FTIR spectra for obtained iron oxides, with zoom in the region of 800-400 cm−1, showing the bands related with Fe-O vibrations. Inset: FTIR spectrum of A6 for the entire region of wavenumber.
XRD pattern of A6, A12, A18, and A24 samples. The Miller indices of reflection are assigned as * for maghemite and # for hematite.
TEM micrographs of the A6 sample presenting two different morphologies (JEOL JEM-1400 at 120 kV).
TEM micrographs of the A18 sample, composed by cubic particles of 15 nm of average size (Zeiss EM10 at 80 kV).
Photoacoustic UV-Vis spectra of A6 and A18 samples.
Determination of Eg from Tauc's equation for (a) direct transitions (m = 0.5) and (b) indirect transitions (m = 2). The curves in bold line are the extrapolation of the Tauc's equation.
ZFC (open symbols) and FC (solid symbols) magnetization curves of A6, A12, A18, and A24 samples at H = 500 Oe.
Dependence of magnetization on temperature in a magnetic field of 10 kOe.
Room-temperature magnetization vs magnetic applied field curves.
Mossbauer spectra for A6, A12, A18, and A24 samples taken at room temperature.
Maghemite and hematite amount (in wt. %) and particle size of each phase for the obtained samples by modified sol-gel method.
Hyperfine parameters and subspectral areas for the obtained iron oxides.
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