Regensburg 2013 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 11: ThyssenKrupp Electrical Steel Dissertationspreis 2013 der AG Magnetismus

MA 11.4: Vortrag

Montag, 11. März 2013, 13:30–13:55, H3

Spin-Resolved Studies of Individual Adsorbed Molecules with Sub*molecular Spatial Resolution — •Jens Brede — Institute of Applied Physics, University of Hamburg

We have investigated the spin- and energy-dependent tunneling through single molecules adsorbed on ferromagnetic thin films, spatially resolved at a sub-molecular level by low temperature spin-polarized scanning tunneling microscopy (SPSTM). In the case of cobalt coordinated Pc (CoPc) molecules the metal ion as well as the organic ligand exhibit a significant energy and spin dependence of STM images: Interestingly, the spin-majority dominated current flow from the organic periphery is in contrast to the spin-minority dominated tunneling current flow from the surrounding ferromagnetic Fe film. The observed inversion of the local spin polarization can explain the puzzling negative GMR values, which have been observed and controversially discussed in the field of molecular spin valves [1,2]. Thereby, our work tackles central aspects which are essential for understanding and designing new molecular spintronic devices.

More recently, phthalocyanine based single-molecule magnets (SMMs) were studied on ferromagnetic nanostructures by SPSTM as promising model systems for spintronic devices, quantum computing, and data storage at the nanoscale. In particular, we revealed the spin-dependent properties of SMMs with the highest reported blocking temperature bis(phthalocyaninato)terbium(III) (TbPC2). Individual spin split molecular orbitals were resolved for the first time with sub-molecular spatial resolution and the magnitude of the substrate induced exchange splitting was determined by spin-resolved tunneling spectroscopy. The unique insight offered by our SPSTM experiments highlights the importance of resolving spin-dependent molecular properties in atomically well-defined environments on a submolecular scale. [1] Xiong et al., Nature 427, 821 (2004) [2] Jiang et al., Phys. Rev. B 77, 035303 (2008)