  We report the effect of varying cobalt thickness on the temperature-dependent
time decay of the electrical resistance of Co/Sb multilayer samples. We find
that for a given temperature, a five fold change in the Co thickness produces a
100 fold change in the characteristic decay time of the resistance. We find
that the characteristic decay time, as a function of temperature, follows an
Arrhenius law. During deposition, the Co evolves single domain magnetic
nanoparticles, on the Sb, in either a Volmer-Weber or Stranski-Krastanov growth
mode. This metastable state is then encased in 2.5 nm of Sb producing an
embedded nanoparticle system. Scanning Tunneling Microscopy (STM) measurements
taken before sample aging (annealing at a given temperature for enough time to
complete the resistance decay) and after aging show that these nanoparticles
undergo morphological transformations during aging. These transformations lead
to well defined time dependent decays in both the magnetization and the
electrical resistance, making this material an excellent candidate for an
electronic time-temperature sensor.
