Enhancement of ferromagnetic properties of NiO:Fe thin film by Li doping

Li and Fe codoped NiO thin films (LixNi0.98−xFe0.02O, x=0–0.05) were obtained by a sol-gel spin-coating method on silicon substrates. Phase composition and microstructure analysis indicated that the film samples contained 20–30nm sized NiO particles. With increasing Li-doping concentration, the current density of the films increased due to the increase of hole carriers. Magnetization measurements revealed that all the thin films showed room-temperature ferromagnetic properties and could be enhanced by Li doping, which should be due to the fact that hole doping makes ferromagnetic coupling interactions between the hole carriers and localized Fe 3d spins more efficient.