Single-Molecule Magnet Mn$_{12}$ on GaAs-supported Graphene: Gate Field Effects From First Principles

TL;DR

This study uses first-principles calculations to explore how gate-induced electron doping affects the magnetic anisotropy energy of a Mn12 single-molecule magnet on graphene supported by GaAs, revealing tunable magnetic properties and proposing a tunneling measurement setup.

Contribution

It provides the first detailed analysis of gate field effects on Mn12 magnetic anisotropy in a graphene-GaAs heterostructure using first-principles methods.

Findings

Electron doping reduces Mn12's magnetic anisotropy energy by about 18%.

Band alignment between graphene and GaAs is highly sensitive to electron doping.

GaAs substrate induces a small bandgap and maintains a strain-free graphene configuration.

Abstract

We study gate field effects on the Mn$_{12}$O$_{12}$(COOH)$_{16}$(H$_2$O)$_4$ | 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 Mn$_{12}$O$_{12}$(COOH)$_{16}$(H$_2$O)$_4$ (Mn$_{12}$). The magnetic anisotropy energy (MAE) of Mn$_{12}$ decreases as the electron doping level increases, due to electron transfer from graphene to Mn$_{12}$ and change in the band alignment between Mn$_{12}$ and graphene. At an electron doping level of $-5.00 \times 10^{13}\, \textrm{cm}^{-2}$, the MAE decreases by about 18% compared with 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.