Realization of Ambient-Stable Room-Temperature Ferromagnetism by Low-Temperature Annealing of Graphene Oxide Nanoribbons.

Graphene oxide nanoribbons (GONRs) annealed at the low temperature of 400 °C (aGONRs-400) are developed as an excellent room-temperature (RT) ferromagnet. The saturated magnetization ( Ms) of aGONRs-400 is high, up to 0.39 emu/g at room temperature, and the RT ferromagnetism (FM) exhibits excellent ambient stability with Ms preserved for over half a year. The preferential distribution of the magnetic phenolic hydroxyl toward the edges, which contributes to the long-range ferromagnetic couplings, was confirmed by X-ray photoemission spectroscopy measurement and gradient annealing analysis. The approach of low-temperature annealing is proved to be efficient both to remove the prominent nonmagnetic epoxy groups on the basal plane of GONRs or transform them to magnetic hydroxyl groups and to preserve the magnetic phenolic hydroxyl at the edges to realize a strong and ambient stable FM.