Observation of a Ferromagnetic Transition Induced by Two-Dimensional Hole Gas in Modulation-Doped CdMnTe Quantum Wells

The presence of a ferromagnetic transition in single, modulation-doped, 8 nm quantum well of ${\mathrm{Cd}}_{0.976}{\mathrm{Mn}}_{0.024}\mathrm{Te}/{\mathrm{Cd}}_{0.66}{\mathrm{Mg}}_{0.27}{\mathrm{Zn}}_{0.07}\mathrm{T}\mathrm{e}:\mathrm{N}$ is evidenced by photoluminescence magnetospectroscopy. The transition is driven by long range Ruderman-Kittel-Kasuya-Yosida interactions between Mn spins, mediated by $2\times {10}^{11}$ holes per ${\mathrm{cm}}^2$. It occurs at 1.8 K, in agreement with a mean-field model.