The Raman spectrum of 2-formylfuran in the liquid phase shows pairs of bands whose temperature and solvent dependence behavior can be interpreted in terms of cis-trans conformational equilibrium. Density functional theory (DFT) calculations performed at the BPW91/6-311+G * and B3LYP/6-311+G * theoretical levels show that the trans-isomer is more stable than the cis-isomer by 2.81 and 3.12 kJ mol −1 , respectively. The theoretical 1H values obtained at these theoretical levels [2.99 kJ mol −1 (BPW91) and 3.2 kJ mol −1 (B3LYP)] are very close to the experimental value 1H = 2.52 kJ mol −1 determined from the plots of logarithmic relative intensities of the band pairs 1673/1692, 1477/1465 and 1396/1371 cm −1 of these isomers against reciprocal temperature. The surface-enhanced Raman spectrum of 2-formylfuran in silver colloid suggests the chemisorption of this molecular species on the silver surface both through the ring oxygen and the oxygen atom of the substituent group, the cis-form being preferred in the adsorption state. The adsorbed molecules are oriented perpendicular or least tilted with respect to the silver surface.

No abstract

In this paper we report our experimental and theoretical studies on the effect of Gd impurity on the physical properties of the Heusler half-metallic ferromagnet Co 2 MnSi. The analysis of the band structures of the doped alloy shows that the half-metallic properties are completely conserved if Gd substitutes Mn atoms. This effect is not determined by the spin-orbit interaction, but through the coupling between the R(4f ) spin with the Mn(3d) itinerant electron spins. We evaluate the strength of such a coupling by calculating, in an ab initio fashion, the total energy of Co 16 GdMn 7 Si 8 compound for a parallel and antiparallel f -d coupling. The obtained magnetic moments of Co or Mn sites are in good agreement with the experimental ones.

International audienceNot Availabl

Abstract:X-ray photoelectron spectroscopy (XPS), magnetization and magnetic susceptibility of Mn 1− Al Ni 3 ( = 0.0, 0.2, 0.4, 0.5, 0.6, 0.7) alloys are reported. X-ray diffraction measurements showed that all investigated samples have the same crystallographic structure as the parent compound (AuCu 3 -structure type). The alloys are disordered for ≤ 0 5, but become almost crystallographically ordered for higher Al concentration. This change in the crystallographic order is reflected both in the magnetization and Curie temperature values. The exchange interaction is ferromagnetic between the pairs of the near-neighbour Mn-Ni and Ni-Ni magnetic moments and antiferromagnetic for Mn-Mn pairs. The last one is present only in the disordered alloys, which leads to smaller values of the magnetization of these alloys in comparison with the ordered ones. The Mn magnetic moment has the fully ordered value of 3.2 µ B in all investigated alloys. The decrease of the Ni magnetic moment as the Al concentration increases may be explained by the hybridization of the Ni 3d and Al 3sp states, which leads to a partial filling of the Ni 3d band. The magnetic susceptibility measurements pointed out the existence of spin fluctuations on Ni sites. 71.20.Lp, 75.20.Hr, 75.30.Cr, PACS (2008): Keywords:transition metal alloys and compounds • magnetic measurements • XPS spectra • local moments • spin fluctuations © Versita Warsaw and Springer-Verlag Berlin Heidelberg.