Magnetism in graphite induced by irradiation of hydrogen or helium ions - A comparative study

To identify the origin of defect-induced magnetism in ion-irradiated graphite, a comparative study of samples of graphite irradiated with hydrogen H+ and helium He+ ions is performed. Directionally dependent magnetic properties, atomic/magnetic force microscopy studies suggest that the induced magnetic moments are located along the vertically aligned grain boundaries. Compared to the case of the hydrogen ion irradiation, the optimal helium irradiation dose is an order of magnitude lower. From this we conclude that the hydrogen chemistry is essentially irrelevant, and the ferromagnetic-like response of the irradiated graphite is due to structural defects regardless of their origin. [GRAPHICS] Surface of HOPG irradiated with H+ and He+ at similar doses. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim