Direct imaging of the magnetic polarity and reversal mechanism in individual Fe3−xO4 nanoparticles

C. Moya, Ó. Iglesias-Freire, N. Pérez, X. Batlle, Amilcar Labarta, A. Asenjo

This work reports on the experimental characterization of the magnetic domain configurations in cubic, isolated Fe3−xO4  nanoparticles with a lateral size of 25–30 nm. The magnetic polarity at remanence of single domain ferrimagnetic Fe3−xO4  nanoparticles deposited onto a carbon–silicon wafer is observed by magnetic force microscopy. The orientations of these domains provide a direct observation of the magneto-crystalline easy axes in each individual nanoparticle. Furthermore, the change in the domain orientation with an external magnetic field gives evidence of particle magnetization reversal mediated by a coherent rotation process that is also theoretically predicted by micromagnetic calculations.