Indium vacancy induced d0 ferromagnetism in Li-doped In2O3 nanoparticles

Highlights: • Effects of Li doping on the d⁰ ferromagnetism in In₂O₃. • The preferred occupation of Li varies from Li_In to Li_i with the increasing dopant. • As the content of Li increases, ferromagnetism changes non-monotonically. • d⁰ ferromagnetism in Li-doped In₂O₃ is related with V_In due to Li-doping. Li-doped In₂O₃ nanoparticles with room temperature d⁰ ferromagnetism were prepared by a sol-gel method. X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence were carried out to investigate the effects of Li incorporation on the lattice defects. As the content of Li increases, non-monotonic changes in shifts of XRD peak (2 2 2) and the intensity ratios of indium vacancies related photoluminescence peak (P_II) with respect to oxygen vacancies related peak (P_I) are observed. Results show that at low doping level (≤2 at.%) Li prefers to occupy In sites, while with further doping the interstitial sites are more favorable for Li. Combined with the consistent non-monotonic change in saturation magnetization, we think that indium vacancies resulting from Li-doping play an important role in inducing d⁰ ferromagnetism in our Li-doped In₂O₃ nanoparticles, and the FM coupling is mainly mediated by the Li_In-O_NN-V_In-O_NN-Li_In chains.