Organometallic Benzene-Vanadium Wire: A One-Dimensional Half-Metallic Ferromagnet

Using density functional theory we perform theoretical investigations of the electronic properties of a freestanding one-dimensional organometallic vanadium-benzene wire. This system represents the limiting case of multidecker ${\mathrm{V}}_n({\mathrm{C}}_6{\mathrm{H}}_6{)}_{n+1}$ clusters which can be synthesized with established methods. We predict that the ground state of the wire is a 100% spin-polarized ferromagnet (half-metal). Its density of states is metallic at the Fermi energy for the minority electrons and shows a semiconductor gap for the majority electrons. We find that the half-metallic behavior is conserved up to 12% longitudinal elongation of the wire. Ab initio electron transport calculations reveal that finite size vanadium-benzene clusters coupled to ferromagnetic Ni or Co electrodes will work as nearly perfect spin filters.

Figure 1

The structure of the $\mathrm{V}({\mathrm{C}}_6{\mathrm{H}}_6)$ wire.

Figure 2

The spin-resolved band structure (left plot) and the DOS (plot in the middle) of the $\mathrm{V}({\mathrm{C}}_6{\mathrm{H}}_6)$ wire in the ferromagnetic phase. The labels at the band structure refer to crystalline orbitals of the wire calculated for the $\Gamma$ point. These functions are shown in the center. The corresponding majority and minority spin orbitals have practically the same shape. The right panel shows values of the HOMO-LUMO gap in two spin channels for ${\mathrm{V}}_n({\mathrm{C}}_6{\mathrm{H}}_6{)}_{n+1}$ clusters as a function of $n$.

Figure 3

Spin-density map for the $\mathrm{V}({\mathrm{C}}_6{\mathrm{H}}_6)$ wire. Local magnetic moments are $1.28{\mu }_B$ at V atom, and $-0.047{\mu }_B$ at each C atom.

Figure 4

Transmission spectra of the ${\mathrm{V}}_3{\mathrm{Bz}}_4$ cluster suspended between either Co (dashed line) or Ni (solid line) electrodes. Inset plots show surfaces of the constant spin-resolved local DOS evaluated at the Fermi energy.

Figure 5

Outer plot: Binding energy $E_{\mathrm{VBz}}$ between V and Bz as a function of the unit cell length. Black and red lines correspond to the low- and high-spin FM states, respectively. Blue line with open circles refers to the AFM state, which for any lattice constants is less preferable as compared with FM state. Inner plot: Behavior of the magnetic moment per unit cell under elongation of the wire.