Morphology Induced Magnetic Anisotropy of Thin Films Deposited on Nanoscale Ripple Substrates

The control of static and especially dynamic magnetic response of ferromagnetic thin films is one of the utmost challenges in applied magnetism. Therefore the adjustment of magnetic anisotropy and the connected resonance frequency, as well as the magnetic damping parameter are of fundamental importance to insure functionality in existing and envisioned spintronic applications.
Here we indirectly tailor the effective magnetic properties of magnetic thin films by changing the morphology of substrates with periodically modulated patterns on the nanometer scale [1]. These well ordered surface modulations (ripple) can be produced by low energy ion beam erosion and are tuneable over a wide range [2]. Thin magnetic films deposited on these ripple surfaces repeat the surface profiles of the patterns and thus an additional uniaxial magnetic anisotropy is induced. Results are shown for thin films of Fe, Co as well as the quasi-Heusler compound Fe3Si. The effective magnetic anisotropy is determined by means of angular- as well as frequency-dependent ferromagnetic resonance measurements using a vector network analyzer based setup. We find a strong uniaxial magnetic anisotropy induced by the ripple surface, which is superimposed on the cubic anisotropy in the case of single crystalline films. Influences of the rippled surface on the magnetic damping parameter will be discussed.
This work is supported by DFG grant FA 314/6-1.

[1] M. Körner et al., Phys. Rev. B 80, 214401 (2009).
[2] J. Fassbender et al., New Journal of Physics 11, 125002 (2009).