  By mapping the hamiltonian of the spin one ferromagnet onto that of the
classical spherical model we investigate the possible phase transitions and the
phase diagram of the spin one ferromagnet. Similarly to what happens in the
spherical model we find no phase transition in one and two dimensions.
Nonetheless, for three dimensions we obtain a phase diagram in which the most
important and unexpected feature is the existence of a
ferromagnetic-paramagnetic transition at low temperatures.
