New method for characterization of magnetic nanoparticles by scanning magnetic microscopy

In this paper, we present a new method for the magnetic characterization of bulk materials, microstructures, and nanostructures. We investigated the magnetic and morphological properties of two colloidal dispersions of iron oxide (Fe3O4) magnetic nanoparticles (MNPs), synthesized by chemical precipitation (co-precipitation) and pulsed laser ablation (PLA) in liquid, by scanning magnetic microscopy (SMM) applied to a small sample with mass on the order of tens of {\mu}g. We evaluated the performance of this technique by comparing magnetization curves and measurements obtained with commercial magnetometers, considered standard. The errors obtained for the saturation and remanent magnetization were approximately 0.18 Am2/kg and 0.6 Am2/kg, respectively. The average size distribution of the NPs estimated from the magnetization curve measurements is consistent with the results obtained by traditional transmission electron microscopy (TEM). The technique can be extended to measure and analyze magnetization curves (hysteresis loops), thus enabling an even more accurate estimation of overall NP sizes.