Glassy and domain states in random dipolar systems

The importance of quenched dipolar and quadrupolar fields in disordered dipolar systems with effective ferroelectric interaction is reviewed. Stable or metastable domain states appear e.g. in K1 - xLixTaO3 (x = 0.063), KTa1 - xNbxO3 (x = 0.017) and PbMg1/3Nb2/3O3. Occasionally, unsmearing of the ferroelectric phase transition is possible by application of an electric field. Spontaneous relaxation towards quadrupolar long-range order is observed in KTa1 - xNbxO3, x = 0.017. In the low-x limit both ferroelectricity and random-field interactions become irrelevant in comparison with the random and frustrated interactions. They give rise to an Ising-type dipole glass transition in K1 - xLixTaO3, x = 0.011.