CrAs Monolayer: Low Buckled 2D Half-Metal Ferromagnet

Ab initio calculations based on density functional theory (DFT) are performed to study the structural, electronic, and magnetic properties of 2D free-standing honeycomb CrAs. It is shown that CrAs has a low buckled stable structure. Magnetic CrAs has larger buckling than nonmagnetic CrAs. 2D CrAs is a ferromagnetic semiconductor at lattice constant a <= 3.71 angstrom, and above this lattice constant CrAs is a half-metal ferromagnet. 2D CrAs is shown to be half-metal ferromagnetic with a magnetic moment of 3.0 mu(B) per unit cell, at equilibrium structure. The dz2 orbital of the eg 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 eg band is mainly dominated by the dz2 orbital of Cr. The dzx/dzy and dxy orbitals of the t2g band are partially occupied in the spin-up state and behave like a metal, whereas they are insulators in the spin-down state. Phonon calculations confirm the thermodynamic stability of 2D CrAs. The ferromagnetic (FM) and antiferromagnetic (AFM) interactions between the Cr atoms reveal that the FM state is more stable than the AFM state of 2D CrAs.