Ferromagnetism and Disorder in Graphene.

Magnetic correlations in carbon-based materials have been reported for many years, but the lack of reproducibility have aroused scepticism about this topic. However, in recent years, the improvement of the characterization techniques has allowed the observation of ferromagnetism and the precise measurement of the impurity amounts in different samples of HOPG and Kish graphite [1]. Besides the ferromagnetic hysteresis loops [2] reported at room temperature, the enhancement of ferromagnetic behavior by proton bombardment of graphite has been observed in samples with an amount of impurities much lower than that needed to produce the saturation magnetization measured [3]. Irradiation induced magnetism in carbon nanostructures has been reported by N and C implantation [4]. A relation between the magnetic properties of pure bulk ferromagnetic graphite and the topographic defects introduced in the pristine material have been reported by comparison of atomic force microscopy (AFM) images and magnetic force microscopy (MFM) [5]. Soft X-ray dichroism spectromicroscopy has been used to analyze the magnetic order of metal free carbon films. A clear evidence of intrinsic ferromagnetic order at room temperature has been obtained in these carbon films that have been irradiated by a focused proton beam [6]. All these experiments suggest that there is a relation between topological defects in the lattice induced by irradiation and the ferromagnetic correlations [6]. We will study the ferromagnetism in a two-dimensional graphene plane by considering disorder, vacancies, and defects in the atomic network. [ABSTRACT FROM AUTHOR]