Proposal of a Skyrmion-Antiskyrmion racetrack memory in rank-1 DMI magnets

Recently, we extended the scope of skyrmions and antiskyrmions and introduced a classification scheme of chiral magnets [1]. Typically investigated Bloch-type skyrmions in B20 alloys and Néel-type skyrmions at (111) oriented interfaces belong to isotropic rank-three Dzyaloshinskii-Moriya (DM) bulk and rank-two DM film magnets with a DM interaction described by a single spiralization constant. Within this class, antiskyrmions are stable only for bulk crystals with certain point group symmetries. New are the anisotropic rank-two DMI film magnets where skyrmions and antiskyrmions can coexist while the determinant of the spiralization tensor determines which of them has lower energy. Finally, zero determinant indicates a rank-one DMI material in which they have the same energy.
Here, we discuss our new classification scheme and give with 2Fe/W(110) an example of an anisotropic rank-two solid for which we conjecture the presence of antiskyrmions. Finally, we discuss the potential of rank-one solids for the design of a racetrack memory based on the coexistence of skyrmions and antiskyrmions [2].

[1] M. Hoffmann et al., Nat. Commun. 8, 308 (2017)
[2] M. Hoffmann et al., to be submitted