Nonmetallic Atoms Induced Magnetic Anisotropy in Monolayer Chromium Trihalides

Magnetic anisotropy (MA) is crucial for realization of long-range magnetic order in two-dimensional (2D) materials and the long-range ferromagnetic order was experimentally demonstrated in monolayer CrI3. Here, using first principles calculations, we systematically investigate the electronic structure and magnetic anisotropy of monolayer chromium trihalides, including CrCl3, CrBr3, and CrI3. We find that the perpendicular magnetic anisotropy in monolayer CrBr3 and CrI3 are mainly induced by the spin-polarized p-orbitals of nonmetallic Br and I atoms but not the magnetic Cr atom. Moreover, the magnetic anisotropy energy (MAE) of the I atom can reach up to 0.71 meV/atom, which is comparable to that of metallic Fe atom at the Fe/MgO interface. By analyzing the density of states and the p-orbital-resolved MAE of I and Br atoms based on the second-order perturbation theory, we find that the matrix element difference between the same spin py and px orbitals of I and Br atoms contributes most to their MAEs. Furt...