Graphene in Multilayered CPP Spin Valves

In this paper, we have sandwiched a single-atom-thick sheet of graphene, a 2-D allotrope of carbon that is exciting tremendous research interest, between two ferromagnetic electrodes. Graphene has already been shown to support spin polarized conduction, when spin polarized electrons were injected into graphene sheets along the plane using magnetic electrodes. Here, we study spin polarized conduction perpendicular the plane of the graphene in conduction perpendicular to plane (CPP) geometry. It was found that graphene was sufficient to reduce the exchange coupling between the magnetic electrodes. We also found that in a NiFe/Au/Graphene/NiFe stack, the graphene channels the spin current perpendicular to the plane and thus produces an enhanced MR effect compared to a simple stack without the graphene. A significant anisotropy was found in the observed magnetoresistance in the cross electrode geometry employed.