Magnetic stability of Fe-9.0 wt.% S/Permalloy multi-layered films in high temperature processes

Magnetic properties and thermal stability of Fe-9.0 wt.% Si/Permalloy multilayered films were investigated. It was clear that the initial permeability μ of the Fe-Si layer decreases after annealing processes above 400°C because of Ni diffusion into Fe-Si alloy and the disorder of the polycrystalline orientation of the Fe-Si (110) texture. In order to obtain a high μm, the Ar pressure dependence of μ was investigated. Using a lower Ar pressure, a film with large Fe-Si/Permalloy thickness ratio has a high initial permeability. The thermal stability was improved because the influence of the Ni diffusion at the boundary was reduced and the Fe-Si (110) texture was not disordered by the Ni diffusion. Depositing each Fe-Si layer in more than 0.6 μm thickness and using a lower Ar pressure, such as 3 mtorr, good soft magnetic properties can be obtained even after annealing at 500°C