Mechanical, Electronic, and Magnetic Properties of NiX2 (X = Cl, Br, I) Layers.

Min Lu,Chuanyun Xiao,Qiushi Yao,Chengxi Huang,Erjun Kan

doi:10.1021/acsomega.9b00056

Abstract

Since the recent experimental discovery of the CrI3 and CrGeTe3 monolayers, van der Waals (vdW) layered transition metal compounds have been recognized as promising candidates to realize 2D ferromagnetic (FM) semiconductors. However, until now, only limited compounds have been proposed to be ferromagnetic semiconductors. Here, on the basis of first-principles calculations, we report that the monolayer, Janus monolayer, and bilayer of NiX2 (X = Cl, Br, I) are intrinsic 2D FM semiconductors. Our results show that exfoliation energy of the NiX2 monolayer is smaller than that of graphene, and all studied NiX2 layers show semiconducting band gaps. The predicted Curie temperature values for NiX2 (X = Cl, Br, I) monolayers ranged from 120 to 170 K with Monte Carlo simulations. For the Janus monolayer, we found that the spin interaction shows a very strong magnetoelectric coupling under an external electric field. Furthermore, for the bilayer of NiX2, our results show that the interlayer coupling is quite weak, indicating the possibility of tuning the magnetic coupling through external manipulations.

Highlights

During the past decade, two-dimensional (2D) materials, such as graphene,[1] h-BN,[2] MoS2,3 and black phosphorus,[4] have received much attention because of their unique properties and potential applications in future nanodevices.[5]
The van der Waals (vdW) layered transition metal compounds have been recognized as promising candidates to realize 2D FM semiconductors because these materials usually possess intrinsic magnetism and can be exfoliated down to monolayers
For the Janus monolayer, we found that the spin interaction shows a very strong magnetoelectric coupling

Summary

Introduction

Two-dimensional (2D) materials, such as graphene,[1] h-BN,[2] MoS2,3 and black phosphorus,[4] have received much attention because of their unique properties and potential applications in future nanodevices.[5]. In early studies, long-range magnetic order is predicted to be prohibited in a 2D system according to the Mermin−Wagner theorem.[6] Recently, Gong et al.7and Huang et al.[8] reported their discovery of long-range ferromagnetic (FM) order in 2D intrinsic semiconductors, Cr2Ge2Te6 and CrI3, which are exfoliated down to atomically thin layers from their van der Waals (vdW) layered bulk materials. These exciting findings promote the studies of 2D magnetic semiconductors to a new stage. The measured Curie temperature (TC) values of these materials are very low (

Methods

Results

Conclusion