Dielectric and anelastic relaxation in PMN-PT relaxors

Measurements of dielectric and anelastic relaxation have been performed on ferroelectric relaxor PMN-10%PT. Both the dielectric and elastic susceptibilities presented the typical relaxor peak, although much less intense in the elastic case. The anelastic measurements have been extended down to 1 K. finding persistence of the acoustic losses down to liquid helium temperatures. This suggests the existence of isolated or loosely interacting ions that remain mobile within double-well potentials with particularly low barriers also when the polar clusters are completely frozen. The imaginary part of the elastic compliance could be fitted with a temperature independent distribution function of the barriers, assuming that relaxation occurs between inequivalent states, with asymmetries of the order of 100 K or more.