Effect of Film Thickness on the High Frequency Magnetic Properties of Polycrystalline Fe–Ga Films

Abstract

This paper describes the effect of film thickness on the high frequency magnetic properties of polycrystalline Fe–Ga films. The damping constant ( $\alpha )$ increases markedly from approximately 0.015 to 0.081 for a film thickness below 20 nm, reaches a maximum value of 0.084 at a thickness of 30 nm, and then decreases to 0.068 as the thickness further increases to 100 nm. All the values are much larger than those of a single crystal Fe–Ga film, indicating that the extrinsic damping overlaps with the intrinsic damping. The inhomogeneous broadening in a zero field [ $\Delta H$ (0)] significantly increases with the film thickness due to the magnetic inhomogeneities, such as anisotropy dispersion and other effects. In addition, $\alpha $ increases markedly as the saturation magnetostriction ( $\lambda _{s})$ increases. This behavior is very similar to those of Ni–Fe and Ni–Fe–M films. Therefore, these results demonstrate that $\alpha $ is correlated with $\lambda _{s}$ regardless of the film thickness, and also sensitive to magnetic inhomogeneities.