Ferromagnetism in sp^(2) carbon

The bulk,pristine sp^(2) carbons,such as graphite,carbon nanotubes,and graphene,are usually assumed to be typical diamagnetic materials.However,over the past two decades,there have been many reports about the ferromagnetism in these sp^(2) carbon materials,which have attracted intense interest for basic research and potential applications.In this review,we focus on the evidence and developments of the emergent ferromagnetism in sp^(2) carbon revealed by nine kinds of experimental methods:magnetic force microscopy(MFM),magnetization measurements with physical property measurement system(PPMS),X-ray magnetic circular dichroism(XMCD),scanning tunneling microscopy(STM),miniaturized magnetic particle inspection(MPI),anomalous Hall effect(AHE),mechanical deflection of carbon nanotube cantilevers,magnetoresistance,and spin-related devices(spin field effect transistor and spin memory).The advantages,conclusions,challenges,and future of these methods are discussed.The ferromagnetism in sp^(2) carbon will open a door to explore exotic physical phenomena and lay the basis for the development of integrated circuit of spintronics,which is fundamentally different from charge-based conventional electronics.