Vector analysis of the magnetic polarity from individual magnetic nanoparticles

•The Fe3O4 nanoparticles were obtained by emulsion method.•The Fe3O4 nanoparticles exhibit a soft magnetic behavior close to superparamagnetic.•The amplitude and phase images of Fe3O4 nanoparticles were obtained separately.•The time-variable magnetization reversal of the Fe3O4 nanoparticles was observed.

Vector analysis from individual Fe3O4 nanoparticles was achieved by magnetic force microscopy (MFM) technique with a micromagnetic modeling, which visualises the vector signals of the magnetic field from Fe3O4 nanoparticles. It is demonstrated that the MFM method combined with micromagnetics can effectively analyze the magnetic charge distribution with varying time. With this technique, the vector distribution of the magnetic field of the individual Fe3O4 magnetic nanoparticles was clearly presented, which will be of great importance for applications in nanobiological systems.