Effect of spin-dependent Mn2+ internal transitions in CdSe/Zn1-x Mnx Se magnetic semiconductor quantum dot systems

CdSe quantum dots (QDs) in a ZnMnSe diluted magnetic semiconductor (DMS) matrix were investigated using both energy- and polarization-selective magneto-photoluminescence (PL). The peaks from Mn2+ internal transition, CdSe QDs, and ZnMnSe barrier were observed in the experiment done using above-barrier excitation. By examining the dependence of the PL peak intensity on magnetic field we were able to identify the competition between the Auger-type energy transfer process (i.e., the energy transfer from band electrons to Mn2+ ions) and energy relaxation into CdSe QDs in this QD system. The role of energy transfer processes between band electrons and Mn2+ ions in the DMS QDs was further studied by using excitation energy below the ZnMnSe band gap, where no change in the intensity of internal Mn2+ transitions with magnetic field was observed, indicating that the energy transfer from carriers excited into the ZnMnSe barrier is indeed responsible for the intensity behavior of these internal Mn2+ transitions observed in DMS QD structures.