Two-dimensional half-metals with intrinsic ferromagnetism hold great potential for applications in spintronics. In this study, we aim to expand the known space of such two-dimensional ferromagnetic (FM) half-metals by investigating a bilayer of Janus VSSe, an FM semiconductor. Its structural, electronic, and magnetic properties are examined using first-principles density functional theory (DFT) based approach, employing the $\mathrm{DFT}+U$ methodology, coupled with the Perdew-Burke-Ernzerhof (PBE) functional. The stability of the bilayer is examined using ab initio molecular dynamics simulations at finite temperatures up to 400 K. To ensure the stability further, the elastic constants of the system were also investigated, and we found that the VSSe bilayer remains stable against structural deformation. The magnetic anisotropy calculations suggest that the VSSe bilayer manifests an easy plane of magnetization similar to its monolayer counterpart. At the $\mathrm{DFT}+U$ level of theory, the considered VSSe bilayer exhibits a tendency towards half-metallicity with a small band gap of 0.11 eV for the majority spin carriers and of 0.60 eV for the minority ones. To induce a transition from a semiconductor to a half-metal, the bilayer is subjected to an external electric field of varying strength normal to the plane. The lack of horizontal mirror symmetry in the bilayer allows bidirectional tuning of the band gap, with different values for the field in “upward” and “downward” directions. The band gaps for the two spin channels increase with increasing upward applied electric field, while the opposite happens for the downward fields, with the majority carrier gap closing at $\approx 0.16$ V/Å, making the material a spin gapless semiconductor. Further increase in the electric field renders the material half-metallic at $\approx 0.18$ V/Å. Given the fact that these values of the external electric field are achievable in the laboratory suggests that the FM Janus VSSe bilayer is a promising candidate for spintronic devices.

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• Density of states
• Elasticity
• Electric polarization
• Electronic structure
• First-principles calculations
• Magnetic anisotropy
• Magnetism
• Mechanical deformation
• Spin-orbit coupling
• Spintronics
• Density functional theory