Size-dependent magnetism and spin-glass behavior of amorphous NiO bulk, clusters, and nanocrystals: Experiments and first-principles calculations

A combined experimental and computational study was carried out to investigate magnetic properties of NiO nanostructures. Remarkable size-dependent magnetism was discovered. Uniform amorphous NiO showed a dominated antiferromagnetic interaction and an ordering temperature of 3.5 K. NiO clusters (up to 1 nm) tend to be ferromagnetic interaction with an ordering temperature of 35 K, accompanied by high magnetization (105 emu g) and a spin-glass behavior. NiO nanocrystals (>2 nm) were found to be antiferromagnetic with uncompensated surface magnetization and shifted hysteresis due to the core-shell interactions.