57Fe Mössbauer spectroscopic study on ulvöspinel Fe2TiO4 has been conducted in a wide temperature range from 16 K to 500 K. The paramagnetic spectra are composed of several high spin Fe2+ doublets even at 500 K, which is rather strange because the point symmetry of the A-site is completely cubic (- 43m). We explain the electric field gradient (EFG) at A-site by the local arrangement of Fe2+ and Ti4+ on the B-site. The spectra were successfully analyzed by four-subspectra model, which is based on the B-site arrangement. The model also fits rather well to the magnetically ordered spectra. Thus the temperature variations of the hyperfine parameters were obtained. The Néel temperature (TN) is estimated to be about 125 K. The quadrupole coupling constants e2 qQ/2 of A-site subspectra show little change around cubic-tetragonal transition temperature (Tt = 163 K), but rapidly increase below TN. From the temperature variation of line width, we found local and dynamic Jahn-Teller distortions around A-site Fe2+ ions in the cubic phase.
ASJC Scopus subject areas
- Condensed Matter Physics
- Nuclear and High Energy Physics
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry