Berlin 2012 – wissenschaftliches Programm
MA 18.9: Vortrag
Dienstag, 27. März 2012, 11:45–12:00, H 0112
Transition metal doped ZnO: Studies from DFT with various types of exchange-correlation treatment — •Sanjeev K. Nayak, Markus E. Gruner, Heike C. Herper, and Peter Entel — Faculty of Physics, University of Duisburg-Essen
Transition metal (TM) doped ZnO has been a long-standing problem. Since the density functional theory (DFT) with local density approximation (LDA) as the exchange-correlation potential underestimates the optical band gap, the impurity state is more likely to overlap with the valence or conduction band and thus the identification of the type of magnetic interaction is hampered. We have used different correction schemes to the exchange-correlation potential to improve the optical band gap of ZnO, namely by adding a orbital specific Hubbard U correlation to the d-orbitals of Zn and TM and by treating the exchange-correlation by the Hartree-Fock exchange through the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid-functional. We focus on the nearest neighbor (n.n.) interactions of TM (TM = Cr, Mn, Fe, Co and Ni) occupying the cationic Zn sites, because in absence of carriers and any lattice defects the n.n. magnetic interaction strength is expected to be the highest. Our preliminary results show that most of the TM in ZnO favor antiferromagnetic interaction. Thus, in the quest for ferromagnetism in ZnO based DMS, focus should be on the role of lattice defects and additional impurities.