Dresden 2009 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 8: Magnetic Coupling Phenomena / Exchange Bias

MA 8.4: Vortrag

Montag, 23. März 2009, 16:00–16:15, HSZ 401

Oscillatory indirect exchange in adatom pairs and triplets — •Jens Wiebe¹, Lihui Zhou¹, Samir Lounis², Elena Y. Vedmedenko¹, Focko Meier¹, Peter H. Dederichs², Stefan Blügel², and Roland Wiesendanger¹ — ¹Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg — ²Institut für Festkörperfoschung and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich

Impurity spins in nonmagnetic metals induce an oscillatory spin-polarization in the conduction electrons, which mediates an alternately ferro- and anti-ferromagnetic coupling between two impurities. This "indirect magnetic exchange" is well known from layered systems investigated in the course of the discovery of the GMR effect and crucially depends on the atomic discreteness within the ferro- and the non-magnetic spacer layers [1]. Here, we measure the indirect exchange between two Co adatoms on a Pt(111) surface with distances of several lattice spacings and compare to calculations using the full-potential Korringa-Kohn-Rostoker method. We have straight experimental access to the exchange energies by measuring the magnetization of each adatom as a function of an applied magnetic field (single-atom magnetization curves [2]) and compare to Monte-Carlo simulations. Indeed, we observe a damped oscillatory behaviour with coupling strengths on the order of 0.1meV reproduced by the calculations. Additionally, we demonstrate magnetic frustration in adatom triplets with almost equilateral shape. [1] P. Bruno and C. Chappert, Phys. Rev. B 46, 261 (1992). [2] F. Meier et al., Science 320, 82 (2008).