Quasi-two-dimensional spin distributions in II-VI magnetic semiconductor heterostructures: Clustering and dimensionality

Spin clustering in diluted magnetic semiconductors (DMS) arises from antife rromagnetic exchange between neighboring magnetic cations and is a strong f unction of reduced dimensionality. Epitaxially grown single monolayers and abrupt interfaces of DMS are, however, never perfectly two dimensional (2D) due to the unavoidable intermonolayer mixing of atoms during growth. Thus the magnetization of DMS heterostructures, which is strongly modified by sp in clustering, is intermediate between that of 2D and 3D spin distributions . We present an exact calculation of spin clustering applicable to arbitrar y distributions of magnetic spins in the growth direction. The results reve al a surprising insensitivity of the magnetization to the form of the inter mixing profile, and identify important limits on the maximum possible magne tization. High-field optical studies of heterostructures containing "quasi- 2D" spin distributions are compared with calculation.