Structural, transport and spectroscopic properties of Ti~(4+) substituted magnetite: Fe_(3-x)Ti_xO_4

摘要

The effect of Ti~(4+) ion on the formation of magnetite, which were prepared by solid-state route reaction method, were studied by resistivity, Raman and ~(57)Fe Moessbauer spectrometry. Resistivity measured in the range of 10＜T＜300K for Ti~(4+) magnetite Fe_(3-x)Ti_xO_4 exhibit first order phase transformations at the Verwey transition T_v for Fe_3O_4, Fe_(2.98)Ti_(0.02)O_4 and Fe_(2.97)Ti_(0.03)O_4 at 123 K, 121 K and 118K, respectively. No first order phase transition was observed for Fe_(2.9)Ti_(0.1)O_4 and small polaron model retraces the semiconducting resistivity behavior with activation energy of about 72 meV. The changes in Raman spectra as a function of doping show that the changes are gradual for samples with higher Ti doping. The Raman active mode for Fe_(2.9)Ti_(0.1)O_4 at ≌ 634.4 cm~(-1) is shifted as compared to parent Fe_3O_4 at =670 cm~(-1), inferring that Mn~(2+) ions are located mostly on the octahedral sites. ~(57)Fe Mossbauer spectroscopy probes the site preference of the substitutions and their effect on the hyperfine magnetic fields confirms that Ti~(4+) ions are located mostly on the octahedral sites of the Fe_(3-x)Ti_xO_4 spinel structure.