  We propose and demonstrate that a EuO-induced and top-gated graphene
ferromagnetic junction can be simultaneously operated as a spin filter as well
as a spin valve. We attribute such a remarkable result to a coexistence of a
half-metal band and a common energy gap for opposite spins in ferromagnetic
graphene. We show that, both the spin filter and the spin valve can be
effectively controlled by a back gate voltage, and they survive for practical
metal contacts and finite temperature. Specifically, larger single spin
currents and on-state currents can be reached with contacts with work functions
similar to graphene, and the spin filter can operate at higher temperature than
the spin valve.
