• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Crescimento de filmes nanom?tricos monocristalinos de Fe/MgO(100) por "SPUTTERING" DC

Souza, Thatyara Freire de 16 July 2007 (has links)
Made available in DSpace on 2014-12-17T15:15:05Z (GMT). No. of bitstreams: 1 ThatyaraFS.pdf: 1656842 bytes, checksum: a24e627a4eabea4a6ac67cca1f9790f8 (MD5) Previous issue date: 2007-07-16 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The research behind this master dissertation started with the installation of a DC sputtering system, from its first stage, the adaptation of a refrigerating system, passing by the introduction of a heating system for the chamber using a thermal belt, until the deposition of a series of Fe/MgO(100) single crystal nanometric film samples. The deposition rates of some materials such as Fe, Py and Cu were investigated through an Atomic Force Microscope (AFM). For the single crystal samples, five of them have the same growth parameters and a thickness of 250?, except for the temperature, which varies from fifty degrees from one to another, from 100?C to 300?C. Three other samples also have the same deposition parameters and a temperature of 300?C, but with thickness of 62,5?, 150?, and 250?. Magneto-optical Kerr Effect (MOKE) of the magnetic curves measurements and Ferromagnetic Resonance (FMR) were made to in order to study the influence of the temperature and thickness on the sample s magnetic properties. In the present dissertation we discuss such techniques, and the experimental results are interpreted using phenomenological models, by simulation, and discussed from a physical point of view, taking into account the system s free magnetic energy terms. The results show the growth of the cubic anisotropy field (Hac) as the sample s deposition temperature increases, presenting an asymptotic behavior, similar to the characteristic charging curve of a capacitor in a RC circuit. A similar behavior was also observed for the Hac due to the increase in the samples thicknesses. The 250˚A sample, growth at 300?C, presented a Hac field close to the Fe bulk value / Os trabalhos desta disserta??o tiveram in?cio com a instala??o de um sistema de sputtering DC, desde a sua etapa inicial, a adapta??o de um sistema de refrigera??o, passando pela implanta??o de um sistema de aquecimento da c?mara atrav?s de uma cinta t?rmica envolvendo a mesma, at? a deposi??o de uma s?rie de amostras de filmes nanom?tricos monocristalinos de Fe/MgO(100). Foram investigadas as taxas de deposi??o para alguns materiais como Fe, Py e Cu, atrav?s de um microsc?pio de for?a at?mica (AFM). Dentre as amostras monocristalinas, cinco possuem praticamente todos os par?metros de crescimento iguais e espessura de 250?, exceto pela temperatura de deposi??o que varia de cinquenta graus de uma pra outra, desde 100?C a 300?C. Outras tr?s amostras possuem os mesmos par?metros de deposi??o e temperatura de 300?C, mas espessuras de 62,5?, 150? e 250?. Foram realizadas medidas das curvas de magnetiza??o por efeito kerr (MOKE) e espectros de resson?ncia ferromagn?nica (FMR) para an?lise da influ?ncia da temperatura de crescimento e da espessura nas propriedades magn?ticas das amostras. ? feita uma abordagem sobre tais t?cnicas durante a disserta??o e os resultados experimentais s?o interpretados de acordo com modelos fenomenol?gicos via simula??o. E discutidos do ponto de vista f?sico, levando em conta os termos da energia livre magn?tica do sistema. Os resultados demonstraram o crescimento do campo de anisotropia c?bica Hac em rela??o ao aumento da temperatura de deposi??o das amostras, apresentando um comportamento assint?tico, semelhante ? curva caracter?stica de carga para um capacitor em um circuito RC. Um comportamento semelhante foi observado para o valor de Hac em fun??o do aumento de espessura das amostras. A amostra de 250?, crescida a 300?C apresentou campo Hac pr?ximo ao do valor para o Fe bulk

Page generated in 0.0888 seconds