Graphene may be set to revolutionize electronics, but its small spin–orbit coupling limits its potential in spintronics. It is now shown, however, that adding hydrogen atoms can greatly enhance the magnetic properties of graphene. This then enabled the observation of the spin Hall effect, essential for controlling spin currents. Graphene’s extremely small intrinsic spin–orbit (SO) interaction1 makes the realization of many interesting phenomena such as topological/quantum spin Hall states2,3 and the spin Hall effect4 (SHE) practically impossible. Recently, it was predicted1,5,6,7 that the introduction of adatoms in graphene would enhance the SO interaction by the conversion of sp2 to sp3 bonds. However, introducing adatoms and yet keeping graphene metallic, that is, without creating electronic (Anderson) localization8, is experimentally challenging. Here, we show that the controlled addition of small amounts of covalently bonded hydrogen atoms is sufficient to induce a colossal enhancement of the SO interaction by three orders of magnitude. This results in a SHE at zero external magnetic fields at room temperature, with non-local spin signals up to 100 Ω; orders of magnitude larger than in metals9. The non-local SHE is, further, directly confirmed by Larmor spin-precession measurements. From this and the length dependence of the non-local signal we extract a spin relaxation length of ∼1 μm, a spin relaxation time of ∼ 90 ps and a SO strength of 2.5 meV.

We report on the first systematic study of spin transport in bilayer graphene (BLG) as a function of mobility, minimum conductivity, charge density, and temperature. The spin-relaxation time ${\tau }_s$ scales inversely with the mobility $\mu$ of BLG samples both at room temperature (RT) and at low temperature (LT). This indicates the importance of D’yakonov-Perel’ spin scattering in BLG. Spin-relaxation times of up to 2 ns at RT are observed in samples with the lowest mobility. These times are an order of magnitude longer than any values previously reported for single-layer graphene (SLG). We discuss the role of intrinsic and extrinsic factors that could lead to the dominance of D’yakonov-Perel’ spin scattering in BLG. In comparison to SLG, significant changes in the carrier density dependence of ${\tau }_s$ are observed as a function of temperature.

Advances in large-area graphene synthesis via chemical vapour deposition on metals like copper were instrumental in the demonstration of graphene-based novel, wafer-scale electronic circuits and proof-of-concept applications such as flexible touch panels. Here, we show that graphene grown by chemical vapour deposition on copper is equally promising for spintronics applications. In contrast to natural graphene, our experiments demonstrate that chemically synthesized graphene has a strong spin–orbit coupling as high as 20 meV giving rise to a giant spin Hall effect. The exceptionally large spin Hall angle ~0.2 provides an important step towards graphene-based spintronics devices within existing complementary metal-oxide-semiconductor technology. Our microscopic model shows that unavoidable residual copper adatom clusters act as local spin–orbit scatterers and, in the resonant scattering limit, induce transverse spin currents with enhanced skew-scattering contribution. Our findings are confirmed independently by introducing metallic adatoms-copper, silver and gold on exfoliated graphene samples.