title: Inverse Charge Transfer in the Quadruple Perovskite CaCu3Fe4O12.
abstract: Structural and spectroscopic analyses revealed that the quadruple perovskite CaCu3Fe4O12 undergoes an "inverse" electron charge transfer in which valence electrons move from B-site Fe to A'-site Cu ions (∼3Cu(∼2.4+) + 4Fe(∼3.65+) → ∼3Cu(∼2.2+) + 4Fe(∼3.8+)) simultaneously with a charge disproportionation transition (4Fe(∼3.8+) → ∼2.4Fe(3+) + ∼1.6Fe(5+)), on cooling below 210 K. The direction of the charge transfer for CaCu3Fe4O12 is opposite to those reported for other perovskite oxides such as BiNiO3 and ACu3Fe4O12 (A = Sr(2+) or the large trivalent rare-earth metal ions), in which the electrons move from A/A'-site to B-site ions. This finding sheds a light on a new aspect in intermetallic phenomena for complex transition metal compounds.
authors.affiliation: Nanoscience and Nanotechnology Research Center, Osaka Prefecture University , 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8570, Japan.
authors.forename: Ikuya
authors.initials: I
authors.lastname: Yamada
authors.affiliation: Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University , 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University , Yoshidaushinomiya-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Naoaki
authors.initials: N
authors.lastname: Hayashi
authors.affiliation: Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University , 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Mori