Spin engineering of carrier-induced magnetic ordering in (Cd,Mn)Te quantum wells

Properties of carrier-induced ferromagnetism in modulation-doped quantum wells of p-type (Cd,Mn)Te are studied by photoluminescence and reflectivity in magnetic field. Valence-band engineering can strongly modify the magnetic properties of a system of localized spins interacting via a 2D hole gas. This is obtained through a strain control of the light-hole (lh)/ heavy-hole (hh) splitting. The axis of easy magnetization can be turned from the growth direction (with a hh gas) to be in-plane (lh gas). It is also found that the strong alloy fluctuations in (Cd,Mn)Te quantum wells containing about 10% of Mn ions are strong enough to significantly modify the magnetic state of the coupled ion-carrier system. A similar effect is observed at moderate Mn content, by restoring the lh/hh degeneracy.