Ferromagnetism and Morphology of Annealed Fe 2 O 3 /Co X O Y /ZnO Thin Films

We have studied thermal solid‐state reactions in the Fe 2 O 3 /Co X O Y /ZnO thin film systems grown using the atomic layer deposition technique. The compound produced after annealing at 700 °C is found to be a complex mixture of three different spinel phases: ZnCo 2 O 4 , CoFe 2 O 4 , and ZnFe 2 O 4 . The magnetic properties of the compound strongly depend on the atomic ratio of Fe 3+ and Co 2+ atoms, which can be set by choosing the corresponding thicknesses of the Fe 2 O 3 and Co X O Y films. In addition, we also find a formation of 100 nm voids at the interface between Fe–Co–Zn–O compound and remaining ZnO film after 1h annealing at 700 °C in argon atmosphere. The formation of these voids shows indirectly the preferential outward diffusion of Zn 2+ ions from ZnO into the Fe 2 CoO 4 phase layer what we prove via our magnetic measurements.