Order parameters in anisotropic two-dimensional ± J Ising lattices

Abstract

We modify the usual isotropic ± J Ising spin glass model introducing stronger interactions by a factor of f (anisotropy factor) along one of the axis. We begin by considering the situation in which concentration of ferromagnetic (F) and antiferromagnetic (AF) interactions are the same, where we study the modification that such axial anisotropy has on the density of states of the system, with particular attention on the modification of the ground level. Splits and merges of levels, as well as decreases and increases of degeneracy are observed for particular values of f. Site order parameters q and p, as well as unfrustrated portion of the lattice h increase substantially in the presence of anisotropy. However, these parameters tend to decrease somewhat for rational values of f which happen to be the same for which merges were noticed. Finally, we study the effect of the variation of relative concentration of F vs. AF bonds on these properties. It is found that far from the equal concentration case order parameters increase even further. All of this indicates that simulation of a spin-glass behavior by this simple system is favored under the introduction of anisotropic interactions.