Evolution of structure and magnetic properties of nanocrystalline FeXN thin films via Ta and Al addition

Nanocrystalline FeAIN and FeTaN films are prepared by direct growth and crystallization of their as-deposited amorphous films, respectively. The two films both show soft magnetism of nanocrystalline, but their uniaxial anisotropy is observed to be different from each other. Measurements of microstructure reveal that Ta addition leads to higher N-solubility in these films, and results in larger lattice dilation and more compressive stress. The uniaxial anisotropy is the consequence of the anisotropic distribution of interstitial N atoms in an α-Fe lattice. Al is easy to react with nitrogen, therefore the α-Fe is purer in the FeAIN film than in the FeTaN film and the stress is tensile in the FeAIN film. The difference in anisotropy may be attributed to the different microstructures in both films.