Effects of Substrate Temperature on Magnetic Properties of Iron Nitride Thin Films Prepared by Ion Assisted Vapor Deposition

The structure and magnetic properties of iron nitride thin films were examined with the substrate temperature as a parameter. The coercivity and squareness ratio decreased with increasing substrate temperature, while the saturation magnetization remained constant. SEM observations revealed that the columnar growth deteriorated at high substrate temperatures. Mössbauer measurements indicated that films consisted of γ'-Fe
₄
N, ε-Fe
_2-3
N and ζ-Fe
₂
N, and that the concentrations of these components were nearly independent of the substrate temperature. Domain replacement was found to be dominant in films prepared at higher substrate temperatures, which implies a change in the paramagnetic distribution. These results suggest that the decrease in coercivity could be attributed to a reduction in the shape anisotropy due to the disordered growth of columns and to a decreased magnetic separation effect by paramagnetic phases in individual columns.