Parametric oscillator based on non-linear vortex dynamics in low resistance magnetic tunnel junctions

Radiofrequency vortex spin-transfer oscillators based on magnetic tunnel junctions with very low resistance area product were investigated. A high power of excitations has been obtained characterized by a power spectral density containing a very sharp peak at the fundamental frequency and a series of harmonics. The observed behaviour is ascribed to the combined effect of spin transfer torque and Oersted-Amp\`ere field generated by the large applied dc-current. We furthermore show that the synchronization of a vortex oscillation by applying a ac bias current is mostly efficient when the external frequency is twice the oscillator fundamental frequency. This result is interpreted in terms of a parametric oscillator.Comment: 4 pages, 4 figure

A comprehensive analysis of the (R13xR13)R13.9{\deg} type II structure of silicene on Ag(111)

In this paper, using the same geometrical approach than for the (2R3x2R3) R30{\deg} structure (H. Jamgotchian et al., 2015, Journal of Physics. Condensed Matter 27 395002), for the (R13xR13)R13.9{\deg} type II structure, we propose an atomic model of the silicene layer based on a periodic relaxation of the strain epitaxy. This relaxation creates periodic arrangements of perfect areas of (R13xR13)R13.9{\deg} type II structure surrounded by defect areas. A detailed analysis of the main published experimental results, obtained by Scanning Tunneling Microscopy and by Low Energy Electron Diffraction, shows a good agreement with the geometrical model.Comment: 20 pages, 9 figure

Technical design and characterization of a ground based solar metrology network on Reunion Island

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.The roadmap of Reunion Island regarding energy is to reach autonomy by 2030. Obviously, renewable energies will play a key role in this ambitious project. However, a couple of years ago, a limit set by the French government relatively to the amount of lethal power injected on the electrical grid stopped the thrust: at any time, intermittent sources should not exceed 30 % of the whole production. This is due to the fragility of the grid: rugged topography, no interconnection. The University of La Reunion through the LE2P lab (Energy, Electronic and Process) decided to search a solution by predicting the solar resource in order to erase part of the intermittency of the production coming from the solar plants. Along this track, the first step is to evaluate precisely the resource and study its spatio-temporal variability. To do so, the LE2P gets engaged in deploying, at ground level, a network of monitoring stations. These units should be capable to produce field data responding to specific requirements in terms of acquisition frequency and quality, compatible with the clustering tools and mapping programs developed beside. Today, LE2P team manages a fleet of more than 15 stations, with various configurations, all over Reunion Island and plans to extend its network to neighboring territories. This article proposes to present in details the different components of a typical station, how they have been selected and how they are maintained. We will also see how the lab gets organized in order to propose top quality data to the solar scientific community.cf201

Technical design and characterization of a ground based solar metrology network on Reunion Island

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.The roadmap of Reunion Island regarding energy is to reach autonomy by 2030. Obviously, renewable energies will play a key role in this ambitious project. However, a couple of years ago, a limit set by the French government relatively to the amount of lethal power injected on the electrical grid stopped the thrust: at any time, intermittent sources should not exceed 30 % of the whole production. This is due to the fragility of the grid: rugged topography, no interconnection. The University of La Reunion through the LE2P lab (Energy, Electronic and Process) decided to search a solution by predicting the solar resource in order to erase part of the intermittency of the production coming from the solar plants. Along this track, the first step is to evaluate precisely the resource and study its spatio-temporal variability. To do so, the LE2P gets engaged in deploying, at ground level, a network of monitoring stations. These units should be capable to produce field data responding to specific requirements in terms of acquisition frequency and quality, compatible with the clustering tools and mapping programs developed beside. Today, LE2P team manages a fleet of more than 15 stations, with various configurations, all over Reunion Island and plans to extend its network to neighboring territories. This article proposes to present in details the different components of a typical station, how they have been selected and how they are maintained. We will also see how the lab gets organized in order to propose top quality data to the solar scientific community.cf201