Edge ferromagnetism of graphene oxide

Using SQUID magnetometry and ferromagnetic resonance we show that the intrinsic ferromagnetism in graphene oxide (GO) is related to the zigzag edges created by breaking GO layers in the process of exfoliation. The 1D magnetic order existing below 2 K is destroyed by spin fluctuations enhanced by spin-flip transitions of the magnetic moments of protons from hydroxyl groups. Dipole-dipole interactions between short ordered segments at zigzag edges result in superferromagnetism below 65 – 75 K and superparamagnetism at higher temperatures. The strong ferromagnetism is observed for GO flakes in vacuum while the weak residual ferromagnetism of GO paper is due to magnetic moments surviving in the closed pores.