Новые публикации

DOI:   https://doi.org/10.1039/D5QI00215J

Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are considered to be at the forefront of the development of next-generation NIR light sources. However, the performance of NIR pc-LEDs is severely limited due to the narrow band emission, low quantum efficiency, and thermal quenching of NIR-emitting materials. Herein, an efficient and thermally stable broadband NIR LaMgGa₁₁O₁₉:Cr³⁺,Yb³⁺ (LMG:Cr³⁺,Yb³⁺) phosphor has been successfully designed by [Cr³⁺–Yb³⁺] co-doping. The broadband emission phenomenon of LaMgGa₁₁O₁₉:Cr³⁺ was confirmed to be due to selective lattice occupancy of Cr³⁺ ions based on the analysis of crystal structures, crystal field calculations, and fluorescence lifetimes. The NIR emission spectra in the range of 1000–1200 nm were enriched by using the highly efficient energy transfer of Cr³⁺ → Yb³⁺ ions and the energy transfer mechanism is discussed in detail. The prepared LMG:Cr³⁺,Yb³⁺ phosphors exhibit highly efficient ultra-broadband NIR emission from 650 to 1200 nm under 440 nm excitation with high internal and external quantum efficiencies of 94.2%/40.5% and excellent luminescence thermal stability of 89.3%@373 K. A NIR pc-LED prototype was fabricated by combining the optimized phosphor with a commercial 440 nm blue LED chip, providing 84.5 mW NIR output power at a 350 mA driving current. Finally, the potential applications of the phosphor in night vision lighting and non-destructive testing were demonstrated. The results show that this work is expected to provide a new strategy for efficient ultra-broadband NIR phosphor design.

https://doi.org/10.1134/S0021364024604706

A one-dimensional photonic crystal with a variable period has been fabricated from porous anodic alumina. A stepwise increase in the period has ensured the broadening of the photonic bandgap from 50 to 170 nm. It has been shown that the introduction of water, alcohol, or acetone into the pores of the crystal allows one to modify the transmission spectrum and to split the passband. It is shown that the combination of angular incidence of light with pore filling makes it possible to use the fabricated crystal as a broad- and narrowband reusable filter.

https://doi.org/10.1134/S2635167624602225

We have shown a novel method for the synthesis of iron silicide nanoparticles on a water-soluble NaCl substrate using thermal layer-by-layer deposition of Fe–Si and post-annealing in ultra-high vacuum. The crystal structure, morphology and optical properties of highly dispersed Fe–Si-containing thin films have been studied. As a result, Fe₃Si nanoparticles were found to spontaneously form on the surface of salt with an excess of iron in a wide stoichiometric range. We propose a simple method to control the geometric shape of synthesized Fe–Si ferromagnetic nanoparticles by preparation of NaCl surface.

https://doi.org/10.1016/j.ceramint.2025.03.189

Antiferroelectric (AFE) ceramic materials, especially those based on lead zirconate (PZ) materials, are renowned for their outstanding energy storage properties, which stem from their unique field-induced phase transitions. These features make them excellent candidates for high-power pulse capacitor applications. However, PZ-based antiferroelectric materials currently suffer significant challenges, including low energy storage density and the inability to simultaneously enhance energy storage efficiency, which greatly impedes their practical application. To address these challenges, this study optimizes both the phase transition and electric breakdown fields, ultimately developing a relaxation antiferroelectric system that facilitates the collaborative improvement of energy storage characteristics. Specifically, Sr²⁺ doped Pb_0.98La_0.02[(Zr_0.5Sn_0.5)_0.88Ti_0.12]_0.995O₃ ceramics were fabricated using the conventional solid-state reaction. The incorporation of Sr²⁺ effectively disrupts the antiparallel polar order of the antiferroelectric phase, thereby stabilizing it. It reduces the potential barrier for phase transition switching and improves the breakdown electric field, thus simultaneously enhancing recoverable energy density and efficiency. The efficiency peaked at 90 % when x = 0.06. Building on this, a viscous polymer processing was used to prepare the ceramic at x = 0.06, showing a recoverable energy density of 6.5 J/cm³ and an energy efficiency of 84 % at 450 kV/cm. Additionally, the ceramic shows remarkable stability within 30–150 °C range, with an efficiency variation of 5.9 %. Furthermore, it performs well in actual discharge energy density (3.22 J/cm³) and power density (131 MW/cm³) at 240 kV/cm.

https://doi.org/10.1016/j.optmat.2025.116924

The orientational structure and spectral properties of a cholesteric layer with planar–conical boundary conditions are studied. Initially, a structure with circular-shaped domains characterized by double twisting of the surface linear defect is formed. Under the influence of an electric field, the domains take the shape of polygons. This system has an asymmetric selective reflection of light: the reflection of right-circularly polarized light close to 100% is observed at a normal incidence of radiation on the sample from the planar boundary conditions, while a selective reflection of light does not occur for radiation incident from the conical anchoring. The light transmission of the sample in the forward direction does not depend on which substrate the radiation falls on. This spectral behaviour is due to the peculiarity of the formation of the domain structure in the cholesteric layer, in which the circular domains are initially located only near the substrate with a conical anchoring. A practically uniform planar cholesteric structure is formed near another substrate with planar boundary conditions. The selective reflection asymmetry is reduced by an applied voltage in the range of 0 to 12 V. The cholesteric transforms into a scattering state at an applied voltage of 12 V <�<72 V and becomes a transparent at �>72 V. Switching off the electric field, under the influence of which the cholesteric is in a transparent state, leads to the restoration of the asymmetry of selective light reflection.

DOI: 10.1109/TDEI.2025.3548971

Using vacuum-arc synthesis, Ultra-high molecular weight polyethylene (UHMWPE)/nano CuO composite samples with a CuO nanoparticle content of 0 to 3 wt.% were obtained. It was found that with an increase in the concentration of nanoparticles, their agglomeration is possible. In addition, with an increase in the concentration of CuO nanoparticles, and accordingly an increase in the time of the polymer modification process, some of the non-polar groups > CH2 are converted into polar groups > C=O, which are easily embedded in the UHMWPE crystal lattice. The electrical properties of pure UHMWPE and UHMWPE/CuO composites were studied by impedance spectroscopy in the frequency range from 10² to 10⁸ Hz and temperatures from 300 K to 420 K. It was found that the dielectric properties of the composite with a CuO nanoparticle content of up to 1 wt.% do not undergo any special changes. The permittivity does not depend on frequency, while the dielectric losses are associated only with through conductivity. With increasing temperature, due to thermal expansion of the polymer and a decrease in its density, the permittivity decreases. With an increase in the nanoparticle content from 2 to 3 wt.% at a frequency of 10⁶ Hz, dielectric relaxation in UHMWPE/nano CuO associated with the formation of polar groups is observed. With increasing temperature, dipole polarization is activated. As a result, dielectric losses increase.

https://doi.org/10.1002/andp.202400319

Fresnel diffraction on double fork-shaped gratings is studied. The trajectories of singularities are found to form two groups of nested spirals, with one originating from each dislocation. The number of spirals nested in each group is found to be equal to the topological charge of the dislocation from which it originates. The influence of the initial distance between dislocations on the trajectories of singularities is examined in detail, and the distinctive characteristics of this dependence are highlighted. The trajectory of the displacement of centroids of singularities from one group of nested spirals during the propagation for various topological charges is investigated. The results demonstrate that the higher the topological of the second dislocation is, the faster the centroid from the first dislocation will shift along the � axis during the propagation. This finding indicates that the trajectory of singularities displacement is not defined by the singularity itself, but rather by the background field, which correlates well with the hydrodynamic approach.

https://doi.org/10.1134/S0021364024603841

The thermodynamic stability and the magnetic and electronic properties of a new two-dimensional magnetic compound (Cr_1 − xFe_x)₃C₂ belonging to the MXen family have been analyzed using ab initio calculations and the cluster approximation. The most stable structure and magnetic configuration of (Cr_1 − xFe_x)₃C₂ have been proposed taking into account the functionalization of the surface with fluorine and oxygen. For the first time, a stable and promising ferrimagnetic MXene (Cr_1/3Fe_2/3)₃C₂ with a high magnetic moment per cell has been discovered, both in the pure form and with the fluorine-functionalized surface.

https://doi.org/10.1134/S0021364024604998

SmFe_{3 – x}Al_x(BO₃)₄ multiferroic single crystals with x = 0–0.28 have been studied in the temperature range T = 3.8−298 K using ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction analysis. An increase in the Mössbauer hyperfine quadrupole splitting with the content of aluminum x impurities has been found. For all studied samples, the Mössbauer Debye temperatures Θ_M of iron ions have been determined in good agreement with the values for iron ions calculated from X-ray diffraction data. It has been shown that the low-temperature Mössbauer spectral lines of single crystals doped with Al in a magnetically ordered state are broadened compared to the corresponding lines of the undoped SmFe₃(BO₃)₄ ferroborate; this broadening is best approximated within the multilevel spin relaxation model. The Néel temperatures T_N of the magnetic phase transition have been determined for all studied SmFe_{3 – x}Al_x(BO₃)₄ samples. It has been (found that the Néel temperature T_N decreases nonlinearly with an increase in the content x of aluminum, and the type of three-dimensional magnetic ordering changes from planar to Ising.

DOI: 10.1021/jacs.4c16602

https://pubmed.ncbi.nlm.nih.gov/40033799/

Aqueous colloids with a high concentration of nanoparticles and free of steric stabilizers are prospective soft materials, the engineering of which is still challenging. Herein, we prepared superparamagnetic colloids with very large, up to 1350 g/L concentration of 11 nm nanoparticles via Fe²⁺ and Fe³⁺ coprecipitation, water washing, purification using cation-exchange resin, and stabilization with a monolayer of citrate anions (ζ potential of diluted dispersions about -35 mV). XRD, XPS, Mössbauer, and FTIR spectra elucidated the defective reverse spinel structure of magnetite/maghemite (Fe₃O₄/γ-Fe₂O₃) with a reduced content of Fe²⁺ cations. The viscosity increases with nanoparticle concentration and depends also on the nature of citrate salt, being one order of magnitude lower for lithium than sodium and potassium as counter-cation. SAXS/USAXS curves show power-law behavior in the scattering vector range between 0.1 and 0.002 nm^-1, suggesting that particles interact forming fractal clusters, which are looser for Na⁺- and denser for Li⁺-citrate stabilizers (fractal dimensions of 1.9 and 2.4, respectively). In parallel, ATR-FTIR found increasing proportions of symmetric O-H stretching vibrations of ice-like interfacial water in the concentrated colloids. We hypothesize that the clusters arise due to the attraction of like-charge particles possibly involving the water shells and hydration of counter-cations; overlapping the clusters and transition to continuous non-Newtonian phases is seen at viscosity vs concentration plots at 700-900 g/L. The results shed new light on the structure of very concentrated nanocolloids and pave the way for their manufacturing and tailoring.

DOIhttps://doi.org/10.1039/D5TC00206K

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) have been widely used in plant cultivation. However, exploring NIR phosphors with specific wavelengths and high efficiency is still the main task. In this paper, a NIR phosphor, Lu₃Ga_5−2xMg_xGe_xO₁₂ (LGMG):0.05Cr³⁺, with an emission center wavelength of 726 nm was investigated. After employing the co-substitution strategy, it was found that the strength of the crystal field in the vicinity of Cr³⁺ gradually weakened, resulting in broadening of the emission spectrum to the full width at half maximum (FWHM) of 155 nm. Notably, the developed phosphors have high IQE values and relatively better thermal stability. After optimization, the absorption spectrum of the obtained broadband near-infrared luminescent phosphor showed a high degree of matching with the absorption spectrum of the phytochrome P_FR. NIR pc-LEDs devices were successfully prepared by combining the LGMG:Cr³⁺ phosphor with commercialized blue LED chips. This phosphor has potential applications in plant lighting to promote plant growth.

DOI: 10.1109/ICCT62929.2024.10875001

a silver irregular micromesh transparent conductors with excellent combination of optoelectric characteristics have been obtained in this work. Broadband measurements of EMI shielding properties irregular mesh transparent conductor have been carried out. It is shown that in the high-frequency region the shielding ability reaches saturation and becomes indistinguishable for 600 nm and 1000 nm thick silver mesh transparent conductors. As expected, the key factor for mesh transparent conductor coatings is the average cell size, which turns out to be the limiting factor for shielding at high frequencies. The experimental data are in agreement with the Kantorovich model.

https://doi.org/10.1134/S0031918X24601975

The effect of the Mn_xGe_y buffer layer on the morphology, transport and magnetic properties of Mn₅Ge₃ thin films grown on substrates Si(111) has been studied. Using X-ray diffraction analysis and atomic force microscopy, it has been found that changing the thickness and structure of the buffer layer with a gradient Mn_xGe_y composition has made it possible to control the crystalline quality and smoothness of epitaxial films. Changes in the microstructure and surface roughness has not affected the temperature of the phase transitions revealed from the temperature dependences of the resistivity and magnetization at 75 and 300 K. It has been shown that the features of the magnetization curve shape for films with different buffer layers have been closely related to the inhomogeneity of the films in thickness and surface roughness while maintaining the micromagnetic constants and orientation of the easy magnetization axis. The value of the change in the magnetic part of entropy ΔS has been calculated to be 2.1 J kg^–1 K^–1 at 1 T, which is comparable with the value for gadolinium and exceeds that for Mn₅Ge₃(001) films grown on GaAs substrates.

 https://doi.org/10.1002/jrs.6784

Nickel-cobalt oxyborates (Ni,Co)₃B₂O₆ with a kotoite-type orthorhombic structure are known as antiferromagnetic materials and are of interest for optical applications and as promising battery anode materials. We report and analyze the results of experimental low temperature Raman studies of the phonon spectra measured in some polarizations of the Ni₃B₂O₆, Ni_2.81Co_0.19B₂O₆, Ni_2.4Co_0.6B₂O₆, Ni_2.07Co_0.93B₂O₆, and Co₃B₂O₆ crystals. Simulations of the density functional theory of Raman spectra of the Ni₃B₂O₆ and Co₃B₂O₆ crystals have been performed and analyzed. The vibrational modes of the Ni₃B₂O₆ and Co₃B₂O₆ crystals were interpreted. Low-wavenumber modes in the Raman spectra are associated with Ni and Co atoms vibrations accompanying BO₃ group deformations. Clear evidence of spin-phonon interaction was found for some specific phonons below ��. The anomalies in the behavior of these phonon modes as a function of the nickel concentration in the crystal have been presented. The position and intensity of the Raman modes decrease when the Ni atoms are replaced by Co atoms.

 https://doi.org/10.1002/andp.202400436

Diffraction of shifted incident beam on double fork-shaped gratings with unit charges has been numerically simulated by the using of the Fresnel diffraction integral. The trajectories of singularities dependance on the position of the incident Gaussian beam have been investigated. For the case of same topological charges of dislocations it is shown that the shift of incident beam along the horizontal axis leads to the shift of singularities trajectories along the vertical axis, and vice versa. It is shown, that these results can be qualitatively predicted by using the hydrodynamic approach. For the case of diffraction on double fork-shaped grating which have dislocations with topological charges of opposite signs, the effect of the incident beam center shift depends on the initial distance between dislocations 2⁢�� as well as the initial positions of positive and negative topological charges. The aforementioned findings shows that the result of diffraction on the double fork-shaped gratings highly depends on the position of the incident beam center, and therefore, it provides the valuable information that can enrich our understanding of the spatial dynamics of optical vortices.

https://doi.org/10.1016/j.jeurceramsoc.2025.117319

Samarium monosulfide (SmS) is a unique tensometric material. For the first time, SmS ceramics for magnetron sputtering films were synthesized. A powder of up to 100 mol% SmS was produced via the reaction of γ-Sm₂S_2.98 with excess metallic samarium vapor. The conditions for target and side reactions were determined. SmS ceramic targets were fabricated by pressing under standard conditions and annealed at high temperatures. Ceramic properties—density, hardness, and compressive strength—improved with increasing pressing pressure. Conditions for stable magnetron discharge over the SmS target were established. The composition of films deposited on silicon substrates varies with the substrate-to-target angle, transitioning from SmS_1.9 to SmS. During magnetron discharge, SmS dissociates into samarium and sulfur, with their distribution approximated by angular equations. High-mass Sm and SmS particles distribute radially, while sulfur concentration forms an ellipse elongated toward low angles. The deposition angle range for SmS was determined.

https://doi.org/10.1134/S1062873824709036

The relative influence of two different crystal structures of the composite compound Bi₂(Sn_0.7Fe_0.3)₂O₇/Bi₂Fe₄O₉ with a ratio of 91/9% studied using Raman scattering method. The Raman spectra were studied in the temperature range 93–520 K and the frequency range 1–2000 cm^–1. The types of lattice vibrations are determined. A decrease of the frequency of Raman spectra modes was found in the regions of phase transitions Bi₂(Sn_0.7Fe_0.3)₂O₇ and Bi₂Fe₄O₉. A new mode 406 cm^–1 has been established, which is a mixed oscillation of SnO₆ in Bi₂(Sn_0.7Fe_0.3)₂O₇ polyhedra (F_2g) at a frequency 400 cm^–1 and stretching vibrations of the FeO₆ octahedral at a frequency 426 cm^–1 Bi₂Fe₄O₉.

https://doi.org/10.1134/S1062873824709371

In the period from winter to spring 2024, a series of measurements of interference reflectograms from layered structures of ice surfaces of freshwater and salt reservoirs of the Krasnoyarsk Territory and the Republic of Khakassia were carried out. These measurements were performed using signals from navigation satellites operating in the L1 band. The experimental data obtained in the form of amplitude-time dependencies were processed using the fast Fourier transform algorithm. Subsequent analysis of the measurement processing results allowed us to conclude that the GNSS reflectometry method is highly sensitive to determining the macrophysical characteristics of ice surfaces with different salinity of reservoirs.

https://doi.org/10.1134/S1062873824709000

We investigated the optoelectric characteristics of transparent conducting structures of oxide/metal/oxide (OMO) type, where In₂O₃ is used as an oxide and Ag is used as a metal. Samples were obtained by magnetron sputtering. The focus is on the influence of the thickness and homogeneity of the silver layer on the optical and electrical properties of the structures. We use an ion etching method to improve performance of silver thin films and reduce thickness. Usually, in the case of poor wetting of the metal oxide substrate, the thin film grows by the island mechanism (Volmer–Weber mechanism), which leads to poor properties of the OMO structures. The proposed method consists of “thinning” the obvious continuous silver films using ion etching, because of which the thin silver films become closer to the films growing by the layer-by-layer mechanism (Frank–van der Merwe mechanism). The results obtained showed that ion etching allows us to achieve higher transparency of the structure without crucial loosing of electrical conductivity. This makes the method promising for further application in optoelectronic devices such as solar cells and displays.

 https://doi.org/10.1002/adfm.202500806

Exploring new types of scintillators, especially fabricating large-area scintillating screens, is essential in applications of life science, industry, and material science. However, the thickness and light scattering in composite scintillator film present a major challenge for balancing the spatial resolution and radioluminescence intensity. Herein, an in situ crystallization route is developed to innovate the preparation of the large-area scintillating screens based on the hybrid copper(I)-based C₆H₈N₂OCuX (X = I and Br), in which carboxymethylcellulose sodium (CMC-Na) contribute to the “CMC-Na membrane” film formation and further increase absorption cross-section for X-ray radiation owing to the existence of Na elements. The choice of halogen can regulate the photoluminescence of C₆H₈N₂OCuX (X = I, Br, and Cl) from cyan to green and then to yellow, and significant scintillation property can be achieved for C₆H₈N₂OCuI with the light yield of 52 000 photons MeV⁻¹ and detection limit of 43.14 nGy s⁻¹. Finally, the high X-ray absorption assisted by CMC-Na, as well as the thin thickness of the composite scintillator films help to realize remarkable spatial resolution above 14 lp mm⁻¹. This study provides a foundation for discovering high-performance copper(I)-based halides scintillators and offers a creative think film preparation method for X-ray imaging.

https://doi.org/10.3390/inorganics13020034

This study explores the phase composition, local atomic structure, and magnetic properties of biogenic nanomaterials synthesized through microbially mediated biomineralization by the sulfate-reducing bacterium Desulfovibrio species strain A2 (Cupidesulfovibrio). Using X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and magnetic measurements, we identified a mixture of vivianite (Fe₃(PO₄)₂·8H₂O) and sulfur-containing crystalline phases (α-sulfur). XRD analysis confirmed that the vivianite phase, with a monoclinic I2/m structure, constitutes 44% of the sample, while sulfur-containing phases (α-sulfur, Fddd) account for 56%, likely as a result of bacterial sulfate-reducing activity. X-ray absorption spectroscopy (XAS) and EXAFS revealed the presence of multiple sulfur oxidation states, including elemental sulfur and sulfate (S⁶⁺), underscoring the role of sulfur in the sample’s structure. Mössbauer spectroscopy identified the presence of ferrihydrite nanoparticles with a blocking temperature of approximately 45 K. Magnetic measurements revealed significant coercivity (~2 kOe) at 4.2 K, attributed to the blocked ferrihydrite nanoparticles. The results provide new insights into the structural and magnetic properties of these microbially mediated biogenic nanomaterials, highlighting their potential applications in magnetic-based technologies.

https://doi.org/10.1107/S2052520624011569

The crystal structures and hyperfine magnetic parameters of EuFe₃(BO₃)₄ and mixed Eu_0.82La_0.18Fe₃(BO₃)₄ were studied over a wide tem­per­a­ture range in order to analyze correlations of the structural and magnetic features and the phase transitions in multiferroic com­pounds of the rare-earth iron borate family. The chemical com­positions of the crystals are reported from X-ray fluorescence analysis. The crystal structures of EuFe₃(BO₃)₄ and Eu_0.82La_0.18Fe₃(BO₃)₄ were determined using single-crystal X-ray diffraction in the temperature range 25–500 K. A structural phase transition is observed in EuFe₃(BO₃)₄ below 89 K which is related to distortions in the inter­atomic distances and angles. The most significant of which are for R—O, R—B, R—Fe, Fe—O and Fe—Fe distances, and the angles between the BO₃ triangles and the ab plane. There is no structural phase transition in lanthanum-doped EuFe₃(BO₃)₄ based on specific heat measurements (2.2–101.3 K) and structure analysis (25–500 K), and the tem­per­a­ture dependences of the inter­atomic distances and angles are smooth. The lengths of the superexchange paths needed for the appearance of a structural phase transition in RFe₃(BO₃)₄ have been proposed. Negative thermal expansion is observed for both com­pounds below 90 K, resulting from a growth of the inter­atomic Fe—Fe distances in the iron chains during cooling. The largest atomic displacement parameters are observed for O atoms (O2), indicating that they have the highest mobility. The magnetic properties of EuFe₃(BO₃)₄ and Eu_0.82La_0.18Fe₃(BO₃)₄ were analyzed using Mössbauer spectroscopy in the tem­per­a­ture range 4.5–298 K. Néel tem­per­a­tures (T_N) of 34.57 (1) and 32.22 (1) K are obtained based on Mössbauer spectroscopy for the pure and doped crystals, respectively. The maximum specific heat capacity tem­per­a­ture dependence related to the magnetic phase transition for the doped crystal is observed at 31.2 K. A violation of the strict arrangement of anti­ferromagnetic ordering in the ab plane in the La-doped crystals at low tem­per­a­tures is suggested. The magnetic contributions of the two structural positions of the iron ions to the Mössbauer spectra could not be distinguished in either pure and doped com­pounds, regardless of whether they are in the paramagnetic and anti­ferro­magnetic regions.

https://doi.org/10.1016/j.jssc.2025.125284

In nonstoichiometric (MnSe)_1‒х(Tm_0.76Se)_х manganese selenide, the temperature and concentration regions with the same sign of carriers determined from the Hall constant and thermoelectric power have been found. The correlation of the temperature dependences of the thermopower and electrosound has been explained within the polaron model. A change in the sign of the longitudinal and transverse Nernst‒Ettingshausen coefficients upon variation in temperature and concentration has been detected. The agree of the temperature dependences of the Nernst‒Ettingshausen coefficients with a change in the electrosound in a magnetic field has been established. The maxima of the thermopower and Nernst‒Ettingshausen coefficients versus temperature have been explained within the model of coupled electron‒hole pairs with dissociation of the pairs and pinning of coupled polarons.

https://doi.org/10.1007/s10948-025-06928-5

In this work, the change in the energy and structure of local many-particle states of HTSC cuprate La2−�Sr�CuO4 under the uniaxial compression along the c-axis is studied. Local copper-oxygen states are obtained using exact diagonalization of the CuO6 octahedron as a part of the GTB method for the five-band p-d model. The dependence of interatomic distances on the c-axis compression is calculated according to Hooke’s law using elastic constants; the influence of interatomic distances on the on-site energies and hopping integrals is obtained using linear extrapolation of the results of ab initio calculations and the theory of MT-orbitals, respectively. The c-axis compression leads to a decrease in the energy of hole states with the nature of the �1� symmetry orbitals. At a pressure value of ��1(�)=11.8 GPa, a spin crossover between the Zhang-Rice singlet and the triplet state �1 occurs. At higher pressures, a second spin crossover between two-hole states and a crossover of single-hole states with different orbital compositions were also detected. Taking into account the competition of various local states with changing the value of uniaxial compression, the effective five-band Hubbard model is formulated to describe the electronic structure of quasiparticle excitations.

DOIhttps://doi.org/10.1039/D4DT03135K

It is known that in a weak magnetic field (H < 1 kOe) at T < T_C ≈ 87 K, rare-earth cobalt oxide LaCoO₃ has ferromagnetic properties. The physical mechanism of the emergence of ferromagnetism in LaCoO₃ still remains unclear. We provided experimental evidence of the ferromagnetism and crystal lattice interconnection – the cause of ferromagnetic ordering is near-surface (defects) structural stresses. A theoretical model is proposed, within the framework of which the mechanism of the emergence of the magnetically ordered state in LaCoO₃ is discussed.

https://doi.org/10.1134/S1062873824708766

We described the synthesis method and presents the results of a study of the magnetic and magnetotransport properties of vertical hybrid structures Fe₃Si/Ge/Mn₅Ge₃/Si. The mechanisms responsible for the detected magnetoresistive effect and the possible contribution of the spin-valve effect, realized through spin injection/extraction into/from germanium, are discussed.

https://doi.org/10.1134/S1062873824708778

We studied the magnetic properties of Ni_{3 – x}Co_xB₂O₆ solid solutions with the kotoite structure, where x = 0; 0.19; 0.6; 0.93; 2. The compounds Ni₃B₂O₆ and Co₃B₂O₆ are antiferromagnets, with their easy axis of magnetization coinciding with the crystallographic directions c and b, respectively. In the Ni_2.81Co_0.19B₂O₆ solid solution, two features are found on magnetization curves, while in other solid solutions there is only one feature. With the cobalt ion concentration x > 0.9, the magnetic moments are predominantly oriented along the b axis.

https://doi.org/10.1134/S1062873824708729

The structure, magnetic properties and ferromagnetic resonance curves of cobalt ferrite particles synthesized by chemical coprecipitation technique have been studied. The possibility of resonant heating of powder in a magnetic anisotropy field of particles is shown, which can find application in medicine for magnetic hyperthermia

https://doi.org/10.1007/s10909-025-03265-8

In the framework of an ensemble of spin-polaron quasiparticles formed owing to the strong coupling between the spins of copper ions and holes on oxygen ions in cuprate superconductors, the temperature dependences of the Hall coefficient �� for undoped, lightly doped, underdoped, optimally doped and overdoped regimes are calculated. The anomalous behavior of kinetic coefficients is considered beyond the relaxation-time approximation within the multi-moment method for solving kinetic equation. Dependences ��(�) calculated in the four-moment approach for noted doping regimes demonstrate the main qualitative peculiarities of the dependences found in the experiments on the Hall effect in cuprates. It is shown that change of the hopping integral of oxygen holes influences on the modification of anomalous sharp drop and change of �� sign observed experimentally at low temperatures in underdoped regime.

https://doi.org/10.1021/acs.cgd.4c01598

Three polymorphs were found to exist for Cs₃ScF₆ in the room temperature range of up to 280 °C. Two phase transitions were identified by differential scanning calorimetry (DSC) analyses at 92 and 196 °C upon heating. In situ high-temperature solid-state NMR, synchrotron and laboratory X-ray diffraction, and neutron powder diffraction were used for structural characterization. The crystal structure of the high-temperature (γ) phase adopts the cubic Fm3̅m (Z = 4) space group with a = 9.6048(7) Å at 250 °C. The other two polymorphs, α and β, have tetragonal symmetry with space groups I4₁/a (Z= 80) and I4/m (Z= 10), and lattice parameters are a = 21.15222(6) Å, c = 38.21648(8) Å and a = 15.0401(2) Å, c = 9.6341(2) Å at RT and 150 °C, respectively.