Engineering the ligand states by surface functionalization: A new way to enhance the ferromagnetism of CrI3

TL;DR

This study demonstrates that surface functionalization of monolayer CrI3 with halogen atoms significantly enhances its ferromagnetic properties, achieving room-temperature ferromagnetism through engineered ligand states.

Contribution

The paper introduces a systematic approach combining theoretical models and first-principles calculations to enhance 2D ferromagnetism via surface functionalization.

Findings

Enhanced magnetic exchange coupling and anisotropy with halogen adsorption.

Achieved room-temperature ferromagnetism (TC=650 K) in fully F-adsorbed CrI3.

Surface engineering as a promising method to improve 2D magnetic materials.

Abstract

The newly discovered 2D magnetic materials provide new opportunities for basic physics and device applications. However, their low Curie temperature (TC) is a common weakness. In this paper, by combining magnetic Hamiltonian, Wannier functions and first-principle calculations, we systematically study the magnetic properties of monolayer CrI3 functionalized by halogen. The magnetic exchange coupling (EX) and magnetic anisotropy (MA) are found to increase significantly by X (X=F, Cl and Br) atom adsorption, and increase along with the coverage of X atom. In the frame work of superexchange theory, the enhanced EX can be ascribed to the reduced energy difference and increased hopping strength between Cr d and I p orbitals, due to the states of I ligand are engineered by X adatom. Besides, the X adatom may provide additional ferromagnetic superexchange channel. Finally, the CrI3 that one side is fully adsorbed by F atoms is found to be a room temperature ferromagnetic semiconductor with TC=650 K. Our results not only give an insightful understanding for the enhancement of ferromagnetism of CrI3 by atom adsorption, but also propose a promising way to improve the ferromagnetism of 2D magnetic materials.