Light controlled and probed ferromagnetism of (Cd,Mn)Te quantum wells

Properties of carrier-induced ferromagnetism in modulation-doped quantum wells of p-type (Cd,Mn)Te are assessed by photoluminescence (PL) and PL excitation spectroscopy. Well-chosen illumination makes it possible to deplete the quantum well and thus to control the strength of the ferromagnetic interactions. Spontaneous local magnetization is proportional to the hole concentration p but the Curie temperature TC varies little over a wide p range, in agreement with the mean-field model for 2D systems. The spatial extension ξ of ferromagnetic correlation is probed by micro- and time-resolved PL and possible mechanisms controlling ξ below TC are discussed.