Propriedades estruturais e magnéticas de ferritas de cobalto e cobre dopadas com gadolínio (gd3+) sintetizadas pelo método de combustão
Co and Cu nanoferrites doped with Gd3+ ions, with general formula Co0,5Cu0,5Fe2-xGdxO4 (x = 0, 0,02, 0,04 e 0,06) were synthesized by combustion method and calcined at 900 ºC. The structural properties were determined by infrared spectroscopy (FTIR), X ray diffraction (XRD) with refinement by Rie...
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Formato: | doctoralThesis |
Idioma: | pt_BR |
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Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/27066 |
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Resumo: | Co and Cu nanoferrites doped with Gd3+ ions, with general formula Co0,5Cu0,5Fe2-xGdxO4 (x =
0, 0,02, 0,04 e 0,06) were synthesized by combustion method and calcined at 900 ºC. The
structural properties were determined by infrared spectroscopy (FTIR), X ray diffraction (XRD)
with refinement by Rietveld method, scanning electron microscopy and the magnetic
characteristics were studied by vibrating sample magnetometer (VSM). FTIR results shows that
Gd3+cations shift the Fe3+
-O
2-
stretches for low values. The results of XRD with refinement by
Rietveld reveal that samples have cubic/spinel structures, additionally ferrites with Gd3+ formed
a secondary phase (GdFeO3), crystallites sizes of all samples were calculated by Scherrer
equation with results in the range 16,84 to 66,51 nm., either the measured lattices parameters
grow with Gd3+ addition. VSM was used to determine parameters such as MS (Saturation
Magnetization), HC (Coercivity), HR (Remmanent Field), HR/HC (Squareness), K (Anisotropy
Constant) and nB (Bohr Magneton). Althought MS values initially increases, reaching the
maximum value for ferrite Co0,5Cu0,5Fe1,98Gd0,02O4, in high concentrations of Gd3+ the Ms
decreases, due the cations migrations between octahedral and tetraedrical sites of magnetic
spinels, furthermore the formation of GdFeO3 also affects the saturation magnetization of
Co0,5Cu0,5Fe1,98Gd0,02O4. HC and K values rise in major concentrations of Gd3+, while the HR
measured were almost constant. Results of HR/HC ratio in the range 0,4 to 0,3 indicates a
magnetic pseudo-single domain formation, moreover results of theoretical and experimental nBs
initially increase with addition of Gd3+
, however in higher concentrations of Gd3+ was observed
a decrease in nB values, it was proposed that the values of magnetic moments are strongly
influenced by cationic distribution and chemical composition of ferrites. The materials
synthesized in this work presented characteristics of soft magnetic materials, with possibilities
of applications in absorption field of radiation in microwave region. |
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