Spin diffusion and non-local spin-valve effect in an exfoliated multilayer graphene with a Co electrode

We fabricated a non-local spin valve with a thin layer of graphite with Co transparent electrodes. The spin-valve effect and spin precession were observed at room temperature. The magnitude of the mangetoresistance increases when temperature decreases. The spin-relaxation time, tau(s), obtained from the fitting of the Hanle curves increases with decreasing temperature with a weak dependence similar to T-0.065 while the spin-diffusion constant D decreases. At room temperature, tau(s) exceeds 100 ps and the spin-diffusion length, lambda(s), is similar to 2 mu m. The temperature dependence of lambda(s) is not monotonic, and it has the largest value at room temperature. Our results show that multilayer graphene is a suitable material for spintronic devices.