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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylova S. N., Gudim I. A., Aleksandrovsky A. S., Vtyurin A. N., Krylov A. S.
Заглавие : Electronic band structures of NdFe3(BO3)4 and NdGa3(BO3)4 crystals: ab initio calculations
Коллективы : Russian Foundation for Basic Research GrantRussian Foundation for Basic Research (RFBR) [20-42-240009]
Место публикации : Ferroelectrics. - 2021. - Vol. 575, Is. 1. - P.11-17. - ISSN 0015-0193, DOI 10.1080/00150193.2021.1888219. - ISSN 1563-5112(eISSN)
Примечания : Cited References: 27. - This work was supported by the Russian Foundation for Basic Research Grant No. 20-42-240009
Предметные рубрики: HOFE3(BO3)4
TEMPERATURE
SPECTRA
GROWTH
Аннотация: NdFe3(BO3)4 and NdGa3(BO3)4 crystals are of great interest due to their physical properties. For example, NdFe3(BO3)4 crystal demonstrates magnetodielectric and magnetopiezoelectric effects, and NdGa3(BO3)4 crystal possesses luminescent and nonlinear optical properties. In this work, the properties of these materials are calculated by the plane-wave pseudo-potential method based on density functional theory. The structures of the crystals are optimized. The electronic structure of NdFe3(BO3)4 and NdGa3(BO3)4 are calculated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Gudim I. A., Vtyurin A. N.
Заглавие : Soft modes in HoFe2.5Ga0.5(BO3)4 solid solution
Коллективы : European Meeting on Ferroelectricity , Russian Foundation for Basic Research GrantRussian Foundation for Basic Research (RFBR) [1802-00754]
Место публикации : Ferroelectrics. - 2020. - Vol. 556, Is. 1. - P.16-22. - ISSN 0015-0193, DOI 10.1080/00150193.2020.1713334. - ISSN 1563-5112(eISSN)
Примечания : Cited References: 14. - This work was supported by the Russian Foundation for Basic Research Grant No 1802-00754.
Предметные рубрики: RAMAN-SCATTERING
SPECTRA
HO1-XNDXFE3(BO3)(4)
Аннотация: The condensation of two soft modes has been found when studying the Raman spectra of the solid solution HoFe2.5Ga0.5(BO3)4 in the temperature range from 7 to 350 K. The first high-temperature soft mode is associated with the structural phase transition from the R32 phase to the P3121 phase. The second soft mode is related to the reveal of the phonon-magnon interaction during magnetic ordering in the crystal. The temperatures of the structural phase transition T1 = 266 K and the magnetic phase transition T2 = 28 K are established. Experimentally interaction between the structural phase transition order parameter fluctuations and the magnetic order parameter fluctuations was found.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Tsikalov D. S.
Заглавие : Spin-wave resonance in gradient ferromagnets with concave and convex variations of magnetic parameters
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory [18-42-243005]
Место публикации : J. Appl. Phys. - 2020. - Vol. 127, Is. 12. - Ст.123903. - ISSN 0021-8979, DOI 10.1063/1.5143499. - ISSN 1089-7550(eISSN)
Примечания : Cited References: 26. - This work was partially supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project (No. 18-42-243005) "Synthesis and investigation of magnetic properties of gradient materials that are characterized by predetermined type of the magnetic parameter change" and the Krasnoyarsk Regional Fund of Science in the framework of participation in the conference "VII Euro-Asian Symposium 'Trends in MAGnetism' (EASTMAG 2019)."
Предметные рубрики: SPECTRA
MODES
Аннотация: The theory of spin-wave resonance in gradient ferromagnetic films with magnetic parameters varying in space described by both concave and convex quadratic functions is developed. Gradient structures such as a potential well, a potential barrier, and a monotonic change in potential between the film surfaces for both quadratic functions are considered. The waveforms of oscillations mn(z), the laws of the dependence of discrete frequencies ωn, and relative susceptibilities χn/χ01 of spin-wave resonances on the resonance number n are studied. It is shown that the law ωn∝n for nnc, where nc is the resonance level near the upper edge of the gradient inhomogeneity, which is well known for a parabolic potential well, is also valid for the potential barrier and for the monotonic change in potential, if these structures are formed by a concave quadratic function. It is shown that the law ωn∝(n−1/2)1/2, which we numerically derived and approximated by the analytical formula, is valid for all three structures formed by a convex quadratic function. It is shown that the magnetic susceptibility χn of spin-wave resonances for nnc is much greater than the susceptibility of resonances in a uniform film. An experimental study of both laws ωn(n) and χn(n) would allow one to determine the type of quadratic function that formed the gradient structure and the form of this structure. The possibility of creating gradient films with different laws ωn(n) and the high magnitude of the high-frequency magnetic susceptibility χn(n) at nnc make these metamaterials promising for practical applications.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Oreshonkov A. S., Shestakov N. P., Molokeev M. S., Aleksandrovsky A. S., Gudim I. A., Temerov V. L., Adichtchev S. V., Pugachev A. M., Nemtsev I. V., Pogoreltsev E. I., Denisenko Y. G.
Заглавие : Monoclinic SmAl3(BO3)4: synthesis, structural and spectroscopic properties
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-03-00750, 18-05-00682, 18-32-20011]
Место публикации : Acta Crystallogr. B. - 2020. - Vol. 76. - P.654-660. - ISSN 2052-5206(eISSN), DOI 10.1107/S2052520620008781
Примечания : Cited References: 38. - Funding for this research was provided by: Russian Foundation for Basic Research (grant Nos. 18-03-00750, 18-05-00682 and 18-32-20011 to AO)
Предметные рубрики: Optical-properties
Luminescence
Spectra
Crystals
Sm
Аннотация: Single crystals of SmAl3(BO3)4 were synthesized by the group growth on seeds method. The crystal structure was solved using a single-crystal experiment and the purity of the bulk material was proved by the Rietveld method. This borate crystallizes in the monoclinic C2/c space group with unit-cell parameters a = 7.2386 (3), b = 9.3412 (5), c = 11.1013 (4) Å and β = 103.2240 (10)°. IR and Raman spectroscopic analyses confirmed the monoclinic structure of SmAl3(BO3)4. Under 532.1 nm excitation, luminescence spectra exhibit bands assignable to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2. The similarity of the luminescence spectra of the trigonal and monoclinic polymorphs is explained by the minor role of Sm—O bond distortion and the primary role of rotational distortion of SmO6 octahedra. The smaller covalency of the Sm—O bond in alumoborates is deduced in comparison with galloborates. Calorimetric measurements did not reveal high-temperature structural phase transitions up to a temperature of 720 K.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ekholm V., Chiuzbaian G. S., Sathe C., Nicolaou A., Guarise M., Simon M., Jaouen N., Luning J., Hague C. F., Gel'mukhanov F., Odelius M., Bjorneholm O., Rubensson, J-E
Заглавие : Core-hole localization and ultra-fast dissociation in SF6
Коллективы : Swedish Research Council (VR)Swedish Research Council; Russian Science FoundationRussian Science Foundation (RSF) [16-12-10109]
Место публикации : J. Phys. B. - 2020. - Vol. 53, Is. 18. - Ст.185101. - ISSN 0953-4075, DOI 10.1088/1361-6455/aba204. - ISSN 1361-6455(eISSN)
Примечания : Cited References: 36. - This work was supported by the Swedish Research Council (VR). The calculations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC). FG acknowledges support within the Russian Science Foundation (Project No. 16-12-10109)
Предметные рубрики: X-RAY-EMISSION
SYMMETRY-BREAKING
AB-INITIO
SPECTROSCOPY
SPECTRA
Аннотация: Resonant inelastic x-ray scattering spectra excited at the fluorine K resonances of SF6 have been recorded. While a small but significant propensity for electronically parity-allowed transitions is found, the observation of parity-forbidden electronic transitions is attributed to vibronic coupling that breaks the global inversion symmetry of the electronic wavefunction and localizes the core hole. The dependence of the scattering cross section on the polarization of the incident radiation and the scattering angle is interpreted in terms of local π/σ symmetry around the S–F bond. This symmetry selectivity prevails during the dissociation that occurs during the scattering process.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shtarev D. S., Shtareva, A., V, Kevorkyants R., Rudakova, A., V, Molokeev M. S., Bakiev, T., V, Bulanin K. M., Ryabchuk V. K., Serpone N.
Заглавие : Materials synthesis, characterization and DFT calculations of the visible-light-active perovskite-like barium bismuthate Ba1.264(4)Bi1.971(4)O4 photocatalyst
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [19-73-10013]; Saint-Petersburg State University [39054581]; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-03-00855]
Место публикации : J. Mater. Chem. C. - 2020. - Vol. 8, Is. 10. - P.3509-3519. - ISSN 2050-7526, DOI 10.1039/c9tc06457e. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 42. - The current research was kindly funded by a grant from the Russian Science Foundation (project No. 19-73-10013). R. K., A. V. R., V. K. R. and T. V. B. acknowledge financial support from Saint-Petersburg State University (Pure ID 39054581). A. V. R. thanks the Russian Foundation for Basic Research for a Grant No. 18-03-00855 that supported studies into the photoinduced hydrophilicity of the bismuthate. The authors are further grateful to the staff of the Khabarovsk Innovation and Analytical Center of the Yu. A. Kosygin Institute of Tectonics and Geophysics of the Far Eastern Branch of the Russian Academy of Sciences, and the Resource Centers of the Research Park at the Saint-Petersburg State University: (i) the Center for Diagnostics of Functional Materials for Medicine, Pharmacology and Nanoelectronics, (ii) the Center for Physical Methods of Surface Investigation, (iii) the Center for Optical and Laser Materials Research, and the laboratories of (iv) Nanotechnology and (v) Nanophotonics for their valuable assistance in carrying out the research and in providing the needed equipment. One of us (N.S.) is grateful to Prof. Angelo Albini and the staff of the PhotoGreen Laboratory at the University of Pavia, Italy, for their continued hospitality.
Предметные рубрики: OXIDE
NIO/SRBI2O4
SPECTRA
DRIVEN
CO2
LA
Аннотация: A perovskite-like barium bismuthate of the BaBi2O4 class, Ba1.264(4)Bi1.971(4)O4, has been prepared by solid-state synthesis and subsequently characterized by a number of experimental techniques (XPS, DRS, SEM, EDX and Raman spectroscopy), as well as by a DFT computational approach using the GGA Perdew–Burke–Ernzerhof (PBE) density functional to determine the energy band structure. XRD peaks were indexed to a rhombohedral cell (R[3 with combining macron]m) with parameters close to Ba0.156Bi0.844O1.422 (i.e., to Ba0.439Bi2.374O4), which upon Rietveld refinement gave Ba1.264(4)Bi1.971(4)O4. The Bi–O bond lengths determined from this refinement (1.86 and 2.31 Å) accorded with the bond lengths estimated from Raman spectra (1.97 and 2.26 Å). DFT calculations revealed the bismuthate to display two bandgaps that correspond to lower-energy indirect (2.28 eV) and to higher-energy direct (2.36 eV) electronic transitions in good agreement with the experimental bandgaps of 2.26 eV and 2.43 eV, respectively, from Tauc plots of DRS spectra. Relative to the indirect bandgap energy of 2.26 eV, the energies of the valence band and of the conduction band were, respectively, +1.14 eV and −1.12 eV. The photoactivity of Ba1.264(4)Bi1.971(4)O4 was examined toward the photoreduction of the greenhouse gas CO2 in aqueous media photoelectrochemically yielding alcohols and alkanes, while in the gas phase in an infrared cell reactor the products were carbon monoxide and alkanes.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shi, Xin, Wu, Yong, Wang, Jian Guo, Kimberg V., Zhang, Song Bin
Заглавие : X-ray transient absorption spectroscopy by an ultrashort x-ray-laser pulse in a continuous-wave IR field
Место публикации : Phys. Rev. A. - 2020. - Vol. 101, Is. 2. - Ст.023401. - ISSN 2469-9926, DOI 10.1103/PhysRevA.101.023401. - ISSN 2469-9934(eISSN)
Примечания : Cited References: 56. - Grants from the National Basic Research Program of China (Grant No. 2017YFA0403200), National Natural Science Foundation of China (Grants No. 11604197, No. 11934004, and No. 11974230), the Science Challenge Program of China (Grants No. TZ2018005 and No. TZ2016005), and the Organization Department of CCCPC are acknowledged. V.K. acknowledges financial support from Swedish Research Council within the State Contract of the Ministry of Education and Science of the Russian Federation for Siberian Federal University for Scientific Research in 2017-2019 (Project No. 3.2662.2017)
Предметные рубрики: MOLECULAR NITROGEN
TIME
DYNAMICS
PHASE
SPECTRA
DECAY
Аннотация: 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→π∗ 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.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belyaev B. A., Drokin N. A., Poluboyarov V. A.
Заглавие : Impedance spectroscopy study of the electrical properties of cation-substituted barium hexaaluminate ceramics
Место публикации : Phys. Solid State. - 2018. - Vol. 60, Is. 2. - P.274-280. - ISSN 1063-7834, DOI 10.1134/S1063783418020063. - ISSN 1090-6460(eISSN)
Примечания : Cited References:18
Предметные рубрики: DIELECTRIC-RELAXATION
LIQUID-CRYSTALS
SPECTRA
Аннотация: We report on the behavior of frequency and temperature dependences of the impedance of a measuring cell in the form of a parallel-plate capacitor filled with barium hexaaluminate ceramics with four aluminum cations replaced by iron (BaO · 2Fe2O3 · 4Al2O3). The measurements have been performed in the frequency range of 0.5–108 Hz at temperatures of 20-375°C. A technique for determining the electrical properties of the investigated ceramics is proposed, which is based on an equivalent electric circuit allowing the recorded impedance spectra to be approximated with sufficiently high accuracy. The established spectral features are indicative of the presence of two electric relaxation times different from each other by three orders of magnitude. This fact is explained by the difference between the charge transport processes in the bulk of crystallites and thin intercrystallite spacers, for which the charge activation energies have been determined.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the effect of an inhomogeneous magnetic field on high-frequency asymptotic behaviors of correlation functions of spin lattices
Место публикации : JETP Letters. - 2018. - Vol. 107, Is. 9. - P.553-557. - ISSN 0021-3640, DOI 10.1134/S002136401809014X. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 39
Предметные рубрики: HEISENBERG PARAMAGNET
SYSTEMS
TIME
RELAXATION
DYNAMICS
SPECTRA
Аннотация: Singular points of spin autocorrelation functions on the imaginary time axis, which determine the arguments of exponential high-frequency asymptotic behaviors, have been analyzed. It has been shown that randomly distributed inhomogeneous magnetic fields expand the wings of spectra of autocorrelation functions and, thereby, intensify the heating of a system subjected to variable magnetic fields, which are used to create effective Hamiltonians or at the saturation of inhomogeneously broadened EPR lines.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. S., Igumenov, A. Yu., Mikhlin, Yu. L., Pchelyakov O. P., Zhigalov V. S.
Заглавие : Reflection electron energy loss spectroscopy of iron monosilicide
Место публикации : Russ. Phys. J.: Springer, 2017. - Vol. 59, Is. 10. - P.1610-1615. - ISSN 1064-8887, DOI 10.1007/s11182-017-0952-7. - ISSN 1573-9228(eISSN)
Примечания : Cited References:14
Предметные рубрики: SCATTERING CROSS-SECTION
SPECTRA
Ключевые слова (''Своб.индексиров.''): iron silicides--iron monosilicide--inelastic electron scattering cross--section spectroscopy--reflection electron energy loss spectroscopy--x-ray photoelectron spectroscopy
Аннотация: X-ray photoelectron spectra, reflection electron energy loss spectra, and inelastic electron scattering cross section spectra of iron monosilicide FeSi are investigated. It is shown that the spectra of inelastic electron scattering cross section have advantages over the reflection electron energy loss spectra in studying the processes of electron energy losses. An analysis of the fine structure of the inelastic electron scattering cross section spectra allows previously unresolved peaks to be identified and their energy, intensity, and nature to be determined. The difference between energies of fitting loss peaks in the spectra of inelastic electron scattering cross section of FeSi and pure Fe are more substantial than the chemical shifts in X-ray photoelectron spectra, which indicates the possibility of application of the fine structure of the spectra of inelastic electron scattering cross section for elemental analysis.
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