Библиотека института физики им. Л.В. Киренского СО РАН

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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belskaya N. A., Khrapova E. K., Ivanova A. A., Eremin E. V., Pavlov S. I., Krasilin A. A.
Заглавие : Structure refinement and magnetic properties of synthetic Co3Ge2O5(OH)4 phyllogermanate
Колич.характеристики :7 с
Место публикации : J. Magn. Magn. Mater. - 2023. - Vol. 587. - Ст.171262. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2023.171262. - ISSN 18734766 (eISSN)
Примечания : Cited References: 51. - The authors are grateful to Dr. N.V. Kazak and Dr. A.A. Levin for a lot of fruitful discussions. Magnetisation measurements were carried out in the Common Access Facility Centres of SBRAS (Krasnoyarsk, Russia) X-ray powder diffraction measurements were performed at the Engineering Centre of St. Petersburg State Institute of TechnologyThe study was supported by grant No. 23-22-00245 of the Russian Science Foundation, https://rscf.ru/project/23-22-00245/
Аннотация: Co3Ge2O5(OH)4 relates to a specific group of 1:1 layered compounds with an ability to form either platy or tubular particles depending on chemical composition. Despite successful synthesis and perspective application, there is a lack of information on its crystal structure and magnetic properties, granted by Co ions. Co3Ge2O5(OH)4 phyllogermanate nanoparticles have been obtained using a hydrothermal method and characterised using powder X-ray diffraction and magnetisation measurements. Triclinic symmetry with a 1:P1 space group has been established. The unit cell contains three layers perpendicular to the c crystallographic direction, with 7.6 Å spacing and –b/3 shift of the middle layer. At a low magnetic field of 100 Oe the compound undergoes a magnetic transition at TN=5.2 K. The field of 9 T is not sufficient to take the sample to a magnetically saturated state with an asymptotic magnetic moment of 2.43 μB/Co2+. The estimations of the intralayer and interlayer exchange constants give values of J1/kB=2.75 K and J2/kB=0.25 K, respectively.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Dudnikov V. A., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Features of spin crossovers in magnetic materials
Колич.характеристики :26 с
Место публикации : Phys. Usp. - 2023. - Vol. 66, Is. 7. - P.647-672. - ISSN 10637869 (ISSN), DOI 10.3367/UFNe.2022.05.039195. - ISSN 14684780 (eISSN)
Примечания : Cited References: 237. - The authors thank the Russian Science Foundation for financial support in the framework of project no. 18-12-00022
Аннотация: We present experimental and theoetical results of spin crossover studies in magnetically ordered materials. The effect of spin crossovers on the electronic structure of transition metal oxides and on the Bose condensation of spin excitons in the vicinity of the spin crossover is considered. A new method for calculating the interatomic superexchange interaction in transition metal oxides is discussed that allows considering selective contributions of excited magnetic cation terms. Changes in the exchange interaction sign are predicted for spin crossovers for d5—d7 ions. In the RCoO3 family of rare-earth cobaltites, the ground state is nonmagnetic, but, as the temperature increases, thermal excitations of high-spin states give rise to a number of experimentally detectable features. In defective RCoO3 samples, stabilization of the high-spin term and ferromagnetic ordering are possible. Dynamical crossovers under external pumping and the dynamics of multiplicity, magnetization, and local lattice distortions are discussed. Geophysical implications of spin crossovers are considered, and metallic properties of Earth's mantle at a depth of 1400—1800 km are predicted.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Exchange interaction between the high spin Co3+ states in LaCoO3
Место публикации : Comput. Mater. Sci. - 2022. - Vol. 204. - Ст.111134. - ISSN 09270256 (ISSN), DOI 10.1016/j.commatsci.2021.111134
Примечания : Cited References: 59. - We are thankful to the Russian Science Foundation, Russia for the financial support under the project 18-12-00022
Аннотация: The formation of the exchange interaction between HS Co3+ ions, which are excited in LaCoO3, is studied within the multielectron approach. Two main contributions appear to be antiferromagnetic (AFM) and ferromagnetic (FM). When the ground state is LS, the total interaction is AFM. The crossover to the HS state may result in the FM ordering. The mean-field magnetic phase diagrams on the plane spin gap-temperature have been calculated without and with spin-orbital interaction in the HS term. Without spin-orbital interaction the reentrant magnetic order is possible. The spin-orbital coupling removes the reentrant phase transition and stabilizes the LS state. For known from experimental data values of the spin gap and exchange interaction, the ideal stoichiometric LaCoO3 is very close to the LS–HS crossover and magnetic ordering border. The violations of local coordination and symmetry of the Co3+-oxygen complexes that take place in the intergrain boundaries, at the surface of single crystals, and in the thin films on the strained substrate, may result in the formation of the HS state and FM order for such materials.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kulbakov A. A., Sarkar R., Janson O., Dengre S., Weinhold T., Moshkina E. M., Portnichenko P. Y., Luetkens H., Yokaichiya F., Sukhanov A. S., Eremina R. M., Schlender P., Schneidewind A., Klauss H. -H., Inosov D. S.
Заглавие : Destruction of long-range magnetic order in an external magnetic field and the associated spin dynamics in Cu2GaBO5 and Cu2AlBO5 ludwigites
Место публикации : Phys. Rev. B. - 2021. - Vol. 103, Is. 2. - Ст.024447. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.103.024447
Примечания : Cited References: 46. - We thank U. Nitzsche for technical assistance. This project was funded in part by the German Research Foundation (DFG) under Grant IN 209/9-1, via Project C03 of the Collaborative Research Center SFB 1143 (project-id 247310070) at the TU Dresden, and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490). O.J. was supported by the Leibniz Association through the Leibniz Competition
Аннотация: The quantum spin systems Cu2M′BO5 (M′=Al,Ga) with the ludwigite crystal structure consist of a structurally ordered Cu2+ sublattice in the form of three-leg ladders, interpenetrated by a structurally disordered sublattice with a statistically random site occupation by magnetic Cu2+ and nonmagnetic Ga3+ or Al3+ ions. A microscopic analysis based on density-functional-theory calculations for Cu2GaBO5 reveals a frustrated quasi-two-dimensional spin model featuring five inequivalent antiferromagnetic exchanges. A broad low-temperature 11B nuclear magnetic resonance points to a considerable spin disorder in the system. In zero magnetic field, antiferromagnetic order sets in below TN≈4.1 K and ∼2.4 K for the Ga and Al compounds, respectively. From neutron diffraction, we find that the magnetic propagation vector in Cu2GaBO5 is commensurate and lies on the Brillouin-zone boundary in the (H0L) plane, qm=(0.45,0,−0.7), corresponding to a complex noncollinear long-range ordered structure with a large magnetic unit cell. Muon spin relaxation is monotonic, consisting of a fast static component typical for complex noncollinear spin systems and a slow dynamic component originating from the relaxation on low-energy spin fluctuations. Gapless spin dynamics in the form of a diffuse quasielastic peak is also evidenced by inelastic neutron scattering. Most remarkably, application of a magnetic field above 1 T destroys the static long-range order, which is manifested in the gradual broadening of the magnetic Bragg peaks. We argue that such a crossover from a magnetically long-range ordered state to a spin-glass regime may result from orphan spins on the structurally disordered magnetic sublattice, which are polarized in magnetic field and thus act as a tuning knob for field-controlled magnetic disorder.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Dudnikov V. A., Ovchinnikov S. G.
Заглавие : Forming a dielectric exciton phase in strongly correlated systems with spin crossover
Место публикации : Phys. Rev. B. - 2021. - Vol. 104, Is. 19. - Ст.195103. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.104.195103
Примечания : Cited References: 46. - The authors thank the Russian Scientific Foundation for financial support under Grant No. 18-12-00022
Аннотация: Formation of the magnetic structure and exciton condensate of local magnetic excitons in strongly correlated systems near the spin crossover under high pressure is considered in terms of the effective Hamiltonian obtained from a two-band Hubbard model in the regime of strong electron correlations. The coexistence of the long-range antiferromagnetic order and exciton condensate and the occurrence of the magnetization caused by the condensation of local magnetic excitons are demonstrated. Transformation of the electronic structure of the antiferromagnetic high-spin insulator into the paramagnetic two-band correlated metal via a narrow-gap antiferromagnetic excitonic semiconductor is obtained.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Single-ion weak antiferromagnetism and spin-flop transition in a two-sublattice ferromagnet
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 7. - P.1165-1171. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420070148
Примечания : Cited References: 26. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk krai, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activity, project no. 18-42-240008 “Effect of the Magnetic Structure on the Magnetodielectric Properties of Oxide Crystallites Containing Stereoactive Pb 2+ and Bi 3+ Ions”
Аннотация: The ground state of a Heisenberg ferromagnet with the noncollinear single-ion anisotropy axes of two magnetic sublattices has been investigated in an external magnetic field applied in the anisotropy axes plane. Noncollinearity of the sublattice local anisotropy axes leads to a new effect called the orientational first-order spin-flop phase transition. The transition field depends on the single-ion anisotropy value and sublattice local axes orientation. An analysis of the stability of magnetic states shows that the transition is accompanied by the hysteretic field dependence of the magnetization. The dependences of the spin-flop transition field, magnetization jump, and susceptibility on the single-ion anisotropy value and axes orientation have been determined. The results obtained are used to explain the field dependence of the magnetization in the PbMnBO4 ferromagnetic crystal.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Belskaya N. A., Moshkina E. M., Bezmaternykh L. N., Vasiliev A. D., Sofronova S. N., Eremina R. M., Eremin E. V., Muftakhutdinov A. R., Cherosov M. A., Ovchinnikov S. G.
Заглавие : Antiferromagnetism of the cation-ordered warwickite system Mn2-xMgxBO4 (x=0.5, 0.6 and 0.7)
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [20-02-00559]; Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science to the research project [18-42243007]
Место публикации : J. Magn. Magn. Mater. - 2020. - Vol. 507. - Ст.166820. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2020.166820. - ISSN 1873-4766(eISSN)
Примечания : Cited References: 39. - The reported study was funded by the Russian Foundation for Basic Research (no. 20-02-00559), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project. 18-42243007.
Предметные рубрики: SPIN-GLASS BEHAVIOR
CRYSTAL-STRUCTURES
SINGLE-CRYSTALS
INSIGHTS
MGFEBO4
Аннотация: X-ray diffraction, heat capacity and magnetic measurements are performed on single crystals of Mn2-xMgxBO4 (x = 0.5, 0.6 and 0.7) with the warwickite structure. The monoclinic symmetry is found for all samples with the space group P21/n. The M1 site is occupied by trivalent Mn ions while the M2 site is occupied by a mixture of divalent Mg and Mn ions. Regular cation and charge distributions are observed, which is unusual for heterometallic warwickites. The local octahedral distortions of M1O6 show the monotonic dependence on the Mg content and are in accordance with the Jahn-Teller distortion. All samples are found to undergo long-range antiferromagnetic ordering with rather low transition temperatures of TN = 16, 14 and 13 K for x = 0.5, 0.6, and 0.7, respectively. The ordering of local octahedral distortions, caused by the strong electron-phonon interaction of the trivalent Mn ions, is proposed to stabilise the cationic ordering and, as a result, the long-range magnetic ordering in the material.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Eremina R. M., Moshkina E. M., Gavrilova T. P., Muftakhutdinov A. R., Gilmutdinov I. F.
Заглавие : Investigation of the Magnetic Properties of Warwickite Mn0.89Mg1.11BO4
Место публикации : Bull. Russ. Acad. Sci. Phys. - 2019. - Vol. 83, Is. 7. - P.792-794. - ISSN 10628738 (ISSN), DOI 10.3103/S106287381907013X
Примечания : Cited References: 3. - This work was supported by the Russian Foundation for Basic Research; the Administration of Krasnoyarsk Krai; and the Krasnoyarsk Krai Science Foundation, project no. 18-42-243007.
Аннотация: The temperature dependences of the magnetic susceptibility in magnetic fields applied parallel and perpendicular to axis с of a Mn0.89Mg1.11BO4 single crystal were measured. Spin ordering typical of an antiferromagnetic with an easy magnetization axis was observed below 16 K. The Dzyaloshinskii–Moriya interaction between spins of manganese ions in Mn0.89Mg1.11BO4 was estimated by analyzing the EPR linewidth. © 2019, Allerton Press, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golosovsky I. V., Vasilev A. I., Mukhin A. A., Ressouche E., Skumryev V., Urcelay-Olabarria I., Gudim I. A., Bezmaternykh L. N.
Заглавие : Complex magnetic order in the Nd(Tb)Fe3(BO3)4 multiferroic revealed by single-crystal neutron diffraction
Место публикации : Phys. Rev. B. - 2019. - Vol. 99, Is. 13. - Ст.134439. - ISSN 24699950 (ISSN) , DOI 10.1103/PhysRevB.99.134439
Примечания : Cited References: 33. - This work was supported by the Russian Grant No. RFBR 16-02-00058. A.A.M. acknowledges the financial support from the Russian Science Foundation (16-12-10531).
Аннотация: Magnetic structure of the substituted multiferroics-ferroborates Nd0.9Tb0.1Fe3(BO3)4 and Nd0.8Tb0.2Fe3(BO3)4 were determined in the framework of a self-consistent refinement of the single crystal neutron diffraction data. The small substitution of Nd for Tb leads to the reorientation of the main antiferromagnetic vector L from the basal plane towards the hexagonal axis. The reorientation takes place via an angular structure for which L does not coincide with the principal crystallographic directions and evolves with temperature due to competing magnetic anisotropies of Fe, Nd, and Tb subsystems. Our refinement at 2 K reveals the existence of distortions in the collinear antiferromagnetic Fe spin arrangement suggested before in other ferroborates. Therefore, besides the main antiferromagnetic vector L, the magnetic structure involves additional fine symmetrized combinations of spin components allowed by symmetry. They coexist with certain L components and could originate from the antisymmetric Dzyaloshinsky-Moriya Fe-Fe exchange interactions. At higher temperatures, the magnetic structure is described by the simple collinear model, where the L vector is deviated from the hexagonal plane. © 2019 American Physical Society.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Magnetic properties and spin crossover in transition metal oxides with d5 Ions at high pressures
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 129, Is. 6. - P.1062-1069. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776119120185
Примечания : Cited References: 33. - This study was supported by the Russian Science Foundation (project no. 18-12-00022)
Аннотация: We analyze the influence of cooperative effects on the magnetic properties and spin crossover between the high-spin (HS) term S = 5/2 and low-spin (LS) term S = 1/2 in Mott–Hubbard dielectrics with 3d5 ions under high pressures. Two cooperation mechanisms (superexchange interaction and effective interaction via the elastic system) are considered. The sign of the exchange interaction changes because of the crossover from the antiferromagnetic in the HS state to the ferromagnetic in the LS state. In view of the large difference between the ionic radii of the HS and LS states, the systems with spin crossover acquire an additional strong coupling via the elastic system. Using the Hubbard operator representation and considering the electronic states of the two terms simultaneously, we obtain the effective Hamiltonian with allowance for the cooperative effects. The magnetic phase diagram and the spin crossover are investigated in the mean field approximation. It is shown that the inclusion of cooperative effects at low temperatures leads to a first-order phase transition between the antiferromagnetic HS state and the ferromagnetic LS state. At higher temperatures, more complicated sequences of phase transitions are possible upon an increase in pressure, including the HS paramagnet–HS antiferromagnet–LS paramagnet and HS antiferromagnet–LS paramagnet–LS ferromagnet transitions.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Andryushin N. D., Zinenko V. I., Pavlovskii M. S., Shinkorenko A. S.
Заглавие : Calculation and Comparison of Electronic, Vibrational, Polarization, and Magnetic Properties of Double Perovskites CaMnTi2O6 and CaFeTi2O6
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 129, Is. 6. - P.1036-1044. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776119110013
Примечания : Cited References: 18. - This work was supported by the Russian Foundation for Basic Research (project no. 18-02-00130-a)
Аннотация: Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of “column” ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P42/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P42/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is Ps = 25 μC/cm2. The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nemtsev A. V., Zhandun V. S., Zinenko V. I.
Заглавие : Ab initio study of the polarization, electronic, magnetic, and optical properties of perovskite SrMO3 (M = Fe, Mn) crystals and thin films containing magnetic ions
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 126, Is. 4. - P.497-505. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776118030056
Примечания : Cited References: 30
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--density functional theory--electronic properties--iron compounds--manganese compounds--optical properties--perovskite--perovskite solar cells--polarization--strontium compounds
Аннотация: The magnetic, electronic, and polarization properties of the SrFeO3 and SrMnO3 compounds with a perovskite structure are calculated using the density functional theory in the bulk and thin-film states. A ferroelectric instability is found to be absent in the bulk state, and the polar mode is softened in the thin-film state of SrMnO3 in the presence of tensile stresses in the substrate. As a result, a polar phase with a polarization of 23 μC/cm2 appears, which agrees with experimental data. The study of the magnetic and electronic properties demonstrates the existence of G-type antiferromagnetic ordering in SrMnO3 and the appearance of a dielectric gap of about 1.5 eV in its thin film. A ferromagnetic phase with metallic conduction in both the bulk and thin-film states is detected in SrFeO3.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Superexchange interaction in magnetic insulators with spin crossover
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 127, Is. 4. - P.713-720. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776118100023
Примечания : Cited References: 34. - This work was supported by the Russian Science Foundation (project no. 18-12-00022).
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--ground state--high pressure engineering--ions--iron compounds--magnetic materials
Аннотация: We present the derivation of a microscopic superexchange Hamiltonian for undoped magnetic insulators with an arbitrary spin. It is established that the sign of the (ferromagnetic or antiferromagnetic) superexchange between magnetic ions in the dn configuration depends on the spin nature of virtual multielectron states dn± 1, viz., low-spin or high-spin partners with S ± 1/2 relative to ground state of the dn configuration with spin S. A macroscopic substantiation is given for the Goodenough–Kanamori rules and simple mean-field estimates connecting the magnetic ordering temperature with the exchange constant. The conventional Anderson superexchange for magnetic materials with spin S = 1/2 and the P/T magnetic phase diagram for ferroborate FeBO3 with spin crossover S = (5/2 ↔ 1/2) at the Fe3+ ion under a high pressure are also reproduced as a test.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bykov A. A., Zobkalo I. A., Dubrovskii A. A., Smirnov O. P., Nikitin S. E., Terent'ev K. Yu., Gavrilov S. V., Shaikhutdinov K. A.
Заглавие : Two-dimensional antiferromagnetic correlations in an La1.4Sr1.6(Mn0.9Co0.1)2O7 single crystal
Место публикации : J. Exp. Theor. Phys.: Maik Nauka-Interperiodica Publishing, 2017. - Vol. 124, Is. 5. - P.786-791. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776117050120
Примечания : Cited References: 20
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--cobalt--cobalt compounds--lanthanum compounds--magnetization--magnetostriction--antiferromagnetic correlations--bi-layer--ferromagnetic orderings--field dependence--lanthanum manganites--single-crystal neutron diffraction--single crystals
Аннотация: The temperature and field dependences of the magnetization, the electrical resistivity, and the magnetostriction of bilayer lanthanum manganite La1.4Sr1.6Mn2O7 single crystals and cobalt-doped La1.4Sr1.6(Mn0.9Cu0.1)2O7 are measured. The magnetostriction of the cobalt-doped compound increases as compared to the initial La1.4Sr1.6Mn2O7 compound, and the magnetization and the magnetoresistance of the former compound change substantially. Powder and single-crystal neutron diffraction patterns are used to detect ferromagnetic ordering in La1.4Sr1.6(Mn0.9Co0.1)2O7 at a temperature below TC ~ 45(2) K, and this ordering coexists with antiferromagnetic correlations, which develop at temperatures below TC ~ 80(5) K. © 2017, Pleiades Publishing, Inc.
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15.

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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16.

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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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Manifestation of spin-charge fluctuations in the spectral and thermodynamic properties of quasi-two-dimensional rare-earth intermetallic compounds
Коллективы : RFBR [16-02-00073-a, 15-42-04372-r-Siberia-a]; Government of the Krasnoyarsk Region; Regional Science Foundation [07/16]; Integrated program II.2P of SB RAS [0358-2015-0002]; Presidential scholarships for young PhDs [SP-1370.2015.5]
Место публикации : Low Temp. Phys.: American Institute of Physics, 2017. - Vol. 43, Is. 2. - P.191-199. - ISSN 1063-777X, DOI 10.1063/1.4977211. - ISSN 1090-6517(eISSN)
Примечания : Cited References:35. - This work was supported by RFBR (Grants Nos. 16-02-00073-a and 15-42-04372-r-Siberia-a), the Government of the Krasnoyarsk Region and the Regional Science Foundation (Ext. Agreement No. 07/16), as well as the Integrated program II.2P of SB RAS (Project No. 0358-2015-0002). One of the authors (A.O.Z.) acknowledges the support by the Presidential scholarships for young PhDs (SP-1370.2015.5).
Предметные рубрики: PERIODIC ANDERSON MODEL
INTERMEDIATE-VALENCE COMPOUNDS
MAGNETIC PHASE-DIAGRAM
HEAVY
SUSCEPTIBILITY
APPROXIMATION
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
LATTICE
METALS
Аннотация: In the framework of the modified periodic Anderson model with exchange interaction in the subsystem of localized states, it is shown that spin-charge fluctuations in quasi-two-dimensional intermetallic compounds with rare-earth ions in the mixed valence state significantly affect both the spectrum of magnetic excitations and the conditions at which the antiferromagnetic phase is realized. The spectral characteristics of the phase were obtained by the method of the diagram technique for Hubbard operators in the one-loop approximation, which allows to account for the spincharge fluctuation contributions to the components of the mass and the force operators. The developed theory allowed to quantitatively describe the pressure dependence of the Neel temperature observed in a quasi-two-dimensional antiferromagnetic heavy-fermion intermetallic compound CeRhIn5. Published by AIP Publishing.
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18.

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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19.

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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20.

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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