Dinâmica generalizada para sistemas magnéticos nanoestruturados
Microwave emission by magnetic materials at well-localized frequencies is of great interest for future nanotechnology applications. In this work a generalized model was developed to study the excitation spectra of nanostructured ferromagnetic systems using micromagnetic simulations with the implem...
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| Formato: | doctoralThesis |
| Idioma: | pt_BR |
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Brasil
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/28783 |
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| Resumo: | Microwave emission by magnetic materials at well-localized frequencies is of great interest
for future nanotechnology applications. In this work a generalized model was developed to
study the excitation spectra of nanostructured ferromagnetic systems using micromagnetic simulations with the implementation of the solving matrix method obtained through
the Landau-Lifshitz equation and the dynamic susceptibility tensor method. The first
part of the work was devoted to the analytical development of the equations of motion
for a nanostructured ferromagnetic system, according to micromagnetic theory, and the
expressions of the resolving matrix elements and the generalized dynamic susceptibility
tensor elements. The theoretical models are then applied to describe the excitation spectra of systems such as uniformly magnetized ferromagnetic nanostripes, domain walls of
ferromagnetic nanostripes coupled to antiferromagnetic vicinal substrates and magnetic
vortices of circular nanodisks. The resolvent matrix allows obtaining the spectral density
of states, and is applied to the study the spectra of domain walls, allowing the characterization of some modes of walls oscillations in a frequency range below the magnetic
domain spectral band. Using the dynamic susceptibility tensor, the spatial distribution of
resonance modes along the entire nanostructure could be identified. Thus, the similarities
and differences between the domain, domain wall and vortex magnetic excitations can
be investigated using the theoretical models developed in this study. Thus, we suggest,
it possible to predict microwave field values to specifically excite each of the observed
oscillation modes. The application of the model developed in systems such as nanodisks
vortices and domain walls pinned by exchange interaction at the multilayer FM/AFM
interface made it possible to identify considerable increases in resonance frequencies. For
magnetic vortices, the smaller the nanodisk diameter, the higher the resonant frequency,
while for domain walls, the narrower the wall (higher interface fields), the higher the
resonant frequency. |
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