Hund's physics and the magnetic ground state of CrOX (X = Cl, Br)

TL;DR

This study uses advanced first-principles calculations to accurately determine the magnetic ground states of layered CrOX materials, emphasizing the importance of Hund's physics in modeling their electronic and magnetic properties.

Contribution

It demonstrates that charge-only DFT+U with explicit on-site interactions accurately reproduces experimental magnetic states, highlighting the significance of Hund's physics in these materials.

Findings

CrOX monolayers are antiferromagnetic, consistent with bulk.

Charge-only DFT+U reproduces experimental magnetic ground states.

Cr t2g-t2g interactions mainly drive antiferromagnetism.

Abstract

To understand the magnetic property of layered van der Waals materials CrOX (X = Cl, Br), we performed the detailed first-principles calculations for both bulk and monolayer. We found that the charge-only density functional theory combined with the explicit on-site interaction terms (so-called cDFT$+U$) well reproduces the experimental magnetic ground state of bulk CrOX, which is not the case for the use of spin-dependent density functional (so-called sDFT$+U$). Unlike some of the previous studies, our results show that CrOX monolayers are antiferromagnetic as in the bulk. It is also consistent with our magnetic force linear response calculation of exchange couplings $J_{\rm ex}$. The result of orbital-decomposed $J_{\rm ex}$ calculations shows that the Cr $t_\textrm{2g}$-$t_\textrm{2g}$ component mainly contributes to the antiferromagnetic order in both bulk and monolayer. Our result and analysis show that taking the correct Hund's physics into account is of key importance to construct the magnetic phase diagram and to describe the electronic structure.