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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Vasilyev A. D., Zwegintsev S. A., Петров, Михаил Иванович, Khrustalev B. P.
Заглавие : Peculiarities of the resistive state of the (Y,Lu)1Ba2Cu3O7-δ superconducting ceramics
Место публикации : Physica C. - 1988. - Vol. 156, Is. 2. - P.249-250. - ISSN 0921-4534
Ключевые слова (''Своб.индексиров.''): ceramic materials--oxides--current voltage characteristics--yttrium barium copper oxides--superconducting materials
Аннотация: The resistive state of the high-Tc superconducting ceramics (Y, Lu)1Ba2Cu3O7-δ has been investigated, a hysteresis instability has been discovered in the current-voltage characteristics (CVC) under a current density j ≈ 1.7 kA cm-2. © 1988.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Khrustalev B. P., Krivomazov S. N., Петров, Михаил Иванович, Vasilyev A. D., Zwegintsev S. A.
Заглавие : Superconductivity near liquid nitrogen temperature in the Sn-Ba-Sr-Y-Cu-O system
Место публикации : Physica C-Superconductivity and its Applications. - 1989. - Vol. 161, Is. 4. - P.493-496. - ISSN 0921-4534, DOI 10.1016/0921-4534(89)90087-7
Ключевые слова (''Своб.индексиров.''): ceramic materials--tin compounds--bulk superconductivity--high temperature superconductors--oxide superconductors--tin barium strontium yttrium copper oxide--superconducting materials
Аннотация: A high-Tc phase was found in the Sn-Ba-Sr-Y-Cu-O system. DC susceptibility data of Sn2Ba2Sr0.5Y0.5Cu3Ox show a single transition to bulk superconductivity with an onset temperature of 86 K. В© 1989.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : On the coordinate of a singular point of time correlation functions for the system of nuclear magnetic moments of a crystal
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2003. - Vol. 97, Is. 1. - P78-84. - ISSN 1063-7761, DOI 10.1134/1.1600799
Примечания : Cited References: 22
Предметные рубрики: DIPOLAR FLUCTUATION SPECTRUM
FREE-INDUCTION DECAY
CROSS-RELAXATION
DOUBLE-RESONANCE
SPIN SYSTEMS
NMR-SPECTRA
LINE SHAPE
IRREVERSIBILITY
ABSORPTION
CAF2
Ключевые слова (''Своб.индексиров.''): absorption spectroscopy--barium compounds--crystallography--lattice constants--magnetic fields--nuclear magnetic resonance--absorption spectrum--dipole-dipole interaction--magnetic field directions--nuclear magnetic moments--magnetic moments
Аннотация: The hypothesis concerning the existence of singular points on the imaginary time axis for a correlation function of a system with the dipole-dipole interaction of nuclear spins of a crystal is verified. Within the framework of the self-consistent fluctuating field theory taking into account the principal corrections related to the correlation of local fields, a result for this coordinate is obtained in terms of the ratios of lattice sums. Experimental values of this coordinate are calculated from the wings of the nuclear magnetic resonance absorption spectrum of a BaF2 crystal for the magnetic field directions along the three crystallographic axes. Good agreement of the theoretical and experimental results justifies this hypothesis. (C) 2003 MAIK "Nauka / Interperiodica".
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bondarev V. S., Sciau P., Savariault J. M.
Заглавие : Heat capacity and thermal expansion study of relaxor-ferroelectric Ba0.92Ca0.08Ti0.76Zr0.24O3
Разночтения заглавия :авие SCOPUS: Heat capacity and thermal expansion study of relaxor-ferroelectric Ba 0.92Ca0.08Ti0.76Zr0.24O3
Место публикации : J. Phys.: Condens. Matter. - 2004. - Vol. 16, Is. 39. - P.7143-7150. - ISSN 0953-8984, DOI 10.1088/0953-8984/16/39/045
Примечания : Cited References: 18
Предметные рубрики: CERAMICS
BA(TI1-XZRX)O-3
PEROVSKITES
Ключевые слова (''Своб.индексиров.''): calorimetry--dielectric properties--ferroelectric materials--perovskite--phase transitions--solid solutions--specific heat--thermal expansion--adiabatic calorimetry--frequency dispersion--polar domains--relaxor ferroelectrics--barium compounds
Аннотация: Heat capacity and thermal expansion of the Ba0.92Ca0.08Ti0.76Zr0.24O3 compound is measured using the methods of adiabatic calorimetry and optic-mechanical dilatometry in the temperature range 100-370 K. Three blurred anomalies on the C-p(T) and alpha(T) dependencies are observed in the temperature range 200-360 K. The results of the studies are discussed together with data on the structure and dielectric properties in the framework of spherical random bond-random field model.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Shaihutdinov K. A., Popkov S. I., Gokhfeld D. M., Petrov M. I.
Заглавие : Magnetoresistive effect in bulk composites 1-2-3 YBCO+CuO and 1-2-3 YBCO+BaPb(1-x)SnxO(3) and their application as magnetic field sensors at 77 K
Разночтения заглавия :авие SCOPUS: Magnetoresistive effect in bulk composites 1-2-3 YBCO + CuO and 1-2-3 YBCO + BaPb1-xSnxO3 and their application as magnetic field sensors at 77 K
Место публикации : Supercond. Sci. Technol.: IOP PUBLISHING LTD, 2004. - Vol. 17, Is. 1. - P175-181. - ISSN 0953-2048, DOI 10.1088/0953-2048/17/1/031
Примечания : Cited References: 27
Предметные рубрики: PHASE-SLIP
SUPERCONDUCTOR
TEMPERATURE
YBA2CU3O7-DELTA
TRANSITION
Ключевые слова (''Своб.индексиров.''): ceramic materials--composite materials--critical current density (superconductivity)--high temperature operations--high temperature superconductors--lead compounds--magnetoresistance--sensors--yttrium barium copper oxides--high temperature superconductor ceramics--magnetic field sensors--magnetoresistive effect--transport current density--oxide superconductors
Аннотация: We have studied the magnetoresistive effect in bulk 1-2-3 YBCO + CuO and 1-2-3 YBCO + BaPb1-xSnxO3 composites prepared using the fast backing technique. We have found that the composites exhibit large magnetoresistance in low magnetic fields ( 100 Oe) for a broad temperature range. We have studied the experimental dependences of resistivity versus magnetic field at various transport current densities. The high-T-C superconductor (HTSC) based composites exhibit a much higher sensitivity to weak magnetic fields at liquid nitrogen temperature, compared to that for pure HTSC ceramics. This effect is attractive for practical applications and the composite materials can be used as active elements in magnetic field sensor devices.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Gokhfeld D. M., Balaev D. A., Shaihutdinov K. A., Kummel R.
Заглавие : Andreev reflections and experimental current-voltage characteristics of break junctions of polycrystalline HTSC
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2004. - Vol. 408: 7th International Conference on Materials and Mechanisms of Superconductive and High Temperature Superconductors (MAY 25-30, 2003, Rio de Janeiro, BRAZIL). - P620-622. - ISSN 0921-4534, DOI 10.1016/j.physc.2004.03.085
Примечания : Cited References: 3
Ключевые слова (''Своб.индексиров.''): andreev reflections--break junction--current-voltage characteristics--andreev reflections--break junction--current-voltage characteristics--andreev reflections--break junctions--elastic scattering--lattice defects--negative differential resistance--electric fields--heuristic methods--hysteresis--microcracks--polycrystalline materials--probability density function--quasicrystals--superconducting materials--yttrium barium copper oxides--current voltage characteristics
Аннотация: The temperature evolution of current-voltage characteristics (CVCs) of break junctions made from polycrystalline Y0.75Lu0.25Ba2Cu3O7 and La1.85Sr0.15CuO4 is investigated. The experimental CVCs have hysteretic features that reflect a part of a curve with negative differential resistance. The temperature evolution of the CVCs is discussed within the framework of the Kummel-Gunsenheimer-Nicolsky theory for superconductor/normal-metal/superconductor junctions considering multiple Andreev reflections. It is shown that the shape of the CVCs of break junctions is determined by the ratio of the number of "short" and "long" intergrain normal regions in the polycrystalline HTSC under investigation. (C) 2004 Elsevier B.V. All rights reserved.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Bezmaternykh L. N., Gudim I. A., Sheptyakov D., Bayukov O. A., Vorotynov A. M., Velikanov D. A., Bovina A. F.
Заглавие : Synthesis and properties of barium ferrigermanate Ba2Fe2GeO7
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2005. - Vol. 47, Is. 11. - P2114-2118. - ISSN 1063-7834
Примечания : Cited References: 14
Предметные рубрики: COPPER METABORATE
Аннотация: The magnetic susceptibility and specific heat of single crystals of the Ba2Fe2GeO7 barium ferrigermanate are investigated. It is revealed that the temperature dependence of the magnetic susceptibility exhibits a kink at a temperature T = 8.5 K. The number of nonequivalent positions of Fe3+ ions and their occupancies are determined using Mossbauer spectroscopy. It is shown that the Fe3+ ions located in tetrahedral positions T2 are ordered incompletely, which is inconsistent with the results obtained previously. An assumption is made regarding the possible ground magnetic state of the Ba2Fe2GeO7 compound. (c) 2005 Pleiades Publishing, Inc.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Bezmaternykh L. N., Gudim I. A., Bayukov O. A., Vorotynov A. M., Bovina A. F., Szymczak R., Baran M., Ritter C.
Заглавие : Spin glass state in crystals of barium ferrigermanate Ba2Fe2GeO7
Разночтения заглавия :авие SCOPUS: Spin glass state in crystals of barium ferrigermanate Ba2Fe 2GeO7
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48, Is. 10. - P1906-1908. - ISSN 1063-7834, DOI 10.1134/S1063783406100155
Примечания : Cited References: 5
Аннотация: The temperature dependence of the magnetization and elastic neutron scattering spectra of Ba2Fe2GeO7 barium ferrigermanate polycrystals are studied. The magnetization is found to depend on the magnetic prehistory of a Ba2Fe2GeO7 sample below T = 8 K. Analysis of the neutron scattering spectra does not reveal long-range magnetic order down to 2 K. Our experimental data indicate the existence of a spin glass state in Ba2Fe2GeO7 polycrystals.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M., Bondarev V., Sciau P., Savariault J. M.
Заглавие : Heat capacity study of relaxors BaTi0.65Zr0.35O3 and BaTi0.60Zr0.40O3
Разночтения заглавия :авие SCOPUS: Heat capacity study of relaxors BaTi0.65Zr0.35O 3 and BaTi0.60Zr0.40O3
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2006. - Vol. 18, Is. 17. - P.4407-4416. - ISSN 0953-8984, DOI 10.1088/0953-8984/18/17/026
Примечания : Cited References: 21
Предметные рубрики: CERAMICS
BA(TI1-XZRX)O-3
BATIO3
Ключевые слова (''Своб.индексиров.''): calorimetry--composition--data reduction--lead compounds--mathematical models--permittivity--specific heat--adiabatic calorimetry--burns temperature--diffuse anomalies--barium compounds
Аннотация: The heat capacity of two relaxors BaTi(1-x)ZrxO(3) (x = 0.35, 0.40) was measured using adiabatic calorimetry in the temperature range 100-360 K. The Cp(T) dependence of both compositions is characterized by the presence of two diffuse anomalies near the Burns temperature T-d and the temperature of the maximum in permittivity T-m in the temperature ranges 250-350 K and 120 200 K. The anomalous heat capacity near T-d was analysed taking into account the distribution of Zr concentration in nanoregions leading to the distribution of their transition temperatures into the polar phase. Excess heat capacity near Tm was discussed in the framework of the spherical random bond-random field model. The results are compared with the data obtained by the same procedures for PbMg1/3Nb2/3O3 studied experimentally earlier.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bondarev V. S., Flerov I. N., Maglione M., Simon A.
Заглавие : Heat capacity and thermal expansion study of Ba0.9Bi0.067(Ti1-xZrx)O-3 ceramics
Разночтения заглавия :авие SCOPUS: Heat capacity and thermal expansion study of Ba 0.9Bi 0.067(Ti 1-xZr x)O 3 ceramics
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2007. - Vol. 19, Is. 34. - Ст.346237. - ISSN 0953-8984, DOI 10.1088/0953-8984/19/34/346237
Примечания : Cited References: 15
Предметные рубрики: BA(TI1-XZRX)O-3
STATE
Ключевые слова (''Своб.индексиров.''): adiabatic calorimeters--temperature range--temperature regions--thermal expansion anomaly--barium--ceramic materials--dielectric properties--expansion--specific heat--zirconium--thermal expansion
Аннотация: For Ba0.9Bi0.067(Ti1-xZrx)O-3 (x = 0.04, 0.15) ceramics, the heat capacity C-p(T) and the thermal expansion alpha(T) were measured using an adiabatic calorimeter and an optical-mechanical dilatometer in the temperature range 100-420 K. Both compounds reveal diffuse heat capacity and thermal expansion anomalies: three anomalies in the temperature regions 150-250 K, 250-300 K (alpha(T) only) and 300-400 K at x = 0.04 and two anomalies in the regions 200 250 K and 250-350 K at x = 0.15. The results obtained are discussed together with the data on the dielectric properties.
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11.

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 : Time relaxation of residual resistance of HTSC-based composites
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). - P1309-1310. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.347
Примечания : Cited References: 5
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): granular htsc--resistance--relaxation--magnetic flux--granular htsc--magnetic flux--relaxation--resistance--copper oxides--crystallites--magnetic flux--magnetic relaxation--magnetization--yttrium barium copper oxides--anderson-like relaxation processes--flux trapping--residual resistance--time relaxation--josephson junction devices
Аннотация: Magnetoresistance curves R(H) and time relaxation of the residual resistance of bulk YBCO + CuO composites have been studied. These composites represent the network of Josephson junctions, where CuO acts as a barrier between YBCO grains. It has been shown that hysteresis of the R(H) dependences is related to the flux trapping within the YBCO crystallites. This flux induces magnetic field in the intergrain media. Time relaxation of the residual resistance is caused by relaxation of the magnetization of YBCO grains. The time dependence of the residual resistance obeys a logarithmic law, which describes the Anderson-like relaxation processes in the YBCO grains. (c) 2007 Elsevier B.V. All rights reserved.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Kazak N. V., Michel C. R., Balaev A. D., Ovchinnikov S. G., Vasil'ev A. D., Bulina N. V., Panchenko E. B.
Заглавие : Effect of strontium and barium doping on the magnetic state and electrical conductivity of GdCoO3
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 8. - P1498-1506. - ISSN 1063-7834, DOI 10.1134/S1063783407080161
Примечания : Cited References: 36
Предметные рубрики: PEROVSKITE
ORDER
OXIDE
BEHAVIOR
GLASSES
LACOO3
PR
GD
SM
ND
Аннотация: A coordinated investigation of the magnetic and electrical properties of polycrystalline cobalt oxide compounds CdCoO3, Gd0.9Ba0.1CoO3, and Gd0.9Sr0.1CoO3 is carried out. Undoped GdCoO3 reveals a low conductivity; a magnetic moment of 7.4 mu(B) per molecule, which is less than the theoretical value for the Gd3+ ion; and an asymptotic Curie temperature of -6 K. Doping GdCoO3 with barium and strontium to substitution of 10 at. % Gd brings about an increase in the conductivity and magnetic transitions at T = 300 K for Gd0.9Ba0.1CoO3 and T = 170 K for Gd0.9Sr0.1CoO3. The magnetization anomalies imply the formation of magnetic clusters. The behavior of the electrical conductivity at high temperatures suggests a variable activation energy. At low temperatures, Mott hopping conduction sets in.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M.
Заглавие : Description of hysteretic current-voltage characteristics of superconductor-normal metal-superconductor junctions
Место публикации : Supercond. Sci. Technol.: IOP PUBLISHING LTD, 2007. - Vol. 20, Is. 1. - P62-66. - ISSN 0953-2048, DOI 10.1088/0953-2048/20/1/011
Примечания : Cited References: 24
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTOR
WEAK LINKS
POLYCRYSTALLINE HTSC
ANDREEV REFLECTION
SIMPLIFIED MODEL
COMPOSITES
TRANSPORT
Ключевые слова (''Своб.индексиров.''): computational methods--current voltage characteristics--electric resistance--josephson junction devices--mathematical models--yttrium barium copper oxides--andreev reflection--metal superconductor junctions--metallic josephson junction--weak links--semiconductor junctions
Аннотация: A simplified model for the current-voltage characteristics of weak links is suggested. It is based on an approach considering the multiple Andreev reflection in a metallic Josephson junction. The model allows one to calculate the current-voltage characteristics of superconductor-normal metal-superconductor junctions with different thicknesses of normal layer at different temperatures. A hysteretic peculiarity of the V(I) dependence is described as a result of the negative differential resistance. The current-voltage characteristics of tin microbridges and high- T-c composite YBCO + BaPbO3 were computed.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Prus A. G., Shaykhutdinov K. A., Gokhfeld D. M., Petrov M. I.
Заглавие : Study of dependence upon the magnetic field and transport current of the magnetoresistive effect in YBCO-based bulk composites
Место публикации : Supercond. Sci. Technol.: IOP PUBLISHING LTD, 2007. - Vol. 20, Is. 6. - P495-499. - ISSN 0953-2048, DOI 10.1088/0953-2048/20/6/002
Примечания : Cited References: 25
Предметные рубрики: CERAMIC SUPERCONDUCTORS
DISSIPATION
TRANSITION
SENSORS
MOTION
FILMS
Ключевые слова (''Своб.индексиров.''): current voltage characteristics--lorentz force--magnetic field effects--magnetic flux--magnetic sensors--magnetoresistance--intergrain boundaries--magnetic field sensor devices--magnetoresistance curves--magnetoresistive properties--yttrium barium copper oxides
Аннотация: The magnetoresistive properties of bulk YBCO + CuO and YBCO + BaPb0.75Sn0.25O3 composites for different orientations of external magnetic field H and macroscopic transport current j have been measured. These composites exhibit large magnetoresistance in weak magnetic fields ( 100 Oe), which makes them promising candidates for practical application in magnetic field sensor devices. The difference between.( T) dependences, magnetoresistance curves R( H) and current - voltage characteristics measured for H parallel to j and H || j is observed indicating the presence of the Lorentz- force- dependent dissipation in the composites. Angular dependences of magnetoresistance R(theta) ( where theta
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15.

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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16.

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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17.

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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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB(1/2)' B(1/2)'' O(3) (B ' = Ga, In, Lu; B '' = Nb, Ta) solid solutions
Разночтения заглавия :авие SCOPUS: Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB′ 1/2B″1/2O3 (B′ = Ga, In, Lu; B″ = Nb, Ta) solid solutions
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 106, Is. 6. - P1109-1117. - ISSN 1063-7761, DOI 10.1134/S1063776108060101
Примечания : Cited References: 29
Предметные рубрики: STATISTICAL-MECHANICS
PEROVSKITES
CRYSTALS
ORDER
RELAXOR
BATIO3
PBTIO3
Ключевые слова (''Своб.индексиров.''): crystal lattices--ferroelectricity--lattice vibrations--solids--ferroelectric (barium strontium titanate)--ferroelectric phase transitions--lattice (co)--lattice dynamics--vibration spectrum--ferroelectric materials
Аннотация: The lattice vibration spectra, rf permittivity, and dynamic Born charges of disordered PbB(1/2)'B(1/2)'' O(3) (B' = Ga, In, Lu; B '' = Nb, Ta) solid solutions are calculated in terms of the generalized Gordon-Kim model. All the compounds are found to have soft modes related to the center (Gamma(15)) and boundary point R (R(15)) of the Brillouin zone; the frequencies of these modes are close. The ferroelectric phase transition temperatures and the spontaneous polarization in the ferroelectric phase are calculated for the solid solutions using a model Hamiltonian in the local mode approximation and the Monte Carlo method. These temperatures for the tantalum compounds are found to be higher than for the niobium compounds, and temperature t(s) increases with the atomic number of ion B'. A model where the antiferroelectric state is related to the condensation of modes Gamma(15) and R(15) is proposed. It is found that, for all compounds except for PbSc(1/2)Nb(1/2)O(3) and PbSc(1/2)Ta(1/2)O(3), the ferroelectric phase, which is only related to the condensation of mode R(15), and the antiferroelectric phase have similar energies. In PbIn(1/2)Ta(1/2)O(3), the antiferroelectric phase turns out to be energetically favorable.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Popkov S. I., Shaykhutdinov K. A., Petrov M. I.
Заглавие : Magnetic field dependence of intergrain pinning potential in bulk granular composites YBCO plus CuO demonstrating large magneto-resistive effect
Разночтения заглавия :авие SCOPUS: Magnetic field dependence of intergrain pinning potential in bulk granular composites YBCO + CuO demonstrating large magneto-resistive effect
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2008. - Vol. 21, Is. 4. - P243-247. - ISSN 1557-1939, DOI 10.1007/s10948-008-0324-1
Примечания : Cited References: 22
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
ACTIVATED PHASE-SLIP
TRANSITION
DISSIPATION
MECHANISM
SENSORS
MODEL
Ключевые слова (''Своб.индексиров.''): bulk granular high-t(c) superconductor--magneto-resistive effect--josephson junction network--inter-grain pinning potential--bulk granular high-t c superconductor--inter-grain pinning potential--josephson junction network--magneto-resistive effect--bulk composites--bulk granular high-t subc/sub superconductor--granular composites--inter-grain pinning potential--josephson junction network--magnetic field dependences--magneto-resistive effect--pinning potential--resistive effects--resistive transitions--wide temperature range--y-ba-cu-o--atmospheric temperature--barium--copper--copper oxides--electric resistance--magnetic field measurement--magnetic fields--magnetoresistance--magnetos--yttrium barium copper oxides--magnetic field effects
Аннотация: The broadening of the resistive transition in magnetic field and isotherms of magnetoresistance of bulk composites Y-Ba-Cu-O + CuO have been studied. These composites exhibit large magneto-resistive effect in a wide temperature range below T (C) due to weakening of Josephson coupling in this system. The broadening of the resistive transition and magnetoresistance are explained well by the Ambegaokar-Halperin (AH) model for phase slip in Josephson junctions. The magnetic field dependence of pinning potential in the intergrain boundaries deduced from AH model found out to be similar to that of critical current of an array of Josephson junctions. The values of pinning energy point out that the large magneto-resistive effect observed in the composites results from flux flow-like processes at the intergrain boundaries.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskii A. A., Shaikhutdinov K. A., Popkov S. I., Gokhfeld D. M., Gokhfeld Yu. S., Petrov M. I.
Заглавие : Mechanism of the hysteretic behavior of the magnetoresistance of granular HTSCs: The universal nature of the width of the magnetoresistance hysteresis loop
Коллективы : Quantum Macrophysics of the Russian Academy of Sciences [3.4]; Krasnoyarsk Regional Science Foundation [18G011]; Foundation for Supporting National Science Projects
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 108, Is. 2. - P241-248. - ISSN 1063-7761, DOI 10.1134/S106377610902006X
Примечания : Cited References: 32. - This study was carried out under the program "Quantum Macrophysics" of the Russian Academy of Sciences and complex integration project no. 3.4 of the Siberian Branch of the Russian Academy of Sciences, and was partly supported by the Krasnoyarsk Regional Science Foundation (grant no. 18G011). D. A. B. and A. A. D. are grateful to the Foundation for Supporting National Science Projects.
Предметные рубрики: CRITICAL-CURRENT-DENSITY
HIGH-TEMPERATURE SUPERCONDUCTOR
CURRENT-VOLTAGE CHARACTERISTICS
EXTERNAL MAGNETIC-FIELD
BA-CU-O
JOSEPHSON MEDIUM
CRITICAL-STATE
FLUX
COMPOSITES
YBA2CU3O7-DELTA
Ключевые слова (''Своб.индексиров.''): barium--calcium--damping--electric resistance--high temperature superconductors--magnetic field effects--magnetic materials--magnetoelectronics--magnetoresistance--stiffness--classical systems--critical densities--experimental datum--external conditions--flux trapping--hysteretic behaviors--josephson vortices--residual resistances--transport currents--universal behaviors--y-ba-cu-o--hysteresis
Аннотация: The hysteretic behavior of the magnetoresistance R(H) of granular high-temperature superconductors (HTSCs) of the Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O, and La-Sr-Cu-O classical systems is investigated for transport current densities lower and higher than the critical density (at H = 0). All systems exhibit universal behavior of the width of the magnetoresistance hysteresis loop: independence of transport current under identical external conditions. This means that flux trapping in HTSC grains is the main mechanism controlling the hysteretic behavior of the magnetoresistance of granular HTSCs, while pinning of Josephson vortices in the intragranular medium makes no appreciable contribution to the formation of magnetoresistance hysteresis (when transport current flows through the sample). Experimental data on relaxation of residual resistance after the action of a magnetic field also confirm this conclusion.
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