  Two-dimensional materials with robust magnetism have drawn immense attention
for their promising application in spintronics. Recently, intrinsic
ferromagnetic vanadium triiodide (VI3) has been synthesized experimentally. To
enhance its spintronics property, we modified VI3 by interstitial doping with
3d transition metals and used first-principles calculations to investigate the
geometric structure, binding energy, electronic property, and magnetism of
pristine VI3 and 3d TM-doped VI3 monolayer. Among eight transition metal (Sc-,
Ti-, V-, Cr-, Mn-, Fe-, Co-, and Ni-) doped VI3 materials, four of them (Ti-,
V-, Mn-, and Ni-doped VI3) show robust magnetism with full spin polarization
near the Fermi energy. Furthermore, our research demonstrates that Ti-doped VI3
results in half-metallic semiconductor properties (HMS), while V- or Ni-doped
VI3 results in half-semiconductor properties (HSC). Surprisingly, Mn-doped VI3
exhibits an unusual bipolar magnetic semiconductor property (BMS). This unique
combination of strong ferromagnetism and 100% spin polarization with a
half-metallic, half-semiconductor, or bipolar semiconductor property renders
3dTM-doped VI3 as potential candidates for next generation semiconductor
spintronics applications. These spin polarized materials will be extremely
useful for spin-current generation and other spintronics applications.
