Direct Evidence of a Graded Magnetic Interface in Bimagnetic Core/Shell Nanoparticles Using Electron Magnetic Circular Dichroism (EMCD)

Interfaces play a crucial role in composite magnetic materials and particularly bimagnetic core/shell nanoparticles. However, resolving the microscopic structure of these nanoparticles is rather complex. Here, we investigate local magnetization antiferromagnetic/ferrimagnetic FeO/Fe3O4 nanocubes by electron circular dichroism (EMCD). The energy-loss spectroscopy (EELS) compositional analysis samples shows presence an oxidation gradient at interface between FeO core Fe3O4 shell. EMCD measurements show that are composed four different zones with distinct moment concentric, onion-type, structure. These areas correlate spatially composition being largest surface decreasing toward core. results combination EELS mapping can provide very valuable information on inner its correlation to microstructure