Ferromagnetism in Cr-, Fe-, and Ni-doped TiO2 samples

Ferromagnetic Cr-, Fe-, and Ni-doped TiO2 nanopowder samples (with 0.2% Cr, Fe, or Ni) were synthesized using the solid-state reaction method. The X-ray diffraction pattern showed that all the samples possessed typical anatase structure, and no other impurity phases were observed. Ultraviolet-visible spectroscopy (UV-vis) measurements revealed that the band gap decreased due to the incorporation of Cr, Fe, or Ni. The photoluminescence results showed the presence of oxygen defect related emission peaks in Cr-, Fe-, and Ni-doped TiO2. Room temperature ferromagnetism is observed in all the Cr-, Fe-, and Ni-doped TiO2 samples. Saturation magnetic moment is the highest for Fe- doped TiO2. The Fe: TiO2 samples were found to have a magnetic moment of 4.58 mu(B)/Fe, and they seem to have greater ferromagnetism than the Cr/Ni-doped TiO2 samples. The structural and magnetic investigations demonstrate that ferromagnetism at room temperature is an intrinsic property of the samples. Thus, ferromagnetism does not originate from clusters or secondary phases; it is due to the Cr/Fe/Ni:TiO2 matrices. This study has shown that substituting a very light percentage of Cr, Fe, or Ni for Ti in TiO2 gives rise to appreciable room temperature ferromagnetic ordering useful for spintronic applications. (C) 2017 Elsevier B.V. All rights reserved.