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O: Oberflächenphysik

O 26: Oxide und Isolatoren I

O 26.1: Vortrag

Samstag, 5. März 2005, 15:00–15:15, TU EB202

Jahn-Teller stabilization of a “polar” metal oxide surface: Fe₃O₄(001) — •Rossitza Pentcheva, Wolfgang Moritz, and Matthias Scheffler — Section Crystallography, Dept. of Earth and Environmental Sciences, LMU München

We present a systematic investigation of the composition, structure and properties of the Fe₃O₄(001)-surface based on density-functional theory (DFT). Using ab initio atomistic thermodynamics [1] we predict that a “polar” termination is the lowest energy configuration over the entire range of accessible oxygen pressures. The stabilization of the surface involves a fundamentally different mechanism, which has not been considered so far: While most of the previous studies proposed an ordering of surface vacancies as the origin of the experimentally observed (√2× √2)R45^∘-reconstruction, here it is explained as a Jahn-Teller distortion of the surface atoms forming a wave-like pattern along the [110]-direction. Both x-ray diffraction (XRD) [2] and low energy electron diffraction (LEED-I/V) analyses support the theoretically predicted model. Calculated STM images and surface core level shifts are compared to available experimental data. The predicted halfmetal-to-metal transition from bulk to the surface is relevant in view of future applications (e.g. in spintronic devices). [1] K. Reuter and M. Scheffler, Phys. Rev. B 65, 035406, (2002). [2] R. Pentcheva, F. Wendler, N. Jedrecy, H.L. Meyerheim, W. Moritz, and M. Scheffler, submitted to Phys. Rev. Lett.