Новые публикации
Nanoscale Structures of Iron Silicides on NaCl (001) Surface: Self-assembly Synthesis, Morphology, and Optical Properties
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.
Enhanced dielectric energy storage properties of PLZST relaxor-antiferroelectric ceramics achieved via phase transition modulation and processing optimization
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 Pb0.98La0.02[(Zr0.5Sn0.5)0.88Ti0.12]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.
Light selective reflection asymmetry in cholesteric layer with planar–conical anchoring
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.
Investigation of the process of structural modification of UHMWPE with CuO nanoparticles on the frequency and temperature dependence of the dielectric characteristics of the composite
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.
Spiral-Like Trajectories of Singularities at Fresnel Diffraction on Double Fork-Shaped Gratings
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.
Study of Stability and Structural and Magnetic Ordering in (Cr1 −xFex)3C2 Magnetic MXene
https://doi.org/10.1134/S0021364024603841
The thermodynamic stability and the magnetic and electronic properties of a new two-dimensional magnetic compound (Cr1 − xFex)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 (Cr1 − xFex)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 (Cr1/3Fe2/3)3C2 with a high magnetic moment per cell has been discovered, both in the pure form and with the fluorine-functionalized surface.
57Fe Mössbauer Spectroscopy Study of SmFe3 –xAlx(BO3)4 (x = 0–0.28) Multiferroics
https://doi.org/10.1134/S0021364024604998
SmFe3 – xAlx(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 ΘM 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 TN of the magnetic phase transition have been determined for all studied SmFe3 – xAlx(BO3)4 samples. It has been (found that the Néel temperature TN decreases nonlinearly with an increase in the content x of aluminum, and the type of three-dimensional magnetic ordering changes from planar to Ising.
Unraveling the Structure and Properties of High-Concentration Aqueous Iron Oxide Nanocolloids Free of Steric Stabilizers
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.
Broadband and high internal quantum efficiency near-infrared phosphors obtained utilizing a chemical unit co-substitution strategy for plant lighting
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, Lu3Ga5−2xMgxGexO12 (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 PFR. 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.
Investigation of Broadband Shielding Effect in Mesh Transparent Conductor with Irregular Structure
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.
Buffer Layer Effect on the Structure, Morphology, and Magnetic Properties of Mn5Ge3 Films Synthesized on Si(111) Substrates
https://doi.org/10.1134/S0031918X24601975
The effect of the MnxGey 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 MnxGey 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.
Raman Spectroscopy and DFT Study of Spin-Reorientation Transition in the Nickel-Cobalt Orthoborates
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, Ni2.81Co0.19B2O6, Ni2.4Co0.6B2O6, Ni2.07Co0.93B2O6, 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.
Fresnel Diffraction of a Shifted Incident Beam on Double Fork-Shaped Gratings
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.
Samarium monosulfide ceramics: Preparation and properties
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-Sm2S2.98 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 SmS1.9 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.
Raman Scattering Study of Structural Phase Transitions in the Iron-Substituted of Bismuth Pyrostannat/Mullite Composite
https://doi.org/10.1134/S1062873824709036
The relative influence of two different crystal structures of the composite compound Bi2(Sn0.7Fe0.3)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(Sn0.7Fe0.3)2O7 and Bi2Fe4O9. A new mode 406 cm–1 has been established, which is a mixed oscillation of SnO6 in Bi2(Sn0.7Fe0.3)2O7 polyhedra (F2g) at a frequency 400 cm–1 and stretching vibrations of the FeO6 octahedral at a frequency 426 cm–1 Bi2Fe4O9.
Investigation of Reservoirs Ice Covers with Different Salinity Using the GNSS Reflectometry
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.
Ion Etching as a Method to Optimize the Optoelectric Parameters of Transparent Conductive Structures In2O3/Ag/In2O3
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.
In Situ Crystallization of Copper(I)-Based Hybrid Halides Assisted by Carboxymethylcellulose Sodium for a Large-Area Scintillation Imaging Screen
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.
Structural and Magnetic Properties of Biogenic Nanomaterials Synthesized by Desulfovibrio sp. Strain A2
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.
Structural and magnetic phase transitions in Eu1-xLaxFe3(BO3)4 (x = 0, 0.18)
https://doi.org/10.1107/S2052520624011569
The crystal structures and hyperfine magnetic parameters of EuFe3(BO3)4 and mixed Eu0.82La0.18Fe3(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 Eu0.82La0.18Fe3(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 Eu0.82La0.18Fe3(BO3)4 were analyzed using Mössbauer spectroscopy in the temperature range 4.5–298 K. Néel temperatures (TN) 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.
Effect of nonstoichiometry on the Hall effect, Nernst‒Ettingshausen effect, and electrosound in (MnSe)1‒х(Tm0.76Se)х manganese selenides
https://doi.org/10.1016/j.jssc.2025.125284
In nonstoichiometric (MnSe)1‒х(Tm0.76Se)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.
Spin Crossover of Local Copper-Oxygen States in the HTSC Cuprate La2-xSrxCuO4 Under the c-Axis Pressure
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.
Ferromagnetism in LaCoO3: relationship between the crystal structure, morphology and magnetic properties
DOIhttps://doi.org/10.1039/D4DT03135K
It is known that in a weak magnetic field (H < 1 kOe) at T < TC ≈ 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.
Magnetoresistive Effect in Vertical Fe3Si/Ge/Mn5Ge3/Si(111) Hybrid Structures
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.
Magnetization of Solid Solutions of Antiferromagnets Ni3 –xCoxB2O6 with the Competing Orientation of Anisotropy Axes
https://doi.org/10.1134/S1062873824708778
We studied the magnetic properties of Ni3 – xCoxB2O6 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 Ni2.81Co0.19B2O6 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.
Natural Ferromagnetic Resonance in Cobalt Ferrite Powders
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
Temperature and Doping Dependences of the Hall Coefficient within the Spin-Fermion Model of Cuprates
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.
Crystal Structures of Three Polymorphs of Cs3ScF6 by Means of Solid-State NMR, X-Ray, and Neutron Diffraction
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.
Ultrafine Ir-IrO2 nanoparticles for decoration of cobalt phthalocyanine films as an active component for highly sensitive detection of nitric oxide
https://doi.org/10.1016/j.mseb.2025.118074
Nitric oxide is an important molecule that plays a crucial role in regulating physiological processes in mammals. To develop a sensitive method for detecting NO, new heterostructures based on cobalt phthalocyanine (CoPc) films decorated with Ir-IrO2 nanoparticles were considered as active layers of chemiresistive sensors for the direct NO detection. Within deposition conditions, Ir-IrO2 nanoparticles with an Ir concentration of 0.48–1.5 µg/cm2, a fraction of IrO2 phase of 10–20 %, and particles sizes from 1 to 3 to 14 nm were obtained on the surface of CoPc films. The influence of these parameters of Ir-IrO2 particles on the sensor response of Ir-IrO2/CoPc heterostructures to NO was investigated using theoretical and practical approaches. Based on DFT calculations, an electronic sensitization mechanism of NO detection by Ir-IrO2/CoPc heterostructures was proposed. These heterostructures are able to detect of NO gas at the ppb level and show the selectively to NOx in the presense of other gases.
Lossless Phase Change Materials for Adjustable Tamm Plasmon Polaritons in the Near-Infrared
https://doi.org/10.1002/adom.202402889
Incorporation of phase-change materials (PCM) into nanophotonic structures is a straightforward method for making them tunable. The binary semiconducting chalcogenide antimony trisulfide (Sb2S3) is a suitable PCM for nanophotonic applications in the near-infrared (NIR) owing to its high refractive index, low optical losses, and wide bandgap. Therefore, in this study, Sb2S3 Tamm plasmon polaritons (TPPs) are fabricated with a focus on their widespread use in nanophotonic applications. For this, a gold film and Sb2S3 are deposited on the distributed Bragg reflector through e-beam evaporation. TPPs are excited at the interface between the distributed Bragg reflector (DBR) and the metal layer. The refractive index, extinction coefficient, and high-Q reflectance spectra of the developed Sb2S3 are measured and analyzed. The Sb2S3 TPPs exhibit a resonance shift of 45 nm caused by the phase change of Sb2S3 from amorphous to crystalline. In addition, the angle-dependent resonance shifts of 85, 76, and 63 nm are achieved by unpolarized, transverse magnetic (TM), and transverse electric (TE) modes near NIR light, respectively. The developed Sb2S3 TPP can be applied in various nanophotonics applications, including optical memory, optical data storage, and LiDAR receiver systems.
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