Irradiation Effect of Ion Beam in FexN Films Prepared by IRD

Magnetic thin films of FexN were prepared by so-called "ion reacting deposition." To clarify the effect of ion beam irradiation during deposition, the difference between use of N2 ions and Ar ions was studied. A low-energy broad-beam ion source (Kaufman type) was directed normal to the substrate, which was set obliquely to the direction of iron vapor incidence. All of the FexN films consisted mainly of paramagnetic ¿-Fe2-3N and ¿-Fe according to Mossbauer measurements; that is, separation into two phases took place in these films. The coercive force Hc of iron films prepared by Ar ion beam irradiation decreased with increasing ion current density, while that of FexN films increased to saturation. This indicates that the ion bombardment did not lead to the increase in Hc. We were able to analyze the film magnetic anisotropy into two different shape anisotropies related to the columnar microstructure of the film. The change in Hc and shape anisotropy in FexN films can be attributed to the anisotropy in the packing density of ¿-Fe, as estimated from the observed saturation magnetization of the films.