Abstract
The ellipsometry measurements (in the energy range ) on cleavage surfaces of single crystals, the measurements of the absorption and reflectance spectra , electrical resistivity, and magnetic susceptibility were carried out for determination of peculiarities of the fundamental absorption spectrum and the conductivity mechanism in single crystals. The energy of fundamental absorption edge associated with the direct transitions was determined as . The absorption band with two maxima at 2.2 and corresponding to the charge transfer transitions was revealed. The polaron band at was discovered and polaron parameters were determined. Peculiarities of IR absorption and dc conductivity of in dependence on oxygen stoichiometry are determined by the superposition of hopping and band conductivity of spin-lattice polarons, and by additional localization of charge carriers under oxygen vacancies ordering.
- Received 9 June 2004
DOI:https://doi.org/10.1103/PhysRevB.70.224406
©2004 American Physical Society