RANDOM-FIELD INDUCED ANTIFERROMAGNETIC, FERROELECTRIC AND STRUCTURAL DOMAIN STATES

The occurrence of metastable or stable domain states on mesoscopic length scales seems to be a widespread property of many solids undergoing phase transitions in the presence of quenched random fields. A survey is given on the experimental evidence of domain states in various magnetic, ferroelectric and structural systems. In particular we discuss phenomena like the excess magnetization of field-cooled diluted uniaxial antiferromagnets and its relaxation. The domain state of the relaxor ferroelectric PbMg1/3Nb2/3O3 is due to the random distribution of B site cations, whereas dipolar quenched impurities give rise to mesoscopic disorder in K1-xLixTaO3 and Sr1-xCaxTiO3. Spontaneously relaxing quadrupolar domain states are observed in KTa1-xNbxO3. They are probably caused by random strain fields due to ionic size mismatch. The same type of random fields determines the critical behavior of the Jahn-Teller compound DyAsxV1-xO4 but merely causes roughening of the natural ferroeleastic twin domain walls.