Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 57: Focused Session: Spin-Orbit Interaction at Surfafces: From the Rashba Effect to Topological States of Matter II
O 57.11: Vortrag
Donnerstag, 26. März 2009, 18:30–18:45, HSZ 02
Spin-orbit induced exchange interactions in magnetic surfaces described by first-order perturbation theory — •Marcus Heide, Gustav Bihlmayer, and Stefan Blügel — Institut für Festkörperforschung (IFF) and Institute of Advanced Simulation (IAS), Forschungszentrum Jülich, Germany
When applying the spin-orbit coupling operator Hso as a perturbation to a Schrödinger-type equation, the first-order term ∑ν ⟨ψν | Hso |ψν ⟩ vanishes for all collinear magnetic structures. Thus, the magnetocrystalline anisotropy is at least a second-order effect in the spin-orbit coupling and cannot be calculated from the expectation values of Hso. However, in systems with low magnetic and spatial symmetry these expectation values do not necessarily vanish: Non-collinear magnetic structures in surface geometries allow for magnetic interactions of Dzyaloshinskii-Moriya type, that are first order in Hso. These interactions can have a significant impact on the magnetic structure of low-dimensional magnets [M. Bode et al., Nature 447, 190 (2007)].
In this talk, we investigate the role of the spin-orbit coupling in ultrathin Fe and Mn films on transition metal surfaces in the framework of density functional theory. Employing the FLEUR code (www.flapw.de), we compare the expectation values of Hso with the higher-order corrections and show that first-order perturbation theory is capable of estimating the antisymmetric exchange interactions in these systems. This allows to use simple models to relate these interactions to the electronic structure. This work is supported by DFG (BI 823/1-1) and ESF EUROCORES Programme SONS (ERAS-CT-2003-980409).