Graphene-based monoatomic chain spintronics: contact-derived half-metallicity, sp2 vs sp

Abstract

Because of the remarkable semi-metallicity and edge states, graphene-based nanoelectronics has become an intense arena in low-dimensional atomic device science and technology. Nowadays, various single atomic chains have been successfully fabricated, which can serve as multi-functional interconnects to bridge atomic devices. Using first principles approach, the spintronic applications of graphene-based carbon atomic chains and boron nitride atomic chains MTJs (magnetic tunnelling junctions) are systematically investigated in this work. The results show that the half-metallicity is only contact-dominated ( sp and sp 2 contacts), which cannot be switched by gate voltages, strain, the length of atomic chains, or the width of zigzag graphene nanoribbon leads. The intrinsic physics is that the electronic coupling in sp junctions provides partial transmission states for both spin currents, while one spin state is completely blocked by the electronic coupling in sp 2 junctions. Therefore, the sp 2 junctions present half-metallicity and remarkable tunnelling magneto-resistance (10 5 %–10 6 %), demonstrating the potential applications as spin-valve. This work discloses the origin of the contact-dominated effect in graphene-based spintronics which is unknown before. • The half-metallicity of graphene-ACs/BNACs junctions is dominated by contacts. • The sp 2 junctions are fully polarzied and not the case in sp junctions. • The tunnelling magneto-resistance of sp 2 junctions can remarkably reach 10 5 %-10 6 %.