Dario Niebieskikwiat
National University of Cuyo
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Publication
Featured researches published by Dario Niebieskikwiat.
Solid State Communications | 2001
M.S. Moreno; J.E Gayone; M Abbate; A Caneiro; Dario Niebieskikwiat; R.D. Sánchez; A. de Siervo; Richard Landers; Guillermo Zampieri
Abstract The valences of Fe and Mo in Sr 2 FeMoO 6 are investigated by means of X-ray absorption and photoemission spectroscopies. We find that the d occupations are similar to those of Fe in Fe 2 O 3 and Mo in MoO 3 . Considering the covalency, however, we argue that the ground state is closer to a Fe +3 (3 d 5 )–Mo +5 (4 d 1 ) configuration than to a Fe +2 (3 d 6 )–Mo +6 (4 d 0 ) configuration.
Journal of Magnetism and Magnetic Materials | 2001
Dario Niebieskikwiat; R.D. Sánchez; A. Caneiro
Abstract We have performed measurements of thermoelectric power, electrical resistivity and DC magnetization in polycrystalline samples of Pr 0.65 Ca 0.35− x Sr x MnO 3 with x =0, 0.02, 0.05, 0.10 and 0.20. The system presents an evolution from a charge-ordered manganite at x =0, with an insulating-like resistivity and low magnetization values, towards a ferromagnetic (FM) metallic state for x =0.20. We show that in the intermediate region a strong competition between the FM double-exchange and the localized charge-ordering occurs, inducing the phase segregation of the two competing states in a wide temperature range. We estimate the temperature ( T ) evolution of the FM phase fraction of the x =0.10 sample and construct a complete T − x phase diagram.
Physica B-condensed Matter | 2002
Dario Niebieskikwiat; A. Caneiro; R.D. Sánchez; J. Fontcuberta
Abstract We study the magnetic and electric properties of polycrystalline Sr 2 FeMoO 6+ δ with controlled oxygen content, for nominal values δ =0 and 0.04. While the magnetization and lattice parameters are the same in both samples, the resistivity and the magnetoresistance are greatly enhanced in the δ =0.04 sample. This behavior is related to the formation of an impurity (insulating) phase at the grain boundaries, thus reinforcing the intergrain tunneling barrier.
Physica B-condensed Matter | 2002
M.S. Moreno; J.E Gayone; M Abbate; A. Caneiro; Dario Niebieskikwiat; R.D. Sánchez; A. de Siervo; Richard Landers; Guillermo Zampieri
Abstract We have used electron spectroscopies to investigate the electronic structure of the double perovskite Sr2FeMoO6. The valence-band photoemission spectra present a well-defined cut-off at the Fermi level, indicative of the metallic character of the material. The O 1s X-ray absorption spectrum presents three peaks, which are in good correspondence with the main structures in the unoccupied density-of-states of DF-LDA calculations. The electron energy-loss spectra present two structures which are also interpreted in terms of transitions between the bands obtained in the DF-LDA calculations.
Physical Review B | 2002
Dario Niebieskikwiat; R.D. Sánchez; Liliana Morales; B. Maiorov
We address the problem of the percolative phase separation in polycrystalline samples of
Physica B-condensed Matter | 2002
R.D. Sánchez; Dario Niebieskikwiat; D.G. Lamas; A. Caneiro; L. E. Hueso; J. Rivas; F. Rivadulla; M. A. López-Quintela
{\mathrm{Pr}}_{0.5\ensuremath{-}\ensuremath{\delta}}{\mathrm{Ca}}_{0.2+\ensuremath{\delta}}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}
Physica B-condensed Matter | 2002
D.G. Lamas; A. Caneiro; Dario Niebieskikwiat; R.D. Sánchez; D. Garcı́a; B. Alascio
for
Physica B-condensed Matter | 2002
Dario Niebieskikwiat; R.D. Sánchez; A. Caneiro; Boris A. Maiorov
\ensuremath{-}0.04l~\ensuremath{\delta}l~0.04
Physical Review B | 2001
Dario Niebieskikwiat; A. Caneiro; R.D. Sánchez; J. Fontcuberta
(hole doping n between
Physical Review B | 2000
Dario Niebieskikwiat; R.D. Sánchez; A. Caneiro; Liliana Morales; M. Vásquez-Mansilla; F. Rivadulla; L. E. Hueso
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