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

Made available in DSpace on 2014-12-17T15:15:00Z (GMT). No. of bitstreams: 1 CharlieSG.pdf: 1382454 bytes, checksum: 2b54a2a0dcd81f1ca374af1328ff8c73 (MD5) Previous issue date: 2006-03-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / n this master s dissertation a Kerr Magneto Optic s magnetometer effect was set up to do characterization of samples type films fine and ultra thin, these samples will be grown after the implementation of the sputtering technique at the magnetism laboratory of of this department. In this work a cooled electromagnet was also built the water and that it reaches close values to 10kOe with a gap of 22 mm including an area of uniform field of 25mm of diameter. The first chapter treats of the construction of this electromagnet from its dimensioning to the operation tests that involve measures of reached maximum field and temperature of the reels when operated during one hour. The second chapter is dedicated to the revision of the magnetism and the magnetization processes as well as it presents a theoretical base regarding the magnetic energies found in films and magnetic multilayer. In the sequence, the third chapter, is especially dedicated the description of the effects magneto opticians the effect kerr in the longitudinal, traverse and polar configurations, using for so much only the classic approach of the electromagnetism and the coefficients of Fresnel. Distinguished the two areas of observation of the effect regarding thickness of the film. The constructive aspects of the experimental apparatus as well as the details of its operation are explained at the room surrender, also presenting the preliminary results of the measures made in one serializes of permalloy films and concluding with the results of the characterization of the first films of iron and permalloy grown here at the theoretical and experimental physics department at UFRN / Nesta disserta??o de mestrado foi montado um magnet?metro de efeito Kerr Magneto-?ptico para fazer caracteriza??o de amostras tipo filme fino e ultrafino, amostras estas que ser?o crescidas ap?s a implementa??o da t?cnica de Sputtering no laborat?rio de magnetismo deste departamento. Neste trabalho tamb?m foi constru?do um eletro?m? arrefecido a ?gua e que atinge valores pr?ximos a 10 kOe com um gap de 22 mm abrangendo uma regi?o de campo uniforme de 25 mm de di?metro. O primeiro cap?tulo trata da constru??o deste eletro?m? desde o seu dimensionamento at? os testes de opera??o que envolvem medidas de campo m?ximo alcan?ado e temperatura das bobinas quando operando durante 1 hora. O capitulo 2 ? dedicado a uma revis?o do magnetismo e dos processos de magnetiza??o bem como apresenta uma base te?rica a respeito das energias magn?ticas encontradas em filmes e multicamadas magn?ticas. Na seq??ncia, o terceiro cap?tulo, ? dedicado a descri??o dos efeitos magneto ?pticos em especial o efeito kerr nas configura??es longitudinal, transversal e polar, utilizando para tanto somente a abordagem cl?ssica do eletromagnetismo e os coeficientes de Fresnel. Distinguindo em seguida, as duas regi?es de observa??o do efeito referentes a espessura do filme. Os aspectos construtivos do aparato experimental bem como os detalhes de sua opera??o s?o explanados no quarto capitulo, apresentando tamb?m os resultados preliminares das medidas efetuadas em uma serie de filmes de Permalloy e finalizando com os resultados da caracteriza??o dos primeiros filmes de ferro e Permalloy crescidos aqui no departamento de f?sica te?rica e experimental da UFRN