An investigation has been made of the propagation characteristics of magnetostatic waves with frequencies in the range 890-990 MHz in a crystal of Yttrium Iron Garnet. The sample was mounted in a two port strip line assembly and magnetised axially along the (100) direction. The experiments were performed at room temperature. Magnetostatic waves were observed in external magnetic fields in the neighbourhood of 500 Cersteds. and to explain the experimental results a non-uniform distribution of magnetisation along the axial direction is proposed for the unsaturated sample. Theoretical results for the demagnetising field and the time delay have been computed using this model to explain the excitation and transmission of the observed magnetostatic waves. / Thesis / Master of Engineering (ME)

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Endohedral metallofullerenes (EMFs) have attracted increasing attention during past decades due to their novel structures and potential applications in a variety of fields such as biomedical applications and molecular electronics. This dissertation addresses the structural characterization and hydrogenation of EMFs. A family of novel large cage yttrium-based TNT EMFs Y₃N@C₂ₙ (n=40-44) was prepared, separated, and structurally characterized for the first time. The structure of Y₃N@C₂ₙ (n=40-44) is proposed by the experimental and computational ¹³C NMR studies. The first ⁸⁹Y NMR results for Y₃N@<I>Iₕ</i>-C₈₀, Y₃N@<I>Cₛ</i>-C₈₄ and Y₃N@<I>D₃</i>-C₈₆ reveal a progression from isotropic to restricted (Y₃N)⁶⁺</sup> cluster motional processes. The di-metallic EMF Y₂C₉₄ is distinguished as a metal-carbide based EMF, Y₂C₂@<I>D₃</i>-C₉₂. The carbide within the cage is successfully detected by ¹³C NMR. The scalar J_Y-C coupling between the yttrium atoms and the C₂ unit within the C₉₂ cage is successfully observed, suggesting the C₂ unit rotates rapidly around the yttrium atoms. Two paramagnetic endohedral metalloheterofullerenes, Y₂@C₇₉N and Gd₂@C₇₉N, were also synthesized and characterized. The EPR study demonstrated that the spin density is mainly localized between the two metallic ions. A spin-site exchange system could be constructed between Y₂@C₇₉N and the organic donor TMPD. Being a unique paramagnetic material, Gd₂@C₇₉N displays an unusual stability over a wide temperature range, which could be very useful in optical and magnetic areas. Functionalization of EMFs is another point of interest in this dissertation. Hydrogenated Sc₃N@C₈₀ was synthesized and characterized. Our study demonstrated that the Sc₃N@C₈₀ can be fully hydrogenated and the pristine Sc₃N@C₈₀ can be recovered from Sc₃N@C₈₀H₈₀ after being heated in vacuum. The hydrogenated EMFs could be potential hydrogen storage materials. / Ph. D.

L’addition d’une liaison N-H sur une double liaison carbone-carbone, nommée réaction d’hydroamination (HA), constitue une voie efficace pour accéder à la formation de composés azotés à partir de précurseurs simples en une seule étape. Des progrès considérables ont été réalisés au cours de ces dernières années dans l’élaboration de systèmes catalytiques efficaces pour cette réaction d’intérêt sur des alcènes. Malgré tout de nombreux défis subsistent car peu de catalyseurs disposent d’un large champ d’application ou encore ils sont limités dans la catalyse de la version intermoléculaire de la réaction à la fois moins favorisée cinétiquement comme thermodynamiquement. Au cours de ces travaux le mécanisme réactionnel, d’activation de la réaction d’HA intramoléculaire, par un complexe d’yttrium a pu être déterminé suite à une étude cinétique. Cette dernière a permis de mesurer un ordre partiel en catalyseur de 1 et un ordre inverse en substrat. D’autre part, le potentiel dans la réaction d’HA de plusieurs systèmes catalytiques basés sur différents groupes de métaux a été évalué. Des complexes pinces tridentes de zirconium ou de hafnium sous forme neutre comme sous forme cationique ont montré de bonnes activités dans la réaction de cyclisation de plusieurs aminoalcènes comportant des amines primaires ou secondaires. L’utilisation d’un complexe d’yttrium a permis d’accéder à une large gamme d’arylethylamines de manière totalement régiospécifique par catalyse de la réaction intermoléculaire d’HA entre des amines secondaires faiblement encombrées et des dérivés du styrène. Ce faisant une étude structure-activité a été conduite mettant à jour une activité remarquable du complexe d’yttrium dans la réaction d’HA intermoléculaire sur la 2-vinylpyridine, ce qui a également permis de montrer une application en procédure tandem de double hydroamination. Enfin une procédure simple de catalyse de la réaction d’HA intermoléculaire sur des dérivés du styrène a pu être mise au point suite à l’utilisation d’un sel de lithium actif à température ambiante. / The addition reaction of an amine across a carbon-carbon double bond, the so-called hydroamination reaction, is one of the most efficient method for the formation of value-added nitrogen-containing compounds. During the last decade, the interest of the scientific community has led to the development of a large number of efficient catalysts for this transformation. Nevertheless many challenges remain. Indeed only a few of the reported catalysts have a wide range of applications or possess good activities in the field of the intermolecular version of the reaction, less favored both kinetically and thermodynamically. In these work the mechanism of intramolecular HA reaction catalyzed by an yttrium complex has been determined by a kinetic study. During the latter a partial order of 1 for the catalyst and a reverse order in substrate were measured. The potential in the HA reaction of several catalytic systems based on different metals was evaluated. Tridentate complexes of zirconium or hafnium in their neutral or cationic form showed good activity in the cyclization reaction of several aminoalkenes bearing primary or secondary amines. The use of an yttrium complex allowed a regiospecific access to wide range of arylethylamines by catalysis of the intermolecular HA reaction between weakly hindered secondary amines and styrene derivatives. A structure-activity study was conducted pointing the noteworthy activity of the yttrium complex in the intermolecular HA reaction with 2-vinylpyridine, which also allowed an application in a tandem di-hydroamination reaction. Finally, a simple procedure for catalyzing the intermolecular HA reaction of styrene derivatives has been developed by using a lithium salt active at room temperature.

Ce travail de thèse a consisté en la synthèse et l’étude de dérivés du macrocycle pyclen (3,6,9,15-tétrazabicyclo[9.3.1]pentadéca-1(15),11,13-triène) pour la complexation de l’90Y3+ et du Gd3+ pour le traitement et le diagnostic du cancer du foie par les techniques respectives de radiothérapie interne et d’IRM. Notre objectif a été de développer des chélates stables et inertes répondant aux critères imposés par le milieu biologique. La lipophilie et la neutralité de ces composés ont également été recherchées en raison des applications visées. Nous avons synthétisé des dérivés du pyclen N-fonctionnalisés par des groupements phosphonate puis développé une série de quatre ligands diversement N-fonctionnalisés par des groupements picolinate et acétate. Ces derniers ont été synthétisés grâce au développement de nouvelles voies de N-fonctionnalisation régiospécifiques. Ces synthèses ont été optimisées et les complexes d’Y3+ et Gd3+ étudiés. Les résultats obtenus nous ont amené à synthétiser un analogue lipophile qui forme avec l’yttrium 90 un excellent chélate pour le traitement du cancer du foie. Enfin, ces études ont mis en évidence le potentiel de certains chélates de Gd3+ à être utilisés comme agents de contraste hépatobiliaires. / This work consisted in the synthesis and study of Y3+ and Gd3+ pyclen derivatives for liver cancer’s treatment and diagnosis by means of internal radiotherapy and MRI techniques. For these applications, the chelates of interest must fulfill numerous criteria: being thermodynamically stable and kinetically inert but also being lipophilic and neutral. In this work, we have synthesized a pyclen derivative N-functionalized by three phosphonate pendant arms and developed four new pyclen derivatives N-functionalized by either picolinate or acetate moities arranged in various way, thanks to the development of new synthetic pathways leading to regiospecific N-functionalization. These syntheses were optimized and the properties of Y3+ and Gd3+ chelates were studied. The good results we have obtained encouraged us to synthesize a lipophilic analogue which forms with yttrium 90 a very promising chelate, suitable for liver cancer’s internal radiotherapy. The gadolinium(III) chelates also show good properties for a use as a liver-specific MRI contrast agent.

Dans cette étude de doctorat, de la poudre de Y3Al5O12 (YAG) a été synthétisé avec plusieurs méthodes: atomisation, synthèse de réaction et co-précipitation. Le procédé de synthèse le plus prometteur, la co-précipitation, a été optimisé pour obtenir une poudre hautement frittable, présentant une phase pure. Le traitement approprié avant frittage, comprenant calcination, efficace dispersion et séchage homogène, a été réalisé. La poudre de YAG a été dispersée avec plusieurs méthodes, avant frittage. Grâce à la technique Spark Plasma Sintering (SPS) une évaluation très rapide de l'influence des différents traitements a été réalisée. Il a été constaté que, pour une poudre obtenue avec une telle synthèse, la méthode de dispersion est cruciale afin de obtenir une transparence élevée du materiaux fritté. En raison de l'aptitude au frittage de la poudre, du traitement approprié avant frittage et de la basse température du cycle effectué par SPS, un matériau à grains fins a été obtenu. Des mesures de spectroscopie de photoélectrons (XPS) ont été effectuées sur la poudre de YAG et sur le matériaux fritté, et plusieurs differences ont été mises en évidence. Quelques hypothèses ont été faites pour expliquer les differences observées, et certains preuves supplémentaires pour les vérifier ont été mises en avant. Une poudre composite alumine-zircone-YAG a été synthétisé à partir d'une poudre d'alumine commerciale, qui a été fonctionnalisé avec chlorures de yttrium et de zirconium. Les traitements de pré-frittage appropriées ont été effectués, comprenant une calcination à basse température et une calcination "rapide", pour favoriser la germination des petits cristallites. Deux méthodes de mise en forme, coulage et pressage, ont été réalisées. Il a été constaté que le coulage permet la production de matériaux céramiques beaucoup plus homogènes. Une caractérisation mécanique préliminaire a été effectuée. Une caractérisation spectroscopique des poudres d'alumine-YAG, traités à basse et haute température, a été réalisée. Il a été mis en évidence que l'état d'hydratation des poudres varie avec la fonctionnalisation par les chlorures. La présence de sites Y sur la surface des poudres composites a été mise en évidence par XPS et à partir des spectres infrarouges (spectroscopie infrarouge par transformée de Fourier, FTIR) des échantillons soumis à des différentes pressions de monoxide de carbone (CO). / In this PhD study, Yttrium aluminum garnet (Y3Al5O12, YAG) powder was synthesised with several methods, i.e. spray drying, reaction synthesis and co-precipitation. The most promising synthesis method, i.e. co-precipitation, was optimized to obtain a pure phase, highly sinterable powder. The appropriate pre-sintering processing, i.e. calcination treatment, e fficient dispersion, homogeneous drying, were performed. YAG powder was dispersed with several methods, prior to sintering. Through Spark Plasma Sintering (SPS) a very fast assessment of the influence of the various treatments was performed. It was found that, for the synthesised powder, the dispersion method is crucial to obtain a high transparency. Due to the high sinterability of the powder and to the appropriate pre-sintering treatment, a low temperature SPS cycle was performed, and a fine-grained material was obtained. X-ray Photoelectron Spectroscopy (XPS) measurements were performed on YAG powder and on the sintered material, and several di fferences were evidenced. Some hypothesis were made to explain the observed di fferences, and some additional proofs to verify them were put forward. A composite Alumina-YAG-Zirconia powder was synthesized, starting from a commercial alumina powder, which was functionalised with Yttrium and Zirconium chlorides. The appropriate pre-sintering treatments were performed, comprising a low temperature calcination and a "fast" calcination, to favour the germination of small crystallites. Two shaping methods, i.e. slip casting and pressing, were performed. It was found that slip casting allows the production of much more homogeneous ceramic materials. A preliminary mechanical characterization was performed. A spectroscopic characterization of Alumina-YAG powders, heat-treated at low and high temperatures, was performed. It was evidenced that the hydration state of the powders changes with chlorides functionalization. The presence of Y sites on the surface of the composite powders was evidenced by X-ray Photoelectron Spectroscopy and from the di fference spectra of powdered samples subjected to various CO pressures.

The field of spintronics emerged from the search for innovative concepts to comply with the ever increasing need for larger data storage. One major subject of spintronics are devices based on pure spin currents. Such devices usually rely on a combination of two materials: first, a magnetic insulator, to carry the spin information, and second, a spin Hall active metal, to convert from spin to charge information and vice versa and thus effectively act as electrical interface. While previously, such bilayers have been studied in detail in various planar structures, lately, curved and/or three dimensional (3D) geometries have gained more and more attention. Especially for magnetic systems, it has been reported that curvature can lead to the materialization of additional interactions such as curvature-induced anisotropy and the Dzyaloshinskii-Moriya-interaction. The latter is closely related to the magnetic topography of the system, which can be deduced from its essential role in the formation of skyrmions. To systematically study curvature- or topology-based effects, artificially designed systems with a controllable curvature are essential. Consequently, providing an experimental platform, which allows the realization of a variety of different geometries is a key step towards accessing this innovative field of magnetism research. In this thesis, we used atomic layer deposition (ALD) to establish such a platfrom. ALD is a chemical vapor deposition technique which enables the conformal coating of arbitrarily shaped objects while maintaining an excellent thickness control of the layers. In conjunction with 3D (nano)printed resist structures, which can be designed in a multitude of different designs, ALD serves as a powerful platform to fabricate 3D micro- or nanostructures. One of the most popular material combination in spintronics consists of yttrium iron garnet (YIG) and platinum. On the one hand, the ferrimagnetic insulator YIG is the ideal candidate for any kind spin transport experiments, due to its very low magnetic damping. Pt, on the other hand, has a large spin-orbitinteraction, which is necessary for an efficient spin to charge conversion. Therefore, the fabrication of 3D spintronic devices from YIG and Pt is highly desirable. In this thesis the successful fabrication of YIG and Pt by ALD is outlined. We validate the usability of the ALD-Pt layers for 3D spintronics by showing that the ALD-Pt layers are spin Hall active with a electrical quality comparable to other deposition techniques. For the fabrication of ALD-YIG, a nanolaminate approach was used, which is based on the alternate deposition of ultra thin layers of two binary ALD processes: ALD-Fe2O3 and ALD-Y2O3. Therefore, these two processes were optimized beforehand to establish the growth conditions. Furthermore, asdeposited ALD layers are often non-crystalline. To characterize, how this reflects in magnetotransport experiments, we used a model system of non-crystalline sputtered YIG and Pt. By rotating the magnetization in three rotation planes, we find the fingerprint of the spin Hall magnetoresistance. We demonstrate that 3D nanoprinted resist templates can be made fit for the deposition of ALD bilayers even at temperatures where the resist is not stable on its own. To enhance the stability of the resist templates, a layer of low temperature ALD-Al2O3 is used. Finally, the deposition of ALD-YIG is described. A subsequent annealing step is used to promote crystallization of the nanolaminates into YIG. Upon characterizing the structural properties, we find that our process is extremely stable with respect to changes in the stoichiometry within the nanolaminate. From additional measurements of the static and dynamic magnetic properties, we conclude that our ALD-YIG are of good quality comparable to other deposition techniques. By enabling the fabrication of high quality YIG and Pt via ALD, we lay the groundwork for studying the electrical and magnetic properties of systems with curvature and/or a nontrivial topography - effectively advancing the research field of 3D spintronics.

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