A study of the surface phase transition in epitaxial antiferromagnetic films by Monte Carlo simulation

In this paper a computer simulation of phase transitions in epitaxial antiferromagnetic films has been performed. The Ising model and Metropolis algorithm have been used for modeling. The cases of different ratio of exchange interaction constants at the surface and in the film volume are considered. It is shown that in films with no more than six monatomic layers, only the usual phase transition takes place. As the surface energy of spin interaction increases, the temperature of this transition grows. The growth rate of the phase transition temperature decreases as the film thickness increases. If the film thickness is more than six monoatomic layers, a surface phase transition may occur in the system. Antiferromagnetic ordering of spins occurs at temperatures above the Ne<acute accent>el point. Phase diagrams of systems with different number of layers are constructed. The tricritical point of the special phase transition has been studied, at this point three lines of the second kind phase transitions intersect. The parameters and temperature of the special transition point for the films of different thickness have been determined. It is shown that the extraordinary transition is a continuous phase transition. The characteristics of the extraordinary phase transition differ from the ordinary second kind phase transition.