Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 2: Towards Molecular Spintronics
DS 2.2: Hauptvortrag
Montag, 25. Februar 2008, 12:15–12:45, H 2013
Coordinated metal centers: Single-molecule magnets and highspin to lowspin switching — •Paul Müller — Institut für Physik der Kondensierten Materie, Universität Erlangen-Nürnberg
Coordinated metal ions are the essential active centers of many molecules. They are quantum dots with an energy spectrum which can be tuned by the coordinating ligands. Even simple complexes with Mn, Fe, Co, or Cu centers show spectacular physical properties. The structural and electronic properties were studied at the single-molecule level by scanning-tunneling microscopy and current-imaging tunneling spectroscopy (CITS). We applied these methods to several single-molecule magnets and a spin-crossover polymer incorporating supramolecular FeII complexes. As the electronic density of states near the Fermi level is dominated by the metal 3d orbitals, CITS spectroscopy can visualize single metal ions in single-molecule magnets, even if these ions are embedded into the sheath of the organic ligand. Therefore, the magnetic state of these ions is accessible to spectroscopy with atomic resolution. CITS measurements of the spin-crossover polymer revealed a high conductivity contrast between monomers in the highspin and in the lowspin state, respectively. Spontaneous switching between these two states was also recorded. This work was done in collaboration with M.S. Alam, V. Dremov, T. Glaser, J. Kortus, Y. Koval, J.-M. Lehn, U. Mitra, A. Postnikov, M. Ruben, R. Saalfrank, M. Stocker, S. Strömsdörfer, and A. Volkov.