title: Spin-dependent transport for armchair-edge graphene nanoribbons between ferromagnetic leads.
abstract: We theoretically investigate the spin-dependent transport for the system of an armchair-edge graphene nanoribbon (AGNR) between two ferromagnetic (FM) leads with arbitrary polarization directions at low temperatures, where a magnetic insulator is deposited on the AGNR to induce an exchange splitting between spin-up and -down carriers. By using the standard nonequilibrium Green's function (NGF) technique, it is demonstrated that the spin-resolved transport property for the system depends sensitively on both the width of AGNR and the polarization strength of FM leads. The tunneling magnetoresistance (TMR) around zero bias voltage possesses a pronounced plateau structure for a system with semiconducting 7-AGNR or metallic 8-AGNR in the absence of exchange splitting, but this plateau structure for the 8-AGNR system is remarkably broader than that for the 7-AGNR one. Interestingly, an increase of the exchange splitting Δ suppresses the amplitude of the structure for the 7-AGNR system. However, the TMR is much enhanced for the 8-AGNR system under a bias amplitude comparable to the splitting strength. Further, the current-induced spin-transfer torque (STT) for the 7-AGNR system is systematically larger than that for the 8-AGNR one. The findings here suggest the design of GNR-based spintronic devices by using a metallic AGNR, but it is more favorable to fabricate a current-controlled magnetic memory element by using a semiconducting AGNR.
authors.affiliation: Department of Physics and Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), Hunan Normal University, Changsha, People's Republic of China.
authors.forename: Benhu
authors.initials: B
authors.lastname: Zhou
authors.forename: Xiongwen
authors.initials: X
authors.lastname: Chen
authors.forename: Benliang
authors.initials: B
authors.lastname: Zhou
authors.forename: Kai-He
authors.initials: KH
authors.lastname: Ding
authors.forename: Guanghui
authors.initials: G
authors.lastname: Zhou
mesh_terms: D004581:Electronics / Q000295:instrumentation; D004867:Equipment Design / Q000295:instrumentation; D005290:Ferric Compounds / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008956:Models, Chemical; D036103:Nanotechnology / Q000295:instrumentation; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D005290:Ferric Compounds; D037742:Nanotubes, Carbon; C001215:ferrite; D007854:Lead; D006108:Graphite