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  • 1970-1974  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Magnetic-field-induced semiconductor-semimetal transition in Bi-Sb alloys (1970)
    Springer
    Journal of low temperature physics 3 (1970), S. 147-174 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Accurate and detailed measurements of the temperature dependence of the longitudinal magnetoresistance of single-crystal Bi-Sb alloys have been made, with static magnetic fields in the range 0–100 kG oriented parallel to the trigonal axis. Alloy concentrations were in the range 8–12 at.% Sb, and temperatures in the range 1–35 K. At very high fields the resistance increases with increasing temperature in a metallic manner with “ideal” and “residual” components, in contrast to the semiconductor behavior observed at zero field or low fields. For the high-field semimetal regime the electrical resistance behaves in a simple manner similar to a metal in zero field, in contrast to the complicated magnetoresistance phenomena for metals in low fields. This behavior can be understood in terms of a simple quasi-one-dimensional extreme-quantum-limit regime. The magnetic-field-induced semiconductor-semimetal transition is associated with an energy gap and changes of the energy-band structure which are of order 1 meV. Thermal activation energies for electrical conduction manifest this gap only at temperatures below approximately 20 K. Activation energies an order of magnitude larger which have been measured at considerably higher temperatures are apparently the direct gap at theL-point in the Brillouin zone and are not directly connected with the semiconductor-semimetal transition. Our results indicate that the zero-field indirectL-T energy gap increases from zero somewhere near 7–8 at. % Sb to values only as large as approximately 1.5 meV at 12 at. % Sb. At the magnetic-field induced transition there occurs evidence of an intermediate “excitonic insulator” phase, a resistance minimum below 10 K reminiscent of the Kondo alloy behavior. This anomalous regime is a property of the semiconductor-to-semimetal transition and cannot be associated with the well-known temperature and magnetic-field “freeze-out” of charge carriers in extrinsic semiconductors, or with magnetic ordering of the Kondo type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628324
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A simple calculation model with great versatility for interelement effects in steel by X-ray fluorescence analysis (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 2 (1973), S. 75-83 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Demands of more rapid and accurate answers for the steel plant made it necessary to develop a computerized system for calculation and control of the analysis performed on X-ray fluorescence and optical emission spectrometers. The interelement effects which occur in X-ray fluorescence analysis are briefly described and the evolution of a model for these corrections is examined. This model includes corrections for absorption and secondary fluorescence as well as overlapping, dead time effects, etc. which are based on simplified theoretical formulae and can be used for a broad field of applications. The parameters in the model have been determined empirically by measuring a wide range of binary alloys. The interelement effects in optical emission analysis are calculated according to a simple emprical formula. The mathematical models have been fitted to a computer (Datasystem Trask P100) which also controls the two separate spectrometers. Examples are given of routine analysis performed by this model on bulk solids of steels and fused glassy borates of sinters, slags and hard metals. Its chief advantage is that the usual requirement for a great number of standards is eliminated.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300020207
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    Paper (German National Licenses)
    Fulltext
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