New Publications

https://doi.org/10.1016/j.ceramint.2024.11.473

The composite material based on the ferrihydrite nanoparticles (5Fe₂O₃ · 9H₂O) encapsulated in SiO₂ matrix was synthesized. Synthesized sample has been characterized by transmission electron microscopy, room-temperature ⁵⁷Fe Mössbauer spectroscopyand X-ray photoelectron spectroscopy. The data obtained have shown (i) the presence of isolated ferrihydrite nanoparticles with an average size of ∼4.3 nm in the SiO₂ matrix and (ii) the complete absence of the nanoparticles binding with the SiO₂ matrix. The temperature dependences of the ac and dc magnetization, as well as the temperature evolution of the Mössbauer spectra point out only the occurrence of the superparamagnetic blocking with decreasing temperature. The analysis of the relaxation time of particle magnetic moments have shown no magnetic interactions in the investigated system. A detailed examination of the magnetization curves has revealed that the non-interacted ferrihydrite nanoparticles formed by two magnetic subsystems: paramagnetic surface spins and the magnetically ordered core. Such magnetic morphology results in the significantly decrease of the anisotropy constant (K = 18 ∙ 10⁵ erg/cm³) compared to interacted nanoparticles. At the same time, a decisive role in the magnetic behavior of the material is played by the subsystem of free spins, which involves about half of all iron atoms on the particle surface.

https://doi.org/10.1002/asia.202401052

Crown ether anchored organic-inorganic hybrid halides have been recently reported as interesting luminescent materials in the visible region of electromagnetic spectrum. Is it possible to develop such crown ether anchored hybrid materials for near infrared emission? Motivated by this question, we designed a new hybrid material, namely, [(18-Crown-6)K][MoOCl₄(H₂O)]. 18-Crown-6 ether bound with K⁺ form the cationic part [(18-Crown-6)K]⁺. The K⁺ of [(18-Crown-6)K]⁺ electrostatically interacts with Cl⁻ of the anionic part [MoOCl₄(H₂O)]⁻, forming the hybrid crystal [(18-Crown-6)K][MoOCl₄(H₂O)]. It crystallizes in orthorhombic crystal system with Pnma space group. The Mo(V) possesses one d-electron (d¹) in  point group symmetry in the [MoOCl₄(H₂O)]⁻ polyhedra. This electronic configuration leads to multiple spin-allowed  transitions along with a ligand to metal charge transfer (LMCT) resulting into multiple optical absorption bands in the near UV-visible-near infrared (NIR) region. The lowest energy  transition via ²E ( ,  )/²E ( ) ²B₂ ( ) leads to NIR PL with peak at 952 nm, but with a poor intensity at room temperature.

Journal of Siberian Federal University - Mathematics and Physics, 17(6), pp. 808-816.

Aptamer GT conjugated with gold nanoparticles is specific for heavy metal ions and can be used for water quality control and environmental monitoring. Circular dichroism (CD) and small- angle X-ray scattering (SAXS) measurements were performed to determine the structure of the aptamer complex with lead (II) ions. Comparison of the measurement results with different options of the spatial structure of the complexes obtained using molecular modeling allowed us to determine how the aptamer changes its conformation due to interacting with the target

Journal of Siberian Federal University. Mathematics & Physics 2024 17(6)

This work presents the results of the experimental studies of the magnetic resonance prop- erties of the Y0:5Sr0:5Cr0:5Mn0:5O3 polycrystalline system. We found that two absorption lines are observed in the magnetic ordering region at T < 80 K in the spectrum. When changing to the paramag- netic region, one of the lines disappears, but a set of weak lines appears, which are identified as belonging to the Mn2+ impurity ions. The temperature behavior of the main peak line width is analyzed within the framework of the single-ion relaxation theory. Mn3+ ions were found to be responsible for the low- temperature peak, and Cr4+ ions are responsible for the high-temperature peak. The constants of the molecular fields acting on the Mn3+ and Cr4+ subsystems have been determined

DOIhttps://doi.org/10.1039/D4CE00943F

With the type, size and quality of experimental samples playing a special role in searching for new materials, single crystal samples are of high value and methods of their fabrication have to be developed and constantly improved, to be adjusted to the peculiarities of an expected compound. The flux technique for producing chromium-containing materials is characterized by the low solubility of Cr₂O₃ used. The study deals with crystallization of Cr-containing borates HoCr₃(BO₃)₄ with a huntite structure and oxyborates Cu₂CrBO₅ with a ludwigite structure in flux systems based on Li₂WO₄. Consideration is given not only to the possibility of growing sizable single crystals of these compounds, but also to a mixed huntite–ludwigite flux system intended to unify the growth technology and to identify the phase boundary of these compounds. The investigation of the phase diagram allowed the secondary phases to be found and analyzed. Powder and single crystal X-ray diffraction and element-sensitive EDX techniques were used to control the composition and structure of the obtained compounds. Orientational thermal and field dependences of magnetization of the obtained crystals HoCr₃(BO₃)₄ and Cu₂CrBO₅ were measured.

https://doi.org/10.1002/asia.202401052

Crown ether anchored organic-inorganic hybrid halides have been recently reported as interesting luminescent materials in the visible region of electromagnetic spectrum. Is it possible to develop such crown ether anchored hybrid materials for near infrared emission? Motivated by this question, we designed a new hybrid material, namely, [(18-Crown-6)K][MoOCl₄(H₂O)]. 18-Crown-6 ether bound with K⁺ form the cationic part [(18-Crown-6)K]⁺. The K⁺ of [(18-Crown-6)K]⁺ electrostatically interacts with Cl⁻ of the anionic part [MoOCl₄(H₂O)]⁻, forming the hybrid crystal [(18-Crown-6)K][MoOCl₄(H₂O)]. It crystallizes in orthorhombic crystal system with Pnma space group. The Mo(V) possesses one d-electron (d¹) in  point group symmetry in the [MoOCl₄(H₂O)]⁻ polyhedra. This electronic configuration leads to multiple spin-allowed  transitions along with a ligand to metal charge transfer (LMCT) resulting into multiple optical absorption bands in the near UV-visible-near infrared (NIR) region. The lowest energy  transition via ²E ( ,  )/²E ( ) ²B₂ ( ) leads to NIR PL with peak at 952 nm, but with a poor intensity at room temperature.

Magnetic Resonance in Solids, 26(3), art. no. 24301

Temperature-dependence measurements specific heat, thermoelectric power, conductivity, and electron paramagnetic resonance measurements were performed on Mn_0.75Co_2.25BO₅ powder at temperatures above 290 K. Single crystals of Mn_0.75Co_2.25BO₅ were grown by the flux method using Bi₂Mo₃O₁₂-based solvent diluted with Na₂CO₃. To investigate EPR and specific heat capacity, the single crystals were ground to powder. The temperature dependencies of the resistance, specific heat, Seebeck constant, and EPR spectra in the range from 290 K to 700 K were obtained. The transition from the dielectric state to the semiconductor state was detected at 348 K, consistent with the change in the fine structure of the EPR spectrum associated with S = 5/2 for the manganese ion Mn²⁺.

DOIhttps://doi.org/10.1201/9781003517139

This book chapter provides a comprehensive overview of the properties of soft nanoferrites, highlighting their unique characteristics and potential applications across various fields. Soft nanoferrites exhibit magnetic softness with low coercivity and remanence, enabling reversible magnetization changes crucial for applications in electronics and data storage. The tunability of their magnetic properties, achieved through size-dependent effects, surface modifications, and compositional adjustments, allows for customization to meet specific application requirements. The high surface area of soft nanoferrites influences their reactivity, catalytic capabilities, and adsorption capacity, making them versatile for applications in catalysis and environmental remediation. Biocompatibility considerations, achieved through surface functionalization, open avenues for biomedical applications such as drug delivery, hyperthermia treatments, and imaging. The ability of soft nanoferrites to respond to external stimuli, such as magnetic fields or changes in pH, adds functionality, enabling applications in sensors and actuators. Thermal stability considerations are crucial for applications involving exposure to elevated temperatures. Achieving colloidal stability and dispersibility is essential for applications in biomedical and nanotechnological fields. With their diverse properties, soft nanoferrites find applications in electronics, data storage, catalysis, biomedical imaging, drug delivery, and magnetic hyperthermia, paving the way for further advancements in materials science and technology.

https://doi.org/10.3390/cryst14110954

Layered A_n+1B_nO_3n+1 (n = 1…∞) Ruddlesden–Popper (RP) phases are a promising system for a variety of applications. Within the RP family, the thermodynamic properties of the phases are essentially additive with variation in the n value, but at present, there are no general approaches that would allow one to evaluate the individual stability of the RP phases and the possibility of their interconversion. The aim of this paper is to present a novel concept for performing a thermodynamic analysis of RP phases using the reciprocal values of the index n. We present an empirical equation ΔG_1/n = ΔG_P + B₁/n + B₂/n², where ΔG_1/n and ΔG_P are the molar Gibbs energies of formation of the Ruddlesden–Popper (RP) phase (AO)_1/nABO₃ and the parent ABO₃ perovskite, respectively, and n is a stoichiometry index of A_n+1B_nO_3n+1 RP phase. The correlation was validated using available thermodynamic data for the systems Sr-Ti-O, Ca-Ti-O, Sr-Zr-O, La-Ni-O, and La-Co-O. For all A-B combinations, the equation quantitatively describes the Gibbs energy of RP phase formation. Predicted values for the non-linear approximation lie within the experimental uncertainty in determining ΔG_1/n. The proposed correlation was used to analyze the relative stability of the RP phases and to determine the feasibility of synthesizing new compounds.

https:// doi.org/10.3897/j.moem.10.3.135986

The design of two-dimensional superatomic materials, which form their atomic structures through covalently bonded clusters with variable chemical compositions, will enable the development of new materials with promised electronic properties that are beneficial for modern nanoelectronics. This paper presents ab initio calculations of the atomic and electronic structures of both bulk and 2D Re6Se8Cl2. The calculations were carried out using density functional theory, incorporating noncollinear spin density and the pseudopotential method. The results include data on the atomic structure, band gap value, formation energy of the Re6Se8Cl2 2D layer, and the redistribution of atomic charges within the structures. The differences in effective masses for electrons and holes in the two-dimensional and bulk Re6Se8Cl2 materials are demonstrated, along with an explanation of how these differences impact their transport properties. The findings are expected to be of great significance for the design, synthesis, and implementation of new two-dimensional superatomic materials with controlled properties in modern nanoelectronics.

https://doi.org/10.3390/polym16223174

Nowadays, the Internet of Things (IOT), electronics, and neural interfaces are becoming an integral part of our life. These technologies place unprecedentedly high demands on materials in terms of their mechanical and electrical properties. There are several strategies for forming conductive layers in such composites, e.g., volume blending to achieve a percolation threshold, inkjet printing, lithography, and laser processing. The latter is a low-cost, environmentally friendly, scalable way to produce composites. In our work, we synthesized AgNW and characterized them using Ultraviolet-visible spectroscopy (UV-vis), Transmission electron microscopy (TEM), and Selective area electron diffraction (SAED). We found that our AgNW absorbed in the UV-vis range of 345 to 410 nm. This is due to the plasmon resonance phenomenon of AgNW. Then, we applied the dispersion of AgNW on the surface of the polymer substrate, dried them and we got the films of AgNW.. We irradiated these films with a 432 nm laser. As a result of the treatment, we observed two processes. The first one was the sintering and partial melting of nanowires under the influence of laser radiation, as a consequence of which, the sheet resistance dropped more than twice. The second was the melting of the polymer at the interface and the subsequent integration of AgNW into the substrate. This allowed us to improve the adhesion from 0–1 B to 5 B, and to obtain a composite capable of bending, with radius of 0.5 mm. We also evaluated the shielding efficiency of the obtained composites. The shielding efficiency for 500–600 nm thick porous film samples were 40 dB, and for 3.1–4.1 µm porous films the shielding efficiency was about 85–90 dB in a frequency range of 0.01–40 GHz. The data obtained by us are the basis for producing flexible electronic components based on AgNW/PET composite for various applications using laser processing methods.

https://doi.org/10.3390/molecules29225424

Oncolytic virotherapy is a promising approach for cancer treatment. However, when introduced into the body, the virus provokes the production of virus-neutralizing antibodies, which can reduce its antitumor effect. To shield viruses from the immune system, aptamers that can cover the membrane of the viral particle are used. Aptamers that specifically bind to the JX-594 strain of the vaccinia virus were developed earlier. However, the parameters for binding to the recombinant virus VV-GMCSF-Lact, developed based on the LIVP strain of the vaccinia virus, may differ due its different repertoire of antigenic determinants on its membrane compared to JX-594. In this work, the spatial atomic structures of aptamers to JX-594 and bifunctional aptamers were determined using molecular modeling. The efficiency of viral particles binding to the aptamers (EC50), as well as the cytotoxicity and stability of the aptamers were studied. The synergistic effect of the VV-GMCSF-Lact combination with the aptamers in the presence of serum was investigated using human glioblastoma cells. This proposed approach allowed us to conduct a preliminary screening of sequences using in silico modeling and experimental methods, and identified potential candidates that are capable of shielding VV-GMCSF-Lact from virus-neutralizing antibodies.

 https://doi.org/10.3390/cryst14110994

On the one hand, Ni3-xCoxB2O6 solid solutions are promising anode materials for lithium batteries, and on the other hand, they have antiferromagnetic properties. This study examines the lattice dynamics of Ni3-xCoxB2O6 solid solutions for x = 0, 1, 2, 3 by means of quantum chemistry and Raman spectroscopy. The vibrational spectra of the compound NiCo2B2O6 have been studied using the polarized Raman spectroscopy method. Good agreement was found between the theoretical and experimental results. As expected, the largest change in frequencies was observed in the modes where the vibrations of the metal ion had a large amplitude. The substitution of cobalt by nickel does not lead to the appearance of soft modes. This fact indicates that the structures of the solid solutions are stable.

 https://doi.org/10.1002/bab.2696

https://doi.org/10.1021/acs.jpcc.4c05812

This work delves into the processes leading to the evolution of nanofocusing plasmonic probes utilized in applications like tip-enhanced Raman spectroscopy, primarily under temperature growth. We identify stable crystallographic configurations of possible plasmonic tips that can withstand external influence, retain their original shape, and preserve their performance to enhance the local electromagnetic field under heat exposure. Employing molecular dynamics simulations, we study the behavior of plasmonic probes in the shape of sharp-edged gold nanotetrahedra as a case study. This makes it possible to observe the evolution of the shape and its impact on the light-concentrating performance of such probes. We identify the origin of shape instability and demonstrate that the migration of surface atoms from the tip area serves as the primary driver of shape variability in highly nonspherical plasmonic nanoparticles. By modeling the optical characteristics of the plasmonic probes utilizing the atomic discrete interaction model and finite element methods, we track alterations in the local electromagnetic field close to the apex of these gold nanotetrahedra at the plasmon resonance wavelength in the process of evolution. This analysis provides insight into the evolution of the field enhancement factor as the plasmonic tips degrade over time.

https://doi.org/10.1021/acsomega.4c02452

Two-dimensional (2D) chromium(III) sulfide has recently attracted increased attention from researchers due to its interesting electronic and magnetic properties and has great potential for application in spintronics and optoelectronics to create sensitive photodetectors. However, the synthesis of 2D Cr₂S₃ crystals is still a challenging task. At present, the mainly used method is vapor deposition, which is a poorly scalable, time-consuming, and expensive process. In this study, liquid-phase exfoliation of bulk chromium sulfide in different solvents (dimethyl sulfoxide (DMSO) and N-Methyl-2-pyrrolidone (NMP)) is demonstrated. It was found that exfoliation using an ultrasonic device with a titanium probe in both solvents produced Cr₂S₃ nanosheets with lateral dimensions ranging from 40 to 200 nm and thicknesses of about 10–15 nm (∼6–10 unit cells). Experiments have shown that under liquid-phase exfoliation (LPE) conditions, partial degradation and oxidation of solvents are observed, which has a significant effect on the exfoliation of chromium sulfide. In particular, it leads to partial hydrolysis and oxidation of 2D Cr₂S₃, as well as adsorption of solvent degradation and polymerization products on its surface, and affects the properties of the obtained material. These observations seem to be important in view of the further use of NMP and DMSO for the exfoliation of bulk nonlayered van der Waals crystals by LPE. A new understanding of the exfoliation process of non-van der Waals compounds based on the chemical interaction between the dispersion medium and the dispersed phase is proposed.

DOI: https://doi.org/10.1039/D4NR03144J

Two-dimensional materials with new physical phenomena are gaining popularity due to their unique properties. In recent years, a new family of layered compounds inspired by the minerals valleriite and tochilinite which are composed of alternating quasi-atomic sheets of transition metal chalcogenides (sulfides and selenides of Fe, Fe–Cu and other metals) and hydroxides of Mg, Al, Fe, Li, etc., assembled via electrostatic interaction, has arisen as a new synthetic platform for 2D materials. In this work, we synthesized a new promising material composed of alternating quasi two-dimensional sulfide Cu_4−xS₂ (x = 1–1.5) and hydroxide (Mg_1−yAl_y)(OH)₂ (y ∼ 0.25) sheets as multilayer flakes with a lateral size of 1–2 μm and a thickness of several tens of nm. The reliable formation of the material was ensured by an excess of aqueous sodium sulfide along with some quantity of Al salt, which was necessary for the self-assembly of the sulfide and hydroxide sheets driven by their opposite electric charges. A series of samples with varying Al/Mg ratios were examined using TEM, EDS, SAED, XRD, XPS, Raman and UV-vis-NIR spectroscopy. Using the Rietveld refinement procedure, the crystal lattice was determined to resemble the space group Pm1 with cell parameters a = b = 3.89 Å and a = b = 3.03 Å for sulfide and hydroxide parts, respectively, and the common parameter c = 12.03 Å. XPS and Raman spectra agree with the chalcocite-like sulfide layers containing Cu⁺ cations, monosulfide anions and few, if any, S–S bonds. UV-vis-NIR spectra show indirect transitions of 0.8 eV and considerable absorption in the near-infrared region. Thermogravimetry and differential scanning calorimetry studies under an Ar atmosphere suggest a slightly endothermic process and a phase transition at 90 °C accompanied, as suggested by conductivity measurements, by a metal–semiconductor transition; the main destruction with a loss up to 15 wt% occurs at ∼510 °C, due to decomposition of hydroxide layers similar to layered valleriite and tochilinite. The (thermo)electrical data show that, contrary to valleriite, which is an n-type semiconductor with mediocre thermoelectric performance, the proposed material is a heavily doped p-type semiconductor exhibiting good thermoelectric efficiency. The new member of the valleriite family of heterolayered quasi-2D materials demonstrates therefore essentially novel promising properties.

https://doi.org/10.1016/j.cjph.2024.10.032

The paper demonstrates the ability to manipulate diffraction order intensity by combining a geometric phase (Pancharatnam–Berry phase) metasurface and a Tamm plasmon polariton based structure. This combination enables the simultaneous occurrence of resonant and non-resonant variations in the phase of the reflected light. It is shown that, when a meta-atom composed of antimony trisulfide undergoes a transition from an amorphous to a crystalline state, accompanied by a change in the polarization of the incident light, there is a redistribution of intensity between 0 and ±1 diffraction orders.

https://doi.org/10.1016/j.chemphys.2024.112528

The work elucidates detailed analysis of X-ray near edge structure of Gd³⁺ ions using Synchrotron studies and deciphers the energy transfer mechanism involved in the stoichiometric ratio of (79-x)B₂O₃ + 10ZnO + 10BaO + xGd₂O₃ + 1Sm₂O₃ (BZBGS; x  = 0, 5, 10, 15, 20 mol.%) glasses. A detailed analysis of the glasses’ optical, structural, and luminescence properties were instigated to understand light emitting and scintillating behaviour. The oxidation state of Gd atom inside the glass found to be + 3. Stimulated emission cross section, radiative transition probability and branching of the metastable state of rare-earth ions were evaluated using Judd-Ofelt model and compared with other reported literature. Photo-Emission spectra were monitored at the UV-C band and X-rays. Luminescence was analysed with various excitation wavelengths and sources. Photoluminescence quantum yield show more than 22 % efficiency and show more than 15 % compared with other reported glasses. Luminescence intensity ratio was analysed and found that the Sm³⁺-ions do not occupy the inversion-symmetry which enhances the luminescence intensity in the present glass system. The CIE and CCT values were evaluated and discussed.

https://doi.org/10.1016/j.matlet.2024.137744

For the first time Ni₄₄Fe₁₉Ga₂₇Co₁₀ single crystals with high-temperature martensitic transformation (M_s = 336 K) and high-temperature superelasticity (373–548 K) under tension and compression were obtained after annealing at 1448 K for 6 h, followed by fast quenching in ice-cold salt water. The increase in temperature is associated with the precipitation of the large γ-particles and the substantial decrease in the precipitation of the nanosized ω-phase, which was observed in the single crystals after annealing at 1448 K for 1 h with slower water quenching.

https://doi.org/10.1016/j.jmmm.2024.172675

The interplay of the magnetically dead layer and structural defects in interacting ultrafine nickel ferrite (NiFe₂O₄) nanoparticles (<d> = 4 nm) have been investigated using transmission electron microscopy, X-ray diffraction, ⁵⁷Fe Mössbauer spectrometry, and static (dc) magnetization and dynamic (ac) susceptibility measurements. According to the magnetic measurement data, there are three magnetic subsystems in NiFe₂O₄ nanoparticles. The first subsystem with the lowest blocking (spin freezing) temperature (T_S = 8 K) involves atomic magnetic moments of magnetically disordered particles with a size of d < 4 nm. The other two subsystems are formed by magnetic moments of the cores of nanoparticles more than 4 nm in size and by correlated surface spins in nanoparticle clusters. The magnetic moments of the ferrimagnetically ordered cores are blocked at a higher temperature (∼40 K). It has been shown that the most significant contribution to the energy dissipation is made upon blocking of the correlated nanoparticle surface spins from the magnetically dead layer on the nanoparticle surface. The magnetic measurements have shown that the thickness of this layer is d_md ≈ 1 nm for a particle with a diameter of < d> = 4 nm. At the same time, the ⁵⁷Fe Mössbauer spectrometry study has revealed a structural disorder penetrating to a depth of up to d_cd ≈ 0.6 nm in a particle with a diameter of < d> = 4 nm. This evidence for a faster violation of the magnetic order than in the case of the crystal order upon moving away from the center of a particle to its periphery.

Two-dimensional materials with new physical phenomena are gaining popularity due to their unique properties. In recent years, a new family of layered compounds inspired by the minerals valleriite and tochilinite which are composed of alternating quasi-atomic sheets of transition metal chalcogenides (sulfides and selenides of Fe, Fe–Cu and other metals) and hydroxides of Mg, Al, Fe, Li, etc., assembled via electrostatic interaction, has arisen as a new synthetic platform for 2D materials. In this work, we synthesized a new promising material composed of alternating quasi two-dimensional sulfide Cu_4−xS₂ (x = 1–1.5) and hydroxide (Mg_1−yAl_y)(OH)₂ (y ∼ 0.25) sheets as multilayer flakes with a lateral size of 1–2 μm and a thickness of several tens of nm. The reliable formation of the material was ensured by an excess of aqueous sodium sulfide along with some quantity of Al salt, which was necessary for the self-assembly of the sulfide and hydroxide sheets driven by their opposite electric charges. A series of samples with varying Al/Mg ratios were examined using TEM, EDS, SAED, XRD, XPS, Raman and UV-vis-NIR spectroscopy. Using the Rietveld refinement procedure, the crystal lattice was determined to resemble the space group Pm1 with cell parameters a = b = 3.89 Å and a = b = 3.03 Å for sulfide and hydroxide parts, respectively, and the common parameter c = 12.03 Å. XPS and Raman spectra agree with the chalcocite-like sulfide layers containing Cu⁺ cations, monosulfide anions and few, if any, S–S bonds. UV-vis-NIR spectra show indirect transitions of 0.8 eV and considerable absorption in the near-infrared region. Thermogravimetry and differential scanning calorimetry studies under an Ar atmosphere suggest a slightly endothermic process and a phase transition at 90 °C accompanied, as suggested by conductivity measurements, by a metal–semiconductor transition; the main destruction with a loss up to 15 wt% occurs at ∼510 °C, due to decomposition of hydroxide layers similar to layered valleriite and tochilinite. The (thermo)electrical data show that, contrary to valleriite, which is an n-type semiconductor with mediocre thermoelectric performance, the proposed material is a heavily doped p-type semiconductor exhibiting good thermoelectric efficiency. The new member of the valleriite family of heterolayered quasi-2D materials demonstrates therefore essentially novel promising properties.

https://doi.org/10.1134/S0021364024602896

It has been shown that stray fields of a superconducting Pearl vortex can form bound states with high-order magnetic skyrmions due to orbital effects of an inhomogeneous magnetic field. By analogy with recent results for skyrmions with the topological charge |Q| = 1 [E. S. Andriyakhina, S. Apostoloff, and I. S. Burmistrov, JETP Lett. 116, 825 (2022)], the centers of high-order magnetic skyrmions in such bound states can be shifted with respect to the center of the superconducting vortex. It has been shown that ponderomotive forces acting on the simplest high-order magnetic skyrmions with the topological charge |Q| = 2 tend to form noncoaxial bound states.

https://doi.org/10.1134/S0021364024603075

Single and polycrystalline samples of Mg_{2 – x}Mn_{1 + x}BO₅ (x = 0.0, 0.2, 0.4) oxyborates have been obtained for the first time by spontaneous crystallization from the solution–melt and through a solid-state reaction. X-ray diffraction studies have shown that compounds are crystallized with increasing manganese content in the ludwigite (space group Pbam)–hulsite (space group P2/m)–orthopinakiolite (space group Pbam) series and belong to the “3 Å wallpaper” borate family. A common property of materials is the presence of octahedral complexes (walls) consisting of manganese ions with a mixed valence at even crystallographic sites. The dc magnetization and specific heat of the Mg_{2 – x}Mn_{1 + x}BO₅ (x = 0.0, 0.2, 0.4) compounds have been studied for the first time. These studies have shown that cooling is accompanied by magnetic transitions, which are due to the ordering of several magnetic subsystems.

https://doi.org/10.1134/S0021364024603002

It is shown that the experimentally detected features in the low-temperature behavior of the magnetization in an external magnetic field perpendicular to the layers of manganese ions of the topological antiferromagnet MnBi₂Te₄ are due to quantum effects induced by the off-diagonal nature of the trigonal component of the crystal field. In this case, the anomalous increase in the magnetization of the material before the spin-flop transition, as well as after it in the phase of “collapsed” sublattices, is explained by the suppression of contributions from quantum effects. The comparison of the results of the theoretical analysis with experimental data has made it possible to refine the parameters of the effective spin model of MnBi₂Te₄ and to establish the important role of the noted trigonal component.

https://doi.org/10.1016/B978-0-443-22232-0.00007-1

Water pollution remains a pressing global concern, with far-reaching implications for public health and the environment. To address this challenge, researchers have explored innovative approaches to develop efficient and sustainable water purification technologies. Soft nanoferrites, a class of magnetic nanomaterials, have emerged as promising candidates for advanced water treatment due to their unique properties and versatile applications. Soft nanoferrites are characterized by their high surface area, excellent magnetic properties, and tunable surface chemistry, making them ideal candidates for removing a wide range of contaminants from water sources. These contaminants include heavy metals, organic pollutants, and pathogens, which pose significant threats to both human health and aquatic ecosystems. This chapter delves into the synthesis methods and functionalization strategies employed to tailor soft nanoferrites for specific water purification applications. Additionally, it explores the mechanisms underlying the adsorption, catalytic degradation, and magnetic separation processes that facilitate the efficient removal of contaminants from water matrices. Soft nanoferrite−based water purification technologies, including their integration into multifunctional filtration systems, magnetically assisted separation processes, and sustainable regeneration approaches using soft nanoferrites in water treatment processes are also discussed. These innovations offer the potential to revolutionize water treatment by providing cost-effective, energy-efficient, and environmentally friendly solutions for addressing water pollution challenges. This chapter provides an insight into the key developments, challenges, and prospects of this emerging field, emphasizing the potential of soft nanoferrites to play a pivotal role in ensuring access to clean and safe water resources worldwide.

https://doi.org/10.1016/j.ceramint.2024.11.048

A representative series of samples consisting of fine ε-Fe₂O₃ nanoparticles uniformly distributed over the SiO₂ xerogel matrix with an iron oxide content of 5–33 wt % has been synthesized and studied by mutually complementary physical methods. It has been shown by the X-ray diffractometry and high-resolution electron microscopy examination that, with increasing iron oxide concentration, the average particle size <d> increases from 4 to 11 nm. According to the X-ray diffractometry and Mӧssbauer spectroscopy data, the samples with an iron oxide content of 5–20 wt % are single-phase, while at the highest Fe₂O₃ concentration (33 wt %), the β-Fe₂O₃ and α-Fe₂O₃ phases arise. As the average particle size <d> increases, a monotonic increase in coercivity H_C and remanent magnetization M_R of the synthesized systems at room temperature is observed, which is indicative of their magnetic hysteresis. The magnetic transition known to occur in the ε–Fe₂O₃ oxide manifests itself in all the investigated samples as a drastic change in the H_C and M_R values at 150–75 K. At the same time, a thorough analysis of the temperature dependence of the real part of the ac magnetic susceptibility χ′ has shown that the particles with a size smaller than a critical value of d_C ∼6.5 nm do not undergo the magnetic transition and have a much lower magnetic anisotropy constant as compared with coarser particles (d > d_C). It has been found that, in the low-temperature region, the magnetic moments of these fine particles experience superparamagnetic blocking. It has been established that the size effects that arise in ultra-fine ε–Fe₂O₃ particles has a serious impact on the macroscopic magnetic properties of the highly dispersed systems based on them.

 https://doi.org/10.3390/su16219606

In this article, the authors developed a novel method for the moisture mapping of the soil surface of agrophytocenosis using a neural network based on synchronized radar and multispectral optoelectronic data from Sentinel-1,2. The significance of this research lies in its potential to enhance precision farming practices, which are increasingly vital in addressing global agricultural challenges such as water scarcity and the need for sustainable resource management. To verify the developed method, data from two experimental plots were utilized. These plots were located on irrigated soybean crops, with the first plot situated on the right bank (plot No. 1) and the second on the left bank (plot No. 2) of the lower Volga River. Two experimental soil moisture geodatasets were created through measurements and geo-referencing points using the gravimetric method (for plot No. 1) and the proximal sensing method (for plot No. 2) employing the Soil Moisture Sensor ML3-KIT (THETAKIT, Delta). The soil moisture retrieval algorithm was based on the use of a neural network to predict the reflection coefficient of an electro-magnetic wave from the soil surface, followed by inversion into soil moisture using a dielectric model that takes into account the soil texture. The input parameter of the neural network was the ratio of the microwave radar vegetation index (calculated based on Sentinel-1 data) to the index (calculated based on the data of multispectral optoelectronic channels 8 and 11 of Sentinel-2). The retrieved soil moisture values were compared with in situ measurements, showing a determination coefficient of 0.44–0.65 and a standard deviation of 2.4–4.2% for plot No. 1 and similar metrics for plot No. 2. The conducted research laid the groundwork for developing a new technology for remote sensing of soil moisture content in agrophytocenosis, serving as a crucial component of precision farming systems and agroecology. The integration of this technology promotes sustainable agricultural practices by minimizing water consumption while maximizing crop productivity. This aligns with broader environmental goals of conserving natural resources and reducing agricultural runoff. On a larger scale, data derived from such studies can inform policy decisions related to water resource management, guiding regulations that promote efficient water use in agriculture.

https://doi.org/10.1016/j.mtcomm.2024.109623

Utilizing density functional theory (DFT), we embarked on a comprehensive investigation of the structural, electronic, and optical properties characteristic of the ferroelectric hybrid (Me2NH2)[NaFe(CN)5(NO)] crystal. The geometry of the crystal structure in the ���21 phase was optimized. We simulated the electronic band structure within the first Brillouin zone. The calculated band gap for the indirect U-X transition is 2.401 eV, indicative of a wide band gap semiconductors. We also simulated the density of electronic states across the Brillouin zone. The simulation of the electronic structure revealed that the crystal comprises both ionic and covalent bonds. We accurately predicted various optical parameters including the dielectric function, conductivity, reflectivity, loss function, absorption, and refractive index. The reflectivity of the crystal does not exceed 21 percent. All calculated optical properties of the (Me2NH2)[NaFe(CN)5(NO)] crystal are anisotropic.

https://doi.org/10.1515/nanoph-2024-0475

We present a solution to a longstanding challenge in nanoplasmonics and colloid chemistry: the anomalous optical absorption of noble metal nanoparticles in the ultrafine size range of 2.5–10 nm, characterized by a rapid long-wavelength shift in plasmon resonance as the particle size increases. Our investigation delves into the impact of alterations in electron density along the radial direction of nanoparticles and the resulting variations in dielectric constants on the spectral positioning of the plasmon resonance. We explore the interplay of the spill-out effect, volumetric compression, and their combined impact in different experimental conditions on electron density variation within the particle volume and its blurring at the particle boundary. The latter effectively forms a surface layer with altered dielectric constants and a size-independent extent. As particle size decreases, the influence of the surface layer becomes more pronounced, especially when its extent is comparable to the particle radius. These findings are specific to ultrafine plasmonic nanoparticles and highlight their unique properties.