Annealing rate tuned magnetization level in polycrystalline ZnO:Cu films

By combing structural characterizations and comparative annealing experiments, we found that uniformly annealed ZnO:Cu films exhibited robust room temperature ferromagnetism, while non-uniform annealed ZnO:Cu films result in magnetism quenching. Due to inhomogeneous Ostwald ripening during nanocrystal films annealing, Cu2+ ions exist in adsorbed state, depressing nanocrystals surface state. The dissociative Cu2+ ions will compensate d0 ferromagnetism and interference dual-donor (Vo and Zni) mediated indirect double exchange process. Hence, for colloidal chemistry constructed particles thin films, annealing control must be uniform, reducing the introduction of magnetic instability.