Computational discovery of ferromagnetic semiconducting single-layerCrSnTe3

Despite many single-layer materials being reported in the past decade, few of them exhibit magnetism. Here we perform first-principles calculations using accurate hybrid density functional methods (HSE06) to predict that single-layer ${\mathrm{CrSnTe}}_{3}$ (CST) is a ferromagnetic semiconductor, with band gaps of 0.9 and 1.2 eV for the majority and minority spin channels, respectively. We determine the Curie temperature as 170 K, significantly higher than that of single-layer ${\mathrm{CrSiTe}}_{3}$ (90 K) and ${\mathrm{CrGeTe}}_{3}$ (130 K). This is due to the enhanced ionicity of the Sn-Te bond, which in turn increases the superexchange coupling between the magnetic Cr atoms. We further explore the mechanical and dynamical stability and strain response of this single-layer material for possible epitaxial growth. Our study provides an intuitive approach to understand and design single-layer magnetic semiconductors for a wide range of spintronics and energy applications.