Enhancing the ferromagnetization of graphite by successive 12C+ ion implantation steps

C-12(+) ion implantation has been shown to be an efficient way to increase the magnetization of highly oriented pyrolytic graphite, and a saturation magnetization of 17.6 emu g(-1) at room temperature has been produced. The implantation was performed in four steps with decreasing ion energy for each step. Increasing the magnetization with the number of implantation steps has shown that the magnetization is correlated to the defect density. The temperature dependence of spin susceptibility calculated according to the electron spin resonance spectra indicates that the magnetism in the sample is intrinsic. The evolution of Raman spectra along with the degree of implantation supplied further evidence to the correlation between in-plane defects and the magnetization of the sample, and explained the decreased magnetization resulting from the final implantation step. (C) 2011 Elsevier Ltd. All rights reserved.