Dielectric dispersion and critical behavior in relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3

A critical behavior of dielectric susceptibility has been discovered in relaxor ferroelectric 0.75Pb(Mg1/3Nb2/3)O-3-0.25PbTiO(3). The real part of permittivity epsilon' was found to follow the relation epsilon'-epsilon(infinity)=chi'proportional to(T-T-0)(-2) at T > T-0, and epsilon'proportional to(T-C-T)(-1) at T < T-C, where T(0)approximate to T-C< T-m; T-m is the temperature of the diffused epsilon'(T) maximum as is typical of relaxors; epsilon(infinity) is the frequency-independent parameter, and chi' is the susceptibility depending on frequency via the "universal" relaxation law chi'proportional to f(n-1). The susceptibility chi' is suggested to originate from the polarization of polar nanoclusters. (C) 2000 American Institute of Physics. [S0003-6951(00)00738-5].