Regensburg 2010 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 29: Magnetic Semiconductors I

MA 29.1: Vortrag

Donnerstag, 25. März 2010, 15:15–15:30, H22

Defect pairing and magnetism in C or N-doped MgO and ZnO: a density-functional study — •Peter Kratzer¹, Hua Wu², Sung Sakong¹, Xin-Gao Gong³, and Matthias Scheffler⁴ — ¹Fakulät für Physik, Universität Duisburg-Essen, D-47048 Duisburg, Germany — ²II. Physikalisches Institut, Universität zu Köln, D-50937 Köln, Germany — ³Fudan University, Shanghai, China — ⁴Fritz-Haber-Institut der MPG, D-14195 Berlin, Germany

It is demonstrated that C or N doping recently proposed as a way to create magnetism in otherwise nonmagnetic oxide insulators is curtailed by formation of defect pairs. Our density-functional calculations show that N-N pairing in MgO lowers the energy by 0.4 eV, leading to a nonmagnetic state. C-C pairing is even exothermic by more than 3 eV, and the resultant (C-C)⁴⁻ molecules with spin=1 couple antiferromagnetically in MgO. However, calculations for C-doped ZnO, when properly treated using the PBE0 hybrid functional, show that the spin-polarized ppπ^* levels resonate with the host conduction band, which could possibly mediate a long-range ferromagnetic order. Magnetism of open-shell impurity molecules is proposed as a possible route to d⁰-ferromagnetism in oxide spintronic materials.