Electron and hole spin relaxation in modulation-doped CdMnTe quantum wells

We report on the electron and hole spin relaxation times in n-type and p-type CdMnTe quantum wells with nonmagnetic barriers measured via the time-resolved magneto-optical Kerr effect in a pump-probe experiment. In addition to the decay of the Kerr effect at short pump-probe delays, we show that the hole spin relaxation time may be also estimated from a phase shift induced during the coherent rotation of the Mn spins. The variations of the spin relaxation times are studied as a function of Mn concentration, doping level, and magnetic field applied parallel to the quantum well plane. The results show that the electron spin relaxation is dominated by the exchange scattering with the Mn ions in the quantum well, and good agreement with theory is obtained provided exciton effects are included. Relatively slow hole spin relaxation is observed in the p-type samples (hole spin lifetime up to 32 ps) as compared to published values for similar diluted magnetic II-VI heterostructures.