Monte Carlo simulations of the Spin-2 Blume-Emery-Griffiths model

Abstract

The magnetic properties of the spin S = 2 Ising system with the bilinear exchange interaction J1SizSjz, the biquadratic exchange interaction J2Siz2Sjz2 and the single-ion anisotropy DSiz2are discussed by making use of the Monte Carlo (MC) simulation for the magnetization <Sz>, sub-lattice magnetizations <Sz(A)> and <Sz(B)>, the magnetic specific heat CM and spin structures. This Ising spin system of S = 2 with interactions J1 and J2 and with anisotropy D corresponds to the spin-2 Blume-Emery-Griffiths model. The phase diagram of this Ising spin system on a two-dimensional square lattice has been obtained for exchange parameter J2/J1 and anisotropy parameter D/J1. The shapes of the temperature dependence of sublattice magnetizations <Sz(A)> and <Sz(B)> are related with abnormal behavior of temperature dependence of <Sz> at low temperatures and affected significantly by the single-ion anisotropy D. The staggered quadrupolar (SQ) ordering turns out to be different largely between Ising systems with the single-ion anisotropy (D ≠ 0) and without the one (D = 0).