Half metallicity and pressure-induced electronic structure of monolayer FeX₂ (X = S, Se)

In this paper, we present the electronic structure and magnetic properties of two members of transition metal dichalcogenides (TMD) family, FeS₂ and FeSe₂ compounds, in two dimensional monolayer form (2H) using first principles density functional calculations. Iron dichalcogenide compounds are not an intensively studied group of materials within TMDs, although they have an intrinsic magnetic moment and a large variety electronic properties like metallic, half metallic, and semiconducting in equilibrium and under strain. We find that FeS₂ system is found to be metallic in equilibrium and turns into a half-metal, with vanishing density of states of minority spins at Fermi level, at an in-plane pressure of ≈13.7 kbar which corresponds to the slight contraction of the lattice. FeSe₂ is an intrinsic half-metal both in equilibrium and under strain in a wide pressure range up to ≈56 kbar. Both structures have increased magnetic moments of 2.00 under pressure compared to their equilibrium phases in which FeS₂ and FeSe₂ have 1.56 and 1.98 magnetic moments, respectively. Half-metallic gaps in minority spin channels are surrounded by localized Fe-d states in all the systems. The bands crossing Fermi level in majority spins are due to d-states of Fe and p-states of S or Se atoms. Spin-orbit effects are not remarkable on the electronic structure of these systems.