Electronic and Magnetic Properties of Nanographites

This chapter discusses electronic and magnetic properties of nanographites. Nanometer-sized systems with open boundaries called nanographites display unusual features where the presence of edges of various shapes determines the electronic states. It is found that the electronic states are strongly influenced by the existence and shape of graphite edge. Zigzag edges produce the localized edge states, which give a sharp peak in the density of states at the Fermi energy. The orbital magnetic susceptibility of nanographites has the intermediate values between those of aromatic molecules and bulk graphites. The orbital magnetic susceptibility can be scaled as a function of the Fermi energy, temperature, and ribbon width. Zigzag ribbons show the large Pauli paramagnetic response at low-temperature due to the existence of the sharp peak in the density of states at the Fermi energy, whereas, in armchair ribbons, the Pauli paramagnetic susceptibility is negligible. It is found that in the activated carbon fiber and graphitized nanodiamonds, the dangling bonds are terminated by other elements. Their magnetic susceptibility shows the Curie–Weiss behavior originating from localized spins. Results suggest that in nanographite systems, the paramagnetic response due to the nonbonding edge states are crucial, resulting in the nonographites assigning completely different systems from bulk graphites and aromatic molecules in the viewpoint of the magnetic properties.