On-surface synthesis of single molecular magnets by contacting magnetic atoms to π-conjugated molecules using STM manipulation

Single organic molecular magnets are promising building blocks for architecting 1-nm-size high functional spintronics device. Tuning of quantum spin states in the single molecules is an important key issue. Although chemical syntheses in liquid solutions have produced several molecular magnets, here we demonstrated on-surface synthesis of single organic molecular magnets. On atomically-flat noble metal surfaces, Fe and Co single atoms were gently adsorbed and manipulated by using a scanning tunneling microscopy (STM) tip to make contact with phthalocyanine and porphyrin single molecules [1-3], simultaneously adsorbed on the same surface. All experiments were performed in ultra-high vacuum (UHV) at 4.6 and 78 K using home-built UHV-STM setups [1-3]. Scanning tunneling spectroscopy dI/dV measurements directly showed how the contacting magnetic atoms affected the local density of states (LDOS) inside the molecule. For example, single Fe atoms have two preferable adsorption sites in one phthalocyanine molecule. Owing to different local ligand fields, the adsorbed Fe atoms at different sites form independent spin configurations. These experimentally obtained LDOS peaks were deeply investigated by theoretical DFT calculations. We also demonstrated a deposition of magnetic atoms on porphyrin monolayer arrays. Surprisingly, depending on the atom, the generated molecule-atom complexes formed different structures. Details will be shown.
References:
[1] T.K. Yamada, et al., Phys. Rev. B 94, 195437 (2016).
[2] E. Inami, et al., Sci. Rep. 8, 353 (2018).
[3] E. Inami, et al., Analytical Chemistry 90, 8954 (2018).