Large area patterned magnetic nanostructures

Abstract

Magnetic nanostructures are attracting considerable interest due to their unique properties and potential applications. There are various challenges associated with the fabrication of highly ordered large area magnetic nanostructures and the understanding of their magnetization reversal processes. This review focuses on the use of the deep ultraviolet lithography technique in fabricating arrays of magnetic nanostructures of varying geometrical parameters over a large area. Using resolution enhancement techniques such as alternating phase shift and chrome-less phase shift masks (PSMs), arrays of ferromagnetic nanostructures with lateral dimensions below the conventional resolution limit have been fabricated. Comprehensive investigation of the relationship between the swing amplitude and the pattern size using alternating PSM lithography is presented. Double patterning and double exposure with shifts are used to significantly improve the pattern density and manipulate the magnetic nanostructures. In addition, results of systematic investigations of evolution of magnetic spin states, in-plane anisotropy and magnetostatic interaction in arrays of elongated Ni80Fe20 rings and their derivatives are presented. The magnetization reversal mechanism, the switching field distributions and the transition fields between different magnetic configurations are found to be strongly dependent on the inter-ring spacing, film thickness and any missing segments of the ring. A comprehensive investigation of the spin states and magnetic anisotropy in magnetic antidot nanostructures is also presented. The detailed magnetization reversal reveals a very strong pinning of domain walls in the vicinity of anti-structures, the strength of which was found to be strongly dependent on the anti-structure geometry and field orientation.