We examine the possibility of using graphene nanoribbons (GNRs) with directly substituted chromium atoms as a spintronic device. Using density functional theory, we simulate a voltage bias across a constructed GNR in a device setup where a magnetic dimer has been substituted into the lattice. Through this first-principles approach, we calculate the electronic and magnetic properties as a function of Hubbard U, voltage, and magnetic configurations. By calculating the total energy of each magnetic configuration, we determine that the initial antiferromagnetic ground state flips to a ferromagnetic state with applied bias. Mapping this transition point to the calculated conductance for the system reveals that there is a distinct change in conductance through the GNR, which indicates the possibility of a spin valve. We also show that this corresponds to a distinct shift in the induced magnetization within graphene.
Physical Review B