Substrate Bias Effect on the Magnetic Properties of Fe-Ta-N Films

The effects of substrate bias on the magnetic properties and structure of Fe-TaN films deposited by a new sputtering method were investigated. Films sputtered using an rf bias of less than 80 W exhibit good soft magnetic properties and have a fine-grained microstructure consisting of α-Fe and TaN. The direction of the in-plane magnetic anisotropy of the films changes with the bias applied to the substrate. For films prepared at an rf bias of over 100 W, the soft magnetic properties deteriorate due to the change in the fine-grain microstructure from bcc-Fe to fcc-γ'-Fe
₄
N(Ta). Sputtered FeTaN/SiO
₂
multi-layered films were also prepared with a substrate bias; in these films, the anisotropy direction of each FeTaN layer was different from that of adjacent FeTaN layers. The resulting multilayered films are isotropic with high permeability and excellent frequency response. Hence, they are suitable for use as laminated head core materials.