Ferromagnetic transition in II-VI semimagnetic QWs

We shortly summarize the main results obtained on the ferromagnetic transit ion induced by a two-dimensional hole gas in II-VI semiconductor quantum we lls. The growth of CdMnTe-CdMgTe quantum wells and their p-type modulation doping using nitrogen is described. Magneto-optical spectra exhibit large Z ecman splitting which allow us to measure the magnetization of the Mn spins . A spontaneous magnetization is observed below a critical temperature T-c approximate to 2 K. In the paramagnetic phase the susceptibility is enhance d and diverges as the temperature is decreased to T-c. These experimental f indings agree with a simplified treatment of the RKKY interaction, taking i nto account the low carrier density achieved in semiconductors. In addition , these systems allow to study the electronic properties of a 2D carrier ga s with complete polarization at low applied magnetic field, at which the sp litting into Landau levels can be neglected. (C) 1999 Elsevier Science B.V. All rights reserved.