Super-Moir\'e Spin Textures in Twisted Antiferromagnets

Abstract

Stacking two-dimensional (2D) layered materials offers a powerful platform to engineer electronic and magnetic states. In general, the resulting states, such as Moir\'e magnetism, have a periodicity at the length scale of the Moir\'e unit cell. Here, we report a new type of magnetism -- dubbed a super-Moir\'e magnetic state -- which is characterized by long-range magnetic textures extending beyond the single Moir\'e unit cell -- in twisted double bilayer chromium triiodide (tDB CrI$_3$). We found that at small twist angles, the size of the spontaneous magnetic texture increases with twist angle, opposite to the underlying Moir\'e periodicity. The spin-texture size reaches a maximum of about 300 nm in 1.1${\deg}$ twisted devices, an order of magnitude larger than the underlying Moir\'e wavelength, and vanishes at twist angles above 2${\deg}$. Employing scanning quantum spin magnetometry, the obtained vector field maps suggest the formation of antiferromagnetic N\'eel-type skyrmions spanning multiple Moir\'e cells. The twist-angle-dependent study combined with large-scale atomistic simulations suggests that complex magnetic competition between the Dzyaloshinskii--Moriya interaction, magnetic anisotropy, and exchange interactions controlled by the relative rotation of the layers produces the topological textures which arise in the super-Moir\'e spin orders.