Investigation of structure and magnetic properties of the as-deposited and post-annealed iron nitride films by reactive facing-target sputtering

► Iron nitride films prepared by reactive facing-target sputtering ► N-rich phases are obtained in as-deposited films with the increase of FN2. ► After being annealed, N-rich phases are decomposed and γ′-Fe4N appears. ► Magnetic characteristics of films are dependent on variation valence states of Fe.