Ferromagnetic State and Phase Transitions

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 natural assumption that spin orientation is inexorably associated with the orientation of its carrier. It follows at once that ferromagnetic state is a property of the crystal structure and 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 consistently for ferromagnetic state and its manifestations.