共查询到20条相似文献,搜索用时 15 毫秒
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J. Rogel-Salazar 《Contemporary Physics》2013,54(4):385-386
Measurements of the Faraday magneto-optical effect and of optical absorption in magnetic garnet crystals and films are reviewed. Earlier work was restricted to measurements in the visible spectrum; these measurements showed that the transparency was sufficient to allow magnetic domains to be studied in relatively thick slabs. Within the last year or so interest has been renewed in extending magneto-optical measurements beyond the visible spectrum. In particular, extremely low absorptions are found in the wavelength range of approximately 1–5 microns. Thie work is, in no small way, spurred by the possibility of developing a light-beam modulator using the Faraday effect in this wavelength range. Recent measurements at very short wavelengths using garnet films are also reported. By extending the short wavelength measurements to 3000 Å, about two orders of magnitude increase in Fareday rotation and optical absorption are observed, compared with the visible spectrum measurements. The Faraday effect has been used to measure magnetic hysteresis loops in single-crystal garnet slabs. Magneto-optical observation of the corresponding domain structures shows them to be particularly simple. Detailed correlation of domain structure and hysteresis loops is described; in addition, an estimate of the domain wall energy and its width is made from these measurements. The garnets referred to in this review are yttrium iron garnet (YIG), gadolinium iron garnet (GdIG), and YIG doped with gallium (YGaIG). 相似文献
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In this paper the effective mass approximation and the k·p multi-band models, describing quantum evolution of electrons in
a crystal lattice, are discussed. Electrons are assumed to move in both a periodic potential and a macroscopic one. The typical
period e{\epsilon} of the periodic potential is assumed to be very small, while the macroscopic potential acts on a much bigger length scale.
Such homogenization asymptotic is investigated by using the envelope-function decomposition of the electron wave function.
If the external potential is smooth enough, the k·p and effective mass models, well known in solid-state physics, are proved
to be close (in the strong sense) to the exact dynamics. Moreover, the position density of the electrons is proved to converge
weakly to its effective mass approximation. 相似文献
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Professor Stig Stenholm 《Contemporary Physics》2013,54(3):279-280
Current activity in the field of magnetic separation is reviewed in fundamental terms. The diverse subject matter is ordered into four main groupings whose characteristics are described in terms of numerous devices, both of present-day and historical significance. Existing as well as potential areas of scientific and commercial operation are discussed. The basic principles of recent major developments in high intensity magnetic Separation are closely examined. 相似文献
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Professor N.C. Wickramasinghe 《Contemporary Physics》2013,54(2):181-182
A simple microscopic deduction of Archimedes' principle as applied to gases is given in terms of the kinetic theory, and some conventional explanations of barometric effects are queried. 相似文献
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《Journal of sound and vibration》1987,115(3):572-573