▎ 摘　　要

The magnetic moment and spin-polarized electron transport properties of triangular graphene flakes surrounded by boron nitride sheets (BNC structures) are studied by first-principles calculation based on density functional theory. Their dependence on the BNC structure is discussed, revealing that small graphene flakes surrounded by large BN segments have a large magnetic moment. When the BNC structure is suspended between graphene electrodes, the spin-polarized charge density distribution accumulates at the edge of the graphene flakes and no spin polarization is observed in the graphene electrodes. We also found that the BNC structure exhibits perfectly spin-polarized transport properties in a wide energy window around the Fermi level. Our first-principles results indicate that the BNC structure provides for the new possibilities for the electrical control of spin.