Computer Simulation of Critical Behavior of Semi-Infinite Antiferromagnetic Material

Abstract

Phase transitions have been computer-simulated using the Monte Carlo method in the three-dimensional antiferromagnetic Ising model for the various ratios of the exchange integrals calculated over the surface and bulk of the system. The phase diagram of the system has been constructed. It has been shown that the phase diagram contains a phase in which the ordering of spins located on the surface takes place at a temperature below the Néel temperature. Contrary to the ferromagnetic Ising model, lines of phase transitions intersect at the tetracritical rather than tricritical point. The dependence of the surface critical exponents on the ratio of the exchange integrals has been obtained. It has been discovered that, at a ratio of the exchange integrals less than a certain value, the surface phase transition exhibits attributes of the phase transition of the third order.