Graphene Spintronics: The Role of Ferromagnetic Electrodes

Abstract

We report a first principles study of spin transport under finite bias through a graphene-ferromagnet (FM) interface, where FM = Co(111), Ni(111). The use of Co and Ni electrodes achieves spin efficiencies reaching 80% and 60%, respectively. This large spin filtering results from the materials specific interaction between graphene and the FM which destroys the linear dispersion relation of the graphene bands and leads to an opening of spin-dependent energy gaps of ≈0.4-0.5 eV at the K points. The minority spin band gap resides higher in energy than the majority spin band gap located near E(F), a feature that results in large minority spin dominated currents.

Graphene spintronics: Spin injection and proximity effects from first principles

“…This is applicable to models of lateral spin injection [67] where our findings could identify the missing bias dependence [107]. The efficiency of our first-principles description of spin injection provides a valuable guidance, before investing a large amount of computer time in more sophisticated quantum transport calculations [98,101] that give an accurate account of finite-bias effects in the ballistic regime, as well as a starting point for detailed studies in more complex systems [108,109].…”

“…9-12 already provide some guidance about spin injection and its possible bias dependence arising from the energy-dependent DOS and Fermi velocities [100], missing in the simple model of spin injection. For an additional understanding of F/Gr spin injection in a diffusive regime, relevant to lateral spin transport and magnetologic gates, it could be possible to take advantage of state-of-the-art codes combining transport with first-principles electronic structure calculations [98,101]. This is a considerable challenge as such codes are computationally demanding and are typically tailored to ballistic transport.…”

The effect of downstream plasma treatments on graphene surfaces

“…The two-dimensional single layer of sp 2 -hybridized carbon atoms has charge carriers that exhibit giant intrinsic mobility, have zero effective mass and can travel for micrometers without scattering at room temperature [1]. In combination with a record thermal conductivity at room temperature (~5000Wm -1 K -1 ) [2], the possibility of structuring and tuning its properties [3] make it an ideal candidate for use in future devices in electronics and energy harvesting such as conducting electrodes [4][5][6][7], switches [8][9][10][11][12], spintronics [13][14][15] and sensors [16][17][18][19]. The quality and surface chemistry of graphene is crucial for these applications, as contamination, impurities, morphology and defects can substantially affect its electronic properties and performance in these devices [20][21][22][23].…”

Raman spectroscopy of the internal strain of a graphene layer grown on copper tuned by chemical vapor deposition

“…In this case, the most stable configuration of graphene on Cu(111) corresponds to one carbon sitting at the top-site (A-site) and the other carbon located at the hollow-site (C-site) [15,16]. The same configuration also applies to graphene on other metallic surfaces [17]. To induce strain, we uniformly expand or compress the in-plane lattice constant of the whole graphene/Cu system.…”