Carrier-density dependence of Faraday rotation and spin splitting in Cd1-xMnxTe

We employ spin-quantum-beat spectroscopy to investigate the carrier-density dependence of the spin-precession frequency and the magnitude of the Faraday rotation of Cd1-xMnxTe samples at fixed magnetic field. We find an onset of saturation of the Faraday rotation at carrier densities as low as 4 x 10(16) cm(-3) and attribute it to electrons (not holes which dominate in other types of experiments). The spin splitting at fixed magnetic field remains density dependent down to 3 x 10(15) cm(-3) (the lowest density accessible in our measurements) which suggests a direct influence of the carrier-density on the sp-d exchange not mediated by screening effects.