Tuning the magnetization by preserving half-metallicity of FeCl2 via embedding transition metal atoms: a DFT study

In this article, the varying magnetization of the modified FeCl2 two-dimensional (2D) layers have been investigated through Density Functional Theory calculations with and without DFT+U method.. Following the optimizations and post-processing electronic analyses regarding the FeCl2 bulk, the two-dimensional layer was created, and the 3d group of transition metal (TM) atoms (from Sc to Ni) were embedded into the defective Cl position in line with the experimental works. The calculations show that while each Fe atom in FeCl2 has 4.00 μ_B magnetization in the pure layer, after embedding transition metal atoms, this value varies in a broad range between 8 to 19 μ_B in completely FM (ferromagnetic) ground state based on only DFT calculations. Between these TM-embedded layers, Ti embedded FeCl2 layer showed half-metallicity in one of two spin channels with and without DFT+U calculations, a prerequisite for spintronic applications. The Projected Density of States (PDOS) of Ti embedded layer, t2g orbitals (dxy, dxz, and dyz) of the neighboring Fe atoms are responsible for the conductivity in the spin-down channel based on DFT calculations. The hubbard parameters completely changes the picture where the non-neighboring atom contribution to the conductive electronic states are dominant. These findings are supported by band gap curves. The bond type identification has been elucidated by ICOHP (integrated crystal orbital Hamiltonian population) and ICOBI (integrated crystal orbital bond index) parameters. PDOS (partial density of states) and pCOHP (partial crystal orbital Hamiltonian) plots were used to identify which bonding-antibonding orbitals were populated. Finally, embedding Ti into Cl defect positions can induce different magnetization levels by preserving half metallicity while the other layers do not provide half-metallicity.