Tuning Magnetism in Layered Magnet VI₃: A Theoretical Study

Abstract

When combined with transition metals with partially filled d-orbitals, magnetism can be incorporated in two-dimensional materials, which greatly expands the scope for fundamental researches and potential applications of these materials. Here, a first-principles study of a new two-dimensional ferromagnet VI3 has been carried out. The structural symmetry, magnetic and electronic properties of VI3 in its bulk and single layer forms have been confirmed and predicted, respectively. Its ferromagnetic Curie temperature is predicted to be reduced by half in its monolayer form. In addition, the cation substitution in its monolayer have also been studied, which can significantly tune the magnetism.

Valence band electronic structure of the van der Waals ferromagnetic insulators: VI$$_3$$ and CrI$$_3$$

“…Even though the magnetic and optical measurements indicate that the strong SOC and U play an important role, the band structure calculations often do not take into account these parameters, erroneously predicting properties such as Dirac half-metallicity or metallic phases 17 , 29 , 42 . The calculations that do account for U predict Mott-insulating ground state, both in monolayer as well as bulk VI , in agreement with the experiments 23 , 25 , 43 .…”

“…Another important observation contradicting the theoretical reports is that the VBM in VI 3 is dominated by the V 3d character and not by I 5p as was the case in CrI 3 43,48 . A qualitative assessment of the orbital character can be made by comparing the electronic structure of these two materials (Figs.…”

“…1f,g. In contrast, the calculations show that the VBM is dominated by iodine www.nature.com/scientificreports/ states in both materials 43,48 . We note that in some other vanadium based vdW systems, such as VSe 2 and VTe 2 , the less-dispersive V 3d states are also at the VBM, while the strongly dispersive Se 4p and Te 5p states are just below it, similar to our results from VI 3 54,55 .…”

“…This is in sharp contrast with the reported theoretical calculations 23 , 26 , where VBM is located at . Furthermore, the absence of on-site Coulomb interactions (U) erroneously predicts a metallic ground state 26 , 43 . Our results show a clear band gap, in line with the optical gap of 0.6–0.67 eV observed in this system 25 , 26 .…”

“…The density functional theory (DFT) calculations 19 using DFT+U also show the dominance of I 5 p orbitals in the VBM of CrI and highlight the importance of SOC for the observed magnetic anisotropy. Moreover, depending on the calculation method and choice of parameters, the resulting electronic structure of the same material may differ significantly, leaving huge discrepancies in predicted material’s properties 43 – 45 , 47 , 48 . These uncertainties emphasize the importance of experimental studies of the electronic structure of these materials.…”