New Publications

Physical Properties of a Frustrated Quasi-One-Dimensional NaCuFe2(VO4)(3) Magnet and Effect of Chemical Pressure Induced by the Substitution of Sodium for Lithium

Drokina, T. V.; Petrakovskii, G. A.; Bayukov, O. A.; Molokeev, M. S.; Vorotynov, A. M.; et al. Physics Of The Solid State

The structural, thermal, static magnetic, and resonance properties of the low-dimensional NaCuFe2(VO4)(3) compound obtained by the solid-phase synthesis have been investigated. In the temperature range of 110-300 K, the electron spin res...

Structure and Thermodynamic Properties of the SmGaGe2O7 Oxide

L. T. Denisova, M. S. Molokeev, L. A. Irtyugoa, V. V. Beletskii, N. V. Belousova, and V. M. Denisov doi:10.1134/s1063783420020109 Physics of the Solid State, 2020, Vol. 62, No. 2, pp. 384–387

The SmGaGe2O7 oxide material has been obtained from initial Sm2O3, Ga2O3, and GeO2 oxides by solid-phase synthesis with annealing in air in the temperature range of 1273–1473 K. The structure of the investigated germanate (sp. gr. P21/c, a = 7.18610(9) Å, b = 6.57935(8) Å, and c = 12.7932(2) Å) has been established by X-ray diffraction and the high-temperature heat capacity has been determined by differential scanning calorimetry. Using the experimental data on Cp = f(T), the thermodynamic properties of the compound have been calculated.

Features of the Behavior of the Barocaloric Effect near Ferroelectric Phase Transition Close to the Tricritical Point

Mikhaleva, E. A.; Flerov, I. N.; Gorev, M., V; Bondarev, V. S.; Bogdanov, E., V Crystals. doi:10.3390/cryst10010051

A detailed study of the effect of temperature and pressure on heat capacity, entropy and hysteresis phenomena near the ferroelectric phase transition in ammonium sulfate (AS) was performed. An analysis of experimental results within the framework of the phenomenological theory showed that taking into account the temperature-dependent part of the anomalous entropy leads to a significant increase in the barocaloric effect (BCE). The maximum values of extensive and intensive BCE near the tricritical point are outstanding: ∆S max BCE ≈ 85 J/kgK, ∆T max AD ≈ 12 K and can be achieved at low pressure ∼0.5 GPa.

Gallium Composition-Dependent Structural Phase Transitions in HoFe3-xGax(BO3)(4) Solid Solutions: Crystal Growth, Structure, and Raman Spectroscopy Study

Evgeniya Moshkina, Svetlana Krylova, Irina Gudim, Maxim Molokeev, Vladislav Temerov, M.S. Pavlovskii, Alexander Vtyurin, and Alexander Krylov. Crystal Growth & Design. doi:10.1021/acs.cgd.9b01387.

Single crystals of solid solutions of HoFe3-xGax(BO3)4 with x = 0, 0.5, 1, 1.5, and 3 were obtained using flux synthesis. The conditions of the synthesis are described in detail. The structural properties of each of the synthesised samples were studied using X-ray powder diffraction analysis at several temperature points (303 K, 403 K, 503 K). The structural parameters of the obtained samples and the “pure” compounds HoFe3(BO3)4 and HoGa3(BO3)4 were compared. The Raman spectra of the obtained solid solutions HoFe3-xGax(BO3)4 were studied in a wide temperature range (T = 10 ÷ 400 K). The vibrational spectra and eigenvectors of the HoFe3Ga(BO3)4 and HoGa3(BO3)4 in R32 phase and HoFe3Ga(BO3)4 in P3121 phase were calculated within density functional theory. The features of the Raman spectra of HoFe2Ga(BO3)4, HoFe2.5Ga0.5(BO3)4, HoFe3(BO3)4 crystals associated with the R32→P3121 structural phase transition, which have a strong dependence on the degree of substitution x, are investigated. Peculiarities of the Raman spectra, which are associated with magnetic ordering in HoFe1.5Ga1.5(BO3)4, HoFe2Ga(BO3)4, HoFe2.5Ga0.5(BO3)4 crystals, were detected.

Synthesis and Magnetic Properties of the Core-Shell Fe3O4/CoFe2O4 Nanoparticles

Balaev, D. A.; Semenov, S. V.; Dubrovskii, A. A.; Krasikov, A. A.; Popkov, S. I. S. S. Yakushkin, V. L. Kirillov, and O. N. Mart’yanov Physics Of The Solid State. doi:10.1134/s1063783420020043

The Fe3O4/CoFe2O4 nanoparticles with a core–shell structure with an average size of 5 nm have been obtained by codeposition from the iron and cobalt chloride solutions. An analysis of the magnetic properties of the obtained system and their comparison with the data for single-phase Fe3O4 (4 nm) and CoFe2O4 (6 nm) nanoparticles has led to the conclusion about a noticeable interaction between the soft magnetic (Fe3O4) and hard magnetic (CoFe2O4) phases forming the core and shell of hybrid particles.

Enhanced green emission and thermal stability of Ba3Si6O12N2:Eu2+ by Ce3+/P5+-doping: Unity energy transfer, charge compensation and lattice strain release

Hao, Jiarui; Tao, Mengxuan; Gao, Zhiyu; Chen, Shuoting; Liu, Yixin; et al. Journal Of Luminescence. DOI: 10.1016/j.jlumin.2019.116995

To optimize luminescence properties of oxonitridosilicate phosphors are extremely necessary for improving lighting quality of white light-emitting diodes (WLEDs). Herein, we designed Ce3+, Eu2+ codoping and P5+<-> Si4+ substitution in the presentative Ba3Si6O12N2:Eu2+ green phosphor to realize an enhancement of luminescence efficiency and thermal stability. Rietveld refinement results of Ce3+, Eu2+, P5+-doped Ba3Si6O12N2 (BSON) confirmed the formation of pure trigonal phase (P-3) of Ba3Si6O12N2 and the successful doping of Ce3+, Eu2+, p(5+) ions. Ce3+ and Eu2+ ions randomly occupy two Ba crystallographic sites. Interestingly, a near unity energy transfer (ET, similar to 100%) from Ce3+ ions to Eu2+ ions is observed. Meanwhile, the doping of P5+ ions into BSON also helps improving the luminescence efficiency and thermal stability, which should be attributed to the charge compensation and the relax of lattice strain. In addition, the white light emitting diodes (WLEDs) fabricated by employing P5+-doped BSON: Eu2+ present a better electroluminescence performance than BSON: Eu2+. This study could serve as a guide in developing optimized oxonitridosilicates phosphors with improved luminescence performances based on complete energy transfer and lattice variations in local coordination environments through cation substitutions, and the as-prepared Ce3+/P5+-codoped Ba3Si6O12N2:Eu2+ could be an excellent green-emitting phosphor for UV-to-Visible LED chips pumped WLEDs.

Triple VTe2/graphene/VTe2 heterostructures as perspective magnetic tunnel junctions

Begunovich, Lyudmila, V; Kuklin, Artem, V; Visotin, Maxim A.; Kuzubov, Alexander A.; Tomilin, Felix N.; et al. Applied Surface Science. DOI: 10.1016/j.apsusc.2020.145315

New perspective 1.4 nm thick spin-polarized triple heterostructures based on graphene sandwiched between two vanadium ditelluride monolayers (VTe2/graphene/VTe2) were studied using ab initio DFT technique. Both possible trigonal prismatic (H-VTe2) and octahedral (T-VTe2) VTe2 phases were considered to design and study graphene-based heterostructures. It was shown that the interaction with graphene changes the electronic structure of 2D T-VTe2 from metallic to half-metallic, making T phase perspective to be used for magnetic tunnel junctions. The electronic subsystem of graphene fragment is slightly hole doped. Calculated tunnel magne-toresistance ratio for the favorable heterostructure configuration estimated within the Julliere model is 220%, which opens a way to use VTe2/graphene/VTe2 as prospective magnetic tunnel junction in novel spintronic nanodevices based on tunnel magnetic resistance and spin transfer torque effects.

The Morphology and Phenotype of Monocyte-Macrophages When Cultured on Bionanofilms Substrates with Different Surface Relief Profiles

Menzyanova, Natalia G.; Pyatina, Svetlana A.; Shabanov, Alexander V.; Nemtsev, Ivan V.; Stolyarov, Dmitry P.; et al. Biomolecules. DOI: 10.3390/biom10010065

The effect of surface relief profiles of alkanoate-based bionanofilms to the monocyte-macrophages (MN-MPhs) from peripheral blood of patients with atherosclerosis was studied in vitro. Patients were subjected to coronary stenting. Cell morphology and phenotype (expression of CD antigens, levels of production of marker cytokines) in vitro were analyzed before and after the installation of stents. It was shown, that the mean square roughness (Rq) of the bionanofilms determined the variability of cell morphology, CD antigens spectraand activity of production interleukins-6 and -10. Also, it was revealed, that the "activity" of the surface topography of biopolymer substrates depends on the functional state of MNs, isolated in different time points: Before and after stenting the ratios of cell morphotypes and production of cytokines in MN-MPhs differed significantly.

Application of DMA 242 C for Quasi-Static Measurements of Piezoelectric Properties of Solids

Turchin, Pavel P.; Turchin, Vladimir, I; Yurkevich, Sergey, V; Sukhodaev, Pavel O.; Raikova, Irina S. Journal Of Siberian Federal University-mathematics & Physics. DOI: 10.17516/1997-1397-2020-13-1-97-103

An experimental device for quasi-static measurements of piezoelectric moduli d(ijk), based on the possibilities of precision variations in mechanical stresses with the device DMA 242 C in the frequency range 0-100 Hz has been developed. A special sample holder and a charge amplifier are used in the measuring scheme. The measurements of piezoelectric moduli values of trigonal piezoelectric single crystalls La3Ga5SiO14 (P321) and YAl3(BO3)(4) (R32), as well as hexagonal ZnO (P6(3)mc) have been carried out.

Magnetic structure of ErFe3(BO3)(4): Spectroscopic and thermodynamic studies

Popova, E. A.; Chukalina, E. P.; Boldyrev, K. N.; et al. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS. DOI: 10.1016/j.jmmm.2019.166374

We report on the high-resolution spectroscopic study of multiferroic ErFe3(BO3)(4). The energies of all eight Kramers doublets of the ground I-4(15/2) multiplet of the Er3+ ion were determined by the high-resolution I-4(13/2) -> I-4(15)/2 infrared luminescence spectra. The spectroscopically determined temperature dependence of the splitting of the ground Kramers doublet was used to calculate the contribution of the erbium subsystem into the specific heat and the magnetic susceptibility of erbium iron borate. The analysis of the thermodynamic properties based on these calculations allowed us to suggest the domain structure in the easy-plane antiferromagnetically ordered iron subsystem, with two magnetically nonequivalent erbium positions in each domain.

Fabrication of Microcrystalline NaPbLa(WO4)(3):Yb3+/Ho3+ Phosphors and Their Upconversion Photoluminescent Characteristics

Lim, Chang Sung; Atuchin, Victor V.; Aleksandrovsky, Aleksandr S.; et al KOREAN JOURNAL OF MATERIALS RESEARCH. DOI: 10.3740/MRSK.2020.30.1.50

SELF-ORGANIZED AGGREGATION OF A TRIPLE OF COLLOIDAL QUANTUM DOTS INTO STABLE STRUCTURES WITH VARIOUS SHAPES CONTROLLED BY A LASER FIELD

Kornienko, Victoria S.; Tsipotan, Aleksei S.; Aleksandrovsky, Aleksandr S.; Slabko, Vitaliy V. 10th Anniversary International Conference On Nanomaterials - Research & Application (Nanocon 2018 (R)) 10TH ANNIVERSARY INTERNATIONAL CONFERENCE ON NANOMATERIALS - RESEARCH & APPLICATION (NANOCON 2018 (R))

Interaction between dielectric particles enhances the Q-factor

Bulgakov, Evgeny; Pichugin, Konstantin; Sadreev, Almas. Advanced Electromagnetics.

We study behavior of resonant modes with a distance between two dielectric resonators shaped as cylinders and disks. We reveal two basic scenarios of evolution of resonances with the distance between the cylinders. For larger distances and respectively weaker interaction of particles the resonances are bound around the resonances of isolated resonators and evolve by spiral way. For shorter distances and respectively stronger interaction the resonances bypass the isolated resonances. Both scenarios demonstrate considerable enhancement of the Q factor compared to the case of isolated particle.

In Situ Electron Diffraction and Resistivity Characterization of Solid State Reaction Process in Cu/Al Bilayer Thin Films

Moiseenko, Evgeny T.; Altunin, Roman R.; Zharkov, Sergey M. METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DOI: 10.1007/s11661-019-05602-5

Engineering novel tunable optical high-Q nanoparticle array filters for a wide range of wavelengths

Utyushev, A. D.; Isaev, I. L.; Gerasimov, V. S.; Ershov, A. E.; Zakomirnyi, V., I; et al. OPTICS EXPRESS DOI: 10.1364/OE.28.001426

The interaction of non-monochromatic radiation with arrays comprising plasmonic and dielectric nanoparticles has been studied using the finite-difference time-domain electrodynamics method. It is shown that LiNbO3, TiO2, GaAs, Si, and Ge all-dielectric nanoparticle arrays can provide a complete selective reflection of an incident plane wave within a narrow spectral line of collective lattice resonance with a Q-factor of 10(3) or larger at various spectral ranges, while plasmonic refractory TiN and chemically stable Au nanoparticle arrays provide high-Q resonances with moderate reflectivity. Arrays with fixed dimensional parameters make it possible to fine-tune the position of a selected resonant spectral line by tilting the array relative to the direction of the incident radiation. These effects provide grounds for engineering novel selective tunable optical high-Q filters in a wide range of wavelengths, from visible to middle-IR. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Charge-transfer plasmons with narrow conductive molecular bridges: A quantum-classical theory

Fedorov, A. S.; Krasnov, P. O.; Visotin, M. A.; Tomilin, F. N.; Polyutov, S. P.; et al Journal Of Chemical Physics. DOI: 10.1063/1.5131734

We analyze a new type of plasmon system arising from small metal nanoparticles linked by narrow conductive molecular bridges. In contrast to the well-known charge-transfer plasmons, the bridge in these systems consists only of a narrow conductive molecule or polymer in which the electrons move in a ballistic mode, showing quantum effects. The plasmonic system is studied by an original hybrid quantum-classical model accounting for the quantum effects, with the main parameters obtained from first-principles density functional theory simulations. We have derived a general analytical expression for the modified frequency of the plasmons and have shown that its frequency lies in the near-infrared (IR) region and strongly depends on the conductivity of the molecule, on the nanoparticle-molecule interface, and on the size of the system. As illustrated, we explored the plasmons in a system consisting of two small gold nanoparticles linked by a conjugated polyacetylene molecule terminated by sulfur atoms. It is argued that applications of this novel type of plasmon may have wide ramifications in the areas of chemical sensing and IR deep tissue imaging. Published under license by AIP Publishing.

New triple molybdate K5ScHf(MoO4)(6): Synthesis, properties, structure and phase equilibria in the M2MoO4-Sc-2(MoO4)(3)-Hf(MoO4)(2) (M = Li, K) systems

Grossman, Victoria G.; Bazarova, Jibzema G.; Molokeev, Maksim S.; at all JOURNAL OF SOLID STATE CHEMISTRY DOI: 10.1016/j.jssc.2019.121143

Subsolidus phase relations in the M2MoO4-Sc-2(MoO4)(3)-Hf(MoO4)(2) = Li, K) systems have been studied by the method of "intersecting cuts". No new triple molybdates have been identified in the Li2MoO4-Sc-2(MoO4)(3)-Hf(-MoO4)(2) system and a new triple molybdate K5ScHf(MoO4)(6) is formed in the K2MoO4-Sc-2(MoO4)(3)-Hf(MoO4)(2) system. The structure of K5ScHf(MoO4)(6), have been determined in space group R (3) over barc through Rietveld analysis of X-ray powder diffraction data. The melting point of molybdate is 999 K. The compound has high ion conductivity (about 10(-3) S cm(-1)).

Magnetic Capacitance in Variable-Valence Manganese Sulfides

Aplesnin, Sergey S.; Kharkov, Anton M.; Filipson, Gleb Yu PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS DOI: 10.1002/pssb.201900637

The permittivity of TmxMn1-xS (0 < x < 0.15) solid solutions is measured in the frequency range of 10(2)-10(6) Hz at temperatures of 300-500 K in magnetic fields of up to 12 kOe. The migration and relaxation conductivity contributions to the electric polarization are established. The relaxation time and activation energy are calculated using the Debye model. A decrease in the capacitance and relaxation time in a magnetic field is observed. The electron polarization relaxation channel provided by recombination of the electron-hole pairs is found using the infrared spectroscopy investigations.

Generation of vortex waves in non-coaxial cylindrical waveguides

Pilipchuk, Artem S.; Pilipchuk, Alina A.; Sadreev, Almas F. JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA DOI: 10.1121/1.5139222

A non-coaxial waveguide composed of a cylindrical resonator of radius R and cylindrical waveguides with the radii r1 and r2, respectively, is considered. The radii satisfy the inequality r1 < r2 < R. The conversion from the channel with zero orbital angular momentum (OAM) into the channels with non-zero OAM is achieved by shifting the center lines of the waveguides relative to the center line of the cylindrical resonator. The center lines of input and output waveguides are shifted relative to each other by the angle D/ in order to twist the output acoustic wave. The conversion efficiency of the input wave with zero OAM into the output wave with non-zero OAM as dependent on the frequency, length of the resonator, and D/ is considered, and the domains where the efficiency can reach almost 100% are found. (C) 2019 Acoustical Society of America.

Exchange Interaction between the Excited States of Magnetic Ions

Ovchinnikov, SG (Ovchinnikov, S. G.)[ 1 ] ; Gavrichkov, VA (Gavrichkov, V. A.)[ 1 ] ; Polukeev, SI (Polukeev, S. I.)[ 1 ] ; Malakhovskii, AV (Malakhovskii, A. V.) PHYSICS OF METALS AND METALLOGRAPHY DOI: 10.1134/S0031918X19130210

Within the framework of the LDA + GTB multielectron approach to the electron structure of Mott-Hubbard insulators a scheme is developed for constructing the effective low-energy Hamiltonian that includes not only the ground state of the magnetic cations, but also the excited terms. The mathematical apparatus of the theory are Hubbard operators built on the many-electron states of the cation in the d(n) configuration. The occupation of the excited term under optical pumping can change the sign of the exchange interaction of the excited cation with the neighboring cation in the ground state. Another variant of the occupation of the excited states is connected with a spin crossover when the excited and the ground terms change over, for example, at high pressure. Examples are given for such crystals as FeBO3, Nd0.5Gd0.5Fe3(BO3)(4) and NiO.

Magnetic Properties and Spin Crossover in Transition Metal Oxides with d(5) Ions at High Pressures

Orlov, Yu S.; Nikolaev, S., V; Ovchinnikov, S. G. JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS DOI: 10.1134/S1063776119120185

We analyze the influence of cooperative effects on the magnetic properties and spin crossover between the high-spin (HS) term S = 5/2 and low-spin (LS) term S = 1/2 in Mott-Hubbard dielectrics with 3d(5) ions under high pressures. Two cooperation mechanisms (superexchange interaction and effective interaction via the elastic system) are considered. The sign of the exchange interaction changes because of the crossover from the antiferromagnetic in the HS state to the ferromagnetic in the LS state. In view of the large difference between the ionic radii of the HS and LS states, the systems with spin crossover acquire an additional strong coupling via the elastic system. Using the Hubbard operator representation and considering the electronic states of the two terms simultaneously, we obtain the effective Hamiltonian with allowance for the cooperative effects. The magnetic phase diagram and the spin crossover are investigated in the mean field approximation. It is shown that the inclusion of cooperative effects at low temperatures leads to a first-order phase transition between the antiferromagnetic HS state and the ferromagnetic LS state. At higher temperatures, more complicated sequences of phase transitions are possible upon an increase in pressure, including the HS paramagnet-HS antiferromagnet-LS paramagnet and HS antiferromagnet-LS paramagnet-LS ferromagnet transitions.

Calculation and Comparison of Electronic, Vibrational, Polarization, and Magnetic Properties of Double Perovskites CaMnTi2O6 and CaFeTi2O6

Andryushin, N. D.; Zinenko, V., I; Pavlovskii, M. S.;at all JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS DOI: 10.1134/S1063776119110013

Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of "column" ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P4(2)/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P4(2)/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is P-s = 25 mu C/cm(2). The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.

Magnetic Interactions, Superconductivity, and Spin-Resonance Peak in Iron-Based Materials

Togushova, Yu. N.; Korshunov, M. M. PHYSICS OF METALS AND METALLOGRAPHY DOI: 10.1134/S0031918X1913026X

Different mechanisms of superconductivity result in specific symmetries and structures of the gap in multiband systems. Here we review the spin fluctuation mechanism of Cooper pairing and discuss the spin resonance feature in the superconducting state of iron-based materials.

Crystal structure and structural phase transition in bismuth-containing HoFe3(BO3)(4) in the temperature range 11-500 K

Smirnova, Ekaterina S.; Alekseeva, Olga A.; Dudka, Alexander P.;at all. ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING AND MATERIALS. DOI: 10.1107/S2052520619010473

An accurate single-crystal X-ray diffraction study of bismuth-containing HoFe3(BO3)(4) between 11 and 500 K has revealed structural phase transition at T-str = 365 K. The Bi atoms enter the composition from Bi2Mo3O12-based flux during crystal growth and significantly affect Tstr. The content of Bi was estimated by two independent methods, establishing the composition as (Ho0.96Bi0.04)Fe-3(BO3)(4). In the low-temperature (LT) phase below T-str the (Ho0.96Bi0.04)Fe-3(BO3)(4) crystal symmetry is trigonal, of space group P3(1)21, whereas at high temperature (HT) above 365 K the symmetry increases to space group R32. There is a sharp jump of oxygen O1 (LT) and O2 (LT) atomic displacement parameters (ADP) at T-str. O1 and O2 ADP ellipsoids are the most elongated over 90-500 K. In space group R32 specific distances decrease steadily or do not change with decreasing temperature. In space group P3(1)21 the distortion of the polyhedra Ho(Bi)O-6, Fe1O(6) and Fe2O(6), B2O(3) and B3O(3) increases with decreasing temperature, whereas the triangles B1O(3) remain almost equilateral. All BO3 triangles deviate from the ab plane with decreasing temperature. Fe-Fe distances in Fe1 chains decrease, while distances in Fe2 chains increase with decreasing temperature. The Mossbauer study confirms that the FeO6 octahedra undergo complex dynamic distortions. However, all observed distortions are rather small, and the general change in symmetry during the structural phase transition has very little influence on the local environment of iron in oxygen octahedra. The Mossbauer spectra do not distinguish two structurally different Fe1 and Fe2 positions in the LT phase. The characteristic temperatures of cation thermal vibrations were calculated using X-ray diffraction and Mossbauer data.

X-ray transient absorption spectroscopy by an ultrashort x-ray-laser pulse in a continuous-wave IR field

Автор:: Shi, Xin; Wu, Yong; Wang, Jian Guo; at all PHYSICAL REVIEW A. DOI: 10.1103/PhysRevA.101.023401

X-ray transient absorption spectra (XTAS) of molecules are theoretically investigated in a femtosecond x-ray pump and continuous-wave (cw) infrared (IR)-control scenario. The scheme is exemplified by a CO molecule resonantly pumped into carbon and oxygen core-excited 1s -> 7r* states by a weak femtosecond x-ray pulse, while dynamic Stark shifts are induced by the cw IR-control radiation. As a result, significant shoulder structures appear in XTAS showing strong dependence on the phase of IR radiation relative to the envelope of the x-ray pulse. Due to a significant difference in the frequencies of the two pulses, the present XTAS scheme provides much clear interpretation of the dynamic Stark effects as compared to the attosecond UV transient absorption scenario. Within the suggested two-level model, where the total spectrum is decomposed as incoherent superposition of contributions from different vibrational excitations weighted by the Franck-Condon Factors, all spectral structures can be well identified and interpreted in a good agreement with the full-scale molecular simulations. Well-characterized XTAS in the proposed IR-control scheme can be applied for fine phase synchronization between IR and x-ray pulses, highly demanded in modern experiments on x-ray free-electron lasers.

Mossbauer Study of the Magnetic Transition in epsilon-Fe2O3 Nanoparticles Using Synchrotron and Radionuclide Sources

Knyazev, Yu. V.; Chumakov, A. I.; Dubrovskiy, A. A.; at all JETP LETTERS, DOI: 10.1134/S0021364019210082

 Nuclear gamma-resonance experiments with energy and time resolved detection are carried out with epsilon-F2O3 nanoparticles and a Co-57(Rh) laboratory Mossbauer source of gamma radiation and a 14.4125 keV synchrotron radiation source on the ID18 beamline (ESRF) in the temperature range of 4-300 K. Both methods show a tremendous increase in the hyperfine field in tetrahedrally coordinated iron positions during the magnetic transition in the range of 80-150 K. As a result, the splitting of the quantum beat peaks in the nuclear scattering spectra is observed in the time interval of 20-170 ns with a periodicity of similar to 30 ns. In addition, the first quantum beat is slightly shifted to shorter times. A correlation between the quadrupole shift and the orbital angular momentum of iron in epsilon-F2O3 nanoparticles is found. The magnetic transition leads to the rotation of the magnetic moment in the tetrahedral positions of iron around the axis of the electric field gradient by an angle of 44 degrees.

Study of the Photovoltage in Mn/SiO2/n-Si MOS Structure at Cryogenic Temperatures

Bondarev, I. A.; Rautskii, M., V; Yakovlev, I. A. SEMICONDUCTORS DOI: 10.1134/S1063782619140045

Lateral photovoltaic effect in metal/insulator/semiconductor hybrid structures is a significant phenomenon for spintronics, as it establishes the interplay between the optical irradiaLateral photovoltaic effect in metal/insulator/semiconductor hybrid structures is a significant phenomenon for spintronics, as it establishes the interplay between the optical irradiation, electronic transport and spin-dependent properties of carriers. In present work we investigated photovoltaic phenomena in Mn/SiO2/n-Si MOS structure. The sample was prepared on a single-crystal n-Si (phosphorus-doped) substrate. The SiO2 layer with thickness of 1.5 nm was formed on the substrate surface by a chemical method. Manganese film with thickness of 15nm was deposited by thermal evaporation in ultrahigh vacuum in the "Angara" chamber. It was observed that at T < 45 K the values of lateral and transversal photovoltage non-monotonically depend on the temperature and such dependences show complex behavior. Features of the photovoltage dependence on temperature, in the region above 20 K are explained by the change of carriers' mobility and the competition between carriers' drift velocity in the electric field of the space-charge region and their diffusion rate in the transverse and lateral directions. Below 20 K, the main contribution into the photovoltage is given by hot electrons injected from surface states levels to the conduction band. A strong magnetic field influence on the photovoltage below 20 K was observed. We associate it with the Lorenz force effect on the hot electrons, although we also don't exclude the presence of mechanisms caused by spin-dependent scattering and recombination of hot electrons at occupied donor states.tion, electronic transport and spin-dependent properties of carriers. In present work we investigated photovoltaic phenomena in Mn/SiO2/n-Si MOS structure. The sample was prepared on a single-crystal n-Si (phosphorus-doped) substrate. The SiO2 layer with thickness of 1.5 nm was formed on the substrate surface by a chemical method. Manganese film with thickness of 15nm was deposited by thermal evaporation in ultrahigh vacuum in the "Angara" chamber. It was observed that at T < 45 K the values of lateral and transversal photovoltage non-monotonically depend on the temperature and such dependences show complex behavior. Features of the photovoltage dependence on temperature, in the region above 20 K are explained by the change of carriers' mobility and the competition between carriers' drift velocity in the electric field of the space-charge region and their diffusion rate in the transverse and lateral directions. Below 20 K, the main contribution into the photovoltage is given by hot electrons injected from surface states levels to the conduction band. A strong magnetic field influence on the photovoltage below 20 K was observed. We associate it with the Lorenz force effect on the hot electrons, although we also don't exclude the presence of mechanisms caused by spin-dependent scattering and recombination of hot electrons at occupied donor states.

Effect of the Additional Se Layer on the Electronic Structure of Iron-Based Superconductor FeSe/SrTiO3

Tikhonova, L. V.; Korshunov, M. M. Journal Of Superconductivity And Novel Magnetism. DOI: 10.1007/s10948-019-05253-y

We use density functional theory to study the structure and the band structure of the monolayer FeSe deposited on the SrTiO3 substrate with the additional layer of Se between them. The top of the SrTiO3 is formed by the double TiOx layer with and without oxygen vacancies. Several structures with different arrangements of the additional Se atoms above the double TiOx layer are considered. Equilibrium structures were found, and the band structures for them were obtained. Near the Gamma = (0,0,0) point of the Brillouin zone, the hole Fermi surface pockets persist and, additionally, an electron pocket appears. Thus, neither the presence of the additional Se layer nor the oxygen vacancies in the double TiOx layer lead to the sinking of hole bands below the Fermi level near the Gamma point. The necessity to include the strong electronic correlations into account is discussed.

Magnetoimpedance Effect in a SOI-Based Structure

Smolyakov, D. A.; Tarasov, A. S.; Yakovlev, I. A.; Volochaev, M. N. Semiconductors. DOI: 10.1134/S1063782619140215

This paper presents the results of the study the transport properties of the SOI-based structure. Measurements were carried out on an alternating current with an external magnetic field in a wide temperature range. The influence of the magnetic field was found. We associate this effect with the influence on the surface states located at the interface, this appears as a change of the energy of their levels. This effect is enhanced by the nanoscale of the silicon channel.

Microstrip Diplexer with Pi-Shaped Matching Circuit

Leksikov, Aleksandr A.; Serzhantov, Alexey M.; Goyorun, Ilya, V; Afonin, Aleksey O.; Ugryumov, Andrey, V; et al. PROGRESS IN ELECTROMAGNETICS RESEARCH LETTERS

We propose a new method to match diplexer channels with a common port in which a II-shaped strip conductor is used as a matching circuit. The applicability of the method is illustrated by simulating and fabricating a microstrip diplexer for GPS/GLONASS applications. The central frequencies of the channels are 1.234 GHz and 1.597 GHz, and their fractional bandwidths are 6.8% and 7.3%, respectively; minimum insertion losses are 1.05 dB and 1.08 dB. The main advantage of the diplexer is its compact size: 16.8 mm x 9.0 mm x 6.4 mm in housing. Using 1D models and a quasi-TEM approach, the frequency-dependent coupling coefficients between the matching circuit and input resonators of the channels are calculated, and the influence of the matching circuit's geometrical parameters on its coupling with diplexer channels is studied.

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