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Structural and physical properties of the vacancy doped systems R(1-x)TiO3 (R = Nd for 0.00< x < 0.33 and Sm for 0.00< x < 0.17) : an investigation of metal-insulator transitions /Amow, Gisele. January 1999 (has links)
Thesis (Ph.D.) -- McMaster University, 1999. / Disk in pocket. Includes bibliographical references (leaves 232-237). Also available via World Wide Web.
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Design and manufacture of a high temperature superconducting magnetic energy storage deviceHawley, Christopher John. January 2005 (has links)
Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 188-200.
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Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic SemiconductorsChang-Hwan Kim January 2003 (has links)
Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); 12 Dec 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2605" Chang-Hwan Kim. 12/12/2003. Report is also available in paper and microfiche from NTIS.
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Proof of principle for Bi₂SR₂CaCu₂O₈₊x react wind sinter magnet manufacturingMerritt, Gary Adam. Schwartz, Justin January 2006 (has links)
Thesis (M.S.)--Florida State University, 2006. / Advisor: Justin Schwartz, Florida State University, College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (viewed Sept. 19, 2006). Document formatted into pages; contains xii, 43 pages. Includes bibliographical references.
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Establishing a process for the fabrication of high-quality HTc SQUIDsRottier, P. A. (Pieter Adriaan) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: High-temperature (HTc) SQUID magnetometers are used in the biomedical field of magnetocardiography
(MCG). The use of MCG enables a much earlier diagnosis of potentially dangerous
conditions than the use of electrocardiography (EeG). For the use of MCG, high-quality
HTc SQUIDs are necessary. These SQUIDs can only be realised if the design and fabrication
processes are well defined and understood. In this thesis an extensive literature review on the
design process explains all the concepts necessary to understand and design a high-quality HTc
SQUID. Then the fabrication process is redefined and characterised.
The SQUIDs are fabricated with YBCO thin films on MgO substrates. The relevant steps
in the process are the pulsed laser deposition (PLD), UV lithography and argon ion milling.
The characterisation of the fabrication process is based on a statistical method called Design
of Experiment (DOE). This enables more information to be obtained about the fabrication
process than before. For the PLO process the important parameters are determined and an
initial optimisation is done. During the characterisation process it is proven that the use of
ozone during PLO has a positive effect on the quality of the YBCO thin film. On the PLD
apparatus the substrate heater and laser-beam profile is improved. The UV lithography process
is analysed and a DOE is proposed for optimisation. A temperature bath is added to the process
to enable better reproducibility. An rf multicusp ion mill is built for argon-ion milling, this
device is tested and shown to provide the required etching capability. / AFRIKAANSE OPSOMMING: Hoë-temperatuur (HTc) SQUID magnetometers word in die biomediese rigting vir magnetokardiografie
(MKG) gebruik. Met MKG kan 'n mens potensieel gevaarlike toestande heelwat
vroeër diagnoseer as wat moontlik is met elektrokardiografie (EKG). HTc SQUIDs van hoë
kwaliteit word benodig vir MKG. Sulke SQUIDs kan slegs vervaardig word as die vervaardiging
en ontwerpsprosesse goed gedefinieer en verstaan word. In hierdie tesis verduidelik 'n omvattende
literatuurstudie oor die ontwerpsproses al die konsepte wat nodig is om 'n SQUID van
hoë kwaliteit te verstaan en te ontwerp. Verder word die vervaardigingsproses geherdefinieer
en gekarakteriseer.
Die SQUIDs word vervaardig met YBCO-dunfilm op MgO-substrate. Die relevante stappe
tydens die vervaardiging is: gepulseerde laser deposisie (PLO), UV-litografie en argon-ioonstraling.
Die karakterisering van die vervaardigingsproses is gebaseer op 'n statistiese metode
genaamd "Design of Experiment" (DOE). Hierdie metode laat 'n mens toe om meer inligting
oor die proses te verkry as wat voorheen moontlik was. Gedurende die karakterisering
word bewys dat die gebruik van osoon gedurende die PLO-proses 'n positiewe invloed op die
kwaliteit van die YBCO-dunfilm het. Die PLO-apparaat se substraatverwarmer en laserstraalprofiel
word verbeter. Die UV-litografieproses word geanaliseer en 'n DOE word voorgestel
vir die optimisering daarvan. Daar word 'n temperatuurbad by die proses gevoeg om die herhaalbaarheid
te verbeter. 'n "Rf multicusp ion mill" word gebou, die toestel word getoets en
daar word aangetoon dat dit die nodige etsvermoë het.
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Techniques for enhancing the PLD growth of superconducting YBCO thin filmsHardie, Graham Lyall 12 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: High Temperature Superconductors (HTS) exhibit exceptional electrical properties that make them
attractive candidates for numerous electronic devices and applications. However, constructing
working devices can be challenging due to fabrication difficulties of these brittle ceramics. This
thesis investigates new methods to make the fabrication of high quality YBa2Cu3O7 (YBCO) thin
films easier and compatible with more materials.
We present the development of a universal add-on method that can be used in situ to improve the
quality of superconducting thin films deposited by Pulsed Laser deposition (PLD). We investigate
the in situ application of electric fields and voltage biasing to improve the thin film growth. Considering
various electrode configurations, we have developed a final electrode design that is stable
and produces reproducible results. By introducing an insulated high voltage (HV) electrode into the
chamber during deposition, the quality of the deposited thin films can be modulated depending on
the polarity of the voltage applied. Applying a positive voltage improves the film quality obtained.
Applying a negative voltage degrades the superconducting properties of the films.
A simple proof-of-concept HTS dual-mode microwave filter was designed, fabricated and tested.
Only the filter produced using our novel PLD technique displayed the correct filtering action upon
cooling to 77K. This is attributed to the thin films better superconducting properties due to our
developed technique. / AFRIKAANSE OPSOMMING: Hoë Temperatuur Supergeleiers (HTS) vertoon aantreklike elektriese eienskappe wat hulle goeie
kandidate maak vir verskeie elektroniese toepassings. Om werkende toestelle te ontwikkel kan 'n
uitdaging wees, as gevolg van die vervaardigings probleme wat bestaan vir hierdie bros keramiek materiaal.
Hierdie tesis ondersoek nuwe metodes om die vervaardiging van 'n hoë gehalte YBa2Cu3O7
(YBCO) dun films makliker en versoenbaar te maak met verskeie materiale.
Ons toon die ontwikkeling van 'n algemene metode wat maklik bygevoeg kan word om in situ die
gehalte van supergeleidende dun films, wat deur gepulseerde laser deponering (PLD) gedeponeer
is, te verbeter. Ons ondersoek die in situ toepassing van elektriese velde en spannings om die
dun film groei te verbeter. Verder oorweeg ons verskeie elektrode konfigurasies en ontwikkel 'n
finale elektrode ontwerp wat stabiel is en herhaalbare resultate produseer. Die kwaliteit van die
gedeponeerde dun films kan gemoduleer word deur die byvoeging van 'n geïsoleerde hoogspannings
(HV) elektrode tydens deponering, afhangende van die polariteit van die aangelegde spanning. 'n
Positiewe spanning verhoog die film kwaliteit, terwyl 'n negatiewe spanning die supergeleidende
eienskappe van die films verlaag.
'n Eenvoudige HTS dubbele-modus mikrogolffilter is ontwerp, vervaardig en getoets, om as toepassings
voorbeeld te dien. Slegs die filter wat geproduseer was met behulp van ons nuwe PLD
tegniek, vertoon die beste filter oordrag by 77K. Dit word toegeskryf aan die beter supergeleidende
eienskappe van die dun film, as gevolg van die toepassing van ons ontwikkelde tegniek.
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Mobilidade de oxigênio intersticial em SM'BA IND.2' C IND.U 'IND.3' 'O IND. 7-'delta' medida através de espectroscopia mecânicaNascimento, Rodney Marcelo do [UNESP] 30 June 2006 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0
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nascimento_rm_me_bauru.pdf: 3217433 bytes, checksum: 4db978f65eff59d8b027881dac872d0f (MD5) / Secretaria de Educação do Estado de São Paulo / Desde a descoberta dos supercondutores com alta Tc, vários trabalhos têm sido efetuados sobre as diferentes propriedades destes materiais. As cerâmicas Y'BA IND.2' C IND.U 'IND.3' 'O IND. 7-'delta' mostraram que tem suas propriedades supercondutoras fortemente afetadas pela quantidade de oxigênio. Mais recentemente, medidas de relaxações anelásticas em 'LA IND.2'CU 'O IND. 4+'delta' mostraram que a remoção deste elemento pode ser relacionada com dois eventos. Um deles é o decréscimo na mobilidade entre dois planos adjacentes CuO e o outro, é o aumento no número de padrões de mobilidade para os octaedros CU 'O IND. 6'. Para SM'BA IND.2' C IND.U 'IND.3' 'O IND. 7-'delta' (SBCO), a possibilidade de uma estequiometria de oxigênio variável e sua alta mobilidade nos planos... / Since the discovery of the high Tc superconductors, several works have been made about the different propoerties of these materials. Y'BA IND.2' C IND.U 'IND.3' 'O IND. 7-'delta' ceramic showed to have its superconducting properties strongly affected by the oxygen content. More recently, anelastic relaxation measurements in 'LA IND.2'CU 'O IND. 4+'delta', showed that the remotion of this element can be related to two events. One is the decrease in mobility between two adjacent CuO planes, and the other is the increase in the number of tilting patterns of the Cu 'O IND. 6' octahedra. For SM'BA IND.2' C IND.U 'IND.3' 'O IND. 7-'delta' (SBCO), the possibility of variable stoichiometry and the high mobility of oxygen in the... (Complete abstract, click electronic access below)
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Efeito da competição entre a supercondutividade e as insinstabilidades de Pomeranchuk no canal de spin / Modulated superconductivity near Pomeranchuk instabilities in the spin chanelPaulo Sérgio de Abreu Bonfim 13 April 2012 (has links)
Nós estudamos a competição entre a instabilidade de Pomeranchuk no canal de spin com momento angular l=1 e uma interação atrativa, favorecendo a formação de um par de
Cooper. Achamos, numa aproximação de campo médio, uma forte supressão da instabilidade de Pomeranchuk via supercondutividade. Além disso, identificamos uma fase supercondutora metaestável com características semelhantes ao estado FFLO. Um líquido de Fermi é, com
exceção de uma dimensão, um estado muito estável da matéria. Por outro lado dois tipos de instabilidades, relacionadas com interações atrativas, são conhecidas: Instabilidades Pomeranchuk e supercondutora. As instabilidades Pomeranchuk ocorrem na presença da interação de dois corpos contendo uma forte componente atrativa no canal de espalhamento para frente com momento angular definido. No contexto da teoria de Landau, a instabilidade ocorre quando um ou mais parâmetros admensionais de Landau nos canais de spin ou carga,
adquirem altos valores negativos. As instabilidades Pomeranchuk no setor de carga quebram a simetria de rotação. Em particular, uma instabilidade em alguns canais produz uma deformação elipsoidal na superfície de Fermi. / We study the competition between a Pomeranchuk instability in the spin channel with angular momentum l = 1 and an attractive interaction, favoring Cooper pair formation. We
find, at mean-field approximation, that superconductivity strongly suppress the Pomeranchuk instability. Moreover, we have found a metastable modulated superconducting phase with similar characteristics of the FFLO state. A Fermi liquid is, except in one dimension, a very stable state of matter. At least two types of instabilities, related with attractive interactions, are known: Pomeranchuk and superconducting instabilities. Pomeranchuk instabilities occur in the presence of two-body interactions containing a strong attractive component in the forward scattering channel with a definite angular momentum. In the context of Landau theory, the
instability sets in when one or more dimensionless Landau parameters in the charge or spin channel, acquire large negative values. Pomeranchuk instabilities in a charge sector
spontaneously break rotational symmetry. In particular, an instability in the some channels produces an ellipsoidal deformation of the Fermi surface.
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Muon spin spectroscopy and high magnetic field studies of novel superconductors and magnetic materialsForonda, Francesca January 2016 (has links)
This thesis investigates a number of novel magnetic materials and high temperature superconductors using high-field magnetometry and muon spin spectroscopy (μSR). The main measurement techniques are briefly described and a study of the dimer material [Cu(pyrazine)(glycine)]ClO<sub>4</sub> is presented to demonstrate the use of the proximity detector oscillator as a susceptometer in high magnetic fields. μSR is a highly effective tool for probing magnetic order, spin freezing and spin dynamics. However, in some circumstances its performance may be impaired by the extent to which it perturbs the material under study. Using μSR, density functional theory and crystal field calculations, I identify an experimental situation in the family of candidate quantum spin ices Pr<sub>2</sub>B<sub>2</sub>O<sub>7</sub> (B = Sn, Zr, and Hf), in which the measured response is dominated by a muon-induced distortion of the local structure. This issue is also addressed in a study of the spin dynamics in the canonical spin ice Ho2Ti2O7. Although computational work indicates a similar muon-induced effect in both Ho<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> and Dy<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub>, the μSR data is not dominated by this perturbation. The remainder of this thesis is concerned with studying the superconducting properties of a number of Fe-based materials, including LiFeP which is found to have an enhanced superfluid stiffness in relation to its transition temperature. Also reported is the effect of structural disorder on the superconducting state in recently discovered Sr<sub>0.3</sub>(NH<sub>2</sub>)<sub>y</sub>(NH<sub>3</sub>)<sub>1-y</sub>Fe<sub>2</sub>Se<sub>2</sub>. Pulsed magnetic field measurements are used to probe the temperature dependence of the upper critical field, giving a maximum value of μ<sub>0</sub>H<sub>c2</sub>(0)≈33(2) T. I also investigate the effect of intercalating additional ammonia, via reversible adsorption and desorption in the related superconductor Li<sub>x</sub>[(NH<sub>2</sub>)<sub>y</sub>(NH<sub>3</sub>)<sub>1-y</sub>]<sub>z</sub>Fe<sub>2</sub>Se<sub>2</sub> (z = 1, 2). These reactions were carried out in situ on the muon beamline so that the superfluid stiffness could be measured using transverse-field μSR on a single sample.
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Elaboration et caractérisation de couches minces supraconductrices épitaxiées de rhénium sur saphir / Growth and charcterization of superconducting epitaxial thin fimls rhenium on sapphireDelsol, Benjamin 25 February 2015 (has links)
Dans les dispositifs électronique, il est prochainement attendu que la réduction de la taille des composant atteingne prochainement la limite quantique. De ce fait, manipuler l'information quantique apparait comme un nouveau challenge. Les Qubits supraconducteurs basé sur la physique du solide et les Jonctions Josephson sont des systèmes prometteurs qui profitent des avantage des technologies de la micro-électronique. Toutefois, le temps de décohérence des états quantique est encore un facteur limitant. Cette limitation est généralement attribuée à la faible qualité cristalline des matériaux utilisés (défauts cristallins, impuretés). La technique d'épitaxie par jets moléculaires a été utilisé pour la croissance de couches minces de rhénium de haute qualité cristalline sur des substrat de saphir dans un environnement Ultra Haut Vide. Le misfit existant entre les réseaux cristallins du rhénium et du saphir est suffisamment bas pour permettre une croissance épitaxiale du rhénium sur le saphir, mais également une croissance d'une barrière tunnel en oxyde d'aluminium monocristallin sur la couche de rhénium elle-même. Afin d'améliorer la qualité cristallographique de la couche de rhénium, des simulations et de nombreuses techniques de caractérisation ont été utilisées. Puis les propriétés supraconductrices des films de rhénium ont été étudié à des températures ultra basses afin de comparer ces propriétés à la qualité cristallographique de nos films. / In electronic devices, it is expected that the quantum limit will soon be reached with decreasing system size. Therefore, manipulating quantum information appears as a new challenge. Solid state Qubits based on superconducting Josephson junction are promising systems which take advantage of microelectronics technology. However, decoherence time of the quantum states is still a limiting factor. This has been generally ascribed to the poor crystallographic quality of the materials used so far (crystallographic defects, impurities). The Molecular Beam Epitaxy (MBE) technique may be used to grow rhenium (Re) films of high quality on sapphire substrates in an Ultra High Vacuum (UHV) environment. So far, the misfit between Re and sapphire is low enough to permit the growth of a single crystal aluminium oxide thin film on top of the Re layer. In order to improve the crystallographic quality of the Re film, some simulations and several characterizations techniques have been used. Then, the superconducting properties of rhenium films have been studied at Ultra Low Temperature in order to compare with their crystallographic qualities.
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