The memory effect was clearly observed in dc-sputtered metallic, magnetic Co-Ag granular films, which indicates the existence of a spin-glass-like phase at low temperatures. However, the memory effect diminished dramatically after the films were annealed at $300°\mathrm{C}$ for $1\mathrm{h}$. It was also found that the memory effect weakened gradually with increasing volume fraction of magnetic clusters. The experimental results indicate that the dipolar interaction is not the major origin for the formation of low-temperature spin-glass-like (SGL) phase in metallic, magnetic granular materials. On the other hand, a Ruderman-Kittel-Kasuya-Yosida-like exchange interaction between the nanoparticles may be responsible for the collective SGL dynamics and the resulting memory effect.

• Received 9 May 2006

DOI:https://doi.org/10.1103/PhysRevB.75.014415