Magnetic domains and magnetization reversal in epitaxial Fe layers patterned by the atomic saw method

Abstract

We present a study of the magnetic domains structure and the magnetization reversal in systems of stripes and dots patterned on Fe films by the atomic saw method. Continuous epitaxial 50 and 20 Å Fe films have been grown by molecular beam epitaxy deposition method, then by applying strain on MgO monocrystalline substrate and controlling the dislocation slipping, micronic iron stripes and dots have been obtained. For the system of 1.4 μm wide stripes characterized by a strong uniaxial magnetic anisotropy (Ha=1500 Oe) resulting from a uniaxial relaxation of Fe lattice parameter, large magnetic domains have been observed by Kerr microscopy imaging. This structure is not directly correlated to the geometry of ribbons. It reveals the strong influence of the mutual dipolar coupling leading to a quasi-collective magnetization reversal. In contrast, Kerr microscopy observations done on samples structured into 1–3 μm dots show that the domain wall propagation is hindered by the net of orthogonal steps generated by the process. The domain architecture is then directly twinned to the geometry of dots. Both dot mean size and effective size dispersion which is imposed by the dipolar field seem to be the two relevant parameters that govern the two steps magnetization reversal. Calculations of coupling dipolar field are done showing its strong influence upon the magnetization reversal in the stripes case.