Significant variation of surface spin polarization through group IV atom (C, Si, Ge, Sn) adsorption on Fe3O4(100)

Abstract

The adsorption of group IV atoms (C, Si, Ge, Sn) on the magnetite Fe₃O₄(100) surface is investigated by density functional theory calculations. All these atoms prefer to bond to the surface oxygen atom which has no tetrahedral Fe(A) neighbor. The spin-up surface states of clean Fe₃O₄(100) are completely removed and half-metallicity is recovered by C adsorption. The spin-up band gap of the C-adsorbed Fe₃O₄(100) surface is wider than that of the H-adsorbed one and closer to the value of bulk Fe₃O₄. For the adsorption of other group IV atoms, the adsorbate–substrate interaction decreases and the adsorbate–adsorbate interaction increases with the increase of atomic number Z. As a consequence, the spin polarization varies from −99.4% (C adsorption) to +44.2% (Sn adsorption) for the electronic states of the adsorbed atom integrated from −0.5 eV to the Fermi level. The ability to tune the surface spin polarization by the choice of adsorbate is of significance for magnetite-based spintronic devices.