Banca de DEFESA: Juliano de Souza Santos

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Juliano de Souza Santos
DATE: 27/05/2023
TIME: 14:30
LOCAL: PLATAFORMA TEAMS
TITLE:

 "Superparamagnetic relaxation of ferrite nanoparticles in systems with dipole interactions"

KEY WORDS:

Keywords: Copper ferrite, nanoparticles, Néel Arrhenius, Vogel Fulcher, dipole interactions, blocking temperature, magnetic susceptibility.

PAGES: 51
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

The project presented here deals with the magnetic relaxation of magnetic
nanoparticles in ferrofluids with variable particle volume fraction. The proposal intends
to investigate the effect of interparticle interactions on the thermally activated mechanism of magnetic moment inversion. From dynamic susceptibility measurements, we will use the Vogel-Fulcher law to better understand the magnetic behavior of magnetic particles in collective regime.

For the investigation of interparticle effects, samples with varied volume fractionswere prepared where the synthesis process was based on the hydrothermal co- precipitation method, followed by a surface treatment with ferric nitrate. Such samples were characterized by X-ray diffraction, atomic absorption spectroscopy, X-ray fluorescence spectroscopy and electron microscopy imaging. The interpretation of the data allowed us to verify the core@shell model, the structural basis of the model idealizedin the elaboration.

The two models that will be cited seek to describe the relationships between some quantities, such as blocking temperature, energy and anisotropy constants, with the average distances between particles. The Vogel-Fulcher model is a variation of the Néel- Arrhenius model and presents an additional temperature factor that represents theinteractions between nanoparticles.

For the analysis of the results, magnetic susceptibility measurements were performed in high and low field. The measures indicated an energy contribution consistent with the additional factor of the Vogel-Fulcher model, making it possible to quantitatively determine it.

BANKING MEMBERS:
Externo à Instituição - FRANCISCARLOS GOMES DA SILVA - UnB
Externo à Instituição - GUILHERME SIQUEIRA GOMIDE - UnB
Presidente - 1218541 - JEROME DEPEYROT
Interna - 1601059 - RENATA AQUINO DA SILVA