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 Cu0.95Mn0.05 and a Cu0.88Mn0.12 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 (0.9T(g)< T<0.96T(g)) in the bulk sample, we find that the waiting time effect (as measured by the time associated with the inflection point of the decay) as a function of increasing temperature, shifts to shorter timescales. For T > 0.96T(g), there is no waiting time effect on the magnetization decay. In the temperature region 0.96T(g)-1.00T(g), all decays collapse onto a single decay curve indicating an end of aging even for long waiting times (t(w) = 10 000s). For the thin film, all effects due to the waiting time disappear at around 0.89T(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.