Structural, optical, and magnetic properties of polycrystalline Co-doped TiO2 synthesized by solid-state method

Highlights: ► Influence of Co doping on the TiO2 tetragonal structure. ► Decrease of the energy band gap after doping with Co atoms. ► Appearance of ferromagnetism in Co-doped TiO2 diluted magnetic semiconductors. - Abstract: We have used a solid-state method to synthesize polycrystalline Co-doped TiO2 diluted magnetic semiconductors (DMSs) with Co concentrations of 0, and 0.5 at.%. X-ray diffraction patterns reveal that Co doped TiO2 crystallizes in the rutile tetragonal structure with no additional peaks. Transmission electron microscopy (TEM) did not indicate the presence of magnetic parasitic phases and confirmed that Co ions are uniformly distributed inside the samples. Optical absorbance measurements showed an energy band gap which decreases after doping with the Co atoms into the TiO2 matrix. Magnetization measurements revealed a paramagnetic behavior for the as-prepared Co-doped TiO2 and a ferromagnetic behavior for the same samples after annealed under a mixture of H2/N2 atmosphere.