Intrinsic defect-mediated magnetism in Fe–N codoped TiO2

• TiO2 nanotube films doped with Fe and N were synthesized by anodic oxidation.
• Magnetic properties of samples were investigated by first-principles calculations.
• The values of the net magnetic moment: Fe–N doped > Fe doped > TiO2 > N doped TiO2.
• The ferromagnetism derived from the spin-split of O 2p, Ti 3d and Fe 3d.
• The ferromagnetisms of samples are strongly correlated with the oxygen vacancies.

In this paper, we investigated room temperature magnetic properties of Fe–N codoped, undoped, Fe doped, and N doped TiO2 samples combing by experiments and first-principles calculations. All the samples fabricated by a two-step anodic oxidation method exhibit the crystal phase of anatase with the shape of nanotube. The calculated net moment values are in the order of Fe–N codoped TiO2 > Fe doped TiO2 > undoped TiO2 > N doped TiO2 with oxygen vacancies existing, which are in accord with the experimental results. The hybridization of Fe 3d, Ti 3d (nearest to the oxygen vacancies) and O 2p (nearest to the Fe defect) led to the spin-split of Fe 3d, Ti 3d and O 2p which devoted to the magnetism. The codoping of oxygen vacancies, N and Fe led to the complete spin-split of Fe 3d, Ti 3d and O 2p for Fe–N codoped TiO2 samples which yield the highest saturation magnetization.

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