Magnetic Skyrmion Formation at Lattice Defects and Grain Boundaries Studied by Quantitative Off-Axis Electron Holography

Abstract

We use in situ Lorentz microscopy and off-axis electron holography to investigate the formation and characteristics of skyrmion lattice defects and their relationship to the underlying crystallographic structure of a B20 FeGe thin film. We obtain experimental measurements of spin configurations at grain boundaries, which reveal inversions of crystallographic and magnetic chirality across adjacent grains, resulting in the formation of interface spin stripes at the grain boundaries. In the absence of material defects, we observe that skyrmions lattices possess dislocations and domain boundaries, in analogy to atomic crystals. Moreover, the distorted skyrmions can flexibly change their size and shape to accommodate local geometry, especially at sites of dislocations in the skyrmion lattice. Our findings provide a detailed understanding of the elasticity of topologically protected skyrmions and their correlation with underlying material defects.

Relaxation dynamics of modulated magnetic phases in the skyrmion host GaV4S8 : An ac magnetic susceptibility study

“…For instance, skyrmion formation mediated by grain boundaries has been observed in chiral magnets [6,32,33]. Moreover, the disorder induced by the structural domain boundaries could possibly lead to a spatial variation of the cycloidal wavelength and the SkL lattice constant.…”

Dzyaloshinskii-Moriya interaction at disordered interfaces from ab initio theory: Robustness against intermixing and tunability through dusting

“…In spite of extensive research efforts over the past years, many fundamental questions remain unresolved. Of particular interest is the relation of DMI with structural inhomogeneities, such as grain boundaries 12 , single atomic defects 13 , step edges, roughness and intermixing. It is evident that the magnetic properties of nano-scale objects alter significantly as a result of such inhomogeneities 14 .…”

Quantification of Magnetic Surface and Edge States in an FeGe Nanostripe by Off-Axis Electron Holography

“…SP-STM has stringent requirements for clean material surfaces and probes only surface spins. Transmission electron microscopy (TEM) based techniques such as Lorentz microscopy (LM) [12,16], off-axis electron holography (EH) [17][18][19], and differential phase contrast (DPC) imaging [20,21] have been used to image magnetic Skyrmions in thin films with sub-10-nm spatial resolution. However, resolving Skyrmionic spin textures in nanostructures is highly challenging because of the required spatial resolution and magnetic sensitivity.…”

“…4(b). The elongation is thought to result from the geometrical confinement effect, with the Skyrmions flexibly changing their shape in response to the specimen geometry [19,20,22]. The elongated distortions became less pronounced with increasing applied magnetic field: the Skyrmions adopted more circular shapes and decreased in size in a 200 mT field [ Fig.…”