Ion induced ferromagnetism combined with self-assembly for large area magnetic modulation of thin films

Abstract

A highly versatile and scalable path to obtain buried magnetic nanostructures within alloy thin films, while maintaining a flat topography, is described. A magnetic pattern of nanoscale periodicity is generated over ∼cm² areas by employing a B2 → A2 structural transition in the prototype Fe₆₀Al₄₀ thin alloy films. The phase transition was induced in the confined regions via ion-irradiation through self-assembled nanosphere masks. In this way, large area patterns of a hexagonal symmetry of ferromagnetic nanostructures embedded within a paramagnetic Fe₆₀Al₄₀ thin film are realized. The depth and lateral distribution of the induced magnetization was investigated by magnetometry and microscopy methods. Magnetic contrast imaging as well as simulations shows that the obtained magnetic structures are well defined, with the magnetic behavior tunable via the mask geometry.