New Publications

Bound states in the continuum in dielectric resonators embedded into metallic waveguide

Bulgakov, E., Pilipchuk, A., Sadreev, A.// All-Dielectric Nanophotonics//

We consider dielectric cavities whose radiation space is restricted by two parallel metallic planes. The TE solutions of the Maxwell's equations of the system are equivalent to the solutions of periodical arrays of dielectric cavities. The system readily allows to achieve bound states in the continuum (BICs) of any type, including topological BICs that depends on the position and orientation of the cavities relative to the planes. This facilitates experimental studies immensely compared to infinite arrays of the cavities. We show the effect of merging topologically protected BICs, which pushes the square asymptotic of the Q-factor to the power degree of 4 or even 6.

Synthesis and Study of Superhigh-Concentrated Organosols of Silver Nanoparticles

Vorobyev, S.A., Flerko, M.Y., Novikova, S.A., (...), Zolotovsky, N.A., Volochaev, M.N.// Colloid Journal//

Due to their unique properties, organosols of silver nanoparticles are widely used in optical and semiconductor devices, to produce electrically and thermally conductive films, as catalysts, antibacterial materials, etc. This work proposes a simple and highly productive method for the preparation of silver organosols, which have a metal concentration as high as 1800 g/L and contain spherical nanoparticles with low polydispersity and a median size of 9.1 nm. The method consists in the initial preparation of silver nanoparticle hydrosols with a concentration of higher than 30 g/L followed by the transfer of the NPs into an organic phase of o-xylene. A set of physical research methods has been employed to study the regularities of the extraction of silver nanoparticles with o-xylene in the presence of cetyltrimethylammonium bromide (CTAB) and ethanol and to determine the optimal process conditions, under which the extraction degree is as high as 62.5%. It has been found that bromine anions contained in CTAB molecules cause the aggregation of some amount of silver nanoparticles with the formation of silver metal sediment in the aqueous phase. According to X-ray photoelectron spectroscopy data, the sediment contains bromide ions (up to 4 at %) on the particle surface. Organosols synthesized under optimal conditions are stable for more than 7 months and withstand repeated cycles of drying and redispersing. Silver organosols have been used to obtain metal films with an electrical conductivity of about 68 500 S/cm, which increases to 412 000 and 509 500 S/cm (87.8% of the electrical conductivity of bulk silver) after thermal treatment at 150 and 250°C, respectively.

Magnetic Structure of Fe5O6: Group-Theoretical Analysis and DFT Calculations

Zhandun, V.S., Kazak, N.V., Vasiukov, D.M.// JETP Letters//

The magnetic structure of Fe5O6 is studied using a combination of the group-theoretical analysis and DFT + U calculations of the electronic spectrum. The calculations are performed for the magnetic k = (0, 0, 0) vector. The magnetic ground state corresponds to the orthogonal ordering of two magnetic subsystems:  the magnetic moments of Fe2+/Fe3+ ions located at the octahedral sites (slabs of octahedra) are directed along the c axis and are antiferromagnetically ordered, whereas the magnetic moments of Fe2+ ions in trigonal prisms forming one-dimensional chains are directed along the b axis and are antiferromagnetically coupled along the c axis. The formation of a nonzero antiferromagnetic component of magnetic moments in the slabs of octahedra directed along the b axis is caused by the effect of magnetic chains on the three-dimensional magnetic structure.

Machine-Learning-Driven Discovery of Mn4+-Doped Red-Emitting Fluorides with Short Excited-State Lifetime and High Efficiency for Mini Light-Emitting Diode Displays

Hong Ming, Yayun Zhou*, Maxim S. Molokeev, Chuang Zhang, Lin Huang, Yuanjing Wang, Hong-Tao Sun, Enhai Song*, and Qinyuan Zhang*// Acs Materials Letters //

The discovery of high-efficiency Mn4+-activated fluoride red phosphors with short excited-state lifetimes (ESLs) is urgent and crucial for high-quality, wide-color-gamut display applications. However, it is still a great challenge to design target phosphors with both short ESL and high luminescence efficiency. Herein, we propose an efficient machine learning approach based on a small dataset to establish the ESL prediction model, thereby facilitating the discovery of new Mn4+-activated fluorides with short ESLs. Such a model can not only accurately predict the ESLs of Mn4+ in fluorides but also quantify the impact of structure features on ESLs, therefore elucidating the “structure-lifetime” correlations. Guided by the correlations, two new Mn4+-doped tetramethylammonium (TMA)-based hybrid fluorides (TMA)2BF6:Mn4+ (B = Sn or Hf) with both short ESLs (τ ≤ 3.7 ms) and high quantum efficiencies (internal QEs > 92%, external QEs > 55%) have been discovered successfully. A prototype displayer with excellent performance (∼124% National Television Standards Committee (NTSC) color gamut) is assembled by employing a (TMA)2SnF6:Mn4+-based white Mini-LED backlight module, demonstrating its practical prospects in high-quality displays. This work not only brings promising candidates for Mn4+-doped fluoride phosphors but also provides a valuable reference for accelerating the discovery of new promising phosphors.

Study of the Magnetic Properties of Neodymium and Samarium Iron Borates by the Method of Erbium Spectroscopic Probe

Chukalina, E.P., Jablunovskis, A., Gudim, I.A.// Optics and Spectroscopy//

Iron borates NdFe3(BO3)4 and SmFe3 (BO3)4 activated with 1% erbium, with ahuntite structure (space symmetry group R32) were investigated by the method of erbium spectroscopic probe. From an analysis of the temperature dependence of the transmission spectra in the region of the 4I15/2 → 4113/2 transition in the Er3+ ion, it was found that both studied compounds order antiferromagnetically at TN ≈ 33 K into an easy-plane magnetic structure. No other phase transitions were found.

Synthesis and Optical Properties of Nickel-Doped Copper Metaborate Crystals

Molchanova, A.D., Moshkina, E.M., Molokeev, M.S., (...), Bovina, A.F., Boldyrev, K.N.// Optics and Spectroscopy//

This work presents information on the growth and spectroscopic study of single crystals of copper metaborate doped with nickel Cu1–xNixB2O4 (x = 0.05, 0.1). In the absorption spectra of both crystals, satellites related to Cu centers distorted by impurity Ni atoms were observed near the lines of zero phonon transitions. Polarization studies in the isotropic ab-plane of the tetragonal crystal Cu1–xNixB2O4 show the presence of linear magnetic dichroism in the magnetically ordered state, which was previously observed both in manganese-doped and undoped copper metaborates CuB2O4. The temperature of magnetic phase transitions into the collinear antiferromagnetic and into helicoidal structures, TN = 19.1 K and T * = 8.6 K, respectively, were determined from the temperature dependence of the dichroic signal.

Phase Diagram and Soft Modes Behavior TbFe3–xGax(BO3)4 Solid Solutions with Huntite Structure

Krylov, A.S., Vtyurin, A.N., Gudim, I.A., Nemtsev, I.V., Krylova, S.N.// Optics and Spectroscopy//

The Raman spectra of four crystals of TbFe3–xGax(BO3)4 solid solutions (x from 0 to 0.54) were studied in the temperature range from 8 to 350 K. The temperatures of structural phase transitions were determined. The observed spectral behavior is characteristic to condensation and restoration of soft modes. Soft modes are associated with a structural phase transition from the R32 phase to the P3121 phase. The Compositions-Temperature phase diagram was constructed.

Determination of the Pore Direction in a Crystalline Metal-Organic Framework by Raman Spectroscopy and Periodic Calculations Based on the Electron Density Functional Theory

Slyusarenko, N.V., Yushina, I.D., Slyusareva, E.A., (...), Vtyurin, A.N., Krylov, A.S.// Optoelectronics, Instrumentation and Data Processing//

A method for the determination of pore orientation in metal-organic framework structures by polarized Raman spectra is proposed. The method involves sensitivity of the line intensity of Raman scattering to the geometry of propagation in a crystal. The operability of the method is shown by DUT-8 (Ni, Co) crystals. The obtained results are interpreted based on analysis of symmetry and direction of vibrations within periodic calculations of the electron density functional theory. The simultaneous approach allowed us to describe the vibrations and to find the principal crystal orientation collinear to the pore direction. The information on the pore orientation is necessary for problems of adsorption and design of complex multicomponent materials based on metal-organic framework.

The phases formed in Sn/Co thin bilayer upon heating

Eremin, L., Matsynin, A., Balashov, Y., (...), Bykova, L., Komogortsev, S.// Journal of Solid State Chemistry//

The structure and phases formed in Sn/Co thin films are interesting both from the solid-state chemistry point of view and due to applications of such a metallic bilayer. The phases forming in thin films Sn/Co obtained by thermal vacuum evaporation on two different substrates SiO2 and MgO(100) at different annealing temperatures have been studied. Annealing above 110°С results in intermetallics formation in the films. The hcp-cobalt is grown in the films on SiO2 substrate, and the fcc-Co is observed on MgO(100) substrate. It is found that the stable α-Co3Sn2 intermetallic is formed at higher annealing temperature in film on MgO(100) substrate. We show that transformations related to mass transfer in the Sn/Co bilayers were up to 500°С and were finished upon reaching the thermodynamically equilibrium phase composition at this temperature.

Terahertz Spectroscopy of Magnetoelectric HoAl3(BO3)4

Kuzmenko, A.M., Ivanov, V.Y., Tikhanovsky, A.Y., (...), Gudim, I.A., Mukhin, A.A.// Optics and Spectroscopy//

Experimental and theoretical study of submillimeter (terahertz) spectroscopic and magnetic properties of the rare-earth aluminum borate HoAl3(BO3)4 were performed at temperatures 3–300K. In the transmittance spectra a number of resonance lines were detected at frequencies 2–35 cm–1 for different radiation polarizations. These modes were identified as transitions between the lower levels of the ground multiplet of the Ho3+ ion split by the crystal field, including both transitions from the ground state to the excited ones and transitions between the excited states. The established excitation conditions of the observed modes and the simulation of the spectra made it possible to separate the magnetic and electric dipole transitions and to determine the energies of the corresponding states, their symmetry, and the matrix elements of the transitions. Low-frequency lines that do not fit into the established picture of the electron states of Ho3+ were also found; these lines, apparently, correspond to the ions with the distorted by defects local symmetry of the crystal field.

Photoinduced Nonlinear Dynamics of Strongly Correlated Systems with Spin Crossover: Autocatalytic Spin Transition

Orlov, Y.S., Nikolaev, S.V., Paklin, N.N.// JETP Letters//

Nonlinear phenomena similar to the Belousov–Zhabotinsky reaction (autocatalytic oscillations of the population of high-spin and low-spin multielectron states of a transition metal ion) in open systems with spin crossover near bistability are considered. The conditions for possible experimental observation of autocatalytic oscillations of the magnetization in magnetically ordered systems with spin crossover are analyzed.

Signatures of quantum chaos and fermionization in the incoherent transport of bosonic carriers in the Bose-Hubbard chain

Muraev, P.S., Maksimov, D.N., Kolovsky, A.R.// Physical Review E//

We analyze the stationary current of Bose particles across the Bose-Hubbard chain connected to a battery, focusing on the effect of interparticle interactions. It is shown that the current magnitude drastically decreases as the strength of interparticle interactions exceeds the critical value which marks the transition to quantum chaos in the Bose-Hubbard Hamiltonian. We found that this transition is well reflected in the nonequilibrium many-body density matrix of the system. Namely, the level-spacing distribution for eigenvalues of the density matrix changes from Poisson to Wigner-Dyson distributions. With the further increase of the interaction strength, the Wigner-Dyson spectrum statistics change back to the Poisson statistics which now marks fermionization of the Bose particles. With respect to the stationary current, this leads to the counter-intuitive dependence of the current magnitude on the particle number.

Doped Mott-Hubbard materials with a low quasiparticle transparency

Gavrichkov, V.A.// Physical Review B//

Based on the Wilson's criterion metal/insulator, extended to materials with strong electronic correlations, we have identified a specific class of the materials, which is not associated with their usual classification into Mott-Hubbard and charge transfer dielectrics. The local symmetry of these materials leads to the disappearance of quasiparticle states (so-called first removal or first extra states) in the Hubbard gap. It is especially unusual for doped materials, in which quasiparticles, being charge carriers, can disappear or appear under external factors without the Mott transition being achieved. In this work, we introduce the so-called “quasiparticle transparency”, and provide specific experiments to identify materials with the low quasiparticle transparency. A number of examples of such materials with a spin crossover under high pressure, showing the Jahn-Teller nature, are considered.

Revolutionizing physics: a comprehensive survey of machine learning applications

Rahul Suresh, Bishnoi, V. Kuklin, Atharva Parikh, Maxim Molokeev, R. Harinarayanan, Gharat, P. Hiba// Frontiers In Physics //

In the context of the 21st century and the fourth industrial revolution, the substantial proliferation of data has established it as a valuable resource, fostering enhanced computational capabilities across scientific disciplines, including physics. The integration of Machine Learning stands as a prominent solution to unravel the intricacies inherent to scientific data. While diverse machine learning algorithms find utility in various branches of physics, there exists a need for a systematic framework for the application of Machine Learning to the field. This review offers a comprehensive exploration of the fundamental principles and algorithms of Machine Learning, with a focus on their implementation within distinct domains of physics. The review delves into the contemporary trends of Machine Learning application in condensed matter physics, biophysics, astrophysics, material science, and addresses emerging challenges. The potential for Machine Learning to revolutionize the comprehension of intricate physical phenomena is underscored. Nevertheless, persisting challenges in the form of more efficient and precise algorithm development are acknowledged within this review.

Modification of Synthetic Valleriite Surface with Gold Nanoparticles: The Roles of Specific Adsorption and Zeta Potential

Karacharov, A.A., Likhatski, M.N., Borisov, R.V., (...), Vorobyev, S.A., Zharkov, S.M.// Colloid Journal//

Layered two-dimensional materials, whose properties dramatically differ from their bulk precursors, are of great theoretical and applied importance. Recently, a layered 2D material, an analog of a natural mineral, valleriite, in which quasi-monoatomic Cu−Fe−S sheets alternate with brucite-like ones, has been prepared using a simple hydrothermal synthesis procedure. The features of the electronic structure of these materials make it possible to propose them as new materials for a wide field of applications such as (electro)photocatalysis, high-capacity batteries, etc. In this work, nanocomposite materials have been prepared via immobilization of gold nanoparticles (AuNPs) from citrate hydrosols on the surface of the synthesized valleriites having different compositions of hydroxide layers, which control the surface charge density. According to X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray microanalysis (EDX), and selected area electron diffraction (SAED) data, AuNPs are immobilized on valleriite nanoflakes, which have lateral sizes of 150–200 nm and thicknesses of several tens of nanometers, as isolated metal nanoparticles with an average diameter of 11 nm. A small amount of aggregates indicates a high affinity of AuNPs for the valleriite surface. The amounts of immobilized gold are the same on all studied valleriites (~0.2%). This finding may be related to the simultaneous sorption of free citrate ions from the AuNP hydrosols, with these ions, according to zeta potential measurements, charging the surfaces of all studied valleriite samples to nearly the same negative value of –40 mV. According to the XPS data, the AuNPs immobilization markedly decreases the magnesium and oxygen contents on the surfaces of the synthesized valleriites due to the partial degradation/dissolution of the brucite layer. In addition, the amount of Fe3+ ions bound to OH groups decreases with a simultaneous increase in the fraction of Fe3+–O species. The TEM data have confirmed the preservation of the layered structure of valleriites after the immobilization of AuNPs.

Optical transmission modulation and spectral properties of self-organized nematic domains

Parshin, A.M., Zyryanov, V.Y., Shabanov, V.F.// Optical Materials//

The modulation and spectral characteristics of self-organized ensembles of nematic domains with the disclination lines non-aligned and aligned in a magnetic field have been studied using an electric field. The obtained experimental voltage dependences of the light transmission agree well with the dependences calculated using the model considerations. These dependences have been compared with the electro-optical characteristics of a homogeneous planar nematic layer. The amplitude component of the optical transmission determined by light scattering and the oscillating component caused by the phase modulation have been examined. The effect of the spectral dispersion of transmission on the electro-optical characteristics of domain ensembles has been evaluated.

Magnetic flux trapping in porous high-Tc superconductors

Gokhfeld, D.// Physica C//

Porosity affects the properties of high-Tc superconductors and can improve their performance by enhancing oxygenation, cryocooling, etc. Among other factors, the presence of pores plays a significant role in the process of magnetic flux trapping. Relationships with the porosity manifest in the irreversibility field, the full penetration field, and the remnant magnetization of the samples. To account for the effect of porosity on the trapped magnetic flux into type-II superconductors, a simple toy model is suggested. Generally, as the porosity increases, the trapped flux and related parameters tend to diminish. However, in the case of microscopic samples, porosity can enhance magnetic flux trapping.

Highly-Efficiency Far-Red Emission in Cr3+ Activated Ca1.8Mg1.2Al2Ge3O12 toward Plant Precise Lighting

Chaowei Yang, Dongwei Zheng, Xikun Zou, Xiangyi Dai, Baoling Tang, Maxim S. Molokeev, Xuejie Zhang, Haoran Zhang, Yingliang Liu, Bingfu Lei// Advanced Optical Materials//

Far-red (FR) region (beyond 700 nm) lighting sources possess special potential for plant lighting. However, it remains a challenge to obtain high-performance Cr3+-doped FR phosphors. This study developed a FR phosphor, Ca1.8Mg1.2Al2Ge3O12:Cr3+ (CMAGG: Cr3+), using the cation substitution strategy. Under 438 nm blue light excitation, the phosphors display FR emission centered at 720 nm with a full width at half maximum (FWHM) of 91 nm. Benefit from the favorable match with the FR phytochrome (Pfr), the phosphor is combined with InGaN blue light chips to create a FR phosphor-converted light-emitting diode (pc-LED), which is used in Italian lettuce growth experiments and it results shown in a 15% increase in fresh weight and a 6.5% increase in dry weight. Notably, supplemental FR light modulated its growth morphology. The results of this study will be useful for further research on novel Cr3+-doped FR phosphors to meet the precise spectral requirements for plant growth.

Two-Dimensional Hybrid Perovskite with High-Sensitivity Optical Thermometry Sensors

Mengyu Guan, Jiarui Hao, Lei Qiu, Maxim S. Molokeev, Lixin Ning*, Zhigao Dai*, and Guogang Li// Inorganic Chemistry //

Optical thermometry has gained significant attention due to its remarkable sensitivity and noninvasive, rapid response to temperature changes. However, achieving both high absolute and relative temperature sensitivity in two-dimensional perovskites presents a substantial challenge. Here, we propose a novel approach to address this issue by designing and synthesizing a new narrow-band blue light-emitting two-dimensional perovskite named (C8H12NO2)2PbBr4 using a straightforward solution-based method. Under excitation of near-ultraviolet light, (C8H12NO2)2PbBr4 shows an ultranarrow emission band with the full width at half-maximum (FWHM) of only 19 nm. Furthermore, its luminescence property can be efficiently tuned by incorporating energy transfer from host excitons to Mn2+. This energy transfer leads to dual emission, encompassing both blue and orange emissions, with an impressive energy transfer efficiency of 38.3%. Additionally, we investigated the temperature-dependent fluorescence intensity ratio between blue emission of (C8H12NO2)2PbBr4 and orange emission of Mn2+. Remarkably, (C8H12NO2)2PbBr4:Mn2+ exhibited maximum absolute sensitivity and relative sensitivity values of 0.055 K–1 and 3.207% K–1, respectively, within the temperature range of 80–360 K. This work highlights the potential of (C8H12NO2)2PbBr4:Mn2+ as a promising candidate for optical thermometry sensor application. Moreover, our findings provide valuable insights into the design of narrow-band blue light-emitting perovskites, enabling the achievement of single-component dual emission in optical thermometry sensors.

The Effect of Dielectric Relaxation Processes on the Complex Dielectric Permittivity of Soils at Frequencies From 10 kHz to 8 GHz-Part II: Broadband Analysis

Pavel P. Bobrov; Elena S. Kroshka; Konstantin V. Muzalevskiy// Ieee Transactions On Geoscience And Remote Sensing //

DOI: 10.1109/TGRS.2023.3340693

This article is the second in a series evaluating the effect of dielectric relaxation processes on the relatively effective complex dielectric permittivity (RCP) of soils. Part II is based on the results of experimental measurements in the frequency range 10 kHz to 8–20 GHz. The broadband dielectric spectrum model includes the high-frequency part as a model of the dielectric mixture and the relaxation part as the sum of three relaxation processes modeled by the Debye and Cole–Cole formulas. For modeling the high-frequency part of the spectrum, the Dobson and Mironov models were considered as possible options. As stated in Part I, the influence of relaxation processes on the imaginary part of the RCP extends up to frequencies of units of gigahertz. The increase in the imaginary part in these models was compensated by unrealistically high values of the specific electrical conductivity of free and bound water. We examined the correspondence of these models to experimental data at frequencies above 2–5 GHz, assuming that the conductivity of bound and free water is zero. The parameters of relaxation processes were found while solving the least-square optimization problem using the technique for determining the continuous distribution of relaxation times (DRTs). Found process parameters depend on the content of clay, organic carbon, and moisture of the samples. The more clay is in the soil, the greater the strength of these processes is. The influence of organic carbon with the conditions being equal consists in the reduction of the real and imaginary parts of RCP.

Characterizing Aptamer Interaction with the Oncolytic Virus VV-GMCSF-Lact

by Maya A. Dymova 1,*ORCID,Daria O. Malysheva 1,2ORCID,Victoria K. Popova 1ORCID,Elena V. Dmitrienko 1ORCID,Anton V. Endutkin 1ORCID,Danil V. Drokov 1,2,Vladimir S. Mukhanov 1,2,Arina A. Byvakina 1,2ORCID,Galina V. Kochneva 3ORCID,Polina V. Artyushenko 4,5ORCID,Irina A. Shchugoreva 4,5ORCID,Anastasia V. Rogova 4,5ORCID,Felix N. Tomilin 5,6ORCID,Anna S. Kichkailo 4,5,Vladimir A. Richter 1 andElena V. Kuligina 1ORCID// Molecules //

Aptamers are currently being investigated for their potential to improve virotherapy. They offer several advantages, including the ability to prevent the aggregation of viral particles, enhance target specificity, and protect against the neutralizing effects of antibodies. The purpose of this study was to comprehensively investigate an aptamer capable of enhancing virotherapy. This involved characterizing the previously selected aptamer for vaccinia virus (VACV), evaluating the aggregation and molecular interaction of the optimized aptamers with the recombinant oncolytic virus VV-GMCSF-Lact, and estimating their immunoshielding properties in the presence of human blood serum. We chose one optimized aptamer, NV14t_56, with the highest affinity to the virus from the pool of several truncated aptamers and built its 3D model. The NV14t_56 remained stable in human blood serum for 1 h and bound to VV-GMCSF-Lact in the micromolar range (Kd ≈ 0.35 μM). Based on dynamic light scattering data, it has been demonstrated that aptamers surround viral particles and inhibit aggregate formation. In the presence of serum, the hydrodynamic diameter (by intensity) of the aptamer–virus complex did not change. Microscale thermophoresis (MST) experiments showed that NV14t_56 binds with virus (EC50 = 1.487 × 109 PFU/mL). The analysis of the amplitudes of MST curves reveals that the components of the serum bind to the aptamer–virus complex without disrupting it. In vitro experiments demonstrated the efficacy of VV-GMCSF-Lact in conjunction with the aptamer when exposed to human blood serum in the absence of neutralizing antibodies (Nabs). Thus, NV14t_56 has the ability to inhibit virus aggregation, allowing VV-GMCSF-Lact to maintain its effectiveness throughout the storage period and subsequent use. When employing aptamers as protective agents for oncolytic viruses, the presence of neutralizing antibodies should be taken into account.

Strain-induced charge ordering above room temperature in rare-earth manganites

Samoshkina, Y., Rautskii, M., Neznakhin, D., (...), Zaikovskii, V., Chernichenko, A.// Dalton Transactions//

Most known mixed manganites containing rare-earth elements demonstrate a pronounced charge ordering (CO) state below room temperature. The behavior of the magnetic susceptibility and electronic magnetic resonance of polycrystalline Pr1−xSrxMnO3/YSZ (x = 0.2 and x = 0.4) films without a pronounced texture indicates the formation of the CO phase in the samples at temperatures close to and above room temperature. Moreover, this phase manifests itself with a typical sign of martensitic transformation. The same phenomenon has been traced for textured polycrystalline La0.7Sr0.3MnO3/YSZ films. Electron microscope data indicate the presence of internal strain within the films, which is probably responsible for the formation of the CO phase. It is assumed that the reasons for the appearance of such strain include the crystallite size and the boundary between them. The results obtained provide the basis for the development of new research and technological tasks for the generation of the high-temperature CO state in various polycrystalline rare-earth manganites, since this state contributes to the manifestation of interesting magnetocaloric, magnetoelectric and multiferroic properties. In addition, recent data has opened up new opportunities for studying the strain-induced phenomena in such materials.

Relaxation of the trapped magnetic flux in a mesoscopic HTS with artificial pinning in the form of submicron holes

Maksimova, A.N., Gokhfeld, D.M., Moroz, A.N., Kashurnikov, V.A.// Chinese Journal of Physics//

Vortex relaxation has been studied in a microsized HTS with various distributions of artificial pinning in the form of submicro-holes. It has been shown that, in some cases, for a superconductor with dimensions up to several micrometers, the time dependences of the trapped magnetic field do not correspond with the collective creep model. The dependences of the trapped-field relaxation rate and vortex activation energy on the magnetizing field (up to 0.5 T) and temperature (up to 50 K) have been obtained. It has been shown that the presence of submicro-holes slightly increases the relaxation rate, mainly due to the decrease in the number of random nanosized pinning centers.

On the use of dual-polarized multi-angular observations of P-band brightness temperature for soil moisture profile retrieval in thawed mineral soil

Konstantin V. Muzalevskiy,Jeffrey P. Walker,Foad Brakhasi,Nan Ye,Xiaoling Wu &Xiaoji Shen// International Journal Of Remote Sensing //

This article investigated the possibility of remotely sensing the soil moisture profile in thawed soil from multi-angular dual-polarized brightness temperature (TB) observations at P-band frequencies of 750 MHz and 409 MHz using a modified Burke model. Moreover, it was found that an excellent agreement (coefficient of determination R2 = 0.999 and root-mean-square error (RMSE) no more than RMSE = 0.6 K) could be achieved between the Njoku coherent brightness temperature model and the modified Burke model by introducing a reflectivity from the air-soil interface that takes into account the phases of the multiple re-reflected waves in the underlying layers. Based on the modified Burke model, the depths from which apparent moisture and temperature could be retrieved in a dielectrically-inhomogeneous, non-isothermal soil were investigated, being approximately ten times less than the depth for which apparent soil temperature could be retrieved. In general, the thickness of the emitting layer depends on the TB look angle and polarization, along with the moisture and temperature profiles of the soil. It was also shown that due to the effect of the Brewster angle, the H-polarization of TB was twice as sensitive (4 K/1%) to changes in volumetric soil moisture than V-polarization (1.9 K/1%). Based on multi-angular (10°-50°) observations of TB at H- and V-polarizations, a method of moisture profile retrieval in the top 5–15 cm soil (depending on surface moisture) was proposed using an exponential fitting function, the parameters of which are found in the course of solving the inverse problem. A decrease in the sensing frequency from 750 MHz to 409 MHz makes it possible to increase the accuracy of soil moisture profiles retrieval by a factor of two, being from RMSE = 1.6% (R2 = 0.946) to RMSE = 0.85% (R2 = 0.982) in the top 15 cm layer of soil. The conducted investigation shows the promise of using P-band observations of TB for soil moisture profile retrieval.

Synthesis of Ni nanoclusters supported on diamond by plasma technique and their electrochemical properties

Nikita Nikolaev a, Victoria Isakova a, Natalia Vnukova a b, Victoria Еlesina a b, Gariy Glushenko a, Yevgeny Tomashevich a c, Grigory Churilov // Diamond And Related Materials //

In this study, particles of synthetic undoped diamond (DN) obtained via the high pressure – high temperature method were coated with a nickel shell using metallic nickel plasma in a two-jet plasma generator with gas vortex and magnetic flux stabilization. Through the use of scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, we observed the formation of a nickel diamond composite with a core-shell structure, where DN serves as the core and Ni nanoclusters form the shell (DN@Ni). The results of voltammetric analysis indicated that DN@Ni, when deposited on a graphite electrode, exhibited significant electrocatalytic activity in the oxidation of methanol and paracetamol in an alkaline electrolyte.

Effect of the spin crossover of local copper-oxygen states on the electronic structure of HTSC cuprates

Makarov, I. A.; Ovchinnikov, S. G.//, e-Print Archive, Condensed Matter//

In this work, the effect of uniaxial pressure along the c axis on the electronic structure of the HTSC cuprate La2-xSrxCuO4 is investigated at the doping levels x = 0.1, 0.15, 0.25. The GTB method within the five-band p-d model framework is used to describe the electron system. The uniaxial compression leads to a significant reconstruction of the electronic structure and a change in the character of low-energy quasiparticle excitations: a large contribution of a1g symmetry orbitals appears at the top of the valence band. The crossover between the local Zhang-Rice singlet and the Emery-Reiter triplet was found at the pressure Pc = 15.1 GPa. The characteristic changes in the electronic structure under pressure occur abruptly as a result of the crossover. In particular, the top of the valence band displaces to the region around the k-point (pi,0), the Fermi contour transforms to the four pockets around (0,0),(2pi,0),(0,2pi),(2pi,2pi) and the one contour around (pi,pi).

A 10 GHz Monolithic Filter Based on Stripline Resonators with a Split Conductor

Govorun, I.V., Belyaev, B.A., Zav’yalov, Y.B., (...), Ugryumov, A.V., Galeev, R.G.// Doklady Physics//

The monolithic design of a compact bandpass filter X-band is made on the technology of multilayered printed circuit boards. Quarter-wave stripline resonators of the filter have two conductors divided by a layer of prepreg having low parameters that bond together the design. This eliminates the influence of the prepreg on the characteristics of the devices, ensuring good repeatability of filters in mass production. To increase the high-frequency stopband of the filter, one of the conductors of each resonator is cut in half by a transverse slit. The constructive sizes of the device were obtained by parametric synthesis using the electrodynamic analysis of its 3D model. The experimental data of the five-order filter are in good agreement with the electromagnetic simulation of filter of the 3D model. The experimental device has a central frequency of the passband of 10 GHz and a fractional bandwidth of 5.7%, and its dimensions and weight are 18.0 × 5.4 × 2.1 mm3 and 0.5 g. The important advantage of the developed design is the possibility of its installation on the board using the surface mounting method.

Revolutionizing physics: a comprehensive survey of machine learning applications

Suresh, R., Bishnoi, H., Kuklin, A.V., (...), Gharat, S., Hiba, P.// Frontiers in Physics//

In the context of the 21st century and the fourth industrial revolution, the substantial proliferation of data has established it as a valuable resource, fostering enhanced computational capabilities across scientific disciplines, including physics. The integration of Machine Learning stands as a prominent solution to unravel the intricacies inherent to scientific data. While diverse machine learning algorithms find utility in various branches of physics, there exists a need for a systematic framework for the application of Machine Learning to the field. This review offers a comprehensive exploration of the fundamental principles and algorithms of Machine Learning, with a focus on their implementation within distinct domains of physics. The review delves into the contemporary trends of Machine Learning application in condensed matter physics, biophysics, astrophysics, material science, and addresses emerging challenges. The potential for Machine Learning to revolutionize the comprehension of intricate physical phenomena is underscored. Nevertheless, persisting challenges in the form of more efficient and precise algorithm development are acknowledged within this review.

Intense charge transfer plasmons in golden nanoparticle dimers connected by conductive molecular linkers

Fedorov, A.S., Visotin, M.A., Lukyanenko, A.V., Gerasimov, V.S., Aleksandrovsky, A.S.// Journal of Chemical Physics//

Golden nanoparticle dimers connected by conjugated molecular linkers 1,2-bis(2-pyridyl)ethylene are produced. The formation of stable dimers with 22 nm diameter nanoparticles is confirmed by transmission electron microphotography. The possibility of charge transfer through the linkers between the particles in the dimers is shown by the density functional theory calculations. In addition to localized plasmon resonance of solitary nanoparticles with a wavelength of 530 nm, the optical spectra exhibit a new intense absorption peak in the near-infrared range with a wavelength of ∼780 nm. The emergent absorption peak is attributed to the charge-transfer plasmon (CTP) mode; the spectra simulated within the CTP developed model agree with the experimental ones. This resonant absorption may be of interest to biomedical applications due to its position in the so-called transmission window of biological tissues. The in vitro heating of CTP dimer solution by a laser diode with a wavelength of 792 nm proved the efficiency of CTP dimers for achieving a temperature increase of ΔT = 6 °C, which is sufficient for hyperthermia treatment of malignant tumors. This indicates the possibility of using hyperthermia to treat malignant tumors using the material we synthesized.

Quantum SU(3)-ferrimagnet on triangular lattice

Martynov, A.S., Dzebisashvili, D.M.// Journal of Magnetism and Magnetic Materials//

Manifestations of quantum effects in the macroscopic properties of frustrated magnets keep attracting considerable interest. We have formulated and studied a simple model of a three-sublattice mixed-spin (�=1,1/2,1/2��(3)-ferrimagnet on triangular lattice in which the strong quantum fluctuations are developed due to combined effect of frustrated exchange bonds, reduced dimensionality and a single-ion easy-plane anisotropy in the spin-1 sublattice. To account correctly for the ��(3) algebra, the Hubbard operators representation of generators is used. Dependencies of the magnetic moments  and �� (for spin-1/2 and spin-1 sublattices respectively), the total magnetic moment , as well as the quadrupole moment, on the anisotropy parameter  are calculated at zero temperature and different ratios �/� of exchange integrals from different sublattices. It is established that for �/�≪1 the critical value ��, at which the system enters the quadrupole antiferromagnetic phase, can be much smaller than both  and . Besides, with an increase in  from zero to �� the total moment  can change its direction several times via taking zero value. Classification of four branches of the spin-wave excitation spectrum of the ��(3)-ferrimagnet is carried out and modification of the spectrum with change in the single-ion anisotropy is analyzed.

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