Dzyaloshinskii-Moriya interaction and nontrivial spin textures in the Janus semiconductor monolayers V<i>XY</i> (<i>X</i> = Cl, Br, I; <i>Y</i> = S, Se, Te)

We present a density functional theory based study of a two-dimensional ferromagnetic Janus VXY (X = Cl, Br, I; Y = S, Se, Te) structure. The dynamical and thermal stabilities of all possible VXY structures consisting of chalcogen and halogen atoms in the 1Tand 2H phases are determined. Among them, only the 1T phases of the VBrS, VIS, and VISe structures are found to be stable. These structures show semiconducting properties and demonstrate spin-orbit-induced valley splittings, reaching 0.1 eV in the VISe monolayer. These structures exhibit in-plane easy axes with Curie temperatures around similar to 100K estimated based on the classical Monte Carlo and quantum Green's function techniques. On the other hand, the absence of inversion symmetry in Janus VXY compounds gives rise to the Dzyaloshinskii-Moriya interaction with the possibility of forming chiral magnetic structures. In the absence of an external magnetic field, Janus VXY monolayers exhibit magnetic chiral structures at 0 K, evidenced by nonzero Q (topological charge) values from Monte Carlo simulations. By applying an out-of-plane magnetic field of around 0.7 T, we observe the formation of skyrmions. At 5 K, the VIS monolayer demonstrates chiral magnetic structures, while VBrS and VISe display Neel-type domain walls. VISe forms a skyrmion lattice at similar to 0.1T which does not persist beyond this value. Since all the structures have an in-plane easy axis, an in-plane magnetic field of around 0.5 T at 0 K gives rise to the formation of bimerons.