Observation of room temperature ferromagnetism in pure La2O3 nanoparticles

In this paper, we report the observation of intrinsic room temperature ferromagnetism in pure La2O3 nanoparticles. Magnetism measurement indicates that all of the samples exhibit room temperature ferromagnetism and the saturation magnetization for the samples decreases with the increase in annealing temperature from 700 to 1,000 degrees C. X-ray photoelectron spectroscopy identifies the presence of oxygen vacancies in the La2O3 nanoparticles. The fitting results of the O 1s spectrum indicate that the variation of the oxygen vacancy concentration is in complete agreement with the change of the saturation magnetization. It is also found that the saturation magnetization of the La2O3 nanoparticles can be tuned by post-annealing in argon or oxygen atmosphere. These results suggest that the oxygen vacancies are largely responsible for the room temperature ferromagnetism in pure La2O3 nanoparticles.