Exploring structural and magnetic properties of nanocrystalline iron oxide synthesized by autocombustion method

• Nanocrystalline Fe2O3 by autocombustion method.
• Structural and magnetic properties of Fe2O3.
• Rietveld powder structure refinement of Fe2O3.
• Magnetic properties of the as prepared and annealed Fe2O3.

The nanocrystalline Fe2O3 is synthesized by solution autocombustion method using glycine as a fuel. The Rietveld refinement results confirm that the as prepared powder is a mixture of Hematite (α-Fe2O3, 80.50 wt%) and Maghemite (γ-Fe2O3, 19.50 wt%) phases and annealed (1000 °C for 5 h) powder is a single hematite phase of Fe2O3. The A1g symmetry bands are observed at 227 and 502 cm−1 and Eg symmetry bands are observed at 293, 411, and 611 cm−1 in hematite phase of Fe2O3. Chemical composition and valence state of the samples was confirmed using XPS studies. It is found that samples are sub-stoichiometric and broadening in the Fe 2p doublet is due to the multiplet splitting effects evidencing unpaired valence electrons. 57Fe Mössbauer spectroscopy analysis was used to further characterize the samples and confirm stoichiometry. Both the samples exhibit magnetically hyperfine split spectra with some special features. The annealed sample indicates the presence of only tetrahedral and octahedral site cations in hematite. The magnetic properties of the samples were studied by using M–H hysteresis curves. The saturation magnetizations of as prepared and annealed samples are 55.22 and 6.36 emu/g, respectively. Annealed sample exhibited larger value of coercivity (1065.6 Oe) and squareness (0.50) compared to the as prepared one (229.25 Oe, 0.28 respectively).