Formation dynamics of free excitonic magnetic polarons in Cd1−xMnxTe

Formation processes of magnetic polarons from excitons were studied in Cd1−xMnxTe with the Mn composition x varying from 0.02 to 0.1 by transient photoluminescence spectroscopy. Two kinds of excitonic magnetic polarons were observed. One is the magnetic polaron composed of the free exciton, which is interacting with neighboring Mn-ion spins by the exchange interaction. The other is the magnetic polaron composed of the exciton bound to the neutral donor by aligning the surrounding Mn spins. The donor bound magnetic polarons appear for x=0.02–0.05 with the binding energy of 0.5–1.0 meV. The free excitonic magnetic polarons arise for x=0.02–0.1, where the binding energy of the free excitonic magnetic polaron varies in the range of 3.5-8.0 meV depending on the Mn composition. The stability of the free excitonic magnetic polaron state is confirmed by the appearance of the strong transient photoluminescence in the wide Mn composition range.