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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aver'yanov E. M., Rumyantsev V. G.
Заглавие : Manifestations of the higher moments of the orientation distribution function of molecules in the spectral properties of an impurity nematic
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 98, Is. 6. - P1146-1151. - ISSN 1063-7761, DOI 10.1134/1.1777627
Примечания : Cited References: 15
Предметные рубрики: LIQUID-CRYSTAL
SCATTERING
PHASES
MATRIX
ORDER
DYES
Ключевые слова (''Своб.индексиров.''): absorption--band structure--impurities--molecular dynamics--polarization--spectrum analysis--distribution function--local field parameters--splitting--temperature dependence--nematic liquid crystals
Аннотация: The polarized electronic absorption spectra, orientation ordering, and the special local field features were studied for push-pull linear dye molecules with strong donor-acceptor electronic conjugation of terminal fragments in the matrix of a nematic liquid crystal. The temperature-induced inversion of the sign of the splitting of polarized impurity absorption bands was observed. This effect was shown to be caused by the statistical character of orientation ordering of impurity molecules and manifestation of the higher moments of the orientation distribution function. The dependence of local field parameters (Lorentz tensor components) of impurity molecules on their orientation ordering was established. This dependence was used to reproduce the temperature dependence of the orientation order parameter of the matrix. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aver'yanov E. M., Gunyakov V. A., Korets A. Y., Akopova O. B.
Заглавие : Experimental solution of the local-field problem in discotic liquid crystals
Место публикации : JETP Letters. - 1999. - Vol. 70, Is. 1. - P.29-35. - ISSN 0021-3640, DOI 10.1134/1.568125
Примечания : Cited References: 14
Предметные рубрики: ORDER
Аннотация: Polarized light-absorption spectra are obtained for single-domain planar-oriented samples of the discotic D-ho. Previously predicted spectral effects induced by resonant dipole-dipole interactions of the molecules are observed. New methods for determining the parameters of the local field in the D-ho phase are developed which take into account the mixing of the molecular excitations. It is shown that the two-dimensional crystalline ordering of the molecular columns decreases the anisotropy of the local field for this phase. (C) 1999 American Institute of Physics. [S0021-3640(99)00613-1].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Quantum Monte Carlo investigation of the 2D Heisenberg model with S=1/2
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 1999. - Vol. 41, Is. 1. - P103-107. - ISSN 1063-7834, DOI 10.1134/1.1130737
Примечания : Cited References: 33
Предметные рубрики: SQUARE-LATTICE
GROUND-STATE
SPIN-CORRELATIONS
ANTIFERROMAGNET
LA2CUO4
EU2CUO4
ENERGY
ORDER
Аннотация: The two-dimensional (2D) Heisenberg model with anisotropic exchange (Delta=1-J(x)/J(z)) and S=1/2 is investigated by the quantum Monte Carlo method. The energy, susceptibility, specific heat, spin-spin correlation functions, and correlation radius are calculated. The sublattice magnetization (sigma) and the Neel temperature of the anisotropic antiferromagnet are logarithmic functions of the exchange anisotropy: 1/sigma + 1 + 0.13(1) ln(1/Delta). Crossover of the static magnetic structural factor as a function of temperature from power-law to exponential occurs for T(c)/J approximate to 0.4. The correlation radius can be approximated by 1/xi =2.05T(1.0(6))/exp(1.0(4)/ T). For La(2)CuO(4) the sublattice magnetization is calculated as sigma=0.45, the exchange is J=(1125=1305) K; for Er(2)CuO(4)J similar to 625 K and the exchange anisotropy Delta similar to 0.003. The temperature dependence of the static structural magnetic factor and the correlation radius above the Neel temperature in these compounds can be explained by the formation of topological excitations (spinons). (C) 1999 American Institute of Physics. [S1063-7834(99)02401-6].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aver'yanov E. M.
Заглавие : Nonlinear coupling between the mean polarizability (gamma)over-bar of molecules and the local-field anisotropy in a liquid crystal and change of the "(gamma)over-bar = const" paradigm
Разночтения заглавия :авие SCOPUS: Nonlinear coupling between the mean polarizability gamma ̄ of molecules and the local-field anisotropy in a liquid crystal and change of the "gammā = const" paradigm; авие SCOPUS: Nonlinear coupling between the mean polarizability gamma ? of molecules and the local-field anisotropy in a liquid crystal and change of the "gamma = const" paradigm
Место публикации : JETP Letters. - 2008. - Vol. 87, Is. 5. - P.258-261. - ISSN 0021-3640, DOI 10.1134/S002136400805007X; \b JETP Letters. - 2008. - Vol. 87, Is. 5. - P.258-261. - Вариант Sopus
Примечания : Cited References: 14
Предметные рубрики: REFRACTIVE-INDEXES
ORDER
Аннотация: The nonlinear relation between the mean effective polarizability (gamma) over bar of molecules and the local-field anisotropy in uniaxial liquid crystals is demonstrated. Stringent constraints on (gamma) over bar from below, indicative of the dependence of on the liquid-crystal state and the change of the "(gamma) over bar = const" paradigm, are established. The theoretical results are confirmed by experiments with nematic liquid crystals having high and low birefringences.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Kazak N. V., Michel C. R., Balaev A. D., Ovchinnikov S. G., Vasil'ev A. D., Bulina N. V., Panchenko E. B.
Заглавие : Effect of strontium and barium doping on the magnetic state and electrical conductivity of GdCoO3
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 8. - P1498-1506. - ISSN 1063-7834, DOI 10.1134/S1063783407080161
Примечания : Cited References: 36
Предметные рубрики: PEROVSKITE
ORDER
OXIDE
BEHAVIOR
GLASSES
LACOO3
PR
GD
SM
ND
Аннотация: A coordinated investigation of the magnetic and electrical properties of polycrystalline cobalt oxide compounds CdCoO3, Gd0.9Ba0.1CoO3, and Gd0.9Sr0.1CoO3 is carried out. Undoped GdCoO3 reveals a low conductivity; a magnetic moment of 7.4 mu(B) per molecule, which is less than the theoretical value for the Gd3+ ion; and an asymptotic Curie temperature of -6 K. Doping GdCoO3 with barium and strontium to substitution of 10 at. % Gd brings about an increase in the conductivity and magnetic transitions at T = 300 K for Gd0.9Ba0.1CoO3 and T = 170 K for Gd0.9Sr0.1CoO3. The magnetization anomalies imply the formation of magnetic clusters. The behavior of the electrical conductivity at high temperatures suggests a variable activation energy. At low temperatures, Mott hopping conduction sets in.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Manske D., Eremin I.
Заглавие : Effective parameters of the band dispersion in n-type high-T-c superconductors
Разночтения заглавия :авие SCOPUS: Effective parameters of the band dispersion in n-type high-Tc superconductors
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2004. - Vol. 402, Is. 4. - P365-370. - ISSN 0921-4534, DOI 10.1016/j.physc.2003.10.017
Примечания : Cited References: 32
Предметные рубрики: DOPED CUPRATE SUPERCONDUCTORS
TIGHT-BINDING METHOD
QUASI-PARTICLES
COPPER OXIDES
LA2-XSRXCUO4
SYMMETRY
MODEL
EVOLUTION
ORDER
Ключевые слова (''Своб.индексиров.''): high-t-c superconductivity--electronic correlations--electron-doped cuprates--electron-doped cuprates--electronic correlations--high-tc superconductivity--approximation theory--atomic physics--band structure--binding energy--charge transfer--correlation methods--doping (additives)--electronic structure--hamiltonians--mathematical models--mathematical operators--oxide superconductors--perturbation techniques--photoelectron spectroscopy--atomic orbitals--conduction band--electron doped cuprates--electron spins--valence band--high temperature superconductors
Аннотация: The electronic structure of electron-doped cuprates is discussed in the regions of small and optimal doping. For optimal doping we obtain the parameters from a simple tight-binding analysis by fitting ARPES data, and for small doping we study the band structure by the generalized tight-binding method that takes strong electronic correlations into account explicitly. This method has also reproduced well the ARPES data for small doping. The effective low-energy Hamiltonian is the t-t'-J model with hopping parameters t and t'. We compare both methods and find very good agreement for the value of t while t' is different because it is caused by the different contribution of the short-range spin correlations. (C) 2003 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : A study of anisotropic Heisenberg antiferromagnet with S=1/2 on a square lattice by Monte-Carlo method
Место публикации : Phys. Status Solidi B. - 1998. - Vol. 207, Is. 2. - P.491-498. - ISSN 0370-1972, DOI 10.1002/(SICI)1521-3951(199806)207:2491::AID-PSSB4913.0.CO;2-G
Примечания : Cited References: 24
Предметные рубрики: EU2CUO4
LA2CUO4
ORDER
MODEL
STATE
Аннотация: The two-dimensional (2D) Heisenberg model (J 0) with anisotropic exchange Delta = 1-J(X)/J(Z) greater than or equal to 0 and with S = 1/2 is studied by the quantum Monte-Carlo method. Energy, susceptibility, specific heat, spin-spin correlation functions, and correlation radius are calculated. The dependence of the Neel temperature T(N)/J = 2/ln(11/Delta) on the exchange anisotropy is determined. The static magnetic factor is very slowly decreased for T/J 0.4. It is assumed to realize topological excitations in the range of these temperatures. The correlation radius of the isotropic Heisenberg model is fitted by the dependence 1/xi = 2.05T(1.0(6))/exp (1.0(4)/T).The temperature behavior of the static structural magnetic factor in La(2)CuO(4) and Er(2)CuO(4) for T T(N) is in agreement with the MC calculations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Молекулярно-оптическая и структурная анизотропия нематической смеси Е7
Место публикации : Жидк. крист. и их практич. использ. - 2019. - Т. 19, № 1. - С. 42-51. - ISSN 1991-3966, DOI 10.18083/LCAppl.2019.1.42; Liq. Cryst. Appl. - ISSN 2499–9644
Примечания : Библиогр.: 20
Предметные рубрики: LIQUID
ORDER
POLARIZABILITY
Ключевые слова (''Своб.индексиров.''): нематические смеси--ориентационный порядок нематических смесей--анизотропия локального поля в нематических смесях--свойства молекул в нематических смесях--нематические смеси, ориентационный порядок нематических смесей, анизотропия локального поля в нематических смесях, свойства молекул в нематических смесях--nematic mixtures--orientational order of nematic mixtures--local-field anisotropy in nematic mixtures--molecular properties in nematic mixtures
Аннотация: Для нематической смеси E7 производных цианобифенила исследована связь показателей преломления nj при поляризациях световой волны вдоль (j = ||) и нормально оптической оси (j = ⊥) с параметрами поляризуемости (компонентами γjα, средним значением γmα = (γ||α + 2γ⊥α)/3, анизотропией δγα = γ||α - γ⊥α) и ориентационным порядком молекул типа α, составляющих смесь. Для смеси введен тензор локального поля с компонентами fj =1+Lj(nj2 – 1). Получена связь компонент тензора Лорентца Lj с компонентами Ljα. Температурные зависимости Lj(Т) для смеси Е7 определены с использованием экспериментальных зависимостей nj(λ,Т) от длины световой волны λ. Подтверждена связь Lj(Ljα). Получена температурная зависимость S(Т) материального параметра порядка смеси. Обнаружено изменение среднего значения γm(Т) = ((γ|| + 2γ⊥)/3 для исследованной смеси за счет изменения S(Т). Показано, что зависимость γm(S) обусловлена противоположными по знаку вкладами от изменения конформации бифенильных остовов молекул и межмолекулярных взаимодействий. Полученные результаты сопоставлены со следствиями использования модельных тензоров fj, известных в литературе для смесей.The relation of the refractive indices nj of the nematic mixture E7 consisting of cyanobiphenyl derivatives for the light-wave polarization along (j = ||) and across (j = ⊥) the optical axis with the polarizability parameters (components γjα, mean value γmα = (γ||α + 2γ⊥α)/3, anisotropy δγα = γ||α - γ⊥α) and orientational order of α-type molecules comprising the mixture was investigated. The local-field tensor with components fj =1+Lj(nj2 – 1) was introduced for the mixture and the relationship between the Lorentz-tensor components Lj and the components Ljα was established. The temperature dependences Lj(Т) for the E7 mixture were obtained using experimental dependences nj(λ,T). The relationship Lj(Ljα) was confirmed. The temperature dependence of the material order parameter S(T) was obtained. The change of the mean value γm(Т) = ((γ|| + 2γ⊥)/3 for the studied mixture due to changing of S(Т) was observed. The dependence γm(S) was shown to be caused by two opposite-sign contributions due to changing conformation of molecular biphenyl cores and intermolecular interactions. The obtained results were compared with the consequences of using model tensors fj, which literature data are known for mixtures.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krakhalev M. N.
Заглавие : Oblique light incidence method to study topological defects in nematic layers with conical boundary conditions
Место публикации : Sci. Rep. - 2021. - Vol. 11, Is. 1. - Ст.17433. - ISSN 2045-2322, DOI 10.1038/s41598-021-96784-9
Примечания : Cited References: 54
Предметные рубрики: CHOLESTERIC FINGERS
DISCLINATIONS
SURFACE
WALLS
ORDER
Аннотация: A polarization microscopy method to investigate the orientational structures and boojums formed in the chiral and achiral nematic layers under conical (tilted) boundary conditions has been developed. Oblique light incidence on nematic layer is used, due to which the phase difference between the ordinary and extraordinary waves depends on the director’s azimuthal angle. The phase difference gets maximal when the director azimuthal angle of achiral nematic φ(x,y)=0 and an azimuthal angle at the center of the chiral nematic layer φ0(x,y)=0 independently of the total twist angle φTOTAL. It has been found that the m=+1 boojums with the phase ξ=±90° and ξ=(−90°+φTOTAL/2) are formed in achiral and chiral nematics, respectively, at the director tilt angle θd/2≅40° at the interface. In addition, the defectless structure of chiral nematic with the periodically variable azimuthal director angle on the substrates has been studied.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedoseev A. D.
Заглавие : Realization conditions and the magnetic field dependence of corner excitations in the topological insulator with superconducting coupling on the triangular lattice
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory [19-02-00348]; Krasnoyarsk Regional Fund of Science [20-42-243005]; "Coulomb interactions in the problem of Majorana modes in low-dimensional systems with nontrivial topology" [19-42-240011]; Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific SchoolsLeading Scientific Schools Program [MK1641.2020.2]
Место публикации : J. Exp. Theor. Phys. - 2021. - Vol. 133, Is. 1. - P.71-76. - ISSN 1063-7761, DOI 10.1134/S1063776121060029. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 38. - This work was supported by the Russian Foundation for Basic Research (project no. 19-02-00348), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research projects: "Study of edge states in oneand two-dimensional topological superconductors" (no. 20-42-243005), "Coulomb interactions in the problem of Majorana modes in low-dimensional systems with nontrivial topology" (no. 19-42-240011), and Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (Project MK1641.2020.2)
Предметные рубрики: EDGE
STATES
ORDER
Аннотация: The studies of the topological properties of systems have recently been extended due to a new concept of higher-order topological insulators and superconductors. Many models were proposed for two-dimensional systems on a square lattice, where corner excitations can appear; however, the problem of existence of such excitations in superconducting systems with a triangular crystal lattice is still poorly understood. Using a topological insulator in the form of a triangle with a chiral superconducting order parameter as an example, we shows that corner excitations can exist in C3-symmetric systems. In spite of a nontopological character, these excitations have energies inside the gap of the first-order edge excitation spectrum over a wide parameter range and are well localized at the corners of the system. Gapless corner excitations are shown to exist in the system at certain parameters. The application of a magnetic field in the system plane removes the triple degeneracy of the corner excitation energy and makes it possible to control the position of the minimum-energy corner excitation using a magnetic field. At the same time the fine adjustment to achieve the gapless excitations at the chosen corner can be made with changing of the magnetic field value.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sukhinin Y. V.
Заглавие : Ising-like model of tilted phase transitions in Langmuir monolayers
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2006. - Vol. 74, Is. 19. - Ст.195423. - ISSN 1098-0121, DOI 10.1103/PhysRevB.74.195423
Примечания : Cited References: 27
Предметные рубрики: MONTE-CARLO-SIMULATION
FATTY-ACID MONOLAYERS
AIR-WATER-INTERFACE
AMPHIPHILE MONOLAYERS
ROTATOR PHASES
ALKANES
DIAGRAM
POTENTIALS
ORDER
Аннотация: Two Ising models on a rectangular lattice (sigma(1) model and sigma(2) model) linked to three- and four-spin interactions are used to describe the sequence of tilted phase transitions in monolayers of amphiphilic long-chain molecules on an air-water surface. Starting from Morse atom-atom potentials self-consistent equations for basic thermal averages are derived in terms of a mean-field approximation. We employ the model for CH3(CH2)(18)COOH at two values of the molecule density and obtain all known tilted phases, including an intermediate one.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aver'yanov E. M.
Заглавие : Local-field anisotropy in cholesteric liquid crystals
Коллективы : Presidium of the Russian Academy of Sciences; Siberian Branch, Russian Academy of Sciences
Место публикации : JETP Letters. - 2009. - Vol. 89, Is. 7. - P.324-327. - ISSN 0021-3640, DOI 10.1134/S0021364009070030
Примечания : Cited References: 12. - This work was supported by the Presidium of the Russian Academy of Sciences ( Basic Research Program, project no. 27.1) and by the Siberian Branch, Russian Academy of Sciences ( Interdisciplinary Basic Research Program, project no. 5).
Предметные рубрики: ORDER
POLARIZABILITY
Аннотация: The first experimental values of the Lorentz tensor components L (j) for the cholesteric and smectic A phases of derivatives of cholesterol have been obtained using the dispersion of the refractive indices in the visible range. The temperature dependence of the components L (j) has been determined; it is invariant with respect to the cholesteric-smectic A phase transition. The effect of the isotropization of the Lorentz and local field tensors with decreasing anisotropy of the molecular polarizability has been revealed.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GOREV M. V., FLEROV I. N., VORONOV V. N., MISYUL S. V.
Заглавие : P = T-PHASE DIAGRAMS OF ELPASOLITES RB2KB3+F6(B3+ = HO,DY,TB)
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1993. - Vol. 35, Is. 4. - P1022-1027. - ISSN 0367-3294
Примечания : Cited References: 16
Предметные рубрики: RIGID SPHERE MODEL
RB2KMIIIF6 ELPASOLITES
TRANSITIONS
ORDER
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB(1/2)' B(1/2)'' O(3) (B ' = Ga, In, Lu; B '' = Nb, Ta) solid solutions
Разночтения заглавия :авие SCOPUS: Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB′ 1/2B″1/2O3 (B′ = Ga, In, Lu; B″ = Nb, Ta) solid solutions
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 106, Is. 6. - P1109-1117. - ISSN 1063-7761, DOI 10.1134/S1063776108060101
Примечания : Cited References: 29
Предметные рубрики: STATISTICAL-MECHANICS
PEROVSKITES
CRYSTALS
ORDER
RELAXOR
BATIO3
PBTIO3
Ключевые слова (''Своб.индексиров.''): crystal lattices--ferroelectricity--lattice vibrations--solids--ferroelectric (barium strontium titanate)--ferroelectric phase transitions--lattice (co)--lattice dynamics--vibration spectrum--ferroelectric materials
Аннотация: The lattice vibration spectra, rf permittivity, and dynamic Born charges of disordered PbB(1/2)'B(1/2)'' O(3) (B' = Ga, In, Lu; B '' = Nb, Ta) solid solutions are calculated in terms of the generalized Gordon-Kim model. All the compounds are found to have soft modes related to the center (Gamma(15)) and boundary point R (R(15)) of the Brillouin zone; the frequencies of these modes are close. The ferroelectric phase transition temperatures and the spontaneous polarization in the ferroelectric phase are calculated for the solid solutions using a model Hamiltonian in the local mode approximation and the Monte Carlo method. These temperatures for the tantalum compounds are found to be higher than for the niobium compounds, and temperature t(s) increases with the atomic number of ion B'. A model where the antiferroelectric state is related to the condensation of modes Gamma(15) and R(15) is proposed. It is found that, for all compounds except for PbSc(1/2)Nb(1/2)O(3) and PbSc(1/2)Ta(1/2)O(3), the ferroelectric phase, which is only related to the condensation of mode R(15), and the antiferroelectric phase have similar energies. In PbIn(1/2)Ta(1/2)O(3), the antiferroelectric phase turns out to be energetically favorable.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Dubrovskii A. A., Semenov S. V., Bayukov O. A., Stolyar S. V., Iskhakov R. S., Ladygina V. P., Ishchenko L. A.
Заглавие : Magnetic properties and the mechanism of formation of the uncompensated magnetic moment of antiferromagnetic ferrihydrite nanoparticles of a bacterial origin
Коллективы : Ministry of Education and Science of the Russian Federation; Siberian Branch of the Russian Academy of Sciences
Место публикации : J. Exp. Theor. Phys.: Pleiades Publishing, 2014. - Vol. 119, Is. 3. - P.479-487. - ISSN 1063-7761, DOI 10.1134/S1063776114080044. - ISSN 1090-6509
Примечания : Cited References: 42. - This work was supported by the Ministry of Education and Science of the Russian Federation (state contract in 2014-2016) and a program of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики: NIO NANOPARTICLES
EXCHANGE BIAS
HYSTERESIS ANOMALIES
FERRITIN
SURFACE
MOSSBAUER
ORDER
SIZE
Аннотация: The magnetic properties of the superparamagnetic ferrihydrite nanoparticles that form as a result of the vital activity of Klebsiella oxytoca bacteria are studied. Both an initial powder with an average number of iron atoms N Fe ∼ 2000–2500 in a particle and this powder after annealing at 140°C for 3 h in air are investigated. The following substantial modifications of the magnetic properties of the ferrihydrite nanoparticles are detected after annealing: the superparamagnetic blocking temperature increases from 23 to 49.5 K, and the average magnetic moment of a particle increases (as follows from the results of processing of magnetization curves). The particles have antiferromagnetic ordering, and the magnetic moment resulting in the superparamagnetism of the system appears due to random spin decompensation inside the particle. For this mechanism, the number of uncompensated spins is proportional to the number of magnetically active atoms raised to the one-half power, and this relation holds true for the samples under study at a good accuracy. The possible causes of the detected shift of magnetic hysteresis loops at low temperatures upon field cooling are discussed.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Tressaud A., Molokeev M. S., Kartashev A. V., Pogoreltsev E. I., Bayukov O. A.
Заглавие : Phase transitions in fluoride KFe2F6 with tetragonal tungsten bronze structure
Коллективы : RFBR [12-02-00056]; Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-924.2014.2]
Место публикации : J. Fluor. Chem.: Elsevier Science, 2014. - Vol. 168. - P.204-211. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2014.09.031. - ISSN 1873-3328
Примечания : Cited References: 14. - This work was supported by RFBR, project no. 12-02-00056, and the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (grant NSh-924.2014.2).
Предметные рубрики: K3FE5F15
490-K
ORDER
Ключевые слова (''Своб.индексиров.''): tetragonal tungsten bronze structure--phase transition--charge ordering--thermal properties
Аннотация: Heat capacity, thermal dilatation, structure, Mossbauer spectra and dielectric permittivity of fluoride KFe2F6 with tetragonal tungsten bronze crystal structure were studied. The as-made sample undergoes two structural phase transitions P4/mbm (T-1 approximate to 340 K) - Pbam (T-2 approximate to 250 K) - G(2) and magnetic phase transformation at T-m approximate to 133 K. Heating up to 600-700 K and subsequent cooling in helium atmosphere leads to a change of phase transition temperatures and diffused anomalies in thermal expansion. The results obtained and influence of thermal prehistory of the sample on its physical properties are discussed in the context of previous studies on related fluorides KFe2F6, which sometimes suggest conflicting structural details. (C) 2014 Elsevier B.V. All rights reserved.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov I. A., Ovchinnikov S. G.
Заглавие : Temperature dependence of the electronic structure of La2CuO4 in the multielectron LDA+GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 121, Is. 3. - P.457-464. - ISSN 1063-7761, DOI 10.1134/S1063776115090174
Примечания : Cited References: 38. - The work was supported by the Russian Science Foundation (project no. 14-12-00061)
Предметные рубрики: Copper oxides
Model
Superconductivity
Excitations
Instability
Spectrum
States
Order
Аннотация: The band structure of La2CuO4 in antiferromagnetic and paramagnetic phases is calculated at finite temperatures by the multielectron LDA+GTB method. The temperature dependence of the band spectrum and the spectral weight of Hubbard fermions is caused by a change in the occupation numbers of local multielectron spin-split terms in the antiferromagnetic phase. A decrease in the magnetization of the sublattice with temperature gives rise to new bands near the bottom of the conduction band and the top of the valence band. It is shown that the band gap decreases with increasing temperature, but La2CuO4 remains an insulator in the paramagnetic phase as well. These results are consistent with measurements of the red shift of the absorption edge in La2CuO4 with increasing temperature. © 2015, Pleiades Publishing, Inc.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Sukhovsky A. A., Ivanov Y. N., Raevsky I. P.
Заглавие : Local structure of disordered PbSc1/2Nb1/2O3 in the region of the diffuse tetragonal phase-rhombohedral phase transition
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 2. - P.316-323. - ISSN 1063-7834, DOI 10.1134/S1063783412020047
Примечания : Cited References: 16. - This study was supported by the Council on Grants from the President of the Russian Federation for Support of the Leading Scientific Schools of the Russian Federation (grant no. NSh-4645.2010.2).
Предметные рубрики: Neutron-diffraction
Order
BaTiO3
PbNiO3
NMR
Аннотация: The local structure of the ferroelectric-relaxor PbSc1/2Nb1/2O3 in the temperature range from 550 to 220 K has been investigated using 45Sc nuclear magnetic resonance. It has been found that, in the paraelectric phase at temperatures below 550 K, the crystal consists of regions of an ordered elpasolite structure and inclusions of the disordered tetragonal perovskite phase with displacements along directions of the [001] type. The relative weight of the tetragonal structure in the region of the paraelectric phase is approximately equal to 0.28. Below the temperature of the phase transition from the disordered modification to the polar phase, the relative weight of the tetragonal phase decreases with decreasing temperature. The tetragonal structure is replaced by the trigonal polar structure. In a wide temperature range (∼50 K), there exists a heterophase structure that is characteristic of relaxors. Note that the correlation length of displacements in the tetragonal phase should be very small to explain the absence of indications of the existence of this phase in the diffraction data.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. M., Nazarov V. G., Zyryanov V. Ya., Shabanov V. F.
Заглавие : Magnetic-field-induced structural transition in polymer-dispersed liquid crystals
Место публикации : Mol. Cryst. Liquid Cryst. - 2012. - Vol. 557, Is. 1. - P.50-59. - ISSN 1542-1406, DOI 10.1080/15421406.2011.632237
Примечания : Cited References: 19. - This study was supported by the Presidium of the Russian Academy of Sciences (Project no. 24.1) and the Siberian Branch of the Russian Academy of Sciences (grant no. 43).
Предметные рубрики: FRANK CONSTANTS
ELECTRIC-FIELD
NEMATIC DROPS
ANISOTROPY
ALIGNMENT
FILMS
ORDER
Ключевые слова (''Своб.индексиров.''): anchoring energy--magnetic field--polymer-dispersed liquid crystals--structural transition--temperature fluctuations
Аннотация: The structural transition occurring in droplets of nematic liquid crystals formed in a polymer in magnetic field is studied. The transition is caused by field-driven weakening of tangential surface anchoring and develops following two scenarios: bipolar structure/homogeneous structure or bipolar structure/radial structure. The first scenario suggests a cyclic transition occurring upon thermal fluctuations without field. The structural transition is considered within a model of the biaxial liquid crystal/polymer interface. The model describes tendency of the nematic director to align tangentially on a droplet's surface, normally under the action of flexoelectric polarization, and axially along the magnetic-field-imposed easy orientation axis.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Freydman A. L., Balaev A. D., Dubrovskiy A. A., Eremin E. V., Temerov V. L., Gudim, I. A.
Заглавие : Direct and inverse magnetoelectric effects in HoAl3(BO3)4 single crystal
Коллективы : Russian Foundation for Basic Research [13-02-12442ofi_m2, 14-02-00307]
Место публикации : J. Appl. Phys.: American Institute of Physics, 2014. - Vol. 115, Is. 17. - Ст.174103. - ISSN 0021-8979, DOI 10.1063/1.4874270. - ISSN 1089-7550
Примечания : Cited References: 34. - This work was supported by Russian Foundation for Basic Research (Project Nos. 13-02-12442ofi_m2 and 14-02-00307). The authors are grateful to V. N. Ilyushchenko for the help in preparing of this manuscript.
Предметные рубрики: POLARIZATION
BEHAVIOR
ORDER
Аннотация: The direct (MEH-) and inverse (MEE-) magnetoelectric effects in the HoAl3(BO3)4 single crystal are studied. Temperature and magnetic field dependences of permittivity of the crystal are investigated. A relation between the investigated effects was established. It was found that the magnetoelectric effect can exist in crystals without magnetic order or spontaneous polarization. It was shown that the phenomena investigated are due to magnetostriction or magnetoelastic effect. The thermodynamic potential was considered for describing magnetoelectric effect at low magnetic fields. The results obtained are explained within a proposed qualitative microscopic model, based on interplay of configuration of 4f- electron subshell of the rare-earth element and applied magnetic or electric field.Изучаются прямой (MEH-) и обратный (МЭА-) магнитоэлектрические эффекты в монокристалле HoAl3(BO3)4 . Зависимости диэлектрической проницаемости кристалла от температуры и магнитного поля исследованы. Была создана связь между исследованными эффектами. Было обнаружено, что магнитоэлектрический эффект может существовать в кристаллах без магнитного порядка или спонтанной поляризации. Было показано, что исследуемые явления происходят из-за магнитострикции или магнитоупругого эффекта. Термодинамический потенциал рассчитывался для описания магнитоэлектрический эффект в слабых магнитных полях. Полученные результаты объясняются в рамках предложенной качественной микроскопической модели, основанной на взаимодействии конфигурации 4f-электронов в подоболочке редкоземельного элемента и внешнего магнитного или электрического поля.
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