Magnetic antidot nanostructures: effect of lattice geometry.

We investigate the effect of lattice geometry on the magnetic anisotropy and transport properties of Ni80Fe20 antidot nanostructures. The structures were fabricated using deep ultra-violet lithography at 248 nm exposure wavelength. For an antidot array with a square lattice, a fourfold magnetic anisotropy with alternating hard axis and easy axis every 45° was observed. The honeycomb and rhomboid antidot lattice, however, both show a sixfold anisotropy, conforming well to the symmetry of their respective lattices. The magnetic hysteresis and micromagnetic simulation of the spin states at remanence show that the magnetization reversal process is very sensitive to the lattice arrangement of the holes. From the magnetotransport measurements, both the current density distribution and the magnetoresistance behaviour are markedly dependent on the antidot lattice geometry, in agreement with our transport simulations.