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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Drokin N. A., Ganiev S. M.
Заглавие : Static and dynamic characteristics of the bulk and contact electric resistivity in CDCR2SE4 under stochastic current instability
Место публикации : Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 7. - P.2122-2128. - ISSN 0367-3294
Примечания : Cited References: 21
Предметные рубрики: OSCILLATIONS
CHAOS
GE
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Frolov G. I., Zhigalov V. S., Polskii A. I., Pozdnyakov V. G.
Заглавие : Study of electroconductivity in cobalt nanocrystalline films
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1996. - Vol. 38, Is. 4. - P1208-1213. - ISSN 0367-3294
Примечания : Cited References: 13
Предметные рубрики: METAL-FILMS
RESISTIVITY
CONDUCTION
ELECTRONS
DENSITY
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : An impurity resistivity of doped manganese perovskites
Место публикации : Physica B: ELSEVIER SCIENCE BV, 1999. - Vol. 259-61: International Conference on Strongly Correlated Electron Systems (SCES 98) (JUL 15-18, 1998, PARIS, FRANCE). - P828-830. - ISSN 0921-4526, DOI 10.1016/S0921-4526(98)00875-8
Примечания : Cited References: 4
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): manganese perovskites--mobility--linear and quadratic magnetoresistance
Аннотация: We present a two-time of relaxation approach at an analysis of a magnetoresistance in ferromagnetic manganese perovskites La(1-x)(Ca,Sr)(x)MnO. To explain a change in the low-held response from predominantly quadratic dR/dH\(H--0) = 0 for T T(c) to linear dR/dH\(H--0) for T T(c) as noted in the measurements in thin films La(0.7)Ca(0.3)MnO(3) we calculated held and temperature dependences of a impurity contribution to a carrier mobility in a framework of the 2p(O)- and 3d(Mn)-scattering model elaborated for manganese perovskites. We obtained the field-dependent impurity contribution to the overall scattering of carriers that show a transition in the low-field (H) dependence of R from quadratic above T(c) to linear below consistent with an experiment. The calculated negative magnetoresistance ratio is sharply peaked at a temperature-near T(c) or below. (C) 1999 Elsevier Science B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Characteristic features of the extrinsic electric resistance in ferromagnets with low carrier density
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1999. - Vol. 41, Is. 1. - P59-66. - ISSN 1063-7834, DOI 10.1134/1.1130731
Примечания : Cited References: 26
Предметные рубрики: QUANTUM TEMPERATURE OSCILLATIONS
MAGNETIC SEMICONDUCTORS
HGCR2SE4
RESISTIVITY
FILMS
Аннотация: Switching from simple semiconductors to more complicated chemical compositions, we encounter mainly nonstoichiometric or undoped compounds. Combined with other characteristic features of d(f) compounds, this can lead, together with the ordinary scattering by spin disorder in magnetic semiconductors, to an unusual impurity contribution to the total scattering of carriers even in intrinsic semiconductors. A unique scheme for calculating the energy structure of the conduction-band bottom of a ferromagnetic semiconductor and the temperature and field dependences of the impurity contribution to the resistivity is proposed on the basis of a model Hamiltonian. The computed magnetoresistance ratio is negative and has a maximum near T-c. A qualitative comparison is made between the results and the experimental temperature dependences of the Hall mobility and magnetoresistance ratio in the ternary semiconductor n-HgCr2Se4, which is nonstoichiometric with respect to the chalcogen. To identify previously unobserved temperature oscillations of the resistance, a careful analysis is made of the low-temperature part of the resistance using the relations obtained. (C) 1999 American Institute of Physics. [S1063-7834(99)01701-3].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Erkaev N. V., Semenov V. S., Jamitzky F.
Заглавие : Reconnection rate for the inhomogeneous resistivity Petschek model
Место публикации : Phys. Rev. Lett.: AMERICAN PHYSICAL SOC, 2000. - Vol. 84, Is. 7. - P1455-1458. - ISSN 0031-9007, DOI 10.1103/PhysRevLett.84.1455
Примечания : Cited References: 16
Предметные рубрики: MAGNETIC RECONNECTION
CURRENT SHEETS
Аннотация: The reconnection rate for the canonical simplest case of steady-state two-dimensional symmetric reconnection in an incompressible plasma is found by matching of an outer Petschek solution and an internal diffusion region solution. The reconnection rate obtained naturally incorporates both Sweet-Parker and Petschek regimes; while the latter is possible only for a strongly localized resistivity.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zakharov Y. V., Titov L. S.
Заглавие : Negative magnetoresistance of iron single-crystal whiskers in the course of magnetization reversal
Разночтения заглавия :авие SCOPUS: Negative Magnetoresistance of Iron Single-Crystal Whiskers in the Course of Magnetization Reversal
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2004. - Vol. 46, Is. 2. - P303-305. - ISSN 1063-7834, DOI 10.1134/1.1649428
Примечания : Cited References: 9
Предметные рубрики: RESISTIVITY
WALLS
Аннотация: The change in the low-temperature resistance of iron single-crystal whiskers during magnetization reversal form a single-domain state to a state with a plane-parallel domain structure is studied theoretically. The negative magnetoresistance (similar to45%) is calculated from the Kubo formula with due regard for the change in the trajectories of conduction electrons in a magnetic induction field of domains. The magnetoresistance thus calculated is of the same order of magnitude as the magnetoresistance obtained in the experiment performed by Isin and Coleman.(C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Petrakovskii G. A., Ryabinkina L. I., Abramova G. M., Kiselev N. I., Romanova O. B.
Заглавие : Influence of magnetic ordering on the resistivity anisotropy of alpha-MnS single crystal
Разночтения заглавия :авие SCOPUS: Influence of magnetic ordering on the resistivity anisotropy of α-MnS single crystal; авие SCOPUS: Influence of magnetic ordering on the resistivity anisotropy of ?-MnS single crystal
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 2004. - Vol. 129, Is. 3. - P195-197. - ISSN 0038-1098, DOI 10.1016/j.ssc.2003.09.028; Solid State Commun. - 2004. - Vol. 129, Is. 3. - P195-197. - Вариант Sopus
Примечания : Cited References: 7
Ключевые слова (''Своб.индексиров.''): anisotropy of resistivity--optical gap--d. anisotropy of resistivity--d. optical gap--antiferromagnetism--band structure--bandwidth--diffractometers--electron transitions--fermi level--hamiltonians--light absorption--magnetic anisotropy--magnetization--single crystals--spectroscopic analysis--x ray diffraction analysis--coulomb repulsion--resistivity anisotropy--semiconducting manganese compounds--d. anisotropy of resistivity--d. optical gap--antiferromagnetism--band structure--bandwidth--diffractometers--electron transitions--fermi level--hamiltonians--light absorption--magnetic anisotropy--magnetization--single crystals--spectroscopic analysis--x ray diffraction analysis--coulomb repulsion--resistivity anisotropy--semiconducting manganese compounds
Аннотация: The resistivity and the optical absorbtion spectra of single crystal alpha-MnS are studied in the temperature range 80-300 K along two directions [100] and [111]. Strong anisotropy of the resistivity, and the shift of absorbtion spectra band edge below T 160 K are explained in terms of model involving delocalized holes in 3d-band manganese ions interacting with localized spins by using the sd-model. (C) 2003 Elsevier Ltd. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Balaev A. D., Ivanova N. B., Ovchinnikov S. G.
Заглавие : Mossbauer magnetization and resistivity studies of Fe1.91V0.09BO4
Разночтения заглавия :авие SCOPUS: Mossbauer magnetization and resistivity studies of Fe1.91V 0.09BO4
Место публикации : Physica B: ELSEVIER SCIENCE BV, 2005. - Vol. 359: International Conference on Strongly Correlated Electron Systems (SCES 04) (JUL 26-30, 2004, Karlsruhe, GERMANY). - P1324-1326. - ISSN 0921-4526, DOI 10.1016/j.physb.2005.01.396
Примечания : Cited References: 8
Предметные рубрики: FE2OBO3
Ключевые слова (''Своб.индексиров.''): mott-hubbard system--magnetism--new materials--magnetism--mott-hubbard system--new materials--crystallization--crystallography--fermi level--ferrimagnetism--magnetism--magnetization--mossbauer spectroscopy--phase transitions--single crystals--x ray diffraction analysis--charge ordering--electron-electron interactions--mott-hubbard system--new materials--iron compounds
Аннотация: Single crystals of Fe1.91V0.09BO4 were prepared by spontaneous crystallization using a solution melt technology for the first time and its structure, electronic and magnetic properties were investigated by X-ray diffraction, Mossbauer spectroscopy, magnetization and electrical measurements. Room-temperature Mossbauer measurements indicate that "localized" (Fe2+, Fe3+) and "delocalized" (Fe2.5+) states in ratio 0.31:0.345:0.345 distributed over two crystallographically non-equivalent positions exist. The results of magnetic measurements show that warwickite is a P-type ferrimagnet below T = 130 K. Resistivity measurements show a variable-range-hopping when electron-electron interactions cause a soft Coulomb gap in the density of states at the Fermi energy. (c) 2005 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Gokhfeld D. M., Popkov S. I., Shaykhutdinov K. A., Petrov M. I.
Заглавие : Hysteretic behavior of the magnetoresistance and the critical current of bulk Y3/4Lu1/4Ba2CU3O7+CuOcomposites in a magnetic field
Разночтения заглавия :авие SCOPUS: Hysteretic behavior of the magnetoresistance and the critical current of bulk Y3/4Lu1/4Ba2Cu3O7 + CuO composites in a magnetic field
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2007. - Vol. 460: 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (JUL 09-14, 2006, Dresden, GERMANY). - P1307-1308. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.346
Примечания : Cited References: 7
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): htsc--resistivity--magnetic field--relaxation--htsc--magnetic field--relaxation--resistivity--crystallites--magnetic fields--magnetic hysteresis--magnetoresistance--yttrium barium copper oxides--superconducting crystallites--superconducting systems--tunnel-type josephson junctions--josephson junction devices
Аннотация: The hysteretic behavior of critical current j(C)(H) and magneto-resistance R(H) of composites Y-Ba-Cu-O + CuO have been studied and presented. The composites represent the network of tunnel-type Josephson junctions where copper oxide acts as a material forming barriers between superconducting (YBCO) crystallites. The characteristic features of R(H) and j(C)(H) dependences are discussed in the frames of the conception of "two level superconducting system" (the Josephson media and HTSC crystallites) which is realized in the composites under study. (c) 2007 Elsevier B.V. All rights reserved.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Ivanova N. B., Rudenko V. V., Ovchinnikov S. G., Vasil'Ev A. D., Knyazev Yu. V.
Заглавие : Conductivity study of Co3O2BO3 and Co 3-xFexO2BO3 oxyborates
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Solid State Phenomena. - 2009. - Vol. 152-153. - С. 104-107. - ISSN 10120394 (ISSN); 390845168X (ISBN); 9783908451686 (ISBN), DOI 10.4028/www.scientific.net/SSP.152-153.104
Ключевые слова (''Своб.индексиров.''): doped cobaltite--electrical conductivity--ludwigite--variable-range hopping--crystal structure--electric conductivity--magnetic materials--single crystals--crystal structure--electric conductivity--magnetic materials--magnetism--single crystals--electrical conductivity--electrical resistivity--experimental data--mott variable-range hopping--oxyborates--temperature regions--variable-range hopping--doped cobaltite--ludwigite--variable range hopping--cobalt--cobalt
Аннотация: Single crystals of cobalt oxyborates Co3O2BO 3 and Co3-xFexO2BO3 were synthesized. The crystal structure and electric properties were investigated. The difference in the electrical resistivity behaviors was found. For parent Co3O2BO3 nor simple activation law, nor Mott variable range hopping (VRH) are acquirable to describe the experimental data in wide temperature region. In contrast for Co3-xFex O 2BO3 Mott's variable-range hopping conductivity clearly dominates.
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11.

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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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaikhutdinov K. A., Popkov S. I., Semenov S. V., Balaev D. A., Dubrovskiy A. A., Sablina K. A., Volkov N. V.
Заглавие : Low-temperature resistivity of polycrystalline (La0.5Eu 0.5)0.7Pb0.3MnO3 in a magnetic fields
Место публикации : J. Phys. Conf. Ser. - 2010. - Vol. 200, Is. SECTION 5. - ISSN 17426588 (ISSN) , DOI 10.1088/1742-6596/200/5/052025
Ключевые слова (''Своб.индексиров.''): antiferromagnetic grains--comparative analysis--ferromagnetic grain--low temperatures--polycrystalline--specific heat measurement--spin dependent tunneling--transport and magnetic properties--antiferromagnetism--electric resistance--europium--grain boundaries--grain size and shape--lanthanum compounds--lead--magnetic field effects--magnetic properties--magnetoresistance--manganese oxide--single crystals--thermal variables measurement--lanthanum
Аннотация: The effect of grain boundaries on magnetoresistance (MR) of manganites have been investigated by the comparative analysis of the properties of single-crystal and polycrystalline (La0.5Eu0.5) 0.7Pb0.3MnO3. While MR of the single crystal is maximum near the Curie temperature and vanishes in the low-temperature region, the polycrystalline (La0.5Eu0.5)0.7Pb 0.3MnO3 sample exhibits high MR in the low-temperature region. In order to clarify the origin of the low-temperature MR, the transport and magnetic properties of the polycrystalline (La0.5Eu 0.5)0.7Pb0.3MnO3 in magnetic fields have been supplemented by study of magnetic properties and specific heat measurements. The results obtained could be attributed to spin-dependent tunneling between ferromagnetic grains through insulating antiferromagnetic grain boundaries. © 2010 IOP Publishing Ltd.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Eremin E. V., Sablina K. A., Sapronova N. V.
Заглавие : Dielectric properties of a mixed-valence Pb3Mn7O15 manganese oxide
Коллективы :
Разночтения заглавия :авие SCOPUS: Dielectric properties of a mixed-valence Pb3Mn7O 15 manganese oxide
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 37. - Ст.375901. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/37/375901
Примечания : Cited References: 14. - This study was supported by the Russian Foundation for Basic Research 'Siberia', project No. 09-02-98003, and the Siberian Branch of the Russian Academy of Sciences, integration project No. 101.
Ключевые слова (''Своб.индексиров.''): cation--lead--manganese derivative--oxide--article--chemical model--chemistry--crystallization--electric conductivity--electronics--methodology--temperature--cations--crystallization--electric conductivity--electronics--lead--manganese compounds--models, chemical--oxides--temperature--ac electric field--analysis of resistivity--carrier hopping--charge ordering--complex dielectric constant--crystal site--debye models--dielectric constants--dielectric spectra--frequency windows--lattice sites--low frequency--manganese ions--mixed valence--mixed valence state--relaxation behaviors--temperature range--electric fields--manganese--manganese oxide--permittivity--single crystals--crystal symmetry
Аннотация: We investigated the low-frequency dielectric properties of a Pb3Mn7O15 single crystal with manganese ions in the mixed-valence state (Mn3+/Mn4+). Dielectric relaxation was found in the frequency window from 20 to 100 kHz in the temperature range 110-180 K. The dielectric spectra of the crystal were analyzed using a Debye model. Estimations made within the model and analysis of resistivity data suggest that the relaxation behavior of the dielectric constant is related to polaronic charge carrier hopping. Around 250 K, charge ordering occurs in the crystal when the Mn3+ and Mn4+ ions are arranged in a specific order among the crystal sites. With a decrease in temperature, an ac electric field can induce a charge hop between the equivalent lattice sites available, related to crystal symmetry. This hopping is equivalent to the reorientation of an electric dipole that yields Debye-type behavior of the complex dielectric constant. The observed anisotropy in the behavior of the dielectric properties and resistivity can be attributed to a pronounced two-dimensional character of the crystal structure.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M.Yu., Val'kov V. V.
Заглавие : Anomalous resistivity and the electron-polaron effect in the two- band Hubbard model with one narrow band
Место публикации : arXiv. - 2011. - Ст.1111.3135
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Bayukov O. A., Ovchinnikov S. G., Vasiliev A. D., Rudenko V. V., Ivanova N. B., Knyazev Yu. V., Bartolom J., Arauzo A.
Заглавие : The superexchange interactions in mixed Co-Fe ludwigite
Место публикации : J. Magn. Magn. Mater. - 2011. - Vol. 323, Is. 5. - P.521-527. - MAR. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2010.09.057
Примечания : Cited Reference Count: 15. - Гранты: This study was supported by the Russian Foundation for Basic Research (Project no. 09-02-00171-a), the Federal Agency for Science and Innovation (Rosnauka) (Project no. MK-5632. 2010.2), Physical Division of the Russian Academy of Science, the program "Strongly Correlated Electrons", project 2.3.1.; The financial support of Spanish MINCYT, MAT08/1077 and Aragonese E-34 project are also acknowledged.Финансирующая организация: Russian Foundation for Basic Research [09-02-00171-a]; Federal Agency for Science and Innovation (Rosnauka) [MK-5632. 2010.2]; Physical Division of the Russian Academy of Science; "Strongly Correlated Electrons" [2.3.1]; Spanish MINCYT [MAT08/1077]; Aragonese E-34 project
Предметные рубрики: TRANSPORT-PROPERTIES
SPECTRA
Ключевые слова (''Своб.индексиров.''): ludwigite structure--magnetic susceptibility--magnetic frustration--mott conductivity--ludwigite structure--magnetic frustration--magnetic susceptibility--mott conductivity--ac susceptibility--cation distributions--crystal data--crystallographic sites--electrical resistivity--iron atoms--low temperatures--ludwigite structure--magnetic behavior--magnetic frustrations--magnetic system--magnetic transitions--mossbauer--mossbauer effects--mott conductivity--mott hopping--superexchange energy--superexchange interaction--temperature regions--trivalent iron--variable range--cobalt--electric conductivity--magnetic susceptibility--magnetism--mossbauer spectroscopy--x ray diffraction--crystal structure
Аннотация: The crystal structure, cation distribution and exchange interactions in the Co2.25Fe0.75O2BO3 ludwigite have been explored through X-ray diffraction, electrical resistivity, ac-susceptibility and Mossbauer effect measurements. The crystal data have shown that iron atoms occupy the most symmetric crystallographic sites Fe4 and Fe2. The complex magnetic behavior with two magnetic transitions near 70 and 115 K at low temperatures was found. The Mossbauer data have displayed the trivalent iron states only. The values of superexchange energies have been estimated for Co3O2BO3 and Co2.25Fe0.75O2BO3 yielding a significant role of frustrations in the ludwigite magnetic system. Variable range Mott hopping conductivity law was proved to be valid in the wide temperature region, pointing out a localized character of charge carriers rather than collective. (C) 2010 Elsevier B.V. All rights reserved.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yurkin G. Yu., Patrin G. S., Velikanov D. A., Beletsky V. V.
Заглавие : Transport properties of FeSi with cobalt impurities
Место публикации : TRENDS IN MAGNETISM. - 2011. - Vol. 168-169. - С. 493-496. - ISSN 10120394 (ISSN); 9783037850213 (ISBN), DOI 10.4028/www.scientific.net/SSP.168-169.493
Ключевые слова (''Своб.индексиров.''): iron monosilicide--kondo effect--magnetization--resistivity--spindependent scattering--superparamagnetic cluster--cobalt--crystals--electric resistance--electron energy loss spectroscopy--kondo effect--magnetic field effects--magnetic properties--magnetization--magnetoresistance--scattering--superparamagnetism--transport properties--cobalt--electric conductivity--electron scattering--impurities--kondo effect--magnetism--magnetization--experimental investigations--kondo models--magnetoresistance properties--resistivity--si crystals--spin dependent scattering--superparamagnetic clusters--crystal impurities--crystal impurities
Аннотация: The results of experimental investigations of Fe1-xCo xSi crystals in the impurity limit are presented in this article. We made an attempt to study changes of magnetic properties and conductivity in mixed Fe1-xCoxSi crystals in the impurity limit. Magnetoresistance properties are well described in the framework of Kondo model. The presence of Co-subsystem leads to the occurrence of spin-dependent channel in electron scattering conduction.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Yu., Val'kov V. V.
Заглавие : Anomalous Resistivity and the Origin of Heavy Mass in the Two-Band Hubbard Model with One Narrow Band
Место публикации : J. Exp. Theor. Phys. - NEW YORK: PLEIADES PUBLISHING INC, 2011. - Vol. 113, Is. 1. - С. 156-171. - JUL. - ISSN 1063-7761, DOI 10.1134/S1063776111060021. - ISSN 1090-6509
Примечания : Cited Reference Count: 87. - RFBRRussian Foundation for Basic Research (RFBR) [08-02-00224, 08-02-00212]; Leverhulme trustLeverhulme Trust; CNRSCentre National de la Recherche Scientifique (CNRS)European Commission [236694], We are grateful to A. S. Alexandrov, A. F. Andreev, A. F. Barabanov, M. A. Baranov, Yu. Bychkov, A. V. Chubukov, D. V. Efremov, P. Fulde, A. S. Hewson, Yu. Kagan, K. A. Kikoin, K. I. Kugel, F. V. Kusmartsev, M. Mezard, Yu. E. Lozovik, P. Nozieres, N. V. Prokof'ev, A. L. Rakhmanov, T. M. Rice, A. O. Sboychakov, G. V. Shlyapnikov, P. Thalmeyer, C. M. Varma, D. Vollhardt, P. Woelfle, and A. Yaresko for the numerous simulating discussions on this subject and acknowledge financial support of the RFBR grants nos. 08-02-00224, 08-02-00212. M. Yu. K. is also grateful to Loughborough University (UK) and LPTMS (Orsay, France) for the hospitality during the final stage of this work and acknowledges financial support from the Leverhulme trust and CNRS (contract no. 236694).
Предметные рубрики: Physics, Multidisciplinary
Аннотация: We search for marginal Fermi-liquid behavior [1] in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron polaron effect [2] and other mechanisms of mass enhancement (related to momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find the tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case for a large mismatch between the densities of heavy and light bands in the strong-coupling limit. We also observe that for low temperatures and equal densities, the homogeneous state resistivity R(T) similar to T-2 behaves in a Fermi-liquid fashion in both 3D and 2D cases. For temperatures higher than the effective bandwidth for heavy electrons T W-h*, the coherent behavior of the heavy component is totally destroyed. The heavy particles move diffusively in the surrounding of light particles. At the same time, the light particles scatter on the heavy ones as if on immobile (static) impurities. In this regime, the heavy component is marginal, while the light one is not. The resistivity saturates for T W-h* in the 3D case. In 2D, the resistivity has a maximum and a localization tail due to weak-localization corrections of the Altshuler-Aronov type [3]. Such behavior of resistivity could be relevant for some uranium-based heavy-fermion compounds like UNi2Al3 in 3D and for some other mixed-valence compounds possibly including layered manganites in 2D. We also briefly consider the superconductive (SC) instability in the model. The leading instability is towards the p-wave pairing and is governed by the enhanced Kohn-Luttinger [4] mechanism of SC at low electron density. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light ones in 2D.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Valkov V. V.
Заглавие : Anomalous resistivity and superconductivity in the two-band Hubbard model with one narrow band (Review)
Место публикации : Low Temp. Phys. - 2011. - Vol. 37, Is. 1. - P.69-82. - ISSN 1063-777X, DOI 10.1063/1.3552118; \b Физика низких температур
Примечания : Cited References: 62. - We thank A.S. Alexandrov, A.F. Andreev, M.A. Baranov, Yu. Bichkov, A.V. Chubukov, D.V. Efremov, A.S. Hewson, K.A. Kikoin, F.V. Kusmartsev, P. Nozieres, T.M. Rice, A.O. Sboychakov, P. Thalmeer, C.M. Varma, D. Vollhardt, P. Woelfle, A. Yaresko and, especially, P. Fulde, Yu. Kagan, K.I. Kugel, and N.V. Prokof'ev for many simulating discussions on this subject and acknowledge the financial support of RFBR grants # 08-02-00224 and 08-02-00212. M.Yu.K. is also grateful to the Leverhulme trust for a grant to visit Loughborough University, where this work was completed.
Предметные рубрики: FERMI-LIQUID BEHAVIOR
MAGNETIC-ALLOYS
HEAVY
DENSITY
SYSTEMS
STATE
UPT3
MECHANISM
PARTICLE
VALENCE
Аннотация: We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron-polaron effects and other mechanisms for mass-enhancement (related to the momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find a tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case with a large mismatch between the densities of heavy and light bands in the strong coupling limit. We also find that for low temperatures and equal densities, the resistivity in a homogeneous state R(T) proportional to T-2 behaves as a Fermi-liquid in both 3D and 2D. For temperatures greater than the effective bandwidth for heavy electrons T W-h*, the coherence of the heavy component breaks down completely. The heavy particles move diffusively in the surrounding light particles. At the same time, light particles scatter on heavy particles as if on immobile (static) impurities. Under these conditions, the heavy component is marginal, while the light component is not. The resistivity approaches saturation for T W-h* in the 3D case. In 2D the resistivity has a maximum and a localization tail owing to weak-localization corrections of the Altshuler-Aronov type. This behavior of resistivity in 3D could be relevant for some uranium-based heavy-fermion compounds such as UNi2Al3 and in 2D, for some other mixed-valence compounds, possibly including layered manganites. We also consider briefly the superconductive (SC) instability in this model. The leading instability tends to p-wave pairing and is governed by an enhanced Kohn-Luttinger mechanism for SC at low electron densities. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light electrons in 2D. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552118]
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19.

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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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Pchelkina Z. V.
Заглавие : Electronic Structure of p-Type La1-xMx2+MnO3 Manganites in the Ferromagnetic and Paramagnetic Phases in the LDA plus GTB Approach
Разночтения заглавия :авие SCOPUS: Electronic structure of p-Type La 1-x M x 2+ MnO 3 manganites in the ferromagnetic and paramagnetic phases in the LDA + GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 5. - P860-876. - ISSN 1063-7761, DOI 10.1134/S1063776111030101
Примечания : Cited References: 47. - This study was supported financially by integration project no. 40 of the Ural and Siberian Branches of the Russian Academy of Sciences, the program "Strong Electron Correlations" of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 10-02-00251-a).
Предметные рубрики: DOUBLE-EXCHANGE
COLOSSAL MAGNETORESISTANCE
THIN-FILMS
PHYSICS
LA1-XSRXMNO3
RESISTIVITY
SEPARATION
TRANSPORT
MODEL
Ключевые слова (''Своб.индексиров.''): complex structure--cubic materials--ferromagnetic phase--half metals--jahn teller effect--metal properties--metal types--orbitals--p-type--paramagnetic phase--paramagnetic phasis--quasi particles--spectral intensity--spin projections--strong electron correlations--barium--density functional theory--electron correlations--electron density measurement--electronic properties--electronic structure--fermi level--ferromagnetic materials--ferromagnetism--manganese oxide--manganites--paramagnetic materials--paramagnetism--valence bands--lanthanum
Аннотация: The band structure, spectral intensity, and position of the Fermi level in doped p-type La1-xMx2+ MnO3 manganites (M = Sr, Ca, Ba) is analyzed using the LDA + GBT method for calculating the electronic structure of systems with strong electron correlations, taking into account antiferro-orbital ordering and using the Kugel-Khomskii ideas and real spin S = 2. The results of the ferromagnetic phase reproduce the state of a spin half-metal with 100% spin polarization at T = 0, when the spectrum is of the metal type for a quasiparticle with one spin projection and of the dielectric type for the other. It is found that the valence band becomes approximately three times narrower upon a transition to the paramagnetic phase. For the paramagnetic phase, metal properties are observed because the Fermi level is located in the valence band for any nonzero x. The dielectrization effect at the Curie temperature is possible and must be accompanied by filling of d(x) orbitals upon doping. The effect itself is associated with strong electron correlations, and a complex structure of the top of the valence band is due to the Jahn-Teller effect in cubic materials. DOI: 10.1134/S1063776111030101
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