Room temperature superparamagnetism in rutile TiO2 quantum dots produced via ECR sputtering

Nanostructures (NS) have been fabricated on rutile TiO2(1 1 0) single crystal surfaces using Ar ion beam sputtering technique. Pronounced quantum confinement effects in TiO2 nanodots lead to reduction in optical reflectance and bandgap widening. Moreover, a direct correlation between the size of NS and magnetic behavior is observed. This suggests that the size of NS plays crucial role in the evolution of magnetic nature. Though the smallest (∼5 nm) NS display superparamagnetic (SPM) behavior, ferromagnetism is observed for larger nanostructures. Single domain nature of TiO2 quantum dots is responsible for the observed SPM behavior.