Electrical tuning of the magnetic properties of two-dimensional magnets: Cr2⁢Ge2⁢Te6

Motivated by growing interest in atomically thin van der Waals magnetic materials, we present an ab initio theoretical study of the dependence of their magnetic properties on the electron/hole density ρ induced via the electrical field effect. By focusing on the case of monolayer Cr2Ge2Te6 (a prototypical 2D Ising ferromagnet) and employing a hybrid functional, we first study the dependence of the gap and effective mass on the carrier concentration ρ. We then investigate the robustness of magnetism by studying the dependencies of the exchange couplings and magneto crystalline anisotropy energy (MAE) on ρ. In agreement with experimental results, we find that magnetism displays a bipolar electrically-tunable character, which is, however, much more robust for hole (ρ > 0) rather than electron (ρ < 0) doping. Indeed, the MAE vanishes for an electron density ρ ≈ −7.5 × 10 13 e × cm−2 , signaling the failure of a localized description based on a Heisenberg-type anisotropic spin Hamiltonian. This is in agreement with the rapid increase of the coupling between fourth-neighbor atoms with increasing electron density.