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The first observation of the ESR spectra of Mn2+, entering substitutionally for Fe2+ in the Van Vleck paramagnet FeS2 (polycrystals), is reported. The data from 5 to 295 K fits the spin-Hamiltonian + , with g = 2.000 ± 0.001, A/β = ?95.0 ± 0.5 Oe and D/β varying from 50 Oe (5K) to 59 Oe (295 K). The temperature dependence of D can be described in terms of a single phonon-mode with frequency ? 145 cm?1. 相似文献
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<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods. 相似文献
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The magnetic susceptibilities (χ) of several natural single crystals of iron pyrite (FeS2) have been measured between 4.2 and 620 K with a force magnetometer. The measured susceptibilities are shown to related to the magnetic impurities present in the samples. For a pure sample, χ = 1.7 × 10?7 emu/g at room temperature, with a small monotonic increase of χ with temperature. The results for a pure sample are interpreted in terms of contributions from diamagnetism and Van Vleck paramagnetism. 相似文献
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For a natural crystal of marcasite, an energy gap of 0.34 eV and an acceptor level at 0.052 eV are determined from temperature-dependent (53–370 K) electrical resistivity measurements. Magnetic susceptibilities and dielectric constants of marcasite and pyrite are compared in view of the large difference in their energy gaps. 相似文献
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CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
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The dielectric constant ?' of FeS2 is measured at 297 K and 77 K and in the frequency range of 500 Hz-100 kHz using a capacitance bridge. A value of ?' = 10.9 ± 0.5 independent of frequency and temperature, is obtained. This value is consistent with the recent reflectivity measurements of Schlegel and Wachter. 相似文献
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John W.Grove 《数学物理学报(B辑英文版)》2010,30(2):563-594
This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described. 相似文献
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In optical wavelength division multiplexed (WDM) systems the dispersion management is a key issue. In optical systems a lot of research is going on to reduce dispersion by selecting proper dispersion compensating techniques and proper modulation format for input data. One way to reduce dispersion is by using dispersion compensating fibers in the WDM systems. This paper analyzes the use of RZ super Gaussian pulse inputs for different WDM systems i.e. for conventional, dense and ultra dense WDM systems employing dispersion compensating fibers. The pulse width and the order of the RZ super Gaussian pulse was varied to evaluate the performance at 40 Gb/s. The experiment showed that to get minimum BER, pulse width of 7.5 ps and 10 ps along with third-order RZ super Gaussian pulse were found suitable and recommended to be used. 相似文献