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247 results on '"Galakhov, V. R."'

3. Erratum to: Several Articles in JETP Letters Published Online First

Author

Ivanov, Yu. B., Soldatov, A. A., Pakhomov, A. V., Arkhipov, M. V., Rosanov, N. N., Arkhipov, R. M., Sturman, B., Podivilov, E., Arbuzov, A., Bondarenko, S., Dydyshka, Ya., Kalinovskaya, L., Rumyantsev, L., Sadykov, R., Yermolchyk, V., Yermolchyk, Yu., Kats, E. I., Shilpashree, S. P., Shastri, Venkataramana, Zakharov, B. G., Galakhov, V. R., Udintseva, M. S., Naumov, S. V., Shamin, S. N., Gizhevskii, B. A., Valba, O., Gorsky, A., Gavryushkin, P. N., Martirosyan, N. S., Rashchenko, S. V., Sagatova, D. N., Sagatov, N. E., Semerikova, A. I., Fedotenko, T. M., Litasov, K. D., Avchyan, B. R., Ghazaryan, A. G., Sargsyan, K. A., and Sedrakian, Kh. V.

Published
2022
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7. Electronic Structure and Resonant X-ray Emission Spectra of Carbon Shells of Iron Nanoparticles

Author

Galakhov, V. R., Shamin, S. N., Mironova, E. M., Uimin, M. A., Yermakov, A. Ye., and Boukhvalov, D. W.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Chemical Physics
Abstract

The electronic structure of carbon shells of carbon encapsulated iron nanoparticles carbon encapsulated Fe@C has been studied by X-ray resonant emission and X-ray absorption spectroscopy. The recorded spectra have been compared to the density functional calculations of the electronic structure of graphene. It has been shown that an Fe@C carbon shell can be represented in the form of several graphene layers with Stone-Wales defects. The dispersion of energy bands of Fe@C has been examined using the measured C Ka resonant X-ray emission spectra., Comment: 8 pages, 2 figures

Published
2013
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8. Carbon States in Carbon-Encapsulated Nickel Nanoparticles Studied by Means of X-Ray Absorption, Emission, and Photoelectron Spectroscopies

Author

Galakhov, V. R., Buling, A., Neumann, M., Ovechkina, N. A., Shkvarin, A. S., Semenova, A. S., Uimin, M. A., Yermakov, A. Ye., Kurmaev, E. Z., Vilkov, O. Y., and Boukhvalov, D. W.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Chemical Physics
Abstract

Electronic structure of nickel nanoparticles encapsulated in carbon was characterized by photoelectron, X-ray absorption, and X-ray emission spectroscopies. Experimental spectra are compared with the density of states calculated in the frame of the density functional theory. The carbon shell of Ni nanoparticles has been found to be multilayer graphene with significant (about 6%) amount of Stone--Wales defects. Results of the experiments evidence protection of the metallic nanoparticles from the environmental degradation by providing a barrier against oxidation at least for two years. Exposure in air for 2 years leads to oxidation only of the carbon shell of Ni@C nanoparticles with coverage of functional groups., Comment: 16 pages, 6 figures, accepted in J. Phys. Chem. C

Published
2011
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9. Electronic Structure of Transition-Metal Dicyanamides Me[N(CN)$_2$]$_2$ (Me = Mn, Fe, Co, Ni, Cu)

Author

Demchenko, D. O., Liu, Amy Y., Kurmaev, E. Z., Finkelstein, L. D., Galakhov, V. R., Moewes, A., Chiuzbaian, S. G., Neumann, M., Kmety, Carmen R., and Stevenson, Kenneth L.

Subjects
Condensed Matter - Materials Science
Abstract

The electronic structure of Me[N(CN)$_2$]$_2$ (Me=Mn, Fe, Co, Ni, Cu) molecular magnets has been investigated using x-ray emission spectroscopy (XES) and x-ray photoelectron spectroscopy (XPS) as well as theoretical density-functional-based methods. Both theory and experiments show that the top of the valence band is dominated by Me 3d bands, while a strong hybridization between C 2p and N 2p states determines the valence band electronic structure away from the top. The 2p contributions from non-equivalent nitrogen sites have been identified using resonant inelastic x-ray scattering spectroscopy with the excitation energy tuned near the N 1s threshold. The binding energy of the Me 3d bands and the hybridization between N 2p and Me 3d states both increase in going across the row from Me = Mn to Me = Cu. Localization of the Cu 3d states also leads to weak screening of Cu 2p and 3s states, which accounts for shifts in the core 2p and 3s spectra of the transition metal atoms. Calculations indicate that the ground-state magnetic ordering, which varies across the series is largely dependent on the occupation of the metal 3d shell and that structural differences in the superexchange pathways for different compounds play a secondary role., Comment: 20 pages, 11 figures, 2 tables

Published
2003
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12. X-ray photoelectron 3s spectra of transition metal oxides

Author

Galakhov, V. R., Uhlenbrock, S., Bartkowski, S., Postnikov, A. V., Neumann, M., Finkelstein, L. D., Kurmaev, E. Z., Samokhvalov, A. A., and Leonyuk, L. I.

Subjects
Condensed Matter - Materials Science
Abstract

We present metal 3s x-ray photoelectron spectra of different transition metal oxides. The values of the 3s exchange splitting for the 3d metal oxides are given as a function of the 3d electron number in the ground state. The spectra were analysed using the simple two-configuration model of the interatomic configuration mixing. The change of the 3s spectra is ascribed to the change of the charge-transfer energy., Comment: 17 pages with 9 embedded postscript figures, uses ioplppt.sty

Published
1999

13. Electronic Structure and Valence Band Spectra of Bi4Ti3O12

Author

Postnikov, A. V., Bartkowski, St., Mersch, F., Neumann, M., Kurmaev, E. Z., Cherkashenko, V. M., Nemnonov, S. N., and Galakhov, V. R.

Subjects
Condensed Matter - Materials Science
Abstract

The x-ray photoelectron valence band spectrum and x-ray emission valence-band spectra (Ti K _beta_5, Ti L_alpha, O K_alpha) of Bi4Ti3O12 are presented (analyzed in the common energy scale) and interpreted on the basis of a band-structure calculation for an idealized I4/mmm structure of this material., Comment: 6 pages + 7 PostScript figures, RevTex3.0, to be published in Phys.Rev.B52 (Oct.95). Figures also available via anonymous ftp at ftp://ftp.physik.uni-osnabrueck.de/pub/apostnik/BiTiO/

Published
1995
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14. ELECTRONIC STRUCTURE OF FeSi

Author

Galakhov, V. R., Kurmaev, E. Z., Cherkashenko, V. M., Yarmoshenko, Yu. M., Shamin, S. N., Postnikov, A. V., Uhlenbrock, St., Neumann, M., Lu, Z. W., Klein, Barry M., and Shi, Zhu-Pei

Subjects
Condensed Matter - Materials Science
Abstract

The full set of high-energy spectroscopy measurements including X-ray photoelectron valence band spectra and soft X-ray emission valence band spectra of both components of FeSi (Fe K_beta_5, Fe L_alpha, Si K_beta_1,3 and Si L_2,3) are performed and compared with the results of ab-initio band structure calculations using the linearized muffin-tin orbital method and linearized augmented plane wave method., Comment: 11 pages + 3 PostScript figures, RevTex3.0, to be published in J.Phys.:Cond.Matter

Published
1995
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16. Spin States of Cobalt Ions and a Metal–Semiconductor Transition in Layered Cobaltites PrBaCo2O5 + δ (δ = 0.52, 0.74).

Author

Solin, N. I., Naumov, S. V., Korolev, A. V., and Galakhov, V. R.

Subjects
IONS, METAL-insulator transitions, MAGNETIC properties, OCTAHEDRA
Abstract

The spin states of Co atoms in PrBaCo2O5 + δ with regard to the paramagnetic contribution of Pr3+ ions have been determined from magnetic property studies for δ = 0.52 and 0.74. Results obtained without considering the paramagnetic contribution of Pr3+ ions are inconsistent with available experimental data. With a decrease in temperature, the metal–insulator transition in PrBaCo2O5.52 becomes sharper according to a sharp change in spin states (from HS/LS to LS/IS) of Co3+ ions. In this case, Co3+ ions occupying octahedra pass from the high-spin state (HS, S = 2) to the low-spin one (LS, S = 0) and those occupying pyramids pass from the LS-state to the intermediate spin state (IS, S = 1), as follows from the available structural data. In PrBaCo2O5.74, the metal–semiconductor transition occurs smoothly from HS/LS to the HS/IS state upon the smooth transition of the Co3+ ion state from (LS, S = 0) to the (IS, S = 1) state in pyramides without change in the spin state of ions Co3+ (HS, S = 2) and Co4+ (LS, S = 1/2) in octahedrons. [ABSTRACT FROM AUTHOR]

Published
2023
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19. Spin States of Cobalt Ions in the Bulk and on the Surface of LaCoO3 Probed by X-ray Absorption, Emission, and Photoelectron Spectra.

Author

Galakhov, V. R., Udintseva, M. S., Smirnov, D. A., Makarova, A. A., and Kuepper, K.

Subjects
*PHOTOELECTRON spectra, *X-ray absorption, *X-ray emission spectroscopy, *COBALT, *PHOTOELECTRONS, *IONS
Abstract

We present X-ray photoelectron, Co and O K X-ray absorption, as well as Co X-ray emission spectroscopy results of studies of the spin states of trivalent cobalt ions in single-crystal cobaltite LaCoO3. We show that at room temperature, in the bulk of a LaCoO3 single crystal, Co3+ ions are in the low-spin state, while high-spin Co2+, high-spin Co3+, low-spin Co3+, and probably also intermediate-spin Co3+ ions are located on the surface. [ABSTRACT FROM AUTHOR]

Published
2023
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35. X-Ray Absorption Co L Spectra for the Determination of the Charge and Spin States of Cobalt Ions in LnBaCo2O5 + δ Cobaltites (Ln = Eu, Gd, Tb).

Author

Galakhov, V. R., Udintseva, M. S., Naumov, S. V., Shamin, S. N., and Gizhevskii, B. A.

Subjects
*X-ray absorption spectra, *RARE earth metals, *TERBIUM, *METAL-insulator transitions, *COBALT, *SHEAR (Mechanics), *X-ray spectra
Abstract

Co L X-ray absorption spectra were used to determine the charge and spin states of ions in LnBaCo2O5 + δ cobaltites (Ln = Tb, Eu and Gd, ). It is shown that with a decrease in the oxygen content in cobaltites (with a decrease in the average charge state of cobalt ions), the Co maximum shifts linearly towards low photon energies. It was found using Co X-ray spectra that the mechanical action on GdBaCo2O5.5 (uniaxial compression and torsion under pressure) leads to the appearance of divalent cobalt ions, i.e., the CoO phase. The CoO phase appears in the sample under pressure even in the absence of shear deformations. Based on the measurements of X-ray absorption spectra at different temperatures, it was found that at 440 K, which is above the metal–insulator transition point, some of the low-spin Co3+ ions in EuBaCo2O5.52 cobaltite octahedra pass into the high-spin state. No change of the spin state of Co ions in EuBaCo2O5.24 with temperature was found. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Unconventional magnetism of non-uniform distribution of Co in TiO2 nanoparticles

Author

Yermakov, A. Y., Boukhvalov, D. W., Volegov, A. S., Uimin, M. A., Zakharova, G. S., Korolev, A. V., Rosenfeld, E. V., Mesilov, V. V., Minin, A. S., Galakhov, V. R., Molochnikov, L. S., Gubkin, A. F., Murzakaev, A. M., and Konev, S. F.

Abstract

High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) analysis, electron paramagnetic resonance (EPR), X-ray absorption spectroscopy (XAS), magnetic methods, and density-functional theory (DFT) calculations were applied for the investigations of Co-doped anatase TiO2 nanoparticles (∼20 nm). It was found that high-spin Co2+ ions prefer to occupy the interstitial positions in the TiO2 lattice which are the most energetically favourable in compare to the substitutional those. A quantum mechanical model which operates mainly on two types of Co2+ – Co2+ dimers with different negative exchange interactions and the non-interacting paramagnetic Co2+ ions provides a satisfactorily description of magnetic properties for the TiO2:Co system. © 2020 Elsevier B.V. Russian Foundation for Basic Research. Ministry of Science and Higher Education of the Russian Federation

Published
2020

48. Magnetic Properties, Electron Paramagnetic Resonance, and Photoelectron Spectroscopy Studies of Nanocrystalline TiO2 Co-Doped with Al and Fe

Author

Yermakov, A. Y., Galakhov, V. R., Minin, A. S., Mesilov, V. V., Uimin, M. A., Kuepper, K., Bartkowski, S., Molochnikov, L. S., Konev, A. S., Gaviko, V. S., and Zakharova, G. S.

Subjects
Condensed Matter::Materials Science, ELECTRON PARAMAGNETIC RESONANCE, Condensed Matter::Superconductivity, TITANIUM DIOXIDE, Physics::Atomic and Molecular Clusters, NANOPARTICLES, Physics::Optics, PHOTOELECTRON SPECTROSCOPY, Condensed Matter::Strongly Correlated Electrons, ALUMINUM DOPING, TRANSMISSION ELECTRON MICROSCOPY
Abstract

Electron paramagnetic resonance, X-ray photoelectron spectroscopy, field dependence of magnetization, X-ray diffraction, and transmission electron microscopy are applied for the characterization of Al-doped TiO2 nanopowders with Fe impurities synthesized by the autoclave-assisted hydrothermal method and annealed in vacuum or in hydrogen. The sizes of the TiO2:(Al, Fe) nanoparticles are estimated to be about 10-20 nm. It is proposed that Al ions are presumably placed in the TiO2 lattice in interstitial positions. Moreover, Fe3+ ions can occupy tetrahedral positions of Ti4+ ions as a result of Al-doping. The results suggest that Al-doped TiO2 nanopowders with Fe impurities annealed in vacuum or hydrogen display both intrinsic and extrinsic ferromagnetic properties.

Published
2020

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