Structural, vibrational and magnetic properties of Ti substituted bulk hematite: α-Fe2−xTi x O3

Ti doped hematite α-Fe2−xTi x O3 (x = 0.0, 0.0206 and 0.0344) samples are synthesized using solid-state ceramic route technique. Single phase and corundum (Al2O3) type structure is revealed from the X-ray diffraction (XRD) pattern. On substitution of Ti at Fe site, all Raman active modes are shifted to higher wave numbers. An additional feature of E u (LO) mode at about 660 cm-1 is observed. The E u mode frequency is decreased and pronounced systematically as a function of Ti doping, and it reaches a value of 658 cm−1 for x = 0.0344. The coercivity Hc (remanence Mr) for x = 0.0, 0.0206 and 0.0344 are determined to be 995 Oe (0.44 emu/mg), 1404 Oe (0.00019 emu/mg) and 2023 Oe (0.00016 emu/mg), respectively. The larger coercivity for Ti doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy. The observed isomer shift (δ) from room temperature Mössbauer data clearly shows the presence of ferric (Fe3+) and Ti4+ ions illustrating strong ferromagnetic ordering up to x = 0.0206 in α-Fe2−xTi x O3 hematite and weak ferromagnetic ordering of α-Fe2−xTi x O3 for x = 0.0344.