This thesis describes the experimental investigation of three different strongly correlated transition-metal oxide systems. The magnetic behaviour of each has been probed using inelastic neutron spectroscopy. A distinctive hour-glass excitation spectrum has been observed in the layered cobaltate La_1.75Sr_0.25CoO₄. This spectrum is similar to that measured in a related cobaltate La_1.67Sr_0.33CoO₄, although it appears broader. The spectrum has been reproduced using a spin wave model derived from a disordered cluster spin glass ground state. Signatures of spin glass behaviour have also been observed in bulk magnetisation measurements of La_1.75Sr_0.25CoO₄. These findings, once more, demonstrate the emergence of an hour-glass spectrum from a ground state that combines quasi-one dimensional magnetic correlations and disorder. Additionally, this study shows that charge and magnetic stripe order persists to lower dopings in La_2-xSr_xCoO₄ than previously thought. The complete magnetic excitation spectrum of the multiferroic compound CuO has been measured for the first time. A high energy, one-dimensional magnetic spectrum is observed and modelled using the Muller ansatz derived for the S=1/2 Heisenberg antiferromagnetic chain. At lower energies, a three-dimension spectrum is observed. The measured spectrum is inconsistent with all previous theoretical estimates of the dominant inter-chain exchange interactions in CuO. The inter-chain dispersion is successfully described by a phenomenological model based on linear spin wave theory. The third material investigated, LuFe₂O₄ demonstrates complex charge and magnetic order, the precise nature of which is still under debate. The full spectrum of in-plane excitations in LuFe₂O₄ has been measured and a complicated dispersion consistent with six magnetic modes is observed. These findings are compatible with structures described by a magnetic unit cell containing six spins. The dispersion can be described by a spin wave model derived from a bilayer structure comprised of charge-rich and charge-poor monolayers. This structure is consistent with the original site-specific model for the 3D magnetic ordering in LuFe₂O₄.

No description available.

[ES] En esta tesis se realiza un estudio de acidez de zeolita LTA con la relación Si/Al 5 y 40 utilizando la técnica de dispersión inelástica de neutrones (INS) en combinación con otras tecnicas como la modelización computacional y la espectroscopía de resonancia magnética nuclear (RMN). Las zeolitas son aluminosilicatos altamente cristalinos que forman parte de un grupo importante de los materiales funcionales. Las zeolitas son extremadamente útiles como catalizadores para muchas reacciones importantes con moléculas orgánicas. Las más importantes son craqueo, isomerización y síntesis de hidrocarburos. Las propiedades catalíticas de una zeolita dependen principalmente de su acidez y ésta depende de tres factores: el número totál de los sitios ácidos, sus fuerzas individuales y su localización individual, estando estos tres factores relacionados. Los parámetros geométricos definidos por localización de los sitios ácidos (es decir, la longitud y los ángulos de enlaces entre los átomos alrededor del sitio ácido) contribuyen de una manera importante a la fuerza ácida. En la literatura hay muchos trabajos de estudios de acidez en zeolita utilizando la espectrometría infrarroja (IR), sin embargo, con esta técnica es imposible medir las vibraciones de flexión (bending modes, 200-1200 cm-1), las bandas más sensibles al entorno local de los centros ácidos, ya que estas bandas se superponen con las bandas de vibración de la red de zeolite (300-1800 cm-1). En esta tesis se realiza un estudio de acidez utilizando la tecnica de INS, que nos permite medir principalmente los modos de vibración de los átomos de H y también nos permite medir todas las bandas de vibración (incluido el bending). Este estudio muestra que la combinación de la alta calidad de las muestras y la sensibilidad del instrumento utilizado permite detectar con alta precisión los sitios ácidos y obtener la información sobre su posición que a su vez nos perimte obtener la posición de los átomos de Al. Con el fin de interpretar los espectros INS se ha realizado un estudio computacional (cálculos ab-initio) con el objetivo de comparar los espectros cálculados con los resultados experimentales y definir el modelo que reproduce la posición mas probable de los centros ácidos en la muestra. / [CA] En aquesta tesi es realitza un estudi d'acidesa de zeolita LTA amb la relació Si / Al 5 i 40 utilitzant la tècnica de dispersió inelastica de neutrons (INS) en combinació d'altres tècniques com la modelització computacional i la espectroscòpia de ressonància magnètica nuclear (RMN ). Les zeolites són aluminosilicats altament cristal·lins que formen part d'un grup important dels materials funcionals. Les zeolites són extremadament útils com a catalitzadors per a moltes reaccions importants amb molècules orgàniques. Les més importants són craqueig, isomerització i síntesi d'hidrocarburs. Les propietats catalítiques d'una zeolita depenen principalment de la seva acidesa i aquesta depèn de tres factors: el nombre total dels llocs àcids, les seves forces individuals i la seva localització individual, estant aquests tres factors relacionats. Els paràmetres geomètrics definits per localització dels llocs àcids (és a dir, la longitud i els angles d'enllaços entre els àtoms al voltant del lloc àcid) contribueixen d'una manera important a la força àcida. En literatura hi ha molts treballs d'estudis d'acidesa en zeolita utilitzant l'espectrometria infraroja (IR), però és impossible mesurar les vibracions de flexió (bending modes, 200-1200 cm-1) amb aquesta tècnica ja que aquestes bandes es superposen amb les bandes de vibració de la xarxa de zeolita (300-1800 cm-1). La tècnica de dispersió inelastica de neutrons (Inelastic neutron scattering) ha estat utilitzada per estudiar l'acidesa de la zeolita LTA amb diferents relacions Si / Al (per tant diferents c.ontinguts de H en la zeolita). En aquesta tesi es realitza un estudi d'acidesa utilitzant la tècnica de INS, que ens permet mesurar principalment els modes de vibració dels àtoms d'H i també ens permet mesurar totes les bandes de vibració (inclòs el bending). Aquest estudi mostra que la combinació de l'alta qualitat de les mostres i la sensibilitat del instrument utilitzat permet detectar amb alta precisió els llocs àcids i obtenir la informació sobre la seva posició que en el seu lloc ens perimte obtenir la posició d'Al. Per tal de interpretar els espectres INS s'ha realitzat un estudi computacional (càlculs ab-initio) amb la comparació dels espectres calculats amb els resultats experimentals. / [EN] This thesis is dedicated to the study of acidity of LTA zeolites with Si/Al ratios 5 and 40 by using the technique of inelastic neutron scattering (INS) in combination with other techniques such as computational modeling and nuclear magnetic resonance (NMR) spectroscopy. Zeolites are crystalline and microporous aluminosilicates which form one of the most important groups of functional materials. Zeolites are widely used as solid acid catalysts for the wide range of important processes regarding organic molecules. The most important are cracking, isomerization reaction and synthesis of hydrocarbons. The catalytic properties of a zeolite depend strongly on its acidity, and this in turns depends on: the total number of acid sites, their individual strength, and their individual location. These three factors are strongly correlated. Geometric parameters that are defined by the location of the acid site (i.e., bond angles and lengths around the acid site) make a remarkable contribution to the acid strength. There are several studies, found in literatures, typically done by Infrared (IR) or Nuclear magnetic resonance (NMR) technique and dedicated to acidity of zeolites. However, the hydrogen bending modes (200-1200 cm-1), which are found to be more sensitive to local environment, cannot be observed by this technique, since these bands overlap with strong bands of the vibrations of zeolitic framework (300-1800 cm-1). INS technique used in this study allows to detect the bands of vibrations of hydrogen atoms in zeolites (including bending modes). Moreover, this study shows that the combination of an extremely high quality of the samples and the sensitivity of the instrument allows to detect with high precision the acid sites of both high-silica and low-silica zeolites and obtain information about their position. This in its turn gives us the possibility to obtain the aluminium location in zeolites. In order to fully understand the INS spectra we performed ab-initio calculations that allow to interpret the experimental bands and choose a structural model that reproduces the probable location of acid sites in the sample. / Lemishko, T. (2019). Inelastic neutron scattering study of Brønsted acidity in LTA zeolite [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/119966

Nuclei at closed shells tend to be spherical and are well-described by the shell model, while those between closed shells are deformed and better described by collective models. The nuclei which are in transitional regions between spherical and deformed may be studied to gain insight into the nature of this transition. The stable isotopes of zirconium and xenon span such transitional regions and are the subject of this dissertation. Gamma-ray spectroscopy following inelastic neutron scattering has been performed on the stable isotopes of Zr as well as 132,134Xe at the University of Kentucky Accelerator Laboratory. Level lifetimes have been measured using the Doppler-shift attenuation method, which allow the determination of transition probabilities that are of utmost importance in elucidating the structure of these nuclei. The lifetime measurements were the focus of the study of the Zr isotopes. Previously measured level lifetimes in 94Zr by our group were called into question by recent electron scattering experiments. This motivated a re-measurement of these lifetimes and led to a study of the role of the chemical properties of the scattering samples employed in the measurements. Various Zr-containing compounds were characterized with powder X-ray diffraction and scanning electron microscopy and were employed as scattering samples. These studies revealed the impact of using amorphous materials and those composed of small particles as scattering samples on the resulting lifetimes, and has important implications for future lifetime measurements employing the Doppler-shift attenuation method. For the xenon experiments, highly enriched (>99.9%) 132Xe and 134Xe gases were converted to solid 132XeF2 and 134XeF2, and were used as scattering samples. The xenon isotopes have not been particularly well-studied as elemental targets are gases under ambient conditions, which introduces difficulties into the measurements. Much new information was obtained for these nuclei, including the placement of many new transitions and levels, and measurement of many new level lifetimes, allowing the determination of reduced transition probabilities. This additional information provided important insight into the structure of these two transitional nuclei.

While neutrino oscillations indicate that neutrino flavors mix and that neutrinos have mass, they do not supply information on the absolute mass scale of the three flavors of neutrinos. Currently, the only viable way to determine this mass scale is through the observation of the theoretically predicted process of neutrinoless double-beta decay (0νββ). This yet-to-be-observed decay process is speculated to occur in a handful of nuclei and has predicted half-lives greater than 10²⁵ years. Observation of 0νββ is the goal of several large-scale, multinational efforts and consists of detecting a sharp peak in the summed β energies at the Q-value of the reaction. An exceptional candidate for the observation of 0νββ is ⁷⁶Ge, which offers an excellent combination of capabilities and sensitivities, and two such collaborations, MAJORANA and GERDA, propose tonne-scale experiments that have already begun initial phases using a fraction of the material. The absolute scale of the neutrino masses hinges on a matrix element, which depends on the ground-state wave functions for both the parent (⁷⁶Ge) and daughter (⁷⁶Se) nuclei in the 0νββ decay and can only be calculated from nuclear structure models. Efforts to provide information on the applicability of these models have been undertaken at the University of Kentucky Accelerator Laboratory using gamma-ray spectroscopy following inelastic scattering reactions with monoenergetic, accelerator-produced fast neutrons. Information on new energy levels and transitions, spin and parity assignments, lifetimes, multipole mixing ratios, and transition probabilities have been determined for ⁷⁶Se, the daughter of ⁷⁶Ge 0νββ, up to 3.0 MeV. Additionally, inaccuracies in the accepted level schemes have been addressed. Observation of 0νββ requires precise knowledge of potential contributors to background within the region of interest, i.e., approximately 2039 keV for ⁷⁶Ge. In addition to backgrounds resulting from surrounding materials in the experimental setup, ⁷⁶Ge has a previously observed 3952-keV level with a de-exciting 2040-keV γ ray. This γ ray constitutes a potential background for 0νββ searches, if this level is excited. The cross sections for this level and, subsequently, for the 2040-keV γ ray has been determined in the range from 4 to 5 MeV.

A collection of studies are reported that focus on the examination of exchange interactions in complexes containing paramagnetic ions with a large magnetic anisotropy. A number of complementary techniques are used to analyse the complicated systems that arise, including high-field high-frequency electron paramagnetic resonance, inelastic neutron scattering, SQUID magnetometry, and ab initio calculations. The nuclearity of the complexes ranges from dimetallic, to trimetallic, to octametallic. A family of five water- and carboxylate-bridged nickel(II) dimetallics are the focus of a magneto-structural correlation study that succeeds in measuring the magnitude of the exchange interaction despite dominating effects from large zero-field splitting effects. Similar work is reported for four cobalt(II) analogues of these compounds, with the relationship between exchange interactions and geometry also being probed by pressure INS. Charge density studies that combine high resolution X-ray and neutron diffraction studies are reported on cobalt and nickel analogues from the same family of dimetallics, revealing strong evidence for non-direct exchange. A family of four trimetallic triangle complexes containing two nickel(II) ions and one chromium(III) ion bridged by a central fluoride and a total of six carboxylates are reported, and the exchange interactions are elucidated from a global model that accounts for the low-field magnetic, heat capacity, and EPR data. Two new octametallic vanadium(III) wheels—where each pair of adjacent metals are bridged by a fluoride and two carboxylates—are reported along with preliminary results from magnetic measurements and solid state proton NMR spectra, which reveal significant field-dependent effects arising from level crossings at high fields.

The aim of nuclear structure studies is to observe and describe the structures and associated symmetries in nuclei, which in turn help us in understanding the nature of nucleon-nucleon interactions in a nucleus as a many-body quantum system. The protons and neutrons as constituents of a nucleus and their interactions are responsible for nuclear properties. The evolution of nuclear structure as a function of valence nucleon number, i.e., the number of nucleons beyond a magic number, can be inferred from the experimental level scheme and transition rates. In particular, the studies of low-lying, low-spin excited states in stable nuclei provide valuable information on the interplay of valence neutrons and protons in nuclear structure. The decay scheme and knowledge of transition strengths in the low-lying states become a benchmark for testing theoretical model predictions and understanding the underlying microscopic foundations of nuclear structure. Along with the experimental techniques, theoretical models have been developed to explain and describe the observed nuclear properties, e.g., shell model, Fermi-gas model, optical and liquid-drop models, and several “collective” models. 94/40Zr50 nucleus with 2 protons and 4 neutrons above the shell closures of the 88/38Sr50 core nucleus is considered as a nearly spherical nucleus. Such nuclei present a vibrational structure; surface vibration of the nucleus about a spherical shape. In addition to the symmetric excitations, in which proton and neutron oscillations are in phase, there are another class of excitations in which the wave function is not fully symmetric with respect to the exchange of protons and neutrons. These states are so called mixed-symmetry (MS) states. Such excitations have been observed in the N= 52 neighboring isotones. In this study, the low-lying structure of 94/40Zr has been studied with the (n, n'ƴ) reaction at the University of Kentucky and Triangle Universities Nuclear Laboratories (TUNL) facilities, to identify symmetric and MS excitations in this nucleus. A decay scheme has been established based on excitation function and coincidence measurements. Branching ratios, multipole mixing ratios, and spin assignments have been determined from angular distribution measurements at En= 2.3, 2.8, and 3.5 MeV. Lifetimes of levels up to 3.4 MeV were measured by the Doppler-shift attenuation method (DSAM), and for many transitions reduced transition probabilities were determined. The experimental results were used for the identification of collective symmetric and mixed-symmetric (MS) multiphonon excitations. The 2+/2 state at 1671.4 keV has been identified as the lowest MS state in 94Zr; B(M1; 2+/ms → 2+/1 ) = 0.31(3) μ2/N. This state has an anomalous decay behavior, i.e., B(E2; 2+/ ms → 0+/1 ) = 7.8(7) W.u., which is unusually large compared to the B(E2; 2+/1 → 0+/1 ) = 4.9(3) W.u. More anomalies were identified in the states above the 2+/ms state. For example, the 4+/2 state at 2330 keV decays strongly to the 2+/1 state, B(E2; 4+/2 → 2+/1 ) = 20+3/−2 W.u., compared to the 4+/1 state at 1469 keV, B(E2; 4+/1 → 2+/1 ) = 0.878(23) W.u. The experimental results revealed additional interesting and unusual properties of the low-lying states in 94Zr. Shell model calculations were performed with the Oxbash code, using the Vlow k interaction. Also, the IBM-2 predictions in the vibrational limit were compared with the experimental results. The results from neither of these nuclear models were in good agreement with the observed transition strengths, e.g., the B(E2; 2+/ms → 0+/1 ) value. These observations may indicate that the contributions of valence nucleons in the low-lying excited states of 94Zr differ from what has been perscribed by the shell model and the IBM-2 model. The effects of the Z = 40 and N = 56 subshell closures should be also considered. In a simple interpretation, the excited states are classified in two distinct categories, i.e., those populating the 2+/2 state and those decaying to the 2+/1 state. This approach suggests that in 94Zr the low-lying states may be related to two-configurations coexistence.

An der Neutronen-Flugzeit-Anlage nELBE des Helmholtz-Zentrums Dresden-Rossendorf sollen Reaktionsquerschnitte mit Relevanz für die nukleare Transmutation bestimmt werden. Die Transmutation hochradioaktiver Abfälle aus abgebrannten Brennelementen thermischer Kernreaktoren in schnellen Neutronenspektren hat das Potential die langlebige Radiotoxizität der Abfälle deutlich zu reduzieren. Zum grundlegenden Verständnis der Physik der Transmutation müssen sowohl Spalt- und Neutroneneinfang-Wahrscheinlichkeiten von Brennelementbestandteilen als auch inelastische Streuquerschnitte an Konstruktionsmaterialien im schnellen Neutronenspektrum mit möglichst kleinen Unsicherheiten bekannt sein. Diese Arbeit beschäftigt sich mit der Messung des inelastischen Neutronen-Streuquerschnittes mit Hilfe einer neu entwickelten Doppel-Flugzeit-Methode. Mit einem kombinierten Aufbau aus Plastik- und BaF2-Szintillationsdetektoren werden die beim Streuprozess emittierten Neutronen und Photonen in Koinzidenz erstmalig nachgewiesen und dadurch der bei der Streuung angeregte Zustand des Zielkerns identifiziert. An nELBE wird weltweit einzigartig der Elektronenstrahl eines supraleitenden Linearbeschleunigers, des ELBE-Beschleunigers, zur Erzeugung schneller Neutronen benutzt. Dieser wird auf einen Kreislauf flüssigen Bleis fokussiert, in dem die Elektronen Bremsstrahlung erzeugen, die wiederum Neutronen aus Bleikernen herauslöst. Durch die kurze Zeitdauer der Elektronenstrahlimpulse von ca. 5 ps kann mit einem kompakten Neutronenquellvolumen auch mit einer kurzen Flugstrecke eine gute Zeitauflösung erzielt werden. Das emittierte Neutronenspektrum hat eine einem Maxwell-Boltzmann-Spektrum ähnliche Verteilung und reicht von etwa 10 keV bis etwa 10 MeV. Bei einem verwendbaren Elektronenstrom von 15 μA beträgt die Quell-Stärke etwa 1,6 · 10^11 n/s. Die Neutronen werden kollimiert und auf eine Probe natürlichen Eisens geschossen, die bei einer Flugstrecke von etwa 6 m positioniert war. Die Probenposition ist von einem Array von bis zu 42 BaF2-Szintillationsdetektoren zur Photonendetektion umgeben. In einem Abstand von 1 m sind fünf 1 m lange Plastik-Szintillationsdetektoren zum Neutronennachweis aufgebaut. Zur Bestimmung des einfallenden Neutronenflusses wurde eine 235U-Spaltkammer verwendet, die bei einer Flugstrecke von etwa 4,3 m zwischen Neutronenquelle und Probe aufgestellt war. Die Signale aller Detektoren werden von einer speziell dafür entworfenen VME basierten Datenaufnahmeelektronik verarbeitet und die Zeit- und Ladungs-Werte bestimmt. Aus dem Detektionszeitpunkt des Photons wird die Flugzeit und damit die Energie des einfallenden Neutrons bestimmt. Aus der Zeitdifferenz zwischen der Photonen- und Neutronendetektion ergibt sich die Flugzeit bzw. Energie des gestreuten Neutrons. Mit Hilfe von Kinematik-Rechnungen können die Ereignisse herausgefiltert werden, die der inelastischen Streuung unter Anregung eines bestimmten Kernniveaus eines bestimmten Isotops entsprechen. Aus dem Verhältnis von eingefallenem Neutronenstrom und nachgewiesenen Streuereignissen jeder Kombination aus einem Plastik- und einem BaF2-Szintillationsdetektor wurde entsprechend der Raumwinkelabdeckung der Detektoren der winkel- und energiedifferentielle inelastische Streuquerschnitt bestimmt.

L’étude des corrélations dans les fluides quantiques est abordée dans cette thèse par le biais de mesures neutroniques de leurs excitations élémentaires. Nos recherches sont motivées par les théories récentes qui permettent désormais de décrire ces excitations jusqu’à des vecteurs d’onde atomiques. Par ailleurs, les nouvelles performances du spectromètre temps de vol IN5 de l’ILL offrent la possibilité de réaliser des mesures précises dans une large gamme d’énergie et de vecteur d’onde. Dans le cas de l’4He, l’isotope bosonique, les mesures de diffusion inélastique ont été réalisées à très basse température, de la pression de vapeur saturante jusqu’à la solidification. Les relations de dispersion des excitations élémentaires correspondantes ont été obtenues avec une grande précision. A des énergies supérieures, nous avons observé dans le facteur de structure dynamique une réponse de multi-excitations très fortement structurée, caractérisée par des seuils correspondant à l’interaction entre les modes élémentaires. En particulier, nous avons observé un phonon “fantôme” associé à l’interaction phonon-phonon. Nos mesures dans l’4He superfluide confirment qualititativement les prédictions de la théorie dynamique à N-corps (2015) et même quantitativement jusqu’à une énergie de 2 meV. Les études effectuées dans le cas de l’3He ont été menées jusqu’à des températures bien inférieures à 100 mK dans une cellule spécialement conçue. Les mesures inélastiques sur cet isotope fermionique ont permis de déterminer avec une grande précision les modes collectifs, zéro-son et paramagnon, ainsi que la bande particule-trou. Couvrant une région encore jamais explorée, elles nous ont permis de confirmer la présence prévue par la théorie d’une excitation de type rotonique dans l’3He liquide massif. Ce mode reste ici confiné dans la bande particule-trou, contrairement au cas de l’3He bidimensionnel. L’ensemble de nos mesures apporte une vision complète du facteur de structure dynamique de ces systèmes modèles pour les bosons et les fermions en interaction, depuis le régime de quasi-particules de Landau et des multi-excitations, jusqu’à la limite des hautes énergies où la dynamique rejoint celle des particules indépendantes. / The effect of correlations in quantum fluids is investigated in the present work by inelastic neutron scattering measurements of their elementary excitations.Recent theories provide us with a detailed description of the dynamics up to atomic wave vectors. In addition, the recent improvement of the time-of-flight IN5 spectrometer at the ILL opens new experimental possibilities in terms of neutron flux and resolution, as well as accessible energy and wave vector ranges. In the case of 4He, the bosonic isotope, the neutron measurements have been performed at very low temperatures, from the saturated vapor pressure up to the melting curve. The dispersion relations of the corresponding elementary excitations have been accurately determined. At higher energies, we observe in the dynamic structure factor a highly structured multi-excitation response, characterized by sharp thresholds due to the coupling of elementary excitations. In particular, we observe a ghost phonon related to phonon-phonon coupling. Our measurements on superfluid 4He confirm the predictions of the dynamic many body theory (2015), the agreement being quantitative up to an energy of 2 meV. The investigations on normal liquid 3He were carried out at temperatures well below 100 mK in a cell specially designed for this purpose. Ourmeasurements on this fermionic isotope yield a high precision determination of the collective modes, zero-sound and paramagnon, as well as the particle-hole band. Since they also cover an unexplored region, we were able to confirm the theoretical prediction of a roton-like excitation in bulk liquid 3He. This mode remains within the particle-hole band, contrarily to the case of two-dimensional 3He. A broad vision of the dynamics of interacting Bose and Fermi systems, going from the Landau quasi-particles and multi-excitations regimes up to the high-energy limit, where the independent particle dynamics is recovered, emerges from our work.

Cette thèse porte sur l'étude de la dynamique de spin dans CeCoIn5 et plus précisément sur l'étude de la "résonance de spin" dans ce composé. CeCoIn5 est le composé à fermions lourds à base de cérium ayant la température de supraconductivité la plus élevé ( Tc = 2.3 K) et présente une supraconductivité non-conventionnelle avec un gap de type d_{x^2-y^2}. Dans l'état supraconducteur, le spectre des excitations magnétiques est radicalement modifié avec l'apparition d'un excitation particulièrement intense appelé "Résonance de spin". Ce type d'excitations a déjà été découvert dans les supraconducteurs haute-températures, dans d'autres composés à fermions lourds et également dans les nouveaux supraconducteurs au Fer. Dans cette thèse, nous étudions l'évolution de la résonance de spin en présence d'un champ magnétique et avec l'introduction d'impuretés magnétiques et non-magnétiques. D'après notre étude, les impuretés vont influer sur la résonance de spin via le gap supraconducteur, en effet la présence d'impuretés diminue le gap supraconducteur et l'énergie de la résonance de spin va diminuer de manière proportionnelle. L'influence du champ magnétique est délicate à considérer mais nos recherches porteraient vers un splitting Zeeman de la résonance de spin en accord avec les modèles développés pour les cuprates. / In this thesis, the spin dynamics of CeCoIn5 has been studied by inelastic neutron scattering. CeCoIn5 presents the highest critical temperature ( Tc = 2.3 K) among heavy fermion Ce-based compounds and shows an unconventionnal supraconductivity with a $d_{x^2-y^2}$-wave gap. The magnetic excitation spectra is radically changed in the supraconducting state with the apparition of an intense excitation named "Spin resonance". This kind of excitation has already been discovered in high-Tc superconductors and even in the new Iron-based superconductors. In this thesis, we focused on the evolution of the spin resonance with the application of a magnetic field and the introduction of magnetic and non-magnetic impurities. From our study, the main effect of impurities is to decrease the superconducting gap which leads to a proportionnal decrease of the resonance energy. The case of magnetic field is more difficult and our researchs suggest a Zeeman splitting of the spin resonance in agreements with the models developped for the cuprates.