Super-Moir\'e Spin Textures in Twisted Antiferromagnets

TL;DR

This paper reports a new super-Moiré magnetic state in twisted double bilayer chromium triiodide, characterized by long-range antiferromagnetic textures that extend beyond the Moiré unit cell, driven by complex magnetic interactions.

Contribution

It introduces the concept of super-Moiré magnetic states with long-range textures in twisted 2D magnets, supported by experimental and atomistic simulation evidence.

Findings

Magnetic textures extend up to 300 nm, much larger than the Moiré wavelength.

Texture size varies with twist angle, peaking at 1.1° and vanishing above 2°.

Formation of antiferromagnetic Néel-type skyrmions spanning multiple Moiré cells.

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.