EXCITON MAGNETIC POLARONS IN (100)-ORIENTED AND (120)-ORIENTED SEMIMAGNETIC DIGITAL ALLOYS (CD,MN)TE

We report on optical studies of exciton magnetic polarons in artificia l crystals of digital alloys of diluted magnetic (semimagnetic) semico nductors built of alternating CdTe and Cd1-xMnxTe layers, each only a few monolayers thick. Specially designed quantum well structures with the digital magnetic alloy in the quantum well region were grown and s tudied experimentally by magneto-optical methods. Precise comparative studies of the structures grown simultaneously either on (120)- or (10 0)-oriented substrates were performed by photoluminescence excitation spectroscopy and photoluminescence under selective excitation. While n o difference in magnetic properties, as measured by the giant Zeeman s plitting of excitonic states, was observed between (120)- and (100)-or iented diluted magnetic structures, the exciton magnetic polaron energ y was found to be by 10-40% larger in (120)-oriented structures than i n (100)-oriented counterparts. This increase is explained by the effec t of the heavy-hole effective mass anisotropy: greater hole mass in [1 20] direction causes an enhancement of an initial exciton localization which, in turn, gives rise to an increase of the magnetic polaron ene rgy. Results of model calculations are in good agreement with experime ntal data.