Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 4: Electron Theory of Magnetism
MA 4.11: Vortrag
Montag, 26. März 2007, 12:45–13:00, H23
On the theory of x-ray absorption spectroscopy in solids: Mixing of the core states by the aspherical effective potential — •Christos Kostoglou1, Matej Komelj2, and Manfred Fähnle1 — 1Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart — 2Jožef Stefan Institute, Jamova 39, SI 1000 Ljubljana, Slovenia
For the early transition metals the spin-orbit splitting of the 2p1/2 and the 2p3/2 core states is rather small. As a consequence, the 2p1/2 and 2p3/2 excitations by x-ray absorption at the L edges exhibit a quantum mechanical mixing which has an influence on the x-ray absorption spectrum. The main source for this mixing is a many-electron effect, i.e., the Coulomb interaction between the core hole (created by the absorption) and the valence electron. We discuss another possible source which so far has never been quantified and which is a one-electron contribution, i.e., the mixing of the two core states by the aspherical part of the static effective potential. We calculate the influence of this mixing on the x-ray magnetic dichroism spectrum of CrO2 within the framework of the pertubation theory for nearly-degenerate states and within the ab-initio density functional electron theory in the LDA+U version. It turns out that the effect of this type of mixing on the spectrum is rather small.