CrAs monolayer: Low buckled two-dimensional half-metal ferromagnet

TL;DR

This study uses ab-initio DFT calculations to reveal that monolayer CrAs is a stable, low-buckled 2D material exhibiting ferromagnetic semiconductor and half-metallic phases depending on lattice constant, with potential spintronic applications.

Contribution

It is the first detailed theoretical investigation of the structural, electronic, and magnetic properties of 2D CrAs, highlighting its half-metallic ferromagnetic behavior and stability.

Findings

CrAs is stable with a low buckled structure.

CrAs transitions from a ferromagnetic semiconductor to a half-metallic ferromagnet with increasing lattice constant.

The ferromagnetic state is more stable than the antiferromagnetic state.

Abstract

\textit{Ab-initio} calculations based on density functional theory (DFT) are performed to study the structural, electronic, and magnetic properties of two-dimensional (2D) free-standing honeycomb CrAs. We show that CrAs has low buckled stable structure. Magnetic CrAs has larger buckling than non-magnetic CrAs. 2D-CrAs is a ferromagnetic semiconductor for lattice constant $a \leq 3.71$\AA, and above this lattice constant CrAs is a half-metal ferromagnet. 2D-CrAs is shown to be half-metal ferromagnetic with magnetic moment of 3.0$\mu_{\rm{B}}$ per unit cell, at equilibrium structure. The $d_{z}^{2}$ orbital of $e_{g}$ band is completely empty in the spin-down state whereas it is almost occupied in the spin-up state, and the magnetic moment in the $e_{g}$ band is mainly dominated by the $d_{z}^{2}$ orbital of Cr. The $d_{zx}/d_{zy}$ and $d_{xy}$ orbitals of $t_{2g}$ band are partially occupied in the spin-up state and behaves as metal whereas they are insulator in the spin-down state. Phonon calculations confirm the thermodynamic stability of 2D-CrAs. The ferromagnetic (FM) and antiferromagnetic (AFM) interaction between the Cr atoms reveal that the FM state is more stable than the AFM state of 2D-CrAs.