The electronic structure and spin asymmetry of metal phthalocyanines (Pcs) (metal = Mn, Fe, Cu, and Mg)
and metal-free Pc thin films of 1-monolayer (ML) thickness on an Fe(100) substrate were investigated using
spin-polarized metastable deexcitation spectroscopy (SPMDS). The surface density-of-states (SDOS) of these
Pcs observed in MDS was almost identical, and thus, insensitivity of the Pc electronic structure to the variation
of the central metal atoms is indicated. On the other hand, the spin asymmetry in the SPMDS measurements
exhibited noticeable differences among Pcs. These results are discussed from the viewpoint of the Pcs electronic
structure calculated by a discrete variational X α method. The fact that differences are found in the spin
asymmetry but not in SDOS among Pcs indicates an important role of the central metal atoms for spin
polarization.
From a structural analysis using low-energy ion scattering spectroscopy, it is shown that Cu-phthalocyanine (CuPc) molecules adsorb on the Fe(100) surface with their planes parallel to the surface when the film thickness is one monolayer, while the structure of the film becomes disordered with an increase in the thickness. This thickness dependence of the CuPc film structure agrees with that determined from the metastable deexcitation spectroscopy (MDS) spectra, and the origins of the CuPc peaks in the MDS spectra are determined. The spin polarization in the molecular orbitals of CuPc on Fe is detected by spin-polarized MDS (SPMDS). The polarity of the spin polarization in the CuPc molecular orbitals is the same as that of the Fe surface. The adsorption of oxygen on Fe prior to the CuPc deposition is found to induce a remarkable difference in the spin polarization of the CuPc orbitals.
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