# Voltage-Controllable Colossal Magnetocrystalline Anisotropy in Single Layer Transition Metal Dichalcogenides

## TL;DR

This study predicts that certain monolayer transition metal dichalcogenides exhibit large, voltage-tunable magnetocrystalline anisotropy, enabling electric field control of spin orientation for advanced memory device applications.

## Contribution

The paper introduces a novel use of monolayer transition metal dichalcogenides with large, voltage-controllable magnetocrystalline anisotropy, demonstrated through density functional calculations.

## Key findings

- CrSe2 and FeSe2 can switch spin orientation from in-plane to out-of-plane.
- Electric fields significantly alter the band structure and MCA.
- Strain enhances the electric field modulation of MCA.

## 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 CrSe_2 and FeSe_2, 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 d-states 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.