Nucleação de paredes de domínio e produto energético máximo em nanocilindros magnéticos tipo Núcleo@Casca
Ferromagnetic structures in confined geometries have attracted great interest, as geometric confinement opens new routes for manipulating fundamental magnetic properties required by major applications such as logic devices, magnetic sensors, nano-oscillators and magnetic memories. We report a theo...
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| Formato: | doctoralThesis |
| Idioma: | pt_BR |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/30143 |
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| Resumo: | Ferromagnetic structures in confined geometries have attracted great interest, as geometric confinement opens new routes for manipulating fundamental magnetic properties
required by major applications such as logic devices, magnetic sensors, nano-oscillators
and magnetic memories. We report a theoretical study of the impact of dipolar interaction
on the magnetic phases of the core@shell rectangular nanocylinders. Our results indicate
that the dipolar interaction between the core and the shell is capable of causing significant
changes in the magnetic phases of the isolated iron (Fe) cylinder and the Ni80Fe20 alloy
ring, known as Permalloy (Py). We show that the geometric parameters of flat Fe@Py
core@shell cylinders can be chosen in such a way to control the nucleation of domain
walls in the Py shell. It is also possible to fine-tuning the domain wall position and width
by using only magnetic energies. On the other hand, bimagnetic nanoparticles combining
different functionalities of two magnetic materials opens new perspectives for key applications such as permanent magnets, recording media, and magnetic hyperthermia. A
theoretical analysis of the impact of the composition of FePt@CoFe2 and FePt@Fe bimagnetic nanocylinders on the maximum energy product (BH)max was performed. (BH)max
is the determining parameter of the permanent magnet quality. The best composition is
determined by the competing trends imposed by the dipolar energy and a ferromagnetic
core@shell interface exchange energy. It was observed that the dipolar interaction has a
negative impact on the intensity of (BH)max for shell thicknesses above a theresehold
value, which depends on the material. The results show that the best shell material is the
one with highest exchange stiffness. |
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