Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 44: Joint Session "Spins in Organic Materials" (jointly with DS)

MA 44.4: Vortrag

Donnerstag, 29. März 2012, 17:30–17:45, H 1012

Theoretical study of dynamical switching of a single spin by exchange forces — •Robert Wieser¹, Vasile Caciuc², Cesar Lazo³, Hendrik Hölscher⁴, Elena Y. Vedmedenko¹, Roland Wiesendanger¹, and Stefan Heinze³ — ¹Institut für Angewandte Physik, Universität Hamburg, D-20355 Hamburg, Germany — ²Peter Grünberg Institut (PGI-1) and Institute for Advanced Simulation (IAS-1), Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany — ³Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany — ⁴Institut für Mikrostrukturtechnik, Forschungszentrum Karlsruhe, P.O. Box 36 70, D-76021 Karlsruhe, Germany

We demonstrate the possibility to dynamically switch the spin of a single atom or molecule with the magnetic tip of an atomic force microscope due to the acting exchange forces. We choose a single transition metal benzene molecule as model system and calculate the exchange interaction with an Fe tip using density functional theory. The exchange energy displays a Bethe-Slater type behavior with ferromagnetic coupling at large tip-sample distance and antiferromagnetic coupling at closer proximity. The exchange energies reach maximum values of a few 10 meV which allows to switch single spins by overcoming the energy barrier due to the magneto-crystalline anisotropy. The spin dynamics of the system was explored by solving the time dependent Schrödinger equation with additional relaxation term. We discuss six possible scenarios, defined by the occurrence of quantum tunneling, relaxation, and tip-sample distance.