Energy transfer from photocarriers into the magnetic ion system mediated by a two-dimensional electron gas in (Cd,Mn)Te/(Cd,Mg)Te quantum wells

An efficient energy-transfer channel from photocarriers to the Mn spin system via a two-dimensional electron gas (2DEG) in n-type modulation-doped ${\mathrm{Cd}}_{0.99}{\mathrm{Mn}}_{0.01}{\mathrm{T}\mathrm{e}/\mathrm{C}\mathrm{d}}_{0.76}{\mathrm{Mg}}_{0.24}\mathrm{Te}$ quantum wells has been found. The energy relaxation of photoexcited carriers is assumed to cause heating of the electron gas, which subsequently leads to an increase of the temperature of the Mn spin system. The mechanism of the energy transfer from the 2DEG to the Mn system involves a spin-flip scattering process originating in a strong electron-Mn exchange interaction. We have observed a suppression of the Mn heating with an increasing magnetic field which results in unusual energy shifts of the exciton, and trion features seen both in the photoluminescence and in reflectivity spectra. A theoretical model has been developed which is in a good agreement with experimental results. In the framework of this model we also analyze the details of the dependence of Mn-ion heating on the electron concentration and on the magnetic ion content.