Strong ferromagnetism of reduced graphene oxide

The ferromagnetism of carbon-based materials has attracted much interest for its possible applications in spintronics devices. In this work, we studied the magnetic properties of reduced graphene oxide (rGO) obtained by high-temperature annealing of graphene oxide (GO) prepared in weak oxidizing conditions. The rGO samples exhibit strong room-temperature ferromagnetism, with saturation magnetization of 0.24 emu/g, about 24 times of the value of rGO prepared in strong oxidizing conditions. Hysteresis negative magnetoresistance (MR) has been observed in rGO, which confirms the intrinsic nature of the observed ferromagnetism. The MR value keeps nearly unchanged below 15 K, and decreases with further increasing temperature, and finally disappears at T ⩾ 50 K. At T = 5 K, the maximum MR ratio of [R(H) − R(0)]/R(0) is about −2.5%. The strong ferromagnetism is attributed to the preserved graphitic structure of weakly oxidized rGO, and the negative MR is due to the spin dependent scattering of defects.