Caracterização de filmes finos magnéticos em altas frequências

• Ano de defesa: 2014
• Autor(a) principal: Kern, Paula Roberta
• Orientador(a): Carara, Marcos André
• Banca de defesa: Melo, Luiz Guilherme Costa , Maziero, Jonas
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria
• Programa de Pós-Graduação: Programa de Pós-Graduação em Física
• Departamento: Física
• País: BR
• Palavras-chave em Português: Microstrip; Permeabilidade; Anisotropia
• Palavras-chave em Inglês: Microstrip; Permeability; Anisotropy
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: http://repositorio.ufsm.br/handle/1/9245

In order to determine the complex permeability of ferromagnetic samples in the GHz range, measurement techniques with transmission lines are most appropriate. These techniques use the modification of the scattering coefficients of the transmission line, induced by the sample, to obtain the permeability. In this work we have presented a shorted microstrip transmission line, suitable for the study of magnetic films as thin as 100 nm, in the 100 MHz - 5 GHz frequency range. The thin film permeability is calculated from the measurements of the reflection coefficient of a microstrip as a function of frequency and magnetic field, in the following situations: with the empty microstrip, loaded only with the substrate and loaded with the ferromagnetic film deposited on the substrate. To evaluate the developed microstrip, it was grown, by magnetron sputtering, Permalloy thin films with thickness ranging from 100 to 1000 nm. In plane magnetization measurements have shown that below a critical thickness, tcr ∼ 275 nm, the thin films present a behavior characteristic of systems with uniaxial anisotropy, this was also confirmed by the study of their dynamic properties. For this films the permeability measurement were well described by the expression called transverse permeability approximation. However, above tcr the hysteresis loops, measured in orthogonal directions, are almost identical and present the shape typical when there is an anisotropy component perpendicular to the film s plane. In these films it were observed the presence of more than just one resonance peak in the permeability spectra.