Manipulation of in-plane uniaxial anisotropy in FeMgO (001) films by ion sputtering

Grazing-incidence Ar+ ion sputtering has been used to produce nanoscale ripples on the surface of the FeMg (001) system. This way, a uniaxial anisotropy with both controllable strength and orientation can be superimposed on top of the cubic anisotropy, resulting in FeMgO (001) films with unusual anisotropy symmetry. By combining longitudinal and transverse Kerr-effect measurements, different switching processes are revealed. Depending on the orientation of the external magnetic field, one-jump, two-jump, and "reverse" two-jump magnetization reversals can be observed. A simple model, which takes into account the relevant anisotropy energies, is developed to explain the experimentally observed switching fields and to evaluate the domain wall pinning energies of the sputtered sample.