Spin magnetic proximity effect in graphene superlattices.

The magnetic proximity effect induces spin splitting in graphene through interfacial exchange coupling, enabling control of spin-resolved band structure, most clearly revealed near charge neutrality where low carrier density enhances spin-dependent transport signatures. Here, we use cobalt contacts to induce magnetic proximity in graphene and probe spin-resolved bands with pure spin currents, observing a gate-tunable inversion of the nonlocal spin signal near the charge neutrality point. Similar inversions occur at satellite neutrality points in graphene-boron nitride aligned superlattices, demonstrating that proximity-induced spin splitting governs spin transport across both primary and reconstructed bands. In a bilayer graphene superlattice device, where a bandgap enhances energy-selective spin filtering, we observe spin polarizations approaching 50% and nonlocal spin resistances exceeding 300 Ω, nearly two orders of magnitude larger than those away from the charge neutrality point. Such electrically controlled spin polarization via proximity interactions at low carrier densities opens opportunities for low-power spintronic devices.