Monte Carlo approach to phase transitions in ferroelectromagnets

A Monte Carlo algorithm based on the hybrid Ising-DIFFOUR model is proposed to investigate the phase transition in ferroelectromagnetic lattice in which the ferroelectric order and antiferromagnetic order coexist below a certain temperature. The Ising spin moment and ferroelectric displacement and their susceptibilities as well, as a function of temperature for systems of different magnetoelectric couplings, are simulated and compared with the mean-field approach. The typical antiferromagnetic transition at Neel point and the ferroelectric transition at Curie point are observed at zero coupling. It is demonstrated that a weak ferromagnetic order can be activated by introducing the magnetoelectric coupling or applying external magnetic field, while the external electric field has little effect on the ferromagnetic ordering behavior. (C) 2000 American Institute of Physics. [S0021-8979(00)06520-8].