Spelling suggestions: "subject:"ion barnets"" "subject:"ion garnet""
1 |
Fibre Optic Magnetic Field Sensors Utilizing Iron Garnet MaterialsSohlström, Hans January 1993 (has links)
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
|
2 |
Численное моделирование динамических доменных структур в магнитных средах : магистерская диссертация / Numerical simulation of the dynamic domain structure in magnetic mediaNesterenko, A. A., Нестеренко, А. А. January 2014 (has links)
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.
|
3 |
Patterning and Characterization of Ferrimagnets for Coherent MagnonicsFranson, Andrew J. January 2020 (has links)
No description available.
|
Page generated in 0.0722 seconds