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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Platunov M. S., Knyazev, Yu. V., Ivanova, N. B., Bayukov O. A., Vasiliev A. D., Bezmaternykh L. N., Nizhankovskii, V. I., Gavrilkin, S. Yu., Lamonova, K. V., Ovchinnikov S. G.
Заглавие : Uniaxial anisotropy and low-temperature antiferromagnetism of Mn2BO4 single crystal
Коллективы : Russian Foundation for Basic Research [13-02-00958, 13-02-00358, 14-02-31051-mol-a], Council for Grants of the President of the Russian Federation [NSh-2886.2014.2, SP-938.2015.5], program of Foundation for Promotion of Small Enterprises in Science and Technology [5468GU1/2014]
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2015. - Vol. 393. - P.316-324. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2015.05.081. - ISSN 18734766(eISSN)
Примечания : Cited References:33. - The authors wish to thank to Prof. M.V.Gorev and Prof J. Bartolome for fruitful discussions, Russian Foundation for Basic Research (Projects no13-02-00958, 13-02-00358, and 14-02-31051-mol-a), Council for Grants of the President of the Russian Federation (Project nos. NSh-2886.2014.2, and SP-938.2015.5). The work of one of coauthors (M.S.P.) was supported by the program of Foundation for Promotion of Small Enterprises in Science and Technology (Grant number 5468GU1/2014) ("UMNIK" program).
Предметные рубрики: MAGNETIC-PROPERTIES
WARWICKITE
OXYBORATE
PARAMETERS
LUDWIGITE
Ключевые слова (''Своб.индексиров.''): antiferromagnets--oxides--magnetic anisotropy--exchange interactions
Аннотация: The Mn2BO4 single crystals have been grown by the flux technique. A careful study of the crystal structure and magnetic properties have been carried out The antiferromagnetic transition at T-N=26 K has been traced through the dc magnetization and specific heat temperature dependences. Magnetic uniaxial anisotropy has been found with easy axis magnetization lying in the ab-plane. The obtained value of effective magnetic moment is assigned to the non-quenched orbital moment of Jahn-Teller Mn3+ ions. The discussion of magnetic properties is based on the superexchange interaction calculations. (C) 2015 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Fedoseev A. D.
Заглавие : Thermodynamic properties of two-layer quasi-two-dimensional antiferromagnets
Место публикации : Theor. Math. Phys.: SPRINGER, 2011. - Vol. 168, Is. 3. - P1216-1224. - ISSN 0040-5779, DOI 10.1007/s11232-011-0099-6
Примечания : Cited References: 16. - This work was supported in part by the Russian Foundation for Basic Research (Grant No. 10-02-00251), the Presidium of the Russian Academy of Sciences (Fundamental Research Program "Quantum Physics of Condensed Matter"), the Siberian Branch of the Russian Academy of Sciences (Integration Project No. 53 and Lavrentiev Competition of Youth Projects, A. D. F.), the Ministry of Education and Science of the Russian Federation (Program "Scientific and Pedagogical Personnel of Innovative Russia" for 2009-2013), and the President of the Russian Federation (Grant No. MK-1300.2011.2, A. D. F.).
Предметные рубрики: HEISENBERG-MODEL
SPIN-WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--high-temperature superconductor--tyablikov approximation--green's function--antiferromagnetism--green's function--high-temperature superconductor--tyablikov approximation
Аннотация: For two-layer quasi-two-dimensional antiferromagnets of type YBaCuO in the Tyablikov approximation, we investigate the dependences of the energy spectrum and the temperature of transition into an ordered state on both the quasi-two-dimensionality parameter and the intensity of the exchange coupling of spin moments located in two close planes. We assume that the exchange parameters inside the CuO (2) planes are much greater than the exchange parameters resulting in coupling between a spin located on a plane of an elementary cell and a spin on another plane of a different elementary cell. The obtained expressions for the N,el temperature and for the sublattice magnetic moment at zero temperature describe the dependences of these quantities on the parameters of interplane exchange interactions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Thermodynamic properties of antiferromagnets with random interactions
Место публикации : Phys. Status Solidi B. - 1984. - Vol. 122, Is. 1. - P.K33-K36. - ISSN 0370-1972, DOI 10.1002/pssb.2221220152
Примечания : Cited References: 5
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M., Bogdanov E. V., Flerov I. N., Laptash N. M.
Заглавие : Thermal expansion, phase diagrams and barocaloric effects in (NH4)(2)NbOF5
Коллективы :
Разночтения заглавия :авие SCOPUS: Thermal expansion, phase diagrams and barocaloric effects in (NH 4)2NbOF5
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 18. - Ст.185901. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/18/185901
Примечания : Cited References: 17. - This work was supported in part by the Krasnoyarsk Regional Foundation for Support of Scientific and Scientific-Technological Investigations and RFBR in the framework of project 'Siberia' (Grant No. 09-02-98001), and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools (project No. Nsh-1011.2008.2).
Предметные рубрики: CRYSTAL-STRUCTURE
SOLID-STATE
OXYFLUORIDE
TRANSITION
ANION
Ключевые слова (''Своб.индексиров.''): antiferromagnets--ferromagnets--heat capacities--high stress--intermediate phase--pippard relations--structural phase transition--transition temperature--uniaxial pressures--financial data processing--phase diagrams--phase transitions--thermal stress--tools--thermal expansion
Аннотация: The thermal expansion along the a, b and c axes of a (NH4)(2)NbOF5 crystal was measured from 120 to 300 K. Anomalies of alpha(T) associated with previously reported phase transitions Cmc2(1) - C-2 - I a were observed along all directions at T-1 = 259.3 K and T-2 = 220.5 K. The analysis of thermal expansion and heat capacity in the frame of the Pippard relations has permitted us to determine the uniaxial pressure derivatives of the transition temperatures dT/d sigma(i). The T-sigma(i) phase diagrams have shown a tendency for the intermediate phase to disappear at high stress along the b and c axes. Intensive and extensive barocaloric effects near the structural phase transitions were found to be comparable with the caloric parameters of some ferroelectrics, ferromagnets and antiferromagnets.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : The study of magnetic properties of the quasi-one-dimensianal spin-1/2 antiferromagnet by Monte-Carlo method
Место публикации : Phys. Low-Dimens. Struct.: V S V CO. LTD, 2000. - Vol. 07.08.2013. - P37-46. - ISSN 0204-3467
Примечания : Cited References: 15
Предметные рубрики: ONE-DIMENSIONAL ANTIFERROMAGNETS
SYSTEMS
CHAINS
CA2CUO3
Аннотация: The thermodynamic quantities, two- and four-spin correlation functions as well as the correlation radius for weakly coupled antiferromagnetic spin chains with S = 1/2 are calculated using the mean-field approximation for the interchain coupling (J(2)) for longitudinal and transverse spin components by quantum Monte Carlo method. Results for the staggered magnetization and Neel temperature are in agreement with general scaling arguments. The value of triplet DeltaS(z) =1 gp in the spectrum of excitations is estimated. The transverse staggered field was found to induce an additional maximum in the correlation radius of the four spin correlation function around T/J(1) approximate to [0.05 divided by 0.075), J(2)/J(1) 0.03.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Mitskan V. A., Petrakovskii G. A.
Заглавие : The magnetoelastic mechanism of singlet phase formation in a two-dimensional quantum antiferromagnet
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 102, Is. 2. - P234-247. - ISSN 1063-7761, DOI 10.1134/S106377610602004X
Примечания : Cited References: 18
Предметные рубрики: GROUND-STATE
SPIN
TRANSITION
CUGEO3
MODEL
Ключевые слова (''Своб.индексиров.''): crystal lattices--elasticity--mathematical models--oscillations--phase diagrams--phase transitions--quantum theory--two dimensional--atomic representation--magnetoelastic mechanism--quantum antiferromagnets--singlet phase formation--antiferromagnetic materials
Аннотация: A model describing the second-order phase transition with respect to the magnetoelastic coupling parameter from the anti ferromagnetic (AFM) to the singlet state in a two-dimensional quantum magnet on a square lattice is proposed. The spectrum of elementary excitations in the singlet and AFM phases is calculated using an atomic representation, and the evolution of transverse and longitudinal branches of this spectrum is studied in the vicinity of the transition point. It is established that the AFM to singlet phase transition is related to softening of the longitudinal branch of oscillations. In the singlet phase, the gap plays the role of a parameter characterizing the distance to the phase transition point. It is shown that the spectrum of transverse oscillations in the AFM phase corresponds to the Goldstone boson. Based on an analysis of the stability of the spectrum of elementary excitations, a phase diagram is constructed that determines the regions of the existence of phases with plaquette-deformed lattices.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : The incommensurate magnetic structure of a tetragonal antiferromagnet with antisymmetric exchange
Место публикации : J. Exp. Theor. Phys. - 2009. - Vol. 109, Is. 6. - P.979-988. - ISSN 1063-7761, DOI 10.1134/S1063776109120097
Примечания : Cited References: 34
Предметные рубрики: FLUCTUATION-INDUCED PHASE
FIELD-INDUCED GAP
COPPER METABORATE
WEAK FERROMAGNETISM
SOLITON LATTICE
SPIN-WAVES
CUB2O4
BA2CUGE2O7
CSCUCL3
CHAINS
Ключевые слова (''Своб.индексиров.''): anti-symmetric--antiferromagnetic sublattices--antiferromagnets--antisymmetric exchange--exchange bonds--ferromagnetic component--ferromagnetic moments--ginzburg-landau functional--incommensurate magnetic structures--mean field approximation--modulation vectors--polarization planes--polarization vectors--symmetry groups--antiferromagnetic materials--antiferromagnetism--crystal orientation--crystal symmetry--ferromagnetic materials--ferromagnetism--magnetic devices--magnetic structure--modulation--polarization--vector spaces--vectors--crystallography
Аннотация: Analysis of the incommensurate magnetic structure that emerges for two coexisting types of the antisymmetric Dzyaloshinski-Moriya exchange interaction (the weakly ferromagnetic component of vector D along the tetragonal axis and the helicoidal component distributed in the tetragonal plane) is carried out for the first time for a tetragonal antiferromagnet. The helicoidal component for each pair of interacting spins has a 2D distribution; its direction in the tetragonal plane depends on the direction of the exchange bond in each pair. The Lifshits invariant of the Ginzburg-Landau functional is obtained, which is responsible for the formation of an incommensurate magnetic structure for such a distribution. It is shown in the mean field approximation that the incommensurate magnetic structure that forms in this case is a nonlinear double helicoid with a modulation vector lying in the tetragonal plane and with a varying angle between the polarization planes of quasi-antiferromagnetic sublattices. The ground state of the magnet is degenerate in the orientation of the modulation vector in the tetragonal plane. The rate of variation in the orientations of moments in the polarization planes passing through the tetragonal axis is controlled by the angle between the directions of the moments and the tetragonal axis. The local weakly ferromagnetic moment remaining in the polarization plane varies in magnitude and sign. The relation between the orientations of the modulation and polarization vectors is derived for the cases of simple and inversion tetragonal axes in the space symmetry group of the crystal.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shklyaev A. A., Barabanov A. F.
Заглавие : The effect of spin correlations on a superconducting phase of the spin polarons in 2D Kondo lattice
Место публикации : J. Phys. Conf. Ser. - 2010. - Vol. 200, Is. SECTION 1. - ISSN 17426588 (ISSN), DOI 10.1088/1742-6596/200/1/012217
Ключевые слова (''Своб.индексиров.''): antiferromagnets--concentration dependence--cuprates--experimental data--hopping integrals--kondo lattice model--kondo lattices--magnetic correlation--spin correlations--spin polaron--superconducting phase--superconducting phase transitions--temperature dependence--copper compounds--correlators--magnetism--phase diagrams--polarons--superconducting magnets--superconductivity--phase transitions
Аннотация: The effect of the magnetic correlators on the spin polaron superconducting phase is studied in terms of 2D Kondo lattice model. It is shown that hopping integrals are renormalized by the magnetic correlators and as a result the Tc phase diagram is changing significantly. By computation the effect of magnetic correlation functions on the concentration dependence of T c was analysed and their substantial role in description of doped antiferromagnets is demonstrated. The obtained phase diagram is in qualitative agreement with experimental data for temperature dependence of the superconducting phase transition with d-type symmetry in cuprates. © 2010 IOP Publishing Ltd.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Temperature-induced weak ferromagnetism in an anisotropic magnetic with competing interactions
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz. - 1991. - Vol. 99, Is. 1. - P.189-193. - ISSN 0044-4510
Примечания : Cited References: 10
Предметные рубрики: ANTIFERROMAGNETS
Аннотация: The region of temperature and exchange with a temperature-induced weak ferro magnetic moment in a magnet with competing interactions in the second coordination sphere and with anisotropic distribution of opposite sign bonds possessing a tensor nature in the first sphere is determined by the Monte Carlo method. The temperature dependence of the susceptibility, specific heat and magnetization in an external field is determined.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bayukov O. A., Gavrilyuk A. M., Zabluda V. N., Lyubutin I. S., Ovchinnikov S. G., Potseluyko A. M., Tomas M., Trojan I. A., Kharlamova S. A.
Заглавие : Studies of magnetic and optic properties of rare-earth gallo-ferroborates by Mossbauer and optical spectroscopy
Место публикации : Physica B: ELSEVIER SCIENCE BV, 2005. - Vol. 359: International Conference on Strongly Correlated Electron Systems (SCES 04) (JUL 26-30, 2004, Karlsruhe, GERMANY). - P1321-1323. - ISSN 0921-4526, DOI 10.1016/j.physb.2005.01.397
Примечания : Cited References: 3
Ключевые слова (''Своб.индексиров.''): strongly correlated electron system--antiferromagnets--borates--antiferromagnets--borates--strongly correlated electron system--antiferromagnetism--cryostats--energy gap--magnetic moments--magnetic properties--mossbauer spectroscopy--optical properties--single crystals--borates--coulomb correlations--liquid helium--strongly correlated electron systems--gadolinium compounds
Аннотация: Magnetic and optical properties of GdFe3-xGax(BO3)(4) single crystals are investigated by Mossbauer and optical spectroscopy. The GdFe3(BO3)(4) multielectron band structure model is derived. A high- and low-spin crossover of Fe3+ ion, a collapse of the magnetic moment, the suppression of Coulomb correlations, and insulator-semiconductor transition are predicted. The jump of an energy gap is measured at pressure 43 GPa. (c) 2005 Elsevier B.V. All rights reserved.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Static and dynamic magnetic properties of coupled spin-1/2 antiferromagnetic chains
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2000. - Vol. 12, Is. 37. - P.8191-8207. - ISSN 0953-8984, DOI 10.1088/0953-8984/12/37/316
Примечания : Cited References: 21
Предметные рубрики: ONE-DIMENSIONAL ANTIFERROMAGNETS
SYSTEMS
SUSCEPTIBILITY
EXCITATIONS
SR2CUO3
CA2CUO3
KCUF3
Ключевые слова (''Своб.индексиров.''): computational methods--copper compounds--correlation methods--functions--magnetic field effects--magnetic properties--magnetization--monte carlo methods--quantum theory--specific heat--thermal effects--excitation spectroscopy--interchain coupling--intrachain couplings--mean-field approximation--spin-spin correlation function--spinons--antiferromagnetic materials
Аннотация: Calculations of the thermodynamic quantities, and the spectra of spinons, triplet excitations, and two-particle spin-singlet (Delta S-z = 0, +/- 1) excitations for a weakly coupled antiferromagnetic S = 1/2 spin chain are made using a mean-field approximation for the interchain couplings (J(2)) by the quantum Monte Carlo method. The mass gaps in these excitation spectra are estimated as functions of the interchain coupling. The critical held H-c, and the temperatures at which the spinon and singlet gaps close (T-1 and T-2, respectively) are obtained. Some peculiarities of the staggered magnetization, the specific heat, and the spin-spin correlation function are found at T-1 = 0.9J(2), T-2 = 1.5J(2), H-c = 3.8J(2), as determined by linear function fitting for J(2)/J(1) 0.15 The intrachain and interchain couplings, and the staggered magnetization for KCuF3, Sr2CuO3, and Ca2CuO3 are estimated, and mass gaps are predicted to exist in the spectra of the spinons and the singlet two-particle excitations.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : OVCHINNIKOV S. G., PETRAKOVSKII O. G.
Заглавие : SPIN-WAVE THEORY OF EASY-AXIS QUASI-2-DIMENSIONAL HEISENBERG ANTIFERROMAGNETS
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1987. - Vol. 29, Is. 6. - P1866-1868. - ISSN 0367-3294
Примечания : Cited References: 5
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Spin wave theory of heavy-fermion antiferromagnets in the framework of the periodic anderson model
Коллективы : "Spin Waves", International Simposium, Физико-технический институт им. А.Ф. Иоффе РАН
Место публикации : Spin Waves 2015, Int. Symp.: abstracts. - СПб., 2015
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GEKHT R. S.
Заглавие : SINUSOIDAL INCOMMENSURATE STRUCTURE IN SPIRAL ANTIFERROMAGNETS
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 1985. - Vol. 55, Is. 8. - P709-711. - ISSN 0038-1098, DOI 10.1016/0038-1098(85)90239-X
Примечания : Cited References: 6
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Single-ion mechanism of weak ferromagnetism and a spin-flop transition in one- and two-position antiferromagnets
Коллективы : Russian Foundation for Basic Research [16-02-00563]
Место публикации : JETP Letters. - 2018. - Vol. 108, Is. 3. - P.196-200. - ISSN 0021-3640, DOI 10.1134/S0021364018150080. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 10. - I am grateful to A.D. Balaev, V.I. Zinenko, and A.I. Pankrats for stimulating discussions. This work was supported by the Russian Foundation for Basic Research (project no. 16-02-00563).
Предметные рубрики: HEISENBERG FERRIMAGNET
PB2FE2GE2O9
CRYSTALS
Аннотация: A system of equations describing the ground state in an external magnetic field has been obtained for a twoposition antiferromagnet with noncollinear axes of single-ion anisotropy of moments of different sublattices. It has been shown that the antiferromagnetism vector changes sign at a spin-flop transition. This leads to a first-order magnetic phase transition with hysteresis in the field dependence of the magnetization. Explicit relations have been obtained between the parameters of a microscopic Hamiltonian and the experimentally observed spontaneous moment and spin-flop transition field. It has been shown that the field dependence of the total magnetic moment of the antiferromagnet with magnetic ions at two crystallographically nonequivalent positions (two-position antiferromagnet) obtained within the two-sublattice model is nonlinear above the transition field at any orientation of the crystal with respect to the magnetic field.
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16.

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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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Quantum spin liquid in the 2D anisotropic Heisenberg model with frustrated next nearest neighbor exchange
Место публикации : Low Temp. Phys. - 1998. - Vol. 24, Is. 8. - P.572-577. - ISSN 1063-777X, DOI 10.1063/1.593639; \b Физика низких температур
Примечания : Cited References: 25
Предметные рубрики: SQUARE-LATTICE ANTIFERROMAGNETS
VALENCE BOND STATES
SYSTEMS
SUPERCONDUCTIVITY
SYMMETRY
Аннотация: The two-dimensional (2D) Heisenberg model with anisotropic exchange (Delta = 1 - J(x)/J(z)) and with negative next nearest neighbor exchange (J(2)) with S = 1/2 is investigated by using the quantum-mechanical Monte-Carlo method. The energy, magnetic moment at a site, heat capacity, and spin-spin correlation functions are calculated. The stability regions for Neel ordering of spins as well as the strip-phase and gapless quantum spin liquid are determined in the interval Delta/2 less than or equal to J(2)/ J(1)less than or equal to 1/(2 Delta). (C) 1998 American Institute of Physics. [S1063-777X(98)00808-1].
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Golovnya A. A., Korovushkin M. M.
Заглавие : Pseudogap formation in copper oxide superconductors with inclusion of spin and charge fluctuations
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 10. - P2001-2004. - ISSN 1063-7834, DOI 10.1134/S1063783411100349
Примечания : Cited References: 15. - This study was supported by the Presidium of the Russian Academy of Sciences (Program "Quantum Physics of Condensed Matter"), the Russian Foundation for Basic Research (project no. 09-02-00127), the Siberian Branch of the Russian Academy of Sciences (Interdisciplinary Integration project no. 53), and the Ministry of Education and Science of the Russian Federation (Russian Federal Targeted Program "Scientific and Scientific-Pedagogical Personnel of the Innovative Russia" in 2009-2013).
Предметные рубрики: ANTIFERROMAGNETS
DYNAMICS
Аннотация: The influence of spin and charge fluctuations on the pseudogap formation in cuprate superconductors has been studied using the diagram technique for Hubbard operators. It has been shown that the joint inclusion of the spin and charge fluctuations leads to the formation of "shadow" bands with a strong modulation of the spectral intensity and to a decrease in the density of electronic states at the Fermi level.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V., Gnatchenko S. L., Kachur I. S., Piryatinskaya V. G., Sukhachev A. L., Gudim, I. A.
Заглавие : Optical and magneto-optical properties of Nd0.5Gd0.5Fe3(BO3)4 single crystal in the near IR spectral region
Место публикации : J. Alloys Compd.: Elsevier, 2012. - Vol. 542. - P.157-163. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2012.07.061
Примечания : Cited References: 23. - The work was supported by the Russian Foundation for Basic Researches Grant 12-02-00026 and by the Russian President Grant SS-1044.2012.2.
Предметные рубрики: MAGNETIC CIRCULAR-DICHROISM
GDFE3(BO3)(4)
YB3+
ER3+
ND3+
Ключевые слова (''Своб.индексиров.''): rare earth compounds--nd3+--antiferromagnets--multiferroics--magnetic circular dichroism--absorption spectra
Аннотация: Polarized optical absorption and magnetic circular dichroism (MCD) spectra of the trigonal multiferroic Nd0.5Gd0.5Fe3(BO3)4 were studied in the region of transitions 4I9/2 → 4F3/2 and 4I9/2 → (4F5/2 + 2H9/2) in Nd3+ ion. Components of the crystal field splitting of the states were identified with the help of MCD and polarized absorption spectra. Splitting of the Nd3+ absorption lines caused by the magnetic ordering were observed. Splitting of Nd3+ ground state in Fe-sublattice exchange field was found to be ∼9 cm−1 at 5.7 K. The Zeeman splitting of some absorption lines in the external magnetic field and changes of the effective Landé factors in the C3-direction as a result of the corresponding optical transitions were found. Peculiarities in the temperature behavior of the absorption lines connected both with the ground and excited states were revealed. Peculiarities connected with the excited states testify to the local crystal distortions in the excited states.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V., Sukhachev A. L., Vasil'ev A. D., Leont'ev A. A., Kartashev A. V., Temerov V. L., Gudim, I. A.
Заглавие : Nature of optical properties of GdFe3(BO3)4 and GdFe2.1Ga0.9(BO3)4 crystals and other 3d5 antiferromagnets
Место публикации : Eur. Phys. J. B: Springer, 2012. - Vol. 85, Is. 2. - P.80. - ISSN 1434-6028, DOI 10.1140/epjb/e2012-20953-1
Примечания : Cited References: 70. - The work was supported by the Russian Foundation for Basic Researches Grant 12-02-00026 and by Russian President Grant NSh-1044.2012.2.
Предметные рубрики: IRON BORATE GDFE3(BO3)4
D-D TRANSITIONS
EARTH FERROBORATES RFE3(BO3)4
ABSORPTION-SPECTRA
OCTAHEDRAL COMPLEXES
ELECTRONIC-STRUCTURE
NEEL TEMPERATURE
FINE-STRUCTURE
EXCHANGE
IONS
Аннотация: Influence of the partial substitution of paramagnetic Fe3+ ions by diamagnetic Ga3+ ions in the trigonal crystal GdFe3 (BO3)4 on its optical and magnetic properties is studied and discussed in connection with problems common for all antiferromagnets containing 3d 5 ions. Polarized optical absorption spectra and linear birefringence of GdFe3 (BO3)4 and GdFe2.1Ga0.9 (BO3)4 single crystals have been measured in the temperature range 85–293 K. Specific heat temperature dependence (2–300 K) and structure of GdFe2.1Ga0.9 (BO3)4 crystal have been also studied. As a result of substitution of 30% Fe to Ga the Neel temperature diminishes from 38 till 16 K, the strong absorption band edge shifts on 860 cm-1 (0.11 eV) to higher energy and the d-d transitions intensity decreases substantially larger than the Fe concentration does. Strong absorption band edge is shown to be due to Mott-Hubbard transitions. Correlation between position of the strong absorption band edge and the Neel temperature of antiferromagnets has been revealed. Properties of the doubly forbidden d-d transitions in the studied crystals and in other antiferromagnets are explained within the framework of the model of the exchange-vibronic pair absorption, which is theoretically analyzed in detail. The model permitted us to determine the connection between parameters of d-d absorption bands (intensity, width and their temperature dependences), on the one hand, and the exchange, spin-orbit and electron-lattice interactions, on the other hand.
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