▎ 摘　　要

We have performed density functional theory calculations of graphene decorated with carbon adatoms, which bind at the bridge site of a C-C bond. Earlier studies have shown that the C adatoms have magnetic moments and have suggested the possibility of ferromagnetism with high Curie temperature. Here we propose to use a gate voltage to fine tune the magnetic moments from zero to 1 mu(B) while changing the magnetic coupling from antiferromagnetism to ferromagnetism and again to antiferromagnetism. These results are rationalized within the Stoner and Ruderman-Kittel-Kasuya-Yosida (RKKY) models. When the SCAN meta-GGA (generalized gradient approximation) correction is used, the magnetic moments for zero gate voltage are reduced and the Stoner band ferromagnetism is slightly weakened in the ferromagnetic region.