Quenching of Co magnetism through hybridization with MoS₂

We present results of a comparative study of the electronic and geometric structure and magnetic properties of thin films (1 – 4 atomic layers) of Co with and without a single layer MoS2 support using density functional theory (DFT) based calculations. We find a relatively weak dependence of magnetization on layer thickness for isolated cobalt films, with both bulk and MoS2 lattice constants, while presence of the MoS2 support leads to total demagnetization of monolayer (1L) Co, and to a gradual growth of the magnetic moment as the number of layers increases. This demagnetization is the result of charge transfer and strong hybridization of the Co and MoS2 electronic states. Consistent with the layer-dependence of magnetization, there is a significant spin splitting, except for 1L Co-MoS2, the only system with partially filled isolated narrow bands near the Fermi level. Inclusion of Spin orbit coupling leads to significant splitting of these bands in all systems. Detailed analysis of the band structure near the Fermi level demonstrates that in bilayer Co-MoS2 there is a notable flat band centered around 0.25eV below the Fermi level. Such a heavy hole band can play an important role in the transport and optical properties of the system. While expansion of isolated Co layers from the bulk to MoS2 lattice constant leads to a significant enhancement of the spin-down density of states at the Fermi level in all systems, presence of the MoS2 support results in decrease of this density of states in all systems, except bilayer Co-MoS2, in which case this density of states increases. Bilayer Co-single layer MoS2 heterostructure may have the potential to be used in modern spintronic devices.