The electrical transport and chemical sensing properties of individual multisegmented Au-poly(3,4-ethylenedioxythiophene)(PEDOT)-Au nanowires have been investigated. Temperature dependent conductivity measurements show that different charge transport mechanisms influence these properties in two types of PEDOT nanowires. Charge transport in PEDOT/poly(4-styrenesulfonic acid) (PSS) nanowires is in the insulating regime of the metal-insulator transition and dominated by hopping, while PEDOT/perchlorate (CIO4) nanowires are slightly on the metallic side of the critical regime. The vapor sensing properties of individual nanowires to water and methanol reflect the fact that the two kinds of PEDOT nanowires operate in different transport regimes. Nanowires in the metallic transport regime show much greater sensitivity to vapor-phase analytes than those in which transport is dominated by hopping.
The microwave induced magnetoresistance in a GaAs/AlGaAs heterostructure was studied at temperatures below 1K and frequencies in the range of 150-400 GHz. A distinct node in the
We discuss the effects of the spin-orbit interaction on heavy atom organic magnets with specific reference to a series of isostructural sulfur-and selenium-based radical ferromagnets of tetragonal space group P42 1 m. Using a perturbative approach, we show the spin-orbit effects lead to a pairwise anisotropic exchange interaction between neighboring radicals that provides an easy magnetic axis running parallel to the c-axis. Estimates of the magnitude of this magnetic anisotropy explain the significant increase in the coercive fields by virtue of selenium incorporation. Complementing this theoretical discussion are the results of ferromagnetic resonance studies, which provide an experimental verification of both the magnitude and symmetry of the spin-orbit terms. Taken as a whole, the results underscore the importance of heavy atoms and crystal symmetry in the design of molecular ferromagnets with large magnetic anisotropy and high ordering temperatures.
We demonstrate a new method for determining the Fermi velocity in quasi-two-dimensional (Q2D) conductors. Application of a magnetic field parallel to the conducting layers results in periodic open orbit quasiparticle trajectories along the Q2D Fermi surface. Averaging of this motion over the Fermi surface leads to a resonance in the interlayer microwave conductivity. The resonance frequency is simply related to the extremal value of the Fermi velocity perpendicular to the applied field. Thus, angle dependent microwave studies enable a complete mapping of the in-plane Fermi velocity. We illustrate the applicability of this method for the highly 2D organic conductor kappa-(BEDT-TTF)2I3.
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