Monte Carlo simulation of a mixed spin 2 and spin 1/2 Ising ferrimagnetic system

The critical behaviour of a mixed ferrimagnetic Ising system on a square lattice in which the two interpenetrating square sublattices have spins sigma (+/-1/2) and S (+/-2, +/-1, 0) has been studied. We carried out exact ground state calculations and performed Monte Carlo simulations to obtain the finite-temperature phase diagram of the model. We found that the system that includes only a nearest-neighbour interaction and the crystal field does not have a compensation point. Also, our study seems to indicate that, contrary to effective-field predictions, there is no tricritical point at nonzero temperature for this model; however a more elaborate analysis will be needed to draw a definite conclusion on this point.