Influence of Cr and Mn substitution on the structural and spectroscopic properties of doped haematite: α-Fe2−xMxO3 (0.0 ⩽ x < 0.50)

• Fe2−xCr/MnxO3 hematites are in single phase and possess corundum type structure.
• Cr and Mn doped hematite Fe2−xMxO3 revels seven Raman active modes.
• Doping allows FWHM to increase with increased Cr and Mn doping concentration.
• Mössbauer spectrum of Fe2−xCr/MnxO3 shows Fe is ferric in nature (+3 oxidation).
• Fe2−xCr/MnxO3 hematites are less magnetic as compared to parent Fe2O3.

Solid-state ceramic route technique is used for synthesizing Cr and Mn doped haematite α-Fe2−xMxO3. The X-ray diffraction pattern identifies the single phase and corundum (Al2O3) type structure of the polycrystalline samples α-Fe2−x MxO3 (M = Cr and Mn; x = 0, 0.10, and 0.50). The Raman measurements of α-Fe2O3 samples shows seven Raman active modes at A1g(1) ≅ 225 cm−1, Eg(1) ≅ 249 cm−1, Eg(2) ≅ 292 cm−1, Eg(3) ≅ 297 cm−1, Eg(4) ≅ 409 cm−1, Eg(5) ≅ 496 cm−1, and A1g(2) ≅ 609 cm−1.On substitution of Cr and Mn (x = 0.1, and 0.50) at Fe site, all Raman active modes are shifted to higher wavenumber. The observed isomer shift values from room temperature Mössbauer data clearly show the presence of ferric (Fe3+) state and strong magnetic ordering in all samples. The observed isomer shift δ values from room temperature Mössbauer data clearly show the Fe is in Ferric (Fe+3) nature. In doped haematite Cr+3 and Mn2+ ions illustrating strong Ferro magnetic ordering up to (x = 0.10) and weak Ferro magnetic ordering for α-Fe2−xMxO3 (x > 0.10) haematite.