Dimensional-crossover studies of magnetic susceptibility in diluted-magnetic-semiconductor superlattices

A planar dc SQUID with integrated pickup loops and field coils has allowed precise ac magnetic susceptibility measurements of Cd1-xMnxTe-CdTe superlattices as a function of temperature and applied magnetic field. The spin-glass transition in 86-Athick magnetic layers broadens and disappears as the thickness is reduced to 18 A, suggesting the inability of the 2D system to support long-range spin-glass order. Novel hysteretic effects are seen in the thinnest layers. © 1987 The American Physical Society.