Two-dimensional Ferromagnetic van der Waals CrX3 (X=Cl, Br, I) Monolayers with Enhanced Anisotropy and Curie Temperature

TL;DR

This study uses first-principles calculations to understand and manipulate the magnetic anisotropy and Curie temperature of 2D CrX3 monolayers, proposing W substitution to enhance perpendicular ferromagnetism.

Contribution

It reveals the origin of in-plane magnetic easy axis in CrCl3 monolayer and proposes W substitution to achieve perpendicular magnetic anisotropy with higher Curie temperature.

Findings

CrCl3 monolayer has in-plane magnetic easy axis due to shape anisotropy.

Substituting Cr with W induces strong perpendicular magnetic anisotropy.

CrWCl6 exhibits a Curie temperature up to 76 K.

Abstract

Among the recently widely studied van der Waals layered magnets CrX3 (X=Cl, Br, I), CrCl3 monolayer (ML) is particularly puzzling as it is solely shown by experiments to have an in-plane magnetic easy axis and, furthermore, all of previous first-principles calculation results contradict this. Through systematical first-principles calculations,we unveil that its in-plane shape anisotropy that dominates over its weak perpendicular magnetocrystalline anisotropy is responsible for the in-plane magnetic easy axis of CrCl3 ML. To tune the in-plane ferromagnetism of CrCl3 ML into the desirable perpendicular one, we propose substituting Cr with isovalent tungsten (W). We find that CrWCl6 has a strong perpendicular magnetic anisotropy and a high Curie temperature up to 76 K. Our work not only gives insight into understanding the two-dimensional ferromagnetism of van der Waals MLs but also sheds new light on engineering their performances for nanodevices.