Hole doping as an efficient route to increase the Curie temperature in monolayer CrI$_3$

TL;DR

This paper demonstrates that hole doping in monolayer CrI$_3$ significantly enhances its magnetic properties, including increasing the Curie temperature above 200 K, by tuning exchange interactions and magnetic anisotropy.

Contribution

It reveals how hole doping can effectively control and enhance magnetic order in 2D vdW magnets, a novel approach for high-temperature 2D magnetism.

Findings

Hole doping increases ferromagnetic exchange interactions.

Hole doping enhances magnetic anisotropy.

Curie temperature exceeds 200 K with high hole concentration.

Abstract

Two-dimensional van der Waals (vdW) magnets offer unprecedented opportunities to control magnetism at the atomic scale. Through charge carrier doping - realized by electrostatic gating, intercalation/adsorption, or interfacial charge transfer - one can efficiently tune exchange interactions and spin-orbit-induced effects in these systems. In this work, through a multi-scale theoretical framework combining density functional theory, spin Hamiltonian modeling, and Wannier-function analysis, we choose monolayer CrI$_3$ to unravel how carrier doping affects the isotropic as well as anisotropic exchange interactions in this prototypical vdW ferromagnet. The remarkable efficiency of hole doping in enhancing ferromagnetic exchange and magnetic anisotropy found in our study was explained through orbital-resolved analysis. Crucially, we demonstrated that unlike the undoped system - where isotropic exchange interactions govern magnetic long-range order - the hole-doped CrI$_3$ exhibits anisotropic terms comparable in magnitude to isotropic ones. Finally, we show that a high concentration of holes in a CrI$_3$ monolayer can increase its Curie temperature above 200 K. This work advances our understanding of doping-controlled magnetism in semiconducting 2D materials, demonstrating how anisotropy engineering can stabilize high-temperature magnetic order.