Recently, a study team led by Prof. TIAN Mingliang in High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL) successfully controlled morphology and formation of magnetic skyrmions and observed the morphological change of the geometrically-confined single skyrmion by electron holography for the first time.

Magnetic storage in hard disk drive technology is based on the controllable formation of magnetic domains and is approaching its limits.

The ability to manipulate domain walls, especially the novel magnetism structure which called skyrmions, instead of domains provides an alternative method to further extend the storage device road map.

The underlying design of race-track memory devices relies on the use of skyrmions as data bit carriers, which move along a ferromagnetic nanostripe that takes on the role of a guiding track.

It is therefore important to controllably form and manipulate skyrmions in nanostructured elements.

Thanks to the joint efforts by Prof. LI Zi'an and Prof. Nikolai S. Kiselev from Germany, DU Haifeng from Prof. TIAN Mingliang's group at CHMFL studied the nucleation and the evolution of the skyrmion in microstructure characterization of nanometer magnetic materials and theoretical simulation.

By using Lorentz Transmission Electron Microscopy (LTEM) and advanced electron holography techniques, they found 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.

The magnetic phase diagram also featured states like distorted helical spirals, pure edge twists and zigzag skyrmion chains.

This discovery amends the cognition that the size of skyrmion has rigidity as well as establishes the foundation of optimizing the design of the skyrmion-based memory devices.

Their work entitled "Control of morphology and formation of highly geometrically confined magnetic skyrmions" was published in Nature Communications.

This work was supported by the National Science Fund for Excellent Young Scholars, and Key Program of the Chinese Academy of Sciences; Youth Innovation Promotion Association, CAS; Collaborative Innovation Center of Advanced Microstructures, Nanjing.

Schematic diagrams of geometrical control of skyrmions

Morphology of magnetic skyrmions in a wedge-shaped FeGe nanostripe that has a width in the range of 45–150 nm by electron holographic imaging