Electronic and magnetic properties of nanographite ribbons

Electronic and magnetic properties of ribbon-shaped nanographite systems wi th zigzag and armchair edges in a magnetic field are investigated by using a tight-binding model. One of the most remarkable features of these systems is the appearance of edge states, strongly localized near zigzag edges. Th e edge state in a magnetic field, generating a rational fraction of the mag netic flux (phi = p/q) in each hexagonal plaquette of the graphite plane, b ehaves like a zero-field edge state with q internal degrees of freedom. The orbital diamagnetic susceptibility strongly depends on the edge shapes. Th e reason is found in the analysis of the ring currents, which are very sens itive to the lattice topology near the edge. Moreover, the orbital diamagne tic susceptibility is scaled as a function of the temperature, Fermi energy , and ribbon width. Because the edge states lead to a sharp peak in the den sity of states at the Fermi level, the graphite ribbons with zigzag edges s how Curie-like temperature dependence of the Pauli paramagnetic susceptibil ity. Hence, there is a crossover from high-temperature diamagnetic to low-t emperature paramagnetic behavior in the magnetic susceptibility of nanograp hite ribbons with zigzag edges. [S0163-1829(99)02111-6].