Magnetic properties of amorphous iron nitride films by ion-beam sputtering

摘要

Amorphous films of magnetic iron nitride have been prepared by reactive ion-beam sputtering. The amorphous microstructure is expected to have several advantages over the crystalline films in terms of high-frequency applications. Films of two different compositions have been prepared by varying the partial pressure of N_2. The structural and magnetic properties of the films have been studied using x-ray scattering, Moessbauer spectroscopy, and magneto-optic Kerr-effect measurements. The films are found to transform into a mixture of nanocrystalline ε-Fe_3N and α-Fe phases in the temperature range 473-523 K. Moessbauer measurements in the nanocrystalline specimens give the composition of the two samples as Fe_(0.83)N_(0.17) and Fe_(0.87)N_(0.13) and saturation magnetization as 176 and 191 emu/g, respectively. The films exhibit excellent surface smoothness, which may be attributed to their amorphous microstructure. The as-deposited films exhibit corecivity of about 54 Oe, which increases upon nanocrystallization. The observed behavior of the coercivity can be understood in terms of a random-anisotropy model taking into account the reduced dimensionality of the system.