Magnetic anisotropy of iridium dimers on two-dimensional materials

Magnetic dimers with very large magnetic anisotropy have great potential in information storage applications. By using density functional theory calculations (DFT), we systematically investigated the magnetic anisotropy energy (MAE) of bi-iridium (Ir2) dimers on four types of graphene-like two-dimensional (2D) material substrates. We considered four possible adsorption sites for Ir2 on each substrate. The Ir2 dimer prefers to remain at the single vacancy site with the largest binding energy for all the 2D materials considered. The spin moment and MAE of Ir2 can be largely affected by the substrate. On the substrate of germanene, the MAE of Ir2 can be enlarged to approximately 100 meV, even with the higher Ir2 areal density of 1.804 nm-2. Moreover, the direction of the easy magnetization axis is determined by the d states in the vicinity of the Fermi level. The present DFT results can be understood with the help of perturbation theory analysis.