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Journal Articles

Elemental substitution effects in multiferroic ${it R}$Fe$$_{2}$$O$$_{4}$$ (${it R}$: rare earths)

Yoshii, Kenji; Funae, Takeshi*; Mizumaki, Masaichiro*; Ejiri, Hiroki*; Ikeda, Naoshi*; Saito, Hiroyuki; Matsumura, Daiju

Physica Status Solidi (C), 12(6), p.841 - 844, 2015/06

 Times Cited Count:1 Percentile:40.68(Physics, Condensed Matter)

We report the effects of elemental substitutions in multiferroic ${it R}$Fe$$_{2}$$O$$_{4}$$ ($$R$$: Y, Ho-Lu, In). The substitution by nonmagnetic Ga$$^{3+}$$ at the Fe site, which has not been reported so far, shows a drastic decrease in the ferrimagnetic transition temperature ($$T_{rm N}$$). This is plausibly owing to the suppression of magnetic interactions between Fe ions, based on our previous results of other substituted systems such as ${it R}$FeCoO$$_{4}$$. Dielectric constants near room temperature were comparable to those of $$R$$Fe$$_{2}$$O$$_{4}$$. The suppression of dielectric loss in this system is suitable to application. The ${it R}$-site substitution was also attempted by the large R$$^{3+}$$ ions such as Dy$$^{3+}$$. The solubility limit was up to about 10% of ${it R}$ ions, as confirmed by XRD and EXAFS measurements. $$T_{rm N}$$ was raised by 5-10 K for Dy$$^{3+}$$ substitution.

Oral presentation

Successive charge-ordering transition in YFe$$_{2}$$O$$_{4}$$

Maeda, Daisuke*; Fukuyama, Ryota*; Kitamura, Satoshi*; Funae, Takeshi*; Matsuo, Yoji*; Ikeda, Naoshi*; Kambe, Takashi*; Kimizuka, Noboru*; Yoshii, Kenji

no journal, , 

We have investigated the successive phase transition in YFe$$_{2}$$O$$_{4}$$, which shows charge-ordering-induced ferroelectricity below about 330 K. This material has been reported to show complex phase transitions below 330 K. In this work we have studied the structure and physical properties of YFe$$_{2}$$O$$_{4}$$ synthesized in a variety of preparation conditions, and have found that slight changes of the conditions led to drastic alternations of physical properties. Details of the results will be shown at the conference.

Oral presentation

Multiferroic behavior and magnetic phase diagram of LuFe$$_{2}$$O$$_{4}$$

Oishi, Daisuke*; Hayakawa, Hironori*; Akahama, Yuji*; Funae, Takeshi*; Matsuo, Yoji*; Ikeda, Naoshi*; Kambe, Takashi*; Kimizuka, Noboru*; Yoshii, Kenji

no journal, , 

We have investigated the multiferroic behavior and the magnetic phase diagram of single-crystalline electronic ferroelectric LuFe$$_{2}$$O$$_{4}$$. Dielectric measurements under an applied magnetic field showed large magneto-capacitance at around room temperature. A complex magnetic phase diagram was obtained from detailed magnetic measurements below about room temperature. More details will be shown at the conference.

Oral presentation

Magnetic and dielectric properties of Lu$$_{2}$$Fe$$_{3}$$O$$_{7}$$

Fukuyama, Ryota*; Yoshii, Kenji; Kuroda, Tomoko*; Kitamura, Satoshi*; Funae, Takeshi*; Matsuo, Yoji*; Ikeda, Naoshi*; Kimizuka, Noboru*; Kambe, Takashi*

no journal, , 

We have investigated the physical properties of Lu$$_{2}$$Fe$$_{3}$$O$$_{7}$$, which has a related structure to the electronic ferroelectric RFe$$_{2}$$O$$_{4}$$ (R: rare earths). Magnetic measurements showed that its magnetic transition temperature was about 260-270 K. Dielectric measurements showed that dielectric constants at room temperature were about 10000. This material also showed a magneto-dielectric effect at around room temperature, a result which is interesting from the viewpoints of both fundamental and applied science.

Oral presentation

Crystal structure and physical properties of RFe$$_{0.56}$$Ti$$_{0.44}$$O$$_{3}$$(R=Lu,Yb)

Hoshiyama, Takuya*; Mori, Shigeo*; Matsuo, Yoji*; Funae, Takeshi*; Kambe, Takashi*; Ikeda, Naoshi*; Kimizuka, Noboru*; Yoshii, Kenji; Michiue, Yuichi*

no journal, , 

We have investigated the crystal structure and physical properties of RFe$$_{0.56}$$Ti$$_{0.44}$$O$$_{3}$$(R=Lu,Yb). The samples were prepared by the solid-state reaction method in air. X-ray and electron diffraction measurements showed that the materials have the same crystal structure as that of multiferroic RMnO$$_{3}$$. Magnetic measurements showed the absence of magnetic transition below 400 K. Dielectric measurements showed the peak of dielectric constant above room temperature, suggesting a existence of ferroelectric phase transition at high temperatures.

Oral presentation

Rare earth substitution effects in multiferroic RFe$$_{2}$$O$$_{4}$$ (R: rare earths)

Yoshii, Kenji; Matsumura, Daiju; Endo, Naruki; Saito, Hiroyuki; Yoneda, Yasuhiro; Nishihata, Yasuo; Funae, Takeshi*; Ejiri, Hiroki*; Kano, Jun*; Kobayashi, Tatsuo*; et al.

no journal, , 

We have investigated the substitution effects at the rare-earth (R) site in multiferroic RFe$$_{2}$$O$$_{4}$$ (R: Y, Ho-Lu) to explore a new phase of this system. From EXAFS measurements for the R atoms, the large R$$^{3+}$$ ions (such as Dy$$^{3+}$$) was partially substituted in RFe$$_{2}$$O$$_{4}$$. Powder X-ray diffraction showed that this material had a single-phase RFe$$_{2}$$O$$_{4}$$-type structure (space group R-3m). The simulated EXAFS spectrum reproduced the characteristics of the experimental spectrum, confirming that R$$^{3+}$$ is actually settled at the rare earth site. The other results, such as the magnetic properties, will be reported at the conference.

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