Polarization interaction and phase transitions in crystals with two interacting subsystems

The influence of the polarization interactions on the state and phase transitions in magnetic-ordered and dielectric crystals with two interacting order parameters has been investigated. Consideration is given to the case when the interaction in one of the subsystems is considerably weaker than that in the other subsystem. It is demonstrated that the polarization interactions in the weak subsystem can substantially affect the state and the character of phase transitions in the strong subsystem. These interactions can bring about the disordering (formation of the random-field state or the state of spin glass) in the critical region near the second-order phase transition in the main subsystem and also the smearing of the phase transition. At the same time, the polarization interactions can give rise to the ordered and disordered states in the weak subsystem.