▎ 摘　　要

In this paper we systematically study electronic structures and excitonic effects in one type of the sawtooth-like graphene nanoribbons. A main feature is that the local magnetism is developed for the certain width and changes with the increase of width. A variety of magnetic orders root in the competition of the short range interaction between the same spin-electrons and long range exchange interaction between opposite spin-electrons. For excitonic effects, the binding energy of degenerate spin triplets T-1 and T-1 is higher than that of To for all studied nanoribbons and is size dependent. We reveal the underlying physical mechanism from the charge distributions of excitons and its correlation with the spin-resolved charge density distributions in the ground state. We find that the electrons and holes in degenerate spin-triplets T-1 and T-1 are closer together and thus the interaction between them is more strong, while the distribution of electrons and holes is relatively more disperse for To, indicating the weaker interaction. We hope that these interesting results are able to be detected in the experiment and these multi -performance samples are better utilized in future device applications. 2016 Elsevier B.V. All rights reserved.