  Spin properties of organic molecules have attracted great interest for their
potential applications in spintronic devices and quantum computing.
Fe-tetraphenyl porphyrin (FeTPP) is of particular interest for its robust
magnetic properties on metallic substrates. FeTPP is prepared in vacuum via
on-surface synthesis. Molecular structure and spin-related transport properties
are characterized by low-temperature scanning tunneling microscope and
spectroscopy at 0.5 K. Density functional theory calculations are performed to
understand molecular adsorption and spin distribution on Au(111). The molecular
structure of FeTPP is distorted upon adsorption on the substrate. Spin
excitations of FeTPP are observed on the Fe atom and high pyrrole groups in
differential conductance spectra. The calculated spin density distribution
indicates that the electron spin of FeTPP is mainly distributed on the Fe atom.
The atomic transmission calculation indicates that electrons transport to
substrate is mediated through Fe atom, when the tip is above the high pyrrole
group.

Mesoscale and Nanoscale Physics