The effect of Cr addition on structure and corrosion resistance in FeTiN nanocrystalline soft magnetic thin films

FeTiN and FeCrTiN thin films were prepared by reactive rf magnetron sputtering. Fe_92.3Ti_2.1N_5.6 (at.%) films showed excellent thermal stability and soft magnetic properties; saturation magnetization (4πM_s)~19.5 kG, coercivity (H_c)~1.2 Oe and effective permeability (μ_eff)~2000 at 100 MHz. However, the corrosion resistance behaviors of the FeTiN films were similar to those of other FeMN films. For improving the corrosion resistance of the FeTiN films without the deterioration of magnetic properties, Cr was added to the FeTiN films. In an as-deposited Fe_90.3Cr_1.2Ti_1.1N _7.4 film, the permeability reached about 2700 at 100 MHz and 4πM_s and H_c showed ~18.6 kG and 1.5 Oe, respectively. From XRD and TEM results, the sizes of α-Fe grains in the FeTiN and FeCrTiN films were observed to be below 10 nm and the grain orientations of the FeCrTiN films were more evenly distributed than the FeTiN films. Also, an addition of Cr in FeTiN films improved the corrosion resistance without the deterioration of soft magnetic properties on FeCrTiN films, caused by the formation of passivation layers in their surface