Defect-mediated ferromagnetism in insulating Co-doped anatase TiO2 thin films

Journal Article · Tue Jul 01 04:00:00 EDT 2008 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.78.014409· OSTI ID:934934

Griffin, K. A. ^[1]; Varela del Arco, Maria ^[2]; Rashkeev, Sergey ^[2]; Pantelides, Sokrates T. ^[3]; Pennycook, Stephen J ^[2]; Krishnan, Kannan M. ^[1]

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1. University of Washington, Seattle
2. ORNL
3. Vanderbilt University, Nashville

The room temperature ferromagnetism recently discovered in transition metal doped oxides makes of them unique materials for new spintronic technologies. However, the mechanism responsible for this behavior has remained elusive. Here we use Z-contrast scanning transmission electron microscopy to image the Co and find that the magnetic phase in Co doped TiO2 films consists of a superstructure of interstitial Co atoms homogeneously distributed in the anatase lattice. Detailed analysis of the energy-loss near edge structure at the Ti L2,3 edge shows that the activation of ferromagnetism by post growth vacuum annealing involves the creation of Co - Ti3+- oxygen vacancy defect complexes. First-principles, spin-polarized density functional theory calculations confirm that these defect complexes have the lowest energy configuration and that their magnetic moment is in agreement with experimental observations.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 934934
• Journal Information: Physical Review B, Journal Name: Physical Review B Journal Issue: 1 Vol. 78
• Country of Publication: United States
• Language: English