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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Cation spin and superexchange interaction in oxide materials below and above spin crossover under high pressure
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [18-12-00022]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 9. - Ст.094409. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.094409. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 65. - We acknowledge the support of the Russian Science Foundation through Grant No. 18-12-00022
Предметные рубрики: EXCHANGE INTERACTION
PHASE-TRANSITIONS
STATE
ELECTRON
IRON
Аннотация: We derived simple rules for the sign of 180° superexchange interaction based on the multielectron calculations of the superexchange interaction in the transition metal oxides that are valid both below and above spin crossover under high pressure. The superexchange interaction between two cations in dn configurations is given by a sum of partial contributions related to the electron-hole virtual excitations to the different states of the dn+1 and dn−1 configurations. Using these rules, we have analyzed the sign of the 180° superexchange interaction of a number of oxides with magnetic cations in electron configurations from d2 until d8: the iron, cobalt, chromium, nickel, copper, and manganese oxides with increasing pressure. The most interesting result concerns the magnetic state of cobalt and nickel oxides CoO, Ni2O3 and also La2CoO4, LaNiO3 isostructural to well-known high-TC and colossal magnetoresistance materials. These oxides have a spin 12 at the high pressure. Change of the interaction from antiferromagnetic below spin crossover to ferromagnetic above spin crossover is predicted for oxide materials with cations in d5(FeBO3) and d7(CoO) configurations, while for materials with the other dn configurations spin crossover under high pressure does not change the sign of the 180∘ superexchange interaction.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kremneva A. M., Fedorov A. V., Bulavchenko O. A., Knyazev Yu. V., Saraev A. A., Yakovlev V. A., Kaichev V. V.
Заглавие : Effect of calcination temperature on activity of Fe2O3-Al2O3 nanocomposite catalysts in CO oxidation
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [17-73-20157]; National center of investigation of catalysts" at Boreskov Institute of Catalysis
Место публикации : Catal. Lett. - 2020. - Vol. 150. - P.3377-3385. - ISSN 1011-372X, DOI 10.1007/s10562-020-03250-8. - ISSN 1572-879X(eISSN)
Примечания : Cited References: 31. - This work was supported by the Russian Science Foundation (Grant No. 17-73-20157). The experiments were performed using facilities of the shared research center "National center of investigation of catalysts" at Boreskov Institute of Catalysis. The authors thank A.Yu. Gladky for the TPR measurements and Z.S. Vinokurov for the XRD measurements.
Предметные рубрики: MOSSBAUER
SPECTROSCOPY
CHEMISTRY
IRON
XPS
ADSORPTION
OXYGEN
FE
Аннотация: Nanocomposite Fe–Al oxide catalysts were prepared by the melting of iron and aluminum nitrates with the subsequent calcination in air at different temperatures. It was found that the catalysts calcined at 450 °C are more active in the oxidation of CO than the catalysts calcined at 700 °C. X-ray diffraction and X-ray photoelectron spectroscopy showed that all the catalysts consist of hematite, α-Fe2O3 nanoparticles, and Al2O3 in an amorphous state. Iron oxide is the active component, which provides the oxidation of CO, while alumina is a texture promoter. The increase in the calcination temperature leads to a minor increase in the average size of hematite nanoparticles and an insignificant decrease in the specific surface area. Kinetic measurements showed that the oxidation of CO over the Fe–Al catalysts calcined at 450 and 700 °C proceeds with the activation energy of 61–69 and 91 kJ/mol, respectively. This means that the low-temperature and high-temperature catalysts contain different active species. Temperature-programmed reduction with CO indicated that the decrease in the calcination temperature improves the reducibility of the Fe-Al nanocomposites. According to 57Fe Mössbauer spectroscopy, the low-temperature catalysts contain hydrated iron oxides (acagenite and ferrihydrite) and a significant amount of highly defective hematite, which is absent in the high-temperature catalyst. These species can provide the enhanced activity of the low-temperature catalysts in the oxidation of CO.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grishina, Svetlana, Kodera, Peter, Goryainov, Sergey, Oreshonkov A. S., Seryotkin, Yurii, Simko, Frantisek, Polozov, Alexander G.
Заглавие : Application of Raman spectroscopy for identification of rinneite (K3NaFeCl6) in inclusions in minerals
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-05-00682]; European Regional Development FundEuropean Union (EU) [ITMS 26240220086]; Vedecka Grantova Agentura MSVVaS SR a SAV [1/0313/20]
Место публикации : J. Raman Spectrosc. - 2020. - Vol. 51, Is. 12. - P.2505-2516. - ISSN 0377-0486, DOI 10.1002/jrs.6005. - ISSN 1097-4555(eISSN)
Примечания : Cited References: 55. - Russian Foundation for Basic Research, Grant/Award Numbers: 18-05-00682, 18-05-00682; European Regional Development Fund, Grant/Award Number: ITMS 26240220086; Vedecka Grantova Agentura MSVVaS SR a SAV, Grant/Award Number: 1/0313/20
Предметные рубрики: SALT MELT
IRON
DEPOSIT
FLUIDS
TRANSFORMATIONS
FERRIHYDRITE
Аннотация: Solid daughter phases in fluid and salt melt inclusions in minerals provide important clues to characterization of mineral‐forming processes. The analysis of the fluid inclusions often requires the exposure of the daughter minerals. Rinneite (K3NaFeCl6), which is a hygroscopic mineral, decomposes in air and cannot thus be identified by conventional methods. A combined approach has been applied for investigation of synthetic and natural rinneite to acquire its diagnostic Raman spectrum for a nondestructive identification. We used natural rinneite inclusions in halite, suitable for applying a complex of methods, to clear up the reference spectrum. Improved high‐resolution X‐ray diffraction (XRD) data obtained from natural rinneite inclusion are comparable with that of previously published, with similar unit cell dimensions. Polarized Raman spectra of natural inclusions were obtained using different geometries and polarization of the incident and scattered light. Interpretation of experimental Raman spectra was performed within the framework of lattice dynamics simulations and group analysis. Individual spectral bands are interpreted in terms of Raman‐active vibrational modes of K3NaFeCl6 structural units. Raman spectrum of synthetic rinneite with main peaks at 75, 91, 103, 143, 167, 171, 187, and 239 cm−1 agrees well with the spectra of rinneite inclusions in halite from the Nepa potash deposit and rinneite daughter minerals in salt melt inclusions hosted by quartz veinlets from the porphyry gold systems in the Central Slovakia Volcanic Field. This provides a firm basis for any future identification of this mineral worldwide, using nondestructive Raman spectroscopy.
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4.

Вид документа : Статья из сборника (выпуск монографической серии)
Шифр издания :
Автор(ы) : Igumenov, A. Yu, Parshin A. S., Kanzychakova V. O., Demin A. M., Andryushchenko T. A., Mikhlin, Yu L., Pehelyakov O. P., Zhigalov V. S.
Заглавие : Factor analysis of inelastic electron scattering cross section spectra of FeSi2
Коллективы : International Scientific Conference Reshetnev Readings
Место публикации : IOP Conf. Ser.: Mater. Sci. Eng. - 2019. - Vol. 467: 21st International Scientific Conference Reshetnev Readings-2017. - Ст.012010. - , DOI 10.1088/1757-899X/467/1/012010
Примечания : Cited References: 21
Предметные рубрики: ENERGY-LOSS SPECTROSCOPY
IRON
Аннотация: Iron disilicide is widely used in creation of such nanotechnology devices as photoelectric converters. The investigation of iron silicide FeSi2 with the method of inelastic electron scattering cross-section spectroscopy was carried out. The decomposition of inelastic electron scattering cross-section spectra of FeSi2 to bulk and surface energy loss components using factor analysis was carried out. The amplitude of energy loss components can be used for identification of their origin.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min V. I., Orlov Yu. S., Zarubin A. E., Ovchinnikova T. M., Ovchinnikov S. G.
Заглавие : Magnetism in spin crossover systems: Short-range order and effects beyond the Heisenberg model
Коллективы : Russian Scientific FoundationRussian Science Foundation (RSF) [18-12-00022]
Место публикации : Phys. Rev. B. - 2019. - Vol. 100, Is. 14. - Ст.144429. - ISSN 2469-9950, DOI 10.1103/PhysRevB.100.144429. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 72. - The authors thank the Russian Scientific Foundation for the financial support under Grant No. 18-12-00022.
Предметные рубрики: LOWER-MANTLE
STATE
TRANSITION
PRESSURE
IRON
SUSCEPTIBILITY
Аннотация: To study non-Heisenberg effects in the vicinity of spin crossover in strongly correlated electron systems we derive an effective low-energy Hamiltonian for the two-band Kanamori model. It contains a Heisenberg high-spin term proportional to exchange constant as well as a low-spin term proportional to spin gap parameter ɛs. Using cluster mean field theory we obtain several non-Heisenberg effects. Near the critical value of spin gap ɛcs there is a magnetic phase transition of first order. In the vicinity of ɛcs in the paramagnetic phase we observe nontrivial behavior of the Curie constant in the paramagnetic susceptibility in the wide range of temperature. Reentrant temperature behavior of nearest-neighbor spin-spin correlations is observed at ɛsɛcs. Finally, the pressure-temperature magnetic phase diagram for ferroperriclase is obtained using the effective Hamiltonian.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pavlovskiy M. S., Zinenko V. I., Shinkorenko A. S.
Заглавие : Effect of a rare-earth ion on the structural instability in RFe3(BO3)4 crystals
Коллективы : Russian Science Foundation [17-72-10122]
Место публикации : JETP Letters. - 2018. - Vol. 108, Is. 2. - P.116-120. - ISSN 0021-3640, DOI 10.1134/S0021364018140114. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 17. - This work was supported by the Russian Science Foundation (project no. 17-72-10122).
Предметные рубрики: Iron
GdFe3(BO3)4
Аннотация: The dynamics of the crystal lattice of RFe3(BO3)4 (R = Pr, Nd, Sm, Gd, Tb, Dy, and Ho) compounds in the high-symmetry R32 phase has been calculated. Significant changes in spectra of compounds with various rare-earth ions have been obtained only near the edge Λ point of the Brillouin zone (qΛ = 1/3(−2b1 + b2 + b3, where b1, b2, and b3 are the reciprocal lattice vectors) for acoustic oscillation branches. A decrease in the frequency of an acoustic mode at the point Λ has been revealed in all studied compounds. This frequency depends on the type of rare-earth ion and decreases from a compound with Pr to a compound with Ho down to imaginary values. Such a behavior of the frequency of the unstable acoustic mode is in good agreement with experimental data on the dependence of the temperature of the R32 → P3121 structural phase transition on the type of rare-earth ion in ferroborates.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Yakushkin S. S., Dubrovskii A. A., Bukhtiyarova G. A., Shaikhutdinov K. A., Martyanov O. N.
Заглавие : Study of the high-coercivity material based on ε-Fe2O3 nanoparticles in the silica gel matrix
Место публикации : Tech. Phys. Lett.: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 42, Is. 4. - P.347-350. - ISSN 10637850 (ISSN), DOI 10.1134/S1063785016040039
Примечания : Cited References: 17. - This study was supported by the Federal Agency for Scientific Organizations of Russia (base budget financing no. V.44.1.15), the Scientific and Educational Center of Energy-Efficient Catalysis at the Novosibirsk State University, and the Russian Foundation for Basic Research (project no. 15-32-50919).
Предметные рубрики: Phase
Field
State
Oxide
Iron
Аннотация: We report the results of investigations of ε-Fe2O3 magnetic nanoparticles obtained by incipient wetness impregnation of silica gel. It was established that the obtained samples with an iron content of 12‒16% mass % containing ε-Fe2O3 nanoparticles with an average size of 10 nm on the silica gel surface exhibit a room-temperature coercivity of about 10 kOe. Along with fabrication simplicity, this fact makes the prepared samples promising for application as a magnetically hard material. © 2016, Pleiades Publishing, Ltd
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Togushova Yu. N., Dolgov O. V.
Заглавие : Uniform impurity scattering in two-band s ± and s ++ superconductors
Коллективы : RFBR [16-02-00098]; Leading Scientific Schools of the Russian Federation [NSh-2886.2014.2]
Место публикации : J. Supercond. Nov. Magn.: Springer, 2016. - Vol. 29, Is. 4. - С. 1089-1095. - ISSN 1557-1939, DOI 10.1007/s10948-016-3385-6. - ISSN 1557-1947(eISSN)
Примечания : Cited References:28. - We are grateful to D.V. Efremov and A. A. Golubov for useful discussions. We acknowledge the partial support by RFBR (Grant 16-02-00098) and President Grant for Government Support of the Leading Scientific Schools of the Russian Federation (NSh-2886.2014.2).
Предметные рубрики: High-temperature superconductivity
Iron
Ключевые слова (''Своб.индексиров.''): multiband superconductivity--impurity scattering--fe-based--superconductors
Аннотация: The s ± and s ++ models for the superconducting state are subject of intense studies regarding Fe-based superconductors. Depending on the parameters, disorder may leave intact or suppress T c in these models. Here, we study the special case of disorder with equal values of intra- and interband impurity potentials in the two-band s ± and s ++ models. We show that this case can be considered as an isolated point and T c there has maximal damping for a wide range of parameters.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. S., Igumenov A. Y., Mikhlin Y. L., Pchelyakov O. P., Zhigalov V. S.
Заглавие : Comparative analysis of characteristic electron energy loss spectra and inelastic scattering cross-section spectra of Fe
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 58, Is. 5. - P.908-914. - ISSN 10637834 (ISSN), DOI 10.1134/S106378341605019X
Примечания : Cited References: 29
Предметные рубрики: Loss-spectroscopy
Quantitative-analysis
Iron
Si
Ge
Аннотация: The inelastic electron scattering cross section spectra of Fe have been calculated based on experimental spectra of characteristic reflection electron energy loss as dependences of the product of the inelastic mean free path by the differential inelastic electron scattering cross section on the electron energy loss. It has been shown that the inelastic electron scattering cross-section spectra have certain advantages over the electron energy loss spectra in the analysis of the interaction of electrons with substance. The peaks of energy loss in the spectra of characteristic electron energy loss and inelastic electron scattering cross sections have been determined from the integral and differential spectra. It has been shown that the energy of the bulk plasmon is practically independent of the energy of primary electrons in the characteristic electron energy loss spectra and monotonically increases with increasing energy of primary electrons in the inelastic electron scattering cross-section spectra. The variation in the maximum energy of the inelastic electron scattering cross-section spectra is caused by the redistribution of intensities over the peaks of losses due to various excitations. The inelastic electron scattering cross-section spectra have been analyzed using the decomposition of the spectra into peaks of the energy loss. This method has been used for the quantitative estimation of the contributions from different energy loss processes to the inelastic electron scattering cross-section spectra of Fe and for the determination of the nature of the energy loss peaks. © 2016, Pleiades Publishing, Ltd.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Togushova, Yu. N., Shestakov V. A., Korshunov M. M.
Заглавие : Impurity-induced smearing of the spin resonance peak in Fe-based superconductors
Коллективы : RFBR [13-02-01395]; President Grant for Government Support of the Leading Scientific Schools of the Russian Federation [NSh-2886.2014.2]; Ministry of education and science of Russia [GF-2, SFU]
Место публикации : J. Low Temp. Phys.: Springer/Plenum Publishers, 2016. - Vol. 185, Is. 5-6. - P.481-487. - ISSN 0022-2291, DOI 10.1007/s10909-016-1577-x. - ISSN 1573-7357(eISSN)
Примечания : Cited References:25. - We acknowledge partial support by the RFBR (Grant 13-02-01395), President Grant for Government Support of the Leading Scientific Schools of the Russian Federation (NSh-2886.2014.2), and The Ministry of education and science of Russia (GF-2, SFU).
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTIVITY
ELECTRONIC-STRUCTURE
IRON
Ключевые слова (''Своб.индексиров.''): fe-based superconductors--spin resonance peak--spin-orbit coupling--impurity scattering
Аннотация: The spin resonance peak in the iron-based superconductors is observed in inelastic neutron scattering experiments and agrees well with predicted results for the extended s-wave (s±) gap symmetry. On the basis of four-band and three-orbital tight-binding models we study the effect of nonmagnetic disorder on the resonance peak. Spin susceptibility is calculated in the random-phase approximation with the renormalization of the quasiparticle self-energy due to the impurity scattering in the static Born approximation. We find that the spin resonance becomes broader with the increase of disorder and its energy shifts to higher frequencies. For the same amount of disorder the spin response in the s± state is still distinct from that of the s++ state.
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