Micro-SQUID technique for studying the temperature dependence of switching fields of single nanoparticles

An improved micro-SQUID technique is presented allowing us to measure the temperature dependence of the magnetisation switching fields of single nanoparticles well above the critical superconducting temperature of the SQUID. Our first measurements on 3 nm cobalt nanoparticle embedded in a niobium matrix are compared to the Neel Brown model describing the magnetisation reversal by thermal activation over a single anisotropy barrier.Comment: 3 pages, 4 figures; conference proceeding: 1st Joint European Magnetic Symposia (JEMS'01), Grenoble (France), 28th August - 1st September, 200

Beam current measurement with logarithmic converter

International audienc

Estimation of the oceanic pCO₂ in the North Atlantic from VOS lines in-situ measurements: parameters needed to generate seasonally mean maps

Automated instruments on board Volunteer Observing Ships (VOS) have provided high-frequency pCO₂ measurements over basin-wide regions for a decade or so. In order to estimate regional air-sea CO₂ fluxes, it is necessary to interpolate between in-situ measurements to obtain maps of the marine pCO₂. Such an interpolation remains, however, a difficult task because VOS lines are too distant from each other to capture the high pCO₂ variability. Relevant physical parameters available at large scale are thus necessary to serve as a guide to estimate the pCO₂ values between the VOS lines. Satellites do not measure pCO₂ but they give access to parameters related to the processes that control its variability, such as sea surface temperature (SST). In this paper we developed a method to compute pCO₂ maps using satellite data (SST and CHL, the chlorophyll concentration), combined with a climatology of the mixed-layer depth (MLD). Using 15 401 measurements of surface pCO₂ acquired in the North Atlantic between UK and Jamaica, between June 1994 and August 1995, we show that the parameterization of pCO₂ as a function of SST, CHL and MLD yields more realistic pCO₂ values than parameterizations that have been widely used in the past, based on SST, latitude, longitude or SST only. This parameterization was then used to generate seasonal maps of pCO₂ over the North Atlantic. Results show that our approach yields the best marine pCO₂ estimates, both in terms of absolute accuracy, when compared with an independent data set, and of geographical patterns, when compared to the climatology of Takahashi et al. (2002). This suggests that monitoring the seasonal variability of pCO₂ over basin-wide regions is possible, provided that sufficient VOS lines are available

Optical control of the spin state of two Mn atoms in a quantum dot

We report on the optical spectroscopy of the spin of two magnetic atoms (Mn) embedded in an individual quantum dot interacting with either a single electron, a single exciton and single trion. As a result of their interaction to a common entity, the Mn spins become correlated. The dynamics of this process is probed by time resolved spectroscopy, that permits to determine the optical orientation time in the range of a few tens of $ns$. In addition, we show that the energy of the collective spin states of the two Mn atoms can be tuned through the optical Stark effect induced by a resonant laser field

Phase and amplitude measurement for the SPIRAL2 accelerator

International audienceThe SPIRAL2 project is composed of an accelerator and a radioactive beam section. Radioactive ions beams (RIBs) will be accelerated by the current cyclotron CIME and sent at GANIL experimental areas. The accelerator, with a RFQ and a superconducting Linac, will accelerate 5 mA deuterons up to 40MeV and 1 mA heavy ions up to 14.5 MeV/u. A new electronic device has been evaluated at GANIL to measure phase and amplitude of pick-up signals. The principle consists of directly digitizing pulses by under-sampling. Phase and amplitude of different harmonics are then calculated with a FPGA by an I/Q method. Tests and first results of a prototype are shown and presented as well as future evolutions

Spin Pumping and Inverse Spin Hall Effect in Platinum: The Essential Role of Spin-Memory Loss at Metallic Interfaces

Through combined ferromagnetic resonance, spin-pumping and inverse spin Hall effect experiments in Co|Pt bilayers and Co|Cu|Pt trilayers, we demonstrate consistent values of spin diffusion length $\ell_{\rm sf}^{\rm Pt}=3.4\pm0.4$ nm and of spin Hall angle $\theta_{\rm SHE}^{\rm Pt}=0.051\pm0.004$ for Pt. Our data and model emphasize on the partial depolarization of the spin current at each interface due to spin-memory loss. Our model reconciles the previously published spin Hall angle values and explains the different scaling lengths for the ferromagnetic damping and the spin Hall effect induced voltage.Comment: 6 pages, 3 figures (main text) and 8 pages supplementary. Published with small modifications in Phys. Rev. Let

Brazilian-European community international symposium on agriculture and the environment

Les conséquences de l'agriculture intensive (y compris l'élevage) sur la ressource en eau et sa qualité sont traitées dans les régions méditerranéennes et tempérées grâce à des exemples français et italiens. Le rôle de l'activité agricole sur le cycle hydrologique est rappelé ainsi que les principales lois sur l'eau avant de dresser le tableau actuel des lieux. Les perspectives et les travaux de recherche contemporains concluent la communication. (Résumé d'auteur

Measurement and Control of the Beam Energy for the SPIRAL2 Accelerator

WEPF32, http://accelconf.web.cern.ch/AccelConf/ibic2013/International audienceThe first part of the SPIRAL2 facility, which entered last year in the construction phase at GANIL in France, will be composed of an ion source, a deuteron/proton source, a RFQ and a superconducting linear accelerator delivering high intensities, up to 5 mA and 40MeV for the deuteron beams. As part of theMEBT commissioning, the beam energy will be measured on the BTI (Bench of Intermediate Test) at the exit of the RFQ. At the exit of the LINAC, the system has to measure but also control the beam energy. The control consists in ensuring that the beam energy is under a limit by taking account of the measurement uncertainty. The energy is measured by a method of time of flight, the signal is captured by non-intercepting capacitive pick-ups. This paper presents also the results obtained in terms of uncertainties and dynamics of measures