End of aging as a probe of finite-size effects near the spin-glass transition temperature

We have measured the growth of the spin glass correlation length through the aging effect. Measurements were made on bulk ${\mathrm{Cu}}_0.95{\mathrm{Mn}}_0.05$ and a ${\mathrm{Cu}}_0.88{\mathrm{Mn}}_0.12$ thin film multilayer with CuMn layer thicknesses of 4.5 nm separated by 60-nm Cu layers. As the glass temperature ${T}_g$ is approached ($0.9{T}_g0.96{T}_g$, there is no waiting time effect on the magnetization decay. In the temperature region $0.96{T}_g\text{--}1.00{T}_g$, all decays collapse onto a single decay curve indicating an end of aging even for long waiting times (${t}_w=10\phantom{\rule{0.16em}{0ex}}000s$). For the thin film, all effects due to the waiting time disappear at around $0.89{T}_f$, where ${T}_f$ is the freezing temperature marking the onset of irreversibility. These results are interpreted in terms of the spin glass correlation length saturating at a constant value after reaching a characteristic length scale, either the size of the crystallites in the bulk, or the thickness of the 4.5-nm film.