  Graphene is a highly promising material in the field of spin electronics.
Recent experiments on electron spin resonance have observed a reduction in the
g-factor of graphene. In our previous paper [J. Phys. Soc. Jpn. 88, 094707
(2019)], we demonstrated that one of sources for this reduction is the
diamagnetic property of graphene. However, the diamagnetic property by itself
does not fully account for the magnitude of the reduction observed in the
experiments. In this paper, we focus on the Rashba effect, which is caused by
the work function existing near the surface of graphene. The Rashba effect
tilts the spin magnetic moment to the in-plane direction of the graphene sheet,
potentially reducing the g-factor. We evaluate this reduction using a simple
model system incorporating the Rashba and spin Zeeman effects. We then
demonstrate that the resultant g-factor is in close agreement with that
observed in the prior experiments, indicating that the Rashba effect is able to
account for the remaining reduction in the g-factor of graphene.
