Ion erosion induced ripples as templates for ultrathin magnetic films – ripple-induced anisotropies

The substrate/interface morphology and roughness plays a crucial role for the determination of the magnetic properties of ultrathin films. An anisotropic roughness can easily create magnetic anisotropy contributions of the same symmetry. It will be demonstrated that ion erosion fabricated ripples can be used to tailor the magnetic anisotropy and lead to a dramatic enhancement of the uniaxial magnetic anisotropy of Permalloy by a factor of up to 20.
By means of 500 eV Ar+ ion erosion a rippled Si surface with a well defined periodicity (20 – 60 nm) and peak to valley height (2 – 5 nm) is created. The surface topography is investigated by means of atomic force microscopy. On top of this naturally oxidized surface, first a metallic buffer layer and then a 9 nm thin Permalloy layer is deposited by means of thermal evaporation. Depending on the buffer layer material (Cr, Mn, Pt, Cu) and thickness (0 – 20 nm) the ripple morphology is reproduced to a variable extent by the Permalloy film. The magnetization reversal behavior and the ripple-induced magnetic anisotropies are investigated by means of magneto-optic Kerr effect measurements and correlated to the interface morphology. An easy route for the tailoring of magnetic anisotropies is shown.