Spin transport in graphite and graphene spin valves

Abstract

Spin transport in graphene devices has been investigated in both local and non-local spin valve geometries. In the nonlocal measurement, spin transport and spin precession in single layer and bilayer graphene have both been achieved with transparent Co contacts. Gate controllable non-local spin signal was also demonstrated in this system. For the local graphite spin valve device, we report MR up to 12% for devices with tunneling contacts. We observe a correlation between the nonlinearity of the I-V curve and the presence of local MR and conclude that tunnel barriers can be employed to surmount the conductance mismatch problem in this system. These studies indicate that the improvement of tunnel barriers on graphene, especially to inhibit the formation of pinholes, is an important step to achieve more efficient spin injection into graphene.