- Conventional electronic transistors involve the control of electronic charge at the nanoscale to realize memory, logic and communication functions. All these electronic charges, however, also carry a spin that remains unutilized in present commercial devices. This has motivated the search for new materials that propagate spin-polarized currents over large distances. Among them the most promising materials for spintronics has been graphene, a truly two-dimensional crystal of carbon atoms with relativistic carriers. Micron-scale spin relaxation lengths have been previously demonstrated in single-layer graphene. In this paper, we show that the two-layered cousin of graphene (called bilayer graphene) is a far more interesting candidate for spintronics. By fabricating spin valves on bilayer graphene we have achieved record room temperature spin relaxation times up to 2 nanoseconds, which are significantly higher than for single layer graphene. Furthermore, the presence of interlayer interaction between the two layers of bilayer graphene makes it a particularly lucrative (profitable) nanoscale material for spintronics – particularly since this interaction can be tuned by electric-field. Spin devices made from exactly two stacked layers of graphene turn out to be remarkably different not only from single-layer graphene but also from all other multilayer graphenes.Our work provides fundamental insight into the unique properties of bilayer graphene for spintronic applications.
