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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel giant magnetoresistance memory effect has been observed in epitaxial Nd0.7Sr0.3MnOz thin films which have previously been found to exhibit a linear increase in conductivity on first application of a magnetic field (B). Here we reported that the conductivity of the films depends not only on the applied field but also on the magnetic history. At T well below the temperature Tp where the zero-field resistivity has a peak, the film enters a high conductivity state [(ΔR/RB)(approximately-greater-than)103] upon application of a magnetic field which persists even when B is reduced to zero. The original "zero'' field state is not recovered until the sample is warmed to T∼Tp. Surprisingly, the dc magnetization exhibits only a weak irreversibility while the magnetoconductivity is markedly hysteretic. That is, while the remanent magnetization is small the remanent magnetic resistivity is 10−3 times the initial zero-field-cooled resistivity. A possible explanation based on a two-component model of semiconducting matrix with embedded shunting paths of ferromagnetic material will be presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 754-759 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Void shape changes induced by electromigration pose reliability problems in Al-based interconnects. Recent observations have shown that a rounded void sometimes collapses to a transverse slit in an interconnect with bamboo-like grain structure. This article provides a linear stability analysis for a circular void that is only partially conductive in an otherwise infinite conductive medium. The relation between the inner conductivity (i.e., the conductivity of the medium in the void) and the critical remote electric field intensity, Ecr, for the linear stability of the void is established. It is proven that when the inner conductivity becomes zero, Ecr goes to infinity, and we can look upon the inner conductivity of a vacuum void as zero. That is why the vacuum circular void is linearly stable. It is also shown that when the inner conductivity is very small, the stability of a void is sensitive to it. From the computational results, we know that if the inner conductivity is 0.1% of that outside the void, the Ecr is only twenty times of that for the dislocation loop case. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3357-3357 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In recent work, multilayers with band-tailored optics for dual energy digital subtraction angiography (DDSA) applications have been designed and tested at SSRL. Control of various multilayer parameters, including period grading, ratio of high-to-low Z material thickness, number of layers, etc., was used to produce reflectors with bandwidths ranging from 0.6%–10% and efficiencies in the 30%–95% range. In this paper, we consider the control of multilayer bandshapes and the implementation of double-reflection multilayer configurations to further control the first harmonic (33 keV) bandwidth and to suppress or eliminate the 66 keV and 99 keV harmonics present on angiography beamlines driven by wiggler or micropole undulator sources. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1427-1429 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetoresistance of epitaxial Nd0.7Sr0.3MnOδ thin films has been studied. A giant magnetoresistance, with more than 4 orders of magnitude change in resistance (−ΔR/RH(approximately-greater-than)106%), was obtained at ∼60 K and a magnetic field of 8 T. This giant magnetoresistance (GMR) ratio is about one order of magnitude larger than the highest value reported previously which was observed in La–Ca–Mn–O film. We have also obtained a large GMR ratio with −ΔR/RH(approximately-greater-than)3000% for H=5 T in an in situ Nd0.7Sr0.3MnOδ thin film, a much larger effect than the previous results in doped manganese oxide films in which a large GMR ratio was obtained only in postannealed samples. Our results also show that the GMR effect in these films can be strongly influenced by the thin-film preparation conditions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 968-970 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new type of hydrogenated nanocrystalline Si film with high electronic conductivity is investigated by means of transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Nearly parallel columnar structures with growth orientation along the [110] zone axis of Si are found from cross-sectional TEM images of the film. HRTEM observation reveals that these columns are composed of nanocrystallites (3–6 nm size) and dendritelike growth morphology, while in the region between columns the texture consists of smaller sized (〈3 nm) grains embedded in a hydrogenated amorphous Si. The volume fraction of the crystalline component is about 58% measured by Raman spectroscopy. The conductivity of the film is very high, about 10−1 (Ω cm)−1. It is considered that this is directly related to the characteristic structure of the film. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1827-1829 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed measurements of voltage–current (E–J) characteristics have revealed a distinct low level resistive tail for silver-sheathed (Bi,Pb)2Sr2Ca2Cu3O10 superconducting tapes. The residual tail is observed at very low voltage (E≤10−8–10−7 V/cm) of the E–J curves and can be described by E∝(J−Jc')n, where Jc' is a field and temperature dependent critical current and n=1.0–1.2. The dynamic resistivity is, typically, in the range of 10−13 Ω cm, but could be as high as 10−11 Ω cm in some specimens. This residual resistance can be induced by a severe thermal cycling treatment, although it may also be intrinsic, i.e., as-grown, to some of the specimens. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1689-1691 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of sample preparation on the resistivity and magnetoresistance (MR) behavior of doped manganese oxides has been studied. Two systems, Nd0.7Sr0.3MnO3−δ and La0.67Ba0.33MnO3−δ thin films, have been chosen for this study. The former has the largest reported MR ratio at 60 K and the latter has a large MR ratio at room temperature. Two processes, deposition at a high temperature and annealing at a high temperature, have opposite influences on the resistivity behavior of these films. The results suggest that oxygen stoichiometry and diffusion are important factors in causing the behavior observed in doped manganese oxide films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3031-3033 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel giant magnetoresistance memory effect has been observed in epitaxial Nd0.7Sr0.3MnOz thin films which have previously been found to exhibit a linear increase in conductivity on first application of magnetic field B. The resistivity of the films depends not only on the instantaneous applied field but also on the magnetic history of the sample. At T well below the temperature Tp, where the zero-field resistivity has a peak, the film enters a high-conductivity state (upon application of a magnetic field) which persists even when B is reduced to zero. The original "zero'' field state is not recovered until the sample is warmed to T∼Tp. Surprisingly, the dc magnetization exhibits only a weak irreversibility while the magnetoconductivity is markedly hysteretic. A possible explanation is proposed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3321-3323 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafast phase dynamics of free-induction decay for carriers in bulk GaAs is studied with differential-phase spectroscopy. The instantaneous phase shifts of the free-induction decay with respect to the excitation pulses are extracted from simultaneously recorded laser pulse autocorrelation and free-induction decay in GaAs. Ultrafast phase dynamics during and immediately after the femtosecond pulse excitation are numerically evaluated with optical Bloch equations using pump pulse and semiconductor exciton parameters as input. Good agreement of the theory with experiment is obtained. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By manipulating the cooling rate from the final heat treatment, we have raised the 77 K, self-field critical current density (Jc) of multifilament (Bi,Pb)2Sr2Ca2Cu3Ox (2223) tapes by a factor of 3, and the irreversibility field (H*) by more than 50%. The Jc of samples cooled in 7.5% O2 from their reaction temperature of 825 °C increased from ∼8 to ∼24 kA/cm2 and H*(77 K) increased from ∼120 to ∼200 mT as the cooling rate was decreased from 5 to 0.016 °C/min. The results unambiguously show that the flux pinning properties of 2223 tapes can be improved by simple changes in wire processing. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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