The details of the interplay between the electronic structure and the magnetic properties of matter represent a state of the art challenge. In the present work spectroscopic investigations on the electronic structure of some interesting materials are presented. The achieved information has been used in order to answer specific questions related to the magnetic behavior of the investigated materials. For the transition metal dicyanamide compounds it is shown that the electronic states arising from carbon and nitrogen remain roughly unchanged for all compositions. A model for the magnetic superexchange interaction was proposed. In this model the geometry of the crystallographic structure accounts for a particular interaction pattern while the occupancy of the 3d transition metal band is the factor which triggers the changeover from antiferromagnetic to ferromagnetic interaction. In the case of six-membered ferric-wheel molecules the comparison between experimental and theoretical data issued estimations for the magnitude of magnetic exchange interactions. The information on the electronic structure of the LaNi5-xMex (Me=Cu, Al) allowed a better understanding of their magnetic behavior. The changes induced in the electronic structure of the parent compound by partial substitutions of nickel by copper or aluminum are discussed.

The presented thesis includes investigations to fully characterize the electronic structure and magnetic properties ofselected manganese containing high-spin molecules by means of various X-ray spectroscopic, magnetic and theoretical methods. The investigations on the Mn4 star-shaped molecule havelead to a number of interesting results. Magneto-chemical studies exhibit very weak exchange coupling constantsbetween the four Mn(II) ions, leading to complicated low lying states in which the ground state is not well separated, resulting from a dominant weak ferromagnetic coupling and a giant moment of up to 20 µB/f.u. XMCD measurements revealed that almost the completemagnetic moment is located around the Mn(II) ions.This is in agreement with only a few charge transfer states foundwithin the detailed X-ray absorption spectroscopic study. The electronic structure and detailed magnetic properties of the star-shaped heteronuclear CrIIIMnII3 complex have been precisely investigated.With XPS the homovalency of Mn and Cr have been verified. The XA-spectra of the manganese and chromium L edges were measured and compared to earlier investigated Mn4 spectra.The combination high-magnetic field magnetic measurements and element selective XMCD of Mn and Cr L edges and quantum model calculations lead to a complete analysis of the magnetic structure of the CrMn3 magnetic core. The III valence state of the manganese ions in MnIII6O2Salox has been verified. From X-ray diffraction, typical Jahn-Teller distorted oxygen octahedra have been found for Mn(III) ions. Comparisons of XPS and XAS spectra of the complex to corresponding spectraof maganite and tetranuclear manganese(II) cluster it was definitely possible to identify MnIII6O2Salox as a pure Mn(III) compound.

The aim of the present work was to develop a detailed picture of the electronic and magnetic properties of a number of interesting transition metal compounds. A number of complementary experimental and theoretical techniques have been applied, special emphasis was given to x-ray spectroscopies. The studies led to a number of results, and the following conclusions can be drawn: The influence of the magnetic ground state (high-spin (FeO) vs. low-spin (FeS2)) with respect to the recorded x-ray spectra was investigated. In particular, by performing RXES on the Fe L edge of the two compounds, very different ratios of La / Lβ integrated intensity for excitation energies close to the L2 edge have been observed. This effect has been explained in terms of the magnetic structure of FeO (high spin), which inhibits Coster-Kronig processes. Special attention has been given to the direct investigation of orbital ordering in a three dimensional CMR manganite, namely La7/8Sr1/8MnO3, by means of x-ray linear dichroism (XLD). We obtained, for the first time, rather strong indications that the coherently distorted Jahn-Teller phase in La7/8Sr1/8MnO3 is accompanied by a predominantly cross type (x2-z2) / (y2-z2) orbital ordering. In addition to manganites the double perovskite Sr2FeMoO6 the combined study by means of x-ray spectroscopies, magnetic measurements and theoretical band structure calculations could resolve some points discussed controversially in the literature. Both, paramagnetic measurements as well as core level spectroscopy of the Fe 2p, Fe 3s and the Mo 3d states suggest a mixed iron valence state involving around 30% Fe3+- Mo5+ and 70% Fe2+ - Mo6+ states in highly ordered Sr2FeMoO6. XPS valence band studies reveal that the Fe 3d states are not extremely localized, and we find evidence that charge transfer between Fe 3d and O 2p states plays an essential role.

The subject of this work subscribes to the international preoccupation regarding the elucidation of magnetic properties of solids. The crystallographic, electronic and magnetic structures of Al-Mn-Ni alloys and compounds have been investigated by X-ray diffraction, magnetization and magnetic susceptibility measurements, X-ray photoelectron spectroscopy (XPS), and band structure calculations. The thesis is organized in 6 Chapters, followed by the summary. Chapter 1 contains a brief theoretical introduction into the magnetism of metallic systems, as well the principles of XPS. The sample preparation details and all the techniques employed in the characterization of the systems are described in Chapter 2. The next 4 Chapters contain the experimental results for Mn1-xAlxNi3, Mn1-xAlxNi, Ni1-xMnxAl, Ni0.7-xAlxMn0.3 systems.

La génération de surfaces présentant des nanostructurations de surface variées et modulables est l’objectif principal de ce travail. L’auto-assemblage de copolymères à bloc ou de nanoparticules d’or a été privilégié, et nécessite pour se faire de moduler finement les interactions aux interfaces substrat/ matériaux déposés. Dans une première partie, un dispositif expérimental de greffage de silane alkyle en voie vapeur est décrit. Cette technique de greffage permet d’aboutir à des surfaces fonctionnalisées soit de façon homogène, soit de façon graduelle et ce, avec un ou deux silanes (substrat respectivement mono ou bi-composant). La robustesse, la simplicité et la flexibilité de notre procédé ont été démontrés par des caractérisations physico-chimique (mesure des propriétés de mouillabilité), chimique (spectroscopie de photoélectrons X) ainsi que par analyse topographique (microscopie à force atomique). Dans une deuxième partie, l’influence des interactions aux interfaces substrat / film sur l’auto-assemblage de copolymères à bloc PS-b-PMMA a été mise en évidence par AFM. A partir des substrats de silicium homogènes en énergie de surface, il a été possible de moduler la nanostructuration sur différents échantillons et à partir des surfaces fonctionnalisées graduellement, cette variation de nanostructuration a pu être obtenue sur un même substrat. Par l’utilisation de copolymère à bloc PS-b-PI, il est par ailleurs possible de générer des films nanostructurés sans préfonctionnalisation du substrat, sans recuit et ce quelle que soit l’épaisseur du film. Dans une troisième partie, l’influence des interactions aux interfaces sur l’assemblage capillaire/convectif dirigé de nanoparticules d’or a été démontré par microscopie à champ sombre. La nature chimique et la densité de greffage des silanes ainsi que la dimension des échantillons ont été modulées pour mettre en évidence le rôle de ces paramètres sur l’assemblage de ces particules. Cette étude montre que les interactions aux interfaces contrôlent l’assemblage des entités chimiques organiques et inorganiques et donc la nanostructuration de surface qui en résulte. / The purpose of this work is to develop a methodology based on the control of interactions at substrate/deposited material interfaces in order to achieve well-defined structures at the nanoscale (nanostructuration). In particular, silane molecules were grafted onto planar substrates to adjust the physico-chemical interactions in order to consequently control block copolymers / gold nanoparticles self-assemblies. The first part describes the experimental set-up developed to graft alkyl silanes through vapor phase strategy. The modification can be finely tuned such that homogeneously or gradually functionalized surfaces with either one or two silanes (or- or two-component substrate, respectively) are obtained. The versatility and simplicity of our process were demonstrated by wettability measurements, X-ray photoelectron spectroscopy and microscopic analysis (AFM) performed on these different surfaces. The second part points out the influence of grafting density and polarity on block copolymers self-assembly. PS-b-PMMA films were first used. With using homogeneously-modified substrates, it has been demonstrated that block copolymers self-assembly depends on substrate surface chemistry, and different cases (dewetting, wetting, parallel or perpendicular orientation of nanodomains) were achieved as a function of the grafting density of silanes on the substrate. Using gradually-modified surface, these different nanostructures were obtained on one unique sample. Moreover, by using appropriate deposition conditions with another block copolymer (PS-b-PI), well-oriented nanostructured films were obtained without pre-functionalization or annealing, regardless of film thickness. In the third part influence of surface chemistry on gold nanoparticles deposited through capillary/convective assembly is investigated and characterized by dark field microscopy. The careful selection of silane in conjunction with appropriate grafting density are adjusted in order to emphasize the impact of these parameters on the assembly process and therefore on the surface nanostructures. This study demonstrates that the control of interfacial interactions dictates the self-assembly of organic or inorganic materials deposited on a planar substrate.