VALENCE FLUCTUATION AND POLARIZATION FLUCTUATION IN LUFE2O4

The anomalous dielectric behavior of mixed valence system LuFe2O4 is i nvestigated. It has been shown that LuFe2O4 undergoes successive phase transitions associated with ordering of charge configuration of Fe io n following the sequence of disorder --> 2D-CDW (charge density wave) --> 3D-CDW state. The stable 3D-CDW phase is characterized by a long p eriod incommensurate antiferroelectric phase. The anomalously high die lectric constant at lower temperature as well as its frequency depende nce is discussed in connection with the motion of the antiphase domain boundaries.