Aging and memory effects in a disordered crystal

Dielectric constant measurements have been performed in the ferroelectric low-temperature phase of a KTa0.973Nb0.027O3 crystal. It is found that aging at a fixed temperature T-pl induces a memory effect: the real part epsilon' and the imaginary part epsilon" of the complex dielectric constant epsilon around T-pl remain weaker than they would be without aging, as long as the temperature stays below T-pl; on the contrary, a sojourn of the sample at temperatures higher than T-pl rapidly erases the dips on epsilon' and epsilon" Similarities with recent results obtained on two spin-glasses are emphasized and discussed.