New Publications

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.

https://doi.org/10.1016/j.optmat.2024.116247

The polarized absorption spectra of the HoAl₃(BO₃)₄ single crystal were studied in the region of f–f transitions ⁵I₈→⁵F₅, ⁵S₂ + ⁵F₄, ⁵F₃ and ⁵F₂ inside the 4f shell of the holmium ion as a function of temperature in the range of 5–90 K. In a number of absorption lines the splitting which are not provided by the local point group D₃ symmetry of holmium ion in the crystal are found. This phenomenon is explained by local changes in the structure in both the excited and ground states of holmium under the influence of a perturbation caused by a photon. This perturbation mixes the ground and excited states and changes the interaction of the atom with its environment. It was also shown that the magnitude of the splitting depends on the polarization of the incident light and on the temperature of the sample.

https://doi.org/10.1080/00150193.2024.2305092

The article presents the results of studies of theBaMg_1/3Ta_2/3O₃ (BMT) complex perovskite crystal using Raman spectroscopy and density functional theory (DFT) calculation. The polarized Raman spectra of a cubic BMT single crystal are obtained in two different geometries in a broad temperature range (5–580 K). The density functional theory calculations of the lattice dynamics and vibrational spectra of the BMT crystal in the Г point of the trigonal phase are carried out. The simulated Raman spectra are analyzed in comparison with the experimental spectra of cubic single crystals and those of ceramics in the trigonal phase. The Raman spectra peculiarities are observed and explained.

https://doi.org/10.1080/00150193.2024.2305091

BaMg_1/3Ta_2/3O₃ (BMT) crystals belong to the family of complex perovskites and are well known for their excellent microwave dielectric properties. In this work, structural optimization of the lattice parameters was performed. Electron density functional theory calculations of the electronic band structure of BMT crystal of the trigonal phase were carried out along Г–A–K–M–L directions of the Brillouin zone. The calculated band gap energy was 3.554 eV. The partial density of states of BMT crystal in P-3 m1 phase was simulated. Top of the valence band was formed by 2p-states of O and bottom of the conduction band – by 5d-states of Ta.

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/10.1111/jace.20155

Despite being the key component in modern electronic devices or power systems, ceramic dielectric capacitors have drawbacks like low energy storage density and efficiency that limit their extensively wide application. This work adopted a different route to improve energy storage performance compared with the frequently utilized composition modification. 0.98Ba_0.65Sr_0.245Bi_0.07TiO₃-0.02Ce Pb-free ceramics with different polyvinyl alcohol (PVA) contents were prepared through viscous polymer processing. The rheological and energy-storing performance were systematically studied. It can be seen that high PVA content results in more pores and larger grain sizes that will deteriorate the breakdown strength of ceramics. The highest breakdown strength reached 420 kV/cm while the concentration of PVA was 5 wt%. The mechanism of grain sizes on breakdown strength is studied by electrical tree simulation based on COMSOL. Viscous polymer processing with proper PVA content is very effective in generating dense and homogenous structures. Finally, the ceramic with 5 wt% PVA possesses a high density of up to 4.41 J/cm³ and an efficiency of about 84.21% at 420 kV/cm. Simultaneously, this ceramic improved stability of both temperature (30–150°C) and frequency (1–300 Hz) at 350 kV/cm, while the η kept above 90% and W_rec exceeding 3.6 J/cm³.

https://doi.org/10.1080/01431161.2024.2408036

In this paper, the changes in the character of time shapes, amplitudes, frequency spectra, and time delay of ultra-wideband (UWB) impulses (duration of 0.33 ns) reflected from the layer of wet sand with a rough upper boundary were investigated. It was shown that the attenuation of UWB impulse amplitude, which is reflected from the upper rough boundary of the sand layer, can be described by the model of Fresnel reflection coefficient for a smooth surface using the Gaussian correction factor (FRGC). At this root-mean-square (RMS), height of soil surface roughness was in the range of ~0–21 mm, but the determination coefficient and RMS error (RMSE) were found to be equal to 0.94 and 0.02, respectively. An experiment close to linear increase/decrease in the propagation time of impulses reflected from the upper/lower boundary of the layer, respectively, was found with increasing the RMS heights of upper boundary. It is shown that the propagation time of such impulses can be described by the modified FRGC model with an error from RMSE = 0.09 ns to RMSE = 0.15 ns. The results of these findings are of practical importance for the interpretation of remote sensing data for precise soil moisture measurements from unmanned aerial vehicle platforms using UWB impulses.

https://doi.org/10.48550/arXiv.2408.16203

The relation of the magnetically dead layer and structural defects in ultrafine interacting NiFe2O4 nanoparticles (<d> = 4 nm) have been investigated using transmission electron microscopy, X-ray diffraction, ^57Fe Mössbauer spectroscopy, and dc magnetization and ac susceptibility measurements. According to the magnetic data, we found out three magnetic subsystems in NiFe2O4 nanoparticles. The first one with the lowest blocking (spin freezing) temperature (TS = 8 K) established by atomic magnetic moments of magnetically disordered particles with the d < 4 nm. The other two subsystems are formed by the magnetic moments of the "core" of nanoparticles having size more than 4 nm and correlated surface spins in nanoparticle clusters, correspondingly. Magnetic moments of ferrimagnetically ordered "core" are blocking at a higher temperature ( \approx 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 nanoparticles' surface. By the magnetic data, the thickness of this layer is dmd \approx 1 nm for a particle with the <d> \approx 4 nm. At the same time or meanwhile, the ^57Fe Mössbauer spectroscopy has revealed a structural disorder penetrating to a depth of up to dcd \approx 0.6 nm in a particle with <d> = 4 nm. This evidences for a faster destruction of the magnetic order as compared with the crystal order upon moving away from the center of a particle to its periphery.

https://doi.org/10.1134/S1063784224070041

Study of the mechanisms of the solid-state reactions in Sn/Fe/Cu thin films is interesting both from a fundamental point of view and from a view of the importance of emerging intermetallics in the technology of solder joints and thin-film lithium-ion batteries. By the integrated approach, including both X-ray phase analysis and local elemental analysis of the cross-sections of the films, the phase composition and the mutual arrangement of phases were studied, at various stages of the solid-state reaction occurring at different temperatures. The observed sequence of the appearing phases differs significantly from the expected one if the mass transfer took place by a volume diffusion through the forming layers.

https://doi.org/10.1007/s10854-024-13521-4

The magnetic, transport and acoustic properties of materials Tm_XMn_1−XSe (0.025 ≤ X ≤ 0.2) have been studied in magnetic fields of up to 12 kOe at temperatures of 80‒600 K. The magnetic phase transition temperatures (T_N) and change in the sign of resistance at DC current in vicinity of the T_N were established. The temperature and concentration ranges corresponding to the maximum magnetoresistance (− 50% for X = 0.025) and magnetoimpedance (12% for X = 0.2) have been determined. The mechanism of relaxation has been established from the impedance spectrum and the activation energy change upon temperature and concentration has been found. The difference between the dc and ac magnetoresistances has been disclosed. The concentration range with hole and electron type carriers is determined. The mobility anomalies in the vicinity of the valence transition have been established. It is shown that the current and electrical resistance in the Tm_XMn_1−XSe compound can be manipulated by ultrasound and a magnetic field. A qualitative difference between the interaction of current and ultrasound in the magnetically ordered and paramagnetic regions is found

https://doi.org/10.1016/j.solidstatesciences.2024.107703

Calorimetric, dilatometric and pressure studies of (NH₄)₃WO₂F₅ were performed over a wide temperature range, including the Pm-3m ↔ Pa-3 phase transition. Comparison of the obtained results with data for related fluorides (NH₄)₃SnF₇ and (NH₄)₃TiF₇ undergoing the same structural changes showed a significant role of chemical pressure in the formation of thermal and barocaloric properties. A decrease in anomalous entropy in oxyfluoride, ΔS₀ = 12.2 J/mol·K, is accompanied by a significant increase in sensitivity to hydrostatic pressure, dT₀/dp = 93 K/GPa, the preservation of a large change in anomalous deformation δ(ΔV/V)₀ = 0.45 % and a small temperature hysteresis, δT₀ < 1 K. This combination of thermal characteristics has led to both a significant increase in extensive and intensive barocaloric parameters in the low pressures area, and to their high reversibility in the modes of increasing and decreasing pressure.

 https://doi.org/10.1002/lpor.202401089

DOI: 10.18083/LCAppl.2024.3.71

The magnetic susceptibility and diamagnetic anisotropy of the mixtures of nematic 5CB with chlorophyll a (Chl. a), chlorophyll b (Chl. b) and carotenoids, which were synthesized in the form of extracts, with different concentrations of components have been studied. The pigments were extracted from finely ground powder of air-dried biomass of the aquatic plant Ceratophyllum demersum L., grown from a laboratory culture. The probable configuration of the molecules of substances in a magnetic field was considered. Taking into account the orientational features of the liquid crystal 5CB, the expressions for the diamagnetic anisotropy of its mixtures with various extracts were derived. Using the Faraday method, with the direct measurement of the force acting on a mixture in a magnetic field, the dependences of longitudinal and transverse components of the magnetic susceptibility and diamagnetic anisotropy of the mixtures on temperature were obtained. The amplitude differences in the temperature dependences of diamagnetic anisotropy for various mixtures were analyzed. The influence of currents in benzene rings of the liquid crystal and in conjugated aromatic porphyrin macrocycles, as well as in aliphatic chains of organic molecules on diamagnetic anisotropy was estimated

 https://doi.org/10.3390/met14090991

The present study considers the samples of an Ti-6Al-4V alloy obtained by selective laser melting with the addition of a 10% Cu-Al powder mixture. The microstructure, elemental composition and phase composition, as well as the physico-chemical properties, have been investigated by the methods of electron microscopy, X-ray phase analysis, and bending testing. The obtained samples have a relative density of 98.5 ± 0.1%. The addition of the Cu-Al powder mixture facilitates supercooling during crystallization and solidification, which allows decreasing the size and changing the shape of the initial β-Ti grains. The constant cooling rate of the alloy typical for the SLM technology has been shown to be able to prevent martensitic transformation. The formation of a structure that consists of β-Ti grains, a dispersed eutectoid mixture of α-Ti and Ti₂Cu grains, and a solid solution of Al in Cu has been revealed. In the case of doping by the 10% Cu-Al mixture, the physico-mechanical properties are improved. The hardness of the samples amounts to 390 HRC, with the bending strength being 1550 ± 20 MPa and deformation of 3.5 ± 0.2%. The developed alloy can be recommended for applications in the production of parts of jet and car engines, implants for medicine, and corrosion-resistant parts for the chemical industry.

https://doi.org/10.1016/j.optmat.2024.116135

The photoluminescence and UV–Vis absorption spectra of copolyamides containing 1,9-anthrazoline with para- and meta-[(substituted carbonyl)amino]phenyl-1-ene moieties in a polymer backbone were studied by a combination of experimental and theoretical approaches. The investigation was accomplished through time-dependent density functional theory electronic structure calculations of small-molecule models mimicking a polymer chain. Theoretical absorption and luminescence spectra of ten atomistic models were compared with corresponding experimental data, and the optical properties of two new luminescent molecules with bromine auxochrome were predicted. An analysis of the optical properties demonstrate an identical effect of the type and position of a substituent on the spectra for para- and meta-[(substituted carbonyl)amino]phenyl-1-ene moieties. It was found that the absorption and luminescence spectra of theoretical para-models demonstrate red shifts relative to the corresponding meta-ones. The same phenomenon was observed in experimental spectra of low-molecular-mass compounds and corresponding copolyamides in solution and bulk. Unique optical properties allow anthrazoline-based polymer compounds to be used in numerous advanced optoelectronic applications with desired optical and electronic characteristics.