Phase diagrams of magnetically disordered bilayers

Abstract

The phase diagrams of magnetically coupled bilayer models composed of two Bethe lattices are exactly evaluated using the partial-partition-function technique. Special attention is devoted to disordered systems in the limit of annealed bond distribution. Correlations between bonds localized in different layers lead to very interesting features. A new percolation threshold in the intralayer-dilution limit is exactly obtained for n-coupled Bethe and square lattices. As competing intralayer parameters are considered, a multiple reentrant behavior appears, which is related to the relative role played by thermal fluctuations on frustration, bond-bond, and spin-spin correlations.