Two Dimensional Diluted Magnetic Semiconductor Systems

We develop a theory for two-dimensional diluted magnetic semiconductor systems (e.g. $\textrm{Ga}_{1-x}\textrm{Mn}_{x}\textrm{As}$ layers) where the itinerant carriers mediating the ferromagnetic interaction between the impurity local moments, as well as the local moments themselves, are confined in a two-dimensional layer. The theory includes exact spatial disorder effects associated with the random local moment positions within a disordered RKKY lattice field theory description. We predict the ferromagnetic transition temperature ($T_{c}$) as well as the nature of the spontaneous magnetization. The theory includes disorder and finite carrier mean free path effects as well as the important correction arising from the {\it finite temperature} RKKY interaction, finding a strong density dependence of $T_{c}$ in contrast to the simple virtual crystal approximation.