Critical phenomena in a mixed spin-3/2 and spin-5/2 Ising ferro-ferrimagnetic system in a longitudinal magnetic field

We apply Monte Carlo simulation techniques to study the magnetic behavior of a mixed Ising system on a square lattice, where spins SA=±3/2,±1/2 alternate with spins σB=±5/2,±3/2,±1/2 in two interpenetrating sublattices A and B, respectively. The Hamiltonian of the system contains an exchange interaction between nearest neighbors and a longitudinal magnetic field. In order to understand the differences between a mixed Ising system with competing interactions with one with cooperating ones, we study both cases, the ferrimagnetic and the ferromagnetic exchange interactions. We calculate the dependence of the total magnetization, the sublattice magnetizations, the energy, and the magnetic susceptibility, with the magnetic field, and their temperature dependence for a fixed field. We found that under the influence of the magnetic field the ferrimagnetic system presents an interesting phenomena associated with a reversal of the sublattice magnetizations at low temperatures. We found that our system has no compensation temperatures. In both, the ferri and the antiferromagnetic cases, the magnetic field smooths the transition between the ordered and the paramagnetic phase. Finally we present a phase diagram with the critical temperatures in terms of the magnetic field for the ferri and ferromagnetic cases.