Spin dynamics of excitons and magnetic ions in Cd1−xMnxTe/Cd1−yMgyTe quantum wells

Abstract Dynamical processes of spin systems of exciton and magnetic ions in diluted magnetic semiconductor quantum wells were studied by using transient pump-and-probe absorption spectroscopy technique. Bleaching of the spin-down exciton absorption peak appeared with a red shift of 10 meV within the lifetime of the pump created excitons, indicating the excitonic magnetic polaron formation due to the s,p–d exchange interaction between excitons and Mn ions. After the excitons recombine, induced absorption at the spin-aligned region of the magnetic ion matrix, which is left by the excitonic magnetic polaron, was observed with and without magnetic fields. These induced absorption signals arose from the local fields projected by the Mn spins that enhanced or suppressed Zeeman splitting of exciton. The decay times of these induced absorption peaks are longer than 3 ns, implying the long-lived spin polarization of the Mn ions. From the energy splitting of the induced absorption peaks, the local field strength of 2.5 T was extracted.