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  • 1
    ISSN: 1572-9605
    Keywords: High-T c superconductivity ; Pb2Sr2Ho0.5Ca0.5Cu3O8 ; single crystal ; upper critical magnetic field ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Anisotropie properties of the single crystal Pb2Sr2Ho0.5Ca0.5Cu3O8 have been investigated by measuring the electrical resistivity in theab-planeρ ab (H, θ,T), which depends on the angleθ between theab-plane and the magnetic-field direction, in various constant fieldsH perpendicular to the current direction. All the angle-dependent values ofρ ab (H, θ,T) at a constant temperature are scaled to be on one curve as a function of reduced field. The anisotropic parameter γ≡(m c * /m ab * )1/2 is estimated as 12–13, which is larger than that of YBa2Cu3O7 and much smaller than that of Bi2Sr2CaCu2O8. It has been concluded that the anisotropy does not always depend on the thickness of the blocking layer but seems to depend on the overlap of the electronic wave functions along thec-axis. Anisotropy in the pinning potential has also been discussed from the resistive tail in the temperature dependence ofρ ab (H,θ,T).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9605
    Keywords: High-Tc superconductivity ; La1.9Bi0.1CuO4+δ ; excess oxygen ; crystal structure ; superconducting transition temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have investigated the relation between the crystal structure and superconductivity in La1.9Bi0.1CuO4+δ , in which the phase separation observed in La2CuO4+δ is suppressed. A phase diagram in theT−δ plane is given for La1.9Bi0.1CuO4+δ with excess oxygen. For very smallδ values, the crystal structure is orthorhombic, and an orthorhombic-tetragonal phase transition occurs markedly atδ ∼ 0.03 in the measured temperature range between 13 and 293 K. Superconductivity is observed in the range of 0.04〈δ〈0.11. This is clear evidence thathigh-T c superconductivity also appears in the tetragonal phase.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 7 (1994), S. 123-126 
    ISSN: 1572-9605
    Keywords: Intercalation ; high-T c superconductivity ; Bi-based copper oxide superconductor ; two-dimensionality ; superconducting transition temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have investigated the stage-1 iodine-intercalation compounds, whose host materials are Bi2Sr2Ca1−x Y x Cu2O8 (Bi-2212 phase) and Bi1.6Pb0.5Sr1.9−x La x Cu1.05O6 (Bi-2201 phase) with variousx values. In the Bi-2212 phase, it has been found that the change inT c through the stage-1 iodine intercalation is due to two effects; a change of the two-dimensionality and an increase in the carrier number. The former effect decreasesT c by about 10 K independent of the carrier number of the host sample. The latter effect shifts thex dependence ofT c to largerx values by about 0.08, taking account of oxygen release from the host samples during the intercalation process. This result is clear evidence for the occurrence of both the change of two-dimensionality and the increase in carrier number about 0.04 per CuO2 unit due to the charge transfer through the stage-1 iodine intercalation. In the Bi-2201 phase,T c decreases by about 10 K through the stage-1 iodine intercalation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 117 (1999), S. 759-763 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stability of A 2 Cu 3 O 4 X 2 (A = Sr, Ba; X =Cl, Br) of the 2342 phase with the Cu 3 O 4 plane, which is composed of the Cu(1)O 2 and extra Cu(2) sublattices, has been studied in the temperature range between 600 °C and 950 °C. Polycrystalline samples of the composition Sr 2−x Ba x Cu 3 O 4 Cl 2−y Br y were prepared by the solid-state reaction method. From the powder x-ray diffraction analysis, we have made the phase diagram (x vs. y vs. heat-treatment-temperature). It has been found that the 2342 phase becomes stable with increasing x and y at high heat-treatment-temperatures instead of a mixture of CuO and the A 2 CuO 2 X 2 (2122) phase with the CuO 2 plane. These results can be explained in terms of the structural matching between the Cu 3 O 4 plane and the A 2 X 2 layer.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In order to study the “ $$\frac{1}{8}$$ effect” in different high-T c oxides from the La-system, muon spin relaxation measurements were applied to the Zn-substituted Bi-2212 system, Bi 2 Sr 2 Ca 1−x Y x (Cu 1−y Zn y ) 2 O 8+δ , around the hole concentration p= $$\frac{1}{8}$$ per Cu. It has been revealed that the magnetic correlation between Cu spins is anomalously enhanced in the Zn-substituted samples at $$p \sim \frac{1}{8}$$ per Cu, proving the existence of the “ $$\frac{1}{8}$$ effect" in the Bi-2212 system as well.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-7357
    Keywords: 74.25.Fy ; 74.62.Dh ; 74.72.Dn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effects of substitution of Y or Bi on the low-temperature structural phase transition, electronic anomaly and superconductivity have been studied in La2-y-xYyBaxCuOφ La2-y-xBiyBaxCuO4 and La1.9-y-xTb0.1BiySrxCuO4 with x = 1/8. Moreover, an electronic anomaly, which is analogous to those observed in La2−xBaxCuO4 and La1.6-xNd0.4SrxCuO4 with x ∼ 1/8, has been found below about 60 K in the thermoelectric power measurements for the Zn-substituted La2−xSrxCu1−yZnyO4 with x ∼ 0.115 and y = 0.01 – 0.02. These experimental results support the conclusions by Tranquada et al. that static order of the stripe correlations of holes and spins, owing to pinning by the low-temperature structure or impurities (Zn in this case), is the origin of the electronic anomaly, leading to the suppression of superconductivity.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1499-1504 
    ISSN: 1573-7357
    Keywords: 74.62 Bf ; 74.72 Jt ; 81.20.−n
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Binary cuprates of Sr2CuO3+δ and SrCuO2 have been synthesized at low temperatures below 500 °C under various values of partial oxygen-pressure $$P_{O_2 }$$ by thermal decomposition of hydroxide precursors, Sr2Cu(OH)6 and SrCu(OH)4, respectively. The tetragonal Sr2CuO3+δ (δ ∼ 0.3) is obtained by the heat-treatment at 400 ° C and $$P_{O_2 }$$ ≥ 0.2 atm. The value of δ appears to be independent of $$P_{O_2 }$$ and unchangeable. On the other hand, the orthorhombic Sr2CuO3+δ (δ ∼ 0) is obtained by the heat-treatment at 400 °C in flowing gas of N2. For 0 〈 $$P_{O_2 }$$ 〈 0.2 atm, a mixture of the tetragonal and orthorhombic phases is obtained. The orthorhombic SrCuO2 is obtained by the heat-treatment at 500 ° C in flowing gas of N2, although the tetragonal SrCuO2, namely, the so-called infinite-layer compound is not obtained.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Anomalies in the thermoelectric power and the Hall coefficient, which are analogous to those observed in La 2−x Ba x CuO 4 with x ∼ 1/8, have been observed in the Zn-substituted La 2−x Sr x Cu 1−y Zn y O 4 with x = 0.115 and y = 0 – 0.025 and with x = 0.15 and y ∼ 0.02. Based on the so-called stripe model, these are explained as being due to the formation of the static order of the stripe-patterned CDW and SDW on account of the pinning by Zn. Accordingly, the long-standing problem on the conspicuous suppression of superconductivity in the Zn-substituted La 2−x Sr x Cu 1−y Zn y O 4 with x ∼ 0.115 is likely to be attributed to this static order.
    Type of Medium: Electronic Resource
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