Row generalization of the fully frustrated triangularXYmodel

Abstract

We have considered the phase diagram, in mean-field theory, of a generalization of the fully frustrated triangular lattice (FFTR) of XY spins. This may be relevant to otherwise isotropic spin systems subject to unidirectional strain along one of the lattice directions. There are two exchange constants, -J and -ηJ, where the latter apply only to bonds in the horizontal direction; for η=1 this row model reduces to the usual FFTR model. We find two ordered phases at low temperatures. For η0.5, the system goes into a spiral state. The line η=0.5 marks a second-order phase transition.