Abstract
Realization of half-metallicity in low dimensional materials is a fundamental challenge for nano spintronics, which is a critical component for next-generation information technology. Using the method of generalized Bloch theorem, we show that an in-plane bending can induce inhomogeneous strains, which in turn lead to spin-splitting in zigzag graphene nanoribbons and results in the highly desired half-metallic state. Unlike the previously proposed scheme that requires unrealistically strong external electric fields, the obtained half-metallicity with sizeable half-metallic gap and high energetic stability of magnetic order of edge states requires only relatively low-level strain in the in-plane bending. Given the superior structural flexibility of graphene and the recent experimental advances in controllable synthesis of graphene nanoribbons, our design provides a hitherto most practical approach to the realization of half-metallicity in low dimensional systems. This work, thus paves a way towards the design of nanoscale spintronic devices through strain engineering.
Highlights
Having one spin channel conducting while the other one insulating, half-metallicity (HM) can provide completely spinpolarized charge carriers
Considering tension and compression, we find that energy levels of both valance band (VB) and conduction band (CB) of edge states shift downwards and upwards with respect to the stress-free case for zigzag graphene nanoribbons (GNR) under tension and compression, respectively, as shown in Fig. 2a, c
We note that the bandgap is almost impervious to strain because the energies of the VB and CB of edge states move in the same direction
Summary
Having one spin channel conducting while the other one insulating, half-metallicity (HM) can provide completely spinpolarized charge carriers This exotic property represents an ideal condition for spintronics which manipulates the spin freedom of electrons for various applications such as logic circuits, data storage and information processing.[1,2,3,4] Since the first theoretical prediction,[5] great efforts have been devoted to identify or design materials with HM properties.[6,7,8,9,10,11,12,13,14] So far, HM has been experimentally demonstrated in bulk systems, e.g., ferromagnetic manganese perovskite.[6] despite great efforts,[7,8,9,10,11,12,13,14] the actual realization of HM in low dimensional materials, especially in two-dimensional (2D) single atomic/molecular layer, has not been realized. The energy levels of the localized edge states on the opposite edges will shift relatively with respect to each other for both spin orientations.[7]
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