  Evidence is summarized attesting that the standard exchange field theory of
ferromagnetism by Heisenberg has not been successful. It is replaced by the
crystal field and a simple assumption that spin orientation is inexorably
associated with the orientation of its carrier. It follows at once that both
ferromagnetic phase transitions and magnetization must involve a structural
rearrangement. The mechanism of structural rearrangements in solids is
nucleation and interface propagation. The new approach accounts coherently for
ferromagnetic state and its manifestations.
