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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Second moment of multiple-quantum NMR and a time-dependent growth of the number of multispin correlations in solids
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 103, Is. 6. - P904-916. - ISSN 1063-7761, DOI 10.1134/S1063776106120089
Примечания : Cited References: 39
Предметные рубрики: NUCLEAR-MAGNETIC-RESONANCE
LINE-SHAPE
SPIN SYSTEMS
DYNAMICS
SPECTRA
COHERENCES
STATE
BEHAVIOR
CRYSTAL
MODEL
Ключевые слова (''Своб.индексиров.''): correlation methods--mathematical models--nuclear magnetic resonance spectroscopy--spectrum analysis--time series analysis--four-spin time correlation--multispin correlations--second moment--time power series--quantum theory
Аннотация: The time evolution of multispin correlations (the growth of the number of correlated spins as a function of time) can be observed directly using the multiple-quantum nuclear magnetic resonance spectroscopy of solids. A quantity related to this number, namely, the second moment n(2)(t) of the intensity distribution of coherences of different orders in the multiple-quantum spectrum can be calculated using the theory proposed in this work. An approach to the calculation of the four-spin time correlation function through which this moment is expressed is developed. The main sequences of contributions in the expansion of this function into a time power series are summed using the approximation of a large number of neighbors both for systems with a secular dipole-dipole interaction and for systems with a nonsecular effective interaction. An exponential dependence of n(2)(t) is obtained. The value of n(2)(t) is additionally calculated using an expansion in terms of orthogonal operators for three model examples corresponding to different limiting realizations of spin systems. It is shown that the results of the microscopic theory at least qualitatively agree with both the results obtained for model examples and experimental results obtained recently for adamantane.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Novikov P. V., Churilov G. N.
Заглавие : Characteristics of the heating dynamics of a graphite conductor taking into account the skin effect
Место публикации : Tech. Phys.: AMER INST PHYSICS, 2000. - Vol. 45, Is. 9. - P1214-1218. - ISSN 1063-7842, DOI 10.1134/1.1318113
Примечания : Cited References: 13
Предметные рубрики: FULLERENES
C-60
SPECTRA
Аннотация: Calculations for a one-dimensional model of RF heating of a cylindrical graphite conductor have been carried out. The heating dynamics are analyzed in the general form. Conductor temperature profiles and the times for heating up to the graphite sublimation temperature as a function of current and frequency have been obtained. A model of conductor heating with partial return of the energy irradiated by the conductor surface has been considered. Frequency and current ranges have been determined to carry out this graphite sublimation method in a chamber with reflecting walls. The problem is associated with carbon vapor production and subsequent synthesis of fullerenes and other carbon structures. (C) 2000 MAIK "Nauka/ Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskaya E. A., Bulina N. V., Churilov G. N., Puzyr' A. P.
Заглавие : A study of the synthesis products of fullerenes with nickel and cobalt
Место публикации : Tech. Phys.: AMER INST PHYSICS, 2001. - Vol. 46, Is. 1. - P42-46. - ISSN 1063-7842, DOI 10.1134/1.1340883
Примечания : Cited References: 15
Предметные рубрики: COMPLEXES
SPECTRA
Аннотация: Qualitative analysis of the products of plasmochemical synthesis of fullerenes with metallic nickel and cobalt has been carried out using electron paramagnetic resonance (EPR) and electron microscopy. These studies show that the synthesis products are mainly fullerenes, metallic nanoparticles coated with an insulating layer, and isolated atomic clusters. (C) 2001 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S. G.
Заглавие : DENSITY OF SINGLE-PARTICLE STATES IN STRONGLY CORRELATED ELECTRON-SYSTEMS IN COPPER OXIDES
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1993. - Vol. 104, Is. 5. - P3719-3734. - ISSN 0044-4510
Примечания : Cited References: 24
Предметные рубрики: DYNAMIC PROPERTIES
BAND
SPECTRA
MODEL
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S. G.
Заглавие : EFFECT OF SUBSTITUTIONAL IMPURITY SPECIES ON THE SUPPRESSION OF MAGNETIC-PROPERTIES OF WEAKLY DOPED COPPER OXIDES
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1994. - Vol. 36, Is. 5. - P1307-1310. - ISSN 0367-3294
Примечания : Cited References: 16
Предметные рубрики: ELECTRONIC-STRUCTURE
SUPERCONDUCTIVITY
LA2CUO4
EXCITATIONS
SPECTRA
WOS
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Density of hole-doped states in strongly correlated electron-systems of copper oxides
Разночтения заглавия :авие SCOPUS: Density of hole-doped states in strongly correlated electron systems of copper oxides
Место публикации : Phys. Rev. B. - 1994. - Vol. 49, Is. 14. - P.9891-9897. - ISSN 0163-1829, DOI 10.1103/PhysRevB.49.9891
Примечания : Cited References: 34
Предметные рубрики: DYNAMIC PROPERTIES
SUPERCONDUCTIVITY
GAP
LA2CUO4
BI2SR2CACU2O8
PHOTOEMISSION
SPECTROSCOPY
SPECTRA
MODEL
BAND
Аннотация: A generalized tight-binding method to calculate quasiparticle band structure and density of states in strongly correlated systems is presented. The band structures of undoped and weakly hole-doped CuO2 layer are calculated. The insulator gap has a charge transfer nature with a minor contribution from a Cu-O Coulomb interaction. Doping results in the appearance of an in-gap state with a simultaneous decrease of the density of states at the band edges in agreement with small cluster results and experimental data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavriliuk A. G., Trojan I. A., Ovchinnikov S. G., Lyubutin I. S., Sarkisyan V. A.
Заглавие : The mechanism of suppression of strong electron correlations in FeBO3 at high pressures
Разночтения заглавия :авие SCOPUS: The mechanism of suppression of strong electron correlations in FeBO 3 at high pressures
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 99, Is. 3. - P566-573. - ISSN 1063-7761, DOI 10.1134/1.1809686
Примечания : Cited References: 18
Предметные рубрики: MAGNETIC COLLAPSE
TRANSITION
SPECTRA
ABSORPTION
STATE
Ключевые слова (''Своб.индексиров.''): crystal structure--high pressure effects--light absorption--parameter estimation--phase transitions--spectrum analysis--crystal field--electron correlations--generalized tight binding method--hybridization--iron compounds
Аннотация: The optical absorption spectra of iron borate (FeBO3) are measured at high pressures up to P = 82 GPa. A mechanism of suppression of strong electron correlations is proposed within the framework of the generalized tight binding method, which leads to the experimentally observed magnetic, electronic, and structural phase transitions. Taking into account peculiarities of the crystal structure of FeBO3 and the strong s-p hybridization of boron and oxygen, it is established that, as the distance between ions varies with increasing pressure, the crystal field parameter begins to play a decisive role in the electron transitions, while the influence of the d band broadening is negligibly small. Parameters of the theory are calculated as functions of the pressure. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Borisov A. A., Gavrichkov V. A., Korshunov M. M.
Заглавие : Prediction of the in-gap states above the top of the valence band in undoped insulating cuprates due to the spin-polaron effect
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2004. - Vol. 16, Is. 8. - PL93-L100. - ISSN 0953-8984, DOI 10.1088/0953-8984/16/8/L04
Примечания : Cited References: 25
Предметные рубрики: ELECTRONIC-STRUCTURE
LA2-XSRXCUO4
MODEL
ANTIFERROMAGNETISM
SPECTRA
OXIDES
Ключевые слова (''Своб.индексиров.''): quasiparticle band structure--spin-polaron effect--antiferromagnetic materials--approximation theory--doping (additives)--electronic structure--hamiltonians--insulation--magnetic fields--strontium compounds--thermal effects--lanthanum compounds
Аннотация: In the framework of the generalized tight binding method we have calculated the quasiparticle band structure and the spectral functions of the undoped cuprates such as La2CuO4, Sr2CUO2Cl2 etc. Due to spin fluctuations the in-gap state appears above the top of the valence band in the undoped antiferromagnetic insulator similar to in-gap states induced by hole doping. In the ARPES experiments the in-gap states can be detected as weak low energy satellites.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivchenko E. L., Voronov M. M., Erementchouk M. V., Deych L. I., Lisyansky A. A.
Заглавие : Multiple-quantum-well-based photonic crystals with simple and compound elementary supercells
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2004. - Vol. 70, Is. 19. - Ст.195106. - ISSN 1098-0121, DOI 10.1103/PhysRevB.70.195106
Примечания : Cited References: 33
Предметные рубрики: EXCITON POLARITONS
DIELECTRIC MEDIUM
OPTICAL LATTICES
BRAGG STRUCTURES
BAND-STRUCTURES
PERIODIC-BRAGG
REFLECTION
ABSORPTION
SPECTRA
ARRAYS
Ключевые слова (''Своб.индексиров.''): article--crystal--crystal structure--elementary particle--light scattering--mathematical analysis
Аннотация: Exciton polaritons in one-dimensional photonic crystals based on multiple quantum well structures are investigated. The effects due to interplay between resonant interaction of light with quantum well excitons, and light scattering from well-barrier interface, are elucidated. Polariton dispersion equations and reflection spectra in structures with two wells in an elementary supercell of the periodic structure are studied. Several examples of different compound elementary supercells are considered. Special attention is paid to structures with the period or the distance between quantum wells satisfying the resonance Bragg condition. Such structures are characterized by a presence of a larger-than-usual polariton stop band. It is shown that in structures with a complex elementary supercell, the width of such a stop band can be significantly enhanced in comparison to that in simple structures.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belyaev B. A., Drokin N. A., Shabanov V. F.
Заглавие : Dielectric and optical properties of a 5-propyl-2-(p-cyanophenyl)-pyridine liquid crystal
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2003. - Vol. 45, Is. 4. - P797-801. - ISSN 1063-7834, DOI 10.1134/1.1569024
Примечания : Cited References: 12
Предметные рубрики: DECIMETER WAVELENGTH RANGE
SERIES
SPECTRA
5CB
Аннотация: The temperature dependences of the dielectric and optical parameters for a 5-propyl-2-(p-cyanophenyl)-pyridine (3CP) liquid crystal are investigated in the vicinity of the nematic-isotropic phase transition. The dielectric spectra of the 3CP compound in the crystalline, nematic, and isotropic phases are measured in the frequency range 1-1000 MHz, and the Debye approximations of the measured spectra are obtained. Analysis of the dependence of the static permittivity on the director orientation with respect to the direction of the electric pump field demonstrates that the angle between the dipole moment and the long axis of the molecule is approximately equal to 15degrees. (C) 2003 MAIK "Nauka / Interperiodica".
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Kazak N. V., Markov V. V., Ovchinnikov S. G., Rudenko V. V., Abd-Elmeguid M. M.
Заглавие : Analysis of the electrical and optical properties of VBO3 single crystals and Fe1-xVxBO3 solid solutions on the basis of a many-electron model of energy band structure
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2004. - Vol. 46, Is. 8. - P1462-1468. - ISSN 1063-7834, DOI 10.1134/1.1788779
Примечания : Cited References: 32. - One of the authors (M.M.A.) would like to thank the Deutsche Forschungsgemeinschaft (SFB608) for financial support. This study was supported by the Russian Foundation for Basic Research (project no. 03-02-16286), the program "Integration" (project no. B0017), and the program of the Division of Physical Sciences of the Russian Academy of Sciences "Strongly Correlated Electrons"
Предметные рубрики: MAGNETIC-PROPERTIES
CALCITE STRUCTURE
PHASE-TRANSITION
FERRIC BORATE
HIGH-PRESSURE
FEBO3
FE1-XCRXBO3
FERROMAGNET
MOSSBAUER
SPECTRA
Аннотация: A many-electron model of the energy band structure of VBO3 and of Fe1 - xVxBO3 solid solutions is proposed with strong electron correlations taken into account. Experimental optical absorption spectra and data on the resistivity are discussed in the framework of the suggested model. Variation in the magnetic and electronic properties of VBO3 and Fe1 - xVxBO3 under high pressure is predicted. For VBO3, a Mott-Hubbard (insulator-metal) transition is expected in the high-pressure phase. In Fe1 - xVxBO3 solid solutions, a nontrivial variation in the properties is predicted, leading to the appearance of a different magnetic state. (C) 2004 MAIK "Nauka / Interperiodica".
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bayukov O. A., Abd-Elmeguid M. M., Ivanova N. B., Kazak N. V., Ovchinnikov S. G., Rudenko V. V.
Заглавие : Mossbauer effect study in Fe1-xVxBO3 solid solutions
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2004. - Vol. 46, Is. 6. - P1088-1094. - ISSN 1063-7834, DOI 10.1134/1.1767250
Примечания : Cited References: 28. - One of the authors (M.M. A.-E.) would like to thank the Deutsche Forschungsgemeinschaft for financial support (SFB 608). This study was supported by the Russian Foundation for Basic Research (project no. 03-02-16286) and the federal program “Integration” (project no. Б0017)
Предметные рубрики: MAGNETO-OPTICAL PROPERTIES
FEBO3 SINGLE-CRYSTALS
FERRIC BORATE
CALCITE STRUCTURE
IRON BORATE
TEMPERATURE
FIELD
SPECTRA
FE3BO6
CRBO3
Аннотация: The Mossbauer effect in the Fe1 - xVxBO3 solid solutions has been measured at 130 and 300 K. The Fe0.05V0.95BO3 composition was studied in the interval 4.2-300 K. The experimental data obtained are described in terms of the model of a dilute magnetic insulator in which atoms of the first coordination sphere provide a major contribution to the hyperfine field at iron nucleus sites. It was found that, at low temperatures, the field H-hf is generated primarily by the iron ion itself and depends only weakly on substitution. The hyperfine interaction parameters in the discrete configuration series 6Fe, 5Fe1V, 4Fe2V, 3Fe3V, and 2Fe4V were determined. The magnitude of the isomer shift suggests that iron in the crystal resides in the trivalent state. (C) 2004 MAIK "Nauka/Interperiodica".
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Churilov G. N., Korets A. Y., Titarenko Y. N.
Заглавие : Preparation of fullerenes and nanotubes in coal plasma jet in kilohertz frequency range
Место публикации : Zhurnal Tek. Fiz.: MEZHDUNARODNAYA KNIGA, 1996. - Vol. 66, Is. 1. - P191-194. - ISSN 0044-4642
Примечания : Cited References: 6
Предметные рубрики: SPECTRA
CARBON
WOS
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14.

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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15.

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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16.

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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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Bayukov O. A., Ovchinnikov S. G., Vasiliev A. D., Rudenko V. V., Ivanova N. B., Knyazev Yu. V., Bartolom J., Arauzo A.
Заглавие : The superexchange interactions in mixed Co-Fe ludwigite
Место публикации : J. Magn. Magn. Mater. - 2011. - Vol. 323, Is. 5. - P.521-527. - MAR. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2010.09.057
Примечания : Cited Reference Count: 15. - Гранты: This study was supported by the Russian Foundation for Basic Research (Project no. 09-02-00171-a), the Federal Agency for Science and Innovation (Rosnauka) (Project no. MK-5632. 2010.2), Physical Division of the Russian Academy of Science, the program "Strongly Correlated Electrons", project 2.3.1.; The financial support of Spanish MINCYT, MAT08/1077 and Aragonese E-34 project are also acknowledged.Финансирующая организация: Russian Foundation for Basic Research [09-02-00171-a]; Federal Agency for Science and Innovation (Rosnauka) [MK-5632. 2010.2]; Physical Division of the Russian Academy of Science; "Strongly Correlated Electrons" [2.3.1]; Spanish MINCYT [MAT08/1077]; Aragonese E-34 project
Предметные рубрики: TRANSPORT-PROPERTIES
SPECTRA
Ключевые слова (''Своб.индексиров.''): ludwigite structure--magnetic susceptibility--magnetic frustration--mott conductivity--ludwigite structure--magnetic frustration--magnetic susceptibility--mott conductivity--ac susceptibility--cation distributions--crystal data--crystallographic sites--electrical resistivity--iron atoms--low temperatures--ludwigite structure--magnetic behavior--magnetic frustrations--magnetic system--magnetic transitions--mossbauer--mossbauer effects--mott conductivity--mott hopping--superexchange energy--superexchange interaction--temperature regions--trivalent iron--variable range--cobalt--electric conductivity--magnetic susceptibility--magnetism--mossbauer spectroscopy--x ray diffraction--crystal structure
Аннотация: The crystal structure, cation distribution and exchange interactions in the Co2.25Fe0.75O2BO3 ludwigite have been explored through X-ray diffraction, electrical resistivity, ac-susceptibility and Mossbauer effect measurements. The crystal data have shown that iron atoms occupy the most symmetric crystallographic sites Fe4 and Fe2. The complex magnetic behavior with two magnetic transitions near 70 and 115 K at low temperatures was found. The Mossbauer data have displayed the trivalent iron states only. The values of superexchange energies have been estimated for Co3O2BO3 and Co2.25Fe0.75O2BO3 yielding a significant role of frustrations in the ludwigite magnetic system. Variable range Mott hopping conductivity law was proved to be valid in the wide temperature region, pointing out a localized character of charge carriers rather than collective. (C) 2010 Elsevier B.V. All rights reserved.
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18.

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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19.

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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20.

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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