Search

Proximity effect between superconductors and ferromagnets may become long range due to the generation of triplet pairs. The recent finding of a long one micron-range unconventional Josephson effect between YBa2Cu3O7 High Tc cuprates separated by a half metallic La0.7Sr0.3MnO3 manganite ferromagnet has uncovered a novel unconventional triplet proximity effect. In this paper we examine the temperature dependence of the critical current of planar Josephson junctions. We find that the critical current –normal resistance product follows the predictions of traditional superconductor-normal metal-superconductor junctions which implies that triplet pairs in a ferromagnet are transported in the diffusive limit similarly to singlet pairs in a normal metal. This result calls for theoretical studies of the new triplet Josephson effect and underlines its potential in future superconducting spintronics.

Ferroelectric oxides with low bandgaps are mainly based on the BiFeO perovskite upon the partial substitution of iron with different cations. However, the structural stability of many of these perovskites is only possible by their processing at high pressures (HP, >1GPa) and high temperatures (HT, >700ºC). Preparation methods under these severe conditions are accessible to powders and bulk ceramics. However, transferring these conditions to the fabrication of thin films is a challenge, thus limiting their use in applications. Here, a chemical solution deposition method is devised, which overcomes many of these restrictions. It is based on the application of an external compressive-stress to the film sample during the thermal treatment required for the film crystallization, promoting the formation and stabilization of these HP perovskites. We demonstrate the concept on BiFeCrO (BFCO) thin films deposited on SrTiO (STO) substrates and with large chromium contents. The resulting BFCO perovskite films show narrow bandgaps (Eg∼2.57 eV) and an excellent ferroelectric response (remnant polarization, P∼ 40 μC cm). The polarized thin films under illumination present a large out-put power of ∼6.4 μW cm, demonstrating their potential for using in self-powered multifunctional devices. This stress-mediated solution deposition method can be extended to other perovskite films which are unviable under conventional deposition methods., This work has been financed by Spanish Projects PID2019-104732RB-I00, MAT2016-76851-R, MAT2017-91772-EXP (AEI/FEDER, UE) and RTI2018-096918-B-C41. I.B. acknowledges financial support from the Ramón&Cajal Spanish Programm. We thank Dr. M. Coll and P. Machado for the deposition of LSMO layers on the STO substrates (Instituto de Ciencia de Materiales de Barcelona ICMAB-CSIC). M.L.-C. and H.X. acknowledges the support from Spanish MINECO for the grant GraPErOs (ENE2016-79282-C5-2-R), the OrgEnergy Excellence NetworkCTQ2016-81911- REDT, the Agència de Gestiód'Ajuts Universitaris i de Recerca (AGAUR) for the support to the consolidated Catalonia research group 2017 SGR 329 and the Xarxa de Referència en Materials Avançats per a l'Energia (Xarmae). ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme / Generalitat de Catalunya.

We investigate the intercalation process of oxygen in-between a PVD-grown graphene layer and different copper substrates as a methodology for reducing the substrate-layer interaction. This growth method leads to an extended defect-free graphene layer that strongly couples with the substrate. We have found, by means of X-ray photoelectron spectroscopy, that after oxygen exposure at different temperatures, ranging from 280 °C to 550 °C, oxygen intercalates at the interface of graphene grown on Cu foil at an optimal temperature of 500 °C. The low energy electron diffraction technique confirms the adsorption of an atomic oxygen adlayer on top of the Cu surface and below graphene after oxygen exposure at elevated temperature, but no oxidation of the substrate is induced. The emergence of the 2D Raman peak, quenched by the large interaction with the substrate, reveals that the intercalation process induces a structural undoing. As suggested by atomic force microscopy, the oxygen intercalation does not change significantly the surface morphology. Moreover, theoretical simulations provide further insights into the electronic and structural undoing process. This protocol opens the door to an efficient methodology to weaken the graphene-substrate interaction for a more efficient transfer to arbitrary surfaces., This work was supported by the Spanish MINECO (GrantsMAT2017-85089-C2-1-R and RYC-2015-17730), the EU via the ERC-Synergy Program (Grant ERC-2013-SYG-610256 NANOCOSMOS), EUGraphene Flagship funding (Grant GrapheneCore3 881603) and the''Comunidad de Madrid'' via the FotoArt-CM project (S2018/NMT-4367). JA acknowledges support from the FPI program of SpanishMINECO (BES-2012-058600).

The Josephson effect results from the coupling of two superconductors across a spacer such as an insulator, a normal metal or a ferromagnet to yield a phase coherent quantum state. However, in junctions with ferromagnetic spacers, very long-range Josephson effects have remained elusive. Here we demonstrate extremely long-range (micrometric) high-temperature (tens of kelvins) Josephson coupling across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7. These planar junctions, in addition to large critical currents, display the hallmarks of Josephson physics, such as critical current oscillations driven by magnetic flux quantization and quantum phase locking effects under microwave excitation (Shapiro steps). The latter display an anomalous doubling of the Josephson frequency predicted by several theories. In addition to its fundamental interest, the marriage between high-temperature, dissipationless quantum coherent transport and full spin polarization brings opportunities for the practical realization of superconducting spintronics, and opens new perspectives for quantum computing. Josephson coupling over micrometres and at tens of kelvins is demonstrated across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7.

Magnetoimpedance spectroscopy was carried out on phase-separated La

The effect of Ni2+ substitution on the magneto-transport properties and the concomitant relationship with the magnetocaloric function of nano-sized La0.7Ca0.3Mn1−xNixO3 (x = 0, 0.02, 0.07, and 0.10) perovskite manganites are reported. All the samples were synthesized using the auto-combustion method. X-ray diffraction analysis studies confirmed the phase purity of the synthesized samples. The substitution of Mn3+ ions with Ni2+ ions in the La0.7Ca0.3MnO3 lattice was also verified using this technique. Rietveld analysis indicated that the volume of the unit cell increased with increasing Ni2+ content. Zero-field-cooled and field-cooled magnetization showed that all samples underwent a paramagnetic-ferromagnetic phase transition, which was concomitant with a metal-insulator transition. A small deviation between the zero-field-cooled and field-cooled magnetization curves was observed when the measurements were carried out in a field of 1000 Oe. The Curie temperature decreased systematically from 264 K for x = 0 to 174 K for x = 0.10. Probably the doping at the Mn3+ sites with Ni2+ ions in the La0.7Ca0.3MnO3 lattice weakened the Mn3+-O-Mn4+ double exchange interaction, which led to a decrease in the transition temperature. The metal-insulator transition also shifted to lower temperatures upon Ni2+ substitution, and the value of the resistivity increased. Different conduction mechanisms were found in different temperature regions. Important physical parameters such as the polaron activation energy were obtained from the fit of the models to the experimental data. Arrot’s plots revealed a second-order nature of the magnetic transition for all the samples, which was also confirmed by Landau’s theory and universal curves. The second-order character of the magnetic phase transition observed in the pristine La0.7Ca0.3MnO3 sample may be attributed to effects of the downsizing of the particle. Interestingly, a notable increase in the value of the magnetic entropy change was observed at Ni2+ doping levels as low as 2%. The magnetoresistance underwent a great change near the magnetic transition temperature, suggesting a close relationship between the magnetocaloric effect and magnetotransport properties in La0.7Ca0.3MnO3 manganites. Such behavior can be attributed to the spin order/disorder feature, which plays a crucial role in both effects. On the other hand, the value of the magnetoresistance of the pristine La0.7Ca0.3MnO3 sample increased upon Ni2+ doping, which is probably related to the downsizing of the particles.

We fabricate large-area atomically thin MoS2 layers through the direct transformation of crystalline molybdenum trioxide (MoO3) by sulfurization at relatively low temperatures. The obtained MoS2 sheets are polycrystalline (~10-20 nm single-crystal domain size) with areas of up to 300×300 µm2 with 2-4 layers in thickness and show a marked p-type behaviour. The synthesized films are characterized by a combination of complementary techniques: Raman spectroscopy, X-ray diffraction, transmission electron microscopy and electronic transport measurements.

In this work we analyze the role of the SiO2 layer in the functionality of Fe3O4/SiO2/Si heterostructures, which have been proved to present a strong potential for spin-based applications. Nevertheless, a complete control of the interfaces properties is fundamental for application. In this work, high quality heterostructures are fabricated avoiding chemical exchange and achieving good quality interfaces. The chemical interaction between the Fe3O4 and SiO2 layers during the heterostructures manufacture is deeply analyzed and its role on the transport, magnetic and magneto transport response is revealed. It is proven that during Fe3O4 deposition a competitive interplay happens between the catalytic action of Fe atoms, the transport of dissociated oxygen through SiO2 and the stabilization of Fe3O4. A defective silicon oxide layer is found to grow on top of the native SiO2 enabling the formation of single phase Fe3O4 layer. Such a defective layer and the granular character of the Fe3O4 determine the magnetic and transport response of the heterostructures. The present results prove that the defects in the SiO2 layer induce the switching of the MR sign, so that anomalous positive MR at RT exceeding 17% at 80 kOe is obtained in heterostructures with 19 nm thick magnetite layer, while conventional negative MR response is obtained for thicker films.

Ferromagnetic low-temperature phase (LTP) of manganese bismuth MnBi (at.%) alloy has been prepared by DC magnetron sputtering onto glass by alternative deposition of Bi and Mn with in-situ annealing. Modifying the temperature during deposition and/or during post-growth annealing leads to different microstructures ranging from quasi-isotropic isolated MnBi micro-particles to larger platelet-like individual ones up to highly coalesced textured film-like areas. These microstructural variations determine the magnetic behaviour, including change in the easy axis direction and possibility of varying coercivity from 4 to 16 kOe at room temperature. In all the cases, coercivity has a positive temperature coefficient, reaching 29 kOe at 500 K, being among the largest reported coercivity for MnBi. Isolated LTP-MnBi microstructures, being homogeneously distributed onto glass, have been grown while avoiding the presence of unreacted Bi regions between the MnBi structures. The possibility of tuning microstructural and magnetic properties, in combination with their time stability, makes them interesting candidates for high temperature permanent magnet applications., This research has been supported by MINECO (Ministerio de Economía y Competitividad) at IMDEA Nanociencia through ENMA-National project (MAT2014-56955-R) and at ICMM-CSIC by MAT2014-52405-C2-2-R; by MINECO through M-era.Net Programme: NEXMAG project (PCIN-2015-126); and by Regional Government (Comunidad de Madrid): NANOFRONTMAG (Ref. S2013/MIT-2850). EC acknowledges MINECO for the Formación Posdoctoral (JdC) program (FPDI-2013).

We present a new protocol to grow large-area, high-quality single-layer graphene on Cu foils at relatively low temperatures. We use C60 molecules evaporated in ultra high vacuum conditions as carbon source. This clean environment results in a strong reduction of oxygen-containing groups as depicted by X-ray photoelectron spectroscopy (XPS). Unzipping of C60 is thermally promoted by annealing the substrate at 800 °C during evaporation. The graphene layer extends over areas larger than the Cu crystallite size, although it is changing its orientation with respect to the surface in the wrinkles and grain boundaries, producing a modulated ring in the low energy electron diffraction (LEED) pattern. This protocol is a self-limiting process leading exclusively to one single graphene layer. Raman spectroscopy confirms the high quality of the grown graphene. This layer exhibits an unperturbed Dirac-cone with a clear n-doping of 0.77 eV, which is caused by the interaction between graphene and substrate. Density functional theory (DFT) calculations show that this interaction can be induced by a coupling between graphene and substrate at specific points of the structure leading to a local sp3 configuration, which also contribute to the D-band in the Raman spectra., Financial support from EU Horizon 2020 research and innovation program under grant agreement No. 696656 (GrapheneCore1-Graphene-based disruptive technologies) and Spanish MINECO (grants MAT2014-54231-C4-1-P,MAT2014-52405-C2-2-R, CSD2009-00013, MAT2015-64110) is acknowledged. JA and NR are supported by the FPI program from MINECO (BES-2012-058600 and BES-2015-072642, respectively). CM and JIM acknowledge the financial support by the “Ramón y Cajal” Program of MINECO (RYC-2014-16626 and RYC-2015-17730, respectively). JIM and GS acknowledge funding from the ERC-Synergy Program (grant ERC-2013-SYG-610256 Nanocosmos). JIM thanks CTI-CSIC for use of computing resources. MK and VV acknowledge funding from ERC-CZ (LL1301) project. GO-I acknowledges FCT for his grant (SFRH/BPD/90562/2012).

We present magnetoresistivity measurements in high-quality single crystals of the Nowotny chimney ladder compound Ru$_2$Sn$_3$. We find a linear and nonsaturating magnetoresistance up to 20 T. The magnetoresistance changes with the magnetic field orientation at small magnetic fields, from a positive to a negative curvature. Above 5 T, the magnetoresistance shows no sign of saturation up to 20 T for any measured angle. The shape of the anisotropy in the magnetoresistance remains when increasing temperature and Kohler's rule is obeyed. We associate the linear and nonsaturating magnetoresistance to a small Fermi surface with hot spots, possibly formed as a consequence of the structural transition. We discuss the relevance of electron-electron interactions under magnetic fields and aspects of the topologically nontrivial properties expected in Ru$_2$Sn$_3$., Comment: 6 pages, 5 figures

We fabricated large-area atomically thin MoS2 layers through the direct transformation of crystalline molybdenum trioxide (MoO3) by sulfurization at relatively low temperatures. The obtained MoS2 sheets are polycrystalline (~10&ndash, 20 nm single-crystal domain size) with areas of up to 300 &times, 300 &micro, m2, 2&ndash, 4 layers in thickness and show a marked p-type behavior. The synthesized films are characterized by a combination of complementary techniques: Raman spectroscopy, X-ray diffraction, transmission electron microscopy and electronic transport measurements.

The persistence of ferroelectricity in ultrathin layers relies critically on screening or compensation of polarization charges which otherwise destabilize the ferroelectric state. At surfaces, charged defects play a crucial role in the screening mechanism triggering novel mixed electrochemical-ferroelectric states. At interfaces, however, the coupling between ferroelectric and electrochemical states has remained unexplored. Here, we make use of the dynamic formation of the oxygen vacancy profile in the nanometer-thick barrier of a ferroelectric tunnel junction to demonstrate the interplay between electrochemical and ferroelectric degrees of freedom at an oxide interface. We fabricate ferroelectric tunnel junctions with a ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ bottom electrode and ${\mathrm{BaTiO}}_{3}$ ferroelectric barrier. We use poling strategies to promote the generation and transport of oxygen vacancies at the metallic top electrode. Generated oxygen vacancies control the stability of the ferroelectric polarization and modify its coercive fields. The ferroelectric polarization, in turn, controls the ionization of oxygen vacancies well above the limits of thermodynamic equilibrium, triggering the build up of a Schottky barrier at the interface which can be turned on and off with ferroelectric switching. This interplay between electronic and electrochemical degrees of freedom yields very large values of the electroresistance (more than ${10}^{6}%$ at low temperatures) and enables a controlled switching between clockwise and counterclockwise switching modes in the same junction (and consequently, a change of the sign of the electroresistance). The strong coupling found between electrochemical and electronic degrees of freedom sheds light on the growing debate between resistive and ferroelectric switching in ferroelectric tunnel junctions, and moreover, can be the source of novel concepts in memory devices and neuromorphic computing.

A gel consists of a network of particles or molecules formed for example using the sol-gel process, by which a solution transforms into a porous solid. Particles or molecules in a gel are mainly organized on a scaffold that makes up a porous system. Quantized vortices in type-II superconductors mostly form spatially homogeneous ordered or amorphous solids. Here we present high-resolution imaging of the vortex lattice displaying dense vortex clusters separated by sparse or entirely vortex-free regions in β-Bi2Pd superconductor. We find that the intervortex distance diverges upon decreasing the magnetic field and that vortex lattice images follow a multifractal behavior. These properties, characteristic of gels, establish the presence of a novel vortex distribution, distinctly different from the well-studied disordered and glassy phases observed in high-temperature and conventional superconductors. The observed behavior is caused by a scaffold of one-dimensional structural defects with enhanced stress close to the defects. The vortex gel might often occur in type-II superconductors at low magnetic fields. Such vortex distributions should allow to considerably simplify control over vortex positions and manipulation of quantum vortex states. Fil: Llorens, José Benito. Universidad Autónoma de Madrid; España Fil: Embon, Lior. Weizmann Institute Of Science.; Israel Fil: Correa, Alexandre. Consejo Superior de Investigaciones Científicas; España. Instituto de Ciencia de Materiales de Madrid; España Fil: González, Jesús David. Universidad del Magdalena; Colombia. Universiteit Antwerp; Bélgica Fil: Herrera, Edwin. Universidad Autónoma de Madrid; España. Universidad Central; Colombia Fil: Guillamón, Isabel. Universidad Autónoma de Madrid; España Fil: Luccas, Roberto F.. Consejo Superior de Investigaciones Científicas; España Fil: Azpeitia, Jon. Consejo Superior de Investigaciones Científicas; España Fil: Mompeán, Federico J.. Consejo Superior de Investigaciones Científicas; España Fil: García Hernández, Mar. Consejo Superior de Investigaciones Científicas; España Fil: Munuera, Carmen. Consejo Superior de Investigaciones Científicas; España Fil: Aragón Sánchez, Jazmín. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina Fil: Fasano, Yanina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina Fil: Milosevic, Milorad V.. Universiteit Antwerp; Bélgica Fil: Suderow, Hermann. Universidad Autónoma de Madrid; España Fil: Anahory, Yonathan. The Hebrew University of Jerusalem; Israel

[EN] Thin films of ferromagnetic LTP-MnBi (Low Temperature Phase of MnBi) have been grown by magnetron sputtering onto quartz substrates. Two particular issues related to LTP-MnBi have been investigated: the strong influence of the growth temperature and the degradation of magnetic properties in time. The temperature dependence on the magnetic, morphological and microstructural properties has been investigated, evidencing drastic changes on the properties of MnBi with small temperature variations. By inducing a gradient of temperature during the growth, two well differentiated regions with different morphology and crystal structure have been observed in a MnBi film sample. On the other hand, aging experiments performed in a different LTP-MnBi sample has led to a notable decrease of 54% in the saturation magnetization after 6 days and a complete loss of ferromagnetic response after 4 months., The authors acknowledge the financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) through NEXMAG (M-era.Net Programme, Ref. No. PCIN-2015- 126), 3D-MAGNETOH (Ref. No. MAT2017-89960-R) and Ref. No. MAT2014-52402-C2-2-R, and from the Regional Government of Madrid through NANOMAGCOST project (Ref. P2018/NMT-4321).

[EN] The report of the Meissner effect in annealed samples of K3Tp (Tp = p-terphenyl) above 120 K has raised the interest in this deceptively simple material concerning superconductivity. We have investigated the structural integrity of the Tp framework in the annealed samples of KxTp at increasing processing time and temperature T. Our experimental studies show that both K2Tp and K3Tp mixing stoichiometries have identical Raman (solid state) and UV–vis (1,2-dimethoxyethane solution) spectra, being consistent with the molecular dianion by density functional theory and time-dependent density functional theory simulations. Magnetization vs T plots show no signs of superconductivity and neither do conductance vs T plots. Searching for potentially active minor byproducts formed during thermal processing, the role of K-doped poly(p-phenylene) has been examined, but it does not seem to explain the reported effects either. Further efforts are needed to explain the nature of this elusive phenomenon., Financial support by the Spanish Ministry of Economy and Competitiveness (FIS2015-64222-C2-1-P, MAT2014-52405-C2-2-R, and MAT2016-78625-C2-1-2-P), the Generalitat Valenciana (Grant PROMETEO/2017/139), and the University of Alicante (VIGROB-285) is gratefully acknowledged. M.C. thanks the VIDI of the University of Alicante for a predoctoral grant. A.G. greatly appreciates the computational resources provided by the Department of Applied Physics of the University of Alicante.

Many practical applications of high T superconductors involve layered materials and magnetic fields applied on an arbitrary direction with respect to the layers. When the anisotropy is very large, Cooper pair currents can circulate either within or perpendicular to the layers. Thus, tilted magnetic fields lead to intertwined lattices of Josephson and Abrikosov vortices, with quantized circulation across and within layers, respectively. Transport in such intertwined lattices has been studied in detail, but direct observation and manipulation of vortices remains challenging. Here we present magnetic force microscopy experiments in tilted magnetic fields in the extremely quasi-two dimensional superconductor BiSrCaCuO. We trigger Abrikosov vortex motion in between Josephson vortices, and find that Josephson vortices in different layers can be brought on top of each other. Our measurements suggest that intertwined lattices in tilted magnetic fields can be intrinsically easy to manipulate thanks to the mutual interaction between Abrikosov and Josephson vortices., Work done in Madrid was supported through grant numbers FIS2017-84330-R, MDM-2014-0377, MAT2014-52405-C2-2-R, RYC-2014-16626, and RYC-2014-15093 of AEI, by the Comunidad de Madrid through program Nanofrontmag-CM (S2013/MIT-2850), by the European Research Council PNICTEYES grant agreement no. 679080, by EU Flagship Graphene Core1 under Grant Agreement no. 696656, by French ANR project OPTOFLUXTRONICS and by EU COST CA16218 Nanocohybri.SEGAINVEX at UAM is also acknowledged. We also acknowledge the support of Departamento Administrativo de Ciencia, Tecnología e Innovación, COLCIENCIAS (Colombia) Convocatoria 784-2017, and the Cluster de investigación en ciencias y tecnologías convergentes de la Universidad Central (Colombia).

We present the structural and magnetic properties of a novel series of La0.67Sr0.22Ba0.11Mn1-xFexO3 (0 ≤ x ≤ 0.3) perovskites prepared by the sol–gel method. These oxides were characterized by x-ray (XRD), neutron powder diffraction (NDP) at room temperature and magnetization measurements versus temperature and various applied magnetic fields. The NPD data, very sensitive to the octahedral tilting, show a crystallographic phase transition from an orthorhombic structure (Pnma) for x = 0 to a rhombohedral structure (R-3c) for Fe-doped samples. Magnetic data show that x = 0 and x = 0.1 perovskites exhibit a paramagnetic–ferromagnetic transition at low temperature, while for 0.2 ≤ x ≤ 0.3 a strong divergence between ZFC and FC curves suggest the presence of antagonistic antiferromagnetic and ferromagnetic interactions. The magnetic entropy change (|ΔSmax|) takes values of 2.46 J kg−1 K−1, 2.43 J kg−1 K−1 and 0.91 J kg−1 for x = 0, x = 0.1 and 0.2, respectively at 5 T. The relative cooling power (RCP) amounts 169 J Kg−1, 241 J Kg−1 and 70 J Kg−1 at 5 T for x = 0, 0.1, 0.2 respectively. These values are compared favorably with those of some others reported manganites, making La0.67Sr0.22Ba0.11Mn0.9Fe0.1O3 a promising candidate for magnetic refrigeration., We acknowledge the financial support of the Spanish Ministry of Economy and Competitivity the project MAT2013-41099-R.

La0.5Ca0.5MnO3 and La0.5Ca0.4Ag0.1MnO3 ceramics have been prepared by sol–gel methods and its magnetic properties, and electronic transport properties have been experimentally investigated. X-ray diffraction data reveal that all samples crystallize in a orthorhombic structure with Pnma space group. Magnetic measurements of La0.5Ca0.5MnO3 show multiple magnetic transitions, a paramagnetic to ferromagnetic and a ferromagnetic to charge-ordered antiferromagnetic. Two metal–semiconductor transitions (Tρ1 and Tρ2) are observed in the electrical resistivity. The electrical resistivity decreases when an external magnetic field is applied rendering a magnetoresistive effect of the order of 75% at the charge-ordered temperature. All the samples clearly reveal the unusual low temperature resistivity minimum, presumably due to the combined effect of weak localization, electron–electron and electron–phonon scattering. The present results are discussed and possible explanations were given based on the related theory and previous reported results., This paper within the frame work of collaboration is supported by the Tunisian Ministry of Higher Education and Scientific Research Grants MAT2011-27470-C02-02 and CSD2009-00013 from the Spanish MINECO are acknowledged.

Many structural phase transitions are of first order, and many superconducting transitions are of second order. Some iron-based materials have a first-order (magneto)structural phase transition and then cross over to a superconducting phase at low temperatures. Using nanoscale imaging, the authors show that this results in separated superconducting and normal regions, each showing a different crystalline structure. In systems having different crystalline phases, it can be energetically favorable to separate a superconductor into patches.

8 pags, 9 figs, 4 tabs, The transparent semiconductor ZnSnO with cubic spinel structure and the isostructural ZnTiO have been magnetically doped with Co. ZnCoSnO and ZnCoTiO exhibit ferrimagnetism below T ≈ 13 K and T ≈ 17 K. Ferrimagnetic moments are evident in M vs H curves below T by small hysteresis. Fits to strictly linear Curie-Weiss plots above T give μ ≈ 4.86 μ and ≈4.91 μ for ZnCoSnO and ZnCoTiO, above theoretical predictions. Impedance spectroscopy data from sintered ceramic can be fitted with a standard equivalent circuit model based on two RC elements for bulk and GB areas. The relative dielectric permittivity of the bulk is ≈20 and ≈30 for ZnSnO and ZnTiO. The semiconducting ZnCoSnO and ZnCoTiOceramics exhibit bulk resistivity of ≈1 10 Ω cm and ≈1 10 Ω cm at 560 K (287 °C), and bulk activation energies of E ≈ 1.2 eV and 1.1 eV., R.S. acknowledges a travel grant (Convenio Internacional) from the Universidad Complutense de Madrid to visit the USACH in Chile. JPG thanks the Spanish MINECO for granting a Juan de la Cierva fellowship. Spanish MINECO grant MAT2014-52405-C2-2-R is also acknowledged.

Multiferroic materials exhibit two or more ferroic orders and have potential applications as multifunctional materials in the electronics industry. A coupling of ferroelectricity and ferromagnetism is hereby particularly promising. We show that the synthetic melanostibite mineral MnFeSbO (R (Formula presented.) space group) with ilmenite-type structure exhibits cation off-centering that results in alternating modulated displacements, thus allowing antiferroelectricity to occur. Massive magnetoelectric coupling (MEC) and magnetocapacitance effect of up to 4000 % was detected at a record high temperature of 260 K. The multiferroic behavior is based on the imbalance of cationic displacements caused by a magnetostrictive mechanism, which sets up an unprecedented example to pave the way for the development of highly effective MEC devices operational at or near room temperature., The authors thank MINECO for funding through projects MAT2013‐44964‐R, MAT2013‐41099‐R, MAT2015‐71070‐REDC, MAT2014‐52405‐C02‐02, CTQ2015‐67755‐C2‐1‐R (MINECO/FEDER) and FPI (BES‐2013‐066112) and Ramon y Cajal (RyC‐2010–06276) fellowships, and Comunidad de Madrid through S‐2013/MIT‐2753 grant.

The effect of composition and particle size on the electrical and magnetic behavior of ZnxCo1-xFe2O4 spinels (x = 0.2 and 0.3) has been studied. Powdered samples of these ferrites have been synthetized by the liquid mix technique and hydrothermal method (in sub and supercritical conditions), leading to average particle sizes of ca. 50 and 10 nm, respectively. They have been characterized by means of X-ray diffraction, Thermogravimetric analysis, Energy-Dispersive X-ray Spectroscopy and impedance and magnetic measurements. Permittivity values up to ca. 500 were registered at 375 K, which remained almost constant at moderate frequencies, between 10 3 and 106 Hz. Stabilization of polarization phenomena is very sensitive to grain size and composition. Dielectric behavior evolves to a relaxor ferroelectric response when grain size becomes nanometric and, particularly, when the sample shows high monodispersion. The conduction mechanism and type of majority charge carriers have been established from Seebeck measurements. The x = 0.3 sample, prepared in supercritical water for the first time, exhibits homogeneous particle size distribution, superparamagnetic behavior and Curie temperature lower than those corresponding to similar microsized samples. The electronic response of the ferrites obtained in supercritical conditions is interpreted considering the possible short scale polarization of nanodomains. © 2014 Elsevier B.V. All rights reserved., Authors are grateful to the CAI centers of the UCM (XRD and electron microscopy) and financial support from Spanish Ministerio de Ciencia e Innovación, Grants MAT2010-20117, MAT2011-27470-C02-02 and CSD2009-00013.

The A-site ordered perovskite oxide CdCu3Mn4O 12 has been synthesized for the first time in polycrystalline form under high pressure (7 GPa) and high temperature (1000 °C) conditions, required to stabilize the small Cd and Cu cations at the A positions of the perovskite. The crystal structure has been studied by X-ray powder diffraction at room temperature. This oxide crystallizes in the cubic space group Im3̄ (no. 204) with the unit-cell parameter a = 7.2179(5) Å at 300 K. The MnO6 network is extremely tilted, giving rise to a square planar coordination for Cu2+ cations. The magnetic characterization shows that this compound is ferrimagnetic with an ordering temperature TC = 347 K, well above room temperature. A metallic behavior is displayed between 10 and 300 K. Negative magnetoresistance (MR) of 15% is achieved at 10 K for H = 9 T; MR is still significant at room temperature, displaying values above 7% for H = 9 T. Density functional theory calculations carried out on the density of states lead to electronic and magnetic features in good agreement with the obtained experimental results. © 2014 American Chemical Society., We thank the financial support of the Spanish Ministry of Science and Innovation to project MAT2010-16404, of the Comunidad de Madrid to project S2009PPQ-1551 (QUIMAPRES), and of the Spanish Consolider Ingenio 2010 Program (project CDS2007-00045). J.S.-B. acknowledges receipt of a Ramón y Cajal Fellowship (RyC-2010-06276) from the Ministerio de Economía y Competitividad.

This Accepted Manuscript will be available for reuse under a CC BY-NC-ND licence after 24 months of embargo period, The antiferromagnet Mn5Si3 has recently attracted attention because a noncollinear spin arrangement has been shown to produce a topological anomalous Hall effect and an inverse magnetocaloric effect. Here we synthesize single crystals of Mn5Si3 using flux growth. We determine the phase diagram through magnetization and measure the magnetoresistance and the Hall effect. We find the collinear and noncollinear antiferromagnetic phases at low temperatures and, in addition, a third magnetic phase, in between the two antiferromagnetic phases. The latter magnetic phase might be caused by strain produced by Cu inclusions. This suggests that fluctuations of the mixed character magnetic ordering in this compound can be easily quenched by stress, This work was supported by the Spanish MINECO (Consolider Ingenio Molecular Nanoscience CSD2007-00010 program, FIS2017-84330-R, MDM-2014-0377, MAT2014-52405-C2-2-R, FJCI-2015-25427 and CSD2009-00013), by the Comunidad de Madrid through program NANOMAGCOST-CM (S2018 NMT-4321) and MAD2D-CM (S2013/MIT-3007) and by EU (Graphene Core1 contract No. 696656, Nanopyme FP7-NMP-2012 SMALL-6 NMP3-SL-2012 310516 and COST CA16218)

SnSe has been recently reported as an attractive thermoelectric material, with an extraordinarily high, positive, Seebeck coefficient. Here, we describe the synthesis, structural, microscopic, and thermoelectric characterization of Sn1–xSbxSe intermetallic alloys prepared by a straightforward arc-melting technique. Sb-doped tin selenide was synthesized as strongly nanostructured polycrystalline pellets. Neutron diffraction studies reveal that Sb is placed at the Sn sublattice in the crystal structure, showing concentrations as high as 30%, and generates a significant number of Sn vacancies, while the increase of the interlayer distances favors the nanostructuration. The material is nanostructured both out-of-plane in nanometer-scale layers and in-plane by ∼5 nm undulations of these layers. This nanostructuring, along with an increased amount of Sn vacancies, accounts for a reduction of the thermal conductivity, which is highly desirable for thermoelectric materials. The phonon mean free path is estimated to be on the order of 2 nm from low temperature, thermal conductivity, and specific heat, in accordance with the nanostructuration observed by high-resolution transmission electron microscopy. The thermal conductivity of SnSe is characterized by three independent techniques to assure a room temperature value of Sn0.8Sb0.2Se of κ ∼ 0.6 W/m K. The freshly prepared Sb-doped compounds exhibit an abrupt change in the type of charge carriers, leading to large, negative Seebeck coefficients, although the arc-melt synthesized pellets remain too resistive for thermoelectric applications. Cold-pressed pellets evolve to be p-type at room temperature, but reproducibly turn n-type around 500 K, with increased electrical conductivity and maximum observed figure of merit, ZT ∼ 0.3 at 908 K.

A new methodology for the preparation of nanostructured magnetic thermoset materials without any kind of metal oxide or metal magnetic nanoparticles has been proposed. The present study focuses on the nanostructuration of thermoset materials based on poly(ionic liquid)s block copolymer and the subsequent production of magnetic nanostructured thermoset. Judicious selection of block copolymer, such as P2VP-b-PMMA, soluble in epoxy and its subsequent quaternization leads to a phase modification of the system, from totally soluble to a nanostructured system. Different degree of quaternization of the pyridine groups showed the range of quaternization values which allowed the nanostructuration of the thermoset. Magnetic material was obtained by anion exchange of the quaternized poly(ionic liquid) block copolymer without using any kind of metal oxide or metal magnetic nanoparticles. The different materials obtained by quaternization of the block copolymers, the anion exchange of the polymeric ionic liquid and thermoset materials were characterized by 1H nuclear magnetic resonance (1H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), high resolution transmission electron microscopy (HR-TEM) and magnetic properties were measured by a superconducting quantum interference device (SQUID). © 2013 American Chemical Society., The present work was supported by POCO European Project (NMP-213939), the PIL-to-MARKET Project (FP7-PEOPLE-IAPP-2008-230747), MAT2011-27470-C02-02, and IMAGINE CSD 2009-00013.

By using films as model systems, a combined study based on experiments and micromagnetic simulations has been performed to get further insight into the magnetic behaviour of M-type SrFeO (SrF) system in the nanosized range. Both nanocrystalline SrF quasi-isotropic and highly anisotropic films have been obtained by sputtering. Tuning of the preferred c-axis orientation, either normal or in the film plane, has been possible by varying the growth parameters and, importantly, with no need of any underlayer. Small changes in the oxygen ratio (up to 2%) and in-situ heating lead to different microstructure, which determine the strong variations of the magnetic behaviour observed, including both magnetization curves, easy axis directions, and their different coercive fields, which vary from 1 kOe to 5 kOe within the sample series. Micromagnetic simulations reproduce the experiments with a model based on a mixed population of randomly distributed SrF grains with in-plane and out-of-plane uniaxial anisotropies. The simulations show that intergranular interactions play the major role on the coercive field behaviour of the SrF system. A microstructure comprising largely uncoupled grains leads to improved magnetic performance of highly c-axis oriented SrF nanostructures., This research has been supported by EU-FP7 NANOPYME Project (No. 310516), MINECO (Ministerio de Economía y Competitividad): ENMA project (MAT2014-56955-R), project MAT2013-48009-C4-1-P, MAT2014-52405-C2-2-R, M-era.Net Programme: NEXMAG project (PCIN-2015-126) and Regional Government (Comunidad de Madrid): NANOFRONTMAG (Ref. S2013/MIT-2850). E.C. acknowledges MINECO for the Formación Posdoctoral (JdC) program (FPDI-2013-16008).

We have prepared a novel series of LaSrBaMnCoxO (0 = x = 0.3) perovskites by a sol-gel method. These oxides were characterized by X-ray diffraction (XRD) and neutron powder diffraction (NPD) at room temperature and magnetization measurements vs. temperature and various applied magnetic fields. The use of NPD data allows us to describe very precisely the octahedral tilting in the orthorhombic structure (Pnma) observed for all the compounds (x = 0 to 0.3); in all the samples with x > 0, Co is distributed at random in the Mn positions of the perovskite. Magnetic susceptibility measurements show that whereas the x = 0 perovskite is ferromagnetic at relatively high temperatures (T C = 360 K), the introduction of Co induces a magnetic glass state (cluster or spin glass). The magnetic entropy change (|δS|) takes values 2.46, 2.43, 1.88 and 1.78 J kg K for x = 0, 0.1, 0.2 and 0.3, respectively. The relative cooling power is 169, 241, 207 and 191 J kg for x = 0, 0.1, 0.2 and 0.3, respectively, at a field change of 5 T. This result suggests that subtle Co doping enhances the magnetocaloric effect in this series, the perovskite LaSrBaMnCoO being a candidate that can be used in magnetic refrigeration., We acknowledge the financial support of the Spanish Ministry of Economy and Competitivity through projects MAT2013-41099-R and MAT2011-27470-C02-02.

The peculiar features of domain walls observed in ferroelectrics make them promising active elements for next-generation non-volatile memories, logic gates and energy-harvesting devices. Although extensive research activity has been devoted recently to making full use of this technological potential, concrete realizations of working nanodevices exploiting these functional properties are yet to be demonstrated. Here, we fabricate a multiferroic tunnel junction based on ferromagnetic LaSrMnO electrodes separated by an ultrathin ferroelectric BaTiO tunnel barrier, where a head-to-head domain wall is constrained. An electron gas stabilized by oxygen vacancies is confined within the domain wall, displaying discrete quantum-well energy levels. These states assist resonant electron tunnelling processes across the barrier, leading to strong quantum oscillations of the electrical conductance., Work supported by Spanish MINECO through grants MAT2014-52405-C02-01 and MAT2014-52405-C02-02, MAT2015-066888-C3-1-R, MAT2015-066888-C3-3-R (MINECO/FEDER) and CAM S2013/MIT-2740. Research at ORNL sponsored by the US Department of Energy (DOE), Basic Energy Sciences (BES), M.V. acknowledges support from Fundación BBVA. G.S. and M.C. acknowledge support from ERC Starting Investigator Grant #239739 STEMOX. J.I.B. acknowledges the Spanish Supercomputing Network (RES) and CeSViMa (project FI-2016-2-0006). J.S. thanks Université Paris Saclay (DÁlembert Program) and CNRS for financing his stay at CNRS Thales.

New complex perovskites of the series CaCu(MnRe)O have been prepared from citrate precursors under moderate pressure conditions of 2 GPa and 1000 °C, in the presence of KClO as oxidizing agent to stabilize Mn/Mn mixed valence. The polycrystalline samples have been characterized by x-ray diffraction, neutron powder diffraction (NPD), magnetic, and magnetotransport measurements. The crystal structures are cubic, space group Im-3. The unit-cell parameters increase from a = 7.2379(2) Å for the parent (x = 0) compound to a = 7.2420(4) Å for CaCu(MnRe)O. Both oxides adopt a superstructure of the perovskites ABO with long-range 1:3 ordering for Ca and Cu ions at the A sublattice. For the compound doped with Re (x = 0.1), the result of a NPD study shows that Re ions are randomly located at the octahedral positions, being the (Mn,Re)O octahedra strongly tilted, with superexchange (Mn,Re)-O-(Mn,Re) angles of 142.03°. Neutron diffraction data clearly show that some Mn ions are located together with Cu at the square-planar 6b positions. The magnetic structure determined from low-temperature NPD data unveils a ferromagnetic coupling between (Mn,Re) spins at octahedral positions and weak antiferromagnetism with (Cu,Mn) spins. Interestingly, an enhancement of the magnetoresistance effect is observed for the Re-doped compound, well beyond that found for the parent perovskite., We thank the financial support of the Spanish Ministry of Economy and Competitiveness to the projects MAT2013-41099-R and RyC-2010-06276.

We have investigated the effect of Mg doping on structural, magnetic and magnetocaloric properties of a novel series of LaSrBaMnMgO (0 ≤ x ≤ 0.2) perovskites elaborated by a sol–gel method. These oxides were characterized by neutron powder diffraction (NPD) at room temperature and magnetization measurements versus temperature and various applied magnetic fields. Rietveld refinements from NPD data indicate an orthorhombic structure (Pnma) for all the compounds (x = 0 to x = 0.2); in all the samples with x > 0, Mg is distributed at random in the Mn positions of the perovskite. Magnetization measurements show a ferromagnetic behavior for x = 0 and x = 0.1 samples, whereas the compound x = 0.2 introduces a magnetic glass state (cluster or spin glass). The magnetic entropy change (|Δ S|) and the relative cooling power are, respectively, 2.46, 1.85 and 0.83 J kg K and 169, 101 and 116 J kg at a field change of 5 T, for all compounds x = 0, 0.1 and 0.2. These results are compared with those of some other reported manganites, helping to understand the magnetic arrangement required for magnetic refrigeration., We acknowledge the financial support of the Spanish Ministry of Economy and Competitivity through Projects MAT2013-41099-R and MAT2011-27470-C02-02.

Ferromagnetic MnAl (L10-MnAl phase) ultrathin films with thickness varying from 1 to 5 nm have been epitaxially grown on a GaAs (001) substrate. A coercivity above 8 kOe has been obtained with no need of a buffer layer by tuning the sample preparation and the growth parameters. Surface and interface analysis carried out by in situ characterization techniques (x-ray photoelectron spectroscopy and low energy electron diffraction), available in the molecular beam epitaxy chamber, has shown the formation of a ferromagnetic interface consisting of Mn-Ga-As-Al, which contribution competes with the MnAl alloyed film. The appearance of this interface provides important information to understand the growth mechanism of MnAl-based films reported in the literature.

Polycrystalline samples of Sr2BIrO6 (B: In, Sc, Fe, Co, Ti) are prepared from citrate precursors using stoichiometric mixtures of Sr(NO3)2, IrO2, In2O3, Sc2O3, FeC2O4, Co(NO3)2, and TiC10H14O5 in aqueous solutions of citric acid and HNO3 followed by heating of the resulting resins (600 °C, 12 h) and calcination in air (1100—1200 °C, 12 h).

The title perovskites (obtained from citrate precursors at 900 °C for 12 h) are characterized by XRD, neutron powder diffraction, and magnetic measurements.

This work was supported by the Spanish MINECO (FIS2014-54498-R, MAT2011-27470-C02-02, and CSD-2009-00013), by the European Union (Graphene Flagship Contract No. CNECT-ICT-604391 and COST MP1201 action), and by the Comunidad de Madrid through programs Nanofrontmag-CM (S2013/MIT-2850) and MAD2D-CM (S2013/MIT-3007).We acknowledge MINECO and CSIC for financial support and for provision of synchrotron radiation facilities and would like to thank the SpLine BM25 staff for assistance in using the beamline

The design of artificial vortex pinning landscapes is a major goal toward large scale applications of cuprate superconductors. Although disordered nanometric inclusions have shown to modify their vortex phase diagram and to produce enhancements of the critical current (MacManus-Driscoll, J. L.; Foltyn, S. R.; Jia, Q. X.; Wang, H.; Serquis, A.; Civale, L.; Maiorov, B.; Hawley, M. E.; Maley, M. P.; Peterson, D. E. Nat. Mater. 2004, 3, 439?443 and Yamada, Y.; Takahashi, K.; Kobayashi, H.; Konishi, M.; Watanabe, T.; Ibi, A.; Muroga, T.; Miyata, S.; Kato, T.; Hirayama, T.; Shiohara, Y. Appl. Phys. Lett. 2005, 87, 1-3), the effect of ordered oxide nanostructures remains essentially unexplored. This is due to the very small nanostructure size imposed by the short coherence length, and to the technological difficulties in the nanofabrication process. Yet, the novel phenomena occurring at oxide interfaces open a wide spectrum of technological opportunities to interplay with the superconductivity in cuprates. Here, we show that the unusual long-range suppression of the superconductivity occurring at the interface between manganites and cuprates affects vortex nucleation and provides a novel vortex pinning mechanism. In particular, we show evidence of commensurate pinning in YBCO films with ordered arrays of LCMO ferromagnetic nanodots. Vortex pinning results from the proximity induced reduction of the condensation energy at the vicinity of the magnetic nanodots, and yields an enhanced friction between the nanodot array and the moving vortex lattice in the liquid phase. This result shows that all-oxide ordered nanostructures constitute a powerful, new route for the artificial manipulation of vortex matter in cuprates., Work at UCM supported by grants MAT2014-52405-C02-01 and Consolider Ingenio 2010-CSD2009-00013 (Imagine), by CAM through grant CAM S2013/MIT-2740. Work done at ICMM supported by Spanish MINECO (Ministry for Economy and Competitiveness) grants MAT2011-27470-C02-02, MAT2014-52405-C02-02, and Consolider Ingenio CSD2009-00013 (Imagine). J.V. acknowledges European Research Council, ERC, grant No. 647100 “SUSPINTRONICS”.

RNiMnO (R = Tb, Ho, Er, Tm) perovskites have been prepared by soft-chemistry techniques followed by high oxygen-pressure treatments; they have been investigated by X-ray diffraction, neutron powder diffraction (NPD), and magnetic measurements. In all cases the crystal structure is defined in the monoclinic P2/n space group, with an almost complete order between Ni and Mn cations in the octahedral perovskite sublattice. The low temperature NPD data and the macroscopic magnetic measurements indicate that all the compounds are ferrimagnetic, with a net magnetic moment different from zero and a distinct alignment of Ni and Mn spins depending on the nature of the rare-earth cation. The magnetic structures are different from the one previously reported for LaNiMnO, with a ferromagnetic structure involving Mn and Ni moments. This spin alignment can be rationalized taking into account the Goodenough-Kanamori rules. The magnetic ordering temperature (T) decreases abruptly as the size of the rare earth decreases, since T is mainly influenced by the superexchange interaction between Ni and Mn (Ni-O-Mn angle) and this angle decreases with the rare-earth size. The rare-earth magnetic moments participate in the magnetic structures immediately below T., We acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness through the projects MAT2013-41099-R and CSD2007-00045 and funding of the Universidad Complutense de Madrid and Banco Santander through the project UCM2014-971703. J.S.-B. acknowledges receipt of a Ramón y Cajal Fellowship (RyC-2010-06276) from the Spanish Ministry of Economy and Competitiveness.

The preparation, crystal structure and magnetic properties of Sr2BIrO6 (B = In, Sc, Fe, Co or Ti) oxides are reported. For B = Sc, Fe, Co or In materials, X-ray and neutron powder diffraction (NPD) studies confirm the presence of 1:1 B-ordered perovskite-like structures crystallizing in the monoclinic I2/m and P21/n space groups, with unit-cell parameters a ≈ √2a0, b ≈ √2a0, c ≈ 2a0 and β ≈ 90°. Sr2TiIrO6 is described as a disordered perovskite with orthorhombic symmetry in the Pbnm space group. For B = Fe and Co, low-temperature NPD data and magnetic measurements indicate the existence of an antiferromagnetic structure resulting from the Fe3+/Co3+ magnetic moment interaction. X-ray absorption spectroscopy corroborates that the oxidation states of B and Ir are 3+ and 5+, respectively. The bond lengths and other structural features are discussed in the framework of other recently reported iridium double perovskites where iridium adopts tetravalent, pentavalent and hexavalent oxidation states, and in the wider context of Sr double perovskites., We thank the Spanish Ministry of Economy and Competitiveness (project MAT2013‐41099‐R) for financial support. Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE‐AC02‐ 98CH10886.

We present very low-temperature scanning tunneling microscopy (STM) experiments on single-crystalline samples of the superconductor β-Bi2Pd. We find a single superconducting gap from the zero-field tunneling conductance. However, the magnetic field dependence of the intervortex tunneling conductance is higher than the one expected in a single-gap superconductor. Such an increase in the intervortex tunneling conductance has been found in superconductors with multiple superconducting gaps. We also find that the hexagonal vortex lattice is locked to the square atomic lattice as expected in crystalline superconductors with anisotropic Fermi surfaces. Moreover, we compare the upper critical field Hc2(T) obtained in our sample with previous measurements and find that Hc2(T) does not increase by reducing the mean free path. We fit Hc2(T) and show that multiband Fermi surface is needed to explain the observed behavior. We propose that β-Bi2Pd is a single-gap multiband superconductor. We anticipate that single-gap superconductivity might often occur in compounds with anisotropic multiband Fermi surfaces., We wish to acknowledge the support of Departamento Administrativo de Ciencia, Tecnología e Innovación, COLCIENCIAS (Colombia) Programa Doctorados en el Exterior Convocatoria 568-2012. This work was supported by the Spanish Ministerio de Economía y Competitividad (FIS2011-23488, MAT2011-27470-C02-02, and CSD2009-00013), by the Comunidad de Madrid through programs NANOFRONTMAG-CM (S2013/MIT-2850) and MAD2D-CM (S2013/MIT-3007) and by AXA Research Fund. We also acknowledge SEGAINVEX workshop of UAM, Banco Santander as well as PEOPLE, Graphene Flagship, and NMP programs of EU (Grant Agreements FP7-PEOPLE-2013-CIG 618321, 604391 and Nanopyme FP7-NMP-2012_SMALL-6 NMP3-SL 2012_310516). Furthermore, we acknowledge European Cooperation in Science and Technology MP1201 action, and discussions with P. Samuely.

We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in LaCaMnO/BaTiO ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30-40% upon applying electric fields on the order of 1 kV/cm to the BaTiO substrate, corresponding to magnetoelectric coupling constants on the order of α = (2-5)·10 s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the LaCaMnO. The magnetic granularity of the LaCaMnO film and the robust magnetoelastic coupling at the LaCaMnO/BaTiO interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite., The authors acknowledge financial support from the Spanish MICINN and MINECO through grants MAT2011-27470-C02-01, MAT2011-27470-C02-02, MAT2014-52405-C2-2-R, MAT2014-52405-C2-1R and CSD-2009-00013.

Neutron strain scanning measurements on a eutectoid steel rod that has been subjected to standard industrial coiling and straightening operations are presented. Strains were determined non-destructively using two different diffractometers, one at a steady-state neutron source and the other at a pulsed spallation neutron source, with measurements made in both the ferrite and cementite components of the pearlitic microstructure. The residual stress state is explained in terms of a simplified analytical model for a two-phase material, which takes into account the successive loading operations contributing to residual stress. The results show that residual stresses generated by bending–straightening operations are significant and are likely to play an important role in the mechanical properties of the final wires.

Residual stress profiles in the three principal directions in a cold-drawn pearlitic rod were calculated by a three-dimensional finite element simulation and measured by synchrotron X-ray diffraction. It has been shown that anisotropy of cold-drawn pearlite has to be considered for accurate simulations of residual stresses of steel wires. 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Residual stress profiles have been measured in the ferrite and cementite phases of a cold-drawn eutectoid steel rod by neutron and synchrotron X-ray diffraction in three orientations (axial, radial and hoop). Neutron diffraction was employed to measure the ferrite stresses, whereas synchrotron radiation was used for ferrite and cementite stresses. Experimental results in the ferrite phase showed excellent agreement between both experimental techniques when gauge volume effects were accounted for. Axial cementite stresses were always tensile, with a maximum value close to 1700 MPa at the rod surface. Radial and hoop cementite stresses were compressive along the diameter of the rod, with a minimum of -1900 MPa at the rod center. A 3D-finite element simulation of the macro residual stresses resulting from cold-drawing showed remarkable agreement with those determined from the experimental measurements in the ferrite and cementite phases.

The OECD Nuclear Energy Agency (NEA) Thermochemical Database Project aims at making available a comprehensive, internally consistent and quality assured chemical thermodynamic database of selected chemical elements. This database should meet the specialized modeling requirements for safety assessments of radioactive waste disposal systems. This paper describes the evolution of the project from its inception in 1984 to the present organization as a semi-autonomous project under the aegis of the OECD NEA. The scientific principles behind the project organization have not been altered and the effort has resulted in the publication of five major reviews on the chemical thermodynamics of inorganic species and compounds of U, Np, Pu, Am and Tc. Currently, a second series of reviews is being prepared updating the existing, CODATA compatible, database and extending it to include selected data on inorganic species of compounds of Ni, Se and Zr as well as organic complexes with citrate, oxalate, EDTA and iso-saccharinic acid with U, Np, Pu, Am, Tc, Ni, Se, Zr and some other competing cations.

Neutron strain scanning has been performed on a neutectoid steel rod at a reactor-based source (REST diffractometer, at NFL) and at a pulsed source (ENGIN diffractometer, at ISIS). The rod is primarily obtained from a drawing process and has been subject to bending and straightening procedures, which induce residual stress. The material exhibits a pearlitic microstructure, with alternating ferrite (90 vol %) and cementite (10 vol %) layers. Strain profiles for the ferritic phase were measured on REST. Both phases were measured on ENGIN and analysed by single-peak (ferrite) and Rietveld refinement (ferrite and cementite) methods. The agreement between REST and ENGIN data is excellent for the three measured directions in the ferritic phase. Total stress profiles have been evaluated by combining phase stresses using the rule of mixtures. The experimental results compare well with analytical models for a two-phase material subject to bending and straightening operations under pure bending and unbending moments with perfect elastic behaviour up to the yield point and plastic Voce behaviour above.

A Monte Carlo code for the simulation of neutron strain scanning experiments on a reactor-based two-axis diffractometer is described. In order to validate this code, several experiments have been performed. A comparison is made between experimental and simulated results for instrumental resolution, primary beam divergence and wavelength distribution in the incident neutron beam. Finally, the application of the simulation results to the analysis of a real neutron strain scanning experiment is outlined.

Local deviations from the average magnetic and atomic structure of La 0.67 Ca 0.33 MnO 3 are explored by combining neutron diffraction and reverse Monte Carlo techniques. Short range FM Mn–Mn spin pair correlations are found to be a majority well above T c , while AF correlations between first neighbour pairs of Mn ions develop preferentially around T c and within those pairs with a distance larger than the average first neighbour Mn–Mn distance. These results agree with the predictions of current theories on phase transitions in double exchange systems.

XANES and EXAFS measurements has been performed in the 10–300 K temperature range in order to investigate the local order around the Fe and Cu ions in two samples with different oxygen stoichiometry: PrBaCuFeO 5.00 and PrBaCuFeO 5.25 . XANES allows determining that extra-oxygen is coordinated to the Fe ions and is not coordinated to the Cu ions. EXAFS data have been analysed in order to obtain the temperature behaviour of the Debye–Waller factor related to the oxygen surrounding the Fe and Cu ions. Additionally, low temperature resistivity data are reported for both samples, they show a variable range hoping mechanism for the conductivity.