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Journal Articles

Effects of oxygen annealing on dielectric properties of LuFeCuO$$_{4}$$

Matsuo, Yoji*; Suzuki, Muneyasu*; Noguchi, Yuji*; Yoshimura, Takeshi*; Fujimura, Norifumi*; Yoshii, Kenji; Ikeda, Naoshi*; Mori, Shigeo*

Japanese Journal of Applied Physics, 47(11), p.8464 - 8467, 2008/11

https://doi.org/10.1143/JJAP.47.8464
 Times Cited Count：11 Percentile：42.15(Physics, Applied)

We have investigated the physical properties of LuFeCuO$$_{4}$$, which is a derivative material of the electronic ferroelectric LuFe$$_{2}$$O$$_{4}$$. From electron diffraction measurements at room temperature, ionic ordering of Fe$$^{3+}$$ and Cu$$^{2+}$$ in the a-b plane was observed. This ordering is similar to that in LuFe$$_{2}$$O$$_{4}$$ and has an electric dipole. The observation of small domains (5-10 nm) indicates the presence of polar regions. Dielectric measurements showed that a peak of dielectric constant appeared at around 500 K, and the peak value was about 1000, indicating that LuFeCuO$$_{4}$$ is a dielectric material. We will present the experimental data on the samples prepared under high-pressure oxygen.

Journal Articles

Magnetic and dielectric properties of HoFe$$_{2}$$O$$_{4}$$ and R$$_{1-x}$$R'$$_{x}$$Fe$$_{2}$$O$$_{4}$$ (R, R': rare earths)

Yoshii, Kenji; Yoneda, Yasuhiro; Maeda, Daisuke*; Yokota, Yusuke*; Michiuchi, Takamasa*; Komatsu, Takuma*; Ikeda, Naoshi*; Matsuo, Yoji*; Mori, Shigeo*

Japanese Journal of Applied Physics, 47(9), p.7599 - 7602, 2008/09

https://doi.org/10.1143/JJAP.47.7599
 Times Cited Count：8 Percentile：33.28(Physics, Applied)

We have investigated the physical properties of HoFe$$_{2}$$O$$_{4}$$ and R$$_{1-x}$$R'$$_{x}$$Fe$$_{2}$$O$$_{4}$$ (R, R': rare earths). Dielectric measurements showed their dielectric constants of 1000 at around room temperature, which is characteristic of the RFe$$_{2}$$O$$_{4}$$ series (R: rare earths). However, the magnetic transition temperatures and the coherency in dielectric response were found to be different from those of RFe$$_{2}$$O$$_{4}$$ reported so far. Interestingly, these materials suggested higher ferroelectric temperatures than those reported so far, suggesting a possibility of application of these materials.

Journal Articles

Effect of oxygen vacancies on charge ordered structure in YFe$$_{2}$$O$$_{4-delta}$$

Mori, Shigeo*; Shinohara, Satoshi*; Matsuo, Yoji*; Horibe, Yoichi*; Yoshii, Kenji; Ikeda, Naoshi*

Japanese Journal of Applied Physics, 47(9), p.7595 - 7598, 2008/09

https://doi.org/10.1143/JJAP.47.7595
 Times Cited Count：12 Percentile：44.62(Physics, Applied)

We have investigated the electronic ferroelectric material YFe$$_{2}$$O$$_{4}$$by means of electron transmission microscopy. The measurement at room temperature showed the charge-ordered structure of Fe ions in the a-b plane, which is the origin of ferroelectricity. An enlargement of unit cell along the c-axis was also observed. These phenomena were not observed at high temperatures around 600 K. That is, the charge ordering in the a-b plane appeared below about 500 K, whreas the enlargement of unit cell along the c-axis was found at room temperature. Below 100 K, an additional enlargement of unit cell along [119] was observed. This behavior is characteristic of YFe$$_{2}$$O$$_{4}$$. These results are discussed in connection with the dielectric properties.

Journal Articles

Local structure of BiFeO$$_3$$-BaTiO$$_3$$ mixture

Yoneda, Yasuhiro; Yoshii, Kenji; Kohara, Shinji*; Kitagawa, Shuji*; Mori, Shigeo*

Japanese Journal of Applied Physics, 47(9), p.7590 - 7594, 2008/09

https://doi.org/10.1143/JJAP.47.7590
 Times Cited Count：24 Percentile：64.31(Physics, Applied)

Local structure analysis of (1-$$x$$)BiFeO$$_3$$-$$x$$BaTiO$$_3$$ mixture was carried out by synchrotron radiation X-ray pair-distribution function (PDF) method. The PDF peak is resolved as a doublet due to the presence of two distinct bond length, Bi-O and Ba-O. Cubic perovskite lattice of (1-$$x$$)BiFeO$$_3$$-$$x$$BaTiO$$_3$$ solid solution distorts locally to accomodate the distinct Bi-O and Ba-O bond lengths.

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