Effects of dipolar interactions on magnetic properties of granular solids

The magnetic behavior of superparamagnetic Co nanoparticles (2-4 nm in diameter) dispersed in an amorphous, insulating SiO2 matrix was studied. Conventional fittings of magnetization curves present mean magnetic moments which diminish with decrease in temperature. In order to treat this anomalous behavior, we have applied the interacting superparamagnetic model (ISP). Mean diameters obtained from transmission electron microscopy (TEM) were compared with values obtained applying ISP model.