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Вид документа : Однотомное издание
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Korshunov M. M., Shneyder E. I.
Заглавие : Lifshitz quantum phase transitions and Fermi surface transformation with hole doping in high-Tc superconductors
Место публикации : arXiv. - 2009. - Ст.arXiv:0909.2308
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Вид документа : Однотомное издание
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Makarov I. A., Shneyder E. I., Togushova Yu.N., Gavrichkov V. A., Korshunov M. M.
Заглавие : Magnetic mechanisms of pairing in strongly correlated electron system of copper oxides [Electronic resource]
Место публикации : arXiv. - 2015. - Ст.eprint arXiv:1510.08640
Примечания : Cited References: 214. - The authors acknowledge support from FCP Scientific and Research-and-Educational Personnel of Innovative Russia for 2009-2013 (GK 16.740.12.0731 and GK 16.740.11.0740), RFBR (Grants 12-02-31534 and 12-02-31597), Siberian Federal University (Theme #F-11), Governmental support of leading scientific schools of Russia (NSh-1044.2012.2), Program of SB RAS #44, Presidium of RAS program #20.7. EIS, IAM, and MMK are grateful to The Dynasty Foundation and ICFPM forthe financial supportIn book.: Recent advances in superconductivity research", ed. by C.B. Taylor, 321 p., Nova Science Publishers Inc. New York, 2013 ISBN: 978-1-62618-406-0, Chapter 6
Предметные рубрики: Condensed matter-- Strongly correlated electrons
Superconductivity
Ключевые слова (''Своб.индексиров.''): strong electronic correlations--cuprates--hubbard operators--electronic structure--quantum phase transitions--magnetic mechanism of pairing
Аннотация: The multielectron LDA+GTB approach has been developed to calculate electronic structure of strongly correlated cuprates. At low energies the effective Hamiltonian of the t−t′−t"−t⊥−J∗−J⊥-model has been derived with parameters coming from the ab initio calculation for LSCO. The electronic structure of LSCO has been calculated self-consistently with the short-range antiferromagnetic order for various doping level. Two Lifshitz-type quantum phase transitions with Fermi surface topology changes have been found at dopings xc1=0.15 and xc2=0.24. Its effect on normal and superconducting properties has been calculated. The interatomic exchange parameter and its pressure dependence has been calculated within LDA+GTB scheme. The magnetic mechanisms of d-wave pairing induced by static and dynamical spin correlations are discussed. Simultaneous treatment of magnetic and phonon pairing results in the conclusion that both contributions are of the same order. For two layer cuprates like YBCO the interlayer hopping and exchange effects on the electronic structure and doping dependence of Tc is discussed as well as the Coulomb interaction induced mechanism of pairing.
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Вид документа : Однотомное издание
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Molokeev M. S., Laptash N. M.
Заглавие : Ferroelastic and ferroelectric phase transitions in fluoro- and oxyfluorometallates
Место публикации : Photonic and electronic properties of fluoride materials: Elsevier, 2016. - Chapter 16. - P.355-381. - (Progress in fluorine science series). - , DOI 10.1016/B978-0-12-801639-8.00016-7
Примечания : Cited References: 92. - The reported study was partially supported by RFBR, research project No. 15-02-02009 a
Предметные рубрики: ELASTIC NEUTRON-DIFFRACTION
ORIENTATIONAL DISORDER
CRYSTAL-STRUCTURES
THERMODYNAMIC PROPERTIES
NONCRITICAL PARAMETERS
CUBIC PEROVSKITES
RAMAN-SCATTERING
SINGLE-CRYSTALS
A2BX4 STRUCTURE
HIGH-RESOLUTION
Аннотация: Different degree of structural disorder is one of the main features of many fluoro- and oxyfluorometallates crystallizing in high symmetry structures. The comprehensive study of these compounds (perovskites, elpasolites, pyrochlores, etc.) enabled to determine a great effect of the size and shape as well as crystallographic sites of cationic and anionic species on the mechanism of structural ordering. Ferroelastic and ferroelectric phase transitions of different order, type, and succession can be realized as a result of chemical and hydrostatic pressure change. It was found that the substitution of monoatomic cations for tetrahedral ammonium group was accompanied by rather significant change of electron density distribution, entropy, and phase diagrams. Some compounds studied were considered to be promising solid-state refrigerants owing to the pronounced barocaloric effect resulting from large entropy and baric coefficient of phase transitions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : The modification of low-temperature magnetic properties of the Fe-based double-zigzag single-chain magnet under irradiation
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2017. - Vol. 440. - P.19-22. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.100
Примечания : Cited References: 14. - This study was supported by the Presidium of the Russian Academy of Sciences, program Actual problems of low temperature physics (project 0358-2015-0005); the Russian Foundation for Basic Research, projects nos. 16-42-243057 (partly with Government of Krasnoyarsk Territory) and 15-42-04372; Technology Support Fund to the research project nos. 14/16. The work of M.S.S. was supported by grant of the President of the Russian Federation (project MK-1398.2017.2).
Предметные рубрики: SPIN-CROSSOVER
MODEL
Ключевые слова (''Своб.индексиров.''): single-chain magnets--light-induced spin crossover--magnetic susceptibility--quantum phase transitions
Аннотация: An exact solution for a generalized Ising model describing single-chain magnet {[FeIII(Tp*)(CN)3]2FeII(bpmh)}·2H2O with alternating high-spin and low-spin iron ions and double-zigzag magnetic topology has been calculated making use of the transfer-matrix technique. The introduction of a statistical ensemble taking into account the presence of iron ions with high-spin (HS) and low-spin (LS) states made it possible to describe the modification of magnetic susceptibility under optical irradiation. It has been shown that joint implementation of iron ions with photoinduced magnetic states and non-magnetic intersite repulsion ions of these states is caused by the difference of the ionic radii of HSFeIIHSFeII and LSFeIILSFeII leads to the quantum phase transitions in the system.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moshkina E. M., Krylov A. S., Sofronova S. N., Gudim, I. A., Temerov V. L.
Заглавие : Crystal growth and Raman spectroscopy study of Sm1-xLaxFe3(BO3)4 ferroborates
Место публикации : Cryst. Growth Des.: American Chemical Society, 2016. - Vol. 16, Is. 12. - P.6915-6921. - ISSN 15287483 (ISSN), DOI 10.1021/acs.cgd.6b01079
Примечания : Cited References: 17. - This work was supported by the Russian Foundation for Basic Research, Project No. 14-02-00307.
Ключевые слова (''Своб.индексиров.''): crystal lattices--iron compounds--raman spectroscopy--single crystals--crystal nucleation--flux methods--internal structure--magnetic phase transitions--magnon scattering--spectral region--temperature range--wave numbers--lanthanum
Аннотация: Sm1-xLaxFe3(BO3)4 (x = 0, 0.75) single crystals were synthesized using the flux method. The crystal nucleation procedure and flux parameters are reported. Conditions for growing the Sm1-xLaxFe3(BO3)4 (x = 0, 0.75) single crystals are described. The prepared crystals were studied by Raman spectroscopy in the temperature range of T = 10-300 K. The spectral region corresponding to temperatures of T = 10-55 K, which involves the temperatures of the magnetic phase transition TN = 32 K for x = 0 and TN = 31 K for x = 0.75, was thoroughly analyzed. Anomalies related to the magnetic ordering established in both compounds were found. The main changes occur in the low-wavenumber region (up to 100 cm-1), where the mode corresponding to magnon scattering arises. This mode is shown to have the internal structure indicative of the occurrence of unstable vibrations (40-80 cm-1). The results obtained are analyzed by calculating the empirical lattice dynamics in Sm1-xLaxFe3(BO3)4 with x = 0 and x = 1. © 2016 American Chemical Society.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : Effect of intersite repulsion on the correlation functions and thermodynamics of an Ising chain with annealed magnetic disorder
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 11. - P.1335-1337. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816110290
Примечания : Cited References: 6. - This work was supported by the Russian Foundation for Basic Research, project nos. 13-02-00073, 14-02-31237, and 15-42-04372.
Ключевые слова (''Своб.индексиров.''): chains--magnetic susceptibility--temperature distribution--thermodynamics--transfer matrix method--correlation function--equilibrium behavior--equilibrium distributions--non-magnetic impurities--quantum phase transitions--repulsion parameter--temperature dependence--transfer matrix technique--phase transitions
Аннотация: An exact solution for a model describing the equilibrium behavior of an ensemble of Ising chains with nonmagnetic intersite repulsion of nearest neighbors and an equilibrium distribution of nonmagnetic impurities is obtained using the transfer matrix technique. The possibility of exciting quantum phase transitions using the intersite repulsion parameter in a system is demonstrated. Proximity to the critical points of these transitions has a substantial effect on the temperature dependence of a system’s magnetic susceptibility. © 2016, Allerton Press, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gerasimova Y. V., Oreshonkov A. S., Laptash N. M., Vtyurin A. N., Krylov A. S., Shestakov N. P., Ershov A. A., Kocharova A. G.
Заглавие : Nature of phase transitions in ammonium oxofluorovanadates, a vibrational spectroscopy study of (NH4)3VO2F4 and (NH4)3VOF5
Место публикации : Spectrochim. Acta A: Elsevier, 2017. - Vol. 176. - P.106-113. - ISSN 13861425 (ISSN), DOI 10.1016/j.saa.2017.01.004
Примечания : Cited References: 48. - This study was partially supported by the Ministry of Education and Science of the Russian Federation and Krasnoyarsk Regional Foundation for Scientific Support and Scientific-Technical Activity. The reported study was partially funded by RFBR according to the research project No. 16-32-00351 mol_a. We thank A.M. Ziatdinov for recording EPR spectra and V.G. Kuryavyi for EDX analysis of (NH4)3VOF5.
Ключевые слова (''Своб.индексиров.''): ammonium oxofluorovanadates--order-disorder--dynamics--phase transitions--infrared--raman
Аннотация: Two ammonium oxofluorovanadates, (NH4)3VO2F4 and (NH4)3VOF5, have been investigated by temperature-dependent infrared and Raman spectroscopy methods to determine the nature of phase transitions (PT) in these compounds. Dynamics of quasioctahedral groups was simulated within the framework of semi-empirical approach, which justified the cis-conformation of VO2F43 − (C2v) and the C4v geometry of VOF53 −. The observed infrared and Raman spectra of both compounds at room temperature (RT) revealed the presence at least of two crystallographically independent octahedral groups. The first order PT at elevated temperatures is connected with a complete dynamic disordering of these groups with only single octahedral state. At lower temperatures, the octahedra are ordered and several octahedral states appear. This PT is the most pronounced in the case of (NH4)3VOF5, when at least seven independent VOF53 − octahedra are present in the structure below 50 K, in accordance with the Raman spectra. Ammonium groups do not take part in PTs at higher and room temperatures but their reorientational motion freezes at lower temperatures.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V., Sokolov V. V., Gudim I. A.
Заглавие : Optical and magneto-optical spectra and electron structure of ErAl3(BO3)4 single crystal
Место публикации : J. Alloys Compd.: Elsevier, 2017. - Vol. 698. - P.364-374. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2016.12.200
Примечания : Cited References: 32. - The work was supported by the Russian Foundation for Basic Researches grant 16-02-00273 and by the President of Russia grant No Nsh-7559.2016.2.
Ключевые слова (''Своб.индексиров.''): electron structure--er3+ ion--f-f transitions--magnetic circular dichroism
Аннотация: Linearly polarized absorption spectra and magnetic circular dichroism (MCD) spectra of ErAl3(BO3)4 single crystal were measured in the range of 10000–27000 cm−1 at 90 K. The Stark components of the ground and excited multiplets of Er3+ ion were identified in terms of the irreducible representations, basing on the linearly polarized absorption spectra. MCD spectra permitted us to measure the Zeeman splitting of some transitions and so to determine changes of the Landé factors along the C3 axis during these transitions. Additionally, the MCD spectra permitted us to identify some states in the |J,±MJ〉function approximation. In particular, it was shown that the ground state of the Er3+ ion in this approximation has MJ = ± 13/2 that corresponds to magnetic moment m = ±7.8 μB. Very intensive f-f vibronic transitions, corresponding to electron transitions from the upper components of the ground multiplet, were revealed. Energies of the local vibrations in a number of the excited states were found.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Klimin S. A., Kashchenko M. A., Bezmaternykh L. N.
Заглавие : Spin-phonon and electron-phonon interactions in multiferroic GdFe3(BO3)4 and TbFe3(BO3)4 evidenced by IR reflection spectroscopy
Коллективы : Russian Science Foundation [14-12-01033]; Swiss National Science Foundation (SNSF); Science and Technology cooperation program "Switzerland-Russia" of the University of Geneva
Место публикации : J. Low Temp. Phys.: Springer/Plenum Publishers, 2016. - Vol. 185, Is. 5-6. - P.538-543. - ISSN 0022-2291, DOI 10.1007/s10909-016-1597-6. - ISSN 1573-7357(eISSN)
Примечания : Cited References:19. - The authors thank Alexey Kuzmenko and Marina Popova for fruitful discussions. This paper was supported by the Russian Science Foundation under Grant No. 14-12-01033, by the Swiss National Science Foundation (SNSF), and by the Science and Technology cooperation program "Switzerland-Russia" of the University of Geneva.
Предметные рубрики: PHASE-TRANSITIONS
GdFe3(BO3)4
CRYSTALS
SPECTRUM
Ключевые слова (''Своб.индексиров.''): multiferroics--ir-active phonons--spin-phonon interaction--coupled--electron-phonon mode
Аннотация: We study temperature-dependent polarized reflection spectra of multiferroic GdFe3(BO3)4 and TbFe3(BO3)4 single crystals. Signatures of spin–lattice interactions in both compounds and of a formation of the electron–phonon coupled mode in TbFe3(BO3)4 are discussed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuzmenko A. M., Mukhin A. A., Ivanov, V. Yu., Komandin G. A., Shuvaev A., Pimenov A., Dziom V., Bezmaternykh L. N., Gudim I. A.
Заглавие : Terahertz spectroscopy of crystal-field transitions in magnetoelectric TmAl3(BO3)4
Коллективы : Russian Foundation for Basic Research [14-02-91000, 15-02-07647, 14-02-00307, 13-02-12442, 15-42-04186]; Sci. school [924.2014.2]; Austrian Science Funds [I815-N16, W-1243, P27098-N27]
Место публикации : Phys. Rev. B: American Physical Society, 2016. - Vol. 94, Is. 17. - Ст.174419. - ISSN 2469-9950, DOI 10.1103/PhysRevB.94.174419. - ISSN 2469-9969(eISSN)
Примечания : Cited References:35. - This work was partially supported by the Russian Foundation for Basic Research (Grants No. 14-02-91000, No. 15-02-07647, No. 14-02-00307, No. 13-02-12442, and No. 15-42-04186), Sci. school-924.2014.2, and by the Austrian Science Funds (Grants No. I815-N16, No. W-1243, and No. P27098-N27).
Предметные рубрики: ELECTRIC POLARIZATION
PHASE-TRANSITIONS
SINGLE-CRYSTALS
Аннотация: Dynamic magnetic properties of magnetoelectric TmAl3(BO3)4 borate have been investigated by terahertz spectroscopy. Crystal-field transitions within the ground multiplet H36 of Tm3+ ions are observed and they are identified as magnetic-dipole transitions from the ground singlet A1 to the next excited doublet E of Tm3+ ions. Unexpected fine structure of the transitions is detected at low temperatures. The new modes are assigned to local distortions of the sites with D3 symmetry by Bi3+ impurities, which resulted in the splitting of the A1→E transition. Two types of locally distorted sites are identified and investigated. The main contribution to the static magnetic susceptibility is shown to be determined by the matrix elements of the observed magnetic transitions. We demonstrate that even in case of local distortions the symmetry of the undistorted crystal is recovered for magnetic and for quadratic magnetoelectric susceptibilities.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Molokeev M. S., Misyul S. V., Krylova S. N., Oreshonkov A. S., Ivanenko A. A., Zykova V. A., Ivanov Y. N., Sukhovsky A. A., Voronov V. N., Safonov I. N., Vtyurin A. N.
Заглавие : Crystal structure and phase transitions of a layered perovskite-like CsScF4 crystal
Коллективы : Russian Foundation for Basic Research [16-02-00102]
Место публикации : CrystEngComm: Royal Society of Chemistry, 2016. - Vol. 18, Is. 43. - P.8472-8486. - ISSN 1466-8033, DOI 10.1039/c6ce01144f
Примечания : Cited References:47. - The authors are grateful to Prof. I. N. Flerov for valuable support and useful discussions. This work was partly supported by the Russian Foundation for Basic Research, Project 16-02-00102. The research is partially conducted within the framework of the state task of the Ministry of Education and Science of the Russian Federation for Siberian Federal University on R&D performance in 2014 (Task 3.2534.2014/K). X-ray data from powders, Raman NMR, and IR spectra were obtained with use the analytical equipment of Krasnoyarsk Center of collective use SB RAS.
Предметные рубрики: NEGATIVE THERMAL-EXPANSION
RAMAN-SCATTERING
LATTICE-DYNAMICS
Аннотация: This work is devoted to the complex research on temperature phase transitions in a CsScF4 crystal. The crystal structure was solved and refined at different temperatures by using the Rietveld method. Structural phase transitions were investigated by using the following spectroscopic methods, some of them for the first time: Brillouin spectroscopy, Raman spectroscopy, IR absorption spectroscopy and NMR. The symmetry analysis of the Brillouin zone center of all phases is presented. The vibrational spectra of the crystal in three phases have been calculated. The structural phase transition mechanism was determined. The transitions at T-1 = 475 K and T-2 = 317.5 K are of displacement type. The Raman soft modes have been associated with rotations of the ScF6 octahedral group.
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Aleksandrov K. S., Aleksandrova I. P., Anistratov A. T., Shabanov, V. F.
Заглавие : Investigation of phase transitions and physical properties of LiNH4SO4
Место публикации : The first Soviet-Japanese symposium on ferroelectricity: abstracts/ предс. орг. ком.: K. S. Aleksandrov, J. Kobayashi ; зам. предс. орг. ком.: A. T. Shuvalov, G. A. Smolensky, T. Nakamura ; секр. орг. ком. A. T. Anistratov ; чл. орг. ком. Y. E. Nesterikhin [и др.]. - Krasnoyarsk, 1976. - С. 85-87 (Шифр В37/T44-647313102)
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bondarev V. S., Mikhaleva E. A., Gorev M. V., Flerov I. N.
Заглавие : Intensive electrocaloric effect in triglycine sulfate under nonequilibrium thermal conditions and periodic electric field
Коллективы : RFBR; Government of Krasnoyarsk Territory [16-42-240428 p_a]
Место публикации : Phys. Status Solidi B. - 2016. - Vol. 253, Is. 10. - P.2073-2078. - ISSN 0370-1972, DOI 10.1002/pssb.201600339. - ISSN 1521-3951(eISSN)
Примечания : Cited References:29. - The reported study was funded by RFBR and Government of Krasnoyarsk Territory according to the research project no. 16-42-240428 p_a.
Ключевые слова (''Своб.индексиров.''): electrocaloric effect--ferroelectrics--nonequilibrium processes--phase--transitions
Аннотация: We present the results of both direct measurements and modeling of the intensive electrocaloric effect ΔTAD in ferroelectric triglycine sulfate under nonequilibrium thermal conditions and periodically varying electric field. In the narrow region around the phase transition temperature TC, a visible difference was observed between the electrocaloric responses at applying ΔTON and removal ΔTOFF of the constant electric field: |ΔTON| |ΔTOFF| and |ΔTON| |ΔTOFF| at T TC and T TC, respectively. The variation of the frequency and profile of the periodic electric field at T TC allowed one to obtain the gradual decrease in the average temperature of the top of the sample compared to the bottom kept at the constant temperature. At low frequency electric field, qualitative agreement was found between the time dependences of the measured experimentally and calculated ΔT values. Experimental and modeling studies of electrocaloric effect ΔTAD in triglycine sulfate showed that the applying/removal of a periodic electric field to/from the bulk sample decreases the average value of the waiving temperature of the top Ttop compared to T ≃ const of the bottom. Both frequency and duty cycle of the electric field impulses strongly affect Ttop.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popova M. N., Chukalina E. P., Boldyrev K. N., Stanislavchuk T. N., Malkin B. Z., Gudim I. A.
Заглавие : Spectroscopy of f-f transitions, crystal-field calculations, and magnetic and quadrupole helix chirality in DyFe3(BO3)4 [Electronic resource]
Место публикации : ArXiv. - 2016. - Ст.1611.07092
Вид и объем ресурса: Electronic text data
Примечания : Cited References: 47. - This work was supported by the Russian Science Foundation (Grant No14-12-01033). I. A. G. thanks L. N. Bezmaternykh for useful comments concerning the crystal growth and the Russian Foundation for Basic Research for a financial support under Grant No 14-02-00307a.
Аннотация: Recently, quadrupole helix chirality and its domain structure was observed in resonant x-ray diffraction experiments on DyFe3(BO3)4 using circularly polarized x rays [T. Usui et al., Nature Materials 13, 611 (2014)]. We show that this effect can be explained quantitatively by calculating the quadrupole moments of the Dy3+ ions induced by the low-symmetry (C2) crystal-field (CF) component. In this work, the CF parameters for the Dy3+ ions in the P3121 (P3221) phase of DyFe3(BO3)4 are obtained from CF calculations based on the analysis of high-resolution temperature-dependent optical spectroscopy data. We also consider the helix chirality of the single-site magnetic susceptibility tensors of the Dy3+ ions in the paramagnetic P3121 (P3221) phase and suggest a neutron diffraction experiment to reveal it.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V.
Заглавие : Origin of the giant circular dichroism of vibronic f-f transitions
Коллективы : Russian Foundation for Basic Researches [16-02-00273]; [Nsh-7559.2016.2]
Место публикации : Mol. Phys.: Taylor & Francis, 2017. - Vol. 115, Is. 14. - P.1687-1690. - ISSN 0026-8976, DOI 10.1080/00268976.2017.1317113. - ISSN 1362-3028(eISSN)
Примечания : Cited References:24. - Russian Foundation for Basic Researches [grant number 16-02-00273]; the President of Russia [grant number Nsh-7559.2016.2].
Предметные рубрики: D-3 LANTHANIDE(III) COMPLEXES
RARE-EARTH IONS
OPTICAL-ACTIVITY
LINE STRENGTHS
Ключевые слова (''Своб.индексиров.''): natural circular dichroism--f-f transitions
Аннотация: Taking into account the space inhomogeneity of the light electromagnetic wave, a new quantum mechanical expression for the natural optical activity (NOA) of electron transitions has been obtained, which is consistent with the phenomenological theory. It is shown that properties of the NOA of parity forbidden f–f transitions substantially differ from those of allowed transitions. The experimentally observed large NOA of the f–f transitions and extremely large (close to unity) NOA of vibrational repetitions of the f–f transitions are qualitatively explained on the basis of the obtained theoretical expression.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogorel'tsev E. I., Mel'nikova S. V., Kartashev A. V., Gorev M. V., Flerov I. N., Laptash N. M.
Заглавие : Thermal, optical, and dielectric properties of Fluoride Rb2TaF7
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-243001]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2017. - Vol. 59, Is. 5. - P.986-991. - ISSN 1063-7834, DOI 10.1134/S1063783417050250. - ISSN 1090-6460(eISSN)
Примечания : Cited References:21. - The reported study was funded by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project no. 16-42-243001.
Предметные рубрики: PHASE-TRANSITIONS
X-RAY
DISORDER
NMR
DIFFRACTION
OXYFLUORIDE
Аннотация: The thermal, optical, and dielectric properties of fluoride Rb2TaF7 were investigated. It was observed that the variation in chemical pressure in fluorides A2+TaF7 caused by the cation substitution of rubidium for ammonium does not affect the ferroelastic nature of structural distortions, but leads to stabilization of the high- and low-temperature phases and enhancement of birefringence. The entropy of the phase transition P4/nmm ↔ Cmma is typical of the shift transformations, which is consistent with a model of the initial and distorted phase structures. The anisotropy of chemical pressure causes the change of signs of the anomalous strain and baric coefficient dT/dp of Rb2TaF7 as compared with the values for its ammonium analog.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Goryainov S. V., Krylov A. S., Polyansky O. P., Vtyurin A. N., Zmeeva N. Y.
Заглавие : In situ Raman spectroscopic study of interaction between phengite and water under P–T conditions typical of subduction zones
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2017. - Vol. 81, Is. 5. - P.590-593. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873817050100
Примечания : Cited References: 14
Ключевые слова (''Своб.индексиров.''): high pressure engineering--spectroscopic analysis--cold subduction--diamond-anvil cell--high temperature and pressure--high-pressure and temperatures--in-situ raman spectroscopy--polymorphic transitions--resistively heated--subduction zones--raman spectroscopy
Аннотация: In situ Raman spectroscopy is used to study the layered mineral phengite K(Al, Mg)2(Si, Al)4O10(OH)2 in water under the high temperature and pressure conditions typical of cold subduction zones (T up to 373°C and P = 12.5 GPa). High pressure and temperature were created in a resistively heated diamond anvil cell. Raman spectra show the high P–T stability of phengite. No reversible polymorphic transitions (overhydration or notable amorphization) are observed. © 2017, Allerton Press, Inc.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Изменение поляризуемости молекул при фазовых переходах изотропная жидкость – нематик – смектик A – кристалл B в жидком кристалле 4O.8
Место публикации : Жидк. кристаллы и их практич. использ. - 2017. - Т. 17, Вып. 2. - С. 6-13. - ISSN 19913966 (ISSN), DOI 10.18083/LCAppl.2017.2.6; \b Liquid Crystals and their Application
Примечания : Библиогр.: 24. - Данная работа выполнена в рамках проекта 0356-2015-0411 Комплексной программы Сибирского отделения РАН № II.2П.
Ключевые слова (''Своб.индексиров.''): поляризуемость мезогенных молекул--фазовые переходы в жидких кристаллах--конформация молекул--межмолекулярные взаимодействия--polarizability of mesogenic molecules--phase transitions in liquid crystals--molecular conformation--intermolecular interactions
Аннотация: Определены температурные зависимости параметров молекулярной поляризуемости (продольной и поперечной компонент, среднего значения и анизотропии) в нематической, смектической А и кристаллической В фазах жидкого кристалла 4-бутилоксибензилиден-4'-октиланилина. Для нематической фазы установлены предсказанные ранее нелинейные зависимости параметров поляризуемости от параметра ориентационного порядка молекул. Обнаружено влияние конденсации одномерной волны плотности при переходе нематик – смектик А и квазидвумерной кристаллизации слабо связанных слоев при переходе смектик А – кристалл В на изменение параметров поляризуемости. Установлена связь изменений поляризуемости в каждой фазе с изменением конформации ароматических остовов молекул и межмолекулярными взаимодействиями.The temperature dependences of molecular polarizability parameters (longitudinal and transverse components, mean value and anisotropy) were determined in nematic, smectic A and crystalline B phases of 4-butyloxybenzylidene-4'-octylaniline (4O.8) liquid crystal. For the nematic phase, the earlier predicted nonlinear dependences of polarizability parameters on the orientational order parameter were revealed. The influence of the one-dimensional density-wave condensation at the nematic - smectic A phase transition and the quasi-twodimensional crystallization of weekly-connected smectic layers at the smectic A - crystal B phase transition on polarizability parameters was discovered. It was established that the changes of polarizability parameters within each phase of the studied liquid crystal are connected either with the change in the conformation of the aromatic molecular cores or with intermolecular interactions.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V., Sokolov V. V., Gudim I. A.
Заглавие : Natural optical activity of f-f transitions in ErAl3(BO3)4 single crystal
Место публикации : Chem. Phys.: Elsevier, 2017. - Vol. 493. - P.102-110. - ISSN 03010104 (ISSN), DOI 10.1016/j.chemphys.2017.06.011
Примечания : Cited References: 50. - The work was supported by the Russian Foundation for Basic Researches grant 16-02-00273 and by the President of Russia grant No Nsh-7559.2016.2.
Ключевые слова (''Своб.индексиров.''): f-f transitions--natural circular dichroism--er3+ ion
Аннотация: Absorption and natural circular dichroism (NCD) spectra of ErAl3(BO3)4 single crystal were measured at 90 K in the range of 10,000–28,200 cm−1. The spectra were decomposed on the Lorentz shape components and the natural optical activities (NOA) of f-f transitions between Stark components of the ground and excited multiplets were found. The NCD spectra permitted us to find out existence of two non equivalent positions of Er3+ ion in one of its excited states, which are due to the local decrease of the crystal symmetry in this state. Very large NOA of a vibronic line was revealed. This phenomenon was accounted for basing on the new quantum mechanical formula for the NOA of electron transitions. The principle difference of the NOA properties of electric dipole allowed and parity forbidden transitions is discussed.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Molokeev M. S., Laptash N. M., Pogoreltsev E. I., Misyul S. V., Flerov I. N.
Заглавие : Sequence of phase transitions in (NH4)3SiF7
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2017. - Vol. 46, Is. 8. - P.2609-2617. - ISSN 14779226 (ISSN), DOI 10.1039/c6dt04874a
Примечания : Cited References: 26. - The reported study was partially supported by RFBR, research project no. 15-02-02009a.
Ключевые слова (''Своб.индексиров.''): group theory--single crystals--x ray diffraction--atomic displacement--double salts--driving forces--group-theoretical analysis--order parameter--polarization optics--temperature changes--hydrogen bonds
Аннотация: Single crystals of silicon double salt (NH4)3SiF7 = (NH4)2SiF6·NH4F = (NH4)3[SiF6]F were grown and studied by the methods of polarization optics, X-ray diffraction and calorimetry. A sequence of symmetry transformations with the temperature change was established: P4/mbm (Z = 2) (G1) ↔ Pbam (Z = 4) (G2) ↔ P21/c (Z = 4) (G3) ↔ P1 (Z = 4) (G4) ↔ P21/c (Z = 8) (G5). Crystal structures of different phases were determined. The experimental data were also interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account critical and noncritical atomic displacements. Strengthening of the N–H⋯F hydrogen bonds can be a driving force of the observed phase transitions.
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