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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 1482-1490 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A temperature gradient imposed across a binary fluid layer with a nonzero Soret coefficient will induce a solute concentration gradient. The ratio of these two gradients is proportional to the separation ratio χ, a property of the fluid. Similarly, the ratio of the thermal and solutal Marangoni numbers, which are nondimensional increments in surface tension due to changes in temperature and concentration, is also proportional to the separation ratio. As a consequence, the stability of a given binary fluid layer with a free surface under zero gravity depends only on the temperature difference, ΔT, imposed across the layer or, equivalently, on the thermal Marangoni number, M, albeit the dependence, is rather complicated. When the gravity is nonzero but of small magnitude, such that the buoyancy effects are not dominant, the stability characteristics of the layer are functions of two parameters, M and R, the thermal Rayleigh number. In this paper, the stability of such a binary layer under zero and reduced gravity by means of linear stability analysis is studied. Results show that the nature of the instability depends on the product χK, where K is a material constant=(α/αS)(γS/γ), with α and αS denoting the volumetric expansion coefficient due to temperature and solute concentration, respectively, and γ and γS the rate of change of surface tension with respect to temperature and solute concentration, respectively. Both χ and K can assume positive and negative values. Under zero gravity, instability at the critical value of M onsets in steady convection if χK〈0 and in oscillating convection if χK(approximately-greater-than)0. For a layer that is being heated from below and K(approximately-greater-than)0, the steady instability in the case of χK〈0 can be rendered stable by subjecting the layer to a gravity of small magnitude. But for χK(approximately-greater-than)0, the effect of gravity is always destabilizing.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Cardiovascular drug reviews 12 (1994), S. 0 
    ISSN: 1527-3466
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, we have shown that magnetic circular dichroism (MCD) can be used to obtain element specific magnetic hysteresis (ESMH) loops of heteromagnetic systems. By using magnetic circular dichroism (MCD) we map the three orthogonal components of the magnetic moment vector of each element of a strongly (90°) coupled Fe30Co70/Mn/Fe30Co70 single crystal trilayer heterostructure as a function of applied magnetic field. The intensity of the MCD of the Mn L2,3 absorption edges clearly shows that the Mn possesses a ferromagnetically aligned net magnetic moment. Furthermore, the individual element specific hystersis curves, when followed through the magnetic reversal process, reveals a detailed description of the magnetization reversal in the presence of both cubic anisotropy and strong exchange. This vividly demonstrates the capability of this technique to analyze the magnetic moment reversal process in the presence of strongly competing interactions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1511-1516 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanisms of strain relaxation and dislocation generation for the 2-μm-thick InxGa1−xAs epilayers grown on (100) InP substrates with 0≤x≤1 were investigated. It was found that the growth mode and dislocation density of the InxGa1−xAs epilayers are not only dependent on the lattice mismatch with respect to InP substrates, but the abundance of Ga atoms and the degree of cation disorder in the alloy composition also play important roles. In the negative mismatched range even with a medium lattice mismatch (e.g., ε=−1.1%), InGaAs alloys with a high degree of cation disorder and containing more Ga atoms (x=0.32–0.37) trigger island growth and introduce high-density V-shaped dislocations. In the positive mismatched range, island growth occurs at x≈0.82 (ε=2%) and few V-shaped dislocations are generated. The difference between these two ranges is due to their different Ga concentrations which introduce different island nucleation centers in the initial growth stage.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3347-3350 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behavior of nitrogen and the formation of nitrogen-oxygen donors in nitrogen-doped Czochralski-silicon crystals (Cz-Si) were studied by the electrical and infrared-absorption measurements in samples annealed in different conditions. Experiments showed that nitrogen-oxygen shallow donors are formed during the nitrogen-doped Cz-Si crystal growth. Nitrogen-oxygen thermal donors are generated in temperature range of 300–550 °C, and the behavior of these thermal donors resembles that of the thermal donors in Cz-Si crystals [P. Wagner, C. Holm, and E. Stirtl, Festkoperprobleme 24, 191 (1984)], but they are monovalent donors with the same levels as those of neutral thermal donors; no new electrically active center is generated in the temperature range of 600–900 °C.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The element specific magnetic hysteresis curves of Fe/Cu/Co trilayer structures can be used in conjunction with the measured magnetoresistance curves to extract the coefficient of the giant magnetoresistance (GMR) independent of magnetic domain effects and incomplete alignment effects, allowing for a measure of the maximum attainable GMR for that trilayer. Information concerning the details of the trilayer switching can be extracted showing that sputtered polycrystalline films of Fe/Cu/Co deposited on Si switch their magnetization directions like multidomain Ising magnets.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Co/Cr multilayers, and single-crystal Co thin films etc. have been grown on MgO and Al2O3 substrates with Cr and Mo as buffer layers by molecular beam epitaxy technique. From the structure and magnetoresistance studies, we have found that the ferromagnetic anisotropy of resistance (AMR) is strongly influenced by the buffer layer, but with negligible effect due to the variation of the structure of Co films. The AMR of Co film on Cr buffer layer is quite small (0.1%); however, the MR of Co/Cr multilayers is almost one order larger than the AMR of Co film on Cr buffer layer. An enhancement factor of 4 for the MR in Co/Cr multilayers by the interface roughness has been observed. This suggests that the effect due to the spin dependent scattering at the interfacial regions of the superlattice is larger than that due to the spin dependent scattering in the ferromagnetic layers for the MR in the Co/Cr multilayer system.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present authors found that Mn–Zn ferrites containing Er2O3 had improved values of σs (specific magnetization) and amplitude permeability. Samples with different addition amount of Er2O3 were sintered at 1180 °C. The results show that Er2O3 addition from 0.02 to 0.1 wt % causes the amplitude permeability to increase from 1070 to 2180. The magnetization can be increased from 91.6 to 92.8 emu/g within the range 0.02–0.1 wt %. Furthermore, the effect of Er2O3 addition was investigated in detail by power-loss analysis and scanning electron microscopy examination of microstructure. We found that samples with Er2O3 less than 0.04 wt % exhibit power loss similar to the sample without Er2O3 addition and with SiO2–CaO contents. Thus we conclude that the amplitude permeability and specific magnetization of Mn–Zn ferrites for high-frequency and high-power use were improved by a small Er2O3 addition (〈0.04 wt %).
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first results employing a new technique for studying heteromagnetic multilayers by element specific magnetic hysteresis measurements. Dramatically different Fe and Co hysteresis curves of Fe/Cu/Co trilayers were obtained by recording the soft x-ray magnetic dichroism1 at their respective L3 absorption edges as a function of the applied magnetic field. The complicated conventional hysteresis curves, obtained by a vibrating sample magnetometer, were resolved into linear combinations of the two individual elemental hysteresis curves, thus determining the average atomic magnetic moments of each element within the multilayer structure (Fe is 2.0±0.08 μB and Co is 1.1±0.04 μB). Furthermore, fine hysteresis features associated with one element, imperceptible in the conventional curves, were also observed, and demonstrate a new and powerful means for studying heteromagnetic multilayer systems.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5810-5810 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, there has been a great deal of interest in x-ray magnetic circular dichroism (MCD) and its applications to the study of magnetic thin films and multilayers due to the dramatically enhanced dichroic effect and its element specific nature. In this work, the soft x-ray magneto-optical Kerr effect, an effect closely related to MCD, is investigated. Detailed comparison between MCD and the Kerr effect is discussed. As an example, recent results from a thin bcc Co film will be presented. In the Kerr effect measurement, specular reflectivity as a function of incident angle and photon energy was measured using both linearly polarized and circularly polarized x rays. To give the largest effect, in the case of linearly polarized light, specular reflectivity was measured in the transverse configuration, while in the case of circularly polarized light, the measurement was carried out in the longitudinal configuration. In both cases very large changes in reflectivity, up to 40% in the linearly polarized case and 75% in the circularly polarized case, were observed near the Co LII and LIII absorption edges upon reversal of the direction of the magnetic field. These results agree very well with a macroscopic model calculation.
    Type of Medium: Electronic Resource
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