Dynamic properties of relaxor ferroelectrics

We calculate the dynamic order parameter and dielectric susceptibility for the relaxor ferroelectrics like PbMg1/3Nb2/3O3, PbSc1/2Ta1/2O3 and Pb1-xLax ZryTi1-yO3. Calculations of temperature and frequency dependence of dielect ric susceptibility show the existence of low-and high-temperature group of maxima obeyed to Vogel-Fulcher (VF) and Arrhenius laws, respectively. The V F law and non-Debye relaxation behavior as well as the stretched exponentia l law of susceptibility time decay were shown to be the consequence of rand om fields distribution which transforms single dipole Arrhenius and Debye l aws into VF and non-Debye, stretched exponential laws, respectively. Compar ison of observed and calculated characteristics of the relaxors is carried out. (C) 1999 American Institute of Physics. [S0021-8979(99)00703-3].