Influence of single-ionized oxygen vacancies on the generation of ferromagnetism in SnO2 and SnO2:Cr nanowires

Abstract

In this work, we report the influence of single-ionized oxygen vacancies (V^{prime}_{{text{O}}}) as a spin ½ system in the ferromagnetic response of undoped and Cr-doped SnO2 nanowires. For this study, undoped and Cr-doped SnO2 nanowires were synthesized by a thermal evaporation method. Raman, Auger, and X-ray photoelectron spectroscopies confirmed the incorporation of Cr3+ ions in the SnO2 lattice. Electron paramagnetic resonance measurements demonstrated the presence of single-ionized oxygen vacancies (V^{prime}_{{text{O}}}) in undoped and Cr-doped nanowires. Complementarily, cathodoluminescence measurements confirmed the presence of VO defects in the samples. Magnetic measurements revealed FM behavior from the undoped SnO2 and Cr-doped SnO2 nanowires, showing magnetization saturation values (MS) of ± 1 × 10–3 and ± 1.6 × 10–3 emu/g, respectively, and magnetic coercivity values (HC) of 180 and 200 Oe. We assign the FM response of nanowires to the presence of single ionized V^{prime}_{{text{O}}} acting as a spin ½ system and to the alignment of magnetic moments of Cr3+ ions, finding that V^{prime}_{{text{O}}} defects dominate in the FM generation.