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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Ovchinnikov S. G., Korshunov M. M., Eremin I. M., Kazak N. V.
Заглавие : Specific features of spin, charge, and orbital ordering in cobaltites
Коллективы : RFBR [09-02-00171-a, 07-02-00226, 09-02-00127]; Federal Agency of Science and Innovation [MK-4278.2008.2]; Presidium of the Russian Academy of Sciences [5, 7]; Leading Science Schools of the Ministry of Education and Science of the Russian Federation [2.1.1/3199]
Место публикации : Phys. Usp.: Turpion Ltd, 2009. - Vol. 52, Is. 8. - P.789-810. - ISSN 1063-7869, DOI 10.3367/UFNe.0179.200908b.0837
Примечания : Cited References: 278. - This work was financially supported by the RFBR (projects 09-02-00171-a, 07-02-00226, and 09-02-00127), the Federal Agency of Science and Innovation (grant MK-4278.2008.2), and the Presidium of the Russian Academy of Sciences Program No. 5, Quantum Physics of Condensed Media (project No. 7). I.M.E.'s work was supported by the program for Leading Science Schools of the Ministry of Education and Science of the Russian Federation (grant 2.1.1/3199).
Предметные рубрики: PEROVSKITE-TYPE OXIDES
METAL-INSULATOR-TRANSITION
HIGH-TEMPERATURE SUPERCONDUCTIVITY
ONE-DIMENSIONAL CA3CO2O6
ELECTRONIC-STRUCTURE
MAGNETIC-PROPERTIES
TRANSPORT-PROPERTIES
STATE TRANSITION
FUEL-CELLS
CRYSTAL-STRUCTURE
Ключевые слова (''Своб.индексиров.''): cobalt oxides--lanthanides--orbital degrees of freedom--orbital ordering--quasi-one-dimensional--spin state--superconducting compounds--theoretical result--calcium--cobalt--lanthanum--oxide minerals--perovskite--spin dynamics--superconductivity--cobalt compounds
Аннотация: Complex cobalt oxides known as cobaltites are reviewed, including LnCoO(3)-based perovskite-structured rare-earth cobaltites (where Ln is lanthanum or a lanthanide), quasi-two-dimensional and quasi-one-dimensional cobaltites of the types LnCo(2)O(5+delta), La2CoO4, and Ca3Co2O8, and NaxCoO2 center dot yH(2)O superconducting compounds. Key experimental and theoretical results are presented, with emphasis on the interplay between charge, spin, and orbital degrees of freedom. Two problems of specific relevance to cobaltites - the spin state instability of Co3+ ions in LnCoO(3), and the nature of superconductivity in NaxCoO2 center dot yH(2)O - are also given significant attention.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Popkov S. I., Shaikhutdinov K. A., Petrov M. I.
Заглавие : Mechanisms of dissipation in a Josephson medium based on a high-temperature superconductor in a magnetic field
Разночтения заглавия :авие SCOPUS: Mechanisms of dissipation in a josephson medium based on a high-temperature superconductor in a magnetic field
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48, Is. 5. - P826-832. - ISSN 1063-7834, DOI 10.1134/S1063783406050039
Примечания : Cited References: 32
Предметные рубрики: RESISTIVE TRANSITION
PHASE-SLIP
TRANSPORT-PROPERTIES
MAGNETORESISTANCE
SYSTEM
MODEL
YBA2CU3O7-X
PENETRATION
COMPOSITES
HYSTERESIS
Аннотация: This paper reports on the results of an investigation into the influence of magnetic fields (0-60 kOe) on the temperature dependences of the electrical resistance R(T) of the Y3/4Lu1/4Ba2Cu3O7 + CuO composites. The structure of these composites is considered to be a network of tunnel-type Josephson junctions in which a nonsuperconducting component (CuO) forms boundaries (barriers) between high-temperature superconducting crystallites. The temperature dependence R(T) of the composites has two steps characteristic of granular superconductors: (i) an abrupt change in the electrical resistance at the critical temperature of high-temperature superconducting crystallites and (ii) a smooth transition to the superconducting state under the influence of the boundaries between the crystallites. The experimental dependences R(T) are analyzed within the Ambegaokar-Halperin model of thermal fluctuations in Josephson junctions and the flux creep model. An increase in the magnetic field leads to a crossover from the Ambegaokar-Halperin mechanism to the flux creep mechanism. The temperature dependences R(T) in the range of weak magnetic fields (from 0 to 10(2) Oe) are adequately described by the relationship following from the Ambegaokar-Halperin model. In the range of strong magnetic fields (from 10(3) to 6 x 10(4) Oe), the dissipation obeys the Arrhenius law R similar to exp(-U(H)/T)], which is characteristic of the flux creep model with a temperature-independent pinning energy U(H). The effective Josephson coupling energies and the pinning energies corresponding to the Ambegaokar-Halperin and flux creep mechanisms are determined.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ivanova N. B., Ovchinnikov S. G., Balaev A. D., Aminov T. G., Shabunina G. G., Chernov V. K., Petukhov M. V.
Заглавие : Comparison of negative magnetoresistance mechanisms in manganese perovskites and chromium spinels
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1999. - Vol. 41, Is. 10. - P1652-1655. - ISSN 1063-7834, DOI 10.1134/1.1131064
Примечания : Cited References: 17
Предметные рубрики: ANISOTROPIC MAGNETORESISTANCE
TRANSPORT-PROPERTIES
THIN-FILMS
ALLOYS
Аннотация: A transition of the field dependence of the electrical resistivity from a square law (similar to H-2) above T-c to a linear function (similar to H) below T-c is observed in the degenerate ferromagnetic semiconductor HgCr2Se4(n). Together with the large negative magnetoresistance, these magnetoelectric effects correspond to effects observed in the perovskite-type oxides La1-xCaxMnOdelta. Inasmuch as the undoped semiconductor HgCr2Se4 is a ferromagnet with approximately the same critical temperature as the doped semiconductor and in view of the total lack of data on the Jahn-Teller effect in this compound, we infer that our results cast doubt on existing hypotheses (polaron and binary exchange) regarding the origin of the giant magnetoresistance in La1-xCaxMnOdelta. Impurity sd scattering is discussed as a possible magnetoresistance mechanism for both compounds. (C) 1999 American Institute of Physics. [S1063-7834(99)01710-4].
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4.

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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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Tambasov I. A., Voronin A. S., Evsevskaya N. P., Kuznetsov, Yu M., Luk'yanenko A. V., Tambasova E. V., Gornakov M. O., Dorokhin, M., V, Loginov, Yu Yu
Заглавие : Experimental study of the thermal conductivity of single-walled carbon nanotube-based thin films
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk Territory; Krasnoyarsk Territorial Foundation for Support of Scientific and RD Activity [18-42-243010]; Russian FederationRussian Federation [SP-2235.2019.1]
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 6. - P.1090-1094. - ISSN 1063-7834, DOI 10.1134/S1063783420060311. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 21. - 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 Activity, project Study of the Thermal Conductivity and Structural Features in Nanostructured Oxide Thin Films Promising for Thermoelectric Applications no. 18-42-243010 and the Scholarships of the President of the Russian Federation (SP-2235.2019.1).
Предметные рубрики: THERMOELECTRIC PROPERTIES
TRANSPORT-PROPERTIES
Аннотация: The single-walled carbon nanotube-based thin films with a thickness from 11 ± 3 to 157 ± 18 nm have been formed using vacuum filtration. The thermal conductivity of the thin films as a function of thickness and temperature up to 450 K has been studied by the 3ω technique. It has been found that, in the region of 49 nm, the supplied heat from a gold strip started propagating with the high efficiency to the thin film plane. The thermal conductivity of the thin films with a thickness of 49 ± 8 nm was measured using the 3ω technique for bulk samples. It has been found that the thermal conductivity of the single-walled carbon nanotube-based thin films strongly depends on their thickness and temperature. The thermal conductivity sharply (by a factor of ~60) increases with an increase in thickness from 11 ± 3 to 65 ± 4 nm. In addition, it has been observed that the thermal conductivity of the thin film with a thickness of 157 ± 18 nm rapidly decreases from 211 ± 11 to 27.5 ± 1.4 W m–1 K–1 at 300 and 450 K, respectively.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Koblischka, Michael R., Naik, Sugali Pavan Kumar, Koblischka-Veneva, Anjela, Murakami, Masato, Gokhfeld D. M., Reddy, Eddula Sudhakar, Schmitz, Georg J.
Заглавие : Superconducting YBCO Foams as Trapped Field Magnets
Коллективы : ANR [ANR-17-CE05-0030]; DFG [DFG-ANR Ko2323-10]; SIT start-up grant
Место публикации : Materials. - 2019. - Vol. 12, Is. 6. - Ст.853. - ISSN 1996-1944, DOI 10.3390/ma12060853
Примечания : Cited References: 62. - This work is part of the SUPERFOAM international project funded by ANR and DFG under the references ANR-17-CE05-0030 and DFG-ANR Ko2323-10, respectively. Further funding by a SIT start-up grant is also gratefully acknowledged.
Предметные рубрики: CRITICAL CURRENT-DENSITY
TRANSPORT-PROPERTIES
SINGLE-GRAIN
BULK
Ключевые слова (''Своб.индексиров.''): high-tc superconductors--ybco--foam--trapped fields--current flow
Аннотация: Superconducting foams of YBa2Cu3Oy (YBCO) are proposed as trapped field magnets or supermagnets. The foams with an open-porous structure are light-weight, mechanically strong and can be prepared in large sample sizes. The trapped field distributions were measured using a scanning Hall probe on various sides of an YBCO foam sample after field-cooling in a magnetic field of 0.5 T produced by a square Nd-Fe-B permanent magnet. The maximum trapped field (TF) measured is about 400 G (77 K) at the bottom of the sample. Several details of the TF distribution, the current flow and possible applicatons of such superconducting foam samples in space applications, e.g., as active elements in flux-pinning docking interfaces (FPDI) or as portable strong magnets to collect debris in space, are outlined.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Popkov S. I., Semenov S. V., Bykov A. A., Sabitova E. I., Dubrovskiy A. A., Shaikhutdinov K. A., Petrov M. I.
Заглавие : Contributions from Inter-grain Boundaries to the Magneto-resistive Effect in Polycrystalline High-T (C) Superconductors. The Underlying Reason of Different Behavior for YBCO and BSCCO Systems
Разночтения заглавия :авие SCOPUS: Contributions from inter-grain boundaries to the magneto-resistive effect in polycrystalline high-TC superconductors. the underlying reason of different behavior for YBCO and BSCCO systems
Место публикации : J. Supercond. Nov. Magn: SPRINGER, 2011. - Vol. 24, Is. 7. - P2129-2136. - ISSN 1557-1939, DOI 10.1007/s10948-011-1166-9
Примечания : Cited References: 30. - This work is supported by program N5 of RAS, project N7.
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
PHASE-SLIP
TRANSPORT-PROPERTIES
TRANSITION
FIELD
COMPOSITES
BULK
TAPES
YBA2CU3O7-DELTA
DISSIPATION
Ключевые слова (''Своб.индексиров.''): bscco--ybco--intergrain boundaries--magnetoresistance--bscco--intergrain boundaries--magnetoresistance--ybco--bscco--bscco system--comparative studies--high tc superconductors--high-field--inter-grain--irreversibility lines--magneto-resistive effect--polycrystalline--resistive transition--standard measurements--weak pinning--ybco--bismuth--electric resistance--grain boundaries--high temperature superconductors--lead--magnetic fields--magnetoelectronics--magnetoresistance--magnetos--superconductivity--yttrium barium copper oxides--semiconductor metal boundaries
Аннотация: In order to clarify the mechanisms in charge of broadening of resistive transition R(T) in magnetic fields of bismuth-based polycrystalline high-T (C) superconductor (HTSC), a comparative study of Bi1.8Pb0.3Sr1.9Ca2Cu3O (x) (BSCCO) and YBa2Cu3O7-delta (YBCO) have been performed. Magnetoresistive effects and irreversibility line obtained from magnetic measurements have been studied. It was established that (1) for YBCO, the smooth part of R(T) dependence unambiguously corresponds to dissipation in the intergrain boundaries for arbitrary magnetic fields; (2) for polycrystalline BSCCO, the smooth part of R(T) dependences correspond to dissipation within intergrain boundary subsystem in the field range H 10(2) Oe only, while standard measurements of R(T) dependences in magnetic field range H 10(2) Oe reflect the dissipation processes occurring both in intergrain boundary and HTSC grain subsystems; (3) for the high-field range, the contribution from intergrain boundaries of BSCCO can be distinguished from magnetoresistance R(H) dependences obtained at high enough current density on textured samples. It is proposed that various magneto-resistive properties of these classical HTSC systems are due comparatively weak pinning in BSCCO.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivantsov R. D., Edelman I. S., Zharkov S. M., Velikanov D. A., Petrov D. A., Ovchinnikov S. G., Lin C.-R., Li O., Tseng Y.-T.
Заглавие : Effects of processing parameters on the morphology, structure, and magnetic properties of Cu1-xFexCr2Se4 nanoparticles synthesized with chemical methods
Место публикации : J. Alloys Compd.: Elsevier, 2015. - Vol. 650. - P.887-895. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2015.08.017
Примечания : Cited References: 36. - The paper was partially supported by the Russian Foundation for Basic Research (grant #14-02-01211), by the President of Russia (grant #NSh-2886.2014.2), and by the Ministry of Education and Science of the Russian Federation (grant #2014/71/1763 in the framework of the state assignment for the Siberian Federal University for 2014-2016). We also thank the Ministry of Science and Technology of Taiwan and the Siberian Branch of RAS (MOST 102-2112-M-153 -002 -MY3) for financial support.
Предметные рубрики: CuCr2Se4 SINGLE-CRYSTALS
TRANSPORT-PROPERTIES
CHROMIUM SPINELS
NANOSTRUCTURES
DIFFRACTION
Li
Ключевые слова (''Своб.индексиров.''): copper selenide--magnetic nanoparticles--visible magnetic circular dichroism
Аннотация: Cu1-xFexCr2Se4 nanoparticles with x = 0, 0.2, and 0.4 were synthesized via thermal decomposition of metal nitrate or chloride salts and selenium powder using different precursor compositions and processing details. Single crystalline nano-belts or nano-rods coexist in the synthesized powder samples with hexagon-shaped plates in dependence on the precursor composition. The belts gathered into conglomerates forming "hierarchical" particles. Visible magnetic circular dichroism (MCD) of Cu1-xFexCr2Se4 nanoparticles embedded into a transparent matrix was investigated for the first time. The similarity of the MCD spectra of all samples showed the similarity of the nanoparticles electronic structure independent of their morphology. Basing on the MCD spectral maxima characteristics, electron transitions from the ground to the excited states were identified with the help of the conventional band theory and the multi-electron approach. © 2015 Elsevier B.V.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskii A. A., Popkov S. I., Gokhfeld D. M., Semenov S. V., Shaikhutdinov K. A., Petrov M. I.
Заглавие : Specific features in the hysteretic behavior of the magnetoresistance of granular high-temperature superconductors
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 11. - P.2155-2164. - ISSN 1063-7834, DOI 10.1134/S1063783412110030
Примечания : Cited References: 52. - This study was supported by the Russian Foundation for Basic Research within the framework of the Regional Competition SIBERIA (project no. 11-02-98007 r-sibir'_a).
Предметные рубрики: CURRENT-VOLTAGE CHARACTERISTICS
WEAK MAGNETIC-FIELDS
CRITICAL-CURRENT DENSITY
T-C SUPERCONDUCTORS
ANGULAR-DEPENDENCE
JOSEPHSON MEDIUM
TRANSPORT-PROPERTIES
CRITICAL-STATE
YBa2Cu3O7-DELTA
COMPOSITES
Аннотация: The behavior of the hysteresis of the magnetoresistance R(H) of granular high-temperature superconductors has been investigated under the conditions where the resistive response of the subsystem of grain boundaries close to saturation. The hysteretic dependences R(H) have been measured for Y1-xPrxBa2Cu3O7 samples at x = 0.11 and 0.04 with the transition temperatures T-C approximate to 85.5 and 91.0 K, respectively. The evolution of the field width of the hysteresis R(H) has been examined by varying the measuring current. The limit of the applicability has been established for the concept of the effective field in the intergranular medium, which was previously proposed for the description of the hysteretic behavior of the magnetoresistance R(H) and thermal magnetic prehistory of the granular high-temperature superconductors. In the studied samples, the approximation of the effective field in the intergranular medium is applicable until the magnetoresistance of the subsystem of grain boundaries exceeds (90 +/- 5)% of the maximum value.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Exotic superconductivity and magnetism in ruthenates
Место публикации : Phys. Usp.: TURPION LTD, 2003. - Vol. 46, Is. 1. - P21-44. - ISSN 1063-7869, DOI 10.1070/PU2003v046n01ABEH001235
Примечания : Cited References: 167
Предметные рубрики: ITINERANT FERROMAGNET SRRUO3
SPIN-TRIPLET SUPERCONDUCTIVITY
STRONGLY CORRELATED ELECTRONS
T-J-MODEL
J-I-MODEL
TRANSPORT-PROPERTIES
MOTT-INSULATOR
FERMI-SURFACE
LAYERED PEROVSKITE
RUTHENIUM OXIDES
Ключевые слова (''Своб.индексиров.''): electronic structure--magnetic properties--magnetism--oxide superconductors--strontium alloys--superconductivity--electron correlations--ruthenates--rutheno-cuprates--spin-triplet pairing--ruthenium compounds
Аннотация: Basic experimental and theoretical results on ruthenates and rutheno-cuprates are reviewed. The electronic structure of various ruthenates and exotic superconductivity in Sr2RuO4 with spin-triplet pairing are described. The complex phase diagram of Ca2-xSrxRuO4, involving competing magnetic phases and metal-insulator transitions, is described, as are the exotic magnetic properties of Sr3Ru2O7 and of the double perovskite Sr2YRuO6, and the coexistence of superconductivity and magnetism in the rutheno-cuprate RuSr2GdCu2O8. Possible applications of Sr2RuO4 and SrRuO3 are considered. The effect of strong electron correlations is discussed, and the properties of ruthenates and cuprates are compared.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Gokhfeld D. M., Dubrovskii A. A., Popkov S. I., Shaikhutdinov K. A., Petrov M. I.
Заглавие : Magnetoresistance hysteresis in granular HTSCs as a manifestation of the magnetic flux trapped by superconducting grains in YBCO+CuO composites
Разночтения заглавия :авие SCOPUS: Magnetoresistance hysteresis in granular HTSCs as a manifestation of the magnetic flux trapped by superconducting grains in YBCO + CuO composites
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 105, Is. 6. - P1174-1183. - ISSN 1063-7761, DOI 10.1134/S1063776107120084
Примечания : Cited References: 53
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTOR
CRITICAL-CURRENT-DENSITY
CURRENT-VOLTAGE CHARACTERISTICS
BA-CU-O
TRANSPORT-PROPERTIES
FIELD
YBA2CU3O7-DELTA
FLUCTUATIONS
FINGERPRINT
NETWORK
Ключевые слова (''Своб.индексиров.''): critical currents--hysteresis--hysteresis loops--josephson junction devices--magnetic flux--magnetoresistance--yttrium barium copper oxides--granular superconductors--hysterestic dependence--negative magnetoresistance--transport current--composite materials
Аннотация: Hysterestic behavior of the magnetoresistance of granular HTSCs and its interaction with the magnetic hysteresis are studied by measuring magnetoresistance R(H) and critical current I-c(H) of composites formed by HTSC Y0.75Lu0.25Ba2CU3O7 and CuO. A network of Josephson junctions is formed in such composites, in which the nonsuperconducting component plays the role of barriers between HTSC grains. Hysteretic dependences R(H) of magnetoresistance are studied in a wide range of transport current density j and are analyzed in the framework of the two-level model of a granular superconductor, in which dissipation takes place in the Josephson medium and the magnetic flux can be pinned both in grains and in the Josephson medium. The interrelation between the hysteresis of critical current I-c(H) and the evolution of the hysterestic dependence R(H) of the magnetoresistance upon transport current variation is demonstrated experimentally. The effect of the magnetic past history on the hysteretic behavior of R(H) and the emergence of a segment with a negative magnetoresistance are analyzed. It is shown for the first time that the R(H) dependences are characterized by a parameter that is independent of the transport current, viz., the width of the R(H) hysteresis loop.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Bykov A. A., Semenov S. V., Popkov S. I., Dubrovskii A. A., Shaikhutdinov K. A., Petrov M. I.
Заглавие : General regularities of magnetoresistive effects in the polycrystalline yttrium and bismuth high-temperature superconductor systems
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 5. - P922-932. - ISSN 1063-7834, DOI 10.1134/S1063783411050052
Примечания : Cited References: 52. - This study was supported by the Russian Academy of Sciences within the program no. 5 (project no. 7).
Предметные рубрики: HIGH MAGNETIC-FIELDS
PHASE-SLIP
RESISTIVE TRANSITION
CU-O
TRANSPORT-PROPERTIES
JOSEPHSON MEDIUM
MIXED-STATE
FLUX-CREEP
T-C
DISSIPATION
Аннотация: The influence of thermomagnetic prehistory on the behavior of a resistive transition R(T) in external magnetic fields of polycrystalline YBa(2)Cu(3)O(7) and Bi(1.8)Pb(0.3)Sr(1.9)Ca(2)Cu(3)O (x) high-temperature supercon-ductors and the Bi(1.8)Pb(0.3)Sr(1.9)Ca(2)Cu(3)O (x) + Ag texture has been investigated. It has been found that, for YBa(2)Cu(3)O(7), the thermomagnetic prehistory exerts a substantial influence on the dissipation in the subsystem of grain boundaries in magnetic fields up to similar to 10(3) Oe, and this effect becomes insignificant in fields higher than similar to 10(4) Oe. This behavior has been explained by the influence of magnetic moments of high-temperature superconductor grains on the effective magnetic field in the intergranular medium. For bismuth high-temperature superconductors, no influence of thermomagnetic prehistory on the resistive transition has been observed; however, this effect manifests itself in current-voltage characteristics at high transport current densities. There is also a radical difference in the behavior of isotherms of the magnetoresistance R(H) for the yttrium and bismuth systems. For YBa(2)Cu(3)O(7), there is a clear separation between the dissipation regimes in the intergranular medium and in grains, which manifests itself even at low transport current densities as a change of sign in the curvature of the dependence R(H). For a texture based on the bismuth high-temperature superconductor, this feature has been observed only at high current densities (comparable to the critical current density at H = 0). This difference in the behavior of magnetoresistive properties of the classical high-temperature superconductor systems under investigation has been explained by relatively low irreversibility fields of the bismuth high-temperature superconductors. In these materials, simultaneous processes of dissipation can occur in an external magnetic field both in the subsystem of grain boundaries between crystallites and in the crystallites themselves.
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