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

This paper describes the effect of film thickness on the high frequency magnetic properties of polycrystalline Fe-Ga films. The damping constant (a) 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, a 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 a is correlated with lambda s regardless of the film thickness, and also sensitive to magnetic inhomogeneities.