M=3 ASHKIN-TELLER-LIKE CUBIC MODEL ON AN FCC LATTICE

Monte Carlo simulations have been used to study a model consisting of three Ising models with nearest neighbor exchange J on a face-centered -cubic lattice, which are coupled together by a constraint. The constr aint requires that the vector sum of the four spins located at the cor ners of any elementary tetrahedron of the lattice not add to zero. Fin ite-size scaling analysis of the Monte Carlo results for L x L x L lat tices with L = 16. 32, and 64 as been used to find that T-c/J = 10.84 +/- 0.01. The finite-size scaling functions for the magnetization and magnetic susceptibility near T-c are consistent with standard m = 3 He isenberg critical exponents, as predicted by renormalization group the ory. Strengthening the four-spin constraint increases the value of the effective negative. Ashkin-Teller four-spin coupling, and drives T-c to infinity. (C) 1996 American Institute of Physics.