Preparation of soft, anisotropic sendust films in the as-deposited state

Abstract

FeSiAlN films have been prepared by N2 reactive deposition from a sendust target by rf magnetron sputtering. Films show excellent magnetic properties in the as-deposited state with well-defined in-plane uniaxial anisotropy, which is highly desirable from a device perspective. Coercivity values of less than 0.5 Oe along the hard-axis direction were measured in 200 nm thick films. Magnetic properties were found to vary with nitrogen and argon flow rate ratio with optimum magnetic properties being produced using 0.2%–1.0% N2 in the sputter gas. Films sputtered in pure Ar showed high coercivity and grains appear to cluster together. The nitrided films by comparison had a drastically reduced coercivity, smaller grain size, and no grain clustering was present. Coercivity was found to increase with film thickness and anisotropy was less pronounced in films thicker than 500 nm. Cross-sectional transmission electron microscopy of thick sendust films showed a clear change in growth morphology with a columnar microstructure being formed above 500 nm.