Oxygen deficiency induced ferromagnetism in Cr-doped TiO2 nanorods

We report the room-temperature ferromagnetism in Cr-doped TiO2 nanorods (NRs) synthesized via the hydrothermal method followed by annealing at 700°C. The transmission electron microscopy showed that the diameter of the NRs is between 40 and 70nm. X-ray diffraction, XPS and Raman technique are used to confirm the absence of magnetic contaminations of metallic Cr clusters or any other phases. To test the oxygen vacancy related ferromagnetism, annealing in oxygen, air and argon are performed. With the changing of annealing atmosphere from oxygen to argon, the saturation magnetization (Ms) of NRs increases. These results strongly prove that the oxygen vacancies play an important role in inducing the ferromagnetism. The shifting and broadening of the most intense Eg(1) mode at 144cm−1 observed by Raman spectroscopy further confirms that the origin of the ferromagnetism in NRs is due to the oxygen vacancies. ► The Cr-doped NRs have been synthesized by hydrothermal method. ► Ferromagnetism of Cr-doped TiO2 NRs is intrinsic property. ► Room-temperature ferromagnetism observed in all the annealed Cr-doped NRs. ► Variation in Ms is attributed due to oxygen vacancies.