Monte Carlo simulations of the spin-2 Blume-Emery-Griffiths model with four-spin interactions

摘要

The magnetic properties of a spin S = 2 Ising system with bilinear exchange interaction J_1, the biquadratic exchange interaction K, four-spin exchange interactions J_4 and crystal field A are discussed using the Monte Carlo simulation. The lattice is divided into two sub-lattices: A and B, for which we compute the magnetizations m_A and m_B. The phase obtained diagrams of this system are deduced in the planes: (T, Δ/J_1), (K/J_1, Δ/J_1), (Δ/J_1, J_4/J_1) and (J_4/J_1, K/J_1). In addition to the usual phases, we found a new phase called nonmagnetic quadratic, for which the magnetizations are m_A ≠ m_B and the quadrupolar moments are so that are q_A= q_B. Furthermore, the behavior of the magnetizations as a function of temperature, crystal field, four-spin exchange interactions and biquadratic exchange interaction are deduced.