  The generation of non-equilibrium electron spin polarization, spin transport,
and spin detection are fundamental in many quantum devices. We demonstrate that
a lattice of magnetic nanodots enhances the electron spin polarization in
monolayer graphene via carrier exchange. We probed the spin polarization
through a resistively-detected variant of electron spin resonance (ESR) and
observed resonance amplification mediated by the presence of the nanodots. Each
nanodot locally injects a surplus of spin-polarized carriers into the graphene,
and the ensemble of all "spin hot spots" generates a non-equilibrium electron
spin polarization in the graphene layer at macroscopic lengths. This occurs
whenever the interdot distance is comparable or smaller than the spin diffusion
length.
