Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1867868 | Physics Letters A | 2008 | 5 Pages |
Abstract
The room-temperature ferromagnetism demonstrated by Co-doped TiO2 films remains a challenge to our understanding, notwithstanding intensive experimental and theoretical investigations. We have calculated the binding energy and spin-polarization of Co atoms doped in the rutile TiO2 (110) surface using first-principles method, aiming to elucidate the relationship between structure and magnetism of Co-doped TiO2 films. In a defect-free surface the binding energy of Co substituting for Ti reduces slightly with the depth into the surface, suggesting a very minor Co depletion near the surface. More interestingly, the stability of ferromagnetic coupling over anti-ferromagnetic coupling of Co atoms decreases rapidly when it goes from surface to the bulk region. The residual ferromagnetism in the surface will give rise to a non-vanishing average magnetic moment of the thin film. The calculated pairing energy of Co is 0.12 eV/Co in the surface layer and 0.20 eV/Co in the middle layer of the film, an indication that Co atoms have a tendency to aggregate in both regions and that pairing will not modify the Co concentration in the direction vertical to the surface.
Related Topics
Physical Sciences and Engineering
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Physics and Astronomy (General)
Authors
X.G. Xu, Y. Jiang, G.H. Yu, Q.L. Liu, W.T. Geng,