Banca de DEFESA: TIBERIO MAGNO DE LIMA ALVES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : TIBERIO MAGNO DE LIMA ALVES
DATA : 26/01/2017
HORA: 10:00
LOCAL: AUDITÓRIO DO DFTE
TÍTULO:

Static magnetic properties of magnetic nanopowders (Co_1,2Fe_1,8-xMn_xO₄ – CoFe₂O₄) and thin films (FeCuNbSiB): Theory and experiment

PALAVRAS-CHAVES:

Magnetic hysteresis, thin films, magnetic nanopowders, modeling and simulation, coherent rotation, magnetic anisotropy, wasp-waisted.

PÁGINAS: 188
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
RESUMO:

Magnetic nanostructures have received great attention from the academic community, not only due to their various technological applications, but from basic physics point of view, displaying behaviors, effects and properties of great interest. In this context, we can mention the anisotropic magnetic properties of FeCuNbSiB ferromagnetic thin films, cobalt ferrites nanopowders with Fe−Mn substitution (Co_1,2Fe_1,8-xMn_xO₄) and also stoichiometric cobalt ferrite itself (CoFe₂O₄). In this work, we have developed three models and numerical systems based on coherent rotation of the magnetization, one for each cited sample above, in order to describe and/or quantifying such anisotropic effects. Through modeling and simulation processes, we found that thin films of FeCuNbSiB, produced by magnetron sputtering technique, had a texture formation of anisotropy axes that can be modeled by a statistical distribution. The numerical calculations applied in longitudinal, transverse and polar measurements of magnetization indicated that, indeed, the dominant mechanism in the magnetic hysteresis of thin films studied here is consistent with coherent rotation of magnetization. The simulations indicated the behavior of difficult saturation in magnetic hysteresis curves of Co_1,2Fe_1,8-xMn_xO₄ nanopowders, at low temperature, could be modeled by a superposition of cubic and uniaxial [001] easy plane configuration anisotropies, compatible with a tetragonal symmetry. The wasp-waisted behavior in magnetic hysteresis curves of CoFe₂O₄ nanopowder could be attributed to effects of dipolar interactions between crystallites with a uniaxial anisotropy in easy plane configuration.

MEMBROS DA BANCA:
Presidente - 1345774 - CLAUDIONOR GOMES BEZERRA
Interno - 1508681 - FELIPE BOHN
Externo à Instituição - FERNANDO LUIS DE ARAUJO MACHADO - UFPE
Externo à Instituição - JACQUES COUSTEAU DA SILVA BORGES - IFRN
Interno - 1675199 - SUZANA NOBREGA DE MEDEIROS
Externo à Instituição - VAMBERTO DIAS DE MELLO - UERN