On the Spin-One Ising Model for an Adsorbed Monolayer

Abstract

A spin-one Ising model previously proposed for an adsorbed monolayer is investigated using a Monte Carlo method for the case of the strong biquadratic nearest-neighbour interaction. It is shown that there exist then two kinds of intermediate phases in addition to two ordered phases which were found in the model with weak biquadratic nearest-neighbour interaction. A phase diagram obtained from the MC data is presented with inclusion of phase boundaries characterizing the existing phase transitions. We show then that the intermediate phases are also predicted from a mean-field theory based on the four-sublattice model, the results of which are compared with the MC results. The conditions for the appearance of one of the intermediate phases are discussed using this mean-field theory.