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In this study we investigate the magnetic properties of Fe-based amorphous thin films. Fe1-x-y-zBxSiyCz, Fe80-xNixB20, Fe80-xMnxB20, and Fe73-xMnxB27 films were deposited on silicon and glass substrates in a DC and RF magnetron sputtering system. Inductive magnetic measurements were performed to investigate the magnetic properties, including induced anisotropy and magnetostriction, of the as-deposited and annealed films using an M-H Looper. The chemical composition of the films was characterized using secondary ion mass spectroscopy (SIMS). The physical thickness of the films was determined by use of a stylus profilometer. The M-H Looper studies indicated that the induced anisotropy (Hk) depends strongly on the nickel concentration as well as on the annealing conditions, specifically the time and temperature of the annealing process. For the same metalloid concentration, the induced anisotropy has a maximum as a function of Ni. For the same nickel concentration and annealing time, it was found that the value of Hk decreases with the increase in annealing temperature. For each composition studied, low temperature long time annealing showed a higher value of Hk compared to high temperature short time annealing. From the magnetostriction values of Fe80-xNixB20 alloys, it was found that the sputter deposited films show similar trend but differ in magnitude when compared with ribbon samples. The magnetostriction of annealed thin films is found to be representative of ribbon samples. A potential composition modification to improve the strength of the field induced anisotropy is the addition of low levels of Mn.

In this dissertation, liquid crystal (LC) materials and devices are investigated in order to meet the challenges for photonics and displays applications. We have studied three kinds of liquid crystal materials: positive dielectric anisotropic LCs, negative dielectric anisotropic LCs, and dual- frequency LCs. For the positive dielectric anisotropic LCs, we have developed some high birefringence isothiocyanato tolane LC compounds with birefringence ~0.4, and super high birefringence isothiocyanato biphenyl-bistolane LC compounds with birefringence as high as ~0.7. Moreover, we have studied the photostability of several high birefringence LC compounds, mixtures, and LC alignment layers in order to determine the failure mechanism concerning the lifetime of LC devices. Although cyano and isothiocyanato LC compounds have similar absorption peaks, the isothiocyanato compounds are more stable than their cyano counterparts under the same illumination conditions. This ultraviolet-durable performance of isothiocyanato compounds originates from its molecular structure and the delocalized electron distribution. We have investigated the alignment performance of negative dielectric anisotropic LCs in homeotropic (vertical aligned, VA) LC cell. Some (2,3) laterally difluorinated biphenyls, terphenyls and tolanes are selected for this study. Due to the strong repulsive force between LCs and alignment layer, (2,3) laterally difluorinated terphenyls and tolanes do not align well in a VA cell resulting in a poor contrast ratio for the LC panel. We have developed a novel method to suppress the light leakage at dark state. By doping positive [Delta][epsilon] or non-polar LC compounds/mixtures into the host negative LC mixtures, the repulsive force is reduced and the cell exhibits an excellent dark state. In addition, these dopants increase the birefringence and reduce the viscosity of the host LCs which leads to a faster response time. Dual-frequency liquid crystal exhibits a unique feature that its dielectric anisotropy changes from positive to negative when we increase the operating frequency. Submillisecond response time can be achieved by switching the frequency of a biased voltage, rather than switching the voltage at a given frequency. In this dissertation, we investigate the dielectric heating effect of dual-frequency LCs. Because the absorption peak of imaginary dielectric constant occurs at high frequency region (~ MHz), there is a heat generated when the LC cell is operated at a high frequency voltage. To measure the transient temperature change of the LC inside the cell, we have developed a non-contact method by utilizing the temperature-dependent birefringence property of the LC. Most importantly, we have formulated a new dual-frequency LC mixture which greatly reduces the dielectric heating effect while maintaining good physical properties. Another achievement in this thesis is that we have developed a polarization independent phase modulator by using a negative dielectric anisotropic LC gel. With ~20 % of polymer mixed in the LC host, the LC forms polymer network which, in turn, exerts a strong anchoring force to the neighboring LC molecules. As a result, the operating voltage increases but the response time is significantly decreased. On the phase shift point of view, our homeotropic LC gel has ~0.08 [pi] phase shift, which is 2X larger than the previous nano-sized polymer-dispersed liquid crystal droplets. Moreover, it is free from light scattering and requires a lower operating voltage. In conclusion, this dissertation provides solutions to improve the performance of LC devices both in photonics and displays applications. These will have great impacts in defense and display systems such as optical phased array, LCD TVs, projectors, and LCD monitors.

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<p> InxGa1_xAs (0.00</= x </= 0.42) metamorphic pseudosubstrate layers (MSLs) were studied as a means to change the lattice constant of the substrates and to modify the growth conditions of InAs quantum dots (QDs) by varying the strain. The MSLs showed symmetrical mosaicity about the 110 axes but the spread was different in the two orthogonal [110] and [110] directions. The anisotropy in the mosaic spread in two < 11 O > directions was correlated to asymmetry of kinks and multilevel-terrace growth front during the growth of InxGa1_xAs buffer layers. X-ray and electron diffraction along with the least squares criterion can interchangeably be employed to determine the lattice constant of the MS Ls. It is possible to grow a defect free MSL with employing a compositional undershoot relative to the terminating buffer layer. Asymmetric tilt was found in an In0.42Ga0.58As MSL grown on a singular (001) GaAs substrate with an initial layer of a low temperature ( < 300 °C) grown InGaP prior to the growth of step-graded InxGa1-xAs (x = 0.02 to 0.42) buffer layers. The tilt around [110] axis was correlated with the imbalance of the tilt component of the Burgers vector (BV) of the 60° α-dislocations. Climb and jog formation of β-dislocations in the presence of P-interstitials were considered as a plausible mechanism for multiplication of the like-sign BV α-dislocations. These results show that an asymmetric tilt boundary can be induced in mismatched heterointerfaces grown on singular substrates. The evolution of InAs QDs on InxGa1-xAs(0.0</= x </= 0.3) MSLs on GaAs substrates was studied. The results indicate that the ratio of the height (h) over lateral diameter (d) of the QDs decreases with decreasing strain (i.e. the morphology of the coherent islands evolve toward a uniform film morphology (h/d=0) with deceasing strain). This evolution is analogous to the current </p> / Thesis / Doctor of Philosophy (PhD)

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19038号 / 農博第2116号 / 新制||農||1031(附属図書館) / 学位論文||H27||N4920(農学部図書室) / 31989 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 木村 恒久, 教授 西尾 嘉之, 教授 髙野 俊幸 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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[pt] Para uma melhor previsibilidade e gerenciamento de reservatórios de hidrocarbonetos é necessário estabelecer modelos constitutivos adequados para representar o comportamento mecânico e hidráulico desses materiais. Durante a produção de hidrocarbonetos, ocorre um aumento das tensões efetivas devido à redução de pressão de poros. Isto pode levar à redução do espaço poroso do reservatório, podendo chegar ao colapso de poros. A compactação dos reservatórios é consequência da alteração do estado de tensões, que produzem deformações elásticas e plásticas, levando eventualmente à ruptura da rocha. Sabe-se que a resistência dos carbonatos está relacionada à porosidade, mineralogia e arranjo dos grãos. Sendo que este tipo de rocha, geralmente, tem um comportamento elastoplástico com características anisotrópicas. O uso de modelos constitutivos avançados é necessário para reproduzir o complexo comportamento de tensão-deformação-permeabilidade das rochas carbonáticas. Os modelos elastoplásticos isotrópicos Lade-Kim e Cam Clay Modificado com Coesão (CCMC), são usados neste trabalho para tentar representar o comportamento geomecânico do travertino; rocha análoga a uma das fácies do Pré-Sal brasileiro. Parâmetros destes modelos para este tipo de rochas dificilmente são encontrados na literatura, sendo sua determinação dependente de ensaios de laboratório cuidadosamente realizados. O presente trabalho tem como objetivo contribuir com o estabelecimento de modelos adequados para representar o comportamento geomecânico da rocha carbonática travertino em função da porosidade. Como parte do presente trabalho foi desenvolvido um modelo anisótropico denominado CALK, baseado no modelo isotrópico de Lade-Kim. Além disso ensaios triaxiais a compressão, hidrostáticos e compressão uniaxial foram realizados em amostras da rocha carbonática travertino com diferentes orientações das camadas em relação ao eixo axial das amostras (paralelo, Beta = 90 graus; ortogonal, Beta = 0 grau; e inclinado, Beta = 45 graus). Os resultados dos ensaios foram usados para estabelecer parâmetros dos modelos constitutivos Lade-Kim e CCMC. O processo de retroanálise foi utilizado, incorporando o algoritmo Lade-Kim, desenvolvido em MATLAB 2017 e FORTRAN 90 nos algoritmos DREAM e MINPACK, respectivamente. Os resultados obtidos indicam que a metodologia proposta e o modelo CALK é capaz de representar adequadamente, o comportamento mecânico do travertino observado em laboratório. / [en] For better predictability and management of hydrocarbon reservoirs it is necessary to establish adequate constitutive models to represent the mechanical and hydraulic behavior of these materials. During the production of hydrocarbons, an increase in effective stresses occur due to the reduction of pore pressure. This can lead to a reduction in the pore space of the reservoir and may lead to pore collapse. The compaction of the reservoirs is a consequence of the alteration of the state of stress, which produce elastic and plastic deformations, eventually leading to failure of the rock. It is known that the resistance of the carbonates is related to the porosity, mineralogy and arrangement of the grains. Since this type of rock usually has an elastoplastic behavior with anisotropic characteristics. The use of advanced constitutive models is necessary to reproduce the complex stress-strainpermeability behavior of sedimentary rocks. The Lade-Kim and Modified Cam Clay with Cohesion (CCMC) isotropic models are used in this work to try to represent the geomechanical behavior of travertine; a rock analogous to one of the Brazilian Pre-Salt facies. Parameters of these models for these type of rocks are seldom found in the literature, and their determination depends on carefully performed laboratory tests. The present work aims to contribute with the establishment of adequate models to represent the geomechanical behavior of travertine carbonate as a function of porosity. As a part of the present work an anisotropic model called CALK was developed, based on the isotropic model of Lade-Kim. In addition, triaxial compression, hydrostatic and uniaxial compression tests were performed on travertine carbonate samples with different orientations of the layers in relation to the axial axis of the samples ( parallel, Beta = 90 degrees , orthogonal, Beta = 0 degrees and inclined, Beta = 45 degrees) The results of the tests were used to establish parameters of the constitutive models Lade-Kim and CCMC. The retro-analysis process was used, incorporating the Lade-Kim algorithm, developed in MATLAB 2017 and FORTRAN 90, to the DREAM and MINPACK algorithms, respectively. The results indicate that the proposed methodology and the CALK model are able to adequately represent the mechanical behavior of the travertine observed in the laboratory.

<p>The study of ultrathin magnetic films offers novel magnetic phenomena due to the reduced symmetry of these 2D systems. The magnetic anisotropy differentiates behaviour in ultrathin films from the bulk environment, as additional anisotropies emerge from the ultrathin film thickness and the inherent strain of ultrathin films. In this work, the in-plane magnetic anisotropy of strained ferromagnetic (FM) ultrathin Co(0001) films grown on a W(110) substrate is measured over a range of temperatures (150-320 K). Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to determine the film structure and thickness. The anisotropy is derived from the quotient of the saturation magnetization and the transverse susceptibility, which are measured using the surface magneto-optic Kerr effect (SMOKE).</p> <p>This work’s second objective is to study the Néel transition in antiferromagnetic (AFM) ultrathin films. The zero net magnetization of AFM materials and the minute sample size of ultrathin films make magnetic measurements impossible with conventional methods. An alternative approach is to study a single AFM ultrathin film that is coupled by the interfacial exchange interaction to a FM ultrathin film. The upper layers of ultrathin Co/W(110) films were oxidized to produce ultrathin CoO/Co/W(110) films, creating an AFM/FM bilayer system. SMOKE measurement of the transverse magnetic susceptibility of the FM Co layer reveal the Néel transition of the AFM layer indirectly through the interfacial exchange interaction.</p> / Master of Science (MSc)