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The presented thesis focused on the study of a new material concept of Ce3+ doped multicom- ponent aluminum garnets (GdLu)3(GaAl)5O12. High purity single crystalline epitaxial films were grown by the method of liquid phase epitaxy from the BaO-B2O3-BaF2 flux with spe- cial emphasis on the elimination of the potential impurities coming from the flux. Combined experimental study of photoelectron yield (under alpha excitation), decay kinetics of fast and delayed recombination in the milisecond time range (under e-beam excitation) and photo-, cathodo- and radio-luminescence spectroscopies were used to characterize the studied mater- ial. The single-step nonradiative energy transfer from the donor Gd3+ to an acceptor Ce3+ was observed in the low Gd, Ce doped LuAG films and established as long-range dipole - dipole interaction. Special attention was devoted to the positive effect of combined Gd and Ga substitution on the extensive suppression of shallow traps, which are responsible for the slow component in the scintillation response. The best obtained scintillation characteristics of the studied epitaxial films were comparable with the top performance bulk crystals. 1

This thesis deals with the subject of fibre optic magnetic field sensors utilizing iron garnet materials. Such materials exhibit a large Faraday rotation which make them advantageous for application in compact mag­netic field sensors. After an introduction, in which fibre optic sensors and optical methods to measure electric current are reviewed, the original research work is summarized. A system for the measurement of the magneto-optic properties of trans­parent materials is described. Measurement results, showing the influence of temperature, magnetic field direction and sample treatment on the magneto-optical proper­ties of YIG-crystals, are presented. The proper­ties of thin magneto-optical waveguiding films have also been studied using different light coupling methods. Measurement results obtained for holo­graphic grating, prism and edge (end-fire) light coupling to different substituted YIG films are presented. It is shown that the launching method may affect the properties to be measured. The design and performance of several versions of extrinsic guided wave fibre optic magnetic field sensors are then reported. The sensors employ substi­tuted YIG (Yttrium Iron Garnet, Y3Fe5O12) thin film waveguides as sensing elements. Polari­zation maintaining fibres were used as feed and return to provide two signal channels. The signals were combined in a balanced measure­ment system, providing insensitivity to both fluctuations in optical power and loss. Sensors have been made both with separate fibres to guide the light to and from the sensing element and with a single fibre for both functions. The two fibre version, although less ”elegant”, is found to have a better performance. This version also makes it possible to determine both the magnitude and sign of the magnetic field. Measurement results indicate a usable measurement range of at least several mT with a noise equivalent magnetic field level of less than 8 nT/root(Hz). The design and performance of multimode fibre optic magnetic field sensors utilizing the Faraday effect in an epitaxially grown thick (YbTbBi)IG film is also described. This type of sensor is found to be linear over a range from 27 mT to less than 270 nT. Sensor prototypes suitable for current monitoring in high voltage transmission lines have also been developed. / QC 20111209 / YIG

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This study describes two families of transition metal oxides (OMT). Because of its potential and diversity of physical properties, the OMT are promising candidates for technological applications. In contrast, physically understand the complex relationship of these properties has been the main challenge of the research in this area. One of the families that was studied in this work are composed of Ruddlesden Popper type (RP), nickel base, of formula Lan+1NinO3n+1. The RP oxides have become more popular in the decade of 80, when it was discovered that a compound of this family, the La2CuO4− can become superconductive when appropriately doped. Another important property associated with the RP oxides is the colossal magnetoresistance, observed in the manganese-based compounds, such as Ca3−xLaxMn2O7. Another family of OMT studied in this work are the compounds garnets type of formula R3Fe5O12 (Where R is rare earth element or Y). This family is known to be rich in physical properties, especially magnetic, The magnetism of these compounds is associated mainly with the ferrimagnetic interaction between ions of Fe3+ in octahedral and tetrahedral coordination. The magnetic moment resulting from interactions of the Fe3+ can orient yourself antiferromagnetic with the network ion R, if it is a rare earth magnetic. A property that has been strongly investigated in compounds garnets is the magnetocaloric effect (EMC). This effect, which tracks the magnetic transitions, is more relevant and meaningful in compounds that are promising candidates for use in magnetic refrigeration. To investigate some of the physical properties of these systems were synthesized compounds (Dy, Y)3Fe3Al2O12 and Lan+1(Ni1−xZnx)nO3n+1 (n = 1, 2, 3 e 0 ≤ x ≤ 0.5). To synthesize the samples used two methods, combustion reaction (RC) and coprecipitation (CP). Both methods have proven effective for obtaining samples with the desired phase. The technique of X-ray diffraction, together with the Rieteveld refinement method was used to extract crystallographic information of the synthesized compounds. Morphological information of samples, such as size, shape and distribution of particles were investigated by the technique of scanning electron microscopy. The micrographs show that regardless of the synthesis method, the particle shape is not well defined and the size distribution is inhomogeneous. Some samples of garnets type, synthesized by CP, have particle size in the nanoscale. Some compounds were characterized by electrical resistivity measurements as a function of temperature, where it was found that the series La2Ni1−xZnxO4 it has semiconducting properties in the temperature range from 10 KM to 300 K. The magnetic properties were investigated by magnetization measurements as a function of temperature and magnetic field, where it was found that the magnetism of both systems is affected by the inclusion of non-magnetic ions. EMC was investigated in two samples of garnets type, the data were obtained from the magnetization as a function of temperature and it was found that the aluminum insert in the structure, replacing the iron, decreased temperature magnetic transition, but also reduced the intensity EMC. / Neste trabalho estudamos duas fam´ılias de ´oxidos de metais de transi¸c˜ao (OMT). Devido ao seu potencial e diversidade de propriedades f´ısicas, os OMT s˜ao promissores candidatos a aplica¸c˜oes tecnol´ogicas. Em contrapartida, compreender fisicamente a complexa rela¸c˜ao destas propriedades tem sido o principal desafio das pesquisas desta ´area.Uma das fam´ılias que estudamos neste trabalho s˜ao compostos do tipo Ruddlesden Popper (RP) a base de n´ıquel, com f´ormula Lan+1NinO3n+1. Os ´oxidos RP tornaram-se mais conhecidos na d´ecada de 80, quando foi descoberto que um composto desta fam´ılia, o La2CuO4− , pode se tornar supercondutor quando apropriadamente dopado. Outra importante propriedade associada com os ´oxidos RP ´e a magnetorresistˆencia colossal, observada em compostos a base de manganˆes, a exemplo do Ca3−xLaxMn2O7. Outra fam´ılia de OMT estudada neste trabalho s˜ao compostos tipo garnets de f´ormula R3Fe5O12 (onde R ´e um elemento terra rara ou Y). Essa fam´ılia ´e conhecida por sua riqueza de propriedades f´ısicas, especialmente magn´eticas. O magnetismo destes compostos est´a associado, principalmente, com a intera¸c˜ao ferrimagn´etica entre os ´ıons de Fe3+ em coordena ¸c˜ao octa´edrica e tetra´edrica. O momento magn´etico resultante das intera¸c˜oes do Fe3+ pode se orientar antiferromagneticamente com a rede do ´ıon R, se ele for um terra rara magn´etico. Uma propriedade que vem sendo investigada nos compostos garnets ´e o efeito magnetocal´orico (EMC). Este efeito, que acompanha as transi¸c˜oes magn´eticas, ´e mais relevante e significativo em compostos que s˜ao promissores candidatos a aplica¸c˜ao em refrigera¸c˜ao magn´etica. Para investigar algumas das propriedades f´ısicas destes sistemas, foram sintetizados compostos (Dy, Y)3Fe3Al2O12 e Lan+1(Ni1−xZnx)nO3n+1 (n = 1, 2, 3 e 0 ≤ x ≤ 0.5). Para a s´ıntese das amostras foram utilizados dois m´etodos, rea¸c˜ao de combust˜ao (RC) e coprecipita¸c˜ao (CP). A t´ecnica de difra¸c˜ao de raios X, aliada ao m´etodo de refinamento Rieteveld, foi utilizada para extrair informa¸c˜oes cristalogr´aficas dos compostos sintetizados. Informa¸c˜oes sobre morfologia das amostras, como tamanho, forma e distribui¸c˜ao das part´ıculas, foram investigadas pela t´ecnica de microscopia eletrˆonica de varredura. As micrografias revelam que independentemente do m´etodo de s´ıntese a forma das part´ıculas n˜ao ´e bem definida e a distribui¸c˜ao de tamanhos n˜ao ´e homogˆenea. Algumas amostras do tipo garnets, sintetizadas por CP, tˆem part´ıculas de tamanho na escala nanom´etrica. Alguns compostos foram caracterizados por medidas de resistividade el´etrica em fun¸c˜ao da temperatura, em que se verificou que a s´erie La2Ni1−xZnxO4 tem propriedades semicondutoras no intervalo t´ermico de 10 K a 300 K. As propriedades magn´eticas foram investigadas por medidas de magnetiza¸c˜ao em fun¸c˜ao da temperatura e do campo magn´etico, em que se verificou que o magnetismo de ambos os sistemas ´e afetado pela inser¸c˜ao dos ´ıons n˜ao magn´eticos. O EMC foi investigado em duas amostras do tipo garnets, os dados foram obtidos das medidas de magnetiza¸c˜ao em fun¸c˜ao da temperatura e se verificou que a inser¸c˜ao do alum´ınio na estrutura, em substitui¸c˜ao ao ferro, causou uma diminui¸c˜ao na temperatura de transi¸c˜ao magn´etica, por´em tamb´em reduziu a intensidade do EMC.

We have investigated the Faraday effect of bismuth-doped rare-earth iron-garnets with varying doping levels of gallium from z = 1.0 to 1.35. We used lutetium to control the film's in-plane magnetic properties and found that gallium doping levels above the compensation point caused a loss of anisotropy control, a canted out-of-plane magnetization in the film, and an extremely weak but linear coercivity above 10 micro-Tesla fields. Using these results we focused on in-plane films to create 8 layer stacks of 500 um thick films to achieve a minimum detectable field of 50 pT at 1 kHz. Unlike previous Magneto-Optic (MO) studies that typically used thin films of approximately 1um thickness, we used approximately 400um thick films to allow experimentation with the final, robust, ideal form the MO sensor would take. We measured what most other MO studies with garnets neglected: the magnetic anisotropy axis or structure within the film. Knowledge of this structure is essential in improving the sensitivity of a stacked MO probe. Studying thick films proved to be key to understanding the magnetic anisotropy and domain properties that can degrade or enhance the sensitivity of the Faraday rotation in bismuth doped rare-earth iron-garnets to an applied magnetic field and to pointing the direction of future research to develop the conditions for rugged magnetometer sensors. / Physics

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The samples of garnets used in this study come from clastic sediments from the drillcores Tř-1 and T-31, selected localities of the České středohoří Mountains and garnet-bearing ultramafic rocks sampled by the drillcore T-7. The contents of the major and some minor elements were determined by an electron probe microanalyzer. The garnets from the sediments were divided into 3 groups according to the contents of the end-members: 1) pyrope-, 2) almandine - pyrope- and 3) grosular - almandine-rich. Garnets from the drillcore T-7 were classified according to individual rock types in which they occurred: lherzolite, hazburgite, pyroxenite, eclogite and granulite. Chemical analyzes of garnets displayed the presence of positive correlations Cr vs. Ca vs. Ti Mn in pyrope grains. The contents of trace elements in garnets were studied by an LA-ICP-MS. After normalization to the CI-reservoir, garnets most often show lherzolite profiles of rare earth elements. Garnets of intense red and purple colors show slightly sinusoidal REE profiles. Inclusions enclosed in garnets were studied by a scanning electron microscope. If their dimensions allowed, the major and minor elements were determined by electron microanalysis for inclusions. Inclusions of amphiboles in association with spinel group minerals, carbonates and...

The samples of garnets used in this study come from clastic sediments from the drillcores Tř-1 and T-31, selected localities of the České středohoří Mountains and garnet-bearing ultramafic rocks sampled by the drillcore T-7. The contents of the major and some minor elements were determined by an electron probe microanalyzer. The garnets from the sediments were divided into 3 groups according to the contents of the end-members: 1) pyrope-, 2) almandine - pyrope- and 3) grosular - almandine-rich. Garnets from the drillcore T-7 were classified according to individual rock types in which they occurred: lherzolite, hazburgite, pyroxenite, eclogite and granulite. Chemical analyzes of garnets displayed the presence of positive correlations Cr vs. Ca vs. Ti Mn in pyrope grains. The contents of trace elements in garnets were studied by an LA-ICP-MS. After normalization to the CI-reservoir, garnets most often show lherzolite profiles of rare earth elements. Garnets of intense red and purple colors show slightly sinusoidal REE profiles. Inclusions enclosed in garnets were studied by a scanning electron microscope. If their dimensions allowed, the major and minor elements were determined by electron microanalysis for inclusions. Inclusions of amphiboles in association with spinel group minerals, carbonates and...

Master's thesis is devoted to the issues of stability spiral domains. It gives an overview of previously submitted behaviors spiral domains. Their features and some discrepancy with experi-ments were marked. For an explanation the experimental results in this paper proposed a model in which were introduced additional internal degrees of freedom - bending deformation of the domain boundary, resizing the inner core and changing the width of the domain. The equations describing the change of geometric parameters of the spiral domain were ob-tained as part of the dissipative model. In the model insulated spiral domain were considered on an endless film. The equations were solved by numerical calculation. The study identified two scenar-ios for the destruction of spiral domains. Discovered scenarios correspond more closely to the ex-perimentally observed than in models with only one degree of freedom. The work consists of four chapters, introduction and conclusion with 63 pages. The paper contains 41 figures and one application. / Магистерская диссертация посвящена вопросам стабильности спиральных доменов. В ней приводится обзор ранее представленных моделей поведения спиральных доменов. Вы-деляются их особенности и некоторое несоответствие экспериментам. Для объяснения экс-периментальных результатов в данной работе была предложена модель, в которой введены в рассмотрение дополнительные внутренние степени свободы – изгибное искажение доменной границы, изменение размера внутреннего ядра и изменение ширины домена. В рамках диссипативной модели были получены уравнения, описывающие изменение всех геометрических параметров спирального домена. В модели рассматривался изолированный спиральный домен на бесконечной пленке. Для решения уравнений применялся численный расчет. В ходе исследования определили два сценария разрушения спиральных доменов. Обнаруженные сценарии в большей степени соответствуют наблюдаемым на опыте, чем в модели только с одной степенью свободы. Работа состоит из четырех глав, введения и заключения общим объемом 63 страницы. В работе содержится 41 рисунок и одно приложение.

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