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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Edelman I. S., Ivanova O., Ivantsov R. D., Petrakovskaja E. A., Velikanov D. A., Zabluda V. N., Hennet L., Thiaudiere D., Saboungi M. L., Zubavichus Y., Stepanov S., Zaikovskii V. I., Artemenko A., Kliava J.
Заглавие : Nanoparticle-containing glasses co-doped with transition and rare earth elements: comparative studies of transparent magnets
Коллективы : International Conference on the Chemistry of Glasses and Glass-Forming Melts (2011 ; Sept.; Oxford, England)
Место публикации : Phys. Chem. Glasses - Eur. J. Glass Sci. Technol. Part B: Society of Glass Technology, 2012. - Vol. 53, Is. 2. - P.37-44. - ISSN 1753-3562
Примечания : Cited References: 22
Предметные рубрики: ANISOTROPY
RESONANCE
FERRITE
Аннотация: A comparative multitechnique study (including transmission electron microscopy, synchrotron radiation, static magnetisation, magnetic circular dichroism and electron magnetic resonance) has been carried out of nanoparticle-containing borate glasses of two different types: (i) with iron and manganese oxide additives and (ii) with iron and rare earth oxide additives. Due to the presence of magnetic nanoparticles, these glasses have a nonlinear magnetic field dependence of magnetization with hysteresis and saturation while remaining transparent in the visible and near-infrared spectral ranges. The nature of the nanoparticles has been identified as manganese ferrite for type (i) glasses and maghemite for type (ii) glasses. The synchrotron radiation studies as well as the computer-assisted electron magnetic resonance provide an insight into the morphological characteristics of the magnetic nanoparticles in the glass.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kova T. A., Val'kov V. V.
Заглавие : Modifying the spin diagram technique for describing quantum magnets with strong fluctuations
Коллективы : International Interdisciplinary Symposium “Ordering in Minerals and Alloys” (14th; 8 -13 Sept. 2011; Rostov-on-Don)
Место публикации : Bull. Russ. Acad. Sci.: Phys.: Allerton Press, 2012. - Vol. 76, Is. 7. - P.768-770. - ISSN 1062-8738, DOI 10.3103/S1062873812070374
Примечания : Cited References: 7. - This work was supported by the Quantum Physics of Condensed Matter Program for Basic Research of the Presidium of the Russian Academy of Sciences; and by the federal target program Scientists and Science Teachers of an Innovative Russia, 2009–2013.
Ключевые слова (''Своб.индексиров.''): elementary excitations--first-order--mass operator--quantum magnets--self-consistent field method--spin operators--magnets--spin fluctuations
Аннотация: Using the diagram technique for spin operators, the exact representations for quantum magnets are obtained that express the Green's functions via the components of mass operator ∑αβ, end factors L and Q, and the Larkin-and Dyson-irreducible part T- irr.The elementary excitation spectrum and mean magnetization are calculated accurate to the first-order contributions on the parameter r0 -3 by the self-consistent field method.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kablov E. N., Piskorskii V. P., Valeev R. A., Volkov N. V., Davydova E. A., Shaikhutdinov K. A., Balaev D. A., Semenov S. V.
Заглавие : Effect of copper on the properties of Pr-Dy-Fe-Co-B sintered magnets
Место публикации : Russ. Metall. (Metally): Pleiades Publishing, 2014. - Vol. 2014, Is. 1. - P.55-59. - ISSN 0036-0295, DOI 10.1134/S0036029514010078. - ISSN 1555-6255
Примечания : Cited References: 15
Аннотация: The effect of copper on the properties of magnets (Pr0.52Dy0.48)13(Fe65Co0.35)80.3 - xCuxB6.7 (x = 0-10) has been studied. Alloying with copper is shown to decrease the sintering temperature and to increase the content of the principal (Pr,Dy)2(Fe,Co)14B magnetic phase. For compositions with x = 1.3-3.3, copper is found to affect the value and sign of the temperature induction coefficient (TIC). It is shown that the effect of copper on the TIC is determined by the substitution of copper ions for iron ions in lattice sites, which are coupled via an antiferromagnetic exchange interaction. © 2014 Pleiades Publishing, Ltd.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : Radiation-induced modification of the temperature dependence of the magnetic susceptibility of a 1D magnet
Коллективы : Russian Foundation for Basic Research [12-02-31130, 13-02-00523, 13-02-98013]
Место публикации : JETP Letters. - 2014. - Vol. 100, Is. 7. - P.455-462. - ISSN 0021-3640, DOI 10.1134/S0021364014190138. - ISSN 1090-6487
Примечания : Cited References: 28. - This work was supported by the Russian Foundation for Basic Research, project nos. 12-02-31130, 13-02-00523, and 13-02-98013.
Предметные рубрики: SINGLE-CHAIN MAGNETS
EASY-PLANE
ARRANGEMENT
MODEL
IONS
Аннотация: TThe excitation spectrum of a catena-[FeII(ClO4)2{FeIII(bpca)2}]ClO4 anisotropic 1D magnet with alternating high-spin and low-spin iron ions has been calculated with the use of the diagrammatic technique for Hubbard operators. This has allowed establishing conformity with the Ising model, for which the magnetic susceptibility has been calculated by the transfer-matrix method. The introduction of a statistical ensemble taking into account the presence of chains with different lengths and iron ions with different spins has allowed describing the modification of the magnetic susceptibility under optical irradiation.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : Low temperature spectral properties of 1D magnets with twisting and mutually orthogonal arrangement of easy planes
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2015. - Vol. 79, Is. 6. - P.734-736. - ISSN 1062-8738, DOI 10.3103/S1062873815060337
Примечания : Cited References: 4. - The work was supported by the Russian Foundation for Basic Research, project nos. 13-02-00523, 13-02-98013, and 14-02-31280).
Аннотация: The exitation spectrum of a ferrimagnetic Heisenberg chain with four sublattices and twisting mutually ortoghonal easy planes is calculated using a diagram technique of atomic representation. It is shown that at low temperatures, the exitation spectrum of elementary excitations of the system is similar to the spectrum of a magnet with an effective easy-axis type anisotropy directed along the line of easy plane intersection. © 2015, Allerton Press, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Komogortsev S. V., Iskhakov R. S., Zimin A. A., Filatov E. Y., Korenev S. V., Shubin Yu. V., Chizhik N. A., Yurkin G. Yu., Eremin E. V.
Заглавие : The exchange interaction effects on magnetic properties of the nanostructured CoPt particles
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2016. - Vol. 401. - P.236-241. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2015.10.041
Примечания : Cited References: 55. - The work has been partially supported by RFBR Grants 15-08-06673, 14-03-00411, 14-03-00129, 15-42-0417115 and it is partly performed in Siberian Federal University within the state contract of the Russian Federation Ministry of Education and Science for 2014-2016 (project number 1792)
Предметные рубрики: CLUSTER BEAM DEPOSITION
BULK MAGNETS
NANOCRYSTALLINE FERROMAGNETS
REMANENCE ENHANCEMENT
THIN-FILMS
COERCIVITY
MICROSTRUCTURE
NANOPARTICLES
IRON
SYSTEM
Аннотация: Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T 3/2 law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as Hc~T 3/2 which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles. © 2015 Elsevier B.V. All rightsreserved.Демонстрируются и обсуждаются различные проявления эффектов обменного взаимодействия в кривых намагниченности наноструктуированных частиц CoPt. Межзеренная обменная константа А в агломератах губчатой структуры кристаллитов оценивается как /A/=(7±1) pJ/m из кривых приближения намагниченности к насыщению, это значение находится в хорошем согласии с /A/=(6.6±0.5) pJ/m, полученным из закона /T/. /2 Блоха. Размерность фрактала обменно-соединенных кристаллических систем в пористой среды неупорядоченного сплава CoPt /d/=(2.60±0.18) оценивалась из кривых приближения намагниченности к насыщению. Коэрцитивная сила уменьшается с температурой по закону /H_c /~/T/. /2 , который, как предполагается, есть следствие уменьшения энергии магнитной анизотропии из-за теплового возбуждения спиновых волн в изучаемых частицах CoPt.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Shustin M. S.
Заглавие : Quantum renormalizations in anisotropic multisublattice magnets and the modification of magnetic susceptibility under irradiation
Коллективы : Russian Foundation for Basic Research [13-02-00523, 14-02-31237, 15-42-04372]
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 121, Is. 5. - P.860-877. - ISSN 1063-7761, DOI 10.1134/S1063776115110175. - ISSN 1090-6509(eISSN)
Примечания : Cited References:46. - This work was supported by the Russian Foundation for Basic Research, project nos. 13-02-00523, 14-02-31237, and 15-42-04372
Предметные рубрики: SINGLE-CHAIN MAGNETS
GLAUBER MODEL
EASY-PLANE
ARRANGEMENT
SYSTEMS
IONS
Аннотация: The dispersion equation of a strongly anisotropic one-dimensional magnet catena-[FeII(ClO4)2{FeIII(bpca)2}]ClO4 containing alternating high-spin (HS) (S = 2) and low-spin (LS) (S = 1/2) iron ions is obtained by the diagram technique for Hubbard operators. The analysis of this equation yields six branches in the excitation spectrum of this magnet. It is important that the crystal field for ions with spin S = 2 is described by the Hamiltonian of single-ion easy-plane anisotropy, whose orientation is changed by 90° when passing from one HS iron ion to another. The U(N) transformation technique in the atomic representation is applied to diagonalize a single-ion Hamiltonian with a large number of levels. It is shown that the modulation of the orientation of easy magnetization planes leads to a model of a ferrimagnet with easy-axis anisotropy and to the formation of energy spectrum with a large gap. For HS iron ions, a decrease in the mean value of the spin projection due to quantum fluctuations is calculated. The analysis of the specific features of the spectrum of elementary excitations allows one to establish a correspondence to a generalized Ising model for which the magnetic susceptibility is calculated in a wide range of temperatures by the transfer-matrix method. The introduction of a statistical ensemble that takes into account the presence of chains of different lengths and the presence of iron ions with different spins allows one to describe the experimentally observed modification of the magnetic susceptibility of the magnet under optical irradiation.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Popkov S. I., Semenov S. V., Balaev D. A., Dubrovskiy A. A., Sablina K. A., Sapronova N. V., Volkov N. V.
Заглавие : Low-temperature resistance and magnetoresistance hysteresis in polycrystalline (La0.5Eu0.5)(0.7)Pb0.3MnO3
Разночтения заглавия :авие SCOPUS: Low-temperature resistance and magnetoresistance hysteresis in polycrystalline (La0.5Eu0.5)0.7Pb 0.3MnO3
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2011. - Vol. 109, Is. 5. - Ст.53711. - ISSN 0021-8979, DOI 10.1063/1.3559303
Примечания : Cited References: 20. - This study was partially supported by the Russian Foundation for Basic Research, Project No. 08-02-00259a and the Lavrentyev Competition of the Young Scientists' Projects of the Siberian Branch of the Russian Academy of Sciences, Project No. 12.
Предметные рубрики: RESISTIVITY MINIMUM
MANGANITES
FILMS
Ключевые слова (''Своб.индексиров.''): antiferromagnets--electrical resistances--ferromagnets--field dependence--inter-grain--lanthanum manganites--low temperatures--low-temperature resistance--polycrystalline--temperature dependence--tunnel contacts--antiferromagnetic materials--europium--ferromagnetic materials--ferromagnetism--hysteresis--lead--magnetic field effects--magnetoelectronics--magnetoresistance--magnets--manganese oxide--paramagnetism--superconducting materials--electric resistance
Аннотация: The behavior of temperature dependences of electrical resistance and magnetoresistance of polycrystalline substituted lanthanum manganite (La0.5Eu0.5)(0.7)Pb0.3MnO3 at low temperatures was thoroughly studied. A broad hysteresis was found in the field dependences of electrical resistance in the low-temperature region. Above 40 K, no hysteresis feature was observed. The temperature T = 40 K corresponds to the temperature of minimum electrical resistance and the temperature T-N to the antiferromagnet-paramagnet phase transition of the material of the intergrain boundaries. In this work we propose a model which explains the observed features of the rho(T) and rho(H) curves at temperatures below T-N by the formation of a network of ferromagnet-antiferromagnet-ferromagnet tunnel contacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3559303]
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Korshunov M. M., Kozeeva L. P., Lavrov A. N.
Заглавие : Peculiarity of interrelation between electronic and magnetic properties of HTSC cuprates associated with short-range antiferromagnetic order
Коллективы :
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 111, Is. 1. - P104-113. - ISSN 1063-7761, DOI 10.1134/S1063776110070101
Примечания : Cited References: 48. - This study was financially supported by the Russian Foundation for Basic Research (project nos. 09-02-01224 and 09-02-00127) and under the program "Quantum Physics of Condensed Media" of the Presidium of the Russian Academy of Sciences (project no. 5.7).
Предметные рубрики: T-J MODEL
NORMAL-STATE
FERMI-SURFACE
RESISTIVITY ANISOTROPY
3-CENTER INTERACTIONS
OPTICAL CONDUCTIVITY
COPPER OXIDES
CUO2 PLANES
SUPERCONDUCTORS
TRANSPORT
Ключевые слова (''Своб.индексиров.''): anisotropic resistivity--antiferromagnetic orders--concentration dependence--cuprates--doping levels--electronic and magnetic properties--fermi surface topology--high temperature superconducting--magnetic orders--magnetic state--maximum values--pseudo-gap--short-range magnetic orders--strong electron correlations--temperature dependence--anisotropy--antiferromagnetic materials--antiferromagnetism--copper compounds--correlators--electronic properties--high temperature superconductors--hole concentration--magnetic properties--neon--superconducting magnets--single crystals
Аннотация: We report on the results of measurements of anisotropic resistivity of RBa(2)Cu(3)O(6 + x) (R = Tm, Lu) high-temperature superconducting single crystals in a wide range of doping levels, indicating a nontrivial effect of magnetic order on the electronic properties of cuprates. In particular, our results visually demonstrate the crossover from the state with moderate anisotropy of resistivity rho (c) /rho (ab) similar to 30 to a strongly anisotropic state with rho (c) /rho (ab) similar to 7 x 10(3) upon cooling as well as upon a decrease in the hole concentration in the CuO(2) planes. It is also shown that anisotropy is sensitive to the magnetic state of CuO(2) planes and attains its maximum value after the establishment of the long-range antiferromagnetic order. The results are discussed in the framework of the theory based on the t-t'-taEuro(3)-J model of CuO(2) layers taking into account strong electron correlations and short-range magnetic order. In this theory, anomalies of spin correlators and Fermi surface topology for a critical hole concentration of p* a parts per thousand 0.24 are demonstrated. The concentration dependence of the charge carrier energy indicates partial suppression of energy due to the emergence of a pseudogap at p p*. This theory explains both the experimentally observed sensitivity of anisotropy in conductivity to the establishment of the antiferromagnetic order and the absence of anomalies in the temperature dependence of resistivity rho (ab) (T) in the vicinity of the N,el temperature.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneyder E. I.
Заглавие : The Interplay of Phonon and Magnetic Mechanism of Pairing in Strongly Correlated Electron System of High-T-c Cuprates
Коллективы :
Разночтения заглавия :авие SCOPUS: The interplay of phonon and magnetic mechanism of pairing in strongly correlated electron system of high-T c cuprates
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2010. - Vol. 23, Is. 5. - P733-736. - ISSN 1557-1939, DOI 10.1007/s10948-009-0633-z
Примечания : Cited References: 26. - This work is supported by the Presidium RAS program N 7 "Quantum physics of condensed matter," the integration project SORAN-UrORAN N 40, and the RFFI Grant 09-02-00127.
Предметные рубрики: PHASE-TRANSITIONS
OXIDE SUPERCONDUCTORS
SYMMETRY
COPPER
MODEL
BAND
BI2SR2CACU2O8+DELTA
LA2-XSRXCUO4
PB
Ключевые слова (''Своб.индексиров.''): high-t-c superconductivity--strong correlated electron systems--mechanisms of superconducting pairing--high-t c superconductivity--mechanisms of superconducting pairing--strong correlated electron systems--ab initio--buckling mode--correlated electron systems--critical temperatures--cuprates--fitting parameters--high-t--isotope effect--low energies--magnetic mechanisms--order of magnitude--phonon mode--strongly correlated electron system--strongly correlated electrons--superconducting pairing--superconductivity mechanism--type theory--buckling--copper compounds--electrons--isotopes--magnetic materials--phonons--superconductivity--superconducting magnets
Аннотация: We consider magnetic mechanism of superconducting pairing in the effective low energy t - t' - t '' - J* model with all parameters calculated ab initio. Interaction of strongly correlated electrons with different phonon modes is also incorporated. In a BCS type theory, the d(x2-y2) gap is given by a sum of magnetic and phonon contributions. The main contribution to the only fitting parameter G is determined by a competition of the breathing and buckling modes. Fitting the parameter G from the isotope effect, we obtain that magnetic and phonon contributions to the critical temperature T-c work together and are of the same order of magnitude.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Popkov S. I., Shaikhutdinov K. A., Mart'yanov O. N., Petrov M. I.
Заглавие : Nonmonotonic Behavior of Magnetoresistance, R(H) Hysteresis, and Low-Temperature Heat Capacity of the BaPb0.75Bi0.25O3 Superconductor in a Magnetic Field: Possible Manifestations of Phase Separation
Коллективы :
Разночтения заглавия :авие SCOPUS: Nonmonotonic behavior of magnetoresistance, R(H) hysteresis, and low-temperature heat capacity of the BaPb0.75Bi0.25O 3 superconductor in a magnetic field: Possible manifestations of phase separation
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 110, Is. 4. - P584-593. - ISSN 1063-7761, DOI 10.1134/S1063776110040059
Примечания : Cited References: 27. - This study was performed under the program no. 5 of the Russian Academy of Sciences (project no. 7).
Предметные рубрики: ELECTRONIC SPECIFIC-HEAT
BAPB1-XBIXO3 SYSTEM
YBA2CU3O7-DELTA
COMPOSITES
TRANSITION
HTSCS
300-K
Ключевые слова (''Своб.индексиров.''): diamagnetic response--effective field--heat capacities--high-t--hysteretic dependence--josephson--low temperature heat capacities--non-monotonic dependence--nonmonotonic behaviors--polycrystalline--spatially inhomogeneous--transport currents--electric resistance--hysteresis--magnetic field effects--magnetic flux--magnetoelectronics--magnetoresistance--phase separation--semiconductor metal boundaries--specific heat--superconducting magnets--superconducting materials--superconductivity--transport properties--magnetic materials
Аннотация: The transport properties (R(T) and R(H) dependences at various values of the transport current in magnetic fields up to 65 kOe) and low-temperature heat capacity in magnetic fields up to 90 kOe of the BaPb0.75Bi0.25O3 superconductor (T-C approximate to 11.3 K) are investigated with the goal of clarifying the mechanisms determining the nonmonotonic behavior and hysteresis of its magnetoresistance R(H). The type of R(H) hysteretic dependences for BaPb0.75Bi0.25O3 is analogous to that observed in granular high-T-c superconductors (HTSCs); however, unlike classical HTSC systems, the field width of the magnetoresistance hysteresis loop for polycrystalline BaPb0.75Bi0.25O3 depends on the transport current. This means that although the mechanisms responsible for the magnetoresistance hysteresis (the influence of the magnetic flux trapped in super-conducting regions on the effective field in Josephson interlayers) are identical in these objects, the transport current in BaPb0.75Bi0.25O3 may considerably affect the diamagnetic response of the superconductor. A considerable effect of transport current on the field in which the R(H) dependences have a peak and exhibit hysterestic properties is observed. Such a behavior can be adequately interpreted using the model of the spatially inhomogeneous superconductor-insulator state proposed by Gorbatsevich et al. [JETP Lett. 52, 95 (1990)]. The nonmonotonic dependence of quantity C/T (C is the heat capacity) on the magnetic field discovered in the present study also agrees with the conclusions based on this model.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Varnakov S. N., Komogortsev S. V., Ovchinnikov S. G., Bartolome J., Sese J.
Заглавие : Magnetic properties and nonmagnetic phases formation in (Fe/Si)(n) films
Коллективы :
Разночтения заглавия :авие SCOPUS: Magnetic properties and nonmagnetic phases formation in (Fe/Si) n films
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 104, Is. 9. - Ст.94703. - ISSN 0021-8979, DOI 10.1063/1.3005973
Примечания : Cited References: 23. - This work was supported by the Russian Academy of Science program "Spintronics," the complex integration project of the Siberian Branch of the Russian Academy of Science. 3.5, the Russian Foundation for Basic Research (Grant No. 07-03-00320), the "Ramon y Cajal" program, and Project No. MAT 2005/01272 of the Spanish Ministry of Education and Science.
Предметные рубрики: FE/SI/FE TRILAYER FILMS
GIANT MAGNETORESISTANCE
ULTRAHIGH-VACUUM
SUPERLATTICES
MULTILAYERS
EXCHANGE
Ключевые слова (''Своб.индексиров.''): activation energy--integral equations--magnetic properties--magnetization--magnets--multilayers--rate constants--silicon--thermal evaporation--vacuum--vacuum evaporation--fe layers--high temperatures--interface layers--irreversible behaviors--kinetic equations--n films--nonmagnetic--nonmagnetic phases--prefactor--quantitative analysis--rate equations--synthetic procedures--temperature dependences--ultrahigh-vacuum systems--phase interfaces
Аннотация: The magnetization of Fe/Si multilayers, grown by thermal evaporation in an ultrahigh vacuum system, was investigated at high temperatures. Magnetization and its temperature dependence up to a high temperature of 800 K depend on individual Fe layer thickness d(Fe). This dependence is the result of the formation of an Fe-Si interface layer (nonmagnetic phase) during the synthetic procedure. The fraction of this Fe-Si nonmagnetic phase is estimated versus dFe. At temperatures higher than 400 K an irreversible decrease in the magnetization occurs. A quantitative analysis of this irreversible behavior is proposed in terms of an exponential diffusion-like kinetic equation for the reaction that produces the Fe-Si nonmagnetic phase. The coefficients of the rate equation are the activation energy E(a) and the prefactor D(0), which have been determined for different d(Fe). (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3005973]
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Klauss H. H., Luetkens H., Klingeler R., Hess C., Litterst F. J., Kraken M., Korshunov M. M., Eremin I., Drechsler S. L., Khasanov R., Amato A., Hamann-Borrero J. E., Leps N., Kondrat A., Behr G., Werner J., Buchner B.
Заглавие : Commensurate spin density wave in LaFeAsO: A local probe study
Место публикации : Phys. Rev. Lett.: AMER PHYSICAL SOC, 2008. - Vol. 101, Is. 7. - Ст.77005. - ISSN 0031-9007, DOI 10.1103/PhysRevLett.101.077005
Примечания : Cited References: 28
Предметные рубрики: LAYERED QUATERNARY COMPOUND
SUPERCONDUCTIVITY
Ключевые слова (''Своб.индексиров.''): arsenic compounds--chlorine compounds--ferromagnetism--magnetic materials--magnetic properties--magnetization--magnets--molybdenum--phase transitions--spin density waves--commensurate spin density wave--external fields--magnetic orders--muon spin relaxations--order parameter--ordered moments--probe measurements--ssbauer spectroscopy--structural phase transition--sublattice magnetizations--temperature dependences--spin dynamics
Аннотация: We present a detailed study on the magnetic order in the undoped mother compound LaFeAsO of the recently discovered Fe-based superconductor LaFeAsO(1-x)F(x). In particular, we present local probe measurements of the magnetic properties of LaFeAsO by means of (57)Fe Mossbauer spectroscopy and muon-spin relaxation in zero external field along with magnetization and resistivity studies. These experiments prove a commensurate static magnetic order with a strongly reduced ordered moment of 0.25(5)mu(B) at the iron site below T(N)=138 K, well separated from a structural phase transition at T(S)=156 K. The temperature dependence of the sublattice magnetization is determined and compared to theory. Using a four-band spin density wave model both, the size of the order parameter and the quick saturation below T(N) are reproduced.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Shaykhutdinov K. A., Popkov S. I., Petrov M. I.
Заглавие : Peculiarities of the time evolution of magnetoresistance of granular HTSC in a constant applied magnetic field
Коллективы :
Место публикации : Solid State Commun. - 2008. - Vol. 147, Is. 7-8. - P.284-287. - ISSN 0038-1098, DOI 10.1016/j.ssc.2008.05.044
Примечания : Cited References: 17. - This work was Supported by program "Quantum macrophysics" No. 3.4 of RAS and integration project No. 3.4 of SB RAS and in part by KSF, grant 18G011. D.A.B. and A.A.D. acknowledge the Russian Science Support Foundation.
Предметные рубрики: CRITICAL-STATE
SUPERCONDUCTORS
COMPOSITES
HYSTERESIS
RESISTANCE
Ключевые слова (''Своб.индексиров.''): superconductors--flux pinning and creep--tunneling--superconductors--flux pinning and creep--tunneling--agricultural products--carbon fiber reinforced plastics--copper oxides--electric conductivity--electric resistance--evolutionary algorithms--ferromagnetism--galvanomagnetic effects--grain (agricultural product)--health--hysteresis--magnetic devices--magnetic field effects--magnetic field measurement--magnetic fields--magnetic materials--magnetoelectronics--magnetoresistance--semiconductor metal boundaries--superconducting magnets--superconductivity--yttrium barium copper oxides--p ,p ,t measurements--applied (co)--applied magnetic fields--constant magnetic field (cmf)--elsevier (co)--evolution (co)--external fields--field induced--flux creep--hysteretic behavior--josephson couplings--low magnetic fields--magnetic (ce)--poly crystalline--superconducting grains--time evolutions--time relaxation--magnetism
Аннотация: The time evolution of the magnetoresistance of bulk YBCO + CuO composites at T = 4.2 K in constant applied magnetic fields was studied to clarify the mechanism of hysteretic behavior of magnetoresistance R(H) of granular HTSC. The composites represent "model" granular HTSC with weakened Josephson coupling between superconducting (YBCO) crystallites. It was found for the first time that on the ascending branch of R(H) dependence, the resistance at H = const decreased with time while on the descending branch, the resistance increased with time in ail applied constant magnetic field. In the range of low magnetic fields (below the minimum point of the descending branch of the R(H) dependence), the resistance at H const decreased again. Similar measurements performed oil pure polycrystalline YBCO at T = 77.4 K have shown that the behavior of evolution of resistance with time is similar to that observed for the composite. This proves the peculiarity of time evolution of maignetoresistance to be a common feature of granular HTSCs. The behavior revealed is well described by the model Of granular HTSC, where the intergrain media is in an effective magnetic field which is the superposition of the external field and the field induced by superconducting grains. The time evolution of resistance reflects the time relaxation of magnetization of HTSC grains due to the intragrain flux Creep Processes. (C) 2008 Elsevier Ltd. All rights reserved.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Mitskan V. A.
Заглавие : Magnetic-field-induced phase transition in a two-dimensional quantum magnet with plaquette distortion
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 105, Is. 1. - P90-93. - ISSN 1063-7761, DOI 10.1134/S1063776107070199
Примечания : Cited References: 10
Предметные рубрики: GROUND-STATE
CRYSTALS
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--magnetic field effects--magnets--phase diagrams--problem solving--spectrum analysis--plaquette distortion--quantum heisenberg magnet--quantum transition--two-dimensional quantum magnet--phase transitions
Аннотация: Magnetic field effect on the structure of the ground state of a two-dimensional quantum Heisenberg magnet is analyzed. A plaquette representation is used to solve the self-consistent problem and calculate the collective excitation spectrum in a magnetic field. Conditions are found for quantum transition between non-magnetic and oblique antiferromagnetic phases. The change in the ground state of the system is associated with disappearance of the gap in the spin excitation spectrum. Effects of frustration and magnetic field on the spectrum are analyzed. A phase diagram of stable singlet and magnetically ordered phases is presented.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Single-ion-anisotropy and electron-spin-resonance linewidth in quasi-low-dimensional heisenberg magnets
Место публикации : Phys. Status Solidi B. - 1988. - Vol. 146, Is. 2. - P.691-696. - ISSN 0370-1972, DOI 10.1002/pssb.2221460229
Примечания : Cited References: 18
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : VALKOV V. V., VALKOVA T. A.
Заглавие : INFLUENCE OF CUBIC ANISOTROPY ON THE GROUND-STATE AND THERMODYNAMIC PROPERTIES OF HEISENBERG MAGNETS
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1984. - Vol. 59, Is. 3. - P617-625. - ISSN 0040-5779, DOI 10.1007/BF01018202
Примечания : Cited References: 18
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : VALKOV V. V., OVCHINNIKOV S. G.
Заглавие : HUBBARD OPERATORS AND SPIN-WAVE THEORY OF HEISENBERG MAGNETS WITH ARBITRARY SPIN
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1982. - Vol. 50, Is. 3. - P306-313. - ISSN 0040-5779, DOI 10.1007/BF01016463
Примечания : Cited References: 32
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Ovchinnikov S. G.
Заглавие : Isotope effect in the model of strongly correlated electrons with the magnetic and phonon superconducting pairing mechanisms
Коллективы : Presidium of the Russian Academy of Sciences [40]; Russian Academy of Sciences; Russian Foundation for Basic Research [09-02-00127]
Место публикации : J. Exp. Theor. Phys. - 2009. - Vol. 109, Is. 6. - P.1017-1021. - ISSN 1063-7761, DOI 10.1134/S1063776109120139
Примечания : Cited References: 42. - This study was financed under programs 5.7 and "Quantum Physics of Condensed Matter" of the Presidium of the Russian Academy of Sciences, integration project no. 40 of the Siberian Branch and Ural Division of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 09-02-00127).
Предметные рубрики: CUPRATE SUPERCONDUCTORS
PHASE-TRANSITIONS
3-CENTER INTERACTIONS
HUBBARD-MODEL
TEMPERATURE
LA2-XSRXCUO4
SYMMETRY
EXCHANGE
COPPER
BI2SR2CACU2O8+DELTA
Ключевые слова (''Своб.индексиров.''): ab initio calculations--calculated values--cooper pairing--isotope effect--magnetic mechanisms--order of magnitude--pairing mechanism--phonon mechanism--strongly correlated electrons--superconducting pairing mechanism--superconducting state--type theory--carrier mobility--electron-phonon interactions--isotopes--superconductivity--superconducting magnets
Аннотация: Peculiarities of the temperature isotope effect in a BCS-type theory describing the exchange and phonon mechanisms of Cooper pairing in a system of strongly correlated electrons are considered. The electron-phonon interaction constant is determined from the fitting of the calculated value of the isotope-effect index to the observed value with the parameters of La(2 - x) Sr (x) CuO(4) obtained from ab initio calculations. The value of this constant indicates that the contribution from the traditional pairing mechanism to the superconducting state is of the same order of magnitude as the contribution from the magnetic mechanism.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Edelman I., Kliava J.
Заглавие : Oxide glasses with magnetic nanoparticles: transparent magnets (Faraday rotation and electron magnetic resonance studies)
Коллективы : RFBR-CNRS [07-02-92174]
Разночтения заглавия :авие SCOPUS: Oxide glasses with magnetic nanoparticles: Transparent magnets (Faraday rotation and electron magnetic resonance studies)
Место публикации : Phys. Status Solidi B. - 2009. - Vol. 246, Is. 10. - P.2216-2231. - ISSN 0370-1972, DOI 10.1002/pssb.200945169
Примечания : Cited References: 87. - This work is supported in part by RFBR-CNRS joint project, grant No 07-02-92174. We are grateful to E. Petrakovskaja and O. Ivanova for measuring and discussing, respectively, the EMR spectra in thermally treated samples and the FR spectral and magnetic field dependences.
Предметные рубрики: SPIN-HAMILTONIAN PARAMETERS
SINGLE-DOMAIN PARTICLES
SUPERPARAMAGNETIC RESONANCE
CRYSTALLIZATION BEHAVIOR
FERRIMAGNETIC RESONANCE
PARAMAGNETIC-RESONANCE
TEMPERATURE-DEPENDENCE
COMPUTER-SIMULATIONS
FINE PARTICLES
BORATE GLASSES
Аннотация: In the first part of this paper we outline the state of the art in the field of magnetic nanoparticles in oxide glasses. We describe the theoretical background of two complementary techniques used for the studies of the state of paramagnetic ions, clusters and magnetic particles in a diamagnetic matrix, viz., magnetooptical Faraday rotation (FR) and electron magnetic resonance (EMIR) and we overview previous results obtained with these techniques for several glass systems. In the second part, we highlight the case of potassium-alumina-borate glasses - a glassy system where doping with paramagnetic oxides results in formation of magnetic particles at very low contents of paramagnetic additions: Fe(2)O(3) and MnO. In the special case when the ratio of the iron and manganese oxides in the charge is 3/2, magnetic nanoparticles with characteristics close to those of manganese ferrite are formed already at the first stage of the glass preparation. After thermal treatment all glasses show FR and EMR spectra attesting to the presence of superparamagnetic nanoparticles, characterized by relatively broad size and shape distributions. The formation of magnetic nanoparticles confers to these glasses magnetic and magnetooptical properties typical of magnetically ordered substances. At the same time, the glasses remain transparent in a part of the visible and near infrared spectral range and display a high FR value. Such properties make them particularly interesting for use as new media for various magneto-optical devices. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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