Fluctuation-induced transitions in an isotropic spatially frustrated lattice model

Abstract

In this paper we discuss the effects of fluctuations on the phase diagram of an isotropic Ising model with ferromagnetic first-neighbor and antiferromagnetic second- and third-neighbor interactions. We find that, in certain cases, there are substantial deviations from mean-field behavior. Thus the phase transitions between the one-dimensional modulated phases and paramagnetic phase are found to undergo fluctuation-induced first-order phase transitions. We also discuss that point of the phase diagram which, within mean-field theory, was predicted to be an isotropic Lifshitz point. It is argued that the existence of such a point is unlikely, and some alternative scenarios are proposed.