Annealing temperature dependent non-monotonic d0 ferromagnetism in pristine In2O3 nanoparticles

Cubic bixbyite In2O3 nanoparticles with room temperature d0 ferromagnetism were prepared by sol-gel method with the air annealing temperature ranging from 500 to 900°C. X-ray diffraction, X-ray photoelectron spectroscopy, Raman-scattering and photoluminescence were carried out to demonstrate the presence of oxygen vacancies. The lattice constant, the atomic ratio of crystal O and In, the Raman peak at 369cm−1, the PL emission peak at 396nm and the saturation magnetization of d0 ferromagnetism all had a consistent non-monotonic change with the increasing annealing temperature. With further considering the relation between the grain size and the distribution of oxygen vacancies, we think that d0 ferromagnetism in our samples is directly related with the singly charged oxygen vacancies at the surface of In2O3 nanoparticles.