  The temperature dependence of the spin relaxation time in multilayer graphene
(MLG) spin valve devices was measured using a non-local magnetoresistance
(NLMR) measurement. A weak localization (WL) was observed from
magnetoresistance (MR) measurements below 70 K, suggesting coherent transport
of the charge carriers. Within the same temperature range, we observed a large
increase in the spin relaxation time and spin diffusion length even though the
diffusion constant Ds was suppressed by the WL. This demonstrated that the spin
relaxation time in MLG could be significantly extended when the charge
experiences quantum interference effect in the coherent charge transport
regime.
