films. Treatment in the quasi-pulsed raster mode resulted in the formation of pits with no pronounced sintered regions on the film surface, a more considerably decreased water contact angle (to 67–76°), and increased roughness of most specimens. Colorimetric assay for assessing cell metabolic activity (MTT) in NIH 3T3 mouse fibroblast culture showed that the number of fibroblasts on the films treated in the continuous wave mode was somewhat lower; treatment in quasi-pulsed radiation mode caused an increase in the number of viable cells by a factor of 1.26 to 1.76, depending on PHA composition. This is an important result, offering an opportunity of targeted surface modification of PHA products aimed at preventing or facilitating cell attachment.

DOIhttps://doi.org/10.1039/D4CE00091A

A series of single crystals of Ni_3−xCo_xB₂O₆ compounds with the kotoite structure and with different concentrations of transition metal ions (x = 0; 0.19; 0.6; 0.93 and 2) were obtained. The lattice parameters and atomic coordinates were determined using X-ray diffraction. The theoretical calculations using the WIEN2k package predict that nickel ions tend to occupy the 4f crystallographic position, while cobalt ions tend to occupy the 2a crystallographic position. The study of the diffuse scattering spectra and comparison of the Racah parameters for the compounds Ni₃B₂O₆ and Co₂NiB₂O₆ provides experimental evidence that nickel ions occupy crystallographic position 4f.

 DOIhttps://doi.org/10.1039/D4NR00710G

Light-trapping devices have always been a topic of intense interest among researchers. One such device that has gained attention is the hot-electron photodetector with a tunable detection wavelength. Photodetectors based on plasmon nanostructures that provide excitation of surface plasmon polaritons are challenging to manufacture. To address this issue, a planar hot-electron photodetector based on a Tamm plasmon polariton localized in a metal–semiconductor-multilayer mirror structure has been proposed in this study. The parameters and materials of the structure were adjusted to ensure perfect absorption at the resonance wavelength. As a result, the photoresponsivity of the proposed device can reach 42.6 mA W⁻¹ at 905 nm. For the first time, the photosensitivity was calculated analytically by solving the dispersion law for the Tamm plasmon polariton.

https://doi.org/10.1021/acs.chemmater.4c00514

Halide double perovskites like Cs₂NaBiCl₆ are good host materials for luminescent dopants like Mn²⁺. The nature of photoluminescence (PL) depends on the local structure around the dopant ion, and doping may sometimes influence the global structure of the host. Here, we unveil the correlation between the temperature-induced (global) structural phase transition of Mn²⁺-doped Cs₂NaBiCl₆ with the local structure and PL of the Mn²⁺ dopant. X-ray diffraction analysis shows Mn²⁺-doped Cs₂NaBiCl₆ is in a cubic (Fm3m) phase between 300 and 110 K, below which the phase changes to tetragonal (I4/mmm), which persists at least until 15 K. The small (∼1%) doping amount does not alter the phase transition behavior of Cs₂NaBiCl₆. Importantly, the phase transition does not influence the Mn²⁺ d-electron PL. The PL peak energy, intensity, spectral width, and lifetime do not show any signature of the phase transition between 300–6 K. The hyperfine splitting in temperature-dependent electron paramagnetic spectra of Mn²⁺ ions also remain unchanged across the phase transition. These results suggest that the global structural phase transition of the host does not influence the local structure and emission property of the dopant Mn²⁺ ion. This structure–property insight might be explored for other transition-metal- and lanthanide-doped halide double perovskites as well. The stability of dopant emission regardless of the structural phase transition bodes well for their potential applications in phosphor-converted light emitting diodes.

https://doi.org/10.1134/S0031918X23602883

The distribution of Co²⁺ ions over sublattices and structurally nonequivalent positions in the unit cell of the crystal lattice of a single crystal of lithium gallium spinel Li_0.5Ga_2.5O₄ is shown. This distribution determines the properties of both mono- and nanocrystalline substances. The distribution is obtained by a special technology and is manifested in the electron paramagnetic resonance (EPR) spectra. The distribution of Co²⁺ ions depends on the structural and magnetic nonequivalence. The structural and magnetic nonequivalence causes a multiminimum behavior of the crystal field potential in the unit cells of single crystals at the locations of Co²⁺ ions. The Co²⁺ ions are found in complexes with tetrahedral and octahedral oxygen ions. Three types of EPR spectra of Co²⁺ ions have been found and investigated. The [Math Processing Error]Cotetr2+ spectrum is attributed to the Co²⁺ ion, which replaces the Ga³⁺ ion located in a tetrahedral oxygen environment. The spectrum of the [Math Processing Error]Cooct2+ ion located in the crystal field with axial symmetry belongs to the Co²⁺ ion replacing the Li⁺ ion located in an octahedral oxygen environment. The spectrum of the [Math Processing Error]Cooct2+ ion located in a low symmetry crystal field belongs to the Co²⁺ ion replacing the Ga³⁺ ion located in an octahedral oxygen environment. The nearest cationic environment of the ion creates rhombic distortions due to the different valence numbers of Li⁺ and Ga³⁺. The results of studying the angular dependences of the spectra show the presence of four and twelve magnetically nonequivalent positions in the unit cells.

Журн. СФУ. Сер. Матем. и физ., 17:2 (2024), 162–168

Предложена новая конструкция ВТСП ограничителя мощности с двумя рабочими полосами. Ограничитель содержит два микрополосковых полосно-пропускающих фильтра. Каждый фильтр состоит из двух четвертьволновых резонаторов, которые связаны между собой через составной полуволновый резонатор, содержащий пленку из высокотемпературного сверхпроводника. Макет устройства в открытом режиме имеет ширины рабочих полос пропускания 10% и 11% с центральными частотами 1.48 ГГц и 2.03 ГГц. Минимальные вносимые потери составили 1.9 дБ и 1.7 дБ для НЧ- и ВЧ-каналов соответственно. Передаточные характеристики устройства были исследованы до уровня СВЧ-мощности 3.15 Вт.

https://doi.org/10.1080/1536383X.2024.2338524/

A fullerene mixture was enriched with endohedral metallofullerenes (EMF) using Lewis acid (TiCl₄), which took 22 min, whereas the standard method requires about 8 h. An algorithm for assessing small-area chromatographic peaks has been proposed, which has improved the accuracy of determination. For example, the area of the C₈₄ peak was 4.24% using the developed program, while the use of chromatograph software estimated the area of this peak to be 1.78%.

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TiO2 photonic crystal nanostructure films are anodic synthesized with pulsed and stepwise voltage changes. The obtained photonic structures were activated by cyclic voltammetry in 0.5M Na2SO4. The photoelectrochemical activity of the electrodes was studied in the water splitting reaction in the wavelength range 360–700 nm. Activation leads to a change in the band gap energy, a red shift in the IPCE spectrum and an increase in its values in the studied wavelength range

https://doi.org/10.1134/S1063774523601296

MnBi₂Te₄, Mn(Bi,Sb)₂Te₄, and MnBi₂Te₄(Bi₂Te₃)_m (m ≥ 1) are assigned to magnetic topological insulators. Successful application of these materials in nanoelectronic devices calls for comprehensive investigation of their electronic structure and magnetic properties in dependence of the Bi/Sb atomic ratio and the number m of Bi₂Te₃ blocks. The magnetic properties of the surface of MnBi₂Te₄, MnBi₄Te₇, and Mn(Bi1−�Sb_x)₂Te₄ compounds (x = 0.43 and 0.32) have been studied using the magneto-optical Kerr effect. It is shown that the temperatures of magnetic transitions on the surface and in the bulk of MnBi₄Te₇ and Mn(Bi, Sb)₂Te₄ differ significantly.

https://doi.org/10.1016/B978-0-32-395195-1.00012-0

We consider dielectric cavities whose radiation space is restricted by two parallel metallic planes. The TE solutions of the Maxwell's equations of the system are equivalent to the solutions of periodical arrays of dielectric cavities. The system readily allows to achieve bound states in the continuum (BICs) of any type, including topological BICs that depends on the position and orientation of the cavities relative to the planes. This facilitates experimental studies immensely compared to infinite arrays of the cavities. We show the effect of merging topologically protected BICs, which pushes the square asymptotic of the Q-factor to the power degree of 4 or even 6.

https://doi.org/10.1134/S1061933X23601294

Due to their unique properties, organosols of silver nanoparticles are widely used in optical and semiconductor devices, to produce electrically and thermally conductive films, as catalysts, antibacterial materials, etc. This work proposes a simple and highly productive method for the preparation of silver organosols, which have a metal concentration as high as 1800 g/L and contain spherical nanoparticles with low polydispersity and a median size of 9.1 nm. The method consists in the initial preparation of silver nanoparticle hydrosols with a concentration of higher than 30 g/L followed by the transfer of the NPs into an organic phase of o-xylene. A set of physical research methods has been employed to study the regularities of the extraction of silver nanoparticles with o-xylene in the presence of cetyltrimethylammonium bromide (CTAB) and ethanol and to determine the optimal process conditions, under which the extraction degree is as high as 62.5%. It has been found that bromine anions contained in CTAB molecules cause the aggregation of some amount of silver nanoparticles with the formation of silver metal sediment in the aqueous phase. According to X-ray photoelectron spectroscopy data, the sediment contains bromide ions (up to 4 at %) on the particle surface. Organosols synthesized under optimal conditions are stable for more than 7 months and withstand repeated cycles of drying and redispersing. Silver organosols have been used to obtain metal films with an electrical conductivity of about 68 500 S/cm, which increases to 412 000 and 509 500 S/cm (87.8% of the electrical conductivity of bulk silver) after thermal treatment at 150 and 250°C, respectively.

https://doi.org/10.1134/S0021364023604244

The magnetic structure of Fe₅O₆ is studied using a combination of the group-theoretical analysis and DFT + U calculations of the electronic spectrum. The calculations are performed for the magnetic k = (0, 0, 0) vector. The magnetic ground state corresponds to the orthogonal ordering of two magnetic subsystems:  the magnetic moments of Fe²⁺/Fe³⁺ ions located at the octahedral sites (slabs of octahedra) are directed along the c axis and are antiferromagnetically ordered, whereas the magnetic moments of Fe²⁺ ions in trigonal prisms forming one-dimensional chains are directed along the b axis and are antiferromagnetically coupled along the c axis. The formation of a nonzero antiferromagnetic component of magnetic moments in the slabs of octahedra directed along the b axis is caused by the effect of magnetic chains on the three-dimensional magnetic structure.

https://doi.org/10.1021/acsmaterialslett.4c00263

The discovery of high-efficiency Mn⁴⁺-activated fluoride red phosphors with short excited-state lifetimes (ESLs) is urgent and crucial for high-quality, wide-color-gamut display applications. However, it is still a great challenge to design target phosphors with both short ESL and high luminescence efficiency. Herein, we propose an efficient machine learning approach based on a small dataset to establish the ESL prediction model, thereby facilitating the discovery of new Mn⁴⁺-activated fluorides with short ESLs. Such a model can not only accurately predict the ESLs of Mn⁴⁺ in fluorides but also quantify the impact of structure features on ESLs, therefore elucidating the “structure-lifetime” correlations. Guided by the correlations, two new Mn⁴⁺-doped tetramethylammonium (TMA)-based hybrid fluorides (TMA)₂BF₆:Mn⁴⁺ (B = Sn or Hf) with both short ESLs (τ ≤ 3.7 ms) and high quantum efficiencies (internal QEs > 92%, external QEs > 55%) have been discovered successfully. A prototype displayer with excellent performance (∼124% National Television Standards Committee (NTSC) color gamut) is assembled by employing a (TMA)₂SnF₆:Mn⁴⁺-based white Mini-LED backlight module, demonstrating its practical prospects in high-quality displays. This work not only brings promising candidates for Mn⁴⁺-doped fluoride phosphors but also provides a valuable reference for accelerating the discovery of new promising phosphors.

https://doi.org/10.1134/S0030400X23060024

Iron borates NdFe₃(BO₃)₄ and SmFe₃ (BO₃)₄ activated with 1% erbium, with ahuntite structure (space symmetry group R32) were investigated by the method of erbium spectroscopic probe. From an analysis of the temperature dependence of the transmission spectra in the region of the ⁴I_15/2 → ⁴1_13/2 transition in the Er³⁺ ion, it was found that both studied compounds order antiferromagnetically at T_N ≈ 33 K into an easy-plane magnetic structure. No other phase transitions were found.

https://doi.org/10.1134/S0030400X23060127

This work presents information on the growth and spectroscopic study of single crystals of copper metaborate doped with nickel Cu_1–xNi_xB₂O₄ (x = 0.05, 0.1). In the absorption spectra of both crystals, satellites related to Cu centers distorted by impurity Ni atoms were observed near the lines of zero phonon transitions. Polarization studies in the isotropic ab-plane of the tetragonal crystal Cu_1–xNi_xB₂O₄ show the presence of linear magnetic dichroism in the magnetically ordered state, which was previously observed both in manganese-doped and undoped copper metaborates CuB₂O₄. The temperature of magnetic phase transitions into the collinear antiferromagnetic and into helicoidal structures, T_N = 19.1 K and T * = 8.6 K, respectively, were determined from the temperature dependence of the dichroic signal.

https://doi.org/10.1134/S0030400X23070081

The Raman spectra of four crystals of TbFe_3–xGa_x(BO₃)₄ solid solutions (x from 0 to 0.54) were studied in the temperature range from 8 to 350 K. The temperatures of structural phase transitions were determined. The observed spectral behavior is characteristic to condensation and restoration of soft modes. Soft modes are associated with a structural phase transition from the R32 phase to the P3₁21 phase. The Compositions-Temperature phase diagram was constructed.

https://doi.org/10.3103/S8756699023060134

A method for the determination of pore orientation in metal-organic framework structures by polarized Raman spectra is proposed. The method involves sensitivity of the line intensity of Raman scattering to the geometry of propagation in a crystal. The operability of the method is shown by DUT-8 (Ni, Co) crystals. The obtained results are interpreted based on analysis of symmetry and direction of vibrations within periodic calculations of the electron density functional theory. The simultaneous approach allowed us to describe the vibrations and to find the principal crystal orientation collinear to the pore direction. The information on the pore orientation is necessary for problems of adsorption and design of complex multicomponent materials based on metal-organic framework.

https://doi.org/10.1016/j.jssc.2024.124693

The structure and phases formed in Sn/Co thin films are interesting both from the solid-state chemistry point of view and due to applications of such a metallic bilayer. The phases forming in thin films Sn/Co obtained by thermal vacuum evaporation on two different substrates SiO₂ and MgO(100) at different annealing temperatures have been studied. Annealing above 110°С results in intermetallics formation in the films. The hcp-cobalt is grown in the films on SiO₂ substrate, and the fcc-Co is observed on MgO(100) substrate. It is found that the stable α-Co₃Sn₂ intermetallic is formed at higher annealing temperature in film on MgO(100) substrate. We show that transformations related to mass transfer in the Sn/Co bilayers were up to 500°С and were finished upon reaching the thermodynamically equilibrium phase composition at this temperature.

https://doi.org/10.1134/S0030400X23020121

Experimental and theoretical study of submillimeter (terahertz) spectroscopic and magnetic properties of the rare-earth aluminum borate HoAl₃(BO₃)₄ were performed at temperatures 3–300K. In the transmittance spectra a number of resonance lines were detected at frequencies 2–35 cm^–1 for different radiation polarizations. These modes were identified as transitions between the lower levels of the ground multiplet of the Ho³⁺ ion split by the crystal field, including both transitions from the ground state to the excited ones and transitions between the excited states. The established excitation conditions of the observed modes and the simulation of the spectra made it possible to separate the magnetic and electric dipole transitions and to determine the energies of the corresponding states, their symmetry, and the matrix elements of the transitions. Low-frequency lines that do not fit into the established picture of the electron states of Ho³⁺ were also found; these lines, apparently, correspond to the ions with the distorted by defects local symmetry of the crystal field.

https://doi.org/10.1134/S0021364023603962

Nonlinear phenomena similar to the Belousov–Zhabotinsky reaction (autocatalytic oscillations of the population of high-spin and low-spin multielectron states of a transition metal ion) in open systems with spin crossover near bistability are considered. The conditions for possible experimental observation of autocatalytic oscillations of the magnetization in magnetically ordered systems with spin crossover are analyzed.