ALBERT

Description: Manipulating magnetisation by the application of an electric field in magnetoelectric multiferroics represents a timely issue due to the potential applications in low power electronics and the novel physics involved. Thanks to its element sensitivity and high spatial resolution, X-ray photoemission electron microscopy is a uniquely suited technique for the investigation of magnetoelectric coupling in multiferroic materials. In this work, we present a setup that allows for the application of in situ electric and magnetic fields while the sample is analysed in the microscope. As an example of the performances of the setup, we present measurements on Ni/Pb(Mg 0.66 Nb 0.33 )O 3 -PbTiO 3 and La 0.7 Sr 0.3 MnO 3 /PMN-PT artificial multiferroic nanostructures.

Description: MoS 2 monolayers, a two-dimensional (2D) direct semiconductor material with an energy gap of 1.9 eV, offer many opportunities to be explored in different electronic devices. Defects often play dominant roles in the electronic and optical properties of semiconductor devices. However, little experimental information about intrinsic and extrinsic defects or impurities is available for this 2D system, and even for macroscopic 3D samples for which MoS 2 shows an indirect bandgap of 1.3 eV. In this work, we evaluate the nature of impurities with unpaired spins using electron paramagnetic resonance (EPR) in different geological macroscopic samples. Regarding the fact that monolayers are mostly obtained from natural crystals, we expect that the majority of impurities found in macroscopic samples are also randomly present in MoS 2 monolayers. By EPR at low temperatures, rhenium donors and sulfur vacancy acceptors are identified as the main impurities in bulk MoS 2 with a corresponding donor concentration of about 10 8–12 defects/cm 2 for MoS 2 monolayer. Electrical transport experiments as a function of temperature are in good agreement with the EPR results, revealing a shallow donor state with an ionization energy of 89 meV and a concentration of 7 × 10 15  cm −3 , which we attribute to rhenium, as well as a second deeper donor state with ionization energy of 241 meV with high concentration of 2 × 10 19  cm −3 and net acceptor concentration of 5 × 10 18  cm −3 related to sulfur vacancies.

Description: ABSTRACT The eastern boundaries of the world's oceans are among the most productive marine regions owing to the wind induced coastal upwelling. In this context, changes in coastal upwelling influence chlorophyll-a (Chl-a) concentration along the Northwest (NW) Iberian Peninsula (IP) coast. This work aimed to evaluate and quantify the influence of meteorological conditions defined by circulation weather types (CWTs) on upwelling and Chl-a variability along the Galician coast. A seasonal (April–September and October–March) characterization of satellite wind-derived upwelling index ( UI ) and Chl-a concentration was performed dividing the Galician coast into three domains: western (North–south orientation), intermediate (Northeast-Southwest orientation) and northern (West–east orientation) segments. Results revealed that UI and Chl-a concentrations were different among the three coastal segments and seasons. The most favourable upwelling conditions and high Chl-a levels occurred during April–September at western coast. During October–March, high-primary production also occurred and therefore a correlation analysis was performed during winter between Chl-a, UI and discharges of the main rivers. Chl-a and discharges were strongly correlated (0.52 for Minho and 0.31 for Nalon), suggesting that Chl-a during this period was related to signal contamination due to river discharge. The probability that Chl-a or UI exceeded a certain value, given the occurrence of a specified CWT was computed. Results showed that along the western coastal segment the strongest relations between CWTs, upwelling and Chl-a concentration were obtained during April–September when N and NE occurred, with probabilities higher than 70% for UI and 30% for Chl-a. During winter only the NW type had statistically significant probabilities for UI (50%) and Chl-a (30%). For the intermediate coastal segment during October–March (April–September), when E type occurred, high probabilities of upwelling and Chl-a were observed [100% (66), 50% (25), respectively]. Finally, at the northern coastal segment, Chl-a probability was highest (40–50%) under the S weather type for both seasons.