Hybrid magneto-optical mode converter made with a magnetic nanoparticles-doped SiO2/ZrO2 layer coated on an ion-exchanged glass waveguide

International audienceThis paper describes the possibility to achieve a TE-TM mode conversion in a magneto-optical hybrid waveguide operating at k¼1550 nm. This hybrid device is made by coating a SiO2/ZrO2 layer doped with magnetic nanoparticles on an ion-exchanged glass waveguide. Soft annealing (90 C) and UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical film. Optical characterizations that have been carried out demonstrated the efficiency of these hybrid structures in terms of lateral confinement and mode conversion. Indeed, TE to TM mode conversion has been observed when a longitudinal magnetic field is applied to the device. The amount of this conversion is discussed taking into account the distribution of light between the layer and the guide, and the modal birefringence of the structure

Influence of alkylphosphonic acid grafting on the electronic and magnetic properties of La2/3Sr1/3MnO3 surfaces

Self-assembled monolayers (SAMs) are highly promising materials for molecular engineering of electronic and spintronics devices thanks to their surface functionalization properties. In this direction, alkylphosphonic acids have been used to functionalize the most common ferromagnetic electrode in organic spintronics: La2/3Sr1/3MnO3 (LSMO). However, a study on the influence of SAMs grafting on LSMO electronic and magnetic properties is still missing. In this letter, we probe the influence of alkylphosphonic acids-based SAMs on the electronic and magnetic properties of the LSMO surface using different spectroscopies. We observe by X-ray photoemission and X-ray absorption that the grafting of the molecules on the LSMO surface induces a reduction of the Mn oxidation state. Ultraviolet photoelectron spectroscopy measurements also show that the LSMO work function can be modified by surface dipoles opening the door to both tune the charge and spin injection efficiencies in organic devices such as organic light-emitting diodes.The research leading to these results was financially supported by the EU project NMP3-SL-2011-263104 HINTS and ANR agency (MELAMIN 2011-NANO-021). S.T. acknowledges the European Union FP7 CIG Marie Curie Actions under project SAMSFERE (FP7/2012–321739) and the Spanish MICINN for his JdC contract. P.S. wishes to thank the Institut Universitaire de France for a junior Fellowship. The research leading to these results was partly funded by the SFB/TRR 88 ‘3MET’ from the DFG. Experiments were performed on the “DEIMOS” beamline at SOLEIL Synchrotron, France (project No. 20100960)

Étude des potentialités de couches minces sol-gel dopées par des nanoparticules magnétiques pour la réalisation de composants magnéto-optiques intégrés

The thesis is devoted to the study of the magneto-optical potentiality of thin films made of magnetic nanoparticles embedded in organic-inorganic sol-gel matrix, which can be used to develop components that have a non reciprocal effect such as optical isolator. Sol-gel gateway allows the fabrication of waveguides of low refractive index and controlled thickness. Its soft chemistry quality made the compatibility with classical integrated technology easier and especially the technology on glass. Concerning the magnetic nanoparticles, they are used to give to the sol-gel matrix an interesting magneto-optical effect. The purpose consists to realize the TE-TM mode conversion. Therefore, two parameters must be controlled : The modal birefringence and the Faraday rotation of the material. Results show that the sol-gel matrix doped with magnetic nanoparticles have an interesting potentiality illustrated by a specific Faraday rotation around 250 °/cm and a modal birefringence of 10^(-4). The combination between these two values allows a conversion rate up than 80 %. In addition, The application of an orthogonal magnetic field during the sol-gel gelation phase induces a decrease of the mode birefringence which allows the possibility the realize a phase matching and a totally efficient mode conversion. Furthermore, the Faraday rotation curve possess a hysteresis phenomena which is characterized by a spontaneous effect around 40 % of the magnitude of the saturated Faraday rotation, that is qr = 100 °/cm. The existence of the residual Faraday rotation without any applied magnetic field opens the way to realize auto-polarized components.Le travail de thèse est consacré à l'étude des potentialités magnéto-optiques de couches minces élaborées par voie sol-gel organique-inorganique et dopées par de nanoparticules magnétiques dans le but de réaliser des composants à effet non réciproque en configuration guidée tel que l'isolateur optique. Le choix de la voie sol-gel se justifie par sa qualité de chimie douce et son aptitude à élaborer des guides de faible indice pour une épaisseur ajustable. L'intérêt porté aux nanoparticules magnétiques s'explique par l'effet magnéto-optique intéressant qu'elles présentent. La finalité de la thèse consiste à réaliser la conversion entre les modes TE-TM. Deux paramètres doivent donc être contrôlés finement pour obtenir un guide d'onde planaire ayant des effets magnéto-optiques intéressants : la biréfringence modale et la rotation Faraday. Les résultats obtenus montrent une très forte potentialité de la matrice sol-gel dopée. Il s'agit d'une rotation Faraday spécifique de 250 °/cm et une biréfringence modale de 10^(-4) ce qui permet de prévoir potentiellement un taux de conversion s'élevant 80 %. De plus, l'application d'un champ magnétique pendant la gélification des couches induit une forte diminution de la biréfringence ce qui permet de prévoir un accord de phase. Une conversion de mode totale est donc potentiellement réalisable. D'autre part, la courbe de la rotation Faraday présente un cycle d'hystérésis caractérisé par une rotation rémanente de 40 % de la valeur de la rotation à saturation, soit qr = 100 °/cm. L'existence d'une telle rotation sans aucun champ appliqué ouvre la voie à la réalisation de composants auto-polarisés

Etude des potentialités de couches minces sol-gel dopées par des nanoparticules magnétiques pour la réalisation de composants magnéto-optiques intégrés

Le travail de thèse est consacré à l'étude des potentialités magnéto-optiques de couches minces élaborées par voie sol-gel organique-inorganique et dopées par des nanoparticules magnétiques dans le but de réaliser des composants à effet non réciproque en configuration guidée tel que l'isolateur optique. Le choix de la voie sol-gel se justifie par sa qualité de chimie douce et son aptitude à élaborer des guides de faible indice pour une épaisseur ajustable. L'intérêt porté aux nanoparticules magnétiques s'explique par l'effet magnéto-optique intéressant qu'elles présentent. La finalité de la thèse consiste à réaliser la conversion entre les modes TE-TM. Deux paramètres doivent donc être contrôlés finement pour obtenir un guide d'onde planaire ayant des effets magnéto-optiques intéressants : la biréfringence modale et la rotation de Faraday. Les résultats obtenus montrent une très forte potentialité de la matrice sol-gel dopée. Il s'agit d'une rotation Faraday spécifique de 250/cm et une biréfringence modale de 10-4 ce qui permet de prévoir potentiellement un taux de conversion s'élevant à 80 %. De plus, l'application d'un champ magnétique pendant la gélification des couches induit une forte diminution de la biréfringence ce qui permet de prévoir un accord de phase. Une conversion de mode totale est donc potentiellement réalisable. D'autre part, la courbe de la rotation Faraday présente un cycle d'hystérésis caractérisé par une rotation rémanente de 40 % de la valeur de la rotation à saturation, soit r = 100/cm. L'existence d'une telle rotation sans aucun champ appliqué ouvre la voie à la réalisation de composants auto-polarisésThe thesis is devoted to the study of the magneto-optical potentiality of thin films made of magnetic nanoparticles embedded in organic-inorganic sol-gel matrix, which can be used to develop components that have a non reciprocal effect such as optical isolator. Sol-gel gateway allows the fabrication of waveguides of low refractive index and controlled thickness. Its soft chemistry quality made the compatibility with classical integrated technology easier and especially the technology on glass. Concerning the magnetic nanoparticles, they are used to give to the sol-gel matrix an interesting magneto-optical effect. The purpose consists to realize the TE-TM mode conversion. Therefore, two parameters must be controlled : the modal birefringence and the Faraday rotation of the material. Results show that the sol-gel matrix doped with magnetic nanoparticles have an interesting potentiality illustrated by a specific Faradray rotation around 250/cm and a modal birefringence of 10-4. The combination between these two values allows a conversion rate up than 80 %. In addition, the application of an orthogonal magnetic field during the sol-gel gelation phase induces a decrease of the mode birefringence which allows the possibility to realize a phase matching and a totally efficient mode conversion. Furthermore, the Faraday rotation curve possess a hysteresis phenomena which is characterized by a spontaneous effect around 40 % of the magnitude of the saturated Faraday rotation, that is r = 100/cm. The existence of the residual Faraday rotation without any applied magnetic field opens the way to realize auto-polarized componentsST ETIENNE-BU Sciences (422182103) / SudocSudocFranceF

What are the effects of environmental factors on Co speciation at magnetite surface?

International audienceMagnetite nanoparticles are abundant in the environment and are notably used for environmental applications due to their unique magnetic, adsorption and redox properties. The stoichiometry of magnetite (Fe(II)/Fe(III)) is dependent on environmental factors (pH, presence of organic ligands, redox conditions), which largely affects magnetite nanoparticles physico-chemical properties, such as redox reaction, but also adsorption of contaminants. However, the joint effects of environmental factors and magnetite stoichiometry on magnetite-metal cations interaction are elusive. This study focuses on Co as an important contaminant, and because Co-doped magnetite nanoparticles are of high interest for nanotechnology applications. Magnetite nanoparticles (~10nm) with different stoichiometries were synthesized by coprecipitation, and partially oxidized using H2O2 to obtain the desired stoichiometry. Batch studies were carried out with different [Co], using three different stoichiometries (0.1, 0.3 and 0.5), at different pH values, and in the presence or the absence of natural organic matter (OM) or atmospheric O2(g). Experimental and modeling results, and XAS and XMCD analysis revealed that interactions between Co and magnetite varied, with favored oligomer formation and surface precipitation at higher stoichiometries. It was also highlighted that the formation of different species of Co depended on environmental conditions with the adsorption of monomers favored at low pH and in the presence of organic matter, and the partial oxidation of Co(II) to Co(III) in aerobic conditions. These results will help to predict the behavior and fate of Co in the environment and to understand the impact of environmental factors for an appropriate use of magnetite nanoparticles for environmental applications, or to synthesize Co-modified magnetite nanoparticles using water as solvent for high technology applications

Phase matched magnetooptic planar waveguide elaborated by magnetic nanoparticles embedded in a organic-inorganic sol-gel matrix

International audienc