  It has been recently shown that the memory of multiple aging stages, a
phenomenon considered possible only below the glass transition of some glassy
systems, appears also above that temperature range in the relaxor ferroelectric
(Pb/La)(Zr/Ti)O_3 (PLZT). Doubts exist whether memory at such high temperature
is intrinsic of the glassy relaxor state or is rather due to migration of
mobile defects. It is shown that the memory in the electric susceptibility and
elastic compliance of PLZT 9/65/35 is not enhanced but depressed by mobile
defects like O vacancies, H defects and mobile charges resulting from their
ionization. In addition, memory is drastically reduced at La contents slightly
below the relaxor region of the phase diagram, unless aging is protracted for
long times (months at room temperature). This is considered as evidence that in
the non relaxor case memory is indeed due to slow migration of defects, while
in the La rich case it is intrinsic of the relaxor state, even above the
temperature of the susceptibility maximum.
