Enhanced magnetic properties and tunable Dirac point of graphene/Mn-doped monolayer MoS₂ heterostructures

Graphene is one of the most promising spintronic materials due to its high carrier mobility. However, the absence of a band gap and ferromagnetic order in graphene seriously limit its applications in spintronics. How to utilize its high carrier mobility as well as mediate its electronic structure remains a challenge. Herein, we design a novel composite, which is composed of graphene and Mn-doped monolayer MoS₂. The magnetic properties and electronic structures of graphene/Mn-doped monolayer MoS₂ heterostructures were studied by using density functional theory (DFT) with the van der Waals (vdW) correlations (DFT-D). We found that the heterostructures show increased magnetic moments and more stable ferromagnetic (FM) states compared with that of isolated Mn-doped MoS₂ monolayer. Our further studies show that many electrons are transferred to Mn-doped MoS₂ monolayer from graphene, which causes the Fermi level to shift down below the Dirac cone about 0.59 eV. The transfered electrons also enhance the FM coupling between Mn ions. Graphene is partially spin polarized because of the magnetic proximity effect, which leads to the spin-dependent gaps for spin-up (16.1 meV) and spin-down (5 meV) at Dirac point, respectively. The introduction of sulfur (S) vacancy to the interface results in a much more stable FM structure and a higher total magnetic moment of the FM state; furthermore, it raises the spin polarization of graphene π orbitals and opens up a small band gap of about 7 meV. These findings propose a new route to facilitate the design of spintronic devices which both need stable ferromagnetism and finite band gap. (paper)