Magnetoresistance effect in vertical NiFe/graphene/NiFe junctions

For convenient and efficient verification of the magnetoresistance effect in graphene spintronic devices, vertical magnetic junctions with monolayer graphene sandwiched between two NiFe electrodes were fabricated in a relatively simple way by transferring CVD graphene onto the bottom ferromagnetic stripes. The anisotropic magnetoresistance contribution was excluded by the experimental result of MR ratio dependence on the magnetic field direction. The spin-dependent transport measurement revealed two distinct resistance states switching under an in-plane sweeping magnetic field. A magnetoresistance ratio of about 0.17% was obtained at room temperature and it showed a typical monotonic downward trend with the bias current. This bias dependence of MR further verified that the spin transport signal in our devices was not from the anisotropic magnetoresistance. Meanwhile, the I-V curve was found to manifest a linear behavior, which demonstrates the ohmic contacts at the interfaces and the metallic transport characteristic of vertical graphene junctions.