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O: Fachverband Oberflächenphysik

O 32: Surface Magnetism and Spin Phenomena

O 32.5: Poster

Dienstag, 17. März 2015, 18:15–21:00, Poster A

Tuning the Magnetic Anisotropy and the Coupling to the Surface in Fe-Octaethylporphyrin-Cl Complexes on Au(111) — •Olof Peters, Benjamin W. Heinrich, Xianwen Chen, Christian Lotze, and Katharina J. Franke — Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

Magnetism in single transition metal atoms is determined by small details in their atomic scale environment. Variations in the ligand field of metal organic complexes can change the molecule's spin state and its zero field splitting. Here, we report the controllable manipulation of a molecule's spin state and magnetic anisotropy by changing its ligand field with the tip of a scanning tunneling microscope.

As a model system we use Fe-octaethylporphyrin-Cl (FeOEP-Cl) complexes adsorbed on a Au(111) surface to study the influences of a Au tip approaching to the molecule's Fe center. Via inelastic electron tunneling spectroscopy we probe spin excitations and observe an increase in the zero-field splitting as the tip-molecule distance decreases. In addition a signature of Kondo screening appears, indicating a different coupling of the molecule to the surface. B-field dependent measurements reveal the expected splitting of the Kondo resonance. We ascribe our results to a modification of the crystal field leading to a shift in the d-level energies.