The slowing down of dipole dynamics upon cooling into nonergodic relaxor phase in classical relaxor $\mathrm{Pb}\left({\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}\right){\mathrm{O}}_3$ crystal is studied using dielectric spectroscopy in the range of ${10}^{-4}–{10}^5\mathrm{Hz}$. 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 $T_f(=213\mathrm{K})$. The values of ${\tau }^{-1}$, $\beta$, and $n$ obey the Vogel-Fulcher law tending to zero at $T_f$.

• Received 21 August 2006

DOI:https://doi.org/10.1103/PhysRevB.74.132102