  In this paper we study the phase diagram of the disordered Ising ferromagnet.
Within the framework of the Gaussian variational approximation it is shown that
in systems with a finite value of the disorder in dimensions D=4 and D < 4 the
paramagnetic and ferromagnetic phases are separated by a spin-glass phase. The
transition from paramagnetic to spin-glass state is continuous (second-order),
while the transition between spin-glass and ferromagnetic states is
discontinuous (first-order). It is also shown that within the considered
approximation there is no replica symmetry breaking in the spin-glass phase.
The validity of the Gaussian variational approximation for the present problem
is discussed, and we provide a tentative physical interpretation of the
results.
