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  • 1
    Electronic Resource
    Electronic Resource
    The effect on the band structure of intercalating NbS2 with first-row transition metals (1983)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 1982-1987 
    Details
    ISSN: 0392-6737
    Keywords: Optical properties and materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si presentano analisi di Kramers-Krönig dei dati di riflettività a incidenza quasi normale (E⊥c; E‖c) per intercalati di metalli di transizione della prima fila del NbS2. Si discutono i cambiamenti negli spettri ottici e nelle strutture di banda in sèguito all'intercalazione.
    Abstract: Резюме Для чередований прослоек NbS2 и переходных металлов первого ряда проводится анализ Крамерса-Кронига данных по отражательной способности (E⊥c; E‖c) при почти нормальном падении. Обсуждаются изменения оптических спектров и зонной структуры, связанные с прослойками.
    Notes: Summary Kramers-Krönig analyses of near-normal incidence reflectivity data (E⊥c; E‖c) are presented for first-row transition metal intercalates of NbS2. Changes in the optical spectra and band structure upon interacalation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457898
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  • 2
    Electronic Resource
    Electronic Resource
    Low-temperature annealing induced superconducting and non-superconducting phase transition in the LaBa"2Cu"3O"7"-"δ compounds
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 229 (1994), S. 268-272 
    Details
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-4534(94)90506-1
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  • 3
    Electronic Resource
    Electronic Resource
    Ordering of Tl and Bi in Bi-doped Tl-1223 high Tc superconductors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 326-330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High Tc superconducting materials with nominal compositions of Tl1-xBix(Sr, Ba)2Ca2Cu3O9 (0≤x≤0.5) have been investigated using x-ray powder diffractometry and electron microscopy. It was found that Tl and Bi cations were in an ordered arrangement in the (Tl, Bi)–O atomic layer. Although the proposed supercell is 4a×4b×4c derived from the basic unit cell of the undoped TlBa2Ca2Cu3O9 (Tl-1223), the basic two-dimensional superlattice in the (Tl, Bi)–O layer is 2a×4b or 4a×2b with Bi cations at the center and the corner of the rectangle, giving an ideal and preferred composition with the Tl:Bi ratio of 3:1. Accordingly, the maximum Bi doping for Tl in the solid solution is 25%. The proposed model of the superstructure was supported by computer simulation of electron diffraction patterns. The mechanism of formation of the superstructure is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362823
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic and transport measurements of Tl-1223 superconductors (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5287-5292 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic measurements have been performed on silver clad Tl-1223 and Tl-2223 tapes and a Tl-1223 single crystal to study the critical current properties of these samples. The Tl-1223 tape is shown by both magnetic and transport experiments to exhibit a highly granular nature, much more severe than that seen in the Tl-2223 tape, and in Bi-2223 tapes fabricated by similar rolling and pressing techniques. This characteristic is explained in terms of the poor grain alignment in the Tl-1223 tape resulting from the spherical morphology of Tl-1223 powders, in contrast with the micaceous and easily aligned Bi-2223 and Bi-2212 materials. However, evidence of a small number of strong intergrain links which remain superconducting at 77 K and 8 T is clear. The Tl-1223 single crystal exhibits clear anisotropic behavior, and this, together with the lack of good crystallographic alignment in the tapes is used to explain the variations in irreversibility line behavior between sample forms. The ratio of the irreversibility fields measured with field parallel and perpendicular to the ab plane is approximately 8. A clear "fish tail'' feature is also observed in magnetic hysteresis curves obtained from the Tl-1223 single crystal. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359282
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  • 5
    Electronic Resource
    Electronic Resource
    Breakdown of the Wiedemann-Franz law in strongly-coupled electron-phonon system, application to the cuprates (2004)
    Springer
    The European physical journal 39 (2004), S. 459-468 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. With the superconducting cuprates in mind, a set of unitary transformations was used to decouple electrons and phonons in the strong-coupling limit. While phonons remain almost unrenormalised, electrons are transformed into itinerent singlet and triplet bipolarons and thermally excited polarons. The triplet/singlet exchange energy and the binding energy of the bipolarons are thought to account for the spin and charge pseudogaps in the cuprates, respectively. We calculated the Hall Lorenz number of the system to show that the Wiedemann-Franz law breaks down due to the interference of the polaron and bipolaron contributions to heat flow. The model provides a quantitative fit to magnetotransport data in the cuprates. Furthermore we are able to extract the phonon component of the thermal conductivity with the use of experimental data and the model. Our results further validate the use of a charged Bose gas model to describe normal and superconducting properties of unconventional superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00218-6
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  • 6
    Electronic Resource
    Electronic Resource
    Enhancement of Microstructural and Magnetic Properties by Li-doping in Tl,Pb-1223 Superconductors (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 143-144 
    Details
    ISSN: 1572-9605
    Keywords: Tl based high Tc superconductors ; synthesis ; Li doping ; microstructure ; magnetization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Polycrystalline Tl0.5Pb0.5Sr2Ca2Cu3LiyOx samples were synthesized. After processing under the same conditions, the Li-doped samples (y = 0.2) showed an average grain size three times larger than that of a typical undoped Tl,Pb-1223 sample (y = 0), and a 30% increase in sample density. The irreversibility line has significantly shifted to higher field with Birr ( 77K) ≅ 12 tesla. The intragranular critical current densities, estimated through the Bean model, are higher in Li-doped samples in temperatures below 77K and external magnetic fields greater than 2 tesla. The Tc,onset, of the Li-doped samples are lowered by typically 2-5 K compared with the undoped samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022643626393
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  • 7
    Electronic Resource
    Electronic Resource
    Critical Current Anisotropy of Tl-1223 Superconductors (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 21-22 
    Details
    ISSN: 1572-9605
    Keywords: Critical current anisotriopy ; thallium ; superconductor ; conductor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A comparative study of the critical current anisotropy of Tl-1223 conductors manufactured by different techniques, prepared from different compositions and originating from different research laboratories is presented and discussed. For highly oriented layers, with the magnetic field (B) parallel to the ab plane, the normalised critical current density (j) versus magnetic field characteristic shows very little drop of j value due to the intrinsic properties of the Tl-1223 phase, while all powder-in-tube conductors show a rapid drop of j value in fields as low as 10 mT. For all powder-in-tube conductors the anisotropy coefficient k shows a very pronounced minima at fields up to 30 mT followed by a monotonic decrease of anisotropy with increase of the magnetic field. This is due to poor grain alignment and a demagnetising effect in the powder-in-tube Tl-1223 tapes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022605123242
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic specific heat of YBa2Cu3O6+x from 1.8 to 300 K (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 243-249 
    Details
    ISSN: 1572-9605
    Keywords: Electronic specific heat ; superconductivity ; pseudogap ; Fermi statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have determined for the first time the electronic specific heatγ(x, T) of YBa2Cu3O6+x for 0.16≤x≤0.97 from 1.8 to 300 K. Weakly superconducting behavior betweenx=0.4 and 0.8 progresses rapidly to strong coupling BCS-like superconducting and metallic normal state behavior forx〉 0.9. However, the continuous development of the entropyS(x, T) withx andT across the entire series suggests a progressive modification of the low-energy spin spectrum with hole doping rather than a simple band model. Fermi statistics andk-space pairing for allx is indicated by the magnitude andT-dependence ofS(x, T). Pseudogap behavior inS(x, T) is observed over a temperature region aboveT c , which increases rapidly with oxygen depletion to around 200 K forx∼0.7. This loss of entropy reflects normal-state correlations apparently unrelated to the superconducting pairing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00730405
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  • 9
    Electronic Resource
    Electronic Resource
    Phase Formation in Tl,Bi-1223 Superconductors by LaAlO3 or LSAT Micro-Particle Addition (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 155-158 
    Details
    ISSN: 1572-9605
    Keywords: Tl based superconductors ; synthesis ; phase formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Polycrystalline (Tl,Bi)(Sr,Ba)2Ca2Cu3Ox (Tl,Bi-1223) samples were synthesized by mixing the precursor with 5wt% micrometer-size LaAlO3 or LSAT particles. These particles appeared to provide suitable surface for epitaxial growth of Tl,Bi-1223 phase. The growth zone is typically 5 - 10 μm thick and several zones can coalesce to form a larger zone. Consequently, there is a dramatic increase in the magnetization signals, indicating the increased superconducting volume fraction. The enhancement is uniform in the external magnetic field. The Tc of the samples was not affected by the additives and the transition remained sharp. The results suggest that a controlled growth of Tl-1223 grain with improved texture can be achieved by adding the growth centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022651828210
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  • 10
    Electronic Resource
    Electronic Resource
    The Mechanism of Surface Decomposition of Tl- and Hg-Containing Superconductors (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 13-14 
    Details
    ISSN: 1572-9605
    Keywords: Surface ; superconductors ; decomposition ; electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The surface chemistry of various Tl- and Hg-containing superconducting oxides has been studied by high resolution transmission electron microscopy. The mechanism of surface decomposition of these materials is discussed. High chemical reactivity of the Tl-O and Hg-O layers seem to be the main course of the decomposition. It is proposed that a surface substitution of Tl and Hg may stabilise the structures without losing superconducting properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022601022333
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