Europium incorporation dynamics within NiO films deposited by sol-gel spin coating: Experimental and theoretical studies

Europium doped NiO thin films were grown onto glass substrates via sol-gel spin coating. The evolution of crystal structure, surface topography, and optical properties of NiO was investigated as a function of Eu doping concentration. AFM observations and XRD analysis revealed that NiO:Eu films composed of nano-sized grains exhibit a polycrystalline cubic bunsenite structure with (200) preferential orientation. Optical study showed that the optical band gap of doped NiO films initially increased with low Eu incorporation ratio then decreased with higher Eu content. However, the Urbach energy increased gradually with Eu doping level. First principle calculations were performed to elucidate the changes on electronic, magnetic and optical properties of NiO due to Eu doping. The incorporation of Eu within NiO host lattice induced a strong hybridization between Eu-f and Ni-d states resulting in important changes of bulk magnetization.