Search

We use resonant soft x-ray diffraction to track the photoinduced dynamics of the antiferromagnetic structure in a NdNiO3 thin film. Femtosecond laser pulses with a photon energy of 0.61 eV, resonant with electron transfer between long-bond and short-bond nickel sites, are used to excite the material and drive an ultrafast insulator-metal transition. Polarization-sensitive soft x-ray diffraction, resonant to the nickel L3 edge, then probes the evolution of the underlying magnetic spiral as a function of time delay with 80 ps time resolution. By modeling the azimuthal dependence of the scattered intensity for different linear x-ray polarizations, we benchmark the changes of the local magnetic moments and the spin alignment. The measured changes are consistent with a reduction of the long-bond site magnetic moments and an alignment of the spins towards a more collinear structure at early time delays.

A gold electrode was derivatized by electrochemical reduction of anthraquinone-2-diazonium tetrafluoroborate (AQ2-N 2+BF 4-) giving an Au-AQ2 modified electrode of a surface coverage below a monolayer. Simulations of cyclic voltammograms using Marcus-Hush-Chidsey theory for 2e - process and assuming a uniform surface were not able to achieve a good fit for the overall shape of the baseline subtracted experimental voltammograms. Subsequently two models of surface inhomogeneity based on Marcus-Hush-Chidsey theory were investigated: a distribution of formal potentials, E o′, and a distribution of electron tunneling distances, r 0. The simulation of cyclic voltammograms involving the distribution of formal potentials allowed a good agreement between theory and experiment. The parameters of the Au-AQ2/Au-AQ2 2- process compared to the parameters of the EPPG-AQ2/EPPG-AQ2 2- process reported previously by Kozub et al. (ChemPhysChem, 12 (2011) 2806) show much faster kinetics, attributed to the higher density of electronic states for a gold electrode. © 2011 by ESG.