High-TC ferromagnetism in multilayer Zn/ZnO films induced by native defects

• High-Tc ferromagnetism is observed in dual-layer and hex-layer Zn/ZnO films.
• The changes of c lattice parameter with temperature are due to the leakage of Zni.
• The ferromagnetism in dual-layer film reduces faster than that in hex-layer film.
• The status of the Zni defect and the heterostructure determine the ferromagnetism.

We synthesized dual-layer and hex-layer Zn/ZnO films by magnetron sputtering and ferromagnetism is found in both of them. In the dual-layer Zn/ZnO film, the saturated magnetization significantly decreases with increasing temperature and the ferromagnetic behavior disappears at 600 °C accompanying with apparent shrinkage of c-axial lattice parameter. In contrast, the ferromagnetic behavior in hex-layer Zn/ZnO film is still remarkable at 600 °C and the change of c-axial lattice parameter with temperature is not obvious. These results indicate that Zn interstitial defect as well as the heterostructure of Zn/ZnO dominates the evolution of ferromagnetism.