Voltage-controllable colossal magnetocrystalline anisotropy in single-layer transition metal dichalcogenides

Abstract

Materials with large magnetocrystalline anisotropy and strong electric field effects are highly needed to develop new types of memory devices based on electric field control of spin orientations. Instead of using modified transition metal films, we propose that certain monolayer transition metal dichalcogenides are the ideal candidate materials for this purpose. Using density functional calculations, we show that they exhibit not only a large magnetocrystalline anisotropy (MCA), but also colossal voltage modulation under external field. Notably, in some materials like CrSe2 and FeSe2, where spins show a strong preference for in-plane orientation, they can be switched to out-of-plane direction. This effect is attributed to the large band character alteration that the transition metal dstates undergo around the Fermi energy due to the electric field. We further demonstrate that strain can also greatly change MCA, and can help to improve the modulation efficiency while combined with an electric field.

Multiferroicity in atomic van der Waals heterostructures

“…Therefore, for spin-conserving transition, SOC elements between occupied and unoccupied states with the same (different) magnetic quantum number through the operator contributes to positive (negative) MAE. For spin-flipping transition, the contribution to MAE is reversed 26 .…”

Synthesis of Ultrathin Metallic MTe2 (M = V, Nb, Ta) Single‐Crystalline Nanoplates

“…The thickness‐dependent CDW phase transitions of TaS 2 and VSe 2 have been studied and may function as an exciting platform for investigating novel many‐body states. As a member of MTMDs, due to strong electron coupling for all neighboring M 4+ –M 4+ pairs, group VB metal tellurides (VTe 2 , NbTe 2 , TaTe 2 ) have been regarded as a potential platform for studying fundamental physical phenomena, such as superconductivity, electro‐catalytic activity, and quantum spin Hall effect, especially magnetism …”

“…Despite these pioneering efforts, the investigation of intrinsic magnetism in 2D materials is still in its infancy. In theoretical investigation, metallic MTe 2 (M = V, Nb, Ta) has been predicted to exhibit intrinsic magnetic ordering . In particular, VTe 2 monolayer is predicted to be a room‐temperature ferromagnetic material with Curie temperatures ( T C ) up to 553 K based on density functional theory because of strong electron coupling in the 3d 1 odd‐electronic configuration of V 4+ .…”

Magnetic Moments Induced by Atomic Vacancies in Transition Metal Dichalcogenide Flakes

“…The energy difference per surface area ( S in units of cm 2 ) between two magnetic configurations whose magnetic‐moment orientations are, respectively, aligned along the x direction and z direction is typically defined as MCA, which is required to be large to stabilize the magnetic order at finite temperature. [ 35 ] The calculated MCA is only 0.0169 erg cm −2 , equivalent to 0.078 meV per magnetic moment. Such a small MCA indicates that the ordered spin states are vulnerable to thermal fluctuations even at a low temperature of ≈0.9 K and thus there exists no long‐range magnetism at the vacancy concentration of ≈4.7 × 10 13 cm −2 .…”