CRITICAL-BEHAVIOR OF THE ANTIFERROMAGNETIC HEISENBERG-MODEL ON A STACKED TRIANGULAR LATTICE

We estimate, using a large-scale Monte Carlo simulation, the critical exponents of the antiferromagnetic Heisenberg model on a stacked trian gular lattice. We obtain the following estimates: gamma/upsilon = 2.01 1 +/- 0.014, upsilon = 0.585 +/- 0.009. These results contradict a per turbative 2 + epsilon Renormalization Group calculation that points to Wilson-Fisher O(4) behaviour. While these results may be coherent wit h 4 - epsilon results from Landau-Ginzburg analysis, they show the exi stence of an unexpectedly rich structure of the Renormalization Group how as a function of the dimensionality and the number of components o f the order parameter.