Effect of metallic surfaces on the electronic structure, magnetism, and transport properties of Co-phthalocyanine molecules

The effects of ferromagnetic Co(111) and paramagnetic Cu(111) substrates on the electronic and magnetic structures of Co-phthalocyanine (CoPc) molecule were systemically investigated by means of a plane-wave ultrasoft pseudopotential ab initio electronic-structure calculations within both the local-density approximation and generalized gradient approximation including van der Waals interaction within the Grimme approximation. A strong chemisorption of the CoPc molecule on the Co(111) substrate and a weaker one on the Cu(111) substrate have been found and explained in terms of charge transfer at the interface and the strength of the hybridization between the molecular orbitals and the substrate states. These combined effects at the interface reduce drastically the magnetic moment of CoPc on Co(111) and suppress it for CoPc on Cu(111). It is also found that the calculated scanning tunneling spectroscopy (STM) images at the vicinity of the Fermi level agree qualitatively with experiment, and the STM magnetoresistance occurs only when the CoPc molecule is deposited on Co substrate and is in qualitative agreement with recent experimental results.