Structural and magnetic modifications in Cr implanted Permalloy

The static and dynamic magnetic properties, especially the magnetic damping behavior, have been investigated as a function of saturation magnetization in thin Permalloy films. Ion implantation doping with Cr in the percentage regime has been used to effectively reduce the Curie temperature and thus the saturation magnetization at room temperature. In order to understand the magnetic modifications the changes in stoichiometry but also the ion induced structural changes have been addressed. As a function of fluence first an improvement of the (111) fiber texture, then a lattice expansion and finally a partial amorphization of the interface near region of the Permalloy layer is found. The region of amorphization can be understood quantitatively by the concentration profiles as a function of depth in combination with irradiation induced damage formation. The magnetic properties change correspondingly. For increasing Cr doping a drop in saturation magnetization and a decrease of the uniaxial magnetic anisotropy is observed. For a fluence of 0.8 x 10^16 Cr/cm^2 (4 at.%) the magnetic damping parameter  increases by a factor of 7. This strong increase is mainly caused by the reduction of the saturation magnetization and the altered sample morphology.