Magnetic and magnetotransport properties of Fe nanoparticles embedded in Ag matrix

Fe20Ag80 and Fe30Ag70 granular thin films have been prepared by the pulsed laser deposition technique under different parameter conditions of pulse frequency and target angular speed. Their influence on the microstructure of the sample, through the analysis of the hysteresis loops, magnetotransport response and magnetooptical Kerr effect, has been investigated. The Fe20Ag80 samples present a superparamagnetic phase, composed of spherical Fe clusters with a mean diameter of 3 nm. The number of Fe nanoparticles increases as both laser pulse frequency and target angular speed increase, thus enhancing their giant magnetoresistance response. The Fe30Ag70 thin films have anisotropic magnetic behaviour and their magnetotransport measurements show giant magnetoresistance and extraordinary Hall effect. These anisotropies suggest the presence of Fe planar particles, which give rise to shape magnetic anisotropy that increases with increasing the target angular speed for a given laser pulse frequency. The planar shape of the Fe particles could be in the origin of the dominant extraordinary Hall effect.