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(Color online) Schematic diagrams of the ZGNR GMR devices. Spin orientation of the AFM states at the transverse electrode regions is determined by the direction of the local magnetic field; ⊙ and ⊗ denote the directions of local magnetic field. The width and length of the ZGNR are labeled by integer W and L, respectively.
(Color online) (a) and (b) are the band structures and conductance curves for the device in P and AP configurations with W = 10 and L = 8. a = 2.46 Å is the unit cell length along the transport direction. Left (right) panel is the band structure for left (right) lead, middle panel is the conductance curve. The dashed lines denote the energy window within which conductance dramatically changes in the P and AP configurations. The red (blue) [or light (dark)] corresponds to the spin up (down) band structure of the AFM state. (c) and (d) show the orbital (wavefunction) symmetries of the two subbands ( for left lead and for right lead) within the dashed-line regions and the corresponding spin density in P and AP configurations. Left (right) panel is the wavefunction for left (right) lead, middle panel is the spin density. The site index denotes the position of the carbon atoms in the unit cell of the lead, as shown in Fig. 1. The red (blue) [or light (dark)] refers to spin up (down), the radius of the circle around each atom corresponds to the value of local spin density.
(Color online) (a) MR of ZGNR device with W = 10 and L = 8. The energy window for the MR effect is bracketed by the dashed lines, Δ = 0.18 eV, within which MR saturates around 100%. (b) The width of the MR energy window (Δ) as a function of ZGNR width (W) with fixed length L = 8. (c) Comparison of conductance in the AP configuration between twodifferent device length L = 8 (solid line) and L = 16 (dot line) with W = 10. (d) Spin density distribution in the AP configuration with W = 10 and L = 16.
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