New Publications

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.

Low-Threshold Bound State in the Continuum Lasers in Hybrid Lattice Resonance Metasurfaces

Jhen-Hong Yang, Dmitrii N. Maksimov, Zhen-Ting Huang, Pavel S. Pankin, Ivan V. Timofeev, Kuo-Bing Hong, Heng Li, Jia-Wei Chen, Chu-Yuan Hsu, Yi-Yun Liu, Tien-Chang Lu, Tzy-Rong Lin, Chan-Shan Yang, Kuo-Ping Chen/ LASER & PHOTONICS REVIEWS / DOI10.1002/lpor.202100118

Bound states in the continuum (BICs) have attracted much attention in recent years due to the infinite quality factor (Q-factor) resonance and extremely localized field. In this study, BICs have been demonstrated by dielectric metasurfaces with hybrid surface lattice resonance (SLR) in the experiment. By breaking the symmetry of geometry, SLR can be easily switched between BICs and quasi-BICs. Comparing with literature, switching between BICs and quasi-BICs is usually accompanied by wavelength shift. Here, a design rule is proposed to prevent the wavelength shift when the Q-factor is changing. Also, such a design also makes subsequent identification of the laser threshold more credible. Due to the high Q-factor, low threshold laser is one of the intuitive applications of BICs. Utilize the high localized ability of BICs, low threshold BICs laser can be achieved by the dielectric metasurface immersed with Rhodamine 6G. Interestingly, due to the high Q-factor resonance of BICs, the laser signals and images can be observed in almost transparent samples. Not only the BICs laser is demonstrated in the experiment, but also the mechanism of BICs is deeply analyzed. This study can help readers better understand this novel feature of BICs, and provide the way for engineer BICs metasurfaces. The device can provide various applications, including laser, optical sensing, non-linear optics enhancement, and single-photon source.

DOI:10.1002/lpor.202100118

Hydrogen bond effects in multimode nuclear dynamics of acetic acid observed via resonant x-ray scattering

Viktoriia Savchenko1,2,3, Victor Ekholm4,5, Iulia Emilia Brumboiu1,6, Patrick Norman1, Annette Pietzsch7, Alexander Föhlisch7,8, Jan-Erik Rubensson4, Johan Gråsjö4,9, Olle Björneholm4, Conny Såthe5, Minjie Dong4, Thorsten Schmitt10, Daniel McNally10, Xingye Lu10, Pavel Krasnov2,3, Sergey P. Polyutov2,3, Faris Gel’mukhanov1,2,3, Michael Odelius11,a), and Victor Kimberg1,2,3,b)/ J. Chem. Phys. 154, 214304 (2021); / https://doi.org/10.1063/5.0049966

A theoretical and experimental study of the gas phase and liquid acetic acid based on resonant inelastic x-ray scattering (RIXS) spectroscopy is presented. We combine and compare different levels of theory for an isolated molecule for a comprehensive analysis, including electronic and vibrational degrees of freedom. The excitation energy scan over the oxygen K-edge absorption reveals nuclear dynamic effects in the core-excited and final electronic states. The theoretical simulations for the monomer and two different forms of the dimer are compared against high-resolution experimental data for pure liquid acetic acid. We show that the theoretical model based on a dimer describes the hydrogen bond formation in the liquid phase well and that this bond formation sufficiently alters the RIXS spectra, allowing us to trace these effects directly from the experiment. Multimode vibrational dynamics is accounted for in our simulations by using a hybrid time-dependent stationary approach for the quantum nuclear wave packet simulations, showing the important role it plays in RIXS.

https://doi.org/10.1063/5.0049966

Shielded open-circuited probe for in-situ measurements of soil permittivity in Very high frequency (VHF) and Ultra high frequency (UHF) bands

Muzalevskiy, Konstantin; Karavaysky, Andrey/ Transactions Of The Institute Of Measurement And Control/ https://doi.org/10.1177/01423312211037791

In this paper, the shielded open-circuited probe operating in the wide frequency range from 75MHz to 2GHz is proposed. The probe is made of an SubMiniature version A (SMA) flange connector. The central rod of the SMA connector emerges from a coaxial transition in the flange and shielded by four rods. The robe design allows us to calculate of the probe reflection coefficient S11 used simple analytical transmission line model (TEM wave mode), the parameters of which were calibrated on a set of substances with a known frequency spectrum of permittivity. The refractive index (RI) and normalized attenuation coefficient (NAC) retrieval technique is based on solving the inverse problem of minimizing the residual norm between measured and calculated frequency spectra of reflection coefficient S11. After calibration, the root-mean-square error (determination coefficient) between the measured and calculated module and phase of the reflection coefficient S11 for the sets of calibration media air, distilled water, butanol, pure ice, water solution with NaCl of salinity of 8.9% do not exceed 0.26dB (0.995) and 0.03 rad (0.999), respectively, in the frequency range from 75MHz to 2GHz. The root-mean-square error (determination coefficient) between the measured RI and NAC spectra for four soil cover samples (variation of the clay fraction from 10.5 g/g to 47.6 g/g) using the proposed probe and a precision coaxial cell not exceeds 0.109 (0.993) and 0.057 (0.986), respectively, in the frequency range from 75 MHz to 2 GHz. As a result, it is experimentally shown that RI и NAC can be measured by the proposed non-precision probe with an error comparable to the precision coaxial cell.

https://doi.org/10.1177/01423312211037791

Evolution of Structural, Thermal, Optical, and Vibrational Properties of Sc2S3, ScCuS2, and BaScCuS3 Semiconductors

Azarapin, Nikita O.; Oreshonkov, Aleksandr S.; Razumkova, Illaria A.; Aleksandrovsky, Aleksandr S.; Maximov, Nikolai G.; et al./ European Journal Of Inorganic Chemistry/ https://doi.org/10.1002/ejic.202100292

In the present work, we report on the synthesis of Sc2S3, ScCuS2 and BaScCuS3 powders using a method based on oxides sulfidation and modification of their properties. The crystal structures and morphology of samples are verified by XRD and SEM techniques. Thermal stability has been studied by DTA which has revealed that Sc2S3 decomposes to ScS through melting at 1877 K. ScCuS2 and BaScCuS3 melt incongruently at temperatures of 1618 K and 1535 K, respectively. The electronic structure calculations show that the investigated compounds are semiconductors with indirect band gap (Eg). According to the diffuse reflection spectroscopy, Sc2S3, ScCuS2 and BaScCuS3 are wide-bandgap semiconductors featured the Eg values of 2.53 eV, 2.05 eV and 2.06 eV, respectively. The band gap decreases with the introduction of copper (I) and barium cations into the crystal structure of the compounds. Variation of local structure has been verified by Raman and infrared spectroscopy. The calculated vibrational modes of ScCuS2 correspond to CuS4 and Sc−S layer vibrations, even though ScS6 octahedra-like structural units can be found in the structure.

 https://doi.org/10.1002/ejic.202100292

Trimetallic magnetite-Ti-Au nanoparticle formation: A theoretical approach

Fedorov, A. S.; Kovaleva, E. A.; Sokolov, A. E.; Visotin, M. A.; Lin, C. R.; et al./ Materials Chemistry And Physics/ https://doi.org/10.1016/j.matchemphys.2021.124847

Geometric, electronic and magnetic structure of planar slabs consisting of magnetite Fe3O4, titanium and gold layers are investigated by DFT-GGA calculations. It is assumed that these slabs can be used to simulate the upper layers of magnetite nanoparticles covered with an intermediate layer of titanium and a gold layer on the surface. Specific energies and spreading parameters (wettability) of the magnetite-gold, magnetite-titanium and titanium-gold interfaces are calculated. The specific energy and spreading parameter of the magnetite-gold interface is found to be negative, while these values of the magnetite-titanium (for thin Ti layer) and magnetite-titan-gold interfaces are significantly positive. This allows us to hope that the intermediate thin layer of titanium at the boundary between the surface of the magnetite nanoparticle and the gold layer stabilizes this three-layer structure and allows obtaining magnetite nanoparticles covered with continuous gold coating.

https://doi.org/10.1016/j.matchemphys.2021.124847

Synthesis, Crystal Structure, and the Optical and Thermodynamic Properties of PrAlGe2O7

Irtyugo, L. A.; Denisova, L. T.; Molokeev, M. S.; Denisov, V. M.; Aleksandrovsky, A. S.; et al./ Russian Journal Of Physical Chemistry A/ https://doi.org/10.1134/S0036024421080124

Germanate PrAlGe2O7 is obtained from initial oxides Pr2O3, Al2O3, and GeO2 via solid-phase synthesis. The crystal structure of the investigated germanate is determined via X-ray diffraction. The luminescence spectra are been determined at room temperature. The effect temperature has on the heat capacity is determined via differential scanning calorimetry. The thermodynamic properties of the complex oxide compound are calculated using the experimental data on Cp = f(T) in the temperature range of 350‒1000 K.

https://doi.org/10.1134/S0036024421080124

Induced magnetic anisotropy of Co-P thin films obtained by electroless deposition

Chzhan, A. V.; Podorozhnyak, S. A.; Zharkov, S. M.; Gromilov, S. A.; Patrin, G. S./ Journal Of Magnetism And Magnetic Materials/ https://doi.org/10.1016/j.jmmm.2021.168129

Co1−x-Px films (x = 0.02–0.05) deposited on cover glass by electroless plating from aqueous solutions in a continuous magnetic field with the strength of 2.5 kOe are presented. It has been found that in the pH range from 7.2 to 9.3, two special areas can be distinguished, they are characterized by the deposition of films with qualitatively different parameters in them. So, the change of the pH of working solutions from 7.2 to 8.7 causes the increase in the value of the induced magnetic anisotropy constant KU from 2.5 × 105 erg/cm3 to 6 × 105 erg/cm3. If the value of the hydrogen index is still increasing, an uneven drop to 5 × 104 erg/cm3 is observed. In the same way, the coercivity HC changes; at first it grows from 700 Oe to 1.5 kOe, and then it drops to Oe units. The concentration of phosphorus in the range of 7.2 to 8.7 increases linearly from 2 to 3 wt%, and in the range of 8.7 to 9.3, it increases from 3 to 5 wt%. The x-ray diffraction data show that the samples obtained at pH < 8.7 are characterized by the presence of the hcp phase of Co (α-Co). The observed reflections of films obtained at pH > 8.7 indicate the fcc-Co (β-Co) with the diffraction peak blurring: the greater the pH value of the samples obtained, the more the diffraction peak blurring. It is shown that the induced magnetic anisotropy in high-coercivity films relates to the modification of the Co lattice. The lattice passes from a distorted fcc to an hcp structure during the growth of crystallites in a magnetic field. The induced magnetic anisotropy appears in films that were obtained in the high pH field due to the ordering of magnetic ions pairs.

https://doi.org/10.1016/j.jmmm.2021.168129

Revisiting the BaBiO3 semiconductor photocatalyst: synthesis, characterization, electronic structure, and photocatalytic activity

Dmitry S. Shtarev, Anna V. Shtareva, Ruslan Kevorkyants, Maxim S. Molokeev & Nick Serpone/ Photochemical & Photobiological Sciences/ DOI: https://doi.org/10.1007/s43630-021-00086-y

This article revisits the properties of BaBiO3 examined extensively in the last two decades because of its electronic properties as a superconductor and as a semiconductor photocatalyst. Solid-state syntheses of this bismuthate have often involved BaCO3 as the barium source, which may lead to the formation of BaBiO3/BaCO3 heterostructures that could have an impact on the electronic properties and, more importantly, on the photocatalytic activity of this bismuthate. Accordingly, we synthesized BaBiO3 by a solid-state route to avoid the use of a carbonate; it was characterized by XRD, SEM, and EDX, while elemental mapping characterized the composition and the morphology of the crystalline BaBiO3 and its thin films with respect to structure, optoelectronic, and photocatalytic properties. XPS, periodic DFT calculations, and electrochemical impedance spectroscopy ascertained the electronic and electrical properties, while Raman and DRS spectroscopies assessed the relevant optical properties. The photocatalytic activity was determined via the degradation of phenol in aqueous media. Although some results accorded with earlier studies, the newer electronic structural data on this bismuthate, together with the photocatalytic experiments carried out in the presence of selective radical trapping agents, led to elucidating some of the mechanistic details of the photocatalytic processes that previous views of the BaBiO3 band structure failed to address or clarify. Analytical refinement of the XRD data inferred the as-synthesized BaBiO3 adopted the C2/m symmetry rather than the I2/m structure reported earlier, while Tauc plots from DRS spectra yielded a bandgap of 2.05 eV versus the range of 1.1–2.25 eV reported by others; the corresponding flatband potentials were 1.61 eV (EVB) and − 0.44 eV (ECB). The photocatalytic activity of BaBiO3 was somewhat greater than that of the well-known Evonik P25 TiO2 photocatalyst under comparable experimental conditions.

Dynamical phase shift in x-ray absorption and ionization spectra by two delayed x-ray laser fields

Viktoriia Savchenko, Faris Gel'mukhanov, Tim Laarmann, Sergey P. Polyutov, and Victor Kimberg/ Phys. Rev. A 104, 013114/ https://doi.org/10.1103/PhysRevA.104.013114

We study theoretically x-ray absorption and ionization spectra of an atom or molecule by two coherent x-ray pulses that show a relative phase shift resulting in a time delay of the pulse envelopes. We demonstrate that the phase modulation of the spectra is shifted with respect to the phase oscillation comb of the x-ray double pulse. The reason for this shift is the dynamics of the process defined by the interplay of the delay time, the pulse width, the detuning, and the lifetime of the core-excited state.

https://doi.org/10.1103/PhysRevA.104.013114

The Effect of Heat Treatment on Electrical Properties of [ZnO/C](25) Multilayer Structure

Pankov, S. Yu; Foshin, V. A.; Kashirin, M. A.; Makagonov, V. A.; Volochaev, M. N. Vii International Young Researchers' Conference - Physics, Technology, Innovations (Pti-2020)/ https://doi.org/10.1063/5.0032291

The effect of heat treatment on magnetoresistance of [ZnO/C]25 multilayered thin films prepared by ion-beam sputtering has been investigated. A decrease in the magnetoresistance with an increase in the annealing temperature was detected, which is associated with a change in the mechanism of electrical transport.

https://doi.org/10.1063/5.0032291

Tunable Meta-Surface Antenna Array with Holographic Beamforming

Lemberg, Konstantin, V; Kosmynin, Aleksey N.; Stupnitsky, Dmitry A.; Grushevsky, Eugene O.; Podshivalov, Ivan, V / 2020 7th All-russian Microwave Conference (Rmc)/ 10.1109/RMC50626.2020.9312354

The paper describes tunable meta-surface antenna arrays operation principle. In such an arrays beamforming is carried out by modulating the coupling coefficients between a wave traveling along the surface and electrically small radiators. It is shown that the law of coupling coefficient modulation can be calculated using the principles of holography on the basis of the given “reference” (corresponding to the excitation of the meta-surface) and “object” (corresponding to the required radiation pattern) waves. The results of numerical simulation of the X-band linear antenna array with liquid crystal control elements, which using the described beamforming principle, are presented.

10.1109/RMC50626.2020.9312354

Mechanical activation of fullerene containing soot during extraction of higher and endohedral metallofullerenes

Victoria I. Еlesina,Grigory N. Churilov,Natalia G. Vnukova,Nikita S. Nikolaev,Gariy A. Glushenko &Victoria G. Isakova/ Fullerenes Nanotubes And Carbon Nanostructures/ https://doi.org/10.1080/1536383X.2021.1966421

For extraction of higher fullerenes and endohedral metallofullerenes (EMF) with yttrium from fullerene-containing carbon soot (soot) obtained by combined spraying of graphite and yttrium oxide powders in an arc plasma, we developed a device (Extractor*) that provides mechanical activation effects on agents combined with filtration. It has been shown that the soot recovery percentage of a mixture of higher fullerenes and EMF with different solvents (carbon disulfide, o-xylene, pyridine) and the EMF mass fraction in the mixture is significantly higher than in the extraction with a Soxhlet apparatus traditionally used for these purposes. The time spent on the extraction process is reduced significantly. Due to a known reaction with titanium chloride (TiCl4) and removal of a solution of empty fullerenes, subsequent bonding of EMF with yttrium into an insoluble complex directly in the extractor allows the product to be significantly enriched with EMF. In general, we were able to significantly reduce both the duration of extraction of the fullerenes mixture and EMF and the production of EMF separately.

The influence of chalcogen atom on conformation and phase transition in chalcogenazinoquinolinium monoiodides

I. Yushina, A. Krylov, I. I. Leonidov, V. Batalov, Y.-S. Chen, S. G. Wang, A. Stash and E. Bartashevich/ Acta Crystallographica Section B-structural Science Crystal Engineering And Materials/ https://doi.org/10.1107/S2052520621004571

Crystalline chalcogenazinoquinolinium monoiodides, where the chalcogen atom is oxygen and sulfur, were studied using a combination of X-ray diffraction, Raman and UV-vis spectroscopies and photoluminescence experimental techniques. Periodic quantum-chemical calculations were performed to characterize the features of electronic structure and vibrational assignment. X-ray diffraction and Raman spectroscopy experiments consistently reveal phase transition of thia­zinoquinolinium monoiodide at low temperatures with the decrease of symmetry to P1. The luminescence study for oxazinoquinolinium monoiodide reveals the excitation maximum at 532 nm and emission at 650 nm with significantly higher intensity than for the thia­zinoquinolinium derivative. The studied chalcogenazinoquinolinium monoiodides demonstrate high values of Stokes shift up to 150 nm.

https://doi.org/10.1107/S2052520621004571

Dynamics of resonant x-ray and Auger scattering

Faris Gel’mukhanov, Michael Odelius, Sergey P. Polyutov, Alexander Föhlisch, and Victor Kimberg/ Reviews Of Modern Physics/ DOI: https://dx.doi.org/10.1103/RevModPhys.93.035001

An overview of both experimental and theoretical results in the field of resonant scattering of tunable soft and hard x-ray radiation is presented, with a main focus on the closely related processes of resonant inelastic x-ray scattering (RIXS) and resonant Auger scattering (RAS). The review starts with an overview of fundamental dynamical aspects of RIXS illustrated for different systems. A detailed analysis of case studies with increasing complexity, considering both gas-phase and condensed matter (liquids and solids) applications, is given. In the review, the most important achievements in investigations of coupled electron-nuclear dynamics and structural aspects in studies of liquids and solids over the last two decades are outlined. To give a perspective on the insights from RIXS and RAS, the x-ray results are discussed against the background of complementary experimental techniques like vibrational infrared absorption and Raman spectroscopy, as well as small-angle x-ray and neutron scattering. Finally, recent achievements in time-resolved studies based on x-ray free-electron lasers are described.

https://dx.doi.org/10.1103/RevModPhys.93.035001

Measurement of Thin Film Magnetic Characteristics in the Radio Frequency Range

Burmitskikh, Anton, V; Boev, Nikita M.; Kleshnina, Sofya A. International Siberian Conference On Control And Communications (Sibcon 2021 )/ DOI: 10.1109/SIBCON50419.2021.9438908

 The paper presents a method for measuring the ferromagnetic resonance spectrum in the radio frequency range (4 MHz). A high-frequency generator operating in the autodyne mode was used to measure the magnetic characteristics of thin ferromagnetic films. Theoretical equations for ferromagnetic resonance excitations have been presented. Experimental results for the samples of nanocrystalline thin permalloy magnetic films with low magnetostriction and different values of the anisotropy field were obtained. Ferromagnetic resonance in the radio frequency range proved to be an excellent mean for measuring the value and direction of the magnetic anisotropy field in thin magnetic films.

DOI: 10.1109/SIBCON50419.2021.9438908

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