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

Abstract

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 $3.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. NiO clusters (up to $1\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$) tend to be ferromagnetic interaction with an ordering temperature of $35\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, accompanied by high magnetization $(105\phantom{\rule{0.3em}{0ex}}\mathrm{emu}∕\mathrm{g})$ and a spin-glass behavior. NiO nanocrystals $(g2\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ were found to be antiferromagnetic with uncompensated surface magnetization and shifted hysteresis due to the core-shell interactions.