Edge-Induced Room-Temperature Ferromagnetism in Carbon Nanosheets

Introducing ferromagnetism in two-dimensional (2D) carbon-based materials, which contain only s–p electrons, is of essential and practical importance. Here, room-temperature ferromagnetism is realized macroscopically in carbon nanosheets (CNs). The scalable CNs without magnetic impurities are prepared through a one-step Wurtz reaction and have amorphous structure with crystallized graphene nanocrystals inside. The zigzag edges of those nanocrystals in CNs can show ferromagnetic coupling even above room temperature and yield a saturation magnetization of ∼0.22 emu/g which is 2 orders of magnitude larger than reported values in defective graphite. Moreover, the results from both first-principle calculation and controllable experiments show that the magnetic properties of CNs were dominated by the distance between zigzag edges. With decreasing interedge distance from 3.6 to 0.8 nm, the ferromagnetism descends and even disappears, implying a switch of magnetic coupling between zigzag edges from ferromagnetic to the antiferromagnetic configuration. These findings provide a viable route for macroscopic realization of 2D graphene-based magnetic materials, which are useful in low dimensional spintronic devices.