A Study on the Weak Ferromagnetism of Nanocrystalline Stannous Oxide Induced by L-Shaped O–Sn–O Vacancies

Nanocrystalline stannous oxide (SnO) powder has been prepared by ball-milling of micrometer-SnO in a nitrogen atmosphere. A cation deficiency of 6.5% was found in the nano-SnO sample by X-ray photoelectron spectroscopy. After annealing at 350, 450, or 550 °C under dynamic vacuum conditions, oxygen vacancies were found in the nano-SnO samples, as verified by electron paramagnetic resonance experiments. The samples displayed weak ferromagnetism; the sample with both 6.5% Sn and at least 7.5% O vacancies showed the maximum saturation magnetization, reaching almost 1.7 × 10–3 emu/g at room temperature. The O vacancies tended to gather around Sn vacancies. An L-shaped defect model composed of one Sn and two O vacancies has been established, and its ferromagnetism has been calculated by a first-principles method. We found that the L-shaped defect induced a magnetic moment of 0.55 μB in the SnO lattice, the main contribution to which came from a spin-polarized electron in the p orbital of a corner Sn atom.