Monte Carlo study of a temperature-driven spin-reorientation transition in an antiferromagnetic system

Employing the Monte Carlo method, we have studied the spin reorientation transition (SRT) in an antiferromagnetic system. We have considered the three-dimensional antiferromagnetic Heisenberg spin system in the presence of two kinds of anisotropic interactions: the single-ion anisotropy interaction and the anisotropic dipolar interaction. We have investigated the thermal behavior of the easy axis of the magnetization and determined the SRT temperature TS with respect to the two kinds of anisotropic energies. We have found that the SRT occurs due to the competition between two anisotropic interactions and the additional entropy contribution at finite temperature. We have demonstrated that the SRT occurs in two types of phase transitions depending on the sign of the fourth-order term in the single-ion anisotropy.