Dans les systèmes de spins quantiques, la frustration et la basse dimensionnalité génèrent des fluctuations quantiques et donnent lieu à des phases exotiques. Cette thèse étudie un modèle d'échelle de spins avec des couplages frustrants le long des montants, motivé par les expériences sur le cuprate BiCu$_2$PO$_6$. Dans un premier temps, on présente une méthode variationnelle originale pour décrire les excitations de basse énergie d'une seule chaîne frustrée. Le diagramme de phase de deux chaînes couplées est ensuite établi à l'aide de méthodes numériques. Le modèle exhibe une transition de phase quantique entre une phase dimérisée est une phase à liens de valence résonnants (RVB). La physique de la phase RVB et en particulier l'apparition de l'incommensurabilité sont étudiées numériquement et par un traitement en champ moyen. On étudie ensuite les effets d'impuretés non-magnétiques sur la courbe d'aimantation et la loi de Curie à basse température. Ces propriétés magnétiques sont tout d'abord discutées à température nulle à partir d'arguments probabilistes. Puis un modèle effectif de basse énergie est dérivé dans la théorie de la réponse linéaire et permet de rendre compte des propriétés magnétiques à température finie. Enfin, on étudie l'effet d'un désordre dans les liens, sur une seule chaîne frustrée. La méthode variationnelle, introduite dans le cas non-désordonné, donne une image à faible désordre de l'instabilité de la phase dimérisée, qui consiste en la formation de domaines d'Imry-Ma délimités par des spinons localisés. Ce résultat est finalement discuté à la lumière de la renormalisation dans l'espace réel à fort désordre. / In quantum spins systems, frustration and low-dimensionality generate quantum fluctuations and give rise to exotic quantum phases. This thesis studies a spin ladder model with frustrating couplings along the legs, motivated by experiments on cuprate BiCu$_2$PO$_6$. First, we present an original variational method to describe the low-energy excitations of a single frustrated chain. Then, the phase diagram of two coupled chains is computed with numerical methods. The model exhibits a quantum phase transition between a dimerized phase and resonating valence bound (RVB) phase. The physics of the RVB phase and in particular the onset of incommensurability are studied numerically and by a mean-field treatment. Afterwards, we study the effects of non-magnetic impurities on the magnetization curve and the Curie law at low temperature. These magnetic properties are first discussed at zero temperature with probability arguments. Then a low-energy effective model is derived within the linear response theory and is used to explain the magnetic properties at finite temperature. Eventually, we study the effect of bonds disorder, on a single frustrated chain. The variational method introduced in the non-disordered case gives a low disorder picture of the dimerized phase instability, which consists in the formation of Imry-Ma domains delimited by localized spinons. This result is finally discussed in the light of the strong disorder real space renormalization.

Les composés en couches avec des ions métaux de transition ont leur bande de conduction dans les orbitales d. On se concentrera dans cette thèse sur les systèmes où le champs cristallin sépare les orbitales en deux sets dégénérés, t2g et eg, où les électrons de conduction sont sur les orbitales eg. C'est le cas pour les dichalcogénures en couches à métaux de transitions et 2H-AgNiO2 qui sont connus pour présenter des ordres de charge, un arrangement périodique des électrons sur le réseau. Les dichalcogénures en couches à métaux de transitions ont divers motifs, des ordres des charge commensurables et incommensurables, parmi eux, des ordres de charge à grande maille unité,comme le motif √13x√13 en étoile de David. 2H-AgNiO2 a un ordre de charge triple mais reste métallique.Dans le but de comprendre leurs ordres de charge, nous avons établi un modèle de Hubbard étendu multibandes et nous avons recentré notre intérêt sur les orbitales eg avec fortes interactions coulombiennes locales. À l'aide d'une approche en liaison forte et de considérations électrostatiques, puis grâce à la méthode de Hartree-Fock non restreinte, nous avons construit le diagramme de phases en fonction de la force des interactions coulombiennes, aussi bien locale qu'à courte portée, et nous avons fait évoluer la structure de bande en utilisant le ratio libre t'/t qui décrit la structure de bande dans les matériaux ayant des orbitales eg. Nous avons révélé un diagramme de phase riche avec plus de dix phases où certaines transitions peuvent être contrôlées par la structure de bande. En particulier, nous avons trouvé des phases pinball liquid, un ordre de charge métallique à trois sites par maille unité, où des charges localisées (pins) sont entourées de charges itinérantes (balls) sur un réseau hexagonal. Des ordres de charges à grande maille unité sont aussi stabilisés, tels que des ordres de charge et d'orbitale incommensurables et un ordre de charge √12x√12, qui rappelle le motif √13x√13 en étoile de David présent dans 1T-TaS2. Ces états électroniques s'avèrent génériques pour le réseau triangulaire demi rempli et sont aussi trouvés dans le cas isotrope, qui correspond au modèle de Hubbard étendu à une bande.Cependant, la méthode de Hartree-Fock non restreinte est problématique pou saisir les propriétés des phases lors d'une forte anisotropie de la structure de bande pour les états de Mott. Pour résoudre ce problème, nous avons établi un hamiltonien type Heisenberg à partir d'une théorie de perturbation. Ensuite, nous avons établit le diagramme de phases de ce nouvel hamiltonien en utilisant une approche classique et la diagonalisation exacte avec une analyse de symétries et l'algorithme de Lanczos pour un système de 24 sites. Mis à part les phases connues du modèle de Heisenberg en présence d'un champ magnétique, les configuration Y et V, le plateau 1/3, la phase ferro-orbitale, l'anisotropie de la structure de bande des orbitales eg conduit à d'autres ordres avec une composante τy ou τx et τz finies, différents ordres en bande et des ondes de densité d'orbitales. / Layered compounds are materials which exhibit charge order and novel phase of matter. This is the case in layered transition metal compounds, which have their band conduction on d-orbitals, a key ingredient to understand their electronic properties. We will focus in this dissertation on systems where the crystal-field splits orbitals into two degenerate subsets, t2g and eg, and where conduction electrons are on eg-orbitals. It is the case for layered transition-metal dichalcogenides and 2H-AgNiO2, which are known to exhibit charge orders, a periodic arrangement of electrons on the lattice. Layered transition-metal dichalcogenides have various pattern, incommensurate or commensurate insulating charge orders, among them large-unit cells charge orders. 2H-AgNiO2 have a charge order but is yet metallic.In order to investigate their charge orders, we derive a generic multiorbital extended Hubbard model and we refine our interest to eg-orbital with strong local Coulomb interactions. With a tight binding approach and electrostatic considerations, then the unrestricted Hartree-Fock method, we build the phase diagrams as a function of the strength of the Coulomb interactions, local and short-range, and we tun the band structure using the ratio $t'/t$ of the $e_g$-orbitals. We unravel a rich phase diagram with more than ten phases where some transitions can be controlled by the band structure. In particular, we found pinball liquid phases, metallic threefold charge orders where localized charges (pins) are surrounded by itinerant charges (balls) on a honeycomb lattice. Phases with large unit-cells are also stabilized, such as incommensurate charge and orbital orders and a √12x√12 charge order. These electronic states are generic for the half-filled triangular lattice and are also found in the isotropic limit, which corresponds to the single-band spinful extended Hubbard model.To capture the properties of phases with strong band structure anisotropy in the Mott state, that unrestricted Hartree-Fock fails to capture, we derived a Heisenberg-like Hamiltonian from perturbation theory. Then, we build the phase diagram of this new effective Hamiltonian using a classical approach and exact diagonalization with a symmetry analysis and Lanczos algorithm for a 24-site cluster. Apart from the known phases of the Heisenberg model in presence of a field, the Y and V configuration, the 1/3 plateau, the ferro-orbital phase, the anisotropy of the band structure of eg-orbitals leads to other ordering with finite τy or τx and τz components, different stripe orders and orbital density waves. We build a rich phase diagram from this new Hamiltonian.

L'objectif de cette thèse était de développer un magnétomètre à force de Faraday pour mesurer des valeurs absolues de l'aimantation à très basse température (30 mK) et fort champ magnétique (16 T) avec une haute sensibilité (10-5 emu). Ce magnétomètre sera principalement utilisé pour sonder les propriétés induites sous champ dans les systèmes magnétiques frustrés.Dans une première partie, je détaille le développement de ce magnétomètre. Cela comprend l'optimisation du réfrigérateur à dilution et de bobines de gradient de champ ainsi que le développement d'une détection capacitive avec un étage amplificateur à froid pour améliorer la sensibilité de la mesure. Les mesures magnétiques préliminaires sont présentées. Les changements nécessaires pour rendre le magnétomètre opérationnel sont discutés.Dans une seconde partie, je présente l'étude expérimentale de systèmes magnétiques frustrés: des grenats de Gadolinium, décrits par des spins classiques, et des composés moléculaires frustrés à base de Cuivre, pour sonder les effets quantiques. Ces mesures ont été réalisées entre 70 mK et 300 K sur les magnétomètres existant à l'Institut Néel.Dans Gd3Ga5O12, nous avons complété le diagramme de phases H-T. Nous avons montré la robustesse de ce diagramme de phases par notre étude sur le composé isomorphe GGd3Al5O12. Nous avons mis en évidence la convergence de toutes les phases observées en un unique point dans les deux systèmes.Dans les systèmes quantiques, nous avons réalisé des études préliminaires sur des clusters Cu44 à base de tétraèdres, et un système triangulaire Cu3. Bien que prometteuses, nous n'avons pas approfondi ces études à cause de problèmes d'échantillons. / The objective of this work was to develop a Faraday force magnetometer to measureabsolute values of the magnetization at very low temperatures (30 mK) andhigh applied magnetic fields (16 T) with a high sensitivity (10-5 emu). This magnetometer will be especially dedicated to the study of the field induced properties of frustrated magnets.In a first part, I present the development of this magnetometer. It involves the optimization of the dilution refrigerator and field gradient coils, and the development of a capacitive detection with a cold amplifier stage to improve the measurement sensitivity. Preliminary magnetic measurements are shown. The changes in the design required to make the magnetometer operational are discussed.In a second part, I focus on experimental studies of frustrated magnets: Gadolinium garnets, described by classical spins, and Copper based frustrated molecular compounds, to probe quantum effects. These measurements were performed from 70 mK to 300 K, with the existing magnetometers at the Institut Neel.In Gd3Ga5O12, we have complemented the H-T phase diagram. This phase diagram was proven to be robust by our study on the isomorphous compound, Gd3Al5O12. We evidence the convergence of all the observed phases to a unique point in both samples.In quantum systems, we performed preliminary studies on Cu44 clusters with tetrahedral motives, and on a triangular system Cu3. Although promising, these studies were not pursued due to sample problems.

The concept of magnetic frustration is a fundamental topic in modern solid-state physics having direct consequences in systems with rich magnetic phases hosting emergent excitations, such as the magnetic monopoles in the spin-ice compounds. One important ingredient of frustration is the lattice that constrains the magnetic spins on it to a site anisotropy and inter-site coupling. Therefore, strong magnetoelastic interactions between the magnetic system and the lattice are expected and investigated in this thesis in detail. At first, I investigate the dependence of the relative length change of single crystals of the classical spin ices \dto{} and \hto{} on the magnetic field and temperature by capacitive dilatometry. In terms of the magnetostriction and thermal expansion \dto{} and \hto{} show qualitatively similar behavior, that seems to be independent of the Kramer or non-Kramers character of the rare-earth ion. The magnitude of the magnetostrictive effect deep in the spin-ice phase at \SI{0.3}{\kelvin} is $\deltaL{} = \SI{2e-5}{}$ and $\SI{2e-4}{}$ for \dto{} and \hto{}, respectively. In numerical simulations using a manifold model, the experimental results could be qualitatively reproduced by a combination of exchange and crystal-field striction. A second highlight of the dilatometric measurements of the spin-ice compounds is the observation of the lattice dynamics. The relaxation processes are rather slow, the longest relaxation times were observed at lowest temperatures and in the field range with magnetostrictive hysteresis, \ie{}, below \SI{0.9}{\tesla} for \dto{} and below \SI{1.5}{\tesla} for \hto{}. I find that the region of longest relaxation coincides well with the kagome-ice phase of the magnetic phase diagrams; the laxation time is of the order of \SI{5000}{\second} ($> \SI{80}{\minute}$). With increasing temperatures the time scale of the relaxation reduces to minutes at around \SI{0.7}{\kelvin} corresponding to the spin-freezing temperature obtained from ac-susceptibility measurements. In the second study I investigate the variation of the magnetic properties in dependence of the lattice constant. A systematic reduction of the lattice constant of \dgsoxx{} can be achieved by substituting the non-magnetic germanium ion in the cubic pyrochlore oxide with silicon. Characteristic properties of a spin-ice phase could be observed in measurements of magnetization, ac susceptibility, and heat capacity. From the temperature shift of the peaks, observed in the temperature-dependent heat capacity, an increase of the strength of the magnetic exchange interaction by a changed ratio of the competing exchange and dipolar interaction is deduced. The new spin-ice compounds are, thus, closer to the phase boundary between spin-ice phase and antiferromagnetically ordered all-in-all-out phase consistent with a reduction of the energy of monopole excitations.

Välbefinnande är en upplevelse som många människor försöker att uppnå. När man inte uppnår välbefinnande kan frustration i stället upplevas i högre grad. Dessa två upplevelser kan skilja sig åt i olika kulturella kontexter samt hur olika kulturer internaliseras. Vilket betyder hur man anpassar och upplever sin kulturella identitet. Denna studie är en psykologisk tvärkulturell enkätstudie, som genomförts på studenter vid svenska universitet och sydafrikanskt universitet. Studien syfte var att se om det fanns en signifikant skillnad mellan de två grupperna. De 59 svarsenkäterna sammanställdes och analyserades i SPSS. Resultatet visar på en signifikant skillnad på upplevelsen av välbefinnande och frustration. På den kulturella sidan var skillnaden inte signifikant. / Well-being is an experience that many people try to achieve. When people aren't so frustrated, I can be more involved. These two experiences may differ in different cultural contexts and how different cultures internal. It is a man who is one of those who is sinful. This study is a psychological cross-cultural survey, conducted on students at The Swedish University and the University of South Africa. The purpose of the study was to see if there was a significant difference between the two groups. The 59 response questionnaires were compiled and lasted in the SPSS. The results show a significant difference between the experience of well-being and frustration. On the cultural side, the difference was not significant.

This paper will cover the correlation between emotions, game graphics and their effect on player performance in competitive video games. In order to analyze and measure player performance, a game demo was made for the purpose of this study. This is a qualitative study with 10 participants that were split into pairs of two. The outcome shows that while game graphics do not have a notable impact on players performance, it does affect feelings of presence and how enjoyable a game is. Whereas emotions on the other hand play a huge role in performance. Positive emotions such as confidence and excitement, show an increase in player performance while negative emotions such as anxiety and frustration have the opposite effect. / Denna uppsats kommer att diskutera korrelationen mellan känslor, spelgrafik, samt deras påverkan på spelarens prestation inom tävlingsspel. För att analysera och mäta spelarens prestation gjordes en speldemo för denna studie. Detta är en kvalitativ studie med 10 deltagare som delades in i par. Resultaten av denna studie är baserade på deltagarnas egna åsikter och deras uppfattning om hur de presterat, med hänsyn till tidigare spelerfarenhet. Resultatet visar att även om spelgrafiken inte har någon nämnvärd inverkan på spelarnas prestanda, så påverkar det känslan av närvaro och hur roligt ett spel är. Medan känslor å andra sidan har en stor påverkan på prestation. Positiva känslor som självförtroende och spänning har en positiv påverkan på spelarens prestation, medan negativa känslor som ångest och frustration har motsatt effekt.

Summary: This diploma thesis deals with the relation between autoimmune processes at biological level (through proven neurological autoimmune disease - multiple sclerosis) and possible autoaggressive processes at the mental level. It is divided into several points. The first one introduces human immunity in general. The first part is followed by immune system description, including autoimmunity and the principle of diseases of this system. Thereafter, psychological aggression is described, in which the division into aggression and auto- aggression fits. This is followed by chapters on projective psychodiagnostics taking into account the detection of various forms of aggression. Then, the thesis focuses on the study of possible auto-aggressive manifestations in patients suffering from the most widespread neurological autoimmune disease, multiple sclerosis. The second half of the thesis describes the author's research on this topic.

Personal inom gymnasiesärskolan arbetar i en verksamhet som kan vara farlig. Det är inte så ovanligt att personal möts av hot och våld i sin vardag. Elever gör rätt om de kan och frustration och stress i situationer som de upplever att de inte kan behärska kan leda till utmanande beteenden. Det är därför personalens uppgift att arbeta förebyggande för att elever inte ska behöva känna stress och frustration. Syftet med denna studie var således att få en fördjupad kunskap om hur personal inom gymnasiesärskolan kan arbeta proaktivt med elever och utmanande beteenden. Elever som upplever att lärmiljön är begriplig, hanterbar och meningsfull behöver inte känna stress och frustration. För att uppnå studiens syfte utfördes intervjuer med elva personal inom två gymnasiesärskolor. I personalens beskrivningar av sin verksamhet visar de att de har ett proaktivt förhållningssätt och att de med metoder, strategier och i sitt bemötande av elever aktivt försöker reducera belastningar så att elever inte ska behöva känna stress och frustration. Det finns dock ramfaktorer som innebär att personalen inte alltid lyckas i det proaktiva arbetet. / Personnel in upper secondary schools for students with special needs work in a field that can be dangerous. It is not uncommon for personnel to be faced with threats and violence in their everyday lives. Students do well if they can and frustration and stress in situations that they find that they cannot master can lead to challenging behaviors. It is therefore the task of the personnel to work preventively so that students do not have to feel stress and frustration. The aim of this study was thus to gain an in-depth knowledge of how personnel in the upper secondary school for students with special needs can work proactively to avoid stress and frustration among students. Pupils who feel that the learning environment is understandable, manageable and meaningful need not feel stress and frustration. To achieve the aim, interviews were carried out with eleven personnel within two upper secondary schools for students with special needs. In the personnel's descriptions of their activities, they show that they have a proactive approach and that, with methods, strategies and in their treatment of pupils, they actively try to reduce pressure so that students do not have to feel stress and frustration. However, there are framework factors that mean that the personnel does not always succeed in the proactive work.

本研究主要是想了解青少年的挫折經驗與挫折容忍度之間的關係,並探討建設性思考與社會支持在其間所扮演的角色. 以臺北市及臺灣省701位國中生生為對象,採問卷調查的方式了解受試在挫折經驗、建設性思考、社會支持及挫折容忍度變項上的狀況.研究結果發現,挫折經驗與挫折容忍度之間成顯著的負相關.而當受試有較建設性的思考方式或有較高的社會支持及對社會支持有較高的滿意度時,其挫折容忍度亦較佳.至於建設性思考是否在挫折經驗和挫折容忍度之間扮演調節變項的部份,本研究只發現學業挫折經驗與積極正向性的思考之間有顯著的交互作用,而人際挫折經驗則與自我侷限性思考有顯著的交互作用;但是在社會支持部份,本研究並無發現其與學業或人際挫折經驗之間有明顯的交互作用.各變項所顯現的性別上的差異則相當符合一般人對男女的刻板印象;受試中,以國三學生的壓力最大,可能亦是輔導最可著力的ㄧ群. 上述的研究結果除可提供作為未來探究有關挫折經驗與挫折容忍度關係時的參考之外,亦可對學校教育及親職教育提供下列幾點建議:1.變化教材或教學方式,以減少學生的挫折經驗;2.提供老師建設性思考的課程,使師生在教學互動中培養建設性的思考,得以提昇挫折容忍度;3.對男女生的挫折經驗所提供的輔導方向應有所不同;4.培養師長、家長都能成為孩子遇到挫折時的社會支持來源;5.針對不同年級的學生提供預防教育課程,改變其對挫折的容忍度. / This research mainly intends to understand the relations between frustration experience and frustration tolerance of teenagers, and discuss the roles the constructive thinking and social support play in these issues.Based on questionnaire survey of 701 senior high school students, four variables-frustration experience, frustration tolerance, social support andconstructive thinking are investigated. The research results show that an obvious negative relation exists between frustration experience and frustration tolerance. Those who have more constructive thinking or receive more social support and accepted by the society have better performance on frustration tolerance. As to the question whether the constructive thinking play the role of a moderator variable between frustration experience and frustration tolerance, this research only found that obvious interactions exist between study frustration experience and positive thinking, as well as between human relation frustration experience and self-restrained thinking. However, the research did not find any obvious interaction between study/human relation frustration experience and social support. The different performance on different variables owing to sex difference complies with the stereotype. The research results also show that the graduating senior high school students suffer the highest pressure and could be the group that the assistance could really do something for.The research results mentioned above could provide useful information for further investigation on the relations of frustration experience and frustration tolerance. They also provide some advice for normal education andparents education: 1. Changing the teaching material or teaching methods in order to reduce the student's frustration experience. 2. Providing training courses with constructive thinking for teachers.It will build up constructive thinking as well as strengthen frustration tolerance both for teachers and students by way of teaching and studying - mutual responses. 3. The assistance provided for male or female students in order to conquer their frustration experience should be different. 4. Cultivating both parents and teachers the ability and willing of providing supports. Whenever teenagers face frustration, parents and teachers can become the source of social support.5. For students of different grades providing suitable preventive education courses in order to enhance their frustration tolerance.

The purpose of the essay is to draw attention to my approach in relation to a boy I choose to call Emil, and how I can increase my understanding of his behavior. I explore conceivable reasons for why he breaks down so often, especially when other children are given attention. Is he simply unusually egoistic, and to a large degree only able to see to his own interests, or am I overlooking the real reasons for his actions. In order to explain the reasons for Emil’s apparent frustration in sensitive situations, I explore the significance of attachment theory. I argue about possible effects of Emil’s parents’ way of describing and guiding him, as well as how I, and my colleagues, risk fulfilling and amplifying negative expectations. As the prime reason for his repeated sense of unhappiness seems linked to a lack of empathy, I explore different ways of understanding this, as well as how I might contribute to fostering compassion. As members of a team, we strive to act in a proper way in relation to Emil. I discuss in what way our consensus can serve the good purpose, as well as how our perceived "truths" risk strengthening dominance. As stressful situations contribute to feelings of irritation regarding Emil’s apparent jealousy, I try to explain how getting closer to one’s own darkness can contribute to an increased sense of respect and understanding. Finally, I examine current views on leadership, where the previous approach focusing largely on the mediation of knowledge has given way to new ideas that stress the importance of creating security as a basis for all learning. I discuss the high demands that are placed on the pedagogue’s sense of awareness and mediating in the children’s acquisition of knowledge, as well as the importance of creating trusting relations.