We examined the structural properties and the electronic and magnetic structures of an Fe3O4 ultrathin film prepared by oxidizing a low-temperature-grown (T=95 K) Fe film on GaAs(100), using the X-ray diffraction, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism measurements. They show no clear contrast to those of an Fe3O4 film that was prepared by oxidizing room-temperature-grown Fe film. The interdiffusions of Ga and As atoms in the Fe3O4 films were further investigated using the resonant Fe3O4(400) diffractions at the Ga K- and As K-edge energies. It is shown that the Fe3O4 film that originated from the room-temperature-grown Fe film contains both Ga and As atoms, while the film that originated from the kinetically-stabilized Fe film contains only Ga atoms. This suggests that the kinetic stabilization in pristine Fe layers can block As interdiffusion effectively even after oxidization. (C) 2012 Elsevier B. V. All rights reserved.