Magnetic anisotropy investigations in single crystalline Fe films on ripple MgO templates

Ion erosion of MgO substrates produces highly ordered surface patterns. The so-called ripples are not only induced along any arbitrary in-plane orientation but outstandingly, they stay crystalline upon ion irradiation. Due to the low lattice mismatch single crystalline Fe films can be grown onto these periodically modulated MgO(100) templates. Despite the intrinsic magnetic property of bcc Fe, i.e. cubic anisotropy, an additional ripple morphology driven uniaxial magnetic anisotropy is introduced. Thus an ensemble of twofold and fourfold symmetry is created, which is confirmed by ferromagnetic resonance and magneto-optic Kerr effect measurements. The orientation and strength of the uniaxial anisotropy, which mainly originates from shape and step-edge contributions, depends on the angle of the ripple ridges elongation with regard to the [100] direction of MgO and on the Fe film thickness, respectively. Theoretical analysis reveals anisotropy fields and orientations of both anisotropy contributions that are in agreement with the experiment.