Influence of additives on the magnetic damping constant of CoIr soft magnetic thin films with negative magnetocrystalline anisotropy

The oriented (CoIr)_100-xP_x (P=B, Ni, and SiO₂) soft magnetic films are prepared. Their morphology is measured using transmission electron microscopy (TEM), and reveals that these films exhibit good crystallinity and high degree of the c-axis orientation. The magnetic properties are thoroughly investigated as a function of doping x. Our results show that all of these films possess negative magnetocrystalline anisotropy as required by possible applications. Both the intrinsic and extrinsic contributions are considered to interpret the broadening of the ferromagnetic resonance spectral linewidth. The intrinsic Gilbert damping is identified as the main cause of the linewidth broadening, while the extrinsic part originating from inhomogeneities only plays a minor role. More interestingly, our results show that the damping constant can be controlled by using the doping method.