Exciton localization in semimagnetic semiconductors probed by magnetic polarons

Peculiarities of optical spectra in diluted magnetic semiconductors are used to find out the characteristic size of the localized exciton state in ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ alloys. Three methods for evaluation of the exciton localization radius are suggested. Two of them are based on spin-related phenomena. The localization radius is calculated from measured magnetic-polaron energies and from the degree of the magnetic-field-induced circular polarization of luminescence. The exciton localization radius is determined for a set of samples with Mn content varying from 0.1 up to 0.4. The results of the two spin-related methods are in good agreement to each other. Their comparison with the results of the third approach based on the exciton linewidth analysis allows the conclusion that both the electron and hole of the exciton are localized within the same volume. This latter method, verified by comparison with two others, is applicable also to a wider class of semiconductor compounds which do not contain magnetic impurities.