Growth and magnetic properties of iron-based oxide thin films deposited by pulsed laser deposition at room temperature

In the present work, room temperature epitaxial growth of Zn-doped iron oxide films (Zn: FeOx) was achieved by pulsed laser deposition, on c-cut sapphire substrates without any high temperature thermal treatments before the growth. The nature of the oxide phases (wüstite and/or spinel) present in the films depends on the oxygen pressure during the laser ablation. At the residual vacuum (2 × 10− 7 mbar), the (111) wüstite (Zn: FeO) textures was obtained in the films, while oxygen pressures between 2 × 10− 5 to 2 × 10− 3 mbar led to the growth of the spinel (Zn: Fe3O4) phase on the c-cut sapphire substrate. Moreover, the species emitted by the target in the 2 × 10− 7 to 2 × 10− 5 mbar range, preserve their high kinetic energy which allows an easy crystallization of the film on the substrate at room temperature, leading to the epitaxial growth of the wustite and spinel phases. Magnetic properties through M(H) curves at 10 K and 300 K, of the wüstite-based film grown under 2 × 10− 7 mbar were studied, and an exchange bias due to the presence of Fe3+ cation in the film is observed. Finally, the possible mechanisms of the room temperature epitaxial growth of the oxide films on the substrate are presented and discussed.