Electrical-field-induced magnetic Skyrmion ground state in a two-dimensional chromium tri-iodide ferromagnetic monolayer

Abstract

Using fully first-principles non-collinear self-consistent field density functional theory (DFT) calculations with relativistic spin-orbital coupling effects, we show that, by applying an out-of-plane electrical field on a free-standing two-dimensional chromium tri-iodide (CrI3) ferromagnetic monolayer, the Néel-type magnetic Skyrmion spin configurations become more energetically-favorable than the ferromagnetic spin configurations. It is revealed that the topologically-protected Skyrmion ground state is caused by the breaking of inversion symmetry, which induces the non-trivial Dzyaloshinskii-Moriya interaction (DMI) and the energetically-favorable spin-canting configuration. Combining the ferromagnetic and the magnetic Skyrmion ground states, it is shown that 4-level data can be stored in a single monolayer-based spintronic device, which is of practical interests to realize the next-generation energy-efficient quaternary logic devices and multilevel memory devices.

Structural and magnetic response of CrI3 monolayer to electric field

“…2, is one to two orders of magnitude smaller than in Refs. [11,12] (more than a factor 20 smaller than in Ref. [11]).…”

“…2 show that the structural response of CrI 3 to the electric field up to 0.6 V/Å is extremely small, for all structural parameters in the wide range of E field values investigated. In particular, considering the E field value of 0.2 V/Å (which is the largest value examined in the previous theoretical work [11,12] and is twice the maximal field value applied in the experimental study [6]), the resulting splitting in the bond distance ∆r [see Fig. 2 [11] in the linear regime for electric fields up to 0.2 V/Å in the CrI 3 monolayer [11,12].…”

“…In particular, considering the E field value of 0.2 V/Å (which is the largest value examined in the previous theoretical work [11,12] and is twice the maximal field value applied in the experimental study [6]), the resulting splitting in the bond distance ∆r [see Fig. 2 [11] in the linear regime for electric fields up to 0.2 V/Å in the CrI 3 monolayer [11,12]. As we show in the Supplementary Material, some non physical settings of the electric field result in such exaggerated (by a factor larger than 20) structural response to E field .…”

Defect-Induced Magnetic Skyrmion in a Two-Dimensional Chromium Triiodide Monolayer

“…Monolayer CrI 3 , in disagreement with the Mermin–Wagner theorem, is known to have long-range ferromagnetic character 3 , 19 that is enabled through the magnetic anisotropy. 3 , 20 This magnetic anisotropy in CrI 3 arises from the spin–orbit coupling in iodine atoms and favors a magnetic easy axis perpendicular to the atomic plane.…”

“…Monolayer CrI 3 , in disagreement with the Mermin–Wagner theorem, is known to have long-range ferromagnetic character 3 , 19 that is enabled through the magnetic anisotropy. 3 , 20 This magnetic anisotropy in CrI 3 arises from the spin–orbit coupling in iodine atoms and favors a magnetic easy axis perpendicular to the atomic plane. 7 , 9 , 20 Magnetic interactions between the chromium ions in a CrI 3 layer arise from a superexchange mechanism between the Cr 3d orbitals and the I 5p orbitals.…”