Insights into the use of Flash Sintering methods to prepare catalytic materials

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Multi-terminal transistor-like devices based on strongly correlated metallic oxides for neuromorphic applications

Memristive devices are attracting a great attention for memory, logic, neural networks, and sensing applications due to their simple structure, high density integration, low-power consumption, and fast operation. In particular, multi-terminal structures controlled by active gates, able to process and manipulate information in parallel, would certainly provide novel concepts for neuromorphic systems. In this way, transistor-based synaptic devices may be designed, where the synaptic weight in the postsynaptic membrane is encoded in a source-drain channel and modified by presynaptic terminals (gates). In this work, we show the potential of reversible field-induced metal-insulator transition (MIT) in strongly correlated metallic oxides for the design of robust and flexible multi-terminal memristive transistor-like devices. We have studied different structures patterned on YBa2Cu3O7−δ films, which are able to display gate modulable non-volatile volume MIT, driven by field-induced oxygen diffusion within the system. The key advantage of these materials is the possibility to homogeneously tune the oxygen diffusion not only in a confined filament or interface, as observed in widely explored binary and complex oxides, but also in the whole material volume. Another important advantage of correlated oxides with respect to devices based on conducting filaments is the significant reduction of cycle-to-cycle and device-to-device variations. In this work, we show several device configurations in which the lateral conduction between a drain-source channel (synaptic weight) is effectively controlled by active gate-tunable volume resistance changes, thus providing the basis for the design of robust and flexible transistor-based artificial synapses

Heavy-mineral provenance signatures during the infill and uplift of a foreland basin : An example from the Jaca basin (southern Pyrenees, Spain)

In the Jaca foreland basin (southern Pyrenees), two main sediment routing systems merge from the late Eocene to the early Miocene, providing an excellent example of interaction of different source areas with distinct petrographic signatures. An axially drained fluvial system, with its source area located in the eastern Central Pyrenees, is progressively replaced by a transverse-drained system that leads to the recycling of the older turbiditic foredeep. Aiming to provide new insights into the source-area evolution of the Jaca foreland basin, we provide new data on heavy-mineral suites, from the turbiditic underfilled stage to the youngest alluvial-fan systems of the Jaca basin, and integrate the heavy-mineral signatures with available sandstone petrography. Our results show a dominance of the ultrastable Ap-Zrn-Tur-Rt assemblage through the entire basin evolution. However, a late alluvial sedimentation stage brings an increase in other more unstable heavy minerals, pointing to specific source areas belonging to the Axial and the North Pyrenean Zone and providing new insights into the response of the heavy-mineral suites to sediment recycling. Furthermore, we assess the degree of diagenetic overprint vs. provenance signals and infer that the loss of unstable heavy minerals due intrastratal dissolution is negligible at least in the Peña Oroel and San Juan de la Peña sections. Finally, we provide new evidence to the idea that during the late Eocene the water divide of the transverse drainage system was located in the North Pyrenean Zone, and areas constituted by the Paleozoic basement were exposed in the west-Central Pyrenees at that time. Our findings provide new insights into the heavy-mineral response in recycled foreland basins adjacent to fold-and-thrust belts

Formation of self-organized Mn3O4 nanoinclusions in LaMnO3 films

et al.We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn3O4) in a pristine perovskite matrix (LaMnO3) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO3 stoichiometric target by Pulsed Laser Deposition, the most favorable mechanism to accommodate Mn2+ cations is the spontaneous segregation of self-assembled wedge-like Mn3O4 ferrimagnetic inclusions inside a LaMnO3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behavior. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn3O4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight (~9°) c-axis tilting. Furthermore, a Ruddlesden-Popper La2MnO4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn3O4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions.Financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Program for Centres of Excellence in R&D (SEV-2015-0496 and SEV 2013-0295), Projects MAT2011-29081 and MAT2015-71664-R and Ministry of Education and Science of Serbia (Grant—III45018) is acknowledged. This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 645658 (DAFNEOX Project). NB thanks the Spanish MINECO for financial support through the FPI program.Peer reviewedPeer Reviewe

Influence of porosity on the critical currents of trifluoroacetate-MOD YBa2Cu3O7 films

The influence of porosity on the superconducting properties have been investigated on YBa/sub 2/Cu/sub 3/O/sub 7/ thin films deposited on LaAlO/sub 3/ [100] substrates by the so-called Trifluoroacetate (TFA) route. Micro-Raman spectroscopy have been used to determine the concentration of c-axis grains /spl delta/ in different samples and their influence on the final film porosity as observed from SEM imaging. This has been compared with measurements of resistivity and critical currents in the same samples. We prove that this /spl delta/ fraction is the main parameter controlling the porosity and hence the normal-state resistivity of the thin films. The optimization of the microstructure of these YBa/sub 2/Cu/sub 3/O/sub 7/ TFA films allow to have high critical currents : J/sub c/ = 3 /spl times/ 10/sup 6/ A/cm/sup 2/ at 77 K

Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001

This research has been funded by the Spanish Ministry of Science and Innovation (projects: AYA2011‐26,522, AYA 2015‐67175‐P, CTQ2015‐62,635‐ERC, and CTQ2014‐60,119‐P to which J.M. Trigo‐Rodríguez and C.E. Moyano‐Cambero acknowledge financial support). The UK Science and Technology Facilities Council is also thanked for funding through grants ST/H002960/1, ST/K000942/1, and ST/L002167/1. ICN2 and ICMAB acknowledge support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grants SEV‐2013‐0295 and SEV‐2015‐0496, respectively. We acknowledge B. Ballesteros and M. Rosado from the ICN2 Electron Microscopy Division, and A. Fernández from the ICTS (National Center of Electronic Microscopy) for the SEM, EDS, and microprobe measurements. We also thank the NASA Meteorite Working Group, and the Johnson Space Center for providing the ALH 84001,82 section. This study was done in the frame of a PhD on Physics at the Autonomous University of Barcelona (UAB) under the direction of J. M. Trigo‐Rodríguez.Peer reviewedPublisher PD

Multiwavelength excitation Raman scattering analysis of bulk and 2 dimensional MoS2: vibrational properties of atomically thin MoS2 layers

In order to deepen the knowledge of the vibrational properties of two-dimensional (2D) MoS2 atomic layers, a complete and systematic Raman scattering analysis has been performed using both bulk single-crystal MoS2 samples and atomically thin MoS2 layers. Raman spectra have been measured under non-resonant and resonant conditions using seven different excitation wavelengths from near-infrared (NIR) to ultraviolet (UV). These measurements have allowed us to observe and identify 41 peaks, among which 22 have not been previously experimentally observed for this compound, and characterize the existence of different resonant excitation conditions for the different excitation wavelengths. This has also included the first analysis of resonant Raman spectra that are achieved using UV excitation conditions. In addition, the analysis of atomically thin MoS2 layers has corroborated the higher potential of UV resonant Raman scattering measurements for the non-destructive assessment of 2D MoS2 samples. Analysis of the relative integral intensity of the additional first- and second-order peaks measured under UV resonant excitation conditions is proposed for the non-destructive characterization of the thickness of the layers, complementing previous studies based on the changes of the peak frequencies

Influence of growth temperature on the pinning landscape of YBa2Cu3O7−δ films grown from Ba-deficient solutions

Cuprate coated conductors are promising materials for the development of large-scale applications, having superior performance over other superconductors. Tailoring their vortex pinning landscape through nanostructure engineering is one of the major challenges to fulfill the specific application requirements. In this work, we have studied the influence of the growth temperature on the generation of intrinsic pinning defects in YBa2Cu3O7-δ films grown by chemical solution deposition using low Ba precursor solutions. We have analysed the critical current density as a function of the temperature, applied magnetic field magnitude and orientation, J c(T,H,θ), to elucidate the nature and strength of pinning sites and correlate the microstructure of the films with their superconducting performance. An efficient pinning landscape consisting of stacking faults and associated nanostrain is naturally induced by simply tuning the growth temperature without the need to add artificial pinning sites. Samples grown at an optimized temperature of 750 °C show very high self-field J c values correlated with an overdoped state and improved J c(T,H,θ) performances.This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom Research and Training Programme 2014–2018 and 2019–2020 under Grant Agreement No. 633 053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. TEM analysis was funded from the EU Horizon 2020 research and innovation program under grant agreement 823717—ESTEEM3. The authors acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the 'Severo Ochoa' Programme for Centres of Excellence in R&D (SEV-2015-0496 and CEX2019-000917-S), SuMaTe RTI2018-095853-B-C21, co-financed by the European Regional Development Fund), the Catalan Government with Grant 2017-SGR-1519 and the EU COST action NANOCOHYBRI CA16218. We also acknowledge the Scientific Services at ICMAB. J A like to thank the UAB PhD program in Materials Science.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Spontaneous in-flight assembly of magnetic nanoparticles into macroscopic chains

Knowing the interactions controlling aggregation processes in magnetic nanoparticles is of strong interest in preventing or promoting nanoparticles’ aggregation at wish for different applications. Dipolar magnetic interactions, proportional to the particle volume, are identified as the key driving force behind the formation of macroscopic aggregates for particle sizes above about 20 nm. However, aggregates’ shape and size are also strongly influenced by topological ordering. 1-D macroscopic chains of several micrometer lengths are obtained with cube-shaped magnetic nanoparticles prepared by the gas-aggregation technique. Using an analytical model and molecular dynamics simulations, the energy landscape of interacting cube-shaped magnetic nanoparticles is analysed revealing unintuitive dependence of the force acting on particles with the displacement and explaining pathways leading to their assembly into long linear chains. The mechanical behaviour and magnetic structure of the chains are studied by a combination of atomic and magnetic force measurements, and computer simulation. The results demonstrate that [111] magnetic anisotropy of the cube-shaped nanoparticles strongly influences chain assembly features.The authors acknowledge the financial support from European Commission H2020 project DAFNEOX (Grant No. 645658). I. S. and Z. K. acknowledge the support of Ministry of Education, Science, and Technological Development of Republic of Serbia – projects ON171017 and III45018. Financial support from Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496), RTI2018-099960-B-I00, and MAT2015-71664-R, co-financed by the European Regional Development Fund, is gratefully acknowledged. I.S. and C.G. acknowledge the financial support received from Proyecto CONICYT PIA/Basal FB 0821 and CONICYT MEC80170122. A.P., V.F. and Z.K. thank Senzor-INFIZ (Serbia) for the cooperation provided during their respective secondments. Numerical calculations were run on the PARADOX supercomputing facility at the Scientific Computing Laboratory of the Institute of Physics Belgrade.We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe