Spin ordering in oxide nanoclusters without magnetic element atoms

•Different spin orderings found in SinO2n+x clusters.•Spins are located on excessive oxygen atoms on cluster surface.•Magnetism is analyzed via Stoner-like criterion for nanoscale non-metal systems. The calculations of spin effects in 20 SinO2n+m nanoclusters with 10⩾m⩾5 and m⩾1 are presented. They include search for the equilibrium atomic structure, the calculations of electron spectra and the energy of different spin orderings. It was found that all SinO2n+m clusters have spin moments, which are located on radical O atoms at the cluster surface. Long radical-to-radical distance weakens their exchange interaction, so energy differences between ferro-, ferri-, and antiferromagnetic states are of 0.01 eV or lower, gaining 0.046 eV only in Si6O13. We analyze this magnetism in terms of electron spectra and individual radical groups. Its similarity to popular molecular magnets based on organic radicals is noticeable. The stability of these SinO2n+m clusters in O2 atmosphere, as well as their relation to silicon technology, is of particular interest for spintronics.