A generalised integer S Ising spin glass model is analysed using the replica
formalism. The bilinear couplings are assumed to have a Gaussian distribution
with ferromagnetic mean = Jo. Incorporation of a quadrupolar interaction
term and a chemical potential leads to a richer phase diagram with transitions
of first and second order. The first order transition may be interpreted as a
phase separation, and contrary to what has been argued previously, it persists
in the presence of disorder. Finally, the stability of the replica symmetric
solution with respect to fluctuations in replica space is analysed, and the
transition lines are obtained both analytically and numerically.Comment: 16 pages, 11 figure