Towards three-dimensional nanoarchitectures: highly ordered bi-layer assembly of tailored magnetic nanowire arrays via template-assisted electrodeposition

The miniaturization of magnetic components down to the nanoscale has generated significant progress in expanding magnetic nanostructures into three dimensions. However, the fabrication methods currently employed are limited by the nanopatterned area of the substrate which restrains further improvement in nanowire (NW) density and surface area(SA)-to-volume (SA : V) ratios. Herein, template-assisted electrodeposition was employed systematically to fabricate vertical bi-layers of Ni and Co/Ni freestanding NW arrays to demonstrate full control of the NW diameter, length, and chemical composition in a layer-by-layer basis, where a high SA : V ratio of 1.4 x 10(8) m(-1) was achieved. Moreover, the magnetic properties of a Co/Ni bilayer assembly were measured. The magnetostatic interactions inhertied from the template geometry lead to an easy axis of magnetization that is perpendicular to the NW axis. In addition, the saturation magnetization from each assembled layer provides an additional contribution to the bulk magnetic anisotropy, where bi-magnetic soft/hard magnetization behavior was observed. Overall, these results demonstrate the potential to open a new path in three-dimensional nanofabrication to design highly ordered vertically assembled NW arrays for numerous applications in nanotechnology research.