New Publications

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

Lim, Chang Sung; Atuchin, Victor V.; Aleksandrovsky, Aleksandr S.; Denisenko, Yuriy G.; Molokeev, Maxim S.; et al. Korean Journal Of Materials Research. DOI: 10.3740/MRSK.2019.29.12.741

New triple tungstate phosphors NaPbLa(WO4)(3):Yb3+/Ho3+ (x = Yb3+/Ho3+ = 7, 8, 9, 10) are successfully fabricated by microwave assisted sol-gel synthesis and their structural and frequency upconversion (UC) characteristics are investigated. The compounds crystallized in the tetragonal space group I4(1)/a and the NaPbLa(WO4)(3) host have unit cell parameters a = 5.3927(1) and c = 11.7961(3) angstrom, V = 343.05(2) angstrom(3), Z = 4. Under excitation at 980 nm, the phosphors have yellowish green emissions, which are derived from the intense S-5(2)/F-5(4) -> I-5(8) transitions of Ho3+ ions in the green spectral range and strong F-5(5) -> I-5(8) transitions in the red spectral range. The optimal Yb3+ :Ho3+ ratio s revealed to be x = 9, which is attributed to the quenching effect of Ho3+ ions, as indicated by the composition dependence. The UC characteristics are evaluated in detail under consideration of the pump power dependence and Commission Internationale de L'Eclairage chromaticity. The spectroscopic features of Raman spectra are discussed in terms of the superposition of Ho3+ luminescence and vibrational lines. The possibility of controlling the spectral distribution of UC luminescence by the chemical content of tungstate hosts is demonstrated.

The Low-Temperature Magnetic State and Magnetic Ordering Temperature of -Fe 2 O 3 Iron Oxide Nanoparticles

Dubrovskiy, Andrey A.; Semenov, Sergey V.; Knyazev, Yuri V.; Popkov, Sergey I.; Yakushkin, Stas S.; et al. Ieee Magnetics Letters. DOI: 10.1109/LMAG.2019.2956674

The -Fe2O3 iron oxide polymorph is a well-known magnetic material with a complex magnetic structure, which undergoes a series of magnetic transitions in different temperature ranges. However, the -Fe2O3 phase diagram is still unclear. We report on the magnetic properties of a sample consisting of -Fe2O3 nanoparticles with an average size of 8 nm embedded in a SiO2 xerogel matrix without an admixture of foreign phases. Along with the features typical of the well-known -Fe2O3 magnetic transition in the temperature range 80150 K, the temperature dependence of magnetization M(T) of -Fe2O3 includes other low-temperature anomalies. In an external field of H 70kOe, there is a noticeable temperature hysteresis of magnetization at 5090 K, and near T & approx; 50 K, the M(T) curves have a characteristic bending, which may be indicative of an additional magnetic transition. The ferromagnetic resonance spectra shows that, near 500 K, a magnetic phase transition occurs, which was previously thought to be a transition to the paramagnetic state. An analysis of the temperature dependence of the ferromagnetic resonance spectra shows that the magnetically ordered phase in -Fe2O3 exists up to about 800 K.

Magnetite Nanocrystals with a High Magnetic Anisotropy Constant due to the Particle Shape

Stolyar, S. V.; Komogortsev, S. V.; Chekanova, L. A.; Yaroslavtsev, R. N.; Bayukov, O. A.; et al. Technical Physics Letters. DOI: 10.1134/S1063785019090116

Chemical solution deposition in the presence of arabinogalactan makes it possible to prepare magnetite nanocrystals in the form of square plates with a high aspect ratio (similar to 1/9). The magnetic anisotropy constant of particles is several times higher than that of spherical magnetite particles, which enhances the hysteretic properties with a small particle volume retained.

Structural features associated with multiferroic behavior in the RX3(BO3)(4) system

Zhang, H.; Liu, S.; Nelson, C. S.; Bezmaternykh, L. N.; Chen, Y-S; et al. Journal Of Physics-condensed Matter. DOI: 10.1088/1361-648X/ab415f

The magnetoelectric effect in the RX3(BO3)(4) system (R = Ho, Eu, Sm, Nd, Gd; X = Fe, Al) varies significantly with the cation R despite very similar structural arrangements. Our structural studies reveal a symmetry reducing tilting of the BO3 planes and of the FeO6 polyhedra in the systems exhibiting low magnetic field induced electric polarization. Neutron scattering measurements reveal a lack of magnetic ordering indicating the primary importance of the atomic structure in the multiferroic behavior of this system.

Fluorescence and photoinduced proton transfer in the protolytic forms of fluorescein: Experimental and computational study

Gerasimova, Marina A.; Tomilin, Felix N.; Malyar, Elena Yu.; Varganov, Sergey A.; Fedorov, Dmitri G.; et al. Dyes And Pigments. DOI: 10.1016/j.dyepig.2019.107851

In contrast to the well-studied absorption spectra of different protolytic forms of fluorescein, the complex structure of the fluorescence spectra in a wide pH range is not completely understood because of the interplay between emission and photoinduced proton transfer in the electronic excited states. We provide insight into this interplay through a combined analysis of the experimental data, obtained by absorption and steady-state fluorescence spectroscopy at pH 0.3-10.5, and the time-dependent density functional theory (TD-DFT). The TD-DFT based computational model is validated on dianion and used to model the spectra of other protolytic forms. The protolytic/tautomeric forms of fluorescein are classified according to the partial charges on the triple chromophore ring, and electronic transitions are analyzed in terms of changes in molecular geometries and orbitals. A linear regression analysis between the calculated and experimental results based on both absorption and well-understood dianionic and cationic fluorescence peaks is used to assign the monoanionic (496 nm), neutral quinoid (550 nm) and neutral zwitterionic (483 nm) fluorescence peaks, whose positions were not clear prior to this work. The values of the excited-state dissociation microconstants pk(a)*for different forms of fluorescein are calculated by means of the Forster cycle in conjunction with the spectroscopic measurements and computational data.

New candidate to reach Shockley-Queisser limit: The DFT study of orthorhombic silicon allotrope Si(oP32)

Oreshonkov, A. S.; Roginskii, E. M.; Atuchin, V. V. Journal Of Physics And Chemistry Of Solids. DOI: 10.1016/j.jpcs.2019.109219

In the present study, the unit cell parameters and atomic coordinates are predicted for the Pbcm orthorhombic structure of Si(oP32) modification. This new allotrope of silicon is mechanically stable and stable with respect to the phonon states. The electronic structure of Si(oP32) is calculated for LDA and HSE06 optimized structures. The band gap value E-g = 1.361 eV predicted for Si(oP32) is extremely close to the Shockley-Queisser limit and it indicates that the Si(oP32) modification is a promising material for efficient solar cells. The frequencies of Raman and Infrared active vibrations is calculated for allotrope Si(oP32).

Crystal texture-dependent magnetic and magnetotransport properties of half-metallic Fe3O4 films grown on oxidized Si substrates by reactive deposition

Balashev, V. V.; Ermakov, K. S.; Samardak, A. Yu; Ognev, A., V; Samardak, A. S.; et al. Journal Of Alloys And Compounds. DOI: 10.1016/j.jallcom.2019.152398

Nanocrystalline magnetite (Fe3O4) films with various preferred crystallite orientations were grown on oxidized silicon surface by reactive iron deposition in an oxygen atmosphere. Depending on the partial pressure of oxygen (P-o2), the evolution of the structural, magnetic, and magnetotransport properties of the grown films was investigated. We found that the growth of films containing only the Fe3O4 phase occurs in a certain P-o2 range, and the magnetite crystallites may have (311) or (110) preferred orientation. It was revealed that films with (311) and (110) textures have a column structure. An increase in the P-o2 leads to a structure transformation from (311) to (110) texture with larger crystallites. A film with (110) texture showed higher values of saturation magnetization, magnetoresistance and spin polarization. The analysis of approach to magnetic saturation revealed that the local magnetic anisotropy of crystallites in textured films is much higher than the anisotropy of bulk magnetite due to the large surface contribution. The FORC diagram method in combination with the approach to magnetic saturation proved the existence of the exchange coupling between large and small grains. Our results open the reliable route for crystal texture-depending manipulation of functional properties of thin magnetite films for advanced spintronic applications. (C) 2019 Elsevier B.V. All rights reserved.

Talbot effect based on a Raman-induced grating

Arkhipkin, V. G.; Myslivets, S. A. Physical Review A. DOI: 10.1103/PhysRevA.100.063835

We theoretically study the Talbot effect resulting from Raman-induced grating based on periodic spatial modulation of the Raman gain and dispersion in the field of a standing pump wave. Features of integer and fractional Talbot effects are demonstrated for one- and two-dimensional (1D and 2D) Raman-induced gratings. It is shown that the intensity of diffraction images can increase due to Raman amplification in the grating. Glass-shaped diffraction patterns are demonstrated for 2D gratings. It is also shown that in the vicinity of the Talbot planes there are planes in which the diffraction patterns are spatially compressed and the intensity becomes greater. The results expand the possibility of using the Talbot effect in various applications.

Electromechanical Properties and Anisotropy of Acoustic Waves Characteristics in Single Crystals YAl3(BO3)(4)

Turchin, Pavel P.; Burkov, Sergey, I; Turchin, Vladimir, I; Yurkevich, Sergey, V; Sukhodaev, Pavel O.; et al. Journal Of Siberian Federal University-mathematics & Physics

Velocity of bulk acoustic waves in base and rotated cuts have been measured by the ultrasonic pulse-echo method and values of C-ijkl(E) and e(ijk) in single crystals YAl3(BO3)(4) have been calculated. The value of disk piezoelectric modu... 

Magnon mode in alpha-MnS Raman spectrum

Gerasimova, Julia V.; Abramova, Galina M.; Zhandun, Vyacheslav S.; Vtyurin, Aleksandr N. Journal Of Raman Spectroscopy

Raman spectra of manganese monosulphide (alpha -MnS) with NaCl structure in the temperature range 5-300 ? are presented. A new peak at 22 cm(-1) has been found at low temperatures. The temperature dependence of this peak made possible to...  

Structural stability of nematic liquid crystal droplets in the light of the catastrophe theory

Parshin, Alexander M. Modern Physics Letters B

Dynamical systems and defects in liquid crystals (LCs) are described using topological methods. Meanwhile, the director field distribution in LC droplets is affected by many bulk and surface factors that are difficult to take into accoun...  

Screening of biopolymeric materials for cardiovascular surgery toxicity-Evaluation of their surface relief with assessment of morphological aspects of monocyte/macrophage polarization in atherosclerosis patients

Menzyanova, Natalia G.; Pyatina, Svetlana A.; Nikolaeva, Elena D.; Shabanov, Alexander, V; Nemtsev, Ivan, V; et al. Toxicology Reports

The morphotypes of human macrophages (MPh) were studied in the culture on nano-structured biopolymer substrates, made from polyhydroxyalcanoates (PHAs) of five various monomer compositions, followed by the solvent evaporation. Its surfac...

Extended Discrete Interaction Model: Plasmonic Excitations of Silver Nanoparticles

Zakomirnyi, Vadim I.; Rinkevicius, Zilvinas; Baryshnikov, Glib V.; Sorensen, Lasse K.; Agren, Hans. Journal Of Physical Chemistry C. DOI: 10.1021/acs.jpcc.9b07410

We present a new atomistic model for plasmonic excitations and optical properties of metallic nanoparticles, which collectively describes their complete response in terms of fluctuating dipoles and charges that depend on the local environment and on the morphology of the composite nanoparticles. Being atomically dependent, the total optical properties, the complex polarizability, and the plasmonic excitation of a cluster refer to the detailed composition and geometric characteristics of the cluster, making it possible to explore the role of the material, alloy mixing, size, form shape, aspect ratios, and other geometric factors down to the atomic level and making it useful for the design of plasmonic particles with particular strength and field distribution. The model is parameterized from experimental data and, at present, practically implementable for particles up to more than 10 nm (for nanorods even more), thus covering a significant part of the gap between the scales where pure quantum calculations are possible and where pure classical models based on the bulk dielectric constant apply. We utilized the method to both spherical and cubical clusters along with nanorods where we demonstrate both the size, shape, and ratio dependence of plasmonic excitations and connect this to the geometry of the nanoparticles using the plasmon length.

Electronic band structure and superconducting properties of SnAs

Bezotosnyi, P. I.; Dmitrieva, K. A.; Sadakov, A. V.; Pervakov, K. S.; Muratov, A. V.; Usoltsev, A. S.; Tsvetkov, A. Yu.; Gavrilkin, S. Yu.; Pavlov, N. S.; Slobodchikov, A. A.; Vilkov, O. Yu.; Rybkin, A. G.; Pudalov, VM . PHYSICAL REVIEW B DOI: 10.1103/PhysRevB.100.184514

We report a comprehensive study of physical properties of the binary superconductor compound SnAs. The electronic band structure of SnAs was investigated using both angle-resolved photoemission spectroscopy (ARPES) in a wide binding energy range and density functional theory (DFT) within generalized gradient approximation (GGA). The DFT/GGA calculations were done including spin-orbit coupling for both bulk and (111) slab crystal structures. Comparison of the DFT/GGA band dispersions with ARPES data shows that the spectrum for the (111) slab much better describes ARPES data than that for the bulk. In addition, we studied experimentally superconducting properties of SnAs by specific heat, magnetic susceptibility, magnetotransport measurements, and Andreev reflection spectroscopy. Temperature dependencies of the superconducting gap and of the specific heat were found to be well consistent with those expected for the single band BCS superconductors with an isotropic s-wave order parameter. Despite spin-orbit coupling present in SnAs, our data show no signatures of a potential unconventional superconductivity, and the characteristic BCS ratio 2 Delta/T-c = 3.48-3.73 is very close to the BCS value in the weak coupling limit.

Resonant x-ray second-harmonic generation in atomic gases

Liu, JC (Liu, Ji-Cai)[ 1,2 ] ; Miron, C (Miron, Catalin)[ 3,4,5 ] ; Agren, H (Agren, Hans)[ 6,7 ] ; Polyutov, S (Polyutov, Sergey)[ 8,9 ] ; Gel'mukhanov, F (Gel'mukhanov, Faris) DOI: 10.1103/PhysRevA.100.063403

We explore the x-ray second-harmonic generation process induced by resonant two-photon absorption in systems with inversion symmetry. We show that this process becomes allowed in the x-ray region due to nondipole contributions. It is found that, although a plane-wave pump field generates only a longitudinal second-harmonic field, a Gaussian pump beam creates also a radially polarized transverse second-harmonic field which is stronger than the longitudinal one. Contrary to the longitudinal component, the transverse second-harmonic field with zero intensity on the axis of the pump beam can run in free space. Our theory is applied to Ar and Ne atomic vapors and predicts an energy conversion efficiency of x-ray second-harmonic generation of 3.2 x 10(-11) and 1.3 x 10(-12), respectively.

Three isomers in a (hydrogen L-Cysteinato)-thallium(I): Crystal structure, spectroscopic and thermal properties

Golovnev, Nicolay N.; Molokeev, Maxim S.; Lesnikov, Maxim K. POLYHEDRON. DOI: 10.1016/j.poly.2019.114141

The isolation of thallium(I) complexes [Tl-2(HCys)(2)](n) (1) and [Tl-4(HCys)(4)](n) (2) {H(2)Cys = L-Cysteine} from aqueous solution by means of crystallization is reported herein. Polar crystals of 1 and 2 were crystallized in P2(1) and P2(1)2(1)2(1) space groups respectively. Elemental analysis, XRD, IR, UV-Vis, TG-DSC and a single crystal X-ray diffraction were applied for characterizing the compounds. Linkage isomers 1 and 2 have 1D and 2D coordination polymeric structures respectively. The lone pair electrons of thallium(I) in 1-2 are stereo-chemically active. In 1, each of two independent Tl+ ions is coordinated by three HCys(-) ions forming TlS3O irregular polyhedron that is linked to each other by vertexes in an infinite chain. In 2, four independent Tl+ ions are coordinated by HCys(-) ions through S and O atoms, forming Tl1S(3)O(2), Tl2S(4), Tl3S(3), Tl4S(3) irregular polyhedrons. The crystallographic independent HCys(-) ions are linked to the metal ion differently, two are mu(3)-S,S,S-, one is mu(4)-O,S,S,S-, and one is mu(4)-O,O',S,S,S-coordinated ligands. The amine group of compounds 1 and 2 is in the form of an ammonium ion (-NH3+). The structures of 1-2 are stabilized by N-H center dot center dot center dot O hydrogen bonds, thallophilic Tl center dot center dot center dot Tl and anagostic Tl center dot center dot center dot H-C interactions. The spectroscopic and thermal properties of compounds were analyzed. (C) 2019 Elsevier Ltd. All rights reserved.

Chiral Optical Tamm States at the Interface between an All-Dielectric Polarization-Preserving Anisotropic Mirror and a Cholesteric Liquid Crystal

Natalya V. Rudakova, Ivan V. Timofeev, G. Bikbaev, Maxim V. Pyatnov, Stepan Ya. Vetrov, and Wei Lee. Crystals 2019, 9(10), 502; doi.org/10.3390/cryst9100502

As a new localized state of light, the chiral optical Tamm state exists at the interface between a polarization-retaining anisotropic mirror and a substance with optical activity. Considering a hybrid structure comprising a metal-free polarization-preserving mirror and a cholesteric liquid crystal, we highlight the high Q factor arising from the all-dielectric framework. The intensity of localized light decreases exponentially with increasing distance from the interface. The penetration of the field into the cholesteric liquid crystal is essentially prohibited for wavelengths lying in the photonic bandgap and close to the cholesteric pitch length. The dielectric mirror has its own photonic bandgap. The energy transfer along the interface can be effectively switched off by setting the tangential wave vector to zero. The spectral behavior of the chiral optical Tamm state is observed both as reflection and transmission resonance. This Fano resonance is analogous to the Kopp–Genack effect. Our analytics are well in line with precise calculations, which may pave a new route for the future development of intelligent design for laser and sensing applications

Controlling multiple diffraction with quasiperiodic gratings

Ikonnikov, D. A.; Arkhipkin, V. G.; Vyunishev, A. M. LASER PHYSICS LETTERS DOI: 10.1088/1612-202X/ab5845

Complex diffraction patterns are formed by sophisticated diffraction gratings. However, the methods of synthesizing of such gratings are complicated and resource intensive. We propose a simple analytical approach to forming one- and two-dimensional quasiperiodic gratings supporting multiple diffraction consisting of a set of diffraction maxima with the specified spatial frequency of certain diffraction order. The structure of a quasiperiodic grating is a superposition of harmonic functions, which provide a discrete spatial spectrum. The number of diffraction maxima, their angular positions, and intensity distribution between them can be controlled by choosing appropriate reciprocal lattice vectors and their amplitudes. This effect confirmed by the experiment opens new possibilities for light shaping, imaging, and radiation coupling.

Electronic band structure and superconducting properties of SnAs

Bezotosnyi, P. I.; Dmitrieva, K. A.; Sadakov, A. V.; Pervakov, K. S.; Muratov, A. V.; et al. Physical Review B. DOI: 10.1103/PhysRevB.100.184514

We report a comprehensive study of physical properties of the binary superconductor compound SnAs. The electronic band structure of SnAs was investigated using both angle-resolved photoemission spectroscopy (ARPES) in a wide binding energy range and density functional theory (DFT) within generalized gradient approximation (GGA). The DFT/GGA calculations were done including spin-orbit coupling for both bulk and (111) slab crystal structures. Comparison of the DFT/GGA band dispersions with ARPES data shows that the spectrum for the (111) slab much better describes ARPES data than that for the bulk. In addition, we studied experimentally superconducting properties of SnAs by specific heat, magnetic susceptibility, magnetotransport measurements, and Andreev reflection spectroscopy. Temperature dependencies of the superconducting gap and of the specific heat were found to be well consistent with those expected for the single band BCS superconductors with an isotropic s-wave order parameter. Despite spin-orbit coupling present in SnAs, our data show no signatures of a potential unconventional superconductivity, and the characteristic BCS ratio 2Δ/Tc=3.483.73 is very close to the BCS value in the weak coupling limit.

Three isomers in a (hydrogen L-Cysteinato)-thallium(I): Crystal structure, spectroscopic and thermal properties

Golovnev, Nicolay N.; Molokeev, Maxim S.; Lesnikov, Maxim K. Polyhedron. DOI: 10.1016/j.poly.2019.114141

The isolation of thallium(I) complexes [Tl2(HCys)2]n (1) and [Tl4(HCys)4]n (2) {H2Cys = l-Cysteine} from aqueous solution by means of crystallization is reported herein. Polar crystals of 1 and 2 were crystallized in P21 and P212121 space groups respectively. Elemental analysis, XRD, IR, UV–Vis, TG-DSC and a single crystal X-ray diffraction were applied for characterizing the compounds. Linkage isomers 1 and 2 have 1D and 2D coordination polymeric structures respectively. The lone pair electrons of thallium(I) in 12 are stereo-chemically active. In 1, each of two independent Tl+ ions is coordinated by three HCys ions forming TlS3O irregular polyhedron that is linked to each other by vertexes in an infinite chain. In 2, four independent Tl+ ions are coordinated by HCys ions through S and O atoms, forming Tl1S3O2, Tl2S4, Tl3S3, Tl4S3 irregular polyhedrons. The crystallographic independent HCys ions are linked to the metal ion differently, two are μ3-S,S,S-, one is μ4-O,S,S,S-, and one is μ4-O,O',S,S,S-coordinated ligands. The amine group of compounds 1 and 2 is in the form of an ammonium ion (–NH3+). The structures of 1–2 are stabilized by NH⋯O hydrogen bonds, thallophilic Tl⋯Tl and anagostic Tl⋯HC interactions. The spectroscopic and thermal properties of compounds were analyzed.

Collective lattice resonances in arrays of dielectric nanoparticles: a matter of size

Kostyukov, Artem S.; Ershov, Alexander E.; Gerasimov, Valeriy S.; Filimonov, Sergey A.; Rasskazov, Ilia L.; et al. Journal Of Quantitative Spectroscopy & Radiative Transfer. DOI: 10.1364/OL.44.005743

Collective lattice resonances (CLRs) in finite-sized 2𝐷 arrays of dielectric nanospheres have been studied via the coupled dipole approximation. We show that even for sufficiently large arrays, up to 100×100

nanoparticles (NPs), electric or magnetic dipole CLRs may differ significantly from the ones calculated for infinite arrays with the same NP sizes and interparticle distances. The discrepancy is explained by the existence of a sufficiently strong cross-interaction between electric and magnetic dipoles induced at NPs in finite-sized lattices, which is ignored for infinite arrays. We support this claim numerically and propose an analytic model to estimate a spectral width of CLRs for finite-sized arrays. Given that most of the current theoretical and numerical researches on collective effects in arrays of dielectric NPs rely on modeling infinite structures, the reported findings may contribute to thoughtful and optimal design of inherently finite-sized photonic devices.

Super-efficient laser hyperthermia of malignant cells with core-shell nanoparticles based on alternative plasmonic materials

Kostyukov, Artem S.; Ershov, Alexander E.; Gerasimov, Valeriy S.; Filimonov, Sergey A.; Rasskazov, Ilia L.; et al. Journal Of Quantitative Spectroscopy & Radiative Transfer. DOI: 10.1016/j.jqsrt.2019.106599

New type of highly absorbing core-shell AZO/Au (aluminum doped zinc oxide/gold) and GZO/Au (gallium doped zinc oxide/gold) nanoparticles have been proposed for hyperthermia of malignant cells purposes. Comparative studies of pulsed laser hyperthermia were performed for Au nanoshells with AZO core and traditional SiO2 (quartz) core. We show that under the same conditions, the hyperthermia efficiency in the case of AZO increases by several orders of magnitude compared to SiO2 due to low heat capacity of AZO. Similar results have been obtained for GZO core which has same heat capacity. Calculations for pico-, nano- and sub-microsecond pulses demonstrate that reduced pulse duration results in strong spatial localization of overheated areas around nanoparticles, which ensures the absence of negative effects to the normal tissue. Moreover, we propose new alternative way for the optimization of hyperthermia efficiency: instead of maximizing the absorption of nanoparticles, we enhance the thermal damage effect on the membrane of malignant cell. This strategy allows to find the parameters of nanoparticle and the incident radiation for the most effective therapy.

Designing High-Performance LED Phosphors by Controlling the Phase Stability via a Heterovalent Substitution Strategy

Cheng, Chen; Ning, Lixin; Ke, Xiaoxing; Molokeev, Maxim S.; Wang, Zelin; et al. Advanced Optical Materials. 10.1002/adom.201901608

Phosphor‐converted white light‐emitting diodes (LEDs) are currently playing key roles in the lighting and display industries and trigger urgent demands for the discovery of “good” phosphors with high quantum efficiency, improved thermal stability, and controllable excitation/emission properties. Herein, a general and efficient heterovalent substitution strategy is demonstrated in K2HfSi3O9:Eu2+ achieved by Ln3+ (Ln = Gd, Tb, Dy, Tm, Yb, and Lu) doping to optimize luminescence properties, and as an example, the Lu3+ substitution leads to improvement of emission intensity and thermal stability, as well as tunable emission color from blue to cyan. The structural stability and Eu2+ occupation via Lu3+ doping have been revealed by the structural elaboration and density functional theory calculations, respectively. It is shown that heterovalent substitution allows predictive control of site preference of luminescent centers and therefore provides a new method to optimize the solid‐state phosphors for LEDs.

Quasi-lumped multimode stripline resonator and filter with good stopband performance

Belyaev, Boris Afanasievich; Serzhantov, Alexey Mikhailovich; Leksikov, Aleksandr Aleksandrovich; Bal'va, Yaroslav Fedorovich; Leksikov, Andrey Aleksandrovich. Microwave And Optical Technology Letters. 10.1002/mop.32173

A novel multimode resonator is proposed, containing five resonant modes that are incorporated in the passband forming. The structure is based on a dielectric substrate suspended in a metallic case that allows solving the problem of electromagnetic compatibility. Due to features of the resonator's structure, several higher modes do not excite that significantly improves the performance of the filter's stopband. The resonator advantages are proved on the bandpass filter (3.1…10.6 GHz) with a small overall size (0.19λ0 × 0.11λ0 × 0.11λ0) and a good stopband performance (first spurious band locates at 29 GHz and suppression is 70 dB).

Synthesis of the Orthorhombic Dy1-xHoxMnO3 Single Crystals and Study of Their Magnetic Properties

Semenov, S., V; Kolkov, M., I; Terent'ev, K. Yu; Pavlovskiy, N. S.; Pavlovskiy, M. S.; et al. Journal Of Superconductivity And Novel Magnetism. 10.1007/s10948-019-5090-8

In this report, we prepared for the first time the orthorhombic Dy1−xHoxMnO3 single crystals with x = 0, 0.1, 0.2, 0.3, and 0.4 using the flux technique. The post-growth processing and chemical and structural characterization of the synthesized samples were performed. Also, we examined the samples obtained by their magnetic properties and the magnetic anisotropy in wide ranges of temperatures and magnetic fields.

Physical principles of the formation of a nanoparticle electric double layer in metal hydrosols

Gavrilyuk, A. P.; Isaev, I. L.; Gerasimov, V. S.; Karpov, S., V Colloid And Polymer Science. 10.1007/s00396-019-04573-8

The Brownian dynamics method is employed to study the formation of an electrical double layer (EDL) on the metal nanoparticle (NP) surface in hydrosols during adsorption of electrolyte ions from the interparticle medium. Also studied is the charge accumulation by NPs in the Stern layer. To simulate the process of the formation of EDL, we took into account the effect of image forces and specific adsorption, dissipative and random forces, and the degree of hydration of adsorbed ions on the EDL structure. The employed model makes it possible to determine the charge of NPs and the structure of EDL. For the first time, the charge of both the diffuse part of EDL and the dense Stern layer has been determined. A decrease in the electrolyte concentration (below c < 0.1 mol/l) has been found to result in dramatic changes in the formation of the Stern layer.

Systematic experimental investigation of filtration losses of drilling fluids containing silicon oxide nanoparticles

A.V.Minakova, E.I.Mikhienkovaa, Y.O.Voronenkovaa, A.L.Neverova, G.M.Zeera, S.M.Zharkov. JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING, 10.1016/j.jngse.2019.102984

This paper presents the results of silicon oxide nanoparticles-incorporated drilling fluid filtration through a porous medium with different permeability. A water-based clay suspension was used as a basic model for creating investigated fluid samples. AlN (aluminium nitride) particles were used as a dispersed phase. The concentration of microparticles varied from 0.5 to 4.00 wt%, while the microparticles size varied from 1 to 10 μm. The concentration of SiO2 nanoparticles was changed within the range of 0.25 and 4.00 wt%, while the nanoparticles size varied from 5 to 100 nm. It was shown that filtration of drilling fluids with nanoparticles inclusions depends on their concentration, size and material, the concentration and size of microparticles and the pore sizes of ceramic filters. The addition of the nanoparticles leads to a significant reduction in filtration of a microsuspension and affects the structure and thickness of a cake formed on the surface of a filter. The main novelty of this work lies in the fact that the effect of the addition of nanoparticles on filtration losses depends on the ratio between nano and microparticles. It was shown that the positive effect of nanoparticle additives on filtration losses is determined not only by the properties of nanoparticles (size and concentration), but also by the properties of microparticles contained in the drilling fluid, as well as the characteristics of the rock (pore size).

Recoil-induced dissociation in hard-x-ray photoionization

i-Cai Liu, Vinícius Vaz da Cruz, Sergey Polyutov, Alexander Föhlisch, and Faris Gel'mukhanov. Phys. Rev. A 100, 053408 – Published 15 November 2019. 10.1103/PhysRevA.100.053408

We predict the recoil-induced molecular dissociation in hard-x-ray photoionization. The recoil effect is caused by electronic and photon momentum exchange with the molecule. We show the strong role of relativistic effects for the studied molecular fragmentation. The recoil-induced fragmentation of the molecule is caused by elongation of the bond due to the vibrational recoil effect and because of the centrifugal force caused by the rotational recoil. The calculations of the x-ray photoelectron spectra of the H2 and NO molecules show that the predicted effects can be observed in high-energy synchrotrons like SOLEIL, SPring-8, PETRA, and XFEL SACLA. The relativistic effect enhances the recoil momentum transfer and makes it strongly sensitive to the direction of ejection of the fast photoelectron with respect to the photon momentum.

Super-Superexchange Influence on Magnetic Ordering in Ni3B2O6 Kotoite

Sofronova, SN; Nazarenko, II . PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 10.1002/pssb.201900060

Using ab initio software package WIEN2k, the calculations of electronic propertiesand of the energies of various magnetically ordered structures are carried out and possible mechanisms of magnetic ordering are analyzed in Ni3B2O6. The superexchange (Ni‐O‐Ni) and super‐superexchange interactions (Ni‐O‐B‐O‐Ni) are calculated, a magnetic ordering model is proposed.

On the Effect of Magnetostatic Interaction on the Collective Motion of Vortex Domain Walls in a Pair of Nanostripes

Orlov, VA (Orlov, Vitaly A.) ; Ivanov, AA (Ivanov, Anatoly A.) ; Orlova, IN (Orlova, Irina N.), PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS V, 256, 10 N 1900113 10.1002/pssb.201900113

The periodic motion of interacting vortex domain walls in a pair of nanostripes has been analytically and numerically investigated. A model consisting of two parallel nanostripes with the domain magnetization structure has been proposed, where domains are separated by vortex walls. The magnetic subsystems of the stripes magnetostatically interact, which causes the existence of normal magnetic vortex motion modes in the latter. Frequencies of the collective magnetization modes have been calculated using empirical expressions for the magnetic energy of interaction between vortex walls. It is shown that not any combinations of the polarity and chirality lead to the resonance magnetization behavior in ac fields.

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