Yamada Ikuya, Etani Hidenobu, Murakami Makoto, Hayashi Naoaki, Kawakami Takateru, Mizumaki Masaichiro, Ueda Shigenori, Abe Hideki, Liss Klaus-Dieter, Studer Andrew J, Ozaki Tomoatsu, Mori Shigeo, Takahashi Ryoji, Irifune Tetsuo
Nanoscience and Nanotechnology Research Center, Osaka Prefecture University , 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8570, Japan.
Inorg Chem. 2014 Nov 3;53(21):11794-801. doi: 10.1021/ic502138v. Epub 2014 Oct 21.
A novel quadruple perovskite oxide CeCu3Fe4O12 has been synthesized under high-pressure and high-temperature conditions of 15 GPa and 1473 K. (57)Fe Mössbauer spectroscopy displays a charge disproportionation transition of 4Fe(3.5+) → 3Fe(3+) + Fe(5+) below ∼270 K, whereas hard X-ray photoemission and soft X-ray absorption spectroscopy measurements confirm that the Ce and Cu valences are retained at approximately +4 and +2, respectively, over the entire temperature range measured. Electron and X-ray diffraction studies reveal that the body-centered cubic symmetry (space group Im3̅, No. 204) is retained at temperatures as low as 100 K, indicating the absence of any types of charge-ordering in the charge-disproportionated CeCu3Fe4O12 phase. The magnetic susceptibility and neutron powder diffraction data illustrate that the antiferromagnetic ordering of Fe ions is predominant in the charge-disproportionated CeCu3Fe4O12 phase. These findings suggest that CeCu3Fe4O12 undergoes a new type of electronic phase in the ACu3Fe4O12 series and that the melting of the charge-ordering in CeCu3Fe4O12 is caused by the substantial decrease in the Fe valence and the resulting large deviation from the ideal abundance ratio of Fe(3+):Fe(5+) = 1:1 for rock-salt-type charge-ordering.
一种新型的四重钙钛矿氧化物CeCu₃Fe₄O₁₂已在15 GPa和1473 K的高压高温条件下合成。(57)Fe穆斯堡尔光谱显示，在约270 K以下存在4Fe(3.5+) → 3Fe(3+) + Fe(5+)的电荷歧化转变，而硬X射线光电子能谱和软X射线吸收光谱测量证实，在整个测量温度范围内，Ce和Cu的价态分别保持在约+4和+2。电子和X射线衍射研究表明，体心立方对称性（空间群Im3̅，编号204）在低至100 K的温度下得以保留，这表明在电荷歧化的CeCu₃Fe₄O₁₂相中不存在任何类型的电荷有序。磁化率和中子粉末衍射数据表明，在电荷歧化的CeCu₃Fe₄O₁₂相中，Fe离子的反铁磁有序占主导地位。这些发现表明，CeCu₃Fe₄O₁₂在ACu₃Fe₄O₁₂系列中经历了一种新型的电子相，并且CeCu₃Fe₄O₁₂中电荷有序的消失是由于Fe价态的大幅降低以及由此导致的与岩盐型电荷有序中Fe(3+):Fe(5+)=1:1的理想丰度比的巨大偏差。
