doctoralThesis
Síntese e caracterizações estrutural e magnética das ferritas de cobalto-manganês (Co1-xMnxFe2O4 E Co1,2Fe1,8-xMnxO4)
Fecha
2015-12-07Registro en:
AMORIM, Bruno Ferreira. Síntese e caracterizações estrutural e magnética das ferritas de cobalto-manganês (Co1-xMnxFe2O4 E Co1,2Fe1,8-xMnxO4). 2015. 100f. Tese (Doutorado em Física) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2015.
Autor
Amorim, Bruno Ferreira
Resumen
The cobalt-manganese ferrites (Co1¡xMnxFe2O4 and Co1,2Fe1,8¡xMnxO4) has a mixed
structure of spinel type and it has been regarded as one of candidates for petitive wide variety of
applications in devices from ultrasonic generation and detection, sensors, transformers, as well
as in medical industry. Ferrites cobalt-manganese nanostructured were produced via mechanical
alloying with subsequent heat treatment and were characterized by X-ray diffraction, X-ray
fluorescence, scanning electron microscopy and magnetization. Samples of Co1¡xMnxFe2O4 and
Co1,2Fe1,8¡xMnxO4 were obtained from the precursor powders Fe3O4, Co3O4 and Mn3O4 which were
stoichiometrically mixed and ground by 10h and heat treated at 900°C for 2h. The diffraction
confirmed the formation of the pure nanocrystalline phases to series Co1,2Fe1,8¡xMnxO4 with an
average diameter of about 94nm. It was found that the lattice parameter increases with the
substitution of Fe3Å by Mn3Å. The x-ray fluorescence revealed that the portions of metals in
samples were close to the nominal stoichiometric compositions. The microstructural features
observed in micrographs showed that the particles formed show very different morphology and
particle size. The magnetic hysteresis measurements performed at low temperature showed
that the saturation magnetization and remanence increased as the concentration of manganese,
while the coercive field decreased. The anisotropy constant (Ke f ), was estimated from the data
adjustments the law of approaching saturation. It was found that the anisotropy decreases
substantially with the substitution of Fe by Mn.