Phase diagram of XY antiferromagnetic stacked triangular lattices

The phase transition in antiferromagnetic stacked triangular lattices with classical XY spins interacting via antiferromagnetic nearest- and next-nearest-neighbor bonds, J 1 and J 2, is studied by means of extensive histogram Monte Carlo simulations. When J 250, the transition is of second order with critical exponents slightly different from those given by other authors. It is shown that in a range of J 2, the transition is of first order. The general phase diagram in the ( J 2 ,T) space (T, temperature! is shown and discussed. @S0163-1829~96!03530-8#