Structural, vibrational and magnetic properties of Ti substituted bulk hematite: Emphasis Type="Italic"α/Emphasis-FeSubscript2?Emphasis Type="Italic"x/Emphasis/SubscriptTiSubscript Emphasis Type="Italic"x/Emphasis /SubscriptOSubscript3/Subscript

摘要

Ti doped hematite α-Fe2?xTixO3 (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 Eu (LO) mode at about 660 cm-1 is observed. The Eu 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 M?ssbauer data clearly shows the presence of ferric (Fe3+) and Ti4+ ions illustrating strong ferromagnetic ordering up to x = 0.0206 in α-Fe2?xTixO3 hematite and weak ferromagnetic ordering of α-Fe2?xTixO3 for x = 0.0344.