Evolution of magnetization in epitaxial Zn1−xFexOz thin films (0     x     0.66) grown by pulsed laser deposition

We demonstrate the development of phases in Zn1−xFexOz thin films with 0 x 0.66, i.e. the end point phases are semiconducting ZnO for x = 0, and ferrimagnetic zinc ferrite (ZnFe2O4) for x = 0.66. With increasing x, the x-ray scattering intensity of the structural ZnO wurtzite phase decreases while that of the (1 1 1)-oriented ZnFe2O4 spinel phase increases. For x > 0.4, single phase spinel layers are obtained. The enhanced formation of the spinel phase is supported by deviations from the usually expected stoichiometric transfer of chemical composition from target to thin film in pulsed laser deposition. We find that all mixed film samples show an excess of iron in relation to the target composition, independent of the growth pressure. The saturation magnetization of the samples increases with x for 0 x 0.66 and shows a ferrimagnetic behavior. The temperature dependence of magnetization points to Curie temperatures well above 400 K for x 0.4. With that, the precise tuning of magnetic performance of the thin layers is possible, yielding a design degree of freedom for application-related requirements.