ABSTRACT
Among topological solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and magnetic Hopfions are three-dimensional objects that can be formed from a closed loop of twisted skyrmion strings. Theoretical models suggest that magnetic Hopfions can be stabilized in frustrated or chiral magnetic systems, and target skymions can be transformed into Hopfions by adapting their perpendicular magnetic anisotropy, but their experimental verification has been elusive so far. Here, we present an experimental study of magnetic Hopfions that are created in Ir/Co/Pt multilayers shaped into nanoscale disks, known to host target skyrmions. To characterize three-dimensional spin textures that distinguish Hopfions from target skyrmions magnetic images are recorded with surface-sensitive X-ray photoemission electron microscopy and bulk-sensitive soft X-ray transmission microscopy using element-specific X-ray magnetic circular dichroism effects as magnetic contrast. These results could stimulate further investigations of Hopfions and their potential application in three-dimensional spintronics devices.
ABSTRACT
The gold nanostructures fabricated on a substrate yield localized surface plasmon resonance. We describe the fabrication and characterization of nanocrescents on a silicon substrate, which are fabricated by depositing a gold film at an oblique angle through nanosphere lithography. Following the etching of the gold perpendicular to the substrate and the removal of the nanospheres by dissolution, nanocrescents with fine nanostructures are generated. By varying the deposition angle of the gold film from 0 degrees to 72 degrees , nanorings, 2D and 3D nanocrescents can be obtained. During the nanocrescent fabrication, we also compared the deposition angle difference between the e-beam and thermal evaporators for oblique depositions of the gold. The 3D nanocrescents fabricated in our experiments are expected to have improved sensitivity in localized surface plasmon resonance measurements when compared to the previously reported 2D nanocrescents, which enable broader biosensor applications. Simulations of the profiles of these 3D nanocrescents using solid geometry show good consistency with the fabricated ones.
