Revisiting the measurement of the spin relaxation time in graphene-based devices

A long spin relaxation time (tau(sf)) is the key for the applications of graphene to spintronics but the experimental values of tau(sf) have been generally much shorter than expected. We show that the usual determination by the Hanle method underestimates tau(sf) if proper account of the spin absorption by contacts is lacking. By revisiting series of experimental results and taking into account the spin absorption, we find that the corrected tau(sf) are longer and, for series of graphene samples of the same fabrication, less dispersed, which leads to a more unified picture of the tau(sf)