Single-Molecule Magnet Mn₁₂ on GaAs-supported Graphene: Gate Field Effects From First Principles

We study gate field effects on the Mn₁₂O₁₂(COOH)₁₆(H₂O)₄ | graphene | GaAs heterostructure via first-principles calculations. We find that under moderate doping levels electrons can be added to but not taken from the single-molecule magnet Mn₁₂O₁₂(COOH)₁₆(H₂O)₄ (Mn12). The magnetic anisotropy energy (MAE) of Mn12 decreases as the electron doping level increases, due to electron transfer from graphene to Mn12 and change in the band alignment between Mn12 and graphene. At an electron doping level of -5.00 × 10¹³ cm^-2, the MAE decreases by about 18% compared with that at zero doping. The band alignment between graphene and GaAs is more sensitive to electron doping than to hole doping since the valence band of GaAs is close to the Fermi level. The GaAs substrate induces a small bandgap in the supported graphene under the zero gate field and a nearly strain-free configuration. Finally, we propose a vertical tunnel junction for probing the gate dependence of MAE via electron transport measurements.