Sputtered polycrystalline iron gratings with a varying stripe width between 0.5 and 3.7 μm at a constant periodicity of 5 μm were studied by Kerr microscopy. The magnetic anisotropy direction is aligned transverse to the stripe length axis. The observed domain processes are directly compared with hysteresis curve measurements. Domain nucleation and the resulting domain structure depend on the external magnetic field direction. Complicated multidomain states are observed down to a stripe width of 1.7 μm. The most narrowly spaced stripes display a simple domain configuration with the average magnetization vector perpendicular to the stripes, along the full film anisotropy axis, indicating dipolar coupling between the elements. With decreasing stripe width and increasing stripe distance, a change to a Landau-Lifshitz-like domain pattern is found. For very narrow stripes, it transforms into a ripple modulated domain structure. Altogether, a continuous transition from full-film-like to single strip-like magnetization behavior with increasing stripe spacing is found. The results are explained by the existing uniaxial magnetic anisotropy together with the shape anisotropy increasing with reduced stripe width. The strong influence of coercivity on the magnetization patterns is shown.
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