Sombrero-Shaped Fe O Nanoelements with Tunable Out-of-Plane and In-Plane Magnetization Components Fabricated by Nano-Imprint Lithography

We report on the magnetization structure of dish- and sombrero-shaped magnetite nanoelements fabricated via defect-free nanoimprint lithography and magnetron sputtering with controllable deposition flux. We demonstrate that as the sputtering time increases, the shape of the magnetite nanoelements evolves from a dish- to sombrero-shape due to the non-directionality of deposition. At remanence, the bottom layer of both nanoelements favors in-plane direction of magnetization driven by their shape anisotropy (aspect ratios > 8:1). Micromagnetic modeling indicates that this bottom layer is a double vortex for the dish-shape but a single vortex pinned by the central cone in the sombrero-shaped nanoelement. In addition, unlike conventional nano-disks, however, both nanoelements have strong out-of-plane components at the edges; an additional out-of-plane component is also found at the center for the sombrero-shaped nanoelements. We conclude that these localized out-of-plane magnetization components are produced due to the complex shape of the elements.