Origin of magnetism and quasiparticles properties in Cr-doped TiO 2

F. Da Pieve, S. Di Matteo, T. Rangel, M. Giantomassi, D. Lamoen, G. M. Rignanese, X. Gonze

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25 Citations (Scopus)

Abstract

Combining the local spin density approximation (LSDA)+U and an analysis of superexchange interactions beyond density functional theory, we describe the magnetic ground state of Cr-doped TiO2, an intensively studied and debated dilute magnetic oxide. In parallel, we correct our LSDA+U (+ superexchange) ground state through GW corrections (GW@LSDA+U) that reproduce the position of the impurity states and the band gaps in satisfying agreement with experiments. Because of the different topological coordinations of Cr-Cr bonds in the ground states of rutile and anatase, superexchange interactions induce either ferromagnetic or antiferromagnetic couplings of Cr ions. In Cr-doped anatase, this interaction leads to a new mechanism which stabilizes a (nonrobust) ferromagnetic ground state, in keeping with experimental evidence, without the need to invoke F-center exchange. The interplay between structural defects and vacancies in contributing to the superexchange is also unveiled.

Original languageEnglish
Article number136402
JournalPhysical Review Letters
Volume110
Issue number13
DOIs
Publication statusPublished - 25 Mar 2013
Externally publishedYes

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