Epitaxial growth and magnetic properties of half-metallic Fe₃O₄ on GaAs(100)

The growth and magnetic properties of epitaxial magnetite Fe₃O₄ on GaAs(100) have been studied by reflection high-energy electron diffraction, x-ray photoelectron spectroscopy, magneto-optical Kerr effect, and x-ray magnetic circular dichroism. The epitaxial Fe₃O₄ films were synthesized by in situ post growth annealing of ultrathin epitaxial Fe films at 500 K in an oxygen partial pressure of 5×10⁻⁵ mbar. The XMCD measurements show characteristic contributions from different sites of the ferrimagnetic magnetite unit cell, namely, Fe_td³⁺, Fe_oh²⁺, and Fe_oh³⁺. The epitaxial relationship was found to be Fe₃O₄(100)⟨011⟩∕∕GaAs(100)⟨010⟩ with the unit cell of Fe₃O₄ rotated by 45° to match that of GaAs(100) substrate. The films show a uniaxial magnetic anisotropy in a thickness range of about 2.0–6.0 nm with the easy axes along the [01̅ 1] direction of the GaAs(100) substrate.