Electronic, optical, and magnetic properties of Fe-intercalated H2Ti3O7 nanotubes:: First-principles calculations and experiments

The electronic structures and optical properties of titanate nanotubes have been studied. It was shown that H2Ti3O7 is a large gap insulator with an energy gap of 3.3 eV, and Fe intercalation into the interlayer region of the layered H2Ti3O7 structure greatly reduces the band gap and improves significantly the visible light absorbtion property of this material. Detailed first-principle calculations revealed that a stable structure exists for the Fe-intercalated H2Ti3O7 structure with a formula FeHTi6O14. The intercalated Fe atoms in the interlayer region of FeHTi6O14 form a one-dimensional (1D) Fe chain along [010], and the overlapped Fe-3d(z)(2) orbitals along the channel result in a delocalized 1D band below the Fermi level extending the absorption edge of FeHTi6O14 well into the visible region. This 1D Fe chain also results in a large exchange splitting between the majority and minority spins, making FeHTi6O14 a promising magnetic insulator with interesting magnetic properties.