  The behavior of the compensation temperature of a mixed Ising ferrimagnetic
system on a square lattice in which the two interpenetrating square sublattices
have spins $\sigma$ ($\pm 1/2$) and spins $S$ ($\pm 1,0$) has been studied with
Monte Carlo methods. Our model includes nearest and next-nearest neighbor
interactions, a crystal field and an external magnetic field. This model is
relevant for understanding bimetallic molecular ferrimagnetic materials. We
found that there is a narrow range of parameters of the Hamiltonian for which
the model has compensation temperatures and that the compensation point exists
only for small values of the external field.
