Nano-precipitates induced room temperature ferromagnetism in heavily Nb-doped titania thin films.

Room temperature ferromagnetism (FM) is observed for annealed heavily niobium doped titania (TNO) thin films on silicon substrates and on glass nanospheres. Precipitation of ~10–30nm-diameter Nb2O5 nanoparticles occurs in the TNO films air-annealed at 600°C or above and enhances their saturation magnetization (Ms). The largest Ms is found in the 800°C annealed 40nm-thick TNO films on glass nanospheres (~6×104 A/m) and the Ms reduces as films increased in thickness or deposited on flat Si substrates or annealed at lower temperature or in hydrogen. This work demonstrates that nano-precipitates and interfaces are both significant factors in achieving enhanced FM in the titania based thin films. [ABSTRACT FROM AUTHOR]