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  • 1
    Electronic Resource
    Electronic Resource
    (Tl, Pb, Bi)Sr2Ca2Cu3Oz superconductors with zero resistance at 120 K (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1281-1283 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have synthesized new superconductors of nearly single phase with zero-resistance temperatures around 120 K employing a novel method for sintering. The samples included a nominal composition of (Tl0.64Pb0.2Bi0.16)Sr2Ca3Cu4Oz. This sample was prepared from the mixture of presynthesized (Tl0.64Pb0.2Bi0.16)Sr2CaCu2Oz (1212 phase), CaO, and CuO powders. The mixed powder was sintered at 920 °C in O2 gas and post-annealed at 400–600 °C in O2 gas. The powder x-ray diffraction revealed that the sample was isostructural with the Tl-based (Tl, Pb, Bi)Sr2Ca2Cu3Oz (1223 phase). The sample exhibited a sharp superconducting transition at Tonsetc=125 K and TR=0c=120 K and the superconducting diamagnetic signal at 10 K was about 20% of a full Meissner effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103174
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  • 2
    Electronic Resource
    Electronic Resource
    The role of boron in Rn+1Con+5B2n systems (R=Y, Sm, Dy; n=0, 1, 2, 3, and ∞) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5911-5913 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic measurements have been made for the systems of Rn+1Co3n+5B2n (R=Y, Sm, Dy; n=1, 2, 3, 4, and ∞) in wide temperature region. The Curie temperature decreases drastically between n=0 and n=1, and slowly with n larger than 1, for all above systems. Three kinds of Co sites with different magnetic moments are proposed. The estimated Sm- and Dy-atomic moments are found to be smaller than the free ion moments in the Dy system with n≥1 and in the Sm system. Magnetic anisotropy constants K1(Co) and K2(Co) have been determined at various temperatures for the Y system, and the Sm-sublattice anisotropy constants K1(Sm) have been estimated and found to take the maximum value at n=1 and decrease with n≥1 in the Sm system. Magnetic anisotropy in the Dy system is found to be planar at all temperatures below the Curie temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354067
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  • 3
    Electronic Resource
    Electronic Resource
    Superconducting Sr0.875Nd0.125CuO2−δ thin films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4047-4051 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-phase Sr0.875Nd0.125CuO2−δ (SNCO) thin films of the "infinite-layer'' structure were fabricated by a pulsed-laser deposition technique. The films directly grown on SrTiO3 (100) substrates had superconductivity onset temperatures around 20 K, but zero resistances were not observed down to 4.2 K. The a-axis length of the film samples did not exceed the values reported for bulk SNCO samples. It was demonstrated that, when deposited onto a Pr2CuO4 buffer layer formed on a SrTiO3 substrate, the a-axis length of the thin film SNCO increased up to 0.395 nm which was comparable to that for bulk SNCO. The film sample exhibited a zero resistance state below 7 K. Thermoelectric-power measurements indicated that the carrier density for the film deposited on a Pr2CuO4 buffer layer was higher than that for the film fabricated without a buffer layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354448
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  • 4
    Electronic Resource
    Electronic Resource
    Stability of superconducting La1.8Sr0.2CaCu2O6 with respect to oxygen partial pressure (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7575-7580 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermodynamical stability of a superconducting La-326 compound, La1.8Sr0.2CaCu2O6, was studied by observing the phase formation at high pressures and decomposition at high temperatures. The superconducting La-326 compound, which was synthesized by means of an oxygen hot isostatic press annealing was found to be stable up to 800 °C at ambient pressure. When post-annealed at temperatures between 600 and 800 °C, the amount of superconductive volume fraction was increased and TcR=0 was also enhanced. When post-annealed at temperatures higher than 800 °C, La-326 started to decompose and the amount of secondary 214(T-structure) phase increased. It was confirmed that high-pressure annealing at an oxygen pressure of 10 atm was required to form the superconducting La-326 phase, which exhibits Tc of higher than 40 K. The high-pressure annealing conditions, such as Ar-to-oxygen ratio and annealing temperature, were optimized in order to make the La-326 phase superconductive. It was concluded that an oxygen pressure of at least 10 atm was required to "superconductor-ize'' the La-326 phase, regardless of the magnitude of total pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354094
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of Tl-based "2234'' superconductors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2347-2350 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nearly single-phase samples of superconducting Tl–Ba–Ca–Cu–O "2234'' were successfully synthesized. The sample sintered in air had Tc of 112 K. Post-annealing of the sintered sample in a high-pressure oxygen gas made its Tc increase up to 115 K. The sample sintered in argon gas had Tc of 90 K. The thermoelectric power (TEP) of the sample was also measured. All the samples showed positive TEP signals. The magnitude of TEP signal decreased as Tc increased. Thus, it was likely that the as-sintered 2234 phase was in an under-doped state with respect to the optimum carrier concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351087
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of superconducting La2−xSrxCaCu2O6 using O2-hot-isostatic-pressing techniques (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3190-3193 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting 326 samples, La2−xSrxCaCu2Oz with x=0.2 and 0.4, which exhibited superconducting onsets at temperatures (Tonc's) higher than 40 K were successfully synthesized using hot-isostatic-pressing (HIP) techniques. As starting materials, powders of conventional carbonates (SrCO3 and CaCO3) and oxides (La2O3 and CuO) were employed. Sintering of the samples was made at a variety of temperatures (Ts) for 72 h in flowing O2 gas (of 1 atm). The sintered samples were post-annealed at various temperatures (Ta) for 6 h in a mixture of 80% Ar gas and 20% O2 gas of the total pressure of 1000 atm by means of HIP techniques. Optimum combinations of Ts and Ta were determined for obtaining superconducting samples. Single-phase samples were obtained only for the composition La1.8Sr0.2CaCu2Oz for which the oxygen content, z, was determined to be 6.01±0.01 by coulometric titration. It was concluded that Ta was a crucially important factor for obtaining superconducting 326 phase with Tonc (approximately-greater-than) 40 K, that is, Ta (approximately-greater-than) 970 °C was required (for 6-h HIP annealing). It was demonstrated that a long HIP annealing was necessary to obtain a significant volume fraction for the superconducting 326 phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348560
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical properties of Nd1.85Ce0.15CuO4−y at high temperatures (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4159-4160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of electrical resistivity of Nd1.85Ce0.15CuO4−y was measured with oxygen partial pressure fixed at 2.08×10−1, 1.8×10−2, 8.1×10−4, and 3.3×10−6 atm. The oxygen partial pressure dependence of resistivity indicated that the charge carriers in Nd1.85Ce0.15CuO4−y were electrons. The temperature dependence of resistivity exhibited a linear metallic behavior at high temperatures and a semiconductorlike behavior at low temperatures, having a minimum at an intermediate temperature. Difficulties are pointed out in obtaining a unified view for the mechanism of normal electrical conduction in Nd1.85Ce0.15CuO4−y .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344978
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties of the Y1−xGdxCo3B2 system : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6540-6542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic properties of Y1−xGdxCo3B2 with x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 have been studied in a wide temperature range from 4.2 to 1250 K. All compounds studied here have the CeCo3B2-type structure which is a derivative of the RCo5 type one. In this system, the Co atom is nonmagnetic down to 4.2 K and the Curie temperature decreases almost linearly with increasing composition x and is expected to vanish at around x=0 (YCo3B2). For the sample with x=0.2, a spin-glass freezing point has been found in addition to the usual ferromagnetic Curie temperature. Gd magnetic moments obtained from the saturation magnetizations at T=4.2 K are generally smaller than those obtained from the Curie–Weiss constants in the high-temperature paramagnetic region, which suggests a slight polarization of the Co atoms antiparallel to the Gd moment in the ferromagnetic region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349900
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  • 9
    Electronic Resource
    Electronic Resource
    Critical current density and microstructure of YBa2Cu4O8 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 384-389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the intragranular critical current density Jc in YBa2Cu4O8 prepared by two routes with different oxygen pressures at various temperatures and applied fields. A relationship between the Jc's and the microstructures observed by transmission electron microscopy is discussed. The magnitude of Jc for the low oxygen processed sample is higher by a factor of 5 than that for the high oxygen pressure sample. Transmission electron microscopy reveals that the sample prepared at high oxygen pressure shows an almost perfect stacking sequence, but the low oxygen pressure prepared one has a severely distorted structure. We conclude that the difference in Jc(H) for the samples must be related to the different microstructures. Jc at a fixed magnetic field shows an exponential temperature dependence similar to that seen in other high-Tc superconductors. The field dependence is Jc∝H−n with n between 0.5 and 1.5, and with the n value becoming larger at higher temperatures. This type of the behavior may arise from the two-dimensional character of YBa2Cu4O8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347726
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  • 10
    Electronic Resource
    Electronic Resource
    Irreversibility line for a Pb-doped Hg-Ba-Ca-Cu-O superconductor (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1301-1303 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By measuring the magnetization hysteresis, we studied the critical current density, Jc, and irreversibility fields, Hirr, of a c-axis aligned Hg-Ba-Ca-Cu-O sample doped with Pb containing the Hg-1223 phase as the main phase. Anisotropy in ΔM was clearly observed in two different magnetic field directions. Even though the Hg-1223 phase contains three CuO2 sheets, the Hirr vs [1-(T/Tc)] curve was located at roughly the same positions as those reported for the Hg-1201 and Hg-1212 phases, indicating that the higher Tc phase, i.e., Hg-1223, is advantageous to the other phases in practical uses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111941
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