Quantitative Analysis of Magnetic Nanoparticles by Means of Magnetic Force Microscopy

Magnetic force microscopy (MFM) is a powerful and simple tool to analyze magnetic materials and structures down to the nano-meter scale. However, there is still a demand for satisfactory models describing measured MFM data quantitatively, thereby allowing us to quantitatively analyze the magnetic properties of the sample. Here, we present an application of the recently proposed pseudo-pole model, which assumes that the tip can be represented by a cone covered homogeneously with dipoles pointing to the tip of the cone. Nano-composites of ferromagnetic Co nanoparticles (NPs) made by inert gas condensation and subsequently deposited non-magnetic SiO
_x
cover layers with different layer thicknesses on single-crystalline Si substrates have been investigated in this paper. We extract quantitative information about the magnetization of individual NPs, as well as their depth below the surface of the SiO
_x
films. In addition, we present an alternative method to extract information about the NP magnetic moment from the width of the NP signal in lift images, which does not require knowledge about the van der Waals interaction. We find good agreement between the magnetic moments determined by both approaches.