Doping effect on charge ordered structure in RFeO(R=Lu and Yb)

Matsuo, Yoji*; Mori, Shigeo*; Hirata, Akihiko*; Yoshii, Kenji  ; Ikeda, Naoshi*

RFeO (R= Ho-Lu,Y) is a novel ferroelectric material in which ferroelectric polarization is caused by the charge ordering (CO) of Fe and Fe. In this work we investigated the CO structure and dielectric/magnetic properties in RFeO and RFeCuO (R=Lu,Yb, M=Cu,Co) by a transmission electron microscopy (TEM), combining with dielectric and magnetic measurements. LuFeCuO is a dielectric compound, which shows the characteristic low-frequency dielectric dispersion. In addition, the Cu substitution in LuFeO suppressed the formation of the CO structure and induced characteristic polar nanodomains with the 5-10nm size. Magnetic measurement revealed that LuFeCuO shows the magnetic transition around 50K, which is much lower than the magnetictransition temperature of 250K in LuFeO. Our experimental results suggest that the polar nanodomains should be responsible for the magnetic/dielectric properties in RFeMO.