Optically controlled spin-polarization memory effect on Mn delta-doped heterostrucutres

We investigated the dynamics of the interaction between the spin-polarization of photo-created carriers and the spin of the Mn ions on InGaAs/GaAs:Mn structures. The carriers are confined in an InGaAs quantum well and the Mn ions come from a Mn delta-layer grown at the GaAs barrier close to the well. Even though the carriers and the Mn ions are spatially separated, the interaction between their spin polarization is demonstrated by time-resolved photoluminescence measurements. Using a pre-pulse laser excitation with an opposite circular-polarization clearly reduces the polarization degree of the quantum-well emission for samples where a strong magnetic interaction is observed. The results demonstrate that the Mn ions acts as a spin-memory and can be optically controlled by the polarization of the photocreated carriers. In turn, the spin polarized Mn ions also affect the spin-polarization of the subsequently created carriers as observed by their spin relaxation time. These effects fade away with increasing time delays between the pulses as well as with increasing temperatures.