Soft magnetic properties of Fe-N and Fe-Si-N thin films sputtered in (Ar+N2) plasma

The soft magnetic properties of sputtered (0~3-wt%) Si-Fe alloy thin films fabricated in (Ar+N₂) plasma were investigated in connection with metallurgical structure. 2.7-wt% Si-Fe film annealed at 400°C shows a high effective permeability μ_eff of about 1600 at 5 MHz. It has been observed that this film consists of α-Fe with a grain size of less than 150 Å and a slight expansion of lattice spacing of the (110) plane. To understand the magnetoelastic effect on permeability, the total magnetic anisotropy in the (110) plane of each grain, U₍₁₁₀₎, was calculated for shear and tetragonal deformation modes. U₍₁₁₀₎ increases with increasing strain for the shear deformation mode, whereas it decreases as the positive strain increases and has a minimum for the tetragonal deformation mode. It is suggested that the decrease in total magnetic anisotropy in each grain through the magnetostrictive anisotropy due to tetragonal deformation and the reduction of grain size are essential for realizing high μ_eff for Fe-Si films