Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 63: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles IV (jointly with TT)
O 63.10: Vortrag
Donnerstag, 29. März 2012, 13:00–13:15, HE 101
Origin of magnetism and qausiparticle properties of Cr-doped rutile and anatase TiO2 — •Fabiana Da Pieve1,2,3, Sergio Di Matteo4, Tonatiuh Rangel2,3, Matteo Giantomassi2,3, Gian-Marco Rignanese2,3, and Xavier Gonze2,3 — 1EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium — 2Unité NAPS, Université Catholique de Louvain,Place Croix du Sud 1, 1348 Louvain-la-Neuve, Belgium — 3ETSF, European Theoretical Spectroscopy Facility — 4Groupe theorique Departement Materiaux et Nanoscience Institut de Physique de Rennes,UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex, France
We studied magnetic ground-state properties, band gaps and quasiparticle excitations in the rutile and anatase phases of Cr-doped TiO2, by combining LSDA+U ab-initio calculations and many-body GW perturbative corrections to LSDA+U results. The position of Cr-impurity states and band gaps found by GW on top of LSDA+U is in good agreement with available experimental data. The magnetic ground-state is characterized by a different geometrical coordination of Cr-ions in rutile and in anatase: interestingly, these constraints, due to correlated hopping (superexchange, direct exchange or F-center exchange) lead to ferromagnetic or antiferromagnetic couplings of Cr-ions depending on the number of O vacancies. We suggest two key experiments that could confirm our calculations by measuring directly Cr-t2g states, which play a central role in our model and in optical properties.