A nanomagnetic polarization amplifier for graphene

The generation of nonequilibrium electron spin polarization, spin transport, and spin detection are fundamental in many quantum operations. We demonstrate that a lattice of magnetic nanodots enhances the electron spin polarization in monolayer graphene. We probed the polarization through a resistively-detected variant of electron spin resonance (ESR) and observed that the resonance amplitudes are amplified by the presence of the nanodots. Each nanodot locally injects a surplus of spin-polarized carriers into the graphene, and the ensemble of all these 'spin hot spots' generates a nonequilibrium polarization in the graphene layer at macroscopic lengths scales whenever the interdot distance is comparable or smaller than the spin diffusion length.