Made available in DSpace on 2014-06-12T18:08:37Z (GMT). No. of bitstreams: 2 arquivo853_1.pdf: 9210682 bytes, checksum: 8d68fe4fb7dc18e9a8509f17dff91061 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Construímos um magnetômetro utilizando dois sensores Hall de GaAs (Toshiba- THS118) operando em um modo diferencial. Cada sensor tem um circuito préamplificador associado a ele e a diferencia de voltagem entre eles é amplificada com um ganho variável de 30 - 7000. Os sensores Hall têm dimensões típicas de 1,5 x 1,7 x 0,6 mm3 e foram montados separados um do outro de 0,71 mm, em uma configuração espacial planar. O magnetômetro foi testado usando tanto correntes dc (Idc) quanto correntes ac (Iac), variando a amplitude de 0,1 a 3 mA. Um amplificador lock-in foi utilizado para a leitura da voltagem Hall para as correntes ac. O controle e a aquisição dos dados foram feitos utilizando uma interface GPIB e o software Labview. A freqüência f das correntes Iac foram variadas de 10 Hz até 1 kHz. O magnetômetro Hall foi montado em um refrigerador de ciclo fechado do tipo Displex (Advanced Research Systems) o qual permite uma variação de temperatura no intervalo de 4 800 K, podendo, inclusive, ser facilmente colocado na presença de um campo magnético. Para aplicações de campos baixos (até 0,003T), foi utilizado um par de bobinas de Helmholtz, enquanto que para campos maiores (até 1 T) foi usado um magneto permanente (Advancing Magnetic-eletronics). A amostra a ser investigada é fixada nas vizinhanças da área ativa de um dos sensores, produzindo uma componente de campo perpendicular à superfície do sensor. Esse sinal, por usa vez, é proporcional a magnetização da amostra. A calibração do magnetômetro foi feita usando uma amostra padrão de Ni, de geometria cilíndrica e com 6,1 mg produzida pela Oxford Instruments. Em seguida, o magnetômetro foi utilizado para medidas de histerese das ligas ferromagneticamente moles Fe64Co7Zr6Nd3B10 e Fe56Co7Ni3B10, a temperatura ambiente, e do nanocompósito (Fe0,6Co0,4)0,35(MnO)0,65 para temperaturas desde ambiente até 10 K. Os resultados obtidos para as ligas amorfas foram comparados com os obtidos usando medidas de susceptibilidade ac em baixas freqüências. Para o nanocompósito (Fe0,6Co0,4)0,35(MnO)0,65 foi possível estudar o comportamento da magnetização de saturação, da remanência e do campo coercivo em função da temperatura. Esses resultados estão em acordo com os obtidos na mesma amostra por magnetometria por amostra vibrante. A dependência do efeito exchange-bias com o campo magnético de resfriamento HR foi investigado pela primeira vez. Foi observado que o campo de exchange-bias HE cresce inicialmente com HR, apresenta um valor máximo de 22,5 mT em torno de HR = 500 mT e, em seguida, decresce monotonicamente com o aumento de HR. A dependência de HE com HR foi explicada qualitativamente utilizando o modelo proposto por Kagerer, Binek e Kleemann

This thesis is a selected edition of thirty-six unpublished letters and fragments from Thomas Henry Hall Caine to Dante Gabriel Rossetti with an introduction and explanatory notes. The letters have been chosen to illustrate Caine's typical interests and concerns as these appear in the body of eighty-six unpublished letters and fragments contained in the Angeli Papers in Special Collections at the University of British Columbia Library. Although the letters are far from being masterpieces of epistolary art, they are of historical interest as a chronicle of the friendship which was initiated by letter. The introduction provides a background for the letters, using, in so far as possible, unpublished contemporaneous material from the Angeli and Penkill Papers. Hall Caine knew Rossetti for less than three years; for two of those years the friendship was conducted almost exclusively by letter, but for the last ten months of Rossetti1s life they lived together. The friendship began when Caine published a eulogistic article on Rossetti's poetry, and sent a copy to him. Caine was then an eager, ambitious, and very naive twenty-six year old Liverpudlian; Rossetti, a known painter and poet of fifty-one, was lonely, frightened, filled with morbid phantasies and a chloral hydrate addict. He was virtually a recluse in his gloomy London house, but Caine's letters revived his interest in literary criticism and during the last years of his life Rossetti taught Caine about literature. His "pupil's" interest and energy also helped to inspire Rossetti on his own behalf, for in 1881 he published a revised edition of Poems and a new book, Ballads and Sonnets. Very shortly after Rossetti*s death, Caine published his Recollections of Dante Gabriel Rossetti (1882), a biography of his friend which included some seventy-five fragments of the "nearly two hundred letters" he had received from Rossetti. In 1908 Caine included a large section on Rossetti in My Life, and in 1928 he produced a considerably altered version of his first biography. Caine became a prolific and popular novelist and playwright, was knighted for his war effort, and made a Companion of Honour "in recognition of his distinction in literature," but in spite of his successes, skepticism remains concerning his reliability as Rossetti's biographer. The doubts must have sprung from Caine's character—he had a romantic sensibility, a flair for seeing the simplest events dramatically, and a distinct taste for self-aggrandizement. However, although contemporaneous materials indicate that he inspired a certain wariness among Rossetti’s intimates, there are no concrete reasons to doubt his veracity in matters of fact. / Arts, Faculty of / English, Department of / Graduate

Projektet har som ambition att skapa en modern stadshusbyggnad som möjliggör ökad samverkan mellan kommunen Nynäshamn och dess medborgare. Byggnaden är konstruerad av 30 bågar av betong som spänner upp de två byggnadsvolymerna. Byggnaden möter Stadshusplatsen i nordväst och Floravägen i sydöst. Den böjda formen skapar öppningar på platsen som underlättar för fotgängare att fritt röra sig mellan och genom byggnaden och därigenom förbinda Stadshusplatsen och Floravägen. Fasaden är täckt av glas för att skapa synlighet för medborgarna att se in på den kommunala administrationens dagliga verksamhet. Fasadelementen mellan de bärande bågarna är vinklade och roterade i förhållande till varandra. Taket är även utformat av vinklade rektanglar. Byggnaden är utformad för att uppfylla de programspecifika kraven med möjlighet till att hantera förändrade krav genom sin öppna struktur. / The project is based on the ambition of creating a modern town hall building which enables increased interaction between the activities of the municipality and its citizens. The building is constructed by 30 concrete arches which forms the two building volumes. The building meets Stadshusplatsen in northwest and Floravägen in southeast. The curved form of the building creates openings at the site which facilitates pedestrians to move freely between and through the building thereby connecting Stadshusplatsen and Floravägen. The facade is covered by glass to create visibility for the citizens to look into the daily activities of the municipality administration. The facade elements are tilted between the arches and rotated in relation to each other. The roof is also being formed by tilted rectangular elements. The building is designed to meet the programme specific requirements with an ability to cope with changing demands by its open structure.

The project is a civic hall in the center of Gnesta, a small municipality connected to Stockholm by the commuter rail.It treats the question of whether the civic hall is built for – or by the inhabitants. / Medborgarnas hus i Gnesta är beläget precis vid pendeltågsstationen och fungerar därför som en representativ byggnad samtidigt som den ska vara en central mötesplats för invånarna. Projektet är en undersökning av begreppet medborgarhus. Är det någonting som byggs för medborgarna, eller av medborgarna?

The approach, that a I chose to fullfil my idea as well as the diploma project, was bassed on solving problems, which I consider as key in the context of the whole urban setting. The parameters which I collected led me through the designing process. The result of my work followed in the foodsteps of the international competition, which took place in this area. transformation of the nonfunctionl part of town and recreat it towards new cultural cluster, where the first flagship suppouse to be this concert hall. In this case was important, to find and melt together all the possitive influences of this urban area.

Thesis (M. Mus.)--University of Melbourne, 1978. / Typescript (photocopy). Includes bibliographical references (leaves [279]-283) and index.

The quantum Hall effect occurs when a conductor carrying a current is placed in a perpendicular magnetic field. If certain conditions are met, such as strong magnetic field and low temperature, the resistivity becomes quantised, taking values of integer or fractional multiples of h/e2. By analysing the movement of electrons in a magnetic field classically and quantum mechanically information about the integer quantum Hall effect and the fractional quantum Hall effect can be gathered, using the two different gauge potentials of Landau gauge and Symmetric gauge. Resistance Metrology is one field of study that the quantum Hall effect has greatly impacted by providing a way to universally maintain the ohm, with significantly less uncertainty than previously. / Den kvantmekaniska hall-effekten uppstår när en strömbärande ledare placeras i ett vinkelrätt magnetfält. Om vissa villkor är uppfyllda, såsom starkt magnetfält och låg temperatur, blir resistiviteten kvantiserad. Given av heltal (integer) eller fraktions-(fractional) multiplar av h/e2. Genom att analysera elektroners rörelse i ett magnetfält klassiskt och kvantmekaniskt fås information om Hall-effekterna; integer quantum Hall effect och fractional quantum Hall effect, med hjälp av de två gauge potentialerna Landau gauge och Symmetrisk gauge. Resistansmetrologi är ett forskningsområde som kvant Hall-effekten har starkt påverkat genom att tillhandahålla ett sätt att universellt upprätthålla ohm-enheten med betydligt mindre osäkerhet än tidigare.

Graphene field effect transistors (GFETs) are considered as a candidate for future high-frequency applications. For their realization, the optimal combination of substrate, graphene preparation, and insulator deposition and composition is required.This optimization must be based on an in-depth characterization of the obtained graphene insulator metal (GIM) stack. Hall effect measurements are frequently employed to study such systems, thereby focussing primarily on the charge carrier mobility. In this work we show how an analysis of the sheet Hall coefficient can reveal further important properties of the GIM stack, like, e.g., the interface trap density and the spacial charge inhomogeneity. To that end, we provide an extensive description of the GIM diode, which leads to an accurate calculation of the sheet Hall coefficient dependent on temperature and gate voltage. The gate dependent inverse sheet Hall coefficient is discussed in detail before we introduce the concept of an equivalent temperature, which is a measure of the spacial charge inhomogeneity. In order to test the concept, we apply it to evaluate already measured Hall data taken from the literature. This evaluation allows us to determine the Drude mobility, even at the charge neutrality point, which is inaccessible with a simple one band Hall mobility analysis, and to shed light on the spacial charge inhomogeneity. The formalism is easily adaptable and provides experimentalists a powerful tool for the characterization of their graphene field effect devices.

No description available.

La loi de Moore est basée sur l’observation empirique qu’environ chaque deux années, le nombre de transistors dans des circuits denses intégrées double. Cette tendance s'est bien maintenue au cours des dernières décennies (années 1970 et suivantes). Cependant, la miniaturisation continue des transistors entraîne une augmentation significative des pertes d’énergie par le courant de fuite, ce qui augmente la consommation d'énergie de veille. Cette perte d’énergie est devenue un problème majeur dans la microélectronique pendant les dernières années, ce qui rend plus difficile le développement des nouvelles technologies. L’une des solutions est de placer des éléments mémoire non-volatile dans le puce, qui retiennent la configuration du transistor pendant la mise hors tension et permettent de le restaurer à la mise sous tension. Les Magnetic Random Access Memories (MRAM) sont considérées par l'ITRS comme un candidat crédible pour le remplacement potentiel de SRAM et de DRAM au-delà du nœud technologique de 20 nm. Bien que les exigences de base pour la lecture et l'écriture d'un élément de mémoire unique sont remplies, l'approche actuelle basée sur Spin Torque Transfer (STT) souffre d'un manque inné de la flexibilité. Le courant électrique entraine le retournement de l’aimantation de la couche ferromagnétique libre par le transfert du moment angulaire d’une couche ferromagnétique adjacent. Ainsi les éléments de mémoire basées sur STT ont deux terminaux dont les voies de courant pour « écriture » et « lecture » sont définies par la forme de «pillar». L’optimisation indépendant des paramètres d’écriture et de lecture reste, donc, très difficile. Au même temps, la densité de courant trop haute, nécessaire pour écrire, conduit à la vieillissement prémature du jonction tunnel. En conséquence, l’intégration MRAM dans la technologie du semi-conducteur reste, donc, difficile.Démonstrations récentes de reversement d’aimantation entrainées par l’injection d’un courant planaire dans des heterostructures métal lourd/ferromagnet ont attiré l’attention croissante sur les couples de spin basé sur le transfert du moment angulaire par l’effet Hall de spin et les effets d’interface. Contrairement à STT-MRAM, la SOT-MRAM a trois terminaux, dont les voies de courant pour « écriture » et « lecture » sont indépendantes. Cela permet d’améliorer les paramètres « écriture » et « lecture » de manière indépendante. Pour contrôler et optimiser les SOT il est nécessaire de comprendre très bien leur origine. Cela reste l’une des plus importantes questions dont on n’a pas une réponse définitive. Dans ce contexte, plusieurs études ont conclu sur un modèle basé seulement sur l’effet Hall de spin, en même temps que d’autres ont suggéré un modèle basé sur une contribution combiné de l’effet Hall de spin et l’effet d’interface.L’objectif de cette thèse est de réaliser une étude systématique sur les effets d’interface sur les SOT dans des heterostructures métal lourde/ferromagnet a base de Pt, avec aimantation planaire.Dans ce but, cette thèse explore trois voies différentes. Premièrement nous avons modifié le rapport entre les effets d’interface et les effets bulk en changeant l’épaisseur de la couche de Pt et en suivant l’évolution des SOT. En deuxième nous avons exploré des différents empilements métal lourde/ferromagnet afin d’étudier différentes interfaces. Finalement, nous avons changé les propriétés des interfaces soit par changer la structure cristalline soit par oxydation. La technique de mesure, la méthode d’analyse de données associé et les aspects théoriques nécessaires pour l’interprétation des données sont aussi détaillés dans ce manuscrit. / Moore’s law is based on empirical observation and states that every two years approximately, the number of transistors in dense integrated circuits doubles. This trend has held up well in the past several decades (1970s and onwards). However, the continuous miniaturisation of transistors brings about a significant increase in leakage current, which increases the stand-by power consumption. This energy loss has become a major problem in microelectronics during the last several years, making the development of new technologies more difficult. One of the solutions that can address this issue is to place non-volatile memory elements inside the chip, that retain the configuration of the transistor during power-off and allow to restore it at power-on. Magnetic Random Access Memories (MRAM) are considered by the ITRS as a credible candidate for the potential replacement for SRAM and DRAM beyond the 20 nm technological node. Though the basic requirements for reading and writing a single memory element are fulfilled, the present approach based on Spin Transfer Torque (STT) suffers from an innate lack of flexibility. The electric current drives the magnetization switching of a free ferromagnetic layer by transferring angular momentum from an adjacent ferromagnet. Therefore, STT-based memory elements are two terminal devices in which the “pillar” shape defines both the “read” and the “write” current paths. Independent optimisation of the reading and writing parameters is therefore difficult, while the large writing current density injected through the tunnel barrier causes its accelerated ageing, particularly for fast switching. Consequently, the integration of MRAM into semiconductor technology poses significant difficulties.Recent demonstrations of magnetization switching induced by in-plane current injection in heavy metal (HM)/ferromagnet (FM) heterostructures have drawn increasing attention to spin-torques based on orbital-to-spin momentum transfer induced by Spin Hall and interfacial effects (SOTs). Unlike STT-MRAM, the in-plane current injection geometry of SOT-MRAM allows for a three-terminal device which decouples the “read” and “write” mechanisms, allowing the independent tuning of reading and writing parameters. However, an essential first step in order to control and optimise the SOTs for any kind of application, is to better understand their origin. The origin of the SOTs remains one of the most important unanswered questions to date. While some experimental studies suggest a SHE (Spin Hall Effect)-only model for the SOTs, others point towards a combined contribution of the bulk (SHE) and interface (Rashba Effect and Interfacial SHE). At the same time, many studies start with a SHE only hypothesis and do not consider interfacial effects. Furthermore, there are not so many systematic studies on the effects of interfaces. This thesis tries to fill in this gap, by providing a systematic study on the effects of interfaces on the SOTs, in Pt-based NM/FM/HM multilayers with in-plane magnetic anisotropy. For this purpose, this thesis explores three different, but related avenues. First, we changed the interface/bulk effect ratio by modifying the Pt thickness and following the evolution of the SOTs. Second, we explored different HM/FM/NM combinations, in order to study different interfaces. And third, we changed the properties of the interfaces by changing the crystallographic structure of the interface and by oxidation. The measurement technique and associated data analysis method, as well as the theoretical considerations needed for the interpretation of the results are also detailed in this manuscript.