▎ 摘　　要

Considering the nickel has an almost perfect in-plane lattice constant match with graphene, vertical Ni/graphene/Ni junctions are fabricated and characterized in this article. In order to improve the interface quality, we employ a modified fabrication process of depositing the ferromagnetic (FM) material on both sides of a suspended graphene membrane assisted with rotating the sample with a slant angle during the bottom FM film growth. The magnetoresistance (MR) ratio of about 0.1% with a low resistance-area product (RA) of 30 Omega.mu m(2) is obtained at room temperature and the device shows a typical metallic behavior with the linear I-V characteristic and T-2-typical temperature dependence of the resistance. Interestingly, the temperature dependence of the MR displays an unusual behavior as the MR ratio reduces with the decreasing temperature, which we believe is due to the antiferromagnetic coupling between the two FM layers competing with the dipole field.