Abstract
The ability to controllably manipulate magnetic skyrmions, small magnetic whirls with particle-like properties, in nanostructured elements is a prerequisite for incorporating them into spintronic devices. Here, we use state-of-the-art electron holographic imaging to directly visualize the morphology and nucleation of magnetic skyrmions in a wedge-shaped FeGe nanostripe that has a width in the range of 45–150 nm. We find that geometrically-confined skyrmions are able to adopt a wide range of sizes and ellipticities in a nanostripe that are absent in both thin films and bulk materials and can be created from a helical magnetic state with a distorted edge twist in a simple and efficient manner. We perform a theoretical analysis based on a three-dimensional general model of isotropic chiral magnets to confirm our experimental results. The flexibility and ease of formation of geometrically confined magnetic skyrmions may help to optimize the design of skyrmion-based memory devices.
Highlights
The ability to controllably manipulate magnetic skyrmions, small magnetic whirls with particle-like properties, in nanostructured elements is a prerequisite for incorporating them into spintronic devices
In a thin crystal of a chiral magnet, the stability of a skyrmion lattice phase will be significantly enhanced[6,25] due to uniaxial anisotropy[28] or spatial confinement[29,30]. In both bulk compounds and thin films, skyrmion crystals have a fixed lattice constant and adopt approximately circular shapes. Both theoretical analysis[31] and experimental observations[6,25] suggest that elliptical distortions of skyrmions in extended systems are associated with a loss of stability, which is referred to as an elliptical or strip-out instability
Because the twists of spins within a skyrmion give rise to a non-trivial magnetization topology, it should be possible to tune its geometrical morphology without changing its topological class[9]
Summary
The ability to controllably manipulate magnetic skyrmions, small magnetic whirls with particle-like properties, in nanostructured elements is a prerequisite for incorporating them into spintronic devices. Skyrmion chains and skyrmion cluster states have been observed in FeGe nanostripes of fixed width[18] and nanodisks[19], respectively, using Lorentz transmission electron microscopy (TEM).
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