Control of saturation magnetization, anisotropy and damping due to Ni implantation in thin Ni81Fe19 layers

The static and dynamic magnetic properties of 20 nm thick Ni81Fe19 films have been investigated as a function of Ni ion fluence up to 1x1016 Ni/cm2 (~ 5 atom-%). The implantation has been performed at 30 keV in order to implant the Ni ions in the center of the ferromagnetic layer and to achieve a rather homogeneous energy distribution throughout the film. With increasing ion fluence the saturation magnetization and the effective magnetic anisotropies (static and dynamic) are reduced. However, the effective magnetic damping is drastically enhanced for higher ion fluences. This increase can be explained mainly by the drop in saturation magnetization in connection with structural changes. In addition ion implantation in an applied magnetic field allows the setting of the uniaxial anisotropy direction irrespective of the initial orientation.