  Here, we report on angle-resolved photoemission studies of the electronic
$\pi$ states of high-quality epitaxial graphene layer on a Ni(111) surface. In
this system electron binding energy of the $\pi$ states shows a strong
dependence on the magnetization reversal of the Ni film. The observed
extraordinary large energy shift up to 225 meV of the graphene-derived
$\pi$-band peak position for opposite magnetization directions is attributed to
a manifestation of the Rashba interaction of spin-polarized electrons in the
$\pi$ band with the large effective electric field at graphene/Ni interface.
Our findings show that an electron spin in the graphene layer can be
manipulated in a controlled way and have important implications for
graphene-based spintronic devices.
