Публикации 2021

Unraveling the Ultrafast Self-assembly and Photoluminescence in Zero-Dimensional Mn2+-Based Halides with Narrow-Band Green Emissions

Zhou, Guojun; Ren, Qiqiong; Molokeev, Maxim S.; Zhou, Yayun; Zhang, Jian; et al./ Acs Applied Electronic Materials/ https://doi.org/10.1021/acsaelm.1c00606

The discovery of narrow-band luminescent materials remains an immense challenge to optimize the performance of white light-emitting diodes (LEDs). So far, the zero-dimensional (0D) Mn2+-based halides with near-unity narrow-band emissions have emerged as a class of promising phosphors in solid-state displays, but the related large-scale synthesis strategies have not been proposed and evaluated. Herein, we report an in situ synthetic process of 0D Mn2+-based halides and utilize (C20H20P)2MnBr4 as a case to investigate the photoluminescence characteristics and the structural essence of ultrafast self-assembly. The bright green emission peak at 523 nm with a full width at half maximum of 48 nm for (C20H20P)2MnBr4 is attributed to the d–d transition (4T16A1) of tetrahedrally coordinated [MnBr4]2– centers, and the fabricated white LED device shows a wide color gamut of 103.7% National Television System Committee (NTSC) standard. Remarkably, the experimental and theoretical results indicate that there are hydrogen bonding of C–H···Br and weak van der Waals interactions between [C20H20P]+ and [MnBr4]2–, resulting in the root for the realization of ultrafast self-assembly in 0D Mn2+-based halides. This work reveals a feasible and general synthesis method for preparing 0D Mn2+-based halides, thereby providing a possibility for their industrial application in solid-state displays.

https://doi.org/10.1021/acsaelm.1c00606

Photoluminescence of pefloxacindi-ium manganese(II) and zinc(II) tetrahalides

Golovnev, Nicolay N.; Gerasimova, Marina A.; Molokeev, Maxim S.; Plyaskin, Mikhail E.; Baronin, Mikhail E./ Journal Of Molecular Structure/ https://doi.org/10.1016/j.molstruc.2021.131468

Mn2+-based hybrid materials have become the hotspot of current research studies owing to their high photoluminescence quantum yield (PLQY), low-cost, environmental friendliness and stability. For the first time, we report the hydrothermal synthesis of two lead-free zero-dimensional luminescent organic-inorganic hybrid compounds, PefH2[MnBr4] (1) and PefH2[MnCl4] (2) (Pef = pefloxacin). They were characterized by elemental analysis, TG-DSC, single-crystal and powder XRD. Compounds 1–2 exhibit a distorted tetrahedral geometry around the manganese(II) metal center, which is isolated from the same centers by bulky pefloxacindi-ium (PefH22+) ions with a Mn···Mn distance of 7.3 Å. Their structures are stabilized by N—H···O, O—H···X (X = Br, Cl), C—H···O and C—H···X hydrogen bands and π–π stacking interaction. Thermal decomposition starts at T > 230°С for 1 and T > 210°С for 2 and proceeds for several stages. Upon UV excitation compounds exhibit a bright green emission with a moderate PLQY of 45% for 1 and 30% for 2. The influence of the halide ion and metal ion on the photoluminescence properties of isostructural compounds PefH2[MX4] (M = Mn, Zn and X = Br, Cl) is discussed.

https://doi.org/10.1016/j.molstruc.2021.131468

Role of Interfaces in the Permittivity Tensor of Thin Layers of a Ferromagnetic Metal

Ovchinnikov, S. G.; Maximova, O. A.; Lyaschenko, S. A.; Yakovlev, I. A.; Varnakov, S. N./ Jetp Letters/ https://doi.org/10.1134/S0021364021150066

It is known from experimental studies that the components of the permittivity tensor ε depend on layer thicknesses of multilayer thin films, and for nanometer layers, it is necessary to additionally consider the interlayer interfaces. This study provides an answer to the question of what is the reason for the influence of these interfaces on film properties. It is shown that the contribution of interband matrix elements for ferromagnetic films with off-diagonal components of the permittivity tensor determines the ratio between the diagonal and off-diagonal components of the tensor ε at a ferromagnetic layer thickness of about 10 nm.

https://doi.org/10.1134/S0021364021150066

Interference oscillations in the optical response of a hybrid-aligned nematic with a surface disclination line to a pulsed magnetic field

Parshin, Alexander M.; Zyryanov, Victor Y.; Shabanov, Vasily F./ Journal Of The Optical Society Of America B-optical Physics/ https://doi.org/10.1364/JOSAB.435189

The propagation of light through a hybrid-aligned nematic layer with a surface disclination line is investigated in a pulsed magnetic field. The experimental dependences of light intensity 𝐼I on time 𝑡t accompanied by interference oscillations are presented. The shift and expansion of the interference extrema as functions of the magnetic field pulse length during the reaction are shown. The 𝐼(𝑡)I(t) dependence for the relaxation process is calculated with allowance for scattering. The calculated 𝐼(𝑡)I(t) dependence agrees well with the experimental dependence over the entire hybrid-aligned nematic layer, except for the surface layer.

Numerical study of structural and magnetic properties of thin films obliquely deposited on rippled substrates

Solovev, P. N.; Izotov, A., V; Belyaev, B. A./ Journal Of Physics-condensed Matter/ https://doi.org/10.1088/1361-648X/ac26fc

Structural modulation in thin films plays a substantial role in the formation of their magnetic properties. By producing topographic patterns in thin films, it is possible to engineer their magnetic response. Here, we report on the numerical study of the relationship between structural and static magnetic properties of thin films obliquely deposited on substrates with the sinusoidal surface. 3D Monte Carlo film growth simulations show that, under certain deposition conditions, an inhomogeneous columnar morphology can form in the films caused by the shadowing effect and the rippled substrate. Calculations of the demagnetizing tensors for these films demonstrate that their columnar structure is the source of the shape-induced uniaxial magnetic anisotropy that varies nonmonotonically with the deposition angle. Micromagnetic simulations of the generated films confirm the uniaxial character of the shape-induced anisotropy, and also show that magnetization reversal occurs via an incoherent rotation of magnetic moments.

https://doi.org/10.1088/1361-648X/ac26fc

Spin-polaron concept in the theory of normal and superconducting states of cuprates

Val'kov, V. V.; Dzebisashvili, D. M.; Korovushkin, M. M.; Barabanov, A. F. Physics-uspekhi/ ttps://doi.org/10.3367/UFNe.2020.08.038829

The review discusses the emergence of the spin-fermion model of cuprates and the formation of the spin-polaron concept of the electronic structure of hole-doped cuprate superconductors. This concept has allowed describing the properties of cuprates in the normal phase as well as the features of superconducting pairing in the unified approach. The derivation of the spin-fermion model from the Emery model in the regime of strong electronic correlations is described, demonstrating the appearance of strong coupling between the spins of copper ions and holes on oxygen ions. Such a strong interaction against the background of the singlet state of the spin subsystem of copper ions (quantum spin liquid) leads to the formation of special Fermi quasiparticles — nonlocal spin polarons. Under doping, the spin-polaron ensemble exhibits instability with respect to superconducting d-wave pairing, whereas superconducting s-wave pairing is not implemented. At the optimal doping, the transition to the superconducting phase occurs at temperatures corresponding to experimental data. It is shown that the superconducting d-wave pairing of spin-polaron quasiparticles is not suppressed by the Coulomb repulsion of holes located on neighboring oxygen ions. It is emphasized that, when the spec-tral characteristics of spin-polaron quasiparticles are taken into account, the calculated temperature and doping dependences of the London penetration depth are in good agreement with experimental data.

ttps://doi.org/10.3367/UFNe.2020.08.038829

Spectroscopy of structurally disordered hydrated iron fluoridotitanate in the regions of vibrational and electronic excitations

Gerasimova, Yu. V.; Aleksandrovsky, A. S.; Laptash, N. M.; Gerasimov, M. A.; Krylov, A. S.; et al./ Spectrochimica Acta Part A-molecular And Biomolecular Spectroscopy/ https://doi.org/10.1016/j.saa.2021.120244

Raman and optical absorption spectra of disordered hydrated iron fluoridotitanate (HITF) single crystal were studied. Temperature transformations of the Raman spectra indicate independent ordering processes of the [TiF6]2− and [Fe(H2O)6]2+ complexes below the structural phase transition. The absorption spectrum in the near-infrared and visible ranges includes transitions from the high spin ground state 5T2 of Fe2+ ion to the excited 5E state and a set of excited triplets. Analysis by Tanabe-Sugano method gives crystal field Dq = 490 cm−1 and Racah parameters B = 340 cm−1 and C = 1904 cm−1. Considerable decrease of B parameter as compared to the free ion value indicates a decrease of interelectron repulsion in the disordered neighborhood of Fe2+ ions.

https://doi.org/10.1016/j.saa.2021.120244

Amino-Functionalized Fe3O4@SiO2 Core-Shell Magnetic Nanoparticles for Dye Adsorption

Lin, Chun-Rong; Ivanova, Oxana S.; Petrov, Dmitry A.; Sokolov, Alexey E.; Chen, Ying-Zhen; et al. / Nanomaterials/ https://doi.org/10.3390/nano11092371

Fe3O4@SiO2 core-shell nanoparticles (NPs) were synthesized with the co-precipitation method and functionalized with NH2 amino-groups. The nanoparticles were characterized by X-ray, FT-IR spectroscopy, transmission electron microscopy, selected area electron diffraction, and vibrating sample magnetometry. The magnetic core of all the nanoparticles was shown to be nanocrystalline with the crystal parameters corresponding only to the Fe3O4 phase covered with a homogeneous amorphous silica (SiO2) shell of about 6 nm in thickness. The FT-IR spectra confirmed the appearance of chemical bonds at amino functionalization. The magnetic measurements revealed unusually high saturation magnetization of the initial Fe3O4 nanoparticles, which was presumably associated with the deviations in the Fe ion distribution between the tetrahedral and octahedral positions in the nanocrystals as compared to the bulk stoichiometric magnetite. The fluorescent spectrum of eosin Y-doped NPs dispersed in water solution was obtained and a red shift and line broadening (in comparison with the dye molecules being free in water) were revealed and explained. Most attention was paid to the adsorption properties of the nanoparticles with respect to three dyes: methylene blue, Congo red, and eosin Y. The kinetic data showed that the adsorption processes were associated with the pseudo-second order mechanism for all three dyes. The equilibrium data were more compatible with the Langmuir isotherm and the maximum adsorption capacity was reached for Congo red. 

https://doi.org/10.3390/nano11092371

Spin-Flop Transition in Co2B2O5 Pyroborate

Kazak, N. V.; Belskaya, N. A.; Moshkina, E. M.; Solovyov, L. A.; Eremin, E. V.; et al.// Jetp Letters/ https://doi.org/10.1134/S0021364021140058

Cobalt pyroborate Co2B2O5 single crystals have been obtained by spontaneous crystallization from solution–melt. Powder X-ray diffraction measurements have revealed the triclinic symmetry P1¯P1¯ with the lattice parameters a=3.1666(7)a=3.1666(7) Å, b=6.1543(6)b=6.1543(6) Å, c=9.2785(12)c=9.2785(12) Å, α=104.240(5)α=104.240(5)∘β=90.841(14)β=90.841(14)∘γ=92.064(16)γ=92.064(16)∘, and V=175.10(5)V=175.10(5) Å3. Magnetic properties have been studied in the temperature range of 4.2–300 K and in magnetic fields up to 90 kOe by measuring the static magnetization and molar heat capacity. A transition to an antiferromagnetic state has been detected at TN = 45 K. A spin-flop transition occurs in the sample in strong magnetic fields.

https://doi.org/10.1134/S0021364021140058

The Role of Periodic Structures in Light Harvesting

Bukhanov, Eugene; Shabanov, Alexandr, V; Volochaev, Mikhail N.; Pyatina, Svetlana A. / Plants-basel/ https://doi.org/10.3390/plants10091967

The features of light propagation in plant leaves depend on the long-period ordering in chloroplasts and the spectral characteristics of pigments. This work demonstrates a method of determining the hidden ordered structure. Transmission spectra have been determined using transfer matrix method. A band gap was found in the visible spectral range. The effective refractive index and dispersion in the absorption spectrum area of chlorophyll were taken into account to show that the density of photon states increases, while the spectrum shifts towards the wavelength range of effective photosynthesis.

 https://doi.org/10.3390/plants10091967

Properties of Degradable Polyhydroxyalkanoates (PHAs) Synthesized by a New Strain, Cupriavidus necator IBP/SFU-1, from Various Carbon Sources

Zhila, Natalia O.; Sapozhnikova, Kristina Yu; Kiselev, Evgeniy G.; Vasiliev, Alexander D.; Nemtsev, Ivan, V; et al. / https://doi.org/10.3390/polym13183142Polymers/

The bacterial strain isolated from soil was identified as Cupriavidus necator IBP/SFU-1 and investigated as a PHA producer. The strain was found to be able to grow and synthesize PHAs under autotrophic conditions and showed a broad organotrophic potential towards different carbon sources: sugars, glycerol, fatty acids, and plant oils. The highest cell concentrations (7–8 g/L) and PHA contents were produced from oleic acid (78%), fructose, glucose, and palm oil (over 80%). The type of the carbon source influenced the PHA chemical composition and properties: when grown on oleic acid, the strain synthesized the P(3HB-co-3HV) copolymer; on plant oils, the P(3HB-co-3HV-co-3HHx) terpolymer, and on the other substrates, the P(3HB) homopolymer. The type of the carbon source influenced molecular-weight properties of PHAs: P(3HB) synthesized under autotrophic growth conditions, from CO2, had the highest number-average (290 ± 15 kDa) and weight-average (850 ± 25 kDa) molecular weights and the lowest polydispersity (2.9 ± 0.2); polymers synthesized from organic carbon sources showed increased polydispersity and reduced molecular weight. The carbon source was not found to affect the degree of crystallinity and thermal properties of the PHAs. The type of the carbon source determined not only PHA composition and molecular weight but also surface microstructure and porosity of the polymer films. The new strain can be recommended as a promising P(3HB) producer from palm oil, oleic acid, and sugars (fructose and glucose) and as a producer of P(3HB-co-3HV) from oleic acid and P(3HB-co-3HV-co-3HHx) from palm oil. 

https://doi.org/10.3390/polym13183142

Magnetic Fractions of PM2.5, PM2.5-10, and PM10 from Coal Fly Ash as Environmental Pollutants

Fomenko, Elena, V; Anshits, Natalia N.; Solovyov, Leonid A.; Knyazev, Yuriy, V; Semenov, Sergey, V; et al. / Acs Omega/ https://doi.org/10.1021/acsomega.1c03187

Characterization of magnetic particulate matter (PM) in coal fly ashes is critical to assessing the health risks associated with industrial coal combustion and for future applications of fine fractions that will minimize solid waste pollution. In this study, magnetic narrow fractions of fine ferrospheres related to environmentally hazardous PM2.5, PM2.5–10, and PM10 were for the first time separated from fly ash produced during combustion of Ekibastuz coal. It was determined that the average diameter of globules in narrow fractions is 1, 2, 3, and 7 μm. The major components of chemical composition are Fe2O3 (57–60) wt %, SiO2 (25–28 wt %), and Al2O3 (10–12 wt %). The phase composition is represented by crystalline phases, including ferrospinel, α-Fe2O3, ε-Fe2O3, mullite, and quartz, as well as the amorphous glass phase. Mössbauer spectroscopy and magnetic measurements confirmed the formation of nanoscale particles of ε-Fe2O3. Stabilization of the ε-Fe2O3 metastable phase, with quite ideal distribution of iron cations, occurs in the glass matrix due to the rapid cooling of fine globules during their formation from mineral components of coal.

https://doi.org/10.1021/acsomega.1c03187

Thermo-optic refraction based switchable optical mode converter

Shetty, Pritam P.; Maksimov, Dmitrii N.; Babu, Mahalingam; Bongu, Sudhakara Reddy; Bingi, Jayachandra / Journal Of Quantitative Spectroscopy & Radiative Transfer/ https://doi.org/10.1016/j.jqsrt.2021.107867

The temporally switchable optical mode conversion is crucial for optical communication and computing applications. This research demonstrates such optically switchable mode converter driven by thermo-optic refraction. The MoS2 nanofluid is used as a medium where the thermal microlens is created by a focused laser beam (pump). The convective thermal plume generated above the focal point of the pump beam within the nanofluid acts as an astigmatic thermal lens. It is discovered that mode conversion of the Laguerre-Gaussian (LG) to the Hermite-Gaussian (HG) beam (vice versa) takes place upon passing through the thermal lens. The topological charge of the LG beam can be easily determined using the proposed mode converter. The mode transformation is explained theoretically as the Fourier components of the LG beam undergoing different optical paths while propagating through the convective plume.

https://doi.org/10.1016/j.jqsrt.2021.107867

The role of SAXS and molecular simulations in 3D structure elucidation of a DNA aptamer against lung cancer

Morozov, Dmitry; Mironov, Vladimir; V. Moryachkov, Roman; Shchugoreva, Irina A.; V. Artyushenko, Polina; et al. / Molecular Therapy-nucleic Acids/ https://doi.org/10.1016/j.omtn.2021.07.015

Aptamers are short, single-stranded DNA or RNA oligonucleotide molecules that function as synthetic analogs of antibodies and bind to a target molecule with high specificity. Aptamer affinity entirely depends on its tertiary structure and charge distribution. Therefore, length and structure optimization are essential for increasing aptamer specificity and affinity. Here, we present a general optimization procedure for finding the most populated atomistic structures of DNA aptamers. Based on the existed aptamer LC-18 for lung adenocarcinoma, a new truncated LC-18 (LC-18t) aptamer LC-18t was developed. A three-dimensional (3D) shape of LC-18t was reported based on small-angle X-ray scattering (SAXS) experiments and molecular modeling by fragment molecular orbital or molecular dynamic methods. Molecular simulations revealed an ensemble of possible aptamer conformations in solution that were in close agreement with measured SAXS data. The aptamer LC-18t had stronger binding to cancerous cells in lung tumor tissues and shared the binding site with the original larger aptamer. The suggested approach reveals 3D shapes of aptamers and helps in designing better affinity probes.

https://doi.org/10.1016/j.omtn.2021.07.015

Silica-Coated Iron Oxide Nanoparticles for DNA Isolation for Molecular Genetic Studies in Hematology

Tyumentseva, Anna, V; Yaroslavtsev, Roman N.; Stolyar, Sergey, V; Saitova, Alina T.; Tyutrina, Ekaterina S.; et al./ Genetic Testing And Molecular Biomarkers/ https://doi.org/10.1089/gtmb.2021.0067

To develop magnetic nanoparticles (MNPs) based on iron oxide for DNA isolation from blood cells for quantitative molecular genetic analyses of the V617F mutation in the Januskinase 2 (JAK2) gene.

https://doi.org/10.1089/gtmb.2021.0067

Classification of the frozen/thawed surface state of Northern land areas based on SMAP and GCOM-W1 brightness temperature observations at 1.4 GHz and 6.9 GHz

Konstantin Muzalevskiy, Zdenek Ruzicka, Alexandre Roy, Michael M. Loranty & Alexander Vasiliev/ Remote Sensing Letters https://doi.org/10.1080/2150704X.2021.1963497

In this letter, the method created earlier by the authors and the information product SPL3FTP_E of the Soil Moisture Active Passive (SMAP) satellite for determining frozen/thawed state of soil surface on the example of test sites placed on North Slope of Alaska, U.S.A., Canada, Finland and Russian Federation were compared. As an indicator of the frozen/thawed state of soil surface, the polarization index calculated on the basis of the reflectivity of soils was proposed. The soil reflectivity was determined in the L-band based on the SMAP radiometric observations at a frequency of 1.4 GHz using the values of brightness temperatures measured by the Global Change Observation Mission – Water 1/Advanced Microwave Scanning Radiometer 2 (GCOM-W1/AMSR2) at a vertical polarization and a frequency of 6.9 GHz, as an estimate of the soil effective temperature. As a result, it was shown that the developed method makes it possible to increase accuracy of the frozen/thawed states determination of soil surface from 3% to 9% in relation to the SMAP data (SPL3FTP_E) for twelve Arctic test sites.

Application of Sentinel-1B Polarimetric Observations to Soil Moisture Retrieval Using Neural Networks: Case Study for Bare Siberian Chernozem Soil

Konstantin Muzalevskiy, and Anatoly Zeyliger/ REMOTE SENSING/ https://doi.org/10.3390/rs13173480/

Sentinel-1 is currently the only synthetic-aperture radar, which radar measurements of the earth’s surface to be carried out, regardless of weather conditions, with high resolution up to 5–40 m and high periodicity from several to 12 days. Sentinel-1 creates a technological platform for the development of new globally remote sensing algorithms of soil moisture, not only for hydrological and climatic model applications, but also on a single field scale for individual farms in precision farming systems used. In this paper, the potential of soil moisture remote sensing using polarimetric Sentinel-1B backscattering observations was studied. As a test site, the fallow agricultural field with bare soil near the Minino village (56.0865°N, 92.6772°E), Krasnoyarsk region, the Russian Federation, was chosen. The relationship between the cross-polarized ratio, reflectivity, and the soil surface roughness established Oh used as a basis for developing the algorithm of soil moisture retrieval with neural networks (NNs) computational model. Two NNs is used as a universal regression technique to establish the relationship between scattering anisotropy, entropy and backscattering coefficients measured by the Sentinel-1B on the one hand and reflectivity on the other. Finally, the soil moisture was found from the soil reflectivity in solving the inverse problem using the Mironov dielectric model. During the field campaign from 21 May to 25 August 2020, it was shown that the proposed approach allows us to predict soil moisture values in the layer thickness of 0.00–0.05 m with the root-mean-square error and determination coefficient not worse than 3% and 0.726, respectively. The validity of the proposed approach needs additional verification on a wider dataset using soils of different textures, a wide range of variations in soil surface roughness, and moisture

https://doi.org/10.3390/rs13173480

Realization Conditions and the Magnetic Field Dependence of Corner Excitations in the Topological Insulator with Superconducting Coupling on the Triangular Lattice

Fedoseev, A. D./ Journal Of Experimental And Theoretical Physics/ https://doi.org/10.1134/S1063776121060029

The studies of the topological properties of systems have recently been extended due to a new concept of higher-order topological insulators and superconductors. Many models were proposed for two-dimensional systems on a square lattice, where corner excitations can appear; however, the problem of existence of such excitations in superconducting systems with a triangular crystal lattice is still poorly understood. Using a topological insulator in the form of a triangle with a chiral superconducting order parameter as an example, we shows that corner excitations can exist in C3-symmetric systems. In spite of a nontopological character, these excitations have energies inside the gap of the first-order edge excitation spectrum over a wide parameter range and are well localized at the corners of the system. Gapless corner excitations are shown to exist in the system at certain parameters. The application of a magnetic field in the system plane removes the triple degeneracy of the corner excitation energy and makes it possible to control the position of the minimum-energy corner excitation using a magnetic field. At the same time the fine adjustment to achieve the gapless excitations at the chosen corner can be made with changing of the magnetic field value.

https://doi.org/10.1134/S1063776121060029

Oblique light incidence method to study topological defects in nematic layers with conical boundary conditions

Krakhalev, Mikhail N. / Scientific Reports/ https://doi.org/10.1038/s41598-021-96784-9

A polarization microscopy method to investigate the orientational structures and boojums formed in the chiral and achiral nematic layers under conical (tilted) boundary conditions has been developed. Oblique light incidence on nematic layer is used, due to which the phase difference between the ordinary and extraordinary waves depends on the director’s azimuthal angle. The phase difference gets maximal when the director azimuthal angle of achiral nematic φ(x,y)=0φ(x,y)=0 and an azimuthal angle at the center of the chiral nematic layer φ0(x,y)=0φ0(x,y)=0 independently of the total twist angle φTOTALφTOTAL. It has been found that the m=+1m=+1 boojums with the phase ξ=±90ξ=±90∘ and ξ=(90+φTOTAL/2)ξ=(−90∘+φTOTAL/2) are formed in achiral and chiral nematics, respectively, at the director tilt angle θd/240θd/2≅40∘ at the interface. In addition, the defectless structure of chiral nematic with the periodically variable azimuthal director angle on the substrates has been studied.

 

Nematic Structures under Conical Anchoring at Various Director Tilt Angles Specified by Polymethacrylate Compositions

Kostikov, Denis A.; Krakhalev, Mikhail N.; Prishchepa, Oxana O.; Zyryanov, Victor Ya/ Polymers/ https://doi.org/10.3390/polym13172993
Dependence of the director tilt angle of nematic liquid crystal (LC) under conical anchoring from the two-component polymer mixture composition has been studied. We varied the ratio of poly(isobutyl methacrylate) (PiBMA), which specifies a conical anchoring for the nematic liquid crystal LN-396, and poly(methylmethacrylate) (PMMA) assigning a tangential alignment for the same nematic. An oblique incidence light technique to determine a tilt angle has been used. It has been shown that the tilt angle increases from 0 to 47.7 when PiBMA:PMMA ratio changes in the range 30:70 to 100:0. The specific optical textures viewed under the polarizing microscope and proper orientational structures have been considered for various compositions of the polymer films. An electric field action on the formed orientational structures has been investigated. The obtained results are promising for the application in various electro-optical LC devices with a conical anchoring in which the director tilt angle is a crucial parameter: a controlled diffraction gratings, an electrically operated achromatic rotators of linear light polarization, etc.
 

 https://doi.org/10.3390/polym13172993

Resonant transmission of fermionic carriers: Comparison between solid-state physics and quantum optics approaches

Kolovsky, Andrey R.; Maksimov, Dmitrii N. / DOI: P10.1103/PhysRevB.104.115115hysical Review B/

We revisit the phenomenon of the resonant transmission of fermionic carriers through a quantum device connected to two contacts with different chemical potentials. We show that, besides the traditional in solid-state physics Landauer-Büttiker approach, this phenomenon can be also described by the non-Markovian master equation for the reduced density matrix of the fermions in the quantum device. We identify validity regions of both approaches in the system parameter space and argue that for large relaxation rates the accuracy of the latter approach greatly exceeds the accuracy of the former.

DOI: P10.1103/PhysRevB.104.115115hysical Review B/

Metastable growth and infrared spectra of CuB2O4:Ni single crystals

Moshkina, Evgeniya; Molokeev, Maxim; Belskaya, Nadejda; Nemtsev, Ivan; Molchanova, Anastasiia; et al. / Crystengcomm/ DOI https://doi.org/10.1039/D1CE00729G

In this work, the formation of CuB2O4:Ni crystals in fluxes based on Li2WO4–Bi2O3–WO3 solvents was studied. The crystallized phases were studied with respect to the WO3 content and the mode of crystal holder insertion. A distinctive feature of the used flux growing mode is the metastable nature of nucleation: the desirable phase was obtained by using a super-cooled crystal holder – under insertion of a crystal holder cooled down to temperatures of the metastable zone. By powder X-ray diffraction, the composition of the obtained samples was analyzed. IR reflection and transmission spectra of the as-synthesized single crystals were recorded and analyzed in comparison with that of “pure” CuB2O4.

DOI: https://doi.org/10.1039/D1CE00729G

Dynamical Immiscibility of Aqueous Carbonate Fluid in the Shortite-Water System at High-Pressure-Temperature Conditions

Goryainov, Sergey, V; Krylova, Svetlana N.; Borodina, Ulyana O.; Krylov, Alexander S. / Journal Of Physical Chemistry C/ https://doi.org/10.1021/acs.jpcc.1c05077

Anhydrous carbonate shortite, Na2Ca2(CO3)3, compressed in water at high pressure–temperature (up to 5 GPa, 350 °C) was studied by Raman spectroscopy. At 3.2 GPa and 250 °C, shortite begins to dissolve, followed by crystallization of aragonite and aragonite’. The unusual behavior of aqueous carbonate fluid was observed at 4.8 GPa and 300–350 °C. This process is characterized by the active formation of microbubbles within 2–60 s that are inserted one into another. Microbubbles are considered to be a result of the two immiscible fluid stratification. This dynamical immiscibility of the fluid accompanies the appearance of several crystalline carbonates and organic molecular crystals. Na-formate and some polymorphs of Ca-formate were observed.

https://doi.org/10.1021/acs.jpcc.1c05077

 

Substrate-mediated lattice Kerker effect in Al metasurfaces

Kostyukov, A. S.; Ershov, A. E.; Bikbaev, R. G.; Gerasimov, V. S.; Rasskazov, I. L.; et al. / Journal Of The Optical Society Of America B-optical Physics/ https://doi.org/10.1364/JOSAB.427939

Surface lattice resonances (SLRs) emerging in regular arrays of plasmonic nanoparticles (NPs) are known to be exceptionally sensitive to the homogeneity of the environment. It is considered necessary to have a homogeneous environment for engineering narrowband SLRs, while in a half-space environment, SLRs rapidly vanish as the contrast between the refractive indices of the substrate and superstrate increases. From this conventional wisdom, it is apparent that the delicate lattice Kerker effect emerging from SLRs and resonances on constituent NPs should be difficult to achieve in a non-homogeneous environment. Using a rigorous theoretical treatment with multipolar decomposition, we surprisingly find and explain a narrowband substrate-mediated lattice Kerker effect in two-dimensional arrays of Al nanocylinders in a half-space geometry. We propose to use this effect for sensing applications and demonstrate its broad tunability across the UV/Vis wavelength range.

https://doi.org/10.1364/JOSAB.427939

Ferromagnetic resonance in a microtube

Fel'k, V. A.; Komogortsev, S. V. Journal Of Applied Physics/ https://doi.org/10.1063/5.0045548
Ferromagnetic resonance fields in a microtube with various ratios of the inner and outer diameter of the tube ββ were studied using micromagnetic simulation. For β<0.15β<0.15, the resonance field agrees with the prediction of the Kittel equation for an infinite ferromagnetic cylinder for both parallel and perpendicular orientation of the applied field to its axis. For β>0.15β>0.15, the resonance field increases from the resonance field of the infinite cylinder and approaches the level of a film magnetized along the plane. This behavior only qualitatively agrees with the prediction made using the calculated demagnetizing factor in the ferromagnetic tube. For β>0.15β>0.15 and the applied transverse field, a number of resonance peaks were observed for the microtube with the outer diameter of 500500 nm, but for nanotubes with the diameters of 5050 and 100 nm, a single peak was observed.

 

https://doi.org/10.1063/5.0045548

Study of Surface Anisotropy of the Interface of Two-layer DyCo/FeNi Films by the Spin-wave Resonance Method

Stolyar, S., V; Yakovchuk, V. Y.; Vazhenina, I. G.; Iskhakov, R. S. Journal Of Superconductivity And Novel Magnetism/ DOI https://doi.org/10.1007/s10948-021-06001-x

Two-layer DyCo/FeNi films were studied by the spin-wave resonance method. The experimental microwave frequency absorption spectra of the two-layer DyCo/FeNi films demonstrate the bulk and surface peaks of the exchange spin modes. The dependence of the surface condition type formed at the interface on the composition of the hard-magnetic layer (before and after the compensation point) was found. The values of the surface anisotropy constant and the type of magnetization pinning at each surface of the FeNi layer were estimated.

Effect of mechanical activation on the thermoelectric properties of Sr1-xSmxTiO3 ceramics

Orlov, Yu S.; Vereshchagin, S. N.; Novikov, S., V; Burkov, A. T.; Borus, A. A.; et al. Ceramics International/ https://doi.org/10.1016/j.ceramint.2021.07.060

The Sr1-xSmxTiO3 (х = 0.025, 0.05, 0.075, 0.1, 0.2) strontium titanate solid solutions were prepared from oxides and carbonates using a conventional ceramic technology based on the mechanochemical activation. The electrical conductivity and Seebeck coefficient of the synthesized compounds were measured in the temperature range from 300 to 800 K. We found that the properties of the samples significantly depend on the preliminary mechanochemical activation. The thermoelectric power factor attains maximum value in the hydrogen reduced samples with concentration of х = 0.05 and 0.075 obtained from nanoparticles: 5.5 μW/(cm · K2) for Sr0.95Sm0.05TiO3 (580 K) and 4.10 μW/(cm · K2) for Sr0.925Sm0.075TiO3 (650 K). An increase in the annealing temperature of mechanically activated samples leads to an even greater increase in electrical conductivity and power factor: 9.2 μW/(cm · K2) for Sr0.925Sm0.075TiO3 (650 K).

https://doi.org/10.1016/j.ceramint.2021.07.060

Effect of optical f - f excitations on the Nd-Fe exchange interaction in Nd ferroborate with multiferroic properties

Gavrichkov, Vladimir A.; Malakhovskii, Alexandr V.; Ovchinnikov, Sergey G. Physical Review B/ Phys. Rev. B 104, 064445 / DOI:https://doi.org/10.1103/PhysRevB.104.064445

We considered the effect of optical pumping at the ff transitions frequency on df superexchange in the rare-earth antiferromagnetic ferroborate Nd0.5Gd0.5Fe3(BO3)4 between Nd3+ ions in the excited states of the 4G5/2, 2G7/2, and Fe3+ in the ground state 6A1. In the ferroborate, df superexchange is directly related to the strong magnetoelectric coupling observed in the ground state of the material. We show that under optical pumping at the frequency of ff transitions 4I9/2(4G5/2+2G7/2) in the Nd3+ ion, the nature of the df interaction changes to FM. The phenomena can be explained by the occupation of the excited Nd3+ “spin pure” states with spin 1/2, or their mixing to the optically excited states with spin 3/2 due to the spin-orbit interaction. Near optically excited ions Nd3+, magnetic frustrations change from FM ordering under the df AFM interaction to AFM ordering under the FM interaction in the basal hexagonal plane.

DOI: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.064445

Cu-Doped TiNxOy Thin Film Resistors DC/RF Performance and Reliability

Shanidze, Lev, V; Tarasov, Anton S.; Rautskiy, Mikhail, V; Zelenov, Fyodor, V; Konovalov, Stepan O.; et al. / Applied Sciences-basel/ https://doi.org/10.3390/app11167498

We fabricated Cu-doped TiNxOy thin film resistors by using atomic layer deposition, optical lithography, dry etching, Ti/Cu/Ti/Au e-beam evaporation and lift-off processes. The results of the measurements of the resistance temperature dependence, non-linearity, S-parameters at 0.01–26 GHz and details of the breakdown mechanism under high-voltage stress are reported. The devices’ sheet resistance is 220 ± 8 Ω/□ (480 ± 20 µΩ*cm); intrinsic resistance temperature coefficient (TCR) is ~400 ppm/°C in the T-range of 10–300 K; and S-parameters versus frequency are flat up to 2 GHz with maximum variation of 10% at 26 GHz. The resistors can sustain power and current densities up to ~5 kW*cm−2 and ~2 MA*cm−2, above which they switch to high-resistance state with the sheet resistance equal to ~200 kΩ/□ (~0.4 Ω*cm) caused by nitrogen and copper desorption from TiNxOy film. The Cu/Ti/TiNxOy contact is prone to ageing due to gradual titanium oxidation while the TiNxOy resistor body is stable. The resistors have strong potential for applications in high-frequency integrated and hybrid circuits that require small-footprint, medium-range resistors of 0.05–10 kΩ, with small TCR and high-power handling capability. 

https://doi.org/10.3390/app11167498

Multiple fermion scattering in the weakly coupled spin-chain compound YbAlO3

S. E. Nikitin, S. Nishimoto, Y. Fan, J. Wu, L. S. Wu, A. S. Sukhanov, M. Brando, N. S. Pavlovskii, J. Xu, L. Vasylechko, R. Yu & A. Podlesnyak / NATURE COMMUNICATIONS/ DOI https://doi.org/10.1038/s41467-021-23585-z

A field-induced incommensurate spin density wave order was observed in the spin-chain material YbAlO3; however, its mechanism is not fully understood. Here, using neutron scattering and numerical calculations, the authors propose a mechanism based on multiple fermion scattering caused by weak inter-chain coupling.

The Heisenberg antiferromagnetic spin-1/2 chain, originally introduced almost a century ago, is one of the best studied models in quantum mechanics due to its exact solution, but nevertheless it continues to present new discoveries. Its low-energy physics is described by the Tomonaga-Luttinger liquid of spinless fermions, similar to the conduction electrons in one-dimensional metals. In this work we investigate the Heisenberg spin-chain compound YbAlO3 and show that the weak interchain coupling causes Umklapp scattering between the left- and right-moving fermions and stabilizes an incommensurate spin-density wave order at q = 2k(F) under finite magnetic fields. These Umklapp processes open a route to multiple coherent scattering of fermions, which results in the formation of satellites at integer multiples of the incommensurate fundamental wavevector Q = nq. Our work provides surprising and profound insight into bandstructure control for emergent fermions in quantum materials, and shows how neutron diffraction can be applied to investigate the phenomenon of coherent multiple scattering in metals through the proxy of quantum magnetic systems.

Операции с документом


Поделиться: