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We present here our research on time-resolved carrier, phonon, and spin dynamics in the diluted-magnetic semiconductor Cd1-xMnxTe [Cd(Mn)Te] system. Our test samples were the high-quality single crystals with the Mn doping concentrations ranging from 9% to 12%, grown by a modified Bridgeman method. Femtosecond optical pump-probe spectroscopy experiments allowed us to study time-resolved dynamics of both the excited carriers and coherent acoustic phonons. Using pump photons with the energy just exceeding the Cd(Mn)Te energy gap, we observed the bleaching effect as excited carriers occupied essentially all available states at the bottom of the conduction band. With the increase of the pump photon energy, the normalized differential reflectivity (ΔR/R) signal changed sign to positive, being dominated by the electron-phonon relaxation process. All our ΔR/R traces, on the delay-time scale well above 100 ps, exhibited very regular oscillations, which were identified, as the signature of coherent acoustic phonons, generated by an electronic and thermal stress introduced at the sample surface by the pump photons. We have also excited our samples with sub-picosecond magnetic transients, generated by a low-temperature-grown GaAs photoconductive switch, and observed the sub-picosecond magneto-optic (Faraday) effect (Mn-ion spin dynamics). The sub-picosecond Faraday response makes this semimagnetic semiconductor an excellent candidate for practical applications in magneto-optics, such as in time-resolved magneto-optical sampling and imaging techniques, or in ultrafast magneto-optical transducers and modulators. In addition, Cd(Mn)Te is a very promising material for ultrafast spintronic and magnetic memory-type devices.
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