DIELECTRIC NONLINEARITY AND THE NATURE OF POLARIZATION RESPONSE OF PBMG1 3NB2/3O3 RELAXOR FERROELECTRIC/

We investigate the non-linear dielectric properties of PbMg1/3Nb2/3O3 (PMN) single crystals and present the following experimental evidence: (a) the absence of the anomaly in the temperature dependence of non-l inear coefficients in the relationship between the electric field and polarization, E(P); (b) large difference between the ''ac'' and ''dc'' non-linear effects; (c) non-analytical behavior of non-linear dielect ric response and the crossover in its field exponents. The fact (a) cl early evidences against the glassy behavior of PMN. The results (b) an d (c) can be understood using the model of the interphase boundary mot ion in PMN.