Releasing latent chirality in magnetic two-dimensional materials

Abstract

Dzyaloshinskii-Moriya interaction (DMI) is at heart of chiral magnetism and causes emergence of rich non-collinear and unique topological spin textures in magnetic materials, including cycloids, helices, skyrmions and other. Here we show that strong intrinsic DMI lives in recently discovered van der Waals magnetic two-dimensional (2D) materials, due to the sizeable spin-orbit coupling on the non-magnetic ions. In a perfect crystal, this intrinsic DMI remains hidden, but is released with any break of point-inversion symmetry between magnetic ions, unavoidable at the sample edges, at ever-present structural defects, with any buckling of the material, or with non-uniform strain on an uneven substrate. We demonstrate such release of latent chirality on an archetypal magnetic monolayer CrI 3 , and discuss the plethora of realizable DMI patterns, their control by nanoengineering and tuning by external electric field, thereby opening novel routes in 2D magnetoelectronics.

Tailoring High-Frequency Magnonics in Monolayer Chromium Trihalides

“…In the case of lattice defects, ab initio calculations reveal DMI vectors of magnitudes up to D = 4.69 meV for CrI 3 and D = 2.60 meV for CrBr 3 in the vicinity of halide vacancies 16 . One thus expects pronounced effects of such strong variations of the local magnetic interactions on the SW propagation in the 2D magnetic materials.…”

“…Figure 3(b) illustrates the expected DMI configuration in the case of a non-uniform uniaxial strain in the wrinkled CrX 3 monolayer. DFT calculations show that the DMI increases linearly with local uniaxial strain, with relatively small magnitude of up to D = 0.08 meV for 6% of local strain 16 .…”

“…3(a)]. Moreover, due to the non-uniform deformation, the corresponding symmetry-breaking gives rise to localized DMI 16 . Figure 3(b) illustrates the expected DMI configuration in the case of a non-uniform uniaxial strain in the wrinkled CrX 3 monolayer.…”

“…4 (e-g)], reveal that the transmitted wave is strongly affected in the case of high density of defects. In order to quantify and compare the SW transmission for different defect densities, we integrate the output SW 16 . The complete exchange matrix for both cases is provided in the supplemental material 26 .…”

“…In this work we investigate the SW propagation in monolayer CrBr 3 and CrI 3 as exemplary representa-tives of 2D magnetic materials. We obtain all relevant magnetic parameters from first-principle calculations on the considered structures 1,16 , and perform spin-dynamics simulations of the SW propagation. We proceed to calculate the SW dispersion relation in the chromium trihalides under strain, revealing the tunability of magnonic behavior by strain-engineering.…”