Electronic and magnetic properties of RuO2 monolayer: DFT+U investigation

A previous theoretical study predicted the stable distorted octahedral (T') phase of RuO2 sheet using first-principles calculations based on density functional theory (DFT). It is a non-magnetic semiconductor with a bandgap of 0.74 eV using hybrid functionals. However, the Ru atom is located in 4d transition metal in the periodic table, and it has half-filled d orbitals. To correct the self-interaction errors which can be seen in this kind of material (which has half-filled d orbitals) Coulomb interactions should be included by using Hubbard + U parameters in the calculations. So, in this study, it is found that the T'-RuO2 sheet prefers an antiferromagnetic ground state with a direct bandgap of 1.77 eV by using DFT + U. In addition, the antiferromagnetic state is switched when charging and discharging the T'-RuO2 sheet. The T'-RuO2 sheet exhibits a large magnetic anisotropy (MAE) of 2.42 meV per Ru atom with an in-plane easy axis (EA). The EA can be tuned into out-of-plane direction by charging the RuO2 sheet. Mean-field approximation based on the 2D classical Heisenberg model predicts a high Neel temperature (T-N) of the T'-RuO2 sheet up to 335 K. The findings expand the potential of the T'-RuO2 sheet for antiferromagnetic spintronic devices.