A Monte Carlo simulation is used to investigate the two-dimensional spin-1 Ising antiferromagnet in the presence of an external magnetic field and a single-ion potential. Comparison is made between the results of this simulation and previous mean-field calculations. The phase diagram and the critical behavior of the model are discussed. In contrast to the mean-field picture, no decomposition of the tricritical point is observed.

• Received 11 August 1986

DOI:https://doi.org/10.1103/PhysRevB.35.3347