▎ 摘　　要

We calculate the spin-dependent conductance in ferromagnetic metal (FM)/graphene(G)/FM lateral junctions using a numerical simulation and study the effects of roughness and electronic states at the FM/G contact on magnetoresistance (MR) in detail. It is shown that the MR ratio can be extremely high in fcc Ni alloy/G/fcc Ni alloy junctions because of a spin-dependent change in the electronic states at the contact. The MR ratio, however, is reduced by introducing roughness into junctions. Conditions for a high MR ratio in FM/G/FM junctions are discussed.