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

The effects of substrate bias on magnetic properties and structures were investigated for FeTaN films deposited by a new sputtering method. Films sputtered with 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 for the films changes with the bias applied to the substrate. For those prepared with an RF bias of more than 100 W, the soft magnetic properties deteriorate because of the change of the fine grain microstructure from bcc-Fe to fcc-γ′Fe4N (Ta). Substrate bias-sputtered FeTaN/SiO2 multilayered films were also prepared in which the anisotropy direction of each FeTaN layer was different from that of the adjacent FeTaN layer. The resultant multilayered films show isotropic high permeability and excellent frequency response, and are suitable for laminated-type head core materials.