Geometric phase transitions and magnetization peaks in phase-separated states of degenerate magnetic semiconductors

On increase in temperature, an abrupt change in the geometry of the ferroma gnetic-antiferromagnetic phase-separated state of degenerate magnetic semic onductors can occur (a geometric phase transition). If the final state is u niform ferromagnetic, a magnetization peak can appear similar to those obse rved in some manganites. If in the initial state the ferromagnetic region i s multiply connected and in the final state simply connected, then an insul ator-to-metal transition takes place with a simultaneous drop in the magnet ization.