Vanadium−Benzimidazole-Modified sDNA: A One-Dimensional Half-Metallic Ferromagnet

Realizing stable half-metallicity in zigzag silicene nanoribbons with edge dihydrogenation and chemical doping

Although many schemes have been proposed to obtain full half-metallicity in zigzag silicene nanoribbons with edge monohydrogenation (H-H ZSiNRs) by chemical modification, the resulted negligible energy difference between the antiferromagnetic (AFM) and ferromagnetic (FM) configurations makes the half-metallicity hardly observable practically. In this work, based on density functional calculations, we find that the ZSiNRs with edge dihydrogenation (H2-H2 ZSiNRs) can be tuned to be half-metallic by replacing the central two zigzag Si chains with two zigzag Al-P chains, and more importantly, the FM-AFM energy difference is significantly increased compared with the H-H cases. The obtained half-metallicity originates from the different potential between two edges of the ribbon after doping, which results in the edge states of two spin channels shifting oppositely in energy. This mechanism is so robust that the half-metallicity can always be achieved, irrespective of the ribbon width. Our finding provides a fantastic way for achieving stable half-metallicity in ZSiNRs.

Spin Transport Properties of One-Dimensional Benzene Ligand Organobimetallic Sandwich Molecular Wires

Organometallic sandwich complexes, composed of cyclic hydrocarbon ligands and transition-metal atoms, display unique physical and chemical properties. In this work, the electronic and spin transport properties of one-dimensional (1D) VBz2 ligand bimetallic sandwich complexes, VBz2-TM (TM = Cr, Mn, and Fe), are systematically investigated using density functional theory and nonequilibrium Green's function method. The results show that all the 1D infinite molecular wires [(VBz2)TM]∞ (TM = Cr-Fe) are found to be thermodynamically stable with high binding energies (∼1.0-3.45 eV). In particular, they are predicted to be ferromagnetic half metals. Moreover, the I-V curves exhibit negative differential resistance for one, two, and three VBz2-TM wires at TM = Cr, Mn, and Fe, respectively, which is of great significance for certain electronic applications. Our findings strongly suggest that the benzene ligand bimetallic sandwich molecular wires are good candidates for potential electronics and spintronics.

Generating pure spin current with spin-dependent Seebeck effect in ferromagnetic zigzag graphene nanoribbons

Pure spin current is of great importance in spintronics and may be achieved by spin dependent Seebeck effect (SDSE) in magnetic systems. Zigzag-edged graphene nanoribbons (ZGNRs) are very well-known 2D magnetic nanostructures. However, perfect and pristine ZGNRs either in the anti-ferromagnetic ground state or in the ferromagnetic (FM) state are not capable of producing pure spin current by SDSE at low temperature. In this work, by density functional theory calculations, we propose a scheme for generating pure spin current using SDSE in FM-ZGNRs by introducing antidots. Specifically, by creating a hexagonal antidot with either armchair edges or zigzag edges in the scattering region, we can get finite Seebeck thermopower for both spin channels with opposite signs, leading to the opposite flow directions of the two spin channels. The mechanism is well explained by the cooperation of the varying localization features of states around the Fermi level and the antidot induced scattering potential. By slightly tuning the chemical potential, pure spin current can be achieved. The size and edge shape effects have also been systematically studied. The findings indicate a novel scheme for thermally generating pure spin current in zigzag graphene nanoribbons and may find important application in graphene based spintronics.

Tensile strain induced half-metallicity in graphene-like carbon nitride

Tensile strain induced half-metallicity in graphene-like carbon nitride, which provides a better way to realize half-metallicity in the experimental.

A new two-dimensional metal–organic framework with high spin-filtering efficiency

A new metal–organic framework, consisting of substituted naphthalene molecules and transition metals, is proposed with good spin filtering properties.

First-principles prediction of metal-free magnetism and intrinsic half-metallicity in graphitic carbon nitride

Transition metal-free magnetism and half-metallicity recently has been the subject of intense research activity due to its potential in spintronics application. Here we, for the first time, demonstrate via density functional theory that the most recently experimentally realized graphitic carbon nitride (g-C4N3) displays a ferromagnetic ground state. Furthermore, this novel material is predicted to possess an intrinsic half-metallicity never reported to date. Our results highlight a new promising material toward realistic metal-free spintronics application.

Doping single-walled carbon nanotubes through molecular charge-transfer: a theoretical study

We study the effect of the molecular charge transfer on the electronic structure of metallic (5,5) and semiconducting (8,0) single-walled carbon nanotubes (SWNTs) induced by surface adsorption of various organic donor-acceptor molecules of different affinities using ab initio density functional theory. Our results, obtained from first-principles spin-polarized calculations show that the adsorption of molecules with different affinities reflects the difference in interaction strength that measure the overall energy of adsorption. Moderate values of the binding energy of these surface adsorbed molecular charge-transfer complexes suggest that the nature of interaction is in the physisorption regime, and mainly governs by Coulombic forces. We also find that the large band gap of semiconducting (8,0) SWNT can be tuned through the surface adsorption of selective organic molecules which gives rise to mid-gap localized molecular levels near the Fermi energy with tuning of band gap region. Interestingly, we find that the metallic (5,5) SWNT and semiconducting (8,0) SWNT turn into semiconducting and metallic nanotubes respectively in presence of selective surface adsorbed molecules, corroborating recent experimental findings. We also suggest that these charge transfer effect can be probed through optical conductivity measurement, as the low-frequency profiles are affected by charge transfer.

Conformational tuning of magnetic interactions in metal-DNA complexes

The alignment of Cu(2+) ions along a modified DNA helix is studied with either hydroxypyridone (H) or bis(salicylaldehyde)ethylenediamine (S-en) metalated base pairs (MBPs). The conformational motion of H-MBP leads to the interlinking of the H-MBPs by an extended Cu-O network that is ferromagnetic, whereas the conformational freezing of the S-en-MBP leads to an ordered pairwise-stacked arrangement that is weakly antoferrimagnetic.

Ab initio study of structural and magnetic properties of TM(n)(ferrocene)(n+1) (TM = Sc, Ti, V, Mn) sandwich clusters and nanowires (n = infinity)

Structural and magnetic properties of multidecker sandwich clusters TM(n)(ferrocene)(n+1) [TM = V, Ti, Sc, Mn, ferrocene=FeCp(2), n = 1-3] and corresponding one-dimensional sandwich nanowires (n = infinity) are studied by means of gradient-corrected density functional theory. The TM(n)(FeCp(2))(n+1) clusters are highly stable polyferrocene-like sandwich structures due to strong Fe-Cp interaction. The total magnetic moment of TM(n)(FeCp(2))(n+1) (TM = V, Ti, Mn) increases linearly with the size n. More strikingly, Ti(n)(FeCp(2))(n+1) and V(n)(FeCp(2))(n+1) (n = 1-3) exhibit high magnetic moments 4, 8, 12 mu(B) and 1, 6, 11 mu(B), respectively. In contrast, Sc(n)(FeCp(2))(n+1) clusters are paramagnetic. The [TM(FeCp(2))](infinity) sandwich nanowires are ferromagnetic semiconductors whose band gap is 0.361, 0.506, 0.51, and 1.310 eV, respectively, for TM = Ti, Sc, V, and Mn. Among the four sandwich nanowires, [V(FeCp(2))](infinity) nanowire possesses the highest magnetic moment (5 mu(B)) per unit cell.

Intrinsic half-metallicity in modified graphene nanoribbons

We perform first-principles calculations based on density functional theory to study quasi-one-dimensional edge-passivated (with hydrogen) zigzag graphene nanoribbons of various widths with chemical dopants, boron and nitrogen, keeping the whole system isoelectronic. The gradual increase in doping concentration takes the system finally to zigzag boron nitride nanoribbons (ZBNNRs). Our study reveals that for all doping concentrations the systems stabilize in antiferromagnetic ground states. Doping concentrations and dopant positions regulate the electronic structure of the nanoribbons, exhibiting both semiconducting and half-metallic behaviors as a response to the external electric field. Interestingly, our results show that ZBNNRs with a terminating polyacene unit exhibit half-metallicity irrespective of the ribbon width as well as applied electric field, opening a huge possibility in spintronics device applications.