Epitaxial growth and magnetic properties of ultrathin iron oxide films on BaTiO3(001)

Abstract

The growth and magnetic properties of ultrathin iron oxide films on BaTiO3(001) substrate have been studied by low energy electron diffraction, x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD), and magneto-optic Kerr effect experiments. The iron oxide films were prepared by both simultaneous oxidation and postgrowth oxidation methods. Assuming a surface structure close to Fe3O4[100], the unit cell was found to be epitaxially grown on BaTiO3[100] unit cell due to small lattice mismatch between the film and the substrate. The films exhibit a uniaxial magnetic anisotropy with the easy-axis along Fe3O4[11¯0] direction. For the films on or above 1.7 nm thickness, the XMCD shows characteristic contributions from different Fe site occupations similar to those of the bulk Fe3O4. On the other hand, the XAS line shape and XMCD of the films in the thickness range 1.2–1.6 nm indicate the lesser occupation of Fe2+ octahedral sites associated with the formation of γ-Fe2O3 phase at lower thicknesses. Our investigations offer further insight into the structure, interface, and magnetic properties of the Fe3O4/BaTiO3 as an interesting system for technological applications.