Aging in K_(1-x)Li_xTa0₃: a domain growth interpretation

The aging behaviour of the a.c. susceptibility of randomly substituted K$_{1-x}$Li$_x$Ta0$_3$ crystals reveals marked differences with spin-glasses in that cooling rate effects are very important. The response to temperature steps (including temperature cycles) was carefully studied. A model based on thermally activated domain growth accounts for all the experimental results, provided one allows for a large distribution of pinning energies, in such a way that `slow' and `fast' domains coexist. Interesting similarities with deeply supercooled liquids are underlined.