Exchange-coupled Fe3O4/L10–FePt bilayer films by controlled oxidation of Fe/Pt multilayer

A Fe3O4/L10–FePt bilayer thin-film magnet was fabricated via a simple one-step process by annealing Fe/Pt multilayer thin films in a N2 gas flow. X-ray diffraction and plane-view selected-area electron diffraction results are identified with magnetite phase (Fe3O4) and L10–FePt. Cross-sectional transmission electron microscopy images show the two phases form a bilayer structure. Magnetic hysteresis loops of the bilayer show single phase behavior which is interpreted as a result of the soft Fe3O4 phase exchange-coupled with the hard L10–FePt phase, consistent with micromagnetic simulation prediction. Such bilayer structure may have potential for coercivity control in high density magnetic recording application.