抄録
Ag-Co granular thin films were prepared by co-evaporation in the low Co concentration range (0.6 to 10 at%). As-prepared sample with Co concentrations of less than 10 at% showed superparamagnetic behavior. After annealing at 300°C for 1 hour, 45% GMR was obtained for the 10 at% sample. Cluster sizes were derived by fitting the magnetization at temperatures above blocking in the superparamagnetic region. The size ranged from 32 to 64 atoms in the as-prepared stage and increased with the length of the annealing periods. The MR ratio at 5 K increased according to the increase of cluster size as the anneal proceeded, however the change in the magneto-resistance (Δρ) decreased with increasing size. It is suggested that zero field resistance may play an important role in the MR ratio.
