Nanolaminated Fe2AB2 and Mn2AB2 (A = Al,Si,Ga,In) materials and the assessment of their electronic correlations

Abstract

Ternary transition metal carbides and nitrides in the so-called MAX phases constitute a rich family of compounds that host interesting electronic and magnetic properties, and thus, these materials have been drawing increasing levels of attention. Similar ternary boride compounds, the MAB phases, have been studied much less despite being equally if not more promising. In this paper, we investigate ${\mathrm{Fe}}_{2}A{\text{B}}_{2}$ and ${\mathrm{Mn}}_{2}A{\text{B}}_{2} (A=\mathrm{Al},\mathrm{Si},\mathrm{Ga},\phantom{\rule{0.28em}{0ex}}\text{and}\phantom{\rule{0.28em}{0ex}}\mathrm{In})$ ternary layered transition metal borides with orthorhombic, hexagonal, and tetragonal crystal structures using first-principles density functional theory (DFT). We assess the reliability of different exchange-correlation functionals for the accurate prediction of the material properties of MAB phases. In addition to the electronic and crystal structures of ${\mathrm{Fe}}_{2}A{\text{B}}_{2}$ and ${\mathrm{Mn}}_{2}A{\text{B}}_{2}$ ($A$ = Ga, In, and Si), we predict the dynamical and thermodynamic stabilities against the competing phases. We conducted bonding analysis to comprehend the bonding characteristic between different atoms, which provides a fundamental understanding whether the exfoliation of these compounds into so-called two-dimensional MBene structures is likely or not. In addition to spin-polarized $\mathrm{DFT}+U$ calculations, which predict ordered magnetic moments, our $\mathrm{DFT}+$embedded dynamical mean field theory calculations predict a significant degree of electronic correlations in the paramagnetic phase of these compounds. These calculations also predict the formation of fluctuating magnetic moments before the onset of a magnetic order in the MAB compounds like an earlier report on the MAX compound ${\mathrm{Mn}}_{2}\mathrm{GaC}$.