SUMARIO: 1. Las nuevas tecnologías conducen a nuevas formas de ciudadanía y sociedad. ¿Cómo pueden las tecnologías de la información cambiar la relación entre los ciudadanos y la toma de decisiones políticas? - 2. ¿Cuál es el nuevo papel de los parlamentarios? ¿Cuál es el nuevo papel de los ciudadanos? - 3. Nueva relación electrónica con los ciudadanos: ¿Está Internet cambiando la actitud política de los ciudadanos?
We report results of structural, optical and electrical transport studies of indium oxide (IO) thin films grown by Pulsed Laser Deposition (PLD) under various oxygen gas pressures and using different substrates at 350° C. We find that the morphology and electrical resistivity of these films which are highly transparent changes drastically as Opressure increases into mbar range, irrespective of substrate. A systematic increase in resistivity, coming mainly from a drop in the electron concentration, is observed as oxygen pressure varies from 0.0004 to 1 mbar. This could permit modulation of IO thin–films' electrical parameters by more than three orders of magnitude suggesting that PLD grown films could be an attractive material for optoelectronic applications. ; We acknowledge support from grants MAT2012-38213-C02-01 and MAT2012-38213-C02-02, and MAT2015-686760-02-1-P and MAT2015-686760-02-2-P from the Ministerio de Economía y Competividad of Spain. These grants are co-funded by ERDF of European Union. Additional support from Diputación General de Aragón (DGA-CAMRADS) is also acknowledged. ; Peer Reviewed
We present a complete structural study of the successive phase transitions observed in the YBaMn2O6compound with the layered ordering of cations on the perovskite A-site. We have combined synchrotron radiation X-ray powder diffraction and symmetry-adapted mode analysis to describe the distorted structures as pseudosymmetric with respect to the parent tetragonal structure. The YBaMn2O6compound shows three consecutive phase transitions on cooling from 603 K down to 100 K. It undergoes a first-order structural transition atT1≈ 512 K from aC2/mcell with a single Mn site to aP21/ccell with two nonequivalent Mn sites. No checkerboard ordering of the two types of MnO6octahedra is revealed, and there is no significant charge segregation. A second transition is observed belowT2≈ 460 K giving rise to a duplication of thec-axis and the occurrence of four nonequivalent Mn sites. These sites are grouped in two pairs, producing, in this case, a checkerboard arrangement in theab-plane with an average charge segregation of Δq≈ 0.4 e-. The observed distortions in this phase disagree with the formation of an orbital-ordered phase. Finally, another structural transition is observed coupled to the magnetic transition atTN≈ 200 K and thec-axis is no longer duplicated. The low-temperature phase is polar with SGP21. It also contains four nonequivalent Mn sites grouped in two pairs. The charge difference between these pairs is increased, achieving a value of Δq≈ 0.7 e-. In this phase, an asymmetric stretching mode favors a Jahn-Teller-like distortion in the expanded MnO6octahedra that could be associated with an ordering ofeg(3dx2-z2/3dy2-z2) orbitals. Our refinements disclose that this phase is ferroelectric with significant polar displacements of the Mn and Obasalatoms along theb-axis. The simultaneous occurrence of ferroelectricity and magnetic ordering indicates that YBaMn2O6can be considered as a type II multiferroic compound and can present magnetoelectric coupling. ; The authors would like to acknowledge the use of Servicio General de Apoyo a la Investigación from Universidad de Zaragoza. Granted beam time at ALBA synchrotron is appreciated (Proposal No. 2018093038). For financial support, the authors thank the Spanish Ministerio de Ciencia, Innovación y Universidades (Project Nos. RTI2018-098537-B-C22 and -C21 co-funded by ERDF from EU, and Severo Ochoa FUNFUTURE, CEX2019-000917-S), and Diputación General de Aragón (Project E12-20R). ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000917-S). ; Peer reviewed
6 páginas, 5 figuras, 1 tabla.-- PACS number(s): 71.30.+h, 75.25.Dk, 75.30.Wx, 78.70.Dm.-- et al. ; X-ray absorption spectroscopy measurements in Pr0.5Ca0.5CoO3 and (Pr,Y)0.55Ca0.45CoO3 compositions reveal that the valence of praseodymium ions is stable and essentially +3 (Pr [4f2]) in the metallic state, but abruptly changes when carriers localize approaching the oxidation state +4 (Pr [4f1]). This mechanism appears to be the driving force of the metal-insulator transition. The ground insulating state of Pr0.5Ca0.5CoO3 is a homogeneous Co3.5-δ state stabilized by a charge transfer from Pr to Co sites: 1/2Pr3++Co3.5→1/2Pr3+2δ+Co3.5-δ, with 2δ ≈ 0.26e-. ; Financial support from MICINN (Spanish government) under Projects No. MAT2006-11080-C02-02 and No. MAT2009-09308, and NANOSELECT under Project No. CSD2007-00041 is acknowledged. The ALICE diffractometer is funded through the BMBF under Contract No. 05KS7PC1. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 226716 ; Peer reviewed
6 páginas, 4 figuras, 1 tabla.-- PACS number(s): 71.30.+h, 61.05.fm, 75.30.Kz, 75.47.De ; Remarkable structural changes take place during the metal to insulator first-order transition in Pr0.50Ca0.50CoO3: a contraction of the unit-cell volume, the bending of the Co-O-Co bond angle, and a decrease in (Pr,Ca)-O bond distance. However, the Co-O bond length and the volume of the CoO6 octahedra remain almost unaltered during the transition. In view of these data and the absence of transition in (Nd2/3La1/3)0.5Ca0.5CoO3, we review the current spin-state transition picture, emphasizing that an active role is played by the A-site Pr cations that could be related with the effect of Pr in 123 superconducting cuprates. ; Financial support from MICINN (Spanish government) under Projects No. MAT2006-11080-C02-02 and No. NANOSELECT CSD2007-00041, Generalitat de Catalunya (Grant No. 2005-GRQ-00509) and FAME European Network of Excellence is acknowledged. ; Peer reviewed
SUMARIO: I. Internet. Su utilidad para la institución parlamentaria.- 1. Precedentes.- 2. Conexión institucional del Senado a Internet.- II. Planteamiento inicial y versiones posteriores.-Primeras ideas.- 2. Primera versión.- 3. Segunda versión.- 4. Tercera versión. - 5. Versión actual-III. Estructura y contenidos. - 1. Información institucional o de carácter normativo.- 2. Los Órganos del Senado.- 3. Los Senadores y los Grupos Parlamentarios.- 4. Información sobre la actividad de la Cámara.- 5. El expediente parlamentario.- 6. Las Publicaciones Oficiales de las Cortes Generales.- 7. El buscador.- 8. Los foros de discusión.- 9. El Pleno en directo.-10. Versiones en inglés y sólo texto.-11. Información de Legislaturas anteriores.- 12. Historia del Senado. - 13. Las Bases de Datos del Senado en la web. -14. Otra información disponible.- IV Actualización de la página web.- V. La seguridad.- 1. Arquitectura y topología de la «zona desmilitarizada» (DMZ).- 2. Equipos y servidores.- VI. Recursos utilizados en el desarrollo informático y mantenimiento.- 1. Recursos humanos.- 2. Software utilizado.- 3. Equipamiento: informático y de comunicaciones.- VII. Estadísticas.- VIII. Evolución futura.
The layered perovskite YBaCuFeO5 (YBCFO) is able to adopt chiral magnetic order up to unexpectedly high temperatures, paving the way to strong magnetoelectric coupling at room temperature. In this perovskite A-site cations are fully ordered whereas the occupancy of the B-sites strongly depend on the preparation process. Though the structure is not geometrically frustrated, the presence of partial Fe3+/Cu2+ disorder at the B-sites produces magnetic frustration. In an effort to increase the spin-orbit coupling in the system, we have synthesized and studied YBaCuFe0.95Mn0.05O5 in single crystal form, where the highly symmetric Fe3+ ions (3d5) are partially substituted with Jahn-Teller active 3d4 Mn3+ ions. We report the structural and magnetic properties of a highly ordered single crystal of this layered perovskite, which are presented in comparison with a polycrystalline specimen (three times more disordered). Single-crystal neutron diffraction measurements reveal two collinear magnetic phases and the lack of incommensurate spiral order. The magnetic phases and transitions found in the crystal grown by the traveling solvent floating zone (TSFZ) method are fully described and analyzed in the light of its high level of Fe/Cu cationic order (~90%). ; This work has received financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (MINCIU), through Projects No. RTI2018-098537-B-C21 and RTI2018-098537-B-C22, cofunded by ERDF from EU, and "Severo Ochoa" Programme for Centres of Excellence in R&D (FUNFUTURE (CEX2019-000917-S)). X.Z. was financially supported by China Scholarship Council (CSC) with No. 201706080017. X.Z.'s and A.R.'s work was done as a part of the Ph.D program in Materials Science at Universitat Autònoma de Barcelona. We also acknowledge ALBA, ILL and D1B-CRG (MINECO) for provision of beam time (dois: 10.5291/ILL-DATA.CRG-2655, 10.5291/ILL-DATA.CRG-2478, 10.5291/ILL-DATA.CRG-2562). ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' ...
The methodology termed scanning transmission electron microscopy in scanning electron microscopy (STEM-in-SEM) has been used in this work to study the uptake of citrate stabilized gold nanoparticles (AuNPs) (average particle sizes of 23.5 ± 4.0 nm) into tissue samples upon in vitro exposure of the dissected gills of the Ruditapes philippinarum marine bivalve to the nanoparticle suspensions. The STEM-in- SEM methodology has been optimized for achieving optimum resolution under SEM low voltage operating conditions (20–30 kV). Based on scanning microscope assessments and resolution testing (SMART), resolutions well below 10 nm were appropriately achieved by working at magnifications over 100k×, with experimental sample thickness between 300 and 200 nm. These relatively thick slices appear to be stable under the beam and help avoid NP displacement during cutting. We herein show that both localizing of the internalized nanoparticles and imaging of ultrastructural disturbances in gill tissues are strongly accessible due to the improved resolution, even at sample thicknesses higher than those normally employed in standard TEM techniques at higher voltages. Ultrastructural imaging of bio-nano features in bioaccumulation experiments have been demonstrated in this study. ; Junta de Andalucía PE2009-FQM-4554, PE2011-RNM-7812, TEP-217 ; European Union CT-REGPOT2011-1-285895
We present a detailed study on the magnetic structure and magnetoelectric properties of several double perovskites R2CoMnO6(R=Ho, Tm, Yb, and Lu). All of these samples show an almost perfect (∼94%) ordering of Co2+ and Mn4+ cations in the unit cell. Our research reveals that the magnetic ground state strongly depends on the R size. For samples with larger R (Ho and Tm), the ground state is formed by a ferromagnetic order (F type) of Co2+ and Mn4+ moments, while R either remains mainly disordered (Ho) or is coupled antiferromagnetically (Tm) to the Co/Mn sublattice. For samples with smaller R (Yb or Lu), competitive interactions lead to the formation of an E-type arrangement for the Co2+ and Mn4+ moments with a large amount of extended defects such as stacking faults. The Yb3+ is partly ordered at very low temperature. The latter samples undergo a metamagnetic transition from the E into the F type, which is coupled to a negative magnetodielectric effect. Actually, the real part of dielectric permittivity shows an anomaly at the magnetic transition for the samples exhibiting an E-type order. This anomaly is absent in samples with F-type order, and, accordingly, it vanishes coupled to the metamagnetic transition for R=Yb or Lu samples. At room temperature, the huge values of the dielectric constant reveal the presence of Maxwell-Wagner depletion layers. Pyroelectric measurements reveal a high polarization at low temperature, but the onset of pyroelectric current is neither correlated to the kind of magnetic ordering nor to the magnetic transition. Our study identified the pyroelectric current as thermally stimulated depolarization current and electric-field polarization curves show a linear behavior at low temperature. Therefore, no clear ferroelectric transition occurs in these compounds. ; We acknowledge ILL and D1B-CRG Ministerio de Economía y Competitividad (MINECO) for beam time allocation (experiment codes CRG-2419, CRG-2154, and 5-31-2233) and the use of Servicio General de Apoyo a la Investigación (SAI), Universidad de Zaragoza. We are thankful for financial support from Spanish MINECO Projects No. MAT2015-68760-C2-1 and No. MAT2015- 68760-C2-2, cofunded by European Regional Development Fund (ERDF) from the European Union, the Severo Ochoa Programme (Grant No. SEV-2015-0946), and DGA (Grant No. E69-CAMRADS). ; Peer reviewed
6 páginas, 4 figuras.-- PACS number(s): 71.30.+h, 78.70.Dm, 75.30.Wx, 75.25.Dk.-- et al. ; X-ray absorption spectroscopy measurements in Pr0.5Ca0.5CoO3 were performed at the Pr M4,5, Pr L3, and Ca L2,3 absorption edges as a function of temperature below 300 K. Ca spectra show no changes down to 10 K while a noticeable thermally dependent evolution takes place at the Pr edges across the metal-insulator transition. Spectral changes are analyzed by different methods, including multiple scattering simulations, which provide quantitative details on an electron loss at Pr 4f orbitals. We conclude that in the insulating phase a fraction [15(±5)%] of Pr3+ undergoes a further oxidation to adopt a hybridized configuration composed of an admixture of atomiclike 4f1 states (Pr4+) and f-symmetry states on the O 2p valence band (Pr3+L̲ states) indicative of a strong 4f-2p interaction. ; We acknowledge financial support from MICINN (Spanish government) under Projects No. MAT2009-09308 and Nanoselect Project No. CSD2007-00041. We acknowledge ILL (and the CRG-D1B), and HZB for the provision of beam time. The ALICE diffractometer is funded through the BMBF under Contract No. 05KS7PC1. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 226716. J.H.M. thanks CSIC for JAEdoc contract. ; Peer reviewed
Under the terms of the license Creative Commons Attribution 3.0 Unported License to their work. ; We present a comparative study of the magnetic transitions in metallic Pr0.50Sr0.50CoO3 (PSCO) perovskites prepared in polycrystalline and thin film forms. As the bulk system, the strained epitaxial PSCO (010) film grown on LAO (100) is metallic in all the temperature range, with a ferromagnetic transition at 225 K, close to Tc ∼ 235 K in the ceramic PSCO specimen. Unlike the bulk system, the PSCO film does not show the second magnetic transition on cooling. In the ceramic sample, the second magnetic transition is coupled to an orthorhombic-to-monoclinic symmetry change. There is a contraction of the average ⟨Pr-O⟩ bond distance in the monoclinic phase below Ta, but the ⟨Co-O⟩ bond length is not modified across the transition. The orthorhombic to monoclinic structural transition stabilizes four short Pr-O2 bonds to basal oxygens in CoO6 octahedra. A strong hybridization of Pr 4f and O 2p orbitals in these bonds can be activated at Ta and probably assist the magnetostructural transition. ; We thank financial support from MICINN (Spanish government) under Projects MAT2009-09308, MAT2012-38213-C02-02, and CSD2007-00041 (NANOSELECT), and the ILL for granting beamtime. J.P-P thanks CSIC for JAE-Pre contract. ; Peer reviewed
The Pr-based cobaltate Pr0.5Ca0.5CoO3 (PCCO) presents in bulk form a singular simultaneous valence and spin-state transition that turns the metallic state into insulator, and displays a large and ultrafast photoresponse in the insulating phase. Epitaxial thin films of PCCO have been grown by deposition on LaAlO3(001) (LAO) substrate, chosen to minimize the mismatch with the film. The films grow epitaxially with two times the substrate periodicity (2a0×2a0×2a0) and the long perovskite axis perpendicular to the surface. We report a reduction of the structural symmetry from Pnma (bulk) to P212121 (film). The P212121 symmetry revealed by synchrotron x ray remains at low temperatures. These PCCO films are metallic, and ferromagnetic below TC=170K, confirming the stabilization of excited Co3+ spin states and the suppression of the concurrent Co spin-state, valence, and metal-insulator transitions. Z-contrast imaging and electron-energy-loss spectroscopy elemental maps reveal long-range ordered oxygen vacancy planes unexpectedly stacking parallel to the interface, in spite of the tensile character of the PCCO/LAO heterostructure. In contrast to the general tendency reported for strained La0.5Sr0.5CoO3−δ (LSCO) films, we show that a nominal tensile strain can be also compatible with the presence of alternating O vacancy planes parallel to the interface, instead of perpendicular to it. That occurs thanks to the double cell of the film and the formation of the (1/2, 1/2, 1/2) superstructure studied in this work. These results expand the possibilities of controlling interfacial physical properties via engineering of ordered oxygen-defect structures in strongly correlated oxides. ; We acknowledge financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN), through Projects No. MAT2015-686760-02-2-P, No. RTI2018-098537-B-C21, and No. RTI2018-098537-BC22, and "Severo Ochoa" Programme for Centres of Excellence in R&D (Grant No. SEV-2015-0496). The former are cofunded by ERDF of European Union, as Project No. EFA194/16 TNSI (POCTEFA/UE-FEDER). We thank also the Spanish MICINN and the Consejo Superior de Investigaciones Científicas for financial support and for provision of synchrotron radiation facilities (Grant No. CRG-BM25B, ESRF). J.G. acknowledges the Ramon y Cajal program (Grant No. RYC-2012-11709). Research at ORNL (STEM-EELS) was supported by the US Department of Energy (DOE), Basic Energy Sciences (BES), Materials Sciences and Engineering Division (SJP and MV). ; Peer reviewed
et al. ; Epitaxial films of SrMnO3 and bilayers of SrMnO3/La0.67Sr0.33MnO3 have been deposited by pulsed laser deposition on different substrates, namely, LaAlO3 (001), (LaAlO3)0.3(Sr2AlTaO6)0.7 (001), and SrTiO3 (001), allowing us to perform an exhaustive study of the dependence of antiferromagnetic order and exchange bias field on epitaxial strain. The Néel temperatures (TN) of the SrMnO3 films have been determined by low-energy muon spin spectroscopy. In agreement with theoretical predictions, TN is reduced as the epitaxial strain increases. From the comparison with first-principles calculations, a crossover from G-type to C-type antiferromagnetic orders is proposed at a critical tensile strain of around 1.6±0.1%. The exchange bias (coercive) field, obtained for the bilayers, increases (decreases) by increasing the epitaxial strain in the SrMnO3 layer, following an exponential dependence with temperature. Our experimental results can be explained by the existence of a spin-glass (SG) state at the interface between the SrMnO3 and La0.67Sr0.33MnO3 films. This SG state is due to the competition between the different exchange interactions present in the bilayer and favored by increasing the strain in the SrMnO3 layer. ; This work was supported by the Spanish Ministerio de Economía y Competitividad through Project Nos. MAT2011-28532-C03-02, MAT2011-27553-C02, MAT2012- 38213-C02-01, and MAT2014-51982-C2 including FEDER funding, by the Aragon Regional Government through projects E26 and CTPP4/11 and by the European Union under the Seventh Framework Programme under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2. N. Marcano acknowledges the support of the Centro Universitario de la Defensa en Zaragoza (through Project 2013-03). ; Peer Reviewed
