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Crystal coherent length

At low temperatures, in a sample of very small dimensions, it may happen that the phase-coherence length in Eq.(3) becomes larger than the dimensions of the sample. In a perfect crystal, the electrons will propagate ballistically from one end of the sample and we are in a ballistic regime where the laws of conductivity discussed above no more apply. The propagation of an electron is then directly related to the quantum probability of transmission across the global potential of the sample. [Pg.111]

The magnetic hyperfine field (Bhf) decreases as structural Al increases. This is to be expected because the diamagnetic Al does not contribute to the magnetic field. Since, however, Bhf (T) is also reduced as the crystal size decreases (even at 4 K), both Al substitution and crystal size (here represented by mean coherence length perpendicular to (111), MCLm, in nm) must be combined to account for the variation of Bhf satisfactorily, (Schwertmann Murad, 1983) i.e. [Pg.45]

The crystal size of soil Fe oxides usually ranges from a few to several hundred nm. A survey of 256 goethites, 101 hematites and 72 lepidocrocites from soils around the world showed maxima in the mean coherent length (MCL) perpendicular to (101), of 15-20 nm for goethite and ca. 40 nm perpedicular to (110), for hematite (Fig. 16.10). These values have been deduced from XRD line broadening using the Scherrer for-... [Pg.455]

Previous studies on phonon confinement in nanocrystals did not account for possible contributions from lattice defects [100-102]. However, the parameter L in (12.3) represents the coherence length and is, therefore, a measure of the distance between dislocation, vacancies, interstitials, impurities, and other defects within the crystal lattice. The assumption that L represents the crystal size is only valid for defect-free crystals, where the surface is considered to limit the propagation of the phonons. This assumption does not hold for imperfect crystals produced by... [Pg.336]

Therefore, while the results above were produced assuming the ND crystals to be larger than 3 nm (L > 3 nm), we now allow vibrational domains (coherence lengths) with L < 3 nm to contribute to the Raman spectrum. In addition, the frequency range used for fitting is extended to 1,100-1,400 cm. ... [Pg.338]


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See also in sourсe #XX -- [ Pg.34 ]




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Coherence length

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