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MA: Fachverband Magnetismus

MA 3: Bio- and Molecular Magnetism

MA 3.8: Talk

Monday, March 14, 2011, 12:45–13:00, HSZ 401

Reversible chemical manipulation of the magnetic properties of Fe-porphyrin molecules on a ferromagnetic substrate — •Christian Felix Hermanns¹, Jorge Miguel², Matthias Bernien¹, Alexander Krüger¹, and Wolfgang Kuch¹ — ¹Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — ²Diamond Light Source, Harwell Science Innovation Campus, OX11 0DE Chilton, Didcot, United Kingdom

Single-molecule magnets are promising building blocks for future spintronic devices. One of the key issues is to gain control over the magnetic properties of adsorbed molecules by external stimuli. We present the results of an X-ray absorption spectroscopy (XAS) study of the adsorption of NO on top of a submonolayer of Fe-octaethlyporphyrin molecules adsorbed on oxygen-covered Co films grown on Cu(001). Fe L_3,2 XAS spectra show that the adsorption of 24 L NO at 120 K does not cause any change of the oxidation state of the Fe ion, which remains in an Fe 3+ valence state. XMCD investigations before and after dosing NO reveal an antiparallel alignment of the Fe spins and the magnetization of the ferromagnetic substrate. Interestingly, after dosing NO, the Fe XMCD signal is reduced by a factor of two, while the spectral shape of the Fe L_3,2 XMCD signal is not modified. The lower Fe magnetization at finite temperatures after dosing NO can be explained by a reduction of the magnetic coupling between the Co substrate and the molecules. Thermal desorption of NO at 350 K recovers the initial Fe XMCD signal and proves the reversibility of the process. This work is supported by the DFG (Sfb 658).