In EPR with linearly polarised microwaves if just the diagonal contributions chi ++( omega ) and chi --( omega ) of the dynamic susceptibility are considered then a discrepancy occurs between the experimentally observed signal and the predictions of theory. By means of the Mori formalism the authors have calculated the non-diagonal contributions chi +-( omega ) and chi -+( omega ) for insulators with dominating isotropic exchange. For rather small linewidth these terms result in a new kind of dynamic shift of the resonance field, whereas for broad lines they give rise to a drastic anomaly of lineshape. All these effects could be verified experimentally in both one- and three-dimensional spin lattices of axial symmetry in the following ways: the dynamic shift expected for narrow lines could be observed in TMMC; lineshape anomalies were studied in the very broad line of CsNiF3; and in MnF2 the critical increase of linewidth near TN allowed variation between the two extreme cases.
Spontaneously ordered Ga0.47In0.53As grown on substrates with the (001) surface tilted 4° towards {111}B are studied using spectroscopic methods as well as x-ray diffraction, transmission electron diffraction and dark-field transmission electron microscopy. The single variant ordering is proved by the absence of one class of the ordering induced 12{111}B superlattice spots in transmission electron diffraction patterns as well as by the tilted polarization of the photoluminescence emerging from the samples cleaved edge. The temperature dependence of the luminescence peak position shows an anomalous behavior at low temperatures and a strong dependence of the peak position on the excitation power. From low temperature absorption measurements, we find a band gap reduction of 37 meV and a valence band splitting of 13.2 meV.
Strain relaxation and exciton localization effects on the Stokes shift in InAs x P 1−x /InP multiple quantum wellsOptical properties of ( Al x Ga 1−x ) 0.52 In 0.48 P at the crossover from a direct-gap to an indirect-gap semiconductor
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