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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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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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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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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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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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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Zhigalov V. S., Bykova L. E., Bondarenko G. N., Rybakova A. N., Matsynin A. A., Tambasov I. A., Volochaev M. N., Velikanov D. A.
Заглавие : High rotatable magnetic anisotropy in epitaxial L10CoPt(111) thin films
Место публикации : JETP Letters. - 2015. - Vol. 102, Is. 6. - P.355-360. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364015180101
Примечания : Cited References: 51. - A We are grateful to L.A. Solov'ev for the help in X-ray studies of the epitaxial orientation of phases in L10CoPt(111) samples. This work was supported by the Russian Foundation for Basic Research (project no. 15-02-00948), in part by the Council the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (project no. SP-317.2015.1), and by the Foundation for the Assistance of the Development of Small Innovative Scientific and Engineering Enterprises (UMNIK).
Предметные рубрики: Co-Pt ALLOYS
ROOM-TEMPERATURE
COERCIVITY
ORIGIN
ORDER
STATE
Аннотация: The evolution of the structural and magnetic properties in epitaxial film systems Co/Pt(111) of equiatomic composition during vacuum annealing has been presented. Annealing to the temperature of 400°C does not lead to the variation of the structural and magnetic properties of the films, which indicates the absence of considerable mixing of the Co/Pt interface. With the increase in the annealing temperature from 400 to 750°C, nanoclusters containing the main magnetically hard L10CoPt(111) phase epitaxially intergrown with the CoPt3 phase are formed. High rotatable magnetic anisotropy has been found in the prepared films. In magnetic fields above the coercive force (H > HC = 8 kOe), the easy anisotropy axis with the angle of lag taken into account can be oriented in any spatial direction. Possible mechanisms of the formation of the rotatable magnetic anisotropy have been discussed. It has been assumed that the high rotatable magnetic anisotropy makes the main contribution to the magnetic perpendicular anisotropy in CoxPt1–x films. © 2015, Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aver'yanov E. M.
Заглавие : Effective refractive index of a quasi-two-dimensional polydomain film of a conjugated polymer
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 58, Is. 1. - P.160-163. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783416010042
Примечания : Cited References: 20
Предметные рубрики: THIN POLYFLUORENE FILMS
OPTICAL-CONSTANTS
LOCAL-FIELD
ANISOTROPY
ORDER
Аннотация: The relation between the effective ordinary refractive index n* = (n o n e )1/2 of a quasi-two-dimensional polydomain uniaxial film of a conjugated polymer F8BT in the visible transparency region and the refractive indices (n o,e ) of uniaxial domains with the optical axes randomly oriented in the plane of the film has been confirmed experimentally. The permissible interval of variations in n* has been established and a strong spectral dispersion of this interval near the long-wavelength electronic absorption band of the film has been demonstrated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N., Tugarinov V. I.
Заглавие : Ground state of an antiferromagnet with uniform antisymmetric exchange in a magnetic field
Место публикации : JETP Letters. - 2010. - Vol. 92, Is. 2. - P.115-119. - ISSN 0021-3640, DOI 10.1134/S0021364010140092
Примечания : Cited References: 12
Предметные рубрики: INCOMMENSURATE
TRANSITION
ORDER
Аннотация: A system of two nonlinear differential equations for sublattice angles is proposed to describe the spin orientation distribution in a planar antiferromagnet with uniform antisymmetric exchange in a magnetic field. This system involves the initial symmetry of the problem and is reduced to a single delay differential equation. The solutions of this system are parameterized by the initial condition imposed on the angle of one sublattice at the hyperbolic singular point of the phase space. The numerical analysis of the stability boundary of soliton solutions demonstrates that the transition to the commensurate phase takes place outside the region where the stochastic solutions appear and is accompanied by the magnetization jump Delta m similar to 10(-1) m.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popova E. A., Vasiliev A. N., Temerov V. L., Bezmaternykh L. N., Tristan N., Klingeler R., Buchner B.
Заглавие : Magnetic and specific heat properties of YFe3(BO3)(4) and ErFe3(BO3)(4)
Коллективы :
Разночтения заглавия :авие SCOPUS: Magnetic and specific heat properties of YFe3(BO3) 4 and ErFe3(BO3)4
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 11. - Ст.116006. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/11/116006
Примечания : Cited References: 26. - This work was supported by DFG grants 436 RUS and HE 3439/6 (FOR 520). The authors are indebted to M N Popova and B Z Malkin for valuable discussions.
Предметные рубрики: LINEAR-CHAIN ANTIFERROMAGNETISM
CRYSTAL-STRUCTURE
GDFE3(BO3)(4)
MULTIFERROICS
BA2COS3
ORDER
Ключевые слова (''Своб.индексиров.''): antiferromagnetic orders--basal planes--experimental data--magnetically ordered state--antiferromagnetism--calorimetry--erbium--magnetic moments--single crystals--specific heat--magnetic domains
Аннотация: The present paper reports on the specific heat and magnetization of the YFe3(BO3)(4) and ErFe3(BO3)(4) single crystals. In both compounds, antiferromagnetic order of the iron spins evolves at T-N = 38 K. The experimental data suggest that the magnetic moments are in the basal plane of the trigonal crystal for both compounds. In the magnetically ordered state the crystal is subdivided into three types of domains, the magnetic moments of the Fe3+ ions being aligned along the a axis within each domain. For ErFe3(BO3)(4), two non-equivalent magnetic positions of the Er3+ ions in each domain are observed.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Janoschek M., Fischer P., Schefer J., Roessli B., Pomjakushin V., Meven M., Petricek V., Petrakovskii G. A., Bezmaternykh L. N.
Заглавие : Single magnetic chirality in the magnetoelectric NdFe3((BO3)-B-11)(4)
Разночтения заглавия :авие SCOPUS: Single magnetic chirality in the magnetoelectric NdFe3( 11BO3 )4
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2010. - Vol. 81, Is. 9. - Ст.94429. - ISSN 1098-0121, DOI 10.1103/PhysRevB.81.094429
Примечания : Cited References: 55
Предметные рубрики: NEUTRON-DIFFRACTION
PHASE-TRANSITIONS
SLOW-NEUTRONS
CRYSTAL
NDFE3(BO3)(4)
EXTINCTION
NUCLEAR
ORDER
MNSI
ANTIFERROMAGNETS
Аннотация: We have performed an extensive study of single crystals of the magnetoelectric NdFe3 ((BO3)-B-11)(4) by means of a combination of single-crystal neutron diffraction and spherical neutron polarimetry. Our investigation did not detect significant deviations at low temperatures from space group R32 concerning the chemical structure. With respect to magnetic ordering our combined results demonstrate that in the commensurate magnetic phase below T-N approximate to 30 K all three magnetic Fe moments and the magnetic Nd moment are aligned ferromagnetically in the basal hexagonal plane but align antiferromagnetically between adjacent planes. The phase transition to the low-temperature incommensurate (IC) magnetic structure observed at T-IC approximate to 13.5 K appears to be continuous. By means of polarized neutron studies it could be shown that in the incommensurate magnetic phase the magnetic structure of NdFe3((BO3)-B-11)(4) is transformed into a long-period antiferromagnetic helix with single chirality. Close to the commensurate-incommensurate phase transition third-order harmonics were observed, which in addition indicate the formation of magnetic solitons.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Eremin I.
Заглавие : Theory of magnetic excitations in iron-based layered superconductors
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2008. - Vol. 78, Is. 14. - Ст.140509. - ISSN 1098-0121, DOI 10.1103/PhysRevB.78.140509
Примечания : Cited References: 31
Предметные рубрики: NEUTRON-SCATTERING
INSTABILITY
STATE
ORDER
MODEL
Аннотация: Based on the effective four-band model we analyze the spin response in the normal and superconducting states of the Fe-pnictide superconductors. While the normal-state spin excitations are dominated by the continuum of the interorbital antiferromagnetic fluctuations and the intraband spin-density wave fluctuations, the unconventional superconductivity yields different feedback. The resonance peak in the form of the well-defined spin exciton occurs only for the interband scattering at the antiferromagnetic momentum Q(AFM) for the s(+/-) (extended s wave) superconducting order parameter and it disappears rapidly for q Q(AFM). The resonance feature is extremely weak for the d(x)(2)-y(2)-wave order parameter due to the specific Fermi-surface topology of these compounds. The essential difference between s(+/-)-wave and d(x)(2)-y(2)-wave symmetries for the magnetic excitations can be used for experimental determination of the superconducting wave-function symmetry.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Eremin I.
Заглавие : Doping evolution of itinerant magnetic fluctuations in Fe-based pnictides
Коллективы :
Место публикации : Europhys. Lett. - 2008. - Vol. 83, Is. 6. - Ст.67003. - ISSN 0295-5075, DOI 10.1209/0295-5075/83/67003
Примечания : Cited References: 18. - We would like to thank B. BUCHNER, S.-L. DRECHSLER, D. EFREMOV, P. FULDE, I. MAZIN, R. MOESSNER and D. PARKER for useful discussions. IE acknowledges support from Volkswagen Foundation.
Предметные рубрики: SUPERCONDUCTIVITY
ORDER
Аннотация: Employing the four-band tight-binding model, we study theoretically the doping dependence of the spin response in the normal state of novel Fe-based pnictide superconductors. We show that the commensurate spin density wave (SDW) transition that arises due to interband scattering between the hole alpha-pockets and the electron beta-pockets disappears already at the doping concentration x approximate to 0.04 reflecting the evolution of the Fermi surfaces. Correspondingly, with further increase of the doping the antiferromagnetic fluctuations are suppressed for x 0.1 and the imaginary part of the spin susceptibility at antiferromagnetic wave vector becomes nearly temperature independent. At the same time, we observe that the uniform susceptibility deviates from the Pauli-like behavior and is increasing with increasing temperature reflecting the activation processes for the alpha-Fermi surfaces up to temperatures of about T = 800 K. With increase of the doping the absolute value of the uniform susceptibility lowers and its temperature dependence changes. In particular, it is a constant at low temperatures and then decreases with increasing temperature. We discuss our results in a context of recent experimental data. Copyright (C) EPLA, 2008
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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) : 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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16.

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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17.

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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18.

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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19.

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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20.

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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