Local Structure Modulation in the Electronic Ferroelectric Oxide LuFe₂O₄

Abstract

We have investigated the physical properties and local atomic structure of LuFe₂O₄, a material belonging to the multiferroic system RFe₂O₄ (R: rare earths) which shows the new type of ferroelectricity owing to the charge ordering of Fe ions. Magnetic measurements showed the ferromagnetic ordering of Fe spins at ～230 K, as reported previously. From dielectric measurements, the dielectric constant (ε') of ～10000 was obtained at around room temperature. In addition, a peak of ε' was observed near the charge-ordering temperature (～330 K). The peak temperature was insensitive to the frequency of AC electric field; this behavior is different from that found in a previous study. The pair-distribution function analysis on a high-energy X-ray diffraction pattern revealed that LuFe₂O₄ has the systematic modulation of the local atomic displacement.