Fig. 2. Intrinsic electron–phonon spin relaxation time of free-standing graphene.

Results are shown (a, b) at room temperature as a function of Fermi energies, c at E_F = 0.1 eV as a function of temperature and d as a function of extrinsic scattering rates. b Out-of-plane spin relaxation by cumulative phonon mode contributions starting with optical (O), adding in-plane acoustic (A), and then including the flexural mode as well, indicating the dominance of acoustic and flexural modes for spin relaxation. Both a and c show an anisotropy between in-plane and out-of-plane lifetimes with a ratio varying in the 0.5–0.7 range, whereas d shows that the lifetime is relatively insensitive to extrinsic scattering rates indicating that this is not the DP mechanism despite the nearly 1/2 ratio, as expected.