Room-temperature ferromagnetism in nanocrystalline Cu/Cu2O core-shell structures prepared by magnetron sputtering

Abstract

Cu/Cu2O core-shell nanoparticles with diameters around 8–9 nm have been fabricated by magnetron sputtering pure Cu targets with subsequent annealing in oxygen. Room-temperature ferromagnetism (FM) was observed in the samples annealed at 150 °C for 10–120 min. The maximum of saturated magnetization is as high as 19.8 emu/cc. The photoluminescence spectra show solid evidence that the FM originates from Cu vacancies in the Cu2O shell of the Cu/Cu2O core-shell nanoparticles. Furthermore, the FM can be modulated by the amount of Cu vacancies through the Cu/Cu2O core-shell interface engineering. Fundamentally, the FM can be understood by the charge-transfer ferromagnetism model based on Stoner theory.