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  • 1
    Electronic Resource
    Electronic Resource
    Importance of controlling the Tl-oxide partial pressure throughout the processing of TlBa2CaCu2O7 thin films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 7186-7191 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: TlBa2CaCu2O7 (Tl-1212) superconducting films 5000–6000 A(ring) thick have been grown on LaAlO3 (100) substrates using oxide precursors in a closed two-zone thallination furnace. Tl-1212 films can be grown with transition temperatures ∼100 K, and critical current densities measured by magnetization of Jcm(5 K)(approximately-greater-than)107 A/cm2 and Jcm(77 K)(approximately-greater-than)105 A/cm2. Processing conditions, substrate temperatures and Tl-oxide source temperatures are found which result in smooth, nearly phase-pure Tl-1212 films. Variations in the respective temperature ramps of the Tl-oxide zone and the substrate zone can greatly influence resulting film properties such as microstructure, morphology, superconducting transition temperature, and critical current density. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360428
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  • 2
    Electronic Resource
    Electronic Resource
    Two-zone equilibria of Tl-Ca-Ba-Cu-O superconductors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1023-1031 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phase equilibria in the Tl-Ca-Ba-Cu-O system have been studied at sample temperatures that are near, but below, the onset of melting. Independent control of the partial pressures of oxygen P(O2) and thallous oxide P(Tl2O) was achieved through the use of a two-zone furnace. Stable ranges of P(Tl2O), P(O2), and sample composition for individual Tl superconductors, including 2122, 2223, 1122, and 1223 (the latter intergrown with about 10% 2223) have been determined. A qualitative understanding of these stable ranges, based on the relative Tl content and formal oxidation state of the cations within a structure type, has been developed. From this information, equilibrium phase diagrams for Tl superconductors with Ca:Ba:Cu ratios of 1:2:2, 2:2:3, and 3:2:4 are proposed. These diagrams provide process information for the two-zone synthesis of bulk materials and thin and thick films. The superconducting transition temperatures of the individual phases produced by near-equilibrium processing are both reproducible and relatively insensitive to changes in the process conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356509
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid thermal processing of YBa2Cu3O7 spun wires (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6382-6388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rapid thermal processing has been utilized to sinter and anneal phase-pure and CuO-rich YBa2Cu3O7 fibers and woven fibers formed by melt spinning a powder/polymer composite. The optimum temperature for sintering the powders varies for the stoichiometric (1025 °C) and 5% CuO-rich fibers (1000 °C), but in both cases the temperature window is extremely narrow (±25 °C). Typical processing consists of a rapid heating (250 °C/s) of the fibers to the sintering temperature in 1 atm of pure oxygen, holding at temperature for 1 s and cooling over a period of 2–3 min. The resulting fibers are orthorhombic YBa2Cu3O7 with large Meissner and shielding fractions, have zero resistance up to 92 K, critical-current densities in zero applied field to 1100 A/cm2 at 76 K, and show clean grain boundaries by transmission electron microscopy. Despite the short processing times, microstructural analysis shows considerable grain growth and evidence of metastable congruent melting of oxygen-rich YBa2Cu3O7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345160
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  • 4
    Electronic Resource
    Electronic Resource
    Spin-dependent transport at silicon grain boundaries (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5059-5069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport of electronic carriers across grain boundaries in n- and p-type silicon has been measured as a function of magnetic field in the presence of a microwave field. The spin-dependent-transport (SDT) signal is observed to have a distinctively different character depending on whether the samples are illuminated with band-gap light or are in the dark. Despite the approximate symmetry of the dark I-V curves, the dark SDT signals, which are only observed for n-type boundaries, are asymmetric, displaying an increased impedance at the resonance condition for one current direction and a decrease for the other. With band-gap illumination, a symmetric SDT signal is seen for all samples which becomes quite large at high light intensities. The line shapes and g values seen for these resonances are similar to those attributed to Si dangling-bond-like defects. The dark SDT effect may be associated with a spin-flip k-vector change which must take place for conduction-band electrons that are thermionically emitted over the grain-boundary double depletion layer. The light-induced SDT effect is well modeled as a spin-dependent change of the light-generated minority carrier flux that modulates the trapped majority-carrier density at the grain-boundary plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350607
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  • 5
    Electronic Resource
    Electronic Resource
    Thickness dependence of electrodynamic properties of TlCaBaCuO thin films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7571-7574 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thickness dependence of electrodynamic properties of Tl2Ca2Ba2Cu3Ox films has been examined after correction for geometrical effects. The surface resistance increases for very thin or thick films as is consistent with the presence of a poorly superconducting layer (phase inclusions or morphology breakdown) as was detected with magnetization measurements. The temperature dependence of surface resistance has been examined at low temperatures and fitted to a multigap model. There was reasonable agreement for moderate thickness films, suggesting why such films have been and will be excellent for applications, while the behavior of other thicknesses may be dominated by grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354008
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  • 6
    Electronic Resource
    Electronic Resource
    Proton NMR and susceptibility measurements in TiCoHx (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3036-3038 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The proton spin-lattice relaxation times (T1) and magnetic susceptibilities (χ) are used to study the effects of hydrogen on the electronic structure properties of the intermetallic compound TiCo. Hydrogen addition systematically decreases both χ(T) and the proton (T1T)−1/2 parameters, which are directly proportional to the local density of the Fermi-level electronic states. The behavior for the TiCoHx is completely opposite to that previously found for several other Ti-based metal hydrides where these parameters tend to increase with hydrogen content. These differences are attributed to the Fermi levels falling on alternate sides of peaks in the densities of electronic states. The present results for TiCoHx are compared with the magnetic properties and the theoretical band structures for the closely related hydride TiFeHx.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335204
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of hydrogen on magnetic properties of amorphous zirconium alloys (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3542-3544 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic susceptibilities χ(T) of the amorphous ternary hydrides of the paramagnetic metallic glasses a-Zr2Pd and a-Zr3Rh have been measured between 7 and 300 K. It has been found that χ(T) of both a-Zr2PdHx and a-Zr3RhHx decrease substantially with increasing hydrogen content. This behavior is primarily attributed to reductions in the densities of the Fermi level electronic states. Although χ(T) for crystalline Zr2Pd (MoSi2 structure type) is smaller than the susceptibility of the a-Zr2Pd glass, χ(T) for a crystallized Zr3Rh sample was found to increase relative to the initial susceptibility for this glass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335055
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic and structural properties of shock-synthesized zinc ferrite (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3814-3816 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-pressure shock-wave loading on stoichiometric mixtures of zinc oxide and ferric oxide powders produces partial conversion to a spinel structure zinc ferrite as shown by x-ray diffraction. The ferrite phase is characterized by a substantial saturation magnetization plus a high-field susceptibility. Since stoichiometric ZnFe2O4 is paramagnetic above 10 K, the magnetic behavior of the shock-synthesized spinel demonstrates that it is a zinc-deficient ferrite. X-ray diffraction data confirm that less zinc oxide is consumed than ferric oxide in producing the recovered spinel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334929
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  • 9
    Electronic Resource
    Electronic Resource
    Anisotropic transport and cation disorder in superconducting Tl2Ca2Ba2Cu3Ox single crystals (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 517-519 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured for the first time the temperature-dependent anisotropic resistivity of several Tl2Ca2Ba2Cu3Ox single crystals. The resistivity ratio between the c axis and the a-b plane orientations in the best crystals is approximately 60 at room temperature. Resistivity data indicate substantial differences in both Tc and the transition width of nominal Tl2Ca2Ba2Cu3Ox plates grown from two different melt compositions. A Tl-O and CuO-rich flux yielded approximately stoichiometric plates with sharp transitions beginning near 113 K, while a Tl-O-rich flux produced plates containing more Tl and less Ba with broad transitions starting near 103 K. These data demonstrate the extreme sensitivity of the superconductivity to cation site disorder in the Tl-Ca-Ba-Cu-O system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104243
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  • 10
    Electronic Resource
    Electronic Resource
    Strongly enhanced flux pinning by high-energy proton irradiation of a Tl2Ca2Ba2Cu3Oy single crystal (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2456-2458 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Flux creep data are reported which clearly demonstrate a dramatic enhancement in the pinning potential for magnetic vortices (fluxoids) in a Tl2Ca2Ba2Cu3Oy single crystal upon irradiation with 4.5 MeV protons. The creep rate is markedly reduced between 5 and 80 K, and the effective pinning potential is quadrupled from ≈100 to ≈400 meV at 20 K in a field of 50 mT. This stronger pinning enhances the magnetization hysteresis and hence the inferred low-field critical current density by a factor of 5 at 40 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103254
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