The dynamical response of a paramagnetic spin system to the exchange field of quasi-zero-dimensional electron-hole pairs in semiconductor quantum dots is investigated by time-resolved spectroscopy. The spin response time is extracted from the transient spectral shift of the photoluminescence signal caused by the dynamical spin alignment of magnetic ions incorporated in the crystal matrix. The formation of this ferromagnetically aligned spin complex is demonstrated to be surprisingly stable as compared to bulk systems, even at elevated temperatures and high external magnetic fields.

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Time-resolved measurements on self-assembled CdSe/ZnMnSe quantum dots are presented. A rather long excitonic decay time of 580 ps is found which indicates a suppression of nonradiative recombination via the internal Mn 2þ transition. The long excitonic lifetime allows for the formation of magnetic polarons, as evidenced by a transient redshift of the luminescence emission with a time constant of 125 ps. In a magnetic field, a decrease of the measured excitonic decay time is observed and a possible mechanism based on an interplay between bright and dark excitons is discussed.

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