Determination of core and shell radii of individual core–shell magnetic nanoparticles by magnetic force microscopy

: The characterization of the thickness of a nonmagnetic coating is a primary issue in the investigation of core-shell magnetic nanoparticles (NPs). Here, a method based on magnetic force microscopy (MFM) is reported in which curves of the magnetic phase shift as a function of the lift height are acquired on selected NPs, corrected for electrostatic artifacts, and analyzed using a two-dipole model to describe the tip-sample magnetic interaction. After calibration of the tip on uncoated magnetic NPs, the thickness of the coating of core-shell NPs is determined. The method is demonstrated on core-shell NPs with a magnetite core and silica shell, highlighting its potential and limitations.