2008

IronI 7100 A Perovskite Containing Quadrivalent Iron as a Charge-Disproportionated Fer-

rimagnet. — The new FeIV-perovskite CaCu3Fe4O12 is synthesized by solid state reac-tion of a mixture of Ca2Fe2O5, CuO, and Fe2O3 in the presence of KClO4 as oxidizing agent (Au capsule, 1300 K, 15 GPa, 30 min). The samples are characterized by powder XRD, Moessbauer spectroscopy, and by electrical resistivity and magnetic susceptibil-ity measurements. The compound crystallizes in the space group Im3 at room temper-ature and in space group Pn3 at 90 K. It undergoes an interesting phase transition to a charge-disproportionated ferrimagnetic state at 210 K. This charge disproportionation is of the CaFeO3 type (2FeIV→FeIII+FeV). — (YAMADA*, I.; TAKATA, K.; HAYASHI, N.; SHINOHARA, S.; AZUMA, M.; MORI, S.; MURANAKA, S.; SHIMAKAWA, Y.; TAKANO, M.; Angew. Chem., Int. Ed. 47 (2008) 37, 7032-7035; Inst. Chem. Res., Kyoto Univ., Uji, Kyoto 611, Japan; Eng.) — W. Pewestorf

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