Made available in DSpace on 2015-03-03T15:16:24Z (GMT). No. of bitstreams: 1 CharlieSG_TESE.pdf: 3311987 bytes, checksum: 5f80153b1b46fc49c2f7148d8e447904 (MD5) Previous issue date: 2010-02-26 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In this work we have developed a way to grow Fe/MgO(100) monocrystals by magnetron sputtering DC. We investigated the growing in a temperature range among 100 oC and 300 oC. Structural and magneto-crystalline properties were studied by different experimental techniques. Thickness and surface roughness of the films were investigated by atomic force microscopy, while magneto-crystalline properties were investigated by magneto-optical Kerr effect and ferromagnetic resonance. Our results show that as we increase the deposition temperature, the magneto-crystalline anisotropy of the films also increases, following the equation of Avrami. The best temperature value to make a film is 300 oC. As the main result, we built a base of magnetoresistence devices and as an aplication, we present measurements of Fe/Cr/Fe trilayer coupling. In a second work we investigated the temperature dependence of the first three interlayer spacings of Ag(100) surface using low energy electron diffraction. A linear expansion model of crystal surface was used and the values of Debye temperatures of the first two layers and thermal expansion coefficient were determinated. A relaxation of 1% was found for Ag(100) surface and these results are matched with faces (110) and (111) of the silver. iv / Neste trabalho foi desenvolvida a metodologia de deposi??o dos filmes monocristalinos de Fe/MgO (100) via magneto sputtering DC. Foi Investigado o crescimento de filmes na faixa de temperatura entre 100 oC e 300 oC. As propriedades estruturais e magnetocristalinas dos filmes foram estudadas por diferentes t?cnicas experimentais. A espessura e a rugosidade da superf?cie foram investigadas por microscopia de for?a at?mica (AFM). A t?cnica de espectroscopia de fotoel?trons excitados por raios-X (XPS) foi utilizada para determinar a pureza da composi??o dos filmes. E as propriedades magn?ticas foram investigadas por resson?ncia ferromagn?tica (FMR) e Efeito Ker Magneto-?ptico (MOKE). O resultados mostram que o aumento da temperatura de deposi??o gera um aumento da anisotropia magnetocristalina segundo um comportamento regido pela equa??o de Avrami. Como resultado principal, foi constru?da a estrutura base para a fabrica??o de dispositivos magnetoresistivos. E, como aplica??o s?o apresentadas as medidas do acoplamento entre uma tricamada de Fe/Cr/Fe/MgO. Em um segundo trabalho, foi investigado a depend?ncia com a temperatura dos primeiros tr?s espa?amentos entre camadas da Ag (100) via t?cnica de difra??o de el?trons. Utilizando um modelo de expans?o linear da superf?cie do cristal, foi determinada a temperatura de Debye, a varia??o percentual da dist?ncia interplanar e o coeficiente de expans?o t?rmica da superf?cie. A relaxa??o encontrada foi de 1% e os resultados s?o confrontados com as faces (110) e (111) da prata

Made available in DSpace on 2014-12-17T15:14:57Z (GMT). No. of bitstreams: 1 EdimilsonFS_DISSERT.pdf: 2546760 bytes, checksum: 08525df56e96d75f8d221757342883b4 (MD5) Previous issue date: 2012-02-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work, we investigated the magnetic properties of a monocrystalline Fe thin film and of Fe(80 ?)/Cr(t)/Fe(80 ?) tri-layers, with the nonmagnetic metallic Cr spacer layer thickness varying between 9 ? < t < 40 ?. The samples were deposited by the DC Sputtering on Magnesium Oxide (MgO) substrates, with (100) crystal orientation. For this investigation, experimental magneto-optical Kerr effect (MOKE) magnetometry and ferromagnetic resonance (FMR) techniques were employeed. In this case, these techniques allowed us to study the static and dynamical magnetization properties of our tri-layers. The experimental results were interpreted based on the phenomenological model that takes into account the relevant energy terms to the magnetic free energy to describe the system behavior. In the case of the monocrystalline Fe film, we performed an analytical discussion on the magnetization curves and developed a numerical simulation based on the Stoner-Wohlfarth model, that enables the numerical adjustment of the experimental magnetization curves and obtainment of the anisotropy field values. On the other hand, for the tri-layers, we analyzed the existence of bilinear and biquadratic couplings between the magnetizations of adjacent ferromagnetic layers from measurements of magnetization curves. With the FMR fields and line width angular dependencies, information on the anisotropy in three layers was obtained and the effects of different magnetic relaxation mechanisms were evidenced. It was also possible to observe the dependence of the epitaxy of the multilayers with growth and sputtering parameters. Additionally it was developed the technique of AC magnetic susceptibility in order to obtain further information during the investigation of magnetic thin films / Nesta disserta??o investigamos as propriedades magn?ticas de um filme monocristalino de ferro e tricamadas com a composi??o Fe(80?)/Cr(t)/Fe(80?), variando as espessuras da camada met?lica n?o magn?tica separadora (Cr) entre 9? < t < 40?. As amostras foram depositadas pela t?cnica Sputtring DC sobre substrato de ?xido de Magn?sio (MgO) com orienta??o cristalina (100). Para esta investiga??o foram utilizadas as t?cnicas experimentais de magnetometria por efeito Kerr Magneto-?ptico (MOKE) e Resson?ncia Ferromagn?tica (FMR). Estas t?cnicas permitiram o estudo das propriedades est?ticas e din?micas da magnetiza??o das multicamadas. Os resultados experimentais foram interpretados com base no modelo fenomenol?gico que leva em considera??o os termos mais relevantes da energia livre magn?tica para descrever o comportamento do sistema. Para o filme monocristalino de ferro, realizamos uma discuss?o anal?tica das informa??es das curvas de magnetiza??o e desenvolvemos uma simula??o num?rica baseada no modelo de Stoner-Wohlfarth, possibilitando o ajuste num?rico das curvas de magnetiza??o experimentais e a obten??o do valor de campo de anisotropia. Para as tricamadas, analisamos a presen?a dos acoplamentos bilinear e biquadr?tico entre as magnetiza??es das camadas ferromagn?ticas adjacentes a partir das medidas das curvas de magnetiza??o. Com as depend?ncias angulares do campo de FMR e da largura de linha obtivemos informa??es sobre as anisotropias presentes nas tricamadas e evidenciamos os efeitos de diversos mecanismos de relaxa??o magn?tica. Tamb?m foi poss?vel observar a depend?ncia da epitaxia das multicamadas com os par?metros de crescimento do Sputtering. Adicionalmente foi desenvolvida, durante o per?odo do mestrado, a t?cnica de susceptibilidade magn?tica AC com o objetivo de obter resultados inovadores na investiga??o de filmes finos magn?ticos