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Matsuo, Yoji*; Shinohara, Satoshi*; Mori, Shigeo*; Horibe, Yoichi*; Yoshii, Kenji; Ikeda, Naoshi*
Materials Research Society Symposium Proceedings, Vol.966 (Internet), 6 Pages, 2007/03
Change of the charge ordered (CO) structure by substituting Cu
for Fe in LuFe
O
was investigated by means of the transmission electron microscopy. The CO structure in LuFeO is characterized by the modulated structure with the wave vector of q=1/3[1 -1 3/2] and the average size of the CO domains can be estimated to be about 10-20nm. On the contrary, the Cu substitution destroyed the CO structure drastically and induced characteristic local lattice distortion, which gives rise to characteristic diffuse scattering in the reciprocal space. High-resolution lattice images revealed that there exist nano-scale clusters, which are characterized as the short-range ordering of the Cu and Fe
ions on the triangular lattice. In addition, the magnetic measurement revealed that LuFeCuO exhibits an antiferromagnetic transition around 50K, which is lower than the Neel temperature of 250K in LuFeO.
Ikeda, Naoshi*; Mori, Shigeo*; Yoshii, Kenji; Matsuo, Yoji*
Materials Research Society Symposium Proceedings, Vol.966 (Internet), 9 Pages, 2007/03
We report ferroelectricity in the triangular mixed valence material RFeO (R=Y, Dy, Ho, Er, Tm, Yb, Lu). This ferroelectricity originates from the polar ordering of Fe and Fe or the polar ordering of electrons on Fe. The electric polarization arising from such electron ordering may not couple with the lattice modulation. The ordering process of Fe and Fe is explained by the frustrated interaction of charges in a triangular lattice. The ferroelectric property of this material is present at room temperature.