Spin-Transport and Dynamics of Excitons in Magnetic Quantum Heterostructures

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w:\awards\awards96\num.doc 9705443 Smith : This is a renewal project directed to the study of the dynamics and transport of spin systems in diluted magnetic semiconductors. The main goals of this research are: (1) To measure the spin transport of exciton magnetic polarons using spatially- and temporally-resolved photoluminescence spectroscopy. (2) Use time-resolved near-field optical microscopy to measure local fluctuations and clusters of Mn-impurities within the ZnMnSe alloy. (3) Measure the dynamics of spin-polarized exciton populations and the effect of phonons, magnetic ion exchange, electron-hole exchange and band mixing on the thermalization times. This research will probe directly the physics of spin interactions using all-optical techniques which are particularly suitable for use in semiconductors. The information gained on spin dynamics in these systems will have application to other spin systems as well, particularly in metallic systems. %%% This is a renewal project targeted towards understanding the fundamental physics of magnetic interactions in novel semiconductors which have been doped with magnetic impurities. Study of these interactions has direct applicability to the technologically important area of magnetic technologies such as magnetic memories (eg. Hard disks), super- sensitive magnetic detectors, and magneto-optical modulators. These novel magnetic semiconductors can be probed with ultrafast optical methods using femtosecond lasers. This allows one to probe the dynamics of these magnetic interactions on a time scale which is impossible to do in the metallic systems. Such information is crucial to the improvement of existing and the development of new magnetic technologies. ***