The effect of nitrogen partitioning on the magnetic properties of FeAlN films

The amount of γ´-Fe₄N phase in FeAlN films has been manipulated by varying the substrate temperature during RF diode sputter deposition. It was found that increasing substrate temperature leads to greater amounts of γ´-Fe₄N precipitation under constant nitrogen flow. It is shown that this precipitation correlates with low coercivities at elevated temperatures and leads to a more negative saturation magnetostriction constant in the films. On the other hand, the magnetostriction constant increases with increasing nitrogen flow at the same substrate deposition temperature. This increase is attributed to the increasing amount of nitrogen in the α-Fe phase. It is shown that the amount of nitrogen in the α-Fe phase is controlling the magnetostriction constant of the film, rather than the γ´-Fe₄N phase