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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Phase diagram of the helical structure of a two-subsystem frustrated antiferromagnet
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 108, Is. 1. - P72-82. - ISSN 1063-7761, DOI 10.1134/S1063776109010105
Примечания : Cited References: 25
Предметные рубрики: GROUND SPIN-STATE
PYROCHLORE ANTIFERROMAGNET
TRIANGULAR-LATTICE
CLASSICAL-THEORY
MODEL
TRANSITION
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--antiferromagnetism--free energy--magnetic devices--magnetic fields--magnetic structure--phase diagrams--vectors--antiferromagnet--antiferromagnetic--antiferromagnetic sublattices--comparative analysis--critical fields--external fields--field boundaries--first derivatives--first-order transitions--helical orderings--helical phase--helical structures--higher temperatures--incommensurate magnetic structures--isotropic exchanges--magnetic subsystems--magnetization jumps--mean-field approximations--minimum free energies--numerical minimizations--spatial displacements--temperature dependences--thermodynamic potentials--variational equations--wave vectors--phase transitions
Аннотация: The expansion of the thermodynamic potential for the two-subsystem antiferromagnet with frustrated intersubsystem isotropic exchange is obtained. It is demonstrated that this expansion contains the first derivatives with respect to the antiferromagnetic vectors of the subsystems, i.e., the Lifshitz invariant. The equation for the temperature-field boundary of the helical phase for the two-subsystem frustrated antiferromagnet is derived by linearizing the variational equations for the minimum free energy within the mean-field approximation. Relationships are obtained for the critical field at T = 0, the angle of canting of moments of the antiferromagnetic sublattices, and the temperature of spontaneous appearance of helical ordering in the absence of an external field. It is revealed that there is a second higher temperature of formation of the helical magnetic structure induced by the magnetic field with the wave vector of the helix nonmonotonically depending on the external field. The phase boundary of the helical phase and the temperature dependence of the orientation of moments of the magnetic subsystem with weak exchange interaction are determined using numerical minimization of the free energy. It is shown that the transition to the commensurate phase is a first-order transition with a small magnetization jump. A comparative analysis of models with different spatial displacements of ions in the subsystems along the direction of the vector of the helical structure is performed. A criterion is proposed for the choice of the direction of the vector of the incommensurate magnetic structure.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Anomalies in the characteristics of electronic structure upon a quantum phase transition to a state with two order parameters and the breaking of time-reversal symmetry
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 6. - P.616-619. - ISSN 10628738 (ISSN), DOI 10.3103/S106287381606040X
Примечания : Cited References: 9
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--electronic structure--phase transitions--temperature distribution--antiferromagnetic order parameter--density of state--landau expansion--periodic anderson model--quantum phase transitions--temperature dependence--time reversal symmetries--two order parameters--quantum theory
Аннотация: Based on the periodic Anderson model, microscopic expressions for the Ginzburg–Landau expansion coefficients in a phase with superconducting and antiferromagnetic order parameters are obtained. Temperature dependences of the order parameters near the temperature of the transition to this phase are established. The emergence of anomalous properties upon the quantum phase transition to the phase with two order parameters is investigated. This transition is accompanied by drastic reconstruction of the density of states, reflected by the interplay between superconductivity and antiferromagnetism. © 2016, Allerton Press, Inc.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Petrakovskii G. A., Kartashev A., Eremin E. V., Temerov V. L.
Заглавие : Low-temperature magnetic phase diagram of HoFe3(BO3)(4) holmium ferroborate: a magnetic and heat capacity study
Разночтения заглавия :авие SCOPUS: Low-temperature magnetic phase diagram of HoFe3(BO 3)4 holmium ferroborate: A magnetic and heat capacity study
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2009. - Vol. 21, Is. 43. - Ст.436001. - ISSN 0953-8984, DOI 10.1088/0953-8984/21/43/436001
Примечания : Cited References: 20
Предметные рубрики: SINGLE-CRYSTAL
DYFE3(BO3)(4)
ND3+
Ключевые слова (''Своб.индексиров.''): antiferromagnetic state--applied magnetic fields--characteristic temperature--crystal axis--heat capacities--low temperatures--magnetic field parallel--magnetic phase diagrams--magnetic phase transitions--magnetization jump--schottky anomaly--spin reorientation transitions--thermal measurements--antiferromagnetic materials--antiferromagnetism--holmium--magnetic fields--phase diagrams--single crystals--specific heat--phase transitions
Аннотация: We present the results of the magnetic and heat capacity study of a magnetic phase diagram of a HoFe3(BO3)(4) single crystal. Two magnetic phase transitions are found in the low-temperature region. The transition from the paramagnetic to easy-plane antiferromagnetic state occurs at T-N = 37.4 K and is independent of an applied magnetic field. The sharp heat capacity peaks and magnetization jumps corresponding to the spontaneous and field-induced spin-reorientation transitions between the easy-axis and easy-plane states are observed below 4.7 K. Also, the additional heat capacity peaks, which can be attributed to the Schottky anomalies with the field-dependent characteristic temperatures, are found. According to the magnetic and thermal measurement data, the magnetic phase diagrams of HoFe3(BO3)(4) for the magnetic field parallel and perpendicular to the crystal axis are constructed.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : SANDALOV I. S., RICHTER M.
Заглавие : FLUX PHASE, NEEL ANTIFERROMAGNETISM, AND SUPERCONDUCTIVITY IN THE T-J MODEL
Разночтения заглавия :авие SCOPUS: Flux phase, Neel antiferromagnetism, and superconductivity in the t-J model
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 1994. - Vol. 50, Is. 17. - P12855-12865. - ISSN 0163-1829, DOI 10.1103/PhysRevB.50.12855
Примечания : Cited References: 27
Предметные рубрики: HUBBARD-MODEL
INSTABILITY
ELECTRONS
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5.

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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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Prosnikov M. A., Smirnov A. N., Davydov, V. Yu, Sablina K. A., Pisarev R. V.
Заглавие : Lattice and magnetic dynamics of a quasi-one-dimensional chain antiferromagnet PbFeBO4
Коллективы : Russian Science Foundation [16-12-10456]
Место публикации : J. Phys.: Condens. Matter: IOP Publishing, 2017. - Vol. 29, Is. 2. - Ст.025808. - ISSN 0953-8984, DOI 10.1088/0953-8984/29/2/025808. - ISSN 1361-648X(eISSN)
Примечания : Cited References:32. - This research was supported by the Russian Science Foundation, grant No. 16-12-10456.
Предметные рубрики: LIGHT-SCATTERING
DIELECTRIC-PROPERTIES
RAMAN-SPECTROSCOPY
Ключевые слова (''Своб.индексиров.''): raman scattering--spin and phonon excitations--spin-phonon interaction--antiferromagnetism--magnetic symmetry analysis--two-magnon scattering
Аннотация: A group of recently synthesized orthorhombic Pnma crystals PbMBO4 (M = Cr, Mn, Fe) demonstrates a number of unusual structural and magnetic properties. We report on polarized Raman scattering study of the lattice and magnetic dynamics in single crystals of an antiferromagnet PbFeBO4 below and above T-N = 114 K. Polarization properties of the observed magnetic excitations below T-N as well as intense quasi-elastic scattering support the quasi-one-dimensional character of the magnetic structure of PbFeBO4. Frequency overlapping of magnetic excitations and low-frequency phonons in the range of 90-200 cm-1 leads to pronounced asymmetric anomalies thus confirming intrinsic coupling of magnetic and lattice subsystems. This conclusion is also supported by observation of anomalous temperature behaviour of higher frequency phonons in the vicinity of T-N. Experimental investigations are supported by relevant magnetic symmetry analysis which allows us to explain previously observed anomalous results.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sun S.-J., Hsu, Hua-Shu, Ovchinnikov S. G., Chen G.-L.
Заглавие : Theoretical investigation of magnetic properties in interfaces of magnetic nanoparticles and amorphous carbons
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2017. - Vol. 432. - P.102-105. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2017.02.001
Примечания : Cited References: 21. - We would like to thank the Ministry of Science and Technology, Taiwan, for the Grant No. MOST 104-2112-M-390-001 and 104-2923-M-390-001-MY3 (Shih-Jye Sun). The work is supported also by the President of Russia program of the leading scientific schools, Grant NSh-7559.2016.2.
Ключевые слова (''Своб.индексиров.''): antiferroelectricity--antiferromagnetism--ferromagnetism--molecular dynamics--nanomagnetics--nanoparticles--spin waves--antiferro-magnetic interactions--antiferromagnetics--kondo interactions--magnetic nano-particles--molecular dynamics simulations--spinwave excitation--theoretical investigations--theoretical modeling--amorphous carbon
Аннотация: Based on the experimental finding of the exchange bias in amorphous carbon samples with embedded Co nanoparticles and on the graphited character of the amorphous carbon interface confirmed by molecular dynamics simulations we have proposed the interface of graphited carbon to be antiferromagnetic. A theoretical model, which comprises the Kondo interactions in the interfaces of Co nanoparticles and the induced antiferromagnetic interactions in the graphited carbons, is employed to evaluate the ferromagnetism of the interfaces of Co nanoparticles. We have shown that the ferromagnetism of interfaces of Co nanoparticles will be enhanced by the increase of antiferromagnetic interaction as well as the increase of electron density in the graphited carbons. In particular, we found that the antiferromagnetic interactions in graphited carbons will change the spin-wave excitation in interfaces of Co nanoparticles from the quasiacoustic mode to the quasioptical one. © 2017 Elsevier B.V.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Microscopic derivation of the Ginzburg-Landau equations for the periodic Anderson model in the coexistence phase of superconductivity and antiferromagnetism
Коллективы : Russian Foundation for Basic Research [13-02-00523]; regional Grant Siberia [15-42-04372]; RF Presidential Grant [SP-1370.2015.5]
Место публикации : J. Low Temp. Phys.: Springer/Plenum Publishers, 2016. - Vol. 185, Is. 5-6. - P.439-445. - ISSN 0022-2291, DOI 10.1007/s10909-015-1410-y. - ISSN 1573-7357(eISSN)
Примечания : Cited References:11. - This work was supported in part by the Russian Foundation for Basic Research, Grant No. 13-02-00523 and regional Grant Siberia No. 15-42-04372. A.O.Z. acknowledges the support of RF Presidential Grant No. SP-1370.2015.5.
Предметные рубрики: HUBBARD-MODEL
Ключевые слова (''Своб.индексиров.''): ginzburg-landau equations--superconductivity--antiferromagnetism--coexistence phase--periodic anderson model
Аннотация: On the basis of the periodic Anderson model, the microscopic Ginzburg-Landau equations for heavy-fermion superconductors in the coexistence phase of superconductivity and antiferromagnetism have been derived. The obtained expressions are valid in the vicinity of quantum critical point of heavy-fermion superconductors when the onset temperatures of antiferromagnetism and superconductivity are sufficiently close to each other. It is shown that the formation of antiferromagnetic ordering causes a decrease of the critical temperature of superconducting transition and order parameter in the phase of coexisting superconductivity and antiferromagnetism.
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9.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : The influence of spin and charge fluctuations on the coexistence phase of superconductivity and antiferromagnetism in heavy-fermion Ce-based compounds
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016): abstracts/ ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk: KIP RAS SB, 2016. - Ст.O2.3. - P.136. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Примечания : References: 2. - This study was funded by the Program of SB RAS 0358-2015-0002 and RFBR project No. 16-02-00073-a. A.O.Z. is grateful for support of the Grant of the President of the Russian Federation SP-1370.2015.5.
Ключевые слова (''Своб.индексиров.''): heavy fermions--antiferromagnetism--superconductivity--ginzburg-landau theory
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min V. I., Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Effect of canted antiferromagnetic order on the electronic structure in the t–J* model within the cluster perturbation theory
Место публикации : J. Exp. Theor. Phys.: Maik Nauka-Interperiodica Publishing, 2016. - Vol. 123, Is. 3. - P.511-519. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776116090065
Примечания : Cited References: 50. - We are grateful to V.V. Val’kov for stimulating discussions. This work was supported by the Russian Science Foundation (project no. 14-12-00061)
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--electronic structure--high temperature superconductors--magnetic fields--antiferromagnetic orderings--cluster perturbation theories--electron-doping--external fields--external magnetic field--non-monotonic dependence--short-range correlations--spectral weight--perturbation techniques
Аннотация: The electronic structure in the two-dimensional t–J* model with canted antiferromagnetic order in an external magnetic field has been calculated within the cluster perturbation theory. In zero external field, the evolution of the Fermi surface with n-type doping has been obtained in good agreement with experimental data on cuprate superconductors. It has been shown that the inclusion of short-range correlations can result in a nonmonotonic dependence of the spectral weight distribution at the Fermi level on the external magnetic field. In contrast to the case of electron doping, such changes in the case of hole doping can be expected at experimentally achievable fields. © 2016, Pleiades Publishing, Inc.
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