Room temperature ferromagnetism and phonon properties of pure and doped TiO2 nanoparticles

Abstract We have considered the origin of RTFM in TiO 2 nanoparticles (NPs). Further we have studied the properties of the E g 1 phonon mode. The phonon frequency of anatase TiO 2 NPs increases whereas in the case of rutile TiO 2 NPs it decreases as the particle size decreases. The phonon damping is always enhanced in the nanosized materials. The hardening of the E g 1 mode and the softening of the E g 3 mode in anatase TiO 2 NPs could be explained with the different anharmonic spin–phonon interaction constants of these modes. The doping effects with different transition metal ions on the E g 1 phonon mode are also discussed.