Abstract
The nanocrystalline powders of Cr-doped SnO₂ with Cr-dopant concentrations of 2, 4 and 6 wt%, were synthesized by a simple hydrothermal method. XRD results, along with the FT-IR and SAED patterns, confirmed the formation of the SnO₂’s tetragonal phase without other impurity phases. Optical analysis revealed a significant decrease in the energy gap of the doped samples from 3.69 to 3.40 eV. X-ray absorption spectroscopy, including x-ray absorption near-edge spectroscopy, was used to qualitatively investigate the valence states of doped Cr. Room temperature ferromagnetism was observed in Cr-doped SnO₂ samples. The highest value of magnetization was found in SnO₂ doped with 4 wt% of Cr (about 4.88 memu/g) and decreased slightly as the Cr concentration increased. The reduction of magnetization with the increase of Cr content happened because antiferromagnetic Cr-O-Cr super-exchange interaction took place within the nearest CrSUP3+/SUP ions through OSUP2-/SUP ions. The oxygen vacancies were induced by the ferromagnetism in the Cr-doped SnO₂ nanocrystalline powders.
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