Micromagnetic structure of domains in Co/Pt multilayers. I. Investigations of wall structure

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Abstract
An analysis of the micromagnetic structure of domains and domain walls in Co/Pt multilayer films is reported. Magneto-optically written domains have been imaged in a scanning transmission electron microscope by using the modified differential phase contrast mode of Lorentz electron microscopy. These have been compared with computer-simulated images based on a two-dimensional model of a circular, perpendicular magnetized domain with a Bloch-like wall structure. Agreement is found for the domain and stray field contrast, but the absence of wall contrast in the experimental images indicates a more complex wall structure in the multilayer than was assumed by the model. In a further series of calculations the magnetic microstructure of a Co/Pt multilayer was modeled by solving the Landau–Lifshitz–Gilbert equations. These suggest that the wall structure varies throughout the thickness of the multilayer, allowing significant saving of magnetostatic energy through the establishment of flux closure paths close to the walls, and are consistent with experimental observations.