Banca de DEFESA: FRANCISCO ADRIANO DE LIMA SANTIAGO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : FRANCISCO ADRIANO DE LIMA SANTIAGO
DATA : 25/01/2018
HORA: 15:00
LOCAL: AUDITÓRIO DO DFTE
TÍTULO:

Magnetostatic Modes and Optical Reflection Spectrum in Aperiodic Rare Earth Superlattices

PALAVRAS-CHAVES:

Rare Earth, Quasicrystals, Quasiperiodic Superlattices, Magnetostatic Modes, Optical Reflectivity.

PÁGINAS: 200
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
RESUMO:

In this thesis we present a theoretical study of the propagation of magnons in the

magnetostatic regime and of electromagnetic waves in aperiodic superlattices of rare earths formed by dysprosium (Dy) and holmium (Ho). The superlattices studied are the quasiperiodic Fibonacci and the deterministic aperiodic Thue-Morse and Double-Period, all of which are constructed through the periodic stacking of unit cells, which are formed by a two-layer substitution rule of type A/B, where this rule depends on the type of sequence considered for the construction of the superlattice. As a consequence of the periodic of the unit cells, it is possible to apply Bloch’s theorem, which together with the matrix-transfer method, allows us to find the bulk and surface magnetostatic modes. These modes present a self-similar behavior of the volume bands, so, at the limit of the generation number , these spectra become a Cantor-type fractal set. It has also been verified scaling and localization properties of these modes, which are different for Dy and Ho. In the propagation of electromagnetic waves we analyze the optical spectrum of reflection (or reflectance) for the same rare earth superlattices. We use here the Drude model to determine the dielectric function of rare earths, which are metals, so we have that reflection is dominant for these systems. We also use the Maxwell equations and the matrix-transfer method, which allows us to obtain the reflection coefficients. Therefore, we analyzed in these structures the spectra for the normal incidence of s-polarized (TE waves) and p-polarized waves (TM waves), where it was observed that they present an autosimilar behavior and a mirror symmetry in their spectra in the near infrared region, with reflectance for both polarizations. In the oblique incidence it was observed that the reflectance is sensitive to the variation of the angle, also varying with the type of superlattice and its generation, where the spectra are different for Dy and Ho. In the far infrared region we have seen that reflectance is dominant in rare earths, as is expected for metals.

MEMBROS DA BANCA:
Presidente - 1519258 - DORY HELIO AIRES DE LIMA ANSELMO
Interno - 1345774 - CLAUDIONOR GOMES BEZERRA
Interno - 1354851 - MANOEL SILVA DE VASCONCELOS
Externo à Instituição - NILSON SENA DE ALMEIDA - UERN
Externo à Instituição - RAIMUNDO NOGUEIRA DA COSTA FILHO - UFC