Room-temperature ferromagnetism in graphitic petal arrays

We report room-temperature ferromagnetism of graphitic petal arrays grown on Si substrates by microwave plasma chemical vapor deposition without catalyst. The samples have been characterized by Raman and X-ray photoelectron spectroscopy to confirm the absence of possible ferromagnetic impurities. The petals exhibit ferromagnetic hysteresis with saturation magnetization of similar to 4.67 emu cm(-3) and coercivity of similar to 105 Oe at 300 K, comparable to the reported behavior of few-layer graphene. Upon O-2 annealing the saturation magnetization and coercivity decreased to 2.1 emu cm(-3) and similar to 75 Oe respectively. The origin of ferromagnetism is believed to arise from the edge defects and vacancies in the petals.