Examination of giant magnetoresistance in Cu-Co granular films with two-particle size distribution

The giant magnetoresistance (GMR) effect and magnetization curves were measured for Cu₈₀Co₂₀ granular thin films above the blocking temperature. Their correlation was analyzed in a unified scheme. When the GMR and the magnetization curves are fitted to the Langevin functions using an averaged single particle size, there is a lack of agreement for both. The discrepancies were removed by assuming that there are two size distributions in the Co nano-particle population. Under such assumptions, good fittings to the experimental curves were achieved for both the GMR and the magnetization, using the same set of parameters. The obtained average particle sizes for the smaller and the larger particles, and their populations, are 1.0 and 2.8 nm, and 0.35 and 0.65, respectively. The study revealed that a certain degree of magnetic bulk scattering is present in this system.