Study of magnetic nanostructures fabricated by nanosphere lithography

Abstract

This thesis presents the advancement in the fabrication processes of nanostructures using polystyrene nanosphere mask. Ion beam etching was used to modify the mask features using Ar, CF4, or O2 gases. Novel magnetic nanostructures such as embedded dots, dumbbell, zigzags, rings and astroids were fabricated by transferring the modified mask features into the substrates. Magnetic force microscopy was used to visualize the domain patterns and results were correlated with micromagnetic simulations. It is found that shape anisotropy becomes progressively dominant when two neighboring triangles are connected to form dumbbell patterns and when further connected to form zigzag nanowires. Astroidal elements and chains were also investigated for their magnetic reversal behavior and its dependence on the number of elements in the chain. The spin strain is observed in astroids as the number of neighboring elements increases and is greatly affected by the spin configurations of the neighboring elements in the chain.