NUMERICAL STUDY OF THE GROUND-STATE PROPERTIES OF A FRUSTRATED-XY MODEL

We study numerically the ground-state morphology and properties of the low-lying states of an XY model with competing interactions for several values of the concentration x and of the ratio between ferromagnetic and antiferromagnetic exchange constants, lambda. If lambda > 1, the ground state is likely to be a spin glass for all nonzero concentrations. In the region lambda less-than-or-equal-to 1, the ground state is a disordered canted ferromagnet for low dilutions with a transition to a pure spin-glass phase at a lambda-dependent critical concentration. The analysis of the spin-spin correlation functions gives insight on the mechanism responsible for the degradation of the magnetic order at low dilutions. An unusual law of decay of correlations suggests that the canted ferromagnetic phase that we find at small-lambda and x may actually be a phase with power-law decay of correlations.