Co/Pt multilayers with perpendicular magnetic anisotropy are irradiated by focused He+ ion beam to locally reduce the anisotropy value. The irradiated spots with a diameter of 100 nm are arranged in a square lattice with 200 nm period. The formation of the nonuniform periodic magnetic structure is observed without changes in the film topography. The spatial symmetry of the magnetic force microscopy signal and the specific shape of magnetization curves indicate the formation of the magnetic bubbles or magnetic vortices within the irradiated spot depending on the irradiation dose. The experimental data are in a good agreement with micromagnetic simulations of the system.

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We report on results of computer micromodelling of anti-vortex states in asymmetrical cross-like ferromagnetic nanostructures and their practical realization. The arrays of cobalt crosses with 1 μm branches, 100 nm widths of the branches and 40 nm thicknesses were fabricated using e-beam lithography and ion etching. Each branch of the cross was tapered at one end and bulbous at the other. The stable formation of anti-vortex magnetic states in these nanostructures during magnetization reversal was demonstrated experimentally using magnetic force microscopy.

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