  Complex electrical permittivity measurements in (1-x)[Pb(Mg1/3
Nb2/3)O3]-xPbTiO3 ceramics for 0.10 x 0.40 were performed in the frequency and
temperature range from 1 kHz to 100 kHz and from 15 to 600 K, respectively.
Unexpected dielectric anomalies, which were frequency dependent, were found at
cryogenic temperatures. It was verified that this dielectric behavior is always
observed, independently of whether the composition presents a "normal"
ferroelectric or a relaxor characteristic. The results were analyzed within the
framework of two current models found in the literature. It was concluded that
none of the proposed mechanisms uniquely satisfies the experimental results in
the composition range investigated here.
