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  • 1
    Electronic Resource
    Electronic Resource
    Tunnel spectroscopy into the YBa2Cu4O8 compound (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1885-1888 
    Details
    ISSN: 0392-6737
    Keywords: Proximity effects, tunneling phenomena and Josephson effects ; Y-based compounds ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have realized planar tunnel junctions using both Y123 and Y124 single crystals as base electrodes and Pb as counterelectrode. The crystals, withT c =90 K (Y123) andT c =80 K (Y124), have been chemically etched and natural barriers were formed by a short air exposure. We have compared the tunneling spectra obtained on both systems. The features at about±18mV of the Y123 compound are still observed in the Y124, while the low-bias structures at ±5 mV are not present in the tunneling characteristics of the Y124 system. Linearity of the background conductance is also observed, with less steep slopes in Y124 that might indicate a reduced interlayer coupling in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02462189
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and characterization of sintered pellets and «Thick» films of Bi2Sr2Y x Ca1−x Cu2O8 (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1695-1699 
    Details
    ISSN: 0392-6737
    Keywords: Bi-based compounds ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A systematic study of yttrium substitution for calcium in the high-temperature superconductor Bi2Sr2CaCu2O8 compound has been performed. The samples of Bi2Sr2Y x Ca1−x Cu2O8 have been prepared by the sintering standard procedure using oxides and carbonates as precursors, weighted to obtain the nominal composition with 0≤x≤1. The real stoichiometric composition of the pellets and uniformity of the samples has been verified by EDS analysis. The grain dimension (≈1 μm) and the good pellet compactness have been established by SEM morphologic observation. By X-ray diffraction analysis the crystalline structure of orthorhombic type has been established. By increasing the yttrium concentration the resistivity dependence on temperature goes from metallic to insulating behaviour. For the superconductive samplesT c decreases for increasing doping percentage. «Thick» films on MgO substrates of Bi2Sr2CaCu2O8 have been obtained by melting-quenching-annealing procedure. These films showed critical temperatures higher than the pellets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02462162
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  • 3
    Electronic Resource
    Electronic Resource
    Resonant modes in Nb baselayer interferometers with two Josephson junctions (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1680-1685 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonances in the current-voltage characteristics of interferometers with two Nb-NbOx-Pb window junctions have been experimentally investigated. The data are compared with the theoretical curves computed both for the voltage and for the magnetic field dependence of the resonance amplitudes. Very good agreement is found in all the range of values of the damping parameter Γ=I0 R/Vr, where Vr is the resonant voltage and I0 and R are the maximum Josephson current and the parallel resistance of each junction. New features that cannot be explained in terms of the existing theory have been observed in devices with larger values of the parameter β=2πLI0/Φ0, where L is the loop inductance, and Φ0 is the flux quantum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334437
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  • 4
    Electronic Resource
    Electronic Resource
    Resonant modes in small inductance superconducting interferometers (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1455-1460 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic field dependence of resonant modes in small inductance two-junction interferometers has been investigated. Both symmetric and asymmetric configurations with equal and different junction size, respectively, have been considered. The experimental data have been compared with the theoretical dependence computed by a simple model of a single junction with a current density peaked at the edges. This model also takes into account the effects due to the field coupled with the junctions. An excellent agreement has been found between theoretical and experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337272
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  • 5
    Electronic Resource
    Electronic Resource
    Epitaxial deposition and properties of Bi2Sr2CaCu2O8+δ/Bi2Sr2YCu2O8+δ/Bi2Sr2CaCu2 O+δ trilayers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 253-255 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have deposited Bi2Sr2CaCu2O8+δ/Bi2Sr2YCu2O8+δ/Bi2Sr2CaCu2 O+δ (2212/22Y2/2212) heterostructures by an in situ dc sputtering technique at high oxygen pressures on (001) SrTiO3 substrates. The formation of highly c-axis oriented trilayers with sharp interfaces is demonstrated by x-ray diffraction and transmission electron microscope (TEM) analysis. Both the top and the bottom 2212 layers are superconducting below 87 K. Tunneling phenomena on junctions fabricated from these trilayers are observed. The conductance versus voltage curves at low temperatures exhibit a change of slope indicative of a gap structure at about 30 mV, a zero-bias peak, as well as linear background at high voltages. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115653
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  • 6
    Electronic Resource
    Electronic Resource
    Microwave fluctuational conductivity in YBa $\mathsf{_{2}}$ Cu $\mathsf{_{3}}$ O $\mathsf{_{7-\delta}}$ (2003)
    Springer
    The European physical journal 37 (2003), S. 277-284 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present measurements of the microwave complex conductivity at 23.9 and 48.2 GHz in YBa2Cu3O $_{7-\delta}$ films, in the fluctuational region above T c . With increasing temperature, the fluctuational excess conductivity drops much faster than the well-known calculations within the time-dependent Ginzburg-Landau theory [H. Schmidt, Z. Phys. 216, 336 (1968)]. Approaching the transition temperature, slowing down of the fluctuations is observed. We discuss the results in terms of a modified Gaussian theory for finite-frequency fluctuational conductivity, where renormalization is introduced in order to account for the $T\rightarrow T_{c}$ regime, and a spectral cutoff is inserted in order to discard high-momentum modes. The data are in excellent agreement with the modified theory, when formulated for three-dimensional, anisotropic superconductors, in the whole experimentally accessible temperature range, and for both frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00057-5
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic field behavior of Fiske steps in long Josephson junctions (1984)
    Springer
    Journal of low temperature physics 54 (1984), S. 489-499 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic field dependence of the maximum current of Fiske steps for long, one-dimensional, Josephson tunnel junctions has been measured. Experimental data obtained from junctions of various normalized lengths are presented; for slightly long junctions a comparison with the theory is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683614
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  • 8
    Electronic Resource
    Electronic Resource
    Static characteristics of superconducting interferometers with Nb-NbO x -PbIn Josephson junctions (1983)
    Springer
    Journal of low temperature physics 51 (1983), S. 55-66 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Planar interferometers with two Nb-NbO x -PbIn junctions have been fabricated. Because of the peculiar configuration adopted, both a symmetric and an asymmetric current bias are possible on the same sample. The loop area is on a plane perpendicular to the cross section of the junctions, and, therefore, the flux coupled to them is negligible. Threshold curves have been measured for different values of the characteristic parameter β=LI 1/Φ0, whereI 1 andL are the maximum Josephson current and the inductance of the interferometer andΦ 0 is the flux quantum. The dependence of the current modulation depth upon β has been also investigated. A comparison of the experimental data with the theory shows quantitative agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683413
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  • 9
    Electronic Resource
    Electronic Resource
    Surface impedance of NbN superconducting thin films by Josephson measurements (1987)
    Springer
    Journal of low temperature physics 69 (1987), S. 363-376 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The microwave quality factorQ of NbN-Pb Josephson junctions has been determined via measurements of the amplitude of Fiske resonant modes in the junctions at different resonant frequencies in the range 30–300 GHz. It is proved that, for our samples, the main contribution to theQ comes from the surface impedance of the filmsR s . Data show that, for NbN,R s ∼v1.5±0.1 atT c =4.2 K in the frequency range considered. The implications of our results for the possible applications of NbN films both in the context of Josephson microwave devices and as a coating material for rf cavities in high-energy physics are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683327
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  • 10
    Electronic Resource
    Electronic Resource
    Bifurcation theory and order of phase transition for proximity effect sandwiches (1978)
    Springer
    Journal of low temperature physics 32 (1978), S. 339-360 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: We use bifurcation theory to study the order of the phase transition for inhomogeneous superconducting systems described by the Ginzburg-Landau equations. Complete qualitative information on the behavior near the critical point can be obtained using these techniques of nonlinear analysis and the calculus of variations. We prove in a rigorous way that there is a secondorder phase transition for a normal-superconducting-normal (N-S-N) proximity sandwich. Moreover, in the case of a magnetic-superconductingmagnetic (M-S-M) proximity sandwich we show the dependence of the order of the phase transition on the coupling constant between the magnetic and superconducting order parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00117957
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