Structures and properties of transition-metal-doped TiO₂ nanorods

Titanium dioxide (TiO₂) doped with magnetic elements is a promising candidate for the applications of spintronic devices. In this work, we have successfully synthesized rutile TiO₂ nanorods doped with a variety of transition metals (Co, Ni, Mn and Fe) through a molten salt method. XRD and Raman results indicate the effective incorporation of dopant ions into TiO₂ lattice. SEM and TEM images demonstrate that most of the samples are grown along the c-axis with the shape of nanorods except 1%Fe-doped sample. The M-H loops indicate that all the samples exhibit weak room temperature ferromagnetism. Whereas, in undoped TiO₂, diamagnetic and ferromagnetic signals are detected at room temperature and the coexistence of the paramagnetic phase is found at 5 K. It is evident that the incorporation of various dopants such as Co, Ni, Mn or Fe into TiO₂ nanostructures gives rise to paramagnetism instead of enhancing the ferromagnetic ordering.