Charge frustration and dielectric dispersion in LuFe2O4

We report the dielectric anomaries at the phase transitions of Lu(Fe2+ Fe3+)O-4, which is considered as a charge and spin frustrated system. Dielectric constant shows a hump, just above the transition from the high temperature two-dimensional to the low temperature three-dimensional charge ordering. A few glassy behaviors were observed at this transition. The presence of spontaneous polarization in the low temperature phase was confirmed by thr measurement of pyroelectricity. A step-wise increase of the dielectric constant with increasing temperature was observed between 150 K and 250 K as in other RFe2O4. These phenomena are explained by the presence of the polar domains with the ordering of Fe2+ and Fe3+ and the motions of the antiphase boundaries between them.