Electrical Control of Ultrafast Magnetic Speeds in Graphene Spin Field-Effect Junctions

We demonstrate ultrafast graphene spin-field-effect junctions, where gate-tunable superdiffusive spin currents across graphene-ferromagnet interfaces enable electric field control of magnetization dynamics in the ferromagnet. By electrostatically tuning the Fermi level in graphene underlying a cobalt thin film, we modulate the ultrafast spin transport across graphene-cobalt interfaces, reducing femtosecond laser-induced demagnetization time from 203 fs in bare cobalt thin films to 93 fs, a more than 100% increase in the rate of magnetization quenching. Supported by superdiffusive spin transport calculations, our findings unlock field-tunable magnetic speeds in devices, paving the way for innovations in subpicosecond spintronic memory-logic operations. Furthermore, this work creates new possibilities for electrical modulation of spin dynamics and ultrafast spin injection into two-dimensional quantum materials, with potential for next-generation quantum sensors and faster magnetic technologies.