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Dive into the research topics where Dario Niebieskikwiat is active.

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Featured researches published by Dario Niebieskikwiat.


Solid State Communications | 2001

Fe and Mo Valences in Sr2FeMoO6

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

Phase separation region in the phase diagram of polycrystalline Pr0.65Ca0.35−xSrxMnO3

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

Enhancement of the low field magnetoresistance by grain boundary modification in Sr2FeMoO6+δ

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

Electronic structure of Sr2FeMoO6

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

Hole-doping dependence of percolative phase separation in Pr 0.5 − δ Ca 0 . 2 + δ Sr 0.3 MnO 3 around half doping

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

Nonlinear behavior of V-I curves at low temperatures in nanoparticles of La2/3B1/3MnO3 with B = Ca, Sr

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

Spin-polarized tunneling in nanostructured La2/3Sr1/3MnO3

D.G. Lamas; A. Caneiro; Dario Niebieskikwiat; R.D. Sánchez; D. Garcı́a; B. Alascio

for


Physica B-condensed Matter | 2002

Asymmetric phase diagram and phase separation in Pr0.5−δCa0.2+δSr0.3MnO3 (−0.04⩽δ⩽0.04)

Dario Niebieskikwiat; R.D. Sánchez; A. Caneiro; Boris A. Maiorov

\ensuremath{-}0.04l~\ensuremath{\delta}l~0.04


Physical Review B | 2001

Oxygen-induced grain boundary effects on magnetotransport properties of Sr 2 FeMoO 6 + δ

Dario Niebieskikwiat; A. Caneiro; R.D. Sánchez; J. Fontcuberta

(hole doping n between


Physical Review B | 2000

High-temperature properties of theSr2FeMoO6double perovskite: Electrical resistivity, magnetic susceptibility, and ESR

Dario Niebieskikwiat; R.D. Sánchez; A. Caneiro; Liliana Morales; M. Vásquez-Mansilla; F. Rivadulla; L. E. Hueso

0.46

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R.D. Sánchez

National University of Cuyo

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A. Caneiro

National University of Cuyo

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Alberto Caneiro

National Scientific and Technical Research Council

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F. Rivadulla

University of Santiago de Compostela

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L. E. Hueso

University of Santiago de Compostela

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Guillermo Zampieri

National University of Cuyo

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M.S. Moreno

National University of Cuyo

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Richard Landers

State University of Campinas

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J. Rivas

University of Santiago de Compostela

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