▎ 摘　　要

Creating a single-carbon vacancy introduces (quasi-)localized states for both sigma and pi electrons in graphene. Theoretically, interactions between the localized sigma electrons and quasilocalized pi electrons of a single-carbon vacancy in graphene are predicted to control its magnetism. However, experimentally confirming this prediction through manipulating the interactions remains an outstanding challenge. Here we report the manipulation of magnetism in the vicinity of an individual single-carbon vacancy in graphene by using a scanning tunnelling microscopy (STM) tip. Our spin-polarized STM measurements, complemented by density functional theory calculations, indicate that the interactions between the localized sigma and quasilocalized pi electrons could split the pi electrons into two states with opposite spins even when they are well above the Fermi level. Via the STM tip, we successfully manipulate both the magnitude and direction of magnetic moment of the pi electrons with respect to that of the sigma electrons. Three different magnetic states of the single-carbon vacancy, exhibiting magnetic moments of about 1.6 mu(B), 0.5 mu(B), and 0 mu(B) respectively, are realized in our experiment. (C) 2019 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.