FARADAY SPECTROSCOPY IN DILUTED-MAGNETIC-SEMICONDUCTOR SUPERLATTICES

We investigate the wavelength and magnetic-field dependence of the Faraday rotation in Cd1-xMnxTe/CdTe superlattices in order to probe the strength of the spin-exchange interaction between the excited carriers and the Mn2+ ions in these systems. Using a modulation technique we are able to optically record changes of the density of aligned Mn2+ spin states <S(z)> in the order of <S(z)>/S(sat) = 6 x 10(-5), where S(sat) is the saturation density. We observe a steplike behavior at the absorption edge reflecting the density of states and a strong excitonic resonance, which is difficult to resolve by conventional spectroscopic methods like photoluminescence excitation or transmission spectroscopy. With decreasing barrier width L(B) we observe below L(B) = 4 nm a decrease of the strength of the spin-exchange interaction indicating the effects of reduced dimensionality.