Banca de DEFESA: SAMUEL JÔNATAS DE CASTRO LOPES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : SAMUEL JÔNATAS DE CASTRO LOPES
DATE: 11/08/2023
TIME: 08:00
LOCAL: Programa de Pós-Graduação em Ciência de Materiais
TITLE:

INFLUENCE OF COMPOSITION MODULATION ON THE MICROSTRUCTURALAND MAGNETIC PROPERTIES OF Ni/Cu NANOWIRES.

KEY WORDS:

nanowires; modulation by composition; anisotropy field.

PAGES: 145
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

In the present work, continuous and composition-modulated magnetic nanowires were electrodeposited into commercial alumina porous membranes with pore diameters of approximately 250 nm. Initially, two samples were synthesized using the chronopotentiometry mode and a conventional working electrode (Au). To optimize the synthesis process, carbon conductive ink commonly used in electron microscopy was employed for the fabrication of the working electrode. To demonstrate the efficiency and reproducibility of this new method, continuous and composition-modulated nanowires were electrodeposited using the chronopotentiometry mode. Morphological characterization indicated the formation of continuous and composition-modulated nanowires. Furthermore, it was proven that the chronopotentiometry method, where the potential is kept constant while the current varies over time, is more efficient in obtaining wires with a more uniform morphology. EDS analysis confirmed that AM-1 and AM-4 consisted of continuous wires, while the other samples were composed of composition- modulated wires. XRD results confirmed that the metallic Ni and Cu present in the wires had a face- centered cubic structure. The W-H method was used to investigate how composition modulation modifies the structural parameters of nickel. Lattice parameter, crystallite size, lattice strain, and dislocation density were calculated. In terms of magnetic characterization, ferromagnetic resonance spectra revealed two distinct resonances. The lower intensity resonance corresponded to the excitation of spins at the material's surface, but further investigations are required. An angular dependence of the resonance field was also observed. Based on the ferromagnetic resonance results, a model was proposed to estimate the wire's anisotropy field and easy magnetization direction. Magnetization versus field curves were obtained using the vibrating sample magnetometry technique. The results demonstrated that the modulation process can influence the easy magnetization direction, coercivity values, and remanence. Additionally, it was possible to investigate how the structural modifications of nickel can influence the magnetic properties of the nanowires.

COMMITTEE MEMBERS:
Externo à Instituição - BARTOLOMEU CRUZ VIANA NETO - UFPI
Presidente - 2457389 - EDUARDO PADRON HERNANDEZ
Externa à Instituição - GILVANIA LUCIA DA SILVA VILELA - UPE
Interno - 3091529 - MICHAEL CABRERA BAEZ
Externo à Instituição - YUSET GUERRA DAVILA - UFPI