Interplay of dopants and defects in magnetic evolution of La and Fe co-doped TiO 2 nanoparticle

Abstract

La and Fe co-doped titanium dioxide nanoparticles with various La concentrations have been synthesized by sol–gel method. All the samples were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy, Fourier transform infrared and magnetic measurement techniques, respectively. The results show that both La and Fe ions have doped into the titanium dioxide lattice, and no secondary phases including La and Fe ions were detected. The magnetic results demonstrated that the prepared La and Fe co-doped titanium dioxide samples had complex magnetic mechanism including room-temperature ferromagnetic and paramagnetic behaviors. The room temperature ferromagnetic behavior decreases while paramagnetic contribution increases with the increasing of La content. The magnetic properties are possibly due to the ferromagnetic coupling between two neighboring Fe3+ ions via oxygen vacancy (F+ center) by forming bound magnetic polarons. Increase in La concentration decreases the proportion of oxygen vacancy, and thereby decreases the ferromagnetic behavior, thus increases the paramagnetic ordering.