Carrier doping modulates the magnetoelectronic and magnetic anisotropic properties of two-dimensional MSi2N4 (M = Cr, Mn, Fe, and Co) monolayers

Abstract

Through extensive density functional theory (DFT) calculations, our investigation delves into the stability, electrical characteristics, and magnetic behavior of monolayers (MLs) of MSi₂N₄. Computational analyses indicate intrinsic antiferromagnetic (AFM) orders within the MSi₂N₄ MLs, as a result of direct exchange interactions among transition metal (M) atoms. We further find that CrSi₂N₄ and CoSi₂N₄ MLs with primitive cells (pcells) exhibit half-metallic properties, with respective spin-β electron gaps of 3.661 and 2.021 eV. In contrast, MnSi₂N₄ and FeSi₂N₄ MLs with pcells act as semiconductors, having energy gaps of 0.427 and 0.282 eV, respectively. When the SOC is considered, the CrSi₂N₄, MnSi₂N₄ and FeSi₂N₄ MLs are metals, while the CoSi₂N₄ ML is a semiconductor. Our findings imply the dynamics and thermodynamic stability of MSi₂N₄ MLs. We have also explored the influence of carrier doping on the electromagnetic attributes of MSi₂N₄ MLs. Interestingly, charge doping could transform CrSi₂N₄, MnSi₂N₄, and CoSi₂N₄ MLs from their original AFM state into a ferromagnetic (FM) order. Moreover, carrier doping transformed CrSi₂N₄ and CoSi₂N₄ MLs from spin-polarized metals to half-metals (HMs). It is of particular note that doping of CrSi₂N₄ MLs with +0.9 e per pcell or more holes caused a switch in the easy axis (EA) to the [001] axis. The demonstrated intrinsic AFM order, excellent thermodynamic and kinetic stability, adjustable magnetism, and half-metallicity of the MSi₂N₄ family suggest its promising potential for applications in the realm of spintronics.