Giant magnetoresistance of dilute Cu(Co) granular films

Granular films of Cu (Co) with Co concentrations from 5.4% to 12% in the as-deposited form had magnetization showing about 60% of the Co as ferromagnetic particles and exhibited giant magnetoresistance (MR) of about 20% at 4.2 K. Annealing at ∼310°C increased the MR to 40% and also increased the saturation magnetization indicating additional Co precipitation. At higher annealing temperatures MR decreased to 1%. The Zhang theoretical model involving polarized conduction electron scattering at particle interfaces seems to give a reasonable description of our results including the quadratic behavior of MR vs [M(H)]2 and MR vs [Ms(T)]2.