After the review of spin interactions in carbon nanostructures in Chapters 7 and 8, and the summary of mechanisms and material properties essential for spintronics in the previous chapter, the present chapter will combine these two domains. In the first place, we will attempt to clarify why carbon nanostructures are of major interest as potential carrier materials in spintronics circuits. Further, we will characterize the physical effects that make these structures relevant as elements of spin networks. Since devices based on these effects have been conceived but are still quite far from the manufacturing stage, our account will be about currently discussed models of these devices, and their experimental examination. We focus on two classes of materials: graphene and carbon nanotubes.

Graphene Spintronics

Graphene is of high interest as nanoelectronic material. Among the features of graphene that motivate this interest are experimentally confirmed electron mobilities as high as 2.00 105 cm2V−1s−1 [347], which is about a hundred times higher than typical mobilities of electrons in silicon. This suggests that graphene-based transistors will function at substantially higher speeds than elements of conventional electronics, while being more efficient in terms of power consumption. Test devices have been shown to be capable of operating at hundreds of gigahertz [348]. Another graphene property of direct relevance for nanotechnological applications is its gate-tunable charge carrier density, resulting from the double-cone structure of the energy surfaces close to the Dirac points. Further, in terms of heat resistance, graphene transistors are distinctly superior to the tools of presently existing electronics, as they have been shown to perform at temperatures higher by 20– 30 ◦C than their silicon counterparts [349]. The challenge of the semi-metallic character of two-dimensional periodic graphene crystals can be met in various ways. Thus, one may tailor a finite band gap in controlled ways by modifying the graphene sheet with adsorbates. In addition, manufacturing electronic devices from the pristine graphene crystal requires its dimensional reduction, associated with the formaton of a finite band gap (see Section 4.5).