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  • 1
    Electronic Resource
    Electronic Resource
    Superconductivity and flux pinning in Y and heavily Pb codoped Bi-2212 single crystals (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7669-7671 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1−xYxCu2O8+y (x=0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x=0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K for the as-grown state, but become metallic with Tc of 65–70 K after air or oxygen annealing. Flux pinning was studied by measuring the hysteresis loop at different temperatures and different fields. A peak effect was observed in all the codoped samples. Results show that at low temperatures, the peak field is smaller than in solely Pb doped crystals and decreases as x increases (x〉0.1). However, the peak field at high temperature for the x=0.05 sample is higher than in heavily Pb doped Bi2212 crystals, indicative of a strong pinning due to the codoping. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356055
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  • 2
    Electronic Resource
    Electronic Resource
    Anisotropy of the critical current in silver sheathed (Bi,Pb)2Sr2Ca2Cu3O10 tapes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1123-1130 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport critical current of Bi:2223 tapes was measured in magnetic fields up to 15 T and at temperatures from 4.2 to 84 K. At high temperatures, the critical current density Jc is strongly anisotropic and the anisotropy increases rapidly with magnetic field, whereas at low temperatures the critical current is less anisotropic and the anisotropy is field independent above 1 T. In the former case we believe we are in a regime, where pinning limits Jc, at least within some parts of the tape, whereas in the latter case the limitation of Jc by Josephson weak links seems to be the dominant mechanism. In addition, a critical current hysteresis induced by flux trapping in a weak link network is observed, which is more pronounced at low temperatures. From transmission electron microscopy observations of the microstructure we find that the "brick'' in the "brick wall'' model turns out to be the colony instead of the grain inside the colony. Additionally it is found that colony boundaries parallel the ab plane and intersected boundaries occur much more frequently than boundaries parallel to the c axis, due to the misalignment of the colonies inside the tape. In a small region near the silver sheath colony misalignment is much smaller and boundaries parallel to the c axis may act as strong links at high temperatures as their interfaces are very clean and well matched. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360346
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  • 3
    Electronic Resource
    Electronic Resource
    Superconductivity in a Ag-doped Bi-Pb-Sr-Ca-Cu-O system (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 493-494 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For the Bi-Pb-Sr-Ca-Cu-O (BPSCCO) system, a consistent set of data for Tc, x-ray diffraction, and scanning electron microscopy shows that Ag additions strongly react with BPSCCO to destabilize the 110 K superconducting phase, resulting in a strong depression in Tc and lattice parameters when samples are treated in air or pure oxygen. This is in contrast to the behavior for the Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems, which do not show such degradation. However, Ag additions show no effects on Tc and lattice parameters when samples are treated under low oxygen pressure. The formation of a low-melting eutectic liquid with Ag2O-PbO-CuO solid solution affects the composition of the superconducting phase and degrades superconductivity, while the eutectic may be suppressed by reducing the oxygen partial pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103298
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  • 4
    Electronic Resource
    Electronic Resource
    Improvement of flux pinning in the Ag-clad Bi-Pb-Sr-Ca-Cu-O wires through the use of a short period melt processing (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2929-2931 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A significant enhancement of the Jc in magnetic field in the Ag-clad Bi-Pb-Sr-Ca-Cu-O (BPSCCO) wires has been achieved by using a short period melt processing. The weak links have been largely eliminated in the melt-processed tapes which exhibits a 3–10-fold increase in the Jc at 77 K and 1 T over the normally processed tapes. For tapes with a thickness 80 μm 60% of melt-processed samples have the Jc values between 10 000 and 27 000 A/cm2 at 77 K in zero field. The irreversibility lines determined using ac susceptibility measurements under dc fields confirmed the improvement of flux pinning in the melt-processed tapes compared with the normally processed tapes. The improved Jc-H characteristics may be attributed to the desirable microstructures produced from the high Tc phase formation-decomposition-recovery process through the use of a short period melting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106823
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  • 5
    Electronic Resource
    Electronic Resource
    Critical currents in silver-sheathed (Bi,Pb)2Sr2Ca2Cu3O10−y superconducting tapes (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3171-3173 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nearly 95 vol % of the 110 K superconducting phase was formed by lead doping in a Bi–Sr–Ca–Cu–O system. The processed 110 K superconducting powders were used to produce long silver-sheathed tapes with a highly textured microstructure by rolling and prolonged sintering. The transport critical current density was measured at 4.0 K to be 0.7×105 A/cm2 (the corresponding critical current is 74 A) at zero field and 1.6×104 A/cm2 at 12 T for H(parallel)ab. At 76 K, the critical current density reached a value of ∼1×104 A/cm2 at zero field for H(parallel)ab and gradually decreased to 419 A/cm2 at 1 T. Excellent grain alignment in the a–b plane led to greatly improved critical current densities under a magnetic field. The relationship between the transport properties and the microstructure of the tapes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105774
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  • 6
    Electronic Resource
    Electronic Resource
    Large low-field magnetoresistance over a wide temperature range induced by weak-link grain boundaries in La0.7Ca0.3MnO3 (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 396-398 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline bulk porous samples with a large number of weak-link grain boundaries and high density polycrystalline bulk samples with strong-link boundaries were synthesized by conventional solid-state reaction and a partial melting technique. The weak-link samples showed large magnetoresistance (MR,Δρ/ρH=[ρ0−ρH]/ρ0), 20–30%, at a low magnetic field of 300 mT and over a wide temperature range from the magnetic transition at 235 to 77 K. The partially melted samples exhibited the same magnetoresistance behavior as that of single crystals with a maximum peak MR of 15% at a narrow temperature range around the ferromagnetic transition. It is suggested that grain boundaries are necessary but not sufficient to account for the MR at low field over a large temperature range. Weak-link grain boundaries rather than strong-link boundaries are responsible for the MR at low field over a large temperature range. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121846
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  • 7
    Electronic Resource
    Electronic Resource
    Injection locking of individual broad-area lasers in an integrated high-power diode array (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 978-980 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental results on the injection locking of individual multimode broad-area high-power laser (one-in-a-time) in a linear array bar consisting of 19 lasers driven by a common current source. Each broad-area laser, capable of generating a beam with a power of 1 W, is injection locked to a single-longitudinal and transverse mode with less than 0.5 mW of injection power. The injection-locked broad-area laser shows very narrow linewidth close to the injection laser regardless of the output power. Our research suggests that the matching of the injection wavelength to one of the free-running modes of lasers in the array is the essential condition for achieving coherent operation of the array via injection locking. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1498501
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties of a novel Pr-Fe-Ti phase : 38th Annual Conference on Magnetism an Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7120-7121 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a systematic study of the (Pr1−xTix)Fe5 alloy series, the (Pr0.65Ti0.35)Fe5 alloy has been found to have a dominant phase with either the rhombohedral Th2Zn17 structure or the newly discovered Nd2(Fe,Ti)19 (S. J. Collocott, R. K. Day, J. B. Dunlop, and R. L. Davis, in Proceedings of the Seventh International Symposium on Magnetic Anisotropy and Coercivity in R-T Alloys, Canberra, July 1992, p. 437) structure, depending on the annealing procedure. Powder-x-ray-diffraction patterns and scanning electron microscopy show that the sample annealed at a temperature of 850 °C followed by 1000 °C has the 2:17 structure whereas annealing at 1000 °C directly leads to the new 2:19 structure. Energy-dispersive x-ray analysis yields Pr:Fe:Ti ratios of 10.7:86.2:3.1 for the Pr2(Fe,Ti)17 phase and 9.2:85.9:4.9 for the Pr2(Fe,Ti)19 phase. 57Fe Mössbauer spectroscopy (at 295 K) gives values for the average 57Fe hyperfine field of 15.7 T for the 2:17 phase and 17.5 T for the 2:19 phase, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356698
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  • 9
    Electronic Resource
    Electronic Resource
    Enhanced flux pinning from CuO inclusions in Bi2Sr2CaCu2Oy crystals (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 533-535 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi2Sr2CaCu2Oy (Bi2212) crystals with CuO inclusions were grown on the surface of KCl flux. The density of CuO incorporations of 109/cm2 was similar to that for Y2BaCuOy in melt-textured YBa2Cu3Oy. The CuO inclusions are needlelike particles with diameter of less than 1 μm. Magnetization measurements show enhanced flux pinning at high magnetic field, compared to crystals without CuO. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364093
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanism of the T"c enhancement in Bi"2Sr"2CaCu"2O"8"+"y by sodium doping
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 185-189 (1991), S. 811-812 
    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(91)91629-I
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