  We report the observation of magnetic and resistive aging in a self assembled
nanoparticle system produced in a multilayer Co/Sb sandwich. The aging decays
are characterized by an initial slow decay followed by a more rapid decay in
both the magnetization and resistance. The decays are large accounting for
almost 70% of the magnetization and almost 40% of the resistance for samples
deposited at 35 $^oC$. For samples deposited at 50 $^oC$ the magnetization
decay accounts for $\sim 50%$ of the magnetization and 50% of the resistance.
During the more rapid part of the decay, the concavity of the slope of the
decay changes sign and this inflection point can be used to provide a
characteristic time. The characteristic time is strongly and systematically
temperature dependent, ranging from $\sim1$x$10^2 s$ at 400K to $\sim3$x$10^5
s$ at 320K in samples deposited at $35 ^oC$. Samples deposited at 50 $^oC$
displayed a 7-8 fold increase in the characteristic time (compared to the $35
^oC$ samples) for a given aging temperature, indicating that this timescale may
be tunable. Both the temperature scale and time scales are in potentially
useful regimes. Pre-Aging, Scanning Tunneling Microscopy (STM) reveals that the
Co forms in nanoscale flakes. During aging the nanoflakes melt and migrate into
each other in an anisotropic fashion forming elongated Co nanowires. This aging
behavior occurs within a confined environment of the enveloping Sb layers. The
relationship between the characteristic time and aging temperature fits an
Arrhenius law indicating activated dynamics.
