Unprecedented Spin-Lifetime of Itinerant Electrons in Natural Graphite Crystals

A long spin-lifetime of electrons is the holy grail of spintronics, a field exploiting the electron angular momentum as information carrier and storage unit. Previous reports indicated a spin lifetime, τ_s near 10 ns at best in graphene-based devices at low temperatures. We detail the observation of τ_s approaching the ultralong 1,000 ns at room temperature in natural graphite crystals using magnetic resonance spectroscopy. The relaxation time shows a giant anisotropy: the lifetime of spins, polarized perpendicular to the graphite plane, is more than 50 times longer than for the in-plane polarization. The temperature dependence of τ_s proves that diffusion of spins to the crystallite edges, where relaxation occurs, limits the lifetime. This suggests that graphite is an excellent candidate for spintronic applications, seamlessly integrating with emerging 2D van der Waals technologies.