Magnetic ground state of semiconducting transition metal trichalcogenide monolayers

TL;DR

This study uses first-principles calculations to explore the magnetic ground states of monolayer transition metal trichalcogenides, revealing the importance of second and third nearest-neighbor interactions and the potential for strain tuning.

Contribution

It uncovers the crucial role of second and third nearest-neighbor exchange interactions in determining magnetic states of monolayer $ABX_3$ materials, a factor overlooked in prior studies.

Findings

CrSiTe3 is an antiferromagnet with zigzag spin texture due to J3.

CrGeTe3 is a ferromagnet with a Curie temperature of 106 K.

Mn-based compounds exhibit antiferromagnetic Neel order.

Abstract

Layered transition metal trichalcogenides with the chemical formula $ABX_3$ have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides. We show that the second and third nearest-neighbor exchange interactions ($J_2$ and $J_3$) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer $\text{CrSiTe}_3$ is an antiferromagnet with a zigzag spin texture due to significant contribution from $J_3$, whereas $\text{CrGeTe}_3$ is a ferromagnet with a Curie temperature of 106 K. Monolayers of Mn-compounds ($\text{MnPS}_3$ and $\text{MnPSe}_3$) always show antiferromagnetic Neel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. Our study suggests that $\text{ABX}_3$ can be a promising platform to explore 2D magnetic phenomena.