Monte Carlo study of the quenched disordered mixed spin-(1, 1/2) Ising model with ferrimagnetic interactions

Abstract

We investigate the quenched random mixed-spin Ising model on a square lattice using Metropolis Monte Carlo simulations, to model binary alloys A_xB_1−x. The system consists of randomly distributed spin-1 (S = 0, ±1) and spin-1/2 (σ = ±1/2) variables, where the lattice is equally occupied by each spin type, corresponding to x = 0.5. Nearest-neighbor interactions are considered, with ferromagnetic coupling between like spins and antiferromagnetic coupling between unlike spins, leading to ferrimagnetic behavior. Results show that at low temperatures, the system exhibits ferrimagnetic ordering evidenced by a reduced net magnetization. As temperature increases, signs of phase transitions are observed near T = 1.1 and 1.0, from the heat capacity and magnetic susceptibility plots, but requires more precision to properly locate the critical temperatures. The fluctuations in the Binder cumulant crossings implies a more complex critical behavior. These results highly suggest the presence of multiple closely-spaced critical points, warranting further analysis to fully resolve the system's critical behavior.