The observation of phase transition in LiF3O4 by Mossbauer spectroscopy

The compound LiFe3O4 is a novel material derived from magnetite by the insertion of Li+ in the spinel structure. As a consequence of the insertion, there is a change of the crystal structure from spinel to rock salt type, with all octahedral sites filled and the tetrahedral ones empty. A model is proposed in which the electron hopping between B-sites is little affected by the Li insertion. Our results also indicate some interesting features: (a) the compound is paramagnetic at room temperature and the Mossbauer spectra can be fitted with four different sites (as expected from the crystallography); (b) it undergoes a kind of structural phase transition in the temperature region 80 K < T < 100 K manifested by relaxation and a large broadening of the linewidths. For temperatures between 100 and 125 K there is anomalous behavior of the hyperfine parameters. For 80 K one sees again the same pattern observed for temperatures above the transition region, i.e., the presence of four well-resolved paramagnetic doublets, characterizing the region ranging from 80 to 125 K as a reentrant one. The antiferromagnetic phase transition is expected to occur around 50 K. This reentrant region where the phase transition occurs is about the same as the region where the Verwey transition in the magnetite is observed. Measurements with other techniques confirm this assumption. To our knowledge, it is the first time that such a behavior is observed in materials related to magnetite.