New Publications

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.

https://doi.org/10.3390/nano14211705

The properties of circularly polarized light has recently been used to selectively reflect chiral metasurfaces. Here we report the more complete basic functionalities of reflectors and absorbers that display various optical phenomena under circularly polarized light at normal incidence as before. For the chiral metamirrors we designed, the circular dichroism in about 0.4 reflection is experimentally observed in visible wavelengths. The experimental results also show high reflectance for right-handed circular polarization with preserved handedness and strongly absorbed left-handed circular polarization at chiroptical resonant wavelengths. By combining a nanobrick and wire grating for our design, we find and offer a new structure to demonstrate the superposition concept of the phase in the same plane that is helpful in effectively designing chiral metamirrors, and could advance development of their ultracompact optical components.

https://doi.org/10.1016/j.molliq.2024.126383

We present a cholesteric liquid crystal (CLC) smart window with both passive and active control mechanisms, capable of reversible thermo-optical switching from high-transmission to low-transmission states as the temperature increases. By incorporating a mixture of a thermoresponsive chiral dopant and a left-handed chiral dopant into dual-frequency liquid crystal (DFLC), we have produced thermosensitive CLC that exhibit weak left-handed chirality at low temperature and enhanced left-handed chirality at rising temperature. This change in chirality strength results in increasing thickness-to-pitch ratio as the ambient temperature increases, transforming the CLC texture from the homeotropic to fingerprint state. Additionally, we doped a dichroic dye into the thermosensitive CLC to promote the contrast ratio between the high-transmission homeotropic and low-transmission fingerprint optical textures. Simultaneously, dielectric anisotropy in the host DFLC at different frequencies allows for adjustable switching temperature and varying transparency level. This advancement in smart window technology offers more control options and holds significant potential for practical applications.

https://doi.org/10.1016/j.jmmm.2024.172613

Absorption and magnetic circular dichroism (MCD) spectra have been studied in the region of ⁵I₈ → ⁵F₂, ⁵S₂, ⁵F₃, and ⁵F₅ absorption bands of the Ho³⁺ ion and in the region of ⁴I_9/2→⁴G_7/2, ²K_13/2, ⁴S_3/2, ⁴F_7/2, ⁴F_5/2 and ²H_9/2 absorption bands of the Nd³⁺ ion in an antiferromagnetic trigonal crystal Ho_0.75Nd_0.25Fe₃(BO₃)₄ in the temperature range from 5 to 90 K. A qualitative change in the shape of the MCD spectra of Ho³⁺ ion was revealed during the spin-reorientation transition at T_R = 6.9 К. Below T_R, in the easy-axis state of the crystal, the MCD spectrum has a shape typical for paramagnets, i.e., it consists of diamagnetic and paramagnetic parts. Just above T_R, in the easy-plane state of the crystal, MCD of Ho³⁺ ion has a spectrum similar to the absorption spectrum, which is typical for the paramagnetic part of the MCD. It was shown, that in the easy-plane state the exchange field of iron, being perpendicular to the external field directed along the C₃ axis, quenches the usual paramagnetic and diamagnetic MCD in Ho³⁺ ion, but creates a condition for the appearance of a large paramagnetic MCD of mixing (B-term). With temperature increasing, the MCD spectrum of Ho³⁺ ion gradually turns into a spectrum typical for paramagnets with the predominance of the sign-changing diamagnetic part, because the influence of the exchange field decreases. The shape of the MCD spectra of Nd³⁺ ions are typical for paramagnets but does not change during the reorientation transition in the rest of the crystal. This means that the magnetic moment of the Nd³⁺ ion does not make a reorientation transition simultaneously with the Fe³⁺ and Ho³⁺ ions of the rest of the crystal. This phenomenon is accounted for by a strong local magnetic anisotropy of the Nd³⁺ ion and by a weak exchange interaction Fe-Nd, which is not enough for rotation of the Nd³⁺ ion moment synchronously with that of the Fe³⁺ ion. The magneto-optical properties of neodymium are controlled by the easy-axis anisotropy of neodymium.

https://doi.org/10.1016/j.ssc.2024.115747

The effect of an electric field on thermal and dielectric properties as well as electrocaloric response in the ferroelectric NH₄HSeO₄ has been studied using a universal multifunctional adiabatic calorimeter. The phase transition temperature between the ferroelectric and incommensurate phases is found to be highly sensitive to the electric field, dT₂/dE ≈ 1.6 K/(kV/cm), at a low electric field strength. The intensive electrocaloric effect at E = 1.35 kV/cm observed by direct measurements, ΔT_AD ≈ 0.045 K, as well as determined indirectly by analyzing the entropy-temperature-electric field phase diagram, ΔT_AD ≈ 0.03 K, is quite large compared to the effects in other ferroelectrics.

https://doi.org/10.1016/j.physb.2024.416664

We report on the results of experimental and theoretical studies of magnetic superlattices [(CoP)_soft/(NiP)_am/(CoP)_hard/(NiP)_am]_n (n = 1, 5, 10, 15, 20, 40, t_CoP = 5 nm, t_NiP = 2 nm) produced by electroless deposition method. Cross-section electron microscopy image shows the layers do not mix and the interfaces between the layers are not blurred. We found the behavior of the magnetic hysteresis loops is similar to the exchange spring. Three peaks of microwave absorption are observed in the electron magnetic resonance spectra. To explain this, a model of a three-sublattice magnet with long-range interlayer interaction due to magnetic proximity effect is proposed. A perpendicular magnetic anisotropy is formed at the interface between the magnetic and non-magnetic layers. The interlayer interaction between the nearest magnetically soft and hard (J₁) layers is found to be negative, the interaction between magnetically soft layers (J₂) is positive, while J₁ is about an order of magnitude greater than J₂.

https://doi.org/10.1016/j.ceramint.2024.10.351

Rare earth doped SrTiO₃ is one of the most promising oxide materials meeting the safety and stability requirements for potential applications in thermoelectric converters. This work aims to assess the feasibility of engineering SrTiO₃-based materials to improve their thermoelectric performance. A comparative analysis of the thermoelectric properties of Sr_0.925Dy_0.075TiO₃ ceramic samples obtained from preliminarily mechanically activated Sr_0.925Dy_0.075TiO₃ nano-powder by two methods – solid-state reaction synthesis and spark plasma sintering – was carried out. Significant differences in the morphology of the samples lead to significant differences in the temperature dependences of electrical resistivity and the Seebeck coefficient. Ceramics obtained by solid-state reaction synthesis exhibit lower porosity and lower electrical resistivity. The thermoelectric power factor of such ceramics is 2–3 times higher than that of samples obtained by spark plasma sintering. The obtained value of thermoelectric figure of merit ZT = 0.41 at T = 673 K for Sr_0.925Dy_0.075TiO₃ is the highest value among n-type oxide thermoelectric ceramics at a given temperature and maintains a tendency to increase with increasing temperature.

https://doi.org/10.3390/molecules29204846

Nickel manganese oxide (NiMnO₃) combines magnetic and dielectric properties, making it a promising material for sensor and supercapacitor applications, as well as for catalytic water splitting. The efficiency of its utilization is notably influenced by particle size. In this study, we investigate the influence of thermal treatment parameters on the phase composition of products from alkali co-precipitation of nickel and manganese (II) ions and identify optimal conditions for synthesizing phase-pure nickel manganese oxide. Ultrafine nanoparticles of NiMnO₃ (with sizes as small as 2 nm) are obtained via liquid-phase ultrasonic dispersion, exhibiting a narrow size distribution. A systematic exploration of the solvent nature (water, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide) on the efficiency of ultrasonic dispersion of NiMnO₃ nanoparticles is provided. It is demonstrated that particle size is influenced not only by absorbed acoustic power, dependent on the physical properties of the used solvent (boiling temperature, gas solubility, viscosity, density) but also by the chemical stability of the solvent under prolonged ultrasonic treatment. Our findings provide insights for designing ultrasonic treatment protocols for nanoparticle dispersions with tailored particle sizes

DOI: 10.23919/INC-USNC-URSI61303.2024.10632342

Accelerated technological progress responds to the dynamic evolution of wireless communication systems, fueled by the advent of 5G, the emergence of 6G, and the pervasive integration of the IoT paradigm. Smart antennas play a pivotal role in this advancement, facilitating electronic beam steering to meet escalating demands for enhanced bandwidth and elevated operating frequencies. The spotlight shifts to reconfigurable reflectarray antennas, gaining prominence over conventional phased arrays. Notably, liquid crystals (LCs) emerge as a promising avenue for creating electronically reconfigurable/switchable reflectarrays, specifically tailored for short millimeter and terahertz waves. LCs, as a unique aggregate state combining solid and liquid features, address current technology limitations. Their uniaxial nature and the ability to manipulate molecule orientation enable effective fine-tuning of dielectric permittivity without drawbacks present in existing technologies.

https://doi.org/10.1016/j.ceramint.2024.10.141

In this work, a novel type of ultrafiltration ceramic membranes with the support based on fine fly ash microspheres and selective layer based on the alumina nanofibers with an aluminosilicate binder is proposed. The average pore sizes of the support and selective layer are 0.46 μm and 29 nm, respectively. The membrane is characterized by the compressive strength of 96 MPa and water permeability of 207 L m⁻² h⁻¹ bar⁻¹. It is shown that the binder provides structural stability of selective layer and adhesion to the support. With increasing the binder content, the water permeability increases, reaches maximum, and then slightly decreases. The developed membranes are used for ultrafiltration of Blue Dextran dyes aqueous solutions with molecular weights of 70 kDa and 500 kDa and concentrations of 50 and 100 mg/L. The dyes rejection varies in the range 97–99 %, while the permeate flux is 100–140 L m⁻² h⁻¹ at the transmembrane pressure of 4 bars. The dye retention occurs via adsorption at the initial stage, which leads to the narrowing of pore size. Further, the dye filtration proceeds mainly due to size effects. The proposed membranes can be employed for dye removal from wastewater, and also allow chemical modification by carbon coating to be employed in electrochemically assisted ultrafiltration. The developed methodology promotes the recycling of thermal energy waste and introduces novel approaches to combine waste and synthesized raw materials in the production of low-cost ceramic membranes.

https://doi.org/10.1016/j.solidstatesciences.2024.107725

The traditional solid-state synthesizing method was employed to prepare Tl_5-xK_xLuZr(MoO₄)₆ (x = 0; 0.1; 0.2; 1; 2) ceramics. Structural characterization was performed through the Rietveld method on the X-ray powder diffraction data. The unit cell parameters are defined for Tl_5-xK_xLuZr(MoO₄)₆ (x = 0; 0.1; 0.2; 1; 2). Impedance spectra were measured at temperatures ranging from 300 to 800 K, covering a frequency range of 1 Hz to 1 MHz. The results show that the electrical conductivity decreases with an incrementing in the x value in the range of x = 0.1–2.0. Tl_4.9K_0.1LuZr(MoO₄)₆ has the best ionic conductivity of this series of molybdates (1.31 × 10⁻³ S cm⁻¹₎, and Tl₅LuZr(MoO₄)₆ has the lowest conductivity (5.51 × 10⁻⁴ S cm⁻¹₎. Activation energy was found out to decrease from 1.32 eV for Tl₅LuZr(MoO₄)₆ to 0.92 eV for Tl_4.9K_0.1LuZr(MoO₄)_6.

https://doi.org/10.1002/adfm.202413524

Hybrid metal halides (HMHs) with time-resolved luminescence behavior promise to be a breakthrough in multi-level anti-counterfeiting, but controlling the dynamic switching between phosphorescence and fluorescence is extremely challenging. Herein, an array of 0D HMHs is constructed by screening the π-conjugated ligand with room-temperature phosphorescence (RTP). Compared to the organic chromophore, (ETPP)₂ZrCl₆ possesses a misaligned stacking and rigid structure, contributing to an improved phosphorescence quantum yield (Φ_P = 27.50%) and an extended phosphorescence lifetime (τ = 0.6234 s), as the intervening of inorganic unit [ZrCl₆]²⁻ suppresses the energy losses caused by nonradiative relaxation and prompts the intersystem crossover (ISC) process. Not only that, the interplay of phosphorescence-fluorescence dual-mode emission can be intelligently controlled by doping the active metal Te⁴⁺, resulting in a dynamic switching between RTP phosphorescence and self-trapped exciton (STE) fluorescence. DFT calculations reveal the governing origins of RTP-STE from the intermolecular ISC channels and spin-orbit coupling (SOC) coefficients. These precise images into periodic pixelated arrays enable the multi-level anti-counterfeiting and information encryption. This work proposes a fluorescence-phosphorescence co-modulating strategy under the premise of dissecting the structural origins for optimizing RTP phosphorescence, which paves the way for designing high-security-level anti-counterfeiting materials.

https://doi.org/10.3390/s24196308

Multilayered [Cu(3 nm)/FeNi(100 nm)]₅/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/[Cu(3 nm)/FeNi(100 nm)]₅ structures were obtained by using the magnetron sputtering technique in the external in-plane magnetic field. From these, multilayer magnetoimpedance elements were fabricated in the shape of elongated stripes using the lift-off lithographic process. In order to obtain maximum magnetoimpedance (MI) sensitivity with respect to the external magnetic field, the short side of the rectangular element was oriented along the direction of the technological magnetic field applied during the multilayered structure deposition. MI sensitivity was defined as the change of the total impedance or its real part per unit of the magnetic field. The design of the elements (multilayered structure, shape of the element, etc.) contributed to the dynamic and static magnetic properties. The magnetostatic properties of the MI elements, including analysis of the magnetic domain structure, indicated the crucial importance of magnetostatic interactions between FeNi magnetic layers in the analyzed [Cu(3 nm)/FeNi(100 nm)]₅ multilayers. In addition, the uniformity of the magnetic parameters was defined by the advanced technique of the local measurements of the ferromagnetic resonance field. Dynamic methods allowed investigation of the elements at different thicknesses by varying the frequency of the electromagnetic excitation. The maximum sensitivity of 40%/Oe with respect to the applied field in the range of the fields of 3 Oe to 5 Oe is promising for different applications.

https://doi.org/10.1007/s10570-024-06212-0

The results of the study of plastic composites from degradable poly(3-hydroxybutyrate) P(3HB) and cellulose-containing natural materials of various origins are presented. For the first time, P(3HB) composites filled with bacterial nanocellulose (BNC) or wood (Pinus sibirica) flour (WF) were produced by melt pressing at 170 °C and 2000 Pa. The influence of the filler type and amount (30, 40, 50, 70 and 90 wt%) on the physicochemical and mechanical properties of the composites and their degradability in soil laboratory microcosms was revealed. The P(3HB)/WF composites compared with P(3HB)/BNC ones were thermally stable; their thermal degradation temperatures were 266 and 227 °C, respectively. Both composites had lower values of Young's modulus and fracture strength compared to P(3HB). As BNC content was increased, Young's modulus and fracture strength of the composites increased from 1831 to 14 MPa to 3049 and 19 MPa, in contrast to P(3HB)/WF, where the values decreased by a factor of 1.5–2.0. The half-life of composites with BNC and WF in soil was 180 and 220 days, respectively. Changes in the structure of the microbial community were determined as depending on the filler type; primary destructors among bacteria and fungi were isolated and identified. Environmentally friendly and completely degradable composites show promise as cellulose-plastic materials for practical application.

https://doi.org/10.3390/rs16193547

In this paper, the advantages of the joint use of MHz- and GHz-frequency band impulses when employing contactless ground penetration radar (GPR) for the remote sensing of biomass, the height of the wheat canopy, and underlying soil moisture were experimentally investigated. A MHz-frequency band nanosecond impulse with a duration of 1.2 ns (average frequency of 750 MHz and spectrum bandwidth of 580 MHz, at a level of –6 dB) was emitted and received by a GPR OKO-3 equipped with an AB-900 M3 antenna unit. A GHz-frequency band sub-nanosecond impulse with a duration of 0.5 ns (average frequency of 3.2 GHz and spectral bandwidth of 1.36 GHz, at a level of −6 dB) was generated using a horn antenna and a Keysight FieldFox N9917B 18 GHz vector network analyzer. It has been shown that changes in the relative amplitudes and time delays of nanosecond impulses, reflected from a soil surface covered with wheat at a height from 0 to 87 cm and fresh above-ground biomass (AGB) from 0 to 1.5 kg/m², do not exceed 6% and 0.09 ns, respectively. GPR nanosecond impulses reflected/scattered by the wheat canopy have not been detected. In this research, sub-nanosecond impulses reflected/scattered by the wheat canopy have been confidently identified and make it possible to measure the wheat height (fresh AGB up to 2.3 kg/m² and height up to 104 cm) with a determination coefficient (R²) of ~0.99 and a bias of ~−7 cm, as well as fresh AGB where R² = 0.97, with a bias = −0.09 kg/m², and a root-mean-square error of 0.1 kg/m². The joint use of impulses in two different MHz- and GHz-frequency bands will, in the future, make it possible to create UAV-based reflectometers for simultaneously mapping the soil moisture, height, and biomass of vegetation for precision farming systems.