Excitonic enhancement of spin relaxation in diluted magnetic semiconductor quantum wells

We performed pump-probe magneto-optical Kerr spectroscopy to explore the role of excitonic effects on the electron and hole spin relaxation in Cd1˛xMnxTe-based quantum well structures. Particularly, important information is obtained from detailed interpretation of the temperature and wavelength dependence of the observed transient magneto-optics in specially engineered structures. In manganese-rich wells the electron spin relaxation is found to be strongly enhanced in the exciton due to the increased mass of the bound electron-hole pair, in agreement with earlier predictions. An even stronger enhancement of the relaxation time is found for the hole spin, which is explained by the additional mixing of heavy-hole and light-hole states in the bound state. In structures where Mn is confined to the barrier region, a different behavior is observed, indicative for a competition of various contributions.