Chiral spin textures: anti-skyrmions, elliptical skyrmions and Néel skyrmions

Magnetic non-collinear spin textures that are chiral are of great current interest. We discuss various spin textures that range from chiral domain walls in synthetic antiferromagnetic racetracks to anti-skyrmions and elliptical skyrmions in inverse tetragonal Heusler compounds to Néel skyrmions in a non-centro-symmetric hexagonal ternary compound. We compare the properties of these distinct spin textures to skyrmions and to magnetic bubbles. We show that the symmetry of the Dzyaloshinskii-Moriya exchange that stabilizes many of these spin textures strongly influences the properties of the spin textures including especially their size, which in some cases, strongly depends on the thickness of the lamella in which they are observed. Using a combination of Lorentz transmission electron microscopy and magnetic force microscopy we show that for anti-skyrmions, which we have observed in several inverse tetragonal Heusler compounds, the diameter of the anti-skyrmion can be varied by more than an order of magnitude from <100 nm to more than 1 micron. This tunability is related to the important role of magnetic dipole-dipole interactions.