Epitaxial thin NiO films grown on Fe(0 0 1) and the effect of temperature

Thin NiO(0 0 1) films have been epitaxially grown on a ferromagnetic Fe substrate. They have been investigated by X-ray photoemission and spin-resolved inverse photoemission spectroscopies, and compared with films grown in the same conditions on Ag(0 0 1). Well ordered and good quality films are obtained in most cases, while defect states within the fundamental gap are detected only in few cases. Upon annealing these films above 600 K a Ni–Fe substitution reaction occurs in the film, leading to the formation of an Fe oxide film at the surface, while Ni atoms dissolve into the substrate.