Spin-lattice relaxation in semimagnetic CdMnTe/CdMgTe quantum wells

The spin-lattice relaxation dynamics of magnetic ions has been studied in semimagnetic semiconductor ${\mathrm{Cd}}_{1-x}{\mathrm{Mn}}_x{\mathrm{T}\mathrm{e}/\mathrm{C}\mathrm{d}}_{0.88}{\mathrm{Mg}}_{0.12}\mathrm{Te}$ quantum wells $(x<~0.032),$ by means of a method based on optical detection of injected nonequilibrium phonons. The relaxation rate is an increasing function of Mn content, external magnetic field and lattice temperature. The energy of phonons active in the spin-lattice relaxation process is found to increase with magnetic field, which can be explained in terms of phonon-induced spin-flip transitions in clusters consisting of the next-nearest-neighbor magnetic ions.