Formation dynamics of free exciton magnetic polarons in bulk-Cd_1-xMn_xTe

In order to understand the density dependence of free exciton magnetic polaron (FEMP) in diluted magnetic semiconductor (DMS) bulk-Cd_1-xMn_xTe (x = 0.05), photoluminescence spectra with exciton densities in the range of 10^10 ∼ 10^19 [cm^-3] were investigated. The free exciton magnetic polaron states showed saturating feature over the exciton density of 1.0x10^14 [cm^-3]. Ferromagnetic polarization of Mn spins via the FEMP formation was observed by the photo-induced time- and spectrum-resolved Faraday rotation measurements only when the case of low exciton density. Preliminary results indicated the disappearance of the ferromagnetic polarization of Mn spin at high density excitation.