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. InFe 2O4 exhibits ferrimagnetic ordering at Tc ∼ 242 K and a dielectric constant (ε) of ∼10000 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 Tc and ε are decreased in the order of InFe2O4, InFeCuO 4, 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 AFe 2O4 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 ε values (δ > ∼1500). In consideration of this property, we discuss the possible applications of these oxides.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry