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  • Articles  (31)
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  • YBCO  (31)
  • Springer  (31)
  • Electrical Engineering, Measurement and Control Technology  (31)
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  • Springer  (31)
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  • Electrical Engineering, Measurement and Control Technology  (31)
  • Physics  (31)
  • 1
    Electronic Resource
    Electronic Resource
    Investigation of the Symmetry of the Pairing State in YBa2Cu3O7−δ Using the Nonlinear Transverse Magnetic Moment: Experimental Results (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 99-103 
    Details
    ISSN: 1572-9605
    Keywords: Nonlinear Meissner effect ; pairing state ; YBCO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Measurements of the nonlinear transverse magnetic moment have been carried out on disk-shaped samples of YBCO, using an ac technique. Numerical calculations for a d x 2 - y 2 pairing state predict a fourfold modulation of this moment as a function of the angle between the applied magnetic and the crystalline axes for a magnetic field applied in the a–b plane of the sample. Our results imply a minimum nonzero gap at all points on the Fermi surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007738123479
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  • 2
    Electronic Resource
    Electronic Resource
    Unusual Photon Energy Dependence of the Cooper Pair Breaking Rate in YBa2Cu3O7−δ Epitaxial Thin Films (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 675-680 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; Cooper pair ; thin films ; ultrafast phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transient photoimpedance response of epitaxial YBa2Cu3O7−δ thin films has been studied using 100 fs Ti:Sapphire laser pulse excitation. Both temperature and photon energy dependence of the fast optical response signal (whose temperature dependence can be explained by a kinetic inductance model involving Cooper pair breaking) were studied. The pair breaking rate is strongly photon energy-dependent, with a resonance around 1.5 eV with a width of only 100 meV, which is very surprising given the strong electron correlation in this metallic system and may be explained in terms of the stripe phase model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007708304186
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  • 3
    Electronic Resource
    Electronic Resource
    Andreev Bound-State Tunneling and ESR Spectroscopy of High-Temperature Superconductors and Observations of Broken Time-Reversal Symmetry (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 703-708 
    Details
    ISSN: 1572-9605
    Keywords: Andreev bound state ; tunneling spectroscopy ; electron paramagnetic resonance spectroscopy ; broken time-reversal symmetry ; YBCO ; BSCCO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An emphasis on reliable materials growth and development of new fabrication techniques has allowed us to investigate the electronic structure of high-temperature superconductors by planar quasiparticle tunneling and electron paramagnetic resonance (EPR) spectroscopies. The quasiparticle (QP) density of states (DoS) is investigated by tunneling into oriented thin films of Y1Ba2Cu3O7 (YBCO) and single crystals of Ba2Sr2Ca1Cu2O8 (BSCCO). Data are obtained as a function of crystallographic orientation, temperature, doping, damage, and applied magnetic field. These data demonstrate that the observed zero-bias conductance peak (ZBCP) is composed of Andreev bound states (ABS) which intrinsically form at a symmetry-breaking interface of an unconventional superconductor, for example, a (110)-surface of d-wave YBCO. Tunneling into doped or ion-damaged YBCO provides a measure of the QP scattering rate below T c. An applied field causes Doppler shift of the ABS, arising from the scalar product between the QP velocity and the superfluid momentum, v F·P s, observed as a splitting in the ZBCP. Magnetic hysteresis of the splitting is consistent with the effects of strong vortex pinning near the interface. The directional field dependence shows that the ABS is highly anisotropic in its transport. These results, plus in-plane crystallographic orientational dependence on single-crystal BSCCO, demonstrate the d-wave symmetry of this superconductor. Below ∼ 8 K and in zero applied field, the ZBCP splits, indicating a transition into a superconducting state with spontaneously broken time-reversal symmetry (BTRS). EPR experiments are used to detect directly the spontaneous formation of the magnetic moments in the BTRS state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007897727833
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  • 4
    Electronic Resource
    Electronic Resource
    Electron Paramagnetic Resonance of Tb3+ Ions in YBa2Cu3O6 (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 895-897 
    Details
    ISSN: 1572-9605
    Keywords: EPR ; YBCO ; rare-earth ions ; impurities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The first observation of electron paramagnetic resonance (EPR) of Tb3+ doped into YBa2Cu3O6 is reported. EPR is used to determine the local symmetry of the rare-earth ion and to study the effect of suppression of high-T c superconductivity by doping. The distance between the lowest singlets of Tb3+ ion Δ ≅ 7.1 GHz ≡ 0.24 cm−1 and g-factor g ∥ ≃ 17.9 have been estimated from measurements. Both these parameters are in a good agreement with the corresponding calculated values. No evidence of Tb4+ ions was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026477519347
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  • 5
    Electronic Resource
    Electronic Resource
    DC SQUIDs based on YBCO step edge junctions (1993)
    Springer
    Journal of superconductivity 6 (1993), S. 391-395 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; dc SQUID ; high-T- c junction ; step edge junction ; Josephson effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We describe the fabrication and testing of dc SQUIDs (Superconducting QUantum Interference Devices) obtained by photolithographic patterning of YBa2Cu3O7−x thin films deposited both on SrTiO3 and MgO substrates. The Josephson junctions in the superconducting loop are of the “step-edge” type, where the weak link is obtained through the growth of grains with different orientations across suitably prepared steps previously etched on the substrate surface. TheI−V characteristics of the devices tested show multiple branches and instabilities having a weak dependence on the external magnetic field, probably due to formation of junction clusters on the substrate step. The SQUID devices showed quantum interference behavior and an easily detectable voltage modulation with the applied magnetic field at a temperature of 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617977
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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of the dominant point defects in tetragonal YBa2Cu3Ox at elevated temperatures (1993)
    Springer
    Journal of superconductivity 6 (1993), S. 313-316 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; oxygen defects ; point defects ; superconductors ; tetragonal phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The manner in which oxygen is incorporated into YBa2Cu3O x (YBCO) at ∼800°C for values ofx close to 6 is shown to be in the form of neutral oxygen interstitials, O i x . The experimental data on which this conclusion is based are obtained from measurements of oxygen partial pressure,P(O2), as a function of compositionx and temperatureT (5.99≤x≤ 6.35, 825≤T≤1120 K). The data are obtained by a solid-state electrochemical method. Other conclusions of this study include: (a) O i x are noninteracting forx ≃ 6. (b) The stoichiometric composition of YBCO isx ≃ 6.0. (c) The reaction enthalpy of oxidation is 179 kJ/mol O2. (d) The Fermi level changes by ≃ −0.2 eV asx increases from 6.05 to 6.35.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617477
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  • 7
    Electronic Resource
    Electronic Resource
    Angular dependence of transport current near critical at fields to 4 T in metalorganic thin films (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 303-308 
    Details
    ISSN: 1572-9605
    Keywords: Critical current ; high temperature superconductor ; thin film ; angular dependence ; magnetic field dependence ; YBCO ; metalorganic preparation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Values of the transport current have been obtained as a function of angle of the magnetic field to the plane of the thin film YBa2Cu3O7−d (YBCO) prepared by metalorganic deposition. Current flowed in thea, b planes at various angles to the applied magnetic fields to 4.2 T. Films with thicknesses near 350 nm were studied. For these thin films andH∥c a secondary maximum is observed whenJ c〉 1 MA/cm2. NearH∥a, b a large increase inI c is observed, and the sharpness, field dependence, and field directional dependence is discussed. The response to currents aboveI c is determined and the fit to a power lawV∼I n shows a strong correlation betweenI c andn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00724558
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  • 8
    Electronic Resource
    Electronic Resource
    Correlation Between the Superfluid Density ns(T) ∝ 1/λ2ab(T) at Low Temperatures and Nanostructures in the a–b Planes of YBCO (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 753-757 
    Details
    ISSN: 1572-9605
    Keywords: high-temperature superconductivity ; YBCO ; thin films ; superfluid density ; critical current ; nanostructures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A correlation between the superfluid density n s(T) ∝ 1/λ2 ab(T) at low temperatures and the nanoscopic disorder in the a–b planes of YBCO thin films has been revealed. It has been found that a degree of this disorder can be determined from the two-component dependence of the critical current density on temperature. These findings are consistent with a discovery of a nanodomain structure in the a–b planes of an optimally doped YBCO [J. Etheridge, Phil. Mag. A73, 643 (1996)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007818300517
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of Oxidation Kinetics of YBa2Cu3O7−x Ceramics by the Acoustic Emission Method (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 275-276 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; acoustic emission ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The oxidation kinetics of YBa2Cu3O7−x ceramics has been investigated by the acoustic emission method. It is observed that the oxidation follows an exponential law. For YBCO the exponential index τ is a specific parameter and is equal to 1.7 s±10%. It is confirmed that the related narrow surface layer is first oxidized, and oxygen dissolution in the material is controlled by the speed of volume diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022688018815
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of Ho addition on the properties of Y-system superconductors (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 95-99 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; Ho addition ; critical current density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract (YHo)Ba2Cu3O7−y is prepared by the powder melting process and its properties are investigated. It is found that Ho addition can change the melting temperature of a Y-system superconductor. TheJ c values of YBCO can be improved by Ho substitution, which is due to the effect of Ho addition on the number and quality of grain boundaries and the size and distribution of 211 particles. The highestJ c value was found to be 50,000 A/cm2 (77 K, 1T,H⊥I) in Y0.8Ho0.2Ba2Cu3O7−y. Our results indicate that the number and quality of grain boundaries have a great influence on the superconducting properties. A discussion is given on the relationship betweenJ c and the size and phase proportion of 211 particles. There are a lot of dense twins in the sample, and many crystal defects exist around the 211 phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618051
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  • 11
    Electronic Resource
    Electronic Resource
    Lithographic patterning of superconducting YBCO films (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 445-449 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; microbridge ; lithography ; etching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Microbridges of YBa2Cu3O7 thin films have been fabricated by conventional photolithography and wet chemical etching using EDTA, and by the lift-off lithography technique. The variation of etch rate with etch time, etchant temperature, and post-deposition sintering temperature has been studied. It has been shown that both techniques are useful for film patterning. However, an additional sintering step is necessary for the chemically etched sample to regain the original film properties. An order of increase in critical current density is observed for the patterned film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620502
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  • 12
    Electronic Resource
    Electronic Resource
    Low-temperature critical field of YBCO (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 269-270 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; high field ; critical field ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have measured the upper critical fieldH C2(T) of YBa2Cu3O7 (YBCO) thin films in magnetic fields up to 140 T forH applied parallel to thec-axis of the film. The critical field in the zero-temperature limit is 138 T, and the temperature dependence does not fit any simple model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00724550
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  • 13
    Electronic Resource
    Electronic Resource
    Microstructures of high-J c melt-textured YBa2Cu3O7−x /Ag superconductors (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 947-950 
    Details
    ISSN: 1572-9605
    Keywords: Critical current density ; Ag addition ; grain alignment ; flux pinning ; defect structure ; YBCO ; melt-texturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Silver has been previously added to the melt-textured YBa2Cu3O7−x in order to increase the critical current density (J c ) of these materials. However, the effect of this addition on theJ c is presently unclear. The purpose of this study is to investigate the effect of silver on both critical current density and the microstructure of the melt-textured YBa2Cu3O7−x superconductors by means of X-ray diffraction, optical polarized microscopy, and transmission electron microscopy (TEM). TheJ c of the MTG YBCO/Ag samples is more than 104A/cm2 under the 5 kOe magnetic field. It has been shown that as the concentration of silver increases, the fraction of the 211 phase dispersed within the 123 matrix decreases. Therefore, theJ c slightly decreases. These results, together with the effect of the 211 phase, dislocations, and other structure defects on flux pinning, are described in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732277
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  • 14
    Electronic Resource
    Electronic Resource
    Experimental determination of the symmetry of the order parameter in YBCO (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 491-494 
    Details
    ISSN: 1572-9605
    Keywords: Superconductivity ; pairing symmetry ; YBCO ; SQUID
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract At present, the symmetry of the order parameter in the high temperature superconductor YBCO is quite controversial. Recent experiments using SQUIDs and Josephson junctions appear to support competing theories, with some experiments supporting a dx2−y2 pairing symmetry for the order parameter and others a s-wave pairing symmetry. We note that a number of factors such as trapped flux, magnetic field gradients and SQUID asymmetries could lead such measurements astray. We use a Scanning SQUID Microscope and a time-reversal invariance test to resolve these experimental problems. We find the order parameter in YBCO has a time-reversal invariant dx2−y2 symmetric component. We estimate the amplitude of anyimaginary s-wave symmetric component to be less than 4% and anyreal s-wave component to be less than 82%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00722838
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  • 15
    Electronic Resource
    Electronic Resource
    Upper critical and irreversibility fields in selectively doped YBa2Cu3O7 (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 619-620 
    Details
    ISSN: 1572-9605
    Keywords: Irreversibility ; critical ; field ; doped ; YBCO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electrical resistivity of (Y1−xPrx)Ba2Cu3O7−gd and YBa2(Cu1−xZnx)3O7−δ thin films and (Y1−x. Tbx)Ba2Cu3O7−δ thin films and single crystals has been measured as a function of 0≤x≤xcrit, 2K≤T≤300K and OTH≤20T. The samples were oriented withc-axis parallel to applied fields. Upper critical field Hc2 and irreversibility field Hirr values have been determined from these measurements. Increased Tb doping appears to shift Hirr to higher temperatures. This coupled with observed twin peaks in magnetization measurements reflects an enhancement of flux pinning. Unlike Tb which does not appear to alterT c , Pr and Zn doping of this system tends to depress bothT c and the slope of the mean field normal phase-mixed phase boundary line (dH c2/dT).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727445
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  • 16
    Electronic Resource
    Electronic Resource
    Studies on microbridges of superconducting YBCO thin film (1996)
    Springer
    Journal of superconductivity 9 (1996), S. 211-216 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; microbridges ; microwave effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Critical current densities of the superconducting Y-Ba-Cu-O (YBCO) films have been observed to decrease with the increase of power of microwave radiation. Presence of Josephson type of junctions in the microbridges has been established from the microwave irradiation and magnetic field studies. BCS energy gap parameter (2Δ/kT c ) has been calculated from thedI/dV characteristics and found to be 3.7 at 13 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00728305
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  • 17
    Electronic Resource
    Electronic Resource
    A new type of biepitaxialc-axis tilted YBCO Josephson junction (1996)
    Springer
    Journal of superconductivity 9 (1996), S. 237-244 
    Details
    ISSN: 1572-9605
    Keywords: Josephson junctions ; YBCO ; grain boundary ; MgO seed layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A novel fabrication procedure of high critical temperature superconductor Josephson junctions (HTCSJJ) has been developed by a 90° rotation of YBa2Cu3O7−x c-axis around an in-plane direction, on the basis of concepts of the biepitaxial technique. YBa2Cu3O7−x grows oriented along (001) direction on a MgO seed layer deposited on a (110) SrTiO3 substrate and along (110) direction on the bare substrate. Josephson junctions of good quality were obtained exhibiting RSJ behavior and features characteristic of HTCSJJ phenomenology. Even if not uniform, in some samples, the nature of the critical currentI c is completely Josephson, as resulting from theI c dependence on the applied magnetic field. The maximum measuredI c R N value atT=4.2K is 2mV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00728309
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  • 18
    Electronic Resource
    Electronic Resource
    Photo-Thermal Transport Effects in a Thick Film YBCO Bolometer Under Magnetic Fields (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 463-469 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; thick film ; vortices ; pinning ; bolometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Thick (~50 μm) YBCO superconducting film bolometers have been fabricated to operate in the temperature range 89–92 K. Responsivities greater than 1 V/W have been achieved by biasing with a current slightly less than that of the critical current, and observing the photo-voltage in the resistive state. The time response of these films due to photo-conduction is slow (ms). The present work concentrates on the resistive transition and the width of the photo-signal peak under the effect of applied magnetic fields. The width of the photo-signal peak over the transition is found to be strongly magnetic field dependent at low field values while at higher field values it has been used to determine a value for the vortex tilt modulus. Further, it is found that a temperature difference in the position of the photo-signal peak relative to that of the dR/dT peak changes with applied field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022657900890
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  • 19
    Electronic Resource
    Electronic Resource
    A Model for the Crystal Growth of YBa2Cu3O y (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 347-352 
    Details
    ISSN: 1572-9605
    Keywords: Crystal growth ; morphology ; YBCO ; terraced crystals ; step growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The crystal growth and crystal morphology are very important properties of YBa2Cu3O y superconductors. In this work, we approach these problems with polycrystals. Several typical crystal morphologies were observed by scanning electron microscopy, and the terraced crystals with a layer-by-layer structure were found to be the major form for the well-grown YBa2Cu3O y . To interpret the results, a step-growth model was proposed. In this model, each crystal terrace is close-packed with crystal particles in order. And the particles, each consisting of tens of crystal cells, are movable during crystal growth. Particles at edges or margins of small crystals can move to their larger neighboring crystals through diffusion. With this particle diffusion, small crystals vanish and large crystals grow larger. This proposed model is confirmed by experimental observations.
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    URL: http://dx.doi.org/10.1023/A:1022646713766
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  • 20
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    A Modal of Twin Domains in YBa2(Cu1−xCox)3Oy (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 129-136 
    Details
    ISSN: 1572-9605
    Keywords: twin domains ; YBCO ; Co-doping ; twin boundary ; model ; electron diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The existence of twin domains in YBa2(Cu1−x Co x )3O y samples was confirmed by many experiments. However, the physical picture of the twin domains has not been reported up to now. By analyzing oxygen content, Cu and Co valences, and Co coordination in those samples, we propose a domain model, which consists of two pairs of parallel zigzag Co-O chains surrounding orthorhombic cells, one along (110) direction and the other along (110) direction. The zigzag Co-O chains are the twin walls, with neighboring walls perpendicular and the opposite ones parallel. The distance between parallel walls (i.e., zigzag Co-O chains) depends upon Co concentration of sample. The twin domain model predicts the geometry, size, and absence of systematic symmetry of the domains. The model also predicts the modulation periodicity of electron diffraction patterns, which depends on Co concentration. All the predictions by the model agree well with the experimental results reported in literatures. Furthermore, the model indicates the possible existence of two domains, which have incommensurable modulation periodicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007742629820
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  • 21
    Electronic Resource
    Electronic Resource
    Specific Heat of YBa2Cu3O7−−δ and (La2−xSrx)CuO4: Evidence for d-Wave Pairing (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 105-111 
    Details
    ISSN: 1572-9605
    Keywords: Specific heat ; YBCO ; LSCO ; d-wave
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract New low-temperature specific-heat data for YBa2Cu3O7−δ, 0≤δ≤0.2, and (La1.85Sr0.15)CuO4 in magnetic fields (H) to 9 T are reported. They show features predicted for the lines of nodes in the energy gap that are expected for d-wave pairing; for H=0, a T 2 term; for H≠0 an H 1/2 T term with a crossover to a more complicated T dependence at higher T and lower H. The results are compared with recent measurements in other laboratories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007790107549
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  • 22
    Electronic Resource
    Electronic Resource
    Specific heat of YBa2Cu3O7 (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 251-255 
    Details
    ISSN: 1572-9605
    Keywords: Specific heat ; impurity ; defects ; YBCO ; superconducting volume fraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Specific heat measurements, including measurements in magnetic fields and at both low temperatures and nearT c , on a number of YBa2Cu3O7 samples have revealed several correlations among strongly sample-dependent parameters. These correlations suggest that the sample dependence of the parameters reflects a sample dependence of the volume fraction of superconductivity, which is in turn correlated with a low concentration of Cu2+ moments. The correlations give a criterion for recognizing the values of the parameters characteristic of the fully superconducting material. Preliminary results on the effects of sample heat treatment are reported. New data on the “linear term” is presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00730406
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  • 23
    Electronic Resource
    Electronic Resource
    Absorption and emission spectra of the YBCO laser plume (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 823-828 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; laser plume ; emission spectroscopy ; absorption spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The plasma produced during laser ablation deposition of thin film YBCO has been studied by optical emission spectroscopy. There is evidence of increased YO band emission in the range 590–625 nm as the ambient oxygen gas pressure confining the plume is increased in the range 30–200 m Torr. Temporal profiles show that close to the target the plume is insensitive to ambient oxygen pressure. It is deduced that the optical emission here is excited by electron impact excitation. Further away from the target there is evidence that two distinct processes are at work. One is again electron excitation; the emission from this process decreases with distance because the expanding plume cools and collisions become less frequent in the expanding gas. The second is driven by oxidation of atomic species expelled at high speeds from the target. The main region of this activity is in the plume sheath where a shock front ensures heating of ambient O2 and reaction of monatomic plasma species to form oxide in an exothermic reaction. Spatial mapping of the emission demonstrates clearly how increasing oxygen gas pressure confines the plasma and enhances the emission intensity from the molecular YO species ejected from the target in a smaller region close to the target. Ba+ is observed as a dominant species only very close to (within 1 mm of) the target. Absorption spectra have been taken in an attempt to examine ground state and cool species in the plume. They reveal the quite surprising result that YO persists in the chamber for periods up to 1 msec. This suggests an explanation for the recent report of off-axis laser deposition in terms of simple condensation. Previously, quasi-ballistic transfer of material from target to substrate has been considered the only significant process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320877
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  • 24
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    Symmetry of the pairing state in the high-T c oxides (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 865-869 
    Details
    ISSN: 1572-9605
    Keywords: Symmetry of the pairing ; gaplessness ; YBCO ; cuprates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract There are conflicting experimental data related to the symmetry of the order parameter in cuprate superconductors. Our previously developed concept, which contains unusuals-wave pairing with a two-gap spectrum, energy gap anisotropy, and gaplessness for a nonstoichiometric state, provides a unified and consistent description of experimental data related to the symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320884
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  • 25
    Electronic Resource
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    Anisotropy of optical constants of YBCO (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 943-946 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; optical constants ; attenuated total reflection ; ellipsometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Otto configuration attenuated total reflection (ATR) measurements of the excitation of surface plasmons in the infrared have been carried out on YBCO films deposited on MgO (100) substrates. The dielectric constants for YBCO at 3.392μm are determined to be −10+15i forc-axis material. The anisotropic nature of the cuprate is seen from films with other orientations: nearlya-axis material has constants of 4.0+7.0i. It is thus not metallic in its optical response along thec-axis which lies parallel to the substrate plane. Ellipsometric measurements in the visible onc-axis material point to a maximum surface plasmon energy of 1 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732276
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  • 26
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    High-Q oscillator measurements of vortex properties in YBa2Cu3O7−δ (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 667-668 
    Details
    ISSN: 1572-9605
    Keywords: Mechanical oscillator ; YBCO ; vortex pinning ; twin boundary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract High-Q oscillators, vibrating with extremely small tilt angles, ∼10−7 radians, were used to study vortex behavior in single crystal YBa2Cu3O7−δ. Systematic changes in the dissipation and frequency of the oscillator were explored for various fields both parallel and perpendicular to twin boundaries. At the small tilt oscillation amplitudes employed here, a number of features were observed which are not evident at the more typically utilized large oscillation amplitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727469
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    Electronic Resource
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    Use of tricrystal junctions to probe the pairing state symmetry of YBa2Cu3O7 (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 679-680 
    Details
    ISSN: 1572-9605
    Keywords: Pairing ; symmetry ; YBCO ; tricrystal ; junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have developed a new method of probing superconducting pairing state symmetry, by using tricrystal devices analogous tos-d corner junctions. Two central peaks are observed in the field-modulated critical currents of frustrated YBCO tricrystal junctions operating in the short junction limit, consistent with predominantly $$d_{x^2 - y^2 } $$ — wave pairing symmetry with little or no imaginarys-wave component. However, our results are consistent with a real combination of larged-wave and smalls-wave components. A single peak is also observed for frustrated tricrystal junctions operating in the long junction limit, and it is shown theoretically that the behaviors ofs- andd-wave superconductors are indistinguishable in this limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727475
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    Electronic Resource
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    RF measurements on a TE011 YBCO cavity at 8 GHz (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 753-757 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; surface resistance ; penetration depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In the present work a cavity fully coated with an YBCO thick film was fabricated using an improved electrophoretic deposition technology with a special attempt to avoid the possible contamination of the superconducting powder during the milling process in the suspension preparation. A microwave experimental set-up was constructed to measure the rf behavior of the cavity in a wide temperature range. The loaded quality factorQ 1 and the shift of the resonant frequency vs. the temperature at various rf magnetic fields have been measured. Furthermore, the surface resistance and the penetration depth determined from the measurements were compared with the numerical calculation in the framework of BCS theory, showing good agreement with the theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727499
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  • 29
    Electronic Resource
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    Large ultrasonic attenuation at Tc in YBa2Cu3O7−x (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 647-648 
    Details
    ISSN: 1572-9605
    Keywords: Ultrasonic ; YBCO ; polaronic condensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We investigated elastic anomalies of sintered YBa2Cu3O7−x (x=0.35) superconductor around the critical temperature (Tc=60 K). We observed the non-symmetric and large attenuation peak (2 dB/cm at 9.7 MHz) at Tc, which was due to the lattice softening caused by the strong correlation between carriers and local lattice distortion. The rapid decrease of ultrasonic attenuation just below Tc suggested a condensation mechanism. These supported the polaronic condensation in high-Tc superconductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727459
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    Electronic Resource
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    New aspects in the microstructure of YBCO melt-textured high-T c superconductors (1996)
    Springer
    Journal of superconductivity 9 (1996), S. 535-538 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; microstructure ; phase ; microanalysis ; pinning ; melt-textured samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The microstructure and phase constitution of bulk textured YBCO samples prepared by the modified MTG method in the longitudinal temperature gradient have been investigated. We found the existence of an unusual phase between stacked platelets. Microanalysis shows that this phase may be characterized as Y-143. This phase forms ellipsoid-like particles with a typical size about 0.05–2μ which can play the role of effective pinning centers. The reason for the phase formation is discussed. We assume that this phase exists commonly in melt-textured samples prepared in the temperature field gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00723527
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    Influence of substrate on the excess electrical noise in the normal state of YBa2Cu3O7-δ thin films (1996)
    Springer
    Journal of superconductivity 9 (1996), S. 307-310 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; electrical noise ; substiates ; normal state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present our studies of the low-frequency excess electrical noise in YBa2Cu3O7-δ thin films in the normal state. We have studied films with varying microstructure deposited on different substrates. The frequency dependence and bias current dependence of the noise power spectral density agree with the behavior expected for noise due to conductance fluctuations. Comparison between films on different substrates shows that the presence of defects such as grain boundaries in the film correlate with significantly enhanced noise levels. The noise levels in our good-quality epitaxial films are several orders of magnitude lower than the anomalously large noise magnitudes reported for YBa2Cu3O7-δ in most of the earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727553
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