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

A long spin relaxation time (τsf) is the key for the applications of graphene to spintronics but the experimental values of τsf have been generally much shorter than expected. We show that the usual determination by the Hanle method underestimates τsf 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 τsf are longer and, for series of graphene samples of the same fabrication, less dispersed, which leads to a more unified picture of the τsf.