  We investigate how spins relax in intrinsic graphene. The spin-orbit coupling
arises from the band structure and is enhanced by ripples. The orbital motion
is influenced by scattering centers and ripple-induced gauge fields. Spin
relaxation due to Elliot-Yafet and Dyakonov-Perel mechanisms and gauge fields
in combination with spin-orbit coupling are discussed. In intrinsic graphene,
the Dyakonov-Perel mechanism and spin flip due to gauge fields dominate and the
spin-flip relaxation time is inversely proportional to the elastic scattering
time. The spin relaxation anisotropy depends on an intricate competition
between these mechanisms. Experimental consequences are discussed.
