Double freezing of dielectric response in relaxor Pb(Mg1/3Nb2/3)O3 crystals

The slowing down of dipole dynamics upon cooling into nonergodic relaxor phase in classical relaxor Pb(Mg1/3Nb2/3)O-3 crystal is studied using dielectric spectroscopy in the range of 10(-4)-10(5) Hz. We discover that two overlapping relaxation processes obeying the Kohlrausch-Williams-Watts law, exp[-(t/tau)(beta)], and the Curie-von Schweidler law, t(-n), respectively, tend to freeze out at the same temperature T-f(=213 K). The values of tau(-1), beta, and n obey the Vogel-Fulcher law tending to zero at T-f.