Abstract

Two types of superparamagnetic nanoparticles, namely magnetite (Fe <inf>3</inf>0 <inf>4</inf>) and iron-platinum (FePt), with their surface modified by oleic acid and oleyleamine were synthesized using the the polyol process and dispersed in n-hexane. Vibrating-sample magnetometry (VSM) was used to characterize the FePt and the magnetic susceptibility of the Fe <inf>3</inf>O <inf>4</inf> was measured as a function of magnetic field and frequency at room temperature. Synchrotron, small-angle, X-ray scattering (SAXS) patterns revealed the polydispersity of the magnetic nanoparticles with average radii below 5 nm. As confirmed by transmission electron microscopy (TEM) images and dynamic light scattering (DLS), the Fe <inf>3</inf>0 <inf>4</inf> nanoparticles had a larger average size. The DLS measurement gave larger radii than those obtained from the SAXS because of the effect of aggregates and surfactants.