  We study the boundary between ferromagnetic and non-ferromagnetic ground
state of a double-exchange system with quenched disorder for arbitrary relation
between Hund exchange coupling and electron band width. The boundary is found
both from the solution of the Dynamical Mean Field Approximation equations and
from the comparison of the energies of the saturated ferromagnetic and
paramagnetic states. Both methods give very similar results. To explain the
disappearance of ferromagnetism in part of the parameter space we derive from
the double-exchange Hamiltonian with classical localized spins in the limit of
large but finite Hund exchange coupling the $t-J$ model (with classical
localized spins).
