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Structural, Spectroscopic and Magnetic Study of Nanocrystalline Cerium-Substituted Magnesium Ferrites
文摘
Effect of cerium substitution in Nanocrystalline magnesium ferrite, \(\hbox {MgCe}_x\hbox {Fe}_{2-x}\hbox {O}_{4}\) (\(x = 0.00, 0.02, 0.04\) and 0.06) synthesized by sol–gel auto-combustion process has been studied. X-ray diffraction reveals the single-phase cubic spinel structure, X-ray density and porosity increase with concentration of ceria. Scanning electron microscopy micrograph shows agglomeration of ceria. Fourier transform infrared spectroscopy confirms the formation of spinel phase with two frequency bands, \({\nu }_{1}\) at around \(590\,\hbox {cm}^{-1}\) and a lower frequency band \({\upnu }_{2}\) at \(430\,\hbox {cm}^{-1}\), which were attributed to intrinsic vibrations of tetrahedral group (A-site) and octahedral groups (B-sites), respectively, based on this the cation distribution is proposed as \((\hbox {Mg}_{y-x}^{2+}\,\hbox {Fe}_{ 1-y+x}^{3+})_{\mathrm{A}}[\hbox {Mg}_{1-y}^{2+}\,\hbox {Fe}_{ 1+y-x}^{3+} \hbox {Ce}_{x}^{3+}]_\mathrm{B}\,\hbox {O}_{4}^{2-}\). The force constant for tetrahedral sites was less than that of octahedral sites. X-ray photoelectron spectroscopy spectra reveals the oxidation state of Fe by two peaks in the region of 712 and 724 eV corresponding to \(2p_{3/2}\) and \(2p_{1/2}\), respectively, with \(\Delta E = 12\) eV. The chemical state of Ce was confirmed by peaks at BE 884 and 902 eV corresponding to \(3d_{5/2}\) and \(3d_{3/2}\), respectively. vibrating sample magnetometer studies show that the magnetization strongly depends on \(\hbox {Ce}^{3+}\) substitutions. Saturation magnetization has decreased up to \(x=0.04\) and then increased which can ascribed to decrease in canting angle. All the samples were in superparamagnetic state.
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