Spin-flip rate of excitonic magnetic polarons in Cd1-xMnxTe/Cd1-yMgyTe quantum wells

The lifetime of excitons in Cd1-xMnxTe/Cd1-yMgyTe single quantum wells was investigated by time-resolved photoluminescence spectroscopy. Spin-flips between dark and bright excitons remarkably change the excitonic lifetime yielding a two-exponential decay in the photoluminescence intensity. The temperature dependence of the two decay times shows that the spin-flip rate depends strongly on the formation of excitonic magnetic polarons. By forming polarons, the spin-flip rate from dark excitons to bright excitons is reduced effectively by the spin-barriers of the polarized Mn ions, which extends significantly the luminescence decay time. (C) 2000 American Institute of Physics. [S0021-8979(00)92008-5].