Acceleration of the spin-lattice relaxation in diluted magnetic quantum wells in the presence of a two-dimensional electron gas

Dynamics of spin-lattice relaxation of magnetic Mn ions in semimagnetic ${\mathrm{Cd}}_{0.99}{\mathrm{Mn}}_{0.01}{\mathrm{T}\mathrm{e}/\mathrm{C}\mathrm{d}}_{0.76}{\mathrm{Mg}}_{0.24}\mathrm{Te}$ quantum wells containing two-dimensional electron gas (2DEG) has been studied by means of an optical detection of injected nonequilibrium phonons. It is found that the spin-lattice relaxation rate is an increasing function of electron concentration and electron temperature. The 2DEG provides an effective channel for the energy transfer from magnetic ions to the lattice. A model accounting for the spin-flip transitions between Mn ions and free electrons describes well our experimental results in a qualitative manner.