  We investigate the ferromagnetic-glassy transitions which separate the
low-temperature ferromagnetic and spin-glass phases in the temperature-disorder
phase diagram of three-dimensional Ising spin-glass models. For this purpose,
we consider the cubic-lattice +-J (Edwards-Anderson) Ising model with bond
distribution $P(J) = p \delta(J - 1) + (1-p) \delta(J + 1)$, and present a
numerical Monte Carlo study of the critical behavior along the line that marks
the onset of ferromagnetism. The finite-size scaling analysis of the Monte
Carlo data shows that the ferromagnetic-glassy transition line is slightly
reentrant. As a consequence, for an interval of the disorder parameter p,
around p=0.77, the system presents a low-temperature glassy phase, an
intermediate ferromagnetic phase, and a high-temperature paramagnetic phase.
Along the ferromagnetic-glassy transition line magnetic correlations show a
universal critical behavior with critical exponents nu=0.96(2) and
eta=-0.39(2). The hyperscaling relation beta/nu = (1 + eta)/2 is satisfied at
the transitions, so that beta/nu = 0.305(10). This magnetic critical behavior
represents a new universality class for ferromagnetic transitions in Ising-like
disordered systems. Overlap correlations are apparently not critical and show a
smooth behavior across the transition.
