  In this work a site diluted antiferromagntic Ising model in the FCC lattice
is studied by Monte Carlo simulation. At low temperatures, we find that as the
external field is increased the transition from the antiferromagnetic phase to
the superantiferromagnetic one occurs through an intermediate phase which is
not present in the undiluted system. This new phase ordering has three distinct
values for the sublattice magnetizations corresponding to one of the phases
found in a recent mean field calculation thus suggesting that in strongly
frustrated systems many novel spins ordering may arises as found
experimentally, for instance, in some pyrochlores.
