Investigation of metallic/oxide interfaces in Pt/Co/AlOx trilayers by hard x-ray reflectivity

International audienceX-ray reflectivity (XRR) is used to determine the oxidation front at the nanometer scale in sputtered perpendicular semi tunnel junctions, as the form Pt/Co/AlOx, by varying the oxidation time tOx of the capping layer. From XRR simulations, we show that the nature of the stack is gradually defined according to the value of tOx. For low tOx values (<40 s), a simple Pt/Co/Al/AlOx multilayer is appearing whereas a Pt/Co/CoO/AlOx architecture takes place for higher tOx. The oxygen-induced magnetic properties obtained by extraordinary Hall effects measurements are explained by the structural results. The increase of Co-O bondings with tOx is at the origin of the appearing of the perpendicular magnetic anisotropy (PMA)

The soil heat flux sensor functioning checks, imbalances' origins, and forgotten energies

International audienceSoil heat flux is an important component of the surface energy balance (SEB) equation. Measuring it requires an indirect measurement. Every used technique may present some possible errors tied with the utilized specific technique, soil inhomogeneities, or physical phenomena such as latent heat conversion beneath the plates, especially in desiccation cracking soil or vertisol. The installation place may also induce imbalances. Finally, some errors resulting from the physical sensor presence, vegetation presence, or soil inhomogeneities may occur and are not avoidable. For all these reasons it is important to check the validity of the measurements. A quick and easy way is to integrate results over 1 year. By consideration of the inert core internal energy conservation law, it is shown that the corresponding integration should be close to zero after a necessary geothermal heat efflux subtraction. However, below-plate evaporation and vegetation-absorbed water or rainwater infiltration may also contribute to the observed short-scale and/or long-scale imbalance generating convective heat fluxes not sensed by the heat flux sensors. Another energy source is usually not included in the SEB equation: rainfall or irrigation. Yet its importance for short- and long-term integration is notable. As an example, the most used sensor, soil heat flux plates (SHFPs), is given

Le monde des chambres

International audienceIn the context of global climate warming, soil GHG effluxes are monitored. Several techniques are used such as eddy covariance or dynamic accumulation chambers. Each technique has its pro and cons and these techniques are complementary

Le monde du flux de la chaleur dans le sols

International audienc

Système de récupération et de téléchargement des données entièrement automatisé et sécurisé

International audienceIn the context of global climate warming, several monitoring scientific stations networks were developed around the world. In Europe, we have an Integrated Carbon Observation System (ICOS) network to which belongs our two cropland stations FR-Lam (class 1) and FR-Aur (class 3)

Chambres Automatiques d’Evapo-Respirationdu Sol

National audienceDescriptions des chambres automatiques et nomades pour la mesure de l'évapo-respiration du sol

Le monde du flux de la chaleur dans le sols

International audienc

Chambres Automatiques d’Evapo-Respirationdu Sol

National audienceDescriptions des chambres automatiques et nomades pour la mesure de l'évapo-respiration du sol

Wind speed influences corrected Autocalibrated Soil Evapo-respiration Chamber (ASERC) evaporation measures

International audienceSoil evaporation concerns water and our life support sources, which are important for agriculture or for climate change prediction science. A simple instrument based on the nonsteady-state (NSS) technique for soil evaporation measurement appears suitable. However, because the NSS chamber technique is highly invasive, special care should be provided to correct the wind speed influence on the evaporation process. Soil evaporation is a complex process that involves many soil and air characteristics. Measurement chamber installation on the soil and its head deployment may perturb these characteristics. We therefore had to minimize differences or to correct the measurements. Most of the differences between bare soil and soil with a deployed chamber head can be minimized, except for the wind speed influences that are not reproducible inside a chamber head. Meanwhile, as the wind influences depend on numerous variables that are not monitorable in real time, a self-calibrating chamber with a corresponding protocol called the Autocalibrated Soil Evapo-respiration Chamber (ASERC) was developed to make the measurements easily corrigible on bare soil with a unique variable (wind speed, WS), regardless of the soil composition, soil texture, and other soil or air meteorological variables. A simple protocol followed by this chamber allows us to determine the soil evaporation wind speed susceptibility (Z) and to correct the measurements achieving 0.95 as the coefficient of determination. Some interesting findings on sandy and clayey soil evaporation measured during laboratory calibration and “slow” sensor simulation will also be reported in the two appendices.L'évaporation du sol concerne l'eau une de nos ressources vitales, importantes pour l'agriculture ou pour la science du changement climatique. Un instrument simple basé sur la technique de chambres dynamiques (NSS) pour la mesure de l'évaporation du sol est approprié. Cependant, comme la technique de la chambre NSS est très invasive, des précautions particulières doivent être prises pour corriger l'influence de la vitesse du vent sur le processus d'évaporation. L'évaporation du sol est un processus complexe qui implique de nombreuses caractéristiques du sol et de l'air. L'installation de la chambre de mesure et le déploiement de sa tête peuvent perturber ces caractéristiques. Il faut donc minimiser les perturbations et corriger les mesures. La plupart des différences entre le sol nu et le sol avec une tête de chambre déployée peuvent être minimisées, à l'exception des influences de la vitesse du vent qui ne sont pas reproductibles à l'intérieur d'une tête de chambre. Pendant le déploiement, comme les influences du vent dépendent de nombreuses variables qui ne sont pas mesurables en temps réel, une chambre d'auto-étalonnée avec un protocole de mesure correspondant appelée la chambre d'évapo-respiration du sol autocalibrée (ASERC) a été développée pour rendre les mesures facilement corrigibles sur sol nu avec une variable unique (vitesse du vent, WS), indépendamment de la composition du sol, de la texture du sol et d'autres variables météorologiques du sol ou de l'air. Un protocole simple suivi par cette chambre nous permet de déterminer la sensibilité d'évaporation du sol à la vitesse du vent (Z) et de corriger les mesures en obtenant 0,95 comme coefficient de confiance. Quelques résultats intéressants sur l'évaporation des sols sableux et argileux mesurés lors de l'étalonnage au laboratoire et de la simulation de capteurs « lents » seront également rapportés dans les annexes

Système de récupération et de téléchargement des données entièrement automatisé et sécurisé

International audienceIn the context of global climate warming, several monitoring scientific stations networks were developed around the world. In Europe, we have an Integrated Carbon Observation System (ICOS) network to which belongs our two cropland stations FR-Lam (class 1) and FR-Aur (class 3)