▎ 摘　　要

The nature of the magnetic states of zigzag graphene nanoribbons (ZGNRs) was explored on the basis of density functional calculations to understand why they are apparently nonmagnetic. Our study shows that the magnetic moments of ZGNRs are destroyed by p-type or n-type carrier doping with similar to 10(13) carriers/cm(2) per ribbon, which is close to the amount of unpaired spins that ZGNRs are expected to have. Thus the extrinsic sources of carrier doping should be removed to observe the expected magnetic character of ZGNRs.