  Spin-orbit coupling (SOC) can provide essential tools to manipulate electron
spins in two-dimensional materials like graphene, which is of great interest
for both fundamental physics and spintronics application. In this paper, we
report the low-field magnetotransport of in situ hydrogenated graphene where
hydrogen atoms are attached to the graphene surface in continuous low
temperature and vacuum environment. Transition from weak localization to weak
antilocalization with increasing hydrogen adatom density is observed,
indicating enhancing Bychkov-Rashba-type SOC in a mirror symmetry broken
system. From the low-temperature saturation of phase breaking scattering rate,
the existence of spin-flip scattering is identified, which corroborates the
existence of magnetic moments in hydrogenated graphene.
