Stability and capping of magnetite ultra-thin films

Abstract

Ultrathin films of Fe3O4 have been grown epitaxially on nearly lattice matched MgO(001). The stability of 4 nm thick films in ambient air and under annealing in an oxygen atmosphere at 200◦C has been studied. By magneto optical and Raman measurements we can confirm the presence of the Fe3 O4 phase and the formation of a maghemite top layer passivating the Fe3 O4 thin film. In a second step we are able to demonstrate that this top layer oxidation in ambient air can be prevented by a 2 nm thick magnesium ferrite passivation layer, while a thicker 20 nm MgO layer prevents oxidation even at elevated temperatures.