2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/27246A crossover from $d$ to $d-1$, and then back to $d$-dimensional critical behavior is argued to be a generic feature characterizing ordering in a $d$-dimensional superlattice composed of atomically {\em thick} films of two ferromagnets. The crossover leads to anomalous changes in the amplitudes of critical singularities. In $d=3$ Heisenberg and $XY$ superlattices large scale critical fluctuations persist over a wide temperature range.31 pages + 4 figures; REVTeX 3.1Condensed Mattertext