Yoshii Kenji, Ikeda Naoshi, Okajima Yuka, Yoneda Yasuhiro, Matsuo Yoji, Horibe Yoichi, Mori Shigeo
Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan.
Inorg Chem. 2008 Jul 21;47(14):6493-501. doi: 10.1021/ic702365k. Epub 2008 Jun 20.
The magnetic and dielectric properties of InFe2O4, InFeCuO4, and InGaCuO4 have been investigated. All these materials are isostructural with RFe2O4 (R = Y, Ho-Lu), which shows ferroelectricity due to iron-valence ordering. InFe2O4 exhibits ferrimagnetic ordering at T(C) approximately 242 K and a dielectric constant (epsilon) of approximately 10,000 at around room temperature. These properties resemble those of RFe2O4; the origins of the magnetic and dielectric phenomena are likely common in InFe2O4 and RFe2O4. From measurements of the other two materials, we found that both T(C) and epsilon are decreased in the order of InFe2O4, InFeCuO4, and InGaCuO4. This result strongly supports the previously reported explanation based on an electron transfer between the Fe-site ions for the corresponding rare-earth systems. Therefore, we propose that the dielectric properties of the oxides isostructural with RFe2O4 are plausibly governed by electron transfer; this situation is different from that of ordinary ferroelectrics and dielectrics, in which the displacement of cations and anions is important. In addition, InFeCuO4 and InGaCuO4 exhibit large epsilon values (epsilon > approximately 1500). In consideration of this property, we discuss the possible applications of these oxides.
对InFe₂O₄、InFeCuO₄和InGaCuO₄的磁性和介电性能进行了研究。所有这些材料都与RFe₂O₄（R = Y，Ho - Lu）同构，RFe₂O₄由于铁价有序化而表现出铁电性。InFe₂O₄在约242 K的居里温度（T(C)）下呈现亚铁磁有序，在室温附近的介电常数（ε）约为10000。这些性质与RFe₂O₄的性质相似；InFe₂O₄和RFe₂O₄中磁现象和介电现象的起源可能相同。通过对另外两种材料的测量，我们发现居里温度（T(C)）和介电常数（ε）均按照InFe₂O₄、InFeCuO₄和InGaCuO₄的顺序降低。这一结果有力地支持了先前基于相应稀土体系中铁位离子间电子转移所报道的解释。因此，我们提出与RFe₂O₄同构的氧化物的介电性能可能受电子转移支配；这种情况与普通铁电体和电介质不同，在普通铁电体和电介质中阳离子和阴离子的位移很重要。此外，InFeCuO₄和InGaCuO₄表现出较大的介电常数（ε > 约1500）。考虑到这一性质，我们讨论了这些氧化物的可能应用。
