Search results for "Ferro"

Integrated frequency shifter in periodically poled lithium tantalate waveguide

2010

A frequency shifting device is fabricated and tested in a ferroelectric waveguide in a low-photorefractivity crystal. Periodic poling for quasi-phase-matching and channels for operation in the near-infrared C-band were obtained in congruent lithium tantalate, demonstrating for the first time both wave confinement and two-stage parametric conversion in such waveguides.

Structural and Magnetic Dynamics in the Magnetic Shape Memory Alloy Ni$_2$MnGa

2014

Magnetic shape memory Heusler alloys are multiferroics stabilized by the correlations between electronic, magnetic and structural order. To study these correlations we use time resolved x-ray diffraction and magneto-optical Kerr effect experiments to measure the laser induced dynamics in a Heusler alloy Ni$_2$MnGa film and reveal a set of timescales intrinsic to the system. We observe a coherent phonon which we identify as the amplitudon of the modulated structure and an ultrafast phase transition leading to a quenching of the incommensurate modulation within 300~fs with a recovery time of a few ps. The thermally driven martensitic transition to the high temperature cubic phase proceeds via…

Les temps de parcours interurbains en France : Une analyse géo-historique

2016

National audience; Un nombre croissant de chercheurs profite des progrès informatiques pour reconstruire les réseaux de transport à l'intérieur de Systèmes d'Informations Géo-Historiques (SIG-H). De tels corpus permettent en effet d'apprécier les effets des investissements successifs dans les infrastructures sur les dynamiques territoriales de long-terme. Cet article présente un SIG-H original, initialement développé au sein du laboratoire ThéMA et complété par des chercheurs de l'IFSTTAR pour le projet de recherche BASECOGV, financé par la DRI dans le cadre du PREDIT. Le projet BASECOGV portant sur les Retombées Economiques Indirectes (REI) des Trains à Grande Vitesse (TGV) en France, le S…

Les réseaux de transport à grande vitesse en France : construction et apports d'un système d'information géo-historique

2016

The originality of this Historical Geographic Information System (SIGH) is that it is focuses on various transport networks (road and railway) at several temporal scale (from 1975 to 2010). The corresponding spatial network offers the possibility to generate spatial and temporal matrices across France, at different dates. These possibilities open important spatial analysis perspectives. They allow for example to assess the effect of investments in high-speed transport supply on the durations of intercity trips, also multiple opportunity in the field of Regional Science and Complex Systems analysis.

L' EVOLUZIONE DEL CONCETTO DI SICUREZZA NELLA GESTIONE DELLA RETE FERROVIARIA

2011

Free Charge Carriers in Mixed Valency Oxides as Possible Mediators of Magnetoelectric Effect

2009

We show, that in a substance with mixed-valence ions, which can supply free carriers and have electric dipole and spin moments, three types of long-range order (ferromagnetic, ferroelectric and magnetoelectric (ME)) can occur at low temperatures. The origin of the effect is that free charge carriers can mediate the multiferroic behavior via spin – spin (RKKY), dipole-dipole and dipole - spin interactions. We show that there is an optimal carrier concentration, at which the strength of ME interaction is maximal and comparable to that of RKKY interaction. Our analysis shows that disorder and finite conductivity in the above substances does not suppress multiferroic effects.

Le procedure di audit della sicurezza sul progetto e sulle infrastrutture in esercizio

2010

Approccio teorico-sperimentale per l'analisi delle condizioni operative di rotatorie urbane non convenzionali

2008

I metodi tradizionali di analisi delle rotatorie cadono in difetto in presenza di schemi organizzativi dell’intersezione, nei quali l’organizzazione geometrica, unitamente alla molteplicità delle situazioni di traffico ed all’inserimento in contesti vincolati, induce comportamenti di guida anche molto distanti da quelli osservabili in rotatorie convenzionali. Quanto evidenziato interessa, in particolare, l’ambito urbano, dove le intersezioni a circolazione rotatoria risultano particolarmente diffuse e si caratterizzano per requisiti geometrico-funzionali spesso distanti da quelli propri delle rotatorie convenzionali. Uno dei maggiori ostacoli che si incontrano nell’analisi delle condizioni …

Chalcogen adsorption and surface magnetism

2000

Abstract Investigations concerning the electronic and magnetic properties of oxygen and sulfur adsorbed on magnetized surfaces were carried out by means of angle and spin resolving photoelectron spectroscopy. Iron(110), a polycrystalline iron alloy, and an amorphous metallic glass (Fe 79 B 16 Si 5 ) served as ferromagnetic substrates. Exchange splittings of the O 2p and S 3p derived levels could be detected, demonstrating a magnetic coupling between the chemisorbate and iron. This observation presents a prerequisite for an induced magnetic moment within the adsorbate overlayer. For sulfur an adsorbate-induced structure only in the minority spin channel near the Fermi level was observed whic…

Surface magnetism studied by photoelectron spectromicroscopy with high spatial and time resolution

2004

Abstract Photoemission electron microscopy (PEEM) is widely used for the study of magnetic surfaces and thin films. Ferromagnetic and antiferromagnetic microstructures are investigated exploiting magnetic circular and linear dichroism in the soft X-ray range using tuneable synchrotron radiation. Local dichroism spectroscopy gives access to magnetic moments of the elements in compounds or multilayer materials. Beyond these achievements, the method bears a high future potential with respect to an increased lateral resolution via aberration correction of the electron optics and a high time resolution in the 100 ps range for the study of dynamic processes. In addition, photoelectron spin polari…