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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Krasikov A. A., Popkov S. I., Balaev A. D., Shaikhutdinov K. A., Kirillov V. L., Mart'yanov O. N.
Заглавие : Magnetic properties of NiO nano particles: Contributions of the antiferromagnetic and ferromagnetic subsystems in different magnetic field ranges up to 250 kOe
Коллективы : Russian Foundation for Basic Research; Government of the Krasnoyarsk Territory; Krasnoyarsk Territorial Foundation [17-42-240138]
Место публикации : Phys. Solid State. - 2017. - Vol. 59, Is. 8. - P.1547-1552. - ISSN 1063-7834, DOI 10.1134/S1063783417080029. - ISSN 1090-6460(eISSN)
Примечания : Cited References:40. - This study was supported by the Russian Foundation for Basic Research, Government of the Krasnoyarsk Territory, and Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activity, project no. 17-42-240138.
Предметные рубрики: EXCHANGE-BIAS
FERRIHYDRITE NANOPARTICLES
HYSTERESIS ANOMALIES
OXIDE
Аннотация: The magnetic properties of antiferromagnetic NiO nanoparticles prepared by thermal decomposition of nickel hydroxocarbonate are investigated. According to the data of magnetization measurements in fields of up to 250 kOe, the magnetic moment linearly grows in strong fields, which is caused by the contribution of the antiferromagnetically ordered nanoparticle core, and the antiferromagnetic susceptibility corresponds to that of bulk polycrystalline NiO. This allowed the antiferromagnetic and ferromagnetic contributions to the total magnetic response of a sample to be quantitatively determined. The latter occurs due to the incomplete spin compensation in an antiferromagnetic nanoparticle caused by defects on its surface. It is demonstrated that to correctly determine the superparamagnetic blocking temperature, it is necessary to take into account the antiferromagnetic susceptibility of the particle core.
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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. - 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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Popkov S. I., Krasikov A. A., Balaev A. D., Dubrovskiy A. A., Stolyar S. V., Yaroslavtsev R. N., Ladygina V. P., Iskhakov R. S.
Заглавие : Temperature behavior of the antiferromagnetic susceptibility of nanoferrihydrite from the measurements of the magnetization curves in fields of up to 250 kOe
Коллективы : Russian Foundation for Basic Research; Government of Krasnoyarsk region; Krasnoyarsk Regional Foundation of Supporting the Scientific and Scientific-Engineering Activity in the framework of the scientific projects [17-42-240138, 17-43-240527]
Место публикации : Phys. Solid State. - 2017. - Vol. 59, Is. 10. - P.1940-1946. - ISSN 1063-7834, DOI 10.1134/S1063783417100031. - ISSN 1090-6460(eISSN)
Примечания : Cited References:45. - This work was supported by the Russian Foundation for Basic Research, the Government of Krasnoyarsk region, the Krasnoyarsk Regional Foundation of Supporting the Scientific and Scientific-Engineering Activity in the framework of the scientific projects nos. 17-42-240138 and 17-43-240527.
Предметные рубрики: FERRIHYDRITE NANOPARTICLES
BACTERIAL FERRIHYDRITE
HYSTERESIS
Аннотация: The cross-breeding problem of the temperature dependence of the antiferromagnetic susceptibility of ferrihydrite nanoparticles is considered. Iron ions Fe3+ in ferrihydrite are ordered antiferromagnetically; however, the existence of defects on the surface and in the bulk of nanoparticles induces a noncompensated magnetic moment that leads to a typical superparamagnetic behavior of ensemble of the nanoparticles with a characteristic blocking temperature. In an unblocked state, magnetization curves of such objects are described as a superposition of the Langevin function and the linear-in-field contribution of the antiferromagnetic “core” of the nanoparticles. According to many studies of the magnetization curves performed on ferrihydrite (and related ferritin) nanoparticles in fields to 60 kOe, dependence χAF(T) decreases as temperature increases, which was related before to the superantiferromagnetism effect. As the magnetic field range increases to 250 kOe, the values of χAF obtained from an analysis of the magnetization curves become lower in magnitude; however, the character of the temperature evolution of χAF is changed: now, dependence χAF(T) is an increasing function. The latter is typical for a system of AF particles with random orientation of the crystallographic axes. To correctly determine the antiferromagnetic susceptibility of AF nanoparticles (at least, ferrihydrite) and to search for effects related to the superantiferromagnetism effect, it is necessary to use in experiments the range of magnetic field significantly higher than that the standard value 60 kOe used in most experiments. The study of the temperature evolution of the magnetization curves shows that the observed crossover is due to the existence of small magnetic moments in the samples.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Balaev D. A.
Заглавие : Peculiarities of magnetic properties of antiferromagnetic nanoparticles
Коллективы : Federal Research Center KSC SB RAS, Kirensky Institute of Physics, Research Institute of Agriculture and Ecology of the Arctic, Siberian Federal Univercity, International school-workshop on actual problems of condensed matter physics
Место публикации : International school/workshop on actual problems of condensed matter physics: Program. Book of abstracts/ ed. S. G. Ovchinnikov. - 2018. - P.9. - ISBN 978-5-904603-08-3
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Platunov M. S., Knyazev Yu. V., Moshkina E. M., Gavrilkin S. Yu., Bayukov O. A., Gorev M. V., Pogoreltsev E. I., Zeer G. M., Zharkov S. M., Ovchinnikov S. G.
Заглавие : Fe-induced enhancement of antiferromagnetic spin correlations in Mn2−xFexBO4
Место публикации : J. Magn. Magn. Mater. - 2018. - Vol. 452. - P.90-99. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2017.12.037
Примечания : Cited References: 34. - This study was supported in part by the grants of: The Council for Grants of the President of the Russian Federation (project nos. SP-938.2015.5, NSh-7559.2016.2), the Russian Foundation for Basic Research (project nos. 16-32-60049 mol_a_dk, 16-32-00206 mol_a, 17-02-00826-a, 16-32-50058). The magnetic measurements were carried out in the Shared Facility Centre of P. N. Lebedev Physical Institute of RAS.
Ключевые слова (''Своб.индексиров.''): sro spin correlations--spin-glass--rehac--magnetic frustrations
Аннотация: Fe substitution effect on the magnetic behavior of Mn2−xFexBO4 (x = 0.3, 0.5, 0.7) warwickites has been investigated combining Mössbauer spectroscopy, dc magnetization, ac magnetic susceptibility, and heat capacity measurements. The Fe3+ ions distribution over two crystallographic nonequivalent sites is studied. The Fe introduction breaks a long-range antiferromagnetic order and leads to onset of spin-glass ground state. The antiferromagnetic short-range-order spin correlations persist up to temperatures well above TSG reflecting in increasing deviations from the Curie-Weiss law, the reduced effective magnetic moment and “missing” entropy. The results are interpreted in the terms of the progressive increase of the frustration effect and the formation of spin-correlated regions.
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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. - 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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Pchelkina Z. V., Nekrasov I. A., Ovchinnikov S. G.
Заглавие : Pressure effect on the energy structure and superexchange interaction in undoped orthorhombic La2CuO4
Место публикации : Int. J. Mod. Phys. B. - 2016. - Vol. 30, Is. 25. - ISSN 02179792 (ISSN), DOI 10.1142/S0217979216501800
Ключевые слова (''Своб.индексиров.''): antiferromagnetic la214--pressure--superexchange interaction
Аннотация: We studied the pressure dependences of the electronic structure and superexchange interaction J(P)=JA−JB (where JA and JB are antiferromagnetic (AFM) and ferromagnetic (FM) contributions) in antiferromagnetic La214 under hydrostatic, uniaxial (along c-axial) 3% compressions and 1% in-plane compressions by the local density approximation with generalized tight-binding method (LDA + GTB cell approach). The changes in J(P) correlated with the experimentally known TC(P) dependence are in accordance with the relation dTC/dP=(∂TC/∂J)(∂J/∂P), where ∂TC/∂J∼0.1. The in-plane pressure more effectively stabilizes the ground singlet two-hole state A1 than the simple hydrostatic pressure, its effect on J and TC is the largest. Within the same cell approach together with the superexchange interaction J(P), the valence band structure was calculated. Its changes with pressure clearly reproduce the k-distribution of the singlet and triplet quasi-particles over the Brillouin zone (BZ).
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Boldyrev K. N., Stanislavchuk T. N., Sirenko A. A., Kamenskyi D., Bezmaternykh L. N., Popova M. N.
Заглавие : Bifurcations of coupled electron-phonon modes in an antiferromagnet subjected to a magnetic field
Место публикации : Phys. Rev. Lett. - 2017. - Vol. 118, Is. 16. - Ст.167203. - ISSN 00319007 (ISSN), DOI 10.1103/PhysRevLett.118.167203
Примечания : Cited References: 26. - This research was supported by the Russian Scientific Foundation under Grant No. 14-12-01033, the President of Russian Federation (MK-3577.2017.2, K. N. B.), and the U.S. Department of Energy under Grant No. DE-FG02-07ER46382 (experiments at U4-IR beam line NSLS-BNL, T. N. S. and A. A. S.). The National Synchrotron Light Source is operated as a user facility for the U.S. Department of Energy under Contract No. DE-AC02-98CH10886. Part of this work was supported by EMFL (Contract No. 26211). M. N. P. thanks B. Z. Malkin and A. V. Popov for helpful discussions.
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--bifurcation (mathematics)--electron-phonon interactions--electrons--magnetic fields--magnetism--temperature--antiferromagnetic crystals--bifurcation points--electron phonon couplings--electronic excitation--external magnetic field--field independents--low temperatures--reflection spectra--phonons
Аннотация: We report on a new effect caused by the electron-phonon coupling in a stoichiometric rare-earth antiferromagnetic crystal subjected to an external magnetic field, namely, the appearance of a nonzero gap in the spectrum of electronic excitations in an arbitrarily small field. The effect was registered in the low-temperature far-infrared (terahertz) reflection spectra of an easy-axis antiferromagnet PrFe3(BO3)4 in magnetic fields Bext-c. Both paramagnetic and magnetically ordered phases (including a spin-flop one) were studied in magnetic fields up to 30 T, and two bifurcation points were observed. We show that the field behavior of the coupled modes can be successfully explained and modeled on the basis of the equation derived in the framework of the theory of coupled electron-phonon modes, with the same field-independent electron-phonon interaction constant |W|=14.8 cm-1. © 2017 American Physical Society.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Influence of antiferromagnetic ordering on the band structure of La2CuO4
Место публикации : J. Exp. Theor. Phys. - 2011. - Vol. 80, Is. 3. - P451. - ISSN 1063-7761
Примечания : Cited References: 40. - We thank the Scientific Council for High-T, Superconductivity for financially supporting the present research as
Аннотация: The band structure of the antiferromagnetic phase of La2Cu04 has been calculated in the generalized tight-binding approximation with consideration of the strong electron correlations in the CuO, layers. It has been shown that the magnetic moment of the sublattice forms as a result of redistribution of the partial spin-up and spin-down densities of states without splitting into energy sublevels. The quasiparticle dispersion law near the bottom of the conduction band is consistent with the result obtained in the t-J model. The changes in the photoemission and inverse photoemission spectra upon the transition from the paramagnetic phase to the antiferromagnetic phase have been predicted. The available experimental data on photoemission from the La2Cu04 valence band are in qualitative agreement with our results. O 1995 American Institute of Physics.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sofronova S. N., Nazarenko I. I.
Заглавие : Ludwigites: From natural mineral to modern solid solutions
Место публикации : Cryst. Res. Technol. - 2017. - Vol. 52, Is. 4. - Ст.1600338. - ISSN 02321300 (ISSN), DOI 10.1002/crat.201600338
Примечания : Cited References: 60. - This study was supported by Russian Foundation for Basic Research (RFBR) and Government of Krasnoyarsk Territory according to the research project No. 17-42-240338.
Ключевые слова (''Своб.индексиров.''): ludwigites--ferrimagnetic--antiferromagnetic--spin-glass--oxyborates
Аннотация: Ludwigites is a type of oxyborates compounds with BO3 groups, which have low-dimensional elements: stairs, zigzag walls, tapes. Such structural features influence on the physical properties of the compounds and cause charge ordering, the existence of two magnetic subsystems, ordered at different temperatures in the perpendicular direction, the quasi-one-dimensional magnetism, spin-glass state. In this survey, we have summarized all known experimental and theoretical studies and analyzed the proposed by the authors mechanisms of phase transitions in the ludwigite structure oxyborates. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Eremina R. M., Moshkina E. M., Muftakhutdinov A. R., Gilmutdinov I. F., Lyadov N. M.
Заглавие : Magnetic properties of the warwickite MnMgBO4
Место публикации : Solid State Commun. - 2019. - Vol. 290. - P.64-66. - ISSN 00381098 (ISSN) , DOI 10.1016/j.ssc.2018.12.019
Примечания : Cited References: 13. - This work was carried out with the financial support of the RFBR , the government of the Krasnoyarsk Region, the Krasnoyarsk Regional Fund of Science and Technology Support in the framework of the scientific project 18 - 42 - 243007 . The work of GIF was funded by a subsidy allocated to Kazan Federal University for state assignments in the sphere of scientific activities (project No. 3.8138.2017/8.9).
Ключевые слова (''Своб.индексиров.''): warwickite--short range order--antiferromagnetic--frustration
Аннотация: Magnetic properties of a new single crystal MnMgBO4 have been studied. It was determined that below 16 K antiferromagnet spin order was observed with the axis of easy magnetization along the c axis crystal. The short antiferromagnetic range order was observed below 100 K. The Curie–Weiss temperature has been determined in single crystal MnMgBO4 as θCW = −98 K and the frustration parameter has been estimated as 6.125.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisova E. A., Komogortsev S. V., Iskhakov R. S., Chekanova L. A., Kalinin Yu. E., Sitnikov A. V.
Заглавие : Spin-wave spectroscopy and magnetostructural studies of Co nanogranular composites
Коллективы : International Symposium on Physics of Materials
Место публикации : Acta Phys. Pol. A. - 2018. - Vol. 134: Proceedings of International Symposium on Physics of Materials (ISPMA 14), Is. 3. - P.623-626. - ISSN 0587-4246, DOI 10.12693/APhysPolA.134.623. - ISSN 1898-794X eISSN
Примечания : Cited References: 25. - This work was supported by RFBR grants nos. 16-03-00256, 16-03-00969.
Предметные рубрики: Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances
Spin-wave resonance
Magnetic anisotropy
Аннотация: Nanogranular Co-SiO2, and Co-CaF2 films are investigated using ferromagnetic resonance and magnetic measurements. The spectrum of standing spin-wave has been registered in the perpendicular experiment configuration for all types of films with the magnetic granules content above 52 vol.%. The dependences of resonance fields Hr of spin modes on the mode number squared Hr(n2) are non-linear. Such behavior is supposed to be the result of the fluctuations of magnetic parameters (the magnetization and the ferromagnetic exchange coupling) in nanocomposite films. A comparison between the magnetic properties of Co-SiO2 granular films and Co-CaF2 films is carried out. The surface anisotropy value Ks of Co-SiO2 films is evaluated from the surface resonance modes of spin-wave resonance spectra as 3.5×10-4s7×10-4 J/m2. The magnetic anisotropy of Co100-x(SiO2)x, Co100-x(CaF2)x films (34s and the surface magnetic anisotropy of films Ks are determined. It is found that surface anisotropy of granules is predominant.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Balaev D. A., Nikitin S. E., Freydman A. L., Krasikov A. A., Balaev A. D., Popkov S. I., Kolkov M. I.
Заглавие : Magnetic and thermodynamic properties and spin-flop-driven magnetodielectric response of the antiferromagnetic Pb2Fe2Ge2O9 single crystals
Коллективы : Russian Foundation for Basic Research [16-02-00563]; RFBR; Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science [18-42-240008]; International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM)
Место публикации : J. Magn. Magn. Mater. - 2019. - Vol. 479. - P.114-120. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2019.02.026. - ISSN 1873-4766(eISSN)
Примечания : Cited References: 23. - This study was supported by the Russian Foundation for Basic Research, project no. 16-02-00563; the reported study was also funded by RFBR and the Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science, to the research project no. 18-42-240008 "Effect of magnetic structure on the magnetodielectric properties of oxide crystals containing stereoactive ions Pb2+ and Bi3+". S.E.N. acknowledges the support of the International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM).
Предметные рубрики: FERROMAGNETISM
TRANSITION
Аннотация: Orthorhombic Pb2Fe2Ge2O9 antiferromagnetic single crystals have been synthesized by a modified pseudo-flux technique and their magnetic, thermodynamic, and magnetodielectric properties have been investigated. It has been found that, below the Ned temperature (45.2 K), iron moments are arranged in a canted antiferromagnetic structure with a weak ferromagnetic moment parallel to the a axis. According to the specific heat measurement data, the T-N value remains invariable in applied magnetic fields of up to 50 kOe within the experimental accuracy. The magnetic entropy in the investigated crystals attains 2Rln(2S + 1) right above T-N, which is indicative of a purely magnetic nature of the transition. It has been shown that the weak ferromagnetic moment is induced by the interplay between the single-ion anisotropy and antisymmetric Dzyaloshinskii-Moriya exchange interaction, with the latter contribution being dominant. It has been established from the angular dependences of the magnetization in three orthorhombic planes that the symmetries of the magnetic and crystal structure are identical. The magnetodielectric properties of the Pb2Fe2Ge2O9 single crystals have been studied at different mutual orientations of the electric and magnetic fields. The most prominent anomalies have been observed in the vicinity of the spin-flop transition in a magnetic field applied along the c axis.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gnatchenko S. L., Kachur I. S., Kurnosov V. S., Piryatinskaya V. G., Malakhovskii A. V., Gudim I. A.
Заглавие : Specific features of Nd3+ Kramers doublets' splitting in an antiferromagnetic crystal NdFe3(BO3)4 in an external magnetic field
Место публикации : Low Temp. Phys. - 2019. - Vol. 45, Is. 8. - P.928-933. - ISSN 1063777X (ISSN), DOI 10.1063/1.5116545
Примечания : Cited References: 27. - A. V. Malakhovskii is grateful for the financial support provided by the RFBR Grant No. 19-02-00034.
Аннотация: The optical absorption spectra of an easy-plane NdFe3(BO3)4 antiferromagnet are measured in the region of the 4I9/2 → 2H11/2 transition of the of Nd3+ ion. The study is performed in the 2-35 K temperature range, in external magnetic fields of up to 65 kOe directed both along the C3 axis and the basal plane of the crystal. The splitting values of the Nd3+ excited states in the exchange field of the Fe3+ subsystem and the g-factors of the 2H11/2 multiplet states are determined. The nontrivial dependences of the splitting of some Nd3+ states in a magnetic field indicate that these states have anisotropic Fe-Nd exchange interaction. © 2019 Author(s).
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popkov S. I., Krasikov A. A., Velikanov D. A., Kirillov V. L., Martyanov O. N., Balaev D. A.
Заглавие : Formation of the magnetic subsystems in antiferromagnetic NiO nanoparticles using the data of magnetic measurements in fields up to 250 kOe
Место публикации : J. Magn. Magn. Mater. - 2019. - Vol. 483. - P.21-26. - ISSN 03048853 (ISSN) , DOI 10.1016/j.jmmm.2019.03.004
Примечания : Cited References: 76. - We are grateful S.V. Semenov and A.A. Dubrovskiy for their help, S.V. Komogortsev and A.D. Balaev for fruitful discussions, and M.N. Volochaev for the TEM measurements. The TEM investigations were carried out on the equipment of the Center of Collective Use of the Federal Research Center “Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences”.The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science, to the research project: «Magnetic reversal of magnetic nanoparticles in strong pulsed magnetic fields - a new approach to the study of dynamic effects associated with the magnetization of magnetic nanoparticles» (project no. 18-42-240012).
Ключевые слова (''Своб.индексиров.''): antiferromagnetic nanoparticle--external magnetic field--low temperature regions--magnetic subsystems--magnetically actives--magnetization curves--paramagnetic subsystems--pulsed magnetic fields--magnetic bubbles
Аннотация: It is well-known that the fraction of surface atoms and the number of defects in an antiferromagnetic particle increase with a decrease in the particle size to tens of nanometers, which qualitatively changes the properties of the particle. Specifically, in antiferromagnetic nanoparticles, spins in the ferromagnetically ordered planes can partially decompensate; as a result, an antiferromagnetic particle acquires a magnetic moment. As a rule, uncompensated chemical bonds of the surface atoms significantly weaken the exchange coupling with the antiferromagnetic particle core, which can lead to the formation of an additional magnetic subsystem paramagnetic at high temperatures and spin-glass-like in the low-temperature region. The existence of several magnetic subsystems makes it difficult to interpret the magnetic properties of antiferromagnetic nanoparticles. It is shown by the example of NiO nanoparticles with an average size of 8 nm that the correct determination of the contributions of the magnetic subsystems forming in antiferromagnetic nanoparticles requires magnetic measurements in much stronger external magnetic fields than those commonly used in standard experiments (up to 60–90 kOe). An analysis of the magnetization curves obtained in pulsed magnetic fields up to 250 kOe allows one to establish the contributions of the uncompensated particle magnetic moment μun, paramagnetic subsystem, and antiferromagnetic particle core. The μun value obtained for the investigated NiO particles is consistent with the Néel model, in which μun ∼ N1/2 (N is the number of magnetically active atoms in a particle), and thereby points out the existence of defects on the surface and in the bulk of a particle. It is demonstrated that the anomalous behavior of the high-field susceptibility dM/dH of antiferromagnetic NiO nanoparticles, which was observed by many authors, is caused by the existence of a paramagnetic subsystem, rather than by the superantiferromagnetism effect.
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Abramova G. M., Gerasimova J. V., Kolesov B., Zhandun V. S., Molokeev M. S., Zharkov S. M., Vtyurin A. N.
Заглавие : The magnon mode in Raman spectra of the antiferromagnetic α-MnS
Коллективы : Российская академия наук, Физико-технический институт им. А.Ф. Иоффе РАН, "Spin Waves", International Symposium
Место публикации : International Symposium "Spin Waves 2018": Program. - 2018. - Sec. 3: Magnonics and propagation of spin waves. - 3-1
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bludov A. N., Pashchenko V. A., Kobets M. I., Bedarev V. A., Merenkov D. N., Gnatchenko S. L., Gudim I. A.
Заглавие : Antiferromagnetic resonance in crystalline PrFe3(BO3)4
Место публикации : Low Temp. Phys. - 2018. - Vol. 44, Is. 2. - P.139-143. - ISSN 1063-777X, DOI 10.1063/1.5020909. - ISSN 1090-6517(eISSN)
Примечания : Cited References: 18
Аннотация: Experimental AFMR studies of crystalline PrFe3(BO3)4 over a wide frequency range of 10–143 GHz at a temperature of 4.2 K have been carried out. The high-frequency properties of praseodymium ferroborate are well described in terms of a model of a two-sublattice antiferromagnet with an “easy axis” anisotropy. An energy gap of 134.3 ± 0.5 GHz is determined and the magnitude of the effective magnetic anisotropy field is estimated to be 1.9 ± 0.1 kOe. An analysis indicates that the spin-orientational phase transition in this compound is a first order transition.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikitin S. E., Wu L. S., Sefat A. S., Shaykhutdinov K. A., Lu Z., Meng S., Pomjakushina, E., V, Conder K., Ehlers G., Lumsden M. D., Kolesnikov, A., I, Barilo S., Guretskii S. A., Inosov D. S., Podlesnyak A.
Заглавие : Decoupled spin dynamics in the rare-earth orthoferrite YbFeO3: Evolution of magnetic excitations through the spin-reorientation transition
Коллективы : US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division; German Research Foundation (DFG) [SFB 1143]; International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM); Laboratory Directed Research and Development Program of Oak Ridge National Laboratory; BFFR [F18KI-022]
Место публикации : Phys. Rev. B. - 2018. - Vol. 98, Is. 6. - Ст.064424. - ISSN 2469-9950, DOI 10.1103/PhysRevB.98.064424. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 70. - We would like to thank A. Sukhanov, O. Stockert, and P. Thalmeier for useful discussions. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory. Part of this work was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. D.S.I. acknowledges funding by the German Research Foundation (DFG) through the Collaborative Research Center SFB 1143 at the TU Dresden (project C03). S.E.N. acknowledges support from the International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM). L.S.W. was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US DOE. S.B. and S.A.G. are supported by BFFR, Grant No. F18KI-022
Предметные рубрики: MAGNON BOUND-STATES
ANTIFERROMAGNETIC CHAIN
NEUTRON-SCATTERING
Аннотация: In this paper, we present a comprehensive study of magnetic dynamics in the rare-earth orthoferrite YbFeO3 at temperatures below and above the spin-reorientation (SR) transition TSR=7.6K, in magnetic fields applied along the a,b, and c axes. Using single-crystal inelastic neutron scattering, we observed that the spectrum of magnetic excitations consists of two collective modes well separated in energy: 3D gapped magnons with a bandwidth of ∼60meV, associated with the antiferromagnetically (AFM) ordered Fe subsystem, and quasi-1D AFM fluctuations of ∼1meV within the Yb subsystem, with no hybridization of those modes. The spin dynamics of the Fe subsystem changes very little through the SR transition and could be well described in the frame of semiclassical linear spin-wave theory. On the other hand, the rotation of the net moment of the Fe subsystem at TSR drastically changes the excitation spectrum of the Yb subsystem, inducing the transition between two regimes with magnon and spinonlike fluctuations. At TTSR, the Yb spin chains have a well defined field-induced ferromagnetic (FM) ground state, and the spectrum consists of a sharp single-magnon mode, a two-magnon bound state, and a two-magnon continuum, whereas at TTSR only a gapped broad spinonlike continuum dominates the spectrum. In this work we show that a weak quasi-1D coupling within the Yb subsystem JYb-Yb, mainly neglected in previous studies, creates unusual quantum spin dynamics on the low-energy scales. The results of our work may stimulate further experimental search for similar compounds with several magnetic subsystems and energy scales, where low-energy fluctuations and underlying physics could be “hidden” by a dominating interaction.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dzebisashvili D. M., Khudaiberdyev A. A.
Заглавие : Quantum oscillations of magnetization in antiferromagnetic semimetals on a triangular lattice
Коллективы : Russian Foundation for Basic Research [16-02-00073, 18-02-00837]
Место публикации : JETP Letters. - 2018. - Vol. 108, Is. 3. - P.189-195. - ISSN 0021-3640, DOI 10.1134/S0021364018150067. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 21. - We are grateful to Prof. V.V. Val'kov for helpful discussions and valuable remarks. This work was supported by the Russian Foundation for Basic Research, project nos. 16-02-00073 and 18-02-00837.
Предметные рубрики: FIELD
Аннотация: The specific features of magnetization in antiferromagnetic semimetals with a low charge carrier density on a triangular lattice in a high magnetic field are studied. It is demonstrated that the well-known plateau in the magnetic field dependence of the magnetization manifesting itself in the subsystem of localized S = 1/2 spins is actually not strictly horizontal but has a slight positive slope. It is found that an abrupt change in the frequency of quantum oscillations of the magnetization in the itinerant subsystem should be observed at the magnetic field values corresponding to the edges of this plateau owing to the strong s-d(f) exchange coupling.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Velikanov D. A., Popkov S. I., Dubynin N. V., Stolyar S. V., Ladygina V. P., Yaroslavtsev R. N.
Заглавие : Pulsed field-induced magnetization switching in antiferromagnetic ferrihydrite nanoparticles
Коллективы : Russian Foundation for Basic Research; Government of the Krasnoyarsk Territory; Krasnoyarsk Territorial Foundation for Support of Scientific and RD Activities [17-42-240138]
Место публикации : Phys. Solid State. - 2018. - Vol. 60, Is. 10. - P.1973-1978. - ISSN 1063-7834, DOI 10.1134/S1063783418100025. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 38. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 17-42-240138.
Предметные рубрики: BACTERIAL FERRIHYDRITE
NIO NANOPARTICLES
250 KOE
HYSTERESIS
Аннотация: The dynamic magnetization switching of ferrihydrite nanoparticles has been investigated by a pulsed magnetometer technique in maximum fields H-max of up to 130 kOe with pulse lengths of 4, 8, and 16 ms. Ferrihydrite exhibits antiferromagnetic ordering and defects cause the uncompensated magnetic moment in nanoparticles; therefore, the behavior typical of magnetic nanoparticles is observed. The dynamic hysteresis loops measured under the above-mentioned conditions show that the use of pulsed fields significantly broadens the temperature region of existence of the magnetic hysteresis and the coercivity can be governed by varying the maximum field and pulse length. This behavior is resulted from the relaxation effects typical of conventional ferro- and ferrimagnetic nanoparticles and the features typical of antiferromagnetic nanoparticles.
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