Two-dimensional transition metal triborides: Monolayers with robust intrinsic magnetism and high spin stability

Abstract

Two-dimensional materials with intrinsic magnetism have provoked comprehensive attentions due to their potential application in spintronics. In this work, a class of stable transition metal triborides, $\mathrm{TM}{\mathrm{B}}_{3}$ ($\mathrm{TM}=\mathrm{Ti}$, V, Cr, Mn, Fe) with various electronic and magnetic features were predicted by density functional theory. Based on static energy, phonon spectrum, and $ab\phantom{\rule{0.16em}{0ex}}initio$ molecular dynamics simulations, all the $\mathrm{TM}{\mathrm{B}}_{3}$ monolayers have thermal and kinetic stability. Meanwhile, $\mathrm{TM}{\mathrm{B}}_{3}\mathrm{s}$ exhibit mechanical anisotropy reflected by Young's modulus and Poisson's ratio. Moreover, $\mathrm{Ti}{\mathrm{B}}_{3}$ and $\mathrm{Fe}{\mathrm{B}}_{3}$ are robust ferromagnetic metals with the respective Curie temperatures of 248 and 367 K. $\mathrm{Cr}{\mathrm{B}}_{3}$ is antiferromagnetic semiconductor with direct bandgap of 513.6 meV and magnetic transform temperatures of as high as 378 K. Finally, it is predicted that the magnetic properties can be further modulated by exerting external strains. Our results may provide new clues for searching and designing two-dimensional magnetic materials.