Made available in DSpace on 2015-03-05T18:10:48Z (GMT). No. of bitstreams: 0 Previous issue date: 26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A meta principal desta pesquisa é realizar um estudo da semântica dos adjetivos objetivando a sua representação em uma ontologia jurídica. O fato motivador desse interesse foi o estudo de ontologias e léxicos computacionais jurídicos e a constatação de que os adjetivos não recebem um tratamento sistemático nessas ferramentas computacionais de conhecimento especializado. A partir dessa constatação, partiu-se para o estudo de ontologias e léxicos computacionais de linguagem não-especializada, buscando elementos práticos e teóricos para a inclusão sistemática, e não ocasional, de adjetivos em uma ontologia jurídica. Esta pesquisa defende que a eficiência no tratamento computacional da linguagem requer uma combinação de teorias. Assim, a metodologia adotada combina diferentes abordagens teóricas. Através do estudo do corpus e construção da ontologia jurídica, percebe-se a importância dos adjetivos para a organização do conhecimento especializado. Nos domínios de conhecimento especializados, os adjetivos têm a fu / The main goal of this research is to study the semantics of the adjectives in order to codify them into a legal ontology. Through a search for legal ontologies and lexicons one verifies that adjectives are not codified systematically into specialized lexicons and ontologies. Taking the codification of adjectives into a legal ontology as the target of this work, one analyzes non-specialized language ontologies and lexicons. The purpose of such analysis is to find practical and theoretical elements for including adjectives systematically into a legal ontology. This research defends the position that integrating linguistic approaches is more fruitful to natural language processing. Therefore, the methodology applied here combines different theoretical approaches. The corpus analysis and legal ontology construction shows the importance of adjectives in organizing the specialized knowledge. In the specialized domains, adjectives have the main function of classifying entities

Made available in DSpace on 2016-12-23T14:08:59Z (GMT). No. of bitstreams: 1 Heloa Ferreira Cristovao.pdf: 812841 bytes, checksum: 71e524e49439abe4acf2da511e7345ab (MD5) Previous issue date: 2013-08-05 / A maioria dos gramáticos acolhe os verbos em duas sessões: uma que trata de aspectos morfológicos; em seguida, dentro de uma perspectiva sintático-semântica, que aborda os verbos quanto à predicação. Isso se configura um problema nesse modelo de análise, visto que, ao considerar os verbos como elementos discretos, em frases descontextualizadas, não se consideram as relações morfológicas, sintáticas, semânticas, pragmáticas e discursivas que só podem ser observadas a partir da língua em uso, dentro do jogo combinatório da linguagem. A partir dessas considerações, a concepção de língua que adotamos se coaduna com aquela proposta pelo Funcionalismo, que defende os estudos de fenômenos linguísticos a partir da análise das estruturas em uso real, priorizando as relações que se estabelecem no contexto comunicativo. Igualmente importante, foi o estudo da estrutura argumental da oração, formada pelo verbo e seus selecionados elementos obrigatórios (argumentos). Com relação aos verbos que serão objeto da pesquisa, orientamo-nos pela classificação realizada por Azeredo (2004, p.180), baseada na proposta de estudo de Cano Aguilar (1981) para a língua espanhola, que arrolou o grupo de verbos codificadores de extensão ou escala no português, entre eles: atravessar, percorrer, subir, abraçar, presidir, contornar, ocupar, preencher, inundar, medir 1 (ele mediu um terreno), medir 2 (o terreno mede 160 m), valer e durar (a viagem durou 80 dias). Em nossa pesquisa, analisaremos a transitividade de um recorte desse grupo, composto pelos verbos subir, ocupar, medir, durar, valer e seu uso na língua portuguesa, que, juntamente com a escolha do referencial teórico, justificam a importância deste estudo, visto que esse fenômeno é mais bem observado em condições reais de comunicação. O corpus é constituído de textos do âmbito jornalístico escrito e o levantamento de dados foi realizado por meio de ferramenta de pesquisa on-line no acervo digital da Revista Veja. Esperamos que o resultado desta pesquisa evidencie que um estudo que tenha como ponto de partida a língua em uso vá muito além das proposições das gramáticas / The most of grammarians welcome verbs in two sessions, namely: the first that deals with morphological aspects, then within a syntactic-semantic perspective, which deals with verbs as the predication. This creates the problem of proposal analysis, given that when considering verbs as discrete elements in non-contextualized sentences, the relationships are not considered morphological, syntactic, semantic, pragmatic and discoursive that can only be observed from the language in use, in game combinatorial language. From these considerations, the design language we adopt is consistent with that proposed by functionalism, which advocates the study of linguistic phenomena from the analysis of the structures in actual use, prioritizing the relationships established in the communicative context. Equally important was the study of argument structure of sentence, formed by the verb and its selected elements required (arguments). With respect to verbs that will be the object of research, we look to the classification performed by Azeredo (2004, p.180), based on the study proposal of Cano Aguilar (1981) for the Spanish language, that enrolled a group of verbs encoders of extent or scale in Portuguese, among them: cross, roam, rise, embrace, preside, contour, occupy, fill, flood, measure 1 (he measured a piece of land), measure 2 (the land measures 160 m), earn and last (the trip lasted 80 days). In our research, we analyze the transitivity of a clipping of this group, consisting of the verbs rise, occupy, measure, last, earn and their use in the Portuguese language, which, together with the choice of theoretical, justify the importance of this study, since this phenomenon is best observed in real communication. The corpus is composed of texts within the journalistic writing and data collection was conducted through a research tool on-line in digital collection of Veja Magazine. We hope that the result of this research it is clear that a study has as starting point the language used go far beyond the propositions of grammars

This study is a detailed investigation of a number of issues in colloquial Sinhala morphosyntax. These issues primarily concern grammatical relations, argument structure, phrase structure and focus constructions. The theoretical framework of this study is Lexical Functional Grammar.¶Chapter 1 introduces the issues to be discussed, followed by a brief introduction of some essential aspects of colloquial Sinhala as background for the discussion in the following chapters. In Chapter 2 we present basic concepts of the theoretical framework of Lexical Functional Grammar.¶ The next three chapters mainly concern grammatical relations, argument structure and clause structure in colloquial Sinhala. Chapter 3 examines grammatical relations. The main focus lies in establishing the subject grammatical relation in terms of various subjecthood diagnostics. We show that only a very small number of diagnostics are reliable, and that the evidence for subject is weaker than assumed previously. All the subjecthood diagnostics that were examined select the most prominent argument in the argument structure as the subject, i.e. 'logical subject'. However, there appear to be no processes in the language that are sensitive to the subject in the grammatical relations structure, i.e. 'gr-subject'. Further, there is no evidence for other grammatical relations like objects. In Chapter 4 we discuss the agentless construction and related valency alternation phenomena. It was previously assumed that the agentless construction, valency alternation phenomena and the involitive construction are all related. We argue that the agentless construction should be treated as a different construction from the involitive construction. We also show that the agentless construction and the involitive construction have contrasting characteristics, and that treatment of them as separate constructions can account for some phenomena which did not receive an explanation previously. The valency alternation phenomena are related to the agentless construction, therefore there is no valency alternation in involitive constructions. It will be shown that verbs undergoing the valency alternation can be distinguished from the other verbs in terms of the lexical semantic properties of individual verbs. Chapter 5 examines the structure of non-verbal sentences in terms of a number of morphosyntactic phenomena. It was previously argued that verbal sentences and non-verbal sentences in colloquial Sinhala differ in terms of clause structure. However, the present study shows evidence to the contrary.¶ The next two chapters deal with modelling contrastive focus and the phrase structure of the language. Chapter 6 is a detailed analysis of the contrastive focus (cleft) construction in various clause types in the language, and proposes a unified syntactic treatment of contrastive focus. Contrastive focus is in some constructions morphologically encoded, while in others it involves both morphological and configurational assignment of focus. The complex interaction between focus markers and verb morphology in various focus constructions is accounted for by general well-formedness conditions applying to the f-structure, and the principles of Functional Uncertainty and Morphological Blocking. In Chapter 7, we discuss the phrase structure of the language, in particular such issues as its non-configurational nature and the lack of evidence for VP. We propose non-configurational S and some functional projections to account for word order freedom under S and to explain certain morphosyntactic phenomena, such as configurational focus assignment. Finally, Chapter 8 summarises the conclusions made in previous chapters.

Low valent nickel (less than +1) complexes are rare in nature, however they are regularly encountered in nitridonickelate chemistry. Ternary alkaline earth nitridonickelates exhibit a variety of interesting crystal structures with respect to their covalently bonded nitridonickelate anionic framework. The coordination geometry of low valent nickel in these compounds presents a unique structural feature with nickel being in linear coordination by nitrogen atoms. The nitridonickelate frameworks of compounds investigated in this work are: Ba2[Ni3N2]: The first ternary alkaline earth nitridonickelates with 2D Ni-N anionic network. The formal oxidation state of Ni is +0.67. Ba2(Ba6N)[NiN]6: The structure is made of o1D helical Ni-N anionic chains. Also, the structural stability of this compound´s structure type was found to occur over a wide range of substitution of Ba by Ca and Sr; a max. of 70 percent Ba could be successfully replaced by Sr and Ca atoms retaining the same structure type. The formal oxidation state of Ni is +0.83. Ba[NiN] and the solid solution series Ba[CuxNi1-xN]: The structure is made of 1D zig-zag Ni-N chains. The solid-solution series is isostructural to Ba[NiN] at lower content of Cu while, at higher content it resembles Ba[CoN] structure type, however at very high Cu content it again transforms to Ba[NiN] structure type. The formal oxidation state of Ni is +1.0. Sr2[Ni(CN)N]: The structure consists of N-Ni-(CN) dumbbells. The compound is the first example of cyano-nitridonickelate. The formal oxidation state of Ni is 0. The handling of the ternary alkaline earth nitridonickelates in specific and also of the other nitridometalates in general suffers greatly due to their being air and moisture sensitive. This requires synthetic methods suitable for air and moisture sensitive samples and also the respective instrumental setup for the measurement of their physical properties under inert atmosphere. Up to now no comprehensive investigation of the physical properties of the ternary alkaline earth nitridonickelates has been made. In this work an emphasis was given to systematically investigate the physical properties of the ternary alkaline earth nitridonickelates and to understand their structure specific physical properties. The common features of the investigated ternary alkaline earth nitridonickelates are: 1. the low valency of nickel. 2. the linear coordination of Ni and octahedral coordination of N. During this investigation the low valent character of nickel was experimentally confirmed with the help of X-ray absorption spectroscopy and the interpretation of magnetic susceptibility data where the magnetic moments of the nickel atoms were always consistent with that of a low valent nickel species. The results obtained from the magnetic measurements and electrical conductivity shows that the alkaline earth nitridonickelates order antiferromagnetically at low temperatures and show temperature dependent metallic conductivity whereas the cyano-nitridonickelate Sr2[Ni(CN)N] does not order at low temperature, is paramagnetic, and exhibits semiconducting behaviour. This investigation has provided a better understanding of ternary alkaline earth nitridonickelates with respect to the different structure they exhibit and their associated physical properties. This work motivates to extend the investigations of the physical properties of other nitridometalates. These also exhibit different crystal structures with respect to their nitridometalate anionic framework and thus, structure specific physical properties are also to be expected.

The diploma thesis explores whether the complementation of infinitives and gerunds, functioning as subject clauses, is different. Expecially it compares syntactic structures, relative length and complexity of the complementations and their roles in functional sentence perspective (whether elements are rather thematic or rhematic etc.). Furthemore it explores whether the form of complementation is affected by the position of infinitive of gerund, it means if there is any difference between the complementations of non-finite verb in initial position and extraposition. The research is based on the relevant academic writing and on authentic instances of gerunds and infinitives from the present sources of literature.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-10-04T15:37:21Z No. of bitstreams: 1 marcelolopesdasilva.pdf: 2035405 bytes, checksum: f42ad3f2f4b21d576dad7666e1d3c360 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-10-04T16:19:02Z (GMT) No. of bitstreams: 1 marcelolopesdasilva.pdf: 2035405 bytes, checksum: f42ad3f2f4b21d576dad7666e1d3c360 (MD5) / Made available in DSpace on 2016-10-04T16:19:02Z (GMT). No. of bitstreams: 1 marcelolopesdasilva.pdf: 2035405 bytes, checksum: f42ad3f2f4b21d576dad7666e1d3c360 (MD5) Previous issue date: 2010-04-05 / Investigam-se as construções com objeto cognato (cOC) na língua portuguesa não apenas quanto às hipóteses gerativistas, mas principalmente com base nas hipóteses sociocognitivas e construcionista-unificacionistas. Verifica-se a ocorrência de tipos de cOC com os verbos intransitivo inergativo, intransitivo inacusativo e transitivo-opcional. Nas cOCs com os verbos intransitivos, ocorre um desencontro sintático-semântico que é licenciado no nível pragmático, para que eles suportem o termo cognato em posição de foco sintático: um espelhamento do padrão transitivo. Tal motivação se baseia, primariamente, na pressuposição de que seja instanciada alguma especificação como fator de identificabilidade para o nome cognato enfocado e, secundariamente, num apenas realce da noção verbal. Essas restrições contextuais para a ocorrência do objeto cognato são descritas nos níveis internos das relações sintático-semânticas, vinculando-se a elas um conjunto de efeitos estilístico-fonografêmicos e aspectualpsicológicos. Verificam-se os seguintes fatos: Que a nominalização efetua, simultaneamente, um recorte dos argumentos verbais e um livre preenchimento informacional no sintagma nominal cognato. Que a repetição do radical verbo-nome coocorre com outras licenças contextuais de repetição, por um lado, aparentando redundância, e por outro, valorizando cada informação nova como parte da cena reconstruída no discurso. Que numa cOC, a especificação, informação nova, concentrase no modificador e/ou no determinante forte e/ou nos sufixos do nome cognato. Que a variação quanto ao número de argumentos instanciados com um mesmo verbo confirma a hipótese de heranças múltiplas, referida como ‘valência emprestada’, associada às licenças pragmáticas para as cOCs serem adequadamente interpretáveis em contextos descritivos. A investigação empírica consiste na verificação de ocorrências no Google, classificadas e parcialmente anexadas no Corpus representativo das cOCs em Português; e a formalização dos dados teóricos consiste na implementação aplicativa aos modelos: Gramática das Construções (CxG), Gramática dos Enquadres Semântico-Cognitivos em Redes (FrameNet), e Gramática das Construções Baseada no Signo (SBCG). Pela investigação das cOCs é reconhecida a interferência direta do nível pragmático nos outros níveis que compõem a gramática, confirmando a maior plausibilidade de uma gramática de contexto ou uma Gramática (Sócio)Cognitiva e (Sócio)Construcionista. / The Portuguese cognate object construction (COC) research goes through generative hypothesis to find solid grounds in usage-based cognitivist and unificationalconstructionist lands. It is observed that COCs occur with optional transitive verbs, with unergative intransitive and also with unaccusative intransitive verbs. The COCs with intransive verbs instantiates a syntatic-semantic mismatch, which non-default relations are pragmatically licensed for them to support the cognate noun in a syntactic focus position: as in a transitive pattern mirrowing. This motivation is based, firstly, on the pressuposition that some specification will be structurally given to identify the cognate noun, and, secondly, it is based on the possibility of a CO to be constructed as a ‘single focus’ of that verbal scenic conceptual reconstruction. Such COCs’ contextual restrictions are explained within syntax-semantics relational levels, to which is bound a set of stylistic-fonographical and aspectual-psychological effects. These following facts are observed: Firstly, that nominalization, simultaneously, pruns verbal arguments and enables free informational filling-up in a cognate noun phrase. Secondly, that nounverbal root repetition occurs among other licenced repetitions, on the one hand, apparently just redundant stuffs, on the other hand, it valorizes each specific new information that, in COs, concentrates on a modifier and/or on a strong determiner and/or even on a cognate noun suffix. Thirdly, that the variation in number of instantiated arguments of a same verb confirms the ‘multiple inheritance’ hypothesis, referred to as ‘borrowed valence’, locally unified to pragmatic licences for adequate interpretability of COCs in descriptive contexts. The empirical approach amounts Google occurrences, partially annexed and classified in a ‘Representative Portuguese COCs Corpus’; and the formalization of theoretical data consists in an applied implementation to the following models: Construction Grammar (CxG), Semantic Frames Grammar (FrameNet), and Sign-Based Construction Grammar (SBCG). By the COCs inquiry, it is recognized a direct pragmatically leveled interference into the other grammatical levels, a sufficient condition to prove the plausibility of a contextual grammar or a (Socio)Cognitive and (Socio)Constructionist Grammar.

In this thesis we analyze machine translation between Czech and Russian languages from the perspective of a linguist. We work with two types of Machine Translation systems - rule-based (TectoMT) and statistical (Moses). We experiment with different setups of these two systems in order to achieve the best possible quality. One of the questions we address in our work is whether relatedness of the discussed languages has some impact on machine translation. We explore the output of our two experimental systems and two commercial systems: PC Translator and Google Translate. We make a linguistically-motivated classification of errors for the language pair and describe each type of error in detail, analyzing whether it occurred due to some difference between Czech and Russian or is it caused by the system architecture. We then compare the usage of some specific linguistic phenomena in the two languages and state how the individual systems cope with mismatches. For some errors, we suggest ways to improve them and in several cases we implement those suggestions. In particular, we focus on one specific error type - surface valency. We research the mismatches between Czech and Russian valency, extract a lexicon of surface valency frames, incorporate the lexicon into the TectoMT translation pipeline and present...

This research aims to find out whether and to what extent the valency of psych-verbs influences the word order in the Dutch sentence. Valency is defined as the ability of a verb to bind a number of elements in order to form a grammatically correct sentence. However, valency has to be seen not only from the syntactic, but also from the semantic point of view. In other words, we are not only interested in the number of elements a verb requires, but also in the semantic features of these elements. It has been noted by a number of linguists that certain verbs allow for the nominal subject to be placed behind the nominal direct or indirect object in the middle field of the Dutch sentence, i.e. between the finite verb and the final verb cluster in the main clause or between the complementizer and the verb cluster in the subordinate clause. This is contrary to the tendency to put nominal subject before the nominal object in the middle field. Most of the verbs described to behave in this manner are called psych-verbs or psychological verbs. These verbs refer to a situation in which an animate entity is subject to a change of psychological state. The analysis of sentences with psych-verbs has shown that animacy is the most important factor to influence word order in the middle field, followed by the...

This doctoral dissertation is concerned with the dynamic processes that are at play in the development of the system of prepositions in contemporary Czech. In the first part, I review different treatments of prepositions as a word class in the Czech linguistic tradition. I use available descriptive accounts to discuss the features of two main subtypes of this category, i.e. primary and secondary prepositions, focusing in particular on the process of 'prepositionalization' of secondary prepositions, i.e. the grammaticalization path that leads to their emergence. The primary focus of the first part of the dissertation is the role of meaning and the semantic features of prepositions as function words, as well as the meaning which prepositions contribute to more complex linguistic items, i.e. the interrelation of prepositions and case marking and valency patterns derived from verbs. I also draw attention to prefixed words which are, in the majority of cases, derived from primary prepositions. I approach meaning mainly from the perspective of cognitive linguistics, employing also the view of construction grammar which treats prepositions both as constructions in their own right and as parts of higher order constructions. Chapter three is concerned with the processes of language change with regards to...

The search for novel technologies like spin-based electronics and suitable materials for respective devices requires a profound understanding of fundamental interactions regarding electron spin and related properties. In the same context, with ongoing device miniaturisation, surface-related phenomena become increasingly important. Here, we study the electronic and magnetic properties of quasi-2D electron states at a metallic surface under the influence of the Rashba effect and exchange coupling to localised 4f moments that order magnetically at low temperatures. Particularly, in the considered systems, both interactions are of similar strengths, a case which is rather unexplored in the literature. Our model system is the (001) surface of intermetallic LnIr2Si2 compounds with ThCr2Si2 structure, where Ln = lanthanide. With this work, we continue our long-term systematic study of the LnT2Si2 compounds with T = Rh, where the Rashba-like spin-orbit coupling is about a hundred times weaker than the exchange interaction. Using ARPES and DFT we explore with GdIr2Si2 and EuIr2Si2 two representatives of the LnIr2Si2 family, which are both characterised by the insensitivity of the 4f shell to the crystal electric field. On the other hand, they have fundamentally different bulk properties. GdIr2Si2 is a robust bulk antiferromagnet with a high ordering temperature of 87 K, whereas EuIr2Si2 is a mixed-valent material with a non-magnetic ground state in the bulk. The mean Eu valency is strongly temperature dependent, changing continuously from a nearly divalent magnetic configuration at room temperature to a nearly trivalent non-magnetic Eu state below 50K. Studying the surface states in both compounds we find that the magnitude of the Rashba-like spin-orbit interaction increases tremendously in comparison to the isoelectronic Rh compounds. This is reflected in a huge splitting of the surface state bands and emphasizes the importance of atomic spin-orbit coupling in high Z elements for the strength of the Rashba effect. Employing DFT, which reproduces the measured band structure very accurately, we find the same exotic triple winding of the electron spin along the isoenergy contours of the surface state bands as reported in terms of a cubic Rashba effect for the Rh compounds. This proves the generic nature of the surface states and their universal properties in the considered LnT2Si2 compounds. With the ordering of the 4f moments at low temperatures, spin structure and surface band dispersion undergo significant changes induced by the exchange interaction. Pronounced asymmetries emerge in the band dispersion, which allow for the determination of the magnetisation axis. We demonstrate that this is even possible if spectral structures originating from different magnetic domains overlap in the spectra. Remarkably, we find respective asymmetries in EuIr2Si2, too, despite the almost trivalent, and thus non-magnetic Eu state at low temperatures. With complementary experimental techniques like x-ray absorption, x-ray linear and circular dichroism as well as by taking photoelectron diffraction into account, we demonstrate that in the surface Si–Ir–Si–Eu four-layer block Eu is nearly divalent and magnetically active. The associated Eu moments order ferromagnetically below 49K. In the case of Eu termination, we find that the 4f moments of the divalent Eu ions at the surface order ferromagnetically below 10K, too, and unveil thus another occurrence of 2D surface-related magnetism in the same non-magnetic bulk compound. Simultaneously, the mixed-valent properties of EuIr2Si2 and the strong temperature dependence of the mean Eu valency are clearly reflected in the electronic structure of the bulk in a smooth expansion of the Doughnut Fermi surface sheet with increasing temperature, which is interpreted as a band-filling effect. Our results show the high tunability of the electron spin by combining spin-orbit coupling and structural inversion asymmetry with the exchange interaction, which is at the heart of spintronics applications. The disclosure of controllable 2D magnetism at the surface of a non-magnetic bulk compound, which is enabled by an instability in the 4f shell, nominates valence fluctuating 4f compounds, especially with Eu and Sm, to be promising candidates for fundamental studies and applications. Our study moreover demonstrates the richness and versatility of 4f physics that may differ significantly at the surface and in the bulk.:1. Introduction 2. Preliminary Studies 2.1. Short introduction to lanthanides and 4f physics 2.2. LnT2Si2 compounds 3. Foundations 3.1. Band structure 3.2. Bulk states, surface states and surface resonances 3.3. The principles of photoelectron spectroscopy 3.4. Angle-resolved photoelectron spectroscopy 3.5. Photoabsorption and resonant photoelectron spectroscopy 3.6. X-ray absorption spectroscopy 3.6.1. X-ray magnetic circular dichroism 3.6.2. X-ray magnetic linear dichroism 3.7. Photoelectron diffraction 3.8. Synchrotron and synchrotron radiation 3.9. Density functional theory 4. Methods 4.1. Experimental details 4.2. DFT calculations 5. GdIr2Si2 5.1. Introduction 5.2. Results and discussion 5.2.1. Paramagnetic phase 5.2.2. Magnetically ordered phase 5.3. Summary 6. EuIr2Si2 6.1. Introduction 6.2. Results and discussion 6.2.1. Photoemission from the Eu 4f shell 6.2.2. ARPES on the Si-terminated surface 6.2.3. X-ray magnetic linear and circular dichroism 6.2.4. Eu termination 6.2.5. Determination of the mean Eu valency in the subsurface layers 6.2.6. Bulk properties 6.3. Summary 7. Conclusion / Die Suche nach neuartigen Technologien wie spinbasierte Elektronik sowie nach geeigneten Materialien für entsprechende Bauteile erfordert ein tiefgreifendes Verständnis der Wechselwirkungen des Elektronenspins und damit verbundener Materialeigenschaften. Mit der zunehmenden Miniaturisierung von Bauteilen gewinnen in diesem Zusammenhang auch Oberflächenphänomene zunehmend an Bedeutung. In dieser Arbeit untersuchen wir die elektronischen und magnetischen Eigenschaften quasizweidimensionaler elektronischer Zustände an metallischen Oberflächen unter dem Einfluss des Rashba-Effekts und der Austauschwechselwirkung mit lokalisierten 4f Momenten, die bei tiefen Temperaturen magnetisch ordnen. Dabei liegt die Besonderheit der untersuchten Systeme darin, dass beide Wechselwirkungen von vergleichbarer Stärke sind. Dieser Fall ist in der Fachliteratur bislang unterrepräsentiert. Unser Modellsystem ist die (001)-Oberfläche intermetallischer LnIr2Si2 Verbindungen mit ThCr2Si2 Struktur, wobei Ln ein Lanthanoidenelement darstellt. Dabei führen wir die langjährige und systematische Untersuchung von LnT2Si2 Verbindungen mit T = Rh fort, in denen die Rashba-artige Spin-Bahn-Kopplung ungefähr 100-mal schwächer als die Austauschwechselwirkung ist. Mit Hilfe von winkelaufgelöster Photoelektronenspektroskopie (ARPES) und Dichtefunktionaltheorie (DFT) erkunden wir mit GdIr2Si2 und EuIr2Si2 zwei Vertreter der LnT2Si2 Familie, die beide durch die Insensibilität der 4f Schale gegenüber dem Kristallfeld ausgezeichnet sind. Zugleich haben sie grundsätzlich verschiedene Volumeneigenschaften. GdIr2Si2 ist ein robuster Volumenantiferromagnet mit einer hohen Ordnungstemperatur von 87K, wohingegen EuIr2Si2 eine gemischtvalente Verbindung mit einem nicht-magnetischen Volumengrundzustand ist. Die mittlere Eu Valenz ist stark temperaturabhängig, sie ändert sich kontinuierlich von einer nahezu zweiwertigen Konfiguration bei Raumtemperatur zu einem beinahe dreiwertigen, nicht-magnetischen Eu Zustand unterhalb von _ 50K. Die Untersuchung der Oberflächenzustände in beiden Verbindungen zeigt, dass die Stärke der Rashba-artigen Spin-Bahn-Kopplung gegenüber den isoelektronischen Rh Verbindungen erheblich zunimmt. Dies spiegelt sich in einer riesigen Aufspaltung der Oberflächenbänder wider und unterstreicht die Bedeutung der atomaren Spin-Bahn-Kopplung in Elementen mit großer Kernzahl Z für die Stärke des Rashba-Effekts. Unsere DFT Rechnungen reproduzieren die gemessene Bandstruktur mit hoher Genauigkeit und offenbaren dieselbe Dreifachwindung des Spins entlang der Konturen konstanter Energie, die schon als kubischer Rashba-Effekt in den Rh Verbindungen beobachtet wurde. Hierin zeigt sich das allgemeingültige Wesen der Oberflächenzustände und deren universelle Eigenschaften in den betrachteten LnT2Si2 Verbindungen. Das Ordnen der 4f Momente bei niedrigen Temperaturen führt zu starken Veränderungen in der Spinstruktur und der Dispersion der Oberflächenbänder durch die einsetzende Austauschwechselwirkung. In der Bandstruktur bilden sich starke Asymmetrien, aus denen die Magnetisierungsachse bestimmt werden kann. Wir zeigen, dass dies sogar dann noch möglich ist, wenn sich spektrale Strukturen überlagern, die von unterschiedlichen magnetischen Domänen stammen. Besonders bemerkenswert ist, dass entsprechende Asymmetrien auch in EuIr2Si2 auftreten, trotz des nahezu dreiwertigen und damit nicht-magnetischen Eu bei tiefen Temperaturen. Mit komplementären experimentellen Methoden wie Röntgenabsorption, linearem und zirkularem Röntgendichroismus als auch durch die Berücksichtigung von Beugungseffekten in der Photoelektronenspektroskopie zeigen wir, dass Eu im Si–Ir–Si–Eu Oberflächenblock beinahe zweiwertig und magnetisch aktiv ist. Die zugehörigen Eu Momente ordnen unterhalb von 49K ferromagnetisch. Im Fall der Eu-Terminierung stellen wir fest, dass auch die 4f Momente der zweiwertigen Eu-Ionen an der Oberfläche unterhalb von 10K ferromagnetisch geordnet sind, und enthüllen damit ein weiteres Vorkommen zweidimensionalen, oberflächenbezogenen Magnetismus in derselben, nichtmagnetischen Volumenverbindung. Gleichzeitig spiegeln sich die gemischtvalenten Eigenschaften von EuIr2Si2 deutlich in der elektronischen Volumenbandstruktur in einer kontinuierlichen Ausdehnung der Doughnut-Fermifläche mit steigender Temperatur wider. Dies interpretieren wir als Bandfüllungseffekt. Unsere Ergebnisse zeigen die hohe Einstellbarkeit des Elektronenspins durch die Kombination von Spin-Bahn-Kopplung und struktureller Inversionsasymmetrie mit der Austauschwechselwirkung, was die Grundlage für Anwendungen in der spinbasierten Elektronik bildet. Die Enthüllung von kontrollierbarem, zweidimensionalem Magnetismus an der Oberfläche einer Verbindung mit instabiler 4f Schale, die im Volumen nicht-magnetisch ist, nominiert gemischtvalente 4f Verbindungen, insbesondere mit Eu und Sm, als vielversprechende Kandidaten für Grundlagenforschung und Anwendungen. Unsere Studie zeigt zudem den Reichtum und die Vielseitigkeit von 4f Systemen, deren Eigenschaften sich an der Oberfläche deutlich vom Volumen unterscheiden können.:1. Introduction 2. Preliminary Studies 2.1. Short introduction to lanthanides and 4f physics 2.2. LnT2Si2 compounds 3. Foundations 3.1. Band structure 3.2. Bulk states, surface states and surface resonances 3.3. The principles of photoelectron spectroscopy 3.4. Angle-resolved photoelectron spectroscopy 3.5. Photoabsorption and resonant photoelectron spectroscopy 3.6. X-ray absorption spectroscopy 3.6.1. X-ray magnetic circular dichroism 3.6.2. X-ray magnetic linear dichroism 3.7. Photoelectron diffraction 3.8. Synchrotron and synchrotron radiation 3.9. Density functional theory 4. Methods 4.1. Experimental details 4.2. DFT calculations 5. GdIr2Si2 5.1. Introduction 5.2. Results and discussion 5.2.1. Paramagnetic phase 5.2.2. Magnetically ordered phase 5.3. Summary 6. EuIr2Si2 6.1. Introduction 6.2. Results and discussion 6.2.1. Photoemission from the Eu 4f shell 6.2.2. ARPES on the Si-terminated surface 6.2.3. X-ray magnetic linear and circular dichroism 6.2.4. Eu termination 6.2.5. Determination of the mean Eu valency in the subsurface layers 6.2.6. Bulk properties 6.3. Summary 7. Conclusion