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

In this work, we report the influence of single-ionized oxygen vacancies (V'(O)) as a spin 1/2 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'(O)) in undoped and Cr-doped nanowires. Complementarily, cathodoluminescence measurements confirmed the presence of V-O defects in the samples. Magnetic measurements revealed FM behavior from the undoped SnO2 and Cr-doped - SnO2 nanowires, showing magnetization saturation values (M-S) of +/- 1 x 10(-3) and +/- 1.6 x 10(-3) emu/g, respectively, and magnetic coercivity values (H-C) of 180 and 200 Oe. We assign the FM response of nanowires to the presence of single ionized V'(O) acting as a spin 1/2 system and to the alignment of magnetic moments of Cr3+ ions, finding that V'(O) defects dominate in the FM generation.