The edge structure and width of graphene nanoribbons (GNRs) are crucial factors for the electronic properties. A combination of experiment and first-principles calculations allows us to determine the mechanism of the hexagonhexagon to pentagon-heptagon transformation. GNRs thinner than 2 nm have been fabricated by bombardment of graphene with high-energetic Au clusters. The edges of the GNRs are modified in situ by electron irradiation. Tensile strain along the edge decreases the transformation energy barrier. Antiferromagnetism and a direct band gap are found for a zigzag GNR, while a fully reconstructed GNR shows an indirect band gap. A GNR reconstructed on only one edge exhibits ferromagnetism. We propose that strain is an effective method to tune the edge and, therefore, the electronic structure of thin GNRs for graphene-based electronics.

A model is introduced in this paper to describe the transition boundaries in perpendicular magnetic recording at extremely high density. In contrary to the previous signal generation models, effects of magnetization transition curvature and the track edge fluctuations are adequately included in the new model that is designed to capture the actual transition boundaries, i.e., the variations of magnetization distribution in both down-track and across-track directions. The model is used to predict the readback waveforms based on the detailed information obtained from micromagnetic simulations taking into account the head and media parameters. The model is therefore suitable for magnetic recording at extremely high densities when the impact of the transition curvature and the track edge effect on the recording performance becomes more significant.