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Träfflista för sökning "L773:1063 777X srt2:(2000-2004)"

Sökning: L773:1063 777X > (2000-2004)

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1.
  • Aleksandrovskii, A. N., et al. (författare)
  • Low-temperature thermal expansion of pure and inert gas-doped fullerite C60
  • 2003
  • Ingår i: Fizika Nizkikh Temperatur (Kharkov). - : AIP Publishing. - 0132-6414 .- 1816-0328. ; 29:4, s. 432-442
  • Tidskriftsartikel (refereegranskat)abstract
    • The low temperature (2–24 K) thermal expansion of pure (single-crystal and polycrystalline) C60 and polycrystalline C60 intercalated with He, Ne, Ar, and Kr has been investigated using the high-resolution capacitance dilatometer. The investigation of the time dependence of the sample length variations deltaL(t) on heating by deltaT shows that the thermal expansion is determined by the sum of positive and negative contributions, which have different relaxation times. The negative thermal expansion usually prevails at helium temperatures. The positive expansion is connected with the phonon thermalization of the system. The negative expansion is caused by reorientation of the C60 molecules. It is assumed that the reorientation is of a quantum character. The inert gas impurities affect the reorientation of the C60 molecules very strongly, especially at liquid helium temperatures. A temperature hysteresis of the thermal expansion coefficient of Kr– and He–C60 solutions has been revealed. The hysteresis is attributed to orientational polyamorphous transformation in these systems.
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2.
  • Aleksandrovskii, A. N., et al. (författare)
  • Effect of argon on the thermal expansion of fullerite C60 at helium temperatures
  • 2001
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics. - 1063-777X .- 1090-6517. ; 27:3, s. 245-246
  • Tidskriftsartikel (refereegranskat)abstract
    • The linear thermal expansion of compacted Ar-doped fullerite C60(ArxC60) is investigated at 2–12 K using a dilatometric method. The thermal expansion of ArxC60 is also studied after partial desaturation of argon from fullerite. It is revealed that argon doping resulted in a considerable change of the temperature dependence of the thermal expansion of fullerite. An explanation of the observed effects is proposed.
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3.
  • Aleksandrovskii, A.N., et al. (författare)
  • Thermal expansion of fullerite C60 alloyed with argon and neon
  • 2001
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - Woodbury : American Institute of Physics. - 1063-777X .- 1090-6517. ; 27:12, s. 1033-1036
  • Tidskriftsartikel (refereegranskat)abstract
    • The linear thermal expansion of compacted fullerite C60 alloyed with argon (ArxC60) and neon (NexC60) are investigated by a dilatometric method. The experimental temperature is 2–12 K. In the same temperature interval the thermal expansion of ArxC60 and NexC60 are examined after partial desaturation of the gases from fullerite. It is found that Ar and Ne alloying affects the temperature dependence of the thermal expansion coefficient of C60 quite appreciably. The libration and translation contributions to the thermal expansion of pure C60 are separated. The experimental results on the thermal expansion are used to obtain the Debye temperature of pure C60. The effects observed are tentatively interpreted.
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4.
  • Aleksandrovskii, A. N., et al. (författare)
  • Thermal expansion of single-crystal fullerite C60 at helium temperatures
  • 2000
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 26:1, s. 75-80
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2–10 K). At temperatures below ~4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed.
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5.
  • Eshchenko, DG, et al. (författare)
  • Muonium diffusion in solid CO2
  • 2001
  • Ingår i: LOW TEMPERATURE PHYSICS. - : AMER INST PHYSICS. - 1063-777X. ; 27:9-10, s. 854-857
  • Tidskriftsartikel (refereegranskat)abstract
    • The quantum diffusion of interstitial muonium atoms in solid CO2 is studied in the temperature range from 5 to 200 K using the technique of muonium spin rotation and relaxation. Muonium exhibits coherent bandlike dynamics between 140 and 160 K. At low tem
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6.
  • Ivanov, Zdravko G., 1949, et al. (författare)
  • Depairing critical currents and self-magnetic field effects in submicron YBa2Cu3O7-delta microbridges and bicrystal junctions
  • 2004
  • Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 30:3, s. 203-207
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on depairing critical currents in submicron YBa 2 Cu 3 O 7-δ microbridges. A small-angle bicrystal grain boundary junction is used as a tool to study the entrance of vortices induced by a transport current and their influence on the I-V curves. The interplay between the depairing and the vortex motion determines a crossover in the temperature dependence of the critical current. The high entrance field of vortices in very narrow superconducting channels creates the possibility of carrying a critical current close to the depairing limit determined by the S-S ′ -S nature of the small-angle grain boundary junction. © 2004 American Institute of Physics.
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7.
  • Krive, Ilya V., et al. (författare)
  • Chiral symmetry breaking and the Josephson current in a ballistic superconductor-quantum wire-superconductor junction
  • 2004
  • Ingår i: Fizika Nizkikh Temperatur. - : AIP Publishing. - 0132-6414 .- 1816-0328. ; 30:5, s. 398-404
  • Tidskriftsartikel (refereegranskat)abstract
    • We evaluate the Josephson current through a quasi-1D quantum wire coupled to bulk superconductors. It Is shown that the interplay of Rashba spin-orbit interaction and Zeeman splitting results in the appearence of a Josephson current even in the absence of any phase difference between the superconductors. In a transparent junction (D [asymptotically equal to] 1) at low temperatures this anomalous supercurrent Jan appears abruptly for a Zeeman splitting of the order of the Andreev level spacing as the magnetic field is varied. In a low transparency (D very much less than 1) junction one has Jan α root D under special (resonance) conditions. In the absence of Zeeman splitting the anomalous supercurrent disappears. We have investigated the influence of dispersion asymmetry induced by the Rashba interaction in quasi-1D quantum wires on the critical Josephson current and have shown that the breakdown of chiral symmetry enhances the supercurrent.
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8.
  • Pashchenko, V. P., et al. (författare)
  • Structural and magnetic inhomogeneity and the NMR of Mn-55 and La-139 in the magnetoresistive ceramics La0.7Ba0.3-xSnxMnO3 -> La0.7-xBa0.3-xMnO3+0.5xLa(2)Sn(2)O(7)
  • 2003
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 29:11, s. 910-916
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of substitution of barium by tin on the phase composition, structural imperfection, and properties of lanthanum manganite perovskites La0.7Ba0.3-xSnxMnO3 (X=0, 0.1, 0.15, 0.2, 0.3) are established by comprehensive studies done by x-ray diffraction, resistive, and magnetic (including NMR on Mn-55 and La-139) methods. It is shown that the introduction of Sn leads to the formation of a pyrochloric phase La2Sn2O7, to an increase in the density of lattice defects of the manganese-enriched main lanthanum manganite phase, and to a substantial decrease of the magnetoresistive effect. The smearing of the metal-semiconductor phase transition temperature is explained by an increase in the inhomogeneity and imperfection of the perovskite structure. The low activation energy is confirmed by a high degree of inhomogeneity and imperfection of the crystal lattice of the samples studied. The broad, asymmetric NMR spectra of Mn-55 and La-139 attest to high-frequency electron exchange between Mn3+ and Mn4+ and nonequivalence of the environment of those ions and La3+ due both to heterovalent ions and to vacancies and clusters.
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9.
  • Shypil, E. V., et al. (författare)
  • Interlayer coupling in Tb/Fe bilayers and Tb/Au/Fe trilayers with sharp or rough interface
  • 2001
  • Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 27:8, s. 650-654
  • Tidskriftsartikel (refereegranskat)abstract
    • Bilayer films Fe/Tb (Tb on Fe) having sharp and Tb/Fe (Fe on Tb) having rough interface were prepared by molecular beam epitaxy to study interlayer magnetic coupling. Magnetic properties of these bilayers were characterized ex situ using ferromagnetic resonance (FMR), polar magneto-optical Kerr effect and SQUID magnetometer. The resulting perpendicular magnetic anisotropy (PMA) is discussed as an effect of interlayer magnetic coupling. PMA was observed in rough as well as in sharp interfaces and the anisotropy energies were estimated. When a monolayer of Au was interposed at the interface of both kinds, PMA was observed to disappear and the overall magnetic moment increased. It was also shown that in ultrathin films demagnetization factor depends on the substrate roughness and should be considered in the FMR data.
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10.
  • Sundqvist, Bertil (författare)
  • Interaction between C60 and gases under high pressure
  • 2003
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics. - 1063-777X .- 1090-6517. ; 29:5, s. 440-444
  • Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
    • A brief review is given of the interaction between fullerite C60 and various gases under elevated pressure. Subjects discussed include the formation of ordered interstitial gas-fullerene compounds, reactions between intercalated gases and fullerene molecules to form new endohedral and exohedral compounds, and changes in the structure and properties of C60 because of intercalated gas atoms or molecules.
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