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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Organic films and electronics, photoorganics; Nanostructures; Plasmonics and nanooptics, Surface chemical reactions and heterogeneous catalysis, Surface dynamics )

O 36.80: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B2

Conductance and Relaxations of Magnetic Single-Atom Contacts — Nicolas Néel¹, Silke Schröder², Cesar Lazo², Paolo Ferriani², Nico Ruppelt¹, •Jörg Kröger³, Stefan Heinze², and Richard Berndt¹ — ¹Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany — ²Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany — ³Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany

Single-atom contacts fabricated from a Cr-covered tip of a scanning tunnelling microscope and Co and Cr atoms adsorbed to Fe double-layer islands on W(110) exhibit spin-dependent conductances. Depending on the alignment of the magnetic moments of the tip apex and the adsorbed atom the conductance varies by ≈ 40 %. Consequently, these contacts represent atom-sized spin valves. Scrutinizing the spin polarization of the current through these contacts in the vicinity of the tunneling-to-contact transition reveals different geometric relaxations depending on the magnetic moment alignment. Concomitant density functional calculations trace these observations to differently strong exchange forces. The tunnelling anisotropic magnetoresistance is explored at the ultimate limit, i. e., at the single-atom scale. Single Co atoms adsorbed to domains and domain walls of a ferromagnetic Fe film on W(110) exhibit an anisotropy of the magnetoresistance of up to 12 % and repeated sign changes as a function of the bias voltage. Financial support by the Deutsche Forschungsgemeinschaft through SFB 668 is acknowledged.