关于石墨烯铁磁性的研究被《自然中国》选为来自中国大陆和香港的突出科学研究成果-Huang Yi

Most known magnets are made of metal. Although several metal-free organic ferromagnets have been discovered, their magnetism can only be observed at very low temperatures. Yi Huang and Yongsheng Chen at Nankai University in Tianjin and co-workers¹ believe they have now found ferromagnetism in graphene-based materials at room temperature.

The researchers first used hydrazine to reduce graphene oxide that had been dispersed in water into single-layer graphene precipitates. They then annealed the graphene precipitates at different temperatures under an argon environment to generate graphene samples.

Magnetization measurements at room temperature showed that graphene samples annealed at 400 and 600 °C had weak ferromagnetism. At very low temperatures, these graphene samples displayed even stronger ferromagnetism. However, a graphene sample that was annealed at 800 °C did not show any ferromagnetism.

The observed room-temperature ferromagnetism is likely to come from the topological defects on graphene. The researchers took great care to ensure their graphene samples were metal-free, which is critical to their conclusions. Moreover, because all samples were made from the same source material, the fact that no ferromagnetism was observed for the graphene sample annealed at 800 °C suggests that impurity is not the cause — or at least not the major cause — of the observed ferromagnetism.

The authors of this work are from:
Key Laboratory of Functional Polymer Materials and Center for Nanoscale Science and Technology, Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, China; State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China.

Reference

Yan Wang, Yi Huang*, You Song, Xiaoyan Zhang, Yanfeng Ma, Jiajie Liang, Yongsheng Chen*, Room-temperature ferromagnetism of graphene. Nano Lett., 2009, 9, 220-224.