Tunable half-metallic properties and spin Seebeck effects in zigzag-edged graphene nanoribbons adsorbed with V atom or V-benzene compound

We investigate the spin transport and thermospin properties of zigzag-edged graphene nanoribbons (ZGNRs) adsorbed with a V atom or V-benzene compound using the spin-polarized density functional theory. It is found that the spin polarization of the transmittance at the Fermi level can be obviously enhanced as the V atom moves from the edge to middle hollow sites. In some cases, ZGNRs with V adsorption can possess half-metallicity with � 100% spin polarization, which is mainly attributed to the appearance of a spin-up localized state from the d orbital of the V atom. When a benzene is covered on the V atom, the sign of spin polarization is altered, and even it approaches 100%. In addition, compared with the ideal ZGNRs, the spin thermoelectric effects of these adsorbed ZGNRs are obviously enhanced in some cases. Meantime, the magnitude of the spin Seebeck coefficient at the Fermi level is nearly equal to that of the charge Seebeck coefficient. Moreover, we also find that the spin thermoelectric properties are rather sensitive to the width of the nanoribbon, and the sign and magnitude of the spin Seebeck coefficient can be modified by the width. Therefore, these adsorbed ZGNRs can be used to design perfect spin-filtering systems and high-performance thermopsin devices. 2015 Published by Elsevier B.V.